An enhanced nodal gradient finite element for non-linear heat transfer analysis

The present work is devoted to the analysis of non-linear heat transfer problems using the recent development of consective-interpolation procedure. Approximation of temperature is enhanced by taking into account both the nodal values and their averaged nodal gradients, which results in an improved finite element model. The novel formulation possesses many desirable properties including higher accuracy and higher-order continuity, without any change of the total number of degrees of freedom. The non-linear heat transfer problems equation is linearized and iteratively solved by the Newton-Raphson scheme. To show the accuracy and efficiency of the proposed method, several numerical examples are hence considered and analyzed

A computational approach based on ordinary state-based peridynamics with new transition bond for dynamic fracture analysis

The recently developed ordinary state-based peridynamics (OSPD) is further enhanced to study elastodynamic propagating crack based on the dynamic stress intensity factors (DSIFs). The displacement discontinuity such as a crack surface is represented by a bond-failure. Variations of the mixed-mode DSIFs with time are evaluated by the interaction integral method for the dynamic crack propagation. In terms of OSPD fracture modeling, numerical oscillation of DSIFs becomes a critical issue during the evolution of a crack. To overcome this numerical oscillation problem, we introduce a new model of bond-failure, the transition bond. The enhanced OSPD approach using the new transition bond model offers accurate and acceptable results, suppressing the numerical oscillation of responses and reflecting an effective approach. The effects of different types of transition bond are numerically analyzed. Accuracy of the DSIFs is examined employing the various damping parameters and effectiveness of the new PD fracture model is verified. The Kalthoff-Winkler impact test is considered for evaluating the mixed-mode DSIFs and the crack paths

Fracture parameter analysis of flat shells under out-of-plane loading using ordinary state-based peridynamics

The present paper is devoted to numerical investigation on fracture parameters of cracked shells subjected to out-of-plane loading using ordinary state-based peridynamics (PD). The nonlocal deformation gradient and equivalent domain integral are introduced to evaluate fracture parameters. To reduce the surface effect and obtain more accurate results, the energy method and volume correction algorithm are considered. Meanwhile, the adaptive dynamic relaxation technique is employed to obtain steady-state solutions. From comparisons between PD results and reference solutions, the proposed PD shell model successfully evaluates fracture parameters in both single- and mixed-mode loading conditions

Dynamic crack arrest analysis by ordinary state-based peridynamics

Dynamic fracture analysis for the crack arrest phenomenon is performed by ordinary state-based peridynamics formulation and discretization employing transition bond concept. Double cantilever beam specimen is chosen for our numerical evidence purpose. The analysis consists of two main phases namely, generation and application (prediction) phases. In the generation phase, the dynamic stress intensity factors of propagating and arrested cracks are estimated by the present formulation for given crack path histories, and good agreement is achieved. As for the application phase, dynamic stress intensity factors well as total crack lengths after crack arrests are in good agræment with the experiments. Moreover, the influence of transition bond concept on the crack arrest behavior is investigated and it is found that the transition bond is very efficient in the simulation of the crack arrest problem such that premature arrests of cracks are observed without transition bond cases

A novel interface constitutive model for prediction of stiffness and strength in 3D braided composites

Owing to the excellent integrated mechanical properties, 3D braided composites have a broad range of engineering applications in aeronautics and astronautics industry. The interface is a critical constituent of 3D braided composites, which plays an important role in the control of mechanical properties of the composites. In this paper, a meso-scale finite element model considering the interface is established to numerically predict the stiffness and strength properties of 3D braided composites. A novel damage-friction combination interface constitutive model is utilized to capture the interface debonding behavior, while 3D Hashin criteria with maximum stress criteria and a gradual degradation scheme are applied to predict the damage evolution of yarns and matrix. A user-material subroutine VUMAT based on finite element package ABAQUS/Explicit is developed for these constitutive models. The stiffness and strength properties of 3D braided composites are derived from the calculated stress-strain curves under typical loading cases. The damage mechanism of constituents especially the interface is revealed in these simulation processes. The effects of the interface parameters on the mechanical properties of composites are investigated, which provides a reference for optimizing design and control of the interface properties of 3D braided composites