Browse Topic: Advanced high-strength steels

Items (307)

Material Characterization of Newly-Developed Advanced High Strength Steels for Prediction of Crash Performance

2025-01-8220

04/01/2025

New highly ductile advanced high strength steel (AHSS) grades with tensile strength greater than 980 MPa have been developed with the aim of achieving a combination of high strength and excellent formability. The new jetQTM-Family [1, 2] offers high local and global ductility, which is expected to contribute to the improvement of vehicle crash performance. For the reliable design and management of vehicle crash performance, material modeling, including work hardening behavior and material failure strain, plays an important role in numerical simulation. Especially, the accuracy of material failure prediction is important for the development of crash performance. In this study, the fracture behaviors of 980jetQTM, 1180jetQTM, and conventional Dual-Phase (DP) steels are investigated through simple tensile and V-bending fracture tests incorporating experimental-numerical hybrid ductile fracture analysis. Based on the experimental results, the ductile fracture parameters in the Hosford

Sato, Kentaro, Sakaidani, Tomohiro, Ohnishi, Yoichiro, Paton, Adrian, Roesen, Hartwig

Elevated Fracture Resistance of Q&P1180 Steel after Forming and Paint-Baking

2025-01-8221

04/01/2025

According to several precedent studies, most of the cold-forming advanced high-strength steel (AHSS) grades can obtain reinforced yield strength from the automotive forming and paint-baking treatments without losing their fracture resistance like some aluminum alloys. Concisely, the mechanism of such behavior can be mainly attributed to the ‘Cottrell Atmospheres,’ some thermally mobilized interstitial atoms that cluster around and impede mobile dislocations during only the yielding stage of the plastic deformation but cannot continue durably enough to affect the fracture. Nevertheless, an exception, Q&P1180, was discovered from precedent studies and characterized in this work. Different from other AHSSs, this grade exhibited distinctively elevated fracture resistance and yield strength after the pre-straining and baking. Such uniqueness was speculated to be caused by 1) no soft ferrite in the microstructure and 2) the transformed fresh martensite induced by the plastic deformation

Hu, Jun, Sun, Yeting, Thomas, Grant

Understanding Forming Characteristics of Different Microstructure Steels within 980MPa and 1180MPa

2025-01-8222

04/01/2025

For electrical vehicle (EV) automotive body-in-white (BIW) structures, protection of passengers and battery in crash event becomes equally important. In addition to energy absorption, intrusion protection for battery and vehicle becomes extremely important and GPa advanced high strength steels (AHSS) including press hardened steels (PHS), DP/MP/CP/GEN3 steels have become material of choice for design for those components. Higher yield strength materials especially in 980/1180MPa MP and CP category are chosen for part design over conventional low yield strength DP. In this study, the forming characteristics including both global and local formability are evaluated and compared among 980 DP/MP grades. Formability test such as forming limit curve (FLC), true fracture strain, V bend, half dome, and hole expansion tests are conducted. Microstructure analysis to understand the effect of different grain structure and phases of DP/MP grades is also accomplished. A T-shape laboratory die trials

Shih, Hua-Chu, Pednekar, Vasant, Shi, Ming, Singh, Jatinder, Tedesco, Sarah, Wu, Wei

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99-07-01-0TOC

02/17/2025

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Tobolski, Sue

Laser Welding Applied to Complex Phase Steel

2024-36-0159

12/20/2024

The development of advanced high-strength steels has become essential in the production of lightweight, safe, and more economical vehicles within the context of the automotive industry. Among the advanced high-strength steels, complex phase steels stand out, characterized by their high formability and high energy absorption and deformation capacity. Laser welding is a technique that applies laser using high energy density as a heat source. It has the advantages that the high welding speed and low heat input compared to other welding methods cause a decrease in deformation, and the narrow width of the weld bead and heat-affected zone allows for the welding of complex parts that would be difficult for other welding methods. Based on a study of a complex phase steel, an analysis was made of the microstructures observed by optical microscopy, the grain boundaries and certain phases contained in this microstructure, as well as the microstructures of each area in the laser welding region

Dias, Erica Ximenes, Reis de Faria Neto, Antonio, Castro, Thais Santos, Martins, Marcelo Sampaio, Santos Pereira, Marcelo

Performance Optimization of Ti-Steel Laser-Welded Joints Based on Optimized Support Vector Machine and Multi-Objective Salp Swarm Algorithm

05-18-02-0010

11/07/2024

The dissimilar welding of titanium to steel enables the integration of the advantageous properties of both metals, facilitating the design of lightweight, corrosion-resistant, and high-strength multifunctional composite structures. However, significant differences in their thermophysical properties pose substantial technical challenges in practical welding scenarios, necessitating careful selection of process parameters to enhance the quality and performance of the weld joint. This article establishes a support vector machine (SVM) model with laser power, welding speed, and laser spot diameter as independent variables, and the maximum residual stress and minimum yield strength of the weld joint as dependent variables. To improve prediction accuracy, the SVM model is optimized using the beluga whale optimization (BWO) algorithm. Taking the established model as the objective function, the multi-objective salp swarm algorithm (MSSA) is employed to optimize the laser welding process

Zhu, Yubin, Meng, Xiangli, Zhang, Xinran

Comparison of Bake Hardening Effects on AHSSs and Extruded Aluminum Alloys Applied in BEV Reinforcement Structures

