Scipedia: WCCM-APCOM 2022

An Efficient Phase Field Model for Fatigue Fracture

Scipedia content — Wed, 06 Jul 2022 16:53:12 +0200

The fatigue phenomenon is difficult to be modeled and simulated because of its natural property, which does not happen imminently but rather after a larger number of cycles. Usually, the simulation of fatigue fracture behavior also requires a lot of computation effort which can be seen as very time-consuming. In this work, we represent an efficient phase field model aiming to handle the cyclic fatigue fracture.

Lateral Resistance of Buried Pipes by Frictional Limit Analysis

Scipedia content — Wed, 06 Jul 2022 17:18:11 +0200

Pipelines are vital means of transportation of liquids and gases over large geographical areas. Regarding buried pipes, they are submitted to thermal and mechanical loads due to their support conditions, pipe-soil friction and the surrounding soil mass. Under high compressive loads carried out by these efforts, loss of stability and buckling may occur. Then, the evaluation of soil lateral resistance that will cause a imminent breakout is important. This work aims the analysis of the soil lateral resistance by frictional limit analysis formulation, considering the soil mass as a deformable body and the pipe as a rigid one. An yield function considering material porosity and material friction angle is considered. The soil lateral resistance forces obtained from the proposed formulation are compared to a those ones considering the limit analysis lower bound found in literature. The fully bounded condition observed in most models is also discussed.

Mechanical Stimuli in Prediction of Trabecular Bone Adaptation: Numerical Comparison

Scipedia content — Thu, 30 Jun 2022 14:33:39 +0200

Adaptation is the process, with which bone responds to changes in loading environment and modifies its properties and organisation to meet the mechanical demands. Trabecular bone undergoes significant adaptation when subjected to external forces, accomplished through resorption of old and fractured bone and formation of a new bone material. These processes are assumed to be driven by mechanical stimuli of bone-matrix deformation sensed by bone mechanosensory cells. Although numerous in vivo and in vitro experimental evidence of trabecular bone morphology adaptation was obtained, the exact nature of mechanical stimuli triggering biological responses (i.e., osteoclastic resorption and osteoblastic formation) is still debated. This study aims to compare different mechanical stimuli with regard to their ability to initiate the load-induced adaptation in trabecular bone. For this purpose, a 2D model of two trabeculae, connected at their basement, with bone marrow in the intertrabecular space was developed. The finite-element method was implemented for the model loaded in compression to calculate magnitudes of several candidates of the bone-adaptation stimuli. A user material subroutine was developed to relate a magnitude of each candidate to changes in the shape of trabeculae.

Numerical Simulation of Neck Propagation in Double Network Hydrogel

Scipedia content — Wed, 06 Jul 2022 17:24:52 +0200

In this study, we at first employ a nonaffine polymer chains network model to account for the irreversible structural change during the deformation of DN gels. And then, a finite element model of the DN gels under simple tension is constructed. On the other hand, neck propagation is one kind of localized instability and there will be a local transfer of strain energy from one part of the model to neighboring parts. To solve such unstable quasi-static problem, an automatic mechanism provided by Abaqus/Standard is employed. The simulation results show that the nonaffine polymer chains network model together with the stablization algorithm for localized transformation of strain energy can be employed to reproduce the phenomenon of neck propagation in DN gels very well.

Proposal of Crack Propagation Criterion Considered Constraint Effect under Extremely Low Cycle Fatigue; Evaluation by 1.5T-CT Specimen

Scipedia content — Wed, 06 Jul 2022 17:27:22 +0200

The prediction of fracture behavior under extremely low cycle fatigue due to excessive loading is necessary for the life assessment of structures. This study evaluates the validity of the crack propagation criterion proposed in a previous study by performing generation phase and application phase analysis based on the results of fracture tests on a 1.5T-CT specimen (SGV410). The analysis show that the crack propagation criterion in the previous study predicted the experimental behavior well, however crack shape was incomplete in reproducing the crack shape.

Proposal of Crack Propagation Condition Criterion Considered Constraint Effect under Extremely Low Cycle Fatigue; Evaluation by 1T-CT and 2T-CT Specimen

Scipedia content — Wed, 06 Jul 2022 17:27:36 +0200

The strength evaluation of structures that requires high reliability, such as power generation facilities, is extremely important. It is necessary to ensure safety under extremely low cycle fatigue caused by earthquakes. However, a highly reliable evaluation method has not yet been developed because of variable fracture toughness due to the constraint effect with large deformation. The crack propagation criterion proposed by the previous study has needed some modification for accurate prediction. In this study, we confirmed whether the crack propagation criterion proposed by previous study can reproduce the fracture behavior of the experiment. Among then, relationship between the number of cycle and crack length, hysteresis loop, reproduction of crack shape were evaluation items.