Stress-corrosion Cracking (SCC) tests were conducted in the near-neutral pH standard solution, NS4, and in an actual soil solution, using four-point bending ala high Stress ratio and low frequency conditions very similar to those of operational pipelines. Pitting incubation appeared first and then pitting initiated and grew in both solutions although. there were many more pits on the specimen tested in soil purged with 5% CO2 +95% N2 than in the Specimen tested in NS4 Solution purged with the same gas. These observations show that samples in soil solution are more susceptible to pitting than those in NS4 solution. When the pit reached a critical size, the increased Stress concentration around the, pits, resulted in transition to a Crack.

Nowadays total joint replacements are widely used in the world, so in average 800,000 joint surgeries are done yearly only in Europe and North America. However implant loosening is and remains as the major issue of all implant failures and therefore causes revision surgery procedures. Studies and experiments have identified poor fixation of implants most likely is the main cause of long term implant failure and in this case the cement-implant interface cavities are very effective due to resultant Stress concentration. In this study the theory of this problem, continuum and mathematical equations for an inhomogeneous material by using Eshelby’s equivalent inclusion method with a spherical void as a special type of inhomogenities is addressed and a new yield criterion with respect to the void’s volume fraction is derived and changes in material elasticity tensor concerning Mori-Tanaka’s theorem also determined, then by using finite element method and remeshing technique a macro scale cement-implant interface cavity is modeled and concerning the loss of strength due to void existence and the interface Stress concentration, the Crack Initiation and propagation  phenomenon is numerically investigated with respect to different orthopedic cement material properties. The results show that Crack propagates at the interface at constant Stress and strain by elastoplastic material and it propagates in cement bulk by considering elastic material properties for cement that both could cause implant loosening even in very small void’s volume fractions in which there are no significant changes in cement yield Stress and elasticity tensor according to analytical solution. But numerical simulation shows that when a homogenous cement structure is achieved via high vacuum mixing method, there is a uniform Stress distribution in the cement structure and no Stress concentration zone forms even at high Stress levels and also there is no appropriate local site for Crack Initiation.

Due to the significant advancement in the mining and tunneling industry, the depth of underground excavation has been considerably increased. As a consequence of increase in depth, the intact rock strength plays a significant role in rock mass failure. Therefore, the study of intact rock failure has become more crucial. Crack damage Stress and Crack Initiation Stress are the two important characteristics of intact rock failure, which have been studied rarely in the shear failure process. This study aims to investigate the Crack damage and Crack Initiation Stresses in the shear failure by numerical modeling of direct shear test (DST) using the discrete element method. First, the micro-mechanical properties of the numerical model were calibrated against physical experiments in uniaxial tension, uniaxial compression and triaxial compression tests. Then, the numerical models were validated by comparing against physical direct shear tests under different normal Stresses. By undertaking the DST under eight different constant normal Stresses, these two Stress levels have been studied in brittle, brittle-ductile transition and ductile failure modes. It was revealed that the Crack Initiation and Crack damage Stresses occur in 70-91 and 85-95 percent of the peak shear strength, respectively. Also, it was observed that the ratio Crack Initiation and Crack damage Stresses to the peak shear strength decrease with an increase in the normal Stress. The outcomes would be useful for studying the structures under shear Stress like landslides and rock bolts.

This paper presents a simple method based on strain energy density criterion to study the Crack Initiation angle by finite element method under biaxial loading condition. The Crack surface relative displacement method is used to eliminate the calculation of the Stress intensity factors which are normally required. The analysis is performed using higher order four node quadrilateral element. The results by finite element method are compared with DET (determinant of Stress tensor criterion) and strain energy density criteria. Finite element results are in well agreement with the experimental and analytical results.

The beneficial effects of Shot peening on fatigue life of mechanical components are well known. However, there are some reports in the literature that indicate inappropriate shot peening parameters tend to reduce the fatigue life. It is therefore, the purpose of this study to find a logical quantitative justification for these observations. Using finite element method, a dynamic elastic-plastic simulation of shot peening was presented. Effect of shot velocity and size on surface morphology after shot peening were examined. Fatigue Crack Initiation life calculation of shot peened specimens revealed that beneficial effect of shot peening significantly vanishes in the case of high velocities and bigger shots.

Present study deals with the prediction of Crack Initiation angle for mixed mode (I/II) fracture using finite element techniques and J-Integral based approach. The FE code ANSYS is used to estimate the Stress intensity factor numerically. The estimated values of SIF were incorporated into six different Crack Initiation angle criteria to predict the Crack Initiation angle. Single edge Crack specimens of Araldite-Hardener were used for the present analysis. Load was applied up to critical limit of the specimens containing Crack at different angles of inclination. The Crack Initiation angle obtained using Stress intensity factor and J-integral based approach were found close to each other and also found to be in good agreement with the available experimental results in literature. It is also investigated that as Crack inclination angle increases material was found to behave in a brittle manner.

In this paper, the continuum damage mechanics model originally proposed by Lemaitre (Journal of Engineering Materials and Technology. 1985; 107: 83-89) is presented through an adaptive finite element method for three-dimensional ductile materials. The macro-Crack Initiation-propagation criterion is used based on the distribution of damage variable in the continuum damage model. The microCrack closure effect is incorporated to simulate the damage evolution more realistic. The Zienkiewicz-Zhu posteriori error estimator is employed in conjunction with a weighted Super convergence Patch Recovery (SPR) technique at each patch to improve the accuracy of error estimation and data transfer process. Finally, the robustness and accuracy of proposed computational algorithm is demonstrated by several 3D numerical examples.

In this paper, an experimental investigation of fatigue Crack growth behavior and fatigue life of Coach Peel (CP) specimens is reported. In this investigation, the CP specimens with 1 and 1.5 mm thickness and from mild steel are used. Specimens are tested by a 25 kN capacity INSTRON 8802 servohydraulic fatigue test machine under constant amplitude but various level loadings. During loading, the Crack length and cycle numbers are measured accurately by a 100X light microscope. Initiation and propagation of spot weld specimens are measured by drawing vertical displacement of the specimen's vs cycle's curves. Results show that Initiation and propagation of Cracks often occur in the plate with less thickness. Also in low level loadings, Cracks propagate longtitudinaly, but in high level loadings, usually nugget pull out and joints, fail catastrophically. The Crack lengths during propagation are nearly unique in both plates with the same thickness.