Combined tension–shear fracture analysis of V-notches with end holes

Abstract

In the present research, two stress-based failure criteria were proposed to predict brittle fracture in components containing V-notches with end holes (VO-notches) under mixed mode I/II loading. The first criterion, called VO-MTS, was an extension of the maximum tangential stress (MTS) criterion, and the second one, called VO-MS, was developed based on the mean stress (MS) failure concept. Two different groups of critical distances were utilized in the predictions. The first group was equal to the critical distances for sharp crack, and the second one was computed by using the mode I fracture test results on notched specimens. To verify the criteria, the theoretical fracture curves were compared with numerous experimental results gathered from 108 new brittle fracture tests performed on the Brazilian disk specimens weakened by central V-notches with end holes and made of PMMA under mode I and mixed mode I/II loadings. It was found that both the criteria provide very good predictions to the experimental results for different mode mixity ratios. Also, found in this research was that the curves are almost independent of the critical distance groups, meaning that one can simply utilize the critical distances of sharp crack in both the VO-MTS and the VO-MS criteria without requiring performing mode I VO-notch fracture experiments. List of symbolsCTSN Compact-tension-shear-notch CZM Cohesive zone model d Total slit length in the VO-BD specimen D Diameter of the VO-BD specimen d c Critical distance of the MS criterion for sharp cracks d c,vo Critical distance of the MS criterion for VO-notch E Young's modulus ERNFT Effective relative notch fracture toughness FE Finite element FFM Finite fracture mechanics FNR Fictitious notch radius K vo eff Effective relative notch fracture toughness K IC Plane-strain fracture toughness of material K vo I Mode I notch stress intensity factor

Influences of the diameter and position of the inner hole on the strength and failure of disc specimens of sandstone determined using the Brazilian split test

“…Because the vertical load is applied in a narrow range of the disc using the above methods, crack initiation may occur at the position of the loading points, which may produce inaccurate results (Fairhurst, 1964;Mellor and Hawkes, 1971). To determine the tensile strength of brittle materials more precisely, discs with different shapes (Fowell, 1995;Lambert and Ross, 2000;Tong et al, 2007;Dai et al, 2010;Keles and Tutluoglu, 2011;Cai, 2013;Surendra, 2013;Hua et al, 2015;Riazi et al, 2015;Lin et al, 2015Lin et al, , 2016 have been proposed, including ring specimens that are placed under a pair of radial loads (Hobbs, 1964;Hudson, 1969). Significant stress and steep stress gradients appear in the specimens, which causes initiation and propagation of the resulting cracks (Wang et al, 2014).…”

Investigation of ductile rupture in U‐notched Al 6061‐T6 plates under mixed mode loading

“…A brief review of the governing equations of the UMTS and UMS criteria presented earlier indicates that the sole unknown parameters are the critical distances. It has several times been demonstrated in the literature that the critical distances of a sharp crack are valid also for notches of various features, for example, V‐notches, U‐notches, V‐notches with end holes (VO‐notches) and key‐hole notches . Thus, the expressions of the critical distances required for drawing the fracture curves are as follows: …”

“…It has several times been demonstrated in the literature that the critical distances of a sharp crack are valid also for notches of various features, for example, V-notches, U-notches, V-notches with end holes (VO-notches) and key-hole notches. [8][9][10][11][12]44,45 Thus, the expressions of the critical distances required for drawing the fracture curves are as follows:…”

“…They are known as the small‐scale yielding (SSY), the moderate‐scale yielding, the large‐scale yielding (LSY) and the gross yielding . The failure analysis in the SSY regime is usually carried out by means of brittle fracture criteria that exist in the field of the linear elastic notch fracture mechanics (LENFM) . This can be performed by neglecting the plastic zone or modifying slightly the brittle fracture criteria according to the notch plastic zone size .…”

“…1 The failure analysis in the SSY regime is usually carried out by means of brittle fracture criteria that exist in the field of the linear elastic notch fracture mechanics (LENFM). [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16] This can be performed by neglecting the plastic zone or modifying slightly the brittle fracture criteria according to the notch plastic zone size. 1 For the other three regimes, the LENFM fracture criteria are no longer valid because the failure mechanism in these regimes is completely different from that in the SSY regime.…”