bluuebunny/crossref_metadata_2025_split huggingface dataset:
A first step towards an in-line shape compensation for UHSS roll forming
Authors: Abeyrathna B , Rolfe B , Weiss M 
Published: November 2019

Abstract
Roll forming is an important sheet metal forming process and is being used increasingly in the automotive industry for the manufacture of structural and crash components from Advanced High Strength Steel (AHSS) and Ultra High Strength Steel (UHSS). In AHSS and UHSS, the material properties can change from coil to coil or within the same coil and this can lead to varying part quality in roll forming. The effect of changes in material properties on part quality depends on the geometry of the part being formed as well as on the process parameters. There is a strong interest in developing in-line shape compensation for roll forming, and this will only be possible if the relationship between part quality, material properties, process- and part shape- parameters is understood.
In this paper, the effect of material properties and both process and geometrical parameters on longitudinal bow is analysed. A new technique is introduced for the identification of variations in the longitudinal bow in a roll formed component based on roll load and torque measurements as well as process parameters and part geometry.
Analysis of material behaviour and shape defect compensation in the flexible roll forming of advanced high strength steel
Authors: Ghanei S , Abeyrathna B , Rolfe B , Weiss M 
Published: November 2019

Abstract
Roll forming is a fast and low-cost forming process with the ability to form a wide range of materials, especially advanced high-strength steels (AHSS) that have limited ductility. However, roll forming is only able to form constant cross-sections along the longitudinal direction of the component, while many automotive components are more complex in shape. Flexible Roll Forming (FRF) uses rolls that have the ability to translate or rotate during production, enabling the manufacture of a part that has a variable cross-section potentially useful for the automotive industry.
Deakin University is equipped with a flexible forming facility that can prototype parts with variable cross-sections. The machine has been developed, patented and manufactured by dataM Sheet Metal Solutions GmbH. Deakin’s Flexible Forming Facility (DFFF) consists of a single forming stand with two opposing robotic arms connected to forming rolls. The flexibly controlled arms form the clamped sheet along a CNC defined bend line while the sheet remains clamped. This facility is capable of creating changes in the cross-section in both width and depth along the part. Moreover, the Deakin facility can form the part in both forwards and backwards directions along the longitudinal dimension of the part. In contrast, conventional FRF facilities use multiple stands of forming rolls, and the forming sequence occurs in a single direction along the part.
The first part of this study compares material deformation in the DFFF in contrast to that of the conventional FRF setup. This study will determine the similarities and differences in the final formed part between DFFF and the forming conditions in conventional FRF. The second step of the study is to investigate the forming properties of the final part when the part has variable depth. An experimental part formed on DFFF was compared to a numerical analysis using COPRA RF FEA to investigate the material flow and the forming defects. The results show that the major shape error is wrinkling. A new forming concept using a blank holder tool was analysed, and it shows promising results in regard to wrinkling reduction.
Influence of the preheating strategy on the deep drawing of extruded magnesium alloy ME20 sheets
Authors: Joghan H Dardaei , Hahn M , Traphöner H , Tekkaya A E 
Published: November 2019

Abstract
Due to the hexagonal crystal structure of magnesium alloys, a high forming limit can only be achieved at elevated temperatures. For the material characterization of extruded magnesium alloy ME20 sheets, at elevated temperatures, the in-plane torsion test and a multi-layer upsetting test were conducted. Also, FLCs were determined at elevated temperatures. For the deep drawing, two different heating strategies are investigated. In the first method, specimens are placed in an oven at 400 °C for around 10 minutes and then rapidly transferred to the tool. In the second method the specimens are directly heated in the deep drawing tool. In both methods the specimens are painted with Bornitrid lubricant. The effect of the preheating on the coefficient of friction is investigated by using strip tensile tests. FEM simulations for the deep drawing comparing two different material models (Barlat 2000, CPB06) are executed. The results show that specimens heated in the tool show a better formability than oven-heated specimens. The numerical results present that there is no significant difference between Barlat 2000 and CPB06 in an isothermal deep drawing condition. The numerical results are in good agreement with the deep drawing experiments which also indicates that the warm FLCs allow for a good failure prediction.
Aging behavior of ultra-fine grained AA 6061 alloy subjected to constrained groove pressing followed by cold rolling
Authors: Changela K , Kumar S , Hariharan K , Ravi Kumar D 
Published: November 2019

