Trapezoidal Thread Research Articles

Surface optimization of trapezoidal thread spindles—tribological analysis and application

Trapezoidal threaded spindles are ideal for supporting heavy loads and are therefore frequently used in heavy-duty lifting systems. Both the forming thread rolling process and the machining thread whirling process can be used to manufacture these lead screws. In order to improve the low efficiency of trapezoidal screw drives, it is crucial to understand and minimize friction losses. As part of a cooperation project between the Institute of Production Engineering and Machine Tools (IFW) and Bornemann Gewindetechnik, research was carried out into adapting the whirling process to optimize the tribological properties of threaded spindles. The process developed makes it possible to reduce the coefficient of friction in trapezoidal screw drives and thus also the required torque. By using whirled microtextures, the friction loss can be reduced by 25.5% and adhesive wear can be significantly reduced.

Biomechanical Analysis of Trapezoidal Thread Screw-Rod Fixation in Pedicle Section of Cervical Spine: A Finite-Element Analysis.

Cervical pedicle screw-rod fixation presents a complex approach in spinal surgery, offering enhanced spine stabilization in variable conditions considering traumatic injuries, degenerative changes, as well as orthopaedic and oncological ailments. This technique employs small diameter screw implants strategically placed to bolster the mechanical integrity of the spine. Notably, it involves minimally invasive procedures, resulting in smaller incisions and reduced patient discomfort. This study aims to assess the effects of trapezoidal thread screws in pedicle sections of the cervical spine during flexion-extension loadings, focusing on factors such as range of motion (ROM), implant stress, and stress on adjacent bone. Utilizing CT scan data, a finite element model of the cervical spine (C2-C7 vertebrae) was prepared. Trapezoidal thread screws were integrated into a single-level pedicle screw-rod fixation at the C5-C6 vertebrae. The C2 vertebra were given a compressive load of 50 N along with a moment of 1 Nm, resulting in the immobilization of the C7. The results indicate a reduction in ROM at the C5-C6 level by 69% to 77% compared to the intact spine during flexion-extension loading, with a slight increase in ROM observed at adjacent cervical spine levels. Stress analysis revealed that the trapezoidal thread screws induced stresses ranging from 24 MPa to 29 MPa in PEEK trapezoidal screw-rod implants, which fall below the material's yield stress. This suggests that the trapezoidal thread profile may be advantageous in minimizing stress concentration, attributed to its larger contact area with the vertebrae bone between the threads.

Simulative surface topography prediction of tribological surfaces on whirled thread flanks

This paper investigates the surface texture on trapezoidal thread flanks manufactured by whirling, which is used for machining long threaded spindles. An analytical and numerical approach for describing surface texture is compared, and texture parameters are developed based on existing methods. Although the analytical model provides a good description of texture height and length, it has limitations in representing the surface as a topography. In contrast, the numerical approach enables detailed modeling of the surface topography on the thread flank as a function of the process parameters. The effective number of flank cutters is found to significantly influence the resulting topography, leading to differences between the measured values and the analytical model within a specified investigation range. Using a material removal simulation, this effect could be explained by the flank cutter position error. In addition, material removal simulation offers great potential for optimizing the surface texture on thread flanks and for tailoring tribologically optimized surfaces in the whirling process.

Investigation of the Mechanical Properties of the Barrel After Geometric Changes on the Mortar

The area close to the firing part as of the muzzle of a 120 mm mortar consists of trapezoidal threads. In order for the 120 mm mortar to hit the target, the target is aimed by giving the required angle with the help of these trapezoidal screw threads. Since it takes a lot of time to set the target in this way, the aim is to develop a hydraulic mechanism that automatically gives an angle to the system by lifting the trapezoidal screw threads instead of mechanically setting the angle to be adjusted easily in the shortest time. Thus, it is intended to convert the mortar into a full-automatic system that can rotate 360° around itself and can be adjusted to the desired angle in a short time and very precisely. The present study is conducted in two steps. At first, thermo-mechanical analyzes for the stresses affecting during firing of the currently used 120 mm mortar with a screw thread were investigated by ANSYS Workbench finite elements method. Then, the status of the mortar after removing the screw threads was examined in the ANSYS Workbench program under the effect of the same stresses and the results were compared between the two mortars and it was examined whether it is safe to remove the screw threads.

