PSI - Issue 33

Yu. Matvienko et al. / Procedia Structural Integrity 33 (2021) 491–497 Author name / Structural Integrity Procedia 00 (2019) 000–000

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a b Fig. 3. Normalized evolution of principal residual strain component �� and �� over lifetime period related to Side A (a) and Side B (b) for different stress ratio � . The coefficient �� � � , � for specimens of given geometrical dimensions is defined by mechanical properties of the material and parameters of loading program. The value of the coefficient �� � � , � in each specific case follows from normalization of Equation (3) taking into account that the total sum in the right-hand side must be equal to one. This is attributed to the definition of limiting values of the damage accumulation function (Matvienko et al. (2021)). A square lying under each normalized �� curve, shown in Fig. 3a and 3b, are represented by itself initial experimental information essential for calculation of the coefficient �� � � , � . This square is denoted as Σ �� � � � . Required coefficients are derived as an inverse proportional values, namely, �� � � , � � � Σ �� � � � ⁄ . The developed procedure leads to an explicit form of the damage accumulation function (3). These functions, obtained for different damage indicators are shown in Fig. 4. Presented curves quantitatively characterize differences in damage accumulation rates depending on stress ratio and coupon face.

a b Fig. 4. Damage accumulation functions � �� � , �� , � � constructed proceeding from �� (a) and �� (b) for different stress ratio � .