MEASrUlNd FORCES AXU WEAR IN' SWITCHIXG APPARATUS 481 



DISPLACEMENT IN MIL-INCHES 

 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 



15 20 25 10 35 40 45 50 55 60 

 VOLTS ON DRIVE 



Fig. 8 — Variation of normal impulse forces with drive voltages for thrcse values 

 of static force. 



B. TangcitU'al Force and Wear Measurements 



To study the effect of tangential forces in producing wear, the trans- 

 ducer was mounted horizontally and the steel ball was replaced by a 

 wire such as are used in some relays. The length of the wire was made 

 short enough so that no lateral vibrations were generated and the motion 

 was strictly tangential. Samples to be studied as shown by Fig. 7 were 

 mounted on top of shear type ceramics which were glued to the pivoted 

 arm in such a way that they responded to tangential forces applied 

 perpendicular to the arm. 



When a piece of A phenolic (which is a paper filled phenolic) was placed 

 on top of the ceramic a series of oscillograph pictures were taken when 

 the total displacement of the wire varied from 0.05 mil inch to 2.0 mil 

 inches and the steady weight on the wire was 40 grams (0.0885 pound). 

 These pictures are shown in Fig. 9. For amplitudes under 0.075 mil 

 inch, the force is a good sine wave which increases with amplitude luitil 

 the maximum force equals the product of normal force times the co- 

 efficient of friction. The force in this region is essentially elastic as is 

 shown bv the fact that the maximum force occurs at the time when 



