A springback prediction method for double-curved plate bent with the multi-point forming method

Stiffened panel as a kind of thin-walled component is widely used in aircraft. A novel stiffened panel manufacturing method has been proposed that the plate is bent into designed shape first with multi-point forming method and then milled into integral panel. However, in the bending process, springback is a great issue. In this paper, an analytical method is proposed to predict the springback of the double-curved bent plate in multi-point forming process. The method takes advantage of the loading force, which is obtained by the stress in the thickness direction, and the arrangement of the punches to calculate the bending moment in the forming process. Through Bezier surface blending method, the profile after springback was constructed. Moreover, the strain and stress variation through thickness during loading and unloading process were also analyzed. And the finite element simulation and bending experiment were conducted to make verification. The results show that the method proposed can effectively predict the springback of the double-curved bent plate in multi-point forming.

Pengaruh Sudut Punch dan Ketebalan Pelat terhadap Springback pada Bending V

The bent plate is inseparable from the phenomenon that determines the size of the resulting bending angle. This phenomenon is called springback. Springback is a condition that occurs on a sheet plate when bending is done where after the punch load is removed the bent sheet plate has a tendency to return to its original form. Mini brake bending V tool with a hydraulic jack system produces springback of 1-5 degrees for punch angle 85 ° radius 2.5 mm and carbon steel material St 42 at thickness 3, 4 and 5 mm. Therefore, this study was conducted to find out how the influence of punch angle and plate thickness on springback. The limitation problem in this study is the thickness of the plates used 2 and 4 mm. The type of method used is bending V bottoming with a die angle of 90 °, the punch angle used is 80, 85, and 90, the punch radius used is 2, 4 and 6 mm, and the plate material used is carbon steel. The research method starts from designing die set, punch and die test aids, and making test specimens, then bending test, bending angle and springback measurements are carried out. Based on the research conducted, the greater the punch angle, the smaller springback produced and the thicker the plate, the smaller springback produced tends to be smaller, where the smallest springback is obtained on a plate thickness of 6 mm with a punch angle of 90 ° 4 mm radius obtained -0.31o.

Опыт кулонометрической оценки коррозионноактивной поверхности аустенитной стали в агрессивном электролите при знакопеременной деформации

Исследовано коррозионное поведение сложнолегированного сплава в растворе 3М НСl при статической деформации переменного знака. Результаты, полученные методом кулонометрической регистрации продуктов коррозии в начальный период взаимодействия металла со средой, обеспечили количественную оценку специфики растворения сплава. Полученные результаты позволили объемным методом в сочетании с методом кулонометрической регистрации продуктов коррозии разработать методологию селективной оценки коррозионного поведения многофазных сплавов в условиях агрессивной среды REFERENCES Berenshtein G. V., Dyachenko A. M., Rusanov A. I. Mekhanohimicheskij effekt rastvoreniya [Mechanochemical effect of dissolution] Report Academy of Sciences of the USSR, 1988, v. 298 (6), pp. 1402–1404. (in Russ.) Rusanov A. I., Uriev N. В., Eryukin P. V., Movchan T. G., Esipova N.E. Effect of the strain sign in corrosion under stress. Mendeleev Commun., 2004, v. 14(2), рр. 58–59. https://doi.org/10.1070/mc2004v014n02abeh001875 Rusanov A. , Ur’ev N. B., Eryukin P. V., Movchan T. G., Esipova N. E. Otkrytie effekta znaka deformacii v yavleniyah korrozii pod napryazheniem [Discovery of the sign deformation effect in stress corrosion phenomena]. Report Academy of Sciences, 2004, v. 395(3), pp. 364-366. (in Russ.) Esipova N. E., Blinov E. B., Movchan T. G., Bannykh O. Corrosion Resistance of a Bent Plate from a High-Nitrogen Nonmagnetic 05Kh22AG15N8M2F Steel in Aggressive Media. Russian metallurgy (Metally), 2007(2), pp. 148-75. Movchan T. G., Esipova N. E., Eryukin P. V., Uryev N. B., Rusanov A. I. Mechanochemical effects in processes of corrosion of metals. Russian Journal of General Chemistry, 2005, v. 75(11), pp. 1681–1686. https://doi.org/10.1007/s11176-005-0491-8 Rusanov A. I. Termodinamicheskie osnovy mekhanohimii [Thermodynamic principles of mechanochemistry]. Saint Petersburg, Nauka Publ., 2006, 221 p. (in Russ.) GOST 9.908-85. Metals and alloys. Interstate standard. (in Russ.) Kuzmak A. E., Kozheurov A. V., Efi menko L. A., Ilyukhin V. I. Kulonometricheskaya ocenka korrozii okoloshovnoj zony svarnogo shva pri deformacionnom starenii [Coulometric corrosion assessment of the heat-affected weld zone during strain aging]. Korroziya: Materialy, Zashchita, 2009(1), pp. 43–46. (in Russ.) Kuzmak A. E., Kozheurov A. V. Kulonometricheskaya ocenka skorosti korrozii uglerodistoj stali [Coulometric corrosion rate assessment for carbon steel]. Zashchita Metallov, 2004, v. 40(3), pp. 315–320. (in Russ.) Kuzmak A. E., Kozheurov A. V., Marin A. V. Coulometric evaluation of infl uence of the welding technology of 12Kh18N10T steel on welded zone corrosion. Korroziya: Materialy, Zashchita, 2005(1), pp. 43-46. (in Russ.)

