Stress Concentration Research Papers - Academia.edu (original) (raw)

2025, Rocky Mountain Geology

The timing and origins of minor faults and extensional fractures (joints) in the San Juan Basin of the Rocky Mountain foreland have generated intense debate. Hypotheses include nearly syn-sedimentary fracturing guided by pre-existing Precambrian weaknesses, syn-Laramide fracturing, and overburden-release jointing during Holocene erosion. Furthermore, the Laramide deformation that formed the San Juan Basin is also poorly resolved, with hypotheses including single-stage, unidirectional shortening and multi-stage, multidirectional shortening. The stress and fracture history of the basin is critical for predicting subsurface fracture trends that can control hydrocarbon and aquifer permeability and production. In order to test fracture and tectonic hypotheses, minor fault (n = 842) and joint (n = 2619) data were collected from 76 outcrops of Jurassic through Paleogene rocks in the northern San Juan Basin. Multiple conjugate sets of minor faults with consistent crosscutting relationships indicate multi-directional shortening with four episodes of deformation: (1) N56E Laramide shortening, (2) N55W shortening, (3) N17E post-Laramide shortening, and (4) N59E post-Laramide extension. Most joint localities show two regional joint sets, a dominant J 1 set and a secondary J 2 set. Joints in J 1 sets have two distinct orientations: a N19W average strike (47 stations) and a N32E average strike (6 stations). J 2 cross-joint sets have a N72E average strike and were probably generated at shallow depths. Subsurface information for the Dakota Sandstone from a well in the basin indicates two sets of N14W-and N18E-striking fractures, similar to J 1 surface joint sets. NE-striking coal cleats are oblique to the main NNE-trending Laramide shortening and perpendicular to the later NW-trending shortening. They may have formed either during earlier shortening related to the Sevier fold-and-thrust belt or during tectonic rebound from the last Laramide shortening. NNE-striking J 1 joints are parallel to the last phase of local shortening and to Miocene mafic dikes, suggesting formation during post-Laramide extension. Subsequent NNW-striking J 1 joints are parallel to local normal faults and may represent either regional Neogene extension or tectonic rebound from the main Laramide shortening. J 2 cross joint sets in sandstones formed perpendicular to both bedding and J 1 joints during uplift and erosion and thus probably do not extend far below the surface. The NNW-and NNE-striking J 1 joints may be open at depth and may act as preferential flow pathways for fluids. Nearer to the surface, systematic cross-joints (J 2 ) increase fracture density, which may be important for shallow aquifers and coalbed methane plays.

2025, AAPG Bulletin

Understanding the diversity of structural trends in the Laramide foreland of the conterminous United States is important to understanding the location, geometry, and fracturing of hydrocarbon reservoirs. East-west basement-cored arches in central Wyoming are oblique to the average northwesterly trend of foreland faults and folds. Tectonic models predict that these arches formed by one of the following mechanisms: north-south-directed thrust faulting; sinistral strike-slip faulting; or northeast-southwest-directed, oblique-slip thrust faulting. In the eastern Owl Creek Mountains, average slip directions given by slickenline directions trend from N37°E to N57°E. Geometric analysis of conjugate faults and stress inversion of minor fault data indicate nearly horizontal compression trending between N48°E and N65°E. In the east-west Casper Mountain structure, more limited minor fault data are consistent with the northeast-southwest compression seen in the eastern Owl Creek arch and indicate an additional stage of extension by normal faulting. The northeast-southwest compression documented by minor faults suggests oblique thrusting with a component of sinistral strike-slip on the underlying, east-west-striking Owl Creek and Casper Mountain thrusts. In this area of the Laramide foreland, east-west arches probably formed during a single stage of oblique slip on thrust ramps connecting northwest-trending arch culminations. This conclusion indicates that trap geometries and reservoir characteristics of foreland hydrocarbon accumulations are dependent on their obliquity to the regional stress field.

2025

A field study of positive inversion is conducted to describe associated structural fabrics and to infer kinematic development of the Palisades Monocline, Grand Canyon, Arizona. These features are then compared to sand, clay and solid rock models of positive inversion to test model results and improve understanding of inversion processes. The N40W 90 oriented Palisades fault underlying the monocline has experienced northeast-southwest Precambrian extension and subsequent northeastsouthwest Laramide contraction. The magnitude of inversion is estimated to be 25% based on vertical offset across the fault, although this does not account for flexure or horizontal shortening. The preferred N50W 90 joint and vein orientation and N50W 68 NE and SW conjugate normal faults are consistent with the Palisades fault and northeastsouthwest extension. The N45E 90 joint orientation and approximately N40W 28 NE and SW conjugate thrust faults are consistent with northeast-southwest contraction. The deformation is characterized by three domains across the fault zone: 1) the hanging wall, 2) the footwall, and 3) an interior, fault-bounded zone between the hanging wall and footwall. Extensional features are preserved and dominate the hanging wall, contractional features define footwall deformation, and the interior, fault-bounded zone is marked by the co-existence of extensional and contractional features. Extension caused a master normal fault and hanging wall roll-over with distributed joints, veins iv and normal faults. During inversion, contraction induced reverse reactivation of existing hanging wall faults, footwall folding and footwall thrust-faulting. Precambrian normal slip along the master normal fault and subsequent Laramide reverse slip along the new footwall bounding fault created an uplifted domain of relatively oldest strata between the hanging wall and footwall. Physical models of co-axial inversion suggest consistent development of the three domains of deformation described at the Palisades fault, however the models often require magnitudes of inversion greater than 50%. Although vertical block motion during horizontal compression is not predicted directly by the Mohr-Coulomb criterion, physical models and analytical solutions (incorporating Mohr-Coulomb criterion) suggest maximum stress trajectories and near vertical failure above high angle basement faults that compare favorably with the Palisades fault zone. v Russell Shapiro told me that no research project is ever complete or finished, but finalized because of a deadline. It appears that this project deadline has come, if not already passed. Many might say that a research project raises even more questions than it answers. The question that comes to my mind is why would someone go to Texas to study a fault in the Grand Canyon. Some questions have no answers, but I am sure every one of the following people has an opinion, which they deserve to speak as they helped this deadline arrive. I feel as though I did not do this research project, but rather integrated all the insightful thoughts of the people who helped. I cannot mention all to whom I am indebted, as it starts with my parents and moves to my many friends, colleagues, teachers, coaches, and professors that I have known from Oak Hall School, The Colorado College, and finally Texas A&M University. Please know that you are all held in high regard. Specific mention must be made of the following people as their contribution directly contributed to this thesis. The advisory research committee includes Dr. Judith Chester (chair), Dr. Brann Johnson and Dr. Will Sager. Academic and research funding came from AAPG Micheal T. Halbouty Grant, ChevronTexaco Scholarships and Houston Geological Society Calvert Memorial Scholarship. Research permitting support came from Barb Alberti and Emma Bennatti of the National Park Service at the Grand Canyon. Materials and logistical support came from Carol Fritzinger of the Grand Canyon Research and Monitoring Center. Materials support came from Stephanie Wyse of the Grand Canyon Research and Monitoring Center (aerial photographs) and Elaine Kennedy of the Geoscience Research Institute (sample of Shinumo quartzite). SEM research support came from Ray Guilmette of Texas A&M University. Computer and software support came from Nathan Davis. Inspirational conversations were provided by Pablo Cervantes and Marty Finn. Endless help in every and all matters and manners provided by the ever patient Jen Bobich.

