The 6061-T651 aluminium alloy is one of the most common aluminium alloys for marine components and general structures. The stress intensity factor (SIF) is an important parameter for estimating the life of the cracked structure. In this paper, the stress intensity factors of a slant-cracked plate, which is made of 6061-T651 aluminum, have been calculated using extended finite element method (XFEM) and finite element method (FEM) in ABAQUS software and the results were compared with theoretical values. Numerical values obtained from these two methods were close to the theoretical values. In simulations of crack growth at different crack angles, the crack propagation angle values were closer to the theoretical values in XFEM method. Also, the accuracy and validity of fatigue crack growth curve were much closer to the theoretical graph in XFEM than the FEM. Therefore, in this paper the capabilities of XFEM were realized in analyzing issues such as cracks.
Performing various experimental, theoretical, and numerical investigations for better understanding of behavioural characteristics of metals under impact loading is of primary importance. In this paper, application of smoothed particle hydrodynamics (SPH) method in impact mechanics is discussed and effective parameters on impact strength of an aluminum plate are investigated. To evaluate the accuracy of smoothed particle hydrodynamics method for simulating impact, Recht and Ipson model is first provided thoroughly for both Rosenberg analytical model and smoothed particle hydrodynamics method, and then plots of initial velocity-residual velocity and initial velocity-absorbed energy for target of aluminum 6061-T651 are presented. The derived information and simulation results expresses that the maximum error percentage of smoothed particle hydrodynamics method in compared with Rosenberg analytical model is within an acceptable range. Therefore, the results of smoothed particle hydrodynamics method verify the Rosenberg analytical model with high accuracy. Results reveal that higher initial impact velocity decreases the time of projectile penetration, and so penetration depth and length as well as the local damage rate of plate increases.
Non-destructive ultrasonic evaluation is one of the methods used for inspection in mechanical engineering. This method has diverse applications in various fields, including industry and medicine. The main purpose of this research is to identify a subcutaneous defect with ultrasonic waves. This is done by sending ultrasonic waves into the skin tissue and receiving backward echoes, simulating them using a software, and calculating the time difference using the speed of sound. In this research, the behavior of longitudinal and transverse waves is investigated in collisions with a defect by describing the genesis and application history as well as the principles and definitions of ultrasonic waves. In the test, first, the method of identifying the subcutaneous defect is explained. Then, the dimensions and stiffness of the defect are determined by analyzing the information obtained from the location. Using the 3.5-MHz probe, the defect was detected at a distance of 1.8 mm, indicating a high level of reliability compared to the sonography imaging device. This was while the 10-MHz probe failed to detect the defect just near the skin surface. The results confirm the choice of this method as a suitable method for detecting the subcutaneous defect.
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