The quantitative analysis of substructure in the martensite/bainite mixed structure, which is obtained from low-carbon NiCrMoV steels under different cooling conditions, was made by means of optical microscope （OM）,...The quantitative analysis of substructure in the martensite/bainite mixed structure, which is obtained from low-carbon NiCrMoV steels under different cooling conditions, was made by means of optical microscope （OM）, scanning electron microscope （SEM）, electron backscatter diffraction （EBSD）, and transmission electron microscope （TEM）, in order to research the effect on toughness. The test results indicate that the toughness of the steel is en- hanced with the decrease in the packet and block size under the condition of the same prior austenite grain size mixed with different ratios of martensite and bainite while the lath width is about 0.38μm. The calculation shows that both the packet and block boundaries have the same hindering effect on crack extension. Furthermore, the effect of the block width on impact energy is much larger than that of the packet. Therefore, the block can be used as microstruc- tural substructure to affect the toughness in low-carbon martensite steels, suggesting that the block size is ＂the effective grain size＂ for controlling toughness.展开更多
Softening behavior of lath martensitic steels is related to the coarsening of laths and dislocation evolution during cyclic deformation.Involving the physical mechanism,we developed a dislocation-based model to study ...Softening behavior of lath martensitic steels is related to the coarsening of laths and dislocation evolution during cyclic deformation.Involving the physical mechanism,we developed a dislocation-based model to study the cyclic plastic response for lath martensitic steels.For a block,we proposed an interfacial dislocation evolution model to physically present the interaction between mobile dislocations in the block and interfacial dislocations by considering the coarsening mechanism of the laths.Moreover,the evolution behavior of backstress caused by dislocation pile up at the block boundary has been considered.Then,a hierarchical model based on the elastic-viscoplastic self-consistent(EVPSC)theory is developed,which can realize the scale transition among representative volume element(RVE),prior austenite grains(PAGs)and blocks.According to the proposed model,the effective mechanical responses including the cyclic hysteretic loop and peak stress at different cycles for lath martensitic steel have been theoretically predicted and investigated.展开更多
In order to provide reliable data for the dynamic design or modification of a tool machine,the dynamic character- istics of the headstock,which is the main component to bear moment,must be obtained precisely.In the pa...In order to provide reliable data for the dynamic design or modification of a tool machine,the dynamic character- istics of the headstock,which is the main component to bear moment,must be obtained precisely.In the paper,the method based on the combination of calculation mode and experiment mode is proposed to analyze the dynamic characteristics of the headstock.The modal parameters and the mode shapes are calculated by ANSYS7.1 software.According to the FEM calculating results,the ex- periment parameters can be selected correctly.The modal parameters of the headstock have to be calculated and identified precisely. On the basis of these modal parameters,the faults of the headstock are shown and its weak points of design are illustrated.A con- clusion is drawn that some reasonable reinforce positions could greatly improve the dynamic characteristics of the system and this ap- proach is proved to be precise and reliable.展开更多
The current research of reliability allocation of CNC lathes always treat CNC lathes as independent series systems. However, CNC lathes are complex systems in the actual situation. Failure correlation is rarely consid...The current research of reliability allocation of CNC lathes always treat CNC lathes as independent series systems. However, CNC lathes are complex systems in the actual situation. Failure correlation is rarely considered when reliabil?ity allocation is conducted. In this paper, drawbacks of reliability model based on failure independence assumption are illustrated, after which, reliability model of CNC lathes considering failure correlation of subsystems is established based on Copula theory, which is an improvement of traditional reliability model of series systems. As the failure time of CNC lathes often obeys Weibull or exponential distribution, Gumbel Copula is selected to build correlation model. After that, a reliability allocation method considering failure correlation