bluuebunny/crossref_metadata_2025_split huggingface dataset:
Evaluation of hole expansion ratio of ultra-high strength martensitic steels produced with various processing routes
Authors: Hannula J. , Plosila P. , Kaijalainen A. , Suikkanen P. , Kömi J. 
Published: June 2023

Abstract
Hole expansion ratio of hot rolled ultra-high strength martensitic steels with tensile strength around 1000 MPa was evaluated. Steels were produced with direct quenching and traditional reheat and quenching processes with final thickness of 3 mm. Achieved yield strength values (Rp0.2) varied between 918 – 1068 MPa depending on the processing route. Mean hole expansion ratios (HER) in direct-quenched (DQ) and direct-quenched and tempered (DQT) conditions were between 22 – 36 %, and no clear improvement was seen after tempering treatment compared to quenched variant. HER values for reheat and quenched (RQ) and reheat, quenched and tempered (RQT) variants were between 31 – 49 %, and the highest values were achieved with RQT steels, which were tempered at 600 °C. Based on the field emission scanning electron microscope with electron backscatter scanning diffraction (FESEM-EBSD) analysis/characterization of martensite grain size, more uniform grain structure was discovered in RQ steels, which could be the reason for improved HER properties. HER values were also compared to tensile test results (uniform elongation, true thickness strain), and formability maps were constructed. However, only minor correlation was found between HER and true thickness strain values.
Development of a novel in-situ measurement method for thermo-mechanically coupled material characterization of high-strength aluminum alloys
Authors: Rigas N , Garcin T , Kuball C-M , Merklein M 
Published: June 2023

Abstract
High-strength aluminum alloys are more and more used for safety and crash-relevant components due to their advantageous density-to-strength ratio. By using thermal-supported forming strategies, failure-free deep drawing is possible for these materials. In this context, the hot form quench process (HFQ®) has shown to be a promising thermally-assisted forming strategy. By using locally tempered forming tools, the production of tailored components with different mechanical properties is possible. However, material characterization and process design with conventional characterization methods are quite challenging in this context. A new approach is the use of ultrasound-assisted material characterization in combination with a thermo-mechanical simulator. Thereby it is possible to perform an in-situ material characterization. So far, this technology is mainly used for steel materials. In this contribution, the potential of an adapted measurement strategy for high-strength aluminum alloys is presented. For this purpose, the influence of different measurement parameters on modified samples and the resulting measurement signal is investigated. With the help of this study, new standards are set for time-bound material characterization under thermo-mechanical stress. As a result, thermally-assisted forming methods can be designed more efficiently and faster in the future.
Characterization of the Mechanical Properties of Selectively Embossed Sheet Metal Materials Under Multi-Axial Loads
Authors: Heinzelmann Pascal , Briesenick David , Liewald Mathias 
Published: June 2023

Abstract
The application of embossed structures close to the sheet surface allows for work hardening to be introduced into sheet metal materials, leading to an improvement in their mechanical properties. So far, this was demonstrated in previous research work via tensile tests with differently embossed dual-phase steel specimens. Since tensile tests only reproduce uniaxial loading of the sheet metal material, no conclusions can yet be drawn about the property modification that can be achieved by near-surface embossing concerning real-life, multi-axial loading scenarios. To get deeper knowledge about the deformation behaviour of embossed components, it is important to consider multi-axial load cases. In the investigations reported in this paper, a multi-axial load case was realized by testing embossed bending specimens of DP600 and DP800 using a three-point bending device. The tests showed an overall improvement in the maximum bending force needed for the three-point bending test due to embossing of the materials investigated. Further, the tests indicated that lower-strength materials get more influenced by embossing than higher-strength materials. By simulating the process of embossing the bending specimens and the subsequent three-point bending test, an even deeper understanding of the material property modification could be generated.
Micro incremental forming of thin SS304 foils and its microstructural study
Authors: Mahajan Peeyush , Patil Jeet , Mishra Sushil 
Published: June 2023

Abstract
Micro-forming of thin foils is challenging due to the size effect, friction effect, and tool design. The conventional macro-forming techniques cannot be directly applied to the thin foils. The incremental forming process (ISF) can be used for thin foils since it possesses higher formability compared to the conventional process. Hence, µ-ISF (micro incremental forming process) experiments were conducted on thin foils of SS304 stainless steel having 50, 100, and 200 µm thickness. As-received foils were further annealed at 950°C with a holding time of 20 mins to achieve strain-free microstructure. The Taguchi L18 orthogonal was applied to optimize the initial processing parameters for, µ-ISF experiments. Using the initial optimized parameters µ-ISF experiments were performed for all the thickness sheets up to the maximum wall angle. It was observed that the higher tool diameter and the lower step depth give the minimum roughness value in the deformed sheet. The tearing mode of failure was observed due to the formation of strain-induced martensite in the deformed sheet. The microstructure and bulk texture analysis relate the orientation and twin fraction with the deformation behaviour. From the texture evolution, it was observed that the brass {110} <112>, Cube {100} <001>, and goss {110} <001> texture component has a greater influence on the formability of SS304 stainless steel thin foils.
Simulation of deep drawing of dual phase steel sheets incorporating tribological behaviour predicted by advanced friction modelling
Authors: Shrivastava Archit , Ravi Kumar D 
Published: June 2023

