Process, deformation

J. A. Schey, Metal Deformation Processes, Marcel Dekker, New York, 1970. 

In this section we shall examine the analogy between the flow of a liquid and the rate of a chemical reaction. This approach has been developed extensively by Eyring and co-workers and has been applied to a wide variety of deformation processes and systems. 

The activated complex theory has been developed extensively for chemical reactions as well as for deformation processes. The full details of the theory are not necessary for us. Instead, it is sufficient to note that k can be written as... 

R. A. Grange, Fundamentals of Deformation Processing Syracuse University Press, Syracuse, New York, 1962, p. 299. 

Nicholas, T., Measurement of Material Properties for High Rate Deformation Processes, Materials Laboratory, Air Force Wright Aeronautical Laboratories Technical Report No. AFWAL-TR-81-4175, Wright-Patterson AFB, OH, 24 pp., February 1982. 

Is the deformation process performed on a single component or on two (or more) components simultaneously (6)... 

It can be argued that the asperities themselves are relatively smooth, as asperities are generally small. Moreover, if they are not totally flattened during the adhesion-induced deformation process, thereby allowing the bulk of the particle to come into contact with the substrate, they must be relatively hard. As such, it has... 

It is necessary to consider the micro-mechanical processes of polymer glasses and elastomers separately as their mechanical properties are so different. In addition, cross-linking profoundly affects the deformation processes in glasses but very little is known about the micro-mechanical processe.s that occur in single phase cross-linked glasses so the latter materials will not be discussed further. 

Let us examine this relation for typical values of the A/B interface = 1 (max energy dissipation in the A layer) I = 1 (max strength of interface with influxes) E = 12,000psi (Tq = 4000 psi /t = 30 mils (10 in) Lc = 4 x lO" in. We obtain for both terms G = 20 pli (energy dissipated) + 0.08 pli (true interface strength with max influxes), or G 20 pli, which says that the measured peel strength is dominated by visco-plastic deformation processes. 

This statement represents an apt, terse description of the elastic-plastic shock-deformation process within the catastrophic shock paradigm. 

These observations were the basis for the proposal that polymers, like ionic crystals, exhibit shock-induced polarization due to mechanically induced defects which are forced into polar configurations with the large acceleration forces within the loading portion of the shock pulse. Such a process was termed a mechanically induced, bond-scission model [79G01] and is somewhat supported by independent observations of the propensity of polymers to be damaged by more conventional mechanical deformation processes. As in the ionic crystals, the mechanically induced, bond-scission model is an example of a catastrophic shock compression model. 

Finally, the phenomenon of shock-induced polarization represents perhaps the most distinctive phenomenon exhibited by shock-compressed matter. The phenomenon has no counterpart under other environments. The delineation of the details of the phenomenon provides an unusual insight into shock-deformation processes in shock-loading fronts. Description of the phenomenon appears to require overt attention to a catastrophic description of shock-compressed matter. In the author s opinion, a study of shock-induced polarization represents perhaps the most intriguing phenomenon observed in the field. In polymers, the author has characterized the effect as an electrical-to-chemical investigation [82G02]. 

Figure 2 Representation of TLCP deformation process in die exit zone (micro scale). Source. Ref. 33.

Agglomerates that are poorly wetted by the polymer contain air in their voids and have a lower apparent volumetric content of solids compared to well-wetted particles, the reason being that in the first case the entire matrix can take part in the deformation process, whereas in case of good wetting conditions a portion of the matrix is caught in the agglomerate and does not become involved in deformation. 

Generally, a variety of mechanical deformation processes cause the nonuniform deformation that results in the formation of residual stresses. This nonhomogeneous deformation in a material is produced by the material s parameters, largely its process parameters such as the tool geometry and frictional characteristics. For example, the rolling of a strip can be accomplished by using relatively cold squeeze rolls. In the rolling process, parameters with a small roll diameter and little reduction produce deformation penetration that is shallow and close to the surface, whereas the interior of the strip remains almost undeformed. After the removal of the deformation forces and a complete... 

The present review shows how the microhardness technique can be used to elucidate the dependence of a variety of local deformational processes upon polymer texture and morphology. Microhardness is a rather elusive quantity, that is really a combination of other mechanical properties. It is most suitably defined in terms of the pyramid indentation test. Hardness is primarily taken as a measure of the irreversible deformation mechanisms which characterize a polymeric material, though it also involves elastic and time dependent effects which depend on microstructural details. In isotropic lamellar polymers a hardness depression from ideal values, due to the finite crystal thickness, occurs. The interlamellar non-crystalline layer introduces an additional weak component which contributes further to a lowering of the hardness value. Annealing effects and chemical etching are shown to produce, on the contrary, a significant hardening of the material. The prevalent mechanisms for plastic deformation are proposed. Anisotropy behaviour for several oriented materials is critically discussed. 

Microindentation hardness normally is measured by static penetration of the specimen with a standard indenter at a known force. After loading with a sharp indenter a residual surface impression is left on the flat test specimen. An adequate measure of the material hardness may be computed by dividing the peak contact load, P, by the projected area of impression1. The hardness, so defined, may be considered as an indicator of the irreversible deformation processes which characterize the material. The strain boundaries for plastic deformation, below the indenter are sensibly dependent, as we shall show below, on microstructural factors (crystal size and perfection, degree of crystallinity, etc). Indentation during a hardness test deforms only a small volumen element of the specimen (V 1011 nm3) (non destructive test). The rest acts as a constraint. Thus the contact stress between the indenter and the specimen is much greater than the compressive yield stress of the specimen (a factor of 3 higher). 

Metal polishing mechanisms appear to be considerably different from silica polishing. The critical event that determines the polishing process in metal CMP appears not only to be influenced by the crystallographic/microstructure deformation process but also to relate to more complex components of slurry [18]. To better understand the removal mechanism in metal CMP, tungsten is chosen, since both industrial and laboratory CMP data are available for this metal, and its abrasion behavior as a metal is similar to that of other ductile metals which have been studied quite extensively under two- and three-body abrasion [66]. 

Any real network must contain terminal chains bound at one end to a cross-linkage and terminated at the other by the end ( free end O of a primary molecule. One of these is indicated by chain AB in Fig. 92, a. Terminal chains, unlike the internal chains discussed above, are subject to no permanent restraint by deformation their configurations may be temporarily altered during the deformation process, but rearrangements proceeding from the unattached chain end will in time re-... 

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