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Technical Paper

Electric Motor Noise in a Lightweight Steel Vehicle

2011-05-17
2011-01-1724
The present work attempts a complete noise and vibration analysis for an electric vehicle at concept stage. The candidate vehicle is the Future Steel Vehicle (FSV), a lightweight steel body with an electric motor developed by WorldAutoSteel [1,2,3]. Measurements were conducted on two small Mitsubishi vehicles that both share the same body, yet one is equipped with an internal combustion engine and the other with an electric motor. The outcome was used as a starting point to identify assets and pitfalls of electric motor noise and draw a set of Noise Vibration and Harshness (NVH) targets for FSV. Compared to a combustion engine, the electric motor shows significantly lower sound pressure levels, except for an isolated high frequency peak heard at high speeds (3500 Hz when the vehicle drives at top speed). The prominence of this peak is lowered by increased use of acoustic absorbent materials in the motor compartment.
Technical Paper

UV-Curable Primer-cum-Paint System for Mild Steels based on Sol-Gel Coating Technology

2009-12-13
2009-28-0052
Sol-based coatings derived from organically modified silanes and metal alkoxides have been investigated for the past two decades for their applicability as barrier coatings for corrosion protection of stainless steels and mild steels. Colored sol-gel coatings can also be generated by the addition of pigments. Recently, lot of attention has been given to use of radiation (UV or NIR) curing for densification of protective coatings on metals/steels. In this context, investigations were carried out on the mechanical and corrosion protection properties of UV-curable transparent and colored sol-gel coatings on mild steels for comparison with a painted substrate.
Technical Paper

LASER SURFACE HARDENING OF CRANKSHAFT

2009-12-13
2009-28-0053
The present work involves systematic study on identification of process parameters and processing conditions for effective laser surface-hardening of automotive crankshaft and its implementation in the industry, utilizing a diode laser integrated to a 6-axis robot and a turn/tilt table. The crankshaft chosen was made of low-alloyed 0.52% C steel and required hardening at two contact regions of bearing/flange seat areas and a pin area (on a different axis than the actual shaft). The subjected areas had features like oil holes, sharp corners and wide areas. The target was to develop laser hardening process resulting in hardened case-depth of above 200 µm with a hardness of 500 - 650 HV at different locations mentioned. Additionally, It was targeted to minimize the processing time and also eliminate any post process machining operations.
Technical Paper

Procedure to Realize the FEM Model of a Tubular Steel Frame for Motorcycles

2009-01-21
2009-26-0061
During the development of a tubular steel frame for motorcycles, it is very important to make FEM calculations in order to evaluate the stress level and the stiffness of the structure. The FEM models must be light in order to reduce calculation time and precise in order to obtain reliable results that can be checked in the following experimental tests. FEM models of tubular frame made using 1D elements (Pipe) have low precision results and are not advisable for this kind of work. It is suggested to use FEM models made using 2D elements (Shell) for sensitivity tests too. In order to obtain the best result using Shell elements, it is very important to choose the right criterion to model the welding parts: the model must represent the right inertia of the tubular welded joint and be both accurate and easy to be modeled.
Technical Paper

Ultimate Load Capacity of Spot Welds Made of Ultra High Strength Steels

2011-04-12
2011-01-0788
Spot welds have two separation modes: interfacial and button pullout. Most of existing publications [8,9,10,11,12] focused on button pullout. This is because for the same sheet metal and gage combination, button pullout leads to higher separation load than interfacial separation. With the push for lighter vehicles, high strength and ultra high strength steels are used. To further reduce mass, welding flanges are getting narrower. The welding tips are getting smaller. The weld nugget diameters are smaller as a result. The separation mode for certain load cases is no longer nugget pullout, but interfacial instead. This lowers the weld's maximum load capacity. In order for CAE simulated prediction to correlate to physical behaviors of vehicle structures, it is important to define and reconfirm separation criteria. New tests and analyses are necessary.
Technical Paper

Vehicle Crash and Steering Column Frequency Simulation of an Aluminum Instrument Panel Structure

