scholarly journals Design Contributions to the Elaboration of New Modeling Schemes for the Buckling Assessment of Hydraulic Actuators

Metals ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 1143
Author(s):  
Virgil Florescu ◽  
Stefan Mocanu ◽  
Laurenţiu Rece ◽  
Daniel Cătălin Motounu ◽  
Aurel Gherghina ◽  
...  
Keyword(s):  
Equilibrium Shape ◽  
Elastic Equilibrium ◽  
Hydraulic Cylinder ◽  
Loss Of Stability ◽  
Classical Approach ◽  
The Finite Element Method ◽  
Operational Safety ◽  
Hydraulic Cylinders ◽  
The Subject ◽  
Lifting Equipment

Hydraulic cylinders represent the main actuating/positioning element for standalone lifting equipment or equipment for various transport platforms. This type of actuator represents a structural component responsible for the operational safety of the equipment it serves. One of the most common and dangerous reasons concerning the end of life for this equipment is the buckling or loss of stability of the elastic equilibrium shape. This article aims to compare the classical approach of the problem in accordance with the strength of materials theory in relation to the numeric algorithms used in the applications for the analysis of structure behavior and the algorithms that are based on the finite element method. The subject of study is a hydraulic cylinder that is installed in a self-lifting platform and because of the manifestation of the phenomenon under analysis, it has led to a technical accident. For this purpose, an estimation of the value for the buckling critical load of the cylinder assembly was carried out.

The Lower Extremity Exoskeleton Coordinated Control Method Based on Human Electromechanical Coupling

2012 ◽  
Vol 220-223 ◽  
pp. 1012-1017
Author(s):  
Qing Guo ◽  
Dan Jiang
Keyword(s):  
Lower Extremity ◽  
Electromechanical Coupling ◽  
Position Control ◽  
Control Method ◽  
Angular Displacement ◽  
Stability Margin ◽  
Hydraulic Cylinder ◽  
Load Force ◽  
Hydraulic Cylinders ◽  
Coupling Characteristics

This paper has introduced electromechanical coupling characteristics in the lower extremity exoskeleton systems, considered model ,according to legs supporting gait when people walking, established the load torque compensation model , and a mathematical model of knee position control system which is made of the servo valve, hydraulic cylinders and other hydraulic components, designed hydraulic cylinder position control loop in case of existing load force interference compensation, and used the method of combining the PID and lead correction network for frequency domain design ,ensured system to meet a certain stability margin. The simulation results show that this position control method can servo on the knee angular displacement of normal human walking, reached a certain exoskeleton boost effect, at the same time, met the needs of human-machine coordinated motion.

Development of hydraulic cylinder diagnostic methods by modeling methods

2021 ◽  
pp. 41-45
Author(s):  
Keyword(s):  
Hydraulic Drive ◽  
Hydraulic Cylinder ◽  
Technical Condition ◽  
Diagnostic Methods ◽  
Technical Diagnostics ◽  
Remaining Service Life ◽  
Construction Machine ◽  
Piston Speed ◽  
Variable Nature ◽  
Hydraulic Cylinders

The hydraulic drive of a construction machine is a complex dynamic system that is subjected to many dynamic loads of a variable nature and operates under conditions of variable external influences caused by various factors. During operation, these loads cause failure of the hydraulic transmission elements. To prevent these malfunctions, technical diagnostics should be applied by determining their current technical condition and remaining service life. The article assesses the working condition of hydraulic cylinders using a mathematical model. Using matlab/simulink software to simulate the hydraulic cylinder and hydraulic piston speed when changing the hydraulic cylinder clearance. The simulation results are presented. Keywords: diagnostic, hydraulic cylinder, simulation, development

Research of throwing areols of underground pipeline in permafrost

2021 ◽  
pp. 21-30
Author(s):  
T. S. Sultanmagomedov ◽  
◽  
R. N. Bakhtizin ◽  
S. M. Sultanmagomedov ◽  
T. M. Halikov ◽  
...  
Keyword(s):  
Finite Element Method ◽  
Experimental Study ◽  
Finite Element ◽  
Strain State ◽  
Operating Temperature ◽  
Operating Conditions ◽  
Loss Of Stability ◽  
Underground Pipeline ◽  
The Finite Element Method ◽  
Permafrost Thawing

Study is due to the possibility of loss of stability of the pipeline in the process of pumping a product with a positive operating temperature and the formation of thawing halos. The article presents the ways of solving the thermomechanical problem of pipeline displacement due to thawing. The rate of formation of a thawing halo is investigated depending on the initial temperatures of the soil and the pumped product. The developed monitoring system makes it possible to study the rate of occurrence of thawing halos in the process of pumping the product. An experimental study on the formation of thawing halos around the pipeline was carried out on an experimental model. A thermophysical comparative calculation of temperatures around the pipeline on a model by the finite element method has been carried out. Keywords: underground pipeline; permafrost; thawing halo; monitoring; operating conditions; stress–strain state.

