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American Society for Testing and Materials

In this paper, a new loading fixture is suggested for exploring mixed mode I/III fracture experimentally. Then, the advantages of the fracture test configuration in comparison with the previously presented ones are introduced. Using finite element analysis, the crack parameters of the associated test specimen are obtained for various mixed mode loading conditions. The numerical results show that the designed loading apparatus can create various mode mixities from pure mode I to pure mode III. Subsequently, a series of fracture tests are conducted on PMMA using the proposed test configuration. It is shown that the results of fracture toughness and fracture angles obtained from the experiments are in relatively good consistency with those predicted from the well-known maximum tangential stress criterion.

A new fixture for fracture tests under mixed mode I/III loading

Fatigue and fracture of engineering materials and structures, and electronics

Determination of CTOD resistance curves in side-grooved Single–Edge Notched Tensile specimens using full field deformation measurements

The dynamic fracture behavior of a prestressed orthogonally woven glass fiber-reinforced composite material was experimentally investigated. A shock tube apparatus was used in conjunction with a tensile pre-loading device to apply nominally Mode-I dynamic loading to pre-tensioned, single edge notched specimens. The specimen response was observed with a stereo high speed camera arrangement, and the full-field displacement and strain distributions near the crack tip were extracted using the 3D digital image correlation technique. Critical stress intensity factors for each specimen were determined from the displacement and strain fields using an over-deterministic approach. The magnitude of the pre-load applied to the specimens was shown to influence the crack tip velocity as well as the dynamic stress intensity factor up to the onset of crack propagation. The effect of fiber orientation on both crack tip velocity and dynamic stress intensity factor was also observed.

Fracture Behavior of Prestressed Composites Subjected to Shock Loading: A DIC-Based Study

In this investigation the nature of the plastic zone ahead of a crack-tip in centrecracked tension, double-edge-notched tension, single-edge-notched tension, compact tension, extended compact tension, and single-edge-notched bend specimens have been assessed by elastic-plastic finite element analyses at different applied load levels (J integral). The magnitudes of the plastic zone size (PZS) in the investigated specimens have been compared using a new reference standard J/aσy where a is crack length and σy is yield stress of the material. The results demonstrate that the PZS is almost invariant with respect to specimen geometry up to a critical value of J/aσy at a specific a/W ratio. However, beyond this critical value, the magnitudes of the PZS are found to depend on the specimen geometry, which has been attributed to the varying in-plane constraints at the crack tip in various specimens.

The effect of specimen geometry on plastic zone size: A study using the J integral

Mode-I fracture behavior of glass-carbon fiber reinforced hybrid polymer composite was investigated based on experimental and finite element analysis. The compact tension (CT) specimen was employed to conduct mode-I fracture test using special loading fixtures as per ASTM standards. Fracture toughness was determined experimentally for along and across the fiber orientation of the specimen. Results indicated that the cracked specimens are tougher along the fiber orientations as compared with across the fiber orientations. A similar fracture test was simulated using finite element analysis software ANSYS. Critical stress intensity factor (K) was calculated at fracture/failure using displacement extrapolation method, for both along and across the fiber orientations. The fractured surfaces of the glasscarbon epoxy composite under mode-I loading condition was examined by electron microscope.

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Fracture Toughness of Glass-Carbon (0/90)S Fiber Reinforced Polymer Composite - An Experimental and Numerical Study

Studies on crack-tip plastic zones are of fundamental importance in describing the process of failure and in formulating various fracture criteria. Minimum plastic zone radius (MPZR) theory is widely used in prediction of crack initiation angle in mixed mode fracture analysis of engineering materials. In this study, shape and size of mixed mode (I/II) crack-tip plastic zones have been estimated by finite element analysis in a four point bend specimen according to von Mises yield criteria. The results obtained are used to analyze the MPZR criterion with respect to the effective stress intensity factor (K eff ) and elastic mode mixity (M e ).

Keywords: minimum plastic zone radius, mixed mode I/II, finite element analysis, mode mixity, four point bend specimen

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On the relationship between stress intensity factor (K) and minimum plastic zone radius (MPZR) for four point bend specimen under mixed mode loading

The studies on crack‐tip plastic zones are of fundamental importance in describing the process of failure and in formulating various fracture criteria. The material fracture by opening mode (mode I) is not solely responsible for fracture propagation. Many industrial examples show the presence of mode II and mixed mode I+II loading in machine/structural components. In the present study, the emphasis is placed on the analysis of the size and shape of the plastic zone at the crack tip under mixed mode (I+II) loading conditions. The shape and size of crack‐tip plastic zones have been estimated by elastic finite element analysis in a Compact Tensile Shear (CTS) specimen under mixed mode loading according to von Mises yield criteria. The results obtained are used to analyze the minimum plastic zone radius (MPZR) criterion for crack‐initiation angle with reference to the loading angle and stress intensity factor.

Finite Element Analysis of Minimum Plastic Zone Radius criterion for crack initiation direction under mixed mode loading

Non-singular terms in the series expansion of the elastic crack-tip stress fields, commonly referred to as the T-stress The T-stress is as an additional stress field characterizing parameter to stress intensity factor (K) in the analysis of cracked bodies T-stress is used as an important constraint parameter in the fracture analysis In this investigation, three-dimensional finite element analyses have been conducted to compute the elastic T-stress considering a single edge notched tensile (SENT) specimen with varied thickness and a/W ratio
The results indicate that the T-stress depends on the specimen thickness and significantly varies along the crackfront from surface to centre of the specimen The T-stress results obtained in the present analysis together with corresponding KI values can be used for analysis of constraint effects in a fracture specimen

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S. K. Kudari

Papers

The effect of specimen geometry on plastic zone size: A study using the J integral

Fracture Toughness of Glass-Carbon (0/90)S Fiber Reinforced Polymer Composite - An Experimental and Numerical Study

On the relationship between stress intensity factor (K) and minimum plastic zone radius (MPZR) for four point bend specimen under mixed mode loading

Finite Element Analysis of Minimum Plastic Zone Radius criterion for crack initiation direction under mixed mode loading

Variation of stress intensity factor and elastic T-stress along the crack-front in finite thickness plates