Key Engineering Materials Vols. 462-463

Abstract: In this study a subroutine was developed and added in the pre-processing module of the frame work of commercial package of ANSYS to distribute the extra masses according to specific assigned centre of gravity (COG). The work further calculate the first bending and torsional natural frequencies of the simplified body in white (BIW) model of automotive in order to maximize these frequencies with final mass constraint. It is found that adding the extra masses symmetrically about longitudinal axis helps to improve the first bending and torsion natural frequencies. However, removing the mass along this axis leads to have higher values in the case of first bending and natural frequencies.

Abstract: A general method is developed to deal with the compressibility of air film and to predict the linear dynamic stiffness and damping coefficients of air-lubricated bearings over the whole range of frequency. Numerical results reveal that both stiffness and damping coefficients are functions of not only the static parameters such as eccentricity and attitude angle, but also the frequency of disturbance. The coefficients are continuous and tend to certain values even when the frequency approaches zero or positive infinity. In general, the direct terms of the dynamic stiffness increase with the increase of the frequency, while the cross-coupling terms tend to an equal value when the frequency becomes infinite, and all the damping coefficients decrease in the higher frequency region and vanish when the frequency approaches positive infinity.

Abstract: In the soil-rock mixed areas where the soils overlie on the rock layer, the rock-socketed retaining piles have been widely used for deep excavations. Up to date, little attention has been paid to performance of the rock-socketed piles used for deep excavation. Therefore, using the two-dimensional finite element program, Plaxis2D, a typical deep excavation engineering supported by rock-socketed piles with the whole embedded portion in rock is analyzed to investigate behavior of the rock-socketed retaining piles in detail. Computation results have shown that for rock-socketed retaining piles used in deep excavations, there exists an ultimate or a maximum rock-socketed depth which can be estimated by the pile diameter. For the ultimate rock-socketed depth, in the final excavation step, the first zero bending moment point of the rock-socketed part of the pile generally locates near the top surface of the rock layer. When the excavated surface is located at the top surface of the rock layer, the corresponding shear force distribution of the rock-socketed pile has an extremum at the same position.

Abstract: Rubber extrusion process is the most complex and important problem in the production of automobile weather strips. To achieve a specified geometry for an extrudate profile, together with a minimum degree of pressure loss, flow balancing of die is required. To attain this objective, the flow characteristics in die channel must be accurately described, and this demands a computational code able to predict complex 3D flow patterns. In this paper, experimental data and tree-dimensional finite volume simulations of the melted rubber flow in die region, during extrusion forming process are presented. For melted rubber flow modeling, the conservation equations of mass, momentum, and energy are solved using a 3D computational code based on the finite volume method. The shear viscosity of the melted rubber flow is described by the power-law and Arrhenius-law models, and the governing equations parameters are interpolated by the least-square fitting of experimental values that gained by Rubber Process Analyzer (RPA). The flow in one of two dies, called plate die, is found to be highly unbalanced. In the second die, by using a feeder plate, the flow at the exit of the die was properly balanced. Experimental results show that for a die with balanced flow rate, extruded profile closely matches the designed profile. Also, reveal that in low-velocity regions of die exit, the profile section tend to contraction.

Abstract: In this paper, the flexural wave propagation and localization in randomly disordered binary periodic beams with the axial load are studied. Based on the continuity conditions, the transfer matrix between the constitutive unit cells is derived. The expression of the localization length in the disordered periodic system is presented. Numerical calculations are performed to illustrate the localization characteristics of the flexural wave. The effects of the axial load on the band gap structures and the localization properties are discussed. From the results, we can observe that the properties of the pass band and stop band for the perfect system can be tuned by the axial load. Moreover, the localization properties of the flexural wave will be strengthened by the higher disordered degree.

Abstract: In this paper, a simulation procedure for tread patch to the road under consideration of contact effects is introduced. In particular, the treadband has been treated as an infinite tensioned beam resting on an elastic foundation. A contact model specially suited for the contact pairing rubber and rough road is developed. The main objective is here to predict the vibration generated from a system mentioned above by locating harmonic point forces representing the exitation of treadband at the contact patch. The simulations are carried out by means of the Finite Element Method in a structure vibration of tire. Exemplary simulation results are presented for 3D models of tire tread block and road. This model can be used as a tire design guide for selecting parameters which produce the minimum noise radiation.

Abstract: Semiconductor packages that use metallization and lead-free solders are increasingly being used in electronic products. In this study, interface reactions and joint-strength reliability were investigated for Sn-3W%Ag-0.5W%Cu solder ball joints joined to Cr/Cu and Cr/Ni-40W% metallization layers that were heat treated at 260°C. The strength of the joint with the Cr/Cu metallization layer decreased as the duration of the heat treatment increased. Sn and Cr interface reactive layers were generated after the loss of Cu in the Cr/Cu metallization layer, but the connection was maintained. By contrast, the connection of the joint to the Cr/Ni-40W metallization layer was relatively stable under the heat treatment conditions investigated.

Abstract: From a view point of engineering application, solid-liquid flow is one of the most practical phenomena, however MPS and other particle methods usually premises a constant size of all particles in the model.　In a realistic phenomenon, the size of those particles is different.　 Koshizuka et al. has proposed new algorithm for solid-liquid flow simulation which is multi-scale DEM-MPS method. The method can calculate solid -liquid flow with a large difference of the particle scale. However, its program code requires a DEM part and a MPS part, and actual phenomenon includes various scales of particles. In order to analyze solid-liquid flow with different particles, modified Laplacian model and variable cut-off radius MPS method is proposed. This modification can directly deals with small particles and large particles. Calculation cost is kept and visualization of the results has more reality by these modifications.

Abstract: In this research, an enhanced force control unit is proposed and implemented on a hydraulic tension-compression fatigue test machine. In this regard, different sensory data, such as force, hydraulic pressure, displacement and oil temperature is acquired and conditioned for controlling different subsystems of the machine. First, the transfer function of the system is identified. Then, a control strategy for applying cyclic force on the specimen with prescribed amplitude and frequency is proposed. The performance of the whole system is examined for the working range of the excitation frequency. In addition, the developed open-architecture controller can be used for testing the real parts found in various branches of industry. It can also be upgraded to be used on a universal fatigue test machine. It is shown that the designed controller can improve the performance of the machine significantly.

Abstract: Cracking due to the restrained shrinkage stress has been frequently observed at early age in concrete structures. Early-age deterioration of concrete due to cracking and higher maintenance cost for poor durability cause serious troubles to concrete structures. Steel slag includes a certain scale mineral such as C2S and C3S, and can be applied in cement and concrete as mineral admixtures. Two tests are outlined to quantify the behaviour of concrete under restrained shrinkage using plate and ring specimens. The results show that mineral admixtures can be used to reduce cracking in concrete. The risk of cracking can be estimated for steel slag concrete, so that it will improve the durability of concrete structures.