The topic of this plenary lecture is “SSAB’s transformation to Fossil Free Steel with the HYBRIT Technology”.
With Luleå as the location of the conference, we will present to you the history of the press hardening process, the invention originated from Luleå. Together with the growing interest and use of the press hardening process, it came an increased need to predictand simulate the process. Something that has been developed here, and still is being further developed.
As a lightweight construction strategy, hot stamped parts of ultra-high-strength steels with tailored properties are increasingly used for crash relevant components in car bodies, e.g. as B-pillars. With the process of tailored carburization, parts can be reinforced locally without increasing the sheet metal thickness. Thus, this process has the potential to be applied to lightweight...
The experimentally recorded FLC are valid only for linear strain paths. A non-linear strain path history but also different sheet thickness to radius of curvature ratios t/r can strongly shift the position of the linear FLC.
In order to correctly account for these effects in the simulation, a numerical prediction of the instantaneous FLC is required. Beside of the M-K model, the Modified...
Constrained groove pressing (CGP) is one of the severe plastic deformation techniques for sheet metals to impose large plastic strain and produce ultrafine-grained (UFG) structures without any change in dimensions. Cross route-constrained groove pressing (Cross-CGP), an advanced version of the conventional CGP process, involves two CGP cycles with an equivalent strain of 2.32 per cycle where...
The increasing demands on part complexity and tailored properties in form of local strength and ductility cannot be met with a conventionally manufactured hot-stamped body part. In order to meet the requirements of safety-relevant body parts, partial hot stamping is increasingly used in the industry. One approach to achieve tailored properties on hot-stamped parts is based on controlled...
Hole expansion ratio of 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)...
Modern car bodies are constantly relying higher proportions of high and ultra-high strength steels. In the past, the increase in material strengths led to a conflict regarding the complexity of component geometries. Limits of material formability were reached and compromises had to be made in part design. By integrating application-oriented problems into the material development, these limits...
The decarbonization of steel sheet metal production process introduces new challenges for the automotive part production process. Especially, the recyclability component, the efforts to increase the steel scrap in the primary steel making process beyond the levels currently used, produces increased variability intervals for certain residual elements outside the levels typically found in the...
Aluminum alloys are being used extensively in the automotive industry to meet the increasing requirements for light weighting. The remarkable strength to weight ratio offered by aluminum alloys combined with good formability makes them suitable for manufacturing of light weight vehicles. Aluminum alloys of 5xxx and 6xxx series are particularly more important for applications in automotive and...
Saving CO2 by replacing fossil fuels with renewable ones has been a goal of research for several years and has become the focus of public discussion at the latest due to the electrification of passenger cars and the much-discussed carbon footprint caused by production. Hot stamping is a process for the production of ultra-high-strength components used for passenger protection in the automotive...
Rubber forming is a flexible forming technology which have widely application on low volume sheet metal forming process. However most of the investigation focus on forming process at room temperature due to the equipment limitation. In this paper a rubber forming system was built which include a die heating system and heat resistant rubber. The blank and die can be heated to a high...
Press hardening grades are widely used in automotive industries for safety-critical structural parts due to its unique combination of high strength, excellent formability, and crash performance. Although general process windows are recommended by steel suppliers, achieving the targeted strength and ductility / fracture strain in the hot-stamped parts is still challenging to some hot...
Robot-assisted flexible flanging (RAFF), a cost-effective and promising forming technology for producing large-size open-edge flanging parts in multi-variety and small batches, is expected to be widely used in aerospace, automotive and other technological industries. Depending on whether the flanging angle of the forming roller is adjusted, the RAFF process of every pass can be summarized as...
Recently, the automobile industry is increasing demand for hot stamping parts due to the growth of eco-friendly vehicles with the lightening and the crash safety performance. In the hot stamping process, a high-temperature heated steel sheet is simultaneously stamped and quenched to manufacture ultra-high-strength components of 1.5GPa or more. However, it takes more than 10 to 15 seconds to...
The manganese-boron alloy 22MnB5 is particularly used for structural and safety-relevant parts in the automotive industry. Parts made from this alloy are usually produced using the hot stamping process. In this process, the sheet is heated to over 950 °C using an industrial roller hearth furnace. The heated sheet is then simultaneously formed and quenched in a cooled tool with a temperature...
