Table 2 Operational classification of wear situations Motion Environment Mechanisms Two-body contact Rolling Without particles Fatigue Adhesive With slip With particles Fatigue Adhesive Abrasive Without slip Fatigue Trends: Wear increases with increasing slip and presence of particles. Adhesive and abrasive wear modes can predominate but with pure rolling fatigue modes predominate. Mildest wear situation. Smooth surfaces preferred Impact With stationary body Fatigue (elastic or plastic) Dry, without particles Fatigue (elastic or plastic) Adhesive Dry, with particles Fatigue (elastic or plastic) Adhesive Abrasive Fluid, without particles Fatigue (elastic or plastic) Adhesive With moving body Fluid, with particles Fatigue (elastic or plastic) Adhesive Abrasive Trends: With stationary body, induced vibrations and misalignment can cause fretting, which tends to increase wear. Plastic deformation generally unacceptable except in short life applications. For lives greater than 10 6 , contact stresses need to be in the elastic range. With moving object, wear increases with the amount of sliding and sliding effects can predominate. Fluid lubrication effects can be very significant. With particles, wear tends to increase. Sliding Dry Fatigue Adhesive Fluid Fatigue Adhesive Unidirectional Particles Fatigue Adhesive Abrasive Large amplitude, dry Fatigue Adhesive Large amplitude, fluid Fatigue Adhesive Large amplitude, particles Fatigue Adhesive Abrasive Small amplitude, dry Fatigue Adhesive Small amplitude, fluid Fatigue Adhesive Cyclic Small amplitude, particles Fatigue Adhesive Abrasive Trends: More than one type of mechanism involved. Fatigue mechanism is mildest and conditions that minimize adhesion and abrasion preferred. Low contact stresses preferred. Mild to severe wear transitions often associated with the transition from elastic to plastic deformation. Predominant mechanisms(s) can change with wear. In mild wear situations, terminal mode often fatigue. With the presence of particles, abrasion tends to become predominant mode. Nature of contact shape, such as large area, conforming, line, and point, can be significant in wear behavior. One-body contact with fluid Impingement Without particles Fatigue Low angle With particles Abrasive (cutting) Without particles Fatigue High angle With particles Fatigue Abrasive (deformation) Flow Without particles None Streamline With particles Abrasive (cutting) Without particles Fatigue Turbulent With particles Fatigue Abrasive Trends: In flow situations, without particles, cavitation wear mechanism. Impinging fluid droplets act like particles. Corrosion effects often present General comments: With fluids other than lubricants, synergistic effects between corrosion and wear often occur. In all situations, oxidative wear effects are probable with metals and ceramics. Operational characterization may be different for different locations on a part. Source: Ref 8 Table 3 Wear models for design Sliding General model V = kL m S n K factor model V = KLS Zero wear model (conditions for zero wear) max 0.54 y 2000( R y ) 9 = (S/W) ( max ) 9 Measurable wear model (a) Variable energy mode d[Q/ ( max W) 4.5 ] = Cd (S/W) Constant energy mode dQ = Cd (S/W) Impact Percussive impact model V = kv m N Zero wear model (condition for zero wear) (b) N 0 = (2000/1 + ) [ R ( / y )] 9 Measurable wear model (c) dV = (V/N) dN + g(9V/ ) d Rolling General model V = kL m N Surface endurance model (condition for surface cracks) N 1 = N 2 Load-stress factor model L e = K 1 {w/[(1/R 1 ) + (1/R 2 )]} log K 1 = [(B - log N)/A] Abrasion General model V = kLS Erosion General model (d) e = KAI Liquid drops model e = K sin n Mv m Particles model e = [K d v n cos n sin ( / ) + K b v m sin m ] M Vibration-induced cavitation model e = K n Jet-induced cavitation model e = Key to symbols A Function of attack angle e Erosion rate I Function of stream intensity L Load L e Endurance load M Erodent rate N Number of impacts N 0 Zero wear life (impacts) Q Cross sectional area of scar S Sliding distance v Velocity of impact (impact model); velocity of drops or particles (erosion model) V Volume of wear v j Velocity of jet W Length of contact area Angle of incidence Ratio of surface damage to subsurface damage in compound impact situations (impact model); tribosystem empirical coefficient (erosion model) Amplitude of vibration Peak contact pressure y Yield point in tension max Maximum shear stress y Yield point in shear C, k, K, K b , K d , m, n, R , R Tribosystem empirical coefficients Source: Ref 8, 9, 10 (a) Zero wear model for sliding can be used to determine C. (b) = 0 for pure impact. (c) For constant-energy mode, g = 0. For variable-energy mode, g = 1. (d) Where K is a function of time, A is a function of angle, and I is a function of stream intensity. References cited in this section 2. A.F. Bower and K.L. Johnson, J. Mech. Phys. Solids, Vol 37 (No. 4), 1989, p 471-493 