2024-01-2240

04/09/2024

At the dawn of battery electric vehicles (BEVs), protection of automotive battery systems as well as passengers, especially from severe side impact, has become one of the latest and most challenging topics in the BEV crashworthiness designs. Accordingly, two material-selection concepts are being justified by the automotive industry: either heavy-gauge extruded aluminum alloys or light-gauge advanced high-strength steels (AHSSs) shall be the optimal materials to fabricate the reinforcement structures to satisfy both the safety and lightweight requirements. In the meantime, such a justification also motivated an ongoing C-STARTM (Cliffs Steel Tube as Reinforcement) Protection project, in which a series of modularized steel tube assemblies, were demonstrated to be more cost-efficient, sustainable, design-flexible, and manufacturable than the equivalent extruded aluminum alloy beams as BEV reinforcement structures. Tangent to this comparative study, the present work shed some light on the

Hu, Jun, Sun, Yeting, Yu, Miao, Wang, Yu-Wei, Thomas, Grant

Effect of Local Ductility on Crash Performance of Automotive Structures Considering Press Forming Strain of Advanced High Strength Steels

2024-01-2241

04/09/2024

A fundamental study on the ductility of high strength steels in crash deformation is carried out to investigate the effect of the local ductility of various materials on automobile crashworthiness, considering the prestrain induced by press forming in the manufacturing process. In this study, a newly developed 980 MPa-grade steels [1], ‘jetQTM’, is investigated to clarify its advantage in term of crashworthiness in comparison with the conventional DP (Dual Phase) and TRIP steels. Quasi-static axial crushing tests are performed to evaluate the crashworthiness of the different types of steel. Based on the experimental results, the effect of the local ductility of high-strength steel on the risk of material fracture is discussed. In this paper, a new bending test method, orthogonally reverse bending, (ORB), is proposed to simulate the fracture that occurs during crash deformation considering press-forming strain. The test method is developed using a combination of the V-bending process

Sato, Kentaro, Sakaidani, Tomohiro, Komine, Shinsuke, Wang, Fangyi, Nakagaito, Tatsuya

Experimental Study on Bendability of Advanced High Strength Steels

2024-01-2860

04/09/2024

Fracturing in a tight radius during bending is one of the major manufacturing issues in forming Advanced High Strength Steels (AHSS). The study investigated the bendability of AHSS under two forming conditions: bending with and without stretched over the die radius. The bendability was evaluated by conducting modified Bending Under Tension (BUT) test for stretch bending and 90o v bend test for bending without stretch. The study also examined the effect of material properties on the limiting bend ratio. Various strength high strength steels, range from 420 MPa to 1700 MPa tensile strength, were selected in the study. Results indicated that critical radius-to-thickness ratios between the two tests are different but correlated in a relationship which was depicted in the bendability diagram. The map and constitutive relation curve derived from limiting bend ratios identified the multiple bendability (stretched and no-stretch) of each strength grade of test steel, which is recommended as

Shih, Hua-Chu

Springback Control through Post-stretching Using Different Hybrid Bead Designs with Tonnage Consideration

2024-01-2859

04/09/2024

Multiple hybrid bead designs were investigated in this study to control the springback on DP780 samples using post-stretching technique. The performance of the four different hybrid bead designs was evaluated by measuring the minimum blank-lock tonnage required to control the springback during a U-channel stamping process. A finite element (FE) model of the U-channel stamping process was developed to simulate the process and predict the minimum blank-lock tonnage required for springback control using each of the hybrid bead designs. It is shown that the developed FE model predicts both the required minimum blank-lock tonnage for post-stretching, and the springback profile, with good accuracy.

Nazari, Sobhan T., Zhu, Feng, Makrygiannis, John, Zhang, Jimmy, Wang, Yu-Wei

Categorization and Properties of Advanced High Strength Automotive Sheet Steels

J2745_202402 (Current)

02/23/2024

This SAE Recommended Practice defines various grades of continuously cast high-strength sheet steels and establishes mechanical property ranges. These sheet steels can be formed, welded, assembled and painted in automotive manufacturing processes. They can be specified as hot-rolled or cold-rolled sheet. Furthermore, they can be coated (hot-dipped galvanized, hot-dipped galvannealed, and electrogalvanized) or uncoated. Not all combinations of strength, dimensions and coatings may be commercially available; consult your steel supplier for details.

Metals Technical Committee

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99-06-01-0TOC

02/12/2024

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Tobolski, Sue

Effect of Spot Weld Parameter on HAZ of Advanced High Strength Steel Joint

2024-26-0187

01/16/2024

To meet different target of light-weighting, lower fuel economy, crash safety and emission requirement, advanced high strength steel (AHSS) is commonly used in automotive vehicles and has become popular now a days. AHSS material up-to 1500 MPa is commonly used for structural components and major reinforcement of automotive BIW. Manufacturing of AHSS material requires precise control of chemical composition, and subsequent rolling and heat treatment to get optimum combination of required phases In most of the AHSS material microstructure, martensite is present along with ferrite or other phases. Hot stamp steel with strength level 1500 MPa strength also have martensite phase in microstructure after press hardening. However during heating and cooling cycle in resistance spot welding, martensite phase tempering affects hardness at Heat Affected Zone (HAZ). Softness at HAZ lower downs shear and tensile strength of joint which impacts fatigue properties of the joint and energy absorption

Jain, Vikas, Misal, Swapnali, Paliwal, Lokesh

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99-05-06-0TOC

12/18/2023

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Tobolski, Sue

Influence of High-Strength, Low-Alloy Steel on Fatigue Life at a Non-Load-Bearing Transverse Welded Attachment

