Evaluation of Interference Genotypes-Energy Release Rate by Using Wedge Splitting Test (original) (raw)
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Respuestas, 2021
El factor de intensidad de esfuerzos (SIF) es un parámetro suficiente para definir el campo de esfuerzos al cual está sujeto un cuerpo agrietado bajo los lineamientos de la mecánica de fractura lineal elástica (LEFM). El valor del factor de intensidad de esfuerzos SIF es una función del esfuerzo aplicado, la longitud de la grieta y la geometría general de la probeta. Existen varios métodos experimentales para calcular este factor de intensidad de esfuerzos, entre los que se destaca el Wedge Splitting Test (WST). En el presente trabajo se calcula el factor de intensidad de esfuerzos para una probeta de WST mediante la técnica de elementos finitos manteniendo una carga constante y realizando variaciones en la longitud de la grieta y la geometría del cuerpo. Los resultados obtenidos se comparan con una correlación numérica tomada de la literatura en donde se constatan resultados satisfactorios para la simulación.
Theoretical and Applied Fracture Mechanics, 1995
The wedge splitting test is performed on notched shaped specimens that enables the determination of energies for large fracture surfaces and material exhibiting brittle behaviour. A stability condition is deduced and found to depend on the Young's modulus and the R-curve behaviour. The latter is defined by the fracture toughness KR and fracture energy R c, both of which depend on the crack length. A stable crack propagation is enhanced by high ratios of K'R/K R and RJK 2. The wedge loading tends to behave like raising the rigidity of the testing machine. The results are applied on an example with a special geometry.
Wedge Splitting Test: Displacement Field Analysis by Multi-parameter Fracture Mechanics
Transactions of the VŠB – Technical University of Ostrava, Civil Engineering Series
Multi-parameter fracture mechanics is nowadays quite extensively applied when cracked structures/specimens are investigated. The reason was that it has been shown that it can be helpful and bring results that are more accurate when for describing of fracture processes a larger region around the crack tip is used. This can be typical for material like concrete or other materials with quasi-brittle behaviour. Various relative crack length configurations were chosen in order to investigate the importance of the higher-order terms of the Williams expansion (WE) on the crack-tip stress field distribution in Wedge splitting test specimen. The higher-order terms were calculated by means of the over-deterministic method from displacements of nodes around the crack tip obtained by a finite element analysis in different radial distances from the crack tip. The effect of the constraint level (second member of WE) was investigated. Although the third and higher terms of the Williams series are very often neglected, their influence on the opening stress values was investigated and discussed.
Letters on Materials, 2020
An instrumented drop weight tear test allows one to obtain the work of fracture of the specimen. This work monotonously but nonlinearly increases with increasing the test temperature, that is, with increasing toughness of the specimen material. However, part of the work is spent on processes that are not directly related to the properties of the material (friction, etc.). In this work, the total energy expenditures for the deformation of specimens of pipe steel of strength class X80 were determined basing on experimentally measured geometry of the 3D images of specimens and tensile curves of the studied steel, adjusted for the strain rate. In the upper half of the specimen, where tensile deformation was preceded by compression, the total plastic deformation was calculated as the sum of compression and tension. The energy of elastic deformation in all cases was 1÷ 5 % of the total energy of deformation (A D). An increase in the test temperature results to monotonous but nonlinear increases of A D from 7.5 kJ at −67°С (brittle fracture) to 15 kJ at −40°С (mixed fracture) and up to 17 kJ at +20°С (ductile fracture). Thus, A D is highly sensitive to the transition from brittle to mixed fracture and slowly sensitive to the transition from mixed to ductile fracture. The ratio of A D and the fracture work of the specimen is about 100 % for brittle fracture, >70 % for mixed fracture, and <70 % for ductile fracture. Thus, this ratio can be used as an indicator of the fracture type.
