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A unique opportunity arose to make a direct comparison of aluminum, sheet molding compound (SMC) and steel using a common hood design. In considering all possible material combinations of inner and outer panels, it was discovered that some of the combinations were incompatible due to material properties. Only the compatible material combinations were considered. Three different joining techniques - welding, bonding and bonded hem flanging - were evaluated. The cost, weight and structural performance of the chosen hood material combinations were established. Areas of further development were identified, including design optimization for specific material combinations.

Resistance to dents and dings, caused by plant handling and in-service use, is generally recognized as an important performance requirement for automotive outer body panels. This paper examines the dent resistance improvements that can be achieved by maximizing surface stretch, through adjustments to the press settings, and substitution of a higher strength steel grade. Initially, the stamping process was optimized using the steel supplied for production: a Ti/Nb-stabilized, ultra low carbon (ULC) grade. The stamping process was subsequently optimized with a Nb-stabilized, rephosphorized ULC steel, at various thicknesses. The formed panels were evaluated for percent surface stretch, percent thinning, in-panel yield strength after forming, and dent performance. The results showed that dent resistance can be significantly improved, even at a reduced steel thickness, thus demonstrating a potential for weight savings.

The commercial validation of a optimized RRIM polyurethane substrate with a novel barrier coat for fascia applications is reviewed which creates cost competitiveness to thermoplastic olefins (TPO), without sacrificing performance. Meeting fascia performance requirements with thinner and lighter RRIM materials containing recyclate and the subsequent application of a barrier coat eliminating the traditional primecoat cycle was investigated.

INDUCTION heating is a process or method by which metal parts are heated by simply placing them in an alternating magnetic field. The action is that of the transformer, whereby electrical energy is transferred or passed over to another isolated electric or secondary circuit by means of the magnetic field; thus, no physical attachments or electrical contacts are necessary to have electrical currents, which are dissipated as heat, flow in the parts to be processed. The strength and frequency of the alternating magnetic field can be selected to produce any desired rate of heating and ultimate temperature. A circuit can be set up to dry lacquer at 160 deg. fahr. on thin sheet-metal parts or to melt in record time immense steel ingots. Induction heating is now commercially applied in automotive production to many processes, and these are specified.

This paper outlines several methodologies which use finite element and experimental models to predict vehicle NVH responses. Trimmed body experimental modal subsystem models are incorporated into the finite element system model to evaluate engine mounting systems for low frequency vibration problems. Higher frequency noise issues related to road input are evaluated using experimentally derived acoustic transfer functions combined with finite element subsystem model responses. Specific examples of system models built to simulate idle shake and road noise are given. Applications to engine mounting, suspension design, and body structure criteria are discussed.

Five bonding processes used in the automotive industry, ranging from structural adhesive to nonstructural and filler, are discussed in this paper. Surface preparation, including use of primers; nature, application, and curing of adhesive; secondary processes; in-line testing and destructive test methods; and repair processes are covered. The integral bonding of disc pad shoe assemblies is detailed. Vinyl plastisol adhesives are used for bonding assemblies. Windshield and backlight bonding is a semistructural adhesive application. Contact bonding cements bond exterior vinyl roof covering to roof panels. A vinyl plastisol sealer replaces solder on the joint between the roof and rear quarter panel.

Five heats of vanadium-microalloyed steel with carbon contents from 0.29% to 0.40% and sulfur contents from 0.031% to 0.110% were forged into automotive spindles and air cooled. Three of the steels were continuously cast whereas the other two were ingot cast. The forged spindles were subjected to microstructural analysis, mechanical property testing, full component testing and machinability testing. The microstructures of the five steels consisted of pearlite and ferrite which nucleated on prior austenite grain boundaries and predominantly on intragranularly dispersed sulfide inclusions of the resulfurized grades. Ultimate tensile strengths and room temperature Charpy V-notch impact toughness values were relatively insensitive to processing and compositional variations. The room temperature tensile and room-temperature impact properties ranged from 820 MPa to 1000 MPa (120 to 145 ksi) and from 13 Joules to 19 Joules (10 to 14 ft-lbs), respectively, for the various steels.

One solution to the problem of spiraling automotive weights is the substitution of thinner high strength steels or thicker aluminum alloy outer body panels. In doing so the dent resistance of these panels must not be sacrificed. This study investigates the dent resistance of doubly curved rectangular panels in various steels and aluminum alloys. Dent depth on the order of magnitude of the panel thickness was studied. An empirical equation is developed that relates dent resistance to the yield strengths, metal thickness, and panel geometry.

THE Junkers 211B engine follows the usual German practice of very large displacements and conservative mean effective pressures and rotative speeds. However, the relative light weight per unit of displacement results in a net weight per horsepower that is not far above its competitors. Fully automatic devices which control propeller speed, manifold pressure, mixture ratio, spark advance, and supercharger gear ratio follow the German policy of removing all possible distractions from the pilot. This is one of three large liquid-cooled engines known to be produced in quantity in Germany; it powers an impressive percentage of the Luftwaffe. While of external appearance and displacement that resemble the Daimler-Benz DB-601 engine, the fundamental construction, detail design practice, and metallurgy of the Junkers 211B are surprisingly different.

LIMITATIONS of the two general methods available for determining hardenability in steel, the authors point out, are that the test piece may not have a sufficient cross-section in which to develop the desired series of cooling rates, and that a special test piece (known as the L-type) must be machined for steels of low hardenability. The method using the Wuerfel bomb described in their paper, they explain, is directed primarily toward removal of these two limitations. Stated in terms of the critical diameter, they report that the results of the method are reproducible within ⅛ in.

