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

2025, … Society Press, http://www. worldses. org …

This paper presents the several possibilities of using the Coons' interpolation in both CAD and CAE applications. It is shown that not only curvilinear surfaces may be interpolated (as it is well known from the literature), but also finite element meshes may be developed in any arbitrarily-shaped domain. Moreover, it is shown how it is possible to built-up isoparametric macro-finite-elements with degrees of freedom appearing at the boundaries only, using global shape functions that are based on the same interpolation. The theory is sustained by one typical two-dimensional application of a U-notched elastic structural member.

2025, Japan Geoscience Union

2025, Welding in the World

Doc. IIW-2201, recommended for publication by Commission XIII "Fatigue of Welded Components and Structure.

2025, Engineering Fracture Mechanics

It is generally accepted that the fatigue crack growth (FCG) depends mainly on the stress intensity factor range (DK) and the maximum stress intensity factor (K max ). The two parameters are usually combined into one expression called often as the driving force and many various driving forces have been proposed up to date. The driving force can be successful as long as the stress intensity factors are appropriately correlated with the actual elasto-plastic crack tip stress-strain field. However, the correlation between the stress intensity factors and the crack tip stress-strain field is often influenced by residual stresses induced in due course. A two-parameter (DK tot , K max,tot ) driving force based on the elasto-plastic crack tip stress-strain history has been proposed. The applied stress intensity factors (DK appl , K max,appl ) were modified to the total stress intensity factors (DK tot , K max,tot ) in order to account for the effect of the local crack tip stresses and strains on fatigue crack growth. The FCG was predicted by simulating the stress-strain response in the material volume adjacent to the crack tip and estimating the accumulated fatigue damage. The fatigue crack growth was regarded as a process of successive crack re-initiations in the crack tip region. The model was developed to predict the effect of the mean and residual stresses induced by the cyclic loading. The effect of variable amplitude loadings on FCG can be also quantified on the basis of the proposed model. A two-parameter driving force in the form of: tot was derived based on the local stresses and strains at the crack tip and the Smith-Watson-Topper (SWT) fatigue damage parameter: D = r max De/2. The effect of the internal (residual) stress induced by the reversed cyclic plasticity manifested itself in the change of the resultant (total) stress intensity factors controlling the fatigue crack growth. The model was verified using experimental fatigue crack growth data for aluminum alloy 7075-T6 obtained under constant amplitude loading and a single overload.

2025, Civil Engineering Journal

Built-up steel girders have many applications in structural engineering, both in bridges and buildings. Flat web steel girders, which are the traditional choice, involve several weaknesses. Girders with corrugated webs were found to be more effective in their load-carrying capacity and deflection than girders with flat webs. In light of this, an effort is made in this work to examine how the addition of triangular corrugated webs influences the load-bearing capacity and deflection of steel girders. This study aimed to determine whether or not the strength of built-up steel with corrugated webs could be improved. A concentrated midspan load was applied to six simply supported steel beams of varying span-to-depth ratios (1.0, 1.833, and 2.5) and web corrugation amplitudes (30 and 60 mm). An increase in ultimate strength of 15.7% to 35.1% was found for webs with triangular corrugations of 30 mm and from 2% to 29.1% for webs with corrugations of 60 mm. A reduction in deflection of up to 35.3% can be attained when using triangular corrugated webs. It was also found that using webs with 30 mm corrugations was more efficient than using webs with 60 mm corrugations. The effect of corrugation was found to fade when the span-to-depth ratio increased to 2.5. This led to the conclusion that using webs of 30 mm amplitude of triangular corrugation could improve the strength and serviceability of steel girders.

2025, Advanced Materials Research

Metal Active Gas (MAG) welding process of steel sheets generates, in the vicinity of the welding joint, the well-known Heat Affected Zone (HAZ) in which the material presents more microstructural defects compared to the original metal. Since high cycle fatigue is largely dependent on the material microstructure features, the HAZ is considered as the weakest zone under high cycle fatigue loading. In addition, the welding causes, in the Heat Affected Zone, irreversible plastic strains that induce important residual stress fields in this critical zone of the structure. Therefore, in order to properly predict the high cycle fatigue life time of the welded automotive components, it is of primordial importance to first identify and then consider, if necessary, the welding induced residual stress field in the structure modeling. In this work, it is found that residual stresses have non-negligible impact on high cycle fatigue lifetime, while its effect is minor in the low cycle fatigue domain.

