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Technical Paper

Performance of Coatings for Underbody Structural Components

The Auto/Steel Partnership established the Light Truck Frame Project Group in 1996 with two objectives: (a) to develop materials, design and fabrication knowledge that would enable the frames on North American OEM (original equipment manufacturer) light trucks to be reduced in weight, and (b) to improve corrosion resistance of frames on these vehicles, thereby allowing a reduction in the thickness of the components and a reduction in frame weight. To address the issues relating to corrosion, a subgroup of the Light Truck Frame Project Group was formed. The group comprised representatives from the North American automotive companies, test laboratories, frame manufacturers, and steel producers. As part of a comprehensive test program, the Corrosion Subgroup has completed tests on frame coatings. Using coated panels of a low carbon hot rolled and pickled steel sheet and two types of accelerated cyclic corrosion tests, seven frame coatings were tested for corrosion performance.
Technical Paper

The Effects of Coating Composition, Substrate, and Welding Machine on the Resistance Spot Welding Behavior of Hot-Dip Galvanized and Galvannealed Sheet Steels

This joint research study by Bethlehem Steel Corporation and the U. S. Steel Group of the USX Corporation reveals that several significant factors affect the welding performance (electrode life) of hot-dip galvanized and galvannealed sheet steels. The statistical analyses of the electrode life data reveal that coating aluminum content affects electrode wear behavior of both the hot-dip galvanized and the galvannealed coatings. Higher levels of aluminum content cause more rapid electrode wear and shorten electrode life. Iron content in the galvannealed coatings seems to have some positive effect on increasing electrode life, but its effect is not nearly as significant as the negative effect of aluminum content. As the Fe/Al coating content ratio of galvannealed coatings increases, electrode life increases. Substrate type also affects electrode life, with the IF grade consistently producing shorter electrode lives.
Technical Paper

Variable Orifice Valve Development and A/C System Performance Testing

First introduced in 1995, the concept of a temperature-responsive Variable Orifice Valve to control refrigerant flow (patent # 5,479,786) has been further developed for use in automotive refrigerant systems. This device is an alternative, to the expansion devices currently used in automotive refrigerant systems and offers the best features of a thermal expansion valve system (similar high ambient performance ) and of a fixed orifice tube system (low cost, high reliability & performance at lower ambients). Typical automotive refrigerant system operation includes wide variations in condenser air flow and refrigerant pressure. The resultant condenser exit refrigerant temperature is a very stable input parameter for the control of this variable orifice valve (VOV).
Technical Paper

Corrosion Performance and Fuel Compatibility of Prepainted Zinc-Nickel Coated Steel for Fuel Tank Applications

Automotive demands for increased service life and use of flexible fuel blends of alcohol and gasoline have propelled the development of new materials for automotive fuel systems. Traditional fuel system materials, i.e., bare or prepainted terne coated steel sheet, which do not meet the new requirements are being replaced with prepainted zinc-nickel coated steel sheet. Automotive fuel tanks and fuel system components made from the new prepainted zinc-nickel steel sheet offer increased service life and compatibility with the entire range of flexible fuel blends. This paper describes the results of several laboratory corrosion studies which examined the environmental corrosion performance and the fuel compatibility of prepainted zinc-nickel coated steel as a function of several system properties. Performance is compared to prepainted terne, prepainted hot dip tin, and prepainted galvanneal.
Technical Paper

Effects of Coating Weight and Pretreatment on the Painted Corrosion Performance of Coated Steel Sheet

A program was initiated to determine corrosion performance of coated sheet products. The program examined the performance of galvannealed, hot-dip galvanized and electroplated zinc coated steel sheet in a variety of cyclic laboratory corrosion tests. Both perforation and cosmetic corrosion susceptibility were evaluated. Materials were pretreated using immersion and spray phosphate systems and were also prepared without a phosphate pretreatment. Results of these studies will be presented in this paper.
Technical Paper

Influence of Strain State on Powdering of Galvannealed Sheet Steel

Galvanneal powdering was examined on a stabilized ultra low carbon steel substrate as a function of strain state using cup drawing and in-plane stretching experiments to simulate deformations encountered in production stampings. Significant powdering was encountered in drawing while minimal powdering occurred in in-plane stretching. Powdering was measured at specific locations and correlated with strains in those locations. A powdering map was generated in strain space using the experimental data. A few measurements of powdering on selected regions of an automotive stamped part are reported.
Technical Paper

Emissions with E85 and Gasolines in Flexible/Variable Fuel Vehicles - The Auto/Oil Air Quality Improvement Research Program

