Thread Pitch Research Articles

The influence of the position and shape geometry of the counter-conical motion transmitter pin on the pitch fluctuation of the spiroid worm machined with adjusted shaft

The difference between the mathematical defined shape of the conical helicoid surface and the operating surface of the spiroid worm produced with axis adjustment on a thread grinding machine results – among other things –in thread pitch fluctuation. During the manufacturing of conical helicoid surfaces the transmission of the rotation from the main spindle to the worm shaft can be realised by a driving pin and an adjusted lathe dog. This article deals with the examination of the fluctuation of the thread pitch parameter occurring when using a counter-conical drive pin. The fluctuation is described here as a function of the position and the shape geometry of the drive pin.

Measurement of Outside Thread Pitch Distance Results of TONGTAI TCS 1500[M] CNC Lath Using Profile Projector

Research has been carried out on the Measurement of the Outer Thread Pitch Distance from the Tongtai Tcs 1500[M] Cnc Lathe Using a Projector Profile. The use of a screw system to unite two components, is almost always found in all industrial technology results from the form of industrial technology with a low level of accuracy (rough) to a very high level of precision (precision). Therefore the screw system has become one of the important factors in industrial progress in all types of production. The higher the level of a component made means the higher the level of accuracy of the thread system. In this study, calculations were carried out to determine the level of precision of a thread made through the machining process using a TONGTAI TCS 1500 [M] CNC lathe. The precision measurement was carried out by measuring using a dimension measuring instrument, namely Profile Projector type HST-CPJ-3000/3000Z. To find out the average value and the value of the screw deviation, a research and measurement process was carried out with several product samples or test objects (sample A, sample B, sample C) where each sample was the same size, namely M15 × 50 P 1.5. The first measurements were made on the major and minor diameters. Because this measurement is more focused on the level of precision of the thread pitch distance, the second measurement is carried out by measuring the dimensions of the distance between the pitches as much as N = 10. From the 10 measuring points of the thread pitch distance, different average values and deviation values will be produced although in the same size.. The purpose of this study was to determine the level of pressure of a thread made through a machining process which in this study used a CNC TONGTAI TCS 1500 [M] lathe. it is known that the overall average value of the three samples is with a major diameter = 14,949 mm, a minor diameter = 13,219 mm, and a thread pitch distance = 1.5309 mm.

Numerical simulation of the thermal-hydraulic characteristics of supercritical carbon dioxide in a wire-wrapped rod bundle

A wire-wrapped spacer was considered in the fuel-assembly design of a supercritical carbon dioxide (SCO2) reactor to improve the heat transfer between the coolant and fuel elements. However, there is still a lack of understanding and detailed evaluation of the performance of the wrapped wire. In this study, the turbulent flow and heat transfer of SCO2 in a rod bundle were numerically investigated considering the fluid–solid conjugate interaction. Emphasis was placed on revealing the effects of wire shape, wire pitch and number of wire thread on the heat transfer and pressure drop. The performance evaluation criterion (PEC) was adopted to evaluate the performance of spacers. It was found that the heat transfer in the wire-wrapped rod bundle was enhanced compared to that in the bare rod bundle. The trapezoid-shaped wire shows a larger PEC than the circular- and rectangular-shaped wires. In addition, the PEC increased with the wire pitch first but declined subsequently, showing a peak with a wire pitch between 180 and 240 mm. The wire-wrapped spacer with two threads was recommended because of its high heat transfer efficiency and relatively low flow pressure drop.

Structural parameters and critical anchorage length of tunnel system bolts made of basalt fibre

Basalt fibre reinforced polymer (BFRP) has the advantages of high tensile strength and good durability; therefore, the anchor bolt developed with BFRP has potential application in tunnel surrounding rock anchorage. This study used meso-scale numerical simulation and laboratory tests to examine the structural parameters of BFRP anchor plate and rod and the critical anchorage length of BFRP cement mortar anchor. The results showed that: 1) the special-shaped truncated cone type anchor plate can convert the axial force into internal tensile stress, which improves the tensile performance of the basalt fibre material. 2) The larger the thread pitch of the BFRP bolt or the smaller the thread height, the more uniform is the shear stress distribution of the bolt thread, and the smaller is the maximum shear stress of the rod and nut. 3) The thread height of 2 mm and thread pitch of 18 mm is the optimal combination. 4) The critical anchoring length of the BFRP cement mortar bolt is 20–40 times its diameter. The findings of this study can provide new and meaningful reference for the application of System Bolts made of Basalt Fiber in tunnel engineering.

