Recently, with the expansion of application of polymer composite materials, high levels of deformation compensation actions have been developed. However, there is a problem of high-temperature viscoelasticity that occurs over time after completing the injection molding process. In this study, changes of mechanical properties of the Moldflow program for injection molding were analyzed to verify the viscoelasticity phenomenon through deformation analysis. In addition, deformation analysis of plastic injection molded products according to arrangement of three ribs was conducted and two products with different geometric shapes of the same function were compared. As a result, it was possible to reflect the viscoelastic effect by reducing the elastic modulus and shear modulus of the material. It was confirmed that the geometric shape with thick ribs formed in multiple longitudinal directions was mainly responsible. On the surface of the product where the rib arrangement was parallel and perpendicular to the flow direction, the orientation was orthogonal to the linear direction and the maximum residual stress was 81.17 MPa, which showed the largest value. It was judged that viscoelastic phenomena could be predicted and that an arrangement of parallel and perpendicular ribs that might intersect should be avoided.

Elastomeric bushings are structural elements that are used in automotive suspension systems. An elastomeric bushing is a hollow cylinder that is contained between an outer steel cylindrical sleeve and an inner steel cylindrical rod. The outer steel cylindrical sleeve is connected to the components of the suspension system and is used to transfer forces and moments from the wheel to the chassis. The elastomeric material reduces the shock and vibration in this connection. Dynamic simulations of the automotive suspension system involve the interaction between many components. The accurate determination of the transmitted forces and moments between the components, the motion of the components, stress in the components, and energy dissipation is affected by the quality of the bushing model. Several Pipkin-Rogers models have been proposed for the axial mode, radial mode, and torsional mode and modified Pipkin-Rogers models have been proposed for the axial mode and torsional mode. In this research, the modified Pipkin-Rogers model for the torsional mode was verified in a frequency-related rotational angle control test. The results showed that the moment outputs of the modified Pipkin-Rogers model were in very good agreement with those of the Pipkin-Rogers model in the sinusoidal rotational angle control test.

Elastomeric bushings are structural elements and used in automotive suspension systems. An idealized bushing is an elastomeric hollow cylinder between an outer steel cylindrical sleeve and an inner steel cylindrical rod. The outer sleeve is connected with the components of the suspension system and transfer forces and moments from the wheel to the chassis. The accurate determination of the transmitted forces and moments among autocomponents, the motion of the components, the stresses in the components, and energy dissipation are affected by the quality of the elastomeric bushing model. Force- Displacement relation, moment-rotational angle relation, and coupled relations for elastomeric bushings are imperative for multi-body dynamics simulations. The boundary value problem in the bushing response leads to force-displacement relation and moment-rotational angle relations which require extensive computation time for implementation. Herein, an explicit moment-rotational angle relation has been introduced for use in multi-body dynamics simulations, a modified Pipkin-Rogers model is proposed and a boundary value problem is formulated for torsional mode elastomeric bushing response. Lianis" experimental equation and Pipkin-Rogers model are used for numerical experimental research. The proposed method and the prediction of the proposed moment-rotational angle relation are observed to exhibit excellent agreement with the original results.

Finite element analysis of CMP process was studied to understand uneven pressure distribution between polishing pad and wafer. Since WIWNU (Within wafer non-uniformity) is mainly influenced by dynamic viscoelastic properties of CMP polishing pad, the dynamic property of the polishing pad has to be understood first for dynamic finite element analysis of the process. To measure viscoelasticity of the polishing pad, time-dependent strain data by load were obtained using a viscoelasticity measurement system capable of measuring deformation by periodic load. Primary and secondary elastic modulus and relaxation time could be achieved for the behavior of the polishing pad by load. Finite element analysis was carried out under the same conditions as viscoelastic measurement. Material properties of the polishing pad were assumed based on results of experiments. By comparing experimental results with analytical results, material properties in the analytical model were modified and FEA was carried out again. It was confirmed that the behavior of the polishing pad by load in the experiment and FEA according to modified material properties were well matched. Through this process, viscoelastic properties of polishing pad were well defined for dynamic analysis of CMP process.

Elastomeric bushings are structural elements used in automotive suspension systems. A bushing is a hollow cylinder between an outer steel cylindrical sleeve and an inner steel cylindrical rod. The steel sleeve is connected to components of the suspension system and transfers forces from wheel to chassis. Force-Displacement relation for elastomeric bushings is critical for multi-body dynamics simulations. A boundary value issue for bushing response leads to force-displacement relation that requires extensive computation time to implement and therefore is unsuitable. Explicit force-displacement relation may be used in multi-body dynamics simulations. The relation is expressed in terms of a force relaxation function. Lianis model, Modified Lianis model, and Pipkin-Rogers model are introduced. Modified Pipkin-Rogers model was proposed and a boundary value issue was formulated for axial mode bushing response. Numerical solutions of the boundary value issue of Modified Pipkin-Rogers model were compared with results of the Pipkin-Rogers model. It is revealed that the method for determining bushing relaxation function and prediction of proposed force-displacement relation is in agreement with the original results.