scholarly journals Effect of mounting and fluid parameters on dynamic damping characteristics of a hydraulic damper

2021 ◽  
Vol 39 ◽  
pp. 56-61
Author(s):  
Wenlin Wang ◽  
Rongyong Li ◽  
Shan Zhu ◽  
Yongming Wu
Keyword(s):  
Hydraulic Damper ◽  
Damping Characteristics ◽  
Dynamic Damping ◽  
Fluid Parameters

Prediction of the in-service performance of a railway hydraulic damper

2016 ◽  
Vol 231 (1) ◽  
pp. 19-32
Author(s):  
Wenlin Wang ◽  
Dingsong Yu ◽  
Rui Xu
Keyword(s):  
High Speed ◽  
Influential Factors ◽  
Service Performance ◽  
Relief Valve ◽  
High Speed Rail ◽  
Hydraulic Damper ◽  
Damping Characteristics ◽  
Model And Simulation ◽  
Wide Range ◽  
Entrained Air

In this study, an improved physical parametric model with key in-service parameters was established and experimentally validated for a high-speed railway hydraulic damper. A subtle variable oil property model was built and coupled into the full model to address the dynamic flow losses and the relief-valve system dynamics. Experiments were conducted to evaluate the accuracy and robustness of the full damper model and simulation, which determined the damping characteristics over an extremely wide range of excitation speeds. Further simulations with in-service conditions and excitations were performed using the validated model, and the results revealed that improper key in-service parameters, such as improper rubber attachment stiffness, entrained air ratios and small mounting clearances, can greatly degrade the damping capability of a hydraulic damper. The obtained physical model includes all the influential factors that have an impact on the damping characteristics, so it will serve as a useful basic theory in the prediction of in-service performance, optimal specification and product design optimization of hydraulic dampers for modern high-speed rail vehicles.

scholarly journals Both stiff and compliant: morphological and biomechanical adaptations of stick insect antennae for tactile exploration

2018 ◽  
Vol 15 (144) ◽  
pp. 20180246 ◽  
Author(s):  
H. Rajabi ◽  
A. Shafiei ◽  
A. Darvizeh ◽  
S. N. Gorb ◽  
V. Dürr ◽  
...  
Keyword(s):  
Mechanical Design ◽  
Somatosensory System ◽  
Model Organism ◽  
Biomechanical Properties ◽  
Structural Features ◽  
Stick Insect ◽  
Fe Model ◽  
Damping Characteristics ◽  
Dynamic Damping ◽  
Active Exploration

Active tactile exploration behaviour is constrained to a large extent by the morphological and biomechanical properties of the animal's somatosensory system. In the model organism Carausius morosus , the main tactile sensory organs are long, thin, seemingly delicate, but very robust antennae. Previous studies have shown that these antennae are compliant under contact, yet stiff enough to maintain a straight shape during active exploration. Overcritical damping of the flagellum, on the other hand, allows for a rapid return to the straight shape after release of contact. Which roles do the morphological and biomechanical adaptations of the flagellum play in determining these special mechanical properties? To investigate this question, we used a combination of biomechanical experiments and numerical modelling. A set of four finite-element (FE) model variants was derived to investigate the effect of the distinct geometrical and material properties of the flagellum on its static (bending) and dynamic (damping) characteristics. The results of our numerical simulations show that the tapered shape of the flagellum had the strongest influence on its static biomechanical behaviour. The annulated structure and thickness gradient affected the deformability of the flagellum to a lesser degree. The inner endocuticle layer of the flagellum was confirmed to be essential for explaining the strongly damped return behaviour of the antenna. By highlighting the significance of two out of the four main structural features of the insect flagellum, our study provides a basis for mechanical design of biomimetic touch sensors tuned to become maximally flexible while quickly resuming a straight shape after contact.

