scholarly journals The limit forming estimation of multi-stage thin-walled vessel forming process

2020 ◽  
pp. 84-92
Author(s):  
Александр Владимирович Казанцев ◽  
Илья Эрнстович Келлер
Keyword(s):  
Technological Process ◽  
Limit State ◽  
Sheet Steel ◽  
Forming Limit ◽  
Strain Diagram ◽  
Intermediate Annealing ◽  
Limit States ◽  
Multi Stage ◽  
Strain Paths ◽  
Thin Walled

Построена численная модель процесса многоэтапного процесса холодной штамповки тонкостенного стального сосуда с учётом технологической наследственности. Использованы соотношения больших пластических деформаций анизотропной оболочки с учетом динамики и контактного взаимодействия с инструментом, реализованные в пакете LS-DYNA. Материальные константы модели Барлата Yld 2000-2d со степенным изотропным деформационным упрочнением для малоуглеродистой листовой стали DC04EK толщиной 0,7 мм определены по данным собственных экспериментов. Кривая предельных деформаций построена по искажению координатной сетки вблизи зон локализации деформации и разрушения сосуда в технологическом процессе, из которого исключен промежуточный отжиг, и по результатам теста на разрушение при одноосном растяжении. Исследованы особенности траекторий деформации в контрольных точках боковой поверхности изделия на каждом этапе технологического процесса, состоящего из последовательности операций вытяжки, раздачи и ссаживания. Расчёты траекторий подтверждены экспериментом на прессовом оборудовании, используемом в качестве испытательного. Оценка качества изделия связывается с остаточным ресурсом пластичности - удалённостью его деформированного состояния от кривой предельных деформаций. Установлено, что операция раздачи заготовки после её вытяжки быстро приближает материал к предельному состоянию и требует предварительного восстановления ресурса пластичности путём отжига. Отмечена перспективность технологий штамповки с меньшими степенями раздачи и с большими степенями ссаживания, способных сохранять ресурс пластичности без промежуточного отжига. A numerical model of multi-stage technological process of cold stamping of a thin- walled vessel made of sheet steel was built taking into account technological heredity. Relations of large plastic deformations of the anisotropic shell is used, taking into account the dynamics and contact interactions with the tool, which was implemented in the LS-DYNA package. Barlat’ plasticity model Yld 2000-2d with the power law of isotropic strain hardening is used with material constants identified from experimental data for low-carbon sheet steel DC04EK 0.7 mm. The forming limit curve was built on the distortion of the coordinate grid near the zones of strain localization and failure of the vessel in the technological process without intermediate annealing and in the failure test under uniaxial tension. The features of the strain paths in the control points of the vessel at each stage of the technological process, including the sequence of operations of drawing, distributing and reduction, are studied. The path calculation was confirmed by an experiment using pressing equipment as a test. The quality estimation of the product is evaluated by the distance of its deformed state from the limit states on the strain diagram. It is established that the operation of distributing the workpiece after its drawing quickly leads to the limit state and therefore requires a preliminary recovering the plasticity resource by annealing. There is a preference for forming the relief of the vessel by smaller degrees of distribution and greater degrees of reduction for elimination of the limit states and the operation of intermediate annealing.

scholarly journals Limit State Analyses in Design of Thin-Walled Marine Structures: Some Aspects on Length-Scales

2018 ◽  
Author(s):  
Jani Romanoff ◽  
Heikki Remes ◽  
Petri Varsta ◽  
Bruno Reinaldo Goncalves ◽  
Ingrit Lillemäe-Avi ◽  
...  
Keyword(s):  
Limit State ◽  
Plate Thickness ◽  
Length Scale ◽  
Marine Structures ◽  
Structural Element ◽  
Limit States ◽  
Strongly Coupled ◽  
Marine Industry ◽  
Non Linear ◽  
Thin Walled

