Characteristics Of Shock Absorber Research Articles

Characterization of Exterior Parts for 3D-Printed Humanoid Robot Arm with Various Patterns and Thicknesses.

Currently, metal is the most common exterior material used in robot development due to the need to protect the motor. However, as soft, wearable, and humanoid robots are gradually being developed, many robot parts need to be converted into artificial skin using flexible materials. In this study, in order to develop soft exterior parts for robots, we intended to manufacture exterior robot arm parts via fused filament fabrication (FFF) 3D printing according to various structural and thickness conditions and analyze their mechanical properties. The exterior parts of the robot arms were manufactured utilizing Shore 95 A TPU (eTPU, Esun, Shenzhen, China), which is renowned for its softness and exceptional shock absorption characteristics. The exterior robot arm parts were modeled in two parts, the forearm and upper arm, by applying solid (SL) and re-entrant (RE) structures and thicknesses of 1, 2, and 4 mm. The mechanical properties were analyzed through the use of three-point bending, tensile, and compression testing. All of the characterizations were analyzed using a universal testing machine (AGS-X, SHIMADZU, Kyoto, Japan). After testing the samples, it was confirmed that the RE structure was easily bendable towards the bending curve and required less stress. In terms of the tensile tests, the results were similar to the bending tests; to achieve the maximum point, less stress was required, and for the compression tests, the RE structure was able to withstand the load compared to the SL structure. Therefore, after analyzing all three thicknesses, it was confirmed that the RE structure with a 2 mm thickness had excellent characteristics in terms of bending, tensile, and compressive properties. Therefore, the re-entrant pattern with a 2 mm thickness is more suitable for manufacturing a 3D-printed humanoid robot arm.

Analysis and research on the dynamic characteristics of shock absorber based on ADAMS

In order to effectively improve safety and stability during transportation, a shock absorber with buffering and self-locking functions was designed. Based on the rigid flexible coupling technology, the working state and dynamic response of the shock absorber were simulated and analyzed. The linear spring was treated as a flexible body, and the cam button, guide pillar, and base were treated as rigid bodies. The modal neutral files required for the rigid flexible coupling dynamic analysis were generated. Based on ADAMS, a dynamic simulation model was established, replacing a part of the rigid model with a flexible model and conducting load response analysis on it. To further improve the vibration reduction effect, the performance of the contact material of the shock absorber was analyzed. Through the calculation of dynamic characteristics, it could be known that the self-locking mechanism had no dead points, and the vibration reduction force response stability was high, meeting the working requirements.

Velocity and load dependent dynamic shock absorber friction at stationary conditions

When it comes to vehicle vertical dynamics, the characteristics of shock absorbers are of high importance. With the increasing use of active suspension systems, it becomes possible to adapt the hydraulic damping force to the road event, while the friction force is not controllable. As a result, friction becomes more relevant and can negatively affect passenger ride comfort. In many mechanical applications, it is observed that friction in lubricated sliding conditions is velocity and load dependent. In contrast, shock absorber friction, and therefore suspension friction, is commonly considered as quasi-static, i.e. characterised by a constant potential. Since the shock absorber is predominantly in motion over a wide velocity range, it is necessary to improve the understanding of friction characteristics especially in the dynamic domain. In this study, modified valve-free shock absorbers are presented that allow the observation of dynamic friction properties experimentally. As not covered by previous studies, the effect of side force (load) as a main parameter to increase friction is investigated. It is observed that its effect varies significantly with velocity and alters the stationary friction-velocity curve, also known as the Stribeck curve. In addition, the shape of the Stribeck curve depends strongly on the shock absorber's oil volume. These novel results emphasise a substantial, interdependent influence of load and velocity on the (elasto-)hydrodynamic properties of the dynamic shock absorber friction force, which was not identified in the literature. The dynamic friction force exceeds the quasi-static friction force multiple times, and also exceeds the hydraulic damping force for considerable side forces in the lower velocity range up to 60 mm/s. Consequently, the total shock absorber force under presence of side force is determined. The findings can be used to improve active suspension control or to improve vehicle simulation by enabling the parametrisation of dynamic shock absorber friction models.

