Advanced Materials Research Vol. 548

Abstract: This article simulates an open pit slope stability using the ANSYS software, which is based on the finite element strength reduction theory, three kinds of slope instability criterion of the strength reduction method are applied to judge whether the slope is on the limit equilibrium state, the incremental search method is used to search the safety factor of the slope stability, and the results show that, the slope body damages when the plastic zone developed from the top to the bottom, in the numerical simulation the finite element iteration calculation didn’t just converge, the corresponding former level of reduction factor is the safety factor, This article can have a guiding significance on the safety production of the open-pit mine.

Abstract: The residual stress introduced in the thin-film process may caused some problems, especially after removing of the sacrificial layers below, the suspended structure may be bended due to the release. In this articles we will develop a new in-situ residual stress detection method based on flexible hinges for thin-film materials, then described the detection principle theoretically and simulated its properties by FEA method.

Abstract: In the article the results of the design and analysis of mathematical model for determining residual stresses in the surface of layer at parts processed by plastic surface deformation (PSD) in which the rollers having an arbitrary shape and size. It is shown that for the calculation of stresses in the surface of layer it should not be defined by them at a forcing point but by a function of contact stresses. Integral equations are obtained for calculating the stresses in the body parts at the processing of PSD rolls of arbitrary size and shape of the stress distribution over the contact area. We found that the tangential and radial residual stresses depend on the magnitude of the force F and its distance from the point at which the voltage is considered in detail. There is a sharp decrease in the influence of forces on the stress in the surface of the part of the distance to the point in question.The calculated data generated by the proposed method are highly matches with data during the experimental investigations. Maximum deviations of the calculated values do not exceed the errors of the experiments and adequate treatment of each other at a significance level of 0.05.

Abstract: Eddy current method can be used for non-destructive assessment of residual stress. In order to relate electrical conductivity change to the residual stresses in the welded joints, piezoresistivity of 5A06 has been investigated using samples heat treated at 2500C and 4000C. These samples represent weld zones with different thermal exposure. A directional eddy current probe with a Hall Effect sensor was used to evaluate stress coefficient of electrical conductivity due to applied uniaxial tensile load on the samples. The electromagnetic forward model was solved using FEM package and linear conductivity inversion was formulated to express probe output in terms of electrical conductivity. The piezoresistivity coefficients of samples, calculated from the derivative of stress-conductivity relation, were compared. The results indicate that coefficients vary inversely with annealing temperature.

Abstract: Forming limit diagram (FLD) is the most appropriate tool used to obtain the safe strain region in sheet metal forming industries. This FLD is based on limiting values of major and minor strains. This Limiting strain is the strain at the onset of fracture / necking in a sheet metal. It is influenced by the material / condition of the material, strain condition in geometrical features of a sheet metal. In this paper, square pattern – square holed, perforated commercial aluminium sheets are considered for the study. The limiting strain for the above perforated sheet metals is predicted using finite element analysis. It is found that the limiting strain is controlled by percentage of open area, ligament ratio and hole size.

Abstract: Dry drilling of aluminum is environmentally friendly machining technique; in the meanwhile it is difficult to carry out due to aluminums gummy behavior and its tendency to adhere to cutting tools which diminishes hole quality. In spite of recent developments in cutting tool technology, HSS tools are still a cost effective choice due to relatively high toughness and feasibility to manufacture complex geometries of HSS drills besides its low price, make this tool a common choice for drilling soft materials such as aluminum. In this study effect of tool wear on thrust force and torque analyzed and hole quality assessed with respect to tool wear along tool life. Dry drilling on aluminum 2024, performed using HSS and HSCo drills at constant feed rate of 0.04 mm/rev and two cutting speeds of 28 and 94 m/min. Results revealed that the abrasive wear on flank face and BUE on chisel edge, margin and cutting lips were dominant mechanisms in all drills. It was found that with propagating the wear land on tool, thrust force and torque increased in both tools.

Abstract: By filament winding technology, a pin hole can be formed in the process of composite manufacturing through wrapped fiber tow around pin, so fiber tows around the pin hole are continued. The paper presents the deformation and stress analysis for this kind of pin hole and compares those with ordinary pin hole. The numerical results show that the wrapped pin hole has a good stress and deformation ability.

Abstract: Currently, self-piercing riveting (SPR) is a major technology used by manufacturers to join aluminium body structures to reduce vehicle weight. Normally, for SPR of one specific stack more than one die, rivet, and velocity combination can be applied. Which parameter combination is chosen is depending on the surrounding joints. In order to increase productivity and reduce the number of robots used, it is preferred to use the same rivet/die combination for as many joints as possible. This means for the same stack, different die may be used. To see the influence of die profiles on joint quality, a DF die, which would generate severe cracks and a DC die, which would generate no cracks or only small cracks, were used to join two stacks with a high strength aluminium alloy, AA6008T61, as the bottom layer. The joint quality was analyzed, and the static and fatigue strengths of these stacks were studied. Results showed that cracks on joint buttons might reduce static and fatigue lap shear strength but had no obvious influence on static and fatigue T peel strength for the joints studied.

Abstract: Vibration is a common phenomenon in cutting process, which is harmful for machining quality and machine tools. This paper focused on the occurrence and characteristics of vibration of the cutting tool and workpiece by changing cutting speed in milling of stainless steels 304. Vibration acceleration signals of both the cutting tool and the workpiece were sampled and analyzed in time domain and frequency domain. Vibration noise and vibration mark were used to judge the occurrence of violent vibration. In the experiments, both self-excited vibration and violent forced vibration were found at different value of cutting speed. Violent forced vibration was easy to be induced owing to interrupted continuous impulsion cutting.The Maximum amplitude of vibration acceleration signals varied with the cutting speed changing. With the cutting speed increased, the probability of violent vibration increased. Bigger amplitude of vibration will not always lead to vibration mark on surface of workpiece, obvious vibration mark only occurred when n=600 r/min and 700 r/min. In order to reduce the impact of violent vibration on machining quality, more attention should also be paid to the static and dynamics characteristics of the cutting tools and workpiece in milling of stainless steels.

Abstract: In this paper, a reasonable model under the thermal void effect of the Insulate Gate Bipolar Transistor is been built. Finite element analysis (FE) is introduced to analyze thermal characteristics of the model. The results indicate that the heat distribution of IGBT is determined of voids with different sizes, positions and the intensity. Besides, the synergy of void effect and heat coupling effect would significantly increase the temperature of the chip.