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To use the bidirectional combined coordinate system, depict their damage
evolving behaviors for some steels, show their intersectional and complicated
correlations : between the positive and negative direction, the positive and
negative sign, the reciprocal relations and the symmetrical and unsymmetrical
cycle relations in the coordinate system for their equations, curves, variables,
material constants; design the calculation programs in whole process, which
include the calculations of strength, of the damage evolving rate, of crack growth
rate and their relative life at the crack forming and growth stage etc. thereby
accomplish so as to connect among each branch disciplines on the modern
mechanics. And also design a lot of the calculation programs and databases for the
typical parts such structures with some crankshaft, cylinder block and connecting
bar under multilevel complex loading etc. Predict it would be accepted and
applied well in the engineering domain, for the economizing fatigue-damagefracture
testing bankroll, also have practical significance.