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Technical Paper

A New Tool for Corrosion Inhibitor Research

2001-03-05
2001-01-1176
Electrochemical techniques such as repassivation potential measurements and electrochemical impedance spectroscopy (EIS) have become important tools in corrosion and corrosion inhibitor research. However, these techniques reflect the response of the total surface area of the exposed sample and cannot distinguish between types of localized corrosion e.g. pitting or crevice corrosion. Current density mapping (CDM) is a technique that uses a fine stainless steel needle, vibrating at a set frequency and scans over the surface of a sample in a plane micrometers above the sample surface. By mapping the current distribution over a surface, sites of localized corrosion can be characterized and the effect of a corrosion inhibitor monitored.
Technical Paper

Aluminum Rail Rivet and Steel Rail Weld DOE and CAE Studies for NVH

2001-04-30
2001-01-1608
Vehicle body with aluminum riveted construction instead of steel welded one will be a big challenge to NVH. In this paper, aluminum and steel rails with the dimensions similar to the rear rail portion of a typical mid-size sedan were fabricated. Rivets were used to assemble the aluminum rails while welds were used to assemble the steel rails. Adhesive, rivet/weld spacing, and rivet/weld location were the three major factors to be studied and their impact on NVH were investigated. The DOE matrix was developed using these three major factors. Modal tests were performed on those rails according to the DOE matrix. The FEA models corresponding to the hardware were built. CAE modal analysis were performed and compared with test data. The current in-house CAE modeling techniques for spot weld and adhesive were evaluated and validated with test data.
Technical Paper

Laminate Dash Ford Taurus Noise and Vibration Performance

2001-04-30
2001-01-1535
Mastic material, constrained or non-constrained with doublers, is the traditional method in adding vibrational damping to a steel structure with the goal of reducing panel vibration and radiated sound. With the use of laminated vibration damped steel (LVDS), Ford has been able to reduce the dash panel vibration and optimize sound package design for powertrain noise attenuation. These NVH benefits are presented as the result of a study completed with a laminated dash on a Ford Taurus.
Technical Paper

Oil Quality with Oil Age in an IDI Diesel Passenger Car Using an On Line Lubricating Oil Recycler Under Real World Driving

2001-05-07
2001-01-1898
A method of cleaning lubricating oil on line was investigated using a fine 1 micron bypass particulate filter, followed by an infra-red heater to remove water and light diesel fractions in the oil. A Ford 1.8 litre IDI diesel passenger car was investigated under real world driving conditions. Comparison was made with the oil quality without the recycler. All the tests were carried out on the same vehicle over 7000 miles with and without the recycler. The results showed that the on line oil recycler cleaning system reduced the rate of reduction of TBN and the rate of increase of TAN by 54% and 50% respectively. The reduction in the rate of carbon accumulation in the oil was 42%. There was also a reduction in fuel dilution. All the wear metals in the oil were greatly reduced by the recycler, the iron was reduced by 76%, the lead was reduced by 85% and the aluminum was totally removed.
Technical Paper

Wheel disk manufacture using Nb-bearing TRIP steels

2000-06-12
2000-05-0285
TRIP (TRansformation Induced Plasticity) steels have been studied frequently because of its superior strength and ductility. The high values of tensile strength and elongation are mainly attributed to the strain induce martensite transformation (SIMT) phenomena of retained austenite. Because of the excellent tensile property combination, TRIP steels have many advantages when the steels are used for automotive applications. To produce as-hot-rolled TRIP steels with better microstructure and mechanical properties, an appropriate chemical composition together with the exact control of cooling in run-out table is major parameter. A 3-step cooling pattern in run-out table (ROT) should be employed to secure sufficient amount of ferrite and resultant carbon enrichment in untransformed austenite. Effective carbon enrichment in untransformed austenite is very important to increase stability of austenite in lower temperature region.
Technical Paper

