Bend Bars Research Articles

Design against splitting failures in reinforced concrete due to concentrated forces and minimum bend diameter of reinforcement

Plastic bending of reinforcement bars against mandrels is the usual procedure to provide bends and hooks for steel reinforcement bars. Minimum mandrel diameters are usually given in to codes of practice, depending on the type of detail and diameter of the bar. These recommendations for the bend diameter ensure a safe transfer of forces, avoiding splitting failures that may potentially limit the resistance of the detail. In most cases, these recommendations are largely based on a number of experimental works performed several decades ago. At that time, these investigations were performed on reinforcement and concrete with lower strengths than currently used. This paper presents the results of a comprehensive research programme on bend detailing and required mandrel diameter to avoid local concrete failures leading to spalling of the concrete cover. The results of an experimental programme are presented, showing the influence of different parameters such as the mandrel diameter, the bending angle and the concrete cover. The tests were instrumented with advanced measurement techniques (fibre-optic measurements and digital image correlation), showing that consistent modelling of the transfer of forces can be performed on the basis of the geometrical and mechanical parameters of the details.

Structural Design of Steel Bar Bending Machine

In order to solve the current situation of the sharp increase of steel consumption in China, a steel bending machine with adjustable support is designed. This design selects a reasonable power source, and designs an efficient deceleration device and executive system. The design of reducer includes belt, gear, shaft and key; The executive system includes rotatable support block, lead screw, lead screw base, bending core, working disc and other parts; and the working performance of the important parts inside the bending machine is analyzed. This design can control the bending speed at 20 meters per minute and the bending diameter at Φ18mm~ Φ28mm.

The effect of hot rolling on the strength and fracture toughness of 90W–7Ni3Fe tungsten heavy metal alloys

Due to their balance of strength, ductility and toughness, liquid-phase sintered tungsten heavy metal alloys (WHAs) are considered to be an attractive alternative to monolithic polycrystalline tungsten (W) for plasma facing components. Here we explore the effect of hot rolling (HR) on the room temperature (RT) mechanical properties of a 90W–7Ni3Fe (by wt%) WHA, at different thickness reductions of 0, 62, 74 and 87%. High elastic-plastic KJm maximum load toughness for LS-oriented pre-cracked bend bars is observed in the 0 and 87% HR WHA, along with stable crack growth. In contrast, the 62 and 74% HR WHA experience elastic fracture, at much lower KIc. The opposite trend is observed in the microhardness, as well as the tensile yield and ultimate stresses, which are lowest in the 0 and 87% HR condition and highest in the 62 and 74% HR WHA. The reason for the difference in strength at 87 versus 74% HR reductions is not fully understood. However, the strength differences partially rationalize the toughness trends. Unfortunately, HR results in highly anisotropic brick-and-mortar microstructures, leading to much lower elastic KIc in the LT-orientation.

Springback Prediction for Pure Moment Bending of Aluminum Alloy Square Tube.

The springback phenomenon occurring during cold forming is the main problem affecting the dimensional accuracy of bent products, especially when bending thin-walled profiles, where there are significant changes in the cross-section geometry. This article presents the results of the analysis of the springback phenomenon occurring during shaping with a pure bending moment of square tubes with the cross-sectional dimensions of 21.5 × 21.5 × 1.8 mm and 25 × 25 × 2.5 mm made of aluminum alloy 6060. The springback characteristics were determined by defining the dependence of the springback coefficient on the set bending radius of the band. The values of the springback coefficient were provided by means of analytical calculations and numerical modeling, which considered changes in the moment of inertia caused by deformation of the cross-section occurring during bending of the pipes. A good agreement of the calculation results with the results of experimental tests was obtained. In addition, the stress state and the state of deformation, as well as the springback characteristics of square-section pipes were compared with the results obtained during bending of a solid bar with the cross-sectional dimensions of 21.5 × 21.5 mm.

Customized Two-Dimensional Computed Tomography-Guided Preoperative Pectus Bar Shaping.

