End Geometry Research Articles

Experimental investigation and numerical simulation of swaging process of tubes for oil country tubular goods

AbstractPremium integrated seamless pipes made from high strength low alloy steels are used to produce oil country tubular goods. Operational requirements of these pipes in petroleum industry lead to an adequate tube end connection with better mechanical strength and sealing properties. Therefore a cold swaging process or calibration of pipe end is necessary for the mechanical threading process of the tube. Applications of typical calibration mandrels result in heavy wear due to higher swaging loads and the optimal necessary geometry of end tube could not be achieved. In this study, a new mandrel geometry with a finished surface was developed to modify the pipe end profile and reduce the wear tool. The investigated pipe made from P110- pipe steel was plastically preformed using a cold swaging process. Experimental measurements of the pipe end geometry after swaging process resulted an increase of the inner tube diameter of approximately 4.9% and an outer tube diameter of 3.7% respectively. Furthermore, a rather constant tube wall thickness was also observed. An Abaqus plug-in was developed to characterize the swaging process of pipe ends. The influence of friction between tool and pipe surfaces on the final geometry of pipe ends and residual stresses in pipe ends due to preforming were numerically predicted. The new designed swaging process resulted a better final pipe end geometry and low tool wear during the preforming of pipe end. The presented plug-in in this work could be used for tool optimization and characterization of swaging process of pipes in oil and gas industries.

Enhancing Heat Transfer Performance in Simulated Fischer–Tropsch Fluidized Bed Reactor through Tubes Ends Modifications

Fluidized bed reactors are essential in a wide range of industrial applications, encompassing processes such as Fischer–Tropsch synthesis and catalytic cracking. The optimization of performance and reduction in energy consumption in these reactors necessitate the use of efficient heat transfer mechanisms. The present work examines the considerable impact of tube end geometries, superficial gas velocity, and radial position on heat transfer coefficients within fluidized bed reactors. It was found that the tapered tube end configurations have been empirically proven to improve energy efficiency in fluidized bed reactors significantly. For example, at a superficial gas velocity of 0.4 m/s, the tapered end form’s local heat transfer coefficient (LHTC) demonstrated a significant 20% enhancement compared to the flat end shape. The results and findings of this work make a valuable contribution to the advancement of complex models, enhance the efficiency of fluidized bed reactor processes, and encourage further investigation into novel tube geometries.

Interaction of fuel spray and air swirl on the combustion of residue oils

Effervescent atomization technology was applied in Waste Lubricant Oils (WLO) combustion. The tests were conducted in a 150 kW prototype boiler with a horizontally oriented cylindrical shape combustion chamber in which the combustion process was studied in terms of the interaction between a swirling air flow and fuel spray pattern. The combustion performance was assessed by continuously monitoring gaseous emissions, particularly carbon monoxide (CO) emission. Two different air feeding strategies were tested, varying in swirl number and six different configurations of the injection nozzle orifice. Three nozzles had a single orifice varying in diameter and discharge end geometry, and the others had three divergent orifice arrangement varying in cone angle and diameter. At the same time, the gas-to-liquid ratio (GLR) of the effervescent atomizer was also investigated, allowing to draw important illations about its influence on the combustion efficiency. The results show that the use of effervescent atomizers allows to burn of WLO, with CO emissions as low as 15 ppm at 8% of oxygen (O2) when using a three orifice of 1 mm with 15° of cone angle nozzle. This result was achieved by applying high-intensity combustion air flow swirl. However, the one orifice nozzles with penetrant spray pattern combined with low swirl intensity air flow also produced satisfactory results. With CO emissions of 27 ppm at 8% of O2 with a 1.2 mm single orifice nozzle. Furthermore, it was also demonstrated that the increment of the GLR in a range between 0.25 and 0.35 can be responsible for the reduction of 40 to 50% of the CO emissions when burning WLO.

