bluuebunny/crossref_metadata_2025_split huggingface dataset:
Numerical analysis of the load paths and the resulting damage evolution during deep drawing of dual-phase steel
Authors: Müller Martina , Herrig Tim , Bergs Thomas 
Published: June 2023

Abstract
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 and evolution offers a lever to increase the performance of components. The final damage state in the component has been shown to be dependent on the prevailing load path by means of the stress and strain states along the process route. The investigation of the stress and strain states requires numerical modelling. From the models, the load path can then be extracted and a correlation can be obtained with the damage that results. The present work investigates the load paths during deep drawing of u-shaped profiles as a function of process set-up and process parameters of dual-phase steel DP800. The resulting load paths are extracted, analyzed and correlated with the numerically predicted damage.
Part quality improvement in flexible roll forming of a combined variable width and depth component
Authors: Abeyrathna B , Rolfe B , Taube R , Oxley B , Weiss M 
Published: June 2023

Abstract
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 automotive part (Sled runner) is produced from 3 high strength steels; the complex component combines shape variations in width and depth. The optimum forming sequence is identified to produce the part without any flange wrinkles. In addition to this, a new over forming technique is introduced to overcome end flare and springback. The experimental results are evaluated and discussed with numerical analysis and suggest that the presented forming technology enables the manufacture of high strength components in accordance with automotive specifications and quality standards.
On-line quality control and tool wear evaluation in trimming process by data analytics techniques
Authors: Garcia-Llamas E. , Castro J. M. Gonzalez , Ramirez G. , Pujante J. 
Published: June 2023

Abstract
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. In a competitive environment where the demand for quality increases continuously and using harder to process high-performance materials, online monitoring and quality control become an attractive prospective. In this regard, application of data analytics techniques offers a promising toolset for fast and efficient analysis. This work presents a pilot demonstration of an instrumented sheet metal cutting line that integrates online quality control and predictive maintenance concepts, namely detection of wear in tools as well as problems arising from the raw material and process. Automated sequential cutting was performed using a straight trimming die mounted on a hydraulic press to cut High-Mn TWIP steel strip. Three piezoelectric force sensors were located in the trimming tool, collecting cycle data. Tests performed included studying the effect of blunting on the M2 (1.3343) tool, as well as the influence of correct lubrication. The resulting data were analyzed through the extraction of several parameters from each cycle to correlate die wear-induced force response evolutions with the shear-induced deformation in High-Mn TWIP steel sheets. Extracted parameters were the maximum and minimum force of each cycle and the impulse (integrated force over time) was computed and segmented by plastic deformation and crack contributions. Our analysis show that advanced algorithms can be used to analyze sensor data on an automated installation, revealing OK/NOK conditions and anomalous events.
Application of a neural network for predicting cutting surface quality of punching processes based on tooling parameters
Authors: Schenek A , Görz M , Riedmüller K R , Liewald M 
Published: June 2023

Abstract
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 surface and a low burr height. In this respect, conventional punching processes can only produce clean cut proportions (CCP) up to 20-50% of the sheet thickness. By means of the so called “concave punch nose design” developed at the Institute for Metal Forming Technology, the geometry of conventional punches could be optimized in such a way that the clean-cut proportion along the cutting surface is significantly increased. The findings reported about in this paper show that the quality parameters of the sheared component edges thereby show highly nonlinear relationships to the tooling and sheet metal material parameters used. In order to quantify these effects, the data from several numerical punching simulations is used to pretrain an artificial neural network (ANN). Input data for the neural network included features of the punch geometry, the size of the clearance, the sheet thickness and the material data of the semi-finished product. The output of the neural network is precise predictions of the achievable cutting surface quality parameters. The experimentally validated findings presented in this paper show that the process design for novel punching processes such as cutting with concave punch nose design is possible, when using a modern machine learning approach.
Formability evaluation based on a constitutive model with stress rate direction dependency considering bifurcation modes
Authors: Oya T , Ito K , Uemura G , Mori N 
Published: June 2023

