Wear development during bit life modify the mechanical response of PDC bits and reduce their efficiency. Contrary to cutting mechanism, friction mechanism on wear flats which develops on the cutters, remains badly understood. A new friction law based on numerical and experimental studies has been stated by the authors. It depends on the material behavior, and relates the applied normal pressure to the wear flat to the subsequent dip angle a into the rock surface. Drilling parameters for PDC bits can then be evaluated, provided a reasonable wear law be postulated. Two different experimental benches have been built up, one for determining the parameters of cutting and friction mechanisms on a single worn cutter, and the other one for determining the global parameters on a small scale drill bench. Preliminary data allow to discuss some hypotheses of the model.

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