This paper describes the use of computer-aided measurement for external metric screw threads. Thread parameters, including thread pitch, thread angle, pitch diameter and major diameter, were measured with CCD cameras ...This paper describes the use of computer-aided measurement for external metric screw threads. Thread parameters, including thread pitch, thread angle, pitch diameter and major diameter, were measured with CCD cameras and image analysis software. New technologies such as digital image processing were used to increase the efficiency of measurements. In this study, by reconstructing the toolmaker’s microscope, the computer-aided semi-automated measuring system was developed, which could evaluate the accuracy of screw thread profile. It is concluded that the measurement accuracy is comparable to that of traditional toolmaker’s microscope method. Key words screw threads - quality inspection - accuracy - digital image processing展开更多
The analysis of the crack on the HRB400 screw-thread steel surface has been carried out by means of metallographic microscope, scanning electron microscope and EDAX. It is shown that the type of inclusions in the crac...The analysis of the crack on the HRB400 screw-thread steel surface has been carried out by means of metallographic microscope, scanning electron microscope and EDAX. It is shown that the type of inclusions in the crack steel samples is mainly class B oxide, C silicate, and the inclusion size of the majority below 10 μm, and a small number of large inclusions are observed. The content of oxygen in the steel is high, and the carbon segregation is the main reason of the crack formation of HRB400 screw-thread steel. The measures to improve the crack formation of HRB400 screw-thread steel are put forward, which provides a powerful basis for the practical production.展开更多
We are developing a speed reducer that can be considered a transformation of a worm gear reducer: the worm is replaced by an inverted roller screw, and the gear is replaced by a threaded chain drive. This configuratio...We are developing a speed reducer that can be considered a transformation of a worm gear reducer: the worm is replaced by an inverted roller screw, and the gear is replaced by a threaded chain drive. This configuration lessens wear, increases load capacity, and improves efficiency. The threaded chain consists of nut-shaped links. This paper presents the results of tests carried out on a prototype with a reduction ratio of 46.展开更多
One of the design methods for closing the end of a pressure cylinder is to screw down a screw plug on the threaded end of the cylinder. In this case, there is the problem of stress concentration in the threaded end of...One of the design methods for closing the end of a pressure cylinder is to screw down a screw plug on the threaded end of the cylinder. In this case, there is the problem of stress concentration in the threaded end of the pressure cylinder. To solve the problem, it is necessary to know accurately the load distribution on the threaded end of the cylinder. To find the load distribution on the threaded end of the pressure cylinder engaged with the screw plug, the following experiments are carried out. Applying the tensile load between the screw plug and the pressure cylinder and regarding the situation above as equivalent to the situation in which the internal pressure is applied, the load distribution is measured with the strain gauge. The influence of thread pitch on the load distribution on the threaded end of the cylinder is presented and an optimum pitch for design is discussed.展开更多