is analyzed based on the model established before. Reliability goal is set first and then failure rates are allocated to subsystems according to the allocation vector through solving the correlation model. Reliability allocation is conducted for t = 1. A real case of a CNC lathe and a numerical case are presented together to illustrate the advantages of the reliability model established consider?ing failure correlation and the corresponding allocation method. It shows that the model accords to facts and real working condition more, and failure rates allocated to all the subsystems are increased to some extent. This research proposes a reliability allocation method which takes failure correlation among subsystems of CNC lathes into consid?eration, and costs for design and manufacture could be decreased.展开更多
According to the reliable data of sixteen CNC lathes, each reliable index of the serial CNC lathes is evaluated before tackling and after tackling. According to the failure analysis, reliable improvement measures of t...According to the reliable data of sixteen CNC lathes, each reliable index of the serial CNC lathes is evaluated before tackling and after tackling. According to the failure analysis, reliable improvement measures of the serial CNC lathes are put forward.展开更多
The tempering behavior was experimentally studied in lath martensitic wear-resistant steels with various Mo/Ni contents after tempering at different temperatures from 200to 600℃.It is shown that a good combination of...The tempering behavior was experimentally studied in lath martensitic wear-resistant steels with various Mo/Ni contents after tempering at different temperatures from 200to 600℃.It is shown that a good combination of hardness（HV）（420-450）and-20℃impact toughness（38-70J）can be obtained after quenching and tempering at 200-250 ℃.The microstructure at this temperature is lath structure with rod-like and/or flake-likeε-carbide with about 10nm in width and 100nm in length in the matrix,and the fracture mechanism is quasi-cleavage fracture combining with ductile fracture.Tempering at temperature from 300to 400℃results in the primary quasi-cleavagefracture due to the carbide transformation from resolved retained austenite and impurity segregation between laths or blocks.However,when the tempering temperature is higher than 500℃,the hardness（HV）is lower than 330 and the fracture mechanism changes to ductile fracture due to the spheroidization and coarsening of cementite.Additions of Mo and Ni have no significant effects on the carbides morphologies at low tempering temperatures,but improve the resistance to softening and embrittling for steels when tempered at above 350℃.展开更多
Based on the mechanism of chip breaking and the principle of semi-solid thixomolding, the lathe process of AZ91D magnesium alloys chips used in semi-solid thixotropic injection molding process was studied. With three ...Based on the mechanism of chip breaking and the principle of semi-solid thixomolding, the lathe process of AZ91D magnesium alloys chips used in semi-solid thixotropic injection molding process was studied. With three kinds of turning tools, such as 31303C5, 31003C and 31303C, different chips were gotten. And by one tool with different lathe parameters, different chips were gotten. The results show that, under the needed condition of the thixotropic injection molding machine, the ideal chips are gotten and the size of magnesium alloy chips must be about 35mm, and the turning tool is chosen, whose chip breaker groove is narrower and the depth of cutting is more than 3mm as well as the amount of feed is larger than 0.3mm. The deformation occurs on the microstructure of the chips, and the residual stress is important to the later microstructure of semi-solid state in injection molding.展开更多
Reliability allocation of computerized numerical controlled（CNC）lathes is very important in industry.Traditional allocation methods only focus on high-failure rate components rather than moderate failure rate compon...Reliability allocation of computerized numerical controlled（CNC）lathes is very important in industry.Traditional allocation methods only focus on high-failure rate components rather than moderate failure rate components,which is not applicable in some conditions.Aiming at solving the problem of CNC lathes reliability allocating,a comprehensive reliability allocation method based on cubic transformed functions of failure modes and effects analysis（FMEA）is presented.Firstly,conventional reliability allocation methods are introduced.Then the limitations of direct combination of comprehensive allocation method with the exponential transformed FMEA method are investigated.Subsequently,a cubic transformed