Search for critical loading condition of the spine–A meta analysis of a nonlinear viscoelastic finite element model

Abstract Spondylolysis is a developmental condition or a stress fracture phenomenon, in which a defect in the pars interarticularis leads to varying degrees of instability in the lumbar spine. A finite element model was used to study the effect of pars defect as well as pars defect combined with varying slip on the change in flexibility of the lumbar motion segments under mechanical loading. Compared to the intact model, a pars defect at L3–L4 level allowed a small increase in motion at L2 with respect to L5 under all loading modes except torsion. Motion of L2 with respect to L5 was further increased by 3% to 20% with 50% translation prior to loading in all loading modes except torsion. Fifty percent translation increased the torsion motion further by 50%. In every model, the increase in motion was greatest under torsion. This study showed that stability of a motion segment in spondylolysis depends on the amount of spondylolisthesis and the loading condition. There was more motion with increased slip in all-loading modes with largest increase with torsion moment load. The type of loading also affects the degree of motion, with torsion creating significant instability.

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Multi-body dynamics co-simulation of hoisting wire rope

The Journal of Strain Analysis for Engineering Design ◽

10.1177/0309324717744146 ◽

2017 ◽

Vol 53 (1) ◽

pp. 36-45 ◽

Cited By ~ 3

Author(s):

Qing Huang ◽

Zhi Li ◽

Hong-qian Xue

Keyword(s):

Finite Element ◽

Finite Element Model ◽

Dynamic Analysis ◽

Dynamic Model ◽

Loading Condition ◽

Element Model ◽

Wire Rope ◽

Body Dynamics ◽

Hoisting System ◽

Multi Body

As more wire ropes with complex construction are used in the hoisting system of a crane, it becomes more necessary to predict the risks of the hoisting operation. Especially the wire rope, dynamic analysis is required to manage the potential risk in advance. Thus, in this article, a co-simulation method based on multi-body dynamics and finite element method is proposed to determine the dynamic responses of a hoisting system and wire rope. We developed a dynamic model of hoisting system based on ADAMS/Cable to formulate the time history response of dynamic force on wire rope, which could be used as the loading condition in the posterior finite element model. A three-dimensional geometric model for the multi-layered strands wire rope with a construction of 1+7+7 / 7+14 wires is implemented in the finite element analysis software ABAQUS, and both static and dynamic analyses are presented. The static analysis result of force–strain relation is compared with several experiment data, and the finite element model is proved accurate and reliable. In the latter case, the force–time curves obtained by dynamic model are imported to finite element model as loading condition to accomplish dynamic analysis. The co-simulation results of hoisting wire rope’s behavior subjected to dynamic loading during the hoisting process are carried out and discussed. The stress distribution and stress spectrum of wire rope are obtained, and the results show that the most dangerous regions are the lateral side of wire rope, especially the contact area of two wires in strands.

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