The optimum models of harvesting yield and net profits of large diameter trees for broadleaved forest were developed, of which include matrix growth sub-model, harvesting cost and wood price sub-models, based on the d...The optimum models of harvesting yield and net profits of large diameter trees for broadleaved forest were developed, of which include matrix growth sub-model, harvesting cost and wood price sub-models, based on the data from Hongshi Forestry Bureau, in Changbai Mountain region, Jilin Province, China. The data were measured in 232 permanent sample plots. With the data of permanent sample plots, the parameters of transition probability and ingrowth models were estimated, and some models were compared and partly modified. During the simulation of stand structure, four factors such as largest diameter residual tree （LDT）, the ratio of the number of trees in a given diameter class to those in the next larger diameter class （q）, residual basal area （RBA） and selective cutting cycle （C） were considered. The simulation results showed that the optimum stand structure parameters for large diameter trees are as follows： q is 1.2, LDT is 46cm, RBA is larger than 26 m^2 and selective cutting cycle time （C） is between 10 and 20 years.展开更多
In order to develop the warming bending technology of the large diameter thin-walled（LDTW） commercial pure titanium alloy CP-Ti tubes, the warm bending mechanism of the extrados and intrados of LDTW CP-Ti tubes was ...In order to develop the warming bending technology of the large diameter thin-walled（LDTW） commercial pure titanium alloy CP-Ti tubes, the warm bending mechanism of the extrados and intrados of LDTW CP-Ti tubes was researched. By EBSD analysis and Vickers hardness test, the changes of microstructure and strength of the tubes at different bending temperatures of 293, 423 and 573 K, were analyzed. The results show： 1） The extrados of the bent tube deforms mainly by slip, along with few twinning, and the preferred orientation is similar to that of the initial tube; the intrados of the bent tube experiences compression deformation mainly by {1 012} tensile twinning, and the twinning makes the preferred orientation of wall materials change sharply. 2） The Vickers hardness values of both the extrados and intrados of the samples after bending increase greatly; the Vickers hardness values of the intrados are much higher than those of the extrados, and Vickers hardness values of the RD-TD planes are always higher than those of the RD-LD planes, which are related to the different deformation mechanisms.展开更多
Considering the transverse inertia effect of pile, the vertical soil layer is studied. The wave propagations in the outer and inner soil dynamic response of a large diameter pipe pile in viscoelastic are simulated by ...Considering the transverse inertia effect of pile, the vertical soil layer is studied. The wave propagations in the outer and inner soil dynamic response of a large diameter pipe pile in viscoelastic are simulated by three-dimensional elastodynamic theory and those in the pile are simulated by Rayleigh-Love rod theory. The vertical and radial displacements of the outer and inner soil are obtained by utilizing Laplace transform technique and differentiation on the governing equations of soils. Then, based on the continuous conditions between the pile and soils, the displacements of the pile are derived. The frequency domain velocity admittance and time domain velocity response of the pile top are also presented. The solution is compared to a classical rod model solution to verify the validity. The influences of the radii and Poisson ratio of pile on the transverse inertia effect of pile are analyzed. The parametric study shows that Poisson ratio and outer radius of pile have significant influence on the transverse inertia effect of large diameter pipe piles, while the inner radius has little effect.展开更多
High-strength pipeline steel and large diameter line pipes are often used to increase the capacity of transportation and reduce the cost associated with the construction and operation of long-distance gas pipeline pro...High-strength pipeline steel and large diameter line pipes are often used to increase the capacity of transportation and reduce the cost associated with the construction and operation of long-distance gas pipeline projects. China＇ s initiatives to construct long-distance natural gas pipelines has brought in new opportunities for the development of X80 line pipes. Baosteel has designed the optimum chemical composition of X80 with high niobium and low molybdenum content. In addition, a welding experimental platform and a finite element model （FEM） have supported the development of X80 UOE pipes in an efficient and economical way. The application and recent development of X80 UOE pipes were introduced in this paper. To comply with the requirements of the Second West-East Gas Pipeline Project （2^nd WEPP ）, X80 pipeline steel with low carbon bainite microstructure was developed by utilizing the optimized composition and TMCP process. The matching welding material, welding procedure and UOE forming processes for 1 219mm outside diameter X80 UOE pipes were also developed. More than 340 000 t of X80 UOE pipes were produced and applied in the 2^nd WEPP. Furthermore, to meet the prospective demand for long-distance gas pipelines with an annual transportation capacity of over 40 billion m3 ,larger size X80 UOE pipes with 1 422 mm OD × 30. 8 mm WT were trial produced recently. DWTT performance, the main technical challenge for heavier wall pipes, was improved by using optimized microstructural design. The newly developed X80 pipes can be potentially used for larger transportation capacity pipelines in China.展开更多
