Design for Crashworthiness of Vehicle Structures via Equivalent Mechanism Approximations and Crush Mode Matching

2004 ◽  
Author(s):  
Karim Hamza ◽  
Kazuhiro Saitou
Keyword(s):  
Cross Sections ◽  
Surrogate Model ◽  
Time History ◽  
Fe Model ◽  
Structural Members ◽  
Direct Optimization ◽  
Nonlinear Springs ◽  
Crashworthiness Design ◽  
Thin Walled ◽  
Equivalent Mechanism

This paper presents a 3D extension to our previous work on vehicle crashworthiness design that utilizes “equivalent” mechanism models of vehicle structures as a tool for the early design exploration. An equivalent mechanism (EM) is a network of rigid links with lumped masses connected by prismatic and revolute joints with nonlinear springs, which approximate aggregated behaviors of structural members during crush. A number of finite element (FE) models of thin-walled beams with typical cross sections and wall thicknesses are analyzed to build a surrogate model that maps the beam dimensions to nonlinear spring properties. Using the surrogate model, an EM model is optimized for given design objectives by selecting the nonlinear springs among the ones realizable by thin-walled beams. The optimum EM model serves to identify a good crash mode (CM), the time history of collapse of the structural members, and to suggest the dimensions of the structural members to attain it. After the optimization, the FE model of an entire structure is “assembled” from the suggested dimensions, which is further modified to attain the good CM identified by the optimum EM model. A case study of a 3D vehicle front half body demonstrates that the proposed approach can help obtain good designs with far less computational resources than the direct optimization of a FE model.

Design Optimization of Vehicle Structures for Crashworthiness Using Equivalent Mechanism Approximations

2004 ◽  
Vol 127 (3) ◽  
pp. 485-492 ◽  
Author(s):  
Karim Hamza ◽  
Kazuhiro Saitou
Keyword(s):  
Cross Sections ◽  
Surrogate Model ◽  
Fe Model ◽  
Lumped Mass ◽  
Direct Optimization ◽  
Nonlinear Springs ◽  
Revolute Joints ◽  
Vehicle Structure ◽  
Computational Resources ◽  
Equivalent Mechanism

A new method for crashworthiness optimization of vehicle structures is presented, where an early design exploration is done by the optimization of an “equivalent” mechanism approximating a vehicle structure. An equivalent mechanism is a network of rigid links with lumped mass connected by prismatic and revolute joints with nonlinear springs approximating aggregated behaviors of structural members. A number of finite element (FE) models of the thin-walled beams with typical cross sections and wall thicknesses are analyzed to build a surrogate model that maps a property of nonlinear spring to the corresponding FE model. Using the surrogate model, an equivalent mechanism is optimized for given design objectives by selecting the properties of the nonlinear springs among the values that can be realized by an FE model. After the optimization, the component FE models corresponding to the optimal spring properties are “assembled” into a FE model of an entire structure, which is further modified for final tuning. Two case studies of a vehicle front substructure are presented, which demonstrate the approach can help obtain a better design with far less computational resources than the direct optimization of a FE model.

scholarly journals STRUCTURAL FIRE BEHAVIOUR OF Z PURLINS

2016 ◽  
Author(s):  
Ivo Schwarz ◽  
Martin Slatinka ◽  
Michal Jandera
Keyword(s):  
Shell Element ◽  
Fe Model ◽  
Structural Members ◽  
Engineering Model ◽  
Fire Behaviour ◽  
Design Standard ◽  
Secondary Load ◽  
Practical Engineering ◽  
Bending Capacity ◽  
Thin Walled

Cold-formed sections are very common and efficient as secondary load-caring structural members. But the current European design standard EN 1993-1-2 sets the limiting temperature for the Class 4 sections to 350°C which is generallyvery conservative approach.This paper is focused on the thin-walled profilebehaviourin case offire. In particular, the paper describes transition from the beam to fibre behaviour of a Z purlin. A sophisticated shell element FE model is shown and compared to the test. Later, a more practical (Engineering) model neglecting the bending stiffness entirely is made and compared to the previous results. The conclusions show, that such simplified description of real behaviour is possible to be used after the bending capacity of the member is exceeded and predicts the forces to connection well.