Numerical Design of a Thread-Optimized Gripping System for Lap Joint Testing in a Split Hopkinson Apparatus.

Currently, few experimental methods exist that enable the mechanical characterization of adhesives under high strain rates. One such method is the Split Hopkinson Bar (SHB) test. The mechanical characterization of adhesives is performed using different specimen configurations, such as Single Lap Joint (SLJ) specimens. A gripping system, attached to the bars through threading, was conceived to enable the testing of SLJs. An optimization study for selecting the best thread was performed, analyzing the thread type, the nominal diameter, and the thread pitch. Afterwards, the gripping system geometry was numerically evaluated. The optimal threaded connection for the specimen consists of a trapezoidal thread with a 14 mm diameter and a 2 mm thread pitch. To validate the gripping system, the load-displacement (P-δ) curve of an SLJ, which was simulated as if it were tested on the SHB apparatus, was compared with an analogous curve from a validated drop-weight test numerical model.

The influence of thread screw parameters on the efficiency of threaded joints

Non-movable threaded joints (bolted connections) and movable threaded joints (power screws) are subassemblies that have a large field of application in the mechanical industry. With these subassemblies, a part of the input energy in the form of torque is spent on overcoming friction on the contact sliding surfaces. These energy losses mostly depend on the geometric and tribological characteristics of the threaded joint. Compared to bolted joints, power screws consume significantly more energy to perform their elementary function. Bolted joints have a much larger field of application in the mechanical industry. In the case of bolted joints metric thread is the most common, and in power screws, threaded joints with a trapezoidal thread. Accordingly, this paper analyses the effects of the coefficient of friction and geometric and kinematic parameters on the energy efficiency of trapezoidal and metric threaded joints. The performed analysis can be used to select the optimal parameters of the threaded joints from the aspect of energy efficiency during the design of new or reconstruction of existing machine structures.

Analysis of expansion performance and parameter sensitivity of solid expandable tubular with thread joint

During the expansion process of the threaded joint of the solid expandable tubular (SET), the thread meshing performance and sealing performance will deteriorate, which seriously hinders the development and application of the SET. In this paper, established the force analysis model of different threads in the bulging process and analysis the finite element model of thread. The meshing performance of φ108 mm × 7 mm SET joints made of 20G steel with three types of thread expansion is analyzed. The most suitable parameter range was obtained by optimizing the five thread parameters such as bearing surface angle, guide surface angle, taper, tooth depth and tooth pitch. The results show that the rectangular and trapezoidal threads are deformed seriously during expansion, and the connection of rectangular and trapezoidal threads is easy to cause the seal failure of the SET system; The effects of various thread parameters on the Mises stress and contact pressure distribution were analyzed. It was found that the Mises stress of the first turn of the special skew trapezoidal thread was the highest, and the Mises stress distribution was high at two ends and low at the middle, with the maximum difference of 160 MPa and the contact pressure distribution was high at two ends and low at the middle, with the maximum difference of 200 MPa. The research results provide technical support for obtaining the SET thread with good meshing performance after expansion.

