In order to improve the reliability of the design and calculation of single piles under the combined vertical and lateral loads, the solutions were presented based on the subgrade reaction method, in which the ultimat...In order to improve the reliability of the design and calculation of single piles under the combined vertical and lateral loads, the solutions were presented based on the subgrade reaction method, in which the ultimate soil resistance was considered and the coefficient of subgrade reaction was assumed to be a constant. The corresponding computational program was developed using FORTRAN language. A comparison between the obtained solutions and the model test results was made to show the validity of the obtained solutions. The calculation results indicate that both the maximum lateral displacement and bending moment increase with the increase of the vertical and lateral loads and the pile length above ground, while decrease as the pile stiffness, the coefficient of subgrade reaction and the yielding displacement of soil increase. It is also shown that the pile head condition controls the pile responses and the vertical load may cause the instability problem to the pile. In general, the proposed method can be employed to calculate the pile responses independent of the magnitude of the pile deflection.展开更多
Once in the hands of end users, such durable equipment as spacecraft, aircraft, ships,automobiles, computers, etc. are in a state of debugging, working or storage. In either state, availability, reliability and super-...Once in the hands of end users, such durable equipment as spacecraft, aircraft, ships,automobiles, computers, etc. are in a state of debugging, working or storage. In either state, availability, reliability and super-efficiency are the ultimate goals, which have been achieved through constant monitoring as well as regular, preventive, routine and corrective maintenance. Although some advanced instruments can visualize certain invisible malfunctioning phenomena into visible ones, deeply hidden troubles cannot be found unless monitoring and testing data are addressed using tools that process the data statistically, analytically and mathematically. Some state-of-theart trouble-shooting and life-predicting techniques and approaches are introduced in this paper.展开更多
In order to utilize water and hydropower resources in China,multitudes of water projects are established or to be constructed as an integral part of the national economy's infrastructure.Under these circumstances,...In order to utilize water and hydropower resources in China,multitudes of water projects are established or to be constructed as an integral part of the national economy's infrastructure.Under these circumstances,there are two outstanding problems:1) a mass of existing dams are in danger and 2) in the southwest water-conservancy construction plan,dozens of existing or planned dams are high dams or even super high dams with heights between 200 and 300 m.In accordance with demands of "the National Program for Medium-and Long-Term Scientific and Technological Development" on the innovation frontier in hydro-structure engineering science,various key problems in science and technology such like stress analysis,ultimate bearing capacity,nonlinearity etc.for high dams,super high dams and sick dams have been investigated.This paper makes a commentary on the advances and results of the researches,then analyzes the advantages and disadvantages of current theoretics and methodologies,and finally presents corresponding research directions and the frontier of innovation.展开更多
Spontaneous combustion of coal is a well-known phenomena around the globe. Apart from the coal itself,burning coal-shales is becoming a problem in the South African coal mines. Serious incidents of spontaneous combust...Spontaneous combustion of coal is a well-known phenomena around the globe. Apart from the coal itself,burning coal-shales is becoming a problem in the South African coal mines. Serious incidents of spontaneous combustion have been reported as a result of self-heating of reactive coal-shales. The intrinsic properties and spontaneous combustion tests of 28 selected coal and coal-shale samples were conducted and a relationship between the two has been established. Intrinsic properties were obtained by using the proximate and ultimate analysis, and spontaneous combustion liability tests results were obtained by using the Wits-Ehac and Wits-CT indices. The experimental results show that intrinsic properties of these materials complement to the spontaneous combustion liability tests results. Comparative analyses of intrinsic properties and spontaneous combustion characteristics indicate similarities between the mechanism of coal oxidation and that of the oxidative processes undergone by coal-shales. For the tested samples, coal samples have a higher intrinsic spontaneous combustion reactivity rating than the coal-shales.Furthermore, an increase in carbon, moisture, hydrogen, volatile matter, nitrogen and a decrease in ash content indicate an increased proneness to self-heating. The concentration of pyrite found in the coal-shales accelerates self-heating. The event of spontaneous combustion can occur if coal-shales absorb sufficient oxygen when subjected to atmospheric conditions.展开更多