The Folded Pneumatic Artificial Muscle (foldPAM): Towards Programmability and Control via End Geometry

Soft pneumatic actuators have seen applications in many soft robotic systems, and their pressure-driven nature presents unique challenges and opportunities for controlling their motion. In this work, we present a new concept: designing and controlling pneumatic actuators via end geometry. We demonstrate a novel actuator class, named the folded Pneumatic Artificial Muscle (foldPAM), which features a thin-filmed air pouch that is symmetrically folded on each side. Varying the folded portion of the actuator changes the end constraints and, hence, the force-strain relationships. We investigated this change experimentally by measuring the force-strain relationship of individual foldPAM units with various lengths and amounts of folding. In addition to static-geometry units, an actuated foldPAM device was designed to produce continuous, on-demand adjustment of the end geometry, enabling closed-loop position control while maintaining constant pressure. Experiments with the device indicate that geometry control allows access to different areas on the force-strain plane and that closed-loop geometry control can achieve errors within 0.5% of the actuation range.

Differential geometry method for minimum hard-way bending 3D design of coils with ReBCO tape conductor

The use of tape conductor poses design challenges for superconducting magnets. Due to its very high aspect ratio, it is hardly possible to bend the conductor over its thin edges (hard-way bending) rather than over its wide side (easy-way bending). Overstraining the conductor causes critical current degradation. In this paper, we propose a new design approach to three-dimensional coil layouts and coil end geometries with tape conductor, which considers the tape’s geometrical limitations. To geometrically describe the conductor surface, we use the thin strip model, also referred to as constant perimeter geometry. To prevent conductor degradation, new optimization criteria valid for three-dimensional geometries are presented, which are prevention of conductor creasing, minimization of overall bending energy, and prevention of over-straining the conductor. We will apply this to two 3D coil designs called helix and canted cosine theta. For the design of the coil ends, we propose a new design method using Bézier splines, which allows for much greater design flexibility than previous methods. Two examples of coil end geometries generated with Bézier splines are presented: the so-called cloverleaf and cosine-theta.

Dieless drawing wire with a given end geometry by realizing temperature distribution evolution

Dieless drawing that has been widely used to produce metal tubes, wires, and rods has more potential for the future, especially in manufacturing high performance screws and nails with specific points. Because there are no dies but heating and cooling system along with drawing platform needed, it is highly flexible and meets the requirements of the steadily asked manufacturing on-demand. Under this trend, this study attempts to propose a heat transfer model that can achieve the required temperature evolution for dieless drawing a wire to form a specific end geometry as a nail point by obtaining the required evolution of heat transfer coefficient and the correspondingly approximated cooling fluid rate. After it is validated with tests on a dieless drawing platform implemented with a cooling system, whose cooling flow rate is controllable, the results show that for a linear end geometry of a stainless steel wire, there is no significant difference between the temperature distribution evolution required and obtained from the experiment. Furthermore, the end geometry of the drawn wire falls within the current industry standard tolerances as well.

Air-knife design for improved drying efficiency in manufacturing flat-panel displays

Abstract With the growing demand for flat-panel displays (FPDs), the size and production conveyance speed of glass are increasing to improve productivity. Improvement of productivity, speed, and efficiency in the drying process used in FPD manufacturing has become an important issue. Therefore, this study aims to improve the drying efficiency by optimizing the primary design variables of an air knife, the most common FPD drying system, through numerical analysis. To optimize the air-knife design, the feasible optimal values were fixed for the slit gap (0.15 mm) and glass gap (1.5 mm), and the optimized dimensions were determined by considering the nonsymmetric distance (0.5 mm) and installation angle (15°) of the end geometry of the air knife channel. The optimized air-knife design improved the drying efficiency by approximately 30% compared to that of the existing system; therefore, it can increase the productivity of the FPD manufacturing process.

