Calculating wear volume

The wear of the rider specimens was determined by measuring the diameter of the wear scar and by calculating wear volume. Data reported are from typical runs selected from several repeated experiments. The specimens were carefully studied and photographed at low magnification using oblique illumination. 

Mass loss from the samples was measured using an analytical balance with an accuracy of 0.1 mg. Wear volume was calculated from the mass loss and the bulk density of each material. Cumulative volume loss was plotted as a function of the amount of erodent impacting on the surface. The steady state erosion rate, defined as the volume loss from the specimen per unit mass of erodent used, was determined from the slope of the linear part of the plot of volume loss against mass of erodent. 

Wear tests were carried out at room temperature imder dry condition. Normal load values of 0.98, 1.96, 2.94, 3.92, and 4.9 N were used. Sliding velocity was fixed at 0.02 m/s, and the sliding distance was 120 mm. Wear of the pin was measured by a gravimetric method using an electronic balance at a 0.0001 g precision. Each worn surface was measured with a profilometer after the wear test to obtain profiles normal to the direction of friction. The profiles were used to calculate the wear rate. The wear rate, w, is defined as w = V/L, where V is the wear volume and L is the sliding distance. Each point of the diagrams from the experimental results is an average of five tests and measiu-ements. 

Chamley also suggested that the volumetric wear rate, as opposed to the LWR, may also be a clinically relevant metric for wear, as the biological stimulus may be related to the volume of wear debris (Chamley, Kamangar, and Longfield 1969). If the femoral head penetrates the cup following a linear trajectory (an assumption that was verified by Chamley s clinical experience with PTFE), the wear volume will be approximated as a cylinder having the projected circular area (A) of the femoral head and a height equal to the dep of penetration. Under this assumption, the volumetric wear rate (VWR) can be calculated as follows ... 

The test duration is dependent upon the period required to achieve a 360-degree contact between the raised portion of the thrust washer and the wear ring. The average wear factor and duration of this break-in period are then reported. The wear factors reported for each compound are based on its equilibrium wear rate independent of break-in wear. Volume wear is calculated as follows ... 

The pin-on-disk test (13) is not a standard for plastic wear testing, but it is the only wear test apparatus t many laboratories have and thus it will be used for plastic, metal, ceramic, etc. It works quite well if this tribosystem simulates the real-life tribosystem of interest. The rider in the pin-on-disk test is usually a ball or a hemispherical-ended pin. Flat-ended pins are used, but they often hydroplane and do not wear flat. Plastic testing laboratories often have molds for flex bw and tensile samples. Ball cavities can easily be put in these same molds to provide molded spheres as riders for a pin-on-disk test. The disk can be made from any counterface of interest. It is particularly easy to measure wear volume from spherical surfaces. A simple calculation using the diameter of the flat worn on the sphere will produce a wear volume measurement that is usually more accurate that can be obtained by mass change measures. This te excels for simulating tribosystems that involve very small normal forces on the plastic member. 

A wear factor [mm /fN m)] x 10 is calculated with the equation W = KxFxVxT, where W is wear volume (mrtf), K is wear factor... 

Where (K) is the dimensional wear factor, (V) the wear volume, (W) the normal load and (x) the sliding distance. The wear volume is calculated from the measured mass through assuming a density of 7.83 g/cc. The mean values observed were 4.65 XIO m N m and 3.32 XlO m N m for the blocks and rings respectively, using a friction modified blend. 

The wear volume can be calculated from the diameter of the wear scar. 

Not only friction forces but also working life is essential when designing a bearing. The calculation below follows the basic energetic wear equation" as proposed by Fleischer [8]. It is based on the wear-specific friction work" vty. This characteristic is an expression of the friction work input into the friction material with reference to the worn volume. For the material combination examined here the wear volume is calculated only from the wom-off volume of the bearing material. The wear-specific friction work is calculated as follows ... 

A pin on flat apparatus (Fig. 2) was used to measure wear rate under concentrated contact and reciprocating motion. The square plate is made of alumina, zirconia or alumina/zirconia nanocomposite ceramics. The pin of medical grade alumina had an end face with 10 mm spherical radius. The lower plate oscillates while the vertical load is applied to the pin by dead weights. Friction force is measured with strain gauges attached to the double leaf springs. Applied load is 30 N, oscillation frequency is 2 c/s, stroke is 10 mm and mean sliding velocity is hence 40 mm/s. Wear test was performed in 30 vol.% bovine serum solution kept at 37 °C. Wear volume of the pin was calculated from the area of the wear surface while the wear volume of the disc was calculated by the weight loss. 

The comparison of the steady state wear rate, defined as the wear volume per unit load and unit sliding distance, is shown in Figure 7. In this study, the result of the initial 10km of sliding was not used for the calculation of the steady state wear rate to exclude any initially high wear. 

