Separation of principal stresses in photoelasticity by means of a computer

It is shown that a separation of principal stresses with different types of experiments using computers is more valid and economical for methods based on the condition of compatibility than for those based on the conditions of equilibrium. This means that first the sum of the principal stresses is determined which combined with their differences gives their values separately. In this method several equations are used of the finite difference type and all can be solved by means of an iteration procedure in computer program form.