Abstract
A novel severe plastic deformation (SPD) route to achieve strengthening of AA 6061 alloy sheets by subjecting them to constrained groove pressing (CGP) followed by cold rolling (CR) is studied in the present work. Solutionized AA 6061 alloy sheets of 3 mm thickness have been subjected to CGP with an equivalent plastic strain of 1.16. The CGP samples have been subsequently cold rolled to reduce the thickness to 1mm (67% reduction) to achieve homogeneous microstructure with ultra-fine grains. It has been observed that yield strength increased significantly due to both CGP and CR. However, the ductility of the processed sample is lower. Therefore, an attempt has been made to study the aging behavior of the processed sample to achieve higher strength along with enhanced ductility through precipitation hardening. Aging of the processed samples was done by isothermal treatment at different temperatures. The microstructure of the deformed and aged samples was characterized by optical microscopy and scanning electron microscopy (SEM). Hardness and tensile tests have been studied to understand the mechanical behavior of deformed and aged samples. From the results, it has been found that processing of this alloy through CGP+CR and subsequent aging improves both strength and ductility due to the combined effect of precipitation hardening and recovery.
Fracture toughness measurements to understand local ductility of advanced high strength steels
Authors: Frómeta D. , Lara A. , Casas B. , Casellas D. 
Published: November 2019

Abstract
The determination of the material parameters that best predict the local ductility of high strength sheet materials has become the focus of active research. Even though several correlations have been proposed, they can sometimes be not accurate enough and discussion is still open on this topic. This paper investigates the suitability of different fracture toughness measurements for local ductility prediction in multiple advanced high strength steels (AHSS). Fracture toughness is characterized by means of essential work of fracture and Khan tear tests. The results show that the essential work of fracture, we, correlates well with different local formability (HER, critical bending angle from V-bending tests and local strain at fracture from uniaxial tensile tests) and crash resistance parameters (energy absorbed in axial impact tests). It confirms that fracture toughness, measured in the frame of fracture mechanics, is a relevant material property to rationalize cracking issues associated to the local ductility of AHSS. On the other hand, it is also shown that Khan tear tests, which are conventionally used to evaluate the fracture resistance of thin metal sheets, can overestimate crack propagation resistance and offer a poor prediction ability for local formability and crash performance.
Enhancement of fracture forming limit by crystallographic texture reformation of AA1050 sheets in Single Point Incremental Forming
Authors: Shrivastava Parnika , Tandon Puneet 
Published: November 2019

Abstract
Single Point Incremental Forming (SPIF) process that results in the formation of sheet metal components leads to higher forming capabilities in comparison to conventional forming strategies. However, the formability in SPIF is critical and limited by the rapid/sudden failure in the sheet material (without material localization) for the components with high wall inclination angles. The state of stresses and strains plays a huge role in determining the forming limits in SPIF, which is complexly governed by various factors such as sheet thickness, lubrication, incremental step depth, tool rotational speed, part geometry, tool dimensions, and geometry, to name a few. The present work focuses on investigating formability of the sheets from its microstructure and crystallographic texture point of view. Preliminary experimentation led to the conclusion that SPIF of the original commercially supplied AA1050 H14 sheets results in early and premature failure. Microstructural investigation of the undeformed sheet showed that the commercially supplied sheets undergo strain hardening due to cold rolling and therefore, results in dislocated and disorientated microstructure and texture. The present work attempts to reform the microstructure of the sheet by preheating at the optimized temperature. Finite element analysis (FEA) of the process led to the observation that the reformed microstructures result in enhanced fracture forming limit strain and reduced stresses in SPIF. This may be attributed to the decrease in the number of dislocations and dislocated grains, and decrease in the surface area of grain boundary per grain with preheating. Improved fracture forming limits due to preheating were experimentally validated by utilizing digital image correlation technique (DIC) for acquiring true strain values subjected to fractured original and different preheated samples.
Experimental study on the mechanical properties of 7xxx aluminium alloy sheet under different heat treatment conditions
Authors: Choi Yumi , Moon Chanmi , Lee Myoug-Gyu 
Published: November 2019