Effect of Roll Configuration on the Leveling Effectiveness of Tail-Up Bent Plate Using Finite-Element Analysis

The finite-element method (FEM) has been used to numerically investigate the effect of work roll configuration on the leveling effectiveness of tail-up bent plates. Leveling is a process used to minimize shape defects, including flatness imperfections and uniformity of internal stresses in shape-critical applications. Leveling plays an important role in delivering the desired plate shape and meeting the required product standards. To simulate the roller leveling effectiveness of tail-up bent plates, an initially flat plate was plastically bent prior to leveling and was passed through the leveling rolls. Leveling effectiveness was estimated by the vertical displacements of tail-up bent plates with two different roll configurations. One configuration adopts a gradually increasing roll gap, while the other configuration maintains the same roll gap in the first two sets of rolls and gradually increases the roll gap for the later rolls. For comparison purposes, the entry and exit roll gaps of the two roll configurations are set to the same roll gap. To verify the accuracy of the numerical simulations, actual leveling experiments were performed using tail-up bent plates. The results show that the roll configuration significantly influences the leveling effectiveness of the tail-up bent plates. Higher leveling effectiveness is obtained for a leveling configuration that imparts more severe deformation at the earlier leveling stages. Through the analysis, the work roll configuration is determined to be essential to increase leveling effectiveness of tail-up bent plates.

An Investigation of Forces during Roller Forming Process

The tubular sections or shells for forming channels, drums, tanks or pressure vessel are manufactured by bending plates generally through three-roller bending machine and then welding the ends of bent plate to form a cylinder or cone. Force exerted on rollers during bending is one of the important criteria which must not exceed the capacity of bending machine. Secondly, Total bender capacity must be utilised during bending of desired curvature, which reduces number of passes and hence time required to attain desired curvature. Thus, it necessary to estimate the forces during bending, based on the roller position, so that it does not exceeds the bender capacity and simultaneously reduces number of passes. In this regards, some analytical models are available to predict the forces during three roller bending process with assumption of constant bend radius during bending. In fact, the radius continuously changes during bending operation which affects the magnitude and the direction of the forces exerted on the roller. An attempt is made to simulate the roller bending using FEA. Variation of curvature of plate and effect of various parameters such as plate thickness, bottom roller inclination and top roller inclination on bending forces during cylindrical and conical bending operation are studied using FEA analysis.