Study of Tapered Threads Parameters Affecting the Quality of the Oil Pipeline Connection

Introduction. With the growth in the production and transportation of gas and oil, the urgency of the problem of tightness of the connection of pipes of the oil and gas range increases. The most common are coupling and streamline threaded connections. Threads of the buttress type, conical trapezoidal, and triangular threads are used. The tightness of the connection depends directly on their quality. The production of pipes and couplings is influenced by many factors. Examples include technological heredity, rigidity of technological equipment, its setting and resetting. The required connection quality is provided by the quality of the elements. The assembly should take into account the possibility of complete interchangeability. The second recommended option is a group assembling. In all cases, control operations are mandatory. The paper presents the results of studies on the distribution of pipe and coupling thread quality parameters in the batch.Materials and Methods. Fragments (tubular parts) of casing pipes with trapezoidal thread and increased tightness (CPTT) and with trapezoidal thread of the buttress profile were studied. They were randomly selected from different batches. When measuring, the samples were fixed in the chuck of 1I611P lathe. The measuring instrument was a clock type 0 accuracy class indicator with a stand. Generally accepted statistical methods were used to evaluate the data obtained.Results. The experiments have found how the tightness of the connection through the method of complete interchangeability is affected by the radial runout of the surfaces of the thread profile tops, the pipe chamfers, and the sealing belt.Discussion and Conclusions. Significant deviations of the values of the thread parameters from the permissible ones were found, which might cause a leak in the connection. Obtaining a high-quality and reliable connection is possible when assembling by the method of incomplete or group interchangeability.

A finite element study and mathematical modeling of lumbar pedicle screw along with various design parameters

BackgroundLumbar pedicle screw is one of the most common and important elements in the field of lumbar surgery. It plays a great role in rectifying the spinal alignment and stabilization providing strength and stability to the affected area of spine. In spinal surgery, minimally invasive techniques and minor incisions are made which makes it less painful for the patients than the traditional methods. Moreover, the screws are not needed to be removed after the surgery which is yet another great advantage of the pedicle screw. MethodIn this study, 3D Finite Element (FE) model of human L4 vertebrae is taken for analysis using image processing tool. Pedicle screw design with varying mechanical and geometrical properties has been carried out at different applied loads on it along with considering the effect of frictional forces between all contact surfaces. ResultMathematical relationship among stress, strain, pitch of the screw and diameter have been developed for different thread profiles which will be beneficial for researchers for further development of pedicle screw implants. ConclusionResults from the different analysis shows that bending stress on the screw for different loads at triangular pitch is higher than the trapezoidal. Hence, trapezoidal thread is efficacious than triangular thread. In case of vertebral bone, the magnitude of stress is less for trapezoidal screw than triangular and stress has a linear relationship with pitch length. In term of strain, triangular thread develops more strain than trapezoidal thread. A set of mathematical relation has been developed for different thread profile based on pitch length, stress and strain which gives the idea about von Mises stress and strain.

The Influence of Surface Treatment on Osseointegration of Endosteal Implants Presenting Decompressing Vertical Chambers: An In Vivo Study in Sheep.

To qualitatively and quantitatively evaluate histologic osseointegration parameters of implants designed with decompressing vertical chambers between the threads with two different surface treatments (TiO2 blasting + maleic acid vs TiO2 blasting + maleic + HCl) in a large translational animal model at 3 and 6 weeks in vivo. Nine female sheep were used, and 72 implants with trapezoidal threads and decompressing vertical chambers of 0.6 mm in diameter and 0.2 mm in depth were placed in the ilium crest. After 3 and 6 weeks, the animals were euthanized, and biomechanical and histomophometric analyses were performed. Survey histologic evaluation indicated intimate contact between the bone and the implants independent of surface treatment at both times in vivo. Bone formation at both time points depicted an intramembranous-type healing pattern between the implant threads. The mean removal torque values for all groups showed a relative increase in removal torque from 3 to 6 weeks. In terms of bone area fraction occupancy analysis, significant differences were found at 6 weeks between surface treatments (P = .046), where the experimental surface yielded higher degrees of bone area fraction occupancy. Conical implants with decompressing vertical chambers between threads presented similar osseointegration parameters regarding bone-toimplant contact and torque-out test values irrespective of surface treatment. However, shifting from a minimally rough to a moderately rough surface (experimental surface with supplemental acid-etching) resulted in significantly improved bone area fraction occupancy at 6 weeks.

Biomechanical influence of thread form on stress distribution over short implants (≤6mm) using finite element analysis.

