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This study concerns a dissimilar materials joining technique for aluminum (Al) alloys and steel for the purpose of reducing the vehicle body weight. The tough oxide layer on the Al alloy surface and the ability to control the Fe-Al intermetallic compound (IMC) thickness are issues that have so far complicated the joining of Al alloys and steel. Removing the oxide layer has required a high heat input, resulting in the formation of a thick Fe-Al IMC layer at the joint interface, making it impossible to obtain satisfactory joint strength. To avoid that problem, we propose a unique joining concept that removes the oxide layer at low temperature by using the eutectic reaction between Al in the Al alloy and zinc (Zn) in the coating on galvanized steel (GI) and galvannealed steel (GA). This makes it possible to form a thin, uniform Fe-Al IMC layer at the joint interface. Welded joints of dissimilar materials require anticorrosion performance against electrochemical corrosion.

The ways in which vehicles are used in the field are continually becoming more diverse. In order to provide the optimum solution with respect to performance and weight, it is necessary to be able to assure vehicle endurance reliability with a high degree of accuracy in relation to the manner of use in each market. This situation has increased the importance of accurately quantifying the ways in which vehicles are used in the field and of designing vehicles with sufficient endurance reliability to match the usage requirements. This report presents a “market model” by which the manner of usage in the field can be treated quantitatively using combinations of environmental factors that influence the road load, drive load and corrosion load, representing typical loads vehicles must withstand.

The life of automotive transmission gears today is often governed by pitting fatigue life. Being able to predict pitting fatigue life accurately is a crucial issue. Pitting fatigue life is substantially influenced by surface hardness and tooth surface geometry. For that reason, this study examined a new method of predicting pitting fatigue life that takes into account changes in these factors over time. This method makes it possible to predict the pitting fatigue life of automotive transmission gears under a wide range of evaluation conditions with markedly better accuracy than conventional methods used previously.

Since 2000, an Aluminum Cosmetic Corrosion task group within the SAE Automotive Corrosion and Protection (ACAP) Committee has existed. The task group has pursued the goal of establishing a standard test method for in-laboratory cosmetic corrosion evaluations of finished aluminum auto body panels. A cooperative program uniting OEM, supplier, and consultants has been created and has been supported in part by USAMP (AMD 309) and the U.S. Department of Energy. Prior to this committee's formation, numerous laboratory corrosion test environments have been used to evaluate the performance of painted aluminum closure panels. However, correlations between these laboratory test results and in-service performance have not been established. Thus, the primary objective of this task group's project was to identify an accelerated laboratory test method that correlates well with in-service performance.

There is an increasing global realization about the need for fuel efficient vehicles. An inexpensive way to accomplish this is through mass reduction, and one of the most effective ways that this can occur is through substituting current materials with magnesium, the lightest structural metal. This document describes the results of a U.S. Automotive Materials Partnership (USAMP) sponsored study [1] that examines why magnesium use has only grown 10% per year and identifies how to promote more widespread commercial applications beyond the 5-6 kg of component currently in vehicles. The issues and concerns which have limited magnesium use are discussed via a series of research and development themes. These address concerns associated with corrosion, fastening, and minimal metalworking/non-traditional casting processing. The automotive and magnesium supplier industries have only a limited ability to develop implementation-ready magnesium components.

The equipment for collecting dilute exhaust samples involves the use of bag materials (i.e., Tedlar®) that emit hydrocarbons that contaminate samples. This study identifies a list of materials and treatments to produce bags that reduce contamination. Based on the average emission rates, baked Tedlar®, Capran® treated with alumina deposition, supercritical CO2 extracted Kynar® and supercritical CO2 extracted Teflon NXT are capable of achieving the target hydrocarbon emission rate of less than 15 ppbC per 30 minutes. CO2 permeation tests were also performed. Tedlar, Capran, Kynar and Teflon NXT showed comparable average permeation rates. Based on the criteria of HC emission performance, changes in measured CO2 concentration, ease of sealing, and ease of surface treatment, none of the four materials could be distinguished from one another.

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.

