Method and apparatus for determining preexisting stresses based on indentation or other mechanical probing of the material

A data processor program product for determining the preexisting stress in a stressed section of material, comprising:

• a medium readable by a data processor;
• and
• data processor program logic recorded in the data processor readable medium and executable by a data processor to define
• means for determining the stress in a stressed section of a material from first data and from second data characteristic of the material, said first data obtained from an indentation test on the stressed section and including at least an loading P-h curve and said second data including the yield strength of the material, said means further including
• means for fitting the loading to curve to a polynomial expression of the form B1h2+B2h3 to means for determining at least first and second constants B1 and B2;
• means for determining at least one additional constant B3 from B1;
• and
• means for determining the stress G in the section of material as a function of the at least one additional constant B3 and the yield strength σy.

A data processor program product for determining the plastic strain in a section of material that has plastically yielded, comprising:

• a medium readable by a data processor;
• and
• data processor program logic recorded in the data processor readable medium and executable by a data processor to define
• means for determining from first data obtained by indenting the section with an indenter and from second data characteristic of the material the plastic strain in the section, the first data including a penetration (h) and a load (P) on the indenter, said means including
• means for determining the residual yield strength as a function of the second data and the first data;
• and
• means for determining the plastic strain in the section of the material from the residual yield strength and said second data.