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Technical Paper

Temperature Measurements During Flash Welding Thin-Walled Door-Frame Components

1991-02-01
910193
This study was conducted to examine the effect of flashing conditions on the resulting temperature profile during flash welding automobile door frames. Previous work on temperature profiles of flash welds has shown that at some point in the welding cycle a steady state temperature is reached, minimizing the need for further flashing. The indication of such a minimum flashing time allows flashing conditions for any application to be optimized. Unfortunately, previous work has been limited to rather heavy section materials, and the results could not be directly applied to the flash welding thin sections typical for door frames. This program was a preliminary study to examine the effects of initial flashing velocity and flashing acceleration on the resulting temperature profiles in U-shaped channel sections. Work was done on a cam driven flash welding machine supplied. Flashing conditions were varied by using cams with different profiles.
Technical Paper

Overview of a Study on Direction-of-Motion Stereotype Strengths for Automobile Controls

1991-02-01
910115
Virginia Polytechnic Institute and State University recently conducted an SAE sponsored research study investigating directional stereotypes of six types of automobile controls: power mirrors, power windows, manual windows, stalks, generic controls, and power door locks. The objective was to determine stereotype strength and the reasons for the strengths. Two hundred subjects participated in this study. This paper provides an overview of the results of the study and recommendations made therefrom.
Technical Paper

New Polymethylpentene Compounds for Automotive Applications

1991-02-01
910046
In recent years plastics have been finding increasing application in underhood performance parts due to good thermal performance, weight reduction, cost savings, and design flexibility. Downsized cars with lower hood lines and smaller engine compartments as well as an increasing dependence on sophisticated electronics have placed stringent demands on the performance of plastic components. Automotive materials have an increasing demand for higher heat, humidity, and chemical resistance. Polymethylpentene (PMP) is a semicrystalline “engineering polyolefin” which melts at 240°C. It has a density of 0.835 g/cc, one of the lowest of all polymer resins. PMP also exhibits high optical clarity, good thermal and chemical resistance, outstanding electrical properties, and good processability. Mechanical properties at room and elevated temperatures are improved by the addition of glass reinforcement.
Technical Paper

Effects of Fiber and Property Orientation on “C” Shaped Cross Sections

1991-02-01
910049
Glass fiber reinforced bumper beams are being used on increasingly more automobiles due to the weight and energy management advantages the materials have over steel. Current bumpers are manufactured using basically three fiber orientations or combinations thereof: 1) Random, chopped and continuous 2) Unidirectional, continuous along the length of the beam 3) 0.90, continuous on the length and perpendicular, woven For the purpose of this paper, the composite used for all FEA models and sample moldings is a 40% continuous glass fiber reinforced, polypropolene resin based, sheet stampable thermoplastic. It is possible to assume that the results can be generatalized to other composites. The finite element analysis found that significant increases in performances were achieved over the conventional fiber orientations.
Technical Paper

Thermomechanical Analysis for the Investigation Solvent Induced and Residual Stresses in an Injection Molded Automotive Headlamp Reflector

1991-02-01
910283
In the continual drive toward better quality and long-term reliability of products, an examination of all factors that affect performance is necessary. For example, in plastic products such as injection-molded headlamp reflectors, the source and distribution of internal stresses plays a crucial role. Specifically, in polycarbonate reflectors, a detailed examination of internal stresses has resulted in considerably improved parts with a lower failure rate during manufacture and testing and hence a higher yield in production. Experimental analysis of a typical polycarbonate headlamp reflector is described throughout the course of this paper. The distribution of internal stresses is determined via a thermomechanical procedure developed for the purpose of this investigation. The same technique has also been used to identify one of the main non-thermal sources of such stress, viz. solvent-induced stresses during the coating of the reflector with MIBK (methylisobutylketone)-based coatings.
Technical Paper

Gas Damped Sensing of Automobile Crashes for Airbag Deployment

1991-02-01
910275
While sensors used to detect front end collisions to deploy air bags are highly reliable, they involve using multiple sensors mounted in the crush zone and have difficulty meeting the sensor requirements for small vehicles such as minivans. A sensor is presented which deals with these drawbacks by employing a novel method of gas damping coupled with a spring mass system. Test results are shown which demonstrate the ability to tailor the degree of damping in the sensor. The theory and test results are presented which show how this sensor is able to react to the crash signal more quickly, a feature enabling its application in non crush zone areas and in vehicles requiring unusually fast reaction times. Its response curve, which provides filtering of short duration inputs, is also discussed. It is this aspect of its performance which can possibly result in a single sensor system meeting the performance requirements for the US market.
Technical Paper

