Area of Compaction to Prevent Uplift by Liquefaction

In this study, shaking table tests, upper seepage flow tests and numerical analyses were conducted to determine the condition of improvement by the compaction method, including the extent of area and the density, to prevent uplift of underground pipes by liquefaction. Based on the results of these investigations, a procedure to determine the improvement conditions was proposed

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

Dynamic fracture analysis of functionally graded materials using ordinary state-based peridynamics

Functionally graded materials are regarded as a special kind of composites capable of eliminating material interfaces and the delamination problems. Stress discontinuity can be avoided owing to smooth composition of the functionally graded ingredients. In this study, a recently emerged effective non-local continuum theory for solving fracture problems in solids and structures, peridynamics, is employed to simulate dynamic wave propagation as well as crack propagation in functionally graded materials. Specifically, the ordinary state-based formulation is adopted. The ordinary state-based formulation is slightly modified for the modelling of functionally graded materials. The averaging technique is employed to determine peridynamic parameters associated with the material properties. Firstly, a benchmark problem is considered to validate the present implementation of ordinary state-based peridynamics for brittle fracture of homogeneous materials. Then, the wave propagation in the functionally graded materials under impact loading is simulated. Finally, dynamic crack propagation in the functionally graded materials is studied. The evaluated crack paths and the displacement waves are compared with reference works including numerical and experimental results. Good agreement between the reference and present results is achieved. It is shown that a simple modification of ordinary state-based formulation has led to simulate dynamic fracture of functionally graded materials

Study on two-dimensional mixed-mode fatigue crack growth employing ordinary state-based peridynamics

Mixed-mode fatigue crack propagation analysis is studied using ordinary state-based peridynamics. By introducing the concept of "remaining life", the fatigue crack nucleation and propagation can be simulated in the PD framework. The PD fatigue modeling and the crack path prediction is carefully investigated. For the comparison purpose, the maximum circumferential stress criterion is introduced. The interaction integral and the peridynamic differential operator is employed to evaluate the fracture mechanics parameters. Two pre-cracked structures under mixed-mode loading conditions are provided with the validations from reference solutions

Evaluation of stress intensity factors under thermal effect employing domain integral method and ordinary state based peridynamic theory

In this article, several thermoelastic benchmark cases are studied within the framework of ordinary state based peridynamic theory (OSPD). By using OSPD, the limitations of geometrical discontinuity in fracture analysis can be overcome. Meanwhile, double nodes can also be avoided during crack definition. A domain integral method with thermal effect is applied in calculating the thermal stress intensity factors (TSIFs). Meanwhile, peridynamic differential operators (PDDO) are utilized to rewrite the spatial derivatives in the domain integral. Numerical investigations of TSIFs in the single and mixed-mode crack scenarios are provided respectively, and verified by the reference solutions. Good agreements between OSPD and the reference solutions show high performance and capability of the proposed method in thermoelastic fracture analysis

Fracture parameter investigations of functionally graded materials by using ordinary state based peridynamics

Static and dynamic fracture parameter analyses of functionally graded materials (FGMs) are conducted by using the ordinary state based peridynamic theory (OSPD). As a meshfree method, OSPD applies an integral equation to describe the motion of objects, avoiding the geometrical singularity in conventional fracture analysis measures. Domain integral method by introducing material gradient terms is employed in evaluating the static and dynamic stress intensity factors (SIFs). Meanwhile, peridynamic di↵erential operator (PDDO) is also applied for the calculation of physical components derivatives. Di↵erent FGM modeling schemes are also examined in the OSPD framework. Cracked FGM structures with mode-I and mixed-mode crack scenarios are under investigation and results are validated by reference solutions. Accuracy and reliability of the proposed method will be examined and discussed