Thread End Research Articles

Modeling of End Face Perpendicularity Error and Its Influence Mechanism on Thread Assembly Clamping Force

The precise control of thread clamping force is the main means to achieve the assembly performance of electromechanical systems. The end face perpendicularity error generated in thread machining causes changes in the meshing contact stress and end face stress after thread fitting, which makes the variations of the relationship between tightening torque and clamping force during the thread tightening process. As a result, the dispersion of the final clamping force is increased after the thread assembly, and the fit of the mounting edge becomes worse, which affects the overall performance of the electromechanical systems. In terms of the above issues, this paper takes a M5 bolt as an example to accurately represent and simulate the end face perpendicularity error and connection performance of the bolting using a computer. A digital twin model for thread clamping is established and the study of thread clamping is conducted. Firstly, the 3D point cloud data considering the perpendicularity error of the end face is obtained, and the NURBS surface numerical model is applied to developing the surface models of thread and end face. Then, a geometric digital twin model of the bolt with perpendicularity error is established using CAD. Furthermore, a physical digital twin model of the tightening process of bolting is established using finite element method. Based on the numerical simulation results, the effect of different perpendicularity errors on the stresses of the thread pair and end face are analyzed, and the variation law of tightening accuracy is determined. The influence mechanism of end face perpendicularity error on the clamping force of bolt assembly is revealed. Finally, by comparing the tightening process with M5 standard bolts, the effect of perpendicularity error on the error in the clamping force prediction is investigated, which provides a theoretical basis for achieving precise control of thread clamping force.

Failure Analysis of Cracked P110 Repaired Tubing Used for Gas Transmission.

With green and low-carbon developments in oil fields, an increasing amount of repaired oil tubing is being used as oil and gas transmission pipelines in China. However, due to differences in manufacturing standards between oil tubing and transmission pipelines, there are inevitably some issues during their use. This paper investigates a case of cracking failure in repaired oil tubing used as a gathering and transportation pipeline. The failure occurred after eight months of operation and was characterized by a circumferential crack at the male thread end of the tubing joint. To determine the root cause of the failure, a series of experiments were conducted on the oil tubing. The experiments included visual inspection, chemical composition analysis, mechanical properties testing, hardness testing, metallographic examination, and microstructure analysis. The results revealed that the thread of the cracked tubing was not tightened to the specified position; the connection between the tubing and the coupling was welded in a circumferential direction; and cracks occurred in the heat-affected zone of the weld. Chemical composition, tensile performance, and the Charpy impact of the tubing meet the requirements of API 5CT for P110 material, and no abnormalities were found in the metallographic structure. The microstructure at the weld toe of the fracture is martensite, and the hardness is 476 HV10. Based on the thermal simulation verification test, when the material of the tubing cools from 1200 °C, which is located in the coarse HAZ temperature zone, the base metal transforms into martensite with a little granular bainite, exhibiting its highest hardness value at 371 HV10, which is higher than the allowable hardness for carbon steel and indicates the material has poor weldability. The reasons for the cracking and failure of the tubing are that the P110 repaired tubing has a high carbon equivalent and poor weldability. During the welding process, martensitic structure was formed at the weld toe, and cold cracks appeared in the heat-affected zone, resulting in failure. To avoid the reoccurrence of such failure, recommendations are proposed.

Incomplete Screw Thread Engagement of Proximal Fragment: A Possible Failure Risk After Internal Fixation for Femoral Neck Fractures.

Background For successful internal fixation for femoral neck fracture, the sliding mechanism of the screw is important because it can induce inter-fragmental compression. The thread should penetrate the fracture line and be located within the proximal fragment. If screw thread engagement is incomplete and a part of the thread remains within the distal fragment, the screw sliding can be disturbed, potentially leading to fixation failure. We hypothesized that screw threadin the fracture is a risk of fixation failure. Methods We studied 133 hips that underwent internal fixation for femoral neck fracture using dual sliding and compression screws (DSCS) with 20 mm threads. The existence of incomplete thread engagement and fixation failure (cut out, perforation, pseudoarthrosis, or femoral neck shortening) were evaluated on anteroposterior hip radiography postoperatively. The distances from the thread end to the fracture line, screw head to the femoral head cortex, and femoral head diameter were measured to analyze their relationships with any incomplete thread engagement and fixation failure. Differences in evaluation data were assessed using Fisher's exact test, Student's t-test, and receiver operating characteristic (ROC) analysis. Results Forty-six cases had at least one screw with incomplete thread engagement, and the other 87 hips had a complete engagement. The failure rate in the group of hips with incomplete thread engagement was significantly higher (7/46, 15.2%) than that in the group of hips with complete thread engagement (3/87, 3.4%) (P = 0.032). Incomplete thread engagement was found in 59 out of 266 screws (22.2%), and a femoral head ≤ 43.9 mm in diameter was associated with an increased risk of incomplete thread engagement. Most incomplete thread engagement screws (81.4%) had < 5 mm thread length within the distal fragment. Conclusion A partially threaded screw is a significant risk of fixation failure after internal fixation for a femoral neck fracture. The smaller femoral head diameter increases the possibility of incomplete thread engagement. Shortening the thread length by 5 mm may help to avoid incomplete thread engagement.

