To address the increasing demand for corrosion-resistant shaft components,a bi-metallic composite shaft comprising carbon steel,which is known for its high thermal strength,and stainless cladding,which offers excellen...To address the increasing demand for corrosion-resistant shaft components,a bi-metallic composite shaft comprising carbon steel,which is known for its high thermal strength,and stainless cladding,which offers excellent corrosion resistance,was introduced.A novel method for manufacturing these composite shaft parts using cross-wedge rolling(CWR)was proposed and explored.Thermal simulation experiments,CWR forming trials and finite element analysis were conducted to examine the coordinated deformation during the CWR process.The results revealed a downhill diffusion pattern of elements from higher to lower-concentration areas,forming a smooth and uniform concentration gradient.When the cladding thickness(CT)ranged from 3 to 4 mm,the trajectories of the points on both the cladding material and the substrate coincided,indicating strong bonding at the transitional interface of the composite shaft.Conversely,with a CT of 5 mm,coordinated deformation between the substrate and cladding material was not achieved.Shear strength tests demonstrated a gradual decrease in strength with increasing CT.The microscopic morphology of the interface showed that the metal grains near both sides of the interface were refined,and the binding interface displayed a slightly curved shape.A viable method was provided for producing high-performance corrosion-resistant composite shaft components using CWR technology.展开更多
The smoke spreading law of urban transportation tunnels with multiple shafts under natural ventilation is studied.A full-scale burning experiment is conducted in an actual tunnel.The study shows that smoke temperature...The smoke spreading law of urban transportation tunnels with multiple shafts under natural ventilation is studied.A full-scale burning experiment is conducted in an actual tunnel.The study shows that smoke temperatures below the tunnel ceiling reduce rapidly along the longitudinal towards the tunnel exits. A noticeable temperature stratification is observed near the fire source.Most fire smoke is exhausted out of the shafts while the number of the smoke shafts in the downstream is more than that in the upstream.Large eddy simulation LES based on computational fluid dynamics CFD is carried out using the fire dynamics simulator FDS software with parallel processing in which the grid size of the fire-domain is set to be 0.083 m.The simulation results of temperatures under the ceiling the smoke fronts and the shafts＇smoke exhaust or air supply agree reasonably with the experimental data. Further simulations indicate that the decreasing ambient temperature or shaft spacing might reduce smoke temperatures under the tunnel ceiling and increase mass flow rates out of the shafts.This study provides technical scientific evidence and supports for the design and construction of such kinds of tunnels.展开更多
The safety of the initial support during the construction of inclined shafts in tunnels traversing through high-hydraulic-pressure surrounding rocks is paramount.This study examines a high-hydraulic-pressure inclined ...The safety of the initial support during the construction of inclined shafts in tunnels traversing through high-hydraulic-pressure surrounding rocks is paramount.This study examines a high-hydraulic-pressure inclined shaft of a tunnel in Western Sichuan Province to analyze the damage characteristics of the initial support and propose a radial drainage and decompression treatment method.Field monitoring was conducted to assess the load and deformation of the initial support structure,and on-site investigations identified the distribution of cracked areas.In addition,numerical simulations were performed to evaluate the force and deformation characteristics of the initial support structure,which were then compared with field observations for validation.The variations in the lateral pressure coefficient and water pressure were evaluated.The results revealed that damage was primarily concentrated in the shoulder,spring line,and knee areas,with the bending moment at the knee increasing by up to 66.9%.The application of the radial drainage and decompression treatment method effectively reduced water pressure loads on the initial support.Post-treatment analysis indicated significant reductions in axial force and bending moment,enhancing structural stability.These findings provide valuable insights for improving the safety and durability of initial support systems in inclined shafts of high-hydraulicpressure railroad tunnels.展开更多
A novel steel–carbon fibre/polyetheretherketone(CF/PEEK)hybrid shaft is proposed,considering the thermal stability,negative coefficient of thermal expansion in fibre orientation,and high stiffness of CF/PEEK,which is...A novel steel–carbon fibre/polyetheretherketone(CF/PEEK)hybrid shaft is proposed,considering the thermal stability,negative coefficient of thermal expansion in fibre orientation,and high stiffness of CF/PEEK,which is expected to suppress the thermal deformation of shafts.A laser-assisted in-situ consolidation(LAC)process,together with its equipment,was developed to manufacture the hybrid shaft.Firstly,the optimal process parameters,including the laser-heated temperature and placement speed,were investigated.A maximum short-beam shear strength of 80.7 MPa was achieved when the laser-heated temperature was 500°C and the placement speed was 100 mm/s.In addition,the failure modes and the effect of environmental temperature on the CF/PEEK samples were analyzed.Both interlayer cracks and inelastic deformation failure modes were observed.The formation and propagation of cracks were further investigated through digital image correlation(DIC).Furthermore,internal defects of the CF/PEEK sample were detected using X-ray tomography scans,and a minimum porosity of 0.23%was achieved with the optimal process parameters.Finally,two steel–CF/PEEK hybrid shafts,with different fibre orientations,were manufactured based on the optimal process parameters.The surface temperature distributions and thermal deformations were investigated using a self-established deformation/temperature measurement platform.The hybrid shaft showed an 85.7%reduction in radial displacement with hoop fibre orientation and an 11.5%reduction in axial displacement with cross fibre orientation compared with the steel shaft.The results indicate that the proposed method has great potential to improve the thermal stability of hybrid shafts and the accuracy of machine tools.展开更多