A Hall Effect Rotary Position Sensor

1991-02-01
910270
Rotary position sensors (RPS) currently are applied widely in engine management systems for throttle position sensing and are being considered for other applications such as drive-by-wire. The potentiometer RPS relies on contact between a resistive element and a wiper and thus has an inherent wear mechanism. This paper describes a noncontacting RPS which is essentially a drop-in replacement for the present device. A linear output Hall Effect IC is key to achieving the required functionality, but it must be combined with a magnetic actuation scheme which provides a very linear and stable magnetic field as a function of input angle and packaging which provides long life and control of mechanical tolerances. Each of these design elements will be discussed.
Technical Paper

Non-Destructive Replication Technique for the Examination of Phosphate Crystal Morphology on Vehicle Assembly Lines

1991-02-01
910295
Destructive or indirect methods have been available for evaluating phosphate crystal morphology on car bodies pretreated on a vehicle production line. Either the panel in question is removed, thereby destroying the car, or flat panels are hung in the window openings with the assumption that the same morphology exists over similar substrate surfaces on the stamped autobody. The replication technique described in this report has proven to be a viable option for examining the phosphate crystal morphologies present on various automobile substrates. The details of this replication technique along with crystal morphologies associated with different substrates and degrees of forming are included in this report.
Technical Paper

Development of Conductible Type Vibration Damping Composite Steel Sheet for Automotive Use

1991-02-01
910294
Vibration Damping Composite Steel Sheets (VDC) have recently been developed as a new material to satisfy the requirements concerning various types of noise and vibration control for various fields such as automobiles, electric appliances and building materials. Requirement for VDC continues to expand, because VDC, consisting of two steel sheets and a layer of visco-elastic synthetic resin, which is sandwiched between the two steel sheets, has an excellent damping capability. However, it is rather difficult to spot weld the VDC, as it has an electrically insulating resin layer. To improve the weldability, metal particle is generally mixed into the resin. For automotive body panels, VDC is required to have not only high vibration damping capability but also superior properties such as weldability, bonding strength and formability. In this study, the effects of metal particle size and volume fraction on these properties have been investigated.
Technical Paper

Development of a New Bake-Hardenable Galvannealed Sheet Steel for Automotive Exposed Panels

1991-02-01
910293
Various types of bake-hardenable steels have been developed and applied to automotive body panels for a weight reduction since 1981. Recently for the improvement in the cosmetic corrosion resistance of the exposed panels, an ultra-low carbon bake-hardenable galvannealed steel was developed and has been produced in a large quantity. The main metallurgical features of the ultra-low carbon bake-hardenable steel are follows, (1) adjustment of bake-hardenability by controlling the total carbon content between 15 and 25 wt.ppm, (2) suppression of TiC formation by controlling Ti content between 48/14 ·N and 48·(N/14+S/32). (3) optimisation of temper rolling condition to eliminate the stretcher strain.
Technical Paper

Bake Hardening Steel Application Study - Key Factors of Dent Resistance Improvement

1991-02-01
910291
On exterior automotive body panels it is generally accepted that the substitution of a bake hardening, BH grade of steel for a drawing quality special killed, DQSK grade improves the dent resistance performance. However, the amount of performance improvement varies depending on the specific body panel and the loading conditions applied. The objective of this study was to quantify and define the key factors related to the dent resistance performance difference. Specifically, body panels of the same part and outer panel gage, one BH the other DQSK, were compared hased on the load required to produce a visible dent and the resulting dent depth. While the results were specific to the panel tested, the key factors to be considered when comparing BH and DQSK panels were identified.
Technical Paper

Study of Parameters that Affect Body Panel Performance Predictions

1991-02-01
910289
Predictions of stiffness, denting energy, and critical buckling loads are integral parts of body panel structural design. The accuracy of these predictions depends upon the method used to simulate field conditions typically imposed upon the panel in service. This paper describes a study conducted to correlate the effects of different supports or boundary conditions and loading methods on the actual panel performance measurements. Specifically, panel stiffness and oil canning load measurements were experimentally made and compared under two different support conditions and indentor geometries. Conclusions are drawn with respect to each of these parameters to offer further insight into better predictions of panel performance during the design phase.
Technical Paper

Prestrain Effects on Static Dent Resistance of Automotive Steels

1991-02-01
910288
In previous investigations, it has been shown that the dent resistance of an auto body panel depends upon the yield strength of the material. However, it is known that the yield strength of steel increases with prestrain due to strain hardening. Panel design and material selection based on the material properties obtained from unstrained sheet steels may lead to inaccurate prediction of the dent resistance of the formed panel. In this study, the effect of prestrain on the static dent resistance of auto body panels was investigated. Using existing empirical relationships between dent resistance and panel properties, it was found that the static dent resistance of an auto panel depends not only on the part geometry and material properties but also on the strain level in the panel. The improvement in dent resistance resulting from a material change from an AKDQ steel to a bake hardenable steel or a high strength steel was determined at different strain levels.
Technical Paper

Automated Application of Silicone Glass Like Coatings for Polycarbonate Headlamp Lenses