Assessment of the Possibility of Validating the Durability Testing Method for Large-Sized Vehicles Based on Changes in Shock Absorber Characteristics—Preliminary Tests

The use of road simulators in vehicle durability tests enables a significant reduction in time related to the implementation of a new product. However, there is still a need to improve the methods of these tests in order to obtain a full correlation between the time of the tests on the simulator with respect to the mileage of the vehicle in real road conditions. The aim of this work is a validation and improvement of the durability testing method for large-sized vehicles. Comparative tests of shock absorbers dismantled from semi-trailers with different mileage and shock absorbers dismantled from semi-trailers after durability tests conducted at the MTS test bench are presented. The relationship between the maximum damping force and the displacement speed of the shock absorber piston was examined. Additionally, the influence of the shock absorber temperature on the damping force was analyzed. As a result of the tests, the dynamic characteristics of the shock absorbers were determined and the relationship between the maximum damping force and the mileage of the trailers was determined. It was found that the load on the trailers during their operation has a significant impact on the change in the characteristics of the shock absorbers. What is new in this publication is the validation of the methodology for conducting durability tests previously proposed by the authors based on the selected component, which is the shock absorber. The authors have not yet encountered in the literature any attempt to validate the methodology for conducting durability tests for large-sized vehicles.

Quasi-static shock absorber friction at low velocity reciprocating sliding conditions

The characteristics of vehicle shock absorbers have a major significance regarding vehicle dynamics, thus affecting vehicle ride comfort, handling and safety. Although much research focuses particularly on the hydraulic damping properties of this vital suspension component, friction properties are not considered in great detail. However, for driving scenarios of low excitation and velocity of the shock absorber due to moderate roughness of the road, the friction force generated by the shock absorbers and the remaining components is particularly important regarding the transfer of vibration from the road to the passenger. Hence, this study investigates the sensitivity of shock absorber friction to various parameters in the quasi-static domain. The effects of side force, temperature, excitation amplitude and waveform are determined for multiple shock absorbers. The results show no significant influence of the amplitude and waveform used in the conducted tests. Contrarily, the friction force strongly depends on the side force, which represents the variable load perpendicular to the shock absorber’s main axis arising during various driving events for MacPherson suspensions. An increased temperature reduces the side force effect.

EXPERIMENTAL STUDY OF THE PERFORMANCE CHARACTERISTICS OF SHOCK ABSORBERS

The article discusses the methodology for determining the performance characteristics of Toyota Prius 20 shock absorbers. The study was conducted using a stand for the diagnosis of shock absorbers developed by the Department of Road Transport of INRTU (Irkutsk National Research Technical University). Tests were carried out for five front suspension shock absorbers, one – a new serviceable shock absorber, the rest – shock absorbers that were previously in operation. The experimental dependences of the change in the resistance force of the shock absorber on the speed of movement of its rod are analyzed. The level of operational characteristics of the shock absorber under study was determined by comparing the obtained parameters with the parameters of the new shock absorber.
 The results of experimental studies are presented in the form of operational characteristics of tested shock absorbers and indicators that determine the level of operational characteristics of shock absorbers. The developed methods and the equipment implementing them make it possible to determine the functional dependencies and the level of performance of shock absorbers that were in the operating conditions of the vehicle.

