scholarly journals Model Tests on the Antibreaking Countermeasures for Tunnel Lining Across Stick-Slip Faults

2020 ◽  
Vol 2020 ◽  
pp. 1-10 ◽  
Author(s):  
Guang-yao Cui ◽  
Xue-lai Wang ◽  
Zheng-zheng Wang ◽  
Dao-yuan Wang
Keyword(s):  
Contact Pressure ◽  
Safety Factor ◽  
Longitudinal Strain ◽  
Operating Conditions ◽  
Structural Safety ◽  
Tunnel Structure ◽  
Stick Slip ◽  
Slip Dislocation ◽  
Dislocation Layer ◽  
Minimum Safety Factor

In order to improve the structural safety and stability of the tunnels crossing stick-slip fault, an indoor model test on the effect of tunnel antibreaking measures under the influence of fault stick-slip movements was conducted. Using contact pressure, longitudinal strain, and safety factor, the antibreaking effect of tunnels was compared and analyzed under 5 kinds of operating conditions, mainly including no measures, structural strengthening, structural strengthening and reducing dislocation layer, structural strengthening and reducing dislocation joint, structural strengthening and reducing dislocation layer, and reducing dislocation joint. The results showed that the longitudinal strain and contact pressure of the tunnel changed markedly (from severe change to more uniform change) when the reducing dislocation measures were adopted in the test, reducing dislocation layer/joint or reducing dislocation layer and reducing dislocation joint. The effect of reducing the fault stick-slip dislocation on the tunnel structure is very limited by only taking structure strengthening measures. The effect of reducing the fault stick-slip dislocation on the tunnel structure is obvious by using the reducing dislocation method, and the minimum safety factor is increased by more than 8 times. The effect of resisting and reducing the fault stick-slip dislocation on the tunnel structure is remarkable by adopting the measures of the structural strengthening and reducing dislocation layer and reducing dislocation joint, and the minimum safety factor is increased by more than 25.45 times. The results can provide reference for the design of antibreaking for the stick-slip fault tunnel in high earthquake intensity and dangerous mountainous areas.

scholarly journals Test on Rigid-flexible Composite Anti-breaking Measure for Tunnels across Stick-slip Fault

2021 ◽  
Author(s):  
Cui Guang-yao ◽  
Song Bohan
Keyword(s):  
Seismic Intensity ◽  
Structural Safety ◽  
Tunnel Structure ◽  
Test Results ◽  
Tunnel Engineering ◽  
Stick Slip ◽  
Breaking Effect ◽  
Secondary Lining ◽  
Dislocation Layer ◽  
Primary Support

Abstract In this paper, based on the F8 stick-slip fault section of Longxi Tunnel in China, the effect of the anti-breaking measure of rigid-flexible composite (reinforcement of the secondary lining & construction of the reducing dislocation layer between the primary support and the secondary lining) is studied by using the method of indoor model test in order to improve the anti-breaking performance of the tunnel across stick-slip fault in the actual tunnel engineering. The test results show that the anti-breaking effect is limited by adopting structural strengthening measures to resist the influence of stick-slip dislocation on the tunnel structure and the anti-breaking effect is obvious by adopting the measures of reducing dislocation layer only. However, the structural safety of the tunnel with stick-slip fault in the strong seismic intensity area can be greatly improved by adopting the anti-breaking measure of rigid-flexible composite, and the structural safety factor can be significantly improved. The research results of this paper can provide a reference for the anti-breaking design of the tunnel across stick-slip fault in the high seismic intensity area.

