Underground coal mining activities are prone to cause movement and breakage in geological strata and also lead to mining subsidence and even ground fissures. Along the direction working panel advancing, ground fissures may occur in roof in front and/or behind working panel. However, the investigations of previous similarity tests in lab only emphasize on the region behind working panel. By impr...

To investigate the impact of crack inclination angle on tensile strength and characteristics splitting failure in rock, split tests were conducted fine-grained sandstone with pre-existing cracks under different conditions. Acoustic emission digital image techniques continuously monitored during tests. The evolution absorbed energy loading processes was calculated discussed, aiming to elucidate ...

The macroscopic pre-cracked line scratch test (MPLST), in which a debonded edge of a film is loaded in in-plane compression, has been modeled as a generic, coupled fracture–buckle problem using simple beam theory. Near cracktip beam rotation (also called root rotation in literature), which always exists due to the eccentric loading in this type of test, has been incorporated into the governing ...

This paper reviews some of the advances that have been made in stress analyses of cracked aircraft components, in the understanding of the fatigue and fatigue-crack growth process, and in the prediction of residual strength of complex aircraft structures with widespread fatigue damage. Finite-element analyses of cracked structures are now used to determine accurate stress-intensity factors for ...

Ultrasonic in situ monitoring of metal alloys has been successfully demonstrated for determining the presence and size of fatigue damage within a stracture. Ultrasonic techniques, however, only provide an estimate of the state of the stracture at that time and do not predict the remaining fatigue life. On the other hand, a statistical crack propagation approach, which models the expected remain...

Numerical simulation of cracked structures is an important aspect in structural safety assessment. In recent years, there has been an increasing rate of development of numerical codes for modeling fracture procedure. The subject of this investigation is implementing automated fracture models in the DYNA3D nonlinear explicit finite element code to simulate pseudo 3-D crack growth procedure. The ...

A study of creep cavities near reheat cracking in AISI Type 316H austenitic stainless steel headers, removed from long-time high temperature operation in nuclear power plants, is reported. It is shown how application of scanning electron microscopy (SEM), cryogenic fractography and small angle neutron scattering (SANS) can be applied, in a complementary way, to observe and quantify creep cavita...

Fracture mode of ductile solids can vary depending on the history of stress state the material experienced. For example, ductile plates under remote in-plane loading are often found to rupture in mode I or mixed mode I/III. The distinct crack patterns are observed in many different metals and alloys, but until now the underlying physical principles, though highly debated, remain unresolved. Her...

Based on the existing research results, a theoretical fracture model of strata under compound impact static and harmonic dynamic load is improved, characteristic parameters (stress intensity factor, T-stress, initiation angle) two far-field stress are determined according to crack dip angle. Additionally, effects distribution field (the angle, degree, number units, area) further calculated disc...

The crack-propagation form may appear as an arbitrary mixed-mode fracture in engineering structure due to irregular internal crack. It is of great significance research the materials with cracks. coupling effect multiple variables (crack height ratio, horizontal deflection angle and vertical angle) on parameters such stress intensity factors T-stress are key points this paper. A three-point ben...