Thread Joint Research Articles

Finite Element Study of a Threaded Fastening: The Case of Surgical Screws in Bone

This paper studies the stress state of a threaded fastening by using Finite Element (FE) models, applied to surgical screws in cortical bone. There is a general interest in studying the stress states induced in the different elements of a joint caused by the thread contact. Analytical models were an initial approach, and later FE models allowed detailed studies of the complex phenomena related to these joints. Different studies have evaluated standard threaded joints in machinery and structures, being the thread symmetric. However, surgical screws employ asymmetric thread geometry, selected to improve the stress level generated in the bone. Despite the interest and widespread use, there is scarce documentation on the actual effect of this thread type. In this work, we discuss the results provided by FE models with detailed descriptions of the contacts comparing differences caused by the materials of the joint, the thread geometry and the thread’s three-dimensional helical effects. The complex contacts at the threaded surfaces cause intense demand on computational resources that often limits the studies including these joints. We analyze the results provided by one commercial software package to simplify the threaded joints. The comparison with detailed FE models allows a definition of the level of uncertainty and possible limitations of this type of simplifications, and helps in making suitable choices for complex applications.

Study on mechanical behaviors of double shoulder drill pipe joint thread

Double shoulder drill pipe joint (DSJ) is a novel thread structure which appears in recent years. Its strength reduced efficiently while the structure design is not appropriately, for the DSJ’s mechanical behaviors weren’t well studied. In this paper a 3D whole structure finite element model of DSJ was established based on the Principle of Virtual Work, and validated the model’s computing results by experimental results. The authors analyzed the stress and strain distribution with the 3D whole structure finite element model’s computing results under torque moment, compression force, tension load, and bend moment. And then acquired the DSJ’s mechanical behaviors under each load. The research works of this paper refer accordance to recognize and design the DSJ.

A Modelling Method of Bolt Joints Based on Basic Characteristic Parameters of Joint Surfaces

Bolt joints are common in machine tools and have a direct impact on the overall performance of the tools. Therefore, the understanding of bolt joint characteristics is essential for improving machine design and assembly. Firstly, According to the experimental data obtained from the experiment, the stiffness curve formula was fitted. Secondly, a finite element model of unit bolt joints such as bolt flange joints, bolt head joints, and thread joints was constructed, and lastly the stiffness parameters of joint surfaces were implemented in the model by the secondary development of ABAQUS. The finite element model of the bolt joint established by this method can simulate the contact state very well.

Strain-Based Casing Design for Cyclic-Steam-Stimulation Wells

Summary An oil field in Xinjiang, China, experienced a casing failure rate of 15 to 30% in thermal wells, mainly relating to inadequate protocols of casing design. This paper presents a new strain-based casing-design method. New material parameters are proposed to build safety-evaluation principles throughout the service life of a thermal well. In addition, a gas-tight thread joint is applied to prevent steam leakage that otherwise would cause a large transversal stress between different formations, and result in slip deformation of the casing string. Field practices have shown that the new method's fitness works better for thermal wells than previously used methods.

THE BASIC PRINCIPLES OF THE INTEGRATED MANAGEMENT OF THE PROCESS OF ASSEMBLY AND THREADING

The subject matter of this article is the issues related to the integrated management of assembling operations of fastening and threading elements at all stages of their implementation. The goal is to develop the generalized structure of the data management system of the process of assembly and threading. The objectives are: to justify the principles of managing the assembly and threading process at each stage of the assembly to improve the efficiency of these operations, to study the power, accuracy and performance characteristics of the connections and to draw the conclusion that suggested the theory of assembly management is efficient. The following results are obtained. The article presents the analytical dependencies of the force indexes of threading in the course of the package and sheet assembly, including the tightening force while joining; the assembly of a multilayered package of dissimilar sheet materials was analyzed. On the basis of the theoretical analysis, the dependences of the power indices of threading during the package and sheet assembly were determined. The assembly of the package of sheet materials was investigated, including a multilayered package of dissimilar materials of a “metal-plastic” type. Conclusions. The process of assembling threaded joints with the use of management principles was used; these principles enable increasing the efficiency of the assembly process, reducing the complexity of the basic operations, and improving the quality of the joints obtained. The use adaptive control of the screwing speed on the main threading transitions is suggested for reducing the torque. The technology of making threaded joints with given properties is developed, the main ways of increasing the efficiency of assembly and threading processes are determined on the basis of the integrated control system for the assembly process.

