Applied Mechanics and Materials Vol. 575

Abstract: In order to solve the problem of size guarantee related to thin-walled structure in traditional milling parameter selection, specific aluminum alloy frame part contains curved surface and thin-walled structure is studied. Numerical analysis is used in milling parameter selection method. Machining errors are calculated and checked based on milling force analysis. The milling process is simulated using finite element software. And aluminum alloy frame part processing is optimized from the angle of milling parameters according to the simulation results. Optimized milling parameters scheme is acquired, the results show that both machining precision and efficiency of the frame part are improved.

Abstract: The purpose of the present study was to discuss the effects of local solidification time and solidus velocity on porosity formation in high strength aluminum alloy casting. With systematic change in the riser size, together with variation of thickness and length, A201 aluminum alloys were cast in 100% silica sand molds. The porosity content of A201 aluminum alloy was affected by the local solidification time and solidus velocity in this study. The correlation between porosity content and solidification time is found to be split into 2 bands, each being associated with one of the two thicknesses of plate castings. The longer the solidification time, the more the porosity content was measured in the A201 aluminum alloy plate casting. And the faster the solidus velocity, the more the porosity content in this study. The porosity content of A201 aluminum alloy was influenced by both of solidification time and solidus velocity at same time in this study. Basically, shorter local solidification time with slow solidus velocity seems get lower porosity content in A201 aluminum alloy castings.

Abstract: Surface hardening on local bolt (C = 0.071%) with Radio Frequency (RF) - plasma nitrocarburizing apparatus has been carried out. Some local bolt component was cleaned with distilled water. The type of material of local bolt component was low carbon steel, carbon concentration 0.071%. After that the local bolt component was cleaned with acetone. The natural oxide layer on the surface of the local bolt material was etched with HF for 1 until 3 minutes. The local bolt component was cleaned again with distillation water. Then the local bolt component was sprayed with nitrogen gas. After that the local bolt component was hardened on the material surface with RF plasma nitrocarburizing at a temperature of 400 °C, for holding time 7 hours. Sample number 1 was sample before nitrocarburization. Sample number 2 was sample after nitrocarburization at a temperature of 400 °C, for 7 hours. Then the local bolt component was cut with mower as samples for microstructure observed. The samples were mounted, polished, and etched for microstructure observation with optical microscope. The surface hardness of the samples was tested with O.M.A.G micro-hardness Vickers, MHX 10, apparatus. The expenses tracking was 300 grf, and the times tracking was 15 seconds. The results show that the hardness of sample of bolt before nitrocarburization was 154.5 Kgf/mm², after the sample was nitrocarburized at a temperature of 400 °C for 7 hours, the maximum hardness on the surface increased up to 205.6 Kgf/mm². Matrixes on the base material were austenite, ferrite, and perlite.

Abstract: In the present paper, results of experimental tests carried out on hybrid (bonded/bolted) and adhesive composite single-lap joints are showed. The laminate adherends were made by unidirectional carbon fiber/epoxy with symmetric stacking sequence. In particular, the tests were carried out to evaluate strength and failure mode of the different joints. These joints were subjected to quasi-static tensile displacement and tests were conducted using a universal testing machine. The maximum tension load that the specimen can bear is determined and the failure process is correlated to the lay-up of the composite and joint type.

Abstract: The lunar roving vehicle (LRV) is an important and indispensable detection tool that not only can travel far from the lunar module and transport, but also need ensure the astronauts safety when driving. Thus, the driving training for the astronauts on the earth is of great significance. However, the same vehicle has the different dynamic properties under the different gravities, and it is not able to train them with same vehicle on the earth. Therefore, a method of earth environment to imitate LRV steering on the lunar surface is required. In this study, to find out the relationship of the vehicles under different gravities, a handling dynamic model of the vehicles under different gravities is built, some parameter relation coefficients of vehicles under different gravities are carried out, and all parameters of the imitating vehicle for training and imitating on the earth are solved. Finally, the simulation results in Vortex show that, the imitating vehicle, which is changed parameters from LRV, can imitate a LRV steering under the lunar gravity on the earth.