function is established in order to overcome these limitations.Properties of the new transformed functions are discussed by considering the failure severity and the failure occurrence.Designers can choose appropriate transform amplitudes according to their requirements.Finally,a CNC lathe and a spindle system are used as an example to verify the new allocation method.Seven criteria are considered to compare the results of the new method with traditional methods.The allocation results indicate that the new method is more flexible than traditional methods.By employing the new cubic transformed function,the method covers a wider range of problems in CNC reliability allocation without losing the advantages of traditional methods.展开更多
This paper introduces a system of computer aided assembly process planning for spindle box of NC lathe. The method of describing assembly information and generating assembly process drawing is presented. The principle...This paper introduces a system of computer aided assembly process planning for spindle box of NC lathe. The method of describing assembly information and generating assembly process drawing is presented. The principles of decision for assembly sequence ar展开更多
The lathes are basic machine tools for manufacturing cylindrical parts. In recent years, the DLseries computer numerical control(CNC) heavy-duty horizontal lathes(HDHLs) have been widely used in the transportation, en...The lathes are basic machine tools for manufacturing cylindrical parts. In recent years, the DLseries computer numerical control(CNC) heavy-duty horizontal lathes(HDHLs) have been widely used in the transportation, energy and aviation industries. High availability of the CNC heavy-duty lathes is demanded to guarantee the efficiency and benefit of these manufacturing industries. As one of the key subsystems of the HDHLs, the feeding control system is studied in this paper on reliability modeling and reliability analysis. The fault tree analysis(FTA) method is used for reliability modelling of the feeding control system. Considering the multiple common cause failure groups(CCFGs) existing in the system, a modified beta factor parametric model is introduced to model the common cause failure(CCF) in system. The reliability of feeding control system is then obtained and the effect of CCF on the reliability of the whole system is studied as well.展开更多
In the present investigation,twinned substructures within lath martensite of two water quenched steels(0.2 wt.%C and 0.8 wt.%C)were studied.The lath martensite has typical hierarchical packet-block-lath with dislocati...In the present investigation,twinned substructures within lath martensite of two water quenched steels(0.2 wt.%C and 0.8 wt.%C)were studied.The lath martensite has typical hierarchical packet-block-lath with dislocation substructure.Besides,laths that are misoriented by<011>/70.5°or<111>/60° and bordered by{011}plane,namely twinned laths,are observed,of which the density increases and the scale decreases as more carbons were presented.Such twinned laths have body centered cubic(bcc)crystal structure,belonging to twinned variants following the classical Kurdjumov-Sachs(K-S)orientation relationship with respect to the parent austenite.Unlike bcc{112}<111>twins,twinned variants produce strong double diffraction and in turn the extra diffraction spots that are commonly observed in the martensite in steels with wide range of carbon contents.展开更多
In this paper,low-and high-strength lath martensite(350 and 640 HV)was fabricated in an IF steel via high pressure martensitic transformation.The microstructure and the softening during their tempering from 200°C...In this paper,low-and high-strength lath martensite(350 and 640 HV)was fabricated in an IF steel via high pressure martensitic transformation.The microstructure and the softening during their tempering from 200°C to 800°C for 1 h were systematically investigated.A carbon-irrelevant tempering process was proposed,exhibiting a three-stage structural evolution pattern depending upon the tempering de-gree(1-(HV-HV FP)/(HV NP-HV FP),where the HV is the instant hardness,HV NP is the non-tempered hard-ness and HV FP is the fully tempered hardness):(1)low tempered(<10%),removing the loose dislocations and dislocation boundaries within martensitic variants;(2)medium tempered(10%-50%),eliminating the martensitic variant laths via the migration of their terminal tips;(3)highly tempered(>50%),clearing up the remained variant laths via the migration of the triple junctions.Martensite-type microstructure is tailored by low-index lamellar variant boundaries and is thus intrinsically thermally stable,whereas the mobile terminal tips decrease the tempering resistance.The underlying mechanism for such carbon-irrelevant process was discussed and the potential effect on the tempering behavior of carbon-contained martensite was highlighted.展开更多
