Mode I圓桿表面裂縫生長性質的探討與應用
A study for evaluating surface crack propagation for Mode I in circular shaft
Date Issued
2004
Date
2004
Author(s)
Tsai, Tzu-Ching
DOI
zh-TW
Abstract
This study purposes to understand the surface crack growth for Mode I in a cylindrical rod and provides an assessed system. The true surface crack growth including various loadings, crack shapes and boundary conditions is a complex problem. The most solutions from the literatures consider a single condition and lack completely evaluated system. In the current work, numerical analysis system and predicted the depth of an elliptical surface crack in a cylindrical have been established. Lastly, these have been applied in industrial applications.
Finite element analysis has been employed to evaluate the stress intensities along the front of an elliptical surface crack in a cylindrical rod. The finite element solution covers a wide range of crack shapes loaded under end-free and end-constrained axial tension, pure bending and rotation bending. Convenient closed form stress intensity expressions along the whole crack front for each of the loading cases have been given in terms of the crack aspect ratio, crack depth ratio and place ratio. Moreover, weight function method has been used to determine the stress intensities subjected to arbitrary loading on the crack face. The above solutions have been compared against a number of representative solutions collected from the literature. It has been found that different finite element results are generally in good mutual agreement. Simultaneously, experimental backtracking results on the end-constrained axial tension case corroborate well with the closed form solution presented.
A Normalized Area-compliance method has been shown to be able to predict the depth of an elliptical surface crack in a cylindrical rod. The new method involves a combination of optical surface crack length measurement and specimen compliance measurement. The accuracy of crack depth prediction using this method has been verified by fractography of fatigue cracked rods.
Measurement procedure of fatigue crack propagation behavior using surface crack in a tension rod has been established. Fatigue crack growth behavior from the crack depth and crack surface measurement agrees well with the crack growth data obtained from the standard compact tension specimen. For industrial applications, miniaturized tension specimen testing technique measured fatigue crack growth and surface crack repair in a rod by the infiltration method have been carried out. Evaluation of the retardation phenomenon using 3-D surface crack closure model has been attempted. Growth behavior prediction from the current model agrees well with a number of current experimental results.
Subjects
疲勞裂縫生長
應力強度因子
表面裂縫
縮小試片
裂縫修補
stress i
surface crack
fatigue crack propagation
Type
thesis