The paper presents the results of a thermo-mechanical analysis of the rolling two stepped shafts.One of the shafts has a toothed step with skew teeth,while the other has a worm winding in the shape of a trapezoidal sc...The paper presents the results of a thermo-mechanical analysis of the rolling two stepped shafts.One of the shafts has a toothed step with skew teeth,while the other has a worm winding in the shape of a trapezoidal screw.The shape of the rolling tools resembles that of the tools used in the Roto-Flo rolling method;yet unlike in Roto-Flo,the shafts are hot-rolled and no centres are used to stabilize the position of the workpiece during the forming process.For the calculations made with use of the DEFORM-3D process simulation system it has been assumed that the rolled shafts are made from 2618 aluminium alloy.As a result of the calculations made,it has been found that the toothed stepped shafts can be formed in one pass by means of the cross rolling process.Additionally,the temperature and strain distribution in the rolled product have been determined as well as some data concerning the forces which are necessary for the rolling process have been obtained.展开更多
In civil and mining operations that involve ground excavation and support, the loads are distributed between the ground and support depending on their relative stiffness. This paper presents the development of concept...In civil and mining operations that involve ground excavation and support, the loads are distributed between the ground and support depending on their relative stiffness. This paper presents the development of conceptual single-degree-of-freedom models, which are used to derive equations for estimating displacements and stresses for ground-support interaction problems encountered in pillars in room-andpillar mining(natural support system), and liners for circular vertical shafts(artificial support systems).For pillar assessment, mine-pillar interaction curves can be constructed using a double spring analogy.Additionally, the effectiveness of different support systems can be evaluated depending on their effect upon the mine-pillar system. For shaft design, an initial estimation of the required lining strength and thickness can be readily made based on a double ring analogue. For both problems, the results from the proposed approach compare well with those obtained by finite element numerical simulations.展开更多
Norwegian hydropower industry has more than 100 years of experiences in constructing more than4000 km-long unlined pressure shafts and tunnels with maximum static head of 1047 m（equivalent to almost 10.5 MPa） reache...Norwegian hydropower industry has more than 100 years of experiences in constructing more than4000 km-long unlined pressure shafts and tunnels with maximum static head of 1047 m（equivalent to almost 10.5 MPa） reached at unlined pressure tunnel of Nye Tyin project. Experiences gained from construction and operation of these unlined pressure shafts and tunnels were the foundation to develop design criteria and principles applied in Norway and some other countries. In addition to the confinement criteria, Norwegian state-of-the-art design principle for unlined pressure shaft and tunnel is that the minor principal stress at the location of unlined pressure shaft or tunnel should be more than the water pressure in the shaft or tunnel. This condition of the minor principal stress is prerequisite for the hydraulic jacking/splitting not to occur through joints and fractures in rock mass. Another common problem in unlined pressure shafts and tunnels is water leakage through hydraulically splitted joints or pre-existing open joints. This article reviews some of the first attempts of the use of unlined pressure shaft and tunnel concepts in Norway, highlights major failure cases and two successful cases of significance, applies Norwegian criteria to the cases and reviews and evaluates triggering factors for failure.This article further evaluates detailed engineering geology of failure cases and also assesses common geological features that could have aggravated the failure. The minor principal stress is investigated and quantified along unlined shaft and tunnel alignment of six selected project cases by using threedimensional numerical model. Furthermore, conditions of failure through pre-existing open joints by hydraulic jacking and leakage are assessed by using two-dimensional fluid flow analysis. Finally, both favorable and unfavorable ground conditions required for the applicability of Norwegian confinement criteria in locating the unlined pressure shafts and tunnels for geotectonic environment different from that of Norway are highlighted.展开更多
The torsional oscillation characteristics on the bending and torsioh coupled vibration of rotary shaft system were investigated using the elasto-dynamic theory and other mathematic methods, such as difference approach...The torsional oscillation characteristics on the bending and torsioh coupled vibration of rotary shaft system were investigated using the elasto-dynamic theory and other mathematic methods, such as difference approach, Fourier transform, and wavelet transform. It is concluded that mass eccentricity and other exciting modalities affect the bending and torsion coupled vibration of rotary shafts. Torsional vibration caused by bending vibration features linearity along with the change of amplitude of bending vibration. Meanwhile, energy spectrum concentrates on high frequency area with the wavelet analysis.展开更多
Composite hollow shafts are used in power transmission applications due to their high specific stiffness and high specific strength.The dynamic characteristics of these shafts are important for transmission applicatio...Composite hollow shafts are used in power transmission applications due to their high specific stiffness and high specific strength.The dynamic characteristics of these shafts are important for transmission applications.Dynamic modelling of these shafts is generally carried out using Equivalent Modulus Beam Theory(EMBT)and Layerwise Beam Theory(LBT)formulations.The EMBT formulation is modified by considering stacking sequence,shear normal coupling,bending twisting coupling and bending stretching coupling.It is observed that modified EMBT formulation is underestimating the shafts stiffness at lower length/mean diameter(l/dm)ratios.In the present work,a new formulation is developed by adding shear deformation along the thickness direction to the existing modified EMBT formulation.The variation of shear deformation along the thickness direction is found using different shear deformation theories,i.e.,first-order shear deformation theory(FSDBT),parabolic shear deformation theory(PSDBT),trigonometric shear deformation theory(TSDBT),and hyperbolic shear deformation theory(HSDBT).The analysis is performed at l/d_(m) ratios of 5,10,15,20,25,30,35,and 40 for carbon/epoxy composites,E-glass/epoxy composites,and boron/epoxy composite shafts.The results show that new formulation has improved the bending natural frequency of the composite shafts for l/d_(m)<15 in comparison with modified EMBT.The effect of new formulation is more significant for the second and third bending modes of natural frequencies.展开更多
