Papers by Keyword: Dynamic Finite Element Analysis

Abstract: In this study, dynamic temperature field in a dissimilar steel joint specimen was numerically analyzed by means of three-dimensional explicit finite element analysis. Fully coupled thermal stress analysis was performed by using FE-code Abaqus/Explicit ver. 6.12. It was assumed that 90% of the plastic work was transferred to heat. Furthermore, dynamic loading tests were conducted with three-point bending specimen extracted from the dissimilar steel joint between a mild steel and a high tensile strength class steel. The specimen included a U-shape notch in the bonded interface. A high-speed infrared camera was used to measure the temperature field near the bonded interface. The temperature field was recorded at a frame rate of 200 Hz during the dynamic loading test. The numerically calculated temperature field near bonded interface showed reasonable agreement with the temperature field measured by the high-speed infrared thermography. The temperature in the soft steel particularly increased during the dynamic loading. On the other hand, the increase in temperature in the hard steel area was relatively few.

Abstract: The purpose of this paper is to present the use of uniform design of experiments method and dynamic finite element analysis in improving the permanent deformation of an on-road bicycle frame which undergoes the drop-mass impact test. Firstly, four dimensional parameters of the bicycle frame are selected as the control factors to be improved. Then, uniform design method is used to construct a set of experiments. Each experiment denotes a specific design of frame. Next, for each experiment, the dynamic finite element analysis package ANSYS/LS-DYNA is employed to simulate the behavior of bicycle frame which undergoes the drop-mass impact test and determine the permanent deformation of the frame. Lastly, the best frame of all the experiments which causes the smallest permanent deformation is selected as the improved version of design. Compared with the original design which causes a permanent deformation of 8.458 mm, the improved version causes a permanent deformation of 7.467 mm. The rate of improvement is 11.7 %.

Abstract: A process to evaluate the paving block design is proposed. A numerical tire model is developed appropriately for the analysis. The contact pressure between the tire and paving block is calculated. Its distribution pattern is compared with the result of the field tests and is found to be in a good agreement. The present study shows that the magnitude and the distribution pattern are sensitive to the roughness of the road surface. The contact pressure induced by the dynamic impact due to a bumpy surface could be several times higher than that contributed from a smooth run-over. The hot spots in paving blocks are identified as a preliminary study of a research project regarding paving block durability. The tire model is composed of half a deformable tire skin, a rigid rim, a suspension, tire mass, and vehicle mass. The tire-block contact, the tire inner pressure, and the dynamic forces due to inertia are considered as the major loads. It is CPU efficient for less than 1200 CPU seconds required on a personal computer in one drive-through simulation. The proposed study shall be the initial investigation using direct pressure measurement on paving blocks. The lab test results will be fed into numerical model to analyze the failure mechanism which may lead to possible design improvements. Wide application can be expected in the future.

Abstract: Residual stress induced by laser single pulse irradiation was analyzed using a dynamic finite element code, ABAQUS/Explicit. The effects of the magnitude and length of a surface pressure pulse having a circular top-hat shape on the final residual stress in Ti-6Al-4V were investigated. A high peak pressure and/or a long pulse duration was effective in generating large compressive residual stress deep beneath the surface. However, large tensile residual stress features occurred near the centre and edge of the laser spot on the surface for high pressure and/or long pulse durations due to a radial focusing effect. Use of shorter pulse durations avoided this. The peak pressure (3GPa) required to induce a surface compressive residual stress across the whole area of the spot was slightly higher than the threshold pressure needed to plastically deform the surface.

Abstract: The paper describes the combined influences of the forward sabot diameter, sabot modulus, and L/D on the stress of the projectile rod traveling in the gun tube. Three types of gun tube profile were simulated. The first profile is perfectly straight. The second profile is monotonously curved tube only by gravity loads (Type A). The third is a changeful curved tube by gravity loads with imagined as-manufactures (Type B). Three-dimensional dynamic finite element analysis method was used for the sabot/rod system transiting in a gun tube. Numerical simulation results showed that the maximum von Mises stress due to in-bore behavior of the sabot/rod system could be decreased by changing the forward sabot diameter in a type B tube. The effect of tube centerline profile on the stress of the rod was analyzed for the conditions mentioned above. The von Mises stress of the rod in the changeful curved tube is as much as 10% higher than that in the straight or monotonously curved tube.