When subjected to simple compression or pure shear, most engineering materials display behaviour similar to their behaviour under tension, although the relevant material constants may be different. Fracture may also occur in the tension face at the clamping end. The Energy absorption of structures and materials Simply supported mm span 25 Rigid-plastic Elastic-plastic Experimental Load P kN 20 Denting—bending 15 Structural collapse 10 5 0 0 10 20 30 40 50 60 Indenter displacement dtl mm a Fully fixed mm span 40 Load P kN 30 Rigid-plastic Elastic-plastic 20 Experimental 10 Membrane stretching Denting—bending—stretching 0 0 10 20 30 40 50 60 70 Indenter displacement dtl mm b 5. Nevertheless, the load—deflection behaviour 1. Such an arrangement can be an energy-absorbing system itself, but it also represents the micro-structural behaviour of cellular solids see Chapter The following example illustrates this point.
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Energy Absorption of Structures and Materials
In a similar way to the behaviour of plastic hinges in a beam, relative rotations are allowed along plastic hinge-lines in a plate or a shell. Actually, I had to decide between the raiders and the imps.
Shear stress—shear strain curves can be obtained by using a torsional bar. Let the initial collapse load of a ring be Po and the current load be P. The total input energy Ein given in Eq. The rig has a minimum mass of kg and a maximum mass of kg, with a maximum speed of One method of overcoming this shortcoming is presented here Lu, a. Empirical formulae were given by Lu b and Ong and Lu In other words, the resistant force from the colliding structure should remain constant during a collision in order to minimise the injury and damage caused by it.
Maximum deformation occurs at the loading point. Stretching is therefore invoked. As the velocity was low, deformation occurred uniformly and simultaneously for all rings and therefore the overall response of the system could be determined by analysing each single ring as in the quasi-static case. This is particularly true for energy-absorbing devices because they are usually one-shot items, i.
Energy Absorption of Structures and Materials – PDF Free Download
It is therefore easy to see that when the impact velocity is the same, a small-scale model which has a smaller linear dimension will experience a higher strainrate than a prototype; this is also indicated in Table 3. Any constant should be purely numerical without a unit. Neither this book nor any part may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, microfilming and recording, or by any information storage or retrieval system, without permission in writing from the publishers.
Thus, a plastic wave develops at the impact end and then propagates towards the distal end. In Chapter 3, dimensional analysis and the closely related concept of small-scale model tests are discussed in the context of energy absorption, whilst conventional experimental methods are introduced.
The beam has one end clamped and the other end simply supported.
Fundamentally, such departure means that the values of all the dimensionless groups are not kept the same for both implaet model and prototype. BC rotates clockwise, whereas A B rotates counter-clockwise. The variation of the velocity of the block with time is depicted in Fig.
As stated in Section 2.
Second, a quasi-static test enables us to observe, with relative ease, the detailed deformation 4c. A two-stage gas gun produces considerably higher velocities still Crozier and Hume, Some people argue that HIC does not reflect rotational impkast, which is believed to cause brain injury.
They should be long enough to minimise the radial movement at the impact face. When f increases further, this ratio reduces, e. In fact, it has been demonstrated in Section 2.
As seen in Ijplast 2. The structure of the book is as follows. The most commonly employed guardrail system in the world consists of a galvanised steel beam shaped in 4s form of a W W-beam and supported on steel tubular or channel section or wood posts, as shown in Fig.
Empirically, Stronge proposed that the energy corresponding to the ballistic limit, which is defined as the velocity when the projectile is either stuck in the target or else exits with negligible velocity, for a spherical-nosed missile with diameter 6.
Line 0E represents the elastic response. Jones and his co-workers Jones et al. The clear similarity between Eq. If, however, in a particular case gravity loads are significant and need to be considered in scaling, adopting a different material for the model may overcome this difficulty; however, the model density must ensure that the overall scaling factor SrSl3 is equal to SmSl2.