MODELING OF IMPACT CONTACT OF INDENTER AND NON-RIGID STEEL CONSTRUCTIONS DURING MEASURMENT OF HARDNESS

The problems of measuring hardness of constructions with insufficient rigidity by the dynamic indentation are discussed. The disadvantages of the existing dynamic hardness testers are described, the operation of which consists in impact indentation and determination of the hardness, depending on the restitution coefficient. Finite-element models of the contact of the indenter and the pipes samples with various wall thicknesses and diameters and cantilevered plates of various thicknesses are developed. Indentation diagrams for the investigated samples of pipes and plates in the coordinate plane of force-displacement are obtained. The results of the simulation have good convergence with the experimental data. With the help of the finite element models the separation of local penetration and deflection of construction is made. It is shown the influence of steel construction deflection on the process of indenter impression into the material tested and the change of indentation parameters as restitution coefficient, contact force, penetration depth and time of the active part of the impact. The limits of possible application of dynamic hardness testers have been determined. The ways of the increasing of the hardness measurement accuracy on the base of the data obtained during impact interaction are shown. It is established that the use of dependences between hardness and the time of the active stage of impact, as well as the ratio of the contact force to the depth of penetration at the loading stage, makes it possible to evaluate the hardness for pipes with the wall thickness exceeding 5 mm and cantilevered plates at the distance from the fixed support up to 100 mm. 

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