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Coupled Weld-Rupture Analysis of Automotive Assemblies

ESI North America-Yogendra Gooroochurn, Ramesh Dwarampudi, Vijay Tunga
ESI US R&D-Megha Seshadri, Ravi Raveendra
  • Technical Paper
  • 2020-01-1076
To be published on 2020-04-14 by SAE International in United States
Lightweight driven design in the automotive industry and the push for Electric Vehicles mandate the use of innovative materials such as Steel (HSS, UHSS, AHSS) and Aluminum alloys. For steel suppliers to meet the strength requirements of high strength steels, they often alloy the steel chemistry (depending on mill capability, rolling capacity, quenching capacity, etc.). When used in welded assembly constructions, these steels, as compared to traditional steels, behave differently. Depending on the welding heat input, the material chemistry and thickness, they either harden or soften in the heat affected zone. Similar behavior is observed with the most commonly used aluminum alloys (5000 and 6000 series) in the automotive sector. For both alloy types, different strengthening mechanism are used to meet their initial strength requirements (by work hardening and by heat treating respectively) but they both undergo softening in the heat affected zone during welding. Regardless of the alloys, the material in the heat affected zone is affected and so is the performance of the weldment during service. FE analyzes of Welding and Performance have…
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Structural Performance Comparison between 980MPa Generation 3 Steel and Press Hardened Steel Applied in the Body-in-White A and B-Pillar Parts

General Motors LLC-Andre Pereira, Adam Ballard, Rajmouli Komarivelli, Haoming Li
United States Steel Corp.-Vasant Pednekar, Guofei Chen
  • Technical Paper
  • 2020-01-0537
To be published on 2020-04-14 by SAE International in United States
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 final crash performance targets. To address these concerns, A-pillar and B-pillar parts were successfully cold stamped using U. S. Steel 980 GEN3 AHSS and assembled in a prototype mid-size…
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Bake Hardening Behavior of DP, TBF, and PHS Steels with Ultimate Tensile Strengths Exceeding 1 GPa

Colorado School of Mines-Brandon W. Blesi, Charles Smith, David K. Matlock, Emmanuel De Moor
  • Technical Paper
  • 2020-01-0536
To be published on 2020-04-14 by SAE International in United States
Third generation advanced high strength steels (AHSS) have been developed combining high strength and formability, allowing for lightweighting of vehicle structural components. These AHSS components are exposed to paint baking operations ranging in time and temperature to cure the applied paint. The paint baking treatment, combined with straining induced from part forming, may lead to increased in-service component performance due to a strengthening mechanism known as bake hardening. This study aims to quantify the bake hardening behavior of select AHSS grades. Materials investigated were press hardenable steels (PHS) 1500 and 2000; transformation induced plasticity (TRIP) aided bainitic ferrite (TBF) 1000 and 1200; and dual phase (DP) 1000. The number designations of these grades refer to minimum as-received ultimate tensile strengths in MPa. Paint baking was simulated using industrially relevant times and temperatures from 15 to 60 min and 120 to 200 °C, respectively. Samples were prestrained 0, 2, or 5 pct to replicate part forming. Bake hardening values ranging from 90 to 140 MPa were observed for DP and TBF grades that were prestrained 2…
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Minimization of High Temperature Oxidation, Aluminum Alloy Heat Treatment

AMS D Nonferrous Alloys Committee
  • Aerospace Standard
  • ARP7500
  • Current
Published 2020-02-05 by SAE International in United States
This recommended practice provides recommendations for minimizing high temperature oxidation (HTO) during the heat treatment of aluminum alloy products and parts. HTO leads to deterioration of properties.
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Microstructural Characterization of Hot Stamped Parts After Partial Hardening

BENTELER Automotive-Tiago Santos Pinheiro
  • Technical Paper
  • 2019-36-0113
Published 2020-01-13 by SAE International in United States
Hot forming is a process that has been on the spotlight of body-in-white recent developments, globally it was estimated that around 500 million parts would be produced in 2018. During the process, a blank of a 22MnB5 steel is heated, above 900 °C, in the austenite field, formed and quenched in the pressing machine, with the goal of producing a part with ultimate tensile strength (UTS) around 1500 MPa, achieved by a fully martensitic microstructure. However, from the point of view of crashworthiness, not all body in white components benefit from a fully martensitic microstructure. Alternative process routes have been proposed to achieve properties that are tailored to the part’s final application. In one of these process variants, known as partial hardening, the blank is heated in a furnace that operates with two parallel zones, each at a different temperature (one zone between 650 and 750 °C and one between 900 and 930°C), resulting in the blank having two main zones with different final temperatures, and a transition zone between them. This difference in temperature…
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Hardening Lightweight Metal Foams with Nanocoating

  • Magazine Article
  • TBMG-35818
Published 2020-01-01 by Tech Briefs Media Group in United States

Bones are strong and stable and can cope with loads almost as well as steel. But despite their strength, they are light enough to be easily moved by humans and animals. The secret lies in the combination of a hard, exterior shell that encases a porous lattice-like network of bone tissue in the interior of the bone. This structure saves on material and reduces weight.