Making an analysis for vibration modal and frequency response of the lathe spindle,respectively by using finite element method based on ANSYS and experiment of CA6140 type lathe in machining,and the calculation result...Making an analysis for vibration modal and frequency response of the lathe spindle,respectively by using finite element method based on ANSYS and experiment of CA6140 type lathe in machining,and the calculation results are compared and analyzed,which verified the accuracy of ANSYS method. Numerical simulation and experimental results show that: Spindle in the first order and fifth order are prone to resonance,but did not reach resonance,the low order natural frequency have more effect than the high order natural frequency of the spindle vibration; by the experiments can conclude that the maximum vibration of the main shaft in the working state is mainly concentrated in the vicinity of its two ends,therefore,the improved bearing is an important way to reduce the vibration of the main shaft and ensure the machining accuracy,and the research results can provide a theoretical reference for the structural optimization design of the lathe.展开更多
For virtually realizing the graphic realism display of DXF machine parts, in AutoCAD2007 graphic drawing environment, an interactive experimental method was taken to realize the display of graphic in DXF, which was ta...For virtually realizing the graphic realism display of DXF machine parts, in AutoCAD2007 graphic drawing environment, an interactive experimental method was taken to realize the display of graphic in DXF, which was taken as the data-exchanged interface and source. Based on depth analysis of DXF data structure, take one drawing of DXF lathe turning rotational part asthe test piece. By VC＋＋6.0 programming, part＇s geometry information could be obtained. Through data processing, 3D data of the test piece could be generated, which is based on 2D data of DXF test piece. Then, OpenGL graphic processing technologies （light, material, texture, map, et al.） were applied on the 3D display of test piece from DXF files or program modules. Finally based on the test report, results of the system functions were shared to prove the realization of system design, and the feasibility of algorithms used. In the developed software, Machine Designers could get a full view of machine parts, and do some proper modifications. The study content and results of our work have some theory and practical significance on the application of program design in the practical projects.展开更多
According to the technique requests of the brake caliper in the process of production, a special fixture of float brake caliper has been developed based on 3 D design in this paper. The development process and verifie...According to the technique requests of the brake caliper in the process of production, a special fixture of float brake caliper has been developed based on 3 D design in this paper. The development process and verified data from 3D modeling and kinematics simulation for this special fixture show that this 3D-designed process can conveniently forecast the assembly interference of the fixture and accurately add the mass of lead brick before the prototype is made. In this way the flutter caused by the unbalanced lathe fixture can be eliminated and the precision of run-out tolerance in cylinder hole compared with machine tool spindle can be improved, thus the processing quality of the cylinder hole in a brake caliper can be greatly guaranteed.展开更多
Many of the high strength,high toughness steels in use or under development are alloy steels with dislocated lath martensitic structures.These microstructures are visually complex,and are difficult to categorize in th...Many of the high strength,high toughness steels in use or under development are alloy steels with dislocated lath martensitic structures.These microstructures are visually complex,and are difficult to categorize in the detail needed to clarify the structure-property relations.However,substantial progress has been made in recent years.In particular,it is now clear that the martensite block element sets the effective grain size that must be controlled to resist brittleness by cleavage fracture.In previous papers at this conference I have discussed the nature and importance of the block structure.In this study I discuss how the block size can be controlled by thermal treatments to achieve superior properties.展开更多