Calculation of the parameters of the electromechanical shock absorber of the high-speed electric train

The article examines the issue of the chassis system of a high-speed electric train with body inclination and a vibration recovery system. The advantages of using an electromechanical shock absorber over hydraulic, pneumatic and similar systems are described. The authors considered the main characteristics of the DC electromechanical shock absorber. The main overall parameters of the shock absorber were presented. Attention is paid to the relevance of using an electromechanical shock absorber of a linear type, in comparison with analogues, including the ability to recover energy. Attention is drawn to the structure of the DC electromechanical shock absorber. The functional control scheme of the electromechanical shock absorber is considered and the control algorithm is described. The calculation areas of the parameters of the electromechanical shock absorber are determined. A 3D model of an electromechanical shock absorber in the Ansys Electronics software environment is presented. A finite-element mesh was built for further calculations of the magnetic field and inductance. In the article, attention is paid to the calculation of the magnetic field in the most intense mode. A picture of the shock absorber's magnetic field at the maximum working clearance was obtained and interim results were discussed. The results of calculating the inductance depending on the operating gap of the shock absorber are presented. Conclusions were made based on the results of calculations of magnetic and electrical parameters of an electromechanical shock absorber based on a linear direct current motor.

The Influence of Interface Roughness on the Vibration Reduction Characteristics of an Under-Platform Damper

Analysis of the vibration reduction characteristics of shock absorbers is crucial for engines. In this study, the fractal theory was applied to the contact surface of an under-platform damper (UPD), and the influence of the excitation force in the same and opposite directions on the roughness of the contact surface was studied. First, based on fractal geometry theory (FGT), the roughness characterization method of a UPD contact surface was proposed. Then, the friction mechanical model of the rough contact surface was established by combining it with a 3D contact mechanical model. Furthermore, a finite element dynamic model of a blade with a UPD structure was set up. Next, the harmonic balance method was used to calculate the nonlinear response characteristics of a blade under different levels of contact surface roughness. Finally, the influence of the contact surface roughness on the vibration reduction ability of a UPD under different excitation modes was analyzed. According to the simulation results, as the contact surface became rougher, the vibration suppression ability of the UPD on the blade became stronger and stronger. With the change in the centrifugal force of the UPD and the amplitude of the same/reverse excitation force, the influencing law of the contact surface roughness on the vibration suppression ability of the UPD remained unchanged, indicating that the rougher the contact surface roughness, the better the vibration suppression effect.

Improving the comfort of truck drivers by using controlled cab suspension shock absorbers

The research addresses the issue of creating a methodology for selecting the damping control law in nonlinear suspension systems and determining the characteristics of controlled shock absorbers in the cab suspensions. The study object is the shock-absorbing support device of the truck cab suspension system. By mathematical modeling of the car dynamics, it is proved the effectiveness of the cab suspension system with controlled shock absorbers and its operability according to the criterion of the possibility of implementing a controlled shock support device in the form of a technical device. Keywords controlled shock absorbers, cab suspension, smoothness running, driver comfort, shock support device

Investigation of Impact Absorption Function of Carbon Plantar Plate for Low Arch Foot

At present, it cannot be said that the impact absorption function of the truss structure of the foot arch during static standing has been elucidated.In this study, the spring constant and the viscous damping coefficient are calculated and examined in order to compare the shock absorption characteristics of the low-arch foot seen in flat feet and the characteristics of the normal-arch foot.In addition, in order to supplement the spring constant and viscous damping coefficient for one case of low arch foot, we investigated using a carbon plantar plate. Six types of carbon plantar plates were compared, with heels and without heels, with 2 layers, 3 layers, and 4 layers.As a result, the low arch foot showed a low spring constant and a high viscous damping coefficient. In the comparison of 6 types of carbon plantar plates, the one with heel showed high spring constant and viscous damping coefficient. The value closest to the normal arch was the 3-layer carbon plantar plate without heel.It was thought that the low-arch foot had a reduced spring function that absorbs impact. The carbon plantar plate with heel cup clearly shows high values of spring constant and viscous damping coefficient, which means that hard to sink the heel.The reason for this is presumed to be the influence of the soft tissue of the heel is likely to collapse due to the heel couter.The carbon plantar plate used this time was not able to compensate for the impact class function of the normal arch foot, so further examination was necessary. However, this research has a small number of subjects, so it is necessary to increase the number of subjects and investigate again. As a future task, we will consider increasing the number of subjects.

