Shock Isolation Research Articles

Experimental Evaluation of the Isolation Effectiveness of Elastic Rail Shock Isolators (ERSI) for Protecting Weapons from Severe Underwater Shock

Experimental Evaluation of the Isolation Effectiveness of Elastic Rail Shock Isolators (ERSI) for Protecting Weapons from Severe Underwater Shock

Design and shock isolation performances of two-layered ring-spring meta-isolation systems

Two-layered ring-spring-resonator (RSR) based meta-isolation system (RSR-M) has been developed to improve shock isolation effect. In the numerical calculations, shock acceleration ratio (SAR), shock displacement ratio (SDR) and relative displacement ratio (RDR) were introduced to evaluate the shock isolation performances of the conventional isolation system (CON) and the RSR-M, considering the effects of the excitation amplitude, the weight of the middle mass block and the stiffness of the lower isolators. The results demonstrate that the SAR of the RSR-M is always smaller than that of the CON, and the SDR of the RSR-M is first larger than that of CON in the shock amplification region and then smaller in the isolation region. The weight of middle mass blocks has little influence on the isolation performance of the RSR-M because of the softening behavior of the isolators. Finally, shock isolation experiments were also carried out to measure the damping ratios of the selected wire rope isolators and further analyze the isolation performance of the RSR-Ms. In general, meta-isolation system provides a new reference and idea for the design of the isolation system of engineering structures in some sense.

Research on a Honeycomb Structure for Pyroshock Isolation at the Spacecraft–Rocket Interface

Honeycomb is a splendid kind of structure for aerospace engineering with the advantages of light weight, good shock absorption, and good structural stability. This article aims to provide methods to isolate Pyroshocks based on a honeycomb structure and guarantee the safety of such equipment against a high-frequency shock response. According to stress wave theory, an equation for stress wave transmittance of the honeycomb structure is derived considering the effect of cell wall length and thickness, where desirable honeycomb parameters are obtained. The complexity of the transfer path of the honeycomb structure is exploited to build the spacecraft–rocket interface, which could increase the impedance of the stress wave dramatically. Both finite element analysis and experiments are carried out to validate the shock isolation strategies. The influence of parameters, such as cell wall length and the thickness of the stainless-steel honeycomb, on the isolation performance is analyzed. It is revealed that the honeycomb structure has a significant effect on Pyroshock isolation performance when the wall length of the honeycomb cell is 8 mm and the thickness of the cell is 0.1 mm.

An integrated Bayesian-principal component approach to macroeconomic resilience: the case of the Central Europe and Baltic macro-region

PurposeIn the fashion of Martin (2012), we develop an innovative application to a standard, well-grounded methodology to investigate resilience in two critical dimensions: recovery and resistance. Our novel approach allows us to investigate the resilience performance to the 2008 financial crisis within countries of this macro-region according to their shock isolation and absorptive capacities.Design/methodology/approachBy individually estimating six open economy DSGE models within the Central Europe and Baltic macro-region, we identify the business-cycle-volatility drivers for each country. Then, we use the outcome of our six estimates to conduct a principal component analysis to determine structural common characteristics required to explain economic resilience in the CEB macro-region.FindingsIn terms of resilience, Central European economies exhibit quite similar paths in terms of recovery, meaning they have similar economic structures. By contrast, Baltic countries behave differently, being outliers in opposite extreme positions. The contrary occurs for resistance: Baltic countries share a similar ranking, whereas Central European economies exhibit substantial differences.Research limitations/implicationsIt is important to acknowledge that a limitation of the analysis is that we explicitly consider each country as a stand-alone open economy which are subject to stochastic disturbances. Precisely, we do not model trade or other interactions across countries within the CEB region and with the rest of the world. Consequently, spillover effects in the aftermath of the shock are not accounted for.Originality/valueWe estimate the relative vulnerability or sensitivity of economies within the macro-region to disturbances and disruptions (resistance) and the speed and extent of recovery from such a disruption or recession (recovery). First, we built two different kinds of measures of resilience by aggregating the estimated parameters through non-centered and centered principal component analysis. Then, we use our model to investigate the relation between financial shock and the economic resilience across the region. The approach can be applied to several case studies, parsimoniously.

