Search Results

Dimensional variation simulation is a computer aided engineering (CAE) method that analyzes the statistical efforts of the component variation to the quality of the final assembly. The traditional tolerance analysis method and commercial CAE software are often based on the assumptions of the rigid part assembly. However, the vehicle functional attributes, such as, ride and handling, NVH, durability and reliability, require understanding the assembly quality under various dynamic conditions while achieving vehicle dimensional clearance targets. This paper presents the methods in evaluating and analyzing the impacts of the assembly variations for the vehicle dynamic performance. Basic linear tolerance stack method and advanced study that applies various CAE tools for the virtual quality analysis in the product and process design will be discussed.

Quasi-static tensile properties of TRIP590 steels from three different manufacturers were investigated using digital image correlation (DIC). The focus was on the post-uniform elongation behavior which can be very different for steels of the same grade owing to different manufacturing processes. Miniature tensile specimens, cut at 0°, 45°, and 90° relative to the rolling direction, were strained to failure in an instrumented tensile stage. True stress-true strain curves were computed from digital strain gages superimposed on digital images captured from one gage section surface during tensile deformation. Microstructural phases in undeformed and fracture specimens were identified with optical microscopy using the color tint etching process. Fracture surface analyses conducted with scanning electron microscopy and energy dispersive spectroscopy were used to investigate microvoids and inclusions in all materials.

A snap-fit is a form-fitting joint, which is used to assemble plastic parts together. Snap-fits are available in different forms like a projecting clip, thicker section or legs in one part, and it is assembled to another part through holes, undercuts or recesses. The main function of the snap-fit is to hold the mating components, and it should withstand the vibration and durability loads. Snap-fits are easy to assemble, and should not fail during the assembling process. Based on the design, these joints may be separable or non-separable. The non- separable joints will withstand the loads till failure, while separable joints will withstand only for the design load. The insertion and the retention force calculation for the snaps are very essential for snap-fit design. The finite element analysis plays a very important role in finding the insertion and the retention force values, and also to predict the failure of the snaps and the mating components during this process.

The SAE Fuel Cell Vehicle (FCV) Safety Working Group has been addressing FCV safety for over 9 years. The initial document, SAE J2578, was published in 2002. SAE J2578 has been valuable as a Recommended Practice for FCV development with regard to the identification of hazards and the definition of countermeasures to mitigate these hazards such that FCVs can be operated in the same manner as conventional gasoline internal combustion engine (ICE)-powered vehicles. SAE J2578 is currently being revised so that it will continue to be relevant as FCV development moves forward. For example, test methods were refined to verify the acceptability of hydrogen discharges when parking in residential garages and commercial structures and after crash tests prescribed by government regulation, and electrical requirements were updated to reflect the complexities of modern electrical circuits which interconnect both AC and DC circuits to improve efficiency and reduce cost.

A task group within the SAE Automotive Corrosion and Protection (ACAP) Committee continues to pursue the goal of establishing a standard test method for in-laboratory cosmetic corrosion evaluations of finished aluminum auto body panels. The program is a cooperative effort with OEM, supplier, and consultant participation and is supported in part by USAMP (AMD 309) and the U.S. Department of Energy. Numerous laboratory corrosion test environments have been used to evaluate the performance of painted aluminum closure panels, but correlations between laboratory test results and in-service performance have not been established. The primary objective of this project is to identify an accelerated laboratory test method that correlates with in-service performance. In this paper the type, extent, and chemical nature of cosmetic corrosion observed in the on-vehicle exposures are compared with those from some of the commonly used laboratory tests

With increasingly stringent emissions regulations and concurrent requirements for enhanced engine thermal efficiency, a comprehensive characterization of the automotive gasoline fuel spray has become essential. The acquisition of accurate and repeatable spray data is even more critical when a combustion strategy such as gasoline direct injection is to be utilized. Without industry-wide standardization of testing procedures, large variablilities have been experienced in attempts to verify the claimed spray performance values for the Sauter mean diameter, Dv90, tip penetration and cone angle of many types of fuel sprays. A new SAE Recommended Practice document, J2715, has been developed by the SAE Gasoline Fuel Injection Standards Committee (GFISC) and is now available for the measurement and characterization of the fuel sprays from both gasoline direct injection and port fuel injection injectors.

This paper analyzes the difference in impact response of the forehead of the Hybrid III and THOR-NT dummies in free motion headform tests when a dummy strikes the interior trim of a vehicle. Hybrid III dummy head is currently used in FMVSS201 tests. THOR-NT dummy head has been in development to replace Hybrid III head. The impact response of the forehead of both the Hybrid III dummy and THOR dummy was designed to the same human surrogate data. Therefore, when the forehead of either dummy is impacted with the same initial conditions, the acceleration response and consequently the head Injury criterion (HIC) should be similar. A number of manufacturing variables can affect the impacted interior trim panels. This work evaluates the effect of process variation on the response in the form of Head Injury Criterion (HIC).