A new method was proposed to predict the limited compaction grouting pressure for the soft soils. Theoretical basis of the method considered the conical shear failure above the grout bulb. Using the Mohr-Coulomb yield...A new method was proposed to predict the limited compaction grouting pressure for the soft soils. Theoretical basis of the method considered the conical shear failure above the grout bulb. Using the Mohr-Coulomb yield criterion as the initial yield function, the limited compaction grouting pressure was determined, according to the softening elastic-plastic model based on the conventional triaxial compression tests to simulate the strain softening soils. The small strain in the elastic zone and large stain in the plastic zone and the rational yield function for the strain softening phase stage, the analytical solutions to the compaction grouting pressure were presented. The results indicate reasonable agreement and show a good potential of the proposed method for rationally optimizing the design of compaction grouting operations.展开更多
The stability of room mining coal pillars during their secondary mining for recovering coal was analyzed. An analysis was performed for the damage and instability mechanism of coal pillars recovered by the caving mini...The stability of room mining coal pillars during their secondary mining for recovering coal was analyzed. An analysis was performed for the damage and instability mechanism of coal pillars recovered by the caving mining method. During the damage progression of a single room coal pillar, the shape of the stress distribution in the pillar transformed from the initial stable saddle shape to the final arch-shaped distribution of critical instability. By combining the shapes of stress distribution in the coal pillars with the ultimate strength theory, the safe-stress value of coal pillar was obtained as 11.8 MPa. The mechanism of instability of coal pillar groups recovered by the caving mining method was explained by the domino effect. Since the room coal pillars mined and recovered by the traditional caving mining method were significantly influenced by the secondary mining during recovery, the coal pillars would go through a chain-type instability failure. Because of this limitation, the method of solid backfilling was proposed for mining and recovering room coal pillars, thus changing the transfer mechanism of stress caused by the secondary mining(recovery) of coal pillars. The mechanical model of the stope in the case of backfilling and recovering room coal pillars was built. The peak stress values inside coal pillars varied with the variance of backfilling ratio when the working face was advanced by 150 m. Furthermore, when the critical backfilling ratio was 80.6%, the instability failure of coal pillars would not occur during the solid backfill mining process. By taking Bandingliang Coal Mine as an example, the coal pillars' stability of stope under this backfilling ratio was studied, and a project scheme was designed.展开更多
This study was performed in two phases of work.In the first stage,four conventional first-order flotation kinetics models were fitted to the measured recoveries data and the best model were selected.In the second stag...This study was performed in two phases of work.In the first stage,four conventional first-order flotation kinetics models were fitted to the measured recoveries data and the best model were selected.In the second stage,influence of pH,solid concentration,water chemistry and the amount of collector dosage were investigated on kinetics parameters including flotation rate constant and ultimate recovery.The results indicated that that perfectly mixed reactor model and Kelsall model gave the best and the weakest fit to the experimental data,respectively.It was observed that flotation rate constant and ultimate recovery were strongly affected by chemical factors investigated especially water quality.The flotation rate constant decreased with increasing the solids content,while ultimate recovery increased to certain value and thereafter reduced.It was also found that the most values of flotation rate constant and ultimate recovery obtained in dosage of collector are 30 and 40 g/t,respectively.展开更多
Based on an extensive experimental program,the paper studies the behavior of HPFRCC under triaxial compression. The experimental parameters are lateral confining pressure and PVA fiber content by volume. The test resu...Based on an extensive experimental program,the paper studies the behavior of HPFRCC under triaxial compression. The experimental parameters are lateral confining pressure and PVA fiber content by volume. The test results indicate that ultimate strength and peak strain are significantly improved with the increases of confining pressure. The confining effect introduced by the fibers becomes minor in triaxial compression tests,where there is relatively high external confining pressure. The axial stress-strain curves with different confining pressure and different PVA fiber content by volume are obtained. Lateral confining pressure constraints the lateral expansion of HPFRCC,so there is a big plastic deformation with its ultimate strength improved. At lower confining pressure,PVA fiber content by volume has some effect on the decreased section of stress-strain curve. According to test results,the paper establishes formula of confining pressure with ultimate strength and axial peak strain respectively.展开更多
