Advanced Materials Research Vols. 44-46

Abstract: In the past decade, hydroformed structural components have been widely used in industrial areas in North American and Europe and there is a large potential market in Asia with the development of automotive industry. An extraordinary feature of tube hydroforming is that a hollow component with a three dimension axis and variable closed-sections can be integrally formed, so that the number of component parts is minimized, weight is reduced and stiffness of the part is increased. The section shapes in many automotive hollow components are complex and it is usually difficult or impossible to hydroform these typical sections directly from circular section tube, so that satisfactory preforms are necessary. In this paper, a method to reduce the friction and calibration pressure through a petal-like cross-section shape preform is presented and its mechanism is analyzed. Preforms for rectangular, trapezoidal and polygonal sections used in hollow components are investigated and satisfactory preforms are obtained. Taking an engine cradle as example, satisfactory preform section shapes have been designed, by which the thickness distribution was controlled and the flash generated from the die-parting surface in the final forming was avoided. So a carefully selected preform process can contribute significantly to the reduction of friction and calibration pressure and it is a dominant factor for successful hydroforming.

Abstract: With the enhancement of the power of engines, pistons are easy to bring crack caused by the alternative mechanical loads. In this paper an estimated formula of the fatigue life is developed by amending the Paris formula on the basis of the study of the fatigue behavior of pistons. It consists of the horny crack life and the surface crack life. As an example, parameters in the formula for one type of piston are determined. The expression of the shape geometry factor and the stress range value are obtained by carrying out the FEA static and dynamic analysis, respectively. The crack parameters are analyzed based on the fatigue theory. The fatigue life of the piston is calculated using these parameters. Finally, the validity of the estimated formula is verified by the experiments.

Abstract: This paper aims to study the uncertainty of the MDOF structural dynamic response, taking not only the interval characteristics of structural physical parameters and geometric dimension, but also the interval characteristics of applied load simultaneously . By means of the description of the interval parameters of uncertain structure with affine forms, the interval structural dynamic equation is studied, and an improved affine arithmetic based on interval division is presented, where correlations between the interval elements in eigenvalue and responses equations are considered, independent uncertain parameters are transformed to affine forms, and the solution of eigenvalue and response equations are transformed into the corresponding certain ones. With general affine arithmetic, the eigenvalue of each order and response bounds are determined by searching for the maximum and minimum in the solutions. Finally, some mathematical examples and a further engineering application confirm the feasibility and validity of this approach.

Abstract: Structural strength and leakage failures are two types of main failures of the bolted flanged connection with octagonal gasket, and they are related to the gasket contact stress and gasket effective contact width to a great extent. The deformation behavior of connection subjected to various bolt loads and medium pressures is studied by numerical simulation. The distribution of the gasket actual contact stress, the change of the gasket average contact stress and gasket effective contact width are discussed. The relationship among the gasket average contact stress, the gasket effective contact width, bolt load and medium pressure are obtained. A model for predicting the leakage rate of the sealing connection with octagonal gasket is developed. Research indicates that the gasket actual contact stress distributes non-uniformly, and at gasket outer flank it is much larger than that at gasket inner flank. Both the gasket average contact stress and the gasket effective contact width increase with increasing bolt load and medium pressure. The leakage rate is largely related to working conditions, gasket contact stress, gasket effective contact area, and so on. The leakage rate decreases with increasing gasket effective contact area and gasket average contact stress, and it increases linearly with increasing medium pressure. The leakage through the octagonal gasket connection shows the characteristic of the laminar flow of incompressible viscous fluid.

Abstract: Under the demand of steel enterprise’s production and consumer’s usage, by way of making up and improving continuous function of steel strip surface defects inspection system on-line, the system of grade assessing of surface quality and defects’ information of strip steel has been set up based on quality statistical method. The system of steel strip surface quality grade assessing standards has been analyzed by many steel enterprises in different countries and gotten the limitations of some of the standards. According to the rules of the National Hardwood Lumber Association of America and the feature of Chinese steel enterprise production, the grade assessing standards of steel strip surface quality has been established. Based on character of steel strip surface defects’ information, through the analysis of the requirement, aim and function, system of grade assessing of surface quality and defects’ information managed of strip steel has been developed to fit the demand of the enterprises and consumers.

Abstract: This paper seeks to develop the analytical method for predicting the compression modulus of 2D plain weave fabric (PWF) composites based on a micro-mechanical curved beam model depicted with sinusoidal shape functions. The modulus calculations are obtained and compared with the experiments, demonstrating that predictions correlate well with the experimental results.

Abstract: Wear condition of journal bearing was experimentally monitored with an On-Line Visual Ferrograph (OLVF) system. The round bearing was made of 45# steel with babbitt alloy bushing and the bearing journal was made of 45# steel. High stress of the water content of 0%,1%,3% in lubricant, 10 times of a normal load of 2200 N, and the rotating speeds at 500, 1000, 2000 rpm were adopted in accelerated experiment. A quantitative index of particle coverage area (IPCA) together with wear debris ferro-image was used to characterize wear degree and wear mechanisms. Three wear stages with corresponding wear debris ferro-images were identified from IPCA variations characterized by bathtub curve trend. The first one was running-in stage characterized by the highest wear debris producing rate and higher large debris content. The second one was normal wear stage characterized by the lowest wear debris producing rate and small normal debris. The final one was failure initiation stage characterized by higher wear debris producing rate and higher large debris content. The corresponding dominant wear mechanisms were micro-ploughing and micro–cutting induced by rough initial surfaces in the running-in stage, local rub due to vibration in the normal stage, and fatigue and abrasive wear in the failure initiation stage.

Abstract: An efficient finite element (FE) method, multivariate quadratic regression approach, is proposed for calculating the fatigue stress spectrum of engineering structures. The calculation starts from a dynamic load history. A regression function is established as a relation from the concurrent components of structural balance force systems into the structural stress. Parameters of the relation are measured by the stress data using an elastic-plastic FE method under selected groups of balance force systems. The selected systems should cover the possible load range with a similar service condition. After passing the fit effect check, the regression equation can transfer the structural load history into the stress history at the preferred position. Application on the determination of fatigue stress spectrum for the bolster of K6 type bogie has indicated availability of the present approach. Some deficiencies have been overcome from the much time cost by transient approach and the entire elastic material relation by quasi-static approach.

Abstract: In top-down, constraint-based variational design environment, user expresses his design intent through a series of construction steps that will be further transferred to design variants maintained by the system. Persistent naming techniques build a bridge between design variants and user design intent. The graph-based coding and decoding method together with parameter information, presented in this paper successfully maintain the user design intent in constraint-based variational design. Besides, the energy of parameter vector field decoding method gives a mathematical definition on comparability between original model and regenerated model.

Abstract: Based on systems engineering theory, complex systems development process is discussed. The integrated model is built, in which the integration methods are introduced. The product development process is not only a continuously evolutional process, but also an improvement process of product model. A conceptual framework for integrated development is proposed. Furthermore, building a full context model to cover life cycle is to leverage the deployment of system engineering process. The result in this paper has a wider implication upon industrial integrated development for complex systems.