| dc.description.abstract | The wear behavior, mechanical properties and microstructure of injection molded ultra high molecular weight polyethylene (UHMWPE) parts has been studied. As far as tensile strength is concerned, the influences of process conditions and cross-sectional dimensions on the tensile strength of a weld line are investigated. In addition, the weld line characteristics of structures and different cross-sections are explored in this study as well. Five specimens, with different cross-sections, are injection molded simultaneously. With the Taguchi method, three process variables including melt temperature, mold temperature, and injection velocity were found to be the most significant. Furthermore, in order to understand more about the effect of the process parameter, the single-factor experiments are used. Experimental results show that the parametric influence is relatively little on the cross-sectional dimensions. The results also show that the tensile strength and surface hardness are affected at injection molding conditions and sliding contact loads. As far as wear behavior is concerned, experimental results show that the different wear contact loads and varied injection molding conditions have an influence for friction coefficient and wear volume loss of UHMWPE specimens. The higher sliding contact load results in a lower friction coefficient. Moreover, lower wear volume loss is often occurred in the specimen molded with the highest injection molding level. The morphologies of the worn surfaces and the cross-section of specimens were examined with optical microscope and scanning electron microscope, respectively. Plastic deformation, grooves and wavelike formation are the main wear mechanism on the surface in wear tests of UHMWPE. As far as microfabrication is concerned, replication accuracy was investigated for microinjection molding and microinjection compression molding. The mold insert was fabricated by stainless steel metal etching method. The mold insert includes rectangular groove of 100 μm, circular groove array of 100–300 μm and square groove array of 100–300 μm. Both the microinjection molded part and the microinjection compression molded part were observed under microscope to compare the replication accuracy. To measure the microstructure profile, a high performance surface profiler was used. Among mold insert, microinjection molded parts and microinjection compression molded parts were measured. The experiment results show that the UHMWPE can be filled in microcavities by microinjection molding and microinjection compression molding technology. The height and shape of microstructure were influenced by injection molding process parameters. For an injection molded part, injection velocity was the most influential factor. The height and shape of microstructure shows that microinjection compression molding was a more stable process than microinjection molding, due to it can provide an enough compression force.
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