2025, The International Journal of Advanced Manufacturing Technology

Steel plate I-girders are widely used in the construction industry worldwide. While numerous studies have explored ways to enhance their benefits, few have simultaneously optimized both key mechanical components-geometry and material-to develop novel and more efficient typologies. This research employs metaheuristic optimization to explore alternatives to traditional I-girders, formulating optimization problems that integrate geometric and material variables in both transverse and longitudinal planes. The objective is to minimize manufacturing costs, accounting for material expenses and seven key production activities such as welding, cutting, or painting, while ensuring compliance with Eurocode 3 specifications. The results indicate that material selection dominates in short-span girders, whereas geometric optimization becomes more critical for longer spans. The most cost-effective solution identified is the transversely hybrid with variable section (THVS) girder, which features tapered geometry and hybrid material distribution between the flanges and the web. Based on these findings, practical design recommendations are provided, including optimal span-to-depth ratios, hybrid ratios, taper angles, and transition positions for variable cross-section configurations. A proposed design methodology incorporating these recommendations is validated through a case study, demonstrating that THVS elements can reduce costs by up to 70% compared to traditional designs. However, challenges related to material availability, fabrication complexity, and local buckling risks must be addressed to fully realize the potential of these designs. Future research should prioritize FEA and experimental testing to refine these typologies and update design codes to better account for tapered and hybrid girders.

2025

The graphite components in an advanced gas-cooled reactor (AGR) core are subjected to fast neutron irradiation, thermal gradients and radiolytic oxidation during the reactor operation. The non-uniform changes in the material properties, irradiation, temperature, and weight loss across a typical graphite moderator brick lead to the generation of significant internal stresses. The internal stresses in a typical moderator brick are tensile at the bore and compressive at the periphery in early life, but later in life the stresses are reversed resulting in tensile stress at the periphery. The presence of sharp near 90° corners (keyway roots) at the brick periphery lead to stress concentrations and possible sites for crack initiation. Unirradiated graphite is a quasi-brittle material that becomes more brittle with increased irradiation. Sharp corners and notches, such as the brick keyways, are stress raisers as the stresses are singular at the notch/corner tip. This is similar to the singularity observed at a crack tip, which needs to be accounted for using fracture mechanics parameters such as the stress intensity factors (SIFs) in finite element assessments. Similarly, notch stress intensity factors (NSIFs) can be used to predict crack initiation at a 90 o corner tip; i.e. crack initiation occurs when the NSIF reaches a critical value. In this paper, a local approach based on strain energy is explored and developed to predict the NSIF values at the keyway roots of an AGR moderator brick. The predicted NSIF values provide an alternative local failure criterion at the keyway roots based on fracture mechanics compared with the current criterion which is based on a series of failure stresses derived from feature tests for various loading configurations. One of the main advantages of this new methodology is that the criteria are not load geometry dependent and can be applied at any of the keyways.

2025, Civil Engineering Journal

Fatigue analysis of tubular joints based on peak stress concentration factor (SCF) is critical for offshore structures as it determines the fatigue life of the joint and possibly the overall structure. It is known that peak SCF occurs at the crown position for in-plane bending (IPB) and at the saddle position for out-of-plane bending (OPB). Tubular joints of offshore structures are under multiplanar bending, comprising IPB and OPB. When a joint is subjected to IPB and OPB loads simultaneously, the peak SCF occurs somewhere between the crown and the saddle. However, existing equations estimate SCF at the crown and saddle only when a joint is subjected to IPB or OPB. It was found that the position and magnitude of peak SCF under simultaneous IPB and OPB depend on the relative magnitudes of these uniplanar load components. The crown and saddle position SCF can be substantially lower than the cumulative peak SCF. Empirical models are proposed for computing peak SCF for KT-joints subjected to multiplanar bending. These models were developed through regression analysis using artificial neural networks (ANN). The ANN training data was generated through 3716 ANSYS finite element simulations. The empirical model was validated using models available in the literature and can determine peak SCF with an error of less than 1.5%.

