液压机上横梁有限元分析及结构优化

以某型液压机上横梁为对象,利用分析软件建立上横梁的有限元模型并进行静力分析计算.在上横梁强度和刚度校核的基础上,利用分析软件结构优化模块对上横梁分别进行拓扑优化和尺寸优化,实现结构优化,减轻上横梁重量.     

Effect of C/Ti ratio on the compressive properties and wear properties of the 50 vol.-% submicron-sized TiCx/2014Al composites fabricated by combustion synthesis and hot press consolidation

In this study, in situ 50?vol.-% TiC_x/2014Al composites with different C/Ti molar ratios (0.6, 0.7, 0.8, 0.9 and 1) were successfully produced by the method of combustion synthesis and hot press consolidation. The microstructure and the mechanical properties of the composites were investigated. Microstructure characterisation of the TiC_x/2014Al composites showed relatively uniform distribution of the TiC_x particles with the particle size in the range of 200–900?nm. With the increase of the C/Ti molar ratio, the yield strength (σ_0.2) and the ultimate compression strength (σ_UCS) increased first then decreased, and the fracture strain (ε_f) increased. The σ_0.2, σ_UCS and the abrasive wear resistance of the 50?vol.-% TiC_x/2014Al composites reached the highest value when the value of the C/Ti molar ratio comes to 0.8. The σ_0.2, σ_UCS and ε_f of the 50?vol.-% TiC_x/2014Al composites with the C/Ti molar ratio of 0.8 are 1094?MPa, 1454 and 6.13%, respectively.     

Structural integrity issues with Gen IV proposals: fast reactors and PBMR

Abstract

Structural integrity issues are discussed for two generation IV reactor concepts: the fast reactor and the high temperature reactor, more specifically, the pebble bed modular reactor. The pebble bed modular reactor and other designs of high temperature reactor are claimed to possess built-in safety features leading to safe shutdown: they do, however, involve >8% enrichment of ²³⁵U. Many high temperature creep, creep–fatigue and stress relaxation issues remain to be addressed. With lead/lead–bismuth cooled fast reactors running at ～500°C, there appear to have been none of the issues in the steam generator experienced with sodium cooling. The aspiration of both reactor types is to operate at high temperatures and to produce hydrogen from water thermochemically. A view has been expressed that temperatures up to 900°C could be achieved using metallic alloys (with ceramics for higher temperatures), but it is concluded that something of the order of 750°C represents a more realistic upper limit for economic service lives.     

Effect of doping level on physical properties of antimony doped nanocrystalline tin oxide films fabricated using low cost spray technique

Abstract

Antimony doped nanocrystalline tin oxide (SnO₂∶Sb) films have been fabricated using a low cost and simple fabrication technique using a perfume atomiser. The X-ray diffraction patterns of the antimony doped tin oxide (ATO) films show that the films are polycrystalline with tetragonal cassiterite structure having (110) plane parallel to the surface of the substrate. The preferred orientation remains constant for all the doping levels (0·5–3·0 at-%) and the degree of preferred orientation increases with increasing doping concentration in the starting solution. The intensity of the (110) plane steadily increases as the doping concentration of antimony increases. The fine quality of AFM images show that the films have homogeneous and uniform surface. The sheet resistance is found to decrease with increasing antimony doping level, attain a minimum value (6·34 Ω sq^?1) when the doping concentration is 2·5 at-% and then increase for further doping.     

Adoption framework for advanced manufacturing technologies

The paper examines the adoption of advanced manufacturing technology (AMT). The general proposition is that the adoption of AMT reflects an interactive learning process, which is described by the extant use of AMT, firm-specific AMT knowledge accumulation, and the transfer of AMT ideas among networks of firms, suppliers, industry associations and government. This general proposition was specified as a structural equation model of Adoption of AMT. Data were based on the experiences of 224 Australian manufacturing companies that have invested and succeeded in using AMT. The results suggest that the adoption of AMT is primarily a function of a firm's assets for AMT, which comprise the resources, capabilities, and competences for developing and using AMT. The relationship between the adoption of AMT and assets for AMT was reciprocal, which implied a process of dynamic accumulation of both technology and human assets — a view consonant with the competence perspective of the firm. Overall, assets for AMT represent the AMT knowledge base of firms, and were shown to have a crucial role in determining the adoption of AMT.     