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Study on Effect of Laser Peening on Inconel 718 Produced by DMLS Technique

Vellore Institute of Technology-Nattudurai Navin Kumar, Aditya Chandrakant Yadav, Kumar Raja, Subramanian Prabhakaran, Chooriyaparambil Damodaran Naiju, Sivaperuman Kalainathan
Published 2019-10-11 by SAE International in United States
In Additive manufacturing, Direct Metal Laser Sintering (DMLS) is a rapid manufacturing technique used for manufacturing of functional component. Finely powered metal is melted by using high-energy fiber laser, by Island principle strategy that produces mechanically and thermally stable metallic component with reduced stresses, thermal gradients and at high precision. Inconel is an austenitic chromium nickel-based superalloy often used in the applications which require high strength and temperature resistant. It can retain its properties at high temperature. An attempt is made to examine the effect of laser shot peening (LSP) on DMLS Inconel 718 sample. Microstructure shows elliptical shaped structure and formation of new grain boundaries. The surface roughness of the material has been increased due to the effect of laser shock pulse and ablative nature. Macro hardness increased to 13% on the surface. Depth wise microhardness was investigated, found to be 17% increase on the sub-layer of the material due to the effect of a hardened matrix formed by precipitation hardening and grain size refinement attributed by laser shock peening. SEM analysis shows larger…
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Appraisal of Tribo Meter Study on 20MnCr5 Alloy Steel under Case Hardened and Shot Peened Condition

Shanthi Gears Limited-Vignesh Nataraj
Sri Krishna College of Engg. and Tech.-Soundararajan Ranganathan, Janarthanan Prakash, Dinu Mathew
Published 2019-10-11 by SAE International in United States
This research is limited to study the strength and wear resistance of 20MnCr5 (SAE 5120) alloy steel under monolithic, case hardened and case hardened with shot peening processing condition. Improve the hardness of the material by enhancing the core and surface strength of case hardened with the shot peened sample. The main objective of this proposed work is to conduct the tribometer test by varying the load of 10, 20, 30 and 40N and sliding speed of 193, 386 rpm respectively on wear rate and coefficient of friction be calculated and recorded for this study. Less wear rate and nominal coefficient of friction were observed for case hardened with the shot peened sample. Load increases wear rate increases and the coefficient of friction decreases when sliding distance increases wear rate decreases and the coefficient of friction increases for all the tested samples due to oxide layer formation. After reaching certain load and sliding speed the curve goes linear because of more contact between pin and disc, so that mechanical amalgamation layer will be formed. On…
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Influence of Retained Austenite on Fatigue Performance of Carburized Gears

Comstar Automotive Tech P Ltd.-Rajeshkumar Ramasamy, Seenuvas Sivathanu, Varatharaj Neelakandan, Thulasirajan Ganesan, Praveen Chakrapani Rao
Published 2019-10-11 by SAE International in United States
SAE 8620 and 20CrMo materials were subjected to carburizing process to obtain the identical hardened layer of HRC 61-64. The carburized surface and core properties of the materials were examined and characterized through optical microstructure to measure the presence of cementite carbides and Retained Austenite (RA). From the results, it was found that the SAE 8620 and 20CrMo materials have 10 % and 14% of RA respectively. Whereas, the core and case structure were free from network carbides. The fatigue test was conducted to correlate the RA and fatigue strength of the materials. It was revealed that material with lower RA has higher fatigue strength than material with higher RA. Higher amount of retained austenite leads to reduction in amount of martensitic and compressive residual stress attributed to lower the contact fatigue strength. Untransformed austenite is metastable and is transformed to untempered martensite, which causes brittleness to the component and leads to premature failure.
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Effect of Cryogenic Treatment on Inconel 718 Produced by DMLS Technique

Vellore Institute of Technology-Chooriyaparambil Damodaran Naiju, Kumar Raja, Nattudurai Navin Kumar, Chandrakant Yadav Aditya, Muniappan Senthil Kumar
Published 2019-10-11 by SAE International in United States
The main purpose of this study is to investigate additive manufactured Inconel super alloy subjected to cryogenic treatment (CT). Cryogenic treatment is mainly used in aerospace, defense and automobile application. Direct metal laser sintering is an additive manufacturing technique used for manufacturing of complex and complicated functional components. Inconel is an austenitic chromium nickel based super alloy often used in the applications which require high strength & temperature resistant. In this work, a study is carried out on microstructure and mechanical properties of additive manufactured Inconel 718 when subjected to cryogenic treatment at three different time intervals. The micro-structural evolution of IN718 super-alloy before and after CT was investigated by both optic microscope and scanning electron microscope. Surface roughness and hardness at different CT time intervals has also analyzed. Additionally, XRD technique was used to analyze the surface residual stress. The result shows after three cycles of cryogenic treatment, the hardness of Inconel 718 has been substantially improved at room temperature. Microstructure shows grains in one of the test condition, a larger number of refined…
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