Abstract: The thin-walled cylindrical parts with ribs, as the main structure of the launch vehicle, has been currently used in block manufacturing mode, which has the disadvantages of long manufacturing cycle, low material utilization rate and limited structural lightweight. Therefore, the integral forming process of the thin-walled cylindrical parts with ribs is an inevitable development...
In sheet metal stamping, the occurrence of strain localization in a deformed sheet is considered the failure. As so, the formability of a sheet metal is conventionally evaluated by using the forming limit diagram. This study presents an evaluation method for detecting the strain localization during experiment based on the digital image correlation. The strain-field distribution on the surface...
Incremental sheet forming (ISF) is an emerging technology for manufacturing sheet metal components with fewer tools and equipment compared to conventional sheet forming. In this process, forming is generally performed without dies and punches and a simple hemispherical shaped tool can be used for shaping the final component. Forming limit in incremental sheet forming can be defined by the...
Warm forming is widely used to enhance formability of aluminum alloy sheets in order to manufacture components with complex shapes. Warm forming results in change of frictional characteristics at the tool-blank interface during forming. Higher friction leads to poor formability, non-uniform strain distribution, higher forming load, and poor surface finish of the component. So it is important...
The paper will present the development of sheet metal forming simulations at Volvo Cars since the late 1980’s until today. Major breakthroughs during the development will be presented as well as the current state of the art. Finally the future challenges for the sheet metal forming community, e.g. sustainable metals, and ideas how to solve these challenges will be presented.
In this study, the hole expansion tests are conducted for the first and third generation high-strength steels (dual-phase steel and quenching & partitioning steel) to investigate the edge fracture behavior. Two edge conditions based on separated manufacturing techniques (waterjet/wire cutting and punching) are prepared and then followed by hole expansion tests to characterize the edge...
Modern hot sheet metal forming processes offer the opportunity, especially in the automotive sector, to meet current demands for ultra-lightweight design. Due to the increased formability at the high process temperatures, high-strength aluminium alloys are increasingly coming into the focus of the industry. However, the complex thermo-mechanical interactions within these processes can lead to...
The present intention to reach fossil-free steel manufacturing will inevitably result in an increase in the use of steel scrap as a raw material for steel production. Consequently, the amounts of elements, seen as impurities, will increase in steels. This has already been seen in electric arc furnace (EAF) processed steels, where the Cu and Sn levels have doubled in some cases after 1980’s....
One limitation of the standardized ISO 16630 hole expansion test is that it provides only one result: limiting hole expansion ratio (HER). In practice, steels with similar HER-values can have different cut edge forming behavior due to possible differences in strain localization tendencies. Digital image correlation (DIC) strain measurement during formability testing allows more in-detail...
It is increasingly important to optimize fabrication processes with regards to the efficient use of resources and to lower their carbon footprint. Especially for the automotive industry, these demands have increased the importance for new for lightweight construction solutions. One approach to achieve lightweight components was the introduction of new, high strength steel sheet materials for...
The effect of strain gradient on the stretch flange deformation limit of steel sheets was investigated by hole expansion test under some forming conditions and by FEM. Hole expansion ratio was changed by changing initial hole diameter and punch shapes. It was clarified that limit deformation strain increases as it does not depend on initial hole diameter or punch shape, and thus strain...
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...
Within the deep drawing process chain, damage develops and evolves – starting with foreign particles from the slag as well as non-metallic inclusions leading to voids, which develop, accumulate and ultimately lead to failure. This damage accumulation and evolution along the process chain decisively influences the performance of components. Accordingly, the influence on the damage accumulation...
Currently, due to the requirement of lightweight in the transportation field, the demand for high-strength aluminum alloy is increasing, but it is difficult for the traditional forming processes to balance the three components of formability, strength and efficiency. In order to solve this problem, a novel stamping process for high-strength AA7075 aluminum alloy sheets is proposed, termed...
Aluminum lithium alloy with many excellent properties such as low density, high elastic modulus, high specific strength has been considered as the most ideal structural material for aerospace. However, the application of Al-Li alloys is always limited in complex structural components, due to its inferior plasticity at room temperature and easy cracking during cold forming. As a novel forming...
The stringer sheet forming process chain enables the cost-effective production of components with significantly increased stiffness for mass markets such as the automotive sector. In the first process step, a stringer is added to a conventional sheet by laser welding. In the subsequent process step, the stringer sheet parts are formed by a deep drawing operation. Previous investigations of...
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...