05-17-01-0002

11/17/2023

This study investigated the influence of high-strength low-alloy steel on the fatigue life of a load-bearing member with a non-load-bearing transverse welded attachment (T-joint). It compared high cycle fatigue data to two fatigue design codes, namely BS 7608 and Eurocode EN 1993-1-9. Different base and filler material combinations of varying material strengths were investigated, resulting in a total of three different specimen configurations. Two material combinations had a high-strength steel (Strenx® 700 MC D) for the base material, with one combination having a matched filler material and the other having an undermatched filler material. The third material combination had a lower-strength steel (S 355 JR AR) for the base material, with a matched filler material. Tensile tests were performed to confirm the base material mechanical properties and weld quality of the manufactured specimens. The investigation showed that there was no significant benefit to using high-strength steel as

Ramsay, Gareth Allan, Venter, Gerhard, Bredell, Johann

Constructing bus structures with stainless steel

23TOFHP08_03

08/01/2023

Outokumpu and collaborators show a possible weight reduction of up to 35% by using high-strength stainless steel in place of carbon steel. The weight of a typical bus could be reduced by up to 35% - more than 1,000 kg (2,205 lbs.) - by using high-strength stainless steel to replace tubular bus-frame elements traditionally manufactured in carbon steel. That is the conclusion of a first-of-its-kind project carried out by stainless-steel manufacturer Outokumpu, together with CAD/CAE solution specialist FCMS, the Munich University of Applied Sciences and RotherCONSULT. Corrosion-resistant stainless steel could offer sustainability combined with reduced maintenance time and costs. In addition, high-strength stainless steel grades have become commercially available that offer significant weight savings. The aim of this project was to examine what that could mean in terms of lower weight and reduced material costs.

Schuberth, Stefan, Rother, Klemens, Pohl, Werner

Computational Material Modelling for Damage Prediction of Advanced High Strength Steel

2023-28-1309

05/25/2023

FEA based simulations are extensively used in automotive industry for improving the product design and reducing the time taken for design and prototyping. FEA based simulations require material data as an input in form of material models. Most commonly used material models for simulation of metallic materials are elastic models and elasto-plastic models, which provide very good correlation till ultimate tensile strength (UTS). For simulation beyond UTS value, elasto-plastic material model has to be used along with material model considering the damage accumulation post UTS. For crash like event in automotive crash, required material models should consider the effect of various stress state conditions (Triaxiality) and strain rate sensitivity of materials along with damage accumulation. In LS Dyna solver, MAT_ADD_EROSION material model (GISSMO) along with MAT_024 is widely used for these applications. This paper will focus on development of GISSMO material model card for advanced high

Mulla, Suhail Mahanmad Hanif, Nemade, Sanket, Vhanaje, Manoj G, Nigade, Sachin Rajendra, Mahajan, Rahul, Santosh Jambhale, Medha

Lightweight Swivel Seat Frame Concepts Using Advanced Steel Grades

2023-01-5021

04/21/2023

The seat frame to be applied to future autonomous vehicles is expected to be rotatable considering various seating configurations. For the rotatable or swivel seat frame, it might be more difficult to secure passenger-related safety performances including seat belt anchorage (SBA) strength than a conventional seat frame because the conventional seat frame has two seat belt anchoring points on the body center pillar whereas those points of the swivel seat frame should be all located within the rotating structures in the seat frame. Since the swivel seat frame adds a structure for rotation, the mass of the swivel seat frame significantly increases compared to the nonrotatable seat frame, which may become an obstacle to reducing the mass of the vehicle. Currently, there are not many cases of mass production of rotating vehicle seats, and there are hardly any reports of mass reduction through advanced steel materials or corresponding numerical safety performance. In this study, the mass of

Kim, Jaehyun

Effect of Local Ductility of Advanced High Strength Steels in 980MPa and 1180MPa Grades on Crash Performance of Automotive Structures

2023-01-0081

04/11/2023

A fundamental study on the ductility of high strength steels under impact deformation is carried out to investigate the effect of the local ductility of various materials on crash performance. In this study, newly developed 980 and 1180 MPa grade steels are investigated to clarify their advantages in term of crash performance compared to conventional DP (Dual Phase) steels. The features of the developed steel, named as jetQ are higher yield strength and higher local ductility due to an optimized microstructure by the quenching and partitioning process (QP) [1, 2]. The bending test according to VDA 238-100 is performed while observing the fracture propagation during the bending test. Fracture strain in the tensile tests is evaluated by a three-dimensional shape measurement technique for the fracture surface. Both three-point bending tests and axial impact tests are performed to evaluate the crashworthiness of different types of steel. The three-point bending test simulates the

Sato, Kentaro, Sakaidani, Tomohiro, Toji, Yuki, Takajo, Shigehiro, Paton, Adrian, Manuela, Irnich, Thiessen, Richard

Characterization and Modeling of Anisotropic Fracture of Advanced High-Strength Steel Sheets

2023-01-0613

04/11/2023

As an engineering approach of balanced complexity and accuracy, the Generalized Incremental Stress-State dependent damage Model (GISSMO) in LS-DYNA® has now been widely adopted by the automotive industry to predict metallic materials’ fracture occurrences in both forming and crashworthiness simulations. Calibration of the nominal GISSMO is typically based on material characterization data along a certain representative material orientation. Nevertheless, many rolled or extruded metallic materials, such as advanced high-strength steel (AHSS) sheets, exhibit accentuated anisotropic fracture behavior, even though, notably, some of these materials show comparatively weak anisotropic plasticity in the meantime. Accordingly, in this work, the deformation and fracture behavior of a selected AHSS grade, Q&P980 steel, was first characterized based on a series of mechanical experiments under simple shear, uniaxial tension, plane strain, and equi-biaxial tension conditions. Then, material models