Research of Simplified B Pillar Model for Roof Crashworthiness

2010 ◽  
Vol 34-35 ◽  
pp. 404-409
Author(s):  
Tao Xu ◽  
Liang Hao ◽  
Yi Wen Li ◽  
Qiang Li
Keyword(s):  
Surrogate Model ◽  
Simplified Model ◽  
Concept Design ◽  
Parallel Connection ◽  
Channel Section ◽  
Early Design ◽  
Nonlinear Springs ◽  
Thin Walled ◽  
Pillar Structure ◽  
Collapse Theories

The B pillar structure, which affects automotive roof crashworthiness, must have a perfect surrogate model to satisfy the early design demands. This work aims to explore the proper approach of simplified model construction. To create the simplified B pillar, the collapse theories of thin-walled hexagonal and channel beams under bending collapse are reviewed and applied to simulate the deforming behavior. Meanwhile, the simplified model is constructed from parallel connection of curved hexagonal and channel section beams. After distributing different rotational nonlinear springs, the same crashworthiness analyses are performed on both simplified and initial FE models to verify the simplified effects. The results demonstrate the potential of the approach and process proposed in developing the simplified model for the concept design of autobody.

Analysis of strain-gauge data from thin-walled structural members subjected to eccentric longitudinal loading

1975 ◽  
Vol 10 (2) ◽  
pp. 104-110 ◽  
Author(s):  
M F Randolph ◽  
E Lightfoot
Keyword(s):  
Cross Sections ◽  
Strain Gauge ◽  
Structural Members ◽  
Skeletal Structures ◽  
Longitudinal Loading ◽  
Gauge Data ◽  
Thin Walled ◽  
Reduced Scale

In full- or reduced-scale tests on skeletal structures, several cross-sections are usually strain-gauged to enable strain distributions to be obtained and stress resultants to be deduced. This paper explains how such measurements are best analysed, with special emphasis on the proper inclusion of longitudinal stresses associated with warping. Two examples are included.

Simulation of Thin-Walled Members with Arbitrary-Shaped Cross-Sections for Static and Dynamic Analyses

2020 ◽  
Vol 20 (12) ◽  
pp. 2050128
Author(s):  
A. H. A. Abdelrahman ◽  
Siwei Liu ◽  
Yao-Peng Liu ◽  
Siu-Lai Chan
Keyword(s):  
Finite Element ◽  
Cross Sections ◽  
Time History ◽  
Finite Element Models ◽  
Closed Form Solutions ◽  
Dynamic Analyses ◽  
Python Scripting ◽  
Thin Walled ◽  
Shell Finite Element ◽  
Dynamic Time

The main objective of this paper is to validate a finite-element (FE) modeling protocol to simulate thin-walled members for static and dynamic analyses. Arbitrary-shaped cross-sections, including open, closed, and multicellular sections can be efficiently modeled for further advanced study. The framework is thoroughly validated and verified using the existing analytical and closed-form solutions, as well as experimental results available in literature. This work is motivated by the higher accuracy of the shell FE-based modeling to capture the local and global complex behaviors of thin-walled members with asymmetric sections. Higher computational expenses, however, are required for such sophisticated shell finite element models (SFEM). Accordingly, a framework hosted in MATLAB and implementing the python scripting technique in ABAQUS, is developed, which includes eigen buckling, static nonlinear, modal frequency and dynamic time-history analyses. For a more modeling convenience, various parameters are incorporated such as imperfections, residual stresses, material definitions, element choice, meshing control, and boundary conditions. Several examples are provided to illustrate the application of the proposed framework, and to prove the robustness and accuracy of the generated FE models. This paper concludes with the efficiency of implementing SFEMs for simulating thin-walled members; thereby, establishing a more accurate and advanced structural analysis.

scholarly journals Eigenproblem Versus the Load-Carrying Capacity of Hybrid Thin-Walled Columns with Open Cross-Sections in the Elastic Range

Materials ◽  
2021 ◽  
Vol 14 (13) ◽  
pp. 3468
Author(s):  
Zbigniew Kolakowski ◽  
Andrzej Teter
Keyword(s):  
Cross Sections ◽  
Carrying Capacity ◽  
Ultimate Load ◽  
Equilibrium Path ◽  
Load Carrying Capacity ◽  
Nonlinear Buckling ◽  
Elastic Range ◽  
Load Carrying ◽  
Thin Walled ◽  
Ultimate Load Carrying Capacity