Determination of Fracture Paramaters of Effective Crack Model by Wedge-Splitting Test
2018
Although the cracked beams have been widely utilized in fracture mechanics of concrete, there have been some advantages of the cubical/cylindrical specimens such as compactness and lightness. In the present work, the wedge-split-tension tests on cubical specimens with different cement contents and water/cement ratios were initially performed for the effective crack model. Finally, some relationships based on regression between the fracture parameters and the strength properties of concrete were derived. The results of the split-tension cube tests look viable and very promising.
Computers & Structures, 2011
The stress intensity factor and the T-stress for the near-crack-tip field for wedge splitting test (WST) specimens with several variants of boundary conditions are computed using finite element software. The WST is a convenient alternative to classical fracture tests (bending, tensile) for the quasi-brittle fracture of building materials. The WST specimen is investigated within the framework of two-parameter fracture mechanics; near-crack-tip stress field parameters are determined and compared with those of the compact tension specimen due to its shape similarity to the WST. The sensitivity of the values of these parameters to the boundary conditions is also shown.
Avoiding fracture instability in wedge splitting tests by means of numerical simulations
2017
In this paper, unstable fracture propagation obtained in a in-house performed experimentalWedge Splitting Test (WST) is simulated by means of the FEM and fracture- based zero-thickness interface elements. In order to obtain a specimen geometry suitable for a stable WST without modifying the remaining significant parameters of the test (machine stiffness and control parameter), additional simulations were performed varying the length of the specimen notch, until a load-COD (Crack Opening Displacement) curve without snap-back was obtained. Finally, a new experimental WST with the modified geometry was carried out leading to a stable load-COD curve. In the simulations, elastic continuum elements were used to represent the rock, the steel loading plates and the test- ing machine compliance via an “equivalent spring”, whereas interface elements were used for the notch and along the potential crack path. The interface elements representing the notch were equipped with linear elastic const...
Materials & Design, 2013
Photoelasticity was utilized as an experimental stress analysis tool to determine the stress intensity factors for the contact problem between a half-plane with an edge crack and an asymmetric tilted wedge. The effect of contact force magnitude as well as the angle, length, and position of the crack on mode I and II stress intensity factors were studied and discussed. Analysis of the experimental results is based on fracture mechanics, optical properties of materials, and the correlation between fringe patterns and the distribution of stress in transparent materials (i.e., polycarbonate). Image processing was utilized to extract details from the images acquired from the plate under loading. The finite element method was also used to calculate the stress intensity factors. Experimental and finite element results were in good agreement; however, there are some limitations on the application of photoelasticity method.
Frattura ed Integrità Strutturale, 2016
The fracture mechanical properties of silicate based materials are determined from various fracture mechanicals tests, e.g. three-or four-point bending test, wedge splitting test, modified compact tension test etc. For evaluation of the parameters, knowledge about the calibration and compliance functions is required. Therefore, in this paper, the compliance and calibration curves for a novel test geometry based on combination of the wedge splitting test and three-point bending test are introduced. These selected variants exhibit significantly various stress state conditions at the crack tip, or, more generally, in the whole specimen ligament. The calibration and compliance curves are compared and used for evaluation of the data from pilot experimental measurement.
Double-Edge Wedge Splitting Test: Preliminary Results
A new testing technique, named Double-Edge Wedge Splitting Test (DEWST), for determining the direct tensile strength of quasi-brittle materials – such as concrete – has been recently developed at the Politecnico di Milano. The principal aim is to simplify the loading device and the test set-up generally used in direct-tension tests: for example, the specimens need not to be glued to the press platens. Moreover, the crack pattern observed in a few preliminary tests is regular, and cracking can be easily controlled via the stroke of the loading machine. The present work aims to investigate the possibility of applying such technique to cha-racterize thermally-damaged plain concrete specimens. Three different concretes were considered (fc = 50, 80 and 90 MPa) and the results are compared to those obtained by means of traditional and well-defined tech-niques (splitting tests on cylinders, four-point bending displacement-controlled tests on prisms), in order to highlight the pros and cons...