Fracture Analysis of Butt Welding Area of 5″ Drill Pipe Internal Thread End in an Oilfield

This paper tested fracture morphology analysis, mechanical properties and chemical, metallographic analysis and micro analysis to find out the factors of fracture in the butt welding area of the internal thread of the 5″ drill pipe, which is made of S135 in the casing pulling process of an oilfield. The results show that the chemical element, tensile strength and yield strength, impact performance, metallographic structure, inclusions in microstructure and grain size of the Fracture drill pipe meet the relevant data of the oilfield and industry standards, but the hardness of the fracture does not meet the requirements of the national standard. The important reason of the fracture of the drill pipe is that the oxide skin was not cleaned before the drill pipe joint was welded with the body. During welding, the oxide skin entered the molten weld metal, and large slag inclusions formed in the weld resulted. The secondary cause is improper subsequent heat treatment of drill pipe weld, which leads to increased weld brittleness and accelerated crack growth. This paper puts forward corresponding countermeasures to improve the quality of the drill pipe’s weld and prevent the failure accidents of drill pipe.

Safety and Effectiveness Outcomes of a Novel Automated Titanium Suture Fastener Device Applied for Heart Valve Surgery in an Ovine Model.

ObjectiveThis study was designed to evaluate the operability, effectiveness, and safety of the automated titanium suture fastener in a preclinical ovine model in comparison with manual tying in a mitral valve annuloplasty ring implantation surgery.MethodsEighteen adult Small-tailed Han sheep were prepared for the surgery of mitral valve annuloplasty ring implantation through lateral thoracotomy under cardiopulmonary bypass (CBP). A total of 12 stitches were performed to secure an annuloplasty ring, with 6 stitches done with the automated fastener and the other 6 by manual tying. The knotting time for the automated fastener or manual tying was recorded, respectively. The firmness of knots, mitral valve integrity, biocompatibility, thrombosis, local reactions, and other aspects were also compared at follow-up time (Days 30, 60, 90, and 180).ResultsOf the 18 sheep, 16 survived to the designated endpoints and were enrolled for further analysis. Compared with the control group, the knotting time was significantly reduced with the automated fastener (p < 0.01). All the annuloplasty rings were tightly secured by 6 fastener clips and 6 hand-made knots without any disengagement or displacement. All the mitral valves were intact without any defect, stenosis, prolapse, valve insufficiency, or perforation. Endothelialization was comparable between the two groups by Day 60. Small red thrombi formed at the thread end of the suture in both groups. No thrombus was found on the surface of the titanium clip. All the thrombi were within the acceptable range for the antithrombotic property. Thrombosis showed no significant difference by Day 60. No significant differences in the inflammatory response and pathological lesions were observed by Day 60. One case of diffuse renal infarction (area ratio = 20%) and 1 case of small focal renal infarction (area ratio < 5%) were caused by thromboembolism.ConclusionsThe automated fastener significantly shortened the procedure time of tying knots for the implantation of the annuloplasty ring in the ovine model, with comparable safety and effectiveness as manual tying.

Analisis Temperatur Pada Proses Extruding Pelet Apung

Extruder is a device that consists of a screw (a type of pressure screw), the thread functions as a propulsion and presses the raw material so that it turns into a semi-solid material. The material is pushed and pressed out through a confined hole (die) at the thread end. The heater gives heat to the material being extruded which is called hot extrusion. The cutting knife is used to even out the size of the extruded cut, and the main feature of the extrusion process is its continuous nature. The extruder is operated under conditions of dynamic equilibrium, that is, the input equals the output, the incoming material is equivalent to the product.

Evolution of Precipitated Phases during Creep of G115/Sanicro25 Dissimilar Steel Welded Joints.

