The corresponding positions of different metal plastic working processes in the plane stress state on a Mises yield ellipse are described.The paper points out that the forming of a workpiece inside its die is correspo...The corresponding positions of different metal plastic working processes in the plane stress state on a Mises yield ellipse are described.The paper points out that the forming of a workpiece inside its die is corresponding to a mass point moving along the ellipse and that its dimensional variation tendency in all directions can be judged according to a correspondence rule of the stress-strain order offered by the author.In addition,the paper also presents the corresponding three-dimensional positions of different metal plastic working processes on the Mises cylinder,from which the deformation force and technological plasticity required in different processes can be compared,and the dimensional variation tendency can be predicted.The analysis method used in this paper is not to calculate the variation of each stress component(σx,σy,σz) by convention,but to emphasize the variation of the stress state in the typical position,which is expressed correspondingly as the varying locus of points in principal stress space,and then based on the analysis the strain result is judged.展开更多
The microstructure evolution of the weld metal （WM） region in a Ni-based 718 superaUoy is discussed. The superalloy sheets were welded using the tungsten inert gas process at different heat inputs. The precipitates ...The microstructure evolution of the weld metal （WM） region in a Ni-based 718 superaUoy is discussed. The superalloy sheets were welded using the tungsten inert gas process at different heat inputs. The precipitates and dendrites in the WM of each joint were analyzed by optical microscopy, scanning electron microscopy, and energy dispersive spectroscopy （ EDS）. Statistics on the dendrite arm spacing and precipitates were obtained from the metallographs. Using the alloy composition determined by EDS and the phase diagram obtained using ThermoCalc, the equilibrium distribution coefficient of Nb, the temperature range of solid/liquid coexistence, and the distribution and morphology of Laves phase in different subregion of the WM were analyzed. There is lamellar segregation, regional segregation, and microsegregation in the WM. As the heat input increases, the arm spacing and the microsegregation increase. At a fixed heat input, the microsegregation rate is smallest in the crater, but with the macrosegregation seriously.展开更多
目的:回顾性观察金属预成冠全冠式远中导板间隙保持器(distal shoe space maintainer,DSSM)在第二乳磨牙早失中的临床治疗效果。方法:收集2021年1月~2024年1月89例因第二乳磨牙早失行全冠式DSSM治疗病例,回顾性分析至少术后1年的临床资...目的:回顾性观察金属预成冠全冠式远中导板间隙保持器(distal shoe space maintainer,DSSM)在第二乳磨牙早失中的临床治疗效果。方法:收集2021年1月~2024年1月89例因第二乳磨牙早失行全冠式DSSM治疗病例,回顾性分析至少术后1年的临床资料和影像学资料,从DSSM保留率、保留状态、间隙丧失情况及DSSM维持时间4个方面分析临床治疗效果。结果:对57例完成随访到DSSM拆除病例进行数据分析,平均维持时间15(12.5,18.0)个月,其中16例出现脱落或提前拆除,第一乳磨牙的慢性炎症和脱焊在DSSM脱落失败的危险因素中有统计学意义(P<0.05),第一乳磨牙的慢性炎症在影响DSSM变形移位的危险因素中有统计学意义(P<0.05)。对84例完成1年随访病例进行数据分析,22例移位变形病例平均间隙丧失2.31(2.14,2.34)mm,62例在位状态良好病例平均间隙丧失0.13(0.09,0.18)mm,两组数据比较差异有统计学意义(P<0.05)。结论:全冠式DSSM在在位保留上有优势,在位良好的病例也达到了良好的间隙保持临床效果,对于术前第一乳磨牙根尖周状态的判断及治疗和咬合管理还需予以改进。展开更多
文摘The corresponding positions of different metal plastic working processes in the plane stress state on a Mises yield ellipse are described.The paper points out that the forming of a workpiece inside its die is corresponding to a mass point moving along the ellipse and that its dimensional variation tendency in all directions can be judged according to a correspondence rule of the stress-strain order offered by the author.In addition,the paper also presents the corresponding three-dimensional positions of different metal plastic working processes on the Mises cylinder,from which the deformation force and technological plasticity required in different processes can be compared,and the dimensional variation tendency can be predicted.The analysis method used in this paper is not to calculate the variation of each stress component(σx,σy,σz) by convention,but to emphasize the variation of the stress state in the typical position,which is expressed correspondingly as the varying locus of points in principal stress space,and then based on the analysis the strain result is judged.
文摘The microstructure evolution of the weld metal （WM） region in a Ni-based 718 superaUoy is discussed. The superalloy sheets were welded using the tungsten inert gas process at different heat inputs. The precipitates and dendrites in the WM of each joint were analyzed by optical microscopy, scanning electron microscopy, and energy dispersive spectroscopy （ EDS）. Statistics on the dendrite arm spacing and precipitates were obtained from the metallographs. Using the alloy composition determined by EDS and the phase diagram obtained using ThermoCalc, the equilibrium distribution coefficient of Nb, the temperature range of solid/liquid coexistence, and the distribution and morphology of Laves phase in different subregion of the WM were analyzed. There is lamellar segregation, regional segregation, and microsegregation in the WM. As the heat input increases, the arm spacing and the microsegregation increase. At a fixed heat input, the microsegregation rate is smallest in the crater, but with the macrosegregation seriously.
文摘目的:回顾性观察金属预成冠全冠式远中导板间隙保持器(distal shoe space maintainer,DSSM)在第二乳磨牙早失中的临床治疗效果。方法:收集2021年1月~2024年1月89例因第二乳磨牙早失行全冠式DSSM治疗病例,回顾性分析至少术后1年的临床资料和影像学资料,从DSSM保留率、保留状态、间隙丧失情况及DSSM维持时间4个方面分析临床治疗效果。结果:对57例完成随访到DSSM拆除病例进行数据分析,平均维持时间15(12.5,18.0)个月,其中16例出现脱落或提前拆除,第一乳磨牙的慢性炎症和脱焊在DSSM脱落失败的危险因素中有统计学意义(P<0.05),第一乳磨牙的慢性炎症在影响DSSM变形移位的危险因素中有统计学意义(P<0.05)。对84例完成1年随访病例进行数据分析,22例移位变形病例平均间隙丧失2.31(2.14,2.34)mm,62例在位状态良好病例平均间隙丧失0.13(0.09,0.18)mm,两组数据比较差异有统计学意义(P<0.05)。结论:全冠式DSSM在在位保留上有优势,在位良好的病例也达到了良好的间隙保持临床效果,对于术前第一乳磨牙根尖周状态的判断及治疗和咬合管理还需予以改进。
