YZ07手扶式振动压路机设计[含CAD高清图纸和文档资料].zip

第 1页 英文原文 Optimize the reliability of mechanical structure design It is now generally recognized that structural and mechanical problems are nondeterministic and, consequently, engineering optimum design must cope with un-certainties，Reliability technology provides tools for formal assessment and analysis of such uncertainties，Thus, the combination of reliability-based design procedure sand optimization promises to provide a practical optimum design solution, i，e ，, a de-sign having an optimum balance between cost and risk， However, reliabilty-based structural optimization programs have not enjoyed the name popularity as their deterministic counterparts， Some reasons for this are suggested， First, reliability analysis can be complicated even for simple systems， There are various methods for handling the uncertainty in similar situations (e， g，, first order second moment methods, full distribution methods)， Lacking a single method, individuals are likely to adopt separate strategies for handling the uncertainty in their particular problems， This suggests the possibility of different reliability predictions in similar structural design situations， Then, there are diverging opinions on many basic issues, from the very definition of reliability-based optimization, including the definition of the optimum solution, the objective function and the constraints, to its application in structural design practice， There is a need to formally consider these itess in the merger of present structural optimization research with reliability-based design philosophy。 In general, an optimization problem can be stated as follows,Minimize subject to the constraints where X is an-dimensional vector called the design vector， f(X) is called 第 2页 the objective function and, “k(X) and }i(X) are, respectively, the inequality and equality constraints， The number of variables n and the number of constraints， L need not be related in any way， Thus, L could be less than, equal to or greater than n in a given mathematical programming problem， In some problems, the value of L might be zero which means there are no constraints on the problem， Such type of problems are called “unconstrained“ optimization problems， Those problems for which L is not equal to zero are known as “constrained“ optimization problems。 Traditionally the designer assumes the loading on an element and the strength of that element to be a single valued characteristic or design value， Perhaps it is equal to some maximum (or minimum) anticipated or nominal value， Safety is assured by introducing a factor of safety, greater than one, usually applied as a reduction factor to strength。 Probabilistic design is propose: as an alternative to the conventional approach with the promise of producing “better engineered“ systems， each factor in the design process can be defined and treated as a random variable， Using method-ology from probabilistic theory, the designer defines the