Theoretical prediction and test validation for frictional action of stacked steel disk springs with low initial cone angle

To examine the frictional action of stacked disk springs with low initial cone angle, axial compression tests were conducted by varying sizes and stacked forms of springs. Each stacked form exhibited stable and predictable behavior and the increase of parallel springs improves frictional dissipation. Lubricating greases can reduce but not eliminate the frictional action. The finite element analysis (FEA) employing friction coefficients from 0.2 to 0.3 can match test results on the whole. Verifications show that some existing predictions, except for the prediction from the standard, can well reflect the frictional action between the end plates and disk springs. Besides, convenient formulas to correctly reflect the frictional action between parallel springs are still needed due to existing theoretical models with either low precision or implicit and complicate calculation of relative sliding deformations between parallel springs. Therefore, based on a method employing either the moment balance or the energy balance, theoretical models and convenient formulas to predict the frictional action for the stacked springs in parallel were proposed. Furthermore, a formula to comprehensively consider the frictional action for springs stacked in both parallel and series was given. The effectiveness of the proposed formulas was verified by comparing with both the FEA and the test results. In addition, possible contacts between springs and the control bar would induce additional frictional actions, which can be compensated in some degree by appropriately adjusting the friction coefficients. Equivalent coefficients that can be employed in the formula of the standard to improve precision were provided.