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Technical Paper

A Cost Effective, New Coating for Multi Layer Steel Exhaust Gaskets

Current trends in environmental and emissions regulations are driving changes in new engine systems, and increasing the need for more effectively sealed joints in exhaust systems. At the high temperatures in these exhaust systems it is difficult for traditional gaskets to provide an effective seal, as they degrade at high operating temperatures. This paper introduces a coating that has both excellent temperature stability and good compliance, thus forming an excellent sealing enhancement for metallic layers in exhaust system gaskets. Temperature stability data is presented along with sealing data, which illustrate the superior performance of this material compared to current systems.
Technical Paper

A Critical Assessment of Forming Limit Prediction Models and Beneficial Modifications to Them

Major forming limit prediction models and calibration methods are reviewed briefly and their advantages and disadvantages are discussed. Two modified Marciniak-Kuczynski (M-K) models and one modified NADDRG (Keeler-Brazier) model are also presented which have some advantages over conventional models. In the first modified M-K model, material non-homogeneity has been substituted for geometrical non-homogeneity to reduce the sensitivity of the traditional model to variations of the initial non-homogeneity. Using this important advantage, a semi-empirical relation is proposed to predict the value of the initial material non-homogeneity. In the second modified M-K model, the conventional calibration method (which requires an experimental point, corresponding to plain strain condition, to find the initial non-homogeneity and calibrate the model) is revised and the uniaxial tensile point, which is easily obtained, is proposed to be used in the calibration process.
Technical Paper

A Critical Review of Different Experimental Approaches to Calibrate Numerical Sheet Forming Simulations

The calibration of yield functions for numerical sheet forming simulations is done using different experimental approaches such as the uniaxial tensile test, the bulge test, etc. How accurately the material behavior of dedicated aluminum, conventional and high strengths steel grades subjected to various loading conditions can be modeled is investigated using e.g. uniaxial tensile test data only. Different formulations of yield functions that are widely used in industry (e.g. Hill'48, Hosford'79, Hill'90) are considered. It is shown that tensile test data is insufficient to successfully calibrate yield functions for numerical sheet forming simulations especially for aluminum and pronounced anisotropic steel. The use of improved formulations of yield functions is emphasized.
Technical Paper

A Cyclic Model of Cosmetic Corrosion for Painted Steel Sheets

To identify the most significant parameters influencing the cosmetic corrosion of cold-rolled and coated steel sheets, stretch deformed panels were phosphated, painted and exposed in real time on an experimental car for 5 years. Based on advanced microanalysis techniques, the morphologies and the chemical composition of the corrosion salts are characterized. Comparisons between accelerated tests and natural exposures are made and corrosion mechanisms are identified. On that basis, a 3-step cyclic model of cosmetic corrosion is presented. Combined with the experimental results, this model outlines the importance of the coating characteristics, the compositions of the corrosion products, the humidity and temperature cycles during the exposure tests (natural or accelerated) and the environmental conditions (salts and polluting gases) on the corrosion mechanisms and the resistance of painted coated steels.
Technical Paper

A Cylinder Pressure Sensor for Internal Combustion Engine

A cylinder pressure sensor using a piezoelectric element which has high temperature resistance has been developed. The thickness shear mode in the element was utilized so as to diminish the pyroelectric effect. A ceramic pressure transfer pin inserted between the piezoelectric element and the stainless steel diaphragm is capable of shielding the heat from the diaphragm of high temperatures and also of insulating electrically the element from the housing. The characteristics of our sensor were evaluated by means of a hydraulic pressure generator and test engine. Our sensor outputs showed good matching with the reference pressure sensor outputs.
Technical Paper

A Deep-Drawing, Hot-Dipped Galvanized Steel for Difficult Forming Applications

Formability of galvanized steel has been one of the key Issues In the automotive industry's transition to more corrosion resistant vehicle parts. This report describes a very ductile and formable grade of continuously annealed, hot dipped galvanized sheet steel that was specifically developed for difficult deep drawing or stretch-forming applications. The report also discusses performance of this grade in automotive stamping plants.
Journal Article

A Demonstration of Local Heat Treatment for the Preform Annealing Process

The preform annealing process is a two-stage stamping method for shaping non age-hardenable (i.e. 5000 series) aluminum sheet panels in which the panel is heat treated in between the two steps to improve overall formability of the material. The intermediate annealing heat treatment eliminates the cold work accumulated in the material during the first draw. The process enables the ability to form more complex parts than a conventional aluminum stamping process. A demonstration of local annealing for this process was conducted to form a one-piece aluminum liftgate inner panel for a large sport utility vehicle using the steel product geometry without design concessions. In prior work, this process was demonstrated by placing the entire panel in a convection oven for several minutes to completely anneal the cold work.
Technical Paper