2025, Civil Engineering Journal

Stress concentration factors are important to determine fatigue life based on the S-N curve methodology, where the lower the stress concentration factor, the higher the fatigue life. In this work, we developed internal ring-reinforced KT-joints, one of the most commonly used joints in the offshore industry, for the most practical ranges with the least stress concentration factors, followed by the formulation of a novel set of parametric equations for determining the stress concentration factors of internal ring-reinforced KT-joints. Using numerical investigation based on a finite element model and a response surface approach with 8 parameters (λ, δ, ψ, ζ, θ, τ, γ, and β) as input and eleven outputs (SCF 0° to SCF 90° and peak SCF), the stress at ten locations around the brace was evaluated, since efficient response surface methodology has been proven to give comprehensive and accurate predictions. The KT-joint with the following parameters: λ=0.951515, δ=0.2, ψ=0.8, ζ=0.31, θ=45.15°, τ=0.60, γ=16.25, and β=0.40 had the least stress concentration factor. The KT-joint with the optimized parameters was validated through finite element analysis. The resulting percentage difference was less than 6%, indicating the applicability of the response surface methodology with high accuracy.

2025, Civil Engineering Journal

Existing models for the evaluation of mechanical properties of corroded reinforcement, defined as a function of the mean cross-sectional loss or mass loss of the reinforcement, are not suitable in the case of chloride-induced corrosion, which causes irregular corrosion attack with pronounced localized damage-pits, whose geometry and spacing have a major influence on the mechanical properties of the reinforcement. Models that consider the irregularity of damage due to chloride corrosion are efficient, but as with models based on cross-sectional or mass loss, it is necessary to extract corroded rebars from the reinforced-concrete structure, which is a destructive procedure that can only be performed to a limited extent on an in-service building. To fill the above gaps, a new method based on the non-destructive measurement of corrosion parameters is proposed. The corrosion depth determined from the monitoring correlates directly with the remaining mechanical properties of the reinforcement; therefore, it is not necessary to determine the remaining cross-sectional area and geometry of the pits. The proposed models are based on experimental research on reinforced-concrete beam specimens subjected simultaneously to sustained loading and accelerated chloride corrosion in an environmental chamber in order to induce corrosion similar to that on real structures.

2025, Journal of Mechanical Design

Bolt-nut connectors play an important role in the safety and reliability of structural systems. Stress concentration due to unequal load distribution can cause fatigue failure in bolt-nut connectors. In this paper, the stress distribution in bolt-nut connectors is studied using an axisymmetric finite element model. Various geometric designs proposed in the literature were studied to determine the extent to which they reduce stress concentrations. Some well known modifications do significantly reduce the stress concentration factor (up to 85%) while other changes produce much more modest changes. The design modifications include things such as grooves and steps on the bolt and nut, and reducing the shank diameter of the bolt. All of the changes also result in a reduction in weight.

2025, European Journal of Dentistry

Objectives The aim of this study was to evaluate using finite element analysis (FEA), the stress distribution in prostheses (lithium disilicate crowns) on monotype zirconia implants with and without cantilever in the anterior region of the maxilla. Materials and Methods From a virtual reconstruction of bone model of the toothed maxilla from a computed tomography, three models (groups) were created: Zr (11–21)—implants placed in the area of 11 and 21 with cantilever; Zr (12–22)—implants placed in the area of 12 and 22 without cantilever; and Zr (11–22)—implants intercalated placed in the area of 11 and 22. In all models, monotype zirconia implant (4.1 × 12.0 mm) was used in single-body configuration. Lithium disilicate crowns were designed on the implants and pontics for all groups. A 150-N load was applied to the prostheses. The materials used were considered isotropic, homogeneous, and linearly elastic. FEA was performed to evaluate the maximum (tensile) and minimum (compressive) p...

