Failure analysis and performance comparison of Triple-LET and LET flexure hinges

A new type of flexure hinge named the Triple Lamina Emergent Torsional (Triple-LET) was proposed in this paper. Its 3D structure was designed, and its equivalent bending stiffness was also derived. Based on the equivalent formula and the finite element simulation analysis, the equivalent bending stiffness of the Triple-LET and the LET flexure hinge with the same overall dimensions were analyzed and compared. It was concluded that under the same torque, the Triple-LET flexure hinge can realize larger deformation than the LET flexure hinge. Thus, the proposed new flexure hinge is presented as a compliant joint suitable for applications where large angular rotation is desired. Failure analyses of the Triple-LET and the LET flexure hinges were also carried out, respectively. The analysis results show that the Triple-LET flexure hinge made of polypropylene can reach 180 degrees with no plastic deformation, while the LET flexure hinge with the same overall dimensions will plastically deform once the bending angle is greater than 161.4 degrees. The results also indicate that the range of bending angles of the Triple-LET flexure hinge made of beryllium bronze is from 0 degrees to 128.2 degrees, which is two times larger than that of the LET flexure hinge. (C) 2016 Elsevier Ltd. All rights reserved.