With the growing global environmental awareness,the development of renewable and green materials has gained increased worldwide interest to substitute conventional materials and are favorable for sustainable economic ...With the growing global environmental awareness,the development of renewable and green materials has gained increased worldwide interest to substitute conventional materials and are favorable for sustainable economic development.This paper proposed a novel eco-friendly sound absorbing structure(NSAS)liner for noise reduction in elevator shafts.The base layer integrated with the shaft walls is a damping gypsum mortarboard,and a rock wool board and a perforated cement mortarboard are used to compose the NSAS.Based on the acoustic impedance theory of porous materials and perforated panels,the sound absorption theory of the NSAS was proposed;the parameter effects of the rock wool board(flow resistivity,porosity,structure factor)and perforated panel(perforated rates,thickness,density,perforated diameter)on NSAS absorption were discussed theoretically for absorption improvement,and experiments were also conducted.Numerical results showed that the perforation rate,the thickness of the perforated plate,and the porosity,flow resistance,and volume density of the rock wool board played a key issue in the absorption performances of the NSAS.Experiments verified the accuracy of the proposed theoretical model.Wideband sound absorption performance of the NSAS at frequencies between 500–1600 Hz was achieved in both numerical analysis and experiments,and the sound absorption coefficient was improved to 0.72 around 1000 Hz after parameter adjustments.The NSAS proposed in this paper can also be made of other renewable materials with preferable structure strength and still has the potential to broaden the absorption bandwidth.It can provide a reference for controlling the elevator shaft noise.展开更多
This paper presents an investigation of non-stationary induction heating process applied to AISI 4340 steel spline shafts based on 3D simulation and experimental validation. The study is based on the knowledge, concer...This paper presents an investigation of non-stationary induction heating process applied to AISI 4340 steel spline shafts based on 3D simulation and experimental validation. The study is based on the knowledge, concerning the form of correlations between various induction heating parameters and the final hardness profile, developed in the case of stationary induction heating. The proposed approach focuses on analyzing the effects of variation of frequency, power and especially scanning speed through an extensive 3D finite element method simulation, comprehensive sensitivity study and structured experimental efforts. Based on coupled electromagnetic and thermal fields analysis, the developed 3D model is used to estimate the temperature distribution and the hardness profile. Experimentations conducted on a commercial dual-frequency induction machine for AISI 4340 steel splines confirm the feasibility and the validity of the proposed modelling procedure. The 3D model validation reveals a great concordance between simulated and measured results, confirms that the model can effectively be used as framework for understanding the process and for assessing the effects of various parameters on the hardening process quality and performance and consequently leads to the most relevant variables to use in an eventual hardness profile prediction model.展开更多
<div style="text-align:justify;"> In most cases, copper ore deposits occur at great depths, so the optimization of excavation costs is of utmost importance to identify the most cost effective and produ...<div style="text-align:justify;"> In most cases, copper ore deposits occur at great depths, so the optimization of excavation costs is of utmost importance to identify the most cost effective and productive mining methods, such as block caving or similar methods specifically developed for these deposits. To be able to apply such methods, it is necessary to have a detailed knowledge of the rock mass in terms of its geomechanical, engineering geological and hydrogeological characteristics. This research aims to reduce geological and geotechnical unknowns, analyze in detail the geological environment, and predict geotechnical conditions for the construction of the shaft. This paper uses the example of Borska Reka Copper Deposit, located in Serbia to illustrate the importance of geotechnical investigation to enable best practice in design and construction of shafts that are over 1000 m deep. </div>展开更多
A reliability based analysis method for a drilled shaft stabilized slope system is presented in this paper. The drilled shaft stabilization mechanisms for the slope were treated as the drilled shaft induced soil archi...A reliability based analysis method for a drilled shaft stabilized slope system is presented in this paper. The drilled shaft stabilization mechanisms for the slope were treated as the drilled shaft induced soil arching, which was quantified by the load transfer factor in the limited equilibrium analysis. However, due to the inherent uncertainties of the soil properties and the model error of the semi-empirical load transfer equation, an extension modification of the deterministic method into a probabilistic method is developed in this paper. The MCS （Monte Carlo simulation） with log-normal random variables has been employed to calculate the probability of failure （Pf） for the drilled shafts/slope system. The developed theories were coded into a computer program for analyzing complex slope geometry and slope profile conditions. Finally, a case study has been performed to illustrate the application analysis of the developed probability approach in drilled shafts/slope system.展开更多
The deformation principles of the steady- state and the unsteady一state of open- die cold extrusion for involute spline shafts are analyzed by means of experiments. On one hand,based on the deformation princ...The deformation principles of the steady- state and the unsteady一state of open- die cold extrusion for involute spline shafts are analyzed by means of experiments. On one hand,based on the deformation principles of the steady- state, data for determining structural parameters of the die, the size of the billet and the constraint condition of this technique are given. On the other hand, according to the principles of the unsteady- state, data for modifying the shapes and sizes of the bil- lets are provided.展开更多
The determination of gas pressure before uncovering coal in cross-cuts and in shafts is one of the important steps in pre- dicting coal and gas outbursts. However, the time spent for testing gas pressure is, at presen...The determination of gas pressure before uncovering coal in cross-cuts and in shafts is one of the important steps in pre- dicting coal and gas outbursts. However, the time spent for testing gas pressure is, at present, very long, seriously affecting the ap- plication of outburst prediction techniques in opening coal seams in cross-cuts and shafts. In order to reduce the time needed in gas pressure tests and to improve the accuracy of tests, we analyzed the process of gas pressure tests and examined the effect of the length of boreholes in coal seams in tests. The result shows that 1) the shorter the borehole, the easier the real pressure value of gas can be obtained and 2) the main factors affecting the time spent in gas pressure tests are the length of the borehole in coal seams, the gas emission time after the borehole has been formed and the quality of the borehole-sealing. The longer the length of the bore- hole, the longer the gas emission time and the larger the pressure-relief circle formed around the borehole, the longer the time needed for pressure tests. By controlling the length of the borehole in a test case in the Huainan mining area, and adopting a quick sealing technique using a sticky liquid method, the sealing quality was clearly improved and the gas emission time as well as the amount of gas discharged greatly decreased. Before the method described, the time required for the gas pressure to increase during the pressure test process, was more than 10 days. With our new method the required time is only 5 hours. In addition, the accuracy of the gas pressure test is greatly improved.展开更多
