Brittle Coatings for Quantitative Strain Measurements

Abstract

Abstract The use of brittle coatings in stress analysis is discussed in this paper. Particular reference is made to the “Stresscoat” materials and method which can effect quantitative analyses within the elastic range by use of brittle coatings alone. In the plastic range, the flaking off of the coating is shown to be caused by a compression component of strain of about 1 per cent. Graphs and illustrations show the effect of such variables as coat thickness, time of dry, temperature and humidity, creep, and bubbles in the coating. Test procedure is outlined. Application of the method to a part from a high-speed sewing machine shows stress values and correlation of results with fatigue failures. Another application illustrated is a plate, penetrated by a bullet, showing elastic and plastic deformations during the impact loading.