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The paper reviews the role of drawbeads in sheet metal stamping. The design of drawbeads is discussed in depth, with treatment of different bead cross sections, bead end shapes, and bead materials. International standards and practices are included. This is followed by the historical development of the modeling of the drawbead restraining force, starting with basic equilibrium approaches, and leading to the use of the finite element method which permits the study of drawbead effects on sheet metal flow in three dimensions. Finally, the potential of active drawbeads is described based upon ongoing research which is directed toward closed-loop computer control of the stamping process through adjustment of the drawbead penetration.

A two-stage finite element method has been used to evaluate the relative denting characteristics of four commercial grades of sheet steel (DQ, BABH, Rephos. IF, and HSLA-50) in a generic laboratory panel geometry. The first stage forming analysis is performed using LS-DYNA3D, a dynamic, nonlinear, explicit finite element analysis code, while the second stage denting analysis is performed using LS-NIKE3D, a large deformation implicit finite element code, in order to avoid dynamic effects. Material thinning and strain hardening during the first stage (forming) as well as bake hardening effects are explicitly accounted for in the subsequent denting analysis. Simulation results indicate that at a 400 N applied load level and a nominal sheet thickness of 0.76 mm, DQ exhibits the highest dent depth (0.86 mm), BABH and Rephos. IF exhibit similar behavior with a dent depth of approximately 0.5 mm, while no visible dent forms in the HSLA-50 grade for the specific panel geometry evaluated.

The use of gas springs with a surge tank to generate blank holding forces in drawing tools is increasing. These gas spring systems are characterized by an almost constant behaviour of the spring force over the spring displacement. To prevent an increase of the normal pressure with increasing stroke in a drawing process, it is advantageous to obtain a degressive force-displacement behaviour of the gas springs. For this reason, a gas spring system was developed to realize a decrease of the blank holding forces over the stroke without large additional expenditure. The technical realization takes place in an exact controlling of the upper and lower pressure chamber of the nitrogen cylinder.

Customer preference for the “eye catching” and aesthetically good looking product has made the car quality a key competitive issue. Manufacturers have no choice but to design and manufacture products to exceptional levels of quality while remaining cost competitive. If excessive costs of “quality” are to be avoided, product and process design standards must be harmonised to ensure that product quality can be designed in from the start of a new product development cycle. However, the subjective nature of the car body aesthetic quality makes it difficult to ensure effective communication across different functions of the organization. Traditionally, product engineers are more used to designing for product performance targets such as stiffness, dentability and weight, while process engineers are primarily concerned with ensuring manufacturing feasibility within an agreed cost target.

Draw simulation of automotive panels generally consists of two steps: binder wrap and punch contact. The binder wrap simulation while providing the necessary initial conditions for the ensuing punch contact simulation, is itself practically important. For instance, one can evaluate the binder design by examining whether the sheet shape inside the die cavity is buckle-free and/or the sheet on the binder is severely wrinkled. The physical process involved in the binder wrap is dominantly quasi-static and complex as it involves contact, friction and buckling phenomenon. Current binder wrap simulation in the automotive industry has been mainly carried out either using proprietary software or dynamic explicit codes with slow speed. This paper presents implicit-static finite element results using ABAQUS/IMPLICIT Code on the binder wrap of several doubly curved laboratory binders and comparisons with test data. Good correlation was obtained.

In automobile companies new techniques of sheet metal forming have been developed and some of them are applied practically in order to solve the social demands to automobile. Sheet materials makers have also developed new materials with good formability in response to the requests of automobile companies. Current topics of sheet metal forming techniques in Japan are; (1) Stamping of high strength steel and aluminum alloy sheets for weight reduction of autobody, (2) Stamping of tailored blanks, (3) Application of new forming techniques such as hydro-mechanical forming and blank holding force control, and (4) Practical application of FEM simulation to die making and stamping processes for the reduction of preparation time and the optimization of forming processes.

A theoretical model for predicting the life cycle of a friction material used in wet friction clutches has been developed and verified. For a given friction material, the degradation mechanism can be identified by performing a Thermal Gravimetric Analysis (TGA) on the samples of worn friction materials. The samples are taken from the friction plates after they undertake various periods of the continuous slip experiments on the full-pack test machine. The degradation rate constants are obtained by performing the TGA experiments on the samples from the continuous slip experiments with different input powers and interface temperatures. The degradation for a dynamic engagement cycle is calculated by integrating the degradation rate with the temperature history near the friction interface as a function of time. The temperature history is predicted by the Borg-Warner computer model for the engagement of a wet clutch [1], which has been verified experimentally.

