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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.

Conventional crawler-type excavators have not had any suspension-like systems for the reduction of the road-induced vibration that is transmitted to an operator. In order to make the operator more comfortable when traveling, two kinds of vibration isolation elements in Fig.1(b) were newly introduced to the under-carriage system and their effects were investigated in this study. One of vibration isolation elements is the flexible bridge[1] made of multilayered rubber on steel plates instead of only steel. The other one is the flexible turn-table[1] between the center frame and cabin. In this experimental study, the effects of the vibration isolation elements on the vibration responses at the seat floor were analyzed for three types of off-roads. As analysis tools, power spectral densities of accelerations at the cabin floor, ride values for the assessment of ride comfort and vibration duration time permissible for human body based on British Standards[2] were used.

Little attention has been paid to static-strain-dependence of dynamic complex modulus of viscolelastic materials so far. Hence, current commercial Finite Element Method(FEM) codes do not take such characteristics into consideration in constitutive equations of viscoelastic materials. Recent experimental observations that static-strain-dependence of dynamic complex modulus of viscolelastic materials, especially filled rubbers, are significant, however, require that solutions somehow are necessary. In this study, a simple technique of using a commercial FEM code, ABAQUS, is introduced, which seems to be far more cost/time saving than development of a totally new software with such capabilities. A correction factor is used to reflect the influence of static-strains in Morman model, which is the base of the ABAQUS.

Motion-sickness is one of the major topics in research of human responses to vibration especially in the very low frequency range. For a study of this motion-sickness, measurements of 6-degree of freedom (DOF) movement of the human head for a long duration must be made. A safety helmet and accelerometers can be employed to measure the 6-DOF human head motion. This paper presents several problems and results in this approach.

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.

Dynamic properties of flexible polyurethane foam materials for car seats are highly complicated. In this paper, characterizations of dynamic stiffness of several foam specimens based on static stiffness obtained from IFD(Indentation Force Deflection) curve measurements are presented. It is observed that dynamic stiffness and its drift with static loading duration in logarithmic scale are proportional to the static stiffness at a given static loading regardless of types and dimensions of the foam. A three degree-of-freedom model of seated human body based on apparent mass measurements together with the characteristics of foam materials were incorporated for transmissibility prediction of the passenger-seat system.

This paper presents a study on using rubber bushing as a sensor for the identification of forces transmitted onto the car body. The method starts from the idea that the transmission forces can be related to the deformation of the rubber bushing multiplied by its stiffness. Deformation of the rubber bushing is estimated from relative vibrations across the bushing. Simple theories are presented to deal with modeling of the rubber bushing and processing of the vibration mesurements on the link and car body to identify the transmission forces. Then, validity of the proposed approach is shown by applications to a suspension system under several driving conditions.