This paper studies the evolution of the microstructure and microhardness in the G115 side of the G115/Sanicro25 dissimilar steel welded joint during the creep process. The joints were subjected to creep tests at 675 °C, 140 MPa, 120 MPa and 100 MPa. A scanning electron microscope equipped with an electron backscattering diffraction camera was used to observe the microstructure of the cross-section. The fracture position of the joint and the relationship between the cavity and the second phase were analyzed. The microstructure morphology of the fracture, the base metal and the thread end was compared and the composition and size of the Laves phase were statistically analyzed. The results show that the fracture locations are all located in the fine-grain heat-affected zone (FGHAZ) zone, and the microstructure near the fracture is tempered martensite. There are two kinds of cavity in the fracture section. Small cavities sprout adjacent to the Laves phase; while large cavities occupy the entire prior austenite grain, there are more precipitated phases around the cavities. The Laves phase nucleates at the boundary of the M23C6 carbide and gradually grows up by merging the M23C6 carbide. Creep accelerates the coarsening rate of the Laves phase; aging increases the content of W element in the Laves phase.

Analysis of Corrosion Behavior on External Surface of 110S Tubing

The failure analysis of 110S tubing during acidizing process was addressed. Results showed that serious pitting corrosion occurred on the outer wall of tubing, and there was no obvious pitting on the inner wall. The maximum pitting depth on the outer wall was 1019 μm. According to the results of simulation corrosion test, needle-shaped pitting appeared on the sample surface in the test without inhibitor, the maximum depth of pitting was 158 μm; and no pitting was found on the sample surface in the test within 1.5% TG501 inhibitor; the original pitting were deepened after spent acid test, and the sample with no pitting at the beginning also showed deep pitting corrosion after 96 hours spent acid test. It was indicated that the spent acid accelerated the development of pitting significantly. The external surface corrosion of the 110S tubing was caused by the chemical reaction between the high-concentration acidifying liquid and the outer wall of the tubing. There is a gap between the tubing and coupling threaded connection, which caused the acid solution entered into the thread position, and hence the severe corrosion of the thread and pin end of the tubing happened, the joint strength was continuously reduced with corrosion development till the tripping of the coupling, and then the lower string dropped. Some suggestions were proposed for avoiding or slowing down this kind of failure based on this study.

Biomechanical analysis of the computer-assisted internal fixation of a femoral neck fracture

The number and spatial configuration of the screws will affect the stability and prognosis of the fractures. In our study, we assessed the biomechanical effects of the double-head cannulated compression screw (DhCCS) and ordinary cannulated compression screw (OCCS) for the treatment of femoral neck fractures by using computer finite element analysis. The original digital imaging and communications in medicine (DICOM)data of a proximal femur were imported into Materialise's interactive medical image control system (MIMICS)software for modeling. Both DhCCS and OCCS 3D-models were obtained by using the 3D scan technique. Using the fracture model and internal fixation assembly model with an inverted triangle, two horizontal and vertical distribution were established in UG software. Next, the displacement and stress distribution were calculated in ANSYS software. The displacement value of the femoral head in the DhCCS group was smaller than that in the OCCS group, and the displacement value in the two horizontal groups was smaller than that in the vertical group. The stress distribution in the DhCCS group was concentrated on the screw rod at the fracture block and thread end, while only at the fracture block in the OCCS group. The stress in the horizontal group was more dispersed on the screws than that in the vertical group. DhCCS has reliable stability for the fixation of femoral neck fractures and applied in the clinical work and 2 horizontal fixation can be used when two screws are selected.

Hydrogen Induced Stress Corrosion Cracking of Fuel Oil Premix Burner Nozzles in a Heavy-duty Gas Turbine Engine

Abstract A number of M8 fuel oil pre-mix (FOPM) burner nozzles in a heavy-duty gas turbine engine were found loosened after some 32,000 operating hours. They were removed and tended to crack in the shaft upon disassembly. It was determined on site that they were fractured at the fillet radius below the head, at the thread's end. A metallurgical root cause investigation was ordered to determine the cause of the cracking. Selected dimensional checks, chemical analyses, microstructural examinations, and evaluations of fuel oil analyses conducted by external sources were performed to achieve the required results. Fractographic studies were not possible in this case due to the corrosion products covering the fracture surfaces. The FOPM burner nozzles fractured due to hydrogen-induced stress corrosion cracking (HISCC). No evidence of pre-existing cracks was found. There are no signs of over-torqueing nor of any other damage caused by manufacturing or assembly; hence this failure was caused by engine service and is not fabrication related.