large diameter internal thread of high-strength steel（LDITHSS） manufactured by traditional methods always has the problems of low accuracy and short life. Compared with traditional methods, the cold extrusion proces...large diameter internal thread of high-strength steel（LDITHSS） manufactured by traditional methods always has the problems of low accuracy and short life. Compared with traditional methods, the cold extrusion process is an effective means to realize higher accuracy and longer life. The low-cycle fatigue properties of LDITHSS are obtained by experiments, and the initiation and propagation of fatigue cracks are observed by scanning electron microscope（SEM）. Based on the mechanical properties, surface microstructure and residual stress, the strengthening mechanism of cold extruded large diameter internal thread（LDIT） is discussed. The results show that new grains or sub-grains can be formed on the surface of LDIT due to grain segmentation and grain refinement during cold extrusion. The fibrous structures appear as elongated and streamlined along the normal direction of the tooth surface which leads to residual compressive stress on the extruded surface. The maximum tension stress of LDIT after cold extrusion is found to be 192.55 k N. Under low stress cycling, the yield stress on thread increases, the propagation rate of crack reduces, the fatigue life is thus improved significantly with decreasing surface grain diameter and the average fatigue life increases to 45.539×10~3 cycle when the maximum applied load decreases to 120 k N. The low cycle fatigue and strengthening mechanism of cold extruded LDIT revealed by this research has significant importance to promote application of internal thread by cold extrusion processing.展开更多
A systematic experimental research work is done for the stability of sunken large diameter cylinder during construction period. It is the first research that gives the method for assessing the stability of the larger ...A systematic experimental research work is done for the stability of sunken large diameter cylinder during construction period. It is the first research that gives the method for assessing the stability of the larger diameter cylindrical structure, a set of values is derived also for the critical stability indices of the large diameter cylinder sunken to the sandy seabed.展开更多
In order to reveal the mechanism and condition of void closure in large diameter steel rod during horizontal- vertical （H-V） groove rolling process, a three-dimensional thermomechanicaily coupled finite element mode...In order to reveal the mechanism and condition of void closure in large diameter steel rod during horizontal- vertical （H-V） groove rolling process, a three-dimensional thermomechanicaily coupled finite element model was es- tablished for 9-stand H-V groove rolling process aiming at a 4150 mm steel rod production line. A spherical hole with diameter from 2 to 10 mm was preset into the center of continuous casting billet with a rectangle cross section of 300 mmX 360 mm in this model to simulate the void defect, and then finite element analyses were carried out to observe and quantify the void shape evolution in each pass on the three orthogonal coordinate plane sections. The re- suits showed that the void was formed roughly in the reduction and extension directions, and crushed gradually from spherical shape to an approximate ellipsoid, micro-crack and finally to be closed. A quantitative analysis was carried out by using elliptic radii and closure ratio to describe this evolution process; it indicated that the longest axis of the ellipsoid coincided with the rolling line, and the second and third axes were alternatively ihorizontal and vertical on the exit cross section according to change of the reduction direction in H-V groove. The void closure behavior during H- V rolling was more complicated than that of common horizontal rolling, and the influence of groove type and the ex- tension coefficient on the void closure ratio was presented. Finally, a pilot rolling experiment was performed on a 5- stand H-V experimental mill to verify the numerical simulation results, and the experimental results are in good agree- ment with the numerical simulation results.展开更多