Multi-objective design optimization of the complete valve system in an adjustable linear hydraulic damper

2010 ◽  
Vol 225 (3) ◽  
pp. 679-699 ◽  
Author(s):  
W L Wang ◽  
X J Yang ◽  
G X Xu ◽  
Y Huang
Keyword(s):  
Design Optimization ◽  
High Speed ◽  
Optimal Result ◽  
Relief Valve ◽  
Valve System ◽  
Hydraulic Damper ◽  
Multi Objective ◽  
Damping Characteristics ◽  
Fitness Value ◽  
Optimization Search

Adjustable linear hydraulic dampers are widely used in high-speed trains to improve their ride comfort and stability, the distinctive damping characteristics of the dampers are intrinsically predetermined by their inner complete valve systems. Therefore, design of the complete valve system parameters for each damper type is of crucial importance. A multi-objective design optimization model for the concept of optimizing both the technical and economic capabilities of a three-valve complete valve system in a hydraulic damper was formulated, based on full damper dynamics modelling. A linear weighted criterion method was used to transform the established multi-objective problem to a single-objective problem, and a computer package employing the genetic algorithm for the optimization search was developed. Implementation of the design optimization was performed, and an optimal result, with about 10.29 per cent improvement of the overall fitness value, was obtained. Simulation results show that the optimal result satisfies all the competing objectives well within the constraints, except for some minor and tolerable tradeoffs in the relief valve response performance. Prototype experiments validated that the prototype dampers have obtained excellent damping characteristics, as expected. Thus, the complete valve system of the hydraulic damper was comprehensively optimized, with respect to both the technical and economic concerns. The approach developed in this work has already been applied to the engineering design of several hydraulic damper products in industry.

Determination of Blade Stresses Under Constant Speed and Transient Conditions With Nonlinear Damping

1996 ◽  
Vol 118 (2) ◽  
pp. 424-433 ◽  
Author(s):  
J. S. Rao ◽  
N. S. Vyas
Keyword(s):  
Numerical Technique ◽  
Nonlinear Damping ◽  
Interfacial Slip ◽  
Rotor Speed ◽  
Transient Conditions ◽  
Life Estimation ◽  
Damping Characteristics ◽  
Dynamic Damping ◽  
Transient Operations

Determination of resonant stresses is an important step in the life estimation of turbomachine blades. Resonance may occur either at a steady operating speed or under transient conditions of operation when the blade passes through a critical speed. Damping plays a significant role in limiting the amplitudes of vibration and stress values. The blade damping mechanism is very complex in nature, because of interfacial slip, material hysteresis, and gas dynamic damping occurring simultaneously. In this paper, a numerical technique to compute the stress response of a turbine blade with nonlinear damping characteristics, during steady and transient operations of the rotor, is presented. Damping is defined as a function of vibratory mode, rotor speed, and strain amplitude. The technique is illustrated by computing the stress levels at resonant rotor speeds for typical operation of a turbomachine.

Experimental research into the low-temperature characteristics of a hydraulic damper and the effect on the dynamics of the pantograph of a high-speed train running in extreme cold weather conditions

2019 ◽  
Vol 234 (8) ◽  
pp. 896-907
Author(s):  
Wenlin Wang ◽  
Yuwen Liang ◽  
Weihua Zhang ◽  
Simon Iwnicki
Keyword(s):  
Low Temperature ◽  
Experimental Research ◽  
High Speed ◽  
Weather Conditions ◽  
Cold Weather ◽  
Temperature Characteristics ◽  
Hydraulic Damper ◽  
Damping Characteristics ◽  
High Speed Trains ◽  
Extreme Cold

There is likely to be a demand to run high-speed trains in extreme cold weather conditions in the near future; therefore, it is important to study the change in the characteristics of the materials and components in an extreme cold environment and their effects on the vehicle system dynamics. Experimental research into the low temperature characteristics of a pantograph hydraulic damper was carried out in this study. The results show that low temperature causes an increase in damping forces, and when the temperature is above the boundary temperature range, most indices of the damping capability increase with the decrease of temperature; when the temperature is below the boundary temperature range, most indices decrease with the decrease of temperature. Key parameters are identified to obtain the theoretical description of low-temperature damping characteristics using a simplified-parametric damper model and the experimental data. A mathematical model of the pantograph–catenary system incorporating the pantograph damper model is then established to calculate the effect of the damper performance on the pantograph dynamics low temperatures. Simulation results show that the lowering performance of the pantograph deteriorates noticeably due to the unstable low-temperature damping characteristics, but the deterioration of the raising performance and contact quality of the pantograph due to the low-temperature characteristics of the damper are less obvious. The results obtained in this study are valuable for understanding the low-temperature characteristics of a hydraulic damper, and instructive in the optimal specification of the pantograph damper for high-speed trains running in cold weather conditions.

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