Treatment of Bending Deformations in Maritime Crash Analyses

2020 ◽  
Author(s):  
Mihkel Kõrgesaar ◽  
Martin Storheim
Keyword(s):  
Plane Stress ◽  
Control Element ◽  
Crash Analysis ◽  
Fracture Criteria ◽  
Shell Elements ◽  
Bending Deformation ◽  
Mechanical Field ◽  
Element Size ◽  
Inherent Nature ◽  
Element Erosion

Abstract This paper focuses on the bending deformation experienced by metallic materials and its characterization during the crash analysis of ship structures. These analyses are conducted with plane stress shell elements for computational reasons. The inherent nature of through thickness plane stress poses restrictions on how the bending associated stress and strain distribution are resolved. Namely, fracture criteria used in crash analysis account bending damage accumulation differently. Most criteria do not specifically address the issue as element erosion is activated once all through thickness integration points have reached the predefined failure condition. However, when elements are bent, material layers (top and bottom) display strong variations in mechanical field variables that are commonly used to control element deletion. Therefore, the focus of current analyses is to show how different fracture criteria account bending deformation and how sensitive are the results depending on the chosen element size.

On Pipe Elbow Elements in ABAQUS and Benchmark Tests

2014 ◽  
Author(s):  
Lingfu Zeng ◽  
Lennart G. Jansson ◽  
Yordan Venev
Keyword(s):  
Peak Stress ◽  
Coarse Mesh ◽  
Pipe Bend ◽  
Shell Elements ◽  
Finite Element Software ◽  
Pipe Elbow ◽  
Element Size ◽  
Benchmark Tests ◽  
Pipe Section ◽  
Insight Into

In this paper, elbow elements in commercial finite element software ABAQUS are reviewed and two commonly used elements, ELBOW31 (2-node, linear) and ELBOW32 (3-node, quadratic), are numerically tested for two Benchmark examples: a cantilever pipe and an in-plane bending pipe bend. Two main issues are studied through the numerical tests: (1) The effect of the element size and the number of ovalization modes chosen for computation; (2) The accuracy of computed deformation and stresses. To gain an insight into the behavior of these elements, a comparison against published results by experiment and computations using elbow elements in software ADINA and MARC, as well as computations using ABAQUS shell elements, is conducted. It is shown that: (i) these elements predict a good peak stress solution with a reasonably coarse mesh and 6 ovalization modes; (ii) the ovalization and the distribution of stresses predicted around the pipe section show, though using a relatively dense mesh, a notable difference as compared to solutions computed by ABAQUS shell elements; (iii) the ADINA elbow element seems to provide, though using a very coarse mesh, a solution closest to analytic and experimental results. It is concluded that there are great needs for in-depth studies on elbow elements regarding reliability and accuracy issues.

Consequences of Using the Plane Stress Assumption for Damage Calculations in Crash Analyses

2014 ◽  
Author(s):  
Carey L. Walters ◽  
Lars O. Voormeeren
Keyword(s):  
Plane Stress ◽  
Stress Triaxiality ◽  
Shell Element ◽  
Element Model ◽  
Offshore Structures ◽  
Two Dimensions ◽  
Shell Structures ◽  
Planar Case ◽  
Lode Parameter ◽  
Shell Elements

Simulation of failure in plate materials (represented as shell elements) is critical for the correct determination of crash performance of ships and offshore structures. This need has traditionally been filled with failure loci that give the failure strain in terms of stress triaxiality. In recent years, a third dimension (Lode parameter) has been introduced in the form of the Modified Mohr Coulomb failure criterion and Lode parameter adjusted Gurson-type models. This development introduces ambiguity for shell structures, in which only two dimensions are represented. The typical way of addressing this is to assume that shell structures fail in plane stress, thus reducing the problem back to 2-D. However, the assumption of plane stress is violated as soon as necking begins, causing different stress triaxialities and Lode parameters than would be expected from the planar case. More importantly, the inhomogenous necked region is then homogenized over the entire shell element. In this paper, the consequences of the through-thickness plane stress assumption are assessed through a finite element model of a plate that is subjected to a far-field stress.