Study of the effect of the expansion cone on the expansion process in solid expandable tubulars with thread joints

As the core technology of petroleum extraction engineering in the 21st century, Solid Expandable Tubular (SET) technology is applied to drilling, well completion, and cementing. However, the expansion process for tubulars in site operation may well lead to stress concentration, leakage, or even fracture failure in thread joints of the tubular assembly due to the irregular deformation of thread teeth. With the aim of studying the issue with regard to the thread joint of J55 steel expandable tubulars, this study extended a series of finite element models using the commercial software ABAQUS to investigate the structural response of tubulars during the expansion process. The simulation results include the stress evolution, deformation of the thread joint of the tubular assembly, and the effect of expansion cone geometry on the expansion consequences. A laboratory experiment was performed to validate the validity of the simulated solution. It was found from results that both the axial and hoop compressive stress concentrations were generated in the thread teeth edges near the contact surfaces of threads during the expansion process due to the mutual squeezing of box and pin thread teeth. An increase of the tubular diameter led to a reduction of wall thickness and axial length due to the law of volume-constancy. The expansion process resulted in a deterioration of the contact condition between the thread teeth. A cone angle of 9° and sizing section length of 65–75 mm were the optimal choice of the geometric size of the expansion cone according to their superior analytical results.

The Analysis of Electrical Energy Consumption of the Impact Screwdriver During Assembly of Fixed Threaded Joints

Abstract The paper deals with the possibilities of reducing the consumption of electrical energy of the impact screwdriver during the assembly of fixed threaded joints. The recommendations related to a decrease in electrical energy consumption would allow reducing product costs but so far there have been no such recommendations from the producers of the tool as to the effective operating regimes of the impact screwdrivers in relation to electrical energy consumption and necessary tightening moment of the nut. The aim of the study is to find out the economical operating mode of the electrical impact screwdriver when assembling fixed threaded joints. By varying the set speed of the rotor head and working time of the impact mechanism, there is an opportunity to determine electrical energy consumption of the tool for the given tightening moment. The results of the experiment show that at the same tightening moment obtained the electrical energy consumption of the impact screwdriver is less at a higher starting set speed of the rotor head but shorter operating time of the impact mechanism than at a lower speed of the rotor head and longer operating time of the impact mechanism.

Development of technological support of qualitative threaded joints of parts made of aluminum alloys

Analysis of existing technological processes of manufacturing parts and assembly of hermetic threaded joints in pneumatic equipment reveals the main factors that determine the quality and productivity of the hole machining. It is shown that for such processes as maintenance of the necessary performance characteristics of the joints, it is necessary to control the parameters of the state of the surface layer in the process of their manufacturing. It is also necessary to be able to calculate them at the design stage of the technological process. Research results of the technological properties of AK12M2 aluminum alloy obtained by die casting are given, namely, modeling of the surface plastic deformation (SPD) of AK12M2 cast aluminum alloy. Also, the properties of the surface before and after SPD and the effect of the deformation angle are compared, taking into account the number of SPD cycles for the surface quality. An analytical and experimental study of machining method of threaded holes with the use of a deforming tool is carried out, taking into account the modeling of the shaping process of inch threads in blind holes by a deforming tool. Formation of a dense surface layer from the porous structure of the material is investigated as an option to increase the tightness. The constructive and technological parameters of the deforming tool for blind holes for pipe cylindrical threads (up to 2) in parts made of aluminum alloys with gas and shrinkage porosity are developed. A possibility of providing a qualitative surface layer of blind holes after PPD of AK12M2 alloy due to the application of a deforming tool in the technological process machining is theoretically proved. New tool designs and practical recommendations on the selection of machining regimes are proposed, ensuring the number of loading cycles – 12–13, the deformation angle – 4 degrees, the deformation rate – ζ=3.77 m/min with a cross-feed rate – S=0.05 mm/rev. A comparison of the quality of threaded joints, obtained by the basic and new machining method and evaluation of economic efficiency is carried out. This allows to reduce the technological cost and obtain economic benefit by reducing the labor intensity of machining and the cost of tools and process fluids.

Effect of contact pressure on fretting fatigue failure of oil-well pipe material

As the result of a full-scale test of a thread joint connecting oil-well casing pipes, fretting fatigue failure at the middle of the thread engagement part was identified. The objective of this study is to understand the mechanism of the fretting fatigue failure at the middle of the contact part. A similar failure mode was reproduced by a bridge-pad type fretting fatigue test under gross slip conditions. It was found that the crack position moved from the contact edge toward the inside of the contact part with the progress of the fretting wear.