Effect of thread depth and thread pitch on the primary stability of miniscrews receiving atorque load : Afinite element analysis.

We have been developing anew type of miniscrew to specifically withstand orthodontic torque load. This study aimed to investigate the effect of thread depth and thread pitch on the primary stability of these miniscrews if stressed with torque load. Finite element analysis (FEA) was used to evaluate the primary stability of the miniscrews. For thread depth analysis, the thread depth was set to 0.1-0.4 mm to construct 7models. For thread pitch analysis, the thread pitch was set to 0.4-1.0 mm to construct another 7models. Atorque load of 6 Nmm was applied to the miniscrew, and the other parameters were kept constant for the analyses. Maximum equivalent stress (Max EQV) of cortical bone and maximum displacement of the miniscrews (Max DM) were the indicators for primary stability of the miniscrew in the 14models. In the thread depth analysis, Max DM increased as the miniscrew thread depth increased, while Max EQV was smallest in model3 (thread depth = 0.2, Max EQV = 8.91 MPa). In the pitch analysis, with an increase of the thread pitch, Max DM generally exhibited atrend to increase, while Max EQV of cortical bone showed ageneral trend to decrease. Considering the data of Max DM and Max EQV, the most appropriate thread depth and thread pitch of the miniscrews in our model was 0.2 and 0.7 mm, respectively. This knowledge may effectively improve the primary stability of newly developed miniscrews.

Research on optimizing the axial force of thread connection of engine connecting rod

The connecting-rod (abbreviate as conrod) bolt is a key part of the crank conrod mechanism, however, due to the structural characteristics of the thread connection, uneven loading between thread teeth and stress concentration at the root of thread teeth are common. In this paper, a finite element model of the conrod bolt was established based on the mesh convergence criterion. The finite element model of the conrod bolt was verfied by Akira Yamamoto analytical method. The influence of thread pitch, pre-tightening force and thread connection length on the distribution of axial stress of the thread was studied, and the stress concentration at the first thread was more serious. To improve the stress distribution of the first thread, the Spiralock anti-loosening thread was replaced to the standard conrod bolt and taken as the research object. The results show that the axial stress distribution of the Spiralock anti-loosing thread is more uniform, the fatigue strength and life are also improved.

INTERNAL FIXATION OF TYPE I CAPITELLUM FRACTURE WITH HEADLESS SCREWS: A CASE REPORT

Background: Capitellum fractures are relatively rare. Distal humeral fractures that include capitellum and trochlea constitute approximately 6% of all distal humeral fractures and 1% of all elbow fractures. Despite the rarity of these injuries, an increasing number of clinical series have emerged, enhancing our understanding of these fractures.Case Report: A 26-year-old woman came to the emergency department with complaints of swelling and localized pain on the lateral side of her left elbow 2 hours after she fell off her motorcycle. Routine imaging such as plain radiographs and computed tomography scanning confirmed the fracture. She underwent open reduction and internal fixation surgery, stabilization of articular fragments with headless screws, and was fixated by a back slab and arm sling. The patient was also encouraged to do early elbow mobilization to avoid contractures and joint stiffness, routine follow-up every two weeks for a ROM evaluation. Preoperative Mayo Elbow-Performance Index score (MEPI) was 15, and postoperative 100.Discussion: The aim of capitellum fracture treatment is anatomical reconstruction and fixation to reduce the risk of non-union. In this case, we performed open reduction, secured two headless screws, which allow rigid fixation at the fracture site, provide fracture site compression through variable thread pitch design, and remained not removed later. These screws are suitable for use in anteroposterior and posteroanterior directions.Conclusion: The patient at two months follow-up has shown significant improvement. Accurate reduction, stable fracture fixation, and early postoperative mobilization were reported to provide good results with a MEPI score of 100.

On the effect of corrugated conical frustum on pool boiling heat transfer

Pool boiling heat transfer as a promising heat transfer mechanism that can provide ample heat dissipation for thermal management applications has been granted much attention. This study puts forward the idea of applying an Inner Corrugated Hollow Conical Frustum (ICHCF) to ameliorate pool boiling heat transfer. The performance of the ICHCF is experimentally investigated for both the stationary and rotating cases. Furthermore, the effect of various geometrical parameters such as the ICHCF height, thread depth, thread pitch, the gap between the ICHCF and boiling surface, and the rotational speed of the ICHCF are studied. Twelve different ICHCFs were fabricated and tested for the purpose of this study. The obtained results demonstrated that increasing the ICHCF height enhances the pool boiling heat transfer coefficient (PBHTC). It was also observed that there is an optimum distance between the conical frustum and the boiling surface. The results also revealed that using smaller pitches and higher thread depths can further improve the PBHTC. The PBHTC enhancement of up to 19.8 % in stationary and 1302 % in rotating modes was obtained compared to a plain surface.