The design and manufacture of spiral tap yet are in r esearch stage at present. This paper mainly introduces how to calculate its geom etric parameters and scientific selection of them with vector method. In additio n...The design and manufacture of spiral tap yet are in r esearch stage at present. This paper mainly introduces how to calculate its geom etric parameters and scientific selection of them with vector method. In additio n, an empiric formula of the tool life of spiral tap with large diameter is esta blished by method of correlation. The practice of design, manufacture and applying proves the advantage of spiral tap by the comparison between the spiral tap and common tap with same size. In the application of spiral tap has got better economic effect. The cutting fea ture and economic effect are obvious, that mean spiral tap greatly better than c ommon tap. The bright and wide prospect are going to come. No greatly increasing the ω can be effective to improve the cutting condition. Scientific selection of cutting speed V can increase the tool life of tapping and life of tapping too l.展开更多
This paper deals with the structure, components, characteristics and work principle of a newly developed automatic arc welding machine for saddle joint seams on large diameter cylinders. The equations for designing th...This paper deals with the structure, components, characteristics and work principle of a newly developed automatic arc welding machine for saddle joint seams on large diameter cylinders. The equations for designing the geometry and dimensions of the cam controlling the moving locus of the welding torch have been derived. This welding machine has successfully been used in automatic welding saddle joint seams on boiler drums with good results and low cost.展开更多
The relationship between the arrangement of tungsten-halogen lamps and the uniformity of irradiance received by the wafer is discussed, and a sort of axial-symmetrical lamps-array is designed to guarantee that the irr...The relationship between the arrangement of tungsten-halogen lamps and the uniformity of irradiance received by the wafer is discussed, and a sort of axial-symmetrical lamps-array is designed to guarantee that the irradiation on the edge is approximately the same as the one on the center of the wafer. The magnitude of temperature on the wafer vs. the power of tungsten-halogen lamps is calculated numerically.展开更多
The method for pulling large diameter single crystals with the abovesaid difficulties avoided is developed.Here the free melt surface does not depend on the growing crystal diameter and remains minimal during the whol...The method for pulling large diameter single crystals with the abovesaid difficulties avoided is developed.Here the free melt surface does not depend on the growing crystal diameter and remains minimal during the whole growing process.The essence of this method is that at the stage of radial crystal growth the melt level in the crucible of a variable cross-section(for instance,in a conical crucible)is raised.展开更多
Based on analyzing method of large diameter hard rock drilling at home and abroad, the authors proposed a set of drilling of large diameter hard rock annular coring in low energy consumption, low cost and high efficie...Based on analyzing method of large diameter hard rock drilling at home and abroad, the authors proposed a set of drilling of large diameter hard rock annular coring in low energy consumption, low cost and high efficiency. The prototype of drilling tools was designed and was made. The experimental result of the prototype indicates that this plan and technology are feasible and reach the anticipated object of design. A set of drilling tools has been offered for the constructs of large diameter hard rock coring.展开更多
The construction of shield tunneling method, there are often phenomena such as tool wear, breakage and collapse of shield tunneling machine, which lead to downtime and affect the construction period. In this paper, ba...The construction of shield tunneling method, there are often phenomena such as tool wear, breakage and collapse of shield tunneling machine, which lead to downtime and affect the construction period. In this paper, based on the actual situation of two large diameter mud and water shield tunneling machine entering the warehouse and changing the tool, the amount of tool wear is counted, calculated, analyzed and optimized design. Conclusion: 1. the rationality of tool alloy height;2. the importance of cutting tool layering and reasonable arrangement;3. increase the number of tools on the same track as much as possible;4. the wear limit of the tool is reasonably determined by calculation to provide theoretical support for the frequency and reasonable tool change time of warehousing;5. reasonable arrangement of cutter head tool to avoid the phenomenon of tool waste.展开更多
The analysis and design of a large diameter shaft assembly scheme is composed of pneumatic impact hammer, elevator and supporting trolley;Firstly, align the large-diameter shaft with the bearing hole. At first, let th...The analysis and design of a large diameter shaft assembly scheme is composed of pneumatic impact hammer, elevator and supporting trolley;Firstly, align the large-diameter shaft with the bearing hole. At first, let the large-diameter shaft enter a part of the bearing hole, and then knock the large-diameter shaft with a pneumatic impact hammer to install the large-diameter shaft into the bearing of large equipment. Thus, the labor intensity of manual installation is reduced, and the installation accuracy and production efficiency are improved. The design makes the installation of large-diameter shaft very convenient and simple, greatly improves the installation efficiency of large-diameter shaft and reduces the labor time of workers, and provides a very good solution for the installation of large-scale equipment shafts.展开更多
