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Previous applications of 980 XK steels in the automotive industry have been limited. However, to meet increased structural requirements of MVSS-301, AMC has incorporated 980 XK steel in the 1977 Gremlin and Hornet underbody rear sill subassemblies. This paper emphasizes how formability and spot weldability characteristics were optimized in order to meet the vehicular crashworthiness required in this structural application. Traditional mild steel design, forming, and spot welding procedures were successfully modified to utilize 980 XK. These modifications are practical and have been successfully incorporated in production operations.

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.

The paper presents a new method, based on standard laboratory cup tests, for predicting the formability of materials; in the example provided, the forming potentials of four new materials are shown. The properties of stretchability and drawability, which are the principal factors defining a material's forming limits, may be assessed using the Olsen spherical cup test and the Swift flat-bottomed cup test. In the shape analysis procedure described, the minimum amount of deformation needed to fix a desired shape is determined. Then necessary adjustments to tooling for optimum sheet metal usage are made based on calculations from a new type of chart showing stretch forming ratio and draw forming ratio, providing a comparison of the formabilities of a number of materials.

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 ambient temperature aging behavior of hot dip coated cold-rolled bake hardenable steel sheets manufactured by an in-line continuous annealing technique has been investigated. These materials exhibit good and uniform mechanical and bake hardening properties as-produced and after aging. For the same chemistry, carbon and nitrogen solute levels can be higher in galvanized (GI) products than in galvannealed (GA) products, with the result, of course, of higher bake hardening and aging indexes. Based on the classical static strain aging theory, the interactions between interstitial solutes and dislocations during the ambient aging of these steel sheets can be classified into four stages. Optimal press forming or stamping operations are best performed in the first or second stages of aging but no significant forming difficulties should be expected even if these operations are conducted during the later aging stages.

Interface friction between sheet metal and tooling in sheet metal forming is examined in different forming modes using laboratory simulative tests. Stretchability is studied by the limiting dome height test; drawability is investigated by a four inch Swift cup draw test and the coefficient of friction is measured by the draw bead simulator under bending and unbending deformation. The responses of the interface friction in six different coated and uncoated steel sheets are studied using seven different lubricants. It is found that the interface friction between sheet metal and tooling is very sensitive to the forming mode and the type of coating. For the same lubricant and coated material, two different forming modes may produce very different results in interface friction. However, overall good and bad lubricants for all forming modes can be determined for a given coated material using these three tests.

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.

Strain analysis of stampings is explained. The system is based on the strain distributions obtained from 0.2 in. inter-locking circle grid patterns etched on blanks. The strain distributions are related to a developed formability limit curve and the mechanical properties of the gridded blank. The evaluation of the graphic relation of the strains to the formability limit enables the press shop to determine what factors should be changed to produce stampings with less scrap and lower cost.

Chrysler Corporation's Jeep and Truck platform implemented a new design and prototype process for the body-in -white of a new pickup truck. A team approach achieved concurrent body design, stamping die design, assembly process development, and assembly tooling development. The first domestic US industry use of a 100% electronic design and release system was instrumental in the process. The new process produced a prototype body-in-white on time at 95 WBVP (weeks before volume production) with the highest level of production-intent components ever achieved within Chrysler at this stage of development.

This paper describes the application of the Design for Manufacture and Assembly (DFMA) method at Chrysler. Attention is focused on the development of the clutch and brake pedal and bracketry system of the PL project in the Small Car Platform. The Chrysler DFMA procedure including competitive evaluation and value engineering was utilized during the initial design phase involving product concept development from the original functional and manufacturing requirements. After the first laboratory tests, a number of key design and manufacturing concerns surfaced and led to a second cycle of DFMA analysis. The procedure permits major design functions and manufacturing and assembly process issues and criteria to be incorporated in the initial design stages.

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.

This paper discusses the development of criteria necessary to establish reliable lunar exploration and construction vehicle concepts. To establish the basis for the development of these criteria, an exploration mission using the presently conceived Apollo launch vehicle system is described. The criteria resulting from the study of the contribution made by the hostile lunar environment and the life support system requirements within the framework of the selected mission are established. Soils testing in a hard vacuum is described, as are tests of models under simulated lunar terrain environment. Two lunar vehicle configurations are reviewed, including design parameters and subsystem development.

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 effects of key alloy and process parameters on the mechanical properties of high strength, highly formable low carbon sheet steels have been determined by a combination of laboratory processing, Taguchi Design of Experiments method, and multiple linear regression analysis. Factors studied include C, Mn, P, hot mill coiling temperature, in-line annealing temperature, and annealing line speed. Tensile strength levels were varied from 40 to 50 kg/mm2 with elongation of 30 to 40%. Annealing conditions were varied from partial to full recrystallization in both the single and α + γ two phase region. Effects of the chemistry and process parameters on the mechanical properties will be discussed, with particular emphasis on conditions required to produce a hot dipped galvannealed product meeting 45 kg/mm2 tensile strength and 35% elongation minimum requirements.

In order to increase the strength and formability of batch annealed sheet steels, design of experiment method was used to set up an experimental matrix with five factors, including C, Mn, P in steels, coiling, and batch annealing temperatures, at two levels. Effects of these factors were analyzed using analysis of variance and linear regression methods for cold spot and hot spot, respectively. Linear regression results showed that higher alloying element contents and coiling temperature will increase strength and deteriorate elongation, which is opposite to the effect of annealing temperature. Analysis of variance showed similar results to those of linear regression, except the effect of C on elongation and effect of coiling temperature on tensile strength and elongation are negligible for cold spot. For hot spot, effect of coiling temperature on tensile strength is small.

This paper outlines the advantage of using galvanized steel to protect critical structural members from corrosion. For example, the mean 2 X 106 cycle fatigue strength for 0.070 and 0.085 in thick galvanized steel was approximately 26,000 psi. It was unaffected by exposure to 96 h of salt spray before testing. Comparable fatigue strength for 0.095 in thick hot rolled steel of nearly equivalent chemistry was about 28,000 psi. Exposed to 96 h of salt spray, it dropped to about 25,400 psi.

The use of tailor welded blank sheets for body-in-white applications has brought many new forming challenges. Mechanical properties of tailor welded blanks measured from the tension test showed significantly higher strengths and lower elongations than in the base metal. The forming limit of tailor welded blanks was significantly reduced when compared to that in the base metal. For the weld made from materials with dissimilar thicknesses/strengths, additional formability issues were also raised in addition to those for the weld made from materials with similar thickness/strength. These issues increase the potential for failure in the lesser thickness/lower strength material in the area immediately adjacent to the weld when the difference in thicknesses or strengths of the two materials increases.

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 high strain rate behavior of three types of low carbon steel has been investigated in the strain rate regime of .006-100 sec-1. These types included hot and/or cold rolled (i) rimmed steels, (ii) aluminum killed steels and (iii) high strength low alloy steels with various combinations of cold rolling and aging treatments. The tensile properties reported at four strain rates in the above range are yield strength, tensile strength, uniform and total elongation, strain hardening exponent and strength coefficient. Strain rate hardening exponent at several strain levels is also reported. New experimental techniques are discussed. The results are presented in tabular form and are discussed with representative graphs. In general, strength increases and ductility decreases with increasing strain rate.

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.