Based on the experimental study and inelastic theory, the ultimate flexuralcapacity of steel encased concrete composite beams are derived. The difference between steel encasedconcrete composite beams with full shear c...Based on the experimental study and inelastic theory, the ultimate flexuralcapacity of steel encased concrete composite beams are derived. The difference between steel encasedconcrete composite beams with full shear connection and beams with partial shear connection,together with the relationship between the inelastic neutral axis of steel parts and concrete parts,are considered in the formulae. The calculation results of the eight specimens with full shearconnection and the three specimens with partial shear connection are in good agreement with theexperimental data, which validates the effectiveness and efficiency of the proposed calculationmethods. Furthermore, the nonlinear finite element analysis of the ultimate flexural capacity of thesteel encased concrete composite beams is performed. Nonlinear material properties and nonlinearcontact properties are considered in the finite element analysis. The finite element analyticalresults also correlate well with the experimental data.展开更多
Based on the functional theory, catastrophe theory, simultaneity principle and the idea of strength reduction method （SRM）, the bearing capacity functional anti SRM of pile group foundation were established, and the...Based on the functional theory, catastrophe theory, simultaneity principle and the idea of strength reduction method （SRM）, the bearing capacity functional anti SRM of pile group foundation were established, and the criteria of ultimate load and the concept of safety storage coefficient （Css） were advanced. The inclined ultimate loads by the static loading test, load increment method （LIM） and SRM are compared. Theoretically, the ultimate load of piles does not change with the loading levels when it is calculated by SRM. When the one strength reduction parameter is applied in the calculation boundary, there are calculating errors because the bearing capacity action of soils happened in the finite zone. The inclined 10adings are 108, 132 and 144 kN, and SSC are 1.07, 0.94 and 0.79, respectively, so the calculation values of ultimate loads are about 115.56, 124.08 and 113.76 kN, respectively. The error between calculations and observation values is less than 6%. But .the error between calculations of LIM and observations is 20%. Because of the effect of inclined loading, the push-rotation phenomenon of screw pile group appears. Under this testing, the ultimate bearing capacity of piles is mostly determined by the horizontal ultimate bearing capacity, and the effect of the vertical component of inclined load should also be considered.展开更多
To obtain magnesium alloys with a low density and improved mechanical properties,Y element was added into Mg−4Li−3Al(wt.%)alloys,and the effect of Y content on microstructure evolution and mechanical properties was in...To obtain magnesium alloys with a low density and improved mechanical properties,Y element was added into Mg−4Li−3Al(wt.%)alloys,and the effect of Y content on microstructure evolution and mechanical properties was investigated by using optical microscopy,scanning electron microscopy and tensile tests.The results show that mechanical properties of as-cast Mg−4Li−3Al alloys with Y addition are significantly improved as a result of hot extrusion.The best comprehensive mechanical properties are obtained in hot-extruded Mg−4Li−3Al−1.5Y alloy,which possesses high ultimate tensile strength(UTS=248 MPa)and elongation(δ=27%).The improvement of mechanical properties of hot-extruded Mg−4Li−3Al−1.5Y alloy was mainly attributed to combined effects of grain refinement,solid solution strengthening and precipitation strengthening.展开更多
Cu-0.45 Cr-0.2 Zr-xLa（x = 0-0.48） alloys were prepared by vacuum casting. The effects of La addition and orientation on the microstructure and properties of the as-cast alloy were investigated by an optical microsco...Cu-0.45 Cr-0.2 Zr-xLa（x = 0-0.48） alloys were prepared by vacuum casting. The effects of La addition and orientation on the microstructure and properties of the as-cast alloy were investigated by an optical microscope, a scanning electron microscope with an energy dispersive X-ray spectrometer, a tensile testing machine and an electrical conductivity tester. The result shows that the addition of La significantly refines the columnar grainsize and decreases the secondary dendrite arm spacing. Trace addition of La improves the room temperature ultimate tensile strength,elongation and electrical conductivity mainly by purifying during melting and casting. The ultimate tensile strength, elongation and electrical conductivity significantly decrease with the increase of La content due to formation of coarse particles and oxides, which severely harm the performance of the Cu-0.45 Cr-0.2 Zr-xLa alloys. The Cu-0.45 Cr-0.2 Zr-0.13 La alloy possesses a good combination of room temperature ultimate tensile strength, elongation and electrical conductivity. In addition, room temperature ultimate tensile strength and electrical conductivity along transverse direction of the ingot are higher than that along longitudinal direction,which is mainly ascribed to different distribution of grain boundary and grain orientation.展开更多