Springback compensation studies on a few selected auto panels from the hot selling Chrysler 300C are presented with details. LS-DYNA® is used to predict the springback behavior and to perform the iterative compensation optimization. Details of simulation parameters using LS-DYNA® to improve the prediction accuracy are discussed. An iterative compensation algorithm is also discussed with details. Four compensation examples with simulation predictions and actual panel measurement results are included to demonstrate the effectiveness of LS-DYNA® predictions. An aluminum hood inner and a high strength steel roof bow are compensated, constructed and machined based on simulation predictions. The measurements on actual tryout panels are then compared with simulation predictions and good correlations were achieved. Iterative compensation studies are also done on the aluminum hood inner and the aluminum deck lid inner to demonstrate the effectiveness of LS-DYNA® compensation algorithm.

Spot Welding is an important welding technique which is widely used in automotive and aerospace industry. One of the keys of checking the quality of the welds is measuring the size of the nugget. In this paper, the Shearographic technique is utilized to test weld joint samples under the thermal loading condition. The goal is to identify the different group of the nuggets (i.e. small, middle, and large sizes, which indicate the quality of spot welds). In the experiments, the sample under test is fixed by a magnet method from behind at the four edges. Thermal loading was applied in the back side and the sample is inspected using the digital Shearographic system in the front side. Results show the great possibility of classifying the nugget size into three groups and the measurement is well repeatable.

Automakers are designing smaller displacement engines with higher power densities to improve vehicle fuel economy, while continuing to meet customer expectations for power and drivability. The specific power produced by the spark-ignited engine is constrained by knock and fuel octane. Whereas the lowest octane rating is 87 AKI (antiknock index) for regular gasoline at most service stations throughout the U.S., 85 AKI fuel is widely available at higher altitudes especially in the mountain west states. The objective of this study was to explore the effect of gasoline octane rating on the net power produced by modern light duty vehicles at high altitude (1660 m elevation). A chassis dynamometer test procedure was developed to measure absorbed wheel power at transient and stabilized full power operation. Five vehicles were tested using 85 and 87 AKI fuels.

The need for accurate virtual prototyping prediction is well documented in the literature. For welded body structures one notable shortcoming has been the ability for finite element analysis (FEA) to accurately predict the failure of welded joints due to cyclic loading. A new approach to representing spot-welds for durability evaluation in automotive sheet metal structures is presented here. Excellent correlation with spot-weld failures in actual tests have been observed through this modeling approach. We present a method of representing spot-welds using the finite element method. This method has shown to be able of predicting the behavior of spot-welds prior to the build of any prototypes or testing. Further, for spot-weld failures we present evidence that reveals which radial quadrant of the spot-weld will contain the failure. This method also allows engineers to determine the mechanism of failure. This paper describes in detail the spot-weld modeling method.

A correlation of aerodynamic wind tunnels was initiated between Chrysler, Ford and General Motors under the umbrella of the United States Council for Automotive Research (USCAR). The wind tunnels used in this correlation were the open jet tunnel at Chrysler's Aero Acoustic Wind Tunnel (AAWT), the open jet tunnel at the Jacobs Drivability Test Facility (DTF) that Ford uses, and the closed jet tunnel at General Motors Aerodynamics Laboratory (GMAL). Initially, existing non-competitive aerodynamic data was compared to determine the feasibility of facility correlation. Once feasibility was established, a series of standardized tests with six vehicles were conducted at the three wind tunnels. The size and body styles of the six vehicles were selected to cover the spectrum of production vehicles produced by the three companies. All vehicles were tested at EPA loading conditions. Despite the significant differences between the three facilities, the correlation results were very good.

Friction stir welding (FSW) shows advantages for joining lightweight alloys for automotive applications. In this research, the feasibility of friction stir welding aluminum for an automotive component application was studied. The objective of this research was to improve the Friction Stir Spot Welding (FSSW) technique used to weld an aluminum closure panel (CP). The spot welds were made using the newly designed swing-FSSW technique. In a previous study (unpublished), the panel was welded from the thin to thick side using both an 8 mm and a 10 mm diameter tool. The 10 mm tool passed various fatigue tests; however, the target was to improve performance of the 8 mm tool, especially to increase the number of cycle before the first crack appearance during fatigue testing. In this study fatigue tests and static strength was recorded for weld specimens that were welded from thick-to-thin with an 8 mm diameter tool.

