Experimental Observation and Constitutive Equations of Fracture Propagation
There is a long list of empirical slow crack growth (SCG) equations that present the crack propagation rate as a function of stress intensity factor (SIF) or energy release rate (ERR).Experiments with crack growth through a heterogeneous stress field reveal the limitations of such type of equations resulting from existence of a process zone (PZ) surrounding the crack.PZ is a material defense against stress concentration caused by the crack and is commonly observed in most of engineering materials.It plays an important role in determination of the direction and rate of fracture propagation.Therefore.the PZ and crack are treated as two coupled elements of one Crack Layer (CL) system and CL propagation is represented by two coupled possesses: (i) the PZ evolution by transformation of the original material into a damaged and often anisotropic PZ material and (ii) crack growth into PZ.The CL driving forces are introduced as the negative derivative of Gibbs free energy with respect to CL geometrical parameters.The constitutive equations of CL propagation are formulated in form of simple relations between the crack and PZ growth rates and corresponding thermodynamic forces.Qualitative analysis of these equations suggests two distinctly different patterns of CL propagation: continuous and discontinuous,stepwise growth.A special experimental setup and test material have been selected to simplify and examine the proposed constitutive equations of CL growth.CL model provides a very good agreement with a large set of experimental data at various load levels.temperatures and specimen geometries.
Crack layer model slow crack growth process zone constitutive equations
Alexander Chudnovsky Zhenwen Zhou Haiying Zhang
Department of Civil and Materials Engineering,University of Illinois at Chicago,60607.USA
国际会议
北京
英文
1-10
2013-06-16(万方平台首次上网日期,不代表论文的发表时间)