In this paper, modification agents with different contents of Sr and La elements were added into Al-Si-Cu-Fe alloy and the effect on refinement of secondary phases and α-Al grain was investigated by optical microscop...In this paper, modification agents with different contents of Sr and La elements were added into Al-Si-Cu-Fe alloy and the effect on refinement of secondary phases and α-Al grain was investigated by optical microscopy, scanning electronic microscopy and X-ray diffractometry. Tensile testing was carried out to characterize the strength of the alloys. The XRD result indicated that Fe9LaSi4 and SrSi2 phases were formed after Sr and La elements were added in the alloys simultaneously. With the help of metallographic analysis techniques, the length of needle-like phases, mainly composed of eutectic Si and β-Fe, was quantified. And the secondary dendrite arm spacing（SDAS） of α-Al grain was also evaluated. The quantification results indicated that the modification agents with different contents of Sr and La elements showed varied refinement effects on the mean length of needle-like phases and SDAS value. When the addition amount increased, the length of needle-like phase and SDAS value were decreased. The minimum mean length of needle-like phases（Sr/La=1：1） and the SDAS value（Sr/La=1：5） were obtained by setting the addition amount of the modification agent at 0.12 wt.%. The yield strength of the alloy was related to the mean SDAS value, whilst the ultimate tensile strength, elongation and hardness values were related to the mean length of needle-like phase.展开更多
Previous studies have shown that product market competition has an important effect on corporate strategies and internal governance mechanisms. Using a sample of China's listed firms from 2004 to 2009, we explore ...Previous studies have shown that product market competition has an important effect on corporate strategies and internal governance mechanisms. Using a sample of China's listed firms from 2004 to 2009, we explore the relationship between product market competition and normal related party transactions and find a significant positive relationship. In addition, we investigate the substitutive effect of product market competition and the cash flow rights owned by ultimate controlling shareholders on the extent of normal related party transactions. In particular, our results suggest a positive relationship between the ultimate controlling shareholders' cash flow rights and normal related party transactions that is strongest in noncompetitive industries and weakens as product market competition increases.展开更多
Although there are many lead-free soldering alloys on the market, none of them have ideal qualities. The researchers are combining binary alloys with a variety of additional materials to create the soldering alloys’ ...Although there are many lead-free soldering alloys on the market, none of them have ideal qualities. The researchers are combining binary alloys with a variety of additional materials to create the soldering alloys’ features. The eutectic Sn-9Zn alloy is among them. This paper investigated the mechanical and electrical properties of Sn-9Zn-x (Ag, Cu, Sb);{x = 0.2, 0.4, and 0.6} lead-free solder alloys. The mechanical properties such as elastic modulus, ultimate tensile strength (UTS), yield strength (YS), and ductility were examined at the strain rates in a range from 4.17 10−3 s−1 to 208.5 10−3 s−1 at room temperature. It is found that increasing the content of the alloying elements and strain rate increases the elastic modulus, ultimate tensile strength, and yield strength while the ductility decreases. The electrical conductivity of the alloys is found to be a little smaller than that of the Sn-9Zn eutectic alloy.展开更多
基金Foundation item： Projects（50708093, 50808159） supported by the National Natural Science Foundation of China
文摘In order to improve the reliability of the design and calculation of single piles under the combined vertical and lateral loads, the solutions were presented based on the subgrade reaction method, in which the ultimate soil resistance was considered and the coefficient of subgrade reaction was assumed to be a constant. The corresponding computational program was developed using FORTRAN language. A comparison between the obtained solutions and the model test results was made to show the validity of the obtained solutions. The calculation results indicate that both the maximum lateral displacement and bending moment increase with the increase of the vertical and lateral loads and the pile length above ground, while decrease as the pile stiffness, the coefficient of subgrade reaction and the yielding displacement of soil increase. It is also shown that the pile head condition controls the pile responses and the vertical load may cause the instability problem to the pile. In general, the proposed method can be employed to calculate the pile responses independent of the magnitude of the pile deflection.
