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Ken-ichiro Mori - One of the best experts on this subject based on the ideXlab platform.
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Review of Shearing Processes of High Strength Steel Sheets
Journal of Manufacturing and Materials Processing, 2020Co-Authors: Ken-ichiro MoriAbstract:Shearing processes of High Strength Steel sheets increasingly applied to lightweight automobile parts were reviewed. With the increase in Strength of the High Strength Steel sheets, shearing operations become hard. First, the sheared edge quality in shearing of High Strength Steel sheets and the effects on the formability and fatigue Strength were shown. Next, ironing processes with a taper punch and a punched slug, a slight clearance punching with a punch having a small round corner and a thickening process of the sheared edge were explained as processes for improving the sheared edge quality. Finally, hydrogen-induced delayed fractures of cold-sheared ultra-High Strength Steel sheets and of hot-trimmed parts were evaluated.
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Bending process for producing uniform angle distribution from ultra-High Strength Steel sheets having thickness distribution
The International Journal of Advanced Manufacturing Technology, 2020Co-Authors: Wataru Ijichi, Ken-ichiro Mori, Sadao MiyazawaAbstract:Because of the elastic deformation of rolling mills in rolling, the edge drop in thickness of rolled ultra-High Strength Steel sheet was remarkable, thus the thickness distribution was not uniform. The distribution of angle before and after unloading in V-bending of the ultra-High Strength Steel sheets having such a thickness distribution was measured. The bend angle was nonuniformly distributed by the insufficient bend angle at the bottom dead centre and springback during unloading. The effects of the bent angle and thickness distribution on the springback in thin and thick edges were discussed. The distribution of bend angle was reduced by bottoming with a three-piece die using a rubber pad. It was found that bottoming with a divided die using a rubber pad in bending is effective in improving the dimensional accuracy of ultra-High Strength Steel sheets having a thickness distribution by finite element simulation and experiment.
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shearing of ultra High Strength Steel sheets with step punch
Procedia Manufacturing, 2018Co-Authors: Ryuji Yonekawa, Kyouhei Sedoguchi, Ken-ichiro MoriAbstract:Abstract The punch with a step was applied to improve the punch life in punching of ultra-High Strength Steel sheets. The contact pressure in punching with the step was reduced due to the early separation of the sheet under tension. Punching with the step punch was carried out for 7000 times in stroke, whereas chipping in the punch occurred at 3000 times in punching without the step. Then, punching with the step punch was applied to the quenched Steel sheet to prevent the occurrence of the delayed cracking of the sheared edge. The delayed cracking occurred, although the residual stress in the sheared edge decreased with increasing the step height. Furthermore, shearing with the step punch was applied to improve the stretch-flangeability of the ultra-High Strength Steel and High Strength Steel sheets.
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Hemming for Joining High Strength Steel Sheets
Procedia Engineering, 2014Co-Authors: Z. Hamedon, Ken-ichiro MoriAbstract:A High Strength Steel sheet is used to make the hollow sections for the body structure of automobiles. The hollow sections, which are typically joined by resistance spot welding have insufficient energy absorption because the joins are not continuous. Thus, to overcome this problem, the hollow section is joined using the hemming process. The hemming of the High Strength Steel sheet was successfully performed using punch with stopper. The High Strength Steel hollow sections joined by hemming and resistance spot welding were then examined by tensile and fatigue tests. The hollow section with hemmed joins showed better performance in both tests. The overlapping joins of the hemmed hollow section have greater Strength as compared to the resistance of spot welding joins.
