ELECTRON ^IICKOSCOPY 



management should establish two distinctly tack of the surface by reactive compounds or 



different groups: a service group and an en- corrosive media and the subsequent rubbing 



tirely separate exploratory research group, or breaking away of the reaction products. 



The two groups carry out radically different The various wear processes may occur singly, 



functions which need no further defining. It simultaneously or in sequence. Progress in 



is unwise to mix the two. wear prevention can be made only after a 



Second, it is imperative that the person- real understanding of the basic mechanisms 



nel in these groups be different. Specifically, has been achieved. Toward this end micro- 



those people in the service group should be scopes and ancillary eciuipment are probably 



adept at preparing specimens, maintaining the most useful and widely used tools avail- 



and operating the instrument, cognizant of able to research workers and investigators 



the limitations of their techniques, and cer- (1). 



tainly conversant with a broad spectrum of The topography, chemical and physical 



people with whom they have to deal. In nature of surfaces can influence the wear 



short, they should be internal consultants, behavior of many materials, thus the starting 



On the other hand, those in the basic re- point of any investigation should be a study 



search group, having their own instruments, of the surfaces involved. Many techniques 



should be primarily chemists, physicists, are available to examine the topography of 



biologists, metallurgists, etc. They should be surfaces but optical methods allow the speci- 



left alone to "get lost" in their particular men to be investigated without destroying 



long-range programs. Communication be- it or subjecting it to strain or wear. Stylus 



tween the two groups should be encouraged methods provide an immediate numerical 



in the interest of mutual assistance. characterization of a surface, but may be 



As to the cost of duplicating equipment it subject to the uncertainty of the extent of 



may be said — and not facetiously — that damage done to soft materials by the stylus 



only money is needed to purchase the itself. The profile microscope (Tolansky (2)), 



instruments. Intelligent, productive people like stylus methods, gives a single line profile 



cannot be so easily obtained, whatever the and it may be necessary to observe many 



available funds may be. In short, equipment different recordings in order to form a com- 



is a comparatively inexpensive investment. prehensive conception of the surface. Ob- 



Franklin a. Hamm serving an enlarged image of the surface 



from above by normal microscopic examina- 

 tion is useful, but permits no conclusion 



WEAR AND LUBRICATION ,. ' ^ru ■ . ^■ 



regardmg roughness, the mterierence micro- 

 Wear may be defined as the displacement scope on the other hand can be used to re- 

 or removal of material from a surface ; it has veal and evaluate minute surface irregulari- 

 many forms, its nature and magnitude being ties. In the image these appear as deviations 

 dependent on a variety of factors. The more in the bands or fringes which represent con- 

 significant of these are speed, load, surface tour lines connecting all points of the same 

 condition, metallurgical structure, the pres- level (Fig. 1). The difference in level between 

 ence of abrasive matter and corrosive en- different fringes corresponds to half a wave- 

 vironment. The wear process can be classified length of the light used. The magnification 

 generally into two main types — mechanical is irrelevant and the geometric shape of the 

 and chemical. Mechanical wear involves test piece plays only a subordinate role, 

 processes which may be associated with In wear studies, suitable selection of the 

 friction, abrasion, fatigue and vibration, method of specimen illumination can extend 

 whereas chemical wear is caused by an at- the versatility and range of the modern 



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