The phenomena that occur during compression of hybrid thin-walled columns with open cross-sections in the elastic range are discussed. Nonlinear buckling problems were solved within Koiter’s approximation theory. A multimodal approach was assumed to investigate an effect of symmetrical and anti-symmetrical buckling modes on the ultimate load-carrying capacity. Detailed simulations were carried out for freely supported columns with a C-section and a top-hat type section of medium lengths. The columns under analysis were made of two layers of isotropic materials characterized by various mechanical properties. The results attained were verified with the finite element method (FEM). The boundary conditions applied in the FEM allowed us to confirm the eigensolutions obtained within Koiter’s theory with very high accuracy. Nonlinear solutions comply within these two approaches for low and medium overloads. To trace the correctness of the solutions, the Riks algorithm, which allows for investigating unsteady paths, was used in the FEM. The results for the ultimate load-carrying capacity obtained within the FEM are higher than those attained with Koiter’s approximation method, but the leap takes place on the identical equilibrium path as the one determined from Koiter’s theory.

scholarly journals Vision-Based Structural FE Model Updating Using Genetic Algorithm

2021 ◽  
Vol 11 (4) ◽  
pp. 1622
Author(s):  
Gun Park ◽  
Ki-Nam Hong ◽  
Hyungchul Yoon
Keyword(s):  
Genetic Algorithm ◽  
Model Updating ◽  
Structural Parameters ◽  
Fe Model ◽  
Structural Members ◽  
Stiffness Reduction ◽  
Before And After ◽  
Scale Test ◽  
Fe Model Updating ◽  
Story Building

Structural members can be damaged from earthquakes or deterioration. The finite element (FE) model of a structure should be updated to reflect the damage conditions. If the stiffness reduction is ignored, the analysis results will be unreliable. Conventional FE model updating techniques measure the structure response with accelerometers to update the FE model. However, accelerometers can measure the response only where the sensor is installed. This paper introduces a new computer-vision based method for structural FE model updating using genetic algorithm. The system measures the displacement of the structure using seven different object tracking algorithms, and optimizes the structural parameters using genetic algorithm. To validate the performance, a lab-scale test with a three-story building was conducted. The displacement of each story of the building was measured before and after reducing the stiffness of one column. Genetic algorithm automatically optimized the non-damaged state of the FE model to the damaged state. The proposed method successfully updated the FE model to the damaged state. The proposed method is expected to reduce the time and cost of FE model updating.

System-wide seismic vulnerability of aging multiple-span multiple-girder bridges in low-to-moderate seismic hazard regions

2021 ◽  
Vol 37 (1_suppl) ◽  
pp. 1626-1651
Author(s):  
John E Lens M.EERI ◽  
Mandar M Dewoolkar ◽  
Eric M Hernandez M.EERI
Keyword(s):  
United States ◽  
Seismic Hazard ◽  
Cross Sections ◽  
Seismic Vulnerability ◽  
Time History ◽  
The United States ◽  
National Database ◽  
Eastern United States ◽  
Girder Bridges ◽  
The Status

This article describes the approach, methods, and findings of a quantitative analysis of the seismic vulnerability in low-to-moderate seismic hazard regions of the Central and Eastern United States for system-wide assessment of typical multiple span bridges built in the 1950s through the 1960s. There is no national database on the status of seismic vulnerability of bridges, and thus no means to estimate the system-wide damage and retrofit costs for bridges. The study involved 380 nonlinear analyses using actual time-history records matched to four representative low-to-medium hazard target spectra corresponding with peak ground accelerations from approximately 0.06 to 0.3 g. Ground motions were obtained from soft and stiff site seismic classification locations and applied to models of four typical multiple-girder with concrete bent bridges. Multiple-girder bridges are the largest single category, comprising 55% of all multiple span bridges in the United States. Aging and deterioration effects were accounted for using reduced cross-sections representing fully spalled conditions and compared with pristine condition results. The research results indicate that there is an overall low likelihood of significant seismic damage to these typical bridges in such regions, with the caveat that certain bridge features such as more extensive deterioration, large skews, and varied bent heights require bridge-specific analysis. The analysis also excludes potential damage resulting from liquefaction, flow-spreading, or abutment slumping due to weak foundation or abutment soils.

A torsion bending element for thin-walled beams with open and closed cross sections

1995 ◽  
Vol 55 (6) ◽  
pp. 1045-1054 ◽  
Author(s):  
H. Shakourzadeh ◽  
Y.Q. Guo ◽  
J.-L. Batoz
Keyword(s):  
Cross Sections ◽  
Thin Walled
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