Wear testing

Table 4. Teflon PFA Fluorocarbon Resin Thrust-Bearing Wear-Test Results ...

The gap between laboratory wear testing and industrial appHcation trials is extremely difficult to bridge, since there is often Httie or no control over testing in the industrial environment. Despite these limitations, several examples of industrial successes involving ion implanted tools have been reported and blind tests of nitrogen-implanted machine tools have been performed, including tool taps, dies, punches, and TiN coated WC cutting inserts (106). 

Mag., 25(1), 131 (1972)] conclude that these measurements are valid when 50 percent corrections are added for the bending energy of the crystal. Kuznetzov ranks other materials by a relative wear test. His results substantiate the efficiencies given earlier. Attempts to measure efficiency of the grinding process by calorimetiy involve errors that exceed the theoretical surface energy of the material being ground. 

Hardness. Though carbon is important, it must be used with proper insight to be most effective. In the form of graphite it usually is detrimental. As hard carbides, the form, distribution, and crystallographic character are important. Even hardness must be used with discretion for evaluating wear resistance it should be considered as an unvalidated wear test until its relation to a given service has been proven. Simple and widely used tests (e.g., for Brinell or Rockwell hardness) tell almost nothing about the hardness of microscopic constituents. 

When formulating a system for optimum abrasion resistance, both the epoxy/resin hardener binder system and the filler blends used appear to have an influence. The simulation of abrasive service loads on industrial floor toppings in a laboratory is not simple, and numerous wear test machines have been devised. Correlation between different wear test machines is not always good, although most... 

The ASTM issues other useful information for the designer that are included in its Special Technical Publications (STPs). Some examples of STPs are STP 701, Wear Tests... 

During the microscale wear test cantilever B was used. First the probe scanned for a set number of times in an area along the X direction, and then the worn surface morphology was measured in a larger area. The worn depth can be calculated by measuring the difference between the worn area and the initial unworn area. 

Figure 7 is the dependence of micro friction force signal of Au film and Si wafer on load. It can be observed that the micro friction force increases with load. Figure 8 is the morphology of Au film on Si wafer after the micro wear test under 50 nN. There is also a relative deep wear scar on the Him. Figure 9 shows the micro wear scar on Si wafer after the micro wear test. The wear scar is shallow even under a load of 110 nN. It is obvious that the Si wafer gives good wear resistance under such experimental conditions. 

For PTFE film and PTFE/Si3N4 multilayers, through the observation of the surface morphology after the micro wear test, it is found that there is obvious worn mark and projection in the edge of worn mark when the load is above 70 nN (Figs. 11 and 12). As to the Si3N4 film, there is no worn mark observed even when the maximum load is used in the micro friction test. 

After the micro wear tests, the dependence of worn depth of PTFE and PTFE/Si3N4 film on load is shown in Fig. 13. The worn depth of both PTFE and PTFE/Si3N4 film is in the nanometer scale. It can be seen that the worn depth increases linearly with load. However, the worn depth of PTFE/Si3N4 multilayers is about one-tenth of PTFE film at the same load. All these results demonstrate that the wear resistance of PTFE/Si3N4 multilayers is greatly improved after micro-assembling of soft and hard layers. 

During the friction and wear tests of PTFE Him, two zones can be classified according to the load. One is the load below 70 nN, the friction force which was created in friction and wear tests is too small to make the PTFE film to shear. Within this zone the friction force increases linearly with the load, and there are no transfer of atoms and no worn marks. The second zone is when the load is above 70 nN, and the friction force created in the friction and wear tests is large enough to force the PTFE molecular atom to slip. So there were obvious worn mark and projection in the film, and the friction force stayed almost constant with load. 

There are two zones in the friction and wear tests of PTFE film. When the load was less than 70 nN, the micro friction force increases with the load. When the load is greater than 70 nN, the friction force of PTFE film is almost constant, and there is obvious worn mark in the PTFE film. 

Road wear is force controlled. This is a fundamental difference to slip-controlled laboratory abrasion test machines or wear tests with a trailer as described above. In force-controlled events the abrasion loss is inversely proportional to the stiffness of the tire whilst under slip control the abrasion is proportional to its stiffness (see Equations 26.18a and 26.19a). 

