科研之友
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摘要
The relationship of short and long crack data is analyzed for the fatigue of 2024-T3 aluminum. The micromacro scale range is selected as the reference state of data measurement. Three transitional functions (TRs) contained in Delta S-macro(micro) are used. They correspond to the micro-macro scale portion of the plot of the crack growth rate da/dN vs the volume energy density (VED) factor increment Delta S-macro(micro). Throughout this work, Delta S is understood to represent the incremental volume energy and not the surface energy. Form-invariance of Delta S-macro(micro), using the transitional functions or variables (mu, sigma, d) justify scale shifting to obtain the corresponding test data for the nano-micro and macro-large scale segments. A straight line relationship is established for finding Delta S-micro(nano) and Delta S-large(macro) from Delta S-macro(micro). The effects of load, material and geometry are locked into the macro-micro data and transferred to the nano-micro and macro-large data by using a transitionalized crack length (TCL) of the two parameter model. A scaling law for non-equilibrium and non-homogeneous (NENH) is derived without violating the first principles. The micro-macro test data for crack lengths 3-55 mm are used to derive short crack data of lengths 0.040-0.043 mm. Data for very long crack lengths 49-260 mm are also obtained analytically. The da/dN of the nano-micro range data covered four orders of magnitude from 10(-7) to 10(-4). The micro-macro range also covered four orders from 10(-3) to 10(0) for da/dN. The macro-large range involved only two orders from 10(-1) to 10(0). In the same way, crack growth in meters for structural applications for time scale measured in years can also be derived from macro-micro test data, which can be regarded as the "Master".
- 出版日期2014-6
- 单位华东理工大学
