穴開き平板のそりにおける空隙含有率の影響
Void Ratio and Warpage of an Injection Molded Plate
菊池博之・小山清人
Kikuchi, Hiroyuki / Koyama, Kiyohito
Warpage of a plate with holes (voids) were investigated with warpage index (ψm1)) and with finite element analysis. ψm is proportional to the difference of total strain and thermal strain. ψm indicates the degree of restriction in thermal shrinkage in an injection molded part. In thermal stress analysis, ψm is calculated with respect to thermal load which is proportional to the product of linear thermal expansion coefficient and temperature difference. A plate with holes is a representation of an internal structure of a plate made with a processing method in which voids are intentionally generated inside the plate. Gas-injection molding or foam-injection molding are two examples of this processing method. Thermal stress analysis and buckling analysis were conducted for plates with voids, which were injection molded with PA66 compounded with 30 weight % glass fiber. Correlations among volumetric void fraction, buckling mode, buckling temperature and ψm were studied. For obtaining anisotropic material properties, flow field in injection molding was calculated, the interaction between the flow field and glass fiber was simulated, and fiber orientation states were calculated. Clear correlation between void fraction and warpage was found.
Key words: Warpage index /Anisotropy /Void ratio /Finite element / Injection molding