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Improvement of Joinability in Mechanical Clinching of Ultra-High Strength Steel Sheets Using Counter Pressure
Advanced Materials Research, 2014Co-Authors: Shoma Nishino, Ken-ichiro Mori, Toru KatoAbstract:A mechanical clinching using counter pressure of a rubber disk was developed to join the ultra-High Strength Steel sheets having low ductility. In the proposed process, the interlock was increased by the increment of metal flow with the counter pressure of rubber disk in the die cavity. The two kind of ultra-High Strength Steel sheets having different ductility were used in the mechanical clinching. The effect of the shape of rubber disk on the deforming behaviour of the sheets was investigated. The joinability was improved under the appropriate shape of rubber disk for both sheets, and then the sheets having 56% of reduction area were successfully joined whereas the sheets were not joined without the counter pressure. Although the joinability of the sheets having 43% of reduction area was improved, the cracks occurred in the upper sheet around the punch sidewall. The maximum static load and the fatigue limit of the joined sheets were measured in the tension-shearing and cross-tension tests. It was effective for the improvement of joinability in the mechanical clinching of ultra-High Strength Steel sheets to use the counter pressure of the rubber disk.
Gregory J. Hancock - One of the best experts on this subject based on the ideXlab platform.
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numerical simulation of High Strength Steel box shaped columns failing in local and overall buckling modes
Journal of Structural Engineering-asce, 2006Co-Authors: Demao Yang, Gregory J. HancockAbstract:An experimental research project was conducted to evaluate the compression stability of High Strength Steel sections. Two buckling modes (“local and overall buckling”) and the interaction between them were investigated. To further study the structural behavior of the columns thoroughly, finite element analyses were performed using ABAQUS. This paper presents a finite element analysis on the postbuckling behavior of thin-walled compression members of High Strength Steel with box-shaped columns fabricated from cold-reduced High Strength Steel plates with nominal yield stress of 550 MPa in 0.42 and 0.60 mm thicknesses. The effect of the input parameters such as the degree of prescribed initial imperfection and the size of the element mesh on the convergence of the solution was investigated and is discussed. The paper also shows the comparison of loads obtained numerically and experimentally with those predicted on the basis of AS/NZS4600 and the North American Specification. Accurate results of the numerical simulations show that the finite element analysis can be used to predict the ultimate loads of thin-walled members including the postbuckling behavior of thin-walled sections. It is demonstrated that the finite element analysis can therefore be used to design and optimize thin-walled sections of High Strength Steel.
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Tests of High Strength Steel columns
Journal of Constructional Steel Research, 1995Co-Authors: Kim J.r. Rasmussen, Gregory J. HancockAbstract:Abstract The paper describes a test programme on columns fabricated from High Strength Steel plates with nominal yield stress of 690 MPa. The programme comprised 13 box and I-section specimens, including fixed-ended stub columns and pin-ended long columns. For the pin-ended columns, two tests were performed for each length using eccentric and concentric axial loading. The purpose of the test programme was to select a curve for High Strength Steel columns with a nominal yield stress of 690 MPa from the multiple column curves used in the Australian Steel structures standard. It is shown that the α b = −0·5 curve is the appropriate curve for box and I-section columns fabricated from flame-cut High Strength Steel plate with a nominal yield stress of 690 MPa. This curve is Higher than the α b = 0 curve for box and I-section columns fabricated from ordinary Steel because the effect of residual stresses is less detrimental to the Strength of High Strength Steel columns than to the Strength of ordinary Steel columns. The paper also shows a comparison of the tests with column design Strengths of the Australian Steel structures standard AS4100, the Load and Resistance Factor Design Specification of the American Institute of Steel Construction, The British Standard BS5950: Part 1, and the draft European Committee for Standardisation (CEN) Eurocode3. The design Strengths are shown to be in close agreement with the tests except for Eurocode3 which conservatively predicts the test Strengths.
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Plate slenderness limits for High Strength Steel sections
Journal of Constructional Steel Research, 1992Co-Authors: Kim J.r. Rasmussen, Gregory J. HancockAbstract:Abstract The paper describes a test programme on stub columns fabricated from BISALLOY 80 Steel plates with nominal yield stress of 690 MPa. The programme comprises 18 box, cruciform and I-section specimens. The slenderness of the component plates are chosen in the vicinity of the yield slenderness limit, beyond which the stub column Strength is reduced below the squash load as a result of local buckling. The purpose of the tests was to determine whether the yield slenderness limits used in the Australian Steel Structures Standard AS 4100 are applicable to BISALLOY 80 Steel plates. The paper also assesses whether the plate Strength rules of the Australian Steel Structures Standard AS 4100, the Load and Resistance Factor Design Specification of the American Institute of Steel Construction (AISC-LRFD), the British Standard BS 5950 Part 1 and the European Convention for Structural Steelwork Eurocode3 are applicable to High Strength Steel. For this purpose, the plate Strength curves of these specifications are compared with the BISALLOY 80 test results and with test results from the USA and Japan on High Strength Steel plates with nominal yield stress of 690 MPa.