The macro and micro design is essential to the biomechanical performance of a short implant. In this study, the implant thread parameters of short implants used in edentulous maxillae will be discussed. The aim of the study is to analyse biomechanical distinctions in different thread parameters over short implants by applying the vertical or oblique load of 130N on dental prosthesis. A 6*5mm implant will be used in posterior maxillae arch, where the molar region locates. The CAD model has been assembled by three parts, a crown, an implant system and a jaw. By applying the vertical or oblique load to the crown, the Von-Mises stresses of cortical bone and trabecular bone will be evaluated in pairs along the lines v1-v2 & a1-a2. The results showed that the reverse buttress thread would induce more stresses in cancellous bone whereas the buttress did the opposite. The trapezoidal thread (V-thread) is more favourable than thereverse buttress thread in accordance to the FEA result. The rectangle threads will induce more uneven stresses in cancellous bones.

The Influence of Implant Design Features on the Bone Healing Pathway: An Experimental Study in Sheep.

This study evaluated how implant design features influence osseointegration. Two implant macrogeometries and surface treatments were evaluated: (1) progressive buttress threads with an SLActive surface (SLActive/BL), and (2) inner and outer trapezoidal threads with a nanohydroxyapatite coating over a dual acid-etched surface (Nano/U). Implants were placed in the right ilium of 12 sheep, and histologic and -metric analyses were conducted after 12 weeks. Percentages of bone-to-implant contact (BIC) and bone area fraction occupancy (BAFO) within the threads were quantified. Histologically, the SLActive/BL group showed greater and more intimate BIC than the Nano/U group. In contrast, Nano/U group depicted woven bone formation within the healing chambers, between the osteotomy wall and implant threads, and bone remodeling was evident at the outer thread tip. Significantly higher BAFO was seen in the Nano/U group than the SLActive/BL group at 12 weeks (P < .042). Different implant design features influenced the osseointegration pathway, supporting further investigations to describe the differences and clinical performance.

Probability of survival and stress distribution of narrow diameter implants with different implant-abutment taper angles.

This study evaluated the probability of survival, failure mode, and stress distribution of narrow diameter implants (NDIs) with internal implant-abutment conical connection comprised of different taper angles and thread designs. Sixty-three NDIs (Ø 3.5× 8.5 mm) were divided according to the taper angle (TA), internal diameter (ID), and trapezoidal thread design (TD) (n=21/group), as follows: (a) 11.5°U (11.5° TA; ID: 2.5 mm; TD: dual threaded); (b) 11.5°S (11.5° TA; ID: 2.5 mm; TD: single threaded); (c) 16°S (16° TA; ID: 2.72 mm; TD: single threaded). They were subjected to step-stress accelerated life testing. The reliability and use-level probability Weibull curves were calculated at 50, 100, and 150 N for a mission of 100,000 cycles and the failure mode was analyzed using a scanning electron microscope. For finite element analysis the von-Mises stress (σvM ) was calculated for the abutment and implant. All groups showed high reliability (above 84%) and failures occurred predominantly in the abutment. In the FEA, 11.5°U showed higher σvM for the implant. All NDIs showed high reliability at clinically challenging loads. The system with greater taper angle showed lower σVm in the implant, and dual threaded implants showed a higher stress concentration in the implant and cortical bone.

Effect of supplemental acid-etching on the early stages of osseointegration: A preclinical model

