Measuring Method for Coefficients of Impulsive Friction and its Applications

A measuring method for coefficients of impulsive friction is presented for the case of slip occurring at the interface of two bodies subjected to impulsive loads. The mechanism of an apparatus is based on the Hopkinson bar method. Three specimens clamped by normal force are sandwiched between two long pressure bars. The loading initiated by impacting the incident pressure bar with the striker bar generates slip between the contact surfaces of specimens. The shearing force on the contact surfaces of specimens is measuring by means of strain gages mounted on the transmitter pressure bar. By measuring coefficients of impulsive friction for steel specimens, it is found that coefficients of impulsive friction decrease with the increase of normal force. The experimental results are useful to clarify the loosening mechanism of screw threads subjected to impulsive loads.