The International Lubricant Standardization and Approval Committee (ILSAC) ATF subcommittee members have compared the two oxidation bench test methods, Aluminum Beaker Oxidation Test (ABOT) and Indiana Stirring Oxidation Stability Test (ISOT), using a number of factory-fill and service-fill ATFs obtained in Japan and in the US. In many cases, the ATFs were more severely oxidized after the ABOT procedure than after the same duration of the ISOT procedure. The relative severity of these two tests was influenced by the composition of the ATFs. The bench test oxidation data were compared with the transmission and the vehicle oxidation test data.

The Automotive Aluminum Alliance in conjunction with SAE ACAP founded a corrosion task group in 2000 with a goal to establish an in-laboratory cosmetic corrosion test for finished aluminum auto body panels, which provides a good correlation with in-service performance. Development of this test involves a number of key steps that include: (1) Establishing a reservoir of standard test materials to provide a well-defined and consistent frame of reference for comparing test results; (2) Defining a real-world performance for the reference materials through on-vehicle tests conducted in the U.S. and Canada; (3) Evaluating existing laboratory, proving ground, and outdoor tests; (4) Conducting statistically designed experiments to evaluate the effects of cyclic-test variables; (5) Comparing corrosion mechanisms of laboratory and on-vehicle tests; and (6) Conducting a round robin test program to determine the precision of the new test. Several of these key steps have been accomplished.

The effects of lubricant oil and fuel properties on low speed pre-ignition (LSPI) occurrence in boosted S.I. engines were experimentally evaluated with multi-cylinder engine and de-correlated oil and fuel matrices. Further, the auto-ignitability of fuel spray droplets and evaporated homogeneous fuel/oil mixtures were evaluated in a combustion bomb and pressure differential scanning calorimetry (PDSC) tests to analyze the fundamental ignition process. The work investigated the effect of engine conditions, fuel volatility and various lubricant additives on LSPI occurrence. The results support the validity of aspects of the LSPI mechanism hypothesis based on the phenomenon of droplets of lubricant oil/fuel mixture (caused by adhesion of fuel spray on the liner wall) flying into the chamber and autoigniting before spark ignition.

Surface roughness of steel sheet for automotive use is one of the most important control items, because the surface roughness influences image clarity of painted surface, press formability and easiness in handling during manufacturing and processing of steel sheets. Laser texturing technology is introduced into a roll finishing process of cold rolling, and new type of regular surface roughness profile can be processed on the surface of steel sheets. Effective application method of this technology is investigated at the present day. In Japan, Laser-textured dull steel sheets are used for outer-panels of automotive body as the first application. And image clarity after painting of outer panels has been successful in improving. Nowadays, Laser texturing technology is actually used for manufacturing the high image clarity steel sheets, and they are manufactured in large quantities. Another application of Laser texturing technology is for the inner parts which require pressformability.

As automobile power needs increase 42-volt electrical systems are being proposed for use in consumer vehicles. One concern when using these new systems is the corrosion resistance of these components, especially in underhood environments. Corrosion is an electrochemical phenomenon and as such can be altered (increased or decreased) by the application of an external current or voltage. Although unintentional, the use of a higher voltage electrical system has the ability to increase corrosion through its normal use. This program evaluated the impact of corrosion on electrical components powered by 14 and 42-volt DC systems. Accelerated corrosion test findings suggested that 42-volt systems may be more susceptible to corrosion, but without proper environmental shielding both supply system can have unacceptable degradation.

The application of both high strength gear steels and shot peening technology has succeeded in strengthening automotive transmission gears. This technology, though, improves mainly the fatigue strength at the tooth root, but not the pitting property at the tooth face. Therefore, demand has moved to the development of new gear steels with good pitting resistance. In order to improve pitting resistance, the authors studied super carburizing which is characterized by carbide dispersion in the case, especially processed with a plasma carburizing furnace. Firstly, the influence of the carburizing temperature and carburizing period on the carbide morphology was investigated and the optimum carburizing conditions were determined. Secondly, the fatigue strength and pitting resistance was evaluated using carbide dispersed specimens.

Durability requirements for exhaust materials have resulted in the increased use of stainless steels throughout the exhaust system. The conversion of carbon steel exhaust flanges to stainless steel has occurred on many vehicles. Ferritic stainless steels are commonly used for exhaust flanges. Flange construction methods include stamped sheet steel, thick plate flanges and powder metal designs. Flange material selection criteria may include strength, oxidation resistance, weldability and cold temperature impact resistance. Flange geometry considerations include desired stiffness criteria, flange rotation, gasket/sealing technique and vehicle packaging. Both the material selection and flange geometry are considered in terms of meeting the desired durability and cost. The cyclic oxidation performance of the material is a key consideration when selecting flange materials.

