ポリアセタール溶接部の低温特性に関する研究

Abstract

This paper discribes an experimental study on the characteristics at low temperature of welded polyacetal (Duracon). The results of some measurements on the mechanical properties, fracture surfaces and X-ray diffraction pattern are reported and discussed.This study intends to clarify the low temperature characteristics of weld comparing with those of base material, and to discuss the change in mechanical properties from room temperature down to the neighborhood of -70°C and fracture in low temperature experiment from a microscopic view point.Notch and load velocity effects on the brittle fracture tendency are also discussed. Testing materials were polyacetal board of 2 mm in thickness, and tests were carried out at low temperature of methylalchohol and dry ice. A heat plate welding apparatus, with which specimens could be secured under fixed contact force, was made in order to carry out the experiment of welding. The following summary can be made of the experimental results. Tendency of low temperature characteristics of the welded material is generally similar to that of the base material, except that a change of elongation occurs at each temperature. Effect of load velocity is observed both on the basic and the welded materials, and brittleness becomes great when the temperature is low and load velocity is high.Notch effect is also observed both on the base and the welded materials, and this effect appears great with the welded material and the base material. Correlations are observed between fractured surface and mechanical testing results, as well as between X-ray differaction pattern and mechanical testing results.