Residual strength and toughness properties of 3D, 4D and 5D steel fiber-reinforced concrete exposed to high temperatures

Conventional single-hooked (3D) steel fibers are one of the most widely used fibers to improve the strength, ductility and toughness properties of plain concrete. Recently, multi-hook 4D and 5D steel fibers with modified end geometries have been widely used in concrete applications as an alternative to 3D conventional steel fibers. The primary aim of this study was to compare mass loss, compressive and flexural strength, and toughness capacities of 3D, 4D and 5D steel fiber-reinforced concrete (SFRC) at room conditions and after high-temperature effects. Fibers were added to cement mortars at 0.5% and 1.5% by volume. All specimens were exposed to temperature effects of 300, 500 and 800 °C. According to the results obtained, the residual strength and toughness capacities of control and 3D, 4D and 5D SFRC specimens decreases significantly at 500 and 800 °C. However, when compared to control concrete, 3D, 4D and 5D SFRC specimens have higher residual compressive and flexural strength and residual toughness capacity after high-temperature effects. Furthermore, 5D steel fibers are more effective than 3D and 4D steel fibers to enhance the residual compressive and flexural strength and residual toughness capacity of concrete due to superior end geometry and higher tensile strength. In addition, this increase was more pronounced when the fiber volume ratio increased from 0.5% to 1.5%.

Failure analysis of simple overlap bonding joints and numerical investigation of the adhered tip geometry effect on the joint strength

Abstract This study was carried out in two stages. In the first step, a numerical study was performed to verify the previous experimental study. In accordance with the previous experimental study data, single lap joints models were created using the ANSYS finite element analysis program. Then, nonlinear stress and failure analyses were performed by applying the failure loads obtained in the experimental study. The maximum stress theory was used to find finite element failure loads of the single lap joints models. As a result of the finite element analysis, an approximate 80 % agreement was found between experimental and numerical results. In the second step of the study, in order to increase the bond strength, different overlap end geometry models were produced and peel and shear stresses in the adhesive layer were compared according to the reference model. As a result of the analyses, significant strength increases were calculated according to the reference model. The strength increase in model 3 and model 5 was found to be 80 % and 67 %, respectively, relative to the reference model.

Determination of Optimal Flat-End Head Geometries for Pressure Vessels Based on Numerical and Experimental Approaches.

The experimental and numerical analyses of the pressure vessels with different flat ends are presented and discussed in the paper. The main aim of the study is to propose the optimal flat head end geometry. The analyses are focused on the comparison of standardized geometries and with the proposed elliptical cut-out. The experimental tests with the application of strain-gauge measurements and numerical modeling of the pressure vessel are conducted. The behavior under low and high pressures and the influence of the residual welding stresses, material properties, and geometrical tolerances on the level of the plastic deformation in the flat end is discussed. It is presented that the rules given in the recent standard are not sufficient for optimal selection of the optimal geometry. It is observed that in certain geometries the deviations of the pipe thickness may lead to a significant increase of the equivalent stresses. The residual welding stresses have a significant influence on the stress and strain level—particularly in the stress relief groove (SRG). The performed study and comparison of the different geometries allow for the proposal of the optimal shape of the flat end. It appeared that the pressure vessels with SRG are the most optimal choice, particularly when elliptic shapes are in use. In some cases (i.e., pipe with wall-thickness equal to 40 mm and the flat end with circular SRG), the optimal configuration is reached for dimensions beyond the admissible by code range.

Tailoring magnetization reversal of a single-domain bar nanomagnet via its end geometry

Nanoscale single-domain bar magnets are building blocks for a variety of fundamental and applied mesoscopic magnetic systems, such as artificial spin ices, magnetic shape-morphing microbots, and magnetic majority logic gates. The magnetization reversal switching field of the bar nanomagnets is a crucial parameter that determines the physical properties and functionalities of their constituted artificial systems. Previous methods on tuning the magnetization reversal switching field of a bar nanomagnet usually relied on modifying its aspect ratio, such as its length, width, and/or thickness. Here, we show that the switching field of a bar nanomagnet saturates when extending its length beyond a certain value, preventing further tailoring of the magnetization reversal via aspect ratios. We showcase a highly tunable switching field of a bar nanomagnet by tailoring its end geometry without altering its size. This provides an easy method to control the magnetization reversal of a single-domain bar nanomagnet. It would enable new research and/or applications, such as designing artificial spin ices with additional tuning parameters, engineering magnetic microbots with more flexibility, and developing magnetic quantum-dot cellular automata systems for low power computing.

