Abstract
When brittle lacquer coating is to be employed to strain analysis of machines and structures, it is required that the coating will, without resorting to heat treatment, present preeminent strain sensitivity, so far as the object bodies to be analysed have large heat capacity, particularly when they are in running state. But since the lacquer coating hitherto processed has been left to air-drying, it is deficient in brittleness, and cracking does not easily develop on the coated surface, because the lacquer used for the coating has, as its basic ingredient, limed wood rosin which contains neutral materials.
In the previous study a report was made of an experiment that was performed with micro structure of the coating with a view to inducing the principle to improve its brittleness. The principle was then applied to preparation of improved lacquer coating, and was verified by presenting the excellent sensitivity simply by curing it at room temperature.
The authors have been engaged in the systematical study of the influence that the basic ingredient of the lacquer coating and the plasticizer will make on the sensitivity by the relative proportion of its content at various levels of temperature and humidity.
As the result of the study improvement of lacquer coating has been made available and its preparation duly made that will always present sensitivity to circ. 800 micro strain under whatever condition of temperature and humidity without subjecting it to heat treatment. Moreover the improved lacquer, with advantage of leaving the cracks made on the coating applied with it staying open after the removal of the load, has made it more easily practicable to work dynamic analysis of the machines and structures. Coating with the improved lacquer was once applied to stress analysis of an aeroplane with wingspan 33000mm in its test flight with successful result.
