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The demand for improved fuel economy in both cars and trucks has emphasized the need for lighter weight components. The application of high strength steel to wheels, both rim and disc, represents a significant opportunity for the automotive industry. This paper discusses the Ranger HSLA wheel program that achieved a 9.7 lbs. per vehicle weight savings relative to a plain carbon steel wheel of the same design. It describes the Ranger wheel specifications, the material selection, the metallurgical considerations of applying HSLA to wheels, and HSLA arc and flash butt welding. The Ranger wheel design and the development of the manufacturing process is discussed, including design modifications to accommodate the lighter gage. The results demonstrate that wheels can be successfully manufactured from low sulfur 60XK HSLA steel in a conventional high volume process (stamped disc and rolled rim) to meet all wheel performance requirements and achieve a significant weight reduction.

The cyclic behavior of single overlap aluminum joints joined through a number of different methods has been investigated using Alcan 5754-O, an alloy that potentially could be used in structural applications. Overlap shear tests of spot welded, clinched and riveted joints are compared on the basis of their fatigue performance. The fatigue response of the spot welded joint was the baseline to which the other fasteners were compared. Test results showed an improvement of approximately 25% for both the mechanical clinch joints and aluminum rivets in fatigue strength at 106 cycles. The most significant improvement in fatigue strength of 100% was found for the self piercing rivets at 106 cycles. The failure behavior of the various joining methods is discussed as well as the surface appearance.

Due to magnesium alloy's poor weldability, other joining techniques such as laser assisted self-piercing rivet (LSPR) are used for joining magnesium alloys. This research investigates the fatigue performance of LSPR for magnesium alloys including AZ31 and AM60. Tensile-shear and coach peel specimens for AZ31 and AM60 were fabricated and tested for understanding joint fatigue performance. A structural stress - life (S-N) method was used to develop the fatigue parameters from load-life test results. In order to validate this approach, test results from multijoint specimens were compared with the predicted fatigue results of these specimens using the structural stress method. The fatigue results predicted using the structural stress method correlate well with the test results.

A new bumper system which provides 8 kph (5 mph) vehicle protection with superior quality, outstanding durability and high value is in production. The system includes five new technologies: Hot stamped, ultra high strength front beam, 970 N/mm2 (160 KSI) which also is the #1 body structure crossmember. Ultra high strength roll formed rear beam 1150 N/mm2 (190 KSI). polypropylene foam isolators designed for controlled energy management Thermoplastic olefin (TPO), injection molded fascias Two component urethane paint for long term color, gloss and scratch resistance. This bumper system, installed on over 100,000 vehicles so far, meets both MPV and passenger car 8 kph standards. Consumer and insurance industry trends indicate increasing demand for Multi Purpose Vehicle (MPV) bumper systems which meet 8 kph criteria. The major competitors in the MPV market (Aerostar, Grand Caravan, Toyota Previa, GM APV's, and Mazda MPV) have either 0 kph or at best 4 kph systems.

In this paper, we introduce a numerically stable 2D computer model for sheet metal forming analysis based on the membrane theory. It simulates both axisymmetrical and plane strain cases with various restraining and friction conditions. We implemented a more realistic material model that accounts for cyclic loading and unloading. Also, the difficult frictional force reversal problem has been overcome. A simulation package released within Ford Motor Company has proven robust and accurate for applications to industrial cases.

The galvanostatic polarization method was used to determine the pitting potentials of candidate wrought aluminum alloys in inhibited ethylene glycol engine coolants. It was shown that the relative value of the pitting potential is an excellent measure of the long-term effectiveness of the coolants in preventing spontaneous pitting and crevice attack in the aluminum heat exchangers. The long-term effectiveness was determined by metallographic examination of aluminum heat exchangers subjected to a four-month, 50,000 mile simulated service circulation test.

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.

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.

Magnesium die-cast alloys are known to have a layered microstructure composed of: (1) An outer skin layer characterized by a refined microstructure that is relatively defect-free; and (2) A “core” (interior) layer with a coarser microstructure having a higher concentration of features such as porosity and externally solidified grains (ESGs). Because of the difference in microstructural features, it has been long suggested that removal of the surface layer by machining could result in reduced mechanical properties in tested tensile samples. To examine the influence of the skin layer on the mechanical properties, a series of round tensile bars of varying diameters were die-cast in a specially-designed mold using the AM60 Mg alloy. A select number of the samples were machined to different final diameters. Subsequently, all of the samples (as-cast as well as machined) were tested in tension.

Sliding door designs are applied to rear side doors on vans and other large vehicles with a trend towards dual sliding doors with power operation. It is beneficial for the vehicle user to reduce the weight of and space occupied by these doors. Alcoa, in conjunction with Ford, has developed a multi-product, multi-material-based solution, which significantly reduces the cost of an aluminum sliding door and provides both consumer delight and stamping-assembly plant benefits. The design was successfully demonstrated through a concept readiness/technology demonstration program.

Using instrumentation designed for the ultrasonic measurement of thickness, a technique has been devised for measuring the isotropic elastic constants of small samples, i. e., samples 1 mm in thickness and a minimum of 5 mm in other dimensions. Young's modulus, the shear modulus and Poisson's ratio are calculated from measurements of density and ultrasonic shear and longitudinal wave velocities. Samples of valve train materials, including chill cast iron, low alloy steel, tool steel, stainless steel, a nickel-base superalloy, and a powder metal alloy were machined from components and analyzed. The magnitude of the measured values of the elastic constants are reasonable when compared with published values. The measurement error on all the constants is estimated to be less than 1%. Moduli determined by this method can be used in finite element analyses to improve designs.