Present paper gives an overview of the factors that affect the strength and structural design of advanced thin-walled marine structures with reduced plate thickness or alternative topologies to those used today in marine industry. Due to production-induced initial deformations and resulting geometrical non-linearity, the classical division between primary, secondary and tertiary responses becomes strongly coupled. Volume-averaged, non-linear response of structural element can be used to define the structural stress strain relation that enables analysis at the next, larger, length scale. This, today’s standard homogenization process needs to be complemented with localization, where the stresses are assessed at the details, such as welds for fatigue analysis. Due to this, the production-induced initial distortions need to be considered with high accuracy. Another key question is the length-scale interaction in terms of continuum description. Non-classical continuum mechanics are needed when consequtive scales are close. Strain-gradients are used to increase the accuracy of the kinematical description of beams, plates and shells. The paper presents examples of stiffened and sandwich panels covering limit states such as fatigue, non-linear buckling and fracture.

Effect of Bending Strain in Forming Limit Strain and Stress of IN-718 Sheet Metal

2015 ◽  
Vol 830-831 ◽  
pp. 238-241 ◽  
Author(s):  
K.Sajun Prasad ◽  
Sushanta Kumar Panda ◽  
Sujoy Kumar Kar ◽  
S.V.S. Narayana Murty ◽  
S.C. Sharma
Keyword(s):  
Sheet Metal ◽  
Forming Limit Diagram ◽  
Dome Height ◽  
Forming Limit ◽  
Forming Process ◽  
Hardening Law ◽  
Bending Strain ◽  
Multi Stage ◽  
Strain Paths ◽  
Von Mises

The forming limit diagram (ε-FLD) was estimated by deforming IN-718 sheet metal in different strain paths using a sub-size limiting dome height test set-up. The bending strains induced due to the use of smaller punch were estimated in all the strain paths, and the corrected ε-FLD was evaluated. The mathematical models such as Hill localized necking, Swift diffuse necking and Storen-Rice bifurcation theories were implemented to predict the limiting strains. In-order to avoid the path dependency of the ε-FLD during multi-stage forming process, stress based forming limit diagram (σ-FLD) was estimated using von-Mises and Hill-48 anisotropy plasticity theory with incorporation of Hollomon power hardening law. It was found that the bending strain influenced the limiting strains and stresses in the forming limit diagram. However, IN-718 material has encouraging formability in stretch forming process. The plot of the equivalent strains versus triaxiality indicated increasing limiting strain of the material in tension-tension mode.

scholarly journals The limit forming estimation of multi-stage thin-walled vessel cold forming technological process

2021 ◽  
pp. 48-60
Author(s):  
I. Keller ◽  
A. Kazantsev ◽  
A. Adamov ◽  
D. Petukhov ◽  
V. Trofimov ◽  
...  
Keyword(s):  
Technological Process ◽  
Cold Forming ◽  
Multi Stage ◽  
Thin Walled

scholarly journals SIMULATION OF MULTI-STAGE COLD FORMING OF A THIN-WALLED VESSEL

2020 ◽  
Vol 82 (1) ◽  
pp. 75-88 ◽  
Author(s):  
I.E. Keller ◽  
A.V. Kazantsev ◽  
A.A. Adamov ◽  
D.S. Petukhov
Keyword(s):  
Numerical Model ◽  
Sheet Steel ◽  
Forming Limit ◽  
Low Carbon ◽  
Limit Curve ◽  
Forming Limit Curve ◽  
Cold Forming ◽  
Coordinate Grid ◽  
Thin Walled ◽  
Press Equipment

The method of construction and attestation of a numerical model of cold stamping of thin-walled products made of anisotropic metal sheet for the design of technological operations is proposed. The relations of the associated law of plastic flow with the Barlat flow function and isotropic strain hardening are used. The method of design and processing the experiment is proposed for their identification. The forming limit curve is approximated numerically by the Marciniak - Kuczynўski method, and for its identification it is proposed to use a failure test under uniaxial tension and press equipment as an experimental. To do this, a coordinate grid is applied to a flat blank by laser engraving, whose distortions near the zones of strain localization and failure of the vessel give additional points of the forming limit curve. The constants of the Peng - Landel potential are found to describe the elasticity of a polyurethane die under large deformations using tests for free and constrained compression. All tests according to the method were performed for low-carbon sheet steel DC04EK 0.7 mm and SKU-PFL polyurethane. A numerical model of the process in the LS-DYNA package is designed using material models from its library. The calculations according to the model were confirmed by experiment, for which the main deformations were determined by the distorted coordinate grid on the workpiece after each operation at the control points. The calculation of the sequence of stages of stamping, drawing and bulging of the workpiece in the production of the vessel with and without intermediate annealing is performed and the dangerous zones and mechanisms of their formation are determined.

