Topology Optimization Design Of Hinged Compliant Mechanisms At Different Scales

Compliant mechanism is a kind of integral mechanism which transfers force or displacement from input end to output end by elastic deformation of its own material.Compared with the traditional rigid mechanism,compliant mechanism has the advantages of no assembly and lubrication,no noise,low friction,high reliability and easy miniaturization.Therefore,compliant mechanisms are widely used in biomedical devices,ultra precision positioning,aerospace,micro mechanical systems and other high-tech fields,and become one of the hot spots in mechanical design industry.At present,topology optimization is the most popular method in compliant mechanism configuration design.However,the results of the traditional topology optimization model of compliant mechanisms generally have virtual hinges,which will lead to the overall deformation of the mechanism concentrated near the virtual hinges.The existence of virtual hinge will lead to some problems such as excessive local strain,stress concentration,difficulty in miniaturization and manufacturing.Therefore,the present paper improves the traditional topology optimization model of compliant mechanisms,and discusses the topology optimization design of hinge-less compliant mechanisms in different scales.The main research contents are as follows.(1)The results of traditional macro topology optimization are analyzed.Based on the traditional topology optimization mathematical model of macro compliant mechanism and the output displacement as the objective function,the pseudo rigid body model with virtual hinge is obtained by numerical calculation,and the shortcomings of the optimization results are analyzed in detail.(2)The topology optimization model of the compliant mechanism without hinges is established in macro scale.Based on the systematic analysis of the internal mechanism of virtual hinge,the traditional optimization model is improved.The geometric gain is used to replace the output displacement in the traditional model as the objective function.The function ensures that the mechanism can meet the output requirements and has high output efficiency.At the same time,the new concept of micro rotation angle is introduced as the constraint condition,based on which the optimization model of hinge-less compliant mechanism is established.A practical mechanism is taken as an example to verify the validity of the model and the effectiveness of avoiding virtual hinge.(3)The topology optimization model of compliant mechanism in micro scale is established by introducing couple stress theory.By introducing the couple stress theory into the improved topology optimization model,the topology optimization design of compliant mechanism is extended to the micro scale.And the topology optimization model of hinge-less compliant mechanism is established at the micro scale.The example shows that the model can effectively complete the design work of hinged compliant mechanism in micro scale.(4)The structural static analysis is carried out for the compliant mechanisms designed by the traditional and improved models.Firstly,based on the optimal topological forms of compliant mechanisms such as reverse displacement,flexible clamp and steering gear designed by traditional and improved optimization models in macro scale,the three-dimensional modeling is carried out.Secondly,according to the actual engineering and production needs,based on the finite element analysis software platform,the corresponding loads and constraints are applied to carry out the finite element analysis.Finally,the advantages of the improved configuration are further illustrated by the deformation modes of different models.(5)For the compliant mechanism designed by the improved macro scale model,the harmonic response analysis is carried out.Based on the static analysis of the structure,the harmonic response analysis of the optimal topological form obtained by the improved model in the macro scale is carried out,so as to obtain the optimal working frequency band in the practical production application of the improved mechanism and improve the efficiency of its work and production.