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提出了一种用于计算比以前所通用的试样参数(即裂纹深度5宽度比a/w、载荷偏心率x/w和半径比r_1/r_2)范围更宽的C型试样的应力强度因子K的新表达式。表达式的基本原理是利用已知的短而深裂纹的K解来建立一个K的无因次表达式。当a/w趋近于0和1时,该无因次K方程式接近于修正的极限值。把以前研究得出的K数值无因次化成这种方程式,而K对a/w的相依性由多变量线性回归法所确定。最终表达式与数值K解之间,对于0.45≤a/w≤0.55,对所有的r_1/r_2和x/w或为0或为0.5时,其误差不超过±1.0％;对于0.2≤a/w≤1,对所有的r_1/r_2以及x/w等于0或0.5时,其误差不超过±1.5％;对于0.2≤a/w≤1,对所有的r_1/r_2以及0≤x/w≤1时,其误差不超过±3％。该表达式的精确性可使其扩大应用于C型试样来测定裂纹扩展阻力曲线及进行疲劳裂纹扩展速率试验。
Proposed a method for calculating the stress intensity of a C-type specimen wider than the range of the previously-used specimen parameters (ie, crack depth 5 width ratio a / w, load eccentricity x / w and radius ratio r_1 / r 2) New Expression of Factor K. The basic principle of the expression is to establish a dimensionless expression of K using the known K-solution of short and deep cracks. When a / w approaches 0 and 1, this dimensionless K-factor approach approaches the revised limit. The K values derived from the previous studies were dimensionless to this equation, while the dependence of K on a / w was determined by multivariate linear regression. The error between the final expression and the numerical K solution does not exceed ± 1.0% for all 0.45 ≤ a / w ≤ 0.55 for all r_1 / r_2 and x / w or 0 or 0.5 for 0.2 ≤ a / w ≤ 1, the error does not exceed ± 1.5% for all r_1 / r_2 and x / w equal to 0 or 0.5; for all r_1 / r_2 and 0≤x / w≤1 for 0.2≤a / w≤1 1, the error does not exceed ± 3%. The accuracy of this expression allows it to be extended for Type C specimens to measure crack propagation resistance curves and for fatigue crack growth rate tests.