Optimum Design of Elastomer-Based Shock Isolation System for a Naval Component

Optimum Design of Elastomer-Based Shock Isolation System for a Naval Component

An investigation of a self-powered low-frequency nonlinear vibration isolation system

High-static-low-dynamic stiffness vibration isolation are of utmost significance in low-frequency vibration isolation. However, their intricate mechanisms are always challenging for environmental vibration changes. In this study, a self-powered nonlinear vibration isolation system with two stages is studied, with the aiming of obtaining the broadband vibration isolation. Magnetic springs of negative stiffness combined with the coil could transform mechanical vibration into electrical energy in lower stage. The feedback electrical energy could power the piezoelectric actuator in the upper stage. Based on the governing equations measured in stable equilibrium, the harmonic balance analysis is used to derive the frequency response functions of the transmissibility and the output power in the mechatronic resonance. The frequency band of vibration isolation extends to the lower frequencies and two resonance peaks reduce to the lower levels. The numerical simulations results validate the analytical solutions. Then the shock isolation performance is illustrated under the round step displacement and rounded pulse displacement. The parameter study demonstrates numerically that introduction of the high-static-low-dynamic stiffness improves the shock isolation performance. Moreover, the lower stage mechanical energy could drive the piezoelectric stack, resulting in high-efficiency shock isolation. Finally, an experiment is employed to prove the high-efficiency vibration isolation.

Research on the vibration isolation performance of a metal rubber-disc spring shock isolation device

In view of the fact that the vibration response of the laser-emitting telescope in the combination of artillery and light equipment cannot meet the target design requirements, this paper designs a new metal rubber-disc spring shock isolation device and conducts experimental research on its vibration isolation performance. The research is conducted from the frequency sweep test and the fixed frequency test. Through the vibration isolation performance test, it is found that the natural frequency of the metal rubber-disc spring shock isolation device is lower than that of the steel wire rope vibration isolator, and the frequency domain where vibration isolation occurs is wider, with better vibration isolation performance. In the fixed frequency test, the acceleration transfer rate of the metal rubber-disc spring composite vibration isolator is significantly better than that of the steel wire rope vibration isolator in the low-frequency range. As the excitation frequency increases, the difference between the acceleration transfer rate of the steel wire rope vibration isolator and the metal rubber-disc spring composite vibration isolator gradually shrinks, and finally converges.

Investigation of a 2-DOF GER fluid damper in cut mode

Dampers incorporating smart materials have attracted significant interest for their application in vibration and shock isolation. Traditionally, these dampers work through shear, flow, and squeeze modes, each unique in its strengths and limitations. However, this study introduces a working mode, termed cut mode, which integrates the strengths of these existing modes. Structurally resembling the flow mode, operationally akin to the shear mode, and behaving similarly to the squeeze mode, the cut mode promises a novel approach to damping. Consequently, extensive research has been conducted at the particle level to develop a mathematical model for the cut mode, grounded in chain formation and breaking mechanisms. Thereafter, a verification prototype damper was designed to demonstrate this concept’s practicality, with the Giant Electrorheological (GER) fluid—a rheological fluid with exceptional yield strength—being employed. This damper features a multilayer cylindrical structure tailored for the cut mode, providing 2-degree of freedom (DOF) damping capabilities. This dual-DOF design is ideal for robotic arm joint applications, as it can offer damping for both axial translation and circumferential rotation simultaneously. In addition, four orifice boards were designed, fabricated, and tested to optimize and enhance the effectiveness of the cut mode further. The results are impressive, the proposed cut mode damper exhibits superior performance characteristics, indicating its great potential for engineering applications.

