A Study of the Dynamics of Low Energy Cushioning Materials Using Scale Models

Woolam, William E.

doi:10.1177/0021955x6800400204

Cited by 19 publications

(11 citation statements)

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“…Various polymer foams are most widely used for this aim. [1,2] Nevertheless, the energy absorption capacity of polymer foam is relatively low because of its low compressive strength. Under the condition of a much higher impact load, an absorber made of polymer foam should, therefore, be voluminous enough to absorb the energy.…”

Section: Introductionmentioning

confidence: 99%

Compressive deformation and energy absorbing characteristic of foamed aluminum

Han

Zhang

Gao

1998

Metall Mater Trans A

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Experiments were carried out to investigate the deformation and energy absorbing characteristics and mechanisms of foamed aluminum (FA) with two different matrices. Some new results were obtained. It is found that, like other cellular solid materials, FA has a stress-strain curve with three distinct regions, i.e., the linear elasticity region, the plastic collapse region or brittle crushing region, and the densification region. The energy absorbing capacity of FA increases by increasing the relative density and the yielding strength. Brittle foam exhibits higher capacity than plastic foam with similar yielding strengths. FA reaches its peak value of energy absorbing efficiency at the strain of about 0.15 to 0.35, depending on the relative density. AlMg10 foam shows higher absorbing capacity and efficiency than Al foam.

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Section: Introductionmentioning

confidence: 99%

Compressive deformation and energy absorbing characteristic of foamed aluminum

Han

Zhang

Gao

1998

Metall Mater Trans A

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“…Generally, deceleration increases with plastic density but decreases with impact energy tending to a minimum value. The calculated deceleration is considered to be proportional to the Janssen factor (Woolam, 1968), except for those test specimens that cracked (mode d) or fractured (mode e), where the minimum point expected in full indention (mode c) was not observed. Lower deceleration/Janssen factor was thought to have higher energy absorption efficiency for that particular impact energy applied during the impact test (Hilyard and Djiauw, 1971;Neto and Mourão, 2002;Zhang and Ashby, 1994).…”

Section: Depth Of Indentmentioning

confidence: 99%

“…The calculated deceleration was thought to be proportional to the Janssen factor (Woolam, 1968) assuming the projectile is fully stopped after embedment distance of d ind , which can be used to evaluate the energy absorption efficiency of a material under impact (Hilyard and Djiauw, 1971;Neto and Mourão, 2002;Zhang and Ashby, 1994).…”

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confidence: 99%

Energy absorption of foamed concrete from low-velocity impacts

Jones

2013

Magazine of Concrete Research

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Foamed concrete has existing uses as an energy absorber for large-scale and low-cost applications, such as explosion prevention in mines and military engineering projects and aircraft arresting systems. However, there is little information enumerating the energy absorption characteristics of different foamed concretes; this paper describes a study that determined these using low-velocity impact tests. A range of foamed concretes were tested with plastic densities varying from 500 to 1400 kg/m 3 , which are typical of those produced commercially. The tests used hemispherical projectiles with a range of masses from 1 . 2 to 8 . 4 kg, dropped from a fixed height of 4 . 7 m. The resulting 'damage' was measured and related to the impact energy imparted to the test specimen. A classification, using five different failure modes, was established and the mode in which the test specimen neither caused 'rebound' of the projectile nor itself fractured was selected as representing 'ideal' energy absorption behaviour.Making the assumption of no energy losses and using the conservation of energy law, the energy absorption capacity of foamed concrete was calculated and was found to vary from 4 to 15 MJ/m 3 for different mixes. The optimum energy absorption was noted for the 1000 kg/m 3 mix at water to cement (w/c) ratios from 0 . 6 to 0 . 7, which allowed a debris field of crushed foamed concrete to form and be pushed into the concrete bubble space ahead of the nose of the projectile, without fracturing. Notation a n nominal deceleration, which is the average deceleration assuming the projectile is fully stopped after indentingpotential energy (J), which for the purposes of these tests was assumed equal to impact energy in the drop test (i.e. any aerodynamic drag was ignored for simplicity) E abs energy absorption per indent volume (MJ/m 3 ) g gravity (taken as 9 . 81 m/s 2 ) h fall height in the drop test (in this case fixed at 4 . 7 m) m projectile mass (kg) R radius of the hemispherical nose of the projectile (¼ 31 . 72 mm) V indent volume duo to embedment of projectile (mm 3 ) v velocity of the projectile before impact (¼ 9 . 6 m/s) w/c water/cement ratio of foamed concrete IntroductionFoamed concrete has reached a mature commercial position in the market and is now widely used for a variety of purposes in the civil engineering and building fields (e.g. McCarthy, 2005, 2006;Jones et al., , 2009). Foamed concrete can be produced with a wide range of recycled and secondary aggregates, and can be easily crushed and reused; therefore, it is a sustainable material (Jones et al., 2012). Polymer foam materials are widely used to absorb impact energy to protect goods in transit and other similar applications, but, based on cost, these materials are not suitable for large-scale applications, such as aircraft runway arrestors (Kazda and Caves, 2007), mines explosion protection (Weiss et al., 1996) and so on. Precast foamed concrete block targets have been used by the military in firing ranges. Bullets enter the foamed concrete block...

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“…There are a few methods [7,8,13] to determine energy absorption in foams to give guidance in making the best choice, such as the Janssen factor J (the ratio of the peak acceleration of a real foam in absorbing a given impact energy to the acceleration of an ideal foam) [7,8], the cushion factor C (a plot of the peak stress divided by the energy absorbed up to that peak stress against the peak stress itself) [9][10][11], and Gibson's modified approach to include the influence of strain rate [15]. All these involve empirical measurements, requiring large amounts of test data.…”

Section: Introductionmentioning

confidence: 99%