Experimental Researches on Nonlinear Strain Paths Forming for Dual Phase Steel

2014 ◽  
Vol 1004-1005 ◽  
pp. 209-213
Author(s):  
Li Bo Pan ◽  
Hong Chuan Zhu ◽  
Ze Hong Lei ◽  
Zhi Jian Zhang
Keyword(s):  
Plastic Strain ◽  
Dual Phase Steel ◽  
Forming Limit Diagram ◽  
Forming Limit ◽  
Strain Diagram ◽  
Dual Phase ◽  
Effective Plastic Strain ◽  
Nonlinear Strain ◽  
Precise Tool ◽  
Strain Paths

Strain paths during sheet metal forming are always complex and nonlinear. Forming limit diagram (FLD) is a common method to determine failure in the past decades. However, it is only suitable for linear strain path condition. Regarding dual phase steel DP780, a special experiment was designed and carried out on Zwick Cupping equipment to get nonlinear strain paths. And the strain status was analyzed in FLD. It was found that FLD cannot predict failure precisely in this case. A new approach proposed by Stoughton and Yoon which based on polar effective plastic strain was introduced to analyze this nonlinear strain paths condition, the result is in good agreement with experiment, which indicated that Polar Effective Plastic Strain Diagram was an effective and precise tool to determine failure especially for complex nonlinear strain paths forming.

Fracture Behavior of a Dual Phase Sheet Steel in Hole Expansion

2007 ◽  
Author(s):  
Yuxiu Zhang ◽  
Yi Liu ◽  
Xin Wu
Keyword(s):  
Crack Initiation ◽  
Sheet Steel ◽  
High Strength Steels ◽  
Forming Limit ◽  
Dual Phase ◽  
Crack Initiation And Propagation ◽  
Forming Process ◽  
Hole Expansion ◽  
Initiation And Propagation ◽  
Strain Paths

It is commonly recognized that for Advanced High Strength Steels (AHSS) the forming limit is mainly controlled by fracture, rather then by localized necking. To date a reliable fracture limit for forming AHSS is not well defined, especially when a practical forming process is under complex strain paths. Hole expansion test has been used by auto industry for assessing fracture-controlled material forming limit. Understanding of crack mechanisms involved in crack initiation and propagation is important for prediction of fracture failure. A dual phase steel with a fine grain and 20–40vol% martensite particles of ∼1μm mean size was used for this study. The results indicate that the hole piercing and blank placement during hole expansion has sensitive impact to the evaluation of edge crack initiation and propagation. Through the comparative study on the “burr up” and “burr down” blank settings the fracture process and the effect of blank preparation, hole expansion, burr geometry effect on crack initiation, and the crack propagation direction and local interaction with microstructure are investigated.

scholarly journals Limit State Analyses in Design of Thin-Walled Marine Structures—Some Aspects on Length-Scales

2019 ◽  
Vol 142 (3) ◽  
Author(s):  
Jani Romanoff ◽  
Heikki Remes ◽  
Petri Varsta ◽  
Bruno Reinaldo Goncalves ◽  
Mihkel Körgesaar ◽  
...  
Keyword(s):  
Limit State ◽  
Plate Thickness ◽  
Length Scale ◽  
Marine Structures ◽  
Structural Element ◽  
Limit States ◽  
Strongly Coupled ◽  
Marine Industry ◽  
Non Linear ◽  
Thin Walled