The circumferential vibration of a gear pair is a parametric excitation caused by nonlinear tooth stiffness,which fluctuates with meshing.In addition,the vibration characteristics of the gear pair become complicated o...The circumferential vibration of a gear pair is a parametric excitation caused by nonlinear tooth stiffness,which fluctuates with meshing.In addition,the vibration characteristics of the gear pair become complicated owing to the tooth profile error and backlash.It is considered that the circumferential vibration of the gear pair is affected by the torsional vibration of the shafts.It is important to understand quantitatively the vibration characteristics of the gear system considering the shafts.Therefore,the purpose of this research was to clarify the nonlinear vibration characteristics of a gear pair considering the influence of the shafts using theoretical methods.To achieve this objective,calculations were performed using equations of motion in which the circumferential vibration of the gear pair and the torsional vibration of the shafts were coupled.The nonlinear tooth stiffness was represented by a sine wave.The influence of tooth separation was considered by defining a nonlinear function using backlash and the tooth profile error.For the numerical calculations,both stable and unstable periodic solutions were obtained by using the shooting method.The effect of the shafts on the gear system vibration were clarified by comparing the results in the cases in which the shaft was not considered,one shaft was considered,and both shafts were considered.展开更多
A new concept for forming eccentric shafts on the basis of the cross-wedge rolling （CWR） process was presented. This concept was based on the application of special guides, which, by acting on a billet, lead to its ...A new concept for forming eccentric shafts on the basis of the cross-wedge rolling （CWR） process was presented. This concept was based on the application of special guides, which, by acting on a billet, lead to its controlled movement in the vertical direction. This movement made possible eccentric cutting of tools into the billet. FEM calculations and experimental rolling tests clearly confirmed the effectiveness of the proposed forming method.展开更多
In this study, the finite element numerical modelling of 2D shaft sections in a Hoek–Brown medium are carried out in a non-hydrostatic stress state in an attempt to predict pressures developing around mine shafts. An...In this study, the finite element numerical modelling of 2D shaft sections in a Hoek–Brown medium are carried out in a non-hydrostatic stress state in an attempt to predict pressures developing around mine shafts. An iterative process of applying support pressure until observing no failure zone around the shaft is used to simulate the required lining support pressure for different shaft models. Later, regression analysis is carried out to find a generic shaft pressure equation representing the rock mass and the stress state. Finally, the developed pressure equation which shows a good agreement with a case study is used in elastic ‘‘thick-walled cylinder" equation to calculate the lining thickness required to prevent the development of a failure zone around the shaft. At the end of the study, a user-friendly object-oriented computer program ‘‘Shaft 2D" is developed to simplify the rigorous shaft lining thickness calculation process.展开更多
Rotary bending fatigue tests were carried out with two kinds of materials, S43C and S50C, using the front engine and front drive shaft （FF shaft） of vehicle. The specimens were induction hardened about 1.0mm depth f...Rotary bending fatigue tests were carried out with two kinds of materials, S43C and S50C, using the front engine and front drive shaft （FF shaft） of vehicle. The specimens were induction hardened about 1.0mm depth from the specimen surface, and the hardness value on the surface was about HRC56-60. The tested environment temperatures were -30, 25 and 80℃ in order to look over effect of the induction hardening and the environmental temperatures on the fatigue characteristics. The fatigue limit of induction hardened specimens increased more about 45% than non-hardened specimens showing that the endurances of S43C and S50C were 98.1 and 107.9MPa in non-hardened samples, 147.1 and 156.9MPa in hardened samplesrespectably. The maximum tensile and compressive stress on the small circular defect was about ＋250 and -450MPa respectively when circular defect is situated on top and bottom. The fatigue life increased 80, 25 and -30℃ in order regardless of hardening. In comparison of the fatigue lives on the basis of tested result at 25℃, the fatigue lives of non-hardened specimens decreased about 35%, but that of hardened specimens decreased about only 5% at 80℃ more than at 25℃. And fatigue life of non-hardened and hardened specimens were about 110% and 120% higher at -30℃ than that of 25℃. Based on the result of stress distribution near the defect, the tensile and compressive stress repeatedly generated by load direction were the largest on the small circular defect due to the stress concentration.展开更多
Currently the service life of CDQ shafts in China is mainly restricted by the properties of the inclined flue bricks.In this work,based on the systematic analysis of the damage mechanism of inclined flue refractories,...Currently the service life of CDQ shafts in China is mainly restricted by the properties of the inclined flue bricks.In this work,based on the systematic analysis of the damage mechanism of inclined flue refractories,high performance mullite-SiC bricks were developed.The bricks were produced by corundum,andalusite,SiC and other high purity raw materials.Metal silicon and alumina ultra micropowder were added to form dispersion multi-phase structure,fortifying the matrix and improving the microstructure.The products have excellent properties such as low porosity,high density,good wear resistance,high refractoriness under load,and good thermal shock resistance.The products can replace the ordinary mullite-SiC bricks and obtain a good service life.展开更多
基金supported by the National Key Research and Development Program of China(No.2022YFE0123700)the National Natural Science Foundation of China(No.52205329)the Beijing Natural Science Foundation(Nos.L212024 and L201010).
