Published: Jan 1937
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Among the many meanings which one finds in the dictionary for the word wear is “impairment by use,” or “loss by the service, exposure, decay or injury incident to ordinary use.” This interpretation suggests more than mere displacement of material as the result of physical contact and is especially useful in discussing wear from the viewpoint of power equipment. In many cases, the impairment by use is certainly due to more than a single influence. For example, there are many cases where corrosion and mechanical or physical action are obviously present together and are jointly responsible for the impairment experienced. It is believed that inability to appreciate such joint action, or failure to determine and treat with the predominant influence, may at times have delayed the solution of some wea problems. Possibly an example from every day observation may better illustrate the point. In the early spring we do not have to look far to find a highway in a worn condition. It is rough and torn, pitted, cracked, and broken; we say it is worn, or that wear has taken place. But many influences have combined to cause the worn state. The physical contact of metal and rubber on the road material; the more serious abrasion at traffic light positions from rapid braking and the accompanying impact and grinding of chains on trucks; the repeated compressive loads, especially from heavier vehicles; the effects of heating and cooling, and freezing and thawing; the erosive effect of rains and flowing water; the dissolving effect of water; the hydraulic pressures set up when rubber presses down into pits full of water; the washing out of subbase soil; the decay of concrete or binder material; these are the various types of influence that go to build up the general condition that we call wear. In the power-equipment field, one encounters two general situations, which are often quite opposed to each other. Power equipment makes use of many moving metal parts. Both moving and fixed metal parts are not only often in contact with each other, but invariably subject to the action of a variety of non-metallic materials in solid, liquid and gasecus form. Some of these materials are abrasive, while others are quite corrosive. Water conditions, the nature of the steam, and the nature of fuels vary greatly throughout the country. Operating conditions will differ in many ways.
Mochel, Norman L.
Metallurgical Engineer, Westinghouse Electric and Manufacturing Co., Philadelphia, Pa.