Materials Science Forum Vols. 697-698

Abstract: Thermal performance determines the normal operation of electronic circuits and power devices. The required cooling capacity is always increasing with the abroad application of electronic system. Especially in high frequency and large power fields, the defection of fan-cooled radiator comes out. By comparison, liquid cooling system possesses better heat stability and conductivity, which not only improves the stability of system, but also reduces the working costs greatly. Cooling capacity of heat sink is mainly determined by the inner mechanical structure, it is necessary to study the different influences of related structure, so as to guide the structural design of heat sink effectively. Based on thermal analysis by changing a single structure parameter, the structural influences on thermal performance are discussed, and the acquired conclusions are of great importance in thermal design practice of heat sink.

Abstract: The characteristic of flow-induced vibration and heat transfer of a cylinder with elastic supporting in two-dimensional fluid flow was numerically investigated by Workbench and CFX software. The numerical results show that, in the same conditions, the greater elastic support stiffness of the cylinder is ,the greater the value and range of fluid speed where the vortex-induced vibration of a circular occurs; With the same elastic support stiffness, the frequency and amplitude of flow-induced cylinder vibrating along transverse direction are much greater than that of in in-line direction(longitudinal direction), and the value and range of fluid speed where the vortex-induced vibration along longitudinal direction of a cylinder occurs is much smaller than that of along transverse direction. When the max vibration velocity of cylinder is much less than the flow speed, the flow-induced cylinder vibration can not reach the effect of heat transfer enhancement.

Abstract: New forms of trapping force are proposed for the design of near-field optical tweezers. Without the limitation of dipole approximation, the trapping force acting on a nano-particle located in near-field region can be solved by direct calculation of Maxwell stress tensor using 3D FDTD method. The new forms are used to design near-field optical trapping with a metal-coated fiber probe. Calculations show that the fiber probe can trap a nano-particle with tens of nanometres diameter to different positions with different distance from the probe tip. In order to achieve higher trapping capability, the feasibility of near-field trapping near the optical fiber probe after adding the AFM metallic probe is shown by analyzing trapping forces along three axis directions. The correctness of new forms is demonstrated by numerical results.

Abstract: The microstructure design satisfying the mass constraint can reduce the structure weight more directly and effectively in comparison with the volume constraint. This paper is devoted to the topology optimization of microstructures with multiphase materials under the mass upper limitation constraint for maximizing the equivalent elastic tensors and their combinations. Firstly, the strain energy method is applied to compute the effective elastic properties of microstructures. In order to make sure that the formulation of mass constraint is linear with separable design variables, DMO (Discrete Material Optimization) model is adopted for the element density interpolation. Therefore, this optimization problem can be solved efficiently by means of mathematical programming approaches, especially the convex programming methods. Besides, the filtering technique is adopted to avoid the checkerboard pattern. There are two categories of numerical examples. In the first category, the modulus and the stiffness ratio of the solid material phase 1 are smaller than the solid material phase 2. In the second category, the modulus of the solid material phase 1 is still smaller than the solid material phase 2, but its stiffness ratio is bigger than the solid material phase 2.

Abstract: The purpose of this paper is to use the topology optimization method to solve the light-weight design problem of large aircraft skin stretch-forming die. The platform of ABAQUS is firstly used for numerical simulation of skin stretch-forming. And the surface load conditions are therefore obtained. The topology optimization is carried out accordingly to maximize the structural stiffness with the material properties and the boundary conditions properly defined. Referring to the obtained topology design, the optimal structure is reconstructed and then evaluated by the non-linear numerical simulation of stretch-forming. Compared with the traditional design, the numerical results have shown that the topology design can improve the stiffness and strength of the stretch-forming die significantly.

Abstract: The purpose of this paper is to introduce the topology optimization method into the lattice style design for the rapid casting SL patterns. During the burnout procedure of the SL resin pattern, the thermal expansion will lead to the crack of the ceramic shell and fail the investment casting. Therefore, the SL patterns are always designed hollowed and some lattice styles are used to fill the cavity to solve the problem. In this paper, we propose to carry out the structural design by assigning the inner part of the SL pattern as the design domain where the material distribution is optimized with topology optimization. The idea is 1) to save the cost of the resin material, 2) to solve the crack problem of the ceramic shell and 3) to maintain certain stiffness for the pattern itself. As a result, we choose to minimize the thermal stress in the ceramic shell as the design objective with the stiffness and material cost of the SL pattern constrained to certain values. The topology optimization is implemented with different definitions of design domain in this paper. Various optimal results are obtained numerically. By comparing the optimal design with the existing lattice style, the newly obtained designs have shown better performances in reducing the stress in ceramic shell and maintaining the stiffness of the SL pattern.

Abstract: The layout of movable components and the topology of the connecting structure are optimized simultaneously in the integrated optimal design of multi-component system for compliance minimization. In this paper, a Heaviside function based approach is developed for sensitivity analysis with respect to location design variables of components. The material discontinuity across the component boundary is approximated as a smooth transition by means of the Heaviside function. This enables the sensitivity analysis with respect to location design variables is carried out in an analytical way as easily as for pseudo-density variables. To demonstrate the validity and efficiency of the new approach, two 3D problems of multi-component system are dealt with for the first time with success.

Abstract: Shape optimization design is carried out in the paper aiming at the feature of openings on curved shells to enhance the structural stability and reduce the stress concentration. In order to make sure that the hole boundary curve are always located on the prescribed curved shell, the parametrical mapping method is employed to describe the hole boundary on the curved shells with shape design variables defined in the intrinsic reference domain. Then, different optimization models are established and the specific sensitivity is calculated for buckling optimization. Finally, it concludes from numerical examples that the structural stability and the intensity benefit together for a curved surface with a large curvature, and they are contradictory for a curved surface with a small curvature.

Abstract: Hydraulic support tester is the key equipment to measure the safety performance and technical performance of the hydraulic support. As an integral part of hydraulic support tester, synchronized loading system bears much load and eccentric load, needs high synchronization precision, and exits mechanical-hydraulic coupling. For these characteristics, building a synchronous loading system platform model, carrying on force analysis of the platform, and then getting four-cylinder pressure at different heights of the loading course are necessary. This research constructs a synchronous control circuit for hydraulic loading system using multi-physic modeling and simulation software—AMESim; simulation is carried out to optimize parameters of PID controllers in order to reduce the four-cylinder position synchronization error. As a conclusion, simulation results validate that appropriate solutions improve the precision and also demonstrate that the designed control system is suit for the synchronization control of the four-cylinder.

Abstract: In this paper, the lightweight design of an aero-engine stator structure is studied as an application case. Different kinds of loading conditions are taken into account. Mathematical formulations of the optimization problem are presented. Two optimization strategies combining shape and topology optimization are tested to get optimal design results.