PurposeTo evaluate the effect of two surface modifications on early osseointegration parameters of conical implants in a translational pre-clinical model. Materials and methodsConical implants with progressive trapezoidal threads and healing chambers were evaluated consisting of two different surface conditions: 1) Implacil surface (IMP Sur), and 2) Implacil surface + Supplemental Acid-etching (IMP Sur + AE). Surface characterization comprised of the evaluation of roughness parameters (Sa, Sq and Sdr), surface energy and contact angle. Subsequently, implants were installed in the ilium crest of nine female sheep (weighing ~65 kg). Torque out, histological and histomorphometric analyses were conducted after 3 and 6 weeks in-vivo. The percentage of bone to implant contact (%BIC) and bone area fraction occupancy within implant threads (%BAFO) were quantified, and the results were analyzed using a general linear mixed model analysis as function of surface treatment and time in-vivo. ResultsSupplemental acid etching significantly increased Sa and Sq roughness parameters without compromising the surface energy or contact angle, and no significant differences with respect to Sdr. Torque-out testing yielded significantly higher values for IMP Sur + AE in comparison to the IMP Sur at 3- (62.78 ± 15 and 33.49 ± 15 N.cm, respectively) and 6-weeks (60.74 ± 15 and 39.80 ± 15 N.cm, respectively). Histological analyses depicted similar osseointegration features for both surfaces, where an intramembranous-type healing pattern was observed. At histomorphometric analyses, IMP Sur + AE implants yielded higher values of BIC in comparison to IMP Sur at 3- (40.48 ± 38 and 27.98 ± 38%, respectively) and 6-weeks (45.86 ± 38 and 34.46 ± 38%, respectively). Both groups exhibited a significant increase in %BAFO from 3 (~35%) to 6 weeks (~44%), with no significant differences between surface treatments. ConclusionSupplemental acid-etching and its interplay with implant thread design, positively influenced the BIC and torque-out resistance at early stages of osseointegration.

Does Subcrestal Position Affect Insertion Torque of Different Implant Designs at Different Bone Densities? An In Vitro Model Study.

To evaluate the insertion torque at the equicrestal and subcrestal positions of three implant designs in synthetic polyurethane blocks simulating different bone conditions. Overall, 72 implants with three different designs (two conical and one cylindrical) were inserted at equicrestal and subcrestal positions (-2 mm) into polyurethane blocks simulating the anterior (0.32 g/cm3) and posterior (0.48 g/cm3) regions of the maxilla. The final insertion torque of all implants was measured using a digital torque meter, and the results were evaluated and statistically analyzed. For all implant systems, insertion torque decreased significantly when placed at the subcrestal position (P < .05), except for cylindrical implants placed in the bone blocks with high cancellous density. The implants with higher body conicity and square threads had higher insertion torque values than the cylindrical and conical implants with a lower body conical angle and trapezoidal threads. The implants inserted into higher-density blocks showed greater stability. The different implant systems lost insertion torque in a nonuniform manner at the subcrestal position and varied according to bone density. Implant design significantly influenced the initial stability at the equicrestal and subcrestal positions, especially in lower-density bone.

An Automated Platform for Surface Plasmon Resonance-Based Sensors

This article presents the design of an automated platform to quickly, efficiently, and accurately manipulate the components required for a typical surface plasmon resonance (SPR) sensing instrument. In traditional SPR platforms, such parts are at prearranged and fixed positions. The proposed solution enables individual and group component movements by adjusting the alignment and positioning to ensure either the proper excitation and detection of the SPR. The platform's mechanical chassis is constructed with an aluminum V-slot profile and trapezoidal thread spindles and nuts to guide the components' displacement. An L-shaped frame specially designed for this purpose holds all the parts. Besides mechanical chassis, microcontrollers, motors, distance sensors, temperature sensors, and a touch-screen compose the automated platform components. The use of the so-called PPBIO biochip operating in the angular interrogation mode (AIM) demonstrates the platform's functioning. The obtained experimental results agree with the ones acquired with a similar but manually adjusted test platform.

More Precise Shaping of Guide Screws with Trapezoidal Thread

How does the thread-cutter configuration with respect to the workpiece axis in roughing affect the shape precision of the external trapezoidal thread and the margin in final grinding? That question is investigated in the present work. An algorithm is outlined for determining the transverse profile of the helical channel in the external trapezoidal thread at the inner, central, and outer diameters. The channel profile calculated from that algorithm determines the cutting-edge profile at the front surface of a cutter positioned perpendicularly to the part’s helical surface for preliminary machining.

