Resistance strain method
The resistance strain method is to measure the internal stress of the test piece by the change of the resistance value caused by the change of the resistance wire stretching. Attach the resistance strain gauge with No. 88 adhesive, weld a certain length of wire, and then use the corresponding insulating paint to completely coat the back of the sample and the strain gauge. After the bridge is balanced, it is placed in the electrolytic tank and electroplated according to the specified current density and time. When the metal coating is deposited on one side of the sample, due to the internal stress of the coating, the strain gauge shrinks accordingly, and the resistance value changes. Take out the sample after plating. , after cleaning and drying, measure the indicated value of the strain on the strain gauge, and calculate the internal stress of the coating according to the following formula: (related instrument: resistivity meter)
(1) Adhesives and insulating coatings should be selected according to the pH value and temperature of the plating solution used; (related instruments: PH meter)
(2) The strain gauge should be tightly attached, and there should be no air bubbles between it and the test piece;
(3) The sample should be fully cleaned before electroplating, but the strain gauge and insulation layer must not be damaged, deformed, broken, and short circuit and open circuit shall be prevented;
(4) In order to prevent the strain value from changing at any time, the measurement interval after plating should be consistent each time.
