(1) Through the experimental study of red mud sand rock in Chongqing under the conditions of uniaxial and triaxial loading, the author analyzes the damage evolution law of the soft rock and the nonlinear fractal features of the crack expansion.

The linear Miner′s law and the high cycle fatigue damage evolution law are adopted for the full-coupled fatigue damage analysis of Qingma Bridge’s longitudinal trusses. The fatigue damage accumulation for the welds is calculated and the corresponding fatigue life is evaluated.

Based on the adoption of elasto-plastic damage theory and effective strain assumption, weld metal coupons were tested under repeated pull and their damage evolution law was determined.

Then, a new a. c. potentialsystem is used to measure the damage evolution law for the steel and its CGHAZ, and correspondingdamage evolution equations are proposed.

According to intrinsic variable theory and equivalent strain assumption,a damage constitutive equation in terms of real strain was established for concrete under uniaxial tension, while damage evolution rule was set up based upon the fact that the Weibull distribution could be used to describe the fracture process of brittle materials,such as concrete.

(1) Through the experimental study of red mud sand rock in Chongqing under the conditions of uniaxial and triaxial loading, the author analyzes the damage evolution law of the soft rock and the nonlinear fractal features of the crack expansion.

Then, a new a. c. potentialsystem is used to measure the damage evolution law for the steel and its CGHAZ, and correspondingdamage evolution equations are proposed.

In dynamic loads, the damage evolution law of concrete in compression differs from in tension; however, Loland model, which is based on research on damage evolution law in tension, can also simulate the damage evolution law well by introducing crack closing factor.

In this paper,the damage evolution law of low cycle fatigue (LCF) of welded blisk is studied,to which the damage mechanics theory is applied. The LCF damage evolution model is built on the basis of strapin variable thermodynamics,the LCF damage characteristics and the coupled strain equivalence principle with damage.

An approach to predict the initiation and propagation of interlaminar damage(delamination)is brought forward based on the contact constraint introduced by the penalty function method: a scalar damage variable is introduced and the degradation of the interface stiffness is established and a damage surface which combines stress-based and fracture-mechanics-based failure criteria is set up to derive the damage evolution law.

The results are analyzed with damage mechanics theory, the evolution laws of this material at the two temperatures are obtained, the comparisons are made with 30Cr2MoV steel at 550℃, and the feasibility of properties.

A new fatigue damage evolution equation was proposed according to the fatigue accumulative damage theory,the effectiveness of which was verified by experimental results.

Although the strain damage threshold ε c is fixed,the stress damage threshold σs and initial modulus of elasticity E0 are exponential and linear decreased with the increasing of water content.

The specimen failure mode, the three-stage evolution rule of the longitudinal strains and the damage evolution law under cyclic loading were analyzed.

A damage evolution law, which allows for the energy dissipation due to the new surface formation as well as the influence of local (thermic) fluctuations is obtained.

Kachanov-Rabotnov's damage evolution law was employed.

A deformation plasticity theory coupled with damage and a damage evolution law are formulated.

The damage evolution law which allows for the kinetic and microstructural properties of a material is obtained on the basis of the kinetic theory of strength.

This model takes into consideration the scale effect and the effect of wet screen sieve of aggregate in which the concept of yield surface is not needed and the difference of damage evolution rule of various graded aggregate concrete is a concern.

The specimen failure mode, the three-stage evolution rule of the longitudinal strains and the damage evolution law under cyclic loading were analyzed.

The damage evolution law which allows for the kinetic and microstructural properties of a material is obtained on the basis of the kinetic theory of strength.

According to the used modelling, the damage evolution law describes the fast initial homogeneous creation of the micro-cracks and then their slow development.

The relative demsity changes can phenomenologically reflect the ductile damage evolution during plastic deformation processes. In view of the above fact, the authors attempt to formulate a ductile damage model through precise measurement of the relative density changes in order to predict the ductile damage evolution and product quality for metal forming processes. However, the density changes during plastic deformation processes are very small. Therefore, the precise measurement of small density changes is...

The relative demsity changes can phenomenologically reflect the ductile damage evolution during plastic deformation processes. In view of the above fact, the authors attempt to formulate a ductile damage model through precise measurement of the relative density changes in order to predict the ductile damage evolution and product quality for metal forming processes. However, the density changes during plastic deformation processes are very small. Therefore, the precise measurement of small density changes is the key to carrying out the project mentioned above. In this paper, the method and equipment for measuring small changes in density are described in detail. The ductile damage evolution during tension and torsion process is studied by measurement of the relative density changes. The results of this study indicate that the precise measurement of small changes in density is a promising way for understanding of the ductile damage evolution during plastic deformation processes.

Presently, damage mechanics has be used successfully in plastic failure and creep damage process , and some damage mechanics models have also been introduced into fatigue study. Effective stress is one of the most important concept in damage mechanics, application of the concept of effective stress lays a foundation for discribing the mechanical behavior of damaged material by the constitutive equation of non-damaged material. The present paper disscussed the definition of effective stress in damage mechanics...

Presently, damage mechanics has be used successfully in plastic failure and creep damage process , and some damage mechanics models have also been introduced into fatigue study. Effective stress is one of the most important concept in damage mechanics, application of the concept of effective stress lays a foundation for discribing the mechanical behavior of damaged material by the constitutive equation of non-damaged material. The present paper disscussed the definition of effective stress in damage mechanics and its physical meaning, and through analysis from the physical pattern of damage and its evolution law, proposed such a definition is not suitable for fatigue damage problem. The authors think that the effective stress should be based on equivalent life in fatigue problem, thereby defined the concept of effective stress in fatigue damage according to the concept of remainder life.

The statistical characteristics of materials parameter in the ductile fracture criterion proposed by the authors was first investigated by means of one step and two steps loading test of spheroidized mild steel (0.2%C) and the formula for estimating the parameter was derived also. It is found that the materials parameter assumes the characteristic of normal distribution and the derived formula is reasonable. The achievements of this study make it possible to reveal the damage evolution and to predict the workability...

The statistical characteristics of materials parameter in the ductile fracture criterion proposed by the authors was first investigated by means of one step and two steps loading test of spheroidized mild steel (0.2%C) and the formula for estimating the parameter was derived also. It is found that the materials parameter assumes the characteristic of normal distribution and the derived formula is reasonable. The achievements of this study make it possible to reveal the damage evolution and to predict the workability of materials during metal forming processees by using the proposed ductile fracture criterion.