-It is very significant to investigate the shot peening mechanism in ensuring a good resistance to fatigue and stress corrosion. This paper reviews the recent advancements in shot peening process. Emphasis is put on the application of numerical simulation techniques and finite element method in residual stress prediction during shot peening process. Different methods related to shot peening modelling and prediction of plastic deformation and surface integrity are reviewed. Some key issues such as algorithms and simulation procedures are discussed.
In this paper, an evolutionary optimization method is presented for weight minimum problem of a 3-dimensional truss structure in terms of nodal coordinates and element cross-sectional areas. The structure is subject to stress, local buckling and displacement constraints. Two types of design variables with different natures are optimized separately: (1) a fully stressed design (FSD) and scaling techniques are applied to sizing variables and (2) the evolutionary node shift method is applied to shape variables. Alternating procedure is utilized to couple the two types of variables and to combine the results. The optimum solution is achieved gradually from the initial configuration design. Two typical truss structures are examined to illustrate the validity of the method.Keywords Combined shape and sizing optimization, Sensitivity analysis, Truss optimum design IntroductionAs the topology of a truss structure is determined in advance, optimization tasks will be focused on the structural shape or geometry and member's sizing, i.e. determining nodal coordinates and cross-sectional areas of elements. The optimum design of a structure should satisfy various constraints such as displacement limits, stress and local stability conditions. As is well known, the optimum shape of a truss depends not only upon its topology, but also upon the distribution of element cross-sectional areas. On the other hand, the structural shape has impacts on the sizing optimum design. Such an inherent coupling of truss shape and element sections explicitly means that the shape or sizing should not be optimized independently. But the simultaneous optimization will lead to a great increase of the variables and make the optimization algorithm quite complicated.The simultaneous optimization of truss shape and sizing variables often deteriorates the convergence due to their couplings (Zhou and Xia 1990). To resolve the difficulties, Gil and Andreu (2001) combine a FSD scheme with a conjugate gradient method for each type of variables. Instead, Hansen and Vanderplaats (1990) employ a member force approximate technique for truss minimum weight design. Svanberg (1981), Zhou and Xia (1990) and Zhang et al. (1998) independently utilize the dual method of a convex programming to solve the problem.In this paper, an evolutionary optimization method is proposed to optimize the shape and sizing of a truss structure for its weight minimization. Nodal coordinates and element cross-sections are considered as design variables. The structure is subject to stress, Euler buckling and nodal displacement constraints in one load case. The first type of constraints provides proper stress levels; the second ensures element stability and the third type of constraints aims at making the structure perform properly. By separation of design variables upon their natures, element sections are optimized with the FSD and scaling techniques while the shape is optimized with the node shift method (Wang et al. 2002). By means of sensitivity analyses, nodal locations are shifted evol...
SUMMARYIn this paper, the position optimization of simple supports is implemented to maximize the fundamental frequency of a beam or plate structure. Both elastic and rigid supports are taken into account. First, the frequency sensitivity with respect to the movement of a simple support is derived using the discrete method. By means of the shape functions of the finite element method, closed-form sensitivity formulations are developed straightforwardly. Then, a heuristic approach, called evolutionary shift method, is presented for optimizing support positions with a fixed grid mesh scheme. Based on the design sensitivity analysis, the support with the highest efficiency is shifted in priority along the elementary edges with the interval (step) of the elementary size. To facilitate the convergence of the process, the interpolation technique is employed to evaluate the solution more accurately. Finally, three numerical examples are presented to demonstrate the validity of the sensitivity analysis and the effectiveness of the optimization method.
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