基金co-supported by the National Natural Science Fundation for Distinguished Young Scholar of China(No.61025014)the National Natural Science Foundation of China(Nos.61174030,61104223,61374126,61374120,61004069 and 61370031)
文摘Once in the hands of end users, such durable equipment as spacecraft, aircraft, ships,automobiles, computers, etc. are in a state of debugging, working or storage. In either state, availability, reliability and super-efficiency are the ultimate goals, which have been achieved through constant monitoring as well as regular, preventive, routine and corrective maintenance. Although some advanced instruments can visualize certain invisible malfunctioning phenomena into visible ones, deeply hidden troubles cannot be found unless monitoring and testing data are addressed using tools that process the data statistically, analytically and mathematically. Some state-of-theart trouble-shooting and life-predicting techniques and approaches are introduced in this paper.
基金supported by the National Natural Science Foundation of China (Grant Nos. 51079046, 50909041, 50809025, 50879024)the National Science and Technology Support Plan (Grant Nos. 2008BAB29B03, 2008BAB29B06)+6 种基金the Special Fund of State Key Laboratory of China (Grant Nos. 2009586012, 2010585212)the Fundamental Research Funds for the Central Universities (Grant Nos. 2009B08514, 2010B20414, 2010B14114)China Hydropower Engineering Consulting Group Co. Science and Technology Support Project (Grant No. CHC-KJ-2007-02)Jiangsu Province "333 High-Level Personnel Training Project" (Grant No. 2017-B08037)the Natural Science Foundation of Hohai University (Grant No. 2008426811)Graduate Innovation Program of Universities in Jiangsu Province (CX09B_163Z)Science Foundation for The Excellent Youth Scholars of Ministry of Education of China (Grant No. 20070294023)
文摘In order to utilize water and hydropower resources in China,multitudes of water projects are established or to be constructed as an integral part of the national economy's infrastructure.Under these circumstances,there are two outstanding problems:1) a mass of existing dams are in danger and 2) in the southwest water-conservancy construction plan,dozens of existing or planned dams are high dams or even super high dams with heights between 200 and 300 m.In accordance with demands of "the National Program for Medium-and Long-Term Scientific and Technological Development" on the innovation frontier in hydro-structure engineering science,various key problems in science and technology such like stress analysis,ultimate bearing capacity,nonlinearity etc.for high dams,super high dams and sick dams have been investigated.This paper makes a commentary on the advances and results of the researches,then analyzes the advantages and disadvantages of current theoretics and methodologies,and finally presents corresponding research directions and the frontier of innovation.
文摘Spontaneous combustion of coal is a well-known phenomena around the globe. Apart from the coal itself,burning coal-shales is becoming a problem in the South African coal mines. Serious incidents of spontaneous combustion have been reported as a result of self-heating of reactive coal-shales. The intrinsic properties and spontaneous combustion tests of 28 selected coal and coal-shale samples were conducted and a relationship between the two has been established. Intrinsic properties were obtained by using the proximate and ultimate analysis, and spontaneous combustion liability tests results were obtained by using the Wits-Ehac and Wits-CT indices. The experimental results show that intrinsic properties of these materials complement to the spontaneous combustion liability tests results. Comparative analyses of intrinsic properties and spontaneous combustion characteristics indicate similarities between the mechanism of coal oxidation and that of the oxidative processes undergone by coal-shales. For the tested samples, coal samples have a higher intrinsic spontaneous combustion reactivity rating than the coal-shales.Furthermore, an increase in carbon, moisture, hydrogen, volatile matter, nitrogen and a decrease in ash content indicate an increased proneness to self-heating. The concentration of pyrite found in the coal-shales accelerates self-heating. The event of spontaneous combustion can occur if coal-shales absorb sufficient oxygen when subjected to atmospheric conditions.