A RANS-VoF Numerical Model to Analyze the Output Power of An OWC-WEC Equipped with Wells and Impulse Turbines in A Hypothetical Sea-State

Wave energy is a renewable source with significant amount in relation to the global demand. A good concept of a device applied to extract this type of energy is the onshore oscillating water column wave energy converter (OWC-WEC). This study shows a numerical analysis of the diameter determination of two types of turbines, Wells and Impulse, installed in an onshore OWC device subjected to a hypothetical sea state. Commercial software FLUENT®, which is based on RANS-VoF (Reynolds-Averaged Navier-Stokes equations and Volume of Fluid technique), is employed. A methodology that imposes air pressure on the chamber, considering the air compressibility effect, is used. The mathematical domain consists of a 10 m deep flume with a 10 m long and 10 m wide OWC chamber at its end (geometry is similar to that of the Pico’s plant installed in Azores islands, Portugal). On the top of the chamber, a turbine works with air exhalation and inhalation induced by the water free surface which oscillates due to the incident wave. The hypothetical sea state, represented by a group of regular waves with periods from 6 to 12 s and heights from 1.00 to 2.00 m (each wave with an occurrence frequency), is considered to show the potential of the presented methodology. Maximum efficiency (relation between the average output and incident wave powers) of 46% was obtained by using a Wells turbine with the diameter of 2.25 m, whereas the efficiency was 44% by an Impulse turbine with the diameter of 1.70 m.

ÇEKME YÜKÜ UYGULANMIŞ BORU YAPIŞTIRMA BAĞLANTILARINDA BİNDİRME UÇ GEOMETRİSİNİN BAĞLANTI DAYANIMINA ETKİSİNİN ARAŞTIRILMASI

Yapıştırma bağlantıları, farklı bağlantı geometrilerinde oluşturulabilmektedir. Yapıştırma bağlantı tasarımlarında yoğun bir şekilde kullanılan ve üzerinde çok sayıda araştırma yapılmış yapıştırma bağlantı şekillerinden birisi de tek tesirli bindirme bağlantılarıdır. Yapılan çalışmalar sonucunda tek tesirli bindirme bağlantılarının bindirme uçlarında oluşan gerilme yığılmalarının hasarın oluşmasında etkin rol oynadığı belirtilmiştir. Tek tesirli bindirme bağlantılarında, bindirme uçlarında, malzeme azaltılması yapılmasının gerilme yığılmalarını düşürdüğü ve bunun sonucu olarak bağlantı dayanımının arttığı yapılan çalışmalardan anlaşılmaktadır. Dolayısıyla, yapıştırılan malzemelerin bindirme uçlarında malzeme azaltılmasının, farklı bağlantı geometrilerinde dayanıma etkisinin araştırılması önemli olmaktadır. Yapılan bu çalışmada, çekme yüküne maruz bırakılmış boru yapıştırma bağlantıları modellenerek, yapıştırılan boruların bindirme bölgesindeki farklı uç geometrilerinin bağlantı mukavemetine etkisi bir sonlu elemanlar analiz programı olan ANSYS kullanılarak araştırılmıştır. Yapılan çalışmada ilk olarak yapıştırılan boruların uç kısımlarındaki et kalınlığının bağlantı dayanımına etkisi araştırılmıştır. Daha sonra, borunun bindirme bölgesi boyunca et kalınlığı, bindirme ucundan itibaren farklı uzunluklarda modellenerek boru ucu uzunluk değişiminin bağlantı dayanımına etkisi çekme yükü altında araştırılmıştır. Sonuç olarak bu çalışma şartlarında ideal tasarımın Model-4 tasarımı olduğu bulunmuştur. Bu tasarımda yapıştırma bağlantılarında kritik bölge olan yapıştırıcı tabakasının dayanımı % 20,5 oranında artmıştır.

