Shape Optimization of Crossed Flexures Leafsprings by Using Fem

Abstract

Crossed flexure pivots made of Leaf-springs are used in an increasingly huge number of applications, many of them require the fatigue life and the rotational capability of the pivots to be maximized. Since these qualities are determined by the endurance limit or the yield stress of the spring material, maximizing them will be necessarily requires reducing the stress level. Partly because of simplicity, are due to manufacturing constraints, the constant thickness for leaf-springs have traditionally been used in various crossed flexure pivots. Whereas, minimizing stress will simply by increase in  the length or by decreasing the thickness of the leaf  is often not viable,  due to spatial constraints and attendant degradation in spring performance.

In the present investigation the scope for stress reduction through shape parameter optimization of the leaf-springs have been studied in detail. To this end, a procedure for combining a linear strain energy formulation and a parametric thickness profile presentation and a series of analysis algorithms is adopted. The resulting final thickness profiles are proven to be not only independent of the angular rotation where the pivot operates, but also linearly scalable to the leaf-springs of any length, and minimum thickness and width. The finite element analysis, the results shows very significant reductions in relative maximum stress, and for the various  pivot configurations. The optimized thickness profiles and their corresponding thickness counterparts are also verified in terms of

stiffness, strain energy. It is finally concluded that shape optimization very much offers great potential for extending the fatigue life and rotational range of crossed flexure pivots.