擠出磨耗之塑性力學分析

Abstract

擠出磨耗是一種近年來才被發現的現象 ，藉由銷盤實驗，可觀察到當負載及轉速達到某臨界值時銷的磨耗情形會突然加劇，此時銷部分的金屬會因高溫而變得較軟，易受剪力移除形成磨屑，且其過程常伴隨著火花。觀察磨屑的組成可發現大部分為金屬而非氧化物，這種情形與氧化磨耗有相當大地不同，我們稱之為擠出磨耗。 金屬軟化遭移除屬於一種塑變行為，故本文從塑性力學觀點並假設粗糙峰為高斯分佈去估算銷的擠出磨耗情形，計算結果顯示理論值與實際情形仍存在著一定的差距，約介於2~10倍之間。 因兩接觸面間的力學行為相當複雜且微觀，我們在計算過程中做了許多簡化及假設，也是導致誤差的主要因素，然而在如此小的數值下進行比較(均小於微米)，我們認為這樣的誤差是可接受的，也說明了利用塑性力學分析擠出磨耗是一個可行的方向。

Extrusion wear is a new phenomenon which was discovered in recent years. We can see from the pin-on-disc testing that the pin wear became severe suddenly when the speed and load exceeded some critical values. Meanwhile, the metal became softer because of high temperature and was sheared by tangential force. Some debris was thus formed with shinning sparks and its components were almost metal, but not oxide. This mechanism is quite different from oxidational wear and is now termed as extrusion wear. In this study, mechanics of plasticity was used to evaluate the extrusion wear of pin with Gaussian distribution assumption of asperity height. The result shows that there was still 2 to 10 times the gap between theoretical and real values. Lots of assumption and simplification was necessary in this study because the interaction between two contacting bodies is complicated and microcosmic. So we thought the gap may be acceptable, and it also indicated that plastic analysis is a feasible direction to analyze the behavior of extrusion wear.