Successful minimally invasive repair of pectus excavatum relies on a pectus bar that closely conforms to the desired shape of the sternum and ribs to produce optimal elevation and remodeling. However, the present method of empirical intraoperative bar shaping is tedious and risks trauma to surrounding structures. To overcome this, we devised a technique using a life-sized computed tomography (CT) printout of the patient's chest wall to guide preoperative bar bending. A 5-cm-wide polymethylmethacrylate block placed on the sternum as the patient underwent chest CT was used as a marker to guide scaling of an axial screenshot of the patient's chest to life-size. This life-size image was printed and the planned correction of the patient's chest wall was traced onto it. The pectus bar was bent according to this template. Patient demographics, Haller index, surgical indications, operative technique, complications, aesthetic and functional improvements, and overall satisfaction were assessed. Thirty patients (4 women) underwent primary minimally invasive repair of pectus excavatum with a single pectus bar shaped preoperatively over an 8-year period. The average age and Haller index was 20.6 years and 5.4, respectively. The mean operative time was 66.4 minutes. Satisfactory sternal elevation was attained with a single attempt at bar insertion in all cases. Two patients had pneumothoraxes that resolved without intervention. The mean follow-up period was 50.1 months. There were no cases of bar migration or recurrence of deformity after bar removal. On a 5-point Likert scale, all patients indicated an improvement in aesthetic appearance (4.6), and patients with physical symptoms (10) reported an improvement in function (4.4). The overall satisfaction score was 4.7. This technique of CT-guided preoperative pectus bar shaping is straightforward, eliminates the need for intraoperative revisions to bar shape, and achieves effective correction of the pectus excavatum deformity. All patients were satisfied with the aesthetic, functional, and overall outcomes.

Degradation of glass fiber reinforced polymer (GFRP) bars in concrete environment

Degradation of tensile, shear and flexure properties of glass fiber reinforced polymer (GFRP) bars is investigated in the paper. Glass fibre reinforced polymer bars, when used in structures exposed to aggressive environments, can significantly increase the lifetime, as compared to structures reinforced with conventional steel. However, the progress in utilization of GFRP bars in concrete structures is hampered due to limited information on durability of these materials. Since long-term durability data are not readily available, accelerated aging tests have been used in this research to study GFRP bar degradation. The bars were kept in a highly alkaline solution heated to 50, 60 and 70 °C for 1, 3 and 5 months, respectively, and after each immersion period, bars were taken out and tested in tension, shear and flexure. The experimental results show that immersion in high pH of the alkaline solution reduces the strength of the bars. The speed of degradation depends on the temperature of the solution. The degradation is then studied using the models for solution ingress into the GFRP bars. The conclusions proposed are that the shear test is a good indicator of the tensile strength degradation, bent bars deteriorate faster than straight bars, and smaller diameter bars deteriorate faster than larger diameter bars; finally, bars under flexural (tensile) strength deteriorate faster than those under direct tensile and shear strengths.

Comparison between Theoretical and Experimental Investigation of Composite Beams with Spiral Shear Connectors.(Dept.C)

Investigation of the behavior of composite beams with different types of shear connectors (spirals and bent bars) extends to include the comparison between the theoretical study and the experimental results of such types of beams. In this paper, a proposed technique for predicting the shear resistance of the spirals as shear connectors in the composite beams is presented. In this- technique, the behavior of the connectors in the elastic and the plastic ranges is analyzed. Hence, a proposed formula to predict the design shear resistance of the spirals is suggested. The comparison between the suggested formula and the experimental results showed a good agreement between them. Moreover, a comparison between the theoretical and the experimental results for the tested composite beams with spirals and bent bars as shear connectors is carried out with respect to ultimate loads. ultimate moment and deflections. The common type of shear connectors as bent bars is compared with spiral connectors as well. A discussion for the given formulae of die beat bar shear resistance in both Egyptian and European (EC4) codes together with the experimental results is conducted which may lead to the modification of the Egyptian formula. The comparison between the present theoretical work and the experimental results has shown good agreement.

Estimating of Bending Force and Curvature of the Bending Plate in a Three-Roller Bending System Using Finite Element Simulation and Analytical Modeling.

