scholarly journals Experimental and Analytical Study on Mechanical Properties of High Rock Temperature Diversion Tunnel

2019 ◽  
Vol 2019 ◽  
pp. 1-11
Author(s):  
Xianchun Yao ◽  
Ning Li ◽  
Kecheng Wan ◽  
Gao Lv ◽  
Mingming He
Keyword(s):  
High Temperature ◽  
Tensile Stress ◽  
Working Conditions ◽  
Temperature Difference ◽  
Laboratory Model ◽  
Support Structure ◽  
Diversion Tunnel ◽  
Supporting Structure ◽  
Circumferential Tensile Stress ◽  
Variation Characteristics

The high temperature of rock used in different working conditions has a significant effect on the deformation characteristics and the mechanics of tunnel lining support structure. A test using a laboratory model is designed to study the quantitative relationship between the temperature difference and the support force. Through the laboratory model test, the strain and stress variation characteristics of the supporting structure of a water diversion tunnel under different surrounding rock temperatures and different water temperatures were simulated. The variation characteristics of the supporting structure under various working conditions, such as a different initial temperature field, different crossing water temperature of the diversion tunnel during runtime, and repairing period after the water is emptied, were analyzed. The relationship between the high-temperature difference between the inner and outer walls of the tunnel lining support structure and the internal temperature stress of the supporting structure was obtained and compared with the results from numerical experiments. The test results showed that a high circumferential tensile stress is created in the support structure of the high-temperature diversion tunnel due to the temperature difference between the inner and outer walls of the support structure caused by water going through the high-temperature diversion tunnel. The radial compressive stress increases by 45–50%, and the circumferential tensile stress increases by 40–60%. The results provide references for the design of the support structure in a high-temperature tunnel.

scholarly journals Fracture Mechanical Analysis of Thin-Walled Cylindrical Shells with Cracks

Metals ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 592
Author(s):  
Feng Yue ◽  
Ziyan Wu
Keyword(s):  
Fracture Mechanics ◽  
Tensile Stress ◽  
Failure Modes ◽  
Cylindrical Shells ◽  
Crack Tip ◽  
Mechanical Analysis ◽  
J Integral ◽  
Thin Walled Structures ◽  
Circumferential Tensile Stress ◽  
Thin Walled

The fracture mechanical behaviour of thin-walled structures with cracks is highly significant for structural strength design, safety and reliability analysis, and defect evaluation. In this study, the effects of various factors on the fracture parameters, crack initiation angles and plastic zones of thin-walled cylindrical shells with cracks are investigated. First, based on the J-integral and displacement extrapolation methods, the stress intensity factors of thin-walled cylindrical shells with circumferential cracks and compound cracks are studied using linear elastic fracture mechanics, respectively. Second, based on the theory of maximum circumferential tensile stress of compound cracks, the number of singular elements at a crack tip is varied to determine the node of the element corresponding to the maximum circumferential tensile stress, and the initiation angle for a compound crack is predicted. Third, based on the J-integral theory, the size of the plastic zone and J-integral of a thin-walled cylindrical shell with a circumferential crack are analysed, using elastic-plastic fracture mechanics. The results show that the stress in front of a crack tip does not increase after reaching the yield strength and enters the stage of plastic development, and the predicted initiation angle of an oblique crack mainly depends on its original inclination angle. The conclusions have theoretical and engineering significance for the selection of the fracture criteria and determination of the failure modes of thin-walled structures with cracks.

Research on Damping Vibration Reduction Design Method of Aeroengine Supporting Structure System

2020 ◽  
Author(s):  
Chao Li ◽  
Binglong Lei ◽  
Yanhong Ma ◽  
Jie Hong
Keyword(s):  
Dry Friction ◽  
Dynamic Stiffness ◽  
Vibration Reduction ◽  
Vibration Response ◽  
Contact Friction ◽  
Friction Damper ◽  
Support Structure ◽  
Response Control ◽  
Structure System ◽  
Supporting Structure

Abstract Typical turbofan engine-support-structure systems having a high thrust-to-weight ratio are light, and the structure primarily comprises a plate and shells. The local vibration response of the support structure is excessively large when different frequency loads are applied. A structural vibration response control method based on dry friction damping is proposed to control the excessive vibration response. A dry friction damper with dynamic suction was designed to enhance the damping characteristics of the rotor supporting structure system in the wide frequency domain, without sacrificing the dynamic stiffness of the structure. The system is designed to effectively control the vibration response of the supporting structure at the working-speed frequency. Through theoretical modeling and simulation analyses, the influence of friction contact and damper structure characteristics on the damping effect is described quantitatively. Furthermore, the design idea and the damping process of the supporting structure are described. The calculation results show that the contact friction of the dry friction damper can consume the vibration energy of the supporting frame. A reasonable design of the contact characteristics and geometric configuration parameters of the damper can further optimize the vibration-reduction effect, and thereby improve the vibration response control design of the supporting structure system of aeroengines.

Multi-Function Manipulator

2012 ◽  
Vol 546-547 ◽  
pp. 1602-1607
Author(s):  
Zu Lin Wang ◽  
Jian Fei Ouyang ◽  
Qiang Fang ◽  
Yuan Liu
Keyword(s):  
High Temperature ◽  
Low Temperature ◽  
Labor Productivity ◽  
Working Conditions ◽  
Deep Water ◽  
Industrial Robots ◽  
Labor Intensity ◽  
Model Design ◽  
Improve Working ◽  
Automation Level

This paper is for ordinary lathe supporting and design the capture of manipulator. Practice has proved, industrial robots can replace the hands of heavy labor, significantly reduce the labor intensity, improve working conditions, and improve labor productivity and automation level. In addition, it can be in high temperature, low temperature, deep water,cosmos, radioactive and other toxic, pollution environment conditions operation, more shows its superiority, with broad prospects. In the paper, the structure of the manipulator model design and Cortex-M0 micro controller (hereinafter referred to as M0) as the main controller in this paper. With multiple steering gear as the basis, make manipulator model, through the realization to the output M0 PWM control more than the steering gear, and finally achieve the acquirement manipulator workpiece, and the workpiece in designated spot.

