Collapsible fluid-filled fabric shock absorber with constant force

Energy absorption is an important challenge shared by multiple different industries including manufacturing, transportation, and protective equipment. This paper presents a novel shock absorption system based on woven fabrics designed to fully collapse and absorb energy at a near-minimum force level. The proposed system exerts an approximately constant force across different impact velocities. This system utilizes a fixed-orifice hydraulic shock absorber with variable contact area over its displacement to provide a nearly-constant force which scales with impact energy. Using analytical fluid dynamics, the contact area needed to produce a constant minimum force is derived. A finite element model of this shock absorber is created to validate the concept. Different impact conditions are simulated. The results confirm that the proposed fabric shock absorber is capable of producing a nearly-constant force across different impact energies. In simulation, the fabric shock absorber follows the ideal constant force profile with an averaged efficiency of 77.8% ± 3.4% which is far above standard foams which have efficiency of only approximately 20%–40%. The proposed system is compared with a cylindrical damper to show performance improvements gained through variable area geometry. Potential applications of this technology include soft devices for space-constrained applications such as contact sport helmets.

Experimental measurements of the shear force on surface mount components simulating the wave soldering process

Purpose This study aims to determine the minimum force required to pull out a surface mount component in printed circuit boards (PCBs) during the wave soldering process through both experimental and numerical procedures. Design/methodology/approach An efficient experimental technique was proposed to determine the minimum force required to pull out a surface mount component in PCBs during the wave soldering process. Findings The results showed that the pullout force is approximately 0.4 N. Comparing this value with the simulated force exerted by the solder wave on the component ( ≅ 0.001158 N), it can be concluded that the solder wave does not exert sufficient force to remove a component. Originality/value This study provides a deep understanding of the wave soldering process regarding the component pullout, a critical issue that usually occurs in the microelectronics industry during this soldering process. By applying both accurate experimental and numerical approaches, this study showed that more tests are needed to evaluate the main cause of this problem, as well as new insights were provided into the depositing process of glue dots on PCBs.

Optimal control of a rocket projectile according to the "minimum force" criterion

The article solves the problem of optimal control of a rocket projectile by its delivery from a given initial position to a given final position, taking into account the air resistance force. The motion of the projectile is described by the vector differential equation of I.V. Meshchersky. The control quality criterion is taken in the form of "minimum force", the minimization of which ensures minimal overloads for the projectile. Three types of the norm of the control force vector are considered. For each of them, an optimal control is obtained that solves the task. The analysis of the results of the numerical experiment is carried out, confirming the general theoretical provisions.

DESIGN AND MODELING OF A TRIPLE-STEPPED BEAM WITH OUT-OF-PLANE MOTION FOR BISTABLE MICROSWITCH APPLICATIONS

Microswitches have been used for many different applications in building, automation, and security due to requiring little force. A novel design of a triple-stepped beam structure for a mechanical bistable microswitch is presented, and it was found that the bistability of the beam can be achieved by applying an electrostatic force which allows a high deflection with small electrode separation. A finite element method analysis has been used to design the bistable microswitch in a certain range of geometries based on the standard of Taiwan Semiconductor Manufacturing Company (TSMC). The simulation results show that the device requires a verylow input force to get to the bistable stages. The maximum force and the minimum force for switching between the bistable stages are 0.85 mN and 0.23 mN, respectively, which is suitable for electrostatic force at a microscale. The bistability is obtained with the second equilibrium at 75.17 µm that guarantees the perfect contact location between the beam and the conduction path (N+) located at 65.45 µm.

Numerical Analysis of Energy Converter for Wave Energy Power Generation-Pendulum System

The wave energy power generation-pendulum system (WEPG-PS) is a four-wheeled instrument designed to convert wave power into electric energy. The first wheel is connected to the pendulum by a double freewheel, the second and third are ordinary wheels, while the fourth is a converter component that is axially connected to the electric generator. This design used the Euler-Lagrange formalism and Runge-Kutta method to examine an ideal dimension and determine the numerical solution of the equation of motion related to the rotation speed of the wheels. The result showed that the WEPG-PS' converter system rotated properly when its mass, length, and moment of inertia are 10 kg, 2.0 m, and 0.25 kgm2, respectively. This is in addition to when the radius of the first, second, third, and fourth wheels are 0.5, 0.4, 0.2, and 0.01 m, with inertia values of 0.005, 0.004, 0.003, and 0.1 kgm2. The converter system has the ability to rotate the fourth wheel, which acts as the handle of an electric generator at an angular frequency of approximately 500 - 600 rad/s. The converter system is optimally rotated when driven by a minimum force of 5 N and maximum friction of 0.05. Therefore, the system is used to generate electricity at an amplitude of 0.3 - 0.61 m, 220 V with 50 Hz. Besides, the lower rotation speed and frequency of the energy converter of the WEPG-PS (300 rad/s) and induction generator (50 Hz) were able to generate electric power of 7.5 kW. ©2020. CBIORE-IJRED. All rights reserved

Fluid flow in the impulse valve of a hydraulic ram

The paper presents the results of a study investigating the equilibrium of forces acting on the closing element of the impulse valve in a water ram at the end of the acceleration stage. Acceleration is one of the three main stages in the working cycle of a water ram. In the first part of the paper, we estimated water velocity based on our earlier experimental measurements. We also calculated the minimum force required for closing the impulse valve. The second part of the paper discusses two variants of a numerical model, which was developed in ANSYS Fluent to determine the result-ant hydrodynamic pressure and, consequently, the forces acting on the head of the impulse valve at the end of the acceleration stage. The main aim of this research was to verify the applicability of numerical modeling in water ram studies. The present study was motivated by the fact that Computational Fluid Dynamics is very rarely applied to water rams. In particular, we have not found any numerical studies related to the equilibrium of forces acting on the closing element of the impulse valve in a water ram.