Hu, Jun, Pan, Hao, Pavlina, Erik, Thomas, Grant

The Jetq-Family - New Highly Ductile AHSS Steel Grades with Improved Technological Properties

2023-01-0080

04/11/2023

New highly ductile AHSS steel grades with tensile strength greater than 980 MPa have been developed with the aim of combining high strength and excellent formability. The new jetQ-Family offers high local and global ductility while still fulfilling standards for resistance towards hydrogen embrittlement and weldability. These improved properties are based on their specifically engineered microstructure, which utilize the TRIP-mechanism in a strengthened matrix. This work shows how the microstructure plays a significant role for the tensile testing as well as hole-expansion. Based on the increased yield strength a better crash performance compared to conventional DP steel grades can be attained. The local ductility is demonstrated with excellent hole expansion ratios and high resistance to sheared edge failure. In combination with improved bending angles and thickness strain at fracture a robust process for manufacturing of components can be achieved. The results are completed by the

Irnich, Manuela, Thiessen, Richard, Paton, Adrian, Sato, Kentaro, Toji, Yuki, Minami, Hidekazu

A Method for Measuring In-Plane Forming Limit Curves Using 2D Digital Image Correlation

05-16-03-0019

04/10/2023

With the introduction of advanced lightweight materials with complex microstructures and behaviors, more focus is put on the accurate determination of their forming limits, and that can only be possible through experiments as the conventional theoretical models for the forming limit curve (FLC) prediction fail to perform. Despite that, CAE engineers, designers, and toolmakers still rely heavily on theoretical models due to the steep costs associated with formability testing, including mechanical setup, a large number of tests, and the cost of a stereo digital image correlation (DIC) system. The international standard ISO 12004-2:2021 recommends using a stereo DIC system for formability testing since two-dimensional (2D) DIC systems are considered incapable of producing reliable strains due to errors associated with out-of-plane motion and deformation. This work challenges that notion and proposes a simple strain compensation method for the determination of FLCs using a low-cost single

Agha, Akshat, Abu-Farha, Fadi

Hydrogen Embrittlement Testing of Ultra High Strength Steels and Stampings by Acid Immersion

J3215_202303 (Current)

03/08/2023

This standard describes a test method for evaluating the susceptibility of uncoated cold rolled and hot rolled Ultra High Strength Steels (UHSS) to hydrogen embrittlement. The thickness range of materials that can be evaluated is limited by the ability to bend and strain the material to the specified stress level in this specification. Hydrogen embrittlement can occur with any steel with a tensile strength greater than or equal to 980 MPa. Some steel microstructures, especially those with retained austenite, may be susceptible at lower tensile strengths under certain conditions. The presence of available hydrogen, combined with high stress levels in a part manufactured from high strength steel, are necessary precursors for hydrogen embrittlement. Due to the specific conditions that need to be present for hydrogen embrittlement to occur, cracking in this test does not indicate that parts made from that material would crack in an automotive environment. Results from this test should be

Metals Technical Committee

BIW Lightweight Potential Applying Uncoated UHS Hot Forming Steel with Increased Tensile Strength

2022-36-0019

02/10/2023

Weight reduction and safety are key factors on the automotive market. Lightweight materials have been widely discussed as an alternative to reduce CO2 emissions levels and fuel efficiency. Press-hardened steels (PHS), such as 22MnB5 steel, are known to combine high ultimate strength resistance and low thickness. To improve this correlation, new generations of ultra-high strength (UHS) hot forming steel grades are under development. Once the mechanical properties improve after the hot forming process it is possible to decrease the thickness keeping the same performance. An example is the 37MnB5 steel which has some adjustments in terms of chemical composition, increasing its hardenability and providing a more refined quenched martensite. A simulation study of weight reduction for a body in white (BIW) application will be presented considering a 37MnB5 steel grade. Additionally, some preliminar results of this steel are discussed. The heat treatment, performed in laboratorial scale

Santana, Dr. Jessica, Gomes Pallu, Lucas, Curti, Gustavo, Hirota, Frederico

A Method for Measuring In-Plane Forming Limit Curves (FLC) using 2D Digital Image Correlation

SAE-PP-0032202/05/2023

With the introduction of advanced lightweight materials with complex microstructures and behaviors, more focus is put on the accurate determination of their forming limits, and that can only be possible through experiments, as the conventional theoretical models for forming limiting curve (FLC) prediction fail to perform. Despite that, CAE engineers, designers, and tool makers still rely heavily on theoretical models due to the steep costs associated with formability testing, including mechanical setup, a large number of tests, and the cost of a stereo digital image correlation (DIC) system. The International Standard ISO 12004-2:2021 recommends using a stereo DIC system for formability testing since 2D DIC systems are considered incapable of producing reliable strains due to errors associated with out-of-plane motion and deformation. This work challenges that notion and proposes a simple strain compensation method for the determination of FLCs using a low-cost single camera (2D) DIC

Agha, Akshat, Abu-Farha, FADI

Effectiveness of 2D Digital Image Correlation in Capturing the Fracture Behavior of Sheet Metal Alloys

