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Ullmann’s Encyclopedia of Industrial Chemistry, 40 Volume Set



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Author: Wiley-VCH

Publisher: Wiley-VCH

Genres:

Publish Date: February 24, 2003

ISBN-10: 3527303855

Pages: 30080

File Type: PDF

Language: English

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Book Preface

Practical experience with industrial equipment,machinery, and plant has shownthat components have only limited service lives. Damage and ultimate failure of the component can occur as a result of changes in the material that originate at the surface, even if the components are designed such that long-term action of the forces alone causes neither fracture nor undue deformation.

If the reactions responsible for the damage are of electrochemical or predominantly chemical nature, the term corrosion is normally used, whereas mechanical damage to the surface of the component is defined as wear. Attempts to avoid a loss of material due to wear, or at least to reduce the loss, concentrate on making the affected surface more resistant to wear. This can be achieved by mechanical, thermal, or thermochemical treatment of the surface or by applying or depositing metallic coatings. Under some circumstances the wear conditions can be changed by design measures so that the danger for the affected component surface is eliminated or reduced to a tolerable level.

With fewexceptions (e.g., running-in of bearings), wear in engineering means an undesired change that causes very high costs every year; in a highly developed, industrialized country this can amount to ca. 1 – 2 % of the gross national product [1].

Plant construction typical of the chemical industry plays an insignificant role, and wear is correctly known as “the problem child of mechanical engineering” [2].

Wear, friction, and lubrication are described under the term tribology as the science of the study, industrial application, and modification of the phenomena and processes occurring between surfaces which are acting against each other and moving relative to one another; this includes boundary surface interactions between solids, and between solids and their gaseous or liquid surroundings. Since at least two components of a system are involved in wear, it is not a pure material characteristic, but only a system characteristic. Wear itself is generally understood as progressive loss of material from the surface of a solid body caused by mechanical action, i.e., contact and relative motion with a solid, liquid, or gaseous phase.


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