Many industries such as shipbuilding require steel bending plates in a wide range of radii, thus bending machines are often designed and produced on a custom basis in shipyards. From a design perspective, however, the bending force and the radius of the bending plate as a function of vertical displacement of the upper roller must be known. In this paper, a hybrid numerical–analytical approach is proposed to investigate the three-roller bending process for two plates of steel used in the naval industry. Firstly, the bending process is modeled using the finite element (FE) method and regression models for the bending force as a function of plate thickness and vertical displacement of the upper roller were constructed. Then, based on the findings from FE analysis, using the bent bar theory, two analytical expressions for the bending force were derived. Using geometric and deformation compatibilities, analytical expressions for the vertical displacement of the upper roller as a function of the curvature of the bending plate were also developed. The FE results suggest that the cross section of the plate is practically a plastic hinge in the tangent area of the upper roller and that the deformation compatibilities must be considered in order to estimate the curvature radius of the bending plate using analytical formulations. These results are of practical importance in designing rolling machines to estimate the setting parameters.

Estimasi Emisi CO2 Pada Pekerjaan Perakitan Baja Tulangan dengan Ruang Lingkup Gate To Install

Reinforcing steel is one of the major construction materials which produces significant CO2 emission. In addition, reinforcing steel is also the main material in various construction Project type. Type of construction project which uses large amounts of reinforcing steel is high-rise buildings. The growth of high-rise buildings almost all over the world tend to increase. The tendency can be shown in Indonesia which has a total of 621 high-rise buildings. With this amount, Indonesia is one of 10 countries which have a significant tendency in the growth of high-rise buildings. Furthermore, the large and small of CO2 emission of reinforcing steel is indicated sourced from the supply chain as well. Hereafter, the reinforcing steel on the site needs some heavy equipment such as bar bending, bar cutter and transportation using tower cranes. The contribution of CO2 emission from the supply chain and install on site becomes important as it contributes in shaping cycles within the construction project. The existence of such cycles can be shown by the source and the amount of CO2 emission produced by each step. By using LCA, the source and amount of CO2 emission from each step can be found. The scope developed in this research is cradle to install. The result of the research shows that the size of CO2 emission in the cradle section range from 99 kg.CO2/m3-171 kg.CO2/m3. Furthermore, the size of CO2 emission in the supply chain section ranges from 10 kg.CO2 / m3-21 kg.CO2/m3. The size of CO2 emission ranges between 1 kg.CO2/m3-5 kg.CO2/m3. The result of the research is that reinforcing steel cradle is the biggest source of CO2 emission. The CO2 emission on the site is the smallest compared to the cradle and supply chain, but they cannot be ignored because they also contribute to and make a big determinant of CO2 emission in the construction project.

Performance of Glass Fiber-Reinforced Polymer Bent Bars

Performance of Glass Fiber-Reinforced Polymer Bent Bars

Behavior of Closing Knee Joints Using L-Shaped Coupler instead of Bending Bars

Behavior of Closing Knee Joints Using L-Shaped Coupler instead of Bending Bars

Development of a frictionally damped boring bar for chatter suppression in boring process

A novel boring bar was developed for chatter reduction of machining processes. By proposing an internal frictional damping structure, additional energy dissipation during bending vibrations was imposed to the boring bar. The structure consisted of some pins longitudinally press-fitted inside the boring bar. This structure resisted against bending of the boring bar during machining processes. After introducing the structure, an analytical model was presented to determine the amount of energy dissipated by the damper. Using the analytical model and finite element modeling (FEM), the most effective configuration was obtained for the proposed frictional damper structure. After determining the best configuration, a damped boring bar specimen was fabricated for experimental comparison with a regular boring bar. The modal and cutting tests were performed on the specimens. The modal test revealed a significant increase in the structural damping of the boring bar. The cutting tests were performed at different depths of cut and different spindle speeds, and the process was investigated through sound analysis and surface finish observation. Experimental comparisons indicated the higher performance of the proposed tool.

Cutting parameters influence analysis on fatigue behaviour of dry turned UNS A97075 alloy after corrosion

Aluminum alloys, particularly series 2000 (Al-Cu) and 7000 (Al-Zn), are widely used for structural elements in aircraft. Machining processes are frequently applied in manufacturing these parts. The actual trend in the machining of these components is to reduce or eliminate the use of lubricants, due to environmental reasons. Among the different techniques, dry machining is commonly used for aluminum alloys. However, dry machining generates higher severe cutting conditions, which may negatively affect the surface integrity and the mechanical properties of the machined parts. In this regard, fatigue life is one of the most important mechanical properties to take into account. Micro-cracks generation and nucleation strongly depend on the surface conditions of the machined parts. Additionally, the addition of Zn to pure aluminum (7000 series) reduces the corrosion resistance. Despite its importance, there is a lack of research devoted to analyze the cutting parameters influence on fatigue behaviour, before and after corrosion, in dry machining of these alloys. Therefore, in this work, the cutting speed and feed rate influence on fatigue behaviour of the UNS A97075 (Al-Zn) alloy has been analyzed. Several rotating bar bending fatigue tests have been carried out, studying and comparing the fatigue life curves obtained as a function of the cutting parameters, before and after an immersion corrosion process. The experimental results have revealed that an increment in the cutting speed and feed rate gives rise to fatigue life reduction.

