Vol 52, No 6 (2016)

Study of the possibility for using a laser ultrasonic technique in nondestructive testing of products that are manufactured by selective laser melting is presented. Procedures of producing samples and carrying out nondestructive testing by the laser ultrasonic technique are described. Mechanical properties of samples that were grown in vertical and horizontal directions have been measured, as well as the speed of ultrasound in these samples. It has been established that the laser-ultrasonic technique is a promising technology for the quality control of products that are obtained by selective laser melting.

Results of experimental research on revealing the dependence of directional characteristics of a pulsed laser thermoacoustic radiator of body ultrasonic waves on the radiator’s energy and geometry parameters are provided. Experimental bench and measurement procedure are described. The results can be used in developing tools for noncontact ultrasonic inspection of metal materials and products.

The article is devoted to ultrasonic testing of weld joints in aerospace industry with an acoustic phased array. Testing planar flaws of lack-of-fusion and joint-root-crack types by sector scanning is considered. A technique is suggested for calculating the probability of detecting flaws (POD) by means of numerical modeling of the ultrasonic-testing procedure with allowance for interferences. A finite-element model has been developed, and 40 cracks with randomly generated geometry have been modeled. Using the modeling results, a conditional crack height at a level of 10% of the echosignal amplitude from a reference reflector has been determined. POD curves have been calculated using the results of numerical experiments.

A new approach has been suggested to revealing acoustic-emission data-flow discords that are related to the formation and growth of flaws. The discords were discovered using a statistical criterion and the Caterpillar SSA principal components method. The approach has proved its consistency when tested on realistic acoustic-emission data-flow models.

Dependences of magnetic leakage field strength during magnetoelastic demagnetization of local magnetization in a steel disk (St3 steel) on the value of its biaxial deformation in the elastic domain have been studied. Deformation-induced mechanical stresses that act in radial and tangential directions have been calculated. Dependences of changes in the normal component of the magnetic leakage field of steel on the effective stress value are given. It is shown that mechanical stresses in a complexly loaded construction can be tested by the value of its magnetoelastic demagnetization.