基金Project (200550) supported by the Foundation for the Author of National Excellent Doctoral Dissertation of ChinaProject (09JJ1008) supported by Hunan Provincial Natural Science Foundation of China
文摘A new method was proposed to predict the limited compaction grouting pressure for the soft soils. Theoretical basis of the method considered the conical shear failure above the grout bulb. Using the Mohr-Coulomb yield criterion as the initial yield function, the limited compaction grouting pressure was determined, according to the softening elastic-plastic model based on the conventional triaxial compression tests to simulate the strain softening soils. The small strain in the elastic zone and large stain in the plastic zone and the rational yield function for the strain softening phase stage, the analytical solutions to the compaction grouting pressure were presented. The results indicate reasonable agreement and show a good potential of the proposed method for rationally optimizing the design of compaction grouting operations.
基金Project(2014ZDPY02)supported by the Fundamental Research Funds for the Central Universities
文摘The stability of room mining coal pillars during their secondary mining for recovering coal was analyzed. An analysis was performed for the damage and instability mechanism of coal pillars recovered by the caving mining method. During the damage progression of a single room coal pillar, the shape of the stress distribution in the pillar transformed from the initial stable saddle shape to the final arch-shaped distribution of critical instability. By combining the shapes of stress distribution in the coal pillars with the ultimate strength theory, the safe-stress value of coal pillar was obtained as 11.8 MPa. The mechanism of instability of coal pillar groups recovered by the caving mining method was explained by the domino effect. Since the room coal pillars mined and recovered by the traditional caving mining method were significantly influenced by the secondary mining during recovery, the coal pillars would go through a chain-type instability failure. Because of this limitation, the method of solid backfilling was proposed for mining and recovering room coal pillars, thus changing the transfer mechanism of stress caused by the secondary mining(recovery) of coal pillars. The mechanical model of the stope in the case of backfilling and recovering room coal pillars was built. The peak stress values inside coal pillars varied with the variance of backfilling ratio when the working face was advanced by 150 m. Furthermore, when the critical backfilling ratio was 80.6%, the instability failure of coal pillars would not occur during the solid backfill mining process. By taking Bandingliang Coal Mine as an example, the coal pillars' stability of stope under this backfilling ratio was studied, and a project scheme was designed.
文摘This study was performed in two phases of work.In the first stage,four conventional first-order flotation kinetics models were fitted to the measured recoveries data and the best model were selected.In the second stage,influence of pH,solid concentration,water chemistry and the amount of collector dosage were investigated on kinetics parameters including flotation rate constant and ultimate recovery.The results indicated that that perfectly mixed reactor model and Kelsall model gave the best and the weakest fit to the experimental data,respectively.It was observed that flotation rate constant and ultimate recovery were strongly affected by chemical factors investigated especially water quality.The flotation rate constant decreased with increasing the solids content,while ultimate recovery increased to certain value and thereafter reduced.It was also found that the most values of flotation rate constant and ultimate recovery obtained in dosage of collector are 30 and 40 g/t,respectively.
基金support from the youth science fund project of China (50908187)Henan provincial natural science research project ( 2010B560006 )Shanxi provinces youth fund project(2009JQ7013)
文摘Based on an extensive experimental program,the paper studies the behavior of HPFRCC under triaxial compression. The experimental parameters are lateral confining pressure and PVA fiber content by volume. The test results indicate that ultimate strength and peak strain are significantly improved with the increases of confining pressure. The confining effect introduced by the fibers becomes minor in triaxial compression tests,where there is relatively high external confining pressure. The axial stress-strain curves with different confining pressure and different PVA fiber content by volume are obtained. Lateral confining pressure constraints the lateral expansion of HPFRCC,so there is a big plastic deformation with its ultimate strength improved. At lower confining pressure,PVA fiber content by volume has some effect on the decreased section of stress-strain curve. According to test results,the paper establishes formula of confining pressure with ultimate strength and axial peak strain respectively.