By analyzing the gas drainage data of 120mm diameter long borehole with high crack and 203mm large-diameter "using hole instead of roadway" gas control technology, the best layer of long borehole with high c...By analyzing the gas drainage data of 120mm diameter long borehole with high crack and 203mm large-diameter "using hole instead of roadway" gas control technology, the best layer of long borehole with high crack zone was found, and the feasibility of replacing high crack drainage was explored through data comparison. It ensures the intensive and efficient production of the mine. The gas control technology of large diameter borehole in coal seam has the advantages of simple technology, fast pore-forming speed and high efficiency, which effectively solves the problem of gas overrun in upper corner, and has reference significance for comprehensive gas control in working face.展开更多
Taking vertical shaft construction of cutter transformation of the Beijing underground diameter shield for example,the design and construction of cutter structure transformation under complex boundary conditions for l...Taking vertical shaft construction of cutter transformation of the Beijing underground diameter shield for example,the design and construction of cutter structure transformation under complex boundary conditions for large diameter shield were discussed.Practice about how to ensure the structure safety of the shaft as well as well-coordinated shield construction was explored,and reliable solutions were provided successfully,which can provide reference for similar projects.展开更多
Machine learning is frequently used in various geotechnical applications nowadays.This study presents a statistics and machine learning model for settlement prediction of helical piles that relates compressive service...Machine learning is frequently used in various geotechnical applications nowadays.This study presents a statistics and machine learning model for settlement prediction of helical piles that relates compressive service load and soil parameters as a group with the pile parameters.Machine learning algorithms such as Decision Trees,Random Forests,AdaBoost,and Artificial Neural Networks(ANN)were used to develop the predictive models.The models were validated using cross-validation techniques and tested on an independent dataset to assess their accuracy and generalizability.Numerical investigation is used here to supplement the field data by simulating various soil conditions and pile geometries that have not been tested in the field.This study compiled numerical results of 3600 models.As the models are well-calibrated and validated,the data from these models can be reasonably assumed to simulate the ground situation.At the end of this study,a comparative analysis of statistic learning and machine learning(ML)was done using the field axial load tests database and numerical investigation on helical piles.It is observed that ML models like Decision Trees and Random Forests provided the better model with R-squared values of 0.92 and 0.96,respectively,for large diameters.The authors believe this study will permit engineers and state agencies to understand this prediction model’s efficacy better,resulting in a more resilient approach to designing large-diameter helical piles for the compressive load.展开更多
This work consists of evaluating the quality of the mechanical parameters of large-diameter steels, i.e. 20, 25, 28 and 32, through a process of recycling scrap metal that fills garages, rubbish dumps, gutters and oth...This work consists of evaluating the quality of the mechanical parameters of large-diameter steels, i.e. 20, 25, 28 and 32, through a process of recycling scrap metal that fills garages, rubbish dumps, gutters and other abandoned sites, as well as imported concrete reinforcing steel sold in the Republic of Guinea. To carry out this important work, a number of mechanical tensile and bending tests and a microscopic analysis combining two devices, an electron microscope and a photographic camera, were carried out. The samples were taken from sampling areas in the major communes of Conakry, namely: Casse Sonfonia, Matoto and Kagbélen. The tensile strength values of the large dimensions 20, 25, 28 and 32 are given in the tables.展开更多
