New insights into the collapsing of cylindrical thin-walled tubes under axial impact load

2007 ◽  
Vol 221 (8) ◽  
pp. 869-885 ◽  
Author(s):  
M Shakeri ◽  
R Mirzaeifar ◽  
S Salehghaffari
Keyword(s):  
Neural Networks ◽  
Impact Load ◽  
Reaction Force ◽  
Plastic Buckling ◽  
Buckling Mode ◽  
Axial Impact ◽  
Geometric Imperfection ◽  
Design Variables ◽  
Initial Geometric Imperfection ◽  
Axisymmetric Plastic

The current paper presents further investigations into the crushing behaviour of circular aluminium tubes subjected to axial impact load. Experiments prove that in order to achieve the real collapsing shape of tubes under axial loads in numerical simulations, an initial geometric imperfection corresponding to the plastic buckling modes should be introduced on the tube geometry before the impact event. In this study, it is shown that the collapsing shape of tube is affected by this initial imperfection and consequently it is shown that by applying an initial geometric imperfection similar to the axisymmetric plastic buckling mode, the tubes tend to collapse in a concertina mode. This phenomenon is studied for circular tubes subjected to axial impact load and two design methods are suggested to activate the axisymmetric plastic buckling mode, using an initial circumferential edge groove and using one- and two-rigid rings on the tube. In each case the broadening of the concertina collapsing region is estimated using numerical simulations. Experimental tests are performed to study the influence of cutting the edge groove on the collapsing mode. In order to optimize the crashworthiness parameters of the structure such as the absorbed energy, maximum deflection in axial direction, maximum reaction force, and mean reaction force, a system of neural networks is designed to reproduce the crushing behaviour of the structure, which is often non-smooth and highly non-linear in terms of the design variables (diameter, thickness, and length of tube). The finite-element code ABAQUS/Explicit is used to generate the training and test sets for the neural networks. The response surface of each objective function (crashworthiness parameters) against the change of design variables is calculated and both single-objective and multi-objective optimizations are carried out using the genetic algorithm.

Dynamic Buckling of Cylindrical Shells under Axial Impact in Hamiltonian System

2012 ◽  
Vol 13 (1) ◽  
Author(s):  
Jia-Bin Sun ◽  
Xin-Sheng Xu ◽  
Chee-Wah Lim
Keyword(s):  
Hamiltonian System ◽  
Critical Load ◽  
Impact Load ◽  
Dynamic Buckling ◽  
Inertia Force ◽  
Elastic Cylindrical Shell ◽  
Symplectic Method ◽  
Buckling Mode ◽  
Axial Impact ◽  
Dual Variables

AbstractIn this paper, the dynamic buckling of an elastic cylindrical shell subjected to an axial impact load is analyzed in Hamiltonian system. By employing a symplectic method, the traditional governing equations are transformed into Hamiltonian canonical equations in dual variables. In this system, the critical load and buckling mode are reduced to solving symplectic eigenvalues and eigensolutions respectively. The result shows that the critical load relates with boundary conditions, thickness of the shell and radial inertia force. And the corresponding buckling modes present some local shapes. Besides, the process of dynamic buckling is related to the stress wave, the critical load and buckling mode depend upon the impacted time. This paper gives analytically and numerically some new rules of the buckling problem, which is useful for designing shell structures.

Analysis of Nonlinear Buckling of a Long-Span Elliptic Paraboloid Suspended Dome Structure

2013 ◽  
Vol 639-640 ◽  
pp. 191-197 ◽  
Author(s):  
Zheng Rong Jiang ◽  
Kai Rong Shi ◽  
Xiao Nan Gao ◽  
Qing Jun Chen
Keyword(s):  
Single Layer ◽  
Buckling Mode ◽  
Nonlinear Buckling ◽  
Elliptic Paraboloid ◽  
Geometric Imperfection ◽  
Long Span ◽  
Initial Geometric Imperfection ◽  
Dome Structure ◽  
Unsymmetrical Loading ◽  
The Stability

The suspended dome structure, which is a new kind of hybrid spatial one composed of the upper single layer latticed shell and the lower cable-strut system, generally has smaller rise-to-span ratio, thus the overall stability is one of the key factors to the design of the structure. The nonlinear buckling behavior of an elliptic paraboloid suspended dome structure of span 110m80m is investigated by introducing geometric nonlinearity, initial geometric imperfection, material elastic-plasticity and half-span distribution of live loads. The study shows that the coefficient of stable bearing capacity usually is not minimal when the initial geometric imperfection configuration is taken as the first order buckling mode. The unsymmetrical loading distribution and the material nonlinearity might have significant effects on the coefficient. The structure is sensitive to the changes of initial geometric imperfection, and the consistent mode imperfection method is not fully applicable to the stability analysis of suspended dome structure.

