Cold Bending Research Articles

Study of the thermal effect of hot and cold working on the mechanical properties of medium carbon steel

Medium carbon steel is widely used in industries due to its favourable strength and flexibility. However, they are highly prone to deformation processes that affect their impact resistance and corrosion rate. This research examines the effects of hot and cold working on the mechanical properties of medium-carbon steel. Experimental tests were conducted on medium carbon steel samples subjected to hot and cold working treatment procedures via funnels for the hot working. Deformation techniques such as rolling and bending are employed by subjecting the materials to a high temperature of 900oC. At the same time, in this study, cold working uses room temperature between 0oC to 22 oC for both rolling and bending. The results show that hot bending improves the hardness property in the bending analysis, having 185.64, as opposed to cold bending, which is 174.33. It can be seen that the cold rolling treatment of medium carbon steel increases the hardness property by 179.84 compared with hot rolling techniques, which have a hardness of 161.63. The results from the rolling test show that the tensile stress at the yield point of the zero slopes is lower during the hot working process, having 598.05090 MPa, compared with the cold working results of 665.43718 MPa. However, the results of the elasticity modules show that hot working increases it with a value of 32885.24170 MPa compared with 28923.17810, respectively. It can be concluded that parameter optimization of the specification of medium carbon steel determined the specific treatment needed for the manufacturing industry to produce quality materials.

Research on the Mechanism and Processability of Roll Forming.

Cold bending forming is a complex forming process, and its product quality is closely related to the forming process parameters. To mitigate issues such as bulging and waviness arising from the extension of the material at the edges during the forming process of thin-walled circular tubes, a comprehensive comparative analysis was conducted on four forming methods. This analysis determined that the combined bending method is the optimal forming technique for the equipment. For the impact of different parameters on the equivalent plastic strain distribution of the product and the force on the rollers, numerical simulations were carried out using the software COPRA (COPRA FEA RF 2023.1) after designing the pattern diagram based on the integrated bending method. The results showed that different processing speeds on the equivalent plastic strain distribution and work hardening of the plate have little effect. As the spacing between the upper and lower rollers increases, the equivalent plastic strain of the plate to a certain extent and the value of the moment of the rollers is significantly reduced. Analyzing the performance characteristics of high-strength steel materials from the aspects of the thickness strain and cross-sectional forming of the plate, this verifies the advantages of forming high-strength steel plates. The numerical simulation results of this study are in good agreement with actual production experimental results.

Mechanical Properties of Glass Plate During Anticlastic Cold Bending

Anticlastic glass surfaces play a significant role in free-form glass facades. For realizing anticlastic surface, cold bending by loading at the corner of the plate is more adaptive and more economic than traditional hot bending method. Previous research on anticlastic cold bending mainly focuses on the description of instability phenomenon and qualitative analysis of parameters. However, the failure mechanisms of glass plates during cold bending and the influence of lamination remains unclear. In this paper, the anticlastic cold bending test was conducted to explore the influence of various factors, including aspect ratio, scale and composition of the plates. Subsequently, an effective finite element model was established and validated by test results, which is used for further explore the cold bending controlling condition for better engineering practice. The failure modes are considered as instability and strength failure. For laminated glass, maximum stresses can be derived from monolithic glass based on equivalent thickness method. The instability is induced by the compression area in the middle surface of glass plate which is significantly influenced by the composition of the laminates. Consequently, thin glass laminates exhibit enhanced stability because a reduced glass to PVB thickness ratio changes the compression area from bi-directional to uni-directional.

Design and analysis of mechanical mechanism of cold-forming equipment for marine profiles

Abstract For the existing cold bending machine with complex structure, low automation, and poor motion accuracy. A cold-forming machine that can be used for cold-forming processing of ship profiles is designed in this paper. Firstly, the general structure of the equipment is described. Secondly, the key mechanical structures, such as the guiding mechanism, the feeding mechanism, and the cold bending mechanism, are explained. Finally, the finite element models of key components were mechanically analyzed. The results show that the mechanical structure design proposed in this paper not only meets the mechanical design requirements needed for the system but also can effectively prevent the profile from slipping during the feeding process and achieve highly accurate automatic cold bending processing of the profile.

