Study on shock absorption performance and damage of a new staggered story isolated system

The new staggered story isolated system is developed according to the base isolated system and the mid-story isolated system. Non-linear finite element model of an eighteen stories new staggered story isolated structure is established. For a comparative analysis, the models of a base isolated structure, a mid-story isolated structure, and an aseismic structure are also established, and their shock absorption performances and damages are analyzed for comparison. The results indicate that the new staggered story isolated structure has a small seismic response, good shock absorption performance which is feasible for application. Besides, the shock absorption performance of the new staggered story isolated structure is a little worse than the base isolated structure but slightly better than the mid-story isolated structure. The bottom of core tube and the story below the frame isolated story have large acceleration response which needs to be paid more attention in design.

The Dynamic Impact Response of 3D-Printed Polymeric Sandwich Structures with Lattice Cores: Numerical and Experimental Investigation

This paper proposes a dynamic drop weight impact simulation to predict the impact response of 3D printed polymeric sandwich structures using an explicit finite element (FE) approach. The lattice cores of sandwich structures were based on two unit cells, a body-centred cubic (BCC) and an edge-centred cubic (ECC). The deformation and the peak acceleration, referred to as the g-max score, were calculated to quantify their shock absorption characteristic. For the FE results verification, a falling mass impact test was conducted. The FE results were in good agreement with experimental measurements. The results suggested that the strut diameter, strut length, number and orientation, and the apparent material stiffness of the lattice cores had a significant effect on their deformation behavior and shock absorption capability. In addition, the BCC lattice core with a thinner strut diameter and low structural height might lead to poor shock absorption capability caused by structure collapse and border effect, which could be improved by increasing its apparent material stiffness. This dynamic drop impact simulation process could be applied across numerous industries such as footwear, sporting goods, personal protective equipment, packaging, or biomechanical implants.

A New Inspiration in Bionic Shock Absorption Midsole Design and Engineering

Inspired by the performance of the ostrich in terms of loading and high-speed moving ability, the purpose of this study was to design a structure and material on the forefoot and heel of the middle soles of sports shoes based on the high cushioning quality of the ostrich toe pad by applying bionic engineering technology. The anatomical dissection method was used to analyze the ostrich foot characteristics. The structure and material of the bionic shock absorption midsole were designed according to the principles of bionic engineering and reverse engineering. F-Scan and numerical simulation were used to evaluate the bionic shock absorption midsole performance. The results showed that the bionic shock absorption midsole decreased the peak pressure (6.04–12.27%), peak force (8.62–16.03%), pressure–time integral (3.06–12.66%), and force–time integral (4.06–10.58%) during walking and brisk walking. In this study, the biomechanical effects to which the bionic shock absorption midsole structure was subjected during walking and brisk walking exercises were analyzed. The bionic midsole has excellent shock resistance. It is beneficial for the comfort of the foot during exercise and might reduce the risk of foot injuries during exercise.

Analysis on the Seismic Performance of Shock Absorption Layer Applied in Tunnel Lining Structure Using Shaking Table Model Tests

Shock absorption layer is a relatively simple and effective aseismic measure, which can bear the adverse effects of surrounding rock deformations and buffer the forces acting on lining structure with seismic action. This paper conducts a series of shaking table model tests to analyze and compare the aseismic performances of tunnel lining structure with and without shock absorption layer in different grades of surrounding rocks, in which the superior thickness of shock absorption layer is determined. Therein, it is concluded that the shock absorption layer has prominent influence on reducing the acceleration responses of surrounding rock and lining structure with seismic excitation. The setting of the shock absorption layer can reduce the acceleration amplitude of tunnel lining with seismic excitation by about half. Furthermore, the setting of 1 cm shock absorption layer will increase the Fourier amplitudes and change the vibration frequencies of surrounding rock and lining structure with seismic excitation, while the setting of 2 cm shock absorption layer can significantly decrease the Fourier amplitudes and keep the vibration frequencies of surrounding rock and lining structure with seismic excitation. Therefore, the aseismic effect of 2 cm shock absorption layer is better than the aseismic effect of 1 cm shock absorption layer, which can both reduce the acceleration amplitude and Fourier amplitude of tunnel lining with seismic excitation while keep its characteristics in frequency domain. This research on the aseismic performance of shock absorption layer can contribute to the construction of tunnel engineering and improve the safety of tunnel lining structure.

Experimental Validation for the Performance of MR Damper Aircraft Landing Gear

The landing gear of an aircraft serves to mitigate the vibration and impact forces transmitted from the ground to the fuselage. This paper addresses magneto-rheological (MR) damper landing gear, which provides high shock absorption efficiency and excellent stability in various landing conditions by adjusting the damping force using external magnetic field intensity. The performance and stability of an MR damper was verified through numerical simulations and drop tests that satisfied aviation regulations for aircraft landing gear. In this study, a prototype MR damper landing gear, a drop test jig, and a two-degree-of-freedom model were developed to verify the performance of the MR damper, with real-time control, for light aircraft landing gear. Two semi-active control algorithms, skyhook control and hybrid control, were applied to the MR damper landing gear. The drop tests were carried out under multiple conditions, and the results were compared with numerical simulations based on the mathematical model. It was experimentally verified that as the shock absorption efficiency increased, the landing gear’s cushioning performance significantly improved by 17.9% over the efficiency achieved with existing passive damping.

Designing Shock Absorbing Composites by Impregnating Woven Fabrics with Shear Thickening Fluids

Millions of sports and recreation-related injuries occur each year. Different shock-absorbing solutions, such as polyethylene and polyurethane foams, are used in helmets and protective equipment, but one area most sports-gear manufacturers have not explored is the usage of shear thickening fluids (STFs). An STF is a material that is soft under normal conditions but acts rigid when stressed or pressured. STF composites were fabricated and tested with the goal of exploring their viability for use in shock-absorption applications, especially for sports. The role of fabric- and particle-type, particle-to-carrier fluid ratios, nano-particle additives, and the thickness of the composite were studied, and were all hypothesized to have an effect on the impact-resistance of the fabricated STF-composites. Drop-tests were conducted by releasing a 1.1-lb. weight from an electromagnet onto the composites. An impact-force sensor was placed underneath. The weight and height of the drop were chosen to simulate the hardest recorded NFL hit. All hypothesized factors were found to affect impact resistance. The combination of nylon-fabric impregnated by an STF mix of propylene-glycol and silica-nanoparticles, with a cerium-oxide nano-particle additive, displayed better shock-absorption behavior than other fabricated composites. All of the STF-composites also outperformed tested commercial shock-absorption materials despite being thinner and more flexible. These results demonstrate the potential of using STF-impregnated textile fabrics for protective composites for sportswear, as well as for non-sport shock-absorption applications, like in military vests and helmets, and aerospace applications. Further research is necessary to work towards a final product which can be used.

How the foot and ankle works (mechanics of the foot)

This chapter examines the mechanics of the foot from the clinician’s perspective. The kinematics, kinetics, muscle balance, and stability of the foot and ankle are complex, as the foot has evolved to provide shock absorption, stability, propulsion, and accommodation. It does this by maintaining a stable, balanced structure in all positions of the foot. The mobility of the joints together with their stabilizing structures (the ligaments of the foot), and the complex balance between muscle tension and tendon position relative to the axis of rotation of the joints, are responsible for this function. As a consequence of this complex dynamic structure, the foot stores a significant amount of energy during ambulation, and its efficient use of this is a major reason for the ability of humans to travel long distances.