Shock Absorber Research Articles

Experimental study on ultrasonic-assisted electrochemical polishing of NiTi alloy

NiTi alloy has a wide range of applications due to its unique superelasticity and shape memory, the superelastic function of NiTi alloy made it had been applied in building shock absorption, advanced bearings and other scenes, the shape memory function made it also applied in the fields of aerospace engine heat exchanger, cardiac medical stent and so on. In order to made NiTi alloy better applied in practice and improve its surface quality, it was crucial to polish it. In this paper, a new method of ultrasonic-assisted electrochemical polishing of NiTi alloy was innovatively proposed, and an ultrasonic electrochemical polishing device was built independently. The effects of ultrasonic amplitude, voltage and temperature on roughness were explored by Box-Behnken experimental design method. The results show that after ultrasonic-assisted electrochemical polishing, the roughness Ra had been reduced from about 2 μm to the minimum of 0.048 μm. The surface quality of NiTi alloy was improved. The impact of micro-jet of cavitation bubble on NiTi alloy mainly occurs in the early stage, and the equivalent stress on the surface of NiTi alloy was annular, showing an increasing and decreasing trend. In the whole ultrasonic electrochemical polishing solution, a large number of micro-jets will impact the surface of NiTi alloy, thus realizing the material removal. This study enhances traditional electrochemical polishing techniques by integrating ultrasonic energy fields, thus broadening the scope of electrochemical polishing applications. Additionally, it presents a novel approach and establishes a foundation for the polishing of NiTi alloys with intricate geometries in additive manufacturing.

Eco-Friendly Cork-Polyurethane Biocomposites for Enhanced Impact Performance: Experimental and Numerical Analysis.

Cork composites are byproducts from wine stopper production, resulting from the agglomeration of cork granules with a thermoset resin. The resulting compound is a versatile and durable material with numerous industrial applications. Due to its unique properties, such as low-density, high-strength, excellent energy absorption, and good thermal and acoustic insulators, cork composites find room for application in demanding industries such as automotive, construction, and aerospace. However, agglomerated cork typically has a polyurethane matrix derived from petrochemical sources. This study focuses on developing eco-friendly porous polyurethane biocomposites manufactured with the used cooking oil polyol modified with cork. Since cork and polyurethane foam are typically used for impact shock absorption, the manufactured samples were subjected to impact loading. The assessment of crashworthiness is performed through 100 J impact tests. A finite element numerical model was developed to simulate the compression of these new composites under impact, and the model validation was performed. The highest specific absorbed energy was obtained for petrochemical polyol composites with the 3% addition of natural or modified cork. The research conducted in this study showcased the feasibility of substituting certain petrochemical components used for the synthesis of the polyurethane matrix with ecological waste vegetable oil components.

Design and development of a novel Four-Links rotational hybrid Energy-Harvesting suspension system compatible with conventional suspension technologies

This study introduces a novel rotational Energy Harvesting Shock Absorber (EHSA), specifically designed for use alongside existing vehicle suspension systems. Addressing issues faced by standalone EHSAs, this design incorporates a four-bar mechanism coupled to a rotary energy recovery system. The proposed EHSA system, dubbed the FL-EHSA (Four Links Energy Harvesting Shock Absorber), is based on link connections and is highly versatile. It has the potential to significantly improve vehicle efficiency by harnessing energy usually wasted by traditional shock absorbers. Using a geometric definition process influenced by various factors such as vehicle suspension type and commercial availability of components, the FL-EHSA system was modeled, and bench-tested to validate the system’s energy recovery potential and performance. The movement of the mechanism was analyzed to achieve the target damping value matching the value of a conventional suspension and to maximize efficiency through DOE analysis and to avoid mechanical locking (singular positions). It explains the effect of backlash in mechanical components through simulation and highlights the importance of using dedicated gearboxes for energy recovery. In addition, this work highlights the untapped potential of four-bar mechanisms in automotive energy recovery applications. Moreover, the proposed design is easily integrated into any vehicle, making it a promising solution for EHSA systems.