Effect of microstructure and bending angle in cold bend pipe of SA 106B on flow accelerated corrosion behavior in simulated pressurized water reactor secondary circuit water environment

The flow-accelerated corrosion (FAC) behavior at different bending angles in bend pipe in simulated secondary circuit water environment of pressurized water reactor (PWR) was investigated. The results indicated that the FAC rates at different bending angles within the bend pipe strongly depended on the ferrite nanocrystallization degree and the mass transfer coefficients. Ferrite nanocrystallization played a dominant effect on FAC, and the mass transfer coefficient played a secondary role on FAC, causing the maximum FAC rate in bend pipe was transferred to the 45° position on the intrados.

Viscoelastic modeling via fractional calculus of the cold bending of laminated glass

A viscoelastic description via fractional calculus is used to theoretically determine the time-varying stress state in single-curvature cold-bent laminated glass. This approach is proven effective when the relaxation function of the polymeric interlayer can be approximated by branches of power laws, as in most commercial materials. Solutions are obtained numerically by approximating the fractional time derivatives with the L1 formula. This conveniently allows to use a variable time step for a phenomenon characterized by two time-scales, corresponding to the loading process and the long-term relaxation. A parametric analysis shows the effects of polymer type, interlayer thickness, deformation history and operating temperature. A comparison is made with the results from the quasi-elastic approximation, which neglects the memory effect of viscoelasticity, showing that, since the interlayer strain is kept constant in the long term, it provides accurate results in term of peak and asymptotic stresses in glass, although the early stages of the deformation history give rise to differences when the structure is far from the layered or monolithic limits. This study can be useful for the optimization of the cold-bending process.

Experimental investigations on the collapse of spiral-stiffened cylindrical shells under external hydrostatic pressure

This paper presents a comprehensive experimental investigation into the collapse behavior of spiral stiffened cylindrical shells under external hydrostatic pressure. Spiral stiffened cylindrical shells with two different pitches and cylindrical shells were designed and fabricated. The fabricated specimens were divided into three groups. Each group has two identical specimens. Test specimens were welded from stainless steel. The shell was formed by cold bending, and the spiral ribs were welded to the surface of the shell to form a spiral stiffened cylindrical shell. Measurements of initial geometric imperfections and shell thickness were performed on the fabricated specimens to verify the accuracy of fabricating. Subsequently, the specimens were placed in a pressure chamber and pressurized until collapsed to obtain the ultimate collapse pressure and collapse modes. In addition, a uniaxial tensile test was conducted on the shell material to obtain its material properties. Experimental results indicated that the fabricated specimens had excellent repeatability and reasonable precision. The presence of a spiral rib effectively boosted the ultimate collapse pressure of the cylindrical shell with a more pronounced strengthening effect observed as the rib density increased.

