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Design of geometric shape for visco-elastic vibration isolation elements is frequently based on experiences, intuitions, or trial and errors. Such practices make it often difficult for drastically different or new concepts to come out. In this paper, both a topological method and a shape optimization method are combined together to find out a most desirable isolator shape efficiently by using two commercial engineering programs, ABAQUS and MATLAB. The procedure is divided into two steps. At first, the topology optimization method is employed to find an initial shape, where material density of each finite element is chosen as either 0 or 1 for physical realization. Based on the initial shape, then, finer tuning is done by the boundary movement method. An illustration of the procedure is presented for a vehicle engine mount and the effectiveness will be discussed.

Several mechanical models with lumped mass were employed in the literature to represent strongly frequency-dependent characteristics of hydraulic engine mounts. Although complex stiffness by the mechanical models showed good agreements with the measured values, there exists a critical pitfall. The fact is that the complex stiffness model was derived at the driving point while measurements were obtained across the mounts. That is, the point stiffness model was mistakenly compared with the transfer stiffness measurement. In this paper, limitations of the mechanical model with lumped mass are discussed by illustrating actual measurement results of the stiffness matrix.