3. K. Johnson, Proc. 20th Leeds-Lyon Symp. Tribology, Elsevier, 1994, p 21 4. F. Aleinikov, Soviet Phys Tech. Phys., Vol 2, 1957, p 505, 2529 5. P. Blau, Friction and Wear Transitions of Materials, Noyes Publications, Park Ridge, NJ, 1989 6. N.C. Welsh, Proc. Royal Society, Vol A257, 1965, p 31 7. S.C. Lim and M.F. Ashby, Acta Metall., Vol 35, 1987, p 1-24 8. R.G. Bayer, Mechanical Wear Prediction and Prevention, Marcel Dekker, 1994 9. P. Blau, Ed., Friction, Lubrication, and Wear Technology, Vol 18, ASM Handbook, ASM International, 1992 10. M. Peterson and W. Winer, Ed., Wear Control Handbook, American Society of Mechanical Engineers, 1980 Design for Wear Resistance Raymond G. Bayer, Tribology Consultant Lubrication Friction is the resistance to relative motion between two bodies in contact. A lubricant is defined as any substance that reduces the friction between two surfaces. The use of these materials is one of the principal ways of reducing wear and extending the life of mechanical equipment. Lubricants provide a low shear interface between surfaces by physically separating those surfaces and by allowing the formation or modification of surface films on those surfaces. While the principal effect of lubrication on wear behavior is associated with the reduction of adhesive wear, the other types of mechanisms can also be affected by the presence of a lubricant. For example, mechanisms that are influenced by shear stresses, such as some deformation and fatigue mechanisms, can be affected by changes in traction caused by the use of a lubricant. Oxidation wear mechanisms can be affected by the changes in surface films resulting from the use of a lubricant. Lubricants can also inhibit or modify the formation of tribofilms. In general, lubricants tend to reduce wear. However, there are some situations in which they can increase wear. For example, they may inhibit the formation of a beneficial tribofilm without providing adequate lubrication. This is often the case in tribosystems in which self-lubricating materials are used. Another example is abrasive wear situations, where abrasive particles tend to agglomerate or where wear debris can clog an abrasive counterface. These actions tend to reduce abrasive wear rates, but in these situations, lubricants tend to prevent the agglomeration or clogging, which leads to a higher wear rate. In abrasive wear situations a lubricant can also reduce the critical angle for cutting, which also tends to increase wear. Lubrication can also affect wear behavior in other ways. In circulating systems, lubricants can provide cooling to the interface and remove wear debris. In non-circulating systems, oil and grease films tend to hold abrasive particles in dirty environments, which can lead to increased wear. Except for abrasive and erosive wear situations, the effective application of lubrication generally results in mild wear behavior. Severe wear behavior in a lubricated situation is often an indication of lubricant breakdown, improper lubricant selection, or an inadequate supply. Even though one of the ways a lubricant works is to separate the surfaces, thick lubricant layers are not required to obtain significant improvements in wear performance. Thin films, even down to monomolecular layers, can have significant effects provided that they are maintained. Lubrication by thin films is often referred to as boundary lubrication. Its effectiveness primarily depends on the ability of the lubricant to coat or react with the surface. With fluids it is possible to generate thicker films as a result of squeeze film effects in the fluid. As a result of these effects it is sometimes possible to achieve complete separation of the surfaces, which virtually eliminates wear. This is referred to as fluid lubrication. (Design procedures for lubrication are beyond the scope of this article and can be found in books on bearing design and fluid lubrication.) The state of lubrication between boundary and fluid lubrication is called mixed lubrication. Wear rates are lower with mixed lubrication than with boundary lubrication (Ref 11). By using almost any lubricant, wear rates are generally reduced by one to two orders of magnitude. However, there can be significant differences in the lubricating abilities of different lubricants, so it is often possible to obtain larger reductions (e.g., several orders of magnitude) by optimizing the selection. Lubricant selection for a wear application often involves two other elements. One is supply of the lubricant. If there is an inadequate supply, wear rate will increase, as shown in Fig. 4. The other is the chemical stability of the lubricant in the application. Generally, when a lubricant degrades, its ability to protect the surface is decreased and wear rates increase. Fig. 4 Effect of oil supply rate on the wear of a high- speed printer component. Wear occurred at the interface between a pivoting type element and a type