ВСТАНОВЛЕННЯ ВПЛИВУ ПАРАМЕТРІВ ПРЕСУВАННЯ НА ПРОЦЕС ГНУТТЯ БУКОВИХ МЕБЛЕВИХ ЗАГОТОВОК

It is substantiated that the technology of cold bending of pre-pressed blanks has a perspective. It was established that the minimum bending radius depends on the direction of pressing and the degree of pressing. It was determined that pressing in the radial and tangential directions does not give the desired effect during bending, which is evidenced by a large number of defects (respectively 47-67% and 34-61%) associated with the specific structure of the wood. In particular, during pressing, the wood cells are deformed along the pressing line, and during subsequent bending, the elongation of the wood in the peripheral part passes across the pressing line and is only partially compensated by the pressed cell walls. It was experimentally established that the results are significantly different when the workpieces are axially pressed. When the degree of pressing is increased from 15 to 25%, the number of high-quality blanks increases and amounts to 83-97%, respectively. This can be explained by the fact that during axial pressing, wood cells are deformed along the line of pressing. During subsequent bending, the elongation of the wood in the peripheral part also takes place along the line of pressing and is compensated to a much greater extent by the pressed cell walls. It was found that when the workpieces are pressed along the axis, uneven pressing along the length occurs, that is, only approximately half of the length of the workpiece is pressed. This is probably the main reason for the defect. Additional research and possibly new technological solutions are needed to solve the problem of uneven pressing during axial pressing. Prospective directions of research into bending processes of beech furniture blanks have been formed, in particular from the development of new bending technologies; optimization of pressing parameters; modeling of bending processes; study of the influence of humidity and temperature; study of the strength and durability of bent blanks.

Exploring bundle bamboo split technique in bending dendrocalamus asper for landscape structure

Bamboo is one of the fastest-growing natural construction materials and is locally available in most developing countries, including South America, Africa, and Asia. Bamboo is a “green gold” plant in the tropical forest. It is a fast-growing monocotyledon species belonging to the Gramineae family (Bambusoideae) and requires a short time for re-production. Bamboo’s physical strength provides builders from ancient times until today an opportunity to use bamboo as a natural and sustainable construction material for building houses and structures. Due to its capability to bend, bamboo is the most preferred material in vernacular construction and lately in Southeast Asia countries which borne new trend in building design. The built-environment professionals, namely landscape architects, architects, and engineers in Malaysia, still lack knowledge of bamboo, especially on bending capabilities, as one of the sustainable construction materials. Less concern was given to researching the capabilities of bamboo’s ability to bend, even though its strength is more than steel and provides various design opportunities compared to other sustainable materials. Different types of bamboo present different strength capacities. Therefore, the aims of this research is to compare and determine their strength capacity, bending criteria and species suitability for design and construction in Malaysia. This paper collects published literature on experimental studies on the different methods of Hot and Cold Bending Methods which allow bamboo to bend to suit designer needs and concentrate on Malaysian Dendrocalamus asper (Buluh Betung), which considered as tough and durable species, as the primary construction material for landscape structures. Bundle Bamboo Split (BBS), identified as one of the bending techniques adopted for an experimental project, using BBS of 0.8m radius, produces a prototype for a landscape structure. The findings indicate observation of works by a team of craftsmen trained by an expert in bamboo construction who used to produce bamboo structures from Bali, Indonesia, highlighted tools and procedures in bamboo construction. In short, this paper will also enhance the use of bamboo as an accessible, durable, creative and sustainable construction material that represents the local identity of Tropical Malaysia Landscape Architecture.

Adjust operating conditions of an in-made house horizontal hydraulic press for a 90° cold bending process

During the cold-bending process, the tooling suffers considerable damage due to excess pressure. This also causes the machines to break down, causing problems in the precision and quality of the metal parts formed. The precision depends on the operating conditions of the press, the tooling employed, and the elastic recovery effect of the material. This study determines the working conditions for a made-in-house horizontal hydraulic press through an experimental design (DOE). This research carried out the V-forming to 90° (ISO 2768-1) of a hot-rolled carbon steel plate, considering pressure, piston permanence time, and recovery factor (Kr). The experimental and statistical analysis ensures accurate forming while the work pressure decreases by 17% and 33%, respectively, regarding the maximum. This reduction will delay the appearance of fatigue damage and have the operating parameters well established; in turn, it will be possible to design tools according to commercial standards.

