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ADVANCES IN IMPACT ENGINEERING

The Crushing Characteristics of Square Tubes With Blast-Induced Imperfections—Part I: Experiments

[+] Author and Article Information
S. Chung Yuen1

Blast Impact and Survivability Research Unit (BISRU), Department of Mechanical Engineering, University of Cape Town, Private Bag, Rondebosch 7701, South Africasteeve.chungkimyuen@uct.ac.za

G. N. Nurick

Blast Impact and Survivability Research Unit (BISRU), Department of Mechanical Engineering, University of Cape Town, Private Bag, Rondebosch 7701, South Africa

1

Corresponding author.

J. Appl. Mech 76(5), 051308 (Jun 17, 2009) (16 pages) doi:10.1115/1.3005977 History: Received February 03, 2008; Revised July 29, 2008; Published June 17, 2009

This two-part article presents the results of experimental and numerical work on the crushing characteristics of square tubes, with blast-induced imperfections, subjected to axial load. In Part I, the experimental studies are presented. The approach in the studies involves creating imperfections on opposite sides at midlength of a square tube by means of localized blast loads to create three types of imperfections; nontouching domes, rebound domes, and capped domes. These imperfections change the geometry and the material properties in the midsection of the tubes and hence affect the crushing characteristics. While the blast-induced imperfections enhance the energy absorption characteristics of the tubes they also affect the lobe formation process. In Part II, the finite element package ABAQUS/EXPLICIT v6.5-6 is used to construct a 12 symmetry model by means of shell and continuum elements to simulate the tube response to the localized blast loads followed by dynamic axial loading in the form of a rigid mass impacting at a specified initial velocity. The hydrodynamic code AUTODYN is used to characterize the localized blast pressure time and spatial history. The predictions show satisfactory correlation with experiments for both crushed shapes and crushed distance.

Copyright © 2009 by American Society of Mechanical Engineers
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Figures

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Figure 1

Schematic and photo of the blast loading setup

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Figure 2

Graph of the impulse versus mass of the explosive for ME ranging from 1gto6g

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Figure 3

Photograph showing the different modes of imperfections

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Figure 4

Schematic of the quasistatic test setup

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Figure 5

Photograph showing as-received square tubes crushed quasistatically in the axial direction (increasing cross-head speed from left to right)

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Figure 6

Photograph showing the transient response of the quasistatically crushed as-received square tube

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Figure 7

Typical axial force-displacement graph for the quasistatically crushed as-received square tube

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Figure 8

Photograph showing the transient response of the quasistatically crushed square tube with circular cut-outs

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Figure 9

Typical axial force-displacement graph for the quasistatically crushed square tube with circular cut-outs

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Figure 10

Photograph showing the transient response of the quasistatically crushed square tube with simple Mode I imperfections (load diameter of 17mm)

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Figure 11

Typical axial force-displacement graph for the quasistatically crushed square tubes with simple Mode I imperfections (load diameter of 17mm)

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Figure 12

Photograph showing the transient response of the quasistatically crushed square tube with rebound dome imperfections

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Figure 13

Typical axial force-displacement graph for the crushed square tube with rebound dome imperfections

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Figure 14

Photograph showing the transient response of the quasistatically crushed square tube with capping imperfections (load diameter of 17mm)

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Figure 15

Typical axial force-displacement graph of the quasistatically crushed square tube with capping imperfections (load diameter of 17mm)

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Figure 16

Photographs showing the Euler buckling postprogressive collapse due to the skew lobe formation

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Figure 17

Photograph showing square tubes with and without imperfections crushed quasistatically

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Figure 18

Mean crush load of geometrically “perfect” and “imperfect” tubes crushed quasistatically

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Figure 19

Ultimate peak load of geometrically perfect and imperfect tubes crushed quasistatically

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Figure 20

Load efficiency of geometrically perfect and imperfect tubes crushed quasistatically

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Figure 21

Photograph of the dynamic axial crush setup

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Figure 22

Graph showing the crushed distance versus the drop energy for tubes with and without imperfections

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Figure 23

Photograph showing tubes collapsing in unstable mode (bolts included for photographic purposes)

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Figure 24

Photographs showing dynamic axially crushed 50mm square as-received and “blast-induced imperfections” tubes with drop mass of 210kg (mass of explosive: 3g)

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Figure 25

Photograph showing dynamic axially crushed 50mm square tubes, exposed to the explosive load 17mm in diameter, from 3.26m drop height with a drop mass of 329kg

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Figure 26

Photographs showing the dynamic axially crushed blasted loaded 50mm tube with a drop mass of 210kg from a 4m drop height (mass of explosive: 3.5g, load diameter: 25mm, crushed distance: 200mm)

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Figure 27

Photographs showing the dynamic axial crushed 50mm the square tubes with blast imperfection caused by a 4.5g of PE4 at a load diameter of 17mm (drop mass: 329kg, nominal drop height: 3.26m)

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Figure 28

Photographs showing the dynamic axial crushed 50mm square tubes with blast imperfection caused by 4.75g of PE4 at a load diameter of 17mm (drop mass: 329kg, nominal drop height: 3.26m)

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Figure 29

Photographs showing dynamic axial crushed 50mm square tubes with and without imperfections caused by an explosive of load diameter of 17mm with a drop mass of 329kg from a nominal height of 3.26m (imperfections in tube Q021 are drilled holes)

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Figure 30

Geometric efficiency of tubes with and without imperfections crushed dynamically

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Figure 31

Photograph showing the comparison between quasistatically and dynamically crushed tubes

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