2025, Fatigue & Fracture of Engineering Materials & Structures

ABSTRACTThe increase of fatigue life in aluminium cruciform joints by weld toe grinding was the focus of the current study. The test data are presented by both a nominal stress range approach and by the more refined structural and notch stress range approaches. The influence of the weld toe angle, weld leg length and weld toe radius on the structural and notch stress concentration factor (SCF) was systematically studied by means of finite element analysis. Experimental data based on 18 pieces of as‐welded and 13 pieces of weld toe‐ground specimens made of 12 mm thick plates showed a significant improvement in fatigue life in aluminium by grinding the weld toe and confirmed the permitted improvement in fatigue life by design codes.

2025, Journal of the Mechanics and Physics of Solids

The effect of grain size on the tensile plastic deformation of ultrafine-grained copper polycrystals is investigated using a two-dimensional simulation of dislocation dynamics. Emphasis is put on the elementary mechanisms governing the yield stress in multislip conditions. Whatever the grain size, the yield stress is found to follow a Hall-Petch law. However, the elementary mechanism controlling slip transmission through the grain boundaries at yield is observed to change with the grain size. For the larger grain sizes, the stress concentrations due to dislocations piled-up at grain boundaries are responsible for the activation of plastic activity in the poorly stressed grains. For the smaller grain sizes, the pile-ups contain less dislocations and are less numerous, but the strain incompatibilities between grains become significant. They induce high internal stresses and favor multislip conditions in all grains. Based on these results, simple interpretations are proposed for the strengthening of the yield stress in ultrafine grained metals.

2025, Composites Part B: Engineering

This paper presents a parametric investigation, based on non-linear finite element modeling, to identify the most effective configuration of carbon fiber-reinforced polymers (CFRP) for strengthening reinforced concrete (RC) dapped-end beams. Following a field application and laboratory tests, it focuses on effects of 24 externally bonded (EBR) and near surface mounted reinforcement (NSMR) configurations on yield strain in steel and the capacity and failure mode of dapped-end beams. The investigated parameters were the mechanical properties of the CFRP, the strengthening procedure and the inclination of the fibers with respect to the longitudinal axis. Two failure scenarios were considered: rupture and debonding of the FRP. The results indicate that high-strength NSM FRPs can considerably increase the capacity of dapped-end beams and the yielding strains in reinforcement can be substantially reduced by using high modulus fibers.

2025, Materials & Design

In this paper, tensile strain energy absorption of two different hybrid modified epoxies has been systematically investigated. In one system, epoxy has been modified by amine-terminated butadiene acrylonitrile (ATBN) and hollow glass spheres as fine and coarse modifiers, respectively. The other hybrid epoxy has been modified by the combination of ATBN and recycled Tire particles. The results of fracture toughness measurement of blends revealed synergistic toughening for both hybrid systems in some formulations. However, no evidence of synergism is observed in tensile test of hybrid samples. Scanning electron microscope (SEM), transmission optical microscope (TOM) and finite element (FEM) simulation were utilized to study deformation mechanisms of hybrid systems in tensile test. It is found that coarse particles induce stress concentration in hybrid samples. This produces non-uniform strain localized regions which lead to fracture of hybrid samples at lower tensile loading and energy absorption levels.

2025, Journal of Nuclear Materials

Numerical and experimental studies were performed to investigate the behaviour of lead-bismuth eutectic (LBE) after solidification. Re-crystallization of LBE is the main phenomenon to consider; it may lead to serious over-stressing of structural materials. The conditions for the target vessel of MEGAwatt PIlot Experiment (MEGAPIE) were especially considered. Some general recommendations were deduced in order to help avoiding dangerous events.

2025

Step-stress experiments are described in which the fatigue damage of an AISI/SAE 8620 steel is found to vary with stress sequence application. The fatigue behavior is studied by using experimental results of Fatigue Limit Resistance before and after imposing damage on several specimens. The influence of the order of application of various stress levels was investigated. For this purpose, increasing and decreasing stress sequences with four steps were applied on the specimens. Besides, damage evaluation was also performed using Barkhausen effect.

2025, STRUCTURES

The article presents the closed-form analytical design formulas for maximal deflections as well as for extremal stresses in adherends and maximal shear stress in the adhesive layer for adhesively bonded composite beams. Nine load and support layouts are considered. Applicability of the proposed formulas is validated with the experimental results reported in the literature [1-12] regarding 60 specimens of 36 types of adhesively bonded beams. Additionally, 36 linear Finite Element models were analyzed in order to compare the numerical simulations with theoretical predictions and recorded experimental data. The relative error of theoretical estimates with respect to FEA results in the majority of cases was within 0-30 %. The proposed formulas were also compared with predictions of the commonly used γ-method-it was found that both approaches provide nearly the same estimates. Relative error of theoretical estimates was analyzed with the use of the similarity theory. It may be conjectured that the proposed formulas provide the best estimates for beams with stiff adherends and relatively flexible adhesives, with the thickness of the bondline t equal 1 %-10 % of the height of the smaller adherend.