carrier backstop . The materials were hardened steel. The wear resulted from a combination of impact and fretting. Source: Ref 12 Types of Lubricants. Lubricants are either fluids or solids. The fluid category includes gases, liquids, and greases. Common solid lubricants are molybdenum disulfide, polytetrafluoroethylene, graphite, and soft metals. Because fluids tend to be displaced easily, other materials are frequently added to enhance their boundary lubrication characteristics. Solid lubricants and reactive compounds are often used in greases and oils for this reason. These types of additives are generally called extreme pressure (EP) additives. Solid lubricants are also used as fillers in plastics to make self- lubricating materials. With these materials the solid lubricants provide lubrication by forming tribofilms on the rubbing surfaces. While fluid films tend to be more easily displaced than solid lubricant films, they have the ability to self-heal. Solid lubricant layers do not. However, this limitation of solid lubricants is removed when they are used as additives and fillers (Ref 13). While lubrication is used to reduce both friction and wear, the effects that a lubricant has on each of these phenomena can be different. As a consequence, the best lubricant for friction reduction is not necessarily the best for wear reduction. Often the coefficients of friction can be similar for different lubricants, while wear rates can differ by orders of magnitude. Table 4 contains data that illustrate these two points. Table 4 Effect of different lubricants on friction and wear for reciprocating sliding in a ball-plane Steel/steel Stainless steel/steel Oil Coefficient of friction Depth of wear, m Coefficient of friction Depth of wear, m A 0.14 1.93 0.16 0.30 B 0.24 0.65 0.13 0 C 0.38 0.95 0.18 0.13 D 0.14 0 0.13 0.45 E . . . . . . 0.16 0.23 References cited in this section 11. E.R. Booser, Ed., Handbook of Lubrication, Vol II, CRC Press, 1984 12. R. Bayer, Wear, Vol 35, 1975, p 35-40 13. E.R. Booser, Ed., Handbook of Lubrication, Vol III, CRC Press, 1994 14. IBM General Products Division Technical Report TR 01.17.142.678, 10 April 1962 Design for Wear Resistance Raymond G. Bayer, Tribology Consultant Material Selection for Wear Applications Some fundamental criteria can be applied in the selection of a material for wear applications. The primary criterion is that the material remain chemically, mechanically, and thermally stable under the operating conditions. A secondary criterion is that the nominal contact stresses be within the elastic range of the material. If either of these criteria is not met, it is likely that severe wear behavior and unacceptably high wear rates will result. For long life under sliding it is generally desirable to have a 2-to-1 or larger ratio between yield point and nominal contact stress. For impact and rolling this ratio can be smaller, approaching 1, and still be acceptable, In abrasive wear situations, it is generally desirable to have the material harder than the abrasives present, or at least of comparable hardness, to minimize wear and obtain long life. A corollary is that if a particular material must be used, the conditions of use need to be changed so that these criteria are satisfied. As stated above, material wear resistance is not an intrinsic property, like elastic modulus or density. It tends to vary with the wear situation and is best viewed as a system response. While there is a general trend for wear to decrease with increasing hardness, there is considerable scatter about that trend. As a consequence, material hardness is generally not a sufficient indicator of wear resistance or wear performance in specific situations. It is often necessary to consider other properties of the material as well. Basically this is because hardness is not the only material property that is associated with wear behavior, and because the differences between materials are not limited to hardness, particularly in the case of different types or classes of materials. Because of the many factors associated with wear behavior, different types of materials tend to be used for different wear situations (Ref 15). Table 5 provides an overview of typical wear applications for different classes of materials. Table 5 Typical wear applications for selected engineering materials Sliding Rolling Materials Unlubric ated wear Lubrica ted wear Abrasi on Unlubric ated wear Lubrica ted wear Abrasi on Impa ct wear Three -body abrasi on Fluid erosi on Cavitati on Drop erosi on Parti cle erosi on Structural alloys Surface treatments X X X X X Hard surfacing X X X X X X X X Soft coatings X X X Alloy steels X X X X X X X X Tool steels X X X X X X X X X Stainless steels Precipitatio n hardened X X X Martensitic X X X X X X Cast irons Graphitic X X X X X X White X X X X High- temperatur e alloys Refractory materials X X X X Superalloys X X X X X Copper- base alloys Bronze X X