Wear rate equation

Elastomers. Ratner and Klitenik(21) obtained a wear rate equation for the abrasion of rubbers and their vulcanizates ... 

Substrate Properties. It is clear from equation 5 that higher hardness of the substrate lowers friction. Wear rate of the film also is generally lower. Phosphate undercoats on steel considerably improve wear life of bonded coatings by providing a porous surface which holds reserve lubricant. The same is tme for surfaces that are vapor- or sandblasted prior to appHcation of the soHd-film lubricant. A number of typical surface pretreatments are given in Table 13 to prepare a surface for solid-film bonding (61). 

Wear is defined as the progressive loss of material from a body caused by contact and relative movement of a contacting solid, liquid, or gas. The importance of understanding and minimizing wear in technical designs is obvious, but still today there are no reliable methods to theoretically predict the lifetime of a new design. Several equations are used to describe wear rates. One example is Archard s well-known law of adhesive wear [512], which describes the material loss per time ... 

The lubricated wear described above is squarely at odds with the behavior illustrated in Fig. 14-6 and with the wear-reducing action of 22% di-t-octyl disulfide in white oil reported by Dorinson and Broman [10] and shown in Table 11-6 (Chapter 11, Section 11.2.1). If Eqn 14-49 is a correct representation of additive action, it should be valid for both the reduction and the increase of wear by such action. To reduce wear, the first term on the right-hand side of the equation must control the overall rate and one way to do so is for the lump removal factor wear rate. But there is no physical necessity that q remains constant for all conditions of load, pressure, speed or state of lubrication. Since in physical terms the predominant effect of the lubricant is to inhibit the asperity adhesion process, it is not unanticipated that the average size of the transferred and detached particles as well as their number will be decreased by lubrication. It is to this latter type of mechanistic process that we must look for an explanation of why such parameters as contact pressure, rubbing speed and material properties affect the balance between the inhibition or promotion of wear by additive action and the transition from smooth lubricated wear to catastrophically damaging wear behavior such as scuffing. 

Wear factor is a proportionality parameter related to the wear of a non-lubricating surface against a mating surface below the PV limit of the material. Equation (3.2) shows the calculation of wear rate of a material. 

The wear rate as expressed in wear volume can be empirically obtained from the Archard s equation (13)... 

The wear rates for the slloxane modified epoxies are given In Table III as a function of the normal load. Also contained In Table III is the value of b as obtained by linear regression of the equation... 

However, the following trends in the wear data were noted. The wear rates of the slloxane modified epoxies and the polylmides were positively correlated with the elastic moduli. In Equation 2,. the stress is proportional to a , and a is proportional to K Hence, stress is proportional to Thus, the data indicate that within a specific polymer system, the wear rate is positively correlated with the magnitude of the maximum stresses in the surface. 

The positive correlation of wear rates with elastic moduli E of the polylmides is consistent with the fatigue model for wear ( ). The reason for this correlation is that the surfaces stresses which are calculated using the Hertzian contact equations are proportional to Higher stresses lead to high wear rates because less stress cycles are required to cause a fatigue failure and produce a wear particle. 

As seen from the wear Equations (25) and (27), in either cases, the wear rate is mainly dependent on the frictional force. This conclusion is in accordance with the results of a number of experimental studies (j -O (Figures 6 and 7) moreover. Southern and Thomas pointed out that the exponent oC is equal to 2 at least for the steady-state rate of wear ) As for the unsteady-state rate of wear, it increases as abrasion proceeds. This result is consistent with the experimental observation (Figure 8) (5 ). 

The wear equation of rubber abrasion in steady state reveals the basic correlation among the material property, running condition and wear characteristic. The wear rate increases with an increase in the frictional force, however, it is inversely proportional to the tensile strength. 

The equation for the full (mean) wear rate as a function of transient time ratio to the full time of friction (ti/t) is obtained by dividing the relation above by t. Since wear rates equalize on transition to mild wear a conclusion has been made that the apparent wear rate increase of one of the alloys at room temperature takes place at the expense of a longer run-in of the other alloy at the severe wear stage. 

In practice, the available hydraulic pressure of the ram limits the die length and the maximum die temperature is limited by the polymefs thermal stabilily. Excessively high hydraulic pressures also accelerate the wear rate of the ram and die seals during operation. Replacement of a seal or ram is costly as such repairs can only be conducted when an extruder is off- line. Generally, for a cylindrical profile, the minimum die residence time required to sufficiently sinter a UHMWPE profile is calculated from the following relationship as shown by Equation 8 (20) ... 

When we include the patients with zero wear, the distribution of wear rates in both studies is summarized as a box plot in Figure 5.8, taking into account the calculation as described in Equation (1). 

The abrasive wear equation predicts that wear rate should be inversely proportional to hardness. This is not the case for the wear of polymers where the correlation is much worse than for metals. The reason for this lies in the difficulty of measuring the hardness of a polymer and separating it from time-dependent effects and the contribution of elastic and plastic effects. A much better correlation is found according to the Ratner-Lancaster correlation, which relates the inverse of the area under the stress-strain curve of a polymer (to the point of tensile failure) to abrasive wear rate (Hutchings, 1992). 

In this expression is the film growth current and kp = M/pnF is a constant taking into account Faradays law (c.f. Section 6.2.2). The second term represents the wear rate of the film in m/s. It is equal to the wear rate per unit length, given by equation (10.19) multiplied by the sliding velocity Vsp... 

Tso and Ho s [47] and Liao s [71] models focus more on the relationship between conditioner parameters and the pad wear rate (MRR). However, Tso and Ho utilize the Preston equation while Liao s model presumes metal cutting theory. On the other hand, Homg s [72] model calculates pad deformation across the pad, which is not accounted for by the other models. These aforementioned models are summarized in Tables 13.5 and 13.6 in terms of model illustration, assumptions, derivations, and main conclusions. 

Sometimes wear factor or specific wear rate is the metric in a PV study. Wear factor is essentially the constant in the Aichard equation that is cited for abrasion and adhesive wear in metals. This equation states that wear volume is proportional to the sliding distance and the normal force. 

Application of the very simple relationship shown in Equation (1) requires knowledge of the dependence of stress intensity factor AK and wear rate on external factors, and this is component specific. These relationships are discussed for a railway rail application in Section 3. However, one of the critical determinants of crack growth rate is crack length, while wear is completely independent of crack length. This provides a simple means to investigate the implications of wear-fatigue interaction. 

Meanwhile, the authors think of the changes in the equations between 1 and V in the case using the harder counterface material as followed. In the present case, the wear rate of the cast iron pin in length, 1, in each region is given by Eq.(8). In the first wear region in which the hardness of the cast... 

This relation has been repeatedly tested for metals, auid a reasonable correlation of wear rate is observed for both the hardness and the counterface topography but only within certain limitations (7), however, for polymers, there are major challenges in the application of equation 1. This can be seen from the data presented in Figures 2a (8) and 2b (9). The wear of polymers certainly does not fit into the Archau d model of wear as a high hardness does not necessarily give low wear. 

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