2025, Journal of Materials Processing Technology

In this paper the extrusion process of a cross-shaped profile was investigated. In particular, the study was focused on the distortion of extruding profiles when the workpiece and die axis are not aligned. The process was simulated using the finite element method (FEM) and the natural element method (NEM), both implemented in an updated-Lagrangian formulation, in order to avoid the burden associated with the description of free surfaces in ALE or Eulerian formulations. Furthermore, an experimental equipment was developed in order to obtain reliable data in terms of deformed entity, required process load and calculated pressure. At the end, a comparison between the numerical predictions and the experimentally measured data was carried out. The main results are presented

2025, Advances in Structural Engineering

This study presents, for the first time, the mechanical behavior of API 5L pipeline steels X42, X52, X60, X70, X80, and X100 with external and internal corrosion defects as well as a combination of both defects that has been named external–internal corrosion defects. The conventional methods to predict failure pressure in corroded pipes, such as B31G, RSTRENG-1, SHELL, DNV-99, PCORRC, and FITNET FFS, have also been discussed in this article. In addition, pipeline failure pressure has been estimated using the finite element method, considering that it is the best approach to calculate actual failure pressure. The external and internal corrosion defect investigated in this research manifests as a rectangular shape with spherical ends at the edges. When the external–internal corrosion defect appears, failure pressure data decrease dramatically because of severe damage. This is due to the decrease in the ligament (effective area) caused by the corrosion defect. To have a good estimation...

2025, Soldagem & Inspeção

The stress concentration factors (SCFs) in welded connections usually occur at zones with high stress levels. Stress concentrations reduce the fatigue behavior of welded connections in offshore structures and cracking can develop. By using the grinding technique, cracking can be eliminated. Stress concentration factors are defined as a ratio of maximum stress at the intersection to nominal stress on the brace. Defining the stress concentration factor is an important stage in the fatigue behavior of welded connections. Several approaches have evolved for designing structures with the classical S-N approach for estimating total life. This work correlates to the stress concentration factors of T-welded connections and the fatigue behavior. Stress concentration factors were computed with the finite element employing 3D T-welded connections with intact and grinding depth conditions. Then, T-welded connections were constructed with A36 plate steel and welded with E6013 electrodes to obtain the stress-life (S-N) approach. The methodology from previous works was used to compute the SCF and fabricate the T-welded connections. The results indicated that the grinding process could restore the fatigue life of the T-welded connections for SCFs values in the range of 1.29. This value can be considered to be a low SCF value in T-welded connection. However, for higher SCF values, the fatigue life decreased, compromising and reducing the structural integrity of the T-welded connections.

2025, Computers and Geotechnics

Coupled finite element analyses of the consolidation and deformation around stone columns have been performed to assess the accuracy of different analytical solutions. The numerical model reproduces the hypotheses of the closed-form solutions. In the model, a rigid load is applied to a unit cell formed by a fully penetrating column and its surrounding soil, and simple elastic or elasto-plastic soil models are used. The surface settlement, the dissipation of the pore pressure and the vertical stress concentration on the column are studied. These soil responses are accurately estimated with closed-form solutions that properly include the radial and plastic strains in the column. However, the surrounding soil does not yield for usual conditions, which reasonably justifies the elastic soil behavior assumed in the analytical solutions. The differences between drained and consolidation analyses are also evaluated. Comparing the numerical results with the closed-form solutions illustrates the implications of the assumptions of each approach.

2025, Materials Science and Engineering: A

Superplastic deformation induced cavitation of aluminium alloys usually results in the material performance degradation. In this study the cavitation behaviour of Al 7475 was characterised, using samples deformed at temperature ranging from 480 to 530°C and at an initial strain rate of 10 -3 s -1 . The results showed that the cavity growth rate parameter increased slightly as the test temperature increased. The cavitation ratio at fracture increased evidently with increasing temperature from 480 to 500°C, and reached a plateau for any further increase of temperature. Various morphological filaments were observed at cavities and fracture surface, as evidence of the presence of liquid phase along grain boundaries. The effects of test temperature and thermal history on cavitation were found to be closely related to the presence of the liquid phase. The presence of liquid phase will improve the ability of the materials to tolerate high volume fraction of cavities before fracture. On the other hand, when liquid phase is anisotropically distributed along grain boundaries, it will cause the preferential interlinkage of cavities along the weak grain boundaries, and result in corporate grain boundary sliding (CGBS). It is concluded that the critical factor is to achieve appropriate quantity, high property, and uniformly distributed liquid phase along grain boundary. This highlights a new clue in searching for an economical and practical way to alleviate cavitation.

2025, Frontiers in Physiology

Tendons represent a bradytrophic tissue which is poorly vascularized and, compared to bone or skin, heal poorly. Usually, a vascularized connective scar tissue with inferior functional properties forms at the injury site. Whether the increased vascularization is the root cause of tissue impairments such as loss of collagen fiber orientation, ectopic formation of bone, fat or cartilage, or is a consequence of these pathological changes remains unclear. This review provides an overview of the role of tendon vasculature in healthy and chronically diseased tendon tissue as well as its relevance for tendon repair. Further, the nature and the role of perivascular tendon stem/progenitor cells residing in the vascular niche will be discussed and compared to multipotent stromal cells in other tissues.

2025, International Journal of Engineering Research and

The usage of heterogeneous materials in situations where large strength to weight ratio is required has been increased substantially over the world in all construction aspects. The behaviour of the plate under each loading is different. Whenever the delamination is located at the middle plane of laminate, the panel exhibits only global buckling, i.e. there is no buckling of delaminated region. Whenever the delamination is close to the surface, the buckling mode is predominantly local. The type of plate also plays a major role in carrying load. This article summarises the numerical study carried out using finite element software ANSYS and Timoshenko's methodology to examine the buckling behaviour of homogeneous and heterogeneous plate element with and without crack. Also the effect of aspect ratio on the buckling behaviour with varying plate thickness for different boundary conditions was also examined.