Trend toward weight reduction of automobile body in Japan

2000-06-12
2000-05-0240
With society demanding automobiles that provide higher fuel efficiency, safety of occupants in collisions and that at the end of their service life can be recycled with low environmental impact, the steel industry is tackling the needs of the automobile industry by developing ever-higher performance steel materials and simulation technologies that can demonstrate the performance of steel materials at the development stage without the need for costly prototype testing. In this paper, weight reduction of automobile body in Japan will be discussed. The main items will be as follows: (1) Development of Automobile Steel Sheets, (2) Materials for Automobile Bodies, (3) Materials and Technologies (Tailored Blanks, Hydroforming and Locally Quenching) for Reducing the Weight of Panels and Reinforcing members, (4) Future Prospects.
Technical Paper

Development of Application Technique of Aluminum Sandwich Sheets for Automotive Hood

2000-06-12
2000-05-0237
Objective of this study was to develop basic techniques in order to apply aluminum sandwich sheets for an automotive hood part. The aluminum sandwich sheet is the material fabricated by adhering two aluminum skins to one polypropylene core. When it has the same bending stiffness as a steel sheet, it is 65% lighter than the steel sheet and 30% lighter than an aluminum alloy sheet. Therefore, it is notified exclusively as good substitutive materials for a steel body to improve the fuel efficiency. Through aluminum sandwich sheet, however, it has relatively lower formability than that of the steel sheet for automotive application. In this study, we fabricated a prototype of the automotive hood panel to develop application techniques of the aluminum sandwich sheet.
Technical Paper

Fatigue Analysis of Spot Welds Subjected to a Variable Amplitude Loading History

2001-03-05
2001-01-0435
A multiaxial spot weld damage parameter and a basic load-life approach are applied to proportional shear and peel loading for a standard SAE variable amplitude loading history. Miner's rule and the rainflow cycle counting method are used to calculate fatigue damage using constant amplitude load-life test data for various ratios of the combined loading. The calculations are compared to test results for an HSLA galv-annealed sheet steel obtained by using the DaimlerChrysler Spot Weld Design Committee multiaxial spot weld test fixture. The applicability of the methods are discussed, as are the crack initiation and propagation behavior of the specimens.
Technical Paper

Side Impact Airbag Testing and Regulation:Deflating a Potentially Explosive Topic

2001-03-05
2001-01-1331
America has been in love with the automobile since the first motorized carriages shared the road with horses. At first this new technology was a pastime for the rich. It was a privilege that was enjoyed by the upper classes of society on weekends and sunny days. As methods of mass production became refined and more economical, the automobile became so commonplace that one would expect to find one in every backyard. Through a depression, world war and a post-war economic and population boom, the automobile helped shape American life we can all identify with today. To date the automotive industry has gone through many changes, modifications and has reinvented itself several times. Transitions in the auto industry and consumer demand have brought the majority of automobiles from giant, gas-guzzling hunks of steel to lightweight, fuel-efficient modes of transportation (taking into exception the ever-present SUV - which shall be mentioned later).
Technical Paper

“Bump Test” of Wet Friction Materials: Modeling and Experiments

2001-03-05
2001-01-1154
In one of the fatigue tests for wet friction materials, “bump test”, an inertia-type rig equipped with a multi-disk assembly is used. One of the steel disks in the assembly has radial bumps for the purpose of creating high local contact pressure and high temperature. Due to the severe contact conditions, a comparative testing for different friction materials can be conducted within a relatively small number of cycles. In the paper, a design of a “bump” assembly used for automotive wet friction materials is described. Based on both experimental tests and advanced contact modeling, non-uniform contact pressure generated by the bumps and resulting temperature are estimated. The computational model is used then to study the influence of the modulus of elasticity of the friction material and reaction plate thickness on the contact conditions. The bump fatigue tests lead ultimately to material failure.
Technical Paper

Development of High Corrosion Resistant Stainless Steels for Automotive Mufflers Based on Condensate Corrosion Test and Field Investigation