Experimental Exploration of Schallamach Waves and Self-Excitation in a Belt-Drive System

2018 ◽  
Author(s):  
Yingdan Wu ◽  
Michael Varenberg ◽  
Michael J. Leamy
Keyword(s):  
Angular Velocity ◽  
Dynamic Behavior ◽  
Oscillation Amplitude ◽  
Operating Conditions ◽  
Drive System ◽  
Belt Drive ◽  
Stick Slip ◽  
Stick Slip Motion ◽  
System Inertia ◽  
Slip Motion

We study the dynamic behavior of a belt-drive system to explore the effect of operating conditions and system moment of inertia on the generation of waves of detachment (i.e., Schallamach waves) at the belt-pulley interface. A self-excitation phenomenon is reported in which frictional fluctuations serve as harmonic forcing of the pulley, leading to angular velocity oscillations which grow in time. This behavior depends strongly on operating conditions (torque transmitted and pulley speed) and system inertia, and differs between the driver and driven pulleys. A larger net torque applied to the pulley generally yields more remarkable stick-slip oscillations with higher amplitude and lower frequency. Higher driving speeds accelerate the occurrence of stick-slip motion, but have little influence on the oscillation amplitude. Contrary to our expectations, the introduction of flywheels to increase system inertia amplified the frictional disturbances, and hence the pulley oscillations. This does, however, suggest a way of facilitating their study, which may be useful in follow-on research.

scholarly journals IMPROVING DYNAMIC REGIME OF ROLLING FOR INCREASING DURABILITY OF BALL-ROLLING MILL ROLLS

2019 ◽  
Vol 61 (12) ◽  
pp. 927-932 ◽  
Author(s):  
V. Yu. Rubtsov ◽  
O. I. Shevchenko ◽  
M. V. Mironova
Keyword(s):  
Contact Pressure ◽  
Rotational Speed ◽  
Rolling Mill ◽  
Experimental Studies ◽  
Rolling Process ◽  
Operating Conditions ◽  
Frequency Method ◽  
Rolling Mills ◽  
Ball Rolling ◽  
Progressive Technology

One  of  the  important  reasons  for  the  downtime  of  ball  rolling  mills  is  replacement  of  rolls  due  to  their  wear  and  tear.  The  degree  and  zones  of  critical  wear  of  ball  rolling  rolls  are  investigated  in  the  article, where the greatest wear is observed over the flanges in zone of billet  capture.  Conditions  necessary  to  capture  the  blank  and  to  perform  rolling  process  are  analytically  determined.  Variable  frequency  method  of  roll  rotations  is  proposed  as  a  progressive  technology  for  blank supply. The results of tests for its variations in accordance with  linear  and  quadratic  law  are  presented.  Known  formulas  determining  average  strain  rate  at  rolls  rotational  speed  change  are  converted  for  linear and quadratic dependences. Experimental studies have been carried  out  in  conditions  of  EVRAZ  Nizhnetagilsky  Metallurgical  Plant  ball rolling mills during rolling of 60mm ball made of Sh-3G steel. Experiments  were  performed  for  given  parameters  of  manual  change  in  rolls rotation speed at blank capture by rollers. The results have shown  a  significant  effect  of  change  in  rotational  speed  on  average  specific  pressure during blank capture. Evaluation of torque-time and average  contact  pressure  for  calculated  and  experimental  data  are  presented.  Empirical characteristics are also described at variable rotational speed  of rolls according to linear and quadratic law. Acceptable convergence  of results of calculated and empirical characteristics is determined. Engineering solution has been proposed for that task. It consists in installation of a thyristor converter. This solution allows reduction of rolls  speed before blank capture. Also, this solution will increase frequency  to  the  nominal  value  according  to  the  given  law  after  blank  capture.  As an obtained result, there is uniform distribution of average contact  pressure over the entire length of the roll under different operating conditions  of  mill  in  automatic  mode. Application  of  this  technique  will  reduce wear degree of the rolling tool. At the same time, productivity  of ball rolling mill will be maintained. Rolls consumption and number  of rolls change will decrease due to rolls wear.

