A new method of measuring the normal and sliding loads associated with multiple point contact is introduced. A multiple point contact is modeled with a steel die with a profile that simulates a rough surface. A very large scale factor is used in modeling this surface. The steel die is placed in contact with a photoelastic model of a half plane and is subjected to a normal load. This normal load is partitioned over the multiple points of contact producing an isochromatic fringe pattern that describes the stress distribution in the local neighborhood of the contact points. A sliding load is then imposed on the model which destroys the symmetry of this fringe pattern. The fringe data in this pattern is sufficient to determine the local loads Pi and Qi and the local coefficient of friction fi = Qi / Pi at each contact point. An overdeterministic method is introduced which gives the solution for Pi, Qi and fi using many data points taken from the isochromatic pattern in the local neighborhood of the contacts.

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