Abstract
Accurately predicting the fractures that occur in materials during forming not only improves quality, but also reduces the amount of material that is discarded. Therefore, as a key technology for digital transformation to achieve carbon neutrality, it is necessary to improve the accuracy of forming analysis and establish an efficient method for predicting forming limits. Formability assessment is typically performed using ductile fracture criteria or experimental forming limit diagrams (FLDs), which require prior fracture testing. The authors have established a forming evaluation method based on three-dimensional local bifurcation theory as a versatile method that does not require destructive testing. This method can follow abrupt changes in the stress field, such as localized necking, by using a flow rule that takes into account the directionality of the stress rate. In this study, the proposed method is applied to the tensile testing and the forming analysis of a square cup drawing to analytically verify the location and onset time of local bifurcation modes that may lead to fracture.
Local and global forming potential of present dual-phase steel developments
Authors: Beier Thorsten , Woestmann Stefan , Sikora Sascha 
Published: June 2023

Abstract
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 are reached and compromises had to be made in part design. By integrating application-oriented problems into the material development, these limits are expanded with respect to the given requirements. Within the present study, for several dual-phase steels with a tensile strength ≥800 MPa, practical laboratory tests are presented and their benefits in press shop application. In particular influencing factors on stretch flange formability are presented and discussed for example cutting parameters, anisotropy, time between cutting and forming or the orthogonal strain gradient.
An evaluation method for experimental necking detection of automotive sheet metals
Authors: Pham Quoc Tuan , Islam Md Shafiqul , Barlo Alexander , Sigvant Mats 
Published: June 2023

Abstract
In sheet metal stamping, the occurrence of strain localization in a deformed sheet is considered a failure. As so, sheet metal’s formability is conventionally evaluated using the Forming Limit Diagram (FLD), which separates the principal strain space into safety and unsafety regions by a Forming Limit Curve (FLC). This study presents an evaluation method for detecting strain localization based on Digital Image Correlation (DIC) during the experiment. The commercial DIC software ARAMIS is adopted to monitor the strain-field distribution on the deformed specimen’s surface. A detailed analysis of the proposed method is presented considering Nakajima tests conducted for two automotive sheet metals: AA6016 and DP800. The identified FLC based on the proposed method is compared with that of well-established methods such as ISO 12004:2-2008 and time-dependent methods. For both investigated materials, the proposed method presents a lower FLC than the others.
Edge fracture of the first and third-generation high-strength steels: DP1000 and QP1000
Authors: Li Z , Chang Y , Rong J , Min J , Lian J 
Published: June 2023

AbstractAdvanced high-strength steels (AHSS) have shown profound progress in improving tensile ductility or global formality in the last decades over three generations. For a complete assessment of both the global and local formability, this study aims to characterize and compare the tensile and edge fracture behavior of the first and third-generation AHSS (dual-phase steel and quenching & partitioning steel) with the same nominal strength level of 980 MPa. Uniaxial tensile tests are performed to characterize the tensile properties. Hole expansion tests are conducted with two edge conditions based on separated preparation techniques (waterjet with polishing and punching) to investigate the edge fracture for both materials. The hole expansion ratios and edge fractures are compared between two materials and two edge conditions. It is concluded that the investigated QP1000 has promoted global formability while the DP1000 shows better local formability due to its damage-tolerant and crack-resistant responses.
Strain evolution during hole expansion testing of 800 MPa tensile strength hot-rolled steels
Authors: Plosila P , Kesti V , Kaijalainen A , Vierelä R , Rautio P , Kömi J 
Published: June 2023

Abstract
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 analysis of strain-state near the cut edge. In this paper, strain evolution during hole expansion testing was investigated for three 800 MPa tensile strength grade hot-rolled strip steels. The steels were selected to have differences in microstructures and anisotropies of mechanical properties. Two different hole expansion test methods with DIC strain measurement were utilized to investigate different edge loading scenarios: in-plane stretching with a flat-top punch and more out-of-plane stretching with a hemispherical punch. Test holes were prepared according to ISO 16630 standard. In order to examine strain evolution and localization during testing, strains were measured with circle-shape sections around the hole in various distances from the cut edge. Strain localization behavior was investigated in different sheet directions and the effect on the hole expansion ratio was evaluated. Results show considerable differences in the cut edge forming behavior between the investigated materials.
Accuracy of stretch flange formability prediction by considering strain gradient for actual car body parts
Authors: Iizuka E , Okada A 
Published: June 2023