文摘Based on the experimental study and inelastic theory, the ultimate flexuralcapacity of steel encased concrete composite beams are derived. The difference between steel encasedconcrete composite beams with full shear connection and beams with partial shear connection,together with the relationship between the inelastic neutral axis of steel parts and concrete parts,are considered in the formulae. The calculation results of the eight specimens with full shearconnection and the three specimens with partial shear connection are in good agreement with theexperimental data, which validates the effectiveness and efficiency of the proposed calculationmethods. Furthermore, the nonlinear finite element analysis of the ultimate flexural capacity of thesteel encased concrete composite beams is performed. Nonlinear material properties and nonlinearcontact properties are considered in the finite element analysis. The finite element analyticalresults also correlate well with the experimental data.
基金Project(51178457) supported by the National Natural Science Foundation of ChinaProject(cstc2012jjys0001) supported by the Natural Science Foundation of Chongqing,ChinaProject(L2011231) supported by the Liaoning Education Department,China
文摘Based on the functional theory, catastrophe theory, simultaneity principle and the idea of strength reduction method （SRM）, the bearing capacity functional anti SRM of pile group foundation were established, and the criteria of ultimate load and the concept of safety storage coefficient （Css） were advanced. The inclined ultimate loads by the static loading test, load increment method （LIM） and SRM are compared. Theoretically, the ultimate load of piles does not change with the loading levels when it is calculated by SRM. When the one strength reduction parameter is applied in the calculation boundary, there are calculating errors because the bearing capacity action of soils happened in the finite zone. The inclined 10adings are 108, 132 and 144 kN, and SSC are 1.07, 0.94 and 0.79, respectively, so the calculation values of ultimate loads are about 115.56, 124.08 and 113.76 kN, respectively. The error between calculations and observation values is less than 6%. But .the error between calculations of LIM and observations is 20%. Because of the effect of inclined loading, the push-rotation phenomenon of screw pile group appears. Under this testing, the ultimate bearing capacity of piles is mostly determined by the horizontal ultimate bearing capacity, and the effect of the vertical component of inclined load should also be considered.
基金The work was supported by the National Natural Science Foundation of China(No.51401115)the Promoted Research Fund for Excellent Young and Middle-aged Scientists of Shandong Province,China(No.BS2013CL034)partially by the Fundamental Research Funds of Shandong University,China(2016JC016).
文摘To obtain magnesium alloys with a low density and improved mechanical properties,Y element was added into Mg−4Li−3Al(wt.%)alloys,and the effect of Y content on microstructure evolution and mechanical properties was investigated by using optical microscopy,scanning electron microscopy and tensile tests.The results show that mechanical properties of as-cast Mg−4Li−3Al alloys with Y addition are significantly improved as a result of hot extrusion.The best comprehensive mechanical properties are obtained in hot-extruded Mg−4Li−3Al−1.5Y alloy,which possesses high ultimate tensile strength(UTS=248 MPa)and elongation(δ=27%).The improvement of mechanical properties of hot-extruded Mg−4Li−3Al−1.5Y alloy was mainly attributed to combined effects of grain refinement,solid solution strengthening and precipitation strengthening.
基金Project supported by the Fund of Independent Innovation in Shandong Province(2013CXB60201)the Science and Technology Development Project of Shandong Province(2014GGX102003)+1 种基金the Independent Innovation and Achievements Transformation Special Project of Shandong Province(2014CGZH0102)the Fundamental Research Funds of Shandong University(2016JC016)
文摘Cu-0.45 Cr-0.2 Zr-xLa（x = 0-0.48） alloys were prepared by vacuum casting. The effects of La addition and orientation on the microstructure and properties of the as-cast alloy were investigated by an optical microscope, a scanning electron microscope with an energy dispersive X-ray spectrometer, a tensile testing machine and an electrical conductivity tester. The result shows that the addition of La significantly refines the columnar grainsize and decreases the secondary dendrite arm spacing. Trace addition of La improves the room temperature ultimate tensile strength,elongation and electrical conductivity mainly by purifying during melting and casting. The ultimate tensile strength, elongation and electrical conductivity significantly decrease with the increase of La content due to formation of coarse particles and oxides, which severely harm the performance of the Cu-0.45 Cr-0.2 Zr-xLa alloys. The Cu-0.45 Cr-0.2 Zr-0.13 La alloy possesses a good combination of room temperature ultimate tensile strength, elongation and electrical conductivity. In addition, room temperature ultimate tensile strength and electrical conductivity along transverse direction of the ingot are higher than that along longitudinal direction,which is mainly ascribed to different distribution of grain boundary and grain orientation.
