Research On Theory And Method For Topology Optimization Of Flexure Hinges

Flexure hinges have been widely applied in precision engineering,Micro/nano manipulator,MSMS,robot,biomedical engineering and so on,and it is the key component of compliant mechanisms.The characteristic of flexure hinges has a great influence on the performance of the compliant precision equipment.The design and optimization of configuration of flexure hinges are very important and have become one of the international research hotspots.At present,most of the flexure hinges are designed at size and shape optimization levels.There are few reports on flexure hinges designed at topology optimization level.Therefore,this paper focus on the design of flexure hinges using topology optimization.The main contents of full text are as follows:To make the flexure hinges have high rotational precision,topology optimization model of hinges is developed based on the rotational precision constraint.The weighted sum of the rotational and axial compliances is set to the objective function,and the axis-drift is set to the constraint.The validity of model is verified using numerical examples.A new high precision quasi-V-shaped flexure hinge(QVFH)is designed based on the topology results.The compliance,precision and stress levels equations of the QVFHs are derived using Castigliano's second theorem,and these equations are examined by FEA and experiment.The performance of QVFHs is analyzed through numerical calculating,and comparison between QVFH and conventional flexure hinges is performed.To reduce the stress concentration of flexure hinges,stress constraint is added to the topology optimization model of hinges.An adaptive normalization of the P-norm of the effective von Mises stresses is adopted to approximate the maximum stress,and a global stress measure is used to control the stress level of flexure hinge.Several numerical examples are performed to indicate the validity of the method.The stress levels of flexure hinges without and with stress constraints are compared.In addition,the effects of mesh refinement and output spring stiffness on the topology results are investigated.The stress constraint effectively eliminates the sharp corners and reduces the stress concentration.In order to improve the compliance of the conventional high-precision notch flexure hinges,we present a topology optimization method to redesign the flexure hinges,and two optimization models are proposed.Numerical examples verified the validity of the method.Compared with the unoptimized flexure hinges,the optimized hinges have higher precision,larger compliance and lower stress levels.Based on the topologies,a new multi-notched flexure hinge(MFH)is presented.Comparisons of performance between MFHs and other flexure hinges are performed in terms of compliance,precision and the maximum stress.Topology of flexure hinges determines their performance.The conventional method is that the topology of hinges is given first,then their performances are calculated.However,it is more reasonable that the performance of hinge is given first,then finding the optimized topology.A simple yet effective optimization model is proposed to design symmetric flexure hinges with prescribed performance based on symmetry constraint.Several numerical examples are performed to indicate the validity of this method.The QVFH and MFH are applied in micro-displacement amplifier and planar 3-DOF compliant mechanisms,respectively.These two mechanisms are compared with the corresponding mechanisms based on right-circular flexure hinge through the finite element simulation and experiment.This paper introduces topology optimization into the conceptual design of flexure hinges,designs flexure hinges at topology level,expands the design space of flexure hinges,enriches the category of hinges and provides a new conceptual design methodologies for flexure hinges.