An importance analysis model for computer numerical control（CNC）lathe subsystems was proposed.The model was based on technique for order preference by similarity to an ideal solution（TOPSIS）and considered the stru...An importance analysis model for computer numerical control（CNC）lathe subsystems was proposed.The model was based on technique for order preference by similarity to an ideal solution（TOPSIS）and considered the structure correlation between subsystems and the complete machine,the fault correlation of each subsystem and so on.The model can obtain a comprehensive sequencing of subsystems based on their importance to the complete machine.It lays a theoretical foundation for reliability allocation.展开更多
Equivalent ways commonly used in engineering works are not effective to estimate the reliability of tandem system based on L-M method. One modified L-M method is an important means to estimate the reliability of CNC l...Equivalent ways commonly used in engineering works are not effective to estimate the reliability of tandem system based on L-M method. One modified L-M method is an important means to estimate the reliability of CNC lathes. A method of using two named confidence limits for the estimation is put forward. Fitting resuits of the sub-systems of CNC machine tools are estimated. And the scattered level of confidence limits facing the reliability matrix of sub-systems can be clearly seen.展开更多
文摘The quantitative analysis of substructure in the martensite/bainite mixed structure, which is obtained from low-carbon NiCrMoV steels under different cooling conditions, was made by means of optical microscope （OM）, scanning electron microscope （SEM）, electron backscatter diffraction （EBSD）, and transmission electron microscope （TEM）, in order to research the effect on toughness. The test results indicate that the toughness of the steel is en- hanced with the decrease in the packet and block size under the condition of the same prior austenite grain size mixed with different ratios of martensite and bainite while the lath width is about 0.38μm. The calculation shows that both the packet and block boundaries have the same hindering effect on crack extension. Furthermore, the effect of the block width on impact energy is much larger than that of the packet. Therefore, the block can be used as microstruc- tural substructure to affect the toughness in low-carbon martensite steels, suggesting that the block size is ＂the effective grain size＂ for controlling toughness.
基金supported by the National Natural Science Foundation of China(Grant Nos.11988102,12002005,11632001,11521202)the Science Challenge Project(Grant No.TZ2018001).
文摘Softening behavior of lath martensitic steels is related to the coarsening of laths and dislocation evolution during cyclic deformation.Involving the physical mechanism,we developed a dislocation-based model to study the cyclic plastic response for lath martensitic steels.For a block,we proposed an interfacial dislocation evolution model to physically present the interaction between mobile dislocations in the block and interfacial dislocations by considering the coarsening mechanism of the laths.Moreover,the evolution behavior of backstress caused by dislocation pile up at the block boundary has been considered.Then,a hierarchical model based on the elastic-viscoplastic self-consistent(EVPSC)theory is developed,which can realize the scale transition among representative volume element(RVE),prior austenite grains(PAGs)and blocks.According to the proposed model,the effective mechanical responses including the cyclic hysteretic loop and peak stress at different cycles for lath martensitic steel have been theoretically predicted and investigated.
基金The financial support for this research is provided by the Natural Science foundation of China(No.50475117)Youth Natural Science Fund of Shanxi(No.20011021)
文摘In order to provide reliable data for the dynamic design or modification of a tool machine,the dynamic character- istics of the headstock,which is the main component to bear moment,must be obtained precisely.In the paper,the method based on the combination of calculation mode and experiment mode is proposed to analyze the dynamic characteristics of the headstock.The modal parameters and the mode shapes are calculated by ANSYS7.1 software.According to the FEM calculating results,the ex- periment parameters can be selected correctly.The modal parameters of the headstock have to be calculated and identified precisely. On the basis of these modal parameters,the faults of the headstock are shown and its weak points of design are illustrated.A con- clusion is drawn that some reasonable reinforce positions could greatly improve the dynamic characteristics of the system and this ap- proach is proved to be precise and reliable.