An Investigation of the Influence of Temperature and Technical Condition on the Hydraulic Shock Absorber Characteristics

The paper presents issues related to the operation of hydraulic shock absorbers. The primary objective was to determine the influence of temperature and the technical condition on the damping properties of a twin-tube hydraulic shock absorber. Three units (one new and two used) of the same type of a shock absorber were used for testing. During the tests, the shock absorber was subjected to sinusoidal excitation at fixed values of frequency and displacement amplitudes. There are few low-temperature tests of shock absorbers available in the literature; thus, great emphasis was placed on this aspect of the study. The characteristics of the shock absorbers were determined from a temperature of −30 °C until a steady-state temperature was reached at a given excitation. The resistance force at this temperature is about 2.5 times higher than at 20 °C. The study shows that such high forces can lead to the failure of shock absorber components (especially the valves). The amount of energy dissipated in a single operating cycle of a shock absorber decreases non-linearly with the increase of the temperature. Understanding the temperature dependence of the shock absorber in combination with the cooling curve allows for the steady-state temperature to be estimated at a given excitation. The study also shows that the installation of used shock absorbers in vehicles is not acceptable. Although there are no external signs of wear, their characteristics can differ significantly from those of new shock absorbers.

Modeling of Thermal Preparation of Shock Absorbers of Trucks

The use of modern materials and technical fluids allows you to operate cars at negative temperatures, but in some regions of the world (for example, in Siberia), the ambient air temperature can fall below 243 K for several weeks or even months. The operation of trucks at such a temperature refers to extreme conditions that force the special preparation of equipment. This preparation consists not only of special maintenance, but also of carrying out some activities that are carried out immediately before starting the engine and driving. The essence of these measures is, among other things, the thermal preparation of the components and assemblies of the vehicle before departure.This work is devoted to the thermal preparation of truck shock absorbers. It is revealed that the use of oils, the kinematic viscosity of which significantly depends on the ambient temperature, is a limiting factor in the winter operation of shock absorbers. The simulation of the operation of electric flexible heaters for shock absorbers in the SolidWorks Flow Simulation environment was carried out and the preheating efficiency was evaluated. It is established that the temperature distribution of the shock absorber fluid during heating of two-pipe shock absorbers occurs unevenly, but despite this, preheating significantly improves the characteristics of shock absorbers and contributes to the safe and long-lasting operation of trucks.

О применении высокопористых алюминиевых сплавов и сотовых конструкций в посадочных устройствах космических аппаратов

The paper presents results of studying mechanical properties and shock-absorbing characteristics of the highly porous aluminum alloys and aluminum alloy cellular structures with the initial average density from 190 to 2250 kg/m3. The study is based on data from foreign publications and experimental results obtained by the authors. Diagrams of deformation are provided illustrating characteristic stages of the deformation process and compaction of the highly porous alloys and cellular structures made of the aluminum alloys. Highly porous alloys are identified, which deformation is close to the idealized. Based on the analysis of experimental data, presence of two groups of materials is shown: the first with deformation diagram without hardening at the compaction stage and the second with hardening. Basics for calculating specific and effective impact absorption energy are provided. Analogue shock absorbers are shown for characteristic stages of the deformation diagrams. Introduction of the effective impact absorption energy is proposed as a criterion to compare the shock absorbers with each other. The results obtained could be used in the development of the single shock absorbers.

Sugarcane waste based synthesized graphene like nanocarbon (GNC) for shock absorption application