Application of Hydraulic Control Make-up and Rreak-up Device in Improvement Design of Drilling rig

Tunnel drilling rig is widely used in coal mine gas drainage, hidden disaster detection and other construction. In view of the serious problem of thread wear when loading and unloading drill pipe thread of underground drilling rig in coal mine, a pure hydraulic control device is developed. By adjusting the corresponding angle parameters of the hydraulic control device, two actions of rotary feeding can be realized, and the thread can be loaded and unloaded automatically according to the thread pitch. The design of the device is completed, and the structure is applied to the improved design of ZDY750L and ZDY2-300LM drilling rigs. The matching control of feed and rotation of the two drilling rigs when loading and unloading the drill pipe is realized, which can reduce the wear of the drill pipe thread when the full hydraulic drilling rig is loading and unloading, and provides a new idea and solution for the implementation of the full hydraulic drilling rig automatic loading and unloading.

Arthroscopic Suture Anchor Design Finite Element Study

AIM: This in-vitro study investigated arthroscopic suture anchors’ main design parameters effect on surrounding bone. METHODS: Thirty-dimensional arthroscopic suture anchor designs’ models were created on engineering CAD software by changing thread profile, pitch, and anchor tip profile as design parameters. These models were imported into ANSYS Workbench for finite element analysis. Bone was simplified and modeled as two coaxial cylinders. Tensile vertical load of 300 N, and oblique at 45º to the vertical axis, were applied to each model as two loading conditions while the simplified bone base was fixed in place as a boundary condition. RESULTS: The finite element analyses on all models under both loading conditions showed stresses within physiological limits on bone. Trapezoidal teeth and inclined cut teeth designs showed the lowest values of stresses and deformations respectively on the bone under oblique loads, while curved tooth and square tooth designs showed the lowest values of stresses and deformations respectively on the bone under vertical loads. General ascending or descending trend was recorded by increasing pitch from 1.2 to 1.5 to 1.8 mm on the total deformation and maximum Von Mises stress on bone and anchor body. Tapered tip slightly increased bone and anchor stresses. CONCLUSION: Arthroscopic anchors thread profile has minor affect on cortical bone behavior. Trapezoidal teeth, square tooth, and inclined cut teeth profiles showed the lowest values of stresses and deformations on cortical bone. Increasing thread pitch of arthroscopic suture anchors increases or decreases stress on the bone, and anchor body according to thread profile edges. Anchor tip profile negligibly affects both deformations and stresses on bone and anchor body.

Finite element simulation and statistical investigation of an orthodontic mini-implant's stability in a novel screw design.

One of the essential aspects of the mini-implant's successful application is its stability after being installed in the bone. The stability of the mini-implant affected the most by its geometry. In the present research, the effect of the geometry-related parameters of the mini-implant on its lateral displacement is investigated by Finite Element (FE) modeling using ABAQUS software. The parameters studied include length, diameter, pitch, and depth of the screw threads; besides, length and angle of the conical section. The Taguchi method was used to prevent many experiments. The mesh convergence tests and experimental tests confirmed the FE model quantitatively and qualitatively. Mean of means and variance analysis determined the parameters significance and their contribution on the stability. The screw diameter and length have the most contribution to mini-implant' displacement. The effect of screw pitch was less than that for length and diameter. The conical section improved the initial stability by creating compressive stress and additional friction in its surrounding bone. No significant effects on the stability of the mini-implant have been observed for the non-threaded part. By examining the effect of thread depth on its stability by defining the ratio of thread depth to the internal diameter and to maintain the strength of the screw the optimal value for internal to external ratio is set at about 0.7.

Improving the fatigue life of the tool-joint of drill pipes by optimizing the variable pitch of the box thread

The reliability of oil drill-strings largely depends on the reliability of tool-joints. It is known that the load along the tool-joint thread is distributed unevenly and it is possible to equalize it by applying a variable thread pitch of a pin or a box. The article describes the optimization method of the pitch change function along the box thread by maximizing of the minimum value of fatigue life in the pin roots. Additionally, the value of the contact pressure on the shoulder, which determines the screw make-up force, is taken into account. To implement the method, we used the Abaqus/CAE and fe-safe software, the parametric axisymmetric finite element model of the tool-joint developed by the authors and the procedures for local (BFGS method) and global (Differential Evolution method) optimization from the SciPy package.