Beryllium copper X X Soft bearing alloys (babbitts) X Carbides X X X X X X X Ceramics X X X X X X Polymers Thermosets X Thermopla stics X X X Elastomers X X X X X X X Carbons X Lubricatin g composites X X Source: Ref 8 Because of the system nature of wear, rankings of materials in terms of their wear resistance often change with the nature of the wear applications or the nature of the wear test used to determine the rankings. For example, rankings obtained from abrasive wear tests are typically not the same as those obtained from nonabrasive wear tests. Similarly, different rankings tend to be obtained in lubricated and unlubricated tests or in high- and low-speed tests, among others. Because of this, wear tests used to rank or evaluate materials for use in specific situations need to simulate the wear application in all essential details (Ref 8, 16, 17, 18, 19, 20, 21). The basic elements that need to be considered in simulation are loading conditions, contact geometry, motions involved, and environmental conditions. Highly wear-resistant materials are often materials that maintain average wear characteristics under extreme conditions, such as high ambient temperatures or a corrosive environment. As a result, these kinds of materials may provide no better and sometimes poorer wear performance than other materials in situations where these extreme conditions do not exist. References cited in this section 8. R.G. Bayer, Mechanical Wear Prediction and Prevention, Marcel Dekker, 1994 15. B. Bhushan and B.K. Gupta, Handbook of Tribology, McGraw-Hill, 1991 16. R.G. Bayer, Ed., Selection and Use of Wear Tests for Metals, STP 615, American Society for Testing and Materials, 1976 17. R.G. Bayer, Ed., Wear Tests for Plastics: Selection and Use, STP 701, American Society for Testing and Materials, 1979 18. R.G. Bayer, Ed., Selection and Use of Wear Tests for Coatings, STP 769, American Society for Testing and Materials, 1982 19. C.S. Yust and R.G. Bayer, Ed., Selection and Use of Wear Tests for Ceramics, STP 1010, American Society for Testing and Materials, 1988, 20. A.W. Ruff and R.G. Bayer, Ed., Tribology: Wear Test Selection for Design and Application, STP 1199, American Society for Testing and Materials, 1993 21. Mechanical Testing, Vol 8, Metals Handbook, 9th ed., American Society for Metals, 1985 Design for Wear Resistance Raymond G. Bayer, Tribology Consultant Wear Models Because of the complex nature of wear behavior, there is no universal wear model that is applicable to all situations. However, there are wear models that can be used for design for specific situations (Ref 8, 9, 10, 22). There are models for generic wear situations, such as rolling and sliding, as well as models for specific devices, such as journal and roller bearings. Table 3 contains a list of models used for sliding, rolling, impact, and erosion. Table 6 lists some application models. These models provide relationships between wear and design parameters in a number of forms. In some cases the relationships are for the amount of wear, others are for wear and erosion rates, and still others are for equivalent wear conditions (i.e., those combinations of load and usage that result in the same amount of wear). Table 6 Application wear models • AFBMA model for ball bearings • AFBMA model for roller bearings • Taylor model for tool wear • PV model for plastic bearings • K factor model for journal bearings • Zero/measurable wear model for journal bearings • Impact wear model for elastomers • Type wear in impact printers AFBMA, Antifriction Bearing Manufacturers' Association. Source: Ref 8, 9, 10, 11 All these models involve one or more empirical coefficients, which are material and environment dependent. While empirical, they tend to be heuristically related to or based on a variety of general physical concepts and mechanisms. These heuristic concepts can often be used as an aid in the application of these models to particular situations. For example, they are often of use in estimating the values for the empirical coefficients, in evaluating the applicability of a model to a given situation, or in extending a model. In-depth treatment of these models and their use can be found elsewhere (Ref 8, 9, 10). While there are a number of different models available for design use, most wear situations encountered in design can be adequately covered with the use of relatively few. The zero wear model for sliding (Ref 8, 23), the measurable wear model for sliding (Ref 8, 24), the zero wear model for impact (Ref 8, 25), the measurable wear model for impact (Ref 8, 26), and the surface endurance model for rolling (Ref 8, 27), summarized in Table 3, are applicable in most engineering situations where abrasion is not predominant. In those situations in which abrasion predominates, the abrasive wear model given in Table 3 provides good correlation with performance. The coefficients of the models are determined from wear