Ben Young - One of the best experts on this subject based on the ideXlab platform.
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Tests on High Strength Steel Hollow Sections: A Review
Proceedings of the Institution of Civil Engineers - Structures and Buildings, 2017Co-Authors: Jia Lin Ma, Tak-ming Chan, Ben YoungAbstract:Advances in technologies have allowed manufacturers to produce Steel plates and sections with Strengths of 690 MPa and Higher. The use of High-Strength Steel has the potential for significantly reducing the material costs and the self-weight of structures. High-Strength Steel hollow sections can be either welded from Steel plates or cold-formed from coils. Tests on different built-up High-Strength Steel hollow sections have been conducted around the globe, including Australia, China, Japan and the USA. The commonly used box-sections were tested; the slenderness limits and member capacities against compression were also studied. To investigate the performance of cold-formed High-Strength Steel hollow sections, the authors initiated a research programme in Hong Kong, which included both experimental and numerical investigations on cold-formed High-Strength Steel hollow sections. The sections include square, rectangular and circular hollow sections. Based on the results, recommendations on section slendernes...
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Material properties of cold-formed High Strength Steel at elevated temperatures
Thin-walled Structures, 2017Co-Authors: Hai-ting Li, Ben YoungAbstract:Abstract This paper presents the material properties of cold-formed High Strength Steel at elevated temperatures. Material properties at elevated temperatures have a crucial role in fire resistance design of Steel structures. The fire resistances of Steel structures in the existing international standards are mainly based on experimental data of hot-rolled mild Steel. However, investigation of High Strength Steel at elevated temperatures is limited. Therefore, a test program has been carried out to investigate the material properties of cold-formed High Strength Steel at elevated temperatures. The coupon specimens were extracted from cold-formed High Strength Steel square and rectangular hollow sections with nominal yield stresses of 700 and 900 MPa at ambient temperature. The coupon tests were carried out through both steady and transient state test methods for temperatures up to 1000 °C. Material properties including thermal elongation, elastic modulus, yield stress, ultimate Strength, ultimate strain and fracture strain were obtained from the tests. The test results were compared with the design values in the European, American, Australian and British standards. The comparison results revealed the necessity of proposing specified design rules for material properties of cold-formed High Strength Steel at elevated temperatures. New design curves to determine the deterioration of material properties of cold-formed High Strength Steel at elevated temperatures are proposed. It is shown that the proposed design curves are suitable for High Strength Steel materials with nominal yield stresses ranged from 690 to 960 MPa at ambient temperature.
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Experimental investigation of cold-formed High Strength Steel tubular beams
Engineering Structures, 2016Co-Authors: Jia Lin Ma, Tak-ming Chan, Ben YoungAbstract:Abstract This paper presents a test program on cold-formed High Strength Steel tubular beams. The nominal 0.2% proof stresses of the High Strength Steel were 700, 900 and 1100 MPa in this study. Twenty-five four-point bending tests on circular, rectangular and square hollow structural sections were conducted. Load-deformation histories and failure modes of the beams were reported. Experimental results were compared against design values calculated from European code, Australian standard and North American specification for hot-rolled and cold-formed Steel structures. In addition, the test Strengths were also compared with the Direct Strength Method predictions. The compactness criteria were assessed by comparing the section slenderness to the slenderness limits in codes.