2025, International Journal of Rock Mechanics and Mining Sciences

The 1991 Randa rockslide in the Swiss Alps involved several complex mechanisms relating to geological, mechanical and hydrological processes for which no clear trigger can be asserted. This paper investigates the concept of progressive failure and the numerical modelling of rock mass strength degradation in natural rock slopes using the Randa rockslide as a working example. Results from continuum (i.e. finite-element) modelling are presented to illustrate a hypothesis, suggesting that initiation of a progressive rock mass degradation process, ultimately leading to failure, began following deglaciation of the valley below. Discontinuum (distinct-element) modelling is then applied to investigate the underlying mechanisms contributing to the episodic nature of the rockslide. Finally, the use of a hybrid method that combines both continuum and discontinuum techniques to model fracture propagation are discussed in the context of modelling progressive slide surface development linking initiation and degradation to eventual catastrophic failure.

2025, Construction and Building Materials

Reclaimed asphalt pavement (RAP), when used as a coarse aggregate, has been shown to reduce bulk concrete strength and modulus. Part I of this study quantifies and compares the interfacial transition zone (ITZ) for mortar with RAP aggregates relative to dolomite aggregates through image analysis of backscattered electron micrographs. The ITZ with RAP aggregates was larger and more porous with less calcium silicate hydrate (C-S-H) and calcium hydroxide (CH) at the asphalt interface compared with dolomite aggregates. The CH morphology was not significantly affected, although the presence of the asphalt layer may be affecting the CH growth. The addition of silica fume reduced the porosity and size of CH particles in the ITZ with RAP, but not sufficiently to be similar to the ITZ of the dolomite mortar. The microstructural changes

2025, Journal of Geophysical Research

Employing analogue and numerical experiments, we investigated the process of plastic creep in the vicinity of stiff inclusions and its role in the formation of shear zones. Analogue experiments were performed on Polymethylmethacrylate (PMMA) models in pure shear (_ e % 10 À4 s À1 ), which produced shear zones at a bulk strain >0.05. The geometrical dispositions of the shear zones do not conform to the stress concentration map derived from the plane theory of elasticity. At the initial stage (e b < 0.03), PMMA models began to deform plastically in four discrete strain localizations, tracking the stress concentration map. These incipient plastic locations develop a new stress field, diverting the zone of plastic yield in the form of multiple shear zones. Finite element models were run to demonstrate the formation of shear zones in this mode. The pattern of shear zones varied with the inclusion geometry. Inclusions of low aspect ratio (<1.5) gave rise to multiple sets of shear zones in their neighborhood. The multiplicity of shear zones tends to progressively decrease toward a single set of conjugate zones when the inclusions have relatively high aspect ratio (>2) and are oriented at an angle (>20°) to the bulk compression direction. Inclusions with a large aspect ratio (>4) developed a single dominant shear zone. The experimental findings can be compared to inclusion-controlled shear zones from naturally deformed rocks.

2025, International Journal of Industrial Ergonomics

The objective of the study was to determine if different trunk muscles fatigued at a different rate in isometric axial rotation. Rotation is associated with a large number of back injuries. The fatigue behaviour may shed some light on possible reasons for such an association. Subjects were stabilized in an upright seated neutral posture in a specially designed and fabricated deviceFaxial rotation tester such that the rotation could occur only in thoraco-lumbar region. Subjects performed isometric trunk rotation at 60% of their previously measured maximal voluntary contraction for a maximum duration of 2 min or less if they could hold no longer. Surface electromyographic (EMG) was measured from seven trunk muscles bilaterally. Power spectra were calculated, the mean median frequency obtained at 10% intervals of the task cycle and compared in time within and between subjects. The EMG amplitudes were significantly different between right and left sides ð po0:01Þ. The initial median frequencies of each muscle were significantly different from the other ð po0:01Þ. The rate of decline of the median frequency for different trunk muscles were different ð po0:01Þ. In isometric trunk rotation different trunk muscles demonstrated a different rate and magnitude of EMG fatigue. The latter is likely to alter the pattern of load sharing between muscles and predisposing musculoligamentous to injury either through stress concentration in deformed tissues or exceeding the strain rate tolerance in fatigue induced jerky motion (micromotion). Low back injury continues to be one of the most common injuries. Rotation of the trunk is associated in over 60% of back injuries. The fatiguing behaviour of the trunk muscles provides an insight into possible control strategies such as reversing the direction of rotation periodically to allow recovery of fatigued muscles while still carrying out the task.

2025, Construction and Building Materials

MA rebar has better high and low cycle fatigue behavior than that of TMT rebar. Fatigue crack initiates form the transverse rib root and propagate along the same region. Stress concentration and high stress triaxiality observed at the... more

2025

he purpose of this study was to assess the clinical performance of bonded composite (Excite/Tetric Ceram-Vivadent) versus a resin-modified glass ionomer cement (Vitremer – 3M) for restoring non-carious cervical lesions. A total of 70 restorations (thirty-five per material) were placed in 30 patients, 18-50 aged, by one operator. Rubber dam was employed in all cases, lesions were pumiced, enamel margins were not beveled, and no mechanical retention was placed. The restorations were directly assessed by two independent evaluators using modified-USPHS criteria for six clinical categories. The ratings for clinical acceptability restorations (alfa plus bravo) were as follows (Tetric Ceram/Vitremer): retention (86%/100%), marginal integrity (100%/100%), marginal discoloration (100%/ 100%), wear (97%/100%), postoperative sensitivity (100%/100%) and recurrent caries (100%/100%). Statistical analysis was completed with Fisher’s exact or Pearson Chi-square tests at a significance level of 5 %...

2025, Journal of Materials Science

Development of smart materials with inherent damage sensing capabilities is of great interest to aerospace and other structural applications. Most of the existing smart materials are based on using embedded sensors for structural health monitoring. However, embedded sensors can lead to undesirable effects such as stress concentration and can cause premature failure. Therefore, using microstructural components for additional function of sensing of the structural health is the only option. Such possibilities exist only in selected few materials. The present study investigates the feasibility of developing fiber-and particlereinforced composites into smart materials. The sensing approach considered is based on the morphology-dependent shifts of optical modes, referred to as the whispering gallery modes (WGMs), of spherical dielectric micro-particles. The WGMs are excited by coupling light from a tunable diode laser using single mode fibers. The WGMs of the micro-particles can be observed as sharp dips in the transmission spectrum through the fiber and are highly sensitive to the morphology of the particle. A minute change in the size, shape, or refractive index causes a shift of the optical modes, which can be interpreted quantitatively in terms of the parameter that caused the change. A theoretical framework is developed for such sensor systems that provides quantitative relations between the stress applied on the micro-particles and corresponding shift in WGMs. These relations are validated against the available experimental results.