Behavior and Design of Web-Slotted Cold-Formed Channels Experiencing Local-Distortional-Global Interactive Buckling

2013 ◽  
Vol 351-352 ◽  
pp. 747-752
Author(s):  
Shuai Liu ◽  
Qi Jie Ma ◽  
Pei Jun Wang
Keyword(s):  
Effective Width ◽  
The Finite Element Method ◽  
Distortional Buckling ◽  
Buckling Mode ◽  
Geometric Imperfection ◽  
Interactive Behavior ◽  
Buckling Behavior ◽  
Initial Geometric Imperfection ◽  
Interactive Buckling ◽  
Shed Light

This article aims to shed light on the nonlinear local-distortional-global interactive behavior of web-slotted channel columns by use of the finite element method. The effects of three kinds of initial geometric imperfection based on different distortional buckling mode were evaluated. It indicates that different distortional buckling mode does little difference on the nonlinear interactive buckling behavior of web-slotted channels. Based on the extensive parametric study, some modifications were made to the traditional Effective Width Method for the practical design of web-slotted channel columns undergoing local-distortional-global interactive buckling.

Dynamic Buckling of Cylindrical Shells under Axial Impact in Hamiltonian System

2012 ◽  
Vol 13 (1) ◽  
Author(s):  
Jia-Bin Sun ◽  
Xin-Sheng Xu ◽  
Chee-Wah Lim
Keyword(s):  
Hamiltonian System ◽  
Critical Load ◽  
Impact Load ◽  
Dynamic Buckling ◽  
Inertia Force ◽  
Elastic Cylindrical Shell ◽  
Symplectic Method ◽  
Buckling Mode ◽  
Axial Impact ◽  
Dual Variables

AbstractIn this paper, the dynamic buckling of an elastic cylindrical shell subjected to an axial impact load is analyzed in Hamiltonian system. By employing a symplectic method, the traditional governing equations are transformed into Hamiltonian canonical equations in dual variables. In this system, the critical load and buckling mode are reduced to solving symplectic eigenvalues and eigensolutions respectively. The result shows that the critical load relates with boundary conditions, thickness of the shell and radial inertia force. And the corresponding buckling modes present some local shapes. Besides, the process of dynamic buckling is related to the stress wave, the critical load and buckling mode depend upon the impacted time. This paper gives analytically and numerically some new rules of the buckling problem, which is useful for designing shell structures.

Elastic-, inelastic and plastic buckling of curved shear webs in closed box girders with vertical stiffeners

2021 ◽  
Author(s):  
Gilles Van Staen ◽  
Philippe Van Bogaert ◽  
Amelie Outtier ◽  
Hans De Backer
Keyword(s):  
Load Capacity ◽  
Slenderness Ratio ◽  
Bending Test ◽  
Initial Stiffness ◽  
Plastic Buckling ◽  
Buckling Mode ◽  
Geometric Imperfection ◽  
Steel Panels ◽  
Curved Panels ◽  
Curved Steel

<p>Curved steel panels are widely used in structures such as ships, aircrafts and bridges. During the last decades, plates with an out-of-plane curvature in the cross-section of the bridge are being used, partly to increase the aesthetics. The elastic buckling behaviour of curved plates is not covered by standards of codes for bridge design, resulting in rather conservative solutions. In the current research, there is investigated how curved steel panels used as a web panel in a closed box girder interacts with shear and bending stresses. Therefore, a double symmetric box is numerical simulated in a three point bending test. The first mode shape found by a LBA is used as an initial geometric imperfection, in order to trigger buckling of the webs. It is proven that when increasing the curvature while keeping a similar slenderness ratio, the buckling mode of a plate can change from elastic to inelastic and even plastic buckling. This behaviour is found back in the webs of the closed steel sections. Slender curved plates have an equal load-deflection path as their straight variant. Inelastic and plastic buckling of the webs results yield zones in the web, eventually combined with geometric deformations. The girders with curved webs are sensitive to imperfections in such a way that slender curved panels have a large reduction in initial stiffness with increasing amplitude. On the other hand, moderate or thick curved panels remain their initial stiffness but have a reduction in their ultimate load capacity.</p>

Parameter Analysis on Stability of a Suspendome

2005 ◽  
Vol 20 (2) ◽  
pp. 115-124 ◽  
Author(s):  
Zhi-Hua Chen ◽  
Yang Li
Keyword(s):  
Structural Parameters ◽  
Engineering Application ◽  
Single Layer ◽  
Parameter Analysis ◽  
Space Structures ◽  
Buckling Mode ◽  
Geometric Imperfection ◽  
Stability Performance ◽  
Initial Geometric Imperfection ◽  
The Stability

As a kind of hybrid space structures, the suspendome system increases the stiffness and improves the stability of the original dome system by the appropriate use of prestressing cables. Based on the engineering application of suspendome in Tianbao Center (completed in China, 2002), the present paper concentrates on the stability performance of the suspendome with a span of 35.4m using different structural parameters, including the rise-span ratio, magnitude and level settings of initial prestressing in cables, connection rigidity and boundary support condition. Stability performances including buckling mode, critical loads and sensitivity to initial geometric imperfection are studied in detail, and contrast analyses with the corresponding singly-layer shells are carried out to study the superiorities of the suspendome over the single-layer shell. Some valuable conclusions are drawn for practical design.