Abstract
Automotive bodies with high strength aluminium alloys have drawn increasing attentions due to their higher strength and lightweight capability. As one of high strength series of aluminum alloys, peak aged 7xxx series aluminum alloys exhibit superior strength of ∼ 600MPa to the conventional lower or moderate strength alloys. However, in spite of the high strength, the lower ductility has been a technical hurdle to be overcome for the material to be applied to press parts at room temperature, which leads to the development of forming technologies at elevated temperature, or namely hot forming. As an alternative to the hot forming, forming trial at room temperature has been made by performing prior solution heat treatment and quenching. This coupled heat treatment and cold forming increases the formability, while the strength needs to be recovered by additional post treatment. The treatment after forming (or deformation) includes natural aging and paint baking process inducing the artificial aging. The objective of the present study is to experimentally investigate the mechanical properties after different heat treatment conditions, which will be utilized for the future finite element simulations for the investigated forming technology.
Forming simulation for TWIP steel
Authors: Gösling M , Thülig T 
Published: November 2019

Abstract
This paper introduces a new generation of industrially available cold rolled TWIP steel. The TWIP900 is a high manganese steel with approx. 19% manganese and shows a stable austenitic structure at room temperature. The focus of the paper is on the forming behavior, which is remarkable compared to other industrially available sheet metal materials. The key figures of this cold rolled narrow strip are a tensile strength of 900 MPa in combination with an elongation at fracture of 40%. The forming behavior of the material is characterized in tensile tests, bulge tests, and Nakazima tests. A material model for forming simulations is set up and a comparison between different material models is done. Then deep drawing experiments are carried out and numerically simulated. Finally, a flanging and springback study is carried out. A comparison between simulation and experiment demonstrates the good quality of currently industrially applied simulation techniques for TWIP steels.
Experimental and finite element analysis of the shear cutting process of electrical steel sheets under various process conditions
Authors: Slota J , Spišák E , Kaščák L’ , Majerníková J 
Published: November 2019

Abstract
Almost every electrical machine consists of the stator and rotor cores, which are made of stacked non-oriented electric steel sheets. Punching and blanking are the two commonly used shear cutting operations for manufacturing electrical machine components. The presented research was aimed to evaluate the shear cutting process of two grades of electrical steel sheets. The shear cutting process causes the formation of residual stresses in the cut segments from the non-oriented electric sheet metal, resulting in increased iron losses. Numerical modeling and experimental research were used to investigate the influence of cutting clearance as well as blunt cutting edge of the shear cutting tool on the residual stresses induced by shear cutting under different shear cutting parameters. The data derived from experiments were applied in finite element analysis of the shear cutting part in the shape of a toroid. Comparison between the results of the experiments and the FE simulations showed that the shear cutting process can be accurately predicted.
The Influence of Residual Stresses Induced by Near-Net-Shape Blanking Processes on the Fatigue Behavior under Bending Loads
Authors: Stahl J. , Müller D. , Pätzold I. , Golle R. , Tobie T. , Volk W. , Stahl K. 
Published: November 2019