Investigation on Al-Al2O3 refractories with Al2O3-Ti2O3 raw material at evaluate temperatures

To explore the phase evolution and performance changes of Al-Al2O3 refractories at high temperature upon adding novel Al2O3-Ti2O3 raw materials, samples with different Al2O3-Ti2O3 contents were heated at 1300 and 1500 °C under N2 atomosphere. The samples were analyzed by XRD, SEM, TG-DSC,industrial CT. The results indicate that the reaction between Ti2O3 and Al proceeds at elevated temperatures under N2, and the Ti2O3 phase transformed from Al-Ti alloy to TiN. At 1300 ℃, Ti2O3 was party reduced by Al and formed Al-Ti alloys with the unreacted Al, and the remaining Ti2O3 was present in a finely dispersed state, exhibiting fine whiskers in the matrix. When the heating temperature increaseds to 1500 ℃, the whiskers in the matrix became coarse due to the gaseous Al2O phase, and Ti2O3 transformed into TiN through Al2O(g) migration. The cold compressive strength and bending strength at ambient temperature of the heated samples were significantly improved.

Assessing the influence of cyclic bending on pearlitic wire's microstructural evolution: a simulation of spiraling and armoring processing effects

Flexible pipelines are widely used offshore for oil and gas transportation and are subjected to several complex stress modes during service. Stress tensors cause different alterations in the macro and microstructure of the material. Therefore, studies involving the relationship between mechanical behavior and the crystallographic orientation of tensile armor wires need deep investigation. This work investigated the role of complex plastic deformation during the spiraling tensile armor on the microstructure and crystallographic texture of pearlitic steel with 0.74 wt%C. A heat-treated sample was prepared as a starting point. Further specimens were subjected to cold bending to investigate the strain accumulation during spiraling and armoring processing and then compared to an industrial twisted tensile armor sample. The microstructural and texture evolution was characterized by scanning electron microscopy, X-ray diffraction, and backscattered electron diffraction. Specimens were submitted to the Vickers microhardness and tensile tests to evaluate the mechanical properties. Results revealed that the bending deformation causes a reduction of (001)//ND fiber and increases the mechanical resistance of the material, which may prevent the onset and crack propagation. (111)//ND fiber increased while (110)//ND decreased, leading to stability in the slip systems. The formation of shear band structural changes resulted from the increase of (110)//ND with armoring and a decrease of (111)//ND fibers. Bending strains enhance the desirable texture components while diminishing the undesirable ones. Deformations to which the materials were subjected provide less mobility of dislocations, which causes an increase in mechanical strength. Little change in texture and microstructure was also observed.

Aspects of Bending High-Borated Austenitic Stainless Steel Sheets for Interim Storage of Spent Nuclear Fuel

The presented work is aimed at the evaluation of the cold bending capacity of high-borated austenitic stainless steel sheets. Due to their excellent neutron-absorbing capability, borated stainless steels belong to the group of tailor-made structural materials widely used for vertical storage baskets for holding spent nuclear fuel assemblies in cooling pools at dry or wet storage facilities. The basket consists of individual fuel assembly cells. Each polygonal cell is usually welded from several steel strips. It would be advantageous to use bent steel semi-product to avoid welded seams as much as possible. Welded seams are difficult to make, and moreover, they are susceptible to corrosion. However, high-borated stainless steels, because of their boron content, show limited hot and cold workability. Thus, their cold bending capacity would be the primary issue. Their austenitic matrix with embedded hard and brittle boride particles is prone to the evolution and fast propagation of dimple transgranular fracture. This work is focused on the bending aspects of borated steel sheets with respect to the most commonly used hexagonal cell geometry. Experimental results provide practical recommendations for the rack design. The damage criterion has also been proposed using FEM simulations in DEFORM®.