基金Project supported by National Natural Science Foundation of China(11364003,51661004,51361003)Guangxi Natural Science Foundation(2012GXNSFBA053143,2014GXNSFAA118025,2016GXNSFDA380022)+3 种基金Scientific Research and Technological Development of Guangxi(GKZ14122001-3)High Level Innovation Team and Outstanding Scholar Program in Guangxi Colleges(the second batch)Center of Ecological Collaborative Innovation for Aluminum Industry in Guangxi(20160337)Guangxi Key Laboratory of Processing for Non-ferrous Metal and Featured Materials(16-380-05)
文摘In this paper, modification agents with different contents of Sr and La elements were added into Al-Si-Cu-Fe alloy and the effect on refinement of secondary phases and α-Al grain was investigated by optical microscopy, scanning electronic microscopy and X-ray diffractometry. Tensile testing was carried out to characterize the strength of the alloys. The XRD result indicated that Fe9LaSi4 and SrSi2 phases were formed after Sr and La elements were added in the alloys simultaneously. With the help of metallographic analysis techniques, the length of needle-like phases, mainly composed of eutectic Si and β-Fe, was quantified. And the secondary dendrite arm spacing（SDAS） of α-Al grain was also evaluated. The quantification results indicated that the modification agents with different contents of Sr and La elements showed varied refinement effects on the mean length of needle-like phases and SDAS value. When the addition amount increased, the length of needle-like phase and SDAS value were decreased. The minimum mean length of needle-like phases（Sr/La=1：1） and the SDAS value（Sr/La=1：5） were obtained by setting the addition amount of the modification agent at 0.12 wt.%. The yield strength of the alloy was related to the mean SDAS value, whilst the ultimate tensile strength, elongation and hardness values were related to the mean length of needle-like phase.
基金supported by the National Nature Science Foundation of China(71263034,70902004)Humanities and Social Science Project of the Ministry of Education of China(10XJC630003)Program of Higher-level Talents at Inner Mongolia University,China(Z20100103)
文摘Previous studies have shown that product market competition has an important effect on corporate strategies and internal governance mechanisms. Using a sample of China's listed firms from 2004 to 2009, we explore the relationship between product market competition and normal related party transactions and find a significant positive relationship. In addition, we investigate the substitutive effect of product market competition and the cash flow rights owned by ultimate controlling shareholders on the extent of normal related party transactions. In particular, our results suggest a positive relationship between the ultimate controlling shareholders' cash flow rights and normal related party transactions that is strongest in noncompetitive industries and weakens as product market competition increases.
文摘Although there are many lead-free soldering alloys on the market, none of them have ideal qualities. The researchers are combining binary alloys with a variety of additional materials to create the soldering alloys’ features. The eutectic Sn-9Zn alloy is among them. This paper investigated the mechanical and electrical properties of Sn-9Zn-x (Ag, Cu, Sb);{x = 0.2, 0.4, and 0.6} lead-free solder alloys. The mechanical properties such as elastic modulus, ultimate tensile strength (UTS), yield strength (YS), and ductility were examined at the strain rates in a range from 4.17 10−3 s−1 to 208.5 10−3 s−1 at room temperature. It is found that increasing the content of the alloying elements and strain rate increases the elastic modulus, ultimate tensile strength, and yield strength while the ductility decreases. The electrical conductivity of the alloys is found to be a little smaller than that of the Sn-9Zn eutectic alloy.
