Applied Mechanics and Materials Vols. 182-183

Abstract: The structural analysis of a cab can examine its performances, and then provide a direction for structural optimization. This paper takes a frame-type cab as the research subject, its finite element model and corresponding test scheme are established, and then its torsion stiffness and modal characteristics are analyzed through both simulation and test. Appropriate variables for optimization are screened according to sensitivity analysis. Finally structural optimization for the cab is conducted, so that its torsion stiffness is improved effectively, and simultaneously the structural lightweight design is accomplished on the premise of maintaining the lower modal frequencies on the original level.

Abstract: In laser processing, optimizing the shortest process time is not equal to optimizing the shortest path, and the spare travel time decided the process time. In this paper, an optimization model for contour path in laser processing is established, in which the minimal spare travel time is taken as objective function, and the improved genetic algorithm is designed to optimize the model. In the optimization of contour path, the processing sequence of loops and starting point in each loop are needed to optimize simultaneously, so the dual integer coding is adopted in the improved genetic algorithm. In the algorithm operational process, the methods of initial solution creating, crossover and mutation that suit with the problem are designed, and the infeasible solutions are avoided. The computing method of fitness value is adjusted, and the improved genetic algorithm takes on some self adapting capability. So the computational efficiency of the method is enhanced.

Abstract: A numerical simulation model for vertical-horizontal rolling process in roughing trains is built according to 3-D rigid-plastic finite element method (FEM), which is validated by comparing the simulation results with measured ones of industrial production. The principle of width deviation appearing on head and tail of slab is investigated by the finite element (FE) simulations. A new polynomial short stroke control (SSC) model is developed based on the comprehensive simulation results and the analyzed results show that, at the aspect of width control, the new SSC model is more effective than the two line one.

Abstract: The dim-small target tracking is a central problem in several related applications. Subjected to the lack of objective information, traditional target tracking is difficult to meet the needs of dim-small target tracking. A dim-small target’s description based on robust spectral features is proposed to solve this problem. By creating a multi-dimensional feature space and extending the limited RGB information to the hyperspectral information, a new type of target’s description is presented to track the dim-small target with hyperspectral features.

Abstract: Single-port gasless laparoscopic surgical instrument (SPGLSI) is a national patented product in minimally invasive surgery filed. The key problems of it are that the luminophor is short of use-life and the illumination of it is often not enough when lighted by the shadowless cold light. In this paper, we first take qualitative and quantitative analysis of the luminophor designed by the conventional method. Then, a novel design method that use double constant current source (DCCS) to light the SPGLSI is proposed. Several tests have shown a much better lighting effeteness for the luminophor has been achieved using the proposed design method.

Abstract: A node split method based on Partition-of-unity method and mesh modified has been developed for numerical simulation of crack growth. The crack tip could be represented by the enrichment function based on Partition-of-unity method. The crack besides the tip always locates on the edge of element by moving the nodes around crack, and the continuity of crack could be kept on. For an example of 2D quadrilateral mesh, mesh processing has been presented on different condition. The simulation results indicate that applying the node split method to simulate crack growth problem can achieve relatively good results even for sparse grid.

Abstract: Water becomes a good application prospect lubricant for its low cost, energy saving, good safety and environment friendly characteristic. A bearing microscopic surface pitting lubrication model was established, the water condition of it was introduced and the effects of the speed and the load on the film thickness were discussed.The result show that with the provided water film thickness increases, the film thickness also increases. However, when it is added to a certain degree, the film thickness will no longer change, there exists a critical point. Under water-lubricated conditions, the film thickness and minimum film thickness are increased greatly with the increase of speed and decreased greatly with the increase of load in both staved and full water conditions.

Abstract: A system reliability analysis technique has been proposed in the paper, based on stochastic response surface method. Each input is translated into standard random variables, and the output is expanded into Hermite polynomial series. The coefficients of the expansion of the response are obtained by a regression method. The amount of calculation can be greatly reduced, compared to conventional reliability methods such as Monte-Carlo simulation. The proposed technique can be applied to any structural type.

Abstract: The microstructure and properties of grade 700MPa steel with large heat input welding and its heat affected zone (HAZ) were investigated by use of the metallography, scanning electron microscopy, mechanical testing and welding thermal simulation. The results showed that the mechanical properties of the steel meet the technical requirements, namely the yield strength R_eL≥570 MPa, the tensile strength 685MPa≤R_m≤830MPa, the elongation A≥17%, the -20°C impact energy KV₂≥54J and the -20°C impact energy of HAZ≥47J. The steel also had good match between strength, toughness and anti-high heat input welding, the microstructure was tempered sorbite with small dispersed composite inclusions, which promoted the formation of acicular ferrite and were beneficial to the improvement of HAZ toughness.

Abstract: In the milling process, the particles experience mechanical stresses at their contact points due to compression, impact, or shear with the mill medium or with other particles. The rate of grinding depends on a number of factors, including the mill parameters, the properties of the grinding media, and the properties of the particles to be ground. SEM photomicrographs show that the mean sizes of final refined powders are about 200–400 nm, and are quite uniformly distributed by wet ball milling, so the quasi-nano powders are very suitable for sintering.