A semi-analytical approach for rapid detection of roller-flange contacts in roller element bearings

For axially loaded cylindrical and tapered roller bearings, the dynamic behaviour of individual rollers, wear and friction losses are strongly influenced by roller-flange contact forces. For a realistic modelling of normal and friction forces of the roller-flange contact, it is essential to determine location and theoretical penetration of this contact. The rapid contact detection is particularly significant for rolling element bearing dynamic modelling in multibody systems. In this paper a semi-analytical algorithm for contact detection is introduced and compared to state of the art methods. The new approach adopts piecewise functions of spheres, cones and tori for modelling of roller end and flange geometry. The location of the contact and its theoretical penetration is calculated using analytical and combined analytical-numerical schemes. The semi-analytical approach proves to be significantly faster and numerically more stable than current contact detection algorithms without compromising precision.

Stability of pinned-rotationally restrained arches

The article aims to find the buckling loads for pinned?rotationally restrained shallow circular arches in terms of the rotational end stiffness, geometry and material distribution. The loading is a concentrated vertical force placed at the crown. A geometrically nonlinear model is presented which relates not only the axial force but also the bending moment to the membrane strain. The nonlinear load-strain relationship is established between the strain and load parameters. This equation is then solved and evaluated analytically. It turns out that the stiffness of the end-restraint has, in general, a significant effect on the lowest buckling load. At the same time, some geometries are not affected by this. As the stiffness becomes zero, the arch is pinned-pinned and as the stiffness tends to infinity, the arch behaves as if it were pinned-fixed and has the best load-bearing abilities.

Experimental Investigation of the Flexural Behavior of Steel Fiber Reinforced Concrete

This research study is conducted to investigate the flexural behaviour of steel fiber reinforced concrete (SFRC) prisms incorporating different types and volume fractions of steel fibers, various grades of concrete, and different specimen depths, all tested under displacement control mode using four-point loading configuration. Two types of steel fibers (hooked end and straight) were incorporated into the concrete mixes at two different dosages (1% and 2%). Concrete mixes with compressive strengths of 40, 50, and 70 MPa were used to cast the samples. Specimen depth was also among the test variables, where prisms of depth 100, 150 and 200 mm were tested to study the size effect on the flexural behaviour of SFRC. Test results indicated that for the straight-end steel fibers, the increase in the fiber volume fraction from 1 to 2% had a noticeable effect on both flexural strength (or Modulus of Rupture, MOR) and associated prism mid-span deflection. However, for the hooked end steel fibers, there was only a limited increase in the same measured values due to reduced workability of the SFRC fresh mix. The test results also have shown that the increase in the concrete compressive strength had only a modest effect on the average MOR value, but a noticeable effect on average mid-span deflection at peak load. The latter was attributed to the relatively long length and the hooked end geometry of the steel fibers. Finally, test results revealed that specimen depth had an impact on the measured flexural strength, where increase in specimen depth was associated with reduced MOR values, a phenomenon that is commonly referred to in the literature as size effect.

Thrombectomy aspiration device geometry optimization for removal of blood clots in cerebral vessels