Imposing tensile stress on an edge of a sheet metal blank is a common condition in many sheet metal forming operations, making edge formability a very important factor to consider. Because edge formability varies greatly among different materials, cutting methods (and their control parameters), it is very important to have access to an experimental technique that would allow for quick and reliable evaluation of edge formability for a given case. In this paper, two existing techniques are compared: the hole expansion test and the tensile test. It is shown that the hole expansion test might not be adequate for many cases, and is prone to overestimating the limiting strain, because the burr on the sheared edge is typically smaller than what is observed in production. The tensile test represents an effective alternative to the hole expansion test. Advantages and disadvantages of each case are discussed.

After establishing the performance requirements and initial design assumptions, CAE concept models are used to set targets for major structural components to achieve desirable crash performance. When the designs of these major components become available they are analyzed in detail using nonlinear crash finite element models to evaluate their performance. All these components are assembled together later in a full car model to predict the overall vehicle crash performance. If the analysis shows that the targets are met, the design drawings are released for prototype fabrication. When CAE tools are effectively used, it will reduce product development cycle time and the number of prototypes. Crash analysis methodology has been validated and applied for steel automotive product development. Recently, aluminum is replacing steel for lighter and more fuel efficient automobiles. In general aluminum has quite different performance from steel, in particular with lower ductility.

Dual Phase (DP) high strength steel is widely used in Europe and Japan for automotive component applications, and has recently drawn greater attention in the North American automotive industry for improving crash performance and reducing weight. In comparison with high-strength low-alloy (HSLA) steel grades with similar initial yield strength, DP steel has the following advantages: higher strain hardening, higher energy absorption, higher fatigue strength, higher bake hardenablility, and no yield point elongation. This paper compares the performance of DP and HSLA steel grades before, during, and after hydroforming. Computer simulation results show that DP steel demonstrates more uniform material flow during hydroforming, better crash performance and less wrinkling tendency.

To improve the energy absorption capacity of front-end structures during a vehicle crash, a novel 12-sided cross-section was developed and tested. Computer-aided engineering (CAE) studies showed superior axial crash performance of the 12-sided component over more conventional cross-sections. When produced from advanced high strength steels (AHSS), the 12-sided cross-section offers opportunities for significant mass-savings for crash energy absorbing components such as front or rear rails and crush tips. In this study, physical crash tests and CAE modeling were conducted on tapered 12-sided samples fabricated from AHSS. The effects of crash trigger holes, different steel grades and bake hardening on crash behavior were examined. Crash sensitivity was also studied by using two different part fabrication methods and two crash test methods. The 12-sided components showed regular folding mode and excellent energy absorption capacity in axial crash tests.

The ability to evaluate the bending fatigue behavior of carburized low alloy steels in a laboratory and relate these measurements to performance of high contact ratio helical gears is important to the design and development of transmissions. Typical methods of evaluating bending fatigue performance of carburized gear steels do not directly represent helical planetary gears because they lack the geometric and loading conditions of planetary pinions. The purpose of this study is twofold; 1) development of a lab fatigue test to represent the fatigue performance of planetary pinion gears tested in a dynamometer and 2) evaluation of the influence of alloy content on bending fatigue performance of two steel alloys. The steels under evaluation were modified 8620M and 4615M alloys machined into bend bars with a notch representing a gear root and carburized to a case depth of approximately 0.35 mm (using the same carburizing cycle as the planetary pinion gears).

The effect of temperature and preload on the bolt load retention (BLR) behavior of AZ91D and AE42 magnesium die castings was investigated. The results were compared to those of 380 aluminum die castings. Test temperatures from 125 to 175°C and preloads from 7 to 28 kN were investigated. The loss of preload for AZ91D was more sensitive to temperature than that observed for AE42, especially at low preloads. In general, retained bolt-load was lowest in AZ91D. All test assemblies were preloaded at room temperature and load levels increased when the assemblies reached test temperature. The load-increase was dependent on the preload level, test temperature, alloy, and results from thermal expansion mismatch between the steel bolt and the magnesium alloy components, mitigated by the onset of primary creep. Thermal exposure (aging) of AZ91D at 150°C improved BLR behavior.

New high-temperature Mg alloys are being considered to replace 380 Al in transmission cases, wherein bolt-load retention, and creep, is of prime concern. One of these alloys is die cast AE42, which has much better creep properties than does AZ91D but is still not as creep resistant as 380 Al. It is thus important to investigate bolt-load retention and creep of AE42 as an initial step in assessing its suitability as a material for transmission housings. To that end, the bolt-load retention behavior of die-cast AE42, AZ91D and 380 Al have been examined using standard M10 bolts specially instrumented with stable high-temperature strain gages. The bolt-load retention test pieces were die cast in geometries approximating the flange and boss regions in typical bolted joints. Bolt-load retention properties were examined as a function of time (at least 100 hours), temperature (150 and 175 °C) and initial bolt preload (14 to 34 kN).

This paper presents the design and operation of a new stepped bore master cylinder (fast-fill) which also integrates the rear brake proportioning valves and brake failure warning device in one major assembly. This design optimizes weight, performance and package together with several unique design features. It incorporates a combination of a plastic reservoir, permanent mold aluminum body, steel pistons, and minaturized steel proportioning valves resulting in a significant weight and cost reduction versus equivalent hydraulic actuation systems.

All automotive brake linings have mechanical strength and thermal expansion properties which vary with orientation. This paper describes laboratory equipment and test procedures which characterize lining strength and expansion behavior, using small specimens. A benchtop testing device is introduced which can be used to perform shear and tensile tests on lining samples and singly-riveted lining assemblies. Results are presented for a representative group of production and experimental linings. Applications are discussed.