FIGURE 26.76 Measured distribution of (a) cornering and (b) fore and aft accelerations in a controlled road wear test for passenger car tires. 

Table 26.7 gives a list of the boundary conditions which define a tire wear test simulation and in fact also an acmal road test. The road surface is the laboratory surface on which the abrasion data for the simulation were obtained. There is as yet no definition of a road surface and even if there were one, it would be of httle use since road surface structures change frequently along the road surface as pointed out earlier. 

Dekempeneer et al. [96] studied the wear behavior of a-C(N) H films deposited by RFPECVD in CH4-N2 atmospheres, with up to 13-at.% N. The wear tests were done in a ball-on-disk tribometer, under air, at fixed 50% relative humidity. The initial friction coefficient was about 0.2 for all samples, and the wear life of the... 

Glicksman, L. R., Mullens, G., and Yule, T. W., Tube Wear Tests in the MIT Scaled Fluidized Bed, Proc. ofEPRI Workshop (1987b)... 

Adhesive transfer processes, release agents in, 21 606-607 Adhesive wear, 15 205-206 Adhesive wear tests, 9 713, 716 Adiabatic converters, in methanol synthesis, 16 309... 

Taber abraser wear test, 9 713-714 Tabersonine, 2 98 Table of Isotopes, 24 754 Table representation, in chemoinformatics, 6 3-6... 

Wear shell specifications, for wet drum ore concentrator, 15 449 Wear surfaces, silicon carbide in, 22 538 Wear testing, 9 713 Weatherability... 

B. ACTA 3-Body Wear Test Method (ACTA)... 

The ACTA 3-body wear testing for experimental polymers was performed according to the method of Pallav et al. (1). Testing results are provided in Table 2. 

Chemical, Physical, and Mechanical Tests. Manufactured friction materials are characterized by various chemical, physical, and mechanical tests in addition to friction and wear testing. The chemical tests include thermogravimetric analysis (tga), differential thermal analysis (dta), pyrolysis gas chromatography (pgc), acetone extraction, liquid chromatography (lc), infrared analysis (ir), and x-ray or scanning electron microscope (sem) analysis. Physical and mechanical tests determine properties such as thermal conductivity, specific heat, tensile or flexural strength, and hardness. Much attention has been placed on noise /vibration characterization. The use of modal analysis and damping measurements has increased (see Noise POLLUTION AND ABATEMENT). 

The initial and steady state wear rates of the siloxane-modified epoxy pins on the steel disks correlated with the inverse of the KIC values which agrees with previous abrasive wear tests 47>. The steady state wear rates on the smooth glass disks were comparable to those on the steel disks. Thus in both cases the wear mechanism is abrasive wear by the wear particles trapped in the interface between the pin end and the disk. 

From these definitions, it can be seen that the more specific meaning of abrasion is wear by the cutting action of hard asperities. The common practice in the rubber industry of using abrasion as a general term for wear probably results from the fact that most wear tests for rubbers use the action of sharp asperities, for example abrasive paper, to produce wear. 

All of the abraders developed for rubber testing, the Akron, DuPont, Dunlop etc, were primarily aimed at testing tyre compounds. Noboru Tokita at al83 have discussed tyre wear testing and point out that it is virtually impossible to simulate the total wear pattern and to determine tread life from laboratory abrasion testers, but many people have tried. The LAT 100 approach using multi conditions would seem to stand the best chance. 

Two-way analysis of variance (and higher classifications) leads to the presence of interactions. If, for example, an additive A is added to a lube oil stock to improve its resistance to oxidation and another additive, B, is added to inhibit corrosion by the stock under load or stress, it is entirely possible that the performance of the lube oil in a standard ball-and-socket wear test will be different from that expected if only one additive has present. In other words, the presence of one additive may adversely or helpfully affect the action of the other additive in modifying the properties of the lube oil. The same phenomenon is clearly evident in a composite rocket propellant where the catalyst effect on burning rate of the propellant drastically depends on the influence of fine oxidizer particles. These are termed antagonistic and synergistic effects, respectively. It is important to consider the presence of such interactions in any treatment of multiply classified data. To do this, the two-way analysis of variance table is set up as shown in Table 1.24. 

---