Papers by Keyword: Damage Constitutive Model

Abstract: The fatigue problem of concrete has long been studied through many different methods. However, the fatigue process and failure patterns of concrete structures have never been well simulated due to the lack of comprehensive understanding of the material properties under fatigue loads. In order to carry out an accurate simulation of the fatigue behavior of concrete structures, this paper proposes a new damage theory based fatigue constitutive model for concrete. The present model adopts two damage variables to describe the degradation of macro mechanical properties of concrete under tension and compression, respectively. And the tensile and compressive damage evolutions are related to the corresponding effective stress spaces. Specifically, by implementing the present model into the nonlinear finite element package, the bending fatigue process of a concrete beam is simulated. Meanwhile a set of numerical tests are presented, through which the validity and effectiveness of the proposed model for the simulation of concrete structures are illustrated.

Abstract: Statistical methods was combined with micromechanics. Based on the parallel bar system, the damage law of the concrete materials subjected to uniaxial compressive stress was simulated. Furthermore, the meso-statistical damage constitutive of concrete materials was studied base on the Weibull’s statistical theory of the strength of materials. While according to constitutive uniaxial compression test of concrete material after freezing and thawing, the parameters m and ε₀ of the model were fitted. Then the freeze-thaw damage constitutive equation of concrete was proposed base on meso-statistical damage mechanics. Finally, the experimental results was compared with theoretical models, and the rationality of the theoretical model was verified.

Abstract: The damage mechanism of loessial soils was studied by the statistical theory.Based on the characteristics strength of loessial soils micro-unit with Weibull distribution, and parameters that described by distribution variable of Drucker-Prager creterion are used, loessial soils damage constitutive model considering damage threshold is established to reflect the full process of loessial soils failure. Conventional triaxial consolidation undrained shear test results of loessial soils are taken as example to verify the model. By comparing theoretical calculation results with test results, it is showed that the statistical damage constitutive model considering damage threshold is reasonable.

Abstract: Rock’s uniaxial compression test is completed and the datum is analyzed, then relationship between loading time and AE amplitude, AE counts sum, AE total energy’s released rate come out. Rock’s critical damage is defined which equal result of one minus ratios of residual strength to critical strength. Based on strain equivalence discipline, damage constitutive models related with acoustic emission characteristic are set up. With damage constitutive models established with AE counts sum and AE total energy serving as damage variables respectively and testing datum, the relationship between rock’s damage and stress and strain is described. Then conclusions come out: 1) damage constitutive model with AE counts sum serving as damage variable manifest rock’s damage increasing process and accords with testing result better; 2) theoretical curve is well consistent with testing curve at rock’s peak strength zone.

Abstract: A viscoplastic constitutive model with void damage is developed to analyze the macroscopic mechanical response and damage mechanism of lead-free solder alloy in CBGA packaging under cyclic thermal loading. The constitutive model is implemented into ABAQUS through its user defined material subroutine. Two-dimensional nonlinear finite element analysis of a ceramic ball grid array(CBGA) package is conducted to simulate the viscoplastic deformation and damage failure process of the lead-free solder joint under cyclic thermal loading. The damage model is helpful for optimization and reliability of electronic package.