Keywords: Sheet metal forming, high strength steels, Edge formability, Chassis, Pre-strain, Hole tension test
Abstract
There is a high level of uncertainty in the prediction of edge cracking during the design and manufacturing of high strength sheet metal products. Edge ductility is a complex parameter to measure since it is not an intrinsic property of the material, but...
Flexible Roll Forming (FRF) is an advanced manufacturing process that can be used to form long and complex part families from hard to form materials for the automotive and truck industry. However, depending on the part complexity and material strength shape defects such as end flare, springback and twist can occur. In this work a high strength truck member (frame rails) is produced from AHSS;...
Keywords: Diaphragm compressor, metal diaphragm, single point incremental forming
Abstract.
This article deals with the development of an elastically foldable, bistable diaphragm geometry, which allows an increase of the compression volume of diaphragm compressors compared to the use of flat diaphragms. Using a Finite Element Model (FEM) in ABAQUS/Standard, a number of membrane geometries...
The use of aluminium alloys with high mechanical properties is very interesting to reduce the weight of parts, especially in the automotive field. However, a formability problem prevents the use of these alloy at room temperature (RT), especially for complex shapes where part failure occurs before complete drawing. The use of a warm forming process, which consists of heating the part between...
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 experiments were conducted on thin foils of SS304...
For decades, the ISO-16630 Hole Expansion Test (HET) has been the industry standard for expressing the edge formability of sheet metals through the Hole Expansion Ratio (HER). However, in recent years, this test has been criticized for its high scatter in results for repeated experiments. This scatter has been suspected to be caused by the operator-reliant post-processing of the test, or...
A Connecting rod (CR) is an essential part of the internal combustion engine. It transmits the energy generated in the combustion chamber to the crankshaft. Conventionally, the connecting rods are solid parts made of steel material forged to the required shape in several steps. This study has designed and simulated a process to manufacture hollow CRs by sheet metal forming processes. The...
Tube hydroforming (THF) is one of the most acceptable unconventional metal forming processes which is widely used to form various tubular components. In this process, tubes are formed into different shapes using internal pressure and axial compressive loads simultaneously to force a tubular blank to conform the shape of a given die cavity. The applications of THF are known in the automotive...
Functional integration and lightweight design are important tasks especially for modern electric vehicles. Development of multi-functional assemblies for the battery box of the future is one of the challenges in the field of electric mobility. The housing must perform many tasks: structural stiffening and sealing (waterproofness) as well as crash protection and thermal management for the...
In this study, various AHSS LWBs and GEN3-980 monolithic blanks were tested using a universal forming tool (UFT) to characterize the global formability such as the maximum draw-depth, and local formability such as necking and weld cracking. Two different LWB fabrication orders between welding and hole-piercing were used to evaluate the effect of the fabrication order on formability.
Both...
Cost and time for die tryouts are significant within the car industry. A major contributing factor is that elastic deflections of 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 presses. However, almost all stamping dies and presses are...
The accurate calibration of constitutive models is critical for the virtual design of stamping of lightweight automotive components using finite-element modelling. Anisotropic plasticity models are commonly calibrated using uniaxial and biaxial tension test data under the assumption of plastic incompressibility and an associated flow rule. However, the deviatoric stress states under which...
The material flow stress is one of the important input data for accurate numerical modeling of sheet metal forming. The standard uniaxial tensile test is widely accepted to characterize the flow stress of sheet metals. However, the range of strain obtained from the tensile test is usually limited to define the material plastic behavior for sheet metal forming. Therefore, the biaxial bulge test...
An Overview of press hardening applications and an attempt to look into the crystal ball. How does press hardening meet the challenges of our time?
Manufacturing Engineering Casting & Stamping within Volvo Cars is continuously evaluating, developing, and implementing new technology.
This presentation gives an overview of recent research and implementations in the area of simulations and virtual tryout of industrial dies.
Volvo Cars has also started the journey towards Smart Manufacturing & Digital Twins, an area with great potential and...
The joints between different lightweight materials play a significant role in multi-material design of structural components for automotive industry, aiming to reduce the vehicle’s weight without compromising performance or safety. Yet, conventional mechanical joining technologies between metals and Carbon Fibre Reinforced Polymers (CFRP) either create the need of drilling a hole in the...
The third generation of AHSSs (3rd Gen-AHSS) offers a good combination of strength and ductility due to the different micro-constituents inherited in the base material microstructure. However, the as-received material needs to be formed at high temperatures to form different parts in the body-in-white structure (BIW). Forming at high temperatures is crucial to reduce the press tonnage...