Geometrically nonlinear composite beam structures: design sensitivity analysis

The purpose of this paper is to develop a finite element model for optimal design of composite laminated thin-walled beam structures, with geometrically nonlinear behavior, including post-critical behavior. A continuation paper will be presented with design optimization applications of this model. The structural deformation is described by an updated Lagrangean formulation. The structural response is determined by a displacement controlled continuation method. A two-node Hermitean beam element is used. The beams are made from an assembly of flat-layered laminated composite panels. Beam cross-section mass and stiffness property matrices are presented.

Design sensitivities are imbedded into the finite element modeling and assembled in order to perform the structural design sensitivity analysis. The adjoint structure method is used. The lamina orientation and the laminate thickness are selected as the design variables. Displacement, failure index, critical load and natural frequency are considered as performance measures. The critical load constraint calculated as the limit point of the nonlinear response is also considered, but a new method is proposed, replacing it by a displacement constraint.     

Optimization of clamped plastic shallow shells subjected to initial impulsive loading

An optimization technique is suggested for shallow spherical shells made of a ductile material and subjected to initial impact loading. The shell under consideration is pierced with a central hole and clamped at the outer edge. The optimal design of the shell of piece-wise constant thickness is established under the condition that the maximal residual deflection attains its minimal value for given total weight. The material of the shell is assumed to obey the Tresca yield condition and associated flow law. By the use of the method of mode form motions the problem is transformed into a particular problem of non-linear programming and solved numerically.     

Multi-objective optimization of skeletal structures under static and seismic loading conditions

Almost every real world problem involves simultaneous optimization of several incommensurable and often competing objectives which constitutes a multi-objective optimization problem. In multi-objective optimization problems the optimal solution is not unique as in single-objective optimization problems. This paper is concerned with large-scale structural optimization of skeletal structures such as space frames and trusses, under static and/or seismic loading conditions with multiple objectives. Combinatorial optimization methods and in particular algorithms based on evolution strategies are implemented for the solution of this type of problems. In treating seismic loading conditions a number of accelerograms are produced from the elastic design response spectrum of the region. These accelerograms constitute the multiple loading conditions under which the structures are optimally designed. This approach for treating seismic loading is compared with an approximate design approach, based on simplifications adopted by the seismic codes, in the framework of multi-objective optimization.     

Optimization of truss bridges within a specified design domain using evolution strategies

This article reports and investigates the application of evolution strategies (ESs) to optimize the design of truss bridges. This is a challenging optimization problem associated with mixed design variables, since it involves identification of the bridge’s shape and topology configurations in addition to the sizing of the structural members for minimum weight. A solution algorithm to this problem is developed by combining different variable-wise versions of adaptive ESs under a common optimization routine. In this regard, size and shape optimizations are implemented using discrete and continuous ESs, respectively, while topology optimization is achieved through a discrete version coupled with a particular methodology for generating topological variations. In the study, a design domain approach is employed in conjunction with ESs to seek the optimal shape and topology configuration of a bridge in a large and flexible design space. It is shown that the resulting algorithm performs very well and produces improved results for the problems of interest.     

STRUCTURAL SHAPE OPTIMIZATION USING EVOLUTION STRATEGIES

The objective of this paper is to investigate the efficiency of combinatorial optimization methods and in particular algorithms based on evolution strategies, when incorporated into shape optimization problems. Evolution strategy algorithms are used either on a stand-alone basis, or combined with a conventional mathematical programming technique. The numerical tests presented demonstrate the computational advantages of the proposed approach which become more pronounced in large-scale optimization problems and/or parallel computing environment.