Semi-analytical torque modeling of Ti-6Al-4V-alloy internal trapezoidal thread extrusion forming with an emphasis on low-frequency torsional vibration

Abstract Conventional cold extrusion is generally considered to be less practical for trapezoidal threads, requiring a relatively large form tapping torque. The machining of it is always based on cutting, but the actual demands of high strength and long life have brought this process to its limits. These requirements drove the present work, which proposes a new process for the fabrication of a Ti-6Al-4V-alloy trapezoidal thread using low-frequency torsional vibration extrusion (LTVE) through a forming tap. A semi-analytical model of torsional vibration extrusion with friction was established by solving the problem of mechanical friction and slip-line field. The influence of low-frequency torsional vibration on the form tapping torque was studied, and the total amounts were determined quantitatively. The conclusion shows that the total tapping torque was composed of the positive pressure load and the friction load on the forming tap. The friction load was generated by the tool/workpiece friction, which is the largest component, accounting for more than 90 %. The introduction of vibration can reduce the friction in the thread form tapping so as to obtain high rheological properties, which is applicable for the low-frequency stage. Finally, a mechanical LTVE tapping excitation device was proposed based on this process method, and an experimental prototype that can meet the requirements of titanium alloy trapezoidal thread machining was developed. Experimental verification indicated that the LTVE forming process had reduced the total form tapping torque. It also proved the method’s overall reliability and effectiveness and the underlying insights needed to guide the thread manufacturing.

Experimental evaluation for internal trapezoidal thread with axial ultrasonic vibration cutting of Ti–6Al–4V

Renewal of the manufacturing process for thread is important in a variety of products and industry applications. Especially for machining the internal trapezoidal thread, the cutting edge is in a semi-closed state, three cutting edges and two cutting tips are in contact with the workpiece, resulting the heat is not easy to spread out. At the same time, the narrow space of the internal thread leads to the poor rigidity of the tool, the instability of the machining state, which seriously affects the surface machining quality of the parts. Here, a new precision processing device of axial ultrasonic-assisted turning (AUAT) is designed, which can achieve the industrial application of machining internal thread parts. The device can work stably at a working frequency of about 28.8 kHz. Secondly, considering that the bottom and flank of the thread need to be machined at the same time, the contact mode of the tool is different between them. The main cutting edge of the tool contacts the workpiece intermittently on the flank tooth, forming the texture surface which is conducive to the transmission of the thread pair. On the bottom teeth, the main cutting edge is always in contact with the workpiece and carries out the axial sawing movement. The high-frequency axial vibration damping effect is obvious, which suppresses the unstable machining state such as chatter and improves the machining surface quality of the bottom teeth. Finally, Ti–6Al–4V trapezoid thread is selected in the verification, in which the separation effect of ultrasonic vibration cutting is verified, the cutting force is tested, and the machined surface topography of the workpiece is analyzed. Experimental results show that the quality of thread was significantly improved in AUAT.

Design Optimization for the Thin-Walled Joint Thread of a Coring Tool Used for Deep Boreholes

Threaded joints are key components of core drilling tools. Currently, core drilling tools generally adopt the thread structure designed by the API Spec 7-1 standard. However, fractures easily occur in this thread structure due to high stress concentrations, resulting in downhole accidents. In this paper, according to the needs of large-diameter core drilling, a core barrel joint was designed with an outer diameter of Φ135 mm and a trapezoidal thread profile. Subsequently, a three-dimensional simulation model of the joint was established. The influence of the external load, connection state and thread structure on the stress distribution in the joint was analyzed through simulations, from which the optimal thread structure was determined. Finally, a connection test was carried out on the threaded joint. The stress distribution in the joint thread was indirectly studied by analyzing gas leaks (i.e., the sealing effect) under axial tension. According to the test data and the simulation results, the final joint thread structure was optimized, which lays a good foundation for the design of a core barrel.