05-16-02-0009

12/14/2022

It is a consensus in academia and the industry that 2D digital image correlation (2D-DIC) is inferior to a stereo DIC for high-accuracy material testing applications. It has been theoretically established by previous researchers that the 2D-DIC measurements are prone to errors due to the inability of the technique to capture the out-of-plane motion/rotation and the calibration errors due to lens distortion. Despite these flaws, 2D-DIC is still widely used in several applications involving high accuracy and precision, for example studying the fracture behavior of sheet metal alloys. It is, therefore, necessary to understand and quantify the measurement errors induced in the 2D-DIC measurements. In this light, the presented work attempts to evaluate the effectiveness of 2D-DIC in mechanical testing required for the generation of fracture strain vs. triaxiality curve for sheet metal. This work presents a direct comparison of fracture strains obtained by 2D-DIC and stereo DIC for four

Agha, Akshat

Hole Expansion Characteristics of Advanced High Strength Steel (AHSS) Grades and Their Effects on Manufacturability in Automotive Industry

2022-28-0350

10/05/2022

Currently, automotive industries are using Advanced High-Strength Steels (AHSS) sheet grades to achieve key requirements like light weighting and improved crash performance. But forming of AHSS grades becomes key challenge due to its lesser ductility and edge fracturing tendency during forming. In general, most of the automotive components undergoes shearing operations like blanking and punching which affects the edge ductility of the steel. AHSS grades possess limited edge ductility compared with conventional steel grades which results in edge fracturing due to tensile strain during stretch flanging operation. Stretch flange-ability is an important formability characteristic, which aids in material selection to avoid edge fracturing of complex shaped parts. Material with better stretch flange-ability possess better edge ductility and hence perform better in stretch flanging of sheet metal. Various test methods have been developed to predict stretch flange-ability behavior of the steel

Udhayakumar, Thendralarasu, Paliwal, Lokesh, Misal, Swapnali, Ponkshe, Shripadraj

TOC

99-04-04-0TOC

09/07/2022

TOC

Tobolski, Sue

Categorization and Properties of Steel Sheet for Automotive Cold Forming Applications

J2947_202204 (Current)

04/01/2022

This SAE Recommended Practice establishes and defines requirements for grades of continuously cast automotive steel sheet that can be formed, welded, assembled, and painted in automotive manufacturing processes. These sheet steels can be specified as hot-rolled, cold-rolled, uncoated, or coated. Steel sheet can be coated by hot dipping, electroplating, or vapor deposition of zinc, aluminum, or organic compounds. Not all combinations of material types, strength levels, and coating types may be commercially available. Consult your steel supplier for availability.

Metals Technical Committee

True Fracture Strain Measurement and Derivation for Advanced High-Strength Steel Sheets

2022-01-0237

03/29/2022

The importance of true fracture strain was initially highlighted in the context of local versus global formability considerations used in material selection among advanced high strength steels (AHSSs) of similar tensile strength. Inspired by the relative studies, a precedent work compared the fracture strain results via either digital image correlation (DIC) based method or optical fracture surface measurement on different AHSS samples. It concluded that the DIC-based testing results generally underestimated the fracture strain. As a continued study, the present work further analyzed the DIC-based testing procedure and attributed such an underestimation mainly to the volume constancy assumption. Furthermore, this work pointed out that also because of the same assumption, the optical fracture surface measurement to some extent overestimated the fracture strain. Nevertheless, it was also observed that different AHSS grades were affected discrepantly by the two methods. Therefore

Hu, Jun, Thomas, Grant, Campbell, Cynthia

Efficient Processing of Material Property Definition to Predict Fracture of AHSS in Crash Analysis

2022-01-0236

03/29/2022

Advanced High Strength Steel (AHSS) with high strength and deformation resistance is applied to automotive components and plays an important role in protecting passengers in the event of a crash, as well as contributing to fuel economy improvement by reducing the weight of the car body. However, due to the low ductility of the AHSS, there is an issue about the occurrence of fracture during a vehicle crash. In order to cope with these problems from the early design stage, preliminary verification is made through crash CAE analysis, but a high level of material property definition is required for fracture prediction. To predict fracture, many tests are required to secure the base data for parameter calculation of a complex fracture model, and a lot of physical time is required to verify the model. This paper aimed to semi-automate the material parameter calculation and verification process for efficient and reliable fracture prediction of AHSS. To this end, a user interface program was

Lee, Kang Hee, Jun, ChulWoong, Choi, Sunyong, Lee, Kyoungteak, Lee, Dong Yul, Kim, Dae Young

A Novel Tensile Testing Method to Characterize the Weld Metal Properties for Laser Welded Blank (LWB) with AHSS

2022-01-0243

03/29/2022

The automotive industry applies Laser Welded Blanks (LWB) to increase the material utilization and light-weighting of the vehicle structure. This paper introduces a novel tensile testing method to characterize the hardening behavior of the weld material with a digital image correlation (DIC) and apply it as a constitutive hardening model in forming simulations with the LWBs of GEN3 steel. Formability tests under biaxial conditions were performed with LWB of GEN3 steel. Experimental results were correlated with finite element analysis (FEA) predictions that were conducted with and without the weld material model. The results show the weld material model for the LWB improves the accuracy of FEA predictions of both necking failures on the base metal as well as cracking on the weld.

