Advanced Materials Research Vols. 189-193

Abstract: The steering column assembly which connects the steering wheel and the steering gear is a very important part of the steering system. This paper presented the optimization design and testing of the steering column upper bearing of an upcoming automobile targeting the 2010-2015 Chinese market. The design problems were formulated into an optimization problem and were solved by Simulated Annealing Algorithm. 6 sample bearings were produced according to the optimization results and tests of steering upper bearing durability, steering shaft looseness and rotation effects performed on each sample to verify the optimized design. According to the test results, the optimal design of the steering column upper bearing is reliable. By using the Simulated Annealing Algorithm, the design time and costs of the steering upper bearing were reduce at least by 2 months and 60,000 USD, respectively.

Abstract: Elbow is a type of components widely used in a piping system, and so it is very important to know the plastic carrying capacity of elbow. In this study, the elastic-plastic behavior of elbows with various ratios of t/rm and relative bending radius R/rm were investigated in detail by using of three-dimensional (3D) non-linear finite element (FE) analyses, assuming elastic-perfectly-plastic material behaviour and taking geometric nonlinearity into account. The analyses indicated that elbow exhibited different behavior obviously at the elastic-plastic states subjected to In-Plane opening bending moment and closing bending moment. The closed form equations of elbow involving effect of tangent pipes were established.

Abstract: The proportion of LED in the lighting area gradually increased. But its high price, the low luminous efficiency, reliability problems restricted its global application. Therefore, for reliability problems, design a thermal structure of 19.2W multi-chip on board aluminum plate LED. Enhance the reliability mainly by settle a piece of silicon between the aluminum plate and the chips. Analyze by finite element method and use the ANSYS simulation software, the simulation for the thermal field is performed. Identify the optimal combination of structural parameters by using the orthogonal experimental method. The maximum steady-state temperature is less than 53.69 °C. Analyze the thermal-structure coupling simulation of the optimization of the thermal structure and reach the maximum thermal stress of 144MPa. So we can say that heat stress in terms of the design is safe and reliable. Eventually arrive at a more ideal LED aluminum plate thermal structure.

Abstract: Numerical and experimental approaches are mutually conducted to investigate the temperature rise in steel machining at high cutting speed. The process is modeled using a fully coupled thermo-mechanical finite element scheme. Cutting tests were carried out at 38 m/s on a ballistic orthogonal cutting set-up equipped with an intensified CCD camera. Analysis of experimental results leads to determine the variables which control heat transfer between the tool and chip. A discussion about the most important parameters controlling the temperature rise at the tool-chip interface is then proposed. The results also show that the temperature-dependence of the frictional stress modeling can improve the accuracy of the numerical simulations.

Abstract: As respects of usage of widespread machining procedures in producing industrial pieces, optimization of this procedure is one of most subject that attract researchers intrest. Finite element analysis based techniques are available to simulate cutting processes and offer several advantages including prediction of tool forces, distribution of stresses and temperatures, estimation of tool wear and residual stresses on machined surfaces, optimization of cutting tool geometry and cutting conditions. Success and reliability of numerical models are heavily dependent upon work material flow stress models in function of strain, strain rate and temperatures. In this paper Johnson-Cook material law, owing to its simplicity, has been used for simulating of Aluminum Alloy AA5083. The model parameters are determined by fitting the data from both quasi-static compression tests at law strain rates and machining tests at high strain rates. For calculating deforming parameters in machining being used analytical theory of Oxley. After getting result from the equation, its accuracy being checked either in compression tests or in machining tests by simulation with abaqus software.

Abstract: The paper is to develop a new approach to analyze the reliability of pressure-reducing valve basing on commercial software Ansys. After introducing the work principle of the pressure-reducing valve containing membrane, the mechanical model of the membrane acted by pressure caused by turbulence is established, base on which the simulated model built in Ansys is made. For the stress response of the membrane is dealt as linear response, so the loads acting on the membrane which consist of two parts, one is constant pressure, and another is harmonic load, are taken as superposition of two parts, and the stress response can be taken as superposition of two kinds of cases in Ansys, that are static analysis and harmonic analysis. Then by mote simulation the statistical character of the stress response can be obtained, such as mean and variance. Using three- parameter S-N equation and constant life fatigue life curve, the equation of the equivalent mean fatigue life is established, basing on the equation and linear cumulative damage theory, the fatigue reliability during certain period can be gotten. At last an example is given to verify above approach.

Abstract: The FEM simulation is used to study the intermediate frequency induced heating process. The temperature distributions and temperature differences are obtained by two kind frequencies of 500 and 1000Hz. It is found that, in this simulation condition, the length of uniform temperature region is about three times of the coil height. It is obvious that, no matter which frequency, the heating rate is very high. With the process of 1000Hz, in less than 20 seconds, the heating temperature can reach a reasonable temperature, and with a process of 500Hz, the temperature can reach a reasonable temperature in more than 40 seconds. It is recommended that the frequency between 500 to 1000Hz could be available for a practical use.

Abstract: Based on a three-body micro-contact mechanism and contact temperature theory, a micro-contact temperature model was developed to investigate the effect of particle size, particle density, and rotational speed on temperature rise between particles and workpieces. The experiments with different particle sizes and rotational speeds verified the feasibility of the micro-contact temperature analysis. The results indicate that contact temperature between particles and workpieces linear increases as particle size and rotational speed increase. The particle density has a negligible effect on maximum contact temperature between particles and workpieces.

Abstract: Many techniques have been developed to analyze the time impact and the costs caused by the disruptions of the project works. However, most were limited on the delay of the critical path and the overall project completion date. In recent years, although more attention has been drawn on the impact of the float loss on the overall project cost, not a single research result has been widely accepted and recognized. This study aims to fill this gap. This research firstly introduces a resource-integrated genetic algorithms (G.A.) model, which will be used to develop an optimal schedule including the timing and quantity for each type of resource required to complete each individual activity. Secondly, by using a case study this research intends to identify the impact of float loss on overall project cost through comparing the as-planned optimal schedule with an after-impacted schedule. Based on the research results this research has identified that the relationship between the float loss and project cost can be expressed as a step function and the time span of total float can be divided into and cost-related float and cost-unrelated float, termed as optimal float, in which the consumption of float will not cause the delay of the project completion date, nor the increase of project cost. The findings refute the traditional concept that the total float belongs to neither the owner nor the contractor, and suggest that the utilization float is free only within the optimal float and the float apportionment will never be reasonable unless the cost of float floss has been taken into consideration.

Abstract: In order to decrease accidents of slips and falls, COFs of rubber samples with different surface roughness were measured by Brungraber Mark II. And the correlation coefficients between roughness parameters and COF were calculated. The rusults have shown that the COF increases with surface roughness and the correlation coefficient between Sq and COF is highest. In general, almost all the roughness parameters used in the study have high correlation with COF. Parameters had the highest correlation with COF depends on the materials used and test conditions.