Long steel piles with large diameters have been more widely used in the field of ocean engineering. Owing to the pile with a large diameter, soil plug development during pile driving has great influences on pile drive...Long steel piles with large diameters have been more widely used in the field of ocean engineering. Owing to the pile with a large diameter, soil plug development during pile driving has great influences on pile driveability and bearing capacity. The response of soil plug developed inside the open-ended pipe pile during the dynamic condition of pile-driving is different from the response under the static condition of loading during service. This paper addresses the former aspect. A numerical procedure for soil plug effect prediction and pile driveabihty analysis is proposed and described. By taking into consideration of the pile dimension effect on side and tip resistance, this approach introduces a dimensional coefficient to the conventional static eqnihbrium equations for the plug differential unit and proposes an improved static equity method for the plug effect prediction. At the same time, this approach introduces a simplified model by use of one-dimensional stress wave equation to simulate the interaction between soil plug and pile inner wall. The proposed approach has been applied in practical engineering analyses. Results show that the calculated plug effect and pile driveabihty based on the proposed approach agree well with the observed data.展开更多
基金This paper was supported by National Strategy Key Project, Research and Paradigm on Ecological Harvesting and Regeneration Tech-nique for Northeast Natural Forest (2001BA510B07-02)
文摘The optimum models of harvesting yield and net profits of large diameter trees for broadleaved forest were developed, of which include matrix growth sub-model, harvesting cost and wood price sub-models, based on the data from Hongshi Forestry Bureau, in Changbai Mountain region, Jilin Province, China. The data were measured in 232 permanent sample plots. With the data of permanent sample plots, the parameters of transition probability and ingrowth models were estimated, and some models were compared and partly modified. During the simulation of stand structure, four factors such as largest diameter residual tree （LDT）, the ratio of the number of trees in a given diameter class to those in the next larger diameter class （q）, residual basal area （RBA） and selective cutting cycle （C） were considered. The simulation results showed that the optimum stand structure parameters for large diameter trees are as follows： q is 1.2, LDT is 46cm, RBA is larger than 26 m^2 and selective cutting cycle time （C） is between 10 and 20 years.
基金Projects(50905144,51275415)supported by the National Natural Science Foundation of ChinaProject supported by the Program for New Century Excellent Talents in University,ChinaProject(B08040)supported by the Program of Introducing Talents of Discipline to Universities,China("111"Project)
文摘In order to develop the warming bending technology of the large diameter thin-walled（LDTW） commercial pure titanium alloy CP-Ti tubes, the warm bending mechanism of the extrados and intrados of LDTW CP-Ti tubes was researched. By EBSD analysis and Vickers hardness test, the changes of microstructure and strength of the tubes at different bending temperatures of 293, 423 and 573 K, were analyzed. The results show： 1） The extrados of the bent tube deforms mainly by slip, along with few twinning, and the preferred orientation is similar to that of the initial tube; the intrados of the bent tube experiences compression deformation mainly by {1 012} tensile twinning, and the twinning makes the preferred orientation of wall materials change sharply. 2） The Vickers hardness values of both the extrados and intrados of the samples after bending increase greatly; the Vickers hardness values of the intrados are much higher than those of the extrados, and Vickers hardness values of the RD-TD planes are always higher than those of the RD-LD planes, which are related to the different deformation mechanisms.
基金Project(U1134207)jointly supported by the National Natural Science Foundation and High Speed Railway Key Program of ChinaProject(NCET-12-0843)supported by the Program for New Century Excellent Talents in University of China+1 种基金Projects(51378177,51420105013)supported by the National Natural Science Foundation of ChinaProjects(2015B05014,2014B02814)supported by the Fundamental Research Funds for the Central Universities,China
文摘Considering the transverse inertia effect of pile, the vertical soil layer is studied. The wave propagations in the outer and inner soil dynamic response of a large diameter pipe pile in viscoelastic are simulated by three-dimensional elastodynamic theory and those in the pile are simulated by Rayleigh-Love rod theory. The vertical and radial displacements of the outer and inner soil are obtained by utilizing Laplace transform technique and differentiation on the governing equations of soils. Then, based on the continuous conditions between the pile and soils, the displacements of the pile are derived. The frequency domain velocity admittance and time domain velocity response of the pile top are also presented. The solution is compared to a classical rod model solution to verify the validity. The influences of the radii and Poisson ratio of pile on the transverse inertia effect of pile are analyzed. The parametric study shows that Poisson ratio and outer radius of pile have significant influence on the transverse inertia effect of large diameter pipe piles, while the inner radius has little effect.