Optimum design of HNBR and PCR-based isolation system to protect a sensitive article stored in a naval vessel container subjected to shock load

In naval engineering, protecting sensitive articles from shock loads is a major concern, as it may lead to adverse consequences. This paper focuses on the design of a novel Hydrogenated Nitrile Butadiene Rubber (HNBR) and Polychloroprene Rubber (PCR)-based shock isolation system to protect a sensitive article stored in a hollow cylindrical naval vessel container (NVC). Firstly, NVC is modeled as a two-degree-of-freedom lumped parameter model (LPM), wherein isolators made of HNBR and PCR materials are modeled with 5-order polynomial nonlinear stiffness and linear damping. The optimal values of the isolator parameters are obtained using a multi-objective genetic algorithm, and corresponding responses to a shock load are found using MATLAB. Furthermore, a three-dimensional (3D) finite element model (FEM) of the NVC is generated in ABAQUS and subjected to shock loading in a transverse direction to conduct a comprehensive dynamic analysis of the isolation system. In 3D simulation, HNBR and PCR materials are modeled using a hyper-viscoelastic model developed based on experimental test data. The 3D simulation results of the NVC for the optimized design of HNBR and PCR isolators agree with the optimized results of the LPM. Moreover, the proposed HNBR and PCR isolators are very effective in shock reduction.

Experimental study on shock isolation of metal rubber-disc spring composite shock absorber under different shock excitation

Due to the instability and aiming accuracy of the onboard laser emission system cannot meet the requirements of its work tasks, it is necessary to carry out vibration isolation optimization design for the laser emission system. This paper designs a metal rubber-disc spring composite shock absorber and conducts relevant experimental research on the shock isolation performance of the metal rubber-disc spring composite shock absorber. The shock isolation performance tests of the shock absorber under different shock excitation conditions with pendulum heights of 300 mm, 600 mm, 900 mm, and 1200 mm were carried out respectively. Through the experiments, it was found that when the pendulum height is 300 mm, the shock isolation effect of the metal rubber-disc spring composite shock absorber is the best, and the shock isolation rate is above 95%.

Design of shock isolator under recoil shock

The shock isolator is used for the protection of important equipment during firing, but due to the complexity of the recoil shock, currently most of them rely on experience for design, other than a more scientific design method. In view of this, this paper analyzes the recoil shock signal, proposes an analytical method to calculate the shock response, and develops a design method of shock isolator for sniper rifle under recoil shock. The reconstructed shock signal is obtained using least squares method, then an analytical calculation method of the response under recoil shock is proposed using the reconstructed waveform and Duhamel integral, the correctness of the analytical method is verified by numerical calculation and experiment. Using the pseudo-velocity shock response spectrum (PVSRS) of recoil shock, and combining with the anti-shock characteristics of protected equipment, a design method of shock isolator for sniper rifle is proposed, and the method is verified by analytical calculation and experiment. This method can provide a basic theoretical basis for the design of shock isolator using on sniper rifle, and can be applied to the design of other similar shock isolators.

Study on the performance of a novel 1DOF isolator with QZS characteristics

A typical one-degree-of-freedom (1DOF) shock isolator that has quasi-zero stiffness (QZS) characteristics consists of two transversal springs and one portrait spring. The transversal springs can provide negative stiffness and the vertical spring is used as a load-bearing component. In this article, an improved 1DOF QZS shock isolator is obtained by utilizing the combination of lateral bars and springs. The displacement transmissibility under the harmonic excitation is obtained and the principle of minimum displacement transmissibility under the condition of system stability is proposed. Finally, numerical simulation is conducted, and the simulation results reflect that the proposed 1DOF QZS isolator significantly performs better than the previous one.

Inescapable foot shock induces a PTSD-like phenotype and negatively impacts adult murine bone.