Experimental study of mechanical properties and residual stresses of expandable tubulars with a thread joint

As the core of drilling technology in the 21st century, expandable tubular technology could solve practical engineering problems including inadequate casing displacement and high-pressure formations in drilling, and it could be applied in many fields such as well workover, cementation, and well completion. However, the difficulties of breakage and leakage at the thread joint in the expansion process limited the development of this technology. This study investigated the effect of the expansion process on various aspects of the J55 steel expandable tube involved in deformation, residual stress, mechanical properties, and microstructure variation by experimentation. The results showed that in the top and root of the box thread zone the residual stresses were relatively high. That is because much wall thickness was lost due to thread cutting in the top zone and the bending moment was generated from the cone mandrel pressing outwards in the root zone of box thread. It was noticeable that the yield and ultimate strength of the expanded tube were increased after the expansion process, which is work hardening. Furthermore, the microstructure of the unexpanded and expanded tubes was similar, and consisted of pearlite surrounded by ferrite. But in the expanded tube, the pearlite and ferrite were more uniformly and compactly distributed.

Model of a new joint thread for a drilling tool and its stress analysis used in a slim borehole

Abstract. The drilling pipe used in slim-borehole drilling performs well due to its low cost and high efficiency. Good sealing properties and coupling strength are the two keys to ensure that the pipe works correctly. In this paper, a 68 mm diameter drilling pipe and its joint are developed. On the basis of Lame's theory, the contact model of the joint thread is represented under different axial force, makeup torque, and pressure difference between inner and outer pipe. This model provides a good reference for judging the quality of sealing of the joint thread. The analysis software ANSYS\\Workbench is applied to stimulate the distribution of contact stress and sealing properties. A premium condition for drilling has been proposed, which provides a good theoretical basis for slim-borehole drilling.

Threaded joints in drives

Refined and engineering methods of calculating threaded joints subjected to rupture force and a tipping torque are developed, in the case where the contact surface roughness of the flanges is Ra ≥ 1.25 μm, with more than 106 loading cycles.

Experimental study of the effect of the threading process on the mechanical and tribological behaviors of the triangular thread

The aim of this work is to develop an experimental device useful to evaluate the friction coefficient in triangular thread joints (M12) manufactured with rolling and machining processes, and therefore, to relate precisely the clamping force to the tightening torque. Experimental static tests of clamp force during 10 tightening–loosening cycles were applied to specific threaded specimens obtained with the rolling and machining process. To analyze the mechanical and tribological behaviors of the manufactured threads, the torque coefficient (K) (nut factor), the average friction coefficient (μm), and the clamped force (F) have been evaluated during 10 cycles of tightening–loosening. The results of this study showed that the range of the variability of the torque coefficient and friction coefficient is between 0.151 and 0.54 and from 0.19 to 0.69 for the rolled thread, respectively. However, these coefficients are between 0.187 and 0.55 and from 0.25 to 0.72 for the machined thread, respectively. The clamping force preserves a linear relationship with the tightening torque and decreases as the number of tightening increases. The use of the rolling process to manufacture the thread joint can preserve a higher mechanical resistance and ameliorate the tribological behavior of the thread compared to the machining process.

Improvement of reference base in the field of metrological assurance of thread joints

We consider the main and essential legislative and applicative issues of metrological assurance of thread joints in the Russian Federation and international practice. Basic limitations of the existing measuring methods of the main thread gage parameter - the pitch diameter of thread - are represented. We give the description of the first echelon state working calibration standard for linear unit, placed in service in D.I. Mendeleyev Institute for Metrology (VNIIM), including the general field of applications and metrological characteristics according to the state verification schedule. The possibilities of etalon application in the field of measurements of thread gages parameters are shown. Technical solutions for reducing the components of uncertainty of measurements of the pitch diameter using the etalon are described: temperature stability; reducing of external vibration effects on measuring procedure; developing of the special software for minimizing human factor and increasing automation level of the measuring procedure. The solutions described have enabled to achieve expanded uncertainty value about 0.7-1.0 microns. As a result, we also propose further ways for development and improvement of the system of metrology assurance in the field of thread joints.