Three Dimensional Seismic Isolation System Using Hydraulic Cylinder

2002 ◽  
Author(s):  
Shinichiro Kajii ◽  
Naoki Sawa ◽  
Nobuhiro Kunitake ◽  
K. Umeki
Keyword(s):  
Seismic Isolation ◽  
Three Dimensional ◽  
Vertical Direction ◽  
Hydraulic Cylinder ◽  
Seismic Load ◽  
3D Seismic ◽  
Isolation System ◽  
Response Characteristics ◽  
Seismic Motion ◽  
Hydraulic Cylinders

A three-dimensional (3D) seismic isolation system for FBR building is under development. The proposed vertical isolation system consists form hydraulic cylinders with water-based liquid and accumulators to support large vertical static load and to realize low natural frequency in the vertical direction. For horizontal isolation, laminated rubber isolator or sliding type isolator will be combined. Because the major part of the feasibility of this isolation system depends on the sealing function and durability of the hydraulic cylinder, a series of feasibility tests of the hydraulic cylinder have been conducted to verify the reliability against seismic load and seismic motion. This paper describes the specification of the seismic isolations system, seismic response characteristics and the results of the feasibility tests of the seal. This study was performed as part of a government sponsored R&D project on 3D seismic isolation.

scholarly journals The Dependence of Selected Technical and Combustion Characteristics of Fire on Moisture Levels in Alternative Fuels

2014 ◽  
Vol 9 (1) ◽  
pp. 25-30
Author(s):  
Martin Kulich
Keyword(s):  
Alternative Fuels ◽  
Combustion Characteristics ◽  
Operating Conditions ◽  
Final Part ◽  
Operational Risks ◽  
Operational Safety ◽  
The Subject

Abstract The subject of this paper is to analyse the influence of moisture on selected technical and combustion characteristics of alternative fuels. The analyses are conducted on the basis of analyses of samples of alternative fuels simulating states of the fuel in expected operating conditions, focusing on the identification of potential operational risks. The final part consists of a set of recommended measures to ensure the operational safety of the practical use of alternative fuels based on the results of the analysis.

scholarly journals Some Aspects Concerning The Impact Of The End Of Stroke On Hydraulic Cylinders

2015 ◽  
Vol 21 (3) ◽  
pp. 821-824
Author(s):  
Niculai Hauk
Keyword(s):  
Numerical Simulation ◽  
Mechanical Systems ◽  
Hydraulic Cylinder ◽  
Important Variable ◽  
Mechanical Impact ◽  
Hydraulic Cylinders ◽  
The Masses ◽  
The Impact ◽  
Simulation Systems ◽  
Classical Calculation

Abstract The increase of speeds for mechanical systems operated with hydraulic cylinder raises risks of mechanical impact of the end of the race. We are considering a number of measures to limit the impact intensity. Its size is estimated according to the masses in motion, to work pressures and to the geometry of the mechanism. Elasticity of the components is also an important variable. This paper presents a method which combines the classical calculation with numerical simulation systems.

scholarly journals Modeling Study on Stiffness Characteristics of Hydraulic Cylinder under Multi-Factors

2017 ◽  
Vol 63 (7-8) ◽  
pp. 447 ◽  
Author(s):  
Hao Feng ◽  
Qungui Du ◽  
Yuxian Huang ◽  
Yongbin Chi
Keyword(s):  
Mechanical System ◽  
Volume Expansion ◽  
Hydraulic Cylinder ◽  
Experimental Results ◽  
Axial Deformation ◽  
Response Characteristics ◽  
Stiffness Model ◽  
Hydraulic Cylinders ◽  
Stiffness Characteristics ◽  
Cylinder Barrel

For a complex mechanical system driven by hydraulic cylinders, the dynamic response characteristics of the mechanical system are significantly affected by the stiffness characteristics of hydraulic cylinders. This paper comprehensively studies the impacts of various factors on the stiffness characteristics of the hydraulic cylinders, including the oil bulk modulus, the air content in the hydraulic oil, the axial deformation of the piston rod, the volume expansion of the cylinder barrel, the volume expansion of the metal pipes and the flexible hoses, and the deformation of the hydraulic cylinder sealing. By combining the theoretical analysis and the experimental results, the level of each impacting factor was quantified, and the stiffness model of the hydraulic cylinder was established. Finally, comparative analysis of the stiffness was conducted by taking the experimental hydraulic cylinder as an example; it was verified that the calculated results of the proposed hydraulic cylinder stiffness model approximated the experimental results. Compared with stiffness models presented in current literature, the average accuracy was improved by more than 15 %.