Kim, Minki, Gu, Jiahui, Kim, Hyunok

Development of New Vehicle Safety Structures by Using Third-Generation Steels

05-15-02-0011

01/06/2022

Research and development efforts in the automotive industry have been long focused on crashworthy, durable vehicles with the lowest mass possible as higher mass requires more energy and, thus, causes more CO2 emissions. One way of approaching these objectives is to reduce the total vehicle weight by using higher strength-to-weight ratio materials, such as Advanced High-Strength Steels (AHSS). Typically, as the steel gets stronger, its formability is reduced. The steel industry has been long developing (so-called) third-generation (Gen3) AHSS for the automotive industry. These grades offer higher formability compared to first-generation (Gen1) and cost less compared to the second-generation (Gen2) AHSS. Transformation Induced Plasticity (TRIP)-aided Bainitic Ferrite (TBF) and Quenching and Partitioning (Q&P) steel families are considered to be the Gen3 AHSS. These grades can be cold-formed to more complex shapes, compared with the Gen1 Dual Phase (DP) and TRIP steels at equivalent

Erzincanlioğlu, Samet, Aydiner, Tamer, Aras, Firat, Çelik, Hafize, Billur, Eren, Karabulut, Semih, Gümüs, Iskender Onder

Optimization of Body-in-White Weld Parameters for DP590 and EDD Material Combination

2021-28-0215

10/01/2021

Body in White (BIW) of an automobile serves as the shell, on which all the components that make up a vehicle, are mounted. The BIW is an assembly of press formed sheet metal components. The sheet metal composition of each component varies based on the form and functionality requirement of that component. The resulting assembly has multiple weld joineries with dissimilar compositions. The weld integrity of the joineries is crucial in maintaining the geometrical and structural integrity of the BIW. The primary welding method used in BIW assembly is Resistance Spot Welding (RSW). The quality of the weld is an outcome of a combination of multiple weld parameters. These parameters are majorly estimated based on the joinery thicknesses and material combinations. Multiple welding and testing iterations are done to fine tune the parameters for an optimum weld joinery. This is a very tedious process which increases the process time of a BIW assembly. This paper studied the impact of critical

Thiruppathi, R, Selvam, Ganesan, Kannan, Muniya Gounder, voppuru, Naga Sheshank Reddy, Baskaran, V

Acura TLX is HONDA'S NEW BODY-BUILD BENCHMARK

21AUTP09_0309/01/2021

All-new for 2021, Acura's midsize sport sedan gets an exclusive platform to go with its structural, materials and dynamic advancements. Body development leader Jeremy Lucas explains. Honda body-engineering presentations have become a much-anticipated highlight of the annual Great Designs in Steel (GDIS) conference in Michigan. Honda's “ACE” vehicle structures are considered by competitors to be benchmarks in overall integrity, occupant protection and mass efficiency. The newest iteration - that of the all-new 2021 Acura TLX - adds dynamic behavior to the other ACE attributes. The TLX's body development leader, Jeremy Lucas, deems the new sport sedan to be “the most exciting project I've been involved with in my 23 years at Honda.” In a recent interview with SAE Media, he also praised the GDIS event, as “an environment in which we in the body-engineering and materials communities can learn from each other.”

Brooke, Lindsay

Effects of Heat Input on Microstructure and Mechanical Properties of Dissimilar Laser-Welded Dual-Phase and Boron Steel Joints

05-15-01-0005

08/31/2021

Heat-affected zone (HAZ) softening occurs during the laser welding of many Advanced High-Strength Steels (AHSS) that are used for body-in-white (BIW) of automobiles, leading to degradation in the mechanical properties of the welded joints. The microstructure and mechanical properties of dissimilar laser-welded AHSS comprising of as-received 22MnB5 with dual-phase (DP) steels (DP600, DP800, and DP 1000) were investigated in this study. Welds were made at welding speeds ranging from 1 m/min to 3 m/min. Irrespective of welding speed, the DP600-22MnB5 joints fractured in the base metal (BM) of 22MnB5 during tensile tests. Likewise, welded joints of DP800-22MnB5 and DP1000-22MnB5 made at 1 m/min and 2 m/min failed in the BM; however, at 3 m/min the failure location of these joints shifted to the fusion zone (FZ). The fractured surfaces of all the welded combinations were characterized by optical and scanning electron microscopy (SEM). Based on fracture energy, joints welded at 2 m/min were

Aderibigbe, Isiaka Akanbi, Popoola, Patricia Abimbola, Sadiku, Rotimi Emmanuel, Biro, Elliot

Lightweight steel on a (COLD) ROLL

21AUTP06_0206/01/2021

A newly developed high-strength steel for cold stamping aims to beat aluminum for EV battery enclosures and other vehicle applications. Automotive OEMs are faced with the difficult task of significantly improving fuel economy and safety, while maintaining a competitive position in the market - as well as investing in the electrified future. This, among other benefits, can be accomplished by utilizing higher-strength steel in the production process. A newly developed and patented cold-roll high-strength steel for cold stamping, known as ColdStamp-Steel, is ideal for producing vehicle body-structure and safety components, including battery enclosures of electric vehicles (EV). The microstructure of ColdStamp-Steel consists of one or more of martensite, ferrite, and retained austenite in different percentages, depending on the steel composition and heat treatment. Also, one or more of carbides, nitrides and carbonitrides are part of the microstructure. The resulting material offers high

Vartanov, Gregory

Strain Amount and Strain Path Effects on Instrumented Charpy Toughness of Baked Third Generation Advanced High Strength Steels