tests that match the conditions required by the model. In most cases not all of the coefficients of the model can be determined simply by measuring wear after a certain amount of time, sliding distance, or number of operations. It is generally necessary to develop a wear curve or series of wear curves that can be analyzed to determine the coefficients for the model. A wear curve is a plot of wear versus time, sliding distance, or number of operations. While laboratory tests are often used to determine values for different materials and environmental conditions, it is sometimes possible to analyze existing hardware data to determine the coefficients. In situations where there is neither available data for the specific materials or environmental conditions involved in the application nor the ability to perform the appropriate tests, it is generally possible to estimate the values, based on published data regarding these models. Such information can be found in Ref 8, 9, 10 and 15. References cited in this section 8. R.G. Bayer, Mechanical Wear Prediction and Prevention, Marcel Dekker, 1994 9. P. Blau, Ed., Friction, Lubrication, and Wear Technology, Vol 18, ASM Handbook, ASM International, 1992 10. M. Peterson and W. Winer, Ed., Wear Control Handbook, American Society of Mechanical Engineers, 1980 11. E.R. Booser, Ed., Handbook of Lubrication, Vol II, CRC Press, 1984 15. B. Bhushan and B.K. Gupta, Handbook of Tribology, McGraw-Hill, 1991 22. K. Ludema and R.G. Bayer, Ed., Tribological Modeling for Mechanical Designers, STP 1105, American Society for Testing and Materials, 1991 23. R.G. Bayer, W.C. Clinton, C.W. Nelson, and R.A. Schumacher, Wear, Vol 5, 1962, p 378-391 24. R.G. Bayer, Wear, Vol 11, 1968, p 319-332 25. P. Engel, T. Lyons, and J. Sirico, Wear, Vol 23, 1973, p 185 26. P. Engel and R.G. Bayer, J. Lubr. Technol., Oct 1974, p 595 27. G. Talbourdet, Paper 54-Lub-14, American Society of Mechanical Engineers, 1954 Design for Wear Resistance Raymond G. Bayer, Tribology Consultant Wear Design Wear design involves four elements (Ref 8): system analysis, modeling, data gathering, and verification. System analysis is the starting point of a wear design. It begins with the examination of the design and the identification of possible wear points or concerns. It then involves the characterization of the tribosystem associated with each one. Initially this characterization may be very general and more qualitative than quantitative. It might simply be the determination of the general nature of the wear situation, such as lubricated sliding at low or moderate temperatures or a particle erosion situation with possible corrosion. As the wear design proceeds, system analysis involves such elements as the determination of loads and contact stresses, detailed characterization of the environment, detailed characterization of the motions involved, and determination of the factors that affect these variables. System analysis also involves the determination of how much wear can be allowed and the establishment of a failure criterion. In general it consists of all those elements needed to implement the modeling and data gathering elements. Modeling. The modeling phase of a wear design approach involves the selection of a model, which provides a basis for the determination of the design. Model selection is basically done by matching the characteristics of the tribosystem to the descriptions of the various wear models and selecting the most appropriate one. Once this is done, the model is then used to determine the values of the design parameters necessary to obtain the desired wear life or performance. Data Gathering. In order to use models in the fashion described above, it is generally necessary to determine the values of one or more empirical coefficients, which generally are material and environment dependent. Existing data may be used for this purpose if they were obtained for conditions that match or simulate the conditions of the current application. If not, appropriate wear tests need to be done to determine those coefficients. Estimates for these coefficients based on theoretical considerations or extrapolation of existing data can also be used, but these are generally less accurate then those obtained from wear tests that simulate the wear situation. In some situations it may be necessary to consider more than one model. This could be because there is inadequate information available to differentiate between models, or because the wear situation is so complex that several different conditions need to be considered. In this case the design parameters should be selected so that adequate wear performance is predicted by all the models. Alternatively, this complexity may be eliminated by doing further system analysis, doing some tests to identify the appropriate model, or introducing elements in the design to eliminate some of the possibilities. For example, damping may be