جستجوی مقالات مرتبط با کلیدواژه « بار شکست » در نشریات گروه « فنی و مهندسی »

In this paper, in order to evaluate the strength improvement of adhesive single lap joints (SLJs), two kinds of adherend geometrical modifications were studied numerically and experimentally. Adherend tapering and adherend notching were considered as the SLJ modification approaches. The taper angle was assumed so that the whole overlap length covered by the taper. On the other side, the optimum values for depth, width and distance from overlap ends as the major notch parameters were acquired by using finite element simulation. Then, the simulated SLJs including an unmodified joint and the modified ones with taper and notch were fabricated and experiments were performed on them. The experiments revealed that both adherend tapering and adherend notching modification methods increase the SLJs strength significantly. In addition, the failure loads of the SLJs with taper modification are a bit less than the failure loads of the ones with notch modification. A similar observation was seen in the results of finite element analyses. The finite element analysis and the experimental results showed that both outer notch and taper modification method could increase the strength of the SLJs significantly.

In this paper, fracture behavior of functionally graded material weakened by U-notches under mode I loading has been investigated. Electro slag remelting process has been used to produce functionally graded specimens in a notch arrester configuration. Hardness test has been utilized to define the position of each layer. Mechanical properties, including elastic modulus and poisson's ratio, vary along the width of U-notched specimens. The critical fracture load (Fcr) was achieved by performing three point bending examination and using force-displacement curve.
Then, the process simulation was done by finite element software. Firstly, Jcr of each specimen was calculated by using critical value of strain energy averaged over a well-defined control volume. Then the critical fracture load was evaluated by means of the J Integral criterion. In this research, the effect of the notch root radius, for a fixed notch depth, on the Jcr value as well as the critical fracture load has been studied. To compare fracture behavior of the FG specimens with the corresponding homogeneous ones, have the same properties with the notch root layer in FG specimen, Fcr and Jcr value of each have been investigated. The average difference between the predicted Fcr by J integral criteria and experimental results is 17.84%. Finally, the effect of number of graded area layers on Jcr and Fcr has been investigated. The results shows, the value of Jcr and Fcr do not be affected while the number the number of layers more than 20.

In the present investigation، first، 48 fracture tests were conducted on the Brazilian disk specimens made of the quasi-brittle polymer Polymethyl-methacrylate and weakened by central V-notches with end holes (VO-notches) under combined tensile-shear loading with different mode mixity ratios. The fracture loads and the fracture initiation angles (FIAs) were experimentally measured. Then، two brittle fracture criteria were developed on the basis of the failure concepts of the maximum tangential stress (MTS) and the mean stress (MS) for predicting the experimental fracture loads and the FIAs، and the theoretical results were obtained in the form of the fracture curves and curves of fracture initiation angle. A very good agreement was shown to exist between the theoretical and the experimental results. Moreover، it was found that both the criteria provide almost identical predictions to the experimental results.