Axial ball strain influence on measurable value of ball indentation by top point of ball

The automated ball indentation method is of special interests for aerospace industry at present time since this method can be used in situ test without making standard specimen. During the ball indentation depth of proposed device testing, applying automated ball indentation for acquisition of force-displacement diagram showed that this device has a minimal dimension chain. This was made possible due to the device original construction allowing measuring of the ball indentation depth by top ball point displacement. Only one element of dimension chain having dimension modifications was an indentation ball. Also the ball indentation numerical solution was presented. The object of this research is the determination of axial strain influence on measurable value of ball indentation by top point of ball and real ball indentation definition applicable in automated ball indentation tests. For the ball and specimen contact analysis ANSYS Multiphysics 15.0 software that realized finite elements method for theory of elasticity problem solution considering two solid contact was used. In the process of investigation it was revealed that relative ball axial strain value remains constant in loading elastic region and depends on ball and specimen modulus of elasticity relation. It is allowed to find relative axial ball strain and real ball indentation depth formulas by knowing ball and specimen modulus of elasticity. Thus, using the proposed device and finding the top ball point allows to determine the real ball indentation depth, considering the axial ball strain contribution that was used in situ test taking into account the force-displacement diagram and possibility to find yield point.