introduced to eliminate possible fretting motions that may contribute to the wear, or seals may be used to eliminate the possibility of abrasive particles in the contact region. Verification. In addition to the normal verification that the design works, it is necessary to verify the validity of different assumptions made in the other three phases. These include examinations to verify that the characteristics of the wear are consistent with the modeling (e.g., correct location and appearance of wear scar). Theoretical versus Empirical Wear Design Approaches. In practice, wear design approaches can be completely theoretical, semi-empirical, or completely empirical. In the completely theoretical approach the basis for selection of a model is a description of the tribosystem. Also, existing empirical coefficients or estimates based on them are used to predict wear behavior using those models. In the semi-empirical approach, some testing is done to determine values for the coefficients or to verify the applicability of a model that was selected on a theoretical basis. In the completely empirical approach the model and coefficients are determined empirically. An example of this might be the use of regression analysis to determine a suitable model. While the completely theoretical approach is most desirable from a design standpoint, it tends to be the least accurate and to be associated with a higher degree of risk. As a result, such approaches should be more conservative and use larger safety factors for establishing designs than those involving some experimental elements. Designing for Preferred Modes of Wear. An important factor in wear design is the recognition that the selection of design parameters and the overall nature of the design affects not only the wear rate but also the wear modes and behavior. Preferred modes of wear can be ensured by proper design. The primary criterion is that the design be selected to ensure mild wear behavior. In two-body, nonabrasive wear situations this generally means that contact stresses should be in the elastic range. In the case of sliding, contact stresses should be a small fraction of the yield strength, generally less than 0.5 and less than 0.2 for very low wear rates. Some form of lubrication should also be used. For rolling and impact, the stresses can be significantly higher (i.e., greater than 0.5) for long life, provided that sliding is not involved. In abrasive wear situations, materials similar in hardness to the abrasives or, preferably, harder than the abrasives should be used. Materials should be compatible with the environment in which they are to be used. A list of other rules for wear design is given in Table 7. Table 7 Design rules for wear applications • Reliance on analytical design procedures increases the degree of conservatism that should be used. • Wear is a system property; utilize all the parameters that influence wear. • Design with the limits and characteristics of the materials in mind. • Design so that a mild wear condition exists. • Minimize exposure to abrasive particles. • Optimize contact to minimize stresses. o Ensure good alignment. o Round corners and edges. • Use a lubricant whenever possible. • Use dissimilar materials. • To increase system life (reduce system wear), it is sometimes necessary to increase hardness of both members. • Rolling is preferred over sliding. • Sliding or fretting motions should be eliminated in impact wear situations. • Impacts should be avoided in sliding contacts. • Elastomers frequently out perform harder materials in impact situations. • Thickness of conventional coatings generally should be greater than 100 m. • Use moderate surface roughness. • Avoid the use of stainless steel shafts with impregnated sintered bronze. • When molded, filled plastics tend to exhibit significant difference between initial and long- term wear behavior. • When glass or other hard fillers are used, the hardness of the counterface should be equal to or greater than that of the filler. For glass, this hardness should be >60 HRC. • The tendency for galling can be reduced by using dissimilar and hard materials of low ductility, lubricating, and reducing contact stresses; stress level above threshold levels for galling should be avoided. • Avoid designs in which fretting motions can occur. • When fretting motions are present, design for optimum sliding wear life and to minimize abrasive wear. • Sacrificial wear design should be considered when satisfactory life cannot be achieved by other means. • Conform to vendor recommendations for optimum wear performance. • Changes associated with design modifications or new applications should be reviewed carefully with respect to their affect on potential wear behavior. Bracketing. One technique that is often helpful in wear design is called bracketing, which is illustrated in Fig. 5. This involves the development of two theoretical wear projections for a design. Different models may be used for each projection. For example, in the case of sliding, one projection might be based on the K-factor model and the other on the combination of the sliding zero wear and measurable wear models. One projection is an optimistic projection, using the [...]