Measuring the Coefficient of Friction at High Load

Publishing Venue

IBM

Related People

Goldmann, LS: AUTHOR [+2][-]

Hultmark, EB: AUTHOR

Abstract

The usual method of measuring the coefficient of friction (f) between two materials (A) and (B), as indicated in Fig. 1, applies to relatively low-compressive loads, often as low as the weight of one of the elements. The value of f thus determined may be extrapolated to higher compressive loads, but only if this added load does not seriously deform either of the surfaces.

Measuring the Coefficient of Friction at High Load

The usual method of measuring the coefficient of friction (f) between two materials (A) and (B), as indicated in Fig. 1, applies to relatively low-compressive loads, often as low as the weight of one of the elements. The value of f thus determined may be extrapolated to higher compressive loads, but only if this added load does not seriously deform either of the surfaces.

Often this is obviously not the case. For example, if a gold-plated KOVAR* plate is pressed against an end-milled piece of steel at sufficiently high load, the milled surface leaves a permanent imprint of the gold plating, which obviously increases f. In cases like this, when f is not independent of load, a method is needed to measure its value at loads appropriate to the application, no matter how high. This technique allows this measurement to be made.

The apparatus for making the measurement is shown in Fig. 2, and consists of two generally L-shaped blocks 1 and 2 mated to form an opening therebetween to receive a block 3. Elongated slots 5 in the legs of the blocks receive screws 4 which are also received in tapped holes 6 in the other block. Surfaces are formed of the material to be tested on blocks 1, 2 and 3, more specifically, a material A is formed on blocks 1 and 2 and material B on sliding block 3.

In operation, blocks 1 and 2 are pushed toward each other with block 3 being pressed in the middle, as indicated in Fig. 2. When the desir...