Proof-Of-Concept of a Thermal Barrier Coated Titanium Cooling Layer for an Inside-Out Ceramic Turbine

2021 ◽  
Author(s):  
Antoine Gauvin-Verville ◽  
Patrick K. Dubois ◽  
Benoit Picard ◽  
Alexandre Landry-Blais ◽  
Jean-Sébastien Plante ◽  
...  
Keyword(s):  
Polymer Composite ◽  
Safety Factor ◽  
Gas Turbines ◽  
High Efficiency ◽  
Cooling Power ◽  
Thermal Barrier ◽  
Inlet Temperature ◽  
Turbine Stage ◽  
Minimum Safety Factor ◽  
Inside Out

Abstract Increasing turbine inlet temperature (TIT) of recuperated gas turbines would lead to simultaneously high efficiency and power density, making them prime candidates for low-emission aeronautics applications, such as hybrid-electric aircraft. The Inside-out Ceramic Turbine (ICT) architecture achieves high TIT by using compression-loaded monolithic ceramics. To resist inertial forces due to blade tip speed exceeding 450 m/s, the shroud of the ICT is made of carbon-polymer composite, wound around a metallic cooling ring. This paper demonstrates that it is beneficial to use a titanium alloy cooling ring with a thermal barrier coating (TBC), rather than nickel superalloys, for the interstitial cooling ring protecting the carbon-polymer from the hot combustion gases. A numerical Design of Experiments (DOE) analysis shows the design trade-offs between the minimum safety factor and the required cooling power for multiple geometries. An optimized high-pressure first turbine stage of a 500 kW microturbine concept using ceramic blades and a titanium cooling ring in an ICT configuration is presented. Its structural performance (minimum safety factor of 1.4) as well as its cooling losses (2% of turbine stage power) are evaluated. Finally, a 20 kW-scale prototype is tested at 300 m/s and a TIT of 1375 K during 4hrs to demonstrate the viability of the concept. Experiments show that the polymer composite was kept below its maximum safe operating temperature and components show no early signs of degradation.

STRUCTURAL ANALYSIS OF CARBON COMPOSITE FRAME FOR FOLDABLE ELECTRIC WHEELCHAIR DEVELOPMENT

2019 ◽  
Vol 19 (07) ◽  
pp. 1940045
Author(s):  
WOO SUK CHONG ◽  
MI YEON SHIN ◽  
CHANG HO YU
Keyword(s):  
Structural Analysis ◽  
Compressive Stress ◽  
Safety Factor ◽  
Carbon Composite ◽  
The Body ◽  
Frame Structure ◽  
Structural Safety ◽  
Maximum Displacement ◽  
Electric Wheelchair ◽  
Maximum Variation

Electric wheelchairs developed so far have difficulties for elderly people to use, because of their bulkiness and heavy weight. To address this problem, this study presents a design for the construction of an electric wheelchair with an application of light duty materials at frame and a foldable structure that can be easily loaded in a narrow space. A structural analysis was performed to evaluate the structural safety of the foldable wheelchair. For the purpose of analysis, a carbon composite was used as the material for the frame; Structure Mechanics Module of COMSOL Multiphysics was used as the analysis software; and for the boundary condition, the lower part of the body frame was fixed, and a load of 150[Formula: see text]kg was applied to the upper part of the wheelchair. According to the results of the structural analysis, a maximum displacement of 2.869[Formula: see text]mm occurred at the handle where the carbon composite was applied, and tensile and compressive stress of 103[Formula: see text]MPa and 107.3[Formula: see text]MPa, respectively, were measured at the seat part of the wheelchair where the load was applied. The safety factors were 7.5 and 5.5 for tensile stress and compressive stress, respectively. A maximum variation of 0.0872[Formula: see text]mm occurred at the aluminum wheel shaft, and a maximum variation of 0.2046[Formula: see text]mm occurred at the joint. The maximum stress was 116.3[Formula: see text]MPa that corresponded to a safety factor of 2.66; this indicates that the wheelchair can be considered to be structurally safe as the safety factor exceeds the initial target of 2.

