Resistance electrical machines measurement

For this purpose, a ball-on-flat friction machine (different device as the Cameron Flint one) was used. The ball is made from AISI 52100 steel which has a diameter of 6 mm. The fnction coefficient and the electrical contact resistance (ECR) were recorded using dedicated electronics (measurement range 1 to 10 ohms). Data is plotted in triboscopic diagrams, as a function of lateral position... 

A convenient method of carrying out such a galvanic test in the laboratory has been described by Wesley in which the vertical circular-path machine is used. Each assembly includes two pairs of dissimilar metals—one pair coupled galvanically while the other pair is left uncoupled in order to determine the normal corrosion rates under the same environmental conditions. The type of motion provided (specimens moving in a vertical circular path) enables electrical connections to be made without mercury cup or commutator and the leads can be connected to a calibrated resistance for current measurements attached to the specimen carrier. 

Specimens were strained in a push-pull mode by an Instron machine, Model TF-DM, which has cross head speeds from 0.05 to 0,5 cm/min and a load capability up to 10" kg. Details of the apparatus for the mechanical and electrical tests are reported elsewhere Only a brief description of the electrical portion is given here. The resistivity was measured by the typical four-probe dc method. A set of voltage leads were soft-soldered across the gauge length of the specimen surface. 

The electrical potential drop method uses the electrical resistance of the specimen to measure the crack length. A constant electrical current is applied between two points of the specimen far away from the crack and the potential drop in the vicinity of the crack is measured. Comparison with a calibration curve allows calculation of the crack length. Obviously, the specimen has to be electrically isolated from the testing machine and the displacement transducer. 

Rmin, the largest tensile strain is present at the outer surface. For a symmetrical sample the strain at this location is Smax = 1.198 h/L, where h is the sample thickness and L the distance between the neutral lines. The faces of the clamps isolate the sample electrically from the machine frame. In the test the resistance of the ITO layer is determined as a function of the distance Lq between the plates (Lo = L + h). The crosshead velocity of the universal testing machine (Instron 5566) during the test is 10 mm/min. The relative resistance increase AR/R is represented as a function of maximum tensile strain in figure 7. The curves, represented in this figure are measured on samples of the same width (15 mm). One sample has a uniform ITO layer over the full width. On the other samples a single ITO line of a defined width is etched. 

For eutectic Sn-Pb wave applications, the rate of dissolution of iron is very low, which ensures good wear and corrosion resistance of parts within a wave machine. However, with lead-free alloys, the Fe contamination was measured to be as much as 10 times greater than for a eutectic Sn-Pb wave [33]. If however, the wave solder machine is modified with proper wear coatings, the contamination of a solder bath of Sn-Bi-Ag-Sb, utilized in production of electrical light ballast was 0.002% Fe after one year of operation [33]. 

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