文摘To address the increasing demand for corrosion-resistant shaft components,a bi-metallic composite shaft comprising carbon steel,which is known for its high thermal strength,and stainless cladding,which offers excellent corrosion resistance,was introduced.A novel method for manufacturing these composite shaft parts using cross-wedge rolling(CWR)was proposed and explored.Thermal simulation experiments,CWR forming trials and finite element analysis were conducted to examine the coordinated deformation during the CWR process.The results revealed a downhill diffusion pattern of elements from higher to lower-concentration areas,forming a smooth and uniform concentration gradient.When the cladding thickness(CT)ranged from 3 to 4 mm,the trajectories of the points on both the cladding material and the substrate coincided,indicating strong bonding at the transitional interface of the composite shaft.Conversely,with a CT of 5 mm,coordinated deformation between the substrate and cladding material was not achieved.Shear strength tests demonstrated a gradual decrease in strength with increasing CT.The microscopic morphology of the interface showed that the metal grains near both sides of the interface were refined,and the binding interface displayed a slightly curved shape.A viable method was provided for producing high-performance corrosion-resistant composite shaft components using CWR technology.
基金The National Natural Science Foundation of China(No.51178217)the Natural Science Foundation of Jiangsu Province(No.BK2011804)
文摘The smoke spreading law of urban transportation tunnels with multiple shafts under natural ventilation is studied.A full-scale burning experiment is conducted in an actual tunnel.The study shows that smoke temperatures below the tunnel ceiling reduce rapidly along the longitudinal towards the tunnel exits. A noticeable temperature stratification is observed near the fire source.Most fire smoke is exhausted out of the shafts while the number of the smoke shafts in the downstream is more than that in the upstream.Large eddy simulation LES based on computational fluid dynamics CFD is carried out using the fire dynamics simulator FDS software with parallel processing in which the grid size of the fire-domain is set to be 0.083 m.The simulation results of temperatures under the ceiling the smoke fronts and the shafts＇smoke exhaust or air supply agree reasonably with the experimental data. Further simulations indicate that the decreasing ambient temperature or shaft spacing might reduce smoke temperatures under the tunnel ceiling and increase mass flow rates out of the shafts.This study provides technical scientific evidence and supports for the design and construction of such kinds of tunnels.
基金supported by the National Natural Science Foundation of China(Grant Nos.42277165,41920104007)the Hubei Natural Science Foundation(Grant No.2023AFD217).
文摘The safety of the initial support during the construction of inclined shafts in tunnels traversing through high-hydraulic-pressure surrounding rocks is paramount.This study examines a high-hydraulic-pressure inclined shaft of a tunnel in Western Sichuan Province to analyze the damage characteristics of the initial support and propose a radial drainage and decompression treatment method.Field monitoring was conducted to assess the load and deformation of the initial support structure,and on-site investigations identified the distribution of cracked areas.In addition,numerical simulations were performed to evaluate the force and deformation characteristics of the initial support structure,which were then compared with field observations for validation.The variations in the lateral pressure coefficient and water pressure were evaluated.The results revealed that damage was primarily concentrated in the shoulder,spring line,and knee areas,with the bending moment at the knee increasing by up to 66.9%.The application of the radial drainage and decompression treatment method effectively reduced water pressure loads on the initial support.Post-treatment analysis indicated significant reductions in axial force and bending moment,enhancing structural stability.These findings provide valuable insights for improving the safety and durability of initial support systems in inclined shafts of high-hydraulicpressure railroad tunnels.
基金supported by the National Nature Science Foundation of China(No.52175440)the Aeronautics Science Foundation of China(No.2023Z049076001)+3 种基金the Science and Technology Innovation Fund of Shanghai Aerospace(No.SAST2022-058)the Open Fund of State Key Laboratory of Mechanical Transmissions(No.SKLMT-MSKFKT-202202)the Key R&D Program of Zhejiang Province(No.2023C01058)the Experimental Technique Project of Zhejiang University(No.SYBJS202302),China.
