Search Results

With the increasing demand for fuel efficient vehicles, technologies like superplastic forming (SPF) are being developed and implemented to allow for the utilization of lightweight automotive sheet materials. While forming under superplastic conditions leads to increased formability in lightweight alloys, such as aluminum, the slower forming times required by the technology can limit the technology to low to mid production levels. One problem that can increase forming time is the reduction of forming pressure due to pressurizing (forming) gas leaks, during the forming cycle, at the die/sheet/blankholder interface. Traditionally, such leaks have been successfully addressed through the use of a seal bead. However, for advanced die technologies that result in reduced cycle times (such as hot draw mechanical performing, which combine aspects of mechanical preforming of the sheet metal followed by SPF), the use of seal beads can restrict the drawing of sheet material into the forming die.

Innovations in mobility are built upon a management of complex interactions between sub-systems and components. A need for CAE tools that are capable of system simulations is well recognized, as evidenced by a growing number of commercial packages. However impressive they are, the predictability of such simulations still rests on the representation of the base components. Among them, a wet clutch actuator continues to play a critical role in the next generation propulsion systems. It converts hydraulic pressure to mechanical force to control torque transmitted through a clutch pack. The actuator is typically modeled as a hydraulic piston opposed by a mechanical spring. Because the piston slides over a seal, some models have a framework to account for seal friction. However, there are few contributions to the literature that describe the effects of seals on clutch actuator behaviors.

Failure mode and fatigue behavior of flow drill screw (FDS) joints in lap-shear specimens of aluminum 6082-T6 sheets made with different processing conditions are investigated based on the experimental results and a structural stress fatigue life estimation model. Lap-shear specimens with FDS joints without clearance hole and lap-shear specimens with stripped FDS joints with clearance hole were made and then tested under quasi-static and cyclic loading conditions. Optical micrographs show the failure modes of the FDS joints without clearance hole (with gap) and the stripped FDS joints with clearance hole under quasi-static and cyclic loading conditions. The fatigue failure mode of the FDS joints without clearance hole (with gap) in lap-shear specimens is similar to those with clearance hole. The fatigue lives of lap-shear specimens with FDS joints without clearance hole are lower than those with clearance hole for given load ranges under cyclic loading conditions.

High-strength aluminum alloys such as 7075 can be formed using advanced manufacturing methods such as hot stamping. Hot stamping utilizes an elevated temperature blank and the high pressure stamping contact of the forming die to simultaneously quench and form the sheet. However, changes in the thermal history induced by hot stamping may increase this alloy’s stress corrosion cracking (SCC) susceptibility, a common corrosion concern of 7000 series alloys. This work applied the breaking load method for SCC evaluation of hot stamped AA7075-T6 B-pillar panels that had been artificially aged by two different artificial aging practices (one-step and two-step). The breaking load strength of the specimens provided quantitative data that was used to compare the effects of tensile load, duration, alloy, and heat treatment on SCC behavior.

In this investigation, spot friction welds in aluminum 6111-T4 lap-shear specimens were tested under both quasi-static and dynamic loading conditions. Micrographs of the spot friction welds after testing were examined to understand the failure modes of spot friction welds in lap-shear specimens under different loading conditions. The micrographs indicate that the spot friction welds produced by this particular set of welding parameters failed in interfacial failure mode under both quasi-static and dynamic loading conditions. The load and displacement histories for lap-shear specimens were obtained under quasi-static and dynamic loading conditions at three different impact velocities. The failure loads of spot friction welds in lap-shear specimens under dynamic loading conditions are about 7% larger than those under quasi-static loading conditions.

Macroscopic constitutive behaviors of aluminum 5052-H38 honeycombs under dynamic inclined loads with respect to the out-of-plane direction are investigated by experiments. The results of the dynamic crush tests indicate that as the impact velocity increases, the normal crush strength increases and the shear strength remains nearly the same for a fixed ratio of the normal to shear displacement rate. The experimental results suggest that the macroscopic yield surface of the honeycomb specimens as a function of the impact velocity under the given dynamic inclined loads is not governed by the isotropic hardening rule of the classical plasticity theory. As the impact velocity increases, the shape of the macroscopic yield surface changes, or more specifically, the curvature of the yield surface increases near the pure compression state.