Verification of a calibration method for 3D screw thread metrology

The novel approach for holistic screw thread calibrations developed by the Physikalisch-Technische Bundesanstalt was published in 2019. A significant achievement has been made in order to meet increasing demands in manufacturing processes and quality assurance, particularly when workpieces with complex geometries are under inspection. This article deals with the verification of the previously presented three-dimensional calibration procedure for screw threads. Screw thread pitch diameters, the lead and flank angles are compared to those determined by the standardized method based on line-like, rather two-dimensional measurements and evaluation. In order to provide a reliable basis for the verification, one thread gauge was calibrated under laboratory conditions for precision metrology. Additionally, calibrations were conducted by three alternating operators on three different coordinate measuring machines to investigate the influence by user and machine. The resulting normalized errors of screw thread determinants under test and reference values are significantly smaller than 0.5 which indicates a high level of agreement.

Lagrange-method-based dynamic analysis of multi-stage planetary roller screw mechanism

Abstract. A rigid-body dynamic model of multi-stage planetary roller screw mechanism (multi-stage PRSM) is proposed in this paper. The structure of multi-stage PRSM is introduced and the motion analysis is presented. The total kinetic energy of the mechanism is calculated. The rotation of the screws and carriers is chosen as generalized degrees of freedom. The generalized forces and motion equations of multi-stage PRSM are derived using the Lagrange method. The transient and steady-state behaviours of multi-stage PRSM are simulated, followed by an analysis of the influence of friction coefficients and thread pitches on the motion and forces acting on the multi-stage PRSM. Taking a two-stage PRSM as an example, the simulation results show that the friction coefficient between screw #1 and screw #2 has a slight effect on efficiency and rotational velocity ratios of carriers to screws. When the sum of the pitches of screws is a constant, the axial component of contact force between screw #1 and roller #1 decreases with the increase in the pitch of screw #1.

The Effect of Threads Geometry on Insertion Torque (IT) and Periotest Implant Primary Stability: A High-Density Polyurethane Simulation for the Anterior Mandible

The implant geometry provides a key role in the osseointegration process and is able to improve the mechanical interaction and primary stability into the bone tissue. The aim of the present investigation was to compare different implant profiles to evaluate their influence on the primary stability on high-density polyurethane block. Methods: A total of 100 implants were used on 20 pcf polyurethane density in the present investigation, i.e., 20 implants for each of 5 groups (A, B, C, D, and E), characterized by different thread pitch and geometry. The insertion torque (IT), and Periotest mean values were recorded during the implant positioning. Results: Mean values for insertion torque values were higher for the group C and group E implant profiles when compared to all other groups (p < 0.01). No significant differences were detected between these two groups (p < 0.05). Lower IT (<20 Ncm2) were presented by groups A, B, and D (p < 0.05). All groups showed negative Periotest values. Group C implants showed the lowest level of Periotest values (p < 0.05). No significant Periotest differences were found between group B and group D and between group A and group E (p > 0.05). Conclusions: Implants with a wider and V-thread profile and a round apex showed a higher stability in a standardized polyurethane foam. Their use could be suggested in high-density bone in clinical practice.

Evaluation of Various Methods to Inspect Bolted Joint Integrity by Torque Measurement

The integrity of bolted joints is often checked after a certain period of running time. These checks are designed to examine whether the target bolt has still properly been tightened with prescribed bolt force staying within acceptable ranges. Three types of inspection methods are commonly used for verification, i.e., the release torque method, the re-tightening torque method and the marking method. Depending on the type of the method, inspections are carried out at the site by either measuring loosening torque, re-tightening torque or tightening torque up to the marked position. In this study, aiming at establishing general guidelines for the inspection methods, characteristics of these methods are examined using rigorous equations that represent the relationship between applied torque and generated bolt force. Torque ratios anticipated to be used as a guideline for each inspection method are comprehensively calculated by varying friction coefficients, nominal diameter and thread pitch. Coefficient of friction values, which affect inspection accuracy, are measured by means of tightening equipment which has been developed to measure relevant values, such as torque and bolt force, with high accuracy.

