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
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
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
The screw threading produce is a important process course.The economics modeling is established in this paper so this process will be investigated.In this paper modeling of process is analyzed.The Q and cost decreases...The screw threading produce is a important process course.The economics modeling is established in this paper so this process will be investigated.In this paper modeling of process is analyzed.The Q and cost decreases with the increasing quantity while the same turn as AC>AFC>MC is found.AC and AFC is main factors to affect quantity then MC do.It fits to concept of them well.The cost AC and AFC is higher upon L=4 than L=6 while MC is higher upon L=6 than L=4.Meantime the TC and VC is higher upon L=6 than that upon L=4,is the near parallel line.The TC>VC is turn to affect cost.There is a difference for them.TC and VC is main effective costs to compare with AC,AFC&MC.The TC and VC become bigger upon K=5 than K=7.展开更多
This article describes three algorithms for distance field generation on triangulated model: brute force algorithm, single-threaded algorithm based on spatial partition and multi-threaded algorithm based on spatial pa...This article describes three algorithms for distance field generation on triangulated model: brute force algorithm, single-threaded algorithm based on spatial partition and multi-threaded algorithm based on spatial partition. Spatial partition algorithm use equidistant network divide the bounding box into equal-sized cubes, calculates the maximum and minimum distances between the sample point and each of the small cubes,taking the minimum value from the maximum distance as the minimum distance from the sample point to the model named d1, comparing d1 with the distance from sample point to every little cube's minimum distance d2, if d1 <d2, the sample point's distance to all triangles inside this cube are greater than d1, skip this cube, otherwise, calculated the distance from the point to all the triangles intersect with the cube, then alternative d1 with the minimum value, circulate all small cubes intersect with the model. Comparing the calculation results, it can be seen that the algorithm about the multi-threaded distance field relative to the other two algorithms in computational speed is greatly improved especially for complex models.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
This paper reports that the etching morphology of dislocations in 8° off-axis 4H-SiC epilayer is observed by using a scanning electronic microscope. It is found that different types of dislocations correspond wit...This paper reports that the etching morphology of dislocations in 8° off-axis 4H-SiC epilayer is observed by using a scanning electronic microscope. It is found that different types of dislocations correspond with different densities and basal plane dislcation （BPD） array and threading edge dislocation （TED） pileup group lie along some certain crystal directions in the epilayer. It is concluded that the elastic energy of threading screw dislocations （TSDs） is highest and TEDs is lowest among these dislocations, so the density of TSDs is lower than TEDs. The BPDs can convert to TEDs but TSDs can only propagate into the epilyer in spite of the higher elastic energy than TEDs. The reason of the form of BPDs array in epilayer is that the big step along the basal plane caused by face defects blocked the upstream atoms, and TEDs pileup group is that the dislocations slide is blocked by dislocation groups in epilayer.展开更多
Pedicle screw is employed in several cases of spine disorders such as fractures, pseudarthrosis, spondylolisthesis, degenerative changes among others. Its essence is to fix the vertebral body in position until fusion ...Pedicle screw is employed in several cases of spine disorders such as fractures, pseudarthrosis, spondylolisthesis, degenerative changes among others. Its essence is to fix the vertebral body in position until fusion is complete. The success of this technique depends on factors like choice of size of screw for a particular pedicle size and shape. Thus, adequate knowledge of the morphometry of lumbar pedicle may avert intraoperative and postoperative complications associated with this technique, especially, neurological impairments. In this study, we determined the vertical and horizontal diameters, interpedicular distance and gender differences of 180 lumbar vertebral pedicles (140 male, 40 female pedicles) using digital vernier calipers. Results revealed a significant increase in pedicle height and width from L2 to L5. Interpedicular distance increased significantly down the vertebrae from L2 to L5. Mean vertical and horizontal diameters, interpedicular distance were not significantly different in both sexes. This study recommends a thorough check of individual’s spinal anatomy in pre-operative assessments.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.
基金the Korea of National Research Foundation,under the Specified Base Program(Grant No.96-0300-11-01-3).
文摘The screw threading produce is a important process course.The economics modeling is established in this paper so this process will be investigated.In this paper modeling of process is analyzed.The Q and cost decreases with the increasing quantity while the same turn as AC>AFC>MC is found.AC and AFC is main factors to affect quantity then MC do.It fits to concept of them well.The cost AC and AFC is higher upon L=4 than L=6 while MC is higher upon L=6 than L=4.Meantime the TC and VC is higher upon L=6 than that upon L=4,is the near parallel line.The TC>VC is turn to affect cost.There is a difference for them.TC and VC is main effective costs to compare with AC,AFC&MC.The TC and VC become bigger upon K=5 than K=7.
文摘This article describes three algorithms for distance field generation on triangulated model: brute force algorithm, single-threaded algorithm based on spatial partition and multi-threaded algorithm based on spatial partition. Spatial partition algorithm use equidistant network divide the bounding box into equal-sized cubes, calculates the maximum and minimum distances between the sample point and each of the small cubes,taking the minimum value from the maximum distance as the minimum distance from the sample point to the model named d1, comparing d1 with the distance from sample point to every little cube's minimum distance d2, if d1 <d2, the sample point's distance to all triangles inside this cube are greater than d1, skip this cube, otherwise, calculated the distance from the point to all the triangles intersect with the cube, then alternative d1 with the minimum value, circulate all small cubes intersect with the model. Comparing the calculation results, it can be seen that the algorithm about the multi-threaded distance field relative to the other two algorithms in computational speed is greatly improved especially for complex models.
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.
基金supported by the National Natural Science Foundation of China (Grant No. 0876061)Shaanxi 13115 Innovation Engineering of China (Grant No. 2008ZDKG-30)the defence Fund of China (Grant No. 9140A08050508)
文摘This paper reports that the etching morphology of dislocations in 8° off-axis 4H-SiC epilayer is observed by using a scanning electronic microscope. It is found that different types of dislocations correspond with different densities and basal plane dislcation （BPD） array and threading edge dislocation （TED） pileup group lie along some certain crystal directions in the epilayer. It is concluded that the elastic energy of threading screw dislocations （TSDs） is highest and TEDs is lowest among these dislocations, so the density of TSDs is lower than TEDs. The BPDs can convert to TEDs but TSDs can only propagate into the epilyer in spite of the higher elastic energy than TEDs. The reason of the form of BPDs array in epilayer is that the big step along the basal plane caused by face defects blocked the upstream atoms, and TEDs pileup group is that the dislocations slide is blocked by dislocation groups in epilayer.
文摘Pedicle screw is employed in several cases of spine disorders such as fractures, pseudarthrosis, spondylolisthesis, degenerative changes among others. Its essence is to fix the vertebral body in position until fusion is complete. The success of this technique depends on factors like choice of size of screw for a particular pedicle size and shape. Thus, adequate knowledge of the morphometry of lumbar pedicle may avert intraoperative and postoperative complications associated with this technique, especially, neurological impairments. In this study, we determined the vertical and horizontal diameters, interpedicular distance and gender differences of 180 lumbar vertebral pedicles (140 male, 40 female pedicles) using digital vernier calipers. Results revealed a significant increase in pedicle height and width from L2 to L5. Interpedicular distance increased significantly down the vertebrae from L2 to L5. Mean vertical and horizontal diameters, interpedicular distance were not significantly different in both sexes. This study recommends a thorough check of individual’s spinal anatomy in pre-operative assessments.
