Study on effect of supporting point friction on stress intensity factor of notched semi-circular bending specimen

In order to investigate the influence of supporting point friction on the stress intensity factor of Notched Semi-Circular Bending(NSCB) specimen samples, the finite element method was used to study the effects of supporting point friction coefficient(f) on the dimensionless stress intensity factor(YI) of NSCB specimens with different dimensionless crack lengths(a/R) and different supporting spans(S/2R).The results show that when a/R or S/2R is constant, YI will gradually decrease and tend to be stable with the increase of f. When f is constant, YI will increase with the increase of a/R or S/2R,and the larger a/R or S/2R is, the more significantly YI is affected by the supporting point friction.The relationship between YI and S/2R,a/R and f after considering friction were actually multiple irregular spatial surfaces, so it was more convenient to carry out interpolation calculation according to the curves in the figure.Finally, the error correction of the mode I fracture test results for two kinds of rock-like materials was carried out based on the calculated results.According to the results, in the mode I fracture of three-point bending test, if the supporting point was fixed, the supporting point friction should be considered in the stress intensity factor calibration.