Thanks to their good mechanical properties and low structural weight, multi-material structures are a promising approach in the automotive industry to lightweight design, body construction and functionalization. Especially metal and plastic are mainly combined to achieve improved properties of the final component compared to mono-material structures.
This paper describes the development of a...
In a deep drawing process, the friction at the sheet metal-die contact interface affects the material flow in the flange as well as in die entry radius region, affecting product quality significantly. The accuracy of predicted drawing force and thinning in deep drawing simulation strongly depends on friction modelling. The Coulomb’s friction model with a constant coefficient of friction is...
Tantalum RO5200 (TaRO5200) is an excellent and new emerging Bio-material with
wide applications. The most important property of TaRO5200 is Osseointegration which helps in integration of direct structural and functional connection between living bone and the surface. The process of forming in at actual is a plastic deformation where in the material is transforming in permanently is some shape...
The use of Advanced High Strength Steel (AHSS) allows for lightweighting of sheet steel components, with maintained structural integrity of the part. This has enabled a wide-spread use of the materials and an ever increasing development of new, even stronger AHSS grades. However, with increased strength comes limited formability. Thus, the use of conventional cold forming processes is not...
Metallic additive manufacturing processes have experienced significant growth in the past decade, with surface cladding being an important application, especially within the context of tools used in the forming and die industries. One of the possible objectives in surface claddings is the improvement of a component’s hardness and wear resistance, with metal matrix composites (MMCs) allowing a...
Abstract: Uncoupled ductile fracture models have gained popularity for accurate prediction of fracture in ductile metallic sheets due to their ease of implementation. Accurate description of anisotropic fracture behavior is an active research field for sheet metal forming. In the present study, three isotropic ductile fracture models, i.e., modified Mohr-Coulomb, Hosford-Coulomb and DF2016...
The edges and corners in the cavity of the forming and cutting tools are the most worn parts of the tools. These areas are the potential to be made and repaired by Additive Manufacturing mainly by DED (Directed Energy Deposition) using materials with superior thermo-mechanical properties in contrast to ordinary materials used for tool bodies. The normal ordinary material which is cheap will be...
Incremental sheet forming (ISF) is an innovative sheet metal forming technique. A small, incremental deformation forms a sheet into the final workpiece. The sustainable and futuristic approach is necessary to depute this technology in real world. Improved formability, minimal set-up cost, and flexibility are some of the major advantages of the ISF process. However, the key challenges are...
A medium Mn steel was fabricated by employing a vacuum induction furnace. After that, the steel was hot rolled in order to achieve a final thickness of 1.5 mm. The resultant microstructure of the sheet was composed of martensite and very little amount of austenite, the ultimate tensile strength in this condition was close to 1600 MPa with a negligible elongation. An intercritical annealing was...
Edge crack sensitivity is one of the critical features of multiphase steels which could limit the application fields of these promising materials which in general offer a significant lightweight engineering potential. Therefore, steel producers have got a vital interest in understanding how the microstructure influences on the edge crack sensitivity. With modern scale-bridging simulation...
The range of blank-holding force (BHF) for which successfully forming of AA1100 in three different tempers is investigated using a combination of experiments and analysis. The experiments involve circular blanks of three different diameters: 35 mm, 37 mm and 40 mm. The thickness of the blanks is 0.51 mm. These are drawn with a punch of 20 mm diameter, i.e., at drawing ratios of 1.75, 1.85 and...
In this study, a new test method using protruding punch was proposed, that can separate bending and stretch deformations. In this test, the blank contact with the top and shoulder of punch, and the bending angle can be constant. After the bending angle becomes constant, stretch deformation can be applied while the bending deformation remains constant. In addition, this test method can control...
Keywords: Formability · Non-linear strain path · Aluminum · Anisotropy· Contact Pressure
Characterization of the in-plane forming limits remains a central aspect of alloy development and is critical for the virtual design of forming operations. Nakazima formability tests represent the most commonly used test method but have so-called process effects of out-of-plane bending, contact pressure...
In this work, we present and evaluate a new approach for prototype tooling in deep drawing based on direct polymer additive tooling. With Fused Deposition Modeling (FDM) a PLA shell is printed additively. Afterwards, these are filled with ultra-high performance concrete (UHPC). UHPC is characterized by its higher strength properties compared to conventional concrete materials, which makes the...