Abstract
Gears manufactured by blanking can be found in many different products like hammer drills or automobiles. Here, only the functional surface, the clean shear, can be used to transmit torque. Therefore, parts in serial production demand a high amount of clean shear, so the required torque can be transmitted with a minimal thickness and part weight. To achieve this, these parts are usually manufactured by fineblanking or related Near-Net-Shape Blanking processes (NNSBPs). Furthermore, the gears are subjected to cyclic loading which can, especially in the highly stressed tooth root, lead to tooth breakage. The effect of different process variants and process parameters on the residual stresses and the fatigue behavior under a pulsating bending load has not been investigated yet. Due to the potential of endurance improvement of blanked gears, this topic is addressed in this paper. To accomplish this, C-shaped profiles are manufactured by five different Near-Net-Shape blanking processes. The investigated processes are fineblanking, precision blanking with and without blank holder, and blanking with a small die clearance with and without a v-ring. The sheet metal material, S355MC (material number 1.0976) with a thickness of 6 mm, is first subjected to a stress relief heat treatment to minimize residual stresses induced by the specimen preparation and to ensure a defined initial residual stress state. After blanking, the residual stresses of the parts are measured. Finally, fatigue strength tests are carried out under a pulsating bending load on the C-shaped profiles with shear-cut edges. The results show that the residual stress state, as well as the part’s fatigue behavior are strongly influenced by the chosen blanking process.
Investigation of a new sheet metal shear cutting tool design to increase the part quality by superposed compression stress
Authors: Senn S , Liewald M 
Published: November 2019

Abstract
Nowadays, a major criterion for the quality of shear cut workpieces is characterised by a smooth final cutting surface. Normally, this surface only can be manufactured by using fine cutting or trimming technology. Major disadvantage of these processes is the complex tooling design caused by a double-acting press and corresponding tool layout. Content of this study is to investigate the impact of a new sheet metal cutting tool design, also called concave nosed punch design, to increase the clean-cut portion in conventional shear cutting. The investigation focuses on sheet metal materials DP600, DC03 and HC420LA with a thickness of 1mm. Using FEA-Software DEFORM 2D, the models of conventional cutting and cutting with new tool design were mapped by comparing cutting surface results and stress distribution in the shearing zone. The main criterion of the optimization of tool design focuses on an enlarged clean-cut area along the cutting surface compared to conventional shear cutting. New tool design shows in numerical investigation a significant increase of clear-cut surface up to 73% compared to conventional cutting surfaces disclosing 35% when using tools according to standard design rules. With the result of the punch optimization in the numerical investigation, two cutting punches with different web widths were manufactured and experimentally investigated. The focus of the experimental investigation was the comparison of the cutting characteristics of smooth cut portion and cutting burr. The influence of the cutting clearance between 5% and 15% on the clean cut portion and the burr was investigated. Metallurgical micrographs show a significant increase in the percentage of smooth cut portion when punching with the new cutting method presented here. For DC03, these concave nose punch design was able to achieve smooth cut percentages of up to 95%. However, using this new punch design, it is possible to sheet metal materials revealing a noticeably performed shearing surface quality.
Prediction of necking & thinning behaviour during hot stamping conditions of 22MnB5 steel
Authors: Singh Amarjeet Kumar , Narasimhan K. 
Published: November 2019

Abstract
Hot stamping is a high-temperature forming operation in which the blank is heated to austenitization temperature, and subsequent forming and quenching operations are done simultaneously. In the current research, forming limits were determined using a thickness gradient-based criterion. For this purpose, the tensile and plane strain mode of deformation were considered. The study was carried out in a wide range of temperatures, viz. 750 °C,800 °C and 850 °C at a constant strain rate of 0.01/s. The experiments were carried out in the thermomechanical simulator (Gleeble-3800), and subsequent measurement of thinning evolution for all the deformed specimens were carried out. It was observed that with the increase in temperature, thickness reduction was less and the distribution of thickness was uniform in tensile specimens and at the point of necking thickness gradient ratio is below 0.92 at various temperatures.
Numerical and experimental study of strain distribution of trip steel sheet using hydraulic bulge test
Authors: Spišák E , Majerníková J , Slota J , Kaščák L’ 
Published: November 2019