文摘A novel steel–carbon fibre/polyetheretherketone(CF/PEEK)hybrid shaft is proposed,considering the thermal stability,negative coefficient of thermal expansion in fibre orientation,and high stiffness of CF/PEEK,which is expected to suppress the thermal deformation of shafts.A laser-assisted in-situ consolidation(LAC)process,together with its equipment,was developed to manufacture the hybrid shaft.Firstly,the optimal process parameters,including the laser-heated temperature and placement speed,were investigated.A maximum short-beam shear strength of 80.7 MPa was achieved when the laser-heated temperature was 500°C and the placement speed was 100 mm/s.In addition,the failure modes and the effect of environmental temperature on the CF/PEEK samples were analyzed.Both interlayer cracks and inelastic deformation failure modes were observed.The formation and propagation of cracks were further investigated through digital image correlation(DIC).Furthermore,internal defects of the CF/PEEK sample were detected using X-ray tomography scans,and a minimum porosity of 0.23%was achieved with the optimal process parameters.Finally,two steel–CF/PEEK hybrid shafts,with different fibre orientations,were manufactured based on the optimal process parameters.The surface temperature distributions and thermal deformations were investigated using a self-established deformation/temperature measurement platform.The hybrid shaft showed an 85.7%reduction in radial displacement with hoop fibre orientation and an 11.5%reduction in axial displacement with cross fibre orientation compared with the steel shaft.The results indicate that the proposed method has great potential to improve the thermal stability of hybrid shafts and the accuracy of machine tools.
基金the Structural Funds under the Innovative Economy Operational Programme (IE OP)financed from the European Regional Development Fund (No.POIG.0101.02-00-015/08)
文摘The paper presents the results of a thermo-mechanical analysis of the rolling two stepped shafts.One of the shafts has a toothed step with skew teeth,while the other has a worm winding in the shape of a trapezoidal screw.The shape of the rolling tools resembles that of the tools used in the Roto-Flo rolling method;yet unlike in Roto-Flo,the shafts are hot-rolled and no centres are used to stabilize the position of the workpiece during the forming process.For the calculations made with use of the DEFORM-3D process simulation system it has been assumed that the rolled shafts are made from 2618 aluminium alloy.As a result of the calculations made,it has been found that the toothed stepped shafts can be formed in one pass by means of the cross rolling process.Additionally,the temperature and strain distribution in the rolled product have been determined as well as some data concerning the forces which are necessary for the rolling process have been obtained.
文摘In civil and mining operations that involve ground excavation and support, the loads are distributed between the ground and support depending on their relative stiffness. This paper presents the development of conceptual single-degree-of-freedom models, which are used to derive equations for estimating displacements and stresses for ground-support interaction problems encountered in pillars in room-andpillar mining(natural support system), and liners for circular vertical shafts(artificial support systems).For pillar assessment, mine-pillar interaction curves can be constructed using a double spring analogy.Additionally, the effectiveness of different support systems can be evaluated depending on their effect upon the mine-pillar system. For shaft design, an initial estimation of the required lining strength and thickness can be readily made based on a double ring analogue. For both problems, the results from the proposed approach compare well with those obtained by finite element numerical simulations.
文摘Norwegian hydropower industry has more than 100 years of experiences in constructing more than4000 km-long unlined pressure shafts and tunnels with maximum static head of 1047 m（equivalent to almost 10.5 MPa） reached at unlined pressure tunnel of Nye Tyin project. Experiences gained from construction and operation of these unlined pressure shafts and tunnels were the foundation to develop design criteria and principles applied in Norway and some other countries. In addition to the confinement criteria, Norwegian state-of-the-art design principle for unlined pressure shaft and tunnel is that the minor principal stress at the location of unlined pressure shaft or tunnel should be more than the water pressure in the shaft or tunnel. This condition of the minor principal stress is prerequisite for the hydraulic jacking/splitting not to occur through joints and fractures in rock mass. Another common problem in unlined pressure shafts and tunnels is water leakage through hydraulically splitted joints or pre-existing open joints. This article reviews some of the first attempts of the use of unlined pressure shaft and tunnel concepts in Norway, highlights major failure cases and two successful cases of significance, applies Norwegian criteria to the cases and reviews and evaluates triggering factors for failure.This article further evaluates detailed engineering geology of failure cases and also assesses common geological features that could have aggravated the failure. The minor principal stress is investigated and quantified along unlined shaft and tunnel alignment of six selected project cases by using threedimensional numerical model. Furthermore, conditions of failure through pre-existing open joints by hydraulic jacking and leakage are assessed by using two-dimensional fluid flow analysis. Finally, both favorable and unfavorable ground conditions required for the applicability of Norwegian confinement criteria in locating the unlined pressure shafts and tunnels for geotectonic environment different from that of Norway are highlighted.
基金SUPPORTED BY NATIONAL NATURAL SCIENCE FOUNDATION OF CHINA( NO. 50475112)NATURAL SCIENCE FOUNDATION OF TIANJIN (NO. 043601411).
文摘The torsional oscillation characteristics on the bending and torsioh coupled vibration of rotary shaft system were investigated using the elasto-dynamic theory and other mathematic methods, such as difference approach, Fourier transform, and wavelet transform. It is concluded that mass eccentricity and other exciting modalities affect the bending and torsion coupled vibration of rotary shafts. Torsional vibration caused by bending vibration features linearity along with the change of amplitude of bending vibration. Meanwhile, energy spectrum concentrates on high frequency area with the wavelet analysis.