The effects of lubricant on lap shear strength of Spot Friction Welded (SFW) joints made of 6111-T4 alloys were studied. Taguchi L8 design of experiment methodology was used to determine the lubricant effects. The results showed that the lap shear strength increased by 9.9% when the lubricant was present at the top surface compared to that of the baseline (no lubricant) whereas the lap shear strength reduced by 10.2% and 10.9% when the lubricant was present in the middle and at the bottom surfaces compared to that of the baseline (no lubricant), respectively. The microstructure analysis showed a zigzag interface at the joint between the upper and the lower sheet metal for the baseline specimen, the specimens with the lubricant at the top and at the bottom. However, a straight line interface is exhibited at the joint between the upper and the lower sheet for the specimen with the lubricant in the middle. The weld nugget sizes of the lap shear tested specimens were measured.

This study compared laser and fine plasma technology for cutting typical electro-galvanized steel and aluminum automotive stampings. Comparisons were made of various aspects of cut quality, accuracy, disturbance of parent material, cycle time, and capital and operating costs. A sensitivity analysis was included to determine how different scenarios would impact the operating costs. It was found that both processes were capable of high quality cuts at 3800mm/min. Capital savings were achievable through the fine plasma system, but careful consideration of the specific application was essential. This work will allow for an advised comparison of options for sheet metal flexible cutting.

As-cast or as-solution treated cast aluminum A319 has copper solutions within its aluminum dendrite. These copper solutions precipitate out to form Al2Cu through a sequence of phase changes and bring with them volume changes at elevated temperatures. These volume changes, referred to as thermal growth are irreversible. The magnitude of thermal growth at a material point is decided by the temperature history of the material point. When an under aged or non heat treated cast aluminum is exposed to non-uniform temperature such as that during engine operation, thermal growth leads to non-uniform volume change and thus additional self balanced stresses. These stresses remain inside material as residual stresses even when the temperature of the material is uniform again. In the present paper, numerical analysis method for thermal growth is developed and integrated into engine operation analysis.

The traditional moveable glass window seal development process has relied heavily on physical prototypes for design verification. Due to frequent styling changes and an overall reduction in design time, physical prototypes for the glass window seals have proven to be inadequate. Utilization of computer aided engineering (CAE) tools is necessary in order to shorten lead time. CAE tools will help to decrease expensive prototyping, free up valuable manufacturing line time, and improve overall quality. A cross functional approach has been applied to expand the scope beyond traditional methods of moveable glass window seal design, such as wedged boarding, into new computerized modeling methods. The CAE was used to address major requirements of the glass window seals including glass velocity, glass stall force, sealing-ability, seal durability, seal assembly, seal appearance, and regulator motor current.

While SAE double inverted flares have been in use for decades, leaking joints continue to be a problem for OEMs in production settings consuming time and energy to detect and correct them before releasing vehicles from the assembly plant. It should be noted that this issue is limited to first-time vehicle assembly; once a flared brake tube joint is sealed at the assembly plant it remains sealed during normal customer usage. From their inception through the late 1980s most brake tubes have been 3/16″ nominal diameter. With the advent of higher flow requirements of Traction Control and Yaw/Stability control systems, larger tubes of 1/4″ and 5/16″ size have also been introduced. While it was known that the first-time sealing capability of the 3/16″ joint was not 100%, leakers were generally containable in the production environment and the joint was regarded as robust.

Phosphorous poisoning on customer-aged catalysts was investigated by material analysis and performance testing. Most of the phosphorus was associated with the oxide components in the washcoat. These contaminants were roughly classified as aluminum phosphate, cerium phosphate, zinc-calcium phosphate. Deactivation of the catalyst with aluminum phosphate was strong and followed a linear correlation from oxalic acid testing. Phosphorus scavenging additives were researched to inhibit increase of aluminum phosphate. According to thermodynamic calculations, lower free energy of compounds of additive and phosphate is expected to prevent formation of aluminum phosphate.