2021-01-0266

04/06/2021

Third generation advanced high strength steels (AHSS) that rely on the transformation of austenite to martensite have gained growing interest for implementation into vehicle architectures. Previous studies have identified a dependency of the rate of austenite decomposition on the amount of strain and the associated strain path imposed on the sheet. The rate and amount of austenite transformation can impact the work hardening behavior and tensile properties. However, a deeper understanding of the impact on toughness, and thus crash performance, is not fully developed. In this study, the strain path and strain amounts were systematically controlled to understand the associated correlation to impact toughness in the end application condition (strained and baked). Impact toughness was evaluated using an instrumented Charpy machine with a single sheet v-notch sample configuration. The instrumented striker provides a load - displacement curve as well as a total impact energy measurement

Hodges, Adam D., Tedesco, Sarah, Anderson, Shane M., Golem, Lindsay, Huang, Gang

Constitutive, Formability, and Fracture Characterization of 3rd Gen AHSS with an Ultimate Tensile Strength of 1180 MPa

2021-01-0308

04/06/2021

The superior formability and local ductility of the emerging class of third generation of advanced high-strength steels (3rd Gen AHSS) compared to their conventional counterparts of the same strength level offer significant advantages for automotive lightweighting and enhanced crash performance. Nevertheless, studies on the material behavior of 3rd Gen AHSS have been limited and there is some uncertainty surrounding the applicability of developed methodologies for conventional dual-phase (DP) steels to this new class of AHSS. The present paper provides a comprehensive study on the quasi-static and dynamic constitutive behavior, formability characterization and prediction, and the fracture behavior of two commercial 3rd Gen AHSS with an ultimate strength of 1180 MPa that will be contrasted with a conventional DP1180. The hardening response to large strain levels was determined experimentally using tensile and shear tests and then validated with 3-D simulations of tensile tests. In

Noder, Jacqueline, Gutierrez, Jon Edward, Zhumagulov, Amir, Khameneh, Farinaz, Ezzat, Hesham, Dykeman, James, Butcher, Cliff

Formability Characterization of 3rd Generation Advanced High-Strength Steel and Application to Forming a B-Pillar

2021-01-0267

04/06/2021

The objective of this study was to assess the formability of two 3rd generation advanced high strength steels (3rd Gen AHSS) with ultimate strengths of 980 and 1180 MPa and evaluate their applicability to a structural B-Pillar for a mid-sized sport utility vehicle. The constitutive behavior including strain-rate effects and formability were characterized to generate the material models for use within AutoForm R8 software to design the B-pillar tooling and forming process. An extended Bressan-Williams instability model was able to deterministically predict the forming limit curves obtained using Marciniak tests. The tooling for the representative B-pillar was designed and fabricated with Bowman Precision Tooling and forming trials conducted for both 3rd Gen steels that had a thickness of 1.4 mm. The 3rd Gen 980 B-pillar was successfully formed in accordance with the predictions of the numerical models while the 3rd Gen 1180 was predicted to have significant failure based upon the in

Gutierrez, Jon Edward, Noder, Jacqueline, Paker, Neil, Bowman, Jamie, Zhumagulov, Amir, Dykeman, James, Malcolm, Skye, Ezzat, Hesham, Butcher, Cliff

Letter from the Guest Editor

05-13-03-001510/29/2020

Letter from the Guest Editor

Weiler, Jonathan

Letter from the Guest Editor

05-14-01-000110/14/2020

Letter from the Guest Editor

Weiler, Jonathan

Materials and Technologies for Lightweighting of Structural Parts for Automotive Applications: A Review

05-14-01-000709/14/2020

Reducing the weight of automotive components is one of the most achievable solutions for lowering the transport carbon footprint. This is the reason for the rapid increase over the last few years in the replacement of conventional alloys (i.e., steel and cast iron) with low-density materials (i.e., aluminum alloys, composites) and in the redesign of components shape in order to remove the unnecessary material (e.g., related to the introduction of additive manufacturing or high-strength materials). Despite this general trend, the use of higher-density metals and massive geometries is still predominant in the production of structural components, especially for heavy vehicles and safety-relevant parts. Aim of the present review is to summarize how this current situation can be overcome. The analysis started with an investigation about the materials that can be used for the production of structural parts, the potential reduction of the component weight and its costs. The scenarios analyzed

Cecchel, Silvia

The Effect of Current Mode on the Crack and Failure in the Resistance Spot Welding of the Advanced High-Strength DP590 Steel

05-14-01-000209/09/2020

The causes of failure due to cracking in the resistance spot welding of the advanced high-strength steels dual-phase 590 (DP590) were investigated using scanning electron microscopy (SEM), optical microscopy, and the tensile-shear test. The results showed that by increasing the current amount, the formation of the melting zone occurred in the heat-affected zone (HAZ), leading to the cracking in this area, reducing the tensile strength and decreasing the mechanical properties; the initiation and growth of cracking and failure in this region also happened. In the HAZ, by increasing the current amount with the softening phenomenon, the recrystallized coarse grains also occurred, eventually resulting in the loss of mechanical properties. The results of the tensile-shear test also indicated that by increasing the current up to 12 kA, the strength was raised, but the ductility was reduced. At a higher current, the decrease in mechanical properties, strength, and ductility was noticeable. The

Ghandi, Arian, Shamanian, Morteza, Salmani, Mohamad Reza

Virtual and physical testing of Third-Generation High Strength Steel

20AUTP09_0309/01/2020

Evaluating a new high-strength steel's ability to improve an existing stamped-steel production part. Developing lightweight, stiff and crash-resistant vehicle body structures requires a balance between part geometry and material properties. High-strength materials suitable for crash resistance impose geometry limitations on depth of draw, radii and wall angles that reduce geometric efficiency. The introduction of Third-Generation Advanced High Strength Steels (AHSS) can potentially change the relationship between strength and geometry and enable improvements in both.