Abstract
In a deep drawing process, friction at the sheet metal-die contact interface affects the material flow in the flange as well as at the die entry affecting product quality significantly. The accuracy of predicted drawing force and thinning in deep drawing simulation strongly depends on friction modelling. The Coulomb friction model with a constant coefficient of friction is generally assumed in simulations. In reality, the actual friction coefficient depends on process variables such as local contact pressure, relative sliding velocity, and strain in the sheet material. In this work, an approach is presented for deep drawing simulation of dual phase (DP600) steel sheets incorporating the effect of these variables on the friction coefficient. Strip drawing tests under conditions similar to that exist in the flange area during deep drawing have been carried out. Deep drawing simulations have been performed using two friction models taking into consideration the variation of friction coefficient with respect to pressure and velocity. The predicted punch force and thickness variation are validated using deep drawing experiments. A considerable improvement in the accuracy of predicted results has been observed when compared to a constant coefficient of friction.
Three Industrial Cases of Sheet Metal Forming Simulations with Elastic Dies
Authors: Pilthammar J , Sigvant M , Islam M S , Schill M , Sjöblom S , Sjöblom V , Lind M 
Published: June 2023

AbstractPrevious research and experience points to many advantages if sheet metal forming is simulated with elastic dies. Some areas that are enabled by simulations with elastic dies are virtual spotting, improved digital twins, and improved production support. A promising method was selected from the literature, and after important modifications it is deemed to be fast and robust for simulating industrial sized dies. The method consists of meshing die solids with a coarse mesh to represent the structural behaviour of the die. The forming surfaces are then represented by a fine shell mesh connected to the solid mesh by tied contacts with an offset. With additional modifications to reduce solver time this yields a robust and flexible way of modelling sheet metal forming with elastic dies. There is an increase in preprocessing and simulation time compared to using rigid tools, but industrial dies can now be modeled within an hour and solved within a working day. It is also easy to update the model by replacing separate parts such as die solids or forming surfaces. One of the main criteria in favor of the selected approach is the realistic modeling of blankholder and cushion systems. In this paper simulations of three industrial cases are demonstrated: one case of virtual die spotting and two cases of production support. The three cases demonstrate the importance and potential of using elastic dies during virtual die tryout, production support, and for cases like digital twins and production control.
Substitutive models of press deflections for efficient numerical die cambering
Authors: Ottosson P , Pilthammar J , Wiklund D , Skåre T , Sigvant M 
Published: June 2023

Abstract
Cost and time for stamping die tryouts are significant within the car industry. A major contributing factor is that elastic deflections of stamping dies and presses are usually not considered during the virtual die design and forming simulation phase. Active surfaces of stamping dies are only cambered based on previous experiences of tool types and stamping presses. However, almost all stamping dies and presses are unique, and available experiences are not valid for new sheet materials. This leads to component deviations and often several loops of tool adjustments are needed. Previously partners within the SMART Advanced Manufacturing research project CAMBER have developed advanced deflection measuring devices to quantify the elastic deformations of stamping presses. Using these measurements, cambering methodologies can be utilized in sheet metal forming simulations. In this paper numerical substitutive stamping press models are described which are capable of compensating for measured stamping press dynamics. The result show that a numerical compensated tool can improve the contact by over 80% compared to the corresponding contact without compensation.
Impact of the process velocities on the quality of free-form bent parts
Authors: Scandola Lorenzo , Tschannerl Jeremias , Maier Daniel , Werner Matthias Konrad , Hartmann Christoph , Volk Wolfram 
Published: June 2023

Abstract
The geometrical accuracy of the bent components as well as their surface quality are crucial parameters to evaluate the feasibility of a bent geometry in free-form bending. In the process the deformation of the part is obtained by displacing and rotating a movable bending head with respect to the fixed holder with a given relative velocity with respect to the feed velocity. High process velocities have a beneficial effect on the realisation of bending radii and angles, but induce high local solicitations on the semi-finished part, which can result in surface defects like indentations and buckles. In this work the impact of the bending head velocity as well as of the feed velocity on the bend’s stability and the arising of indentations is investigated. Experimental tests with different head and feed velocity are conducted on mild, moderate and severe bends keeping the same kinematics. The resulting bending radii, angles and surface defects are evaluated. The results allow to identify the parameters having the highest influence on the quality of bent profiles and to propose a compromise between geometrical stability and surface quality.
Study of the Influence of part features on springback and its robustness
Authors: Niu Chao , Hu Zhili , Zhang Jian , Han Fei 
Published: June 2023