2025, Mécanique & Industries

Les tubes en plastiques utilisés pour le transport d'eau et de gaz continuent à être le sujet de beaucoup d'études qui traitent divers aspects de comportement de matériaux. Des statistiques récentes indiquent que plus de 90 % de systèmes de distribution de gaz nouvellement installés dans le monde entier sont exclusivement construits en polyéthylène (PE) en raison de sa facilité d'installation et de coûts relativement bas. Les essais à charge constante montrent deux mécanismes généraux de propagation de fissure : une rupture ductile qui est dominée par des déformations homogènes à grande échelle dans le volume et une rupture fragile qui commence aux points de concentration des contraintes. Ce travail vise à étudier la transition fragile-ductile de fatigue dans les tubes de polyéthylène et la caractérisation de la zone d'endommagement associée. La méthode proposée est basée sur la mesure de deux paramètres de fatigue : la vitesse de propagation de la fissure, obtenue à différents niveaux de charge et le taux de travail irréversible qui est calculé à partir des boucles instantanées d'hystéréisis. Les corrélations obtenues, pour des charges maximales de fatigue entre 20 % et 35 % de la contrainte au seuil d'écoulement, donnent des taux de restitution d'énergies critiques moyens de 211 J.m -2 et de 695 J.m -2 respectivement pour des régimes fragile et ductile.

2025

In this paper, a modified circular microstrip patch antenna fed by a microstrip line feed is presented. The main aimwas to improve the narrow bandwidth of microstrip patch antennas while at the same time ensuring that otherimportant parameters of the antenna such as gain, efficiency, and impedance matching are not affected. The shapeof the patch was modified by adding some parts to it and removing some parts from it with the aim of achieving awider bandwidth. High frequency structural simulator (HFSS) was used to simulate and analyze the designed patch.Simulated results of return loss, VSWR, and Z parameters were then presented. Based on simulated results, theshape presented showed satisfactory operation in the frequency range 1647-1968 MHz which is within the L-band.The modified circular microstrip patch antenna showed remarkable improvement in bandwidth as compared toconventional microstrip patch antenna for return loss of less than -10 dB. The antenna also showed good impedancema...

2025

The implementation of Adaptive Mesh Refinement (AMR) within the geotechnical software package PLAXIS 2D is described in this paper. A recovery-based algorithm is used which aims to reduce the discretisation error by refining the mesh during the solution process. The error is estimated with a Zienkiewicz-Zhu-type error estimator but based on the incremental deviatoric strain instead of stress. The deviatoric strain field is compared with an improved field calculated by superconvergent patch recovery. Once elements with large errors have been detected, mesh refinement takes place. A combination of regular subdivision and longest-edge bisection is employed. Mapping history variables from the old mesh to the new mesh is accomplished by using the recovered solutions and the shape functions. The AMR algorithm is demonstrated for a biaxial compression test.

2025

In order to better understand the effect of stressed-oxidation, the performance of woven Sylramic-iBN fiber-reinforced slurry cast melt-infiltrated (MI) composites were tested in creep and fatigue under non-oxidizing conditions. Initially creep and fatigue tests were performed at 1204 °C in an argon atmosphere; however, it was observed that sufficient oxidizing species existed in the environment to degrade the composites in a manner similar to air environments. Therefore, creep and fatigue tests were performed at 1204 °C in a vacuum environment which showed no evidence of oxidation and superior properties to composites subjected to stressed-oxidation conditions. The mechanical results and microscopy of the vacuum and argon are compared to the behavior of these composites tested in air. It was found that the stress rupture properties of the vacuum-tested composites could be predicted from single fiber creep rupture data assuming reasonable values for the Weibull modulus. 15. SUBJECT TERMS stressed-oxidation, Sylramic-iBN, melt-infiltrated (MI) composites 16. SECURITY CLASSIFICATION OF: 17. LIMITATION

2025, Composites Part A-applied Science and Manufacturing

A new model based on finite fracture mechanics is proposed to predict the openhole tensile strength of composite laminates. Failure is predicted when both stressbased and energy-based criteria are satisfied. The material properties required by the model are the laminate unnotched strength and fracture toughness. No empirical adjusting parameters are required. Using experimental data obtained in quasiisotropic carbon-epoxy laminates it is concluded that the model predictions are very accurate, resulting in improvements over the traditional strength prediction methods. It also is shown that the proposed finite fracture mechanics model can be used

2025

Polyvinyl chloride commonly abbreviated PVC is thermoplastic that is a polymer of vinyl chloride. Resins of polyvinyl chloride are hard, but with the addition of plasticizers a flexible plastic can be made. The good performance and low cost of rigid polyvinyl chloride commonly abbreviated PVC-U products make this polymer very suitable for many applications. Pipelines in water and sewer systems are the most common applications of PVC-U. Using PVC-U pipes in this study is a new and different from the common applications. The pipes will be used here to sustain axial loads for sub-surface stormwater storage and infiltration purposes. This study was conducted to investigate theoretically and experimentally the behavior and the capability of PVC-U pipes with and without existing of radial holes (orifices) in its wall to sustain the axial loads. Behavior of PVC-U pipes was investigated theoretically by modeling the pipe system using ANSYS Release 9.0 finite element code. The pipe was model...

2025, Construction Science

This publication presents the model and the modeling results of dolomite ceramics deformation under uniaxial load with respect to the composite structure of dolomite ceramics. The main modelling objective was to investigate the dependence of mechanical properties of dolomite ceramics on the mechanical properties and volume proportions of its components -clay and dolomite, assuming the composite structure of dolomite ceramics. The dependencies of theoretical integral elasticity module and local stress concentration coefficients on elastic moduli and volume proportions of were investigated by means of mathematical experiment, and presented as curves, thus making conclusions about the impact of mechanical properties and volume proportions of components on the expected elastic module and tension/compression strength of dolomite ceramics.