General Motor's Corvette product engineering was given the challenge to find mass reduction opportunities on the painted body panels of the C6 Z06 through the utilization of carbon fiber reinforced composites (CFRC). The successful implementation of a carbon fiber hood on the 2004 C5 Commemorative Edition Z06 Corvette was the springboard for Corvette Team's appetite for a more extensive application of CFRC on the C6 Z06 model. Fenders were identified as the best application for the technology given their location on the front of the vehicle and the amount of mass saved. The C6 Z06 CFRC fenders provide 6kg reduction of vehicle mass as compared to the smaller RRIM fenders used on the Coupe and Convertible models.

A co-operative program initiated by the Automotive Aluminum Alliance and supported by USAMP continues to pursue the goal of establishing an in-laboratory cosmetic corrosion test for finished aluminum auto body panels that provides a good correlation with in-service performance. The program is organized as a task group within the SAE Automotive Corrosion and Protection (ACAP) Committee. Initially a large reservoir of test materials was established to provide a well-defined and consistent specimen supply for comparing test results. A series of laboratory procedures have been conducted on triplicate samples at separate labs in order to evaluate the reproducibility of the various lab tests. Exposures at OEM test tracks have also been conducted and results of the proving ground tests have been compared to the results in the laboratory tests. Outdoor tests and on-vehicle tests are also in progress. An optical imaging technique is being utilized for evaluation of the corrosion.

Various heat resistant alloys are being introduced for use in automobile emission equipment, such as thermal reactors and catalytic converters. For the past several years Japan has been developing alloys which emphasize oxidation resistance. Therefore, oxidation phenomena have been thoroughly researched and clarified. On the other hand, embrittlement, which is a marked deterioration similar to oxide deterioration, has not been studied sufficiently. The major subjects of investigation were the two forms of embrittlement in austenitic heat resistant alloys, caused by the precipitation of σ phase and the absorption of Nitrogen. Useful information was obtained from these results.

Excellent fuel economy and high performance have been urgent in Japanese automobile industries. With increasing engine power, many of the power train components have to withstand higher loads. Differential pinion gear being one of those highly stressed parts, excellent fatigue and shock resistance have been demanded. At first the fundamental study on the fatigue and impact crack behavior of carburized components was studied and the new grade composed of 0.18%C-0.7%Mn-1.0%Cr-0.4%Mo was alloy designed. Furthermore, Si and P is reduced less than 0.15 and 0.015%, respectively aiming at the reduction of intergranular oxidation and improved case toughness. The differential gear assembly test has proved that the new grade shows three times as high impact strength as that of conventional steel, SCM418, and almost the same as that of SNCM420 containing 1.8%Ni.

Japan Automobile Standards Organization (JASO) Engine Oil Sub-committee have been working on the unification of the engine oil evaluation test procedures in Japan. The Engine Oil Sub-committee participated in the recent activity of the worldwide engine oil standardization of SAE and ISO. As one of the chain of activities, JASO tests M328, M331, and M333 (valve train wear, detergency and high temperature oxidation respectively) were conducted on the REOs of ASTM and CEC to find the correlation. The detergency tests (varnish and sludge) showed good correlation with the ASTM REOs. CEC good and poor reference oils seemed to give good results in JASO valve train wear test, while ASTM reference oils unexpectedly gave opposite results in Japanese valve train wear tests.

Nissan’s variable compression turbo (VC-Turbo) engine has a multilink mechanism that continuously adjusts the top and bottom dead centers of the piston to change the compression ratio and achieve both fuel economy and high power performance. Increasing the exhaust gas recirculation (EGR) rate is an effective way to further reduce the fuel consumption, although this increases the exhaust gas condensation in the cylinder bores, causing a more corrosive environment. When the EGR rate is increased in a VC-Turbo engine, the combined effect of piston sliding and exhaust gas condensation at the top dead center accelerates the corrosive wear of the thermal spray coating. Stainless steel coating is used to improve the corrosion resistance, but the adhesion strength between the coating and the cylinder bores is reduced.