The new Chrysler six-speed transaxle makes use of an underdrive assembly to extend a four-speed automatic transmission to six-speed. It is achieved by introducing double-swap shifts. During double-swap shift, learning the initial clutch torque capacity of the underdrive assembly's subsystem has a direct impact on the shift quality. A new method is proposed to compute and learn the initial clutch torque capacity of the releasing element. In this paper, we will outline a new mathematical method to compute and learn the accurate starting point of the clutch torque capacity for double swap shift control. The performance of the shift is demonstrated and the importance of the adaptation to shift quality is highlighted. An nth order lookup table is presented; this table contains n rows and m columns. Every row defines a relationship between the dependent variable such as actuator duty cycle and one independent variable such as transmission oil temperature, input torque or battery voltage.

Tuned mass dampers (TMDs) or vibration absorbers are widely used in the industry to address various NVH issues, wherein, tactile-vibration or noise mitigation is desired. TMDs can be classified into two categories, namely, tuned-to-resonance and tuned-to-discrete-excitation. An overwhelming majority of TMD applications found in the industry belong to the tuned-to-resonance category, so much of information is available on design considerations of such dampers; however, little is published regarding design considerations of dampers tuned-to-discrete-excitation. During this study, a problem was solved that occurred at a discrete excitation frequency away from the primary resonance frequency of a steering column-wheel assembly. A solution was developed in multiple stages. First the effects of various factors such as mass and damping were analyzed by using a closed-form solution.

An experiment was conducted testing a powertrain package consisting of a four cylinder four valve engine coupled to a four speed automatic transmission in a dynamometer test cell. Cylinder pressure transducers, an encoder, and other instrumentation were used to measure transient combustion events. The transient cycle chosen for testing was a Cold 80 of the Federal Test Procedure (FTP) that produces a standardized fuel economy value. After analyzing the combustion events, a determination was made between the spark advance delivered and a revised spark advance for optimum combustion efficiency. Based upon the relationship between spark advance and fuel consumption, a prediction for the improved fuel consumption was made. The testing was then repeated to evaluate the revised spark advance and the fuel economy benefits in comparison to the predicted values.

Ring gear bolts in differentials are often modified in size to accommodate the additional clamp load that is required due to an increase in torque from a vehicle's powertrain. Depending on a given program several constraints need to be considered. These include cost, validation time, reliability / durability and timing for implementation. In this paper, a Finite Element Analysis (FEA) procedure for analyzing stresses in ring gear bolts within a rear differential assembly is outlined and the computational results are then compared to quasi-static bench test results that were developed to measure bending and tension loads in the ring gear bolts during loading and unloading of the axle pinion. A dynamometer test is then developed to duplicate the failure mode and provide a comparison of the design changes proposed and the expected improvement in durability.

Efficient methods for simulating operators performing part handling tasks in manufacturing plants are needed. The simulation of part handling motions is an important step towards the implementation of virtual manufacturing for the purpose of improving worker productivity and reducing injuries in the workplace. However, industrial assembly tasks are often complex and involve multiple interactions between workers and their environment. The purpose of this paper is to present a series of industrial simulations using the Human Motion Simulation Framework developed at the University of Michigan. Three automotive assembly operations spanning scenarios, such as small and large parts, tool use, walking, re-grasping, reaching inside a vehicle, etc. were selected.

Magnesium alloy extrusions offer potentially more mass saving compared to magnesium castings. One of the tasks in the United States Automotive Materials Partnership (USAMP) ?Magnesium Front End Research and Development? (MFERD) project is to evaluate magnesium extrusion alloys AM30, AZ31 and AZ61 for automotive body applications. Solid and hollow sections were made by lowcost direct extrusion process. Mechanical properties in tension and compression were tested in extrusion, transverse and 45 degree directions. The tensile properties of the extrusion alloys in the extrusion direction are generally higher than those of conventional die cast alloys. However, significant tension-compression asymmetry and plastic anisotropy need to be understood and captured in the component design.

This paper presents a simplified approach for formability simulation of automotive body structural sections in the early design stage of vehicle development process. Plane strain approach is investigated for its applicability and accuracy by comparing the analytical results with the measured results of automotive body side panel. The plane strain approach was tried based on the fact that for a certain section location of a stamped panel, the minor strains are relatively small and negligible compared to the major strains. The state of plane strain can be induced mainly through symmetry and applied boundary conditions. This approach is both cost effective and time saving for analyzing sheet metal formability in early vehicle development stage, since only few sections of the entire panel need be analyzed.