Optimizing additively manufactured mouthguards: An evaluation of multi-layer materials for improved shock absorption and durability compared to conventionally fabricated samples

Optimizing additively manufactured mouthguards: An evaluation of multi-layer materials for improved shock absorption and durability compared to conventionally fabricated samples

Material Optimization in Formula One Seat Fit Based on Structural and Biomechanical Analysis

F1 drivers have reported that they suffer a long-term lower back pain due to ‘Porpoising’ effect, it is a series of bounce that is generated due to Aerodynamic downforce. This downforce is part of drag reduction principle that pulls the air underneath the vehicle, thereby creating an incredible speed of 200 to 230 mph. Also at 200 mph speed, the driver experiences a high amount G-forces up to six times during the race. This can be simply avoided by increasing the ground clearance of vehicle but at the same time it also reduces the max speed of the vehicle. Hence, without compromising the speed, Design optimization is done for driver’s seat-fit through Computational methods of Biomechanical modelling and simulation for determining the optimum Seat Angle for Postural Ergonomics. As an additional Reinforcement and Shock absorption in seat material to protect driver’s spine from the resulting dynamics, Material optimization is done by selecting Graphene as the suitable material over the existing Carbon fiber material. Finite element method was carried out for structural analysis of seat-fit model. The stress, strain and deformation values were found to be lesser in Graphene model when compared to Carbon fiber. The simulation results will provide a solution for eliminating the higher risk of spine injury or pathological condition of a sportsman and thereby improves the sporting performance. Key Word: Motorsports, Computational Biomechanics, Ergonomics, Design optimization, Material optimization, Finite element analysis, Spine Injury prevention

Correction: Vibration analysis and control of semi-active suspension system based on continuous damping control shock absorber

Correction: Vibration analysis and control of semi-active suspension system based on continuous damping control shock absorber

Preliminary Nose Landing Gear Digital Twin for Damage Detection

An increase in aircraft availability and readiness is one of the most desired characteristics of aircraft fleets. Unforeseen failures cause additional expenses and are particularly critical when thinking about combat jets and Unmanned Aerial Vehicles (UAVs). For instance, these systems are used under extreme conditions, and there can be situations where standard maintenance procedures are impractical or unfeasible. Thus, it is important to develop a Health and Usage Monitoring System (HUMS) that relies on diagnostic and prognostic algorithms to minimise maintenance downtime, improve safety and availability, and reduce maintenance costs. In particular, within the realm of aircraft structures, landing gear emerges as one of the most intricate systems, comprising several elements, such as actuators, shock absorbers, and structural components. Therefore, this work aims to develop a preliminary digital twin of a nose landing gear and implement diagnostic algorithms within the framework of the Health and Usage Monitoring System (HUMS). In this context, a digital twin can be used to build a database of signals acquired under healthy and faulty conditions on which damage detection algorithms can be implemented and tested. In particular, two algorithms have been implemented: the first is based on the Root-Mean-Square Error (RMSE), while the second relies on the Mahalanobis distance (MD). The algorithms were tested for three nose landing gear subsystems, namely, the steering system, the retraction/extraction system, and the oleo-pneumatic shock absorber. A comparison is made between the two algorithms using the ROC curve and accuracy, assuming equal weight for missed detections and false alarms. The algorithm that uses the Mahalanobis distance demonstrated superior performance, with a lower false alarm rate and higher accuracy compared to the other algorithm.

Evaluation of reliability indicators of shock absorbers struts of M1 category cars in conditions of violation of established market relations between end users of spare parts and suppliers

Introduction. Over the past two years, there has been a violation of established market relations between end users of spare parts and suppliers. This led, on the one hand, to a significant increase in the cost of automotive components, and, on the other, to a reorientation of the market to new alternative manufacturers and suppliers. The main purpose of the work was a statistical assessment of the reliability indicators of the most expensive suspension element – the McPherson suspension strut, in the conditions of replacing the original struts with analogues available on the market.Methods. The study of the operational reliability of systems, components and assemblies of M1 cars was conducted in a dealership during 2022-2023. The study mainly involved cars with a sedan body and a McPherson front suspension. At the same time, the reason for contacting the service, the mileage of the car, as well as the types of work performed were recorded in each work order. The experimental data were processed using MSExcel and MatLab software from MathWorks.Resultsand conclusions. The conducted research allowed us to conclude that the appeals on the suspension of the car are almost twice as high as other appeals. The most expensive elements – the front shock struts, account for up to a third of all suspension failures. To assess the reliability indicators of alternative racks, the failure distribution law (normal), the probability of failure and uptime are determined, and the parameters of the distribution law are determined: mathematical expectation, standard deviation and coefficient of variation. It was found that the resource of the rear shock absorbers is at least 30% more, and there are significantly fewer calls at the service station. Thus, the operation of a car with racks from alternative manufacturers is quite reasonable, despite the fact that the resource of racks from alternative manufacturers is usually lower than that of the original brands.