A new sintered composite friction material consisting of mechanically-alloyed copper-based composite powders has been developed. It has a unique microstructure of fine hard particles that are embedded in the matrix of the copper-based primary particles. This friction material reduces abrasive wear and/or seizures that are often caused by hard particles which become detached from the matrix, because the hard particles in this material are bonded tightly to the matrix even under harsh service conditions. The fine hard particles are also very useful for improving high friction force when contacting a surface material. Therefore, this new friction material provides a higher friction coefficient than the conventional material containing coarse hard particles. Furthermore, this friction material is less abrasive to the surface material than the conventional one.

The physical and chemical properties of a mineral-based (Fluid-M) and a partial-synthetic-based (Fluid-PS) automatic transmission fluid were compared by the analyses of Gel Permeation Chromatography (GPC), Thermogravimetry (TG), Fourier Transform Infrared Spectroscopy (FTIR), Nuclear Magnetic Resonance (NMR), Gas Chromatography (GC), viscometry, thermo-oxidative stability, torque response curve shape and metal-to-metal wear preventive characteristics. The effects of various properties of Fluid-M and Fluid-PS on wet friction material performance were investigated from the viewpoints of compressibility, durability, tensile strength, surface interactions and friction-pressure-speed-temperature characteristics. Friction material specifications for partial-synthetic fluid applications will be different from those for mineral-based fluid applications. GPC showed that Fluid-PS has a higher concentration and a lower molecular weight of VI Improver than Fluid-M.

Friction performance of paper-based materials for wet clutches in automotive automatic transmissions is influenced by the entire structure of the material, which is characterized by a combination of porosity and visco-elasticity. In the clutch plate engagement process, the coefficient of friction is higher when the porosity of the material is higher. In this paper, visco-elasticity of the material was measured by a testing apparatus which was originally designed and built. It has become clear that the compressive visco-elastic deformation increases as the porosity becomes higher. The relationship between the compressive visco-elastic deformation of the material and the friction torque curve of the clutch plate was also analyzed. It was found that the friction torque curve of a clutch plate is influenced by the visco-elasticity of the material as well as the porosity.

Various wet friction materials, in which different fillers are compounded on the surface of fibrillated fiber base, were prepared. The friction properties of these materials were pursued at various slip speeds, loads and oil temperatures. Streibeck Diagrams of the data were obtained, and the effect of fillers on the frictional characteristics was investigated. The following results were obtained; (1) The slope of the Streibeck Diagram should be positive to have smooth frictional characteristics. (2) Abrasive powders effectively improved the slip characteristics of friction materials. (3) The effect of the abrasive fillers was further improved by using less compliant paper.

Contour hardening of small gears, such as automotive transmission gears, is beneficial due to the higher strength characteristics and lower distortion. In the past, conventional induction hardening was not used due to its inability to produce a contour case pattern. However, carburizing also has inherent problems such as abnormal carburized layer, distortion due to high temperatures and long heating time, and retained austenite. The Micropulse system, using both high and low frequencies, has been developed to alleviate some of the problems with traditional induction hardening. This Micropulse process makes it possible to produce a contour hardened pattern on a variety of gearing. This process is very rapid, as final heat time normally does not exceed 0.250 seconds. The advantages to the Micropulse process include: high hardness, fine microstructure, high residual compressive stress, and low distortion.

The banded microstructure of pearlite and ferrite in normalized alloy steel is susceptible to thermal distortion during carburizing process due to its unidirectional orientation parallel to rolling direction. The planetary gears with material of banded microstructure have been experienced in high thermal distortion during carburizing and quenching process and result in uneven surface hardness and effective case depth at the inside of pinion gear after honing. These defects played failure initiation site roles in durability test during development of new automatic transmission. The galling between the contacting components in severe lubricating system was the main failure mechanism. Double normalizing at 920 °C was designed to resolve the banded microstructure of normalized alloy steel. The microstructure and grain size of the double heated steel became equiaxed and fine due to homogenizing and recrystallization through double heat treatment.