Abstract
This paper presents a numerical and experimental study of strain distribution in a spherical cup drawn from TRIP steel RAK 40/70 by hydraulic bulge test. The strain distribution was measured based on the data obtained by coordinate measuring machine (CMM) to identify the wall thickness and plastic anisotropy through measuring the circularity. Numerical modelling of hydraulic bulge test was performed in two types of finite element code – explicit as well as implicit. Hill’s family plasticity models with a combination of two types of the hardening curves were used in the simulation model of the bulging process. The FE analysis was compared with the experimental study. The results indicate that the model is applicable to describe the wall thickness, strain distribution and bulged profile.
On the Design of Novel Multi-failure Specimens for Ductile Failure Testing
Authors: Williams Bruce W. , M. Simha C. Hari 
Published: November 2019

Abstract
To quantify uncertainty in the failure response of metallic alloys, conventional experiments may not be suitable owing to the lack of significant scatter in stress states that lead to ductile tearing. In contrast, our testing experience indicates with structures containing strategically located cutouts lead to multiple failure paths and display sufficient scatter in the failure response. Accordingly, we describe the design of dog-bone shaped structures with an ensemble of cutouts, so that at least three different failure paths are observed. In conjunction with Digital Image correlation for full-field displacement measurement and numerical computations, we show how multiple failure paths are obtained when these samples are used. Tests on 2-mm thick 6061-T61 aluminum sheets were conducted using a novel guillotine-style fixture that allows the use of high-speed press. The latter allows testing at strain rates as high as 1 1/s. The primary purpose of this article is to make the case for the use of these samples that not only minimize number of tests required to garner data to calibrate stress-based damage models that capture the entire failure envelope of the material, but also display sufficient scatter that allows quantification of uncertainty in the failure response.
AA1100-O cylindrical cup-drawing using 3D servo-press
Authors: Ha J , Breunig A , Fones J , Hoppe F , Korkolis Y P , Groche P , Kinsey B L 
Published: November 2019

Abstract
In this paper, the flexibility of a 3D servo-press is used as the inspiration to numerically demonstrate the ability to improve the final product, in this case reduced equivalent plastic strain, increased forming depth, and reduced punch force, during cylindrical cup-drawing. The material investigated is AA1100-O which exhibits significant anisotropy, i.e., r-values of 0.45 to 1.2 in 45 degree and transverse direction to rolling, respectively. This leads to earing during cup-drawing, which is used to validate numerical simulation efforts. A unique 3D servo-press at the Institute for Production Engineering and Forming Machines at the Technische Universität Darmstadt allows for tilting and orbital motion of the blank holder and with this a variation of the blank-holding force during the punch progression. Numerical simulations are used to demonstrate improvements with respect to equivalent plastic strain and forming depth.
Bayesian Model-based State Estimation for Mass Production Metal Forming
Authors: Havinga Jos , Mandal Pranab K , Boogaard Ton van den 
Published: November 2019

Abstract
Modern metal forming factories produce large amounts of data, such as process forces and product geometries. These data contain indirect information about fluctuations in the manufacturing process, such as changes in temperature, material properties and lubrication conditions. In this work, Bayesian inference is used to obtain a probabilistic estimate of the process state based on force measurements in mass production metal forming. The procedure requires statistical assumptions about process state variations, which are often not known as it is usually not possible to directly measure the process state in-line. It is shown that unknown statistical model parameters can be estimated simultaneously with the process state. This leads to an improvement in the accuracy of the state estimate. The procedure is studied using pseudo-data from a mass production sheet bending process, using a finite element model with ten parameters. The material, friction and process parameters are estimated based on process force measurements.