2025

The goal of this work is to analyse the severity of semi-elliptical crack defects and to study the degree of damage in the poly-ethylene pipe in bending during the crack propagation. The semi-elliptical cracks are considered in this work located in different position in the wall of the pipe. The three finite element method based on the computation of the J integral was used to analyse the fracture behaviour of these structures. The effect of the position, shape and size of the crack on the J integral values was highlighted. The effects of strain rate and the temperature on the J integral values were also examined. The obtained results show that the strain rates have a strong influence on the J integral values especially for circumferential crack at higher bending moment. However, the energy for circumferential crack is more important compared to axial crack. The effect of the depth of the crack becomes important when the ratio (a/t) reaches a critical value of 0.6 (a/t = 0.6), especially when the ratio a/c is weak (semi-elliptical crack, a/ c = 0.2) where the J integral values becomes independently of the crack depth, this conclusion is opposite to the above for the poly-ethylene pipe subjected to internal pressure. We recall finally, that the temperature effect on circumferential cracks behaviour is more important compared to the axial cracks at critical crack size (a/c = 0.2 and a/t = 0.6). It is also shown that in the wall of pipe, the internal cracks are more dangerous than the external cracks.

2025

Bounds on the trace mappings defined on the Sobolev space W^{1,1}(Omega) and the space LD(Omega)LD(Omega)LD(Omega) of integrable stains are obtained. Such bounds correspond to stress concentration--the ratio between the maximal stress in a body and the maximum of the traction applied to its boundary. The analysis leading to the bounds may be described in the mechanical context of stress theory and stress concentration.

2025, Computers & Mathematics with Applications

2025, International Journal of Innovative Research in Science, Engineering and Technology

A number of analytical and numerical techniques are available for the two dimensional study of stress concentration around the hole(s) and notches in isotropic and orthotropic plates subjected to in-plane or transverse loading conditions. The influence of the structural dimension D/A (where D is hole diameter and A is plate width) ratio upon stress concentration factor for different cases is studied in the present work. Peculiarity in Stress concentration factor for different stresses like i³x, i³y, i³xy, i³von and deflection for different materials is observed. Stress concentration factor for all stresses shows marked mitigation upon introduction of auxiliary holes. Finite element method has been adopted for analysis and the results have been presented in graphical forms with discussion. The finite element formulation and its analysis are carried out using ANSYS package. This research work can provide structure engineers a simple and efficient way to estimate the effect of SCF ...

2025

Problem of defect such as dislocations, crack, cavities, and inhomogeneities, which may be produced in piezoelectric materials during their manufacturing process, can arise when the material is subjected to mechanical and electrical loads. Stress concentrations due to these defects can give rise to critical crack growth and subsequent mechanical failure. In fracture mechanics a crack is an absence of bonds between two neighboring atom layers. Stress distribution near the crack tip depends on the form of the fracture surface formation. In this article, stress intensity factor or safety factor has been calculated and plotted vs. stress for mode I of PZT-4 ceramic (piezoelectric material) as part of micro-sensors and nanorobots.

2025, Materials Today: Proceedings

2025, Journal of KONES Powertrain and …

The main subject of the w ork was numerical and experimental dynamic studies of t op-hat thin-walled elements joined by spot welding. Spot weld diameter and pitch distance were the main parameters describing geometrical shape of examined... more

2025, International Journal of Mechanical Sciences

This study presents a hierarchical analysis framework to examine the stress-strain distributions in notched fiber-reinforced ceramic-matrix composite (CMC) laminates and correlates microstructural variability with macroscopic mechanical responses. Hierarchical models are employed, including a finite element (FE) model incorporating an inelastic constitutive model for CMC laminates, an analytical model that captures inelastic deformation resulting from matrix cracking and a micro-mechanical model developed to assess fiber break displacement due to fiber failure, accounting for the interfacial shear response between fibers and the matrix. Both the analytical and FE models produce accurate stress predictions; however, the results are nonconservative. The strain predictions are validated against digital image correlation data under moderate strain conditions, with the analytical model providing more conservative strain estimates. A domain map of the elastic-inelastic transition near the notch edge, as a function of applied stress and notch size, is presented to assist in predicting stress and strain distributions. Simultaneous analysis of stress and strain distributions reveals that inelastic strains in the concentration region reduce peak stresses, thus mitigating stress concentration. Quantitative analysis of microstructural features using X-ray tomography demonstrates a strong correlation between microstructural variations and the stress state in the stress concentration region of the notched CMCs. The results indicate that hierarchical analytical modeling correlates stress distributions with the microstructure ahead of notches, offering new insights into the behavior of the notched CMCs.