The Chrysler Corporation made use of a thermosetting polyester sheet-molding-compound (SMC) to provide an efficient, neat-appearing, and economical station wagon air deflector for its 1969 full-size station wagons. This marked Chrysler's first usage of this material for a major automotive body component.

Seats play an important role in determining customer satisfaction and safety. They also represent three to five percent of the overall vehicle cost and weight. Therefore, automotive manufacturers are continuously seeking ways to improve the areas of comfort, safety, reliability, cost and weight within the seat system. The purpose of this paper is to review the development of an automotive front seat constructed of injection molded nylon frames and metal mechanisms. This development program was initiated for the purpose of reducing vehicle weight while increasing the reliability and safety of the front seats. This paper will review the material and process selection decision, a design overview, the performance criteria and the results of tests performed on the injection molded front seats.

Advances in computerized solid modeling techniques allow the realistic representation of exterior body panels as solid models, at the concept stage of part design. A flow chart of the process is presented on the use of solid models to create exterior body panels. The flow chart allows a study of the process and is extended to the next generation of capabilities.

Higher horsepower per liter engines have put more demand on the crankshaft, often requiring the use of forged steel. This paper examines cost reduction opportunities to offset the penalties associated with forged steel, with raw material and machinability being the primary factors evaluated. A cost model for crankshaft processing is utilized in this paper as a design tool to select the lowest cost material grade. This model is supported by fatigue and machinability data for various steel grades. Materials considered are medium carbon, low alloy, and microalloy steels; the effects of sulfur as a machining enhancer is also studied.

The seat can play an important part in improving occupant safety during a car impact. This paper discusses research done to determine how characteristics of seat design affect occupant safety. Impact simulator tests have been run which determine how variation of five specific seat characteristics affect FMVSS 208 occupant injury criteria. These tests simulated a 48.3 km/h (30 mi/h) frontal Oarrier impact using a 50th percentile male anthropomorphic device restrained by a two-point passive shoulder belt system. The five seat characteristics tested were the following: 1) Seat Frame Angle, 2) Seat Frame Structure, 3) H-Point Distance Above the Seat Frame, 4) Energy Absorption of the Seat Frame, and 5) Seat Cushion Foam Firmness. Test results show that the first characteristic can improve all injury criteria. The other four will improve some injury criteria at the expense of others.

Fastener failure due to hydrogen embrittlement is of significant concern in the automotive industry. These types of failures occur unexpectedly. They may be very costly to the automotive company and fastener supplier, not only monetarily, but also in terms of customer satisfaction and safety. This paper is an overview of a program which one automotive company initiated to minimize hydrogen embrittlement in fasteners. The objectives of the program were two-fold. One was to obtain a better understanding of the hydrogen embrittlement phenomena as it relates to automotive fastener materials and processes. The second and most important objective, was to eliminate hydrogen embrittlement failures in vehicles. Early program efforts concentrated on a review of fastener applications and corrosion protection systems to optimize coated fasteners for hydrogen embrittlement resistance.

The Finite Element predictions of the physical response of foams during impact by a rigid body (such as, the Hybrid III head form) is determined by material law equations generally approximated based on the theory of elastoplasticity. However, the structural aspect of foam, its discontinuous nature, makes it difficult to apply the laws of continuum mechanics and construct constitutive equations for foam-like material. One part of the problem relates to the state of stress. In materials such as steel, the state of hydrostatic stress does not affect the stress strain behavior under uniaxial compression or tension in plastic regime. In other words, when steel is subject to hydrostatic pressures the stress strain characteristic can be predicted from a uniaxial test. However, if the stresses acting on a section of foam are triaxial, the response of a head-form may be different than predicted from uniaxial test data.

A computer-controlled body panel testing machine has been used to quantify stiffness and dent resistance of body panels at Chrysler. The influence of yield strength and local reinforcement on the mechanical behavior of automotive door panels has been investigated. Medium strength steels in the range of 210 -240 MPa yield strength have produced significant improvements in dent resistance over a 160 MPa yield strength steel. Considerable improvements in dent resistance can also be attributed to the use of local, adhesively attached, glass fiber reinforcement patches. The effects of boundary conditions and panel shape on stiffness and dent resistance are illustrated in this application.

A systematic life cycle management (LCM) approach has been used by Chrysler Corporation to compare existing and alternate hydraulic fluids and lubricating oils in thirteen classifications at a manufacturing facility. The presence of restricted or regulated chemicals, recyclability, and recycled content of the various products were also compared. For ten of the thirteen types of product, an alternate product was identified as more beneficial. This LCM study provided Chrysler personnel with a practical purchasing tool to identify the most cost effective hydraulic fluid or lubricant oil product available for a chosen application on an LCM basis.

To understand how the passenger compartment cavity interacts with the surrounding panels (roof, windshield, dash panel, etc) a numerical panel contribution analysis was performed using FEA and BEA techniques. An experimental panel contribution analysis was conducted by Reiter Automotive Systems. Test results showed good correlation with the simulation results. After gaining some insight into panel contributions for power train noise, an attempt was made to introduce beads in panels to reduce vibration levels. A fully trimmed body structural-acoustic FEA model was used in this analysis. A network of massless beam elements was created in the model. This full structural-acoustic FEA model was then used to determine the optimal location for the beads, using the added beams as optimization variables.