... Bayer, Ed., Selection and Use of Wear Tests for Metals, STP 615, American Society for Testing and Materials, 1976 17 R.G Bayer, Ed., Wear Tests for Plastics: Selection and Use, STP 701, American Society for Testing and Materials, 1979 18 R.G Bayer, Ed., Selection and Use of Wear Tests for Coatings, STP 769, American Society for Testing and Materials, 1982 19 C.S Yust and R.G Bayer, Ed., Selection and Use... Testing and Materials, 1988, 20 A.W Ruff and R.G Bayer, Ed., Tribology: Wear Test Selection for Design and Application, STP 1199, American Society for Testing and Materials, 1993 21 Mechanical Testing, Vol 8, Metals Handbook, 9th ed., American Society for Metals, 1985 22 K Ludema and R.G Bayer, Ed., Tribological Modeling for Mechanical Designers, STP 1105, American Society for Testing and Materials, ... Telephone and Telegraph Corp., 1956, Chapter 20 18 S Ramo and J.R Whinnery, Fields and Waves in Modern Radio, 2nd ed., John Wiley and Sons, Chapman & Hall, 1953 19 D.K Chang, Field and Wave Electromagnetics, 2nd ed., Addison-Wesley, 1990 20 J.P Schaffer, A Saxena, S.A Antolovich, T.H Sanders, and S.B Warner, The Science and Design of Engineering Materials, Irwin, 1995 Properties Needed for Electronic and. .. Rymaszewski, and A.G Klopfenstein, Ed., Microelectronics Packaging Handbook, Part 3, Subsystem Packaging, 2nd ed., Chapman & Hall, 1997 Properties Needed for Electronic and Magnetic Applications Eugene J Rymaszewski, Rensselaer Polytechnic Institute Overview of Electric and Magnetic Parameters and Materials Properties Electric voltage, current, and power are fundamental electrical units V, I, and P They... Oxford University Press, 1984 3 S.K Ghandhi, VLSI Fabrication Principles, 2nd ed., John Wiley & Sons, 1994 4 P.S Neelakanta, Handbook of Electromagnetic Materials, CRC Press, 1995 5 R Tummala, E.J Rymaszewski, and A.G Klopfenstein, Ed., Microelectronics Packaging Handbook, Part 1, 2nd ed., Chapman & Hall, 1997 6 S.P Murarka and M.C Peckerar, Electronic Materials Science and Technology, Academic Press, 1989,... determine the maximum load that can be applied to a design for a given lifetime and not have the depth of wear exceed the surface roughness level Expressions for the allowable load were developed for a number of different geometries and motions, as shown and described in Fig 7, 8, 9, and 10 and Tables 8, 9, 10, and 11 Table 8 Key to symbols used in Fig 7, 8, and 9 Symbol a E Hm K L L' N no nr P Description... one Fig 5 Bracketing analysis (a) The design is satisfactory and no further modifications are required (b) A design change is needed (c) Further work is needed to identify satisfactory materials and, if applicable, the correct model for the wear situation Design Modifications While the focus of the wear design methodology is the avoidance of wear problems in new designs, it can also be applied to the... Prediction and Prevention, Marcel Dekker, 1994 Design for Wear Resistance Raymond G Bayer, Tribology Consultant Methods for Wear Design In most cases a wear design starts out with a general design outline based on function This design outline defines the generic shapes, motions, and environment It may also provide some limits on the type of materials and method of lubrication that can be used Based... temperature and frequency ranges, and the power-handling capability The very recent challenges are presented by the quest for the lowest manufacturing and assembly costs and smallest area or volume Such challenges drive development of "embedded" resistors, as well as capacitors and inductors, labeled imbedded passives (Ref 13) They are produced with thin films of proper composition, dimensions, and processing... with widely varying structural dimensions and demands on their properties As a rule, mutually compatible sets of materials must be employed, placing further demands on their properties Small, inexpensive items, such as handheld calculators, are designed for the lowest manufacturing cost, which often precludes repair (a "throwaway" product) The more expensive, and more complex, products usually consist . Testing and Materials, 1976 17. R.G. Bayer, Ed., Wear Tests for Plastics: Selection and Use, STP 701, American Society for Testing and Materials, 1979 18. R.G. Bayer, Ed., Selection and. Testing and Materials, 1982 19. C.S. Yust and R.G. Bayer, Ed., Selection and Use of Wear Tests for Ceramics, STP 1010, American Society for Testing and Materials, 1988, 20. A.W. Ruff and. Ed., Tribology: Wear Test Selection for Design and Application, STP 1199, American Society for Testing and Materials, 1993 21. Mechanical Testing, Vol 8, Metals Handbook, 9th ed., American