2025, Advanced Technologies & Materials

Welded joint is a critical region of a welded structure and fracture mechanics analysis is inevitable in the structural integrity assessment of all welded structures. This paper shows the determining of parameters of the fatigue crack for constituents of welded joints produced of high strength low alloyed steel. The applied methodology refers to the Paris relation where the link was established between the variable load quantity or the corresponding stress intensity factor range and crack growth per cycle. Results have shown that the position of the notch and crack initiation affect the values of the stress intensity range of fatigue threshold ΔKth and parameters in the Paris’ equation. This is mostly expressed when determining growth parameters of the fatigue crack in heat affected zone of HSLA steel, where different changes of growth speed of the fatigue crack clearly express differences in structure of the crack pass.

2025, Journal of Pipeline Science and Engineering

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2025, Acta Scientiarum-technology

This work proposes a methodology for defective pipe elastoplastic analysis using the Euler Bernoulli beam-pipe element formulation. The virtual work equation is modified to incorporate the stress concentration factor in beam-pipe element formulation. The stress concentration factor is evaluated a priori by a 2D or 3D finite element model according to the defect profile. In this work, a semicircular defect and a rectangular defect are considered. The stress concentration factor is inserted into the beampipe element elastoplastic formulation, and several applications are presented to show the applicability of the proposed method.

2025, Engineering Transactions

WC/Co ceramic metal-matrix composites are characterized by very high mechanical properties that allow for application of the composites mostly in production of different types of cutting tools. By combining in a composite structure a phase of brittle hard wolfram carbide (WC) grains with a metallic interface of cobalt (Co) that exhibits plastic properties, a geometrically complex microstructure with significantly different mechanical properties of the combined phases is created, see Fig. 1a. The presence of the elastic-plastic interface material, i.e. Co binder, in the composite structure is the reason for initiation of technological defects – mainly material porosity. During material loading pores start to coalesce and finally one can observe creation of microcracks system distributed along interfaces. The aim of the paper is to show the previously formulated model [1, 2] of the polycrystalline composite to be extended towards cracks development around the junctions of the interfac...

2025, Engineering Transactions

WC/Co ceramic metal-matrix composites are characterized by very high mechanical properties that allow for application of the composites mostly in production of different types of cutting tools. By combining in a composite structure a phase of brittle hard wolfram carbide (WC) grains with a metallic interface of cobalt (Co) that exhibits plastic properties, a geometrically complex microstructure with significantly different mechanical properties of the combined phases is created, see Fig. 1a. The presence of the elastic-plastic interface material, i.e. Co binder, in the composite structure is the reason for initiation of technological defects – mainly material porosity. During material loading pores start to coalesce and finally one can observe creation of microcracks system distributed along interfaces. The aim of the paper is to show the previously formulated model [1], [2] of the polycrystalline composite to be extended towards cracks development around the junctions of the interf...

2025

Statistical analysis reveals that mechanical damage is the first cause of incidents on gas transmission pipelines. They can be created by third party activities such as excavator tooth impact or by interaction between the pipe and rocks. To manage the damaged pipeline safely without useless cost, there is a need to investigate the mechanical behaviour of dented pipelines under a varying internal pressure. The purpose of this study is to characterize the stress and strain field around defects in pipes submitted to cyclic pressure loadings in order to estimate their residual lifetime. Full 3D finite element analyses of the denting process followed by cyclic loading are performed. Full-scale experiments on dented sections are planned.

2025

Utilizing 3D design procedures in manufacturing industry is well matured in industrial R&D. The shape of the components, design of the machine or the vehicle, assembly and finally the whole production are designed virtually through computational methods, which naturally offer flexibility and speed to the design phase. Simulation and virtual verification of the designed components is rapidly increasing and can further shorten R&D phase dramatically. However, virtual material values or models available for digital design and simulation are still limited. Due to the lack of digital material values the huge potential of tailored performance can not be fully exploited. We at VTT have recognized that for the economic and ecologic use of materials, digital design tools for material design are a necessity of the digital design chain. Development of new materials and understanding of material and process behaviour is always a complex equation of crossing interactions. Physical and chemical phenomena are affected from the nano-and/or molecular level up to macroscopic level. Interactions between the material performance, properties, microstructure and processing methods need to be understood more deeply. For this purpose, modelling skills have developed rapidly in recent decades, with the support of increased numerical calculation capacity and commercial multi-level and multi-physics software development. At VTT we have a great capacity and potential for exploiting this competence. It is recognised that there are many activities related to materials and process modelling in various scales, based on various methodologies and targeting various applications. At VTT we have a strong vision to bring this knowledge better together creating opportunities for multiscale approaches as well as to offer a platform for cross learning experiences. At the same time, it is clear that good modelling goes hand in hand with experimental verification. Modelling creates more detailed understanding of phenomena, while experimental verification directs the model to correctly reflect and predict the real world phenomena. Also in this sense VTT can offer a 360 service as VTT's competences are well recognised in many fields combining modelling and in experimental research. Research programmes play essential roles in VTT's day-to-day operation. They are the main vehicle for implementing VTT's strategy. The programmes produce comprehensive technology-based solutions aiming at industry renewal and thus have a great impact on the society and industries. They also provide a platform for longer-term interaction and collaboration with VTT's clients, financiers and other stakeholders. Last, but not least, the programmes encourage transdisciplinary research and new openings within VTT. In this publication we are presenting some highlights from our current modelling activities obtained in VTT's MultiDesign innovation programme. We hope they will inspire new ideas in your mind on what could be done and obtained via digital approach to design. We are happy to discuss your thoughts further as to how we could help you take MultiDesign approaches to the next level for the benefit of industry, research community, and society at large.

