Advanced Materials Research Vols. 446-449

Abstract: Beam reinforcement is reduced to mechanics behavior of structures of multilayer materials in this paper. An analytical method is presented based on Hamiltonian system. In the system, displacements and stresses are pairs of dual variables. The state vectors of the system describe directly connective conditions on the interfaces of two materials and structures so that the rule of normal and shear stresses on the interface can be revealed. Based on the criterion of lamination crack, the interface strength is determined. Results show that the lamination crack correlates highly with the ratios of material constants and geometrical parameters of structures. The result and conclusion provide a design criterion for structure reinforcement.

Abstract: We use the distributed cohesive element method to simulate the dynamic fracture in structural specimen and arbitrary crack path is predicted. The focus in on convergence of the cohesive crack path as an approximation of the real crack as the spatial characteristic mesh size h approaches zero. We propose the structured mesh is satisfactory in capturing the real crack shape as we refine the mesh because the crack Hausdorff distance converges. However, the length of cohesive crack path does not converge as the mesh is refined. There is a finite length deviation between predicted cohesive crack path and physically real crack path on structured mesh.

Abstract: In this paper, a series of mixed visco-plastic analyses for assembles of three types of asphalt are made using finite element method. Governing equations are derived for motion and deformation for particles, including coupling of rigid body motion and deformation for deformable bodies. Nonlinear viscous analysis is made for the assemblies using an implicit discrete element method. Among particles, three different contact types, cohering, rubbing and sliding, are taken into account. The numerical model is applied to simulate the compaction of aggregates consisting of mixed particles of different nonlinear viscous incompressible material. After minor modification, the application of the proposed numerical model to industry is possible.

Abstract: The quasi-Green’s function method (QGFM) is applied to solve the bending problem of simply supported trapezoidal shallow spherical shells on Winkler foundation. A quasi-Green’s function is established by using the fundamental solution and the boundary equation of the problem. And the function satisfies the homogeneous boundary condition of the problem. Then the differential equation of the problem is reduced to two simultaneous Fredholm integral equations of the second kind by the Green’s formula. The singularity of the kernel of the integral equation is overcome by choosing a suitable form of the normalized boundary equation. The comparison with the ANSYS finite element solution shows a good agreement, and it demonstrates the feasibility and efficiency of the proposed method.

Abstract: The paper studies a new mechanical model of pre-twisted Timoshenko beam. But it is different from the conventional Timoshenko straight beam; the proposed new Timoshenko beam element takes separate interpolation polynomial functions both flexure bending displacement and angular displacement. According to the relationship between bending moment and shear, the relationship between of bending displacement and angle displacement is derived, more accurate to consider the effects of shear deformation, come up with a new initial reverse Timoshenko beam element stiffness matrix. Finally, by calculating the pre-twisted rectangle section beam example, and contrasting three-dimensional solid finite element using ANSYS, the comparative analysis results show that pre-twisted Timoshenko beam element stiffness matrix has good accuracy.

Abstract: The researches of non-oriented silicon steel are mainly focused on the effect of main processing parameters on the microstructure and magnetic properties, but there have been few studied about its flow stress until now. In this paper, the non-oriented silicon steel 50A1300 of hot forming is studied by thermal-mechanical simulation method. The hot deformation behavior of the steel is explored and the flow stress model of the steel is established based on the creep mechanism. The model has good accuracy and is feasible.

Abstract: Based on the geometric deformation of the Euler-Bernoulli beam element, the geometric nonlinear Euler-Bernoulli beam element based on U.L. formulation is derived. The element’s transverse first-order displacement field is constructed using the cubic Hermite interpolation polynomial, and the first-order Lagrange interpolation polynomial is used for the axial displacement field. Then the additional displacements induced from the rotation of the elemental are included into the transverse and longitudinal displacement fields, so those displacement fields are expressed as the quadratic function of nodal displacement. Afterwards the nonlinear finite element formulas of Euler-Bernoulli beam element under the form of U.L. formulation are derived using Cauchy strain tensor and the principle of virtual displacements. The total equilibrium equation and tangent stiffness for large displacement geometric nonlinear analysis of frame are obtained in the total coordinate system. The correctness of this element is proved by typical example.

Abstract: A dynamic cavity-expansion penetration model for concrete targets impacted by non-deformable projectile is developed. Based on the dynamic cavity-expansion penetration model, the equations of the final penetration depth were determined including the effect of additional mass and sliding frictional coefficient. The predicted final Penetration depth was compared with the depth of penetration data and a good agreement was achieved. The analysis indicated the additional mass was negligible compared to the mass of the projectile and independent of the striking velocity. When the friction between the concrete and the nose surface is assumed to be negligible, the final penetration depth increases slightly. The relationship between the principle stress difference at failure and unconfined compressive strength was determined by curve fitting.

Abstract: A material parameter identification method is proposed for functionally graded materials (FGMs) which are modeled by the isoparametric graded finite elements (IGFE). The material parameter identification problem is formulated as the problem of minimizing the objective function defined as a square sum of differences between the measured displacement and the computed displacement by the IGFE. Levenberg-Marquardt optimization method, in which the sensitivity analysis of displacements with respect to the material parameters is based on the finite difference approximation method, is used to solve the minimization problem. Numerical example is given to illustrate the validity of the proposed method for parameter identification.

Abstract: Based on the traditional mechanical model of straight beam, the paper makes a systematic analysis and research on the pre-twisted Euler beam finite element numerical model. The paper uses two-node model of 12 degrees of freedom, axial displacement interpolation function using 2-node Lagrange interpolation function, beam transverse bending displacements (u and υ) still use the cubic displacement, bending with torsion angle displacement function using cubic polynomial displacement function. Firstly, based on the author previous literature on the flexure strain relationship, the paper deduces the element stiffness matrix of the pre-twisted beam. Finally, by calculating the pre-twisted rectangle section beam example, and contrasting three-dimensional solid finite element using ANSYS, the comparative analysis results show that pre-twisted Euler beam element stiffness matrix has good accuracy.