A study involving the removal of blood clots in cerebral vessels by aspiration thrombectomy is presented. A robust design for the distal end geometry of a catheter is obtained that, together with adequate suction conditions, could avoid potential damage in the artery or fragmentation the thrombus. The optimization process of the parameters is undertaken by a Design of Experiments (DOE) that has been prepared based on Robust Design theories. In particular, 27 experiments are run for one factor at 9 levels (catheter geometry) and up to 9 factors at 3 levels. The experiments are formulated with virtual models that are solved with computing tools. Co-simulation between Computer Fluid Dynamics (CFD) and Finite Elements Method (FEM) structural analysis was used to obtain the suction conditions and the behavior of the blood clot during the intervention process. By comparing the results of the 27 experiments, the highest values of the suctioning force are obtained for a hole pattern based catheter design, that also gives the lowest risk for clot damage (based on the stress value obtained). Direct aspiration and designs based on conical catheter distal ends, give less robust solutions (results are not stable when the conditions of the environment change). Our study investigated the distance between the catheter and the clot, and it was noted that if the catheter was far from the clot, the suction generated a vessel narrowing and consequent potential damage. Up to 90 kPa could be applied when suctioning at a maximum distance equal to the diameter of the vessel between the distal end of the catheter and the proximal end of the clot. A maximum suctioning force of 0,514N was achieved without damage to the artery or the clot. This research enables us to determine and use the most representative parameters and geometries to be tested in in-vitro and in-vivo experiments. In this virtual study, hypothesizes are assumed with regard to the material properties, but the robustness of the design process allows to expect similar results in future in-vitro and in-vivo tests.

Multiaxial fatigue assessment of tube-tube steel joints with weld ends using the peak stress method

In the context of fatigue design of welded structures, the peak stress method (PSM) is a rapid numerical technique in engineering that applies an approach based on notch stress intensity factors (NSIFs). To estimate NSIFs, the PSM requires only a single stress value calculated using either 2D or 3D finite element (FE) models discretised using coarse meshes, with the adoptable element size being some orders of magnitude larger than required to calculate the NSIFs based on local stress fields. In this study, the PSM was applied to the fatigue assessment of tube-tube steel joints with weld ends subjected to combined loadings: pure axial, pure torsion, in-phase and out-of-phase axial-torsion loadings, all with two load ratios, i.e., R = 0 and R = −1. Experimental fatigue results generated in a previous study by some of the authors have been reanalysed in this study through the application of PSM to 3D FE models, including an idealised weld end geometry. The experimental fatigue crack initiation location was properly estimated using PSM, and there is good agreement between the experimental results and the relevant PSM based design curve.

Design of Caliber Rolls Incorporating Load Path Dependent Damage Evolution

Caliber rolling is an important forming process to produce semi-finished parts. In caliber rolling, the process route can be varied with respect to the caliber geometry at intermediate passes without changing the initial and end geometry. Usually these intermediate passes are optimized with regard to the filling degree, which depends on the axis ratio of the oval caliber and on the area reduction in each pass. In order to improve the service life of products, this paper considers the damage evolution additionally. For a roll-sequence round-oval-round two rolling routes are found with adequate filling degree in each roll pass. The variation of the process route leads to a significantly different loading path, which is defined as the strain-dependent development of stress triaxiality and Lode parameter. In this study, the influence of the loading path variation on the damage evolution is investigated. Meanwhile, damage criteria, e.g. Oyane criterion, are applied to predict the progressive damage level. The results indicate a remarkable difference in damage at the end of the process due to the loading path variation and higher damage always occurs near the symmetric axis of the workpiece according to FE simulations.

Effect of probe geometry on fluid flow near laboratory-scale quench probes

ABSTRACTInternational standards for cooling curve analysis use flat-end cylindrical quench probes; however, changing the probe end may lead to a better performance. To assess the effect of probe geometry on the flow near the solid–liquid interface, computational fluid dynamics (CFD) simulations of velocity and pressure fields under low-temperature conditions were carried out. To validate the mathematical model, tests were performed in a laboratory-scale device to visualise streamlines around the probe. The variables studied were probe end geometry (flat-end, hemispherical-end, and conical-end) and water free-stream velocity. From the simulations, it was observed that the flat-end cylindrical probe distorts the flow pattern near the probe end. This distortion agrees with the computed dynamic pressure field, and it is attributed to the decreasing velocity in that region. Streamlines around the conical-end and the hemispherical-end probes suggests more favourable hydrodynamic conditions for cooling curve tests. The measured cooling curves were more reproducible when using the conical-end probe, which may be explained based on variability in the collapse of the vapour film and the advancing of the wetting front. Videos taken during the quench tests showed different initial vapour film geometry, depending on the probe geometry, that can be explained using the computed streamlines.