A value for Tj A was calculated for each cell in the local contact analysis and compared to the wear regimes identified from wear test data (as shown in Figure 3 and Table 1). The corresponding wear coefficient, K, for each wear regime was used to calculate the wear volume per cell, WDceii. The depth of wear per cell is then given by ... 

Post-test disc wear tracks were measured with a 2-D Talysurf profilometer. For each wear track, four measurements were carried out and the average of the four measurements was used to calculate the disc volume loss, see equation (1). Pin wear scars were measured under optical microscopy. The average of two diameters (the largest and the smallest diameter across the wear scar) was used to calculate the volume loss of the pin [23], see equation (2) while the height of the worn pin can be... 

The wear volumes calculated from the measurement of the wear width and wear depth of the wear tracks are shown in Figure 9. In comparing the wear volume, the treated region with a slit width of 0.4 mm shows about half the wear volume of the untreated specimen. The wear volume decreases further to about one fifth and one sixth for slit width of 0.8 mm and 1.2 mm, respectively. This demonstrates that the electron beam excited plasma device is suitable equipment for increasing the wear resistance of stainless steel materials with narrow gap features. 

Fig. 24.7. Volumes of minerals precipitated during a reaction model simulating the evaporation of seawater as an equilibrium system at 25 °C, calculated using the Harvie-Mpller-Weare activity model. Abbreviations Ep = Epsomite, Hx = Hexahydrite.

Classical, macroscopic devices to measure friction forces under well-defined loads are called tribometers. To determine the dynamic friction coefficient, the most direct experiment is to slide one surface over the other using a defined load and measure the required drag force. Static friction coefficients can be measured by inclined plane tribometers, where the inclination angle of a plane is increased until a block on top of it starts to slide. There are numerous types of tribometers. One of the most common configurations is the pin-on-disk tribometer (Fig. 11.6). In the pin-on-disk tribometer, friction is measured between a pin and a rotating disk. The end of the pin can be flat or spherical. The load on the pin is controlled. The pin is mounted on a stiff lever and the friction force is determined by measuring the deflection of the lever. Wear coefficients can be calculated from the volume of material lost from the pin during the experiment. 

The DIN abrader is used extensively for wear testing. The test uses a metal drum (150-mm diameter) that is covered with a 60 mesh corundum abrasive cloth. The drum revolves at 40 revolutions per minute and the sample moves down the length of the drum. The 16-mm-diameter sample travels a distance of 40 m during the test. From the loss in weight of the sample and its density, the volume loss is calculated. Three runs are normally carried out to obtain an average result. 

N HC1, hydrochloric acid add 16.7 mL concentrated HC1 (12 M HC1) to 100 mL ice cold water dilute with water to 1 L volume. (Prepare in the hood wear a face shield, rubber gloves, and a rubber apron.) Standardize the acid solution by titration against the standardized 0.2 N NaOH solution. Write the calculated normality on the bottle of the standardized HC1 solution. 

The rate of O2 consumption can be calculated by formulas similar to the preceding. A portable machine called a rospiromelcr can be used to collect samples of exhaled gas during various types of work. The samples are automatically collected at intervals and stored in a bag. The machine also records the total volume of gas exhaled during the time it is worn. An agricultural worker is shown wearing the machine in Figure 5.17. 

The taking of tooth impressions to assess wear in vivo has become popular in recent years, as silicone impression materials are available with excellent detail reproduction and good dimensional stability. Several authors [35-38] have reported the use of these materials to capture the dimensions of selected teeth (or teeth surfaces) over a period of time. The silicone impressions are scanned using a profilometry system, typically a laser profilometer, to build an electronic image of the tooth surface. Several scans of the same tooth or surface, taken over a period of time, can then be electronically overlaid and subtracted, to calculate the change in surface contour, or the volume of material removed. This technique can only work if the two scans are precisely overlaid. To avoid... 

The coefficient of thermal expansion must also be accounted for in design calculations. The normal operating temperature for transmission applications is 120°C. A material must be able to operate at this temperature and not expand to a greater volume than the mating parts allow. The coefficient of friction (p) of the material should be considered as well when designing a dynamic seal. Rotating shafts require a lower value for p in order to reduce wear. 

This is the wear equation of rubber abrasion in unsteady state. Assuming that the steady state has been reached when the number of revolution is equal to N, on the basis of Equations(14,a) and (14,b), the sum of volume loss of a tongue after another N revolutions, i.e., from N to 2N revolutions, can be calculated by... 

The polymeric tlbial components were coated with pure aluminium, some lOoX thick in a vacuum evaporation unit to improve the quality of the holographs. This film was removed in Isopropyl alcohol before each wear test. Holographs of the unworn and worn tlbial components were assessed and the volume of material removed (V) in a known period was estimated by simple geometrical procedures. The loading cycle enabled ( PdX) to be evaluated and an equivalent wear factor (k) was calculated from the relationship. 

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