2025, Japan Geoscience Union

Venus has been regarded as a twin planet to the Earth, because of density, mass, size and distance from the Sun. However, the Magellan mission revealed that plate tectonics is unlikely to work on the Venus. The plate tectonics is one of the most important mechanism of heat transport and material circulation of the Earth, consequently, its absence might cause the different tectonic evolution between Earth and Venus. Rheological structure is a key to inferring mantle structure and convection style of planet interiors because the rock rheology controls strength and deformation mechanism. In previous study, the behavior of Venusian lithosphere has been inferred from the power-law type flow law of dry diabase. They indicated that lower crust can be weaker than upper mantle, which might result decoupling at the crust-mantle boundary (Moho depth) and mantle convection without crustal entrainment. However, the power-law creep cannot be applicable to infer the rheological structure at Moho depths, because the dislocation-glide control creep (Peierls mechanism) is known to become dominant at relatively low temperatures in materials with a relatively strong chemical bonding such as silicates. In this study, we conduct two-phase deformation experiments to directly investigate rheological contrast between plagioclase (crust) and olivine (mantle) and discuss the difference between these planets in terms of rheological behaviors. Moreover, one-dimensional and two-dimensional numerical calculation is performed to evaluate the influence of the strength contrast on the Venusian tectonics. Our experiments using solid-medium deformation apparatus directly determine the relative strength between plagioclase (crust) and olivine (mantle) without any extrapolating of flow law. The experimental conditions were ranging 2GPa and 600-1000 degrees under dry conditions. The experimental results show that olivine is expected to always be stronger than plagioclase. This result contradicts to that inferred from powerlaw creep of olivine and plagioclase, suggesting that Peierls mechanism could be dominant deformation mechanism in both olivine and plagioclase at relatively low temperatures. In the case of the Earth, rheological structure of oceanic lithosphere is constrained well by Byerlee's law and power-law type flow law. The oceanic crust and mantle lithosphere are strongly coupled mechanically because the Moho has no strength contrast, so that they could move and subduct together into the deep. In contrast, our experimental results imply that large strength contrast exists at Moho in Venus, resulting decouple of the motion between the crust and mantle lithospheres because the weak lower crust acts as a lubricant. Also one-dimensional numerical calculations show us that the surface velocity becomes more sluggish in the model with larger strength contrast (from two-digit to four-digit difference in viscosity) at Moho. Therefore the crustal part is less likely to be involved to mantle convection when strength contrast gets larger and larger. In fact, two-dimensional simulations suggest that the crustal portion cannot subduct with the mantle lithosphere if the strength contrast exists at Moho

2025, Nat Resour Modeling

This thesis reports studies on the large deformation and lubrication properties of emulsionfilled gels and the way these properties are related to the sensory perception of the gels. The design of the studies included polymer and particle gels containing oil droplets of which the interaction with the gel matrix was varied, resulting in droplets either bound or unbound to the matrix. The unique combination of gel matrices and droplet-matrix interactions allowed to obtain a representative overview of the effect of the oil droplets on the properties studied. The molecular properties of the gel matrices determined the way the large deformation properties of the gels depended on the deformation speed. Polymer gels showed a predominantly elastic behaviour. Particle gels showed a more viscoelastic behavior. The effect of the oil content on the Young's modulus of the gels was modulated by the droplet-matrix interactions, in agreement with existing theories. Bound droplets increased the Young's modulus of the filled gels, whereas unbound droplets decreased it. Oil droplets embedded in the gel matrix acted as stress concentration nuclei. They also increased energy dissipation due to friction between structural elements of the gel (oil droplets and gel matrix). Stress concentration resulted in a decrease of the fracture strain for all gels and in a decrease of the fracture stress for polymer gels. For gels with nonaggregated bound droplets, a reduction in oil droplet size had the same effect on their rheological properties as an increase in oil volume fraction. The lubrication properties of the gels strongly depended on both the molecular and functional properties of the gel matrix and the oil content. For each type of gel matrix, the lubrication behaviour was affected by the 'apparent viscosity' of the broken gels, which in turn depended on the droplet-matrix interactions. The sensory perception of emulsion-filled gels appeared to be dominated by the properties of the gel matrix and by the oil content. Polymer gels were perceived as more melting, whereas particle gels were perceived as more rough. With increasing oil content both types of gels became more creamy and spreadable. The increase in spreadability and part of the increase in creaminess could be explained with the effect of the oil droplets on the breakdown properties of the gels. Since for all gels the scores for creaminess increased with increasing oil content, the release of oil droplets during oral processing could not completely explain the perception of oil-related sensory attributes. It is therefore concluded that the perception of these attributes is mediated by the lubrication properties of the broken gel. The large deformation and lubrication behaviour of the gels were the most important parameters related to sensory perception. Both parameters were affected by the droplet-matrix interaction. As a matter of fact, the droplet-matrix interaction affected the fracture behaviour of the filled gels, which was related to their spreadability, and the 'apparent viscosity' of the broken gels, which controlled the lubrication properties of these systems. gels. Particulate (or particle) gels consist of clusters of aggregated particles forming a continuous structure throughout the enclosing volume. Milk protein gels fall into this class. Only the last two classes of gels are of relevance for food products. A typical characteristic of foods is their complexity, due to the presence of many different components and ingredients. Several food products can be described as gels filled with emulsion droplets (or emulsion-filled gels). Milk is an emulsion of fat globules in a colloidal suspension of casein micelles. Many different food products of the food industry are based on the gelation of milk, resulting in a continuous matrix of interconnected swollen casein particles entrapping dispersed fat globules. Each application makes use of a specific physicochemical gelation mechanism. In cheese-making, gelation is achieved by the enzymatic activity of rennet, which causes the removal of the hydrophilic moiety of -casein. This results in the aggregation of casein by hydrophobic and Van der Waals interactions . Not only fresh curd, but also cheese, the end product derived from further processing of curd, can be described as a (strong) gel containing dispersed fat globules. In the production of yoghurt and other acidified dairy products, inorganic calcium phosphate gradually dissolves as the pH of milk decreases from the natural value of 6.7 . Furthermore, as the pH decreases the surface charges of the casein micelles are protonated. This causes the collapse of the hydrophilic moiety of -casein, which results in Chapter 1 control of these mechanisms requires thorough knowledge of both the effect of emulsion droplets on the physicochemical and mechanical properties of emulsion-filled gels, and of the role played by these properties in the sensory perception of these systems. These aspects are at the moment not satisfactorily covered by the scientific literature. Rheology deals with the relationships between forces and deformations of materials. In the case of foods the goals are to 'understand the effect of processing on products, to probe the system's structure and to reveal critical aspects of food texture' . For rheological measurements of viscoelastic solid foods, three different regimes can be distinguished based on the nature of the relationship between stress ( ) and strain ( ) (Figure .1). In the first regime (I), called the linear regime, a linear relation between stress and strain can be observed; in other words Hooke's law is obeyed. In the second regime (II) the relationship between stress and strain is nonlinear. Beyond the nonlinear regime fracture of the material occurs (fracture regime, III). Measurements performed in the linear regime are called small-deformation measurements. In the linear regime, the deformation applied does not affect the structure of the material, and the ratio between stress and the accompanying strain is independent of the strain . Measurements performed in the nonlinear and fracture regimes are called largedeformation measurements, or, when they are mainly focussed on the determination of the fracture properties of the material, fracture measurements. The rheological properties of gels have mainly been studied at small deformation. This holds also for the effect of emulsion droplets on the rheological properties of emulsion-filled gels (

2025, ITM Web of Conferences

The paper presents the results of numerical investigation for stress distribution near runner blade-crown/band junctions. Starting with the geometrical investigation of the geometries for a real turbine, different junction geometries were identified. Eight different junction geometries were numerically investigated in order to determine the stress distribution. The applied load for structural analysis was the pressure distribution, obtained from a Computational Fluid Dynamics analysis of the runner blade. The results of the stress distribution will allow to quantify the effect of different junction geometry on stress concentration and integrity of the runner.