Dual-phase steels (DP steels) consist of ferrite and hard martensitic phase. As they combine high strength and good formability at low production costs, they are widely used for automotive applications. Compared with the DP steels with lower strength, the DP1180 steel is more special for the volume fraction of martensite is higher than that of ferrite. In this paper, the evolving plastic...
In recent decades deep drawing of 5xxx and 6xxx aluminum alloy sheets has increasingly been applied for producing lightweight car body components. Because of frictional heat the surface temperature of the drawing tools may notably increase during series production of these components, even though the deep drawing process is basically performed at room temperature. This work investigates the...
The objective of this study is to design patchwork blank manufactured by friction stir spot welding(FSSW) using crystal plasticity finite element method (CPFEM). During FSSW, frictional heat and plastic flow cause local changes in microstructure and mechanical properties between joints. Therefore, patchwork blanks are manufactured by predicting the strengthening contribution of local...
Stamping simulation are accurately representing the reality today. Various quality requirements like splits, wrinkles but also springback and surface appearance are predicted. In orderto effectively execute the tryout process the process setup of the simulation has to be reproduced. However, the try-out process can be accelerated if specific information out of the simulation has been...
Anisotropy plays a significant role in engineering, especially in the field of sheet metal forming. This particular characteristic stems mainly from the crystallographic structure of the metals and the influence of the rolling process, inducing preferred orientations of the grains. In this context, the crystal plasticity theory plays an important role as it accounts for the anisotropic nature...
Fracture characterization of automotive metals under simple shear deformation is critical for the calibration of advanced fracture models employed in forming and crash simulations. Great strides in shear fracture characterization have been made over the past decade with several novel geometries proposed. However, in-plane shear tests of high ductility materials have proved challenging since...
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...
ABSTRACT
The calibration of material data to properly describe the stress response of a specific material under various loading conditions in finite element analysis (FEA) is still a challenging task. Not only that new steel grades or aluminum alloys are investigated by the material manufacturers to enhance certain characteristics of their product such as stiffness, strength, or maximum...
The use of press-hardening steels (PHSs) in automotive bodies creates the opportunity of producing thinner but higher-strength components. PHS1800, a grade of PHSs with a strength level of around 1.8 GPa after hot stamping, is a candidate material for vehicle anti-intrusion structures. The current study aims to investigate the formability of this steel during the hot-stamping process. A novel...
Proportions of high- and ultra-high strength steels are constantly increasing in modern car bodies. In the press shop there are uncertainties concerning the application of steels with strength higher than 1000MPa particularly concerning shear cutting processes. To support the steel user regarding a tool material and coating and the wear behavior, long-term shear cutting test had been carried...
Sheet metal forming (SMF) simulations are traditionally carried out with rigid active forming surfaces. This means that the elasticity and dynamics of presses and die structures are ignored. The only geometries of the tools included in the simulations are the active forming surfaces. One reason for this simplification is the large amount of computational power that is required to solve finite...
Forming limit experiments such as the Nakazima and Marciniak tests are important for the development of accurate sheet metal necking models. However, the testing procedure is time consuming. As a consequence, few experimental campaigns combine different material orientations and pre-straining experiments. We present an automated device for high-throughput FLC testing. Stereo digital image...
In this work, Vanadis 6 cold work tool steel was vacuum austenitized, room temperature quenched, differently cryogenically treated (-75, -140 and -196 °C for different durations) and double tempered, in the range 170 – 530 °C. Two kinds of wear performance assessment were used: pin-on-disc and reciprocating sliding wear tests, by using a ball-on-flat contact configuration. Pin-on-disc testing...
Quenched and Partitioned (Q&P) steels are designed to be high strength, while maintaining good formability for weight and cost savings in vehicle design. These steels are alloyed with C and Mn, for austenite stabilization, and Si for carbide suppression. It has been well established that Mn banding will occur during solidification of steels, as Mn has low solubility in δ-ferrite and will be...
Deep drawing processes are greatly influenced by the blank holder forces, as well as their local distribution. In current deep drawing tools, this pressure distribution is dominated by the compliance of the specific machine the tool is mounted on. Therefore, each tool must be manually polished to enable the desired distribution of the blank holder pressure. This regularly causes problems when...
Sheet metal forming (SMF) simulations are traditionally carried out with rigid tool surfaces. This research aims to enable simulations with elastic dies for industrial-sized stamping dies. This is important for die try-out, digital twins, production control, and other topics in the current frontier of SMF research. No method in the literature is fully developed for simulations with industrial...