2025, Earth-Science Reviews

To assess the probability of a volcanic eruption during an unrest period, we must understand magma-chamber rupture and dyke propagation to the surface, as well as dyke arrest at depth in the volcano. Dyke propagation and arrest depend strongly on the local stresses in the individual mechanical layers which constitute the volcano. The local stresses are primarily determined by the loading conditions (tectonic stress, magmatic pressure, or displacement) and the mechanical properties of the layers. In the absence of stress monitoring of volcanoes, the local stresses must be inferred from models, either analytical or numerical. This paper reviews many analytical and numerical models of local stresses around magma chambers, as well as analytical models and numerical examples of dyke-injection and eruption frequencies. Most analytical models of magma chambers ignore the mechanical properties of the individual layers and their contacts, assume the volcano to behave as a homogeneous, isotropic, elastic half space or a semi-infinite plate, and are of two main types: nuclei of strain and cavities. The best-known nucleus of strain is the point-source Mogi model, used to explain surface deformation as a result of either increase or decrease in magma pressure in a chamber whose depth is also inferred from the surface data. The model explains stresses and displacements far away from the chamber, but neither the stress concentration around the chamber, which determines if and where chamber rupture and dyke injection take place, nor the shape, size, and likely tectonic evolution of the chamber. In the cavity or (two-dimensional) hole model the magma chamber has a finite size. Thus, the local stresses at, and away from, the boundary of a chamber can be calculated. For various loading conditions, an analytical cavity model gives a crude indication of the local stresses in a volcano and its surface deformation. However, variation in mechanical properties, and contacts, between layers are ignored. The analytical cavity model thus cannot be used for detailed analyses of the local stresses in a composite volcano. The numerical models presented here show that the local stresses in a volcano depend strongly on the magma-chamber geometry and the mechanical properties of its layers which are often contrasting, particularly at shallow depths. For example, lava flows, welded pyrolastic units, and intrusions may be very stiff (with a high Young's modulus), whereas young and non-welded pyroclastic and sedimentary units may be very soft (with a low Young's modulus). Consequently, the local stresses may change abruptly from one layer to the next; for example, one layer may favour dyke propagation while an adjacent layer favours dyke arrest. No dyke-fed eruption can occur if there is any layer along the potential path of the dyke to the surface where the stress field is unfavourable to dyke propagation. If such a layer occurs, the dyke normally becomes arrested and an eruption is prevented. The present results indicate that during unrest periods composite volcanoes commonly develop local stresses that arrest dykes and prevent eruptions, in agreement with field observations. These results underline the need for in situ stress monitoring of volcanoes to assess the probability of dyke-fed eruptions.

2025

The majority of hydrocarbon reservoirs worldwide are fractured reservoirs, mostly hosted by sedimentary rocks. Fracture development in reservoirs is still poorly understood, and so is the associated permeability. Here we present new results on fracture networks in limestone and shale layers, part of the Lias Group of Early Jurassic (about 200 Ma), from Kilve, Southwest England. The fractures are mostly joints (extension or mode I fractures). The apertures of 300 measured fractures range from 0.1 to 16 mm, the great majority being in the range 0.1-2 mm, and follow a crude power-law size distribution. The fracture frequency is significantly higher in the limestone layers than in the shale layers, many of the limestone fractures becoming arrested (stopping their propagation) at the contacts with shale layers. More specifically, of the fractures that meet contacts there is similar number of arrested and penetrating fractures, whereas many fractures that penetrate change their attitude o...

2025, Fusion Engineering and Design

The target elements of the WENDELSTEIN 7-X (W7-X) divertor are designed to sustain a stationary heat flux of 10 MW/m 2 and to remove a maximum power of 100 kW. CFC Sepcarb ® NB31 tiles are bonded to a water-cooled CuCrZr heat sink in two steps: active metal casting (AMC ® ) of an AMC ® -copper interlayer to CFC tiles, electron beam welding (EBW) or hot isostatic pressing (HIP) of the AMC ® -NB31 tiles to CuCrZr. The key target of the pre-series phase is the qualification of this bond based on a series of examinations. The introduction of silicon during the AMC ® process significantly improved the strength of the joint between CFC and AMC ®copper. The strength of the bond is preserved after either EBW or HIP processes. High heat flux testing carried out in the ion beam facility GLADIS exhibited a too high percentage of defective tiles. Pre-series activities have been extended to reduce the stress concentration at the interface between tiles and heat sink by optimizing the design.

