Numerical Analysis of Unsaturated Soil Slopes under Rainfall Infiltration Based on the Modified Glasgow Coupled Model

An ABAQUS UMAT subroutine was used for the secondary development of the established coupled hydromechanical constitutive model of unsaturated soil considering the effect of the microscopic pore structure. Combined with Euler’s backward implicit integration algorithm, a numerical program was established for simulating the proposed model. The developed numerical program was used to simulate the rainfall infiltration process of an actual slope engineering example, and the effects of rainfall intensity and rainfall duration on the pore pressure, fluid velocity, and displacement of the unsaturated soil slope were analyzed. The results show that the developed numerical program can reasonably analyze the changes in the seepage field and displacement field of unsaturated soil slopes under rainfall infiltration.

On the existence of a unique class of yield and failure criteria comprising Tresca, von Mises, Drucker–Prager, Mohr–Coulomb, Galileo–Rankine, Matsuoka–Nakai and Lade–Duncan

In this paper, it is mathematically demonstrated that classical yield and failure criteria such as Tresca, von Mises, Drucker–Prager, Mohr–Coulomb, Matsuoka–Nakai and Lade–Duncan are all defined by the same equation. This can be seen as one of the three solutions of a cubic equation of the principal stresses and suggests that all such criteria belong to a more general class of non-convex formulations which also comprises a recent generalization of the Galileo–Rankine criterion. The derived equation is always convex and can also provide a smooth approximation of continuity of at least class C 2 of the original Tresca and Mohr–Coulomb criteria. It is therefore free from all the limitations which restrain the use of some of them in numerical analyses. The mathematical structure of the presented equation is based on a separate definition of the meridional and deviatoric sections of the graphical representation of the criteria. This enables the use of an efficient implicit integration algorithm which results in a very short machine runtime even when demanding boundary value problems are analysed.

Time Integration and Assessment of a Model for Shape Memory Alloys Considering Multiaxial Nonproportional Loading Cases

The paper presents a numerical implementation of the ZM model for shape memory alloys that fully accounts for non-proportional loading and its influence on martensite reorientation and phase transformation. Derivation of the time-discrete implicit integration algorithm is provided. The algorithm is used for finite element simulations using Abaqus, in which the model is implemented by means of a user material subroutine. The simulations are shown to agree with experimental and numerical simulation data taken from the literature.

Aeroelasticity Analysis of Rotor Using Dynamics of Multibody Systems

An aeroelastic model and its simulation method of a rotor system are presented. The aeroelastic mode of a rotor is deduced using the multibody system dynamics. The motion equations of the components of rotor system are independent by using Lagrange’s multiplier method, and the differential and algebraic equations are obtained. Equations of the component including joints are deduced to simplify constraint. The angular constraint equations, expressed by Rodriguez parameters, are modified by introducing a nominal motion to avoid singularities caused by large rotations. A large deformation blade component is incorporated. According to the nonlinear implicit expression and high stiffness ratio of the system equations, an implicit integration algorithm combined with the Broyden method is developed, which exhibits excellent numerical stability and good computational efficiency without calculating the Jacobian matrices and their inverse matrices. To verify the validity of the developed method, the transient analysis and aeroelastic analysis of model rotors are imple-mented. The influence of the stability analysis methods, blade structure models on computation is also studied. It demonstrates that the developed method is useful for improving the computation precision of aeroelastic analysis.

A New Constitutive Model for Anisotropic Sheet Metal with Isotropic Ductile Damage

In this paper, a new constitutive model for anisotropic material with isotropic damage is proposed by extending the Rousselier’s model. In this new model, the damage of anisotropic material is treated as a scalar and the Hill 1948 yield function is employed. A full-implicit integration algorithm which can be used in the finite element (FE) simulation is developed. The integration formula is coded into FE model by Abaqus/Explicit using User Material Subroutine and the fracture process is simulated by element deletion. The tensile tests of sheet metal of two different materials, 08 boiling steel and 1Cr18Ni9Ti, are taken under 3 directions. By simulations for specimen under tension, the evolutions of the damage variable are obtained. By comparing the load-displacement curve of the experiments with the simulation results, the validation of this model is verified.