Leakage Analysis of a High Pressure Flange Connection Under Bending Moments: An Analytic Procedure

2014 ◽  
Author(s):  
Matthias Bortz ◽  
Rolf Wink
Keyword(s):  
High Pressure ◽  
Contact Pressure ◽  
Fluid Pressure ◽  
Safety Margin ◽  
Bending Moment ◽  
Operating Conditions ◽  
Bending Moments ◽  
Spherical Lens ◽  
Flange Connection ◽  
Bolt Stress

High pressure flange connections for LDPE plants are designed using lens ring gaskets and bolted flange connections. The sealing principle is to achieve a high contact pressure between the spherical lens shape and the conical tube end. This contact pressure must exceed the fluid pressure by a safety margin under all operating conditions. Bending moments acting on the flange connection will create an uneven distribution of contact pressure over the lens ring surface. In this paper a procedure is shown to analyse the influence of the bending moment under consideration of internal pressure on a flange connection using 3-dimensional finite element models. The variations in bolt stress and distribution of contact pressures due to the bending moment are of specific interest. A first approach will be provided to derive some simplified design rules regarding leakage assessment of such flange connections.

An investigation into contact pressure distribution in bolted joints

2014 ◽  
Vol 228 (18) ◽  
pp. 3405-3418 ◽  
Author(s):  
JT Stephen ◽  
MB Marshall ◽  
R Lewis
Keyword(s):  
Pressure Distribution ◽  
Contact Pressure ◽  
Applied Load ◽  
Plate Thickness ◽  
Operating Conditions ◽  
Bolted Joints ◽  
Bolted Joint ◽  
Contact Pressure Distribution ◽  
Engineering Structures ◽  
Peak Value

Bolted joints are widely used in modern engineering structures and machine designs due to their low cost and reliability when correctly selected. Their integrity depends on quantitative representation of the contact pressure distribution at the interface during design. Because of the difficulty in reaching and assessing clamped interfaces with traditional experimental methods, presently bolted joint design and evaluation is based on theoretical analysis, with assumptions to quantify pressure distribution at the clamped interface, which may not represent their true operating conditions. The present work utilises a non-intrusive ultrasonic technique to investigate and quantify the pressure distribution in bolted joints. The effect of variation in plate thickness on the contact pressure distribution at bolted interfaces under varying axial loads is investigated. While it was observed that the contact pressure at the interface increases as the applied load increases, the distance from the edge of the bolt hole at which the distribution becomes stable is independent of the applied load on the bolted joint. However, the contact pressure distribution was observed to vary with the plate thickness. Although the variation in the peak value of the average contact pressure distribution in bolted joints does not depend on the plate thickness, the distance from the edge of bolt hole at which the value of the distribution becomes stable increases as the plate thickness is increased. It was also observed that the edge of the bolt head affected the position of the peak value of the contact pressure distribution at the interface, though its effect was dependent on plate thickness. Furthermore, a model based on a Weibull distribution has been proposed to fit the experimental data and a good correlation was observed.

Numerical Simulation Method Research on Pellet-Cladding Mechanical Interaction Based on ABAQUS Software

2020 ◽  
Author(s):  
Changbing Tang ◽  
Yongjun Jiao ◽  
Yuanming Li ◽  
Yi Zhou ◽  
Kun Zhang
Keyword(s):  
Performance Analysis ◽  
Contact Pressure ◽  
Nuclear Fuel ◽  
Local Stress ◽  
Simulation Method ◽  
Operating Conditions ◽  
Effective Control ◽  
Mechanical Interaction ◽  
Fuel Performance ◽  
Abaqus Software