Effect of thread profile variation on pullout and bending strength of a pedicle screw

Pedicle screw is an important instrument in treatment of spinal degeneration or disease. However, the pedicle screw failure still occurs due to the screw loosening, fracture and pullout. There are few factors that affected the pedicle screw performance as reported by previous research but still lacking study related to the pedicle screw thread profile. Thus, the aim of this research is to investigate the effect of variation of thread pitch on the pullout and bending strength of pedicle screw. The research is carried out by constructing 3D pedicle screw models (model 1-6), importing the models into ANSYS, meshing and post processing analysis. The equivalent or Von-Mises stress used to compare the bending and pullout performance of the pedicle screws. Based on the obtained finite element analysis result, the single thread pedicle screw (model 3) has the optimum performance in bending while the model 4 is the optimum in pullout performance. While, for the dual threaded pedicle screw, the model 6 which has coarse thread pitch at screw tip is better than model 5 (fine thread). Thus, it can be conclude that both the single and dual threaded pedicle screw with coarse thread pitch has lower maximum equivalent stress than fine thread pitch, which is means it has better bending and pullout performance.

Thread turn milling simulation

The study shows that the high-performance thread turn-milling process with a synchronous rotation of the helical milling cutter and the workpiece is not widely adopted since there are no reliable methods to estimate the organic thread formation errors. The thread is machined as an envelope curve along the elementary surfaces of each cut shifted along the workpiece axis by a fraction of the thread pitch inversely proportional to the number of the cutter teeth. Domestic and international researchers tried to analytically estimate the thread formation errors at the part face. Such an approach failed to produce acceptable results since thread turn-milling is a three-dimensional process. We analyzed the thread formation errors in 3D using COMPAS 3D CAD system and developed a simulation model. We modelled a reference 3D thread machined on the workpiece; a 3D resulting thread; a single cutter tooth path in the plane perpendicular to the workpiece axis; 3D cut by a single cutter tooth. We also simulated the entire process and made a 3D model of the machining errors by subtracting the reference part geometry from the 3D thread model, and estimated the errors. The results were checked for consistency (max deviations) and acceptability for each dimension. The undercut dimensions were obtained by subtracting the 3D part model from the 3D reference model. Conversely, the overcut dimensions were obtained by subtracting the 3D reference model from the 3D part model.

Influence of short implant thread pitch and depth to primary stability on D4 bone density: A laboratory study

Aim: To determine the influence of short dental implant thread pitch and depth to primary stability on D4 bone density. Materials and Methods: Two short implants from BT Safe and Superline with different thread pitches and depths were used in this laboratory study and were divided into two groups. Artificial polyurethane (PU) bone block 0.32 g/cm3 was prepared, and each implant was inserted following manufacturer’s instruction. A Smartpeg was attached to each implant and transducer probe Osstell pointed stable to small magnet on the top of Smartpeg until beeping and the screen gave the implant stability quotient (ISQ) result. This procedure was repeated 20 times for every implant with four different 90o orientations or from buccal, lingual, mesial, and distal directions. The average ISQ value was calculated for statistical analysis. Data distributed normally and independent group t-test were performed to determine which group of short dental implants had better primary stability on D4 bone density. Results: Superline implant with shorter thread pitch and deeper thread depth has a final ISQ mean value of 65.9±0.76. BT Safe implant with longer pitch and shallow thread depth have a final ISQ mean value of 63.3±0.95. Conclusion: Shorter pitch and deeper thread depth have better primary stability of short dental implant on D4 bone density.

WEAR MECHANISMS OF DIAMOND-LIKE CARBON COATED TOOLS IN TAPPING OF AA6351 T6 ALUMINIUM ALLOY

The AA6351 T6 is an Al-Si-Mg alloy, widely used and easily accessible on the market, with low silicon content, sufficient to form magnesium silicates. The present work aims at analyzing the wear mechanisms acting over High-Speed Steels – HSS-E, Diamond-Like Carbon – DLC coated tools during the tapping operation of AA6351 T6 aluminum alloy. It was used a thread cutting tap with four helical flutes, diameter ϕ = 12 mm, and 1.5 mm thread pitch (M 12 x 1.5). Dry ambient was adopted to focus on the DLC performance. Ninety-six threads were machined using one single tool, and wear analysis was performed between the first and last threads. The main results showed aluminum adhesiveness, plastic deformations with more accentuated flank wear in the entry threads of the cutting tap, in addition to the detachment of the DLC coating. On the threads produced, several material detachments marks (adhered to the tool) were observed, as well as groove marks. These findings may help users in selecting appropriate cutting conditions as well as cutting atmospheres that can mitigate the tool wear.