Analysis And Research On Tolerance Interval Of Complex Dimension Chain

Tolerance analysis is to meet the requirements of product function,performance,appearance and assemblability,under the premise of reasonable definition and distribution of tolerance parts and products,optimize product design,so as to produce qualified products with the lowest cost,it is of great significance to reduce product cost and improve product quality.Tolerance analysis mainly adopts extreme value method and statistical method,but extreme value method has the shortcoming of too conservative,which often leads to the manufacturing difficulty and high cost.Statistical methods need to know the statistical distribution rule of each dimension deviation variable in the dimension chain,and a large amount of uncertainty information is needed to judge the statistical distribution form of each loop in the dimension chain.Especially for complex dimension chain,it is almost impossible to determine the distribution form of closed loop dimension variable.With the development of computer aided tolerance design?CAT?technology,new tolerance analysis methods of dimension chain have been paid more and more attention to overcome the defects of traditional tolerance analysis methods.Because the common difference interval analysis method does not need to know the probability distribution rule of each ring in the dimension chain,it represents the change of the uncertain parameters through the change interval,which is easy to be calculated by computer programming,so it has obvious advantages to calculate and deal with the tolerance analysis problem of the complex dimension chain.Based on the national natural science fund project "function of tolerance design based on axiomatic design theory and method research?51475219?" and "Jiangsu province,graduate student scientific research and practice of innovation project"?SJCX18₁038?funding to carry out some research work,put forward "complex dimension chain tolerance interval analysis research" master's thesis topic.The main research contents are as follows:?1?This paper summarizes the research status of CAT at home and abroad,briefly introduces the concept of tolerance analysis,discusses the principle and calculation method of dimension chain,and puts forward the main problems and contents of research on this basis.?2?Relevant theories of interval analysis method were studied,Newton method andKrawczyk algorithm for solving nonlinear interval parameter equations were analyzed by interval analysis method,and MATLAB software program was written to study and analyze the selection of safe iterative interval in interval parameter equation.?3?In order to solve the problem that extreme value method is too conservative in the calculation of dimension chain,especially difficult to deal with complex planar dimension chain including Angle ring and low calculation accuracy,each dimension and tolerance in the dimension chain are expressed in the form of interval number,and the dimensional chain equations are calculated by tolerance interval analysis method.Taking the core structure of a machine gun as an example,the interval analysis program written by MATLAB-INTLAB toolbox was used to solve the problem,and the interval truncation method was used to obtain a more reliable target value range of the closed loop,and the results obtained by the software analysis of CETOL6?statistical method?were compared and analyzed.?4?In view of the spatial RSSR mechanism for assembly,the traditional model of error and clearance random variables on clearance error tolerance is commonly used in modeling,and using the probability analysis method of tolerance analysis problem,considering the gap and the change of length size deviation of cases by adopting the method of vector projection,planar projection contains geometric deviation information of mechanism motion model is established,based on the interval analysis method,analyzes the mechanism in multiple instantaneous position throughout the organization in the gap and the change of rod long structure joints connecting rod and a handle the effects of angular displacement;The nonlinear interval equation is constructed and solved by interval analysis method.The results of tolerance interval analysis are compared with the simulation results of UG software.