Experimental Investigation of a Miniature Ejector Using Water as Working Fluid

2020 ◽  
Vol 12 (6) ◽  
Author(s):  
Jingming Dong ◽  
Qiuyu Hu ◽  
Yuxin Xia ◽  
He Song ◽  
Hongbin Ma ◽  
...  
Keyword(s):  
Experimental Investigation ◽  
High Temperature ◽  
Working Conditions ◽  
Thermal Energy ◽  
Nozzle Exit ◽  
Cooling System ◽  
Area Ratio ◽  
Coefficient Of Performance ◽  
Working Fluid ◽  
Condensing Pressure

Abstract This paper presents an experimental investigation of a miniature ejector using water as the working fluid. The investigated ejector cooling system can utilize the thermal energy to be removed to power the cooling system and maintain the temperature of an electronic component below ambient temperature. The effects of working conditions, nozzle exit position (NXP), and area ratio on the coefficient of performance (COP) of ejector performance were investigated. Experimental results show that the miniature ejector can function well when the temperature in the high-temperature evaporator (HTE) ranges from 55 °C to 70 °C and can achieve a COP (coefficient of performance) of 0.66. With an increase of the NXP, the COP decreases, while the critical condensing pressure first increases and then decreases. As the area ratio of the miniature ejector increases, the COP increases, and the critical condensing pressure decreases.

Thermodynamic peculiarities of alpha-type Stirling engines for low-temperature difference power generation: Optimisation of operating parameters and heat exchangers using a third-order model

2013 ◽  
Vol 228 (11) ◽  
pp. 1936-1947 ◽  
Author(s):  
Benedikt Hoegel ◽  
Dirk Pons ◽  
Michael Gschwendtner ◽  
Alan Tucker ◽  
Mathieu Sellier
Keyword(s):  
High Temperature ◽  
Low Temperature ◽  
Temperature Difference ◽  
Heat Exchangers ◽  
Operating Parameters ◽  
Heat Sources ◽  
Third Order ◽  
Concentrated Solar Energy ◽  
Stirling Engines ◽  
Temperature Heat

Low-temperature heat sources such as waste heat and geothermal energy in the range from 100 ℃ to 200 ℃ are widely available and their potential is largely untapped. Stirling engines are one possibility to convert this heat to a usable power output. Much work has been done to optimise Stirling engines for high-temperature heat sources such as external combustion or concentrated solar energy but only little is known about suitable engine layouts at lower temperature differences. With the reduced temperature difference, changes become necessary not only in the heat exchangers and the regenerator but also in the operating parameters such as frequency and phase angle. This paper shows results obtained from a third-order simulation model that help to identify beneficial parameter combinations, and explains the differences of low and high-temperature engines.

Tests on High-Pressure Water Rotational Jetting Ventilation Cooling Characteristic

2012 ◽  
Vol 594-597 ◽  
pp. 2073-2076
Author(s):  
Zhong Fei Ma ◽  
Li Chen ◽  
Fu Qin Wang
Keyword(s):  
Experimental Study ◽  
High Pressure ◽  
High Temperature ◽  
Cooling Rate ◽  
Temperature Difference ◽  
Water Pressure ◽  
Obvious Effect ◽  
Guide Vanes ◽  
Parabolic Growth ◽  
Pressure Water

In order to improve the cooling effect and practical applicability of falling temperature technique on high-temperature workplaces, the aeration and cooling principle of the high pressure water rotational jetting ventilation were analysed, and the experimental study was carried out. The results show that water pressure and cooling rate are an approximation of parabolic growth relationship, different structure of jet tube and temperature difference on water and gas also have an obvious effect on the cooling amplitude and air quantity. the guide vanes installed may improve effect of ventilation and cooling the capacity on high pressure water rotational jetting.

Cracking Mechanism of Long Concrete Bedding Cushion and Prevention Method

2010 ◽  
Vol 163-167 ◽  
pp. 880-887 ◽  
Author(s):  
Zhen Yang Zhu ◽  
Sheng Qiang ◽  
Min Zhi Liu ◽  
Hai Bo Wang
Keyword(s):  
High Temperature ◽  
Temperature Difference ◽  
Temperature Fluctuation ◽  
Control Measure ◽  
Temperature Drop ◽  
Thermal Control ◽  
Cold Season ◽  
Control Measures ◽  
3D Fem ◽  
Cracking Mechanism

The long concrete bedding cushions are more vulnerable to cracking than the dam concrete, even the cushion is much shorter than the dam block, especially those constructed in hot season and the off period lasts long. The cracking mechanism of such cushion is studied and presented in this paper. There are several reasons contribute to the cracks of bedding cushion, but the thermal stress is the main factor. The temperature distribution is always unevenly during the construction period of bedding cushion. During the long off period, temperature drop in local high temperature zone, temperature fluctuation and temperature difference between inside and surface are the main factors causing cracks for bedding cushion without proper thermal control measures. Some thermal control measures are always used in practical engineering, but it can not always effectively prevent bedding cushion from cracking. Reasonable water pipes cooling measure, which can prevent local high temperature at the early age of construction, and effective heat preservation measures in cold season, which can reduce temperature difference between inside and surface and temperature fluctuation, are necessary to prevent cracking. One bedding cushion of concrete dam is numerically stimulated by 3D FEM, and effective temperature control measure is proposed in this paper.

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