Field indentation microprobe for structural integrity evaluation

An indentation microprobe for the automated measurements of mechanical and physical properties of a metallic structure in the field, which comprises:

• a head member adapted for movement in X and Y directions in a plane substantially parallel to a surface of said metallic structure;
• attaching means for releasably attaching said head member rigidly to said surface of said metallic structure;
• load applying means operatively coupled to said head member and said attaching means;
• a load cell means mounted to said head member, said load cell means having an axis substantially perpendicular to said surface of said metallic structure, said load cell means adapted to provide an output signal corresponding to a load applied and/or released to said metallic structure by said load applying means;
• an indenter holder carried by said load cell means and adapted for axial movement along said axis of said load cell means, said indenter holder having an exposed end;
• a ball indenter carried by said exposed end of said holder, said ball indenter having a selected diameter;
• a displacement transducer means mounted on said load cell means, said displacement transducer means adapted to provide an output signal in proportion to movement of said indenter into and out of said surface of said metallic structure;
• at least one ultrasonic transducer means carried by said load cell means toward said surface, said ultrasonic transducer means adapted to provide an output signal in proportion to thickness and/or crack size of said metallic structure;
• a video camera means carried by said head member for viewing said surface proximate said ball indenter and for measuring the final plastic diameter of an indentation produced in said surface by said ball indenter;
• a data acquisition system for receiving said output signals from said load cell means, said ultrasonic transducer means and said displacement transducer means;
• and
• a computer means, including pre-selected data processing and control programs, operatively coupled to said load applying means via said data acquisition system to automatically and cyclically and incrementally apply and release loads, at a specified strain rate, to said indenter holder and thus, to -aid indenter at a given single location on said surface, feedback of direct data or data from subsequent calculations is used as applicable for test operation control in conjunction with said pr-e-selected computer programs, and to analyze data received by said data acquisition system during said cyclic application and release of said loads to calculate, according to the principles and relationships of elastic or plastic material behavior or both, the true-stress/true-plastic-strain curve, the strain-hardening exponent, the strength coefficient, the elastic modulus, the yield strength, Luders strain, the shift in the ductile-to-brittle transition temperature for steel plates a-d welds, and the fracture toughness of said metallic structure at said given location, and to evaluate the integrity of said metallic structure utilizing said measured mechanical and physical properties.

An indentation microprobe for automatically and non-destructively determining mechanical properties of a structure in the field, which comprises:

• a head member adapted for movement in X and Y directions in a plane substantially parallel to a surface of said structure;
• attaching means for releasably attaching said head member rigidly to said surface of said structure;
• load applying means operatively associated with said head member and said attaching means;
• a load measuring means mounted to said head member having an axis substantially perpendicular to said surface of said structure, said load measuring means adapted to provide an output signal of load applied to said structure by said load applying means;
• an indenter holder carried by said load measuring means and adapted for axial movement along said axis of said load measuring means, said indenter holder having an exposed end;
• an indenter carried by said exposed end of said holder, said indenter having a selected size and configuration;
• a displacement transducer means mounted on said load measuring means, said displacement transducer means adapted to provide an output signal in proportion to movement of said indenter into said surface of said structure;
• a data acquisition system for receiving said output signal from said load cell and said output signal from said displacement transducer means;
• and computer means, including pre=selected computer programs, connected to said load applying means through said data acquisition system to automatically and cyclically apply and release selected increasing loads to said indenter holder, and, thus, to said indenter, at a given position on said surface, and to analyze data received by said data acquisition system during said cyclic application and release of said loads to compute and produce an information signal corresponding to said mechanical properties of said structure at said given position.