文摘High-strength pipeline steel and large diameter line pipes are often used to increase the capacity of transportation and reduce the cost associated with the construction and operation of long-distance gas pipeline projects. China＇ s initiatives to construct long-distance natural gas pipelines has brought in new opportunities for the development of X80 line pipes. Baosteel has designed the optimum chemical composition of X80 with high niobium and low molybdenum content. In addition, a welding experimental platform and a finite element model （FEM） have supported the development of X80 UOE pipes in an efficient and economical way. The application and recent development of X80 UOE pipes were introduced in this paper. To comply with the requirements of the Second West-East Gas Pipeline Project （2^nd WEPP ）, X80 pipeline steel with low carbon bainite microstructure was developed by utilizing the optimized composition and TMCP process. The matching welding material, welding procedure and UOE forming processes for 1 219mm outside diameter X80 UOE pipes were also developed. More than 340 000 t of X80 UOE pipes were produced and applied in the 2^nd WEPP. Furthermore, to meet the prospective demand for long-distance gas pipelines with an annual transportation capacity of over 40 billion m3 ,larger size X80 UOE pipes with 1 422 mm OD × 30. 8 mm WT were trial produced recently. DWTT performance, the main technical challenge for heavier wall pipes, was improved by using optimized microstructural design. The newly developed X80 pipes can be potentially used for larger transportation capacity pipelines in China.
基金Supported by National Natural Science Foundation of China(Grant No.51372216)Jiangsu Science and Technology Plan Project of China(Grant No.BE2015113)Natural Science Foundation of the Jiangsu Higher Education Institutions of China(Grant No.BKJB460016)
文摘large diameter internal thread of high-strength steel（LDITHSS） manufactured by traditional methods always has the problems of low accuracy and short life. Compared with traditional methods, the cold extrusion process is an effective means to realize higher accuracy and longer life. The low-cycle fatigue properties of LDITHSS are obtained by experiments, and the initiation and propagation of fatigue cracks are observed by scanning electron microscope（SEM）. Based on the mechanical properties, surface microstructure and residual stress, the strengthening mechanism of cold extruded large diameter internal thread（LDIT） is discussed. The results show that new grains or sub-grains can be formed on the surface of LDIT due to grain segmentation and grain refinement during cold extrusion. The fibrous structures appear as elongated and streamlined along the normal direction of the tooth surface which leads to residual compressive stress on the extruded surface. The maximum tension stress of LDIT after cold extrusion is found to be 192.55 k N. Under low stress cycling, the yield stress on thread increases, the propagation rate of crack reduces, the fatigue life is thus improved significantly with decreasing surface grain diameter and the average fatigue life increases to 45.539×10~3 cycle when the maximum applied load decreases to 120 k N. The low cycle fatigue and strengthening mechanism of cold extruded LDIT revealed by this research has significant importance to promote application of internal thread by cold extrusion processing.
文摘A systematic experimental research work is done for the stability of sunken large diameter cylinder during construction period. It is the first research that gives the method for assessing the stability of the larger diameter cylindrical structure, a set of values is derived also for the critical stability indices of the large diameter cylinder sunken to the sandy seabed.