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Design of High Strength Steel columns at elevated temperatures
Journal of Constructional Steel Research, 2008Co-Authors: Ju Chen, Ben YoungAbstract:Abstract The main objective of this paper is to study the behaviour and design of High Strength Steel columns at elevated temperatures using finite element analysis. In this study, equations predicting the yield Strength and elastic modulus of High Strength Steel and mild Steel at elevated temperatures are proposed. In addition, stress–strain curve model for High Strength Steel and mild Steel materials at elevated temperatures is also proposed. The numerical analysis was performed on High Strength Steel columns over a range of column lengths for various temperatures. The nonlinear finite element model was verified against experimental results of columns at normal room and elevated temperatures. The effects of initial local and overall geometrical imperfections have been taken into consideration in the analysis. The material properties and stress–strain curves at elevated temperatures used in the finite element model were obtained from the proposed equations based on the material tests. Two series of box and I-section columns were studied using the finite element analysis to investigate the Strength and behaviour of High Strength Steel columns at elevated temperatures. Both fixed-ended stub columns and pin-ended slender columns were considered. The column Strengths predicted from the finite element analysis were compared with the design Strengths predicted using the American, European and Australian specifications for hot-rolled Steel columns at elevated temperatures by substituting the reduced material properties. In addition, the direct Strength method, which was developed for the design of cold-formed Steel columns at normal room temperature, was also used in this study to predict the High Strength Steel column Strengths at elevated temperatures. The suitability of these design rules for High Strength Steel columns at elevated temperatures is assessed. Generally, it is shown that the American and European specifications as well as the direct Strength method conservatively predicted the column Strengths of High Strength Steel at elevated temperatures. The European Code predictions are slightly more conservative than the American Specification and the direct Strength method predictions.
K. Akita - One of the best experts on this subject based on the ideXlab platform.
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springback behaviour in bending of ultra High Strength Steel sheets using cnc servo press
International Journal of Machine Tools & Manufacture, 2007Co-Authors: Ken-ichiro Mori, K. AkitaAbstract:The springback behaviour of ultra-High-Strength Steel sheets in bending was investigated under controlled conditions using a CNC servo press. Although the ultra-High-Strength Steel sheets are attractive in reducing weight of cars, the amount of springback of the ultra-High-Strength Steel sheets in the forming is very large due to High Strength. The CNC servo press has the function of accurately controlling the motion by two servo motors. The effects of the material, the finishing reduction in thickness, the forming speed and the holding time at the bottom dead centre on the amount of springback in V-shaped bending were examined. The scatter of the springback for the ultra-High-Strength Steel sheets was improved by using real thickness and not nominal thickness of each individual sheet in the control of the punch stroke. The amount of springback for the ultra-High-Strength Steel sheet in the V-shaped bending was much larger than that for the mild Steel sheet, and the amount was decreased by the finishing reduction in thickness direction because of uniform stress distribution. The effects of the forming speed and the holding time at the bottom dead centre were small. The amount of springback for the Steel sheets was almost proportional to the ratio of the tensile Strength to the elastic modulus.
Demao Yang - One of the best experts on this subject based on the ideXlab platform.
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numerical simulation of High Strength Steel box shaped columns failing in local and overall buckling modes
Journal of Structural Engineering-asce, 2006Co-Authors: Demao Yang, Gregory J. HancockAbstract:An experimental research project was conducted to evaluate the compression stability of High Strength Steel sections. Two buckling modes (“local and overall buckling”) and the interaction between them were investigated. To further study the structural behavior of the columns thoroughly, finite element analyses were performed using ABAQUS. This paper presents a finite element analysis on the postbuckling behavior of thin-walled compression members of High Strength Steel with box-shaped columns fabricated from cold-reduced High Strength Steel plates with nominal yield stress of 550 MPa in 0.42 and 0.60 mm thicknesses. The effect of the input parameters such as the degree of prescribed initial imperfection and the size of the element mesh on the convergence of the solution was investigated and is discussed. The paper also shows the comparison of loads obtained numerically and experimentally with those predicted on the basis of AS/NZS4600 and the North American Specification. Accurate results of the numerical simulations show that the finite element analysis can be used to predict the ultimate loads of thin-walled members including the postbuckling behavior of thin-walled sections. It is demonstrated that the finite element analysis can therefore be used to design and optimize thin-walled sections of High Strength Steel.