Lube-Tech PUBLISHED BY LUBE: THE EUROPEAN LUBRICANTS INDUSTRY MAGAZINE
the capability to provide guaranteed or specific performance properties and must be repaired in order to restore the predefined nominal condition. Wear-out (connotated in German as “Abnutzung”) is defined in DIN 31051-2019 (section 3.3.1) as follows:
“Degradation of the wear reserve caused by chemical and/or physical processes”.
Note 1: Such processes are caused by different stresses, e.g. by friction, corrosion, fatigue, ageing, cavitation, fracture, etc. Note 2: Wear-out is unavoidable.
DIN 50320:1953-11 and TGL 0-50320, April 1963, described wear-out as follows: “The term ‘wear-out’ should be used as a generic term for mechanical impact (wear), chemical or electrochemical impact (corrosion) as well as for thermal and other impacts” (see 2.i.).
Thus, the use of the word stem “wear-out” in connection with combined or complex stress is emphasised in GfT worksheet no. 7 (2002) under entry no. 2 “Abnutzung-Wear-Usure” as “undesirable reduction in the utility value of objects due to mechanical, chemical, thermal, and/or electrical energy effects (see also DIN 31051)”.
“Depreciation for wear-out of fixed assets” is firmly anchored in business management, accounting and tax law. Wear-out parts and wear parts are eventually synonymous variants. This creates a certain conceptual coherence between tribology, engineering and business administration (accounting). Overall, this results in a tripartite division into the terms “spare part, wear part and wear out part”.
Definition of ‘wear part’
As part of an intensive consensus finding process, GfT suggests to condense the following definition by limitation to tribological stresses [6]:
“A wear part is a replaceable part, subassembly or assembly identical to and inter-changeable with
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the object it is intended to replace, all with the purpose of restoring the loss of function caused by wear mechanisms impairing either product or part.”
Note: Wear mechanisms according to GfT worksheet 7 (2002): adhesion, abrasion, surface fatigue, tribochemical reaction.
Definition of “wear-out part” The term “wear-out” appears today as a new coinage, but it had been predefined in the past (see Chapter 2). Since an object no longer functional is widely considered and in daily language termed as “worn”, the term ‘wear part’, terminologically restricted to tribological aspects, is commonly used in a much broader sense. A seal, for example, usually fails due to shrinkage, swelling, and post-crosslinking, but not due to “wear”. Nevertheless, a seal showing leakage is generally considered worn.
The word stem “wear-out” covers functional/value losses due to complex or combined stresses and leads to the term “wear-out part,” which distinguishes it from a wear part. The extension of the term “wear part” for mechanical components or for systematically designed product systems beyond immediate tribology results in the following definition for the term “wear-out part”: “A wear-out part is a replaceable part, component, device, subsystem, functional unit, operating medium or system identical to and interchangeable with the object it is intended to replace, for the purpose of restoring the value or function of a faulty or defective product or a part consumed as intended.”
Note: In addition to tribological wear, also corrosion, degradation, oxidation, diffusion and fatigue. can be subsumed as failure mechanisms (defects) or reasons for a reduction in functionality or value.
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