目的:采用有限元分析方法,评估传统椎弓根轨迹置钉(traditional trajectory,TT)技术与改良皮质骨轨迹置钉(modified cortical bone trajectory,MCBT)技术在不同骨质疏松条件下的腰椎生物力学性能差异。方法:采用CT扫描技术获取骨质疏松...目的:采用有限元分析方法,评估传统椎弓根轨迹置钉(traditional trajectory,TT)技术与改良皮质骨轨迹置钉(modified cortical bone trajectory,MCBT)技术在不同骨质疏松条件下的腰椎生物力学性能差异。方法:采用CT扫描技术获取骨质疏松患者的腰椎断层图像,然后对L4腰椎结构进行三维重建并进行验证。通过改变骨密度,在骨量减少(A1)、中度骨质疏松(A2)、重度骨质疏松(A3)中分别构建两种钉道设计。一种在TT技术中使用传统双螺纹椎弓根螺钉(TT组),直径6mm,全长45mm;另一种在MCBT技术中使用的变径全皮质骨螺纹螺钉(MCBT组),直径4~5.5mm,全长45mm。分析不同骨质疏松条件下,两种钉道设计对螺钉轴向抗拔出力、螺钉稳定性(上、下、左、右工况的载荷位移比,即螺钉尾端向其垂直轴的上、下、左、右位移0.1mm时载荷值与其位移的比值)以及腰椎活动度(前屈、后伸、侧弯及轴向旋转时)的影响。结果:在轴向抗拔出力方面,MCBT组在A1、A2、A3中较TT组分别提高93.5%、96.5%、98.5%。在稳定性方面,上、下、左、右工况在A1、A2、A3下,MCBT组螺钉的载荷位移比,相对于TT组分别提升42.2%、40.8%、41.7%;49%、49%、51.5%;82.4%、81.5%、85.2%;73.1%、70.8%、72.5%。在腰椎活动度方面,前屈时在A1、A2、A3下,TT组较MCBT组增加25%、26.6%、28.7%;后伸时在A1和A2下,TT组比MCBT组增加24.5%、22.9%,而在A3下,差异无显著性意义(P>0.05);而在侧弯和轴向旋转时,MCBT组在A1、A2、A3下相比TT组仅有轻微增加(P>0.05)。结论:在不同程度骨质疏松分级下,MCBT技术仅在椎体轴向旋转和侧屈时的稳定性上弱于TT技术,但在轴向抗拔出力、螺钉稳定性及椎体前屈、后伸时的稳定性上优于TT技术。展开更多
文摘This paper describes the use of computer-aided measurement for external metric screw threads. Thread parameters, including thread pitch, thread angle, pitch diameter and major diameter, were measured with CCD cameras and image analysis software. New technologies such as digital image processing were used to increase the efficiency of measurements. In this study, by reconstructing the toolmaker’s microscope, the computer-aided semi-automated measuring system was developed, which could evaluate the accuracy of screw thread profile. It is concluded that the measurement accuracy is comparable to that of traditional toolmaker’s microscope method. Key words screw threads - quality inspection - accuracy - digital image processing
文摘The analysis of the crack on the HRB400 screw-thread steel surface has been carried out by means of metallographic microscope, scanning electron microscope and EDAX. It is shown that the type of inclusions in the crack steel samples is mainly class B oxide, C silicate, and the inclusion size of the majority below 10 μm, and a small number of large inclusions are observed. The content of oxygen in the steel is high, and the carbon segregation is the main reason of the crack formation of HRB400 screw-thread steel. The measures to improve the crack formation of HRB400 screw-thread steel are put forward, which provides a powerful basis for the practical production.
文摘We are developing a speed reducer that can be considered a transformation of a worm gear reducer: the worm is replaced by an inverted roller screw, and the gear is replaced by a threaded chain drive. This configuration lessens wear, increases load capacity, and improves efficiency. The threaded chain consists of nut-shaped links. This paper presents the results of tests carried out on a prototype with a reduction ratio of 46.
文摘One of the design methods for closing the end of a pressure cylinder is to screw down a screw plug on the threaded end of the cylinder. In this case, there is the problem of stress concentration in the threaded end of the pressure cylinder. To solve the problem, it is necessary to know accurately the load distribution on the threaded end of the cylinder. To find the load distribution on the threaded end of the pressure cylinder engaged with the screw plug, the following experiments are carried out. Applying the tensile load between the screw plug and the pressure cylinder and regarding the situation above as equivalent to the situation in which the internal pressure is applied, the load distribution is measured with the strain gauge. The influence of thread pitch on the load distribution on the threaded end of the cylinder is presented and an optimum pitch for design is discussed.
文摘目的:采用有限元分析方法,评估传统椎弓根轨迹置钉(traditional trajectory,TT)技术与改良皮质骨轨迹置钉(modified cortical bone trajectory,MCBT)技术在不同骨质疏松条件下的腰椎生物力学性能差异。方法:采用CT扫描技术获取骨质疏松患者的腰椎断层图像,然后对L4腰椎结构进行三维重建并进行验证。通过改变骨密度,在骨量减少(A1)、中度骨质疏松(A2)、重度骨质疏松(A3)中分别构建两种钉道设计。一种在TT技术中使用传统双螺纹椎弓根螺钉(TT组),直径6mm,全长45mm;另一种在MCBT技术中使用的变径全皮质骨螺纹螺钉(MCBT组),直径4~5.5mm,全长45mm。分析不同骨质疏松条件下,两种钉道设计对螺钉轴向抗拔出力、螺钉稳定性(上、下、左、右工况的载荷位移比,即螺钉尾端向其垂直轴的上、下、左、右位移0.1mm时载荷值与其位移的比值)以及腰椎活动度(前屈、后伸、侧弯及轴向旋转时)的影响。结果:在轴向抗拔出力方面,MCBT组在A1、A2、A3中较TT组分别提高93.5%、96.5%、98.5%。在稳定性方面,上、下、左、右工况在A1、A2、A3下,MCBT组螺钉的载荷位移比,相对于TT组分别提升42.2%、40.8%、41.7%;49%、49%、51.5%;82.4%、81.5%、85.2%;73.1%、70.8%、72.5%。在腰椎活动度方面,前屈时在A1、A2、A3下,TT组较MCBT组增加25%、26.6%、28.7%;后伸时在A1和A2下,TT组比MCBT组增加24.5%、22.9%,而在A3下,差异无显著性意义(P>0.05);而在侧弯和轴向旋转时,MCBT组在A1、A2、A3下相比TT组仅有轻微增加(P>0.05)。结论:在不同程度骨质疏松分级下,MCBT技术仅在椎体轴向旋转和侧屈时的稳定性上弱于TT技术,但在轴向抗拔出力、螺钉稳定性及椎体前屈、后伸时的稳定性上优于TT技术。