Prediction of Distortion Produced in Welded Structures During Straightening Process Using the Inherent Strain Method

2016 ◽  
Author(s):  
Hector Olmedo Ruiz Valdes ◽  
Naoki Osawa ◽  
Hidekazu Murakawa ◽  
Sherif Rashed
Keyword(s):  
Local Heating ◽  
Three Dimensional ◽  
Angular Distortion ◽  
Simulation Code ◽  
Shell Elements ◽  
Narrow Region ◽  
Element Size ◽  
Inherent Strain ◽  
Inherent Strain Method ◽  
Equivalent Nodal Forces

In order to optimize the straightening process, it is necessary to predict the deformation due to local heating. Numerical simulation is an advantageous way to do this. In this study, Osaka University’s inherent strain based welding simulation code JWRIAN is modified so that inherent strain’s equivalent nodal forces are calculated in cases where the inherent strain confines within narrow region whose size is smaller than element size. In the developed code, the initial strain force vector and element stiffness matrix’s non-linear term which includes stress components are integrated using higher order (e.g. 20 × 20 × 6 for 4-nodes shell elements) Gauss-Legendre quadrature while other quantities are evaluated by using ordinary order (2 × 2 × 2) quadrature. The validity of the developed software is examined by comparing rectangular plate’s angular distortion due to gas line heating calculated by three-dimensional thermal-elastic-plastic analysis and that calculated by the developed system.

Fracture Criteria of Rubber-Like Materials under Plane Stress Loadings

2008 ◽  
pp. 767-768 ◽  
Author(s):  
A. Hamdi ◽  
M. Nait-Abdelaziz ◽  
N. Ait Hocine ◽  
P. Heuillet
Keyword(s):  
Plane Stress ◽  
Fracture Criteria

Crush Simulation of Car Using LSDYNA

2012 ◽  
Vol 433-440 ◽  
pp. 2326-2331 ◽  
Author(s):  
Eriki Ananda Kumar ◽  
R. Ravichandra ◽  
Devaraj Kanisin
Keyword(s):  
Ultimate Strength ◽  
Physical Phenomenon ◽  
Time Integration ◽  
Shell Element ◽  
Operating Conditions ◽  
Crash Analysis ◽  
Shell Elements ◽  
Solution Algorithms ◽  
Routine Manner ◽  
Highly Nonlinear

The paper is concerned with FEA procedures are now used abundantly in automotive industry. Linear static and dynamic analyses are conducted in a routine manner, and nonlinear analysis is increasingly pursued. Two analysis fields in which highly nonlinear conditions are simulated are the crash and crush analysis of complete motorcar models. The purpose of a crash analysis is to see how the car will behave in a frontal or sideway collision. In a crash analysis the crashing of a car at about 30mph and above is considered. Various crash codes have been developed based on explicit time integration, special shell elements for this specific analysis results have been compared with laboratory test data, and the simulations have proved very valuable. In crush analysis, a quite different physical phenomenon is considered. Here the purpose is to establish the ultimate strength of the car body in a static situation. The ultimate strength affects the behavior of the car under various operating conditions, such as when the car overturns in an accident. While crash analysis of cars have been carried out with mush success, a crush analysis is much more difficult to achieve. The reasons for this greater difficulty lie in the fact that a slow-speed, almost static analysis requires increased robustness and efficiency in the solution algorithms. Specifically, for the crush analysis, the shell element mush be of high predictive capability, and be robust and computationally efficient for static analyses.

Plane Stress, Plate and Shell Elements

1997 ◽  
pp. 123-133
Author(s):  
A. Muttoni ◽  
J. Schwartz ◽  
B. Thürlimann
Keyword(s):  
Plane Stress ◽  
Shell Elements ◽  
Plate And Shell

Computing cell tractions from particle displacements on silicone rubber substrata

1994 ◽  
Vol 52 ◽  
pp. 162-163
Author(s):  
Tim Oliver ◽  
Akira Ishihara ◽  
Ken Jacobsen ◽  
Micah Dembo
Keyword(s):  
Plane Stress ◽  
Linear Elasticity ◽  
Silicone Rubber ◽  
Mathematical Analysis ◽  
Elastic Recovery ◽  
Video Images ◽  
Cell Traction Forces ◽  
Latex Beads ◽  
Cell Traction ◽  
Better Than

In order to better understand the distribution of cell traction forces generated by rapidly locomoting cells, we have applied a mathematical analysis to our modified silicone rubber traction assay, based on the plane stress Green’s function of linear elasticity. To achieve this, we made crosslinked silicone rubber films into which we incorporated many more latex beads than previously possible (Figs. 1 and 6), using a modified airbrush. These films could be deformed by fish keratocytes, were virtually drift-free, and showed better than a 90% elastic recovery to micromanipulation (data not shown). Video images of cells locomoting on these films were recorded. From a pair of images representing the undisturbed and stressed states of the film, we recorded the cell’s outline and the associated displacements of bead centroids using Image-1 (Fig. 1). Next, using our own software, a mesh of quadrilaterals was plotted (Fig. 2) to represent the cell outline and to superimpose on the outline a traction density distribution. The net displacement of each bead in the film was calculated from centroid data and displayed with the mesh outline (Fig. 3).

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