We report on the synthesis, characterization, and shock absorption characteristics of Graphene like Nano Carbon (GNC) prepared by the combustion of biomass (sugarcane waste) using the Rapid Thermal Chemical Vapor Deposition (RT-CVD) technique. Post synthesis, the samples were purified by subjecting them to intercalation and annealing. The synthesised GNCs were then characterised by Raman, Infrared, and UV spectroscopy, together with microscopy. In analysis, the GNCs were observed to be rectangular in shape, thick, having sharp edges and corners, and having an area ∼50–200 μm2 with wrinkles on it. TEM images showed that GNCs exhibit smooth wrinkle contours with bits of dark showing conjugated graphene layers stacked together having multiple defects and dislocations. In Raman spectroscopy, D peak is observed at ∼1335 cm−1 and G peak is observed at ∼1591 cm−1 indicating GNC consists of sp2 and sp3 hybridised complex phases. The Crystalline Length (La), Disordered Length (LD) and Defect Density (nD) have been estimated to be 21.26 nm, 9.60 nm and 1.084 × 10−12/cm2 respectively. FTIR spectra revealed that C-C is present at ∼1420 cm−1 and C-O-C is present at 900 cm−1. In Uv measurements, no typical absorption peak was observed due to the micrometre size of GNC. The shock absorption properties of GNCs were investigated by subjecting them to pressure (~1.5 GPa) using a Split Hopkinson Pressure Bar (SHPB). The obtained mechanical parameters revealed that GNCs absorbed ∼65% of incident energy and ∼15% transmitted, demonstrating their utility in the development of armour, shock and blast mitigating blocks, defense, and space applications.

The influence of shock absorber characteristics’ nonlinearities on suspension Frequency Response Function estimation and possibilities of simplified characteristics modelling

The paper shortly presents shock absorber design evolution and resulting achieved characteristics. The way in which suspension performance is evaluated is described giving information about models used for suspension parameter tuning during simulation testing of suspension transmissibility (FRF - Frequency Response Function) for most important suspension assessment criteria. More detailed information about models of shock absorber (damper) nonlinearities of characteristics allows for description of methods of linear and nonlinear suspension models FRF estimation. Testing linear suspension model is possible with the use of analytical transfer function formulas which were used to verify methods for estimation FRF using estimated power spectral density functions of excitation and response signals. Designing appropriate input signal allowing to get useful response signals was necessary to for the success of this research. Proposed FRF estimation method was used for linear estimation of nonlinear suspension for a given range of working condition. It was demonstrated that there is no single value of a damping coefficient which would make the linear model responses similar to the responses of the nonlinear one. Then the bilinear model was proposed, giving good damper static nonlinear characteristic.

Theoretical and experimental research on damping characteristics of CDC shock absorber

CDC (Continuous Damping Control) shock absorber is the typical representative of the stepless valve-controlled type, which has the advantages of low cost and stable performance. Based on the throttling characteristics of the CDC valve, the damping force mathematical model of the CDC shock absorber is established. Through simulation analysis, the indicator characteristics and speed characteristics of the CDC shock absorber under different input currents and speeds are obtained. A CDC shock absorber testbed is built to study damping characteristics, and the results are compared with the simulation results. The results show that the indicator diagram obtained by simulation and experiment is smooth without distortion, and the speed characteristic diagram is smooth without a large mutation point. The experimental values of damping force are slightly larger than the simulation values. The relative error between the simulation data and the experimental data is basically less than 10% and the model has high accuracy. When the input current is the same, the damping force increases with the increase of piston rod speed. When the speed of the piston rod is the same, the damping force of the rebound and compression stroke decreases with the increase of input current.

Effect of blowing agent concentration of ultra‐low density NBR/PVC composite foams on compressive behavior and energy‐absorption characteristics

AbstractUltra‐low density nitrile butadiene rubber (NBR)/polyvinyl chloride (PVC) composite foams that exhibit satisfactory compressive behavior and energy absorption characteristics were prepared by one‐step compression molding. The properties of the NBR/PVC foams, including the density, hardness, cell morphology, compressive behavior, energy absorption characteristics, and shock absorption characteristics, were studied with various concentrations of azodicarbonamide (AC). Further that, the ideality factor and the energy absorption efficiency of the NBR/PVC foams at a low stress for application in compression and energy absorption were determined. The results revealed that the densities of polymeric foams were crucial in determining the uniformity of cell size and energy absorption characteristics of the composite foams. With increasing AC content, the density of the NBR/PVC foams decreased linearly, whereas the uniformity of cell size and the foaming ratio increased; furthermore, the hardness and compression modulus gradually decreased, and the linear elastic region in the compressive stress–strain curves became narrow. When the applied stress was less than 100 kPa, the foams with a high AC content exhibited higher energy absorption compared to foams with a low AC content capacity because of the deformed cell wall and lower elastic modulus; however, the relation between AC contents and energy absorption was complicated above 100 kPa. The optimum springrate ratio was found at the concentration of 25 phr of the AC blowing agent.