Behavioural Study of High Carbon Steel Material in Hot and Cold Working Media: A Review

Due to its exceptional mechanical properties, such as its high strength and hardness, high-carbon steel is utilised extensively in various industries. The way of behaving of high-carbon steel is impacted by various handling strategies, for example, hot working and cold working, which can influence its microstructure and mechanical properties. The review aims to Study the behaviour of high-carbon steel material in hot and cold working media. Also, to look at the effects of hot and cold working on the macrostructure of the high carbon steel and the mechanical properties such as hardness, comprehension, impact tests, tensile stress and strain analysis. From the review, the hot and cold working processes, such as bending, rolling, and squeezing, for the result obtained from the hardness test shows the hardness value for hot rolling is higher than that of cold rolling (it is generally expected for hardness obtained from cold rolling should be higher than that from hot rolling) this may be due to the variations in the rolling parameters. While the hardness obtained from cold bending s higher than that from hot bending, and the hardness value obtained from hot squeezing is higher than that of cold squeezing. The results for hot bending of high-carbon steel show improved ductility and reduced risk of cracking compared to cold bending. This viable finding is highly significant to manufacturers to enable the production of sustainable materials for structural applications.

Mechanical behaviour of frame-supported insulating glass during cold bending

Cold bending is a low-cost, high-yield method for building an insulating glass curtain wall with a complex shape. However, the interaction between the glass plate and the sealing materials on the boundary makes the cold bending stress more complex. To study the stress in the insulating glass plate during unidirectional cold bending, an expression for the cold bending stress was derived by dividing the stress into three parts: the stresses generated by longitudinal sealing materials and transverse sealing materials and the bending stress of the glass plate itself. Nine pieces of insulating glass were used in the unidirectional cold bending test to verify the accuracy of the stress expression. The results show that the experimental stress nephograms of the upper glass surface are in good agreement with the theoretical values. The maximum stress occurs in the middle of the longitudinal edge; the maximum difference is 6.82%, indicating that the stress expression reflects the stress state of the insulating glass plate in cold bending. The stress caused by the longitudinal sealing materials accounts for the largest proportion of cold bending stress at the point of maximum stress; the stress caused by the transverse sealing materials is negligibly small. Accordingly, the expression is simplified, and expressions for the maximum cold bending stress of the glass are presented for specific curved surfaces.

10.4: A 2.3‐inch Automotive AMOLED Display with Small Bending Radius

10.4: A 2.3‐inch Automotive AMOLED Display with Small Bending Radius

Analysis of the principle and test quality on real-time photoelastic stress monitoring of borosilicate glass cold bending molding

Glass bending is an important process in glass device manufacturing, and real-time stress detection is essential for regulating bending mold pressure. A three-point bending experiment is used to simulate the glass cold bending forming process, and the feasibility of the photoelastic method to detect the real-time bending stress in the pure cold bending state is analyzed. The conventional division-of-amplitude polarimeter is optimized to obtain a smaller spot diameter, fewer system conditions, and a wider stress detection range. The Stokes parameter error of the optimized system is 0.05, and the optical path difference measurement accuracy is 4.284 nm. The test quality of the photoelastic stress detection system during the three-point bending was not affected by the glass size or bending span. However, the various curvatures of the incident surface were found to cause different stress values in unloaded glass and fluctuations in y-values (the distance from the test beam to the neutral surface of the glass) to occur outside the normal range. The less the curvature of the glass is, the closer it is to normal incidence, and the more accurate the stress value is. After the heat treatment of the borosilicate glass, the experimental results show that the isotropic structure of the glass does not change significantly. The exploration of testing quality of bending stress provides an effective reference for practical high-precision bending glass manufacturing.

Local and Global Interactive Buckling Capacity of Thin-Walled Box-Section Members of BS700 High-Strength Steel under Axial Compression