2001-03-05
2001-01-0640
Automotive exhaust gas condensate causes severe corrosion inside mufflers. Corrosive condensate became a problem following the introduction of three-way catalytic converters in exhaust systems. The authors previously established a new laboratory test method that simulates condensate corrosion. This test method contributed to the development of new stainless steels for automotive mufflers. The addition of molybdenum (Mo) and copper (Cu) to ferritic stainless steels was found to be effective in improving condensate corrosion resistance, and the effect was arranged using the index [%chromium (Cr)+3×%Mo+1.5×%Cu]. A field test was carried out to investigate the corrosion behavior of mufflers under actual conditions. Aluminized steels showed severe damage by general corrosion. On the other hand, 19%Cr-Cu ferritic stainless steel exhibited excellent corrosion resistance. The corrosion behavior in the field test showed good agreement with the results of the laboratory test.
Technical Paper

Thin Walled Steel Tube Pre-Bending for Hydroformed Components - Bending Boundaries and Presentation of a New Mandrel Design

2001-03-05
2001-01-0642
For auto-body structures, thin walled hydroformed and laser beam welded hollow steel sheet sections are recommended as a replacement for mainly spot-welded box-shape components. Such components have the same strength but a lighter weight. Pre-bending into the required shape prior to the hydroforming step is difficult to realize in the case of thin wall thicknesses in combination with small bending diameters and relatively large tube diameters. There are bending limits with respect to buckling or cracking which have still to be clearly defined. The boundaries for the cold rotary draw bending process are fixed in the so called “bending diagram”. This diagram in itself is insufficient. Based on simple equations in combination with numerical calculations, an analytical equation was drawn up to better define the boundary conditions. This also takes into account the influence of the material.
Technical Paper

A Vehicle Micro Corrosion Environmental Study of Field and Proving Ground Tests

2001-03-05
2001-01-0646
This paper presents the progress of an ongoing vehicle micro corrosion environment study. The goal of the study is to develop an improved method for estimating vehicle corrosion based on the Total Vehicle Accelerated Corrosion Test at the Arizona Proving Ground (APG). Although the APG test greatly accelerates vehicle corrosion compared to the field, the “acceleration factor” varies considerably from site-to-site around the vehicle. This method accounts for the difference in corrosivity of various local corrosion environments from site-to-site at APG and in the field. Correlations of vehicle microenvironments with the macroenvironment (weather) and the occurrence of various environmental conditions at microenvironments are essential to the study. A comparison of results from APG versus field measurements generated using a cold rolled steel based corrosion sensor is presented.
Technical Paper

Development of Pitting Resistant Steel for Transmission Gears

2001-03-05
2001-01-0827
It was found that pitting resistance of gears is strongly influenced by resistance to temper softening of carburized steel. The investigation about the influence of chemical compositions on hardness after tempering revealed that silicon, chromium and molybdenum are effective elements to improve resistance to temper softening and pitting resistance. Considering the production of gears, molybdenum is unfavorable because it increases hardness of normalized or annealed condition. Developed new steel contains about 0.5 mass% of silicon and 2.7 mass% chromium. The new steel has excellent pitting resistance and wear resistance. Fatigue and impact strength are equivalent to conventional carburized steels. Cold-formability and machinability of the new steel are adequate for manufacturing gears because of its ordinary hardness before carburizing. The new steel has already been put to practical use in automatic transmission gears. Application test results are also reported.
Technical Paper

Design Tool on Fatigue for 3D Components With Consideration of Residual Stresses

2001-03-05
2001-01-0828
This paper presents a fatigue design tool for three dimensional components with taking the residual stresses into account. The residual stresses are present in many mechanical components and play an important role in the fatigue problem of structure. By using the cyclic behaviors of material, a simplified method to calculate residual stress relaxation has been proposed in the first part of this paper. Secondly, a method to predict fatigue life with taking the stabilized residual stresses into account is presented. This design tool is based on the finite element method. It has been applied to shot-peened 35NCD16 grade steel. The different fatigue parameters often used in material research are studied. An experimental investigation about this material had been done by Bignonnet[1]. The results of study show that this design tool on fatigue developed by LASMIS[2] is able to take into account different loading parameters.
Technical Paper