2011-04-12
2011-01-0765
Recent changes to the U.S. CAFÉ (Corporate Average Fuel Economy) requirements have caused increased focus on alternative vehicle component designs that offer mass savings while maintaining overall vehicle design and performance targets. The instrument panel components comprise approximately 6% of the total vehicle interior mass and are thus a key component of interest in mass optimization efforts. Typically, instrument panel structures are constructed of low carbon tubular steel cross car members with welded stamped steel component brackets. In some cases, instrument panel structures have incorporated high strength low alloy (HSLA) steels to reduce mass by reducing gage. In this study, aluminum low mass instrument panel structure concept designs are developed. This paper illustrates the differences between a HSLA steel solution and four different aluminum instrument panel structure designs.
Technical Paper

The Effect of Strain on Stainless Steel Surface Finish

2011-04-12
2011-01-0774
The bright surface finish of exterior automotive moldings made from stainless steel can become hazed and reflections distorted as a result of forming done during the manufacturing processes. Bright moldings are frequently used to give styling differentiation accents to vehicle exteriors. Stainless steel provides cost effective differentiation with a material that is durable and relatively easy to form to shapes desired by the stylist. Because of the desirable attributes of stainless steel, an understanding of the threshold of unacceptable surface appearance is necessary to maximize showroom appeal and avoid customer complaints that result in warranty claims. This paper quantifies the effect that manufacturing strain and strain rate have on the surface finish of 436M2 stainless steel. Controlled experiments were conducted on production grade stainless steel strips subjected to a variety of strain and strain rates typical of manufacturing processes.
Technical Paper

Automotive Mass Reduction with Martensitic Stainless Steel

2011-04-12
2011-01-0427
Martensitic stainless steels are ideally suited for structural components and assemblies, satisfying the requirements of high strength, toughness and corrosion resistance with ease of forming in the annealed state. New developments in welding and thermal processing, coupled with increased demands for high strength lightweight structures, are positioning martensitic stainless as a cost effective alternative to conventional lightweighting materials. Several examples are shown, including the development of fully martensitic (UNS S41000) automotive subframes, door beams, B-pillars, seat rails, tow hooks and fuel rail assemblies. The excellent mechanical properties of hardened martensitic stainless allow for notable weight savings, achieving 35% or greater weight reduction relative to baseline designs.
Technical Paper

Achieving a Lightweight and Steel-Intensive Body Structure for Alternative Powertrains

2011-04-12
2011-01-0425
FutureSteelVehicle’s (FSV) objective is to develop detailed design concepts for a radically different steel body structure for a compact Battery Electric Vehicle (BEV). It also will identify structure changes to accommodate larger Plug-In Hybrid (PHEV) and Fuel Cell (FCEV) vehicle variants. The paper will demonstrate seven optimised structural sub-systems that contribute to the programme's 35 percent mass reduction goals and meet its safety and life cycle emissions targets. It will explain the advanced design optimisation process used and the resulting aggressive steel concepts.
Technical Paper

Weight Reduction Using Massive Carbide Free Thin Walled Ductile Iron Produced via Lost Foam Casting

2011-04-12
2011-01-0426
Significant research has been conducted with the goal of obtaining thin walled ductile iron for use in lighter weight designs. A review is made of the past efforts to achieve thin walled ductile iron. Most past efforts resorted to costly processes or non-standard production practices. Lost Foam Casting (LFC) is an alternate foundry process which used in conjunction with standard melt shop practices results in a massive carbide free structure when used with thin section size. Chemistry, hardness tests, microstructures, and design improvements of a case study are reviewed.
Journal Article

A Study of Anisotropy and Post-Necking Local Fracture Strain of Advanced High Strength Steel with the Utilization of Digital Image Correlation