Abstract
The effect of the strain gradient on the stretch flange deformation limit of steel sheets was investigated by hole expansion tests under various forming conditions and by FEM forming simulations. The hole expansion ratio was changed by changing the initial hole diameter and punch shapes. This study clarified the fact that deformation limit strain increases, as it does not depend on the initial hole diameter or punch shape, and thus the strain gradient increases. The deformation limit thickness strain of the stretch flange portion could be changed by changing the strain gradient. These results suggest that the formability of the stretch flange deformation area should be determined from not only the maximum principal strain but also the strain gradient. Then, the accuracy of stretch flange formability prediction by considering the strain gradient for actual car body parts in mass production was investigated. The maximum principal strain and the strain gradient of the parts were calculated by FEM or measured in the press part. These results suggest that the formability of the stretch flange deformation area for actual car body parts could not be predicted by not only the maximum principal strain or the thickness reduction, but also the conventional FLD. This investigation verified the accuracy of stretch flange formability prediction by considering the strain gradient for actual car body parts.
Forming of a cylindrical cup in 7075-T6 under warm temperature conditions
Authors: Royne S , Laurent H , Maillard A 
Published: June 2023

Abstract
The high mechanical properties of aluminum alloys are very interesting for reducing the weight of parts in the automotive sector. However, a formability issue prevents the use of these alloys at room temperature especially for complex shapes where part failure occurs before full drawing. The use of a warm forming process, which consists of heating the part between 150°C and 250°C for aluminium alloys, allows to increase formability and therefore to perform complex shapes. In this study, the forming of a cylindrical cup in 7075-T6 is carried out at 200° C in two steps by two successive reductions in the diameter of the blank. Numerical simulations of these two forming steps are performed with Abaqus. The influence of friction coefficient is analysed in these two forming steps by comparing the evolutions of punch force.
Determination of Edge Fracture Limit Strain for AHSS in the ISO-16630 Hole Expansion Test
Authors: Barlo A , Sigvant M , Kesti V , Islam M S , Pham Q T , Pilthammar J 
Published: June 2023

Abstract
With the increased demand for application of sustainable materials and lightweight structures, the sheet metal forming industry is forced to push existing materials to the limits. One area where this is particular difficult is when it comes to assessing the formability limit for sheet edges. 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 variations in the cutting conditions for the different test specimens. This study investigates the impact of shifting the evaluation point of the test from the through-thickness crack to the onset of surface failure on the reported scatter, as well as performs inverse modeling of the Hole Expansion Test to obtain an edge limit strain value.
The Investigations on Formability of Tantalum RO5200 Thin Foils: Bio-Material.
Authors: Kulkarni Omkar , Kakandikar Ganesh 
Published: June 2023

Abstract
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 without occurrence of any type of defect of failure. Few different types of failure enlisted are local necking, wrinkling, earing etc. In recent days transforming from macro level to micro level is now trending part of life. The most difficult part in moving towards micro level forming which means forming sheets under 100 microns thickness, is control over process. Hence this gives significance and rise for the investigations over forming at micro level and prediction of mechanical and formability properties at micro level. This research work posited in this paper focusses on the plotting of Forming limit curve (FLC) which is one of the methods to investigate formability of ultra-thin foil of TaRO5200 with sheet thickness 80 microns (μm). The experiments performed for FLC plotting were based on the Nakkajima test following the ASTM 2218-14 standards. The FLCs are plotted experimentally and via numerical simulation as well which in comparison shows a good agreement. The variance obtained between experimental and numerical simulation is up to 15%. Which in another words can be stated as numerical simulation is 15% safer in design than the experimental work. The novelty of the work lies in testing of the bio material and defining FLC by performing experiments via newly designed tool for the specific sheet thickness of 80 μm following the ASTM standards. Microstructural study is also performed on the specimen prior and after forming test to analyse and understand the physics along with mechanism of the material in test. The material behaviour is also explained in the microstructural study section.
Effect of the intercritical annealing in the formability and microstructure of a medium Mn steel sheet
Authors: Hernández-Rivera J L , González-Castillo A C , Ramos Azpeitia M O , Garay-Reyes C G 
Published: June 2023