Abstract: Mechanical system degradation always leads to the unstable and nonlinear characteristics in the dynamic responses of the system to some extent. Conventional spectral methods based on Fourier transform have limited value in showing up fault information deviating from linearity. Higher order spectral analysis (HOSA) had been reported to be effective in providing information on nonlinear response. Bispectrum as one of higher order signal analysis tools found to be a useful tool in identifying nonlinear behavior of mechanical system due to vibration faults. This paper provides an introductory treatise of to Bispectrum, and reviews its applications in machinery vibration faults detection that includes misalignment, bearing and gear faults, and cracked shafts. The effectiveness and limitation of this technique are also reported for these faults based on published literature.

Abstract: In general, when evaluating the effect of a sedan vehicle’s tire tread pattern design on the noise generated, the noise is measured by first carving the tires and then using expensive laboratory equipment to perform the measurements. The advantages of using this method are that the experimental results and the noise level produced from the tires (that go into mass production) feature minimal differences and that reliable tested data are produced. The disadvantages of this method are that molds must be created to produce slicks, and that substantial time is invested in the process of artificial carving and performing subsequent experiments, all of which increase the tire development time and cost. Therefore, the effect of a sedan vehicle’s tire tread pattern design on rolling noise was predicted in this study by employing the numerical calculation methods used in calculating fluid mechanics. The experimental results obtained by the Automotive Research & Testing Center (ARTC) were used to test the improved tread pattern designs to validate the reliability of the method proposed in this study and that the tire development time can be effectively shortened

Abstract: This paper presents the analysis of smart hybrid composite plate with embedded shape memory alloy (SMA) wires subjected to low-velocity impact. The SMA wires were embedded within the layers of the composite laminates and the numerical calculation was used in the impact analyses of the laminated hybrid composite plate. The laminated plate theory, first-order shear deformation theory and minimal potential energy principle was utilized to solve the governing equations of the hybrid composite plate analytically. Energy absorption of hybrid composites can be successfully analyzed using analysis of variance (ANOVA). The results indicated that temperature effect is significant during the transition phase and SMA can effectively improve impact-resistance of the hybrid composite laminated plate. In addition, this hybrid structure is an advanced design concepts that can strengthen the impact resistance capability and enhance the carrying loading efficiency of the structure.

Abstract: A study is undertaken to characterize the Neck Force (NF) of a CRS restrained 3 year old child occupant involved in lateral and oblique side impact. The Response Surface Method is used to map the parameter sensitivity upon the NF for impact speed of 32.2 km/h (20 mph) both individually as well as cross interactively. Design of Experiments is used with Latin Hypercube Sampling involving six predictors. A study of the response plots and statistical data obtained provide insights on the characteristic of each predictor with respect to the neck forces sustained. Greater parameter significance affecting neck forces is seen for narrow impact angles (φ ≤ 60°). Singularly, the impact angle parameter is revealed to be largely the most sensitive parameter to affect neck force especially at narrow angles. The critical range for this is identified to be between angles 50° and 70° while a secondary critical range is observed for angles below 34°.

Abstract: pH control is significant in electrodeposition because they affect the characteristics of electrolyte and the deposit. This paper mainly analyses the processing conditions of electrolyte pH value on the electrodeposited SAC. Sn2+ ions will be obtained from the tin methane sulphonate acid while the Cu2+ and Ag+ ions will be obtained from their respective sulfate salts. Ammonium acetate helps in raising the pH of the bath. The FESEM analysis was carried out to examine the morphology of the electrodeposited nanocomposites. A variety of morphological patterns for the electrodeposits with different electrolyte pH is obtained. At low pH (2) electrolyte value, the electrodeposits show a very poor quality with rough surface. With increasing pH value (2.5), the averaged grain sizes decreased. The surfaces of the films electrodeposited at this pH value are generally quite smooth, uniform and compact. Later increment of pH values (3~4) has lead to the formation of porous and non-uniform electrodeposits. From the study, it is possible to observe that, even with the same composition, the deposits have different morphologies under different controlled parameter.