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Stabilization of rock slopes
Published in Duncan C. Wyllie, Christopher W. Mah, Rock Slope Engineering, 2017
Duncan C. Wyllie, Christopher W. Mah
A critical feature of shed design is the weight and energy absorption characteristics of the cushioning material. Ideally the cushion should both absorb energy by compression, and disperse the point impact energy so that the energy transmitted into the structure occurs over a large area. Furthermore, the cushion should remain intact after impact so it does not need to be replaced. The effectiveness of the material can be expressed as the difference between the “weight impact force” induced by boulder impact, and the “transmitted force” that is absorbed by the structure (Figure 12.26(a)). Gravel is the most commonly used cushioning material because it is inexpensive and widely available. However, the disadvantage of gravel is its weight, and there is a point where the gravel layer is so thick that its weight exceeds the rock fall impact loading. Rubber tires have also been used, but it is found that they are highly compressible with little energy absorption. A viable alternative to gravel is reinforced Styrofoam that is an effective energy absorbing material with low unit weight, which allows for some saving in the dimensions of the structure (Mamaghani et al., 1999). The disadvantage of Styrofoam is its cost compared to gravel, so the cost benefit of its use should be carefully evaluated. Figure 12.26(b) shows typical force–deformation characteristics of gravel, Styrofoam and rubber tires (Yoshida, 2000).
Continuous Improvement in a Production Line
Published in Abdul Al-Azzawi, Advanced Manufacturing for Optical Fibers and Integrated Photonic Devices, 2017
Some packaging materials are used inside the box to protect the product during transportation. Cushioning materials are used to fill up the space around the product. These cushioning materials can be hard and soft. The cushioning materials type, size, and specifications depend on the product sensitivity and shipping destination. The cushioning materials can be bubble wraps, packing peanuts, blank newspapers, kraft papers, Styrofoam, plastics, cardboard sheets, electrostatic bags, polyethylene form sheets, etc. When fragile items such as glass, prisms, mirrors, and other optical items can be shipped using a good method to package them, it is by a combination of bubble wrap and peanuts, as shown in Figure 9.2(a). A polyethylene form sheet can also be added in between the items, as shown in Figure 9.2(b).
Design and Mechanics of Running Shoes
Published in Franz Konstantin Fuss, Aleksandar Subic, Martin Strangwood, Rabindra Mehta, Routledge Handbook of Sports Technology and Engineering, 2013
The main purpose of any cushioning material is to distribute the shock force over a longer time, as softer materials have a longer contact time on impact and thereby reduce the shock spike. As important as the shock spike is for bone physiology and mechanics, it is detrimental for the articular cartilage. Syndromes described in the literature have been attributed (more indirectly than directly) to too much jogging with insufficient shoes on hard ground; these include knee pain syndromes, Achilles tendonitis, shin splints and plantar fasciitis. The patellofemoral pain syndrome or ‘runner’s knee’ is allegedly caused by excessive pronation associated with internal tibial rotation. This causes the patella to shift slightly relative to the femoral condyles. Owing to the imbalanced position of the patella, the cartilage pressure increases in the patellofemoral joint, leading to painful symptoms (Shorten 2000).
A novel method for estimating an individual’s deviation from their habitual motion path when running
Published in Footwear Science, 2019
Matthieu B. Trudeau, Steffen Willwacher, Gillian Weir, Eric Rohr, Christopher Ertel, Gert-Peter Bruggemann, Joseph Hamill
The increase in the popularity of running and exercise began in the 1970s. Along with this interest in exercise came the development of sports shoes with a special emphasis on the biomechanics of footwear. The evaluation of running footwear focused on two guiding principles for footwear design: (1) decreasing the risk of running-related injuries; and (2) improving performance. In terms of reducing the probability of running footwear as a risk factor for running-related chronic injuries via footwear design, two foci have been studied extensively: (1) cushioning the shoe; and (2) rearfoot pronation. Cushioning is thought to provide greater shock attenuation (i.e., reduce the load on the body from the foot/ground collision). Pronation refers to a three-axis movement at the sub-talar joint consisting of calcaneal eversion, dorsiflexion and foot abduction. However, pronation is also a lay term that refers to the motion of the foot relative to the leg and is synonymous with calcaneal eversion. It is generally thought that an increase in pronation or calcaneal eversion is often related to a decrease in rearfoot stability.
Dynamic cushion, quasi-static stab resistance, and acoustic absorption analyses of flexible multifunctional inter-/intra-bonded sandwich-structured composites
Published in The Journal of The Textile Institute, 2021
Ting-Ting Li, Zhike Wang, Xiayun Zhang, Liwei Wu, Ching-Wen Lou, Jia-Horng Lin
Materials used for cushioning products include foam plastic, corrugated boards, and novel fibrous cushioning materials. Corrugated boards cannot recover from an impact easily. Foam plastic has a good buffering effect but becomes a source of environmental pollution. Composite materials such as warp-knitted spacers and fibermats made of textile fibers can effectively disperse and absorb impact energy when being impacted. Researchers have studied the energy absorption of these two composites under energy absorption and different impact behaviors. Liu et al. (2012, 2014) found that the warp-knitted spacer fabrics (WKSF) can be used as qualified materials for protection due to their high-energy absorption capacity and low contact peak force. They also indicated that impact behaviors from hemispherical shaped and plane-formed are different, and fabric curvature decreased the impact energy absorption which hence affected the force attenuation property of spacer fabrics (Liu et al., 2012, 2014). Chang et al. (2017) used a drop hammer to study the energy absorption effect of the WKSF at the initial impact energy. They found that the greater the absolute value of the negative Poisson’s ratio is, the better the energy absorption ability and impact resistance are, but the initial impact energy insignificantly affected the energy absorption (Chang et al., 2017). Lu et al. (2015) studied the STF-impregnated WKSF and after finite element simulation, they found that WKSF/STF composite can be used as damping or energy-absorbing materials under impact. Yan et al. (2015, 2017) prepared a cushion composite fabrics composed of reconstituted Kevlar, glass, and polyester fibers, and showed that they have high impact resistance and excellent dynamic cushioning properties.