Abstract This paper gives an overview of the factors that affect the strength and structural design of advanced thin-walled marine structures with reduced plate thickness or alternative topologies to those used today in the marine industry. Due to production-induced initial deformations and resulting geometrical non-linearity, the classical division between primary, secondary, and tertiary responses becomes strongly coupled. Volume-averaged, non-linear response of structural element can be used to define the structural stress–strain relation that enables analysis at the next, larger, length scale. This, today’s standard homogenization process, needs to be complemented with localization, where the stresses are assessed at the details, such as welds for fatigue analysis. Due to this, the production-induced initial distortions need to be considered with high accuracy. Another key question is the length-scale interaction in terms of continuum description. Non-classical continuum mechanics are needed when consecutive scales are close. Strain-gradients are used to increase the accuracy of the kinematical description of beams, plates, and shells. The paper presents examples of stiffened and sandwich panels covering limit states such as fatigue, non-linear buckling, and fracture.

Pull-Out Performance of T-Stub End Plate Connected To Concrete Filled Thin-Walled Steel Tube (CFTST) using Lindapter Hollo-Bolts

2018 ◽  
Vol 15 (1) ◽  
pp. 59
Author(s):  
NAZRUL AZMI AHMAD ZAMRI ◽  
CLOTILDA PETRUS ◽  
AZMI IBRAHIM ◽  
HANIZAH AB HAMID
Keyword(s):  
Limit Load ◽  
Steel Tube ◽  
Limit States ◽  
End Plate ◽  
Pull Out ◽  
Pullout Load ◽  
Thin Walled ◽  
Stub End ◽  
Concrete Filled Steel Tubes ◽  
Ultimate Limit

The application of concrete filled steel tubes (CFSTs) as composite members has widely been used around the world and is becoming popular day by day for structural application especially in earthquake regions. This paper indicates that an experimental study was conducted to comprehend the behaviour of T-stub end plates connected to concrete filled thin-walled steel tube (CFTST) with different types of bolts and are subjected to pullout load. The bolts used are normal type bolt M20 grade 8.8 and Lindapter Hollo-bolt HB16 and HB20. A series of 10 mm thick T-stub end plates were fastened to 2 mm CFTST of 200 mm x 200 mm in cross-section. All of the specimens were subjected to monotonic pull-out load until failure. Based on test results, the Lidapter Hollo-bolts showed better performance compare to normal bolts. The highest ultimate limit load for T-stub end plate fasten with Lindapter Hollo-bolt is four times higher than with normal bolt although all end plates show similar behaviour and failure mode patterns. It can be concluded that T-stub end plate with Lindapter Hollo-bolt shows a better performance in the service limit and ultimate limit states according to the regulations in the design codes.

Combined flexure and torsion of I-shaped steel beams

1989 ◽  
Vol 16 (2) ◽  
pp. 124-139 ◽  
Author(s):  
Robert G. Driver ◽  
D. J. Laurie Kennedy
Keyword(s):  
Limit State ◽  
Bending Moment ◽  
Phase Behaviour ◽  
Inelastic Interaction ◽  
Steel Beams ◽  
Ultimate Limit State ◽  
Second Phase ◽  
Design Standards ◽  
Limit States ◽  
Interaction Diagram

Design standards provide little information for the design of I-shaped steel beams not loaded through the shear centre and therefore subjected to combined flexure and torsion. In particular, methods for determining the ultimate capacity, as is required in limit states design standards, are not presented. The literature on elastic analysis is extensive, but only limited experimental and analytical work has been conducted in the inelastic region. No comprehensive design procedures, applicable to limit states design standards, have been developed.From four tests conducted on cantilever beams, with varying moment–torque ratios, it is established that the torsional behaviour has two distinct phases, with the second dominated by second-order geometric effects. This second phase is nonutilizable because the added torsional restraint developed is path dependent and, if deflections had been restricted, would not have been significant. Based on the first-phase behaviour, a normal and shearing stress distribution on the cross section is proposed. From this, a moment–torque ultimate strength interaction diagram is developed, applicable to a number of different end and loading conditions. This ultimate limit state interaction diagram and serviceability limit states, based on first yield and on distortion limitations, provide a comprehensive design approach for these members. Key words: beams, bending moment, flexure, inelastic, interaction diagram, I-shaped, limit states, serviceability, steel, torsion, torque, ultimate.

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