A new method to design compliant mechanisms based on the inverse beam finite element model

• An inverse finite element model (IFEM) to design compliant mechanisms is proposed.
• Solutions of IFEM exactly fit a specified design shape under known service loads.
• One can arrive at a feasible design in few iterations, without using optimization.
• Expertise of the designer may be sufficient to circumvent flaws of the method.

The motivation of this work is to introduce the inverse finite element method (IFEM) as a new method for the design of compliant mechanisms that must fit a prescribed shape after undergoing large elastic deformations under known service loads. This specific task is typical of a variety of mechanisms where the deformed shape and the responsible loads are known, while the problem is to determine the unloaded shape, i.e., the manufacturing shape of the mechanism.The potentialities and the limitations of the IFEM are shown with three applications in the medical field: 1) a microgripper whose deformed shape is dictated by the object to hold; 2) a valve that must by-pass a prescribed flow rate when it is deformed under a prescribed pressure; and 3) a folder of an intra-ocular lens (IOL) whose deformed shape is determined by the optimal shape of the folded IOL.