2025, AIP Conference Proceedings

2025

Investigation of axial opening is performed during regular generator overhaul. We have implemented metal magnetic memory method (MMM), which does not require cleaning or preparation of investigated surface. Work technique consists of ferro probe mechanism connected by cables to IKN defectoscope. On the basis of performed measurements of magnet field Hp, automatically defines the value of filed gradient Kin. Detailed data processing is done through specially prepared software. The paper presents investigation results in thermal power plant "Nikola Tesla" -Obrenovac.

2025

The thickness of the adhesive has a major influence on the shear strength of bonded assemblies. This work is based on a study of the fatigue behavior of two cracked aluminum (2024 T351) plates repaired by patch (graphite/epoxy) under cyclic loading. For this we used a computer code to study the propagation of fatigue cracks to predict the life of the plates repaired named AFGROW. The first plate was repaired using an adhesive made from date palm waste whereas the second plate was repaired using FM-73 adhesive. The results obtained from this study show that, despite the low shear modulus of the adhesive made from date palm waste and the very low film thickness, the joint bonded with the latter gives good joint strength and a lifetime (number of cycles) similar to the joint bonded with the FM-73 adhesive when the thickness of the joint of the adhesive is greater than that of the adhesive made by the waste of the date palm. This shows that the strength of the bonded joint increases rapidly from very low thicknesses (less than a few hundredths of a millimeter). Finally, we recommend using the adhesive made from date palm waste for patch repair as well as for applications such as lightweight construction, electric vehicles or solar panels.

2025, Structural Optimization

In a shell structure, the discontinuity at the intersection of two shells causes stress concentration. This paper presents a procedure which couples the Curvature Function Method with the FAST1 structural shell analysis program to find a fully stressed thickness profile which keeps the stress at the discontinuities at the nominal stress value. The Curvature Function Method is a zero-order method that requires only stress values along the shell, not gradients of the stresses with respect to the design variables, and the resulting thickness profile has C 2 continuity. Although the method is independent of the structural analysis program used to determine stress values, Fast1 provides a particular advantage because it allows the user to model complex shells with only a few large shell elements and still retain a sufficiently accurate solution. Thus both preparation and computation times are reduced substantially. Convergence of different initial designs to one final design using this procedure is demonstrated for a cylinder-cone intersection problem. This procedure is also applied to two other shell models with multiple discontinuities to find their fully stressed thickness profiles. The procedure presented in this paper provides a practical technique and tool to aid the design engineer, although the fully stressed design may not be the theoretically optimal design of minimum weight.

2025, Journal of dentistry

To explore the effect of adhesive failure and defects between the crown and cement on the stress distribution within all-ceramic crowns and the corresponding risk of failure. An IPS e.max crown of lithium disilicate produced by CAD/CAM for a first mandibular molar was modeled using finite element analysis based on X-ray micro-CT scanned images. Predefined debonding states and interfacial defects between the crown and cement were simulated using the model. The first principal stress distribution of the crown and cement was analyzed under a vertical occlusal load of 600 N. A concept of failure risk was proposed to evaluate the crown. Stress concentrations in the crown were identified on the occlusal surface surrounding the region of loading, beneath the area of loading and at the margin of the interior surface. Stress concentrations in the cement were also evident at the boundary of the debonded areas. The lower surface of the crown is safe to sustain the 600 N vertical load, but the ...

2025, International journal of clinical and experimental pathology

This study addresses the morphopathogenesis of Achilles tendinosis, using a rat model and presenting quantitative analysis of time-dependent histological changes. Thirty Wistar rats were used, randomly split in experimental and control groups. Animals of the experimental group were submitted to a treadmill running scheme. Five animals of each group were euthanized at four, eight and sixteen weeks. Achilles tendons were collected and processed routinely for histopath sections. Slides were stained by Hematoxylin-Eosin, Picrosirius Red, Alcian Blue, AgNOR, TUNEL and evaluated morphometrically. Cellular density decreased slightly along the time and was higher in the experimental group than in controls at fourth, eighth and sixteenth weeks. Fiber microtearing, percentual of reticular fibers and glycosaminoglycans content increased along the time and were higher in experimental group than in controls at all-time intervals. AgNOR labeling here interpreted as a marker of transcription activ...

2025, Computational Materials Science

On the basis of the relaxation element method, the stress ®eld from the con®guration of three pores in the plane under uniaxial tensile loading was calculated. The model of development of sites of localised plastic deformation in a polycrystal with absolutely hard inclusion was represented. A comparison of results, obtained by the relaxation element method and that, made by ®nite element method has been performed.

2025

A mathematical model is presented which defines the adhesive shear strain distribution for an adherend with bonded multilayer reinforcements which are stepped at their ends. In this one-dimensional formulation each step is allowed to be of different thickness and modulus, and of variable step length. A procedure is then given to improve the design of such reinforcements through minimising the peak adhesive shear strain which typically occurs near their stepped ends. It is shown that to achieve a 20% reduction in peak adhesive shear strain for a typical stepped patch consisting of unidirectional laminae, the first step adjacent to the patch end needs to be much longer than the remaining steps. For the case where cross-ply laminae are used in conjunction with unidirectional laminae, the maximum shear strain in the adhesive layer can be reduced by about 60%. The results also indicate that reduced peak adhesive shear strains lead to a smoother transition of load from the plate to the patch. This suggests that a patch design which minimises peak adhesive shear strains will also reduce the undesirable stress concentration in the repaired structure, outside the patched region.