МАТЕМАТИЧЕСКАЯ МОДЕЛЬ ГАСИТЕЛЯ КОЛЕБАНИЙ ВАГОНА НА ОСНОВЕ ВЯЗКОГО ТРЕНИЯ

The work objective is to develop a mathematical model of the force characteristics of shock absorbers based on viscous friction, including elastomeric ones. For this purpose, the following tasks are solved in the work: the existing approaches to the mathematical modelling of hydraulic shock absorbers are analysed, a mathematical model based on hydraulic equations (the Darcy–Weisbach equation) is proposed, the developed mathematical model is verified and the results are compared with the results obtained based on the existing approach.
 Research methods: the equation of fluid flow through holes with hydraulic friction; D'Alembert's principle for composing the equation of car swaying motions; the Euler method for numerical integration of the differential equation.
 The novelty of the work consists in the fact that a mathematical model of the power characteristics of shock absorbers with viscous friction is proposed, based on the quadratic dependence of the reaction on the deformation rate. 
 The results are the study of car swaying motions based on the traditional and proposed approaches. The proposed mathematical models can be used to develop shock absorbers with improved characteristics when designing passenger cars.

Fabrication of natural fibre based industrial safety helmet

In all industries, the safety helmet is considered as one of the most significant parts of personal protection equipment worn by workers to protect against head injuries caused due to falling items. The majority of head injuries caused by falling objects are serious, and they can even be deadly. Thermal discomfort, heavyweight, and plastic material are among the issues that workers face when wearing industrial safety helmets. Many researchers are striving to enhance the quality of the material used in safety helmets by using advanced materials like polymers, natural fibres, and composites in order to improve the shock absorption characteristics. The aim of this research is to improve the strength of the helmet by combining different materials such as glass fibre, jute fibre, and banana fibre (mat/chopped) with epoxy resin to form a composite helmet. Three-layer and five-layer composite helmets of different stacking sequences are fabricated by hand layup technique and tested for shock absorption resistance, penetration resistance, flammability resistance, electrical resistance, and water absorption conforming to the Indian standard specification for industrial safety helmets (IS 2925). The results revealed that both the fabricated composite helmets satisfy the requirements of IS 2925, which are lighter and more eco-friendly, and are suitable for replacing conventional industrial safety helmets.

Numerical model of interation of package of open shells with a weakly compressible filler in a friction shock absorber

The problems of protecting equipment, structures and operators from the harmful effects of vibrations are among the most painful topics of modern mechanical engineering. In this research an original design of a friction shock absorber is presented in which the principle of operation is based on the contact interaction of a package of open shells with weakly compressible deformable filler. The proposed design is simple and technologically advanced, suitable for operation under high dynamic loads and at the same time has a compact transverse dimension. Such shock absorbers are projected to be used in the mining and oil and gas industries. A finite element model of a friction shock absorber with two contact pairs has been constructed: the first contact pair is "filler - package of open shells"; the second contact pair is "inner shell of the package - outer shell". The contacting bodies were presented as separate arrays of finite elements and the conditions of frictional interaction on the contact surfaces were set in the form of Coulomb's law. We considered the behavior of such a structurally nonlinear system under the action of a monotonic and nonmonotonic load. In the course of the study, the main operational characteristics of the shock absorber including the strength, rigidity, hysteresis characteristics and natural frequencies were determined. The possibility of adjusting the rigidity and shock-absorbing characteristics of the proposed device is discussed.