FIELD: ultrasonic method for measuring internal mechanical stresses. SUBSTANCE: method consists in introduction of pulses of transverse waves into tested object, reception of passed signal in free and stressed states, determination of ultrasonic wave velocity that is indicative of stress value. Ultrasonic waves are introduced from nut lateral flat in plane square to nut axis. Reception is effected on the other flat of nut, trying to get signal maximum value. Difference of velocities in free and stressed states is determined by value of shift of receiving converter. Signals in free and stressed states may be received from one tightened nut using nut regions adjacent to free and contacting the tightened object flats of nut. When measuring small stresses, use is made of signal enveloping nut over internal edges. EFFECT: higher accuracy and confidence of measurement results and extended field of application of ultrasonic measurement method due to selection of optimal conditions of introduction and reception of ultrasonic oscillations. 3 cl, 2 dwg