Post-traumatic stress disorder (PTSD) is associated with osteopenia, osteoporosis and increased fracture risk in the clinical population. Yet, the development of preclinical models to study PTSD-induced bone loss remains limited. In this study, we present a previously unreported model of PTSD in adult female C57BL/6 mice, by employing inescapable foot shock and social isolation, that demonstrates high face and construct validity. A subset of mice exposed to this paradigm (i.e. PTSD mice) display long-term alterations in behavioral and inflammatory indices. Using three-dimensional morphometric calculations, cyclic reference point indentation (cRPI) testing and histological analyses, we find that PTSD mice exhibit loss of trabecular bone, altered bone material quality, and aberrant changes in bone tissue architecture and cellular activity. This adult murine model of PTSD exhibits clinically relevant changes in bone physiology and provides a valuable tool for investigating the cellular and molecular mechanisms underlying PTSD-induced bone loss.

Blast wave attenuation of nonlinear meta-isolation system: Theoretical analysis and experimental validation

In the field of protective engineering, wire rope isolators are usually applied in the isolation floor to mitigate the impact and vibration induced by explosive blast. In this paper, two kinds of meta-isolation systems were proposed and designed based on the local resonance, and investigated by means of theoretical analysis, numerical calculation and experimental research. First, the force-displacement hysteresis loops of the selected wire rope isolators are obtained by the cyclic loading tests, and identified by a mathematical model to make preparations for numerical calculation. Then, in order to discuss the influence of mass ratio, stiffness ratio and damping ratio on the shock isolation, the two-degree-of-freedom (TDOF) linear and nonlinear models are studied based on the mode superposition method and fourth-order Rugga-Kutta method respectively. Finally, the blast-induced ground shock experiments were conducted to evaluate the isolation efficiencies of conventional isolation systems and meta-isolation systems. The experiment results reveal that the isolation efficiency of meta-isolation system can increase by 10% points vertically and 16% points horizontally compared to conventional systems, which indicates that the meta-isolation system has great potential to be adopted in the engineering structures and provides a new idea and reference for protective engineering.

Negative stiffness metamaterial with directional stability in uniform fields

Negative stiffness metamaterials have been widely studied due to their unusual properties and potential applications in shape reconfiguration, shock isolation, and reusable energy absorption, but their stability in fields has been less studied. In this work, a theoretical framework for determining the stability of negative stiffness metamaterials in a uniform field is established. More importantly, the concepts of directional stability and semi-directional stability are proposed for the metamaterials that have different stability in different field directions; metamaterials with different physical feature distributions are designed and prepared to achieve such ability, and the finite element simulation is used for theory verification and parameter study. The proposed metamaterial has the potential to be applied as field direction detectors and field-sensitive electrical relays.

Response of Shock Isolators with Piecewise Linear Asymmetric Damping

The output of a single-degree-of-freedom (SDOF) piecewise linear system with asymmetric damping and linear stiffness excited by Dirac impulse excitation is studied. Analytical solutions of the response for piecewise linear systems are obtained by replacing the equation of motion with Dirac excitation by a homogeneous differential system with zero initial displacement and a given initial velocity. A significant improvement of the response consisting in a substantial reduction in the after-shock vibrations was obtained. The obtained results are applied to the damping optimization of a shock isolation system for forging hammers.

Shock Isolation of Light Vehicle Suspension by Modified Eye Leaf Spring

Background: Rickshaws are a popular and inexpensive mode of transportation in Bangladesh for short-distance travel. However, the eye leaf spring in a typical rickshaw suspension system does not provide adequate shock isolation. The coil spring-damper suspension system is more effective, but is costly and not affordable for most manufacturers. Thus, the goal is to modify the eye leaf spring to be inexpensive but a safe and comfortable suspension. Aim: The study aimed to modify the material and structure of the leaf spring to limit the stiffness and the shock energy within a certain range suitable for the rickshaw’s suspension. The focus of the study was on modifying the spring structure, which could be cost-effective. Methods: In this study, flexible bolted joints and EVA sheets have been used to change the spring structure. The study compared the performance of the modified spring with the typical eye leaf spring. Results: The modified eye leaf spring provided improved shock isolation and a more comfortable ride compared to the typical eye leaf spring. The changes made to the spring, such as the use of flexible bolted joints and EVA sheets, limited the stiffness and shock energy within a certain range suitable for the rickshaw’s suspension. The modified spring was also found to be cost-effective. Conclusion: The study has demonstrated the feasibility of using a modified eye leaf spring for light vehicle suspensions, specifically for rickshaws. The modifications made to the spring structure, such as using flexible bolted joints and EVA sheets, provided improved shock isolation, a more comfortable ride, and cost-effectiveness. The modified spring offers an inexpensive solution for manufacturers to produce rickshaws with a safer and more comfortable suspension system.