Macek, Bryan, Lutz, Justin

A New Testing Method to Evaluate Edge Cracking with Considerations of the Shear Clearance and Press Speed

2020-01-0758

04/14/2020

As the automotive industry increasingly adopts Advanced High Strength Steel (AHSS) for the vehicle light-weighting and crashworthiness, the edge cracking significantly increases in stamping AHSS. Different lab-scale test methods such as the ISO standard hole-expansion test and the half specimen dome test are available to evaluate edge formability. However, none of these lab-scale testing methods emulates production conditions such as various shear clearances, part complexity, and shearing speed associated with the mechanical or hydraulic press operation. To address these limitations of the available testing methods, a new punching and stamping test was developed. This paper introduces the simulation and experimental approach in developing this unique testing method to design the peanut-shaped hole that is sensitive to edge cracking in stamping. Three different sheet materials, DP780, 980 GEN3, and aluminum 6016-T4 were tested to validate the reliability of the newly developed testing

Gu, Jiahui, Zoller, Laura, Kim, Hyunok

Calibration and Validation of GISSMO Damage Model for A 780-MPa Third Generation Advanced High Strength Steel

2020-01-0198

04/14/2020

To evaluate vehicle crash performance in the early design stages, a reliable fracture model is needed in crash simulations to predict material fracture initiation and propagation. In this paper, a generalized incremental stress state dependent damage model (GISSMO) in LS-DYNA® was calibrated and validated for a 780-MPa third generation advanced high strength steels (AHSS), namely 780 XG3TM steel that combines high strength and ductility. The fracture locus of the 780 XG3TM steel was experimentally characterized under various stress states including uniaxial tension, shear, plane strain and equi-biaxial stretch conditions. A process to calibrate the parameters in the GISSMO model was developed and successfully applied to the 780 XG3TM steel using the fracture test data for these stress states. The calibrated GISSMO fracture card for 780 XG3TM steel was then validated in simulations of wedge-bend tests, two notched tensile tests and axial crash tests of octagonal, 12-sided and 16-sided

Chen, Guofei, Huang, Lu, Link, Todd M., Tyan, Tau, Aekbote, Krishnakanth

Structural Performance Comparison between 980MPa Generation 3 Steel and Press Hardened Steel Applied in the Body-in-White A and B-Pillar Parts

2020-01-0537

04/14/2020

Commercially available Generation 3 (GEN3) advanced high strength steels (AHSS) have inherent capability of replacing press hardened steels (PHS) using cold stamping processes. 980 GEN3 AHSS is a cold stampable steel with 980 MPa minimum tensile strength that exhibits an excellent combination of formability and strength. Hot forming of PHS requires elevated temperatures (> 800°C) to enable complex deep sections. 980 GEN3 AHSS presents similar formability as 590 DP material, allowing engineers to design complex geometries similar to PHS material; however, its cold formability provides implied potential process cost savings in automotive applications. The increase in post-forming yield strength of GEN3 AHSS due to work and bake hardening contributes strongly toward crash performance in energy absorption and intrusion resistance. The viability of using cold stamped 980 GEN3 AHSS as a replacement for PHS has often been challenged due to concerns about formability and capability to meet

Pednekar, Vasant, Pereira, Andre, Ballard, Adam, Chen, Guofei, Komarivelli, Rajmouli, Li, Haoming

Third Generation 980 Class AHSS: A Viable Alternative to Replace Press-Hardenable Steels (PHS) in Automotive Rear Rail Applications

2020-01-0534

04/14/2020

Commercially available Third Generation Advanced High Strength Steels (GEN3 AHSS) are qualified by automakers worldwide. With an excellent combination of strength and ductility, GEN3 AHSS are cold-formable and have shown potential to replace press hardenable steels (PHS) in structural applications. With overall formability equivalent to 590DP, U. S. Steel 980 GEN3 AHSS (980 XG3™ AHSS) may achieve cold-formed component geometries similar to those achieved by hot-formed PHS. Furthermore 980 GEN3 AHSS demonstrates a substantial increase in post-forming yield strength due to the combined effects of work-hardening and bake-hardening-thereby contributing strongly toward crash energy management performance. The technical challenges and attributes of cold-formed 980 GEN3 AHSS are explored in this paper for an automotive rear rail application (currently PHS), including: formability analysis, wrinkling elimination and springback compensation. A successful rear rail stamping trial was run with EG

Pednekar, Vasant, Khutorsky, Alex, Lad, Sanjay, Babymony, Manikandan, Nigam, Praveen Kumar

High Strain Rate Tensile Behavior of 1180MPa Grade Advanced High Strength Steels

2020-01-0754

04/14/2020

Tensile behavior of advanced high strength steel (AHSS) grades with strengths up to 980 MPa has been extensively studied. However, limited data is found in literature on the tensile behavior of steels with tensile strengths of the order of 1180 MPa, especially at nominal strain rates up to 500/s. This paper examines tensile flow behavior to fracture of four different 1180 MPa grade steels at strain rates of 0.005/s, 0.5/s, 5/s, 50/s and 500/s using an experimental methodology that combines a servo-hydraulic tester and high speed digital image correlation. Even though the strength increase with the strain rate is consistent between the four different materials, the total elongation increase with the strain rate varies widely. Some insights as to why this occurs from examination of the steel microstructure and variation of retained austenite with strain are offered.

Savic, Vesna, Hector, Louis, Alturk, Rakan, Enloe, Charles

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