基金Sponsored by National Natural Science Foundation of China(51005197,51101136)
文摘In order to reveal the mechanism and condition of void closure in large diameter steel rod during horizontal- vertical （H-V） groove rolling process, a three-dimensional thermomechanicaily coupled finite element model was es- tablished for 9-stand H-V groove rolling process aiming at a 4150 mm steel rod production line. A spherical hole with diameter from 2 to 10 mm was preset into the center of continuous casting billet with a rectangle cross section of 300 mmX 360 mm in this model to simulate the void defect, and then finite element analyses were carried out to observe and quantify the void shape evolution in each pass on the three orthogonal coordinate plane sections. The re- suits showed that the void was formed roughly in the reduction and extension directions, and crushed gradually from spherical shape to an approximate ellipsoid, micro-crack and finally to be closed. A quantitative analysis was carried out by using elliptic radii and closure ratio to describe this evolution process; it indicated that the longest axis of the ellipsoid coincided with the rolling line, and the second and third axes were alternatively ihorizontal and vertical on the exit cross section according to change of the reduction direction in H-V groove. The void closure behavior during H- V rolling was more complicated than that of common horizontal rolling, and the influence of groove type and the ex- tension coefficient on the void closure ratio was presented. Finally, a pilot rolling experiment was performed on a 5- stand H-V experimental mill to verify the numerical simulation results, and the experimental results are in good agree- ment with the numerical simulation results.
文摘The design and manufacture of spiral tap yet are in r esearch stage at present. This paper mainly introduces how to calculate its geom etric parameters and scientific selection of them with vector method. In additio n, an empiric formula of the tool life of spiral tap with large diameter is esta blished by method of correlation. The practice of design, manufacture and applying proves the advantage of spiral tap by the comparison between the spiral tap and common tap with same size. In the application of spiral tap has got better economic effect. The cutting fea ture and economic effect are obvious, that mean spiral tap greatly better than c ommon tap. The bright and wide prospect are going to come. No greatly increasing the ω can be effective to improve the cutting condition. Scientific selection of cutting speed V can increase the tool life of tapping and life of tapping too l.
文摘This paper deals with the structure, components, characteristics and work principle of a newly developed automatic arc welding machine for saddle joint seams on large diameter cylinders. The equations for designing the geometry and dimensions of the cam controlling the moving locus of the welding torch have been derived. This welding machine has successfully been used in automatic welding saddle joint seams on boiler drums with good results and low cost.
基金Foundationfor Key Youth Teachers from Hunan Province(521105237) Natural Science Foundation of HunanUniversity(521101805)
文摘The relationship between the arrangement of tungsten-halogen lamps and the uniformity of irradiance received by the wafer is discussed, and a sort of axial-symmetrical lamps-array is designed to guarantee that the irradiation on the edge is approximately the same as the one on the center of the wafer. The magnitude of temperature on the wafer vs. the power of tungsten-halogen lamps is calculated numerically.
文摘The method for pulling large diameter single crystals with the abovesaid difficulties avoided is developed.Here the free melt surface does not depend on the growing crystal diameter and remains minimal during the whole growing process.The essence of this method is that at the stage of radial crystal growth the melt level in the crucible of a variable cross-section(for instance,in a conical crucible)is raised.
文摘Based on analyzing method of large diameter hard rock drilling at home and abroad, the authors proposed a set of drilling of large diameter hard rock annular coring in low energy consumption, low cost and high efficiency. The prototype of drilling tools was designed and was made. The experimental result of the prototype indicates that this plan and technology are feasible and reach the anticipated object of design. A set of drilling tools has been offered for the constructs of large diameter hard rock coring.
文摘The construction of shield tunneling method, there are often phenomena such as tool wear, breakage and collapse of shield tunneling machine, which lead to downtime and affect the construction period. In this paper, based on the actual situation of two large diameter mud and water shield tunneling machine entering the warehouse and changing the tool, the amount of tool wear is counted, calculated, analyzed and optimized design. Conclusion: 1. the rationality of tool alloy height;2. the importance of cutting tool layering and reasonable arrangement;3. increase the number of tools on the same track as much as possible;4. the wear limit of the tool is reasonably determined by calculation to provide theoretical support for the frequency and reasonable tool change time of warehousing;5. reasonable arrangement of cutter head tool to avoid the phenomenon of tool waste.