Anti-shock performance of a cockroach-inspired structure

Shock leads to negative impacts on both engineering practices and human comfort in daily life. Many species in nature possess significant shock resistance capacities. This paper introduces a cockroach-inspired structure (CIS) for effectively isolating large-amplitude shocks. The shock responses of CIS are evaluated using the Runge-Kutta method and assessed by four indices: time history response, energy conversion, shock transmissibility, and shock response spectrum. The numerical results show that the hardening effect induced by CIS leads to a leftward shift phenomenon, which can reduce transient response time and expand shock isolation area. By adjusting the geometric parameters, the damping force can be increased to improve the shock isolation performance; the stored potential energy and converted kinetic energy can be minimized, enabling the payload to quickly stabilize its position. The experimental results show that CIS achieves a significant 91.5% reduction in peak absolute acceleration. In summary, this study lays the groundwork for exploring the potential of insect-inspired structures in mitigating shocks.

Shock Isolation of an Orthogonal Six-DOFs Platform With High-Static-Low-Dynamic Stiffness

Abstract A novel approach to enhance the shock vibration environment of multi-directions using a high-static-low-dynamic stiffness supported orthogonal six-degrees-of-freedom (DOFs) nonlinear vibration isolation (OSNVI) system is presented in this paper. By combining spring positive stiffness and magnetic negative stiffness, the proposed system achieves high-static-low-dynamic stiffness. Under the multi-directions half-sine vibration, the dynamic equation of the OSNVI is obtained. Both dynamic and static analysis methods are utilized to explore the effect of various parameters on the shock isolation performance of the OSNVI from both the time and frequency domains. The results indicate that the proposed OSNVI can efficiently suppress multi-direction shocks at the cost of only one second. Although a nonlinear jump is usually not expected, the nonlinear jump of the OSNVI could improve the load capacity by increasing the spring stiffness without changing the shock isolation frequency band. Finally, a shock experiment is employed through a three-axis shaker platform to validate the shock isolation performance of the orthogonal six-DOF nonlinear vibration isolator. The proposed OSNVI provides a promising approach to suppress the multi-directional shock vibrations.

A re-usable negative stiffness mechanical metamaterial composed of Bi-material systems for high energy dissipation and shock isolation

Mechanical metamaterials with negative stiffness (NS) effects are able to dissipate mechanical energy repeatedly according to the “snap-back” strategy. Nevertheless, the strategy is merely efficient when a plethora of NS cells are lined together in series. Limitations of the strategy bring challenges to ameliorate the capacity of energy dissipation for the NS. In the present research, an unique re-usable NS mechanical metamaterial made up of Bi-material systems was suggested and fabricated, which is able to dissipate energy even supposing such metamaterial was merely made up of a single unit. To get a thorough knowledge of the metamaterial’s quasi-static mechanical characteristics, a combination of loading-unloading experiments and finite element method (FEM) has been conducted. The effects of structural arguments on the mechanical characteristics were then revealed employing the experimentally authenticated numerical model. The metamaterial possesses outstanding re-usability and a large capacity for energy dissipation, according to the findings of quasi-static tests. Finally, plate-impact tests were executed to explore the cushion performances of this metamaterial. The presented Bi-material NS mechanical metamaterial demonstrated notable potential in energy dissipation and shock isolation.