An in vitro system to investigate IOL: Lens capsule interaction

Posterior capsule opacification (PCO) is the most common complication associated with intraocular lens (IOL) implantation. Unfortunately, current in vitro models cannot be used to assess the potential of PCO due to their failure to simulate the posterior curvature of the lens capsule (LC) and IOL, a factor known to affect PCO pathogenesis in clinic. To overcome such a challenge, a new system to study IOL: LC interaction and potentially predict PCO was developed in this effort. It is believed that the interactions between an IOL and the lens capsule may influence the extent of PCO formation. Specifically, strong adhesion force between an IOL and the LC may impede lens epithelial cell migration and proliferation and thus reduce PCO formation. To assess the adhesion force between an IOL and LC, a new in vitro model was established with simulated LC and a custom-designed micro-force tester. A method to fabricate simulated LCs was developed by imprinting IOLs onto molten gelatin to create simulated three dimensional (3D) LCs with curvature resembling the bag-like structure that collapses on the IOL post implantation. By pushing the LC mold vertically downward, while measuring the change in position of the bending bar with respect to its start position, the adhesion force between the IOLs and LCs was measured.An in vitro system that can measure the adhesion force reproducibly between an IOL and LC with a resolution of ~1 μN was established in this study. During system optimization, the 10% high molecular weight gelatin produced the best LC with the highest IOL: LC adhesion force with all test lenses that were fabricated from acrylic foldable, polymethylmethacrylate (PMMA) and silicone materials. Test IOLs exerted different adhesion force with the 3D simulated LCs in the following sequence: acrylic foldable IOL > silicone IOL > PMMA IOL. These results are in good agreement with the clinical observations associated with PCO performance of IOLs made of the same materials. This novel in vitro system can provide valuable insight on the IOL: LC interplay and its relationship to clinical PCO outcomes.

Bending reinforced concrete beams with glass fiber reinforced polymer bars: an experimental analysis

abstract: There is a recurring need to construct in places where environmental aggressiveness is very high, such as tidal-splash sites, chemical industries, etc. In these places, steel bars, commonly used for concrete reinforcement, can suffer deterioration, losing cross-sectional area and consequently the resistant capacity. In this regard, Glass Fiber Reinforced Polymers (GFRP) bars can replace steel because of its high strength to harsh environments, low weight and high tensile strength. Thus, this work aimed to compare reinforced concrete beams with steel bars and GFRP bending bars using the procedures indicated in ABNT:NBR 6118 and ACI 440.1R-15, respectively. Experimental three-point flexural tests were performed on six concrete beams, three reinforced with steel bars and three reinforced with GFRP bars. The beams were designed for centered point loads of 23.5 kN, 37.5 kN and 57 kN, and for each load one beam was reinforced in steel and one in GFRP. As main conclusions, it can be said that the beams reinforced with GFRP bars presented greater transverse displacements due to the low modulus of elasticity of this material. In addition, the beams presented rupture loads close to each design load, showing agreement in the recommendations of the two normative documents. Comparing the maximum loads of steel and GFRP beams, ratios of +9.3%, -3.2% and -3% were obtained for beams designed for 23.5 kN, 37.5 kN and 57 kN, respectively. Also, that variations in design loads cause greater variation in the longitudinal reinforcement rate of GFRP bar-beams compared to steel-bar beams.

Продольно-поперечный изгиб многослойного стержня из физически нелинейного материала

В работе рассматриваются многослойные бетонные стержни постоянного поперечного сечения. Закон деформирования каждого слоя стержня принят в виде аппроксимации полиномом третьего порядка. Предполагается, что на защемленный стержень действуют квазистатические продольные и поперечные нагрузки и сила тяжести. Рассматриваемые задачи решаются методом Бубнова-Галеркина. The paper considers multilayer concrete rods of constant cross-section. The deformation law for each layer of the bar is adopted as an approximation by a third-order polynomial. It is assumed that quasi-static longitudinal and transverse loads and gravity act on the restrained rod. The problems under consideration are solved by the Bubnov-Galerkin method.