2011-04-12
2011-01-0992
The automotive industry has a strong need for lightweight materials capable of withstanding large mechanical loads. Advanced high-strength steels (AHSS), which have high tensile strength and formability, show great promise for automotive applications, yet if they are to be more widely used, it's important to understand their deformation behavior; this is particularly important for the development of forming limit diagrams (FLD) used in stamping processes. The goal of the present study was to determine the extent to which anisotropy introduced by the rolling direction affects the local fracture strain. Three grades of dual-phase AHSS and one high-strength low-alloy (HSL A) 50ksi grade steel were tested under plane strain conditions. Half of the samples were loaded along their rolling direction and the other half transverse to it. In order to achieve plane strain conditions, non-standard dogbone samples were loaded on a wide-grip MTS tensile test machine.
Technical Paper

Suitable Stainless Steel Selection for Exhaust Line Containing a Selective Catalytic Reduction (SCR) System

2011-04-12
2011-01-1323
Due to the evolution of emission control standards, new pollution control systems will be necessarily used for off-road vehicles and trucks exhaust systems and in the near future for passenger cars. Indeed, the will to reduce NOx emission through Euro 5 (2009) and then to Euro 6 (2014) and American EPA Tier 4 (2008-2015) imposes the implementation of a new after-treatment system within the exhaust line. One of the most promising technologies takes advantage of the reduction feature of ammonia (NH₃) on NOx. This system called Selective Catalytic Reduction (SCR) couldn't be developed by storing directly ammonia as a reduction agent on the vehicle due to its high toxicity and flammability. It is why urea is used as an ammonia generator through thermolysis reaction.
Technical Paper

Adhesive Bonding Performance of GA Coated 590 MPa Tensile Strength Steels

2011-04-12
2011-01-1052
Advanced high strength steels (AHSS) are becoming major enablers for vehicle light weighting in the automotive industry. Crash resistant and fracture-toughened structural adhesives have shown potential to improve vehicle stiffness, noise, vibration, and harshness (NVH), and crashworthiness. They provide weight reduction opportunity while maintaining crash performance or weight increase avoidance while meeting the increasing crash requirement. Unfortunately, the adhesive bonding of galvanneal (GA)-coated steels has generally yielded adhesive failures with the GA coating peeling from the steel substrate resulting in poor bond strength. A limited study conducted by ArcelorMittal and Dow Automotive in 2008 showed that GA-coated AHSS exhibited cohesive failure, and good bond strength and crash performance. In order to confirm the reliable performance, a project focusing on the consistency of the adhesive bond performance of GA-coated steels of 590 MPa strength level was initiated.
Journal Article

Investigation on Dynamic Recovery Behavior of Boron Steel 22MnB5 under Austenite State at Elevated Temperatures

2011-04-12
2011-01-1057
Hot forming process of ultrahigh strength boron steel 22MnB5 is widely applied in vehicle industry. It is one of the most effective approaches for vehicle light weighting. Dynamic recovery is the major softening mechanism of the boron steel under austenite state at elevated temperatures. Deformation mechanism of the boron steel can be revealed by investigation on the behavior of dynamic recovery, which could also improve the accuracy of forming simulations for hot stamping. Uniaxial tensile experiments of the boron steel are carried out on the thermo-mechanical simulator Gleeble3800 at elevated temperatures. The true stress-strain curves and the relations between the work hardening rate and flow stress are obtained in different deformation conditions. The work hardening rate decreases linearly with increasing the flow stress.
Technical Paper

Characterization of Edge Fracture in Various Types of Advanced High Strength Steel

2011-04-12
2011-01-1058
In vehicle crash events there is the potential for fracture to occur at the processed edges of structural components. The ability to avoid these types of fractures is desired in order to minimize intrusion and optimize energy absorption. However, the prediction of edge cracking is complicated by the fact that conventional tensile testing can provide insufficient data in regards to the local fracture behavior of advanced high strength steels. Fracture prediction is also made difficult because there can be inadequate data on how the cutting processes used for hole piercing and blanking affect the edge condition. In order to address these challenges, research was undertaken to analyze edge fracture in simple test pieces configured with side notches and center holes. Test specimens were made from a number of advanced high strength steels including 590R (C-Mn), 780T (TRIP), 980Y (dual phase) and hot stamp 1500 (martensitic).
Technical Paper