The local and global buckling capacity of the thin-walled box-section members formed by cold bending of ten BS700 high-strength steel (HSS) specimens are experimentally determined through an axial compression test. The mechanical properties of the materials are evaluated through material performance test, and a material model suitable for finite element analysis is proposed. The initial geometric imperfection of the members is measured, and it is found that the maximum initial deflection can be 1/1000 of the length of the members, as specified in the Chinese code. Based on the test, the ultimate bearing capacity and failure modes of the component with local and global interactive buckling are obtained. Further, a finite element model is established, and the corresponding results are compared with the test results. Furthermore, the test results are compared with those obtained using the existing specifications. The results show that the failure modes of the specimens are primarily local and global buckling failure. The influence of residual stress and initial geometric imperfection is considered in the proposed finite element model. Comparing the ultimate bearing capacity and load-displacement curves with the corresponding test results, it is found that the finite element model can effectively reproduce the test results. By comparing the test results with those obtained based on the steel structure design codes of China, the United States, and Europe, it is found that the test results are all higher than the existing code results, and the Chinese and European codes are relatively conservative with a difference of more than 20%, while the difference between the test results and the American code results is nearly 10%. Therefore, it is necessary to further improve the calculation methods of local and global buckling capacity of thin-walled box-section members of BS700 HSS under axial compression.

Analytical calculation of sheet curvature in four-roll mills at tubes production

Stationary bending of sheet metal on the electromechanical rolling mills demonstrates high productivity and efficiency, relevant for any modern enterprise. Regardless of the number of shafts, the operating principle of the mills is not complicated. The sheet blank is installed in the gap between the shafts, which rotate in different directions. Passing between the cylinders, the sheet bends and takes the desired shape. The main assortment of finished products, produced with the help of rollers, are details in the form of a cylinder, cone or oval. The cold bending method, which is the basis of the working process, does not destroy the metal and does not have a negative influence on its structure, as it sometimes happens during prolonged thermal exposure on metal alloys. The popularity of roller mills is largely due to their relatively low cost, as well as minimal outlay on maintenance and exploitation. If the company needs a cheaper and more economical mills, it is worth paying attention to manual models. For larger companies, the four-roller mills equipped with CNC-systems and operating in automatic regime are recommended. Modern models, produced by leading manufacturers, are favorably distinguished by visibility and ease of exploitation, attractive design, guaranteed safety and reliability. Such equipment is in demand in mass production, where high productivity and trouble-free operation of mills are appreciated. It is impossible to guess the sheet blank curvature in rolling new type of tube. This paper is devoted to the solution of this important problem and to analytical calculation of blank curvature in the four-roller mills.

Investigations on the Cold Bending Behaviour of a Double Glazing Unit with a Rigid Edge-Spacer Frame

Free-form façades with bent glass are becoming increasingly popular. As bending glass provides it with a better resistance to out-of-plane loads, it can result in thinner glass. A promising new technique is to cold bend thin glass plates with a stiff structural edge into a hyperbolic paraboloid (hypar), and to subsequently lock the corners to create a self-contained, self-stressed system. In this study, the bending process of specially-fabricated double glazing units (‘panels’) is investigated with a focus on a local instability phenomenon. The hypothesis that this instability is affected by edge stiffness of the plate, is tested by using 30x30 mm GFRP profiles as spacers along the perimeter of the glass. These were bonded to the glass using Dow 993 silicone adhesive. Four 1.5x1.5 m panels were produced in total, three with 4mm fully toughened (FT) glass, and one with 1.1 mm chemically toughened (CT) glass. The panels were cold bent in a series of laboratory experiments. A numerical model was developed to provide further insight on the mechanical response and to predict the outcome of the experiments. With the sizes of panels used it was not possible to form a hypar. Due to the small thickness of the glass, one the diagonals would always straighten when cold-bent. The 4 mm FT panels failed when the bottom plate fractured at a corner displacement of around 150 mm and a total load of 2.6 kN. The bottom plate of the CT 1.1 mm was also the first to fracture, at a corner displacement of 120 mm and a total load of 1.4 kN. The top and bottom plates came into contact in the centre of the plate when the corner displacement was around 50 mm for the FT 4 mm panels, and around 30 mm for the CT 1.1 mm panel. The numerical model predicted this contact and the overall behaviour of the panel up to a corner displacement of 60 mm. It was concluded that the glass was too thin to create a hypar with this panel size. The experimental data generated along with the numerical model are useful for future research and developments.