2025, Geophysical Journal International

We present the results of a dense seismological experiment in the western part of the Gulf of Corinth (Psathopyrgos-Aigion area), one of the most active rifts in the Aegean region for which we have precise tectonic information. The network included 51 digital stations that operated during July and August 1991, covering a surface of 40 x 40 km2. Among the 5000 recorded events with M L ranging between 1.0 and 3.0, we precisely located 774 events. We obtained 148 well-constrained focal mechanisms using P-wave first motions. Of these, 60 also have mechanisms obtained by combining the P-wave first motions with the S-wave polarization directions. The observed seismicity is mainly located between 6 and 11 km depth. Most of the fault-plane solutions correspond to E-W-striking normal faulting, in agreement with the geological evidence. Most of the well-determined mechanisms indicate a nodal plane dipping 10-25" due north and a steep south-dipping plane. A similar asymmetry is also seen in the seismicity distribution and in the overall geological structure of the Corinth Rift. We discuss this evidence and the inference of a deep detachment zone, a structure where the major faults seen at the surface appear to root. A large part of the microseismic activity appears to cluster in regions near the junctions of the main faults with the proposed detachment zone. This feature of the microseismicity is interpreted in terms of stress transfer and stress concentration in regions of probable nucleation of future large earthquakes.

2025, Metals

An extensive literature review was conducted primarily to develop a comprehensive understanding of the quantitative behavior of residual stress (RS) distribution in weld joints. Based on prior data, various levels of the peak RS and distribution profiles were applied to a finite element analyses (FEA) model as an initial loading to evaluate the effect of RS on the Mode-I stress intensity factor (SIF), K I . The RS was not found to have a significant effect on the SIF values when the peak RS was less than 300 MPa. The enhanced effect of RS on the K I values was found to be more pronounced at a lower crack ratio, while the analytical form of the RS distribution had a minor effect. The effective boundary corrections function, F Residual , was derived under the effect of RS for 1T CT specimen for various crack geometries of the crack ratio, (a/W) of 0.2, 0.40, 0.50, 0.60, and 0.75, and with peak RS varying from 100 MPa to 600 MPa. The obtained effective function of K I can be employed to quantitatively evaluate the effect of RS on the fatigue performance of welded joints.

2025, Rakenteiden Mekaniikka

Welding is a commonly applied joining method in many applications in arctic and marine conditions, e.g., in ship and offshore structures, and energy production equipment. Such applications are usually subjected to fluctuating load conditions, and during a decades-long service, they may experience millions of load cycles. Consequently, fatigue strength design and acceptable flaw sizes in the welded details of these structures are among the most important design criteria. Multiple fatigue strength assessment approaches exist for assessing the fatigue strength of a welded detail. The present study introduces a numerical and analytical fatigue strength assessment, conducted on a non-load-carrying X-joint, which is a representative joint type used in many steel constructions. Fatigue analyses are carried out following the DNVGL-RP-C203 and BS7910:2013 fatigue design guidelines for offshore steel structures. The stress intensity factors (SIFs) for linear elastic fracture mechanics (LEFM) analyses were obtained using three different methods: the weight function approach, the analytical equations provided in the IIW Recommendations, and by conducting numerical crack propagation analysis using the Franc2D software. All three methods had a good agreement particularly for short crack depths, indicating the applicability of the analytical approaches for the fatigue analyses. The results showed that the consideration of degree of bending at the welded detail is crucial due to the distinguishing notch stress factors of membrane and bending loading, and different stress distributions in the through-thickness direction. In addition, it was found that the LEFM-based fatigue life assessments are significantly more conservative than the life predictions obtained using the structural hot-spot and effective notch stress approaches.