Effects of Applied Stress on Atmospheric Corrosion and Pitting Characteristics of 304 Stainless Steel

The effects of applied stress, ranging from tensile to compressive, on atmospheric pitting corrosion of stainless steel 304L (SS304L) were analyzed through laboratory exposure and localized corrosion experiments. Pitting characteristics, analyzed through optical profilometry, scanning electron microscopy, and electron backscatter diffraction, were obtained after exposure for 50 days of an SS304L four-point bend bar to simulated seawater conditions at 50°C and 35% RH. Additionally, localized electrochemical measurements were carried out on an unexposed SS304L four-point bend bar to analyze the effects of applied stress on the corrosion susceptibility in analogous chloride solutions. In the tested, simulated seawater environment, the applied stress showed no effect on the pitting characteristics due to the aggressivity of the 4g/m2 loading of simulated seawater. Pitting depth, surface area, roundness, and distribution were found to be largely stochastic and rely on the available cathodic area and preexisting microstructure. However, through localized corrosion experiments in more benign environments, containing lower Cl- concentrations, the effects of stress on corrosion susceptibility start to become noticeable from the open circuit potential (OCP) measurements. A measurable decrease in the OCP indicated increased susceptibility to corrosion in the region of applied tensile stress as compared to the compressively stressed region. These findings indicate that stress may be less of a contribution to corrosion susceptibility than Cl- concentration under the exposure conditions examined.Sandia National Laboratories is a multi-mission laboratory managed and operated by National Technology & Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International Inc., for the US Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525. SAND2020-4490 A

Mechanical Properties of 2Y-TZP Fabricated from Detonation Synthesized Powder

Yttria stabilized zirconia (Y-TZP) is frequently used in dental and engineering applications due to its high strength and fracture resistance. In this study, 2Y-TZP samples were manufactured from commercially available powder produced by detonation synthesis. Tests of the mechanical properties exhibited an unusual combination of both very high strength and toughness. The materials show a very weak correlation between toughness and grain size. The transformability, measurable by XRD, cannot explain the high toughness. Fractographic analysis revealed a broad transformation affected zone with secondary cracks and shear bands on the tensile side of bending bars which can be made responsible for the high toughness and non-linear stress–strain curves.

Численное и физическое моделирование деформирования стержня при осевом нагружении в канале. Часть 1

In two parts of the work, numerical and physical modeling of the deformation of the bar in the channel under axial compression is carried out. The regularities of nonlinear bending of the bar in the plane are revealed. Bar shapes are determined by the load history and can differ at the same force value. The solution is to find the shape with the lowest potential energy. The first part of the work describes the numerical model of the bar and the results of its application. The shapes of the bar bending under gradual loading are obtained, the studies coinciding with V.I. Feodosev’s analytical solution. Further research shows that the solution to the problem has a more complex ramified structure with various additional shapes. Deformation of the bar under gradual loading occurs in the form of a sequential variant appearance of bending waves in the bar under forces determined by the degree of non-uniformity of the lengths of potentially unstable sections and forming a range of shape instability. In variant transitions from one initial shape with a loss of stability, it is possible to obtain various subsequent shapes that differ in the sequence of deformation of the sections with one number of half-waves, or the number of generated half-waves. When a straight bar is loaded in one step, an increase in the force leads to a sequential increase in the number of bending half-waves in the corresponding ranges of the existence of shapes. The results obtained can be applied to the analysis of the operation of such bar objects as drill, casing, tubing strings in the well and cased pipelines, pipelines in the well and tunnel.

Modeling the pure bending of plates with analog circuit models

Previous work created a way to model flexural bending of Euler-Bernoulli beams as an analog circuit model [C. J. Childs and S. C. Thompson, J. Acoust. Soc. Am. 145, 1895 (2019)]. Further work has been completed to expand the modeling technique from one-dimension into two-dimensions. This allows for enhanced accuracy in modeling physical structures, including a Timoshenko bar or pure bending of plates. The modeling technique will be presented to show bending of plates with comparable accuracy and computational resource advantages, as seen with the Euler-Bernoulli model.