Abstract The cladding acts as the first barrier to prevent the release of radioactive fission products, requiring its structural integrity to be maintained throughout the whole operation period of nuclear reactor. Therefore, cladding failure due to PCI (pellet claading mechanical interaction) should be avoided as much as possible in fuel design and operating conditions. At the same time, it is necessary to achieve effective control of the cladding stress by limiting the power growth rate etc. However, in the manufacturing process of fuel rod, the MPS (missing pellet surface) defect is inevitably generated. This defect may lead to a substantial increase in the local stress of the cladding, which in turn exceeds its corresponding stress limit, resulting in cladding failure. Accurate simulation of fuel performance caused by such defects will help prevent such failures. The traditional fuel performance analysis codes are based on a 1.5D analysis framework and cannot handle the local asymmetry problem of fuel such as the MPS defect. In order to accurately simulate the PCI phenomenon caused by the MPS defect, this research establishes a fuel performance analysis code based on the ABAQUS software and this code is suit for the 2D and 3D conditions. Based on the established analysis code, the irradiation-thermal-mechanical behavior of nuclear fuel under typical II transient conditions was studied, and the sensitivity analysis of the influence of different MPS sizes on the local stress of cladding was carried out. The simulation results show that :(1)the mises stress, contact pressure and equivalent creep strain of the cladding may be unevenly distributed due to the MPS defect.(2)the MPS defect will result in a more severe contact pressure on cladding during power transient period, which may lead to failure of cladding and should be prevented. The simulation method established in this research could be very help for the performance analysis for the nuclear fuel rods.

scholarly journals Study on the Model Test of the Antibreaking Effect of Fiber Reinforced Concrete Lining in Tunnel

2020 ◽  
Vol 2020 ◽  
pp. 1-11
Author(s):  
Guang-yao Cui ◽  
Xue-lai Wang ◽  
Dao-yuan Wang
Keyword(s):  
Reinforced Concrete ◽  
Safety Factor ◽  
Model Test ◽  
Active Fault ◽  
Fiber Reinforced Concrete ◽  
Structural Safety ◽  
Concrete Lining ◽  
Fiber Reinforced ◽  
Hybrid Fiber ◽  
Earthquake Intensity

In order to study the antibreaking effect of the fiber reinforced concrete lining in the tunnel, this paper takes the a subway tunnel engineering project in F2-3 section of Jiujiawan fault as the research background and carries out the antibreaking model test of the fiber reinforced concrete lining in the active fault zone of high earthquake intensity. The results show that the antibreaking effect of the principle stress and the longitudinal strain of the fiber reinforced concrete lining are 30%∼40% and 80%∼90%, respectively, and the minimum value of the structural safety factor is increased by 4∼5 times. The antibreaking effect of hybrid fiber reinforced concrete lining is better than that of steel fiber reinforced concrete lining. The safety of steel polypropylene hybrid fiber reinforced concrete tunnel lining is the highest, and its minimum structural safety factor is 1.62. In the aspect of improving the antibreaking effect of the tunnel, the toughening effect of fiber reinforced concrete is stronger than that of reinforcing. The research results are of great significance to improve the antibreaking effect of tunnels in active fault areas with high earthquake intensity.

Tube-to-Tubesheet Joints: Maximum Tensile Stress and Contact Pressure Due to Thermal Loading and Temperature Cycling

2002 ◽  
Author(s):  
Mahdi A. Allam ◽  
Andre Bazergui ◽  
Luc Marchand ◽  
Michel Derenne
Keyword(s):  
Finite Element ◽  
Residual Stresses ◽  
Finite Element Model ◽  
Contact Pressure ◽  
Thermal Loading ◽  
Element Model ◽  
Maximum Tensile Stress ◽  
Temperature Cycling ◽  
Operating Conditions ◽  
Service Reliability

Service reliability and durability of tubular heat exchangers and steam generators are much dependent on the proper response of the tube-to-tubesheet joints to the operating conditions. In this paper a 2-D axisymmetric finite element model is proposed and compared to a 3-D finite element solution for the purpose of predicting the temperature effect on the residual contact pressure and maximum tensile residual stresses of such joints. A parametric study using the finite element results shows that, although thermal loading and temperature cycling have a negligible effect on the maximum tensile residual stresses, the room-temperature initial residual contact pressure may be completely relieved following the initiation of plastic deformation in either the tube or the tubesheet during thermal loading. A comparison between the results of the proposed finite element model and those obtained from the literature shows good agreement. A simplified analytical approach, which may be used for the design of tube-to-tubesheet joints, is also proposed to predict the joint behavior at the operating conditions.

Sign in / Sign up

Export Citation Format

Share Document