This paper proposes an approach for muti-defects reduction using a segmented blank holder force (S-BHF) distribution that the blank holder force (BHF) with a segmented distribution. In particular, a strategy based on finite element method, deep neural network and response surface method (FEM-DNN-RSM) techniques is constructed and optimized is used to determine the optimal S-BHF distribution...
The deployment of Press Hardened Steels (PHSs) in the Body-In-White structures that took place during the two last decades is at the origin of a breakthrough weight saving on vehicles while guaranteeing the safety requirements of the automotive industry. The production of parts with complex shapes and a high strength between 1500-2000MPa was made possible by taking advantage of the hot...
ABSTRACT
In finite element analysis (FEA), improving the accuracy of the prediction capability of material cards to obtain the correct stress response of a specific material is still a major challenge in the field of forming technology. Furthermore, new aluminium alloys or steel grades are steadily released by the material manufacturers, differing in their attributes such as stiffness,...
Recent developments aimed at reducing cumulative CO2 emissions in the energy sector and e-mobility are leading to an increase in the production volumes of formed components made from thin metallic foils used for alternative energy supply concepts. Thus, components such as bipolar plates in fuel cells and a variety of parts in e-motors and batteries are being manufactured in ever higher...
To improve the accuracy of forming simulations advanced friction models are increasingly used in industry. These models account for the physical properties of the sheet, tool and lubrication and describe the tribological conditions during the forming operation. One of the main influencing factors on the tribology system, and therefore the friction coefficient, is the surface roughness of the...
Hot stamping is a commonly used procedure to manufacture components from high strength steels, which are used for parts of car bodies. Against the background of production efficiency and costs, there is a number of factors which determine the performance of tools used in hot stamping, e.g. cycle time in production and lifetime of the tools. Main requirement is a high wear resistance, while...
The Yoshida-Uemori model is a combined hardening model coupled with the elastic evolution modulus which depends on the equivalent plastic strain. This model is implemented in the most used FEA stamping codes with occasionally some variations in the form of material cards. The material cards are requested regularly by the car manufacturers, in order to get a more accurate prediction of...
Knowledge of the interfacial heat transfer coefficient (HTC) between a blank and water-cooled tool is critical in the design of automotive parts made of press hardenable steels [1]. A physics-based model was developed to predict and explain the transient behavior of the HTC in the hot stamping of Al-Si coated 22MnB5 steel. The surface of the austenitized blank was modelled from its measured...
High requirements on the CO² emission of cars, lead to the production of new filter systems with complex geometries. In this paper, the effect of manufacturing oval tubular components instead of circular components for the exhaust system is investigated numerically and experimentally. For this purpose, the manufacturing process is divided into the forming process and the stuffing process. In...
Manufacturing problems resulting from lubricant supplier changes are relatively common in automotive press shops. Computer-aided processes and tool design detect a significant proportion of manufacturing noises before tools are physically produced. In modern forming codes, an enhanced Coulomb model is used to numerically model the friction phenomena associated with lubrication. In laboratory...
Dimensional deviations of stamped car body components caused by elastic springback still represent a significant problem for the development of the stamping tools. First, the springback causes deviations of the part in vertical direction to the part surface. Second, the surface area of the part is being changed by elastic membrane stresses resulting in a contraction of the surface but,...
Virtual experiments based on crystal plasticity simulations are a common approach to predict the texture-induced plastic anisotropy of polycrystalline sheet metals. Such simulation approaches utilise a crystal plasticity constitutive model that describes the deformation behaviour of single crystals on the base of crystallographic slip. However, there are different mathematical formulations of...
The energy transition towards sustainable mobility requires developing alternative propulsion methods to combustion engines. One of these alternatives is hydrogen-powered fuel cells. A key component that guarantees the energy performance and durability of Proton-Exchange Membrane (PEM) hydrogen fuel cells are the bipolar plates.
For transportation applications, bipolar plates are required to...
Demands for lightweightening 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...
Special AI applications are gaining more and more importance as replacements for material models in metal forming and are used in manyareas of digital twins, such as soft sensors or predictive tools. The main advantage of AI models in this field is found by the capability of code of programming itself based on the simulated or experimental data provided, without the need for explicit...