基金National Natural Science Foundation of China(Grant Nos.51135003,U1234208)National Basic Research Program of China(973 Program,Grant No.2014CB046303)+3 种基金High-class CNC Machine Tools and Basic Manufacturing Equipment of Important National Science and Technology Specific Projects(Grant No.2013ZX04011-011)National Key Laboratory of Mechanical System and Vibration Project(Grant No.MSV201402)Scientific Research Business Fund of Central Colleges and Universities(Grant No.N150304006)Excellent Talents Support Program for Colleges and Universities in Liaoning Province of China(Grant No.LJQ2014030)
文摘The current research of reliability allocation of CNC lathes always treat CNC lathes as independent series systems. However, CNC lathes are complex systems in the actual situation. Failure correlation is rarely considered when reliabil?ity allocation is conducted. In this paper, drawbacks of reliability model based on failure independence assumption are illustrated, after which, reliability model of CNC lathes considering failure correlation of subsystems is established based on Copula theory, which is an improvement of traditional reliability model of series systems. As the failure time of CNC lathes often obeys Weibull or exponential distribution, Gumbel Copula is selected to build correlation model. After that, a reliability allocation method considering failure correlation is analyzed based on the model established before. Reliability goal is set first and then failure rates are allocated to subsystems according to the allocation vector through solving the correlation model. Reliability allocation is conducted for t = 1. A real case of a CNC lathe and a numerical case are presented together to illustrate the advantages of the reliability model established consider?ing failure correlation and the corresponding allocation method. It shows that the model accords to facts and real working condition more, and failure rates allocated to all the subsystems are increased to some extent. This research proposes a reliability allocation method which takes failure correlation among subsystems of CNC lathes into consid?eration, and costs for design and manufacture could be decreased.
文摘According to the reliable data of sixteen CNC lathes, each reliable index of the serial CNC lathes is evaluated before tackling and after tackling. According to the failure analysis, reliable improvement measures of the serial CNC lathes are put forward.
基金Sponsored by National Basic Research Program(973Program)of China(2010CB630800)
文摘The tempering behavior was experimentally studied in lath martensitic wear-resistant steels with various Mo/Ni contents after tempering at different temperatures from 200to 600℃.It is shown that a good combination of hardness（HV）（420-450）and-20℃impact toughness（38-70J）can be obtained after quenching and tempering at 200-250 ℃.The microstructure at this temperature is lath structure with rod-like and/or flake-likeε-carbide with about 10nm in width and 100nm in length in the matrix,and the fracture mechanism is quasi-cleavage fracture combining with ductile fracture.Tempering at temperature from 300to 400℃results in the primary quasi-cleavagefracture due to the carbide transformation from resolved retained austenite and impurity segregation between laths or blocks.However,when the tempering temperature is higher than 500℃,the hardness（HV）is lower than 330 and the fracture mechanism changes to ductile fracture due to the spheroidization and coarsening of cementite.Additions of Mo and Ni have no significant effects on the carbides morphologies at low tempering temperatures,but improve the resistance to softening and embrittling for steels when tempered at above 350℃.
文摘Based on the mechanism of chip breaking and the principle of semi-solid thixomolding, the lathe process of AZ91D magnesium alloys chips used in semi-solid thixotropic injection molding process was studied. With three kinds of turning tools, such as 31303C5, 31003C and 31303C, different chips were gotten. And by one tool with different lathe parameters, different chips were gotten. The results show that, under the needed condition of the thixotropic injection molding machine, the ideal chips are gotten and the size of magnesium alloy chips must be about 35mm, and the turning tool is chosen, whose chip breaker groove is narrower and the depth of cutting is more than 3mm as well as the amount of feed is larger than 0.3mm. The deformation occurs on the microstructure of the chips, and the residual stress is important to the later microstructure of semi-solid state in injection molding.
基金Supported by National Natural Science Foundation of China(Grant Nos.51135003,51205050,U1234208)Key National Science & Technology Special Project on"High-Grade CNC Machine Tools and Basic Manufacturing Equipments"(Grant No.2013ZX04011011)+1 种基金Research Fund for the Doctoral Program of Higher Education of China(Grant No.20110042120020)Fundamental Research Funds for the Central
文摘Reliability allocation of computerized numerical controlled（CNC）lathes is very important in industry.Traditional allocation methods only focus on high-failure rate components rather than moderate failure rate components,which is not applicable in some conditions.Aiming at solving the problem of CNC lathes reliability allocating,a comprehensive reliability allocation method based on cubic transformed functions of failure modes and effects analysis（FMEA）is presented.Firstly,conventional reliability allocation methods are introduced.Then the limitations of direct combination of comprehensive allocation method with the exponential transformed FMEA method are investigated.Subsequently,a cubic transformed function is established in order to overcome these limitations.Properties of the new transformed functions are discussed by considering the failure severity and the failure occurrence.Designers can choose appropriate transform amplitudes according to their requirements.Finally,a CNC lathe and a spindle system are used as an example to verify the new allocation method.Seven criteria are considered to compare the results of the new method with traditional methods.The allocation results indicate that the new method is more flexible than traditional methods.By employing the new cubic transformed function,the method covers a wider range of problems in CNC reliability allocation without losing the advantages of traditional methods.