Tribological behaviors of PTFE-based composites filled with bronze microparticles

2019 ◽  
pp. 089270571987520
Author(s):  
Amine Charfi ◽  
Sameh Neili ◽  
Mohamed Kharrat ◽  
Maher Dammak
Keyword(s):  
Wear Behavior ◽  
Normal Load ◽  
Optical Microscope ◽  
Hydraulic Systems ◽  
Friction Behavior ◽  
Excessive Pressure ◽  
Research Article ◽  
Hydraulic Cylinders ◽  
Perfect Contact ◽  
The Subject

This research article deals with commercial polytetrafluoroethylene (PTFE)-based composites filled with 30% of bronze microparticles. This shade is used as guide rings in hydraulic cylinders. After a certain number of slip cycles, seal wear is one of the main causes of leaks in the hydraulic systems. To solve this problem, it is essential to act on the seal materials to increase its lifetime and consequently the lifetime of hydraulic systems. Excessive pressure on the seal causes a significant wear while a light contact causes lubricant leak. For both situations, we have a failure of the system. For this reason, it is necessary to have a perfect contact between the seal and the metal surface and simultaneously with minimal wear. This problem is the subject of our research works. We analyze, in this article, the tribological behavior of a PTFE/bronze composite under dry and lubricated sliding conditions for different frequencies and loads. An alternating linear motion ball/plane tribometer has been used to characterize friction and wear behavior of the material. Micrographic observation of wear track was taken with the optical microscope. The results showed the good friction behavior of material for low values of loads and frequencies and essentially for 33 N of load with 1 Hz frequency or for 81 N as normal load with 0.75 Hz frequency as well as lubrication improve the wear rate of the PTFE/bronze composite. Under lubrication, load and frequency become inversely proportional to friction coefficients.

scholarly journals A Self-Contained Electro-Hydraulic Cylinder with Passive Load-Holding Capability

Energies ◽  
2019 ◽  
Vol 12 (2) ◽  
pp. 292 ◽  
Author(s):  
Damiano Padovani ◽  
Søren Ketelsen ◽  
Daniel Hagen ◽  
Lasse Schmidt
Keyword(s):  
Energy Efficiency ◽  
Cost Efficiency ◽  
Tracking Error ◽  
Hydraulic Cylinder ◽  
Position Tracking ◽  
Hydraulic Systems ◽  
Practical Applications ◽  
Hydraulic Cylinders ◽  
External Loads ◽  
Boom Crane

Self-contained electro-hydraulic cylinders have the potential to replace both conventional hydraulic systems and the electro-mechanical counterparts enhancing energy efficiency, plug-and-play installation, and reduced maintenance. Current commercial solutions of this technology are limited and typically tailor-made, whereas the research emphasis is primarily on cost efficiency and power applications below five [kW]. Therefore, there is the need of developing more flexible systems adaptable to multiple applications. This research paper offers a contribution in this regard. It presents an electro-hydraulic self-contained single-rod cylinder with passive load-holding capability, sealed tank, capable of recovering energy, and scalable up to about eighty [kW]. The system implementation on a single-boom crane confirms its feasibility: The position tracking error remains well within ±2 [mm], oscillations are limited, and the overall energy efficiency is about 60 [%] during actuation. Concerning the passive load-holding devices, it is shown that both vented and non-vented pilot-operated check valves achieve the desired functioning and can hold the actuator position without consuming energy. Additional observations about the size and the arrangement of the load-holding valves are also provided. In conclusion, this paper demonstrates that the proposed self-contained cylinder can be successfully extended to several practical applications, especially to those characterized by overrunning external loads and the need of securing the actuator position.

Internal leakage identification of hydraulic cylinder based on intrinsic mode functions with random forest

2019 ◽  
Vol 233 (15) ◽  
pp. 5532-5544 ◽  
Author(s):  
Lin Li ◽  
Yixiang Huang ◽  
Jianfeng Tao ◽  
Chengliang Liu
Keyword(s):  
Random Forest ◽  
Hydraulic Cylinder ◽  
Support Vector ◽  
Hydraulic Systems ◽  
Intrinsic Mode Functions ◽  
Random Forest Algorithm ◽  
Mode Decomposition ◽  
Empirical Mode Decomposition Method ◽  
Hydraulic Cylinders ◽  
Experimental Pressure

Monitoring for internal leakage of hydraulic cylinders is vital to maintain the efficiency and safety of hydraulic systems. An intelligent classifier is proposed to automatically evaluate internal leakage levels based on the newly extracted features and random forest algorithm. The inlet and outlet pressures as well as the pressure differences of two chambers are chosen as the monitoring parameters for leakage identification. The empirical mode decomposition method is used to decompose the raw pressure signals into a series of intrinsic mode functions to obtain the essence in experimental signals. Then, the features extracted from intrinsic mode functions in terms of statistical analysis are formed the input vector to train the leakage detector. The classifier based on random forest is established to categorize internal leakage into proper levels. The accuracy of the internal leakage evaluator is verified by the experimental pressure signals. Moreover, an internal leakage evaluator is established based on the support vector machine algorithm, in which the wavelet transform is applied for feature extraction. The accuracy and efficiency of different classifiers are compared based on leakage experiments. The results show that the classifier trained by the intrinsic mode function features in terms of random forest algorithm may more effectively and accurately identify internal leakage levels of hydraulic cylinders. The leakage evaluator provides probability for online monitoring of the internal leakage of hydraulic cylinders based on the inherent sensors.

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