文摘The analysis and design of a large diameter shaft assembly scheme is composed of pneumatic impact hammer, elevator and supporting trolley;Firstly, align the large-diameter shaft with the bearing hole. At first, let the large-diameter shaft enter a part of the bearing hole, and then knock the large-diameter shaft with a pneumatic impact hammer to install the large-diameter shaft into the bearing of large equipment. Thus, the labor intensity of manual installation is reduced, and the installation accuracy and production efficiency are improved. The design makes the installation of large-diameter shaft very convenient and simple, greatly improves the installation efficiency of large-diameter shaft and reduces the labor time of workers, and provides a very good solution for the installation of large-scale equipment shafts.
文摘By analyzing the gas drainage data of 120mm diameter long borehole with high crack and 203mm large-diameter "using hole instead of roadway" gas control technology, the best layer of long borehole with high crack zone was found, and the feasibility of replacing high crack drainage was explored through data comparison. It ensures the intensive and efficient production of the mine. The gas control technology of large diameter borehole in coal seam has the advantages of simple technology, fast pore-forming speed and high efficiency, which effectively solves the problem of gas overrun in upper corner, and has reference significance for comprehensive gas control in working face.
文摘Taking vertical shaft construction of cutter transformation of the Beijing underground diameter shield for example,the design and construction of cutter structure transformation under complex boundary conditions for large diameter shield were discussed.Practice about how to ensure the structure safety of the shaft as well as well-coordinated shield construction was explored,and reliable solutions were provided successfully,which can provide reference for similar projects.
文摘Machine learning is frequently used in various geotechnical applications nowadays.This study presents a statistics and machine learning model for settlement prediction of helical piles that relates compressive service load and soil parameters as a group with the pile parameters.Machine learning algorithms such as Decision Trees,Random Forests,AdaBoost,and Artificial Neural Networks(ANN)were used to develop the predictive models.The models were validated using cross-validation techniques and tested on an independent dataset to assess their accuracy and generalizability.Numerical investigation is used here to supplement the field data by simulating various soil conditions and pile geometries that have not been tested in the field.This study compiled numerical results of 3600 models.As the models are well-calibrated and validated,the data from these models can be reasonably assumed to simulate the ground situation.At the end of this study,a comparative analysis of statistic learning and machine learning(ML)was done using the field axial load tests database and numerical investigation on helical piles.It is observed that ML models like Decision Trees and Random Forests provided the better model with R-squared values of 0.92 and 0.96,respectively,for large diameters.The authors believe this study will permit engineers and state agencies to understand this prediction model’s efficacy better,resulting in a more resilient approach to designing large-diameter helical piles for the compressive load.
文摘This work consists of evaluating the quality of the mechanical parameters of large-diameter steels, i.e. 20, 25, 28 and 32, through a process of recycling scrap metal that fills garages, rubbish dumps, gutters and other abandoned sites, as well as imported concrete reinforcing steel sold in the Republic of Guinea. To carry out this important work, a number of mechanical tensile and bending tests and a microscopic analysis combining two devices, an electron microscope and a photographic camera, were carried out. The samples were taken from sampling areas in the major communes of Conakry, namely: Casse Sonfonia, Matoto and Kagbélen. The tensile strength values of the large dimensions 20, 25, 28 and 32 are given in the tables.
基金supported by the National Natural Science Foundation of China (Grant No.50309009)the National High Technology Research and Development Program of China(863 Program,Grant No.2004AA616100)
文摘Long steel piles with large diameters have been more widely used in the field of ocean engineering. Owing to the pile with a large diameter, soil plug development during pile driving has great influences on pile driveability and bearing capacity. The response of soil plug developed inside the open-ended pipe pile during the dynamic condition of pile-driving is different from the response under the static condition of loading during service. This paper addresses the former aspect. A numerical procedure for soil plug effect prediction and pile driveabihty analysis is proposed and described. By taking into consideration of the pile dimension effect on side and tip resistance, this approach introduces a dimensional coefficient to the conventional static eqnihbrium equations for the plug differential unit and proposes an improved static equity method for the plug effect prediction. At the same time, this approach introduces a simplified model by use of one-dimensional stress wave equation to simulate the interaction between soil plug and pile inner wall. The proposed approach has been applied in practical engineering analyses. Results show that the calculated plug effect and pile driveabihty based on the proposed approach agree well with the observed data.