Automotive demands for increased service life and use of flexible fuel blends of alcohol and gasoline have propelled the development of new materials for automotive fuel systems. Traditional fuel system materials, i.e., bare or prepainted terne coated steel sheet, which do not meet the new requirements are being replaced with prepainted zinc-nickel coated steel sheet. Automotive fuel tanks and fuel system components made from the new prepainted zinc-nickel steel sheet offer increased service life and compatibility with the entire range of flexible fuel blends. This paper describes the results of several laboratory corrosion studies which examined the environmental corrosion performance and the fuel compatibility of prepainted zinc-nickel coated steel as a function of several system properties. Performance is compared to prepainted terne, prepainted hot dip tin, and prepainted galvanneal.

Type 409 (UNS S40900) ferritic stainless steel was developed more than 30 years ago specifically for automotive exhaust systems where it has subsequently found extensive use. Performance of this 11 Cr- Ti alloy for the most part has been good. However, recent failures of exhaust system components demonstrate that the T409 alloy can become sensitized in weld heat-affected zones and suffer intergranular corrosion. Results of a broad study of commercial heats illustrate that weld heat-affected zones of T409 are stabilized when titanium plus columbium or titanium alone meets the criterion: Experimental procedures used to establish this criterion are described, including development of a test to detect sensitization. Also the benefits of stabilizing with titanium in combination with columbium are discussed.

The corrosion mechanism of zinc coated steel sheets in automotive bodies was studied in field vehicle tests and several types of accelerated tests. Perforation corrosion starts in unpainted areas of lapped parts, and proceeds in the following steps: i) galvanic protection by the Zn coating, ii) protection by corrosion products, and iii) corrosion of the steel substrate and perforation. Although the corrosion processes were the same in all the cases tested, the corrosion rate depended significantly on the environment, such as atmospheric exposure conditions and the part of the automotive body. In accelerated corrosion environments, Zn coating is largely ineffective against perforation corrosion because galvanic protection and protection by corrosion products cannot be maintained over the long term.

Doors were removed from recycle-yard vehicles in Syracuse, N. Y. and examined in the laboratory as part of an on-going field study on corrosion behavior trends in the de-icing salt region of the U. S. Lower doors, including hem-flange internal surfaces, were examined, and performance trends as a function of materials selection, age and mileage were determined. The results to date on doors from 167 Syracuse vehicles are indicative of the nature and history of salt-induced corrosion in the region, and they indicate the degree of benefit from galvanized construction and body design features.

The Corrosion Task Force of the Automotive/Steel Partnership (A/SP) and the Society of Automotive Engineers' Automotive Corrosion and Prevention (SAE/ACAP) committee are working cooperatively on the development of an improved laboratory test for perforation corrosion. This paper gives the results of testing a set of standard SAE perforation corrosion test specimens for up to 160 cycles in the environment of J 2334, the new SAE cyclic test for cosmetic corrosion. SAE J 2334 was found to provide a clear distinction among the test materials. In general, the results indicate that the perforation corrosion resistance of coated products is much greater than that of cold rolled steel, and that it also increases with coating mass, as well as with application of a barrier organic coating. Magnetite (Fe3O4) was the predominant iron corrosion product found in the crevices of the perforation corrosion test specimens. Smaller amounts of goethite (α-FeOOH) were also found.

The use of cyclic corrosion tests which consist of salt spraying, humidifying, and drying phases is desirable in the evaluation of the corrosion performance of automotive body panels. In this work, coupons of zinc-coated steel and of cold rolled steel were exposed to a defined cyclic corrosion test (CCT) which has shown to be suitable for simulating diverse outdoor conditions for evaluating the cosmetic corrosion of precoated steel. Micro-environment data in the gap of lapped panel specimens, such as wetness, corrosion rate of test materials, pH value, chloride content, have been obtained during the CCT test. The galvanic current flowing between a gold electrode and the test materials was measured to monitor the degree of wetness inside the crevice. The results show that the surface of the test materials never became really dry even during the dry period of the CCT cycle. Furthermore, the wetness during wet and dry periods in the crevice increased with increasing number of CCT cycle.

The presence of marred and scratched areas detract from the appearance of current automotive topcoat systems. Although the final determination of the extent of the damage to the paint surfaces must be made by human visual evaluation, machine estimation of this damage has value in being a tool for screening large numbers of different paint technologies. Scattered light from marred regions (both single and multiple scratches) in an automotive basecoat/clearcoat system was generated and collected in a goniophotometer. The areas under the intensity/angle curves were obtained using an extended trapezoidal rule for numerical integration. This technique shows promise in correlating goniophotometric data with human evaluation of marred areas. This technique may be of value in screening different paint technologies and chemistries.