文摘Composite hollow shafts are used in power transmission applications due to their high specific stiffness and high specific strength.The dynamic characteristics of these shafts are important for transmission applications.Dynamic modelling of these shafts is generally carried out using Equivalent Modulus Beam Theory(EMBT)and Layerwise Beam Theory(LBT)formulations.The EMBT formulation is modified by considering stacking sequence,shear normal coupling,bending twisting coupling and bending stretching coupling.It is observed that modified EMBT formulation is underestimating the shafts stiffness at lower length/mean diameter(l/dm)ratios.In the present work,a new formulation is developed by adding shear deformation along the thickness direction to the existing modified EMBT formulation.The variation of shear deformation along the thickness direction is found using different shear deformation theories,i.e.,first-order shear deformation theory(FSDBT),parabolic shear deformation theory(PSDBT),trigonometric shear deformation theory(TSDBT),and hyperbolic shear deformation theory(HSDBT).The analysis is performed at l/d_(m) ratios of 5,10,15,20,25,30,35,and 40 for carbon/epoxy composites,E-glass/epoxy composites,and boron/epoxy composite shafts.The results show that new formulation has improved the bending natural frequency of the composite shafts for l/d_(m)<15 in comparison with modified EMBT.The effect of new formulation is more significant for the second and third bending modes of natural frequencies.
基金supported by Opening Foundation of Key Laboratory of New Technology for Construction of Cities in Mountain Area,Ministry of Education,China(LNTCCMA-20210104)This work was also supported by the Natural Science Foundation of China(Grant No.51408113)the Natural Science Foundation of Jiangsu Province,China(Grant No.BK20140632).
文摘With the growing global environmental awareness,the development of renewable and green materials has gained increased worldwide interest to substitute conventional materials and are favorable for sustainable economic development.This paper proposed a novel eco-friendly sound absorbing structure(NSAS)liner for noise reduction in elevator shafts.The base layer integrated with the shaft walls is a damping gypsum mortarboard,and a rock wool board and a perforated cement mortarboard are used to compose the NSAS.Based on the acoustic impedance theory of porous materials and perforated panels,the sound absorption theory of the NSAS was proposed;the parameter effects of the rock wool board(flow resistivity,porosity,structure factor)and perforated panel(perforated rates,thickness,density,perforated diameter)on NSAS absorption were discussed theoretically for absorption improvement,and experiments were also conducted.Numerical results showed that the perforation rate,the thickness of the perforated plate,and the porosity,flow resistance,and volume density of the rock wool board played a key issue in the absorption performances of the NSAS.Experiments verified the accuracy of the proposed theoretical model.Wideband sound absorption performance of the NSAS at frequencies between 500–1600 Hz was achieved in both numerical analysis and experiments,and the sound absorption coefficient was improved to 0.72 around 1000 Hz after parameter adjustments.The NSAS proposed in this paper can also be made of other renewable materials with preferable structure strength and still has the potential to broaden the absorption bandwidth.It can provide a reference for controlling the elevator shaft noise.
文摘This paper presents an investigation of non-stationary induction heating process applied to AISI 4340 steel spline shafts based on 3D simulation and experimental validation. The study is based on the knowledge, concerning the form of correlations between various induction heating parameters and the final hardness profile, developed in the case of stationary induction heating. The proposed approach focuses on analyzing the effects of variation of frequency, power and especially scanning speed through an extensive 3D finite element method simulation, comprehensive sensitivity study and structured experimental efforts. Based on coupled electromagnetic and thermal fields analysis, the developed 3D model is used to estimate the temperature distribution and the hardness profile. Experimentations conducted on a commercial dual-frequency induction machine for AISI 4340 steel splines confirm the feasibility and the validity of the proposed modelling procedure. The 3D model validation reveals a great concordance between simulated and measured results, confirms that the model can effectively be used as framework for understanding the process and for assessing the effects of various parameters on the hardening process quality and performance and consequently leads to the most relevant variables to use in an eventual hardness profile prediction model.
文摘<div style="text-align:justify;"> In most cases, copper ore deposits occur at great depths, so the optimization of excavation costs is of utmost importance to identify the most cost effective and productive mining methods, such as block caving or similar methods specifically developed for these deposits. To be able to apply such methods, it is necessary to have a detailed knowledge of the rock mass in terms of its geomechanical, engineering geological and hydrogeological characteristics. This research aims to reduce geological and geotechnical unknowns, analyze in detail the geological environment, and predict geotechnical conditions for the construction of the shaft. This paper uses the example of Borska Reka Copper Deposit, located in Serbia to illustrate the importance of geotechnical investigation to enable best practice in design and construction of shafts that are over 1000 m deep. </div>
文摘A reliability based analysis method for a drilled shaft stabilized slope system is presented in this paper. The drilled shaft stabilization mechanisms for the slope were treated as the drilled shaft induced soil arching, which was quantified by the load transfer factor in the limited equilibrium analysis. However, due to the inherent uncertainties of the soil properties and the model error of the semi-empirical load transfer equation, an extension modification of the deterministic method into a probabilistic method is developed in this paper. The MCS （Monte Carlo simulation） with log-normal random variables has been employed to calculate the probability of failure （Pf） for the drilled shafts/slope system. The developed theories were coded into a computer program for analyzing complex slope geometry and slope profile conditions. Finally, a case study has been performed to illustrate the application analysis of the developed probability approach in drilled shafts/slope system.
文摘The deformation principles of the steady- state and the unsteady一state of open- die cold extrusion for involute spline shafts are analyzed by means of experiments. On one hand,based on the deformation principles of the steady- state, data for determining structural parameters of the die, the size of the billet and the constraint condition of this technique are given. On the other hand, according to the principles of the unsteady- state, data for modifying the shapes and sizes of the bil- lets are provided.