2025, Journal of Constructional Steel Research

Misalignments and distortions in welded plate components act as stress raisers and can significantly decrease the fatigue strength of welded connections. This paper investigates the effect of the plate misalignment of transverse attachments on the fatigue behavior of axially-loaded non-load-carrying cruciform (NLCX) joints. Experimental fatigue tests with and without the plate misalignment are carried out for fillet-welded NLCX joints. The test specimens were fabricated of S1100 ultra-highstrength steel grade, and the fatigue tests were conducted using an applied stress ratio of R = 0.1. Numerical finite element analyses were conducted to obtain the stress concentrations induced by the misalignment. In addition, varied geometry parameters were applied to investigate their effect on the magnitude of stress concentrations. Stress concentrations were obtained using the structural hot spot stress method applying linear surface extrapolation and 1 mm below depth methods, and the effective notch stress concept with the reference radius of 1 mm. Experimental fatigue tests showed a decrease of up to 12% in fatigue strength depending on the degree of misalignment. The highest stress concentration was induced when the misalignment to the joint width ratio was e/L = 0.2-0.4. Structural stresses cannot be estimated using the linear surface extrapolation. Instead, structural stress at the 1 mm depth and effective notch stress concept accurately evaluated the misalignment effect on the fatigue performance of NLCX joints, and provided a good correspondence between the theoretical and experimental fatigue strength estimations.

2025, IOP Conference Series: Materials Science and Engineering

This paper presents the fundamental investigation on crack propagation rate (CPR) and Stress Intensity Factor (SIF) for a typical fatigue and welded specimens which are Compact Tension (CT) and Single Edge Notch Tension (SENT) as well as Butt and longitudinal T-joint. The material data of austenitic stainless steel SS316L was used to observe crack propagation rate with different initial crack length and different tensile load was used for the fracture mechanics investigation. The geometry of the specimens was modelled by using open source software CASCA while Franc 2D was used for post processing based on Paris Erdogan Law with different crack increment steps. The analysis of crack propagation using fracture mechanics technique requires an accurate calculation of the stress intensity factor SIF and comparison of the critical strength of the material (KIC) was used to determine the critical crack length of the specimens. it can be concluded that open source finite element method software can be used for predicting of fatigue life on simplified geometry.

2025, SPIE Proceedings

We have developed microshutter array systems at NASA Goddard Space Flight Center for use as multi-object aperture arrays for a Near-Infrared Spectrometer (NIRSpec) instrument. The instrument will be carried on the James Webb Space Telescope (JWST), the next generation of space telescope, after the Hubble Space Telescope retires. The microshutter arrays (MSAs) are designed for the selective transmission of light from objected galaxies in space with high efficiency and high contrast. Arrays are close-packed silicon nitride membranes with a pixel size close to 100x200 µm. Individual shutters are patterned with a torsion flexure permitting shutters to open 90 degrees with minimized stress concentration. In order to enhance optical contrast, light shields are made on each shutter to prevent light leak. Shutters are actuated magnetically, latched and addressed electrostatically. The shutter arrays are fabricated using MEMS bulk-micromachining and packaged utilizing a novel single-sided indium flip-chip bonding technology. The MSA flight system consists of a mosaic of 2 x 2 format of four fully addressable 365 x 171 arrays. The system will be placed in the JWST optical path at the focal plane of NIRSpec detectors. MSAs that we fabricated passed a series of qualification tests for flight capabilities. We are in the process of making final flight-qualified MSA systems for the JWST mission.

2025

Stress concentrations are present at cut-outs, notches, and generally at free edges in woven CFRP structures. Under cyclic loading, damage initiates from these stress raisers and progresses into the laminate, leading to strength reduction and structural failure. The present contribution provides a literature review summarizing analytical, experimental and numerical investigations regarding damage initiation and propagation in the presence of free edges and at notches in thin plain-woven 2D CFRP laminates. For free edges, initiation of damage is given as interlaminar matrix cracking. Modelling approaches for the progression by cohesive zone models or linear-elastic fracture mechanics are summarized. Recent advances using image correlation and numerical modelling are presented. In terms of notches, a brief survey of relevant literature is given, followed by a more detailed treatment of the damage progression originating from a circular hole. Additionally, the shortcomings of standard specimens with holes for fatigue damage progression investigations are addressed, since both mechanisms, damage from the free edge and the hole, interact. Latest research to uniquely identify the damage emanating from the hole is presented.

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.