Abstract
The influence of part geometry on twist springback was studied by a A-pillar inner plate. The part structural parameters was divided into cross-section and longitudinal axis, and the response surface model was established to analyze the influences of various structural parameters on the twist springback. The results show that the straight line 1, straight line 3, angle 2 and angle 4 of the cross section have a significant effect on the twist springback. In addition, the twist springback increases continuously with increasing of total length and ratio of arc to straight line and the decreasing of radius in the longitudinal axis. After adding features through the angular edges along the longitudinal direction, the maximum springback at the part end drops from -10.92mm to -2.934mm. The springback robustness analysis of this part were also analyzed, the results show that the maximum springback is strongly related to material yield strength, and the robustness is improved greatly after adding part features.
Effect of strain mode and blank orientation on waviness for paint appearance of automotive outer panels
Authors: An Y G , Carless L , Chezan A R , Schouten F , Appelman M , Toose M , vanVeldhuizen B 
Published: June 2023

Abstract
Paint appearance is an important requirement for outer automobile panels. Since the last decade automotive manufacturers started reducing paint thickness to address environmental concerns. As a result, the surface roughening of steel substrate due to stamping becomes a critical factor for paint appearance. Although much research work has been conducted on surface roughening, limited research has been focused on waviness and stamping conditions in the pressing of highly formable sheet steels. In this work, the effect of strain mode and blank orientation on waviness evolution has been investigated. It was found that strain mode has a strong influence on waviness, in addition to strain magnitude. Also, the relative orientation of the applied major strain and the direction of the roughness profile relative to the rolling direction affects waviness. When surface waviness is compared at the same surface major strain, the waviness is highest in equibiaxial stretch, followed by plane strain tension in the rolling direction, and then plane strain tension in the transverse diction. When waviness is plotted against thickness strain, the waviness in plane strain tension stretched in the rolling direction is highest, independent of the roughness profile measurement direction. The waviness in equibiaxial stretching is almost the same as that in plane strain tension stretched in the transverse direction.
Formed developables - a new class of sheet metal parts
Authors: Bhuva J , Weiss M , Rolfe B , Jiao J , Paulino M 
Published: June 2023

Abstract
Sheet metal parts are broadly classified as stamped parts versus folded developables. While stamped parts are parts manufactured using conventional sheet metal forming techniques, folded developables are curved developable connections produced by the virtue of the classical theory of folded developables. However, folding is not suitable for parts where material integrity cannot be compromised at the fold lines. In such cases, forming techniques can be used to introduce a distributed curvature and avoid material self-intersection at the curved fold axis. This paper combines the two genres to introduce a third class of parts called the formed developables. A developable shaped, thin sheet metal of very high strength and reasonable inextensibility is formed by flange drawing over a die radius. The die tool establishes the required curved bend axis, and the die radius is small enough to introduce a distributed curvature. A developable connection is successfully formed where the two connected corrugations are mirror images of each other. While no tearing or wrinkling is observed, experimental strain measurements highlight significant surface strains in the transverse direction while marginal stretching strains are observed in the forming direction. A trend of equal and opposite transverse strains strongly suggests that the major deformation in this geometrical process, and in-turn the shape of the final part, is driven by the involved geometrical parameters.
Innovative experimental setup for the investigation of material models with regard to strain hardening behavior
Authors: Maier L , Eder M , Norz R , Volk W 
Published: June 2023

Abstract
Sheet metal formed parts are often produced in multistage processes. The multi-directional deformations that occur in this process pose a challenge for sufficiently accurate modeling of the material behavior. In this paper, we present an experimental methodology and its potential that serves as a basis for a comprehensive validation of material models with respect to multi-directional deformation. Therefore, we present the experimental results of pre-strained DP600 specimens, which we afterwards subjected by the MUC-Test. The MUC-Test has already been established as a methodology for validating material models under proportional loading. By using pre-strained specimens, this methodology can be extended to non-linearities in the load history. For the purpose of the paper, we pre-strain the sheet material in three conditions: uniaxial tension, plane strain and equibiaxial tension. Thus, we show that the MUC-Test is suitable for the representation of multi-directional strain histories and useful for comprehensive validation of material models.
Experimental characterization of forming behavior of 3rd GEN AHSS
Authors: Champolivier E , Brancherie D , Feissel P , Gaied S , Canourgues J-F 
Published: June 2023