Shaking Table Testing and Numerical Study on Aseismic Measures of Twin-Tube Tunnel Crossing Fault Zone with Extra-Large Section

As transportation networks continue to expand into mountainous regions with high seismic activity, ensuring the seismic safety of tunnels crossing active faults has become increasingly crucial. This study aimed to enhance our understanding of the impact of fault zones on the seismic behavior of tunnels and to provide optimized seismic design recommendations through a comprehensive experimental and numerical investigation. The focus of this research is the Xiangyangshan Highway Tunnel in China, which intersects a significant longitudinal fault. Large-scale shake table tests were performed on 1:100 scale physical models of the tunnel to analyze the seismic responses under various ground motion excitations. Detailed three-dimensional finite difference models were developed in FLAC3D and calibrated based on the shake table results. The tests indicated that strains, earth pressures, and accelerations experience localized amplification within 10–20 m of the fault interface compared to undisturbed ground sections. Common seismic mitigation measures, such as rock grouting, seismic joints, and shock absorption layers, were observed to effectively reduce the amplified seismic demands. Grouting, in particular, led to an average reduction of up to 56.3% in circumferential strain and 38.5% in earth pressure. It was concluded that 6 m thick grouted zones and 20 cm thick rubber interlayers between tunnel lining shells provide optimal structural reinforcement against the effects of fault zones. This study provides valuable insights for improving the seismic resilience of underground transportation corridors in seismically active regions.

Research on Inertial Force Attenuation Structure and Semi-Active Control of Regenerative Suspension

To improve the energy recovery ability of the energy-regenerative suspension, a transmission is generally used to increase the motor speed, but this results in a significant increase in the equivalent inertial mass of the suspension. The research on energy-regenerative suspension has been ongoing for more than 20 years, but there have been few product applications, mainly due to the failure to solve the problem of the deterioration of suspension performance caused by equivalent inertial mass. This paper proposes a new suspension configuration with the suspension shock absorber connected to a high-frequency vibration reduction structure and establishes a vibration transmission model. Through frequency domain analysis, it has been conclusively proven that the new-configuration can significantly reduce both the sprung mass acceleration and relative dynamic load of the energy regenerative suspension. On the basis of frequency domain analysis, a scheme based on PWM control of the dissipation resistance value of the energy regenerative suspension is proposed, and through bench comparison experiments, it has been verified that the new-configuration suspension can eliminate the oscillation of the damping force curve of the shock absorber and significantly improve the suspension performance. Further experiments show that using the skyhook semi-active control algorithm the new-configuration suspension can further reduce the sprung mass acceleration and relative dynamic load.

Unsteady Multiphase Simulation of Oleo-Pneumatic Shock Absorber Flow

The internal flow in oleo-pneumatic shock absorbers is a complex multiphysics problem combining the interaction between highly unsteady turbulent flow and multiphase mixing, among other effects. The aim is to present a validated simulation methodology that facilitates shock absorber performance prediction by capturing the dominant internal flow physics. This is achieved by simulating a drop test of approximately 1 tonne with an initial contact vertical speed of 2.7 m/s, corresponding to a light jet. The flow field solver is ANSYS Fluent, using an unsteady two-dimensional axisymmetric multiphase setup with a time-varying inlet velocity boundary condition corresponding to the stroke rate of the shock absorber piston. The stroke rate is calculated using a two-equation dynamic system model of the shock absorber under the applied loading. The simulation is validated against experimental measurements of the total force on the shock absorber during the stroke, in addition to standard physical checks. The flow field analysis focuses on multiphase mixing and its influence on the turbulent free shear layer and recirculating flow. A mixing index approach is suggested to facilitate systematically quantifying the mixing process and identifying the distinct stages of the interaction. It is found that gas–oil interaction has a significant impact on the flow development in the shock absorber’s upper chamber, where strong mixing leads to a periodic stream of small gas bubbles being fed into the jet’s shear layer from larger bubbles in recirculation zones, most notably in the corner between the orifice plate and outer shock absorber wall.