Abstract
A medium Mn steel (MMS) was cast by employing a vacuum induction furnace. After that, the steel was hot rolled (HR) in order to achieve a final thickness of 1.4 mm. The microstructure of the sheet was found to be composed of martensite and a little amount of austenite, the Ultimate Tensile Strength (UTS in this processing condition was close to 1600 MPa and a negligible elongation was found. An intercritical annealing (IA) heat treatment was applied to the steel to promote the austenite reversion and increase its amount and stability. Previous thermodynamic simulations and experimental results were used to determine the temperature and time parameters of the IA. After the steel was subjected to this heat treatment, it exhibited an elongation close to 35% and an UTS close to 1100 MPa. Bendability testing was carried out in that condition in order to correlate it with the microstructural changes in the sheet. It was found that the critical bending angle was higher in the IA condition in comparison with the HR state.
Experiments and simulations of the drawing envelope of commercially pure aluminum
Authors: Carter Adrian J. , Chen Kelin , Korkolis Yannis P. 
Published: June 2023

Abstract
The range of blank-holding force (BHF) for which deep drawing of AA1100-H24 is successful is investigated using a combination of experiments and simulations. 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 2.0, respectively, using a custom, modular forming apparatus where the BHF can be controlled at will, between 0 and 2,400 N. The experiments are performed in an Instron 8872 servo-hydraulic frame that allows precise measurements of the punch force and displacement. The working envelopes are determined experimentally in the space of BHF and draw depth, which can be categorized into three regimes: wrinkling, safe and tearing. It is found that grey zones exist between the three regimes. These experiments are then simulated in Abaqus/Standard, using two types of elements: axisymmetric and shell. In the latter case, plastic anisotropy is introduced, using the Yld2000-2D anisotropic yield function. Wrinkling and tearing failure are triggered by inducing suitable geometric imperfections. It is shown that the models are able to reproduce the experiments well. This serves as a verification of the modelling framework, which can then be used for the simulations of more complex forming processes.
Experimental characterization and prediction of forming limit diagrams of PHS1800 during hot stamping
Authors: Samadian Pedram , He Ruijian , George Ryan , Butcher Clifford , Worswick Michael J 
Published: June 2023

Abstract
The use of press-hardening steels (PHSs) in automotive bodies creates the opportunity of producing thinner, higher-strength components. PHS1800, an Al-Si coated PHS grade with ultimate tensile strength of around 1.8 GPa after hot stamping, is a candidate material for vehicle anti-intrusion applications. The current study aims to investigate the formability of this steel during the hot-stamping process. A custom Marciniak punch test and in situ digital image correlation (DIC) techniques were used to determine the in-plane forming limits of this steel during quenching from an austenitic temperature. The carrier blank thickness and geometry were exploited to quench the surrounding material of the specimens while promoting localization in their central regions. Approximately linear strain paths ranging from uniaxial to biaxial stretching were obtained in the tests while avoiding friction and out-of-plane bending. The forming limit curves (FLCs) of the material under various hot-stamping conditions were then predicted using the Marciniak-Kuczyński (MK) model, taking into account the temperature and strain-rate histories. The predicted limit strains were in good accord with the measured data.
Strength enhancement and uniform strain distribution through cross route-constrained groove pressing
Authors: Kumar Sunil 
Published: June 2023

Abstract
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 square sample is rotated by 90° after performing every cycle of CGP. The strain path in the sheet during conventional CGP and cross-CGP significantly affects the homogenization of mechanical properties. Sheets of low carbon steel are processed through conventional-CGP and cross-CGP routes. The ability to sustain the maximum strain has been increased in the cross-CGP process due to uniform strain distribution. The tensile strength and hardness in the sheet processed through cross-CGP are higher than that of conventional CGP, especially at higher pass numbers. Tensile behavior and hardness in two different orientations (parallel and perpendicular to the groove direction) have been found to be almost the same in the cross-CGP processed sheet.