INFLUENCE OF THE THREADED TOOL JOINT RUNNING ON THE FRICTION COEFFICIENT AND TORQUE MOMENT

The question of influence of a number of cycles of the threaded tool joint screwing - unscrewing on the coefficients of friction and as a consequence on the final value of the torque moment is considered in this article. To study this question the tests were carried out in order to: to identify the influence of a number of grip pings and torque moments on the final result of a torque moment at screwing a new nipple with a new clutch; to identify the influence of a number of grip pings and torque moments on the final result of a torque moment on screwing a new nipple with the previously operated clutch. The coefficients of friction for the tool joint thread in dependence on a number of screwing-unscrewing cycles and also in dependence on the clutch and nipple state were obtained empirically. On the basis of the obtained data, the dependence diagram of the friction coefficient of a number of cycles of screwing - unscrewing was plotted. As a result of this experiment the following information was obtained: The threaded joint running for the threaded tool joint without a surface treatment using a lubricant is in increasing the coefficient of friction; The difference in the coefficient of friction and a torque -dependent moment between the first cycle of screwing - unscrewing and the subsequent ones is considerable and as a result must be taken into account in the analysis of the spontaneous torque moment problem. A number of cycles of screwing - unscrewing was obtained on which reaching the torque moment becomes equal to the one calculated theoretically and the further screwing operations don't lead to the increasing the torque moment.

Analytical Seismic Fragility Analyses of Fire Sprinkler Piping Systems with Threaded Joints

For the first time, an analytical modeling methodology is developed for fire sprinkler piping systems and used to generate seismic fragility parameters of these systems. The analytical model accounts for inelastic behavior constituents of the system, including: threaded joints, solid braces, hangers, and restrainers. The model incorporates a newly developed hysteresis model for threaded tee joints that is validated by the experimental results of several tee subassemblies. The modeling technique at the subsystem level is validated by using the experimental results of a sprinkler piping system. The methodology is used to obtain the seismic response of the fire sprinkler piping system of University of California, San Francisco Hospital under a suite of 96 artificially generated triaxial floor acceleration histories. After the component fragility parameters are obtained for the components of the system, three system-level damage states are defined, and a joint probabilistic seismic demand model is utilized to develop system fragility parameters.

Use of Nitrocarburizing for Strengthening Threaded Joints of Drill Pipes from Medium-Carbon Alloy Steels

Nitrocarburizing is tested at the Drill Equipment Plant for reinforcing threaded joints of drill pipes for units with retrievable core receiver (RCR). The effect of the nitrocarburizing on the mechanical properties of steels of different alloying systems is considered. Steels for the production of threaded joints of drill pipes are recommended.

Analysis of High Pressure Gas Cylinder Preload of Screw Connection

High pressure gas cylinder thread joint is the weak link in high pressure gas cylinders, The cylinders in use and the operating process, the main causes of cylinder screw thread failure is the improper preload. In this paper, cylindrical high-pressure cylinders threaded,connection for example,according to the bottleneck and the bottlevalve for high pressure gas cylinder structure, material and mechanical characteristics, establishing 3D solid model of the high-pressure cylinders connected by using the finite element software ANSYS, 3D model is applied to high pressure cylinders, thread connection analysis.

622 軸直角方向負荷下のねじ締結体のすべり・ゆるみ挙動

The thread joint has been frequently used for the efficient productivity and maintainability as a machine element. However, many troubles such as loosening of bolted joints or fatigue failure of bolt were often experienced. Many attentions must be paid on the improvement of the strength and the reliability of the thread joints. It is generally said that the fastening axial force rapidly decreases by the rotation loosening of nuts if the relative slippage on the interfaces between nuts and fastened body goes beyond a certain critical limit. This critical relative slippage (Scr) that prescribes the upper limit for preventing the loosening behavior has been estimated according to the theoretically obtained equation considering the bending deformation of bolt and the geometrical constraint condition. In this paper, we present the investigated results of the deformation behavior of bolt-nut joint under transverse loading condition. The bending moment of bolt is measured by the quasi-static loading test. The reaction force moment by nut used in the equation for estimating the Scr is evaluated by the comparison of experimental and analytical results from estimated equation. The new equation for estimating the reaction force moment which agrees with measured value is examined and proposed.

The Detection of Battery Screwdriver’s Optimal Working Modes when Assembling Fixed Threaded Joint Considering Allowable Tightening Torque in Case of Equal Screw Length

In presented paper, the screwdriver’s electric power consumption studies depending on the corresponding fixed threaded joint’s assembly time are carried out. So far there are no recommendations from the tool manufactures for screwdriver’s optimal operating modes (the conclusion is made on the base of the attached instructions which provide instrument manufacturers), when evaluating this aspect upon taking into account the electrical power consumption and assembly time for different types of fixed threaded joints (wood, metal, plastic, etc.) and also taking into account obtainable tightening moments. In the examined literature sources which deal with the opportunities concerning the optimization of the automated assembly processes of fixed threaded joints, not enough attention is paid to the reduction of the instrument’s energy consumption which is one of the main tasks in the industrial process because it directly impacts production costs.