Abstract
Third generation of Advanced High Strength Steels (3rd GEN AHSS) for cold stamping combine superior formability and ductility at higher strengths. Their combination with the Laser Welded Blanks (LWB) technology is one answer to improve safety and weight reduction of vehicules for automakers. In this study, a Nakazima test is used to evaluate the forming behavior of LWB based 3rd GEN AHSS and to estimate their Forming Limit. Tests equipped with a Digital Image Correlation (DIC) system are carried out for several materials combinations in order to understand the influence of the weld on LWB formability. The experimental results are used to determine the critical area during this forming test and a dedicated FLC for each material combination. The location of the onset of failure is investigated, from optical observations, DIC data as well as modeling. It appears that different failure locations are obtained depending on both AHSS combination and strain paths. In order to improve the accuracy of the determination of the onset of the failure, a method is proposed to evaluate the failure risk in base metal and in the vicinity of the weld. The improvement of failure prediction will be very helpful to analyze part formability and provide design recommendations.
Proposal of a New Tool for Pre-Straining Operations of Sheet Metals and an Initial Investigation of CR4 Mild Steel Formability
Authors: Barlo A , Sigvant M , Islam M S , Pérez Ll , Olofsson E , Al-Fadhli M , Pham Q T , Pilthammar J , Odenberger E-L 
Published: June 2023

Abstract
With the increased focus on reducing carbon emissions in the automotive industry, more advanced materials are introduced to reduce the vehicle weight, and more complex component geometries are designed to both satisfy customer demands and to optimize the vehicle aerodynamically. With the increase in component complexity, the strain paths produced during the forming operation of car body components often display a highly non-linear behavior which makes the task of failure prediction during the manufacturing feasibility studies more difficult. Therefore, CAE engineers need better capabilities to predict failure induced by strain path nonlinearity. This study proposes a new tool designed for creating bi-linear strain paths, by performing a pre-strain of a sheet large enough to cut out Nakajima specimens to perform the post-straining in any direction. From five pre-straining tests the tool present a stable pre-straining operation with a uniform strain field in a radius of 100 [mm] from the centre, corresponding to the region of interest of a Nakajima specimen. From the five pre-strained samples, different Nakajima specimens are cut transverse and longitudinal to the rolling direction and a failure prediction approach in an alternative, path independent evaluation space was used to predict the onset of necking with promising results.
Prediction strategy for the forming and stuffing of non-circular tube
Authors: Stennei M , Clausmeyer T , Grodotzki J , Rosenthal S , Stiglmair M , Tekkaya A. E. 
Published: June 2023

Abstract
The manufacturing of exhaust filter systems for cars typically comprises the forming of a tube and the later stuffing of the formed product with a ceramic monolith and an elastomer mat for filtration. It is shown, that for oval tubes the stuffing process leads to inhomogeneous deformation of the final product wherefore it must be considered when designing the tools for the forming step. The high number of iterations for the tool design can hence be reduced. Additionally, under certain conditions, the necessity of simulating the forming process is shown to no longer be given. The reason for this is that during the stuffing step, no plastic deformation is introduced in the tubes. Consequently, the forming history, including local strain and residual stress distributions, do not need to be explicitly considered. A simplified methodology is presented based on these findings, which can find the required cross-section geometry of the tube entering the stuffing process. The goal of the previous forming process therefore is to produce exactly that geometry, which can be done using conventional forming process planning approaches.
Wear characteristics of the tool in the cold stamping process of ultra high strength steel sheets by establishing a novel wear test method based on the progressive die
Authors: Bang J , Kim M , Bae G , Song J , Lee M G 
Published: June 2023

Abstract
Demands for lightweighting and crashworthiness of the vehicle body have increased. For this purpose, advanced high strength steel to the automobile body was regarded as a solution with respect to manufacturing cost and impact energy absorption. However, increasing the strength of the automotive steel sheet lead to a diversity of problems caused by the tool wear due to higher forming load than that of commonly used steel sheets. Hence, systematic wear experiment and evaluation methods are required to quantitatively and qualitatively evaluate the tool wear amount in the sheet metal forming process. In this study, a methodology is proposed to quantitatively evaluate the wear of sheet metal forming tool based on the experimental results. In order to carry out a systematic wear test and save the time and cost, the progressive die set was designed to be suitable for wear test. The designed testing machine can simultaneously test four types of punches made under various tooling conditions such as materials, shapes, and coatings. Through the measurement of the wear depth, roughness, and surface imaging of the punch and product roughness, which represent the wear characteristics, quantitative evaluation methods for tool wear in the sheet metal forming process are established. By referring to the wear test results, it is confirmed that it is appropriate to analyze the reasonable tool wear characteristics by using the proposed methodology for quantifying the tool wear in the sheet metal forming process.