文摘This paper introduces a system of computer aided assembly process planning for spindle box of NC lathe. The method of describing assembly information and generating assembly process drawing is presented. The principles of decision for assembly sequence ar
基金the National Science and Technology Major Project of China(No.2014ZX04014-011)
文摘The lathes are basic machine tools for manufacturing cylindrical parts. In recent years, the DLseries computer numerical control(CNC) heavy-duty horizontal lathes(HDHLs) have been widely used in the transportation, energy and aviation industries. High availability of the CNC heavy-duty lathes is demanded to guarantee the efficiency and benefit of these manufacturing industries. As one of the key subsystems of the HDHLs, the feeding control system is studied in this paper on reliability modeling and reliability analysis. The fault tree analysis(FTA) method is used for reliability modelling of the feeding control system. Considering the multiple common cause failure groups(CCFGs) existing in the system, a modified beta factor parametric model is introduced to model the common cause failure(CCF) in system. The reliability of feeding control system is then obtained and the effect of CCF on the reliability of the whole system is studied as well.
基金supported financially by the Hundred Outstanding Creative Talents Projects in Hebei University,Chinathe Project Program of Heavy Machinery Collaborative Innovation Center,the National Natural Science Foundation(Grant No.51231006,51171182 and 51471039)。
文摘In the present investigation,twinned substructures within lath martensite of two water quenched steels(0.2 wt.%C and 0.8 wt.%C)were studied.The lath martensite has typical hierarchical packet-block-lath with dislocation substructure.Besides,laths that are misoriented by<011>/70.5°or<111>/60° and bordered by{011}plane,namely twinned laths,are observed,of which the density increases and the scale decreases as more carbons were presented.Such twinned laths have body centered cubic(bcc)crystal structure,belonging to twinned variants following the classical Kurdjumov-Sachs(K-S)orientation relationship with respect to the parent austenite.Unlike bcc{112}<111>twins,twinned variants produce strong double diffraction and in turn the extra diffraction spots that are commonly observed in the martensite in steels with wide range of carbon contents.
基金the Natural Science Foundation-Steel and Iron Foundation of Hebei Province(No.E2021203051)the Hundred Outstanding Creative Talents Projects in Universities of Hebei Province,China,and the Project Program of Heavy Machinery Collaborative Innovation Center,China.
文摘In this paper,low-and high-strength lath martensite(350 and 640 HV)was fabricated in an IF steel via high pressure martensitic transformation.The microstructure and the softening during their tempering from 200°C to 800°C for 1 h were systematically investigated.A carbon-irrelevant tempering process was proposed,exhibiting a three-stage structural evolution pattern depending upon the tempering de-gree(1-(HV-HV FP)/(HV NP-HV FP),where the HV is the instant hardness,HV NP is the non-tempered hard-ness and HV FP is the fully tempered hardness):(1)low tempered(<10%),removing the loose dislocations and dislocation boundaries within martensitic variants;(2)medium tempered(10%-50%),eliminating the martensitic variant laths via the migration of their terminal tips;(3)highly tempered(>50%),clearing up the remained variant laths via the migration of the triple junctions.Martensite-type microstructure is tailored by low-index lamellar variant boundaries and is thus intrinsically thermally stable,whereas the mobile terminal tips decrease the tempering resistance.The underlying mechanism for such carbon-irrelevant process was discussed and the potential effect on the tempering behavior of carbon-contained martensite was highlighted.
