Papers by Author: H.K. Lee

Abstract: A relationship of residual stress distribution and surface molding states on polymeric materials is presented in thin-walled injection molding. The residual stress is computed by computational numerical analysis, observed with stress viewer and birefringence. The residual stress on polymeric parts can allude the surface quality as well as flow paths. The residual stress distribution on polymeric parts is related with thickness, gate layout, and polymer types. Molecular orientation on polymeric parts is also important in thin wall injection molding. The residual stress and molecular orientation are related to the surface molding states intimately. Analysis of the residual stress is validated through photo-elastic method and surface molding states..

Abstract: Molding characteristics are presented for the surface pattern of polymeric materials in injection molding. They are related to the polymer properties and surface roughness of the etched mold. The polymer structure and the mold roughness can affect roughness deviation and surface duplication quality on polymers. Experiments are performed with respect to the surface roughness analysis. It is expected that the duplication properties can contribute to molding process of surface pattern in injection molding.

Abstract: A shape design optimization of the boom system in high ladder vehicle modeled by 3-dimensional finite elements is carried out. The structural analysis is performed using 3-D FEA (Finite Element Analysis) giving the results of displacements, stresses and natural frequencies. The section height and width of the boom is controlled by the FEA result data. The subproblem approximation method is implemented for the optimal shape based on displacement and principal stress. In the meantime, Lanzcos algorithm method is implemented in order to find the natural frequency of the system. The optimal models obtained by three different optimization processes are compared with the initial model and evaluated for economic conditions respectively. It is found that the different shape optimization processes give the different shape optimization results, which suggest their unique optimal shapes under their necessary design condition.

Abstract: Residual stress distribution and surface molding state of polymeric materials are presented for thin-walled injection molding. The residual stress is computed by computational numerical analysis, observed with a stress viewer and birefringence. The residual stress on the surface of the polymeric part can indicate the surface quality as well as flow paths. The residual stress distribution of the polymeric part is related with the part’s thickness, the gate layout, and the polymer type. Molecular orientation, affected by flow paths, is simulated and validated by observing the birefringence of the polymeric specimens. The residual stress and molecular orientation are closely related to the surface molding states.