Maximizing Electric Power Recovery through Advanced Compensation with MPPT Algorithms

The present investigation introduces an advanced methodology for maximum power point tracking (MPPT) applied to a piezo harvester scheme. A comprehensive rectifier circuit, equipped with an embedded MPPT component, is established to optimize energy production by monitoring a DC-DC inverter connected to the rectifier. Furthermore, the system’s sensitivity error has been finely tuned to dynamically adjust its impedance unit in real time, thereby optimizing load acquisition. This innovative approach seamlessly integrates the MPPT algorithm into the piezo harvester circuit. Moreover, the vehicle’s road handling is significantly augmented through the incorporation of a robust steering front and an active differential control system. Leveraging the MPPT module, the rectifier consistently achieves a power recovery efficiency exceeding 85%, independent of varying load conditions. Additionally, a DC-DC converter circuit has been seamlessly integrated to finely adjust the output voltage to meet specified levels. Numerical simulations demonstrate the effectiveness of the harvesting scheme, extracting a substantial output power of 90 W with an overall efficiency of 70%. The improved MPPT approach, employing angles of arrival (AoA) DV-Hop control strategies, minimizes the system’s power consumption based on the Global Positioning System (GPS). The utilization of Harris Hawks optimization (HHO) and the generation of quadrants in the four-quadrant operation mode of DC motors in the wireless sensor network (RCSFs) have been significantly enhanced in this study. Simulations reveal that, at a velocity of 50 km/h, shock absorbers utilizing the received signal strength indication (RSSI) can harvest between 60 and 90 W on a class C road, based on the time of arrival (TOA). Striking a balance in ride comfort using the time difference of arrival (TDOA) as a trade-off constitutes approximately 30% of the piezoelectric harvester (PEH) system’s power consumption when operating in active suspension mode, optimized by particle swarm optimization (PSO).

Experimental Investigation of a Flexible Airframe Taxiing Over an Uneven Runway for Aircraft Vibration Testing

<div>The ground vibration test (GVT) is an important phase in a new aircraft development program, or the structural modification of a certified aircraft, to experimentally determine the structural vibrational modes of the aircraft and their modal parameters. These modal parameters are used to validate and correlate the dynamic finite element model of the aircraft to predict potential structural instabilities (such as flutter), assessing the significance of modifications to research vehicles by comparing the modal data before and after the modification and helping to resolve in-flight anomalies. Due to the high cost and the extensive preparations of such tests, a new method of vibration testing called the taxi vibration test (TVT) rooted in operational modal analysis (OMA) was recently proposed and investigated as an alternative method to conventional GVT. In this investigation, an experimental setup was constructed to further investigate the applicability of the TVT to flexible airframes encountered in fixed-wing autonomous aerial systems with oleo-pneumatic shock absorber landing gears in a tricycle configuration. The influence of the taxiing speed and the landing gear–shock absorber damping setting on the outcome of the TVT is also investigated. The taxiing speed was found to strongly influence the success of the test with an optimal taxiing speed existing for the assembled airframe that allows for the best TVT outcome. The shock absorber damping setting was found to increase the level of the airframe excitation during the TVT; however, it did not impact its outcome as compared to the taxiing speed. Certain modes were not identified during the TVT tests, which was attributed to the way the assembled aircraft is secured to the moving belt and to the lack of sufficient excitation through taxiing. The experimental vibrational modes were successfully matched against the modes obtained from the normal modal analysis of an uncorrelated flexible multibody dynamics model. Further investigations are suggested before the TVT method can be deemed suitable for all classes of fixed-wing aerial systems.</div>

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%.

Analysis of Load Distribution Effect of Jack Support Shock Absorber

According to recent statistics from the Ministry of Land, Infrastructure and Transport, 40% of domestic buildings are in a serious state of deterioration and are more than 30 years old. Accordingly, the dismantling of old buildings is increasing; however, collapse accidents frequently occur during dismantling. During building dismantling, a jack support is placed at the bottom of the slab to reinforce insufficient slab strength. In this study, a shock absorber was developed to address jack support problems. The developed impact dampening device was designed to be mounted at the bottom of the jack support. Therefore, not only could the length of the jack support be adjusted independently, but it could also be applied to various load environments owing to its three-stage shock absorbing device configuration. Consequently, applying the developed shock absorber to various building dismantling scenarios and confirming it through a numerical analysis showed a relatively excellent load distribution effect when applied to all supports.