基金financially supported by Independent Innovation Research Fund of Wuhan University of Technology(No.2014-ND-B1-09)
文摘Making an analysis for vibration modal and frequency response of the lathe spindle,respectively by using finite element method based on ANSYS and experiment of CA6140 type lathe in machining,and the calculation results are compared and analyzed,which verified the accuracy of ANSYS method. Numerical simulation and experimental results show that: Spindle in the first order and fifth order are prone to resonance,but did not reach resonance,the low order natural frequency have more effect than the high order natural frequency of the spindle vibration; by the experiments can conclude that the maximum vibration of the main shaft in the working state is mainly concentrated in the vicinity of its two ends,therefore,the improved bearing is an important way to reduce the vibration of the main shaft and ensure the machining accuracy,and the research results can provide a theoretical reference for the structural optimization design of the lathe.
文摘For virtually realizing the graphic realism display of DXF machine parts, in AutoCAD2007 graphic drawing environment, an interactive experimental method was taken to realize the display of graphic in DXF, which was taken as the data-exchanged interface and source. Based on depth analysis of DXF data structure, take one drawing of DXF lathe turning rotational part asthe test piece. By VC＋＋6.0 programming, part＇s geometry information could be obtained. Through data processing, 3D data of the test piece could be generated, which is based on 2D data of DXF test piece. Then, OpenGL graphic processing technologies （light, material, texture, map, et al.） were applied on the 3D display of test piece from DXF files or program modules. Finally based on the test report, results of the system functions were shared to prove the realization of system design, and the feasibility of algorithms used. In the developed software, Machine Designers could get a full view of machine parts, and do some proper modifications. The study content and results of our work have some theory and practical significance on the application of program design in the practical projects.
文摘According to the technique requests of the brake caliper in the process of production, a special fixture of float brake caliper has been developed based on 3 D design in this paper. The development process and verified data from 3D modeling and kinematics simulation for this special fixture show that this 3D-designed process can conveniently forecast the assembly interference of the fixture and accurately add the mass of lead brick before the prototype is made. In this way the flutter caused by the unbalanced lathe fixture can be eliminated and the precision of run-out tolerance in cylinder hole compared with machine tool spindle can be improved, thus the processing quality of the cylinder hole in a brake caliper can be greatly guaranteed.
文摘Many of the high strength,high toughness steels in use or under development are alloy steels with dislocated lath martensitic structures.These microstructures are visually complex,and are difficult to categorize in the detail needed to clarify the structure-property relations.However,substantial progress has been made in recent years.In particular,it is now clear that the martensite block element sets the effective grain size that must be controlled to resist brittleness by cleavage fracture.In previous papers at this conference I have discussed the nature and importance of the block structure.In this study I discuss how the block size can be controlled by thermal treatments to achieve superior properties.
基金Supported by the Project of Jilin Province(20150101025JC)the National Natural Science Foundation of China(51175222)
文摘An importance analysis model for computer numerical control（CNC）lathe subsystems was proposed.The model was based on technique for order preference by similarity to an ideal solution（TOPSIS）and considered the structure correlation between subsystems and the complete machine,the fault correlation of each subsystem and so on.The model can obtain a comprehensive sequencing of subsystems based on their importance to the complete machine.It lays a theoretical foundation for reliability allocation.
基金Sponsored by the National Natural Science Foundation of China(Grant No.40774048)
文摘Equivalent ways commonly used in engineering works are not effective to estimate the reliability of tandem system based on L-M method. One modified L-M method is an important means to estimate the reliability of CNC lathes. A method of using two named confidence limits for the estimation is put forward. Fitting resuits of the sub-systems of CNC machine tools are estimated. And the scattered level of confidence limits facing the reliability matrix of sub-systems can be clearly seen.
