机械模具类外文翻译 ------- 现在设计优化方法基础.doc

The integration of optimization techniques with Finite Element Analysis(FEA) and CAD is having pronounced effects on the product design process.This integration has the power to reduce design costs by shifting the burden from the engineer to the computer.Furthermore,the mathematical rigor of a properly implemented optimization tool can add confidence to the design process.Generally,an optimization method controls a series of applications,including CAD software as well as FEA automatic solid meshers and analysis processors.This combination allows for shape optimizations on CAD parts or assemblies under a wide range of physical scenarios including mechanical and thermal effects.
Modern optimization methods perform shape optimizations on components generated within a choice of CAD packages.Ideally,there is seamless data exchange via direct memory transfer between the CAD and FEA applications without the need for file translation.Furthermore,if associativity between the CAD and FEA software exists,any changes made in the CAD geometry are immediately reflected in the FEA model.In the approach taken by ALGOR,the design optimization process begins before the FEA model is generated.The user simply selects which dimension in the CAD model needs to be optimized and the design criterion,which may include maximum stresses,temperatures or frequencies.The analysis process appropriate for the design criterion,and,if necessary without any humen intervention,the CAD geometry is updated.Care is taken such that the FEA model is also updated using the principle of associativity,which implies that constraints and loads are preserved from the prior analysis.The new FEA model,including a new high-quality solid mesh,is now analyzed,and the results are again compared with the design criterion.This process is repeated until the design criterion is satisfied.Fig.7.1 shows the procedure of shape optimization.
如今，综合运用机械设计方法、有限元分析方法和计算机辅助设计技术进行产品设计过程产生了深远的影响。这种综合运用的手段将工程师身上的设计重担交由计算机完成，因而降低了产品的设计成本。此外，正确运用优化设计中严谨的数学推理也可以提高产品的设计的可靠性。优化方法决定了产品设计过程中的精度问题，包括CAD软件建模的准确度，有限元分析中网格划分的正确度以及分析处理器的计算精度等，这种方法能够在考虑机械，热等许多实际情况的影响下，对CAD系统构建的零部件、装配体的结构进行优化。
现代优化设计技术能够对CAD软件构建的零件结构进行优化。从优化设计理论的角度上说，CAD格式的文件和FEA格式的文件之间不需要任何的格式转换，就可以实现数据的无缝交换。这时这两个文件之间存在关联性，对CAD文件所做的任何修改在相应的FEA文件中都能反映出来。例如，在使用有限元分析软件ALGOR对某零部件或装配体计算时，根本不需要建立其有限元模型就可以进行优化设计。用户只要挑选出零部件或装配体CAD模型中需要优化的几何尺寸，确定相应的设计准则（如最大应力、最高温度和最大频率），然后运行相应的分析计算过程，该软件通过计算、比较，就可以完成CAD模型的结构优化，并且整个过程通常不需要使用者参与。需要注意的是，CAD与FEA格式文件之间的关联性使得FEA模型更新了，但约束和施加的载荷保持不变，因此需要对更新过后的有限元模型进行计算，对整个过程不断重复迭代，直到最终的计算结果满足设计要求为止。图7.1所示的是零部件形状优化流程图。