Comparisons of Current Concepts for Press Hardened Steel Tailor Welded Blanks and Tailor Rolled Blanks on Center Pillar Reinforcements

2011-04-12
2011-01-1059
Press hardened steels (PHS) are commonly used in automotive structural applications because of their combination of extremely high strength, load carrying capacity and the ability to form complex shapes in the press hardening process. Recent adoption of increased roof crush standards, side impact requirements and the increased focus on CO2 emissions and mass reduction have led autmotive manufacturers to significantly increase the amount of PHS being designed into future vehicle designs. As a way to further optimize the use of these steels, multi-gauge welded blanks of PHS and multi-material blanks of PHS to microalloyed steels of various thickness have been developed to help achieve these requirements. More recently, tailor rolled PHS, whereby the steel is rolled such that the thickness changes across the width of the sheet, have been developed.
Technical Paper

Investigation of Stamping Tooling Durability for Dual Phase Steels

2011-04-12
2011-01-1060
Advanced High-Strength Steels (AHSS) have become an essential part of the lightweighting strategy for automotive body structures. The ability to fully realize the benefits of AHSS depends upon the ability to aggressively form, trim, and pierce these steels into challenging parts. Tooling wear has been a roadblock to stamping these materials. Traditional die materials and designs have shown significant problems with accelerated wear, galling and die pickup, and premature wear and breakage of pierce punches. [1] This paper identifies and discusses the tribological factors that contribute to the successful stamping of AHSS. This includes minimizing tool wear and galling/die pick-up; identifying the most effective pierce clearance (wear vs. burr height) when piercing AHSS; and determining optimal die material and coating performance for tooling stamping AHSS.
Technical Paper

Bake Hardening Behavior of Advanced High Strength Steels under Manufacturing Conditions

2011-04-12
2011-01-1053
The demand for the reduction of vehicle weight advanced the development of High Strength Steels. In the 80's, Bake Hardening Steels were developed for parts which are manufactured at high stretch forming capacities, specifically utilizing the increase in strength during the paint process. At the end of the 90's, the demand for even higher strength levels led to the development of Advanced High Strength Steels, e.g. Dual Phase Steels, TRIP-Steels, Martensitic Steels or Complex Phase Steels. Since then, the portion of high strength steels in vehicle bodies has been increasing constantly. In addition to the high strength level, they also possess a remarkable bake hardening potential. Currently, this potential is not taken into consideration sufficiently. The use of Advanced High Strength Steels increases the demands on the production in dealing with these materials. Process windows, such as for welding or painting, are narrowed down further.
Technical Paper

Application of Advanced High Strength Stainless Steel for Mass Reduction in Automotive Structures - A Front Bumper Beam Case Study

2011-04-12
2011-01-1054
The front bumper of a current production vehicle, which is made of hot-stamped 15B21 aluminized steel, was studied for mass and cost reductions using the Advanced High Strength Stainless Steel product NITRONIC® 30 (UNS Designation S20400) manufactured by AK Steel Corporation. This grade of stainless steel offers a combination of high ductility and strength, which was utilized to significantly modify the design of the bumper beam to incorporate geometry changes that improved its stiffness and strength. The structural performance of the bumper assembly was evaluated using LS-Dyna-based CAE simulations of the IIHS 40% Offset Full-Vehicle Impact at 40 mph with a deformable barrier, and the IIHS Full Width Centerline 6 mph Low-Speed Impact. Optimization of the bumper beam shape and gauge was performed using a combination of manual design iterations and a multi-objective optimization methodology using LS-Opt.
Technical Paper

Properties of a Newly Developed Galvannealed Steel Sheet with Modified Surface

2011-04-12
2011-01-1056
Since galvannealed steel sheets (GA) are widely used for automobile body parts, they require excellent features such as press formability, resistant spot weldability and phosphatability. We have focused on improving the press formability of GA since the late 1990s, and have developed a new type of surface modified GA which has a lower friction coefficient than conventional GA. The developed surface modified GA based on mild steel is now used by all automakers in Japan, especially for those parts such as side panels that are difficult to form. This paper describes the features of the surface modified GA.
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