Exhaust and evaporative emissions from three flexible/variable fuel vehicles (FFV/VFV) were measured as the vehicles operated on E85 fuel (a mixture of 85% ethanol and 15% gasoline) or on gasoline. One vehicle was a production vehicle designed for ethanol fuels and sold in 1992-93 and the other two vehicles were prototypes which were recalibrated 1992 model year methanol FFV's. The gasolines tested were Industry Average Fuel A and a reformulated gasoline Fuel C2 that met California 1996 regulatory requirements. The gasoline component of Fuel E85 was based on the reformulated gasoline. The major findings from this three-vehicle program were that E85 reduced NOx 49% compared to Fuel A and 37% compared to Fuel C2, but increased total toxics 108% (5 mg/mi) and 255% (20 mg/mi), respectively, primarily by increasing acetaldehyde. The NOx effect was significant for both engine-out and tailpipe emissions.
Technical Paper

Reduction of Passenger Car Road Noise Using Computational Analysis

The noise within a car interior affects the customers' perception of quality, hence the need for noise control in cars. The arrival of structural finite element analysis (FEA) and acoustic boundary element analysis (BEA) has created the possibility of quickly performing many computational design changes. Thus, effective noise control solutions can be predicted without many vehicle prototypes. Computational analysis of the passenger compartment of an existing four-door car was performed to predict and reduce road noise. This analysis guided the development of structural changes that would reduce the sound pressure levels at the driver's and rear passenger's ear locations. Laboratory tests of these structural modifications in a prototype vehicle confirmed that the sound levels were reduced.
Technical Paper

U.S. Automotive Corrosion Trends Over the Past Decade

Since 1985, the Body Division of the Automotive Corrosion and Prevention Committee of SAE (ACAP) has conducted biannual surveys of automotive body corrosion in the Detroit area. The purpose of these surveys is to track industry wide corrosion protection improvements and to make this information available for public consumption. The survey consists of a closed car parking lot survey checking for perforations, blisters, and surface rust. This paper reports the results of the five surveys conducted to date.
Technical Paper

Effects of Substrate and Phosphate Type on the Painted Corrosion Performance of Galvanneal Coated Sheet

Galvannealed sheet steel is gaining acceptance by automotive manufacturers due to its combination of properties and cost. Galvanneal can be produced by several processes including the most common method termed the “hot” line hot dip coating process, but also using “flux” line hot dip coating application. Similarly, several types of phosphate coatings: Zn, Zn-Ni, and Zn-Ni-Mn phosphates can be applied to these materials prior to painting to enhance paint adhesion and painted corrosion resistance. This manuscript reports the affects of commercial phosphate type and galvanneal type (based on production method and properties) on the corrosion performance of galvanneal. In addition, painted corrosion performance of galvanneal is compared to painted corrosion performance of electroplated zinc. The manuscript also describes the use of electrochemical methods as one alternative to conventional test methods resulting in substantial time savings.
Technical Paper

Effects of Pretreatment Variables on the Corrosion Performance of Galvanneal

Corrosion resistance has been the major impetus toward increased use of galvanneal and other coated sheet products by the automotive industry. Galvanneal has the additional advantages of good weldability, due to the iron in the coating, and a higher surface porosity which leads to better paint adhesion. The porosity of the galvanneal surface, however, could also lead to reduced cleanability. This paper reports the effects of pretreatment variables on galvanneal phosphatability and resulting painted corrosion performance. The studies showed that the rust preventative oil applied and the alkaline cleaner used to clean samples prior to phosphating had significant effects on carbon residuals after cleaning. The painted corrosion performance of galvanneal panels with various levels of residual carbon showed a much smaller effect within a given cyclic test. The studies also indicated significant differences in performance depending on the type of cyclic test performed.
Technical Paper

Sheet Steel Surface Treatments for Enhanced Formability

Surface friction is an important characteristic which influences the formability of sheet steel products. Numerous friction tests have been developed, and many previous investigations have reported effects of surface characteristics, coatings, lubrication, etc., on formability. Recently, increased attention has been focussed on reducing friction via the application of solid film lubricants or special surface post-treatments such as phosphates, metallics/intermetallics, etc. This paper presents the results of selected laboratory evaluations conducted using a variety of steels and surface treatments. Formability was measured using Limiting Dome Height and Drawbead Simulator friction testing, along with Limiting Draw Ratio testing in one instance. The examples highlight some potential opportunities which may be considered for improving formability in industrial stamping operations.
Technical Paper