Improving joint features and tensile shear properties of friction stir lap welded joint by an optimized bottom-half-threaded pin tool

To increase the lap shear failure load of friction stir lap welding (FSLW) joint, a tool with a bottom-half-threaded pin was designed in the present study. Using 7N01-T4 aluminum alloy as the research object, tools with the bottom-half-threaded pin and the traditional full-threaded pin were used to fabricate lap joints. Results showed that the thread end position on the pin greatly influenced the material flow behavior. The material concentrated zone using the bottom-half-threaded pin mainly located above the lap interface, which is beneficial to suppress the hook and cold lap. The lap shear failure load of the FSLW joint using the bottom-half-threaded pin was 17,644.7 N, which is equal to 122.8 % of the joint using the full-threaded pin.

Experiments on Effects to Rock Bolt Pretension by Thread Rolling Accuracy

Pretension is a key factor affecting the performance of rock bolt. It is usually applied on the bolt by tightening the nut. The efficiency of the torque-to-pretension conversion is significantly influenced by the thread rolling accuracy. In this study, the influence of the thread rolling accuracy upon the pretension is investigated. Factors influencing the thread rolling efficiency, i.e., rock bolt material quality, rolling technic and equipments, are examined. To study the relationship between torque and pretension, a laboratory table was specially designed and a series of tests were carried out on the rock bolts with different thread accuracy. The result indicates that the higher the thread rolling accuracy, the higher the coefficient of torque-to-pretension conversion. And the coefficient can be improved by daubing lubrication oil on the thread. In China, the rock bolt thread encounters the issue of low rolling accuracy which results in coarse thread surface. As a result, the efficiency of the torque-to-pretension conversion is greatly reduced. In addition, the rock bolt is susceptible to break at the thread end. Essential approach to resolve these issues is to significantly improve the thread rolling accuracy by adopting advanced equipment.

Off-the-Job Microsurgical Training on Dry Models: Siberian Experience

Microsurgical training has become an obligatory part of many neurosurgical training programs. To assess the cost and effectiveness of acquiring and maintaining microneurosurgical skills by training on an off-the-job basis using dry models. A dry off-the-job microneurosurgical training module was set up. Training exercises involved microdissection in a deep operation field, suturing and tying on gauze, untying, pushing of thread end, and microanastomosis. The time to complete the task and success rate were evaluated. The total cost of all necessary equipment and expendables for the training module was US$910. Fifteen residents participated in the continuous off-the-job training. The average time taken to perform the anastomosis decreased after the month of training from 90 to 20 minutes. Authors revealed that at 2 months, the total time and time to complete anastomosis increased significantly for the participants who discontinued practice after the first month, compared with those who just practiced suturing on gauze after the first month (P < 0.01). The average Northwestern Objective Microanastomosis Assessment Tool score was 36 for novice and 65 for experienced participants. The dry off-the-job training showed to be readily available and can be helpful for microsurgical training in the low-income regions of the world. Our data suggest that microsurgical training should be continuous and repetitive. Simulation training may benefit from models for repetitive training of relevant technical part-skills.

Fracture characteristics in rock bolts in underground coal mine roadways

• Examine fractured bolts obtained from underground roadways in a number of coal districts in China. • Investigate rock bolt fracture mechanisms . • Explain major reasons of fracture occurring in the thread end of rock bolt. • Provide technical approaches to resolve bolt fracture problems.

1020 有限要素法解析による圧力円筒ねじ端の荷重分布へ及ぼすピッチの影響(OS01-4 機械要素とトライボロジー,オーガナイズドセッション 1:「機械要素とトライボロジー」)

1020 有限要素法解析による圧力円筒ねじ端の荷重分布へ及ぼすピッチの影響(OS01-4 機械要素とトライボロジー,オーガナイズドセッション 1:「機械要素とトライボロジー」)

Case study of Ti6Al4V pedicle screw failures due to geometric and microstructural aspects

Pedicle screws are widely used alternatives to improve the spine fusion in the treatment of several spine diseases. However, the screw fracture rates are still high nowadays. Efforts to provide design and material selection should be encouraged. This paper deals with the analysis of design issues related to failure event of 10 Ti6Al4V pedicle screws explanted from five patients who had rupture before 5years in use. The objective of this study was to correlate the mechanical failure with the geometric and microstructural concerns. Bending fatigue was the main mechanism responsible for the failures. Fractures occurred near the thread end or at intermediate thread level. In some cases environmental assisted cracking (EAC) was associated with failure initiation. The formation of lamellar or platelike microstructure, the small thread root radius and surface roughness were factors related to failures.

