SAE J3175:2019 pdf free

SAE J3175:2019 pdf free.Road Vehicles – Friction Materials – Finished Brake Pad Normalized Elastic Constant of Friction Material
a. Because of triggering delays in the instrumentation and propagation delays in the piezoelectric sensors, it is necessary to calibrate the system using a test sample where the propagation time is known or measured independently. A propagation timing standard with known shear waves must be accurate to +0.2 μs. Stainless steel is recommended for calibration due to its uniform physiochemical properties. The calibration block whose transit time for shear waves has been measured independently should be used and should be 15 to 26 mm in thickness.
b. Performing a calibration involves making a transit time measurement using shear wave transducers on the calibration block. The measurement is then compared the known transit time of the calibration standard, TSstandard, and the offset correction factor, T oftset (calibration factor), is calculated as shown in Equation 1. The measurement of the calibration block should occur using the first anti-node (valley) of the waveform. Calibration should be performed at the beginning of each measurement session. Drift in the system delay calculated by the calibration sample is allowable under the condition that the range of any ten consecutive calibration measurements shall be S0.15 μs. If the sample measures outside this range, duplicate the measurement N=5 times to ensure a repeatable system delay with a range of≤0.10 μS.The total drift in system delay of the calibration sample shall not exceed 0.50 μs.
The brake pad is in finished condition with or without paint, with or without wear indicator or other hardware that does not interfere with sensor contact, without the presence of an insulating shim. Number of measurements per brake pad can vary depending on mold holes, chamfers, and slots with sensors at a minimum of 3 mm from any of these features. Average all of the measurements on a given pad for the final average modulus for a given brake pad. Typically, measurements per brake pad range from 2 to 4. Locating jigs should be used such that the measurement locations are the same location on a given brake pad.SAE J3175 pdf free download.