The modeling of material behavior for both plasticity and fracture requires the development of increasingly accurate tests. On the one hand, the development of DIC allows to revisit tests such as the bulge test or the in-plane torsion. On the other hand, recent results show the enormous value of using robotics to perform mechanical tests. The benefits are an unmatched combination of speed,...
Formability analysis of sheet metals is not a new process; even the significance of analysing formability of sheets is an important factor for the industrial applications. Sheet metals are sharing majority of application in various industries, in specific aerospace and automotive industries. For the last 30 years, researchers performed their works on the sheet metal and their forming...
In times of scarce raw materials, the concept of alternative lubricants occupies a special role. In this context, water-based lubricants offer many advantages over mineral oil-based lubricants in terms of disposal, handling and savings. However, water alone is not suitable for lubrication in industrial environments due to its physical and biological limitations, so additives must be added. For...
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...
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...
Formability under hot stamping process depends on various process parameters and tribological conditions. Friction is one of the critical parameter for better understanding of formability at elevated temperatures. It was found that with increase in the temperature friction coefficient increases, however in some literature it is reported that with increase in temperature friction coefficient...
Keywords: Digital Transformation, Real Time, IIoT, Digital Sensor, Industry 4.0
ABSTRACT
In recent years, one of the main challenges in industry has been obtaining work parameters in real time for later analysis to understand the process better. The purpose is to obtain substantial information about the process for better decision-making, i.e., what happens during manufacturing to...
In this paper, the AUTOFORM stamping simulation software is used to analyze the formability and springback of A pillar part, and the influence of part features on springback and its robustness was studied. The results show that when stamped with the third generation advanced high strength steel QP1180, the maximum local thinning rate of the part is 0.157 without cracking risk. And the maximum...
Production tolerances and specifications are increasingly being tightened by OEMs and final user in the metal stamping sector. For this reasons, intelligent controllers that can modify the process to obtain a stable production considering the most influencing process fluctuations are more and more demanded. The generation of metamodels using numerical simulation and their use in modern...
In order to save resources in component production, the use of finite element (FE) simulations is state of the art during the design of the process. Thus, expensive tool modifications can be prevented and laborious experimental tests can be reduced. For a high accuracy of a FE simulation, realistic material data is required to model the material behaviour. Unlike the flow behaviour, the...
Lightweight materials and lightweight technologies gained significant attention from all EV vehicle manufacturers. Aluminium has been commonly used as a lightweight replacement for steel in the automotive industry for many years. High-strength aluminium alloys have high specific strength, and their formability increases significantly at elevated temperatures. New manufacturing technologies...
High-strength steels are widely used in the body in white of vehicles offering a good balance between crashworthiness and lightweight design. The increased requirements of heavier electric vehicles in terms of fatigue resistance and crashworthiness highlighted that chassis parts have remarkable lightweighting potential. However, applying these grades in chassis parts is not straightforward, as...
Appearance of an automobile is one of the appealing points to customers. Character lines in outer panels such as hood and door panels play an important role to make automobiles attractive, and a sharp character line which has a ridge of small curvature radius is much more preferred to a blunt character line. However, a skid line, a kind of appearance defect, is apt to generate along the...
Sheet metal is an extremely common form of use in broad engineering sectors and represents the main consumption of steel and aluminum in Europe. All production processes where sheet metal is used require cutting operations. Therefore, it is an extremely relevant procedure, common and of great economic importance in material-intensive sectors such as automotive, construction and engineering....
Punching represents one of the most frequently used manufacturing processes in the sheet metal processing industry. Thereby, one of the most important quality criteria for such punching processes constitutes the geometric shape of the cutting surface. High cutting surface qualities are usually characterized by the lowest possible edge draw in, a high clean cut, as well as a small fracture...
In this research, coefficients of anisotropy yield function Yld2004-18p were determined with a displacement field of a limiting dome height (LDH) test using a deep neural network (DNN) model. Finite element analyses of the LDH test were conducted with different sets of yield function coefficients, and the r-direction displacement fields in a cylindrical coordinate system were extracted to...
Paint appearance is an important requirement for outer automobile panels. Since the last decade automotive manufactures start reducing paint thickness for environment issues. As a result, the surface roughening of steel substrate due to stamping becomes a critical factor for paint appearance. Although many research work has been conducted on surface roughening, limited research has been...
Stress measurement errors in the tension-shear tests using a cruciform specimen are evaluated. The tension-shear test method was proposed by Minki et al (2022). A servo-controlled biaxial tensile testing apparatus is used as the testing machine. The gauge area (GA) of the tension-shear specimen receives normal stress, σxx, and shear stress, σxy; however, the stress distribution in the GA is...
