This paper investigates experimentally and numerically the influence of geometry and loading conditions on the fracture response of rock materials. Seven different test samples namely “Edge-Notched-Disc-Bend (ENDB), Semi-Circular-Bend (SCB), Three-Point-Bend-Inclined-Crack (TPB-IC), Single-Edge-Notched-Bending (SENB), Asymmetric-Three-Point-Bend (ATPB), Edge-Notched-Disc-Compression (ENDC) and Double-Notched-Disc-Compression (DNDC)” made of a marble rock were manufactured and tested under bending and compressive loading conditions. The results showed that the failure loads of all samples increase with the change of pure mode I to pure mode III. However, the corresponding fracture toughness values of ENDB, SCB, TPB-IC, SENB and ATPB specimens decreased, while the ENDC and DNDC samples experienced an increase in the fracture toughness. Among the studied specimens, only the ENDB, ENDC and DNDC samples presented pure mode III with KIIIc/KIc ratio ranging from 0.735 for the ENDB specimen to 2.076 for the DNDC sample. The highest mode-I fracture toughness among all the studied specimens was obtained for the SENB and TPB-IC samples, with a value of 1.54 MPa m0.5, while the lowest value was obtained for the DNDC specimen with a value of 1.21 MPa m0.5. The sign and the magnitude of T-stress considerably depended on the loading condition and geometry of the specimens. The crack trajectories of all specimens under study were also investigated.

Fracture parameters of a bi-material plate containing a cener crack and subjected to biaxial tensile loading was calculated numerically. Based on the crack tip stress field obtained numerically in a bi-material joint and using the finite element over deterministic (FEOD) method, the stress intensity factors (KI and KII) and also non-singular T-stress terms, were determined for different material properties and biaxial loading cases. Due to asymmetry of loading and material properties in the investigated dissimilar plate, the center crack experinces mixed mode I/II fracture in general. By increasing the bi-material constant value, which shows the difference between the mechanical properties of two materials, the amplitude of stress intensity factor decreases. The obtained results from this method were in good agreement with the displacment field method prevousiuly reported by other researchers.

Over the past decades, high entropy alloys (HEAs) have attracted continuously increasing research efforts because of their technological promise for structural applications and their scientific interest as a multi-component alloy exhibiting an overall random solid solution structure with high mixing entropy at high temperature. In this summary, we briefly review the recent studies focused on the structure and mechanical behavior of HEAs, covering the important issues from phase stability to elastic modulus, mechanical strength, hardness and fatigue resistance. Finally, we highlight a few key findings recently reported for HEAs and discuss the outstanding issues yet to be resolved.

The amount of damage induced by brittle fracture of cracked bodies depends considerably on the path of fractures. Therefore, prediction of the trajectory of fracture using suitable theoretical fracture criteria is very important for cracked structures. In this paper, using higher-order terms of Williams’s series expansion and the maximum tangential stress criterion, the mixed mode I/II crack growth path of an angled crack plate subjected to biaxial far field loading is investigated theoretically. To evaluate the accuracy of the theoretical results, they are compared with the experimentally reported trajectories for the angled crack plate specimen. It is shown that by taking into account the higher order terms of the Williams series expansion a very good agreement is observed between the experimental and theoretical mixed mode fracture paths in the angled crack problem. It was also observed that the theoretically determined initial angle of crack growth is consistent with the experimental results.

The aim of the present work was to develop a guideline for approving the railway axles made of C35 steel and containing surface and/or in-body defects after manufacturing. First, several through and part-through circular cracks were modeled on the surface and in the body of the axle at its critical cross-section. Then, the permissible size of such cracks was determined by using the fracture mechanics. To verify the validity of the guideline, the theoretical result for the semi-circular surface crack was compared with the allowable size prescribed by the international railway standard. A very good agreement was found to exist between the predicted and the standard values.