1991-02-01
910286
Silicone hardcoating and plastic headlamp lenses were first developed in the late 1970's due to the growing trend, in automobile design, towards weight reduction as well as a desire for design flexibility. A few creative people presented the auto industry with a plastic substitute that replaced glass and offered new design possibilities. Ford Motor company presented data to the National Highway Safety Traffic Administration indicating that the chance of total failure for a plastic headlamp component was less than for a glass sealed beam headlamp. General Electric's LEXAN polycarbonate with it's excellent impact and high temperature resistance, good optics, flame retardant and light weight was selected as a perfect candidate for glass replacement in headlamps.
Technical Paper

A New Approach to Vehicle Interior Control

1991-02-01
910472
In order to meet increasing demands for safety and comfort in a vehicle compartment, automatic adjustment of seat, mirrors, steering wheel has been developed. The multiplex wiring system was constructed for the automatic adjustment of the cockpit elements to drivers preferred positions or to physique-matched settings based on ergonomic data. This paper describes the construction of the multiplex system and functions of automatic adjustment of the cockpit elements for comfortable driving position and better visibility.
Technical Paper

High Frame Rate Flow Visualization and LDV Measurements in a Steady Flow Cylinder Head Assembly

1991-02-01
910473
The purpose of this work was to develop a high speed flow visualization system which could be used to observe the behavior of the air flow in a steady flow cylinder head assembly. This type of experimental rig has been used by engineers for many years to evaluate valve discharge coefficients. This study is believed to be the first high speed flow visualization of the air flow in a system of this type. Particular emphasis was placed on the characterization of intake generated swirl and tumble motions within the cylinder. A 40 watt copper vapor laser was used to expose motion picture films at 5000 frames per second. The light scattering medium was phenolic microballoons. Based on the flow visualization results, selected LDV measurements were made to quantify the visual observations. A propylene glycol aerosol was used for seeding in the LDV experiments.
Technical Paper

Hot-Gas Spin Testing of Ceramic Radial Turbine Rotor at TIT 1400 C

1991-02-01
910401
The reliability of silicon nitride radial turbine rotors for automotive gas turbine was evaluated with hot-gas spin test and reliability analysis. The turbine rotors were made of a newly developed silicon nitride, having a 4 point bending strength higher than 700 MPa at 1400°C. The turbine rotors withstood at a turbine tip speed of 500m/s at TIT 1400°C, the same level as the rated condition of turbine rotors for the two-shaft type automotive gas turbines. The reliability of turbine rotors is discussed in relation to the hot-gas spin test results and failure probability analysis using CARES program developed by NASA as well as three-dimensional flow analysis and finite element analysis.
Technical Paper

The State of Polyurethane Structural Adhesive Technology in the Transportation Industry

1991-02-01
910386
The purpose of this paper is to outline the current state of polyurethane bonding technology in the transportation industry. The paper focuses on the strengths and limitations of this technology and the reasons for its long-term success in the market place. Significant advances have been made in the range of end use applications for polyurethane structural adhesives. The introduction of the new General Motor's Lumina, Silhouette, and Transport mini vans has created the largest assembly line use of structural adhesive to bond SMC body panels to date. Molders and manufacturers of more traditional SMC assemblies have made noteworthy improvements in productivity with fast cure bonding cycles and simplified production processes using polyurethane technology. Auto makers have continued to capitalize on the cost and performance benefits of bonded composite body vehicles for specialty niche markets.
Technical Paper

Advances in Thermoset Injection Molding

1991-02-01
910384
Injection molding of thermosetting materials such as low profile SMC/BMC composites found increasing application in the transportation industry in the eighties. Such automotive parts as front end panels and rear/hatchback doors have grown in usage. The rear doors have reached exceptional production levels of 2500/day in a single plant. The injection process offers the advantages of greater automation for the mass production of body panel parts compared to compression molding. However, the injection molding of fiber reinforced low profile composites suffers from a severe reduction in physical properties. This is particularly true for impact strength which can be one-third that of similar compression molding materials. A primary reason for this is due to the degradation of the reinforcement during the processing/molding. Efforts at increasing the physical properties through processing changes have many times caused problems with the surface smoothness of the moldings.
Technical Paper

Optimization of an SMC System for Maximum Surface Smoothness - GM APV Van Hood Case Study

1991-02-01
910385
Sheet Molding Composite (SMC) technology has advanced significantly in the surface smoothness and appearance of compression molded automotive exterior body component parts over the past five years. An example of that new technology is the General Motors' APV Van Hood. As judged visually on vehicles and measured quantitatively in the laboratory, not only by the SMC molder and fabricator, but by other SMC molders and the automotive customer, this SMC hood sets a new SMC industry standard for surface appearance for thermoset composite exterior automotive body panels. The appearance of the GM APV Van Hood was the result of a total system approach to material and process optimization. Teamwork and partnership concepts contributed significantly and leveraged the application of technology.
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