Wear Impact

This wear consists of (i) erosive wear and (ii) percussive wear. Erosion can occur by jets, liquid droplets, and implosion of bubbles formed in the fluid and streams of solid particles. Solid particle erosion occurs by the impingement when discrete solid particles strike the surface and the contact stress arises from the kinetic energy of the particles flowing in an air or liquid stream as it encounters the surface. Wear debris formed in erosion occurs as a result of repeated impacts (60). Neighboring particles may exert contact forces, and flowing fluid when present will cause drag. Under some conditions, gravitational force may be important. 

The erosive wear mechanism, as in the case of abrasion, involves both plastic deformation and brittle fracture. The particle velocity and impact angle combined 

Slug flow is the dominant flow regime in multiphase systems. Flow visualization has shown that bubbles distort and elongate in the vicinity of a pipe wall in a manner similar to collapsing bubbles. The corrosion rate increases because of a thinning of the mass transfer and corrosion product layers, as well as because of localized damage of the corrosion product film. 

Percussion is a repetitive solid body impact, such as that encountered in print hammers in high-speed electromechanical applications and high asperities of the surfaces in a gas bearing. Repeated impacts lead to loss of solid material. Percussive wear occurs by hybrid wear mechanisms consisting of a combination of adhesive, abrasive surface fatigue, fracture, and tribochemical wear (60). 

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Arnold, A.C. and I.M. Hutchings. "The Mechanisms of Erosion of Unfilled Elastomers by Solid Particle Impact." Wear 138 (1990) 33-46. 

Impact wear includes erosive and percussive wear. Erosion can occur by jets, liquid droplets, and implosion of bubbles formed in the fluid and streams of solid particle. Solid... 

These observations of char, flow, and structural change indicate significant temperature rises in the impacted zones of these materials, with the implication that thermal parameters are significant in the impact wear process. Consequently, a thermogravimetric analysis of these mate-... 

The large influence of surface friction effects observed in these impact war tests indicates the significance of induced parasitic vibrations in polymer impact wear. Since it is quite likely that vibration will occur under most impact conditions, it is expected that there should be a strong relationship between polymer wear phenomena under sliding and impact conditions. 

Since several different wear characteristics were noted for the materials tested (e.g.y charring, flow, and brittle behavior), it can be inferred that there is no unique mechanism associated with impact wear of polymer thin films. Further, because of this aspect and the probability that the same mechanisms do not occur under impact testing conditions (Charpy and Izod), it is reasonable to infer that there is little correlation between impact wear resistance and impact strength. This latter point may be illustrated by considering polycarbonate. Even though it has the highest impact strength of any unfilled polymer (4), it exhibits the poorest wear behavior in this study. 

A strong correlation does not exist between impact strength and impact wear resistance. 

Granite is used to form tank liners (bottoms, walls and covers) and skid caps and skid bars in and between tanks in continuous acid pickling lines for the descaling of steel. The acid baths are commonly 10-15% solutions of HCI or H2SO4, and FeCIs or Fe2 S04>3 at temperatures of about 200°F. The granites selected for use as skid caps and tank liners are generally quartz-rich because they are resistant to the abrasive and impact wear of the sliding steel as well as the corrosion from the acid baths. 

Polymer wear can take place in various modes, e.g., adhesive, abrasive, transfer, fatigue, and tribo-chemical. In reality, several mechanisms can also operate simultaneously. If impaction is involved, an impact wear can be the chief mechanism. The predominance of any one type of wear can be influenced by the form of polymers, e.g., thermoplastics, elastomers or composites. 

Several mechanisms of polymer wear have been discussed in the literature (5-7) adhesive wear, abrasive wear, fatigue wear, tribo-chemical wear, corrosive wear and impact wear. We shall limit this discussion to the four basic mechanisms shown in Figure 1. Neither corrosive(5) nor impact wear(8,9) are common, and we do not plan to discuss these in this paper. 

Engel, P.A., "Impact Wear of Materials," Elsevier, Amsterdam (1978). 

Where abrasive impact wear occurs in hammer mills, such as those used for comminution of raw coal in power stations, continuous replacement of plain plates of unalloyed steel is preferred to the application of substantially more expensive materials with only moderately improved service lives. 

A seismic interaction is an interaction initiated by an earthqnake that leads to influences between items or between an item and the operator that conld impair their capability to perform their assigned safety function. Interactions may be mechanical (hammering, impact, wear and explosion), chemical (release of toxic or asphyxiant substances), radiological (an increase in dose) or by means of an earthquake induced fire or flood. 

Oka, Y.I. Ohnogi, H Matsumura, M, (1997), The impact angle dependence of erosion damage caused by solid particle impact. Wear 203-204, 573-579. 

The aim of the nanoimpact testing was to investigate the impact wear-resistance of the ion-implanted Si and Si02 samples using the Impact Module of the Micro Materials NanoTest system. The pendulum impulse technique was used. A solenoid connected to a timed relay was used to produce the probe impacts on the surface, as shown schematically Figure 1 (note magnetic rather than mechanical means was used to actuate the solenoid in this work). The probe was accelerated from 13 microns from the surface for each impact. 

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