Digital Labour Platforms as Shock Absorbers: Evidence from the COVID-19 Pandemic in Mozambique

Abstract Digital labour platforms have grown five-fold over the past decade, enabling significant expansion of gig work worldwide. We interrogate the critique that these platforms tend to amplify aggregate shocks for registered workers. Based on the universe of records from a matching platform for manual freelancers in Mozambique, we analyse how task supply and demand altered with the onset of COVID-19. Treating the pandemic as a structural break, which extends to an event study analysis, we find it was associated with a net increase in tasks demanded per worker, but no clear change in supply growth (new registrations). While these general trends are evident across multiple market segments, there is also evidence of relatively higher demand for female as compared to male workers during the pandemic. This suggests digital labour markets can help some workers adjust to economic shocks in low-income contexts.

Graphene-Based Hybrid Fillers for Rubber Composites.

Graphene and its derivatives have been confirmed to be among the best fillers for rubber due to their excellent properties, such as high mechanical strength, improved interface interaction, and strain-induced crystallization capabilities. Graphene rubber materials can be widely used in tires, shoes, high-barrier conductive seals, electromagnetic shielding seals, shock absorbers, etc. In order to reduce the graphene loading and endow more desirable functions to rubber materials, graphene-based hybrid fillers are extensively employed, which can effectively enhance the performance of rubber composites. This review briefly summarizes the recent research on rubber composites with graphene-based hybrid fillers consisting of carbon black, silica, carbon nanotubes, metal oxide, and one-dimensional nanowires. The preparation methods, performance improvements, and applications of different graphene-based hybrid fillers/rubber composites have been investigated. This study also focuses on methods that can ensure the effectiveness of graphene hybrid fillers in reinforcing rubber composites. Furthermore, the enhanced mechanism of graphene- and graphene derivative-based hybrid fillers in rubber composites is investigated to provide a foundation for future studies.

Experimental Study on Wooden Pin Reinforcement of the Typical Mortise-Tenon Joints of Ancient Timber Frames

ABSTRACT The ancient timber frames is the precious architectural heritage of China. The seismic performance of mortise tenon joints (MTJ) directly affects the seismic performance of the ancient timber frames. This study presents a method that utilizes wooden pins to reinforce MTJs, enhancing the seismic performance of timber frame structures. The quasi-static test and finite element model were carried out to study the mechanical properties of the MTJ reinforced by the wood pins. From the failure state of the MTJs, it is found that the main deformation is the slip deformation between mortise and tenon. The mutual friction between the mortise and the tenon has a certain energy dissipation and shock absorption effect. The deformation state, stress distribution, stiffness degradation curve, etc. of the MTJ were obtained by finite element model of the MTJ. Additionally, the study confirms that reinforced MTJ can help restrict displacement changes within the wooden frame. The results show the bearing capacity of MJT reinforced with wooden pins is approximately 11.3% higher compared to that of MTJ without reinforcement. The reinforcement of wood pins effectively controls the horizontal displacement of the wooden frame, which is reduced by about 50%–62% compared with the unreinforced wooden frame. The locating the wooden pin-reinforced MTJs in the outer columns and middle layer columns reduces structural displacement, which is 31.53% in X derection, 5% in Y derection, 25.86% in Z derection.

Biomechanical stresses in a residually stressed idealized intervertebral disc

Intervertebral discs are soft biological tissues that have an important function in accommodating the movement of the spine during which the discs deform and act as shock absorbers to protect the spine from damage. Therefore, it is important to understand and model their mechanical properties to predict their response under various loading conditions. Towards this end, a simplified geometry of a single intervertebral disc, consisting of the nucleus pulposus within the anulus fibrosus, is modelled as a nonlinearly elastic solid. Pre-existing residual stresses in the unloaded state are taken into account in the radial and circumferential directions. In particular, the nucleus pulposus is considered to be isotropic, which becomes anisotropic with residual stress, while the anulus fibrosus consists of fibre families described by two standard reinforcing anisotropic models. The stress components associated with compressive and torsional deformations are determined analytically and illustrated for a simple constitutive model.

Nonbank lenders as global shock absorbers: Evidence from US monetary policy spillovers

We show that nonbank lenders act as global shock absorbers from US monetary policy spillovers. For identification, we exploit monetary policy surprises and the global syndicated lending market, where detailed loan-level data allow us to compare the participation of banks and nonbanks in the same loan. When US policy tightens, dollar credit to non-US firms falls, but nonbanks increase credit supply (relative to banks), thereby mitigating the total credit reduction. This relative increase is stronger for riskier non-US firms, proxied by emerging market firms, high-yield firms, or firms in countries with stronger capital inflow restrictions. Finally, there are real effects associated with the international nonbank channel of monetary policy, as firms with better access to nonbank credit relatively increase total corporate debt, investment, and employment.