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Journal Article

Mass Benchmarking Using Statistical Methods Applied to Automotive Closures

2015-04-14
2015-01-0574
Understanding the lightweighting potential of materials is important in making strategic decisions for material selection for a new vehicle program. Frequently benchmarking is done to support these decisions by selecting a reference vehicle which is believed to be mass efficient, then using the teardown mass data to set targets for the vehicle under design. In this work, rather then considering a single benchmark vehicle or a small set of vehicles, we looked at a large sample of vehicles over a range of sizes and segments (approximately 200 vehicles). Statistical methods were used to identify mass drivers for each subsystem. Mass drivers are the attributes of the vehicle and subsystem which determine subsystem mass. Understanding mass-drivers allows comparisons across vehicle size, segments, and materials. Next, we identified those vehicles which had subsystems which were much lighter than the average after adjusting for mass drivers. This set was defined as mass-efficient designs.
Journal Article

Failure Mode and Fatigue Behavior of Dissimilar Laser Welds in Lap-Shear Specimens of Aluminum and Copper Sheets

2014-04-01
2014-01-1986
Failure mode and fatigue behavior of dissimilar laser welds in lap-shear specimens of aluminum and copper sheets are investigated. Quasi-static tests and fatigue tests of laser-welded lap-shear specimens under different load ranges with the load ratio of 0.1 were conducted. Optical micrographs of the welds after the tests were examined to understand the failure modes of the specimens. For the specimens tested under quasi-static loading conditions, the micrograph indicates that the specimen failed through the fusion zone of the aluminum sheet. For the specimens tested under cyclic loading conditions, two types of failure modes were observed under different load ranges. One failure mode has a kinked crack initiating from the interfacial surface between the aluminum and copper sheets and growing into the aluminum fusion zone at an angle close to 90°.
Journal Article

Driver Preference for Fore-Aft Steering Wheel Location

2013-04-08
2013-01-0453
The fore-aft location of the steering wheel relative to the pedals is a critical determinant of driving posture and comfort. Current SAE practices lack quantitative guidance on steering wheel positioning. This paper presents a model of subjective preference for fore-aft steering wheel position across a range of seat heights. Sixty-eight men and women evaluated the steering wheel positions in a total of 9 package conditions differentiated by seat height and fore-aft steering wheel position. Numerical responses were given on a 7-point scale anchored with the words “Too Close”, “Just Right”, and “Too Far”. A statistical analysis of the results demonstrated that the preferred fore-aft steering wheel position was affected by seat height and driver stature. An ordinal logistic regression model was created that predicts the distribution of subjective responses to steering wheel location. The model can be used to calculate the preferred steering wheel position for individuals or populations.
Journal Article

Development of a Methodology for Simulating Seat Back Interaction Using Realistic Body Contours

2013-04-08
2013-01-0452
Seat comfort is driven in part by the fit between the sitter and seat. Traditional anthropometric data provide little information about the size and shape of the torso that can be used for backrest design. This study introduces a methodology for using three-dimensional computer models of the human torso based on a statistical analysis of body shapes for conducting automated fit assessments. Surface scan data from 296 men and 417 women in a seated posture were analyzed to create a body shape model that can be adjusted to a range of statures, body shape, and postures spanning those typical of vehicle occupants. Finite-element models of two auto seat surface were created, along with custom software that generates body models and postures them in the seat. A simple simulation technique was developed to rapidly assess the fit of the torso relative to the seat back.
Technical Paper

Modeling of Stiffened Panels Using the Energy Finite Element Analysis

2011-05-17
2011-01-1696
Stiffened panels are encountered in many engineering systems since the stiffeners comprise the mechanism which provides support and rigidity to the panel's skin. Either a mechanical excitation or an acoustic load can be applied on a stiffened panel creating vibration that is transmitted in all panel components. Mechanical excitation tends to be localized in nature, originating from operating machinery mounted on the panel, while the acoustic excitation tends to be distributed over the entire panel, since it typically originates from an external acoustic source which creates an acoustic field impinging on the entire panel. In the Energy Finite Element Analysis (EFEA) various degrees of fidelity are possible when modeling the response of a stiffened panel. In this paper, the theoretical background and the corresponding implications associated with each alternative modeling approach are presented first.
Technical Paper

Design of Rotorcraft Gearbox Foundation for Reduced Vibration and Increased Crashworthiness Characteristics

2011-05-17
2011-01-1704
Vehicle design is a complex process requiring interactions and exchange of information among multiple disciplines such as fatigue, strength, noise, safety, etc. Simulation models are employed for assessing and potentially improving a vehicle's performance in individual technical areas. Challenges arise when designing a vehicle for improving mutually competing objectives, satisfying constraints from multiple engineering disciplines, and determining a single set of values for the vehicle's characteristics. It is of interest to engage simulation models from the various engineering disciplines in an organized and coordinated manner for determining a design configuration that provides the best possible performance in all disciplines. The multi-discipline design process becomes streamlined when the simulation methods integrate well with finite element or computer aided design models.
Journal Article

Energy Finite Element Analysis Developments for Vibration Analysis of Composite Aircraft Structures

2011-05-17
2011-01-1734
The Energy Finite Element Analysis (EFEA) has been utilized successfully for modeling complex structural-acoustic systems with isotropic structural material properties. In this paper, a formulation for modeling structures made out of composite materials is presented. An approach based on spectral finite element analysis is utilized first for developing the equivalent material properties for the composite material. These equivalent properties are employed in the EFEA governing differential equations for representing the composite materials and deriving the element level matrices. The power transmission characteristics at connections between members made out of non-isotropic composite material are considered for deriving suitable power transmission coefficients at junctions of interconnected members. These coefficients are utilized for computing the joint matrix that is needed to assemble the global system of EFEA equations.
Technical Paper

Failure Mode of Laser Welds in Lap-Shear Specimens of HSLA Steel

2010-04-12
2010-01-0973
Failure mode of laser welds in lap-shear specimens of high strength low alloy (HSLA) steel is investigated in this paper. The experimental results from quasi-static tests show that the laser welds failed in a ductile necking/shear failure mode near the heat affected zone. In order to understand the failure mode of these welds, a finite element analysis under plane strain conditions was conducted to identify the effects of the different plastic behaviors of the base metal, heat affected zone, and weld metal on the ductile failure. The results of the finite element analysis show that the higher effective stress-plastic strain curves of the weld metal and the heat affected zone results in the necking/shear failure mode. The deformed shape of the finite element model near the weld matches well with that of a failed weld.
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