Effects of Steel Surface Texture on Appearance After Painting

An extensive investigation was conducted to assess the influence of steel sheet surface finish (i.e. topography or “texture”) on painted surface appearance. Ten sets of steel panels representing a variety of shot blast, EDT, laser, and bright surface textures were painted simultaneously using advanced solvent-based luxury vehicle paint systems. Paint appearance was measured using a relatively new Autospect instrument and also in terms of conventional Distinctness of Reflected Image (DOI). The results are discussed in detail with respect to 1) the influence of different steel surface textures on paint appearance, 2) the evolution of surface topography during painting, and 3) the implications of this work.
Technical Paper

An Experimental Study of In-Cylinder Air Flow in a 3.5L Four-Valve SI Engine by High Speed Flow Visualization and Two-Component LDV Measurement

In-cylinder flows in four-valve SI engines were examined by high frame rate flow visualization and two-component LDV measurement. It is believed that the tumble and swirl motion generated during intake breaks down into small-scale turbulence later in the cycle. The exact nature of this relationship is not well known. However, control of the turbulence offers control of the combustion process. To develop a better physical understanding of the in-cylinder flow, the effects of the cylinder head intake port configuration and the piston geometry were examined. For the present study, a 3.5L, four-valve engine was modified to be mounted on an AVL single cylinder research engine type 520. A quartz cylinder was fabricated for optical access to the in-cylinder flow. Piston rings were replaced by Rulon-LD rings. A Rulon-LD ring is advantageous for the optical access as it requires no lubrication.
Technical Paper

Effects of Gasoline Composition on Evaporative and Running Loss Emissions - Auto/Oil Air Quality Improvement Research Program

Evaporative and running loss emissions were measured in a fleet of ten (1 989) current and seven (1983-85) older vehicles with fuels whose compositions varied in aromatic, olefin, and MTBE content and 90 percent distillation temperature (T9O). Emission compositions from each test were analyzed for individual hydrocarbon species. The individual hydrocarbon profiles were used to calculate evaporative and running loss emission reactivities using Carter maximum incremental reactivity (MIR) and maximum ozone reactivity (MOR) scales. Ozone reactivity estimates were expressed as Ozone Forming Potential (gO3/test) and Specific Reactivity (gO3/gNMOG) for both reactivity scales. The data were analyzed by regression analysis to estimate changes in the mass and reactivity of evaporative emissions due to changes in fuel composition. Previous studies have focused on how fuel volatility affects evaporative emissions without regard for the chemical composition of the fuels.
Technical Paper

Recent Progress in the Development of Forming Limit Curves for Automotive Sheet Steels

Forming Limit Diagrams (FLD) are extensively used in North American press shops during tooling trials and in production for problem identification/resolution. The Keeler-Goodwin FLC shape and the correlation developed by Keeler and Brazier (based on n-value and thickness) have been widely accepted as the Standard FLC Method to predict forming limit curves for commercial steels. In this paper, the Standard FLC Method is reviewed, and an alternative approach used at the authors' laboratory (Bethlehem FLC Method) is described. The two methods are discussed in the context of more recent experimental determinations of FLC's for a variety of “modern” sheet steels including DQSK, Interstitial Free and Bake-Hardening steels, as well as coated sheet products. Some specific press-shop examples are also presented, which further highlight the value to industry of re-examining the Standard FLC Methodology used in circle-grid analysis.
Technical Paper

Dent-Resistant Brake-Hardening Steels for Automotive Outer-Body Applications

Bake-hardening steels are finding increased usage in automotive outer-body applications to achieve an improvement in dent resistance and, in some cases, a sheet thickness reduction as well. This paper reviews (1) bake-hardening specifications and measurements, (2) processing and properties of various types of bake-hardening steels and (3) effects of pre-strain, ambient aging and baking conditions on the hardening response.
Technical Paper

Requirements for Improved Battery Design and Performance

Smaller, hotter engine compartments, increased electrical loads, and stringent customer requirements place ever increasing demands on automotive battery performance. Current battery designs and shortcomings are discussed as well as the necessity for improved designs. Topics also include temperature effects, state of charge, charge efficiency, customer usage and requirements, battery age, and dealership handling practices. Present SAE test procedures are reviewed and new rating requirements are suggested to meet today's vehicle applications. Special dealership programs also reveal various methods to improve performance. In addition, power and thermal management for tomorrow's vehicles is discussed. The supporting documents are compiled from various studies conducted between 1984 and 1988 encompassing over 5,000,000 Chrysler vehicles. The data reflects direct comparisons from the field on a warm versus cold climate basis.
Technical Paper

Plastic Bumper Beam Manufacturing Analysis

The manufacturing analysis of molded plastic parts is described in detail. A PC based program is presented to analyze the material and capital cost. The program listing is included.