High Frequency Fatigue Crack Propagation Behavior of a Spheroidal Graphite Cast Iron

2001-03-05
2001-01-0831
Owing to the combination of high strength and good ductility, spheroidal graphite cast iron (SGI) has been widely used in the automotive industry. The application of the damage-tolerance design approach to the mechanical parts subjected to high frequency vibration loading necessitates a more reliable determination of crack propagation threshold. In this study, the fatigue crack propagation behavior of a SGI (ferrite in matrix with about 5% pearlite) was investigated experimentally at a frequency of 20 kHz and the stress ratio of R=-1 and R=0.1. The propagation threshold was determined at a very slow rate of 10-11 m/cycle. The results of these tests have been compared with those of conventional fatigue test. Effects of cyclic loading frequency have been discussed. It is shown that the threshold stress intensity value is smaller at ultrasonic frequency. The observations of the fracture surface at SEM show that there is less oxidation at very high frequency in all propagation regimes.
Technical Paper

Improvement of Fatigue Strength of Nitrided High-Strength Valve Springs by Application of a New Super Fine Shot-Peening Technology

2001-03-05
2001-01-0834
The peening of fine steel beads with diameters less than 80μm (referred to as SS Treatment in this paper) on the surface of nitrided and then conventionally shot-peened (with 0.6mm diameter cut steel wires) high-strength helical springs made from developed high strength valve spring wire, was found to effectively improve spring fatigue strength. This improved fatigue strength is mainly the result of very high compressive residual stress caused by work hardening of the spring surface layer without inducing deleterious surface qualities such as harmful surface micro-fissuring or surface roughness.
Technical Paper

A Computational Methodology for Fatigue Life Prediction Under Multiaxial Non-Proportional Loading

2001-03-05
2001-01-0837
A methodology for predicting the fatigue initiation life in metals experiencing multiaxial non-proportional loading is presented. The methodology utilizes nonlinear finite-element analysis to determine the stress distribution of the loaded component. This distribution is used in conjunction with a physically based damage law to determine the cycles to failure. The damage law is based on the fatigue prediction method introduced by Dang Van [1], and further developed by Papadopoulos [2] and Morel [3]. The fatigue damage initiation is treated as the persistent crystalline slip phenomenon taking place on the order of a grain or few grains. The damage variable is chosen to be the accumulated plastic strain at this scale. The initiation life is determined when the damage variable reaches a critical value. The developed methodology is applicable to both in-phase and out-of-phase loading, without any empirical adjustment parameter.
Technical Paper

Review of CAE Fatigue Analysis Techniques for Spot-Welded High Strength Steel Automotive Structures

2001-03-05
2001-01-0835
Durability assessment of automotive structures with resistance spot welds is an important part of automotive development. Down-gauging of vehicle body structures permitted by high strength steels brings added challenges to joint design. As a result, more accurate fatigue life analysis of joints is called for by automotive engineers, especially as part of the computer-aided engineering (CAE) evaluations in the early stage of model development. This paper will review, evaluate and compare spot-weld fatigue assessment techniques suitable for use in the CAE environment. Particular attention is paid to the process of generating technique-specific spot-weld fatigue property curves. The focus is then switched to two of the most promising techniques, which are evaluated in detail. The validity of the two techniques and the associated fatigue data are then demonstrated on fatigue life predictions of simple and complex components.
Technical Paper

Development of Tooling for a Light Weight Steel Kühl Wheel

2001-03-05
2001-01-0750
Kühl Wheels utilize a system of offset, sheet steel spokes to form the structure between hub and rim. This allows a wheel with adequate strength to sustain radial, cornering and torque loads while providing weight as well as styling advantages. Initial development of welded prototype wheels is described, including laboratory and field test results. The development of a single piece, steel, stamped wheel center based on the early prototypes is described. Critical aspects of the design are shown and geometric requirements are discussed. Wheel model analyses carried out by finite element methods are presented. Development of tooling and ultimately stamped prototypes is discussed and shown. Finally, test results from wheels assembled from the stamped wheel centers are presented and compared with the analytical predictions.
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