Localized Plastic Buckling of a Heavy Beam on a Contacting Surface

1986 ◽  
Vol 108 (2) ◽  
pp. 146-150 ◽  
Author(s):  
H. D. Yun ◽  
S. Kyriakides
Keyword(s):  
Axial Load ◽  
Large Deflection ◽  
Limit Load ◽  
Axial Loads ◽  
Plastic Buckling ◽  
Geometric Imperfection ◽  
Initial Geometric Imperfection ◽  
Beam Mode

The paper considers the uplifting of a long elastoplastic heavy beam on a rigid flat foundation caused by an axial load. The problem is studied through a large deflection formulation. The beam is considered to possess a localized initial geometric imperfection. It is found that the load-deflection response is characterized by a limit load. Plastic effects can precipitate the limit load and cause a more localized type of deformation with higher curvatures. The problem is presented as a model for the “beam mode buckling” of pipelines due to earthquake-caused axial loads.

The Influence of Initial Geometric Imperfection on the Localized Buckling of Pressure Vessel Under Internal Pressure

2004 ◽  
Author(s):  
Li Wan ◽  
Wei-ming Tao ◽  
Xin-xin Wu ◽  
Shu-yan He
Keyword(s):  
Internal Pressure ◽  
Transition Region ◽  
Pressure Vessel ◽  
External Pressure ◽  
Pressure Vessels ◽  
Arc Length ◽  
Plastic Buckling ◽  
Geometric Imperfection ◽  
Initial Geometric Imperfection ◽  
Geometrical Imperfections

Pressure vessels are widely used in nuclear engineering and buckling is a common mechanical phenomenon in structure. The buckling problem of pressure vessels under external pressure has been researched for many years. This paper focuses on the influence of initial geometric imperfection on the localized elastic-plastic buckling of pressure vessel under internal pressure. The localized plastic buckling occurred in the transition region in the torispherical end closure of a pressure vessel is analyzed by FEM. By introducing two types of initial geometrical imperfections, the arc-length method of modified Riks/Ramm procedure is performed to simulate the buckling process during loading. The first type of imperfection is displacement, into the region where it is circumferentially compressed. The second type of imperfection is the irregular thickness of the vessel, also into the region where it is circumferentially compressed. The initial critical point is captured within the buckled region, and the corresponding initial buckling load is calculated. The results show that both artificial geometric imperfections can seduce the buckling. Furthermore, after the first buckling initiated, the succeeding loading will lead to more wrinkles within the compressive transition region. And then the case that with two distributed imperfections is also analyzed. It can be seen that the interaction between the imperfections is very weak before or even after the first buckling occurred, which means the buckling is fairly localized.

Determination of collapse moment of different angled pipe bends with initial geometric imperfection subjected to in-plane bending moments

2021 ◽  
pp. 095440622199640
Author(s):  
Manish Kumar ◽  
Pronab Roy ◽  
Kallol Khan
Keyword(s):  
Finite Element ◽  
Cross Section ◽  
Circular Cross Section ◽  
Initial Imperfection ◽  
Bend Angle ◽  
Bending Moments ◽  
Element Analysis ◽  
Geometric Imperfection ◽  
Initial Geometric Imperfection

From the recent literature, it is revealed that pipe bend geometry deviates from the circular cross-section due to pipe bending process for any bend angle, and this deviation in the cross-section is defined as the initial geometric imperfection. This paper focuses on the determination of collapse moment of different angled pipe bends incorporated with initial geometric imperfection subjected to in-plane closing and opening bending moments. The three-dimensional finite element analysis is accounted for geometric as well as material nonlinearities. Python scripting is implemented for modeling the pipe bends with initial geometry imperfection. The twice-elastic-slope method is adopted to determine the collapse moments. From the results, it is observed that initial imperfection has significant impact on the collapse moment of pipe bends. It can be concluded that the effect of initial imperfection decreases with the decrease in bend angle from 150∘ to 45∘. Based on the finite element results, a simple collapse moment equation is proposed to predict the collapse moment for more accurate cross-section of the different angled pipe bends.

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