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The Neck
Published in Melanie Franklyn, Peter Vee Sin Lee, Military Injury Biomechanics, 2017
Kwong Ming Tse, Jianfei Liu, Victor P.W. Shim, Ee Chong Teo, Peter Vee Sin Lee
The incidence of acute neck injuries is a major concern in pilot ejection, and rocket sled tests have been used to mimic the ejection process (Arnaiz 1986; Burton 1999; Vasishta et al. 2003; David et al. 2011). However, rocket sled tests are highly expensive and there are limited facilities worldwide. There are also a limited number of reports on experiments that simulate vertical ejection on cadaveric head–neck complexes because of the practical difficulties in conducting these tests (Gaynor et al. 1962; Stemper et al. 2009). Hence, most pilot ejection sled tests have been performed using ATDs. To evaluate neck injury risk due to two helmet supported masses, Perry (1994) performed an experimental ejection on an Advanced Dynamic Anthropomorphic Manikin (ADAM), equipped with Concept VI and ANVIS 49/49 helmets and seated on an Advanced Concept Ejection Seat (ACES) II and B-52 seats using a vertical deceleration tower. It was found that both helmets did not induce any neck injury, as the neck loads are less than the maximum (1800 N) required for neck fracture. It was also found that a helmet supported mass with a weight of 2.7 kg or less and having a centre of gravity from −0.51 to 2.79 cm and 1.02 to 3.56 cm on the anatomical x and y axes, respectively, did not result in neck injury. Another series of Gz impact tests using an ATD was conducted by Shender et al. (2000), where the aim of the tests was to determine the effect of varying the helmet’s weight and its centre of gravity position during pilot ejection. It was found that for a helmet weight of 1.4 kg to 2.5 kg, the +12 Gz manoeuvre would give rise to a neck load ranging from 1010 N to 1112 N and a bending moment ranging from 78 Nm to 112 Nm.
Control of hygrothermal vibration of viscoelastic magnetostrictive laminates resting on Kerr’s foundation
Published in Mechanics Based Design of Structures and Machines, 2023
Ashraf M. Zenkour, Hela D. El-Shahrany
High-speed transportation systems, railway track, solid propellant rocket motors, and rocket-sled technology represent application examples of the structural systems which require foundations to reduce their oscillation. The one-parameter Winkler elastic foundation consists of closed-spaced linear springs where this model deals only with the normal loading. Pasternak (1954) modeled a novel model to develop Winkler’s foundation by introducing a shear layer to deal with the shear loads. Kerr (1964, 1965) developed Pasternak’s model by adding an extra spring layer above the shear layer to avoid the occurrence of the concentrated line reactions along the free edges of the structures. Under uniform dynamic loading, hygrothermal load, and lateral concentrated, Barati and Zenkour (2018) used a higher-order refined beam theory to study the size-dependent forced vibration of a functionally graded nanobeam supporting by Kerr’s foundation. In the hygrothermal environment, Barati (2017) analyzed the dynamic response of an inhomogeneous porous nanobeam embedded in a Kerr-type foundation and exposed to concentrated and distributed loads. The previous literature indicates that there is no study for covering the vibration and damping behavior of a visco-magneto-elastic composite plate with a core of homogenous material. Also, for the first time in the literature, the structure analysis that combined the viscoelastic and intelligent plies with considering some impacts such as Kerr-type foundations and hygrothermal loads is presented in the current work, so, the objective of the present study is the vibration response analysis of a visco-magnetoelastic composite plate with a homogenous core resting on Kerr’s elastic foundation in a hygrothermal environment. The medium is modeled as a three-parameter Kerr-type foundation which contains a shear layer connected with two spring layers. The main differential equations of exponential shear deformation theory included hygrothermal and Kerr foundation effects are presented and solved analytically according to Navier’s method. several numerical examples are carried out to investigate the significant effects on vibration damping behavior of a visco-magneto-elastic plate are discussed in detail. The novel work can be providing a reference framework for future studies in this field and it can be developing advanced engineering applications.