基金supported by the National Basic Research Program of China (No.2006CB202204-3).
文摘The determination of gas pressure before uncovering coal in cross-cuts and in shafts is one of the important steps in pre- dicting coal and gas outbursts. However, the time spent for testing gas pressure is, at present, very long, seriously affecting the ap- plication of outburst prediction techniques in opening coal seams in cross-cuts and shafts. In order to reduce the time needed in gas pressure tests and to improve the accuracy of tests, we analyzed the process of gas pressure tests and examined the effect of the length of boreholes in coal seams in tests. The result shows that 1) the shorter the borehole, the easier the real pressure value of gas can be obtained and 2) the main factors affecting the time spent in gas pressure tests are the length of the borehole in coal seams, the gas emission time after the borehole has been formed and the quality of the borehole-sealing. The longer the length of the bore- hole, the longer the gas emission time and the larger the pressure-relief circle formed around the borehole, the longer the time needed for pressure tests. By controlling the length of the borehole in a test case in the Huainan mining area, and adopting a quick sealing technique using a sticky liquid method, the sealing quality was clearly improved and the gas emission time as well as the amount of gas discharged greatly decreased. Before the method described, the time required for the gas pressure to increase during the pressure test process, was more than 10 days. With our new method the required time is only 5 hours. In addition, the accuracy of the gas pressure test is greatly improved.
文摘The circumferential vibration of a gear pair is a parametric excitation caused by nonlinear tooth stiffness,which fluctuates with meshing.In addition,the vibration characteristics of the gear pair become complicated owing to the tooth profile error and backlash.It is considered that the circumferential vibration of the gear pair is affected by the torsional vibration of the shafts.It is important to understand quantitatively the vibration characteristics of the gear system considering the shafts.Therefore,the purpose of this research was to clarify the nonlinear vibration characteristics of a gear pair considering the influence of the shafts using theoretical methods.To achieve this objective,calculations were performed using equations of motion in which the circumferential vibration of the gear pair and the torsional vibration of the shafts were coupled.The nonlinear tooth stiffness was represented by a sine wave.The influence of tooth separation was considered by defining a nonlinear function using backlash and the tooth profile error.For the numerical calculations,both stable and unstable periodic solutions were obtained by using the shooting method.The effect of the shafts on the gear system vibration were clarified by comparing the results in the cases in which the shaft was not considered,one shaft was considered,and both shafts were considered.
基金Item Sponsored by Polish State Committee for Scientific Research(N50802431/1444)
文摘A new concept for forming eccentric shafts on the basis of the cross-wedge rolling （CWR） process was presented. This concept was based on the application of special guides, which, by acting on a billet, lead to its controlled movement in the vertical direction. This movement made possible eccentric cutting of tools into the billet. FEM calculations and experimental rolling tests clearly confirmed the effectiveness of the proposed forming method.
文摘In this study, the finite element numerical modelling of 2D shaft sections in a Hoek–Brown medium are carried out in a non-hydrostatic stress state in an attempt to predict pressures developing around mine shafts. An iterative process of applying support pressure until observing no failure zone around the shaft is used to simulate the required lining support pressure for different shaft models. Later, regression analysis is carried out to find a generic shaft pressure equation representing the rock mass and the stress state. Finally, the developed pressure equation which shows a good agreement with a case study is used in elastic ‘‘thick-walled cylinder" equation to calculate the lining thickness required to prevent the development of a failure zone around the shaft. At the end of the study, a user-friendly object-oriented computer program ‘‘Shaft 2D" is developed to simplify the rigorous shaft lining thickness calculation process.
文摘Rotary bending fatigue tests were carried out with two kinds of materials, S43C and S50C, using the front engine and front drive shaft （FF shaft） of vehicle. The specimens were induction hardened about 1.0mm depth from the specimen surface, and the hardness value on the surface was about HRC56-60. The tested environment temperatures were -30, 25 and 80℃ in order to look over effect of the induction hardening and the environmental temperatures on the fatigue characteristics. The fatigue limit of induction hardened specimens increased more about 45% than non-hardened specimens showing that the endurances of S43C and S50C were 98.1 and 107.9MPa in non-hardened samples, 147.1 and 156.9MPa in hardened samplesrespectably. The maximum tensile and compressive stress on the small circular defect was about ＋250 and -450MPa respectively when circular defect is situated on top and bottom. The fatigue life increased 80, 25 and -30℃ in order regardless of hardening. In comparison of the fatigue lives on the basis of tested result at 25℃, the fatigue lives of non-hardened specimens decreased about 35%, but that of hardened specimens decreased about only 5% at 80℃ more than at 25℃. And fatigue life of non-hardened and hardened specimens were about 110% and 120% higher at -30℃ than that of 25℃. Based on the result of stress distribution near the defect, the tensile and compressive stress repeatedly generated by load direction were the largest on the small circular defect due to the stress concentration.
文摘Currently the service life of CDQ shafts in China is mainly restricted by the properties of the inclined flue bricks.In this work,based on the systematic analysis of the damage mechanism of inclined flue refractories,high performance mullite-SiC bricks were developed.The bricks were produced by corundum,andalusite,SiC and other high purity raw materials.Metal silicon and alumina ultra micropowder were added to form dispersion multi-phase structure,fortifying the matrix and improving the microstructure.The products have excellent properties such as low porosity,high density,good wear resistance,high refractoriness under load,and good thermal shock resistance.The products can replace the ordinary mullite-SiC bricks and obtain a good service life.
