On the I–II mixed mode fracture of granite using four‐point bend specimen

Experimental and theoretical works are performed on the mixed-mode I/II brittle fracture of cement concrete tested by edge cracked semicircular bend specimens. Theoretical background of the traditional fracture criteria including strain energy density, maximum tangential stress, and maximum tangential strain (MTSN) are introduced. The ability of each fracture criterion in prediction of the fracture test data is investigated. The comparison between the evaluations by the traditional criteria and the experimental data shows that none of them are capable of successfully estimating the fracture resistance of cement concrete. An enhanced version of the MTSN criterion is then employed to predict the test data. It is demonstrated that the extended MTSN criterion can successfully predict the test data in a higher accuracy than traditional criteria.

Section: Resultsmentioning

confidence: 99%

Tangential strain‐based criteria for mixed‐mode I/II fracture toughness of cement concrete

Mirsayar

Razmi

Berto

2017

“…The concept of the SIF‐based criterion by Dong was also coupled with the maximum circumferential stress criterion to investigate mixed mode I–II fracture in concrete . In addition, a generalized maximum tangential stress criterion considering T‐stress was also employed to analyse the fracture of granite under four‐point bend loading . However, all studies mentioned earlier do not pertain to specimens with blunt notches or U‐notches.…”

Section: Introductionmentioning

confidence: 99%

Experimental and numerical investigations on fracture process zone of rock–concrete interface

Dong

Yang

Zhou

et al. 2016

A crack propagation criterion for a rock–concrete interface is employed to investigate the evolution of the fracture process zone (FPZ) in rock–concrete composite beams under three‐point bending (TPB). According to the criterion, cracking initiates along the interface when the difference between the mode I stress intensity factor at the crack tip caused by external loading and the one caused by the cohesive stress acting on the fictitious crack surfaces reaches the initial fracture toughness of a rock–concrete interface. From the experimental results of the composite beams with various initial crack lengths but equal depths under TPB, the interface fracture parameters are determined. In addition, the FPZ evolution in a TPB specimen is investigated by using a digital image correlation technique. Thus, the fracture processes of the rock–concrete composite beams can be simulated by introducing the initial fracture criterion to determine the crack propagation. By comparing the load versus crack mouth opening displacement curves and FPZ evolution, the numerical and experimental results show a reasonable agreement, which verifies the numerical method developed in this study for analysing the crack propagation along the rock–concrete interface. Finally, based on the numerical results, the effect of ligament length on the FPZ evolution and the variations of the fracture model during crack propagation are discussed for the rock–concrete interface fracture under TPB. The results indicate that ligament length significantly affects the FPZ evolution at the rock–concrete interface under TPB and the stress intensity factor ratio of modes II to I is influenced by the specimen size during the propagation of the interfacial crack.

“…The energy approach, Equation , is traceable to Irwin, see, eg, . It may also be written in terms of J , eg, or G , eg, :

K_{eq} = \sqrt{K_{I}^{2} + K_{II}^{2}} .

…”

Section: Review Of the Concept Of Equivalent Stress Intensity Factormentioning

confidence: 99%

“…Richard remarks that the choice of the geometry for a mixed mode fracture mechanics specimen should bear in mind the following aspects: full range of mode I/mode II combinations, specimen compactness, ease of manufacture, possibility of precracking under mode I, clamping and loading easy to accomplish, simple test procedure and evaluation, possibility of plane stress or plane strain, small fracture loads. Three‐point and four‐point bend specimens, traditionally used for mode I studies, may be used for mixed mode I‐II choosing adequate relative locations for loads and crack plane. Figures and present the case of three‐point and four‐point bending specimens; K I and K II stress intensity factor calibrations are given, eg, in Wang et al and Belli et al, respectively.…”

Section: Planar Specimens For Mixed Mode Evaluationmentioning

confidence: 99%

Mixed mode fatigue and fracture in planar geometries: Observations onK_eqand crack path modelling

Tavares

Reis

Freitas

et al. 2019

The mixed mode I‐II fatigue and fracture is briefly reviewed, addressing experimental and numerical modelling aspects, and focusing on planar specimens. One major challenge concerns the determination of equivalent stress intensity factor (Keq) in mixed mode situations. Several approaches were compared through the determination of Keq/KI over a wide range of values of KI/KII or KII/KI. Whereas all different approaches converge to the same value as KI/KII increases, the same does not happen for large KII/KI, where differences between values of Keq persist. In the regions of 0 < KI/KII < 2 and 0 < KII/KI < 2, no stable trend of results can be defined. Experimental fatigue crack growth results are presented for Al alloy AA6082‐T6. Compact tension specimens, modified with holes, and four‐point bending specimens under asymmetrical loading promoting mixed mode situations, were subjected to fatigue crack growth tests, where crack path and crack growth rate were measured. The presentation of the fatigue crack growth data was made using a Paris law based upon Keq. Differences in the Paris law constants were found for the different Keq criteria. Recent developments in numerical techniques, as the implementation of the extended finite element method (XFEM) in finite element software packages allows to determine accurately crack paths in mixed mode fracture. This article highlights concepts for mixed‐mode fatigue and fracture and supporting data, identifying challenges still to be overcome.