Wpływ warunków pracy tarczowego podciągacza nici na charakterystykę ściegu czółenkowego

Analysis of literature described in the dissertation showed the complexity of phenomena of machine stitch creation processes. The reference to the lockstitch proves particularly difficult working conditions of needle thread. Tools forming the stitch (needle, bobbin, needle thread take-up, thread tensioner, transporter of the textile package) cause the weakening of thread inserted into the seam structure, what can lead to thread breakage. Hence, a great attention is paid to the action on thread of stitch forming mechanisms in the sewing machines.A particular role of thread take-up mechanism was stressed during discussing the process of thread control conditions by the take-up in the lockstitch machines. Characteristic working phases of the take-up were distinguished i.e., supplying by the thread and drawing of thread end during the stitch tightening. One has paid the attention to the conditions of interlacement location in the material and the possibility of correcting them by the improving the structure of the thread take-up mechanism. Changing the stitch tightening modelling process was to achieve this aim. So, a physical model, and next a mathematical model of the zone of stitch creation were elaborated. Due to the possibility of configuration of multibarrier take-ups creation a model of the stitch tightening considering the take-up disc was built.The presented results of model research required the experimental verification. The dynamic tensions in threads and the thread strength decrease after the sewing through process as well as a reaction of the take-up to changes thread length in the link of the stitch were studied. Carrying out the experimental analysis required the building the take-up disc installed on the chosen machine. Thus, there is a need for elaboration of the methodology of the take-ups disc designing using genetic algorithms as well as a classical programming in Fortan and C++ languages. The determination of requirement take-up disc configuration was preceded by a definition of the curve of the thread controlled by the take-up disc. Next, one made an estimation of defined curve of the thread controlled by take-up disc with a software called “Take-up disc 2.0” elaborated on the basis of genetic algorithm.The designed and built thread take-up disc allow decreasing peaks of strength of the stitch tightening over twice of the basic value, which is the significant achievement from a technical-technological point of view. Moreover, it causes the decrease of thread breaking strength losses. In the case of the takeup disc, holding the position of the interlacement in the stitch link on the set level requires the extending the part of machine working cycle corresponding to the stitch tightening in comparison to the generally used take-ups.

203 圧力円筒におけるテーパねじ端の荷重分布(第1報)(材料力学V)

203 圧力円筒におけるテーパねじ端の荷重分布(第1報)(材料力学V)

A Rapid Change in Magnetic Connectivity Observed Before Filament Eruption and Its Associated Flare

To gain insight to the cause of filament eruptions and flares on the Sun, we observed a filament that erupted in active region NOAA 8597. The observations consisted of Hα filtergrams at three wavelengths (line center and ±0.5 A) and line-of-sight magnetograms. All were taken on 1999 June 24 at Big Bear Solar Observatory. We found from the time sequence of Hα images that the filament eruption was preceded by a rapid change in connectivity in a bundle of filament threads. The thread bundle was initially sharply curved near its one end of the filament and suddenly flipped and then became straight in the new orientation. The flipped segment of the thread bundle swept over a 100'' × 50'' area on the solar surface in about half an hour. At the latter stage of the connectivity change, we observed a downward draining of material along the thread bundle that had a transverse component of 50 km s-1. After that, the filament body split into two parallel parts, one part erupted while the other part remained, and the two-ribbon flare occurred. We also found canceling magnetic features in the vicinity of the initial location of the thread end, which displayed a flux decrease during the Hα connectivity change. Our results show clear and direct evidence that magnetic reconnection takes place in the low atmosphere prior to eruption. This preeruption reconnection seems to be very different from a posteruption coronal reconnection, which is believed to lead to a two-ribbon flare.

A basic study of the effect of flying ink on tone reproduction using electrostatically attracted ink jets

This paper describes the results of the first quantitative examination of ink flight peculiar to the electrically extracted ink jet method using dielectric ink. In the state of ink flight determined by this method, a continuous cylindrical liquid thread is formed at the nozzle tip, then the ink at the thread end turns into corpuscles and spreads out in mist. The author has already reported the method used for observation and the recording method for tone reproduction. In this paper, an examination was made of the details of average and instantaneous structures of the state of ink flight, covering the wide area from the nozzle tip to the area past the electrodes, and the effect of the state of ink flight on the recording for tone reproduction was studied on the basis of the examination results. Detailed examinations were made of differences in tone, density distribution, and the relation of nozzle diameter to liquid thread diameter and to corpuscle diameter by varying the applied voltages and ink pressures. The results indicate that the ink jet which scatters in an atomized state from the liquid thread is effective in application to a high-quality recording for tone reproduction. © 1997 Scripta Technica, Inc. Electr Eng Jpn, 120(1): 55–61, 1997