Effects of impact velocity on the crush behavior of aluminum 5052-H38 honeycomb specimens are investigated by experiments. An impact test machine using pressurized nitrogen was designed to perform dynamic crush tests. A test fixture was designed such that inclined loads can be applied to honeycomb specimens in dynamic crush tests. The results of dynamic crush tests indicate that the effects of impact velocity on the normal and inclined crush strengths are significant. The trends of the inclined crush strengths for specimens with different in-plane orientation angles as functions of impact velocity are very similar to that of the normal crush strength. Experimental results show similar progressive folding mechanisms for honeycomb specimens under pure compressive and inclined loads. Under inclined loads, the inclined stacking patterns were observed. The inclined stacking patterns are due to the asymmetric locations of the horizontal plastic hinge lines.

MIG weld failures are commonly seen in chassis and frame structures in automobile industry. Until now, testing and CAE analysis based on local stresses in the vicinity of MIG weld were driving the design of these welds. With the advent of advanced methods and tools, it is possible to estimate fatigue life of MIG welds and support the design in the early stages of the vehicle program. Recently, fatigue damage models are developed for assessing the durability of MIG welds in aluminum auto structures. These damage models are based on advanced technologies like mesh-insensitive structural stress method, virtual node method, estimation of notch stress intensities and life predictions based on two-stage crack growth law. This paper outlines the theoretical aspects involved in deriving the master S-N curve.

An experimental study of the acoustic characteristics of automotive catalytic converters is presented. The investigation addresses the effects and relative importance of the elements comprising a production catalytic converter assembly including the housing, substrate, mat and seals. Attenuation characteristics are measured for one circular and one oval catalytic converter geometry, each having 400 cell per square inch substrates. For each geometry, experimental results are presented to address the effect of individual components in isolation, and in combination with other assembly components. Additional experiments investigate the significance of acoustic paths around the substrate and through the peripheral wall of the substrate. The experimental results are compared to address the significance of each component on the overall attenuation.

The use of Friction Stir Welding (FSW) is a robust process to use in the assembly of aluminum automotive components. The advantages include: minimal distortion, higher tensile strength, lower costs and improved weld capability than other joining processes. Though a simple process, there are key parameters that must be carefully selected to optimize the weld. This paper will focus on the use of FSW to assemble extrusions into automotive components.

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.

Piston wetting can be isolated from the other sources of HC emissions from DISI engines by operating the engine predominantly on a gaseous fuel and using an injector probe to impact a small amount of liquid fuel on the piston top. This results in a marked increase in HC emissions. In a previous study, we used a variety of pure liquid hydrocarbon fuels to examine the influence of fuel volatility and structure on the HC emissions due to piston wetting. It was shown that the HC emissions correspond to the Leidenfrost effect: fuels with very low boiling points yield high HCs and those with a boiling point near or above the piston temperature produce much lower HCs. All of these prior tests of fuel effects were performed at a single operating condition: the Ford World Wide Mapping Point (WWMP). In the present study, the effects of load and engine speed are examined.

Traditionally, door seals are designed to achieve good wind noise performance, water leakage and door closing effort in a vehicle design and development process. However, very little is known concerning the effect of door seal design on vehicle squeak and rattle performance. An earlier research work at Ford indicates a strong correlation between the diagonal distortions of body closure openings (in a low frequency range 0 - 50 Hz) and overall squeak and rattle performance. Another research at Ford reveals that relative accelerations between door latch and striker in a low frequency region (0 - 50 Hz) correlate well with door chucking performance. The findings of this research work enable engineers to assess squeak and rattle and door chucking performance using vehicle low frequency NVH CAE models at a very early design stage.

The history behind Polymer Class “A” Body Panels for automotive applications is very interesting. The driving factors behind these applications have not changed significantly over the past sixty years. Foremost among these factors is the need for corrosion and dent resistance. Beginning with Saturn in 1990, interest in polymer body panels grew and continues to grow up to the present day, with every new global application. Today, consumers and economic factors drive the industry trend towards plastic body panels. These include increased customization and fuel economy on the consumer side. Economic factors such as lower unit build quantities, reduced vehicle mass, investment cost, and tooling lead times influence material choice for industry. The highest possible performance, and fuel economy, at the lowest price have always been a goal.