Accurate prediction of fractures that occur in a material during forming not only improves quality, but also reduces the amount of material that is discarded. Formability evaluation is generally performed using ductile fracture criteria or experimental forming limit diagrams (FLDs), but these require fracture tests to be conducted beforehand. The authors have established a formability...
The deep drawing of paperboard has shown beneficial results in the packaging industry for different goods. High productivity, economical process routes and geometrical freedom are the three most important process benefits. Paper as a material combines compostability and recyclability while being manufactured from renewable resources. However, formed paper shows wrinkling due to the material...
In the conflict between lightweight design and crash safety of high-strength steel components failure models for crash simulation have to be calibrated precisely. Especially the negative strain rate effect concerning the shear failure strain of high-strength steel sheets as well as the fact that ductile shear failure occurs immediately and without previous necking are safety-critical aspects....
Process monitoring in forming technology can serve as a basis for transparent manufacturing and closed-loop control systems. Particularly, sensor systems associated with tool clamping interfaces offer great potential for robust inline process monitoring. However, the direct evaluation of only one sensor or even pure sensor data is hardly sufficient or not possible due to complex...
Springback analysis of an industry-type “shotgun” part had been accomplished for benchmarking aluminum stampings. The previous analysis demonstrated that for aluminum stampings, an accurate springback prediction can be obtained using Yoshida-Uemori model (Y-U model) considering material kinematic hardening behavior. However, that study was conducted using the Hill-48 and Barlat-89 yield...
Thanks to their very important strength in addition to their considerable formability and ductility, the newly developed Advanced High-Strength Steel (AHSS) allow carmakers to save mass on the vehicles they produce. However, before industrial implementation by OEMs, any grade has to be approved. The bending test defined in VDA238-100 standard is a key indicator of the material ductility and is...
High-strength aluminum alloys have drawn a lot of attention because of the expanding demand for lightweight vehicle design in the automotive sector. Due to poor formability at room temperature warm and hot forming have been advised. However, warm and hot forming methods need more steps in the production process and an advanced tooling system. In contrast, since ordinary tools can be used,...
The requirements of high reliability, long life and lightweight in aerospace field have been greatly improved. It is urgent to replace the tailor-welded structure with integral one. Aviation aluminum alloy with light weight and high strength has been applied to a class of thin-walled curved parts with integral structure. However, compared with the conventional aluminum alloy, high strength...
Both advanced high strength steels and aluminum alloys gained increasing popularity because of the constant effort to meet the social pressure of reducing the vehicle weight while keeping their safety. The ratio between material strength and weight is much higher when compared to other materials, while the ductility is similar. Thus, the high springback after forming is one of the...
The present study is concerned with the prediction of deformation in incremental sheet forming (ISF) for a Ti6Al4V sheet. To investigate anisotropic and asymmetric behaviors, uniaxial tension and compression tests were conducted along the rolling direction (RD), diagonal direction (DD), and transverse direction (TD). A representative yield function for a HCP material, the...
As automakers are challenged to improve safety and weight reduction, they continue to search for new solutions to meet the higher performance demands of body structures. The combination of the Laser Welded Blanks (LWB) technology with 3rd generation of Advanced High-Strength Steels (AHSS) for cold stamping is responding to that challenge. The new Fortiform® (3rd generation of AHSS) based LWB...
The distortional hardening model has been widely used to describe the nonlinear behavior such as Bauschinger effect, permanent softening, and nonlinear transient behavior. Unlike the kinematic hardening model, the distortional hardening model mainly adopted the rotation and contraction of the yield surface under plastic deformation and showed the higher accuracy than the kinematic hardening...
Stretch-flangeability investigations have been performed by means of ISO16630 conical hole expansion tests for some automotive cold rolled AHSS advanced high strength steels with different cutting clearances (5-7%, 12%, 20% and 26-27%).
The HV0.025 Vickers micro-hardness (25g load) increases between bulk material and cut edge vicinity. This bulk to edge hardness hardening decreases with...
A developable surface is one that can be flattened into a plane without distortion. Thin sheet metal is often treated as a developable surface. The classical theory of folded developables proves that curved crease, origami-style folding can be applied to thin sheet metal of high strength to manufacture parts with rather complex geometries. However, its applications are found to be limited to...