A Design Tool for Tuning and Optimizing Carburizing and Heat Treat Processes

A software tool has been developed to aid designers and process engineers in the development and improvement of heat treat processes. This tool, DANTE™, combines metallurgical phase transformation models with mass diffusion, thermal and mechanical models to simulate the heating, carburization, quenching and tempering of steel parts. The technology behind the DANTE software and some applications are presented in this paper.
Technical Paper

A Detailed Analysis of Proper Safety Features Implementation in the Design and Construction of Modern Automotive LPG and CNG Containers

Paper describes analysis of the design process of modern automotive LPG and CNG containers. Over decade experience in the field of both computer based analysis as well as in the real conditions testing has been collected and presented in the paper. Authors present the potentials of modern FEM methodologies in the optimization and production of lightweight steel containers. It has been proved that the most sophisticated numerical analysis have to be followed by the construction verification, particularly considering direct exposure to fire. Bonfire test have become obligatory for both liquid and compressed gases containers. Properly chosen fire protection system, together with the adequate level of quality of materials applied for its production together with proper directing of the gas flowing out from safety devices are the essential factors defining gas containers fire safety.
Technical Paper

A Detailed Examination of Weldability Lobes for a Range of Zinc-Coated Steels

The objective of this study was to investigate the weld ability of four tyes of coated steels. These materials include: uncoated, hot-dipped galvanized, electro-galvanized and galvannealed steels. “Statistically significant” weld ability lobes were evaluated for each material. Dynamic resistance traces were also evaluated. The following conclusions were obtained from the results. The minimum-nominal current range/lobe width ratio indicated the mode of button growth and correlated well with the expulsion button size. The lobe width/standard deviation ratio was found to be a measure of weld stability. The dynamic resistance traces on uncoated steel correlated very well with the observed button size; however, similar correlations could not be made with respect to the zinc coated steels. It was found that the variability of the averaged dynamic resistance traces were consistent with the variability of the corresponding weldability lobes.
Technical Paper

A Development Procedure to Improve the Acoustical Performance of a Dash System

This paper discusses a development procedure that was used to evaluate the acoustical performance of one type of dashpanel construction over another type for a given application. Two very different constructions of dashpanels, one made out of plain steel and one made out of laminated steel, were studied under a series of different test conditions to understand which one performs better, and then to evaluate how to improve the overall performance of the inferior dashpanel for a given application. The poorly performing dashpanel was extensively tested with dashmat and different passthroughs to understand the acoustic strength of different passthroughs, to understand how passthroughs affect the overall performance of the dash system, and subsequently to understand how the performance can be improved by improving one of the passthroughs.
Technical Paper

A Development of 780MPa Hot Rolled High Strength Steel for Application to Automotive One-Piece Front Lower Control Arm

Automakers are putting ever more emphasis on their environmental and energy efficiency efforts through improving the fuel consumption of vehicles. One way of saving energy is to reduce the total weight of the vehicle by using high strength steel. Hyundai steel developed a new 780 MPa grade of hot rolled high strength steel with excellent stretch flange formability in which the ferrite matrix is strengthened by ultra-fine, nano-sized precipitates. The material developed in our study met the material requirement of OEM's material specification with 780 MPa tensile strength and 55% hole extension ratio. Steel grades of 780 MPa were applied to develop front lower control arm for automotive chassis. In order to evaluate the performance of materials, primary design, durability and strength analysis of materials were prepared in collaboration with suppliers. Prototype of front lower control arm was fabricated and durability test and strength test were performed.
Technical Paper

A Development of Composite Material Suspension Arm

Various approaches have been developed recently to apply light weight technology to automotive vehicles which focuses on fuel efficiency by reducing weight and hence are environmentally friendly. This paper shows that composite materials suspension arm which is made up engineering plastic and steel have more than equal to strength and stiffness compared to forged steel. Also Composite materials suspension arm presents lightweight and low cost.
Journal Article

A Development of the Fretting Fatigue Analysis Techniques for Engine Aluminum Block

Periodically, engine block-bearing cap structure is subject to the mixed bearing load from combustion and inertia mass of crank. Recently, due to the trend of lightness, cast steel is replaced with aluminum in the material of gasoline engine block. And, the load acting on the main bearing cap is rapidly rising due to the increase of engine power. Therefore, in the development stage, fretting fatigue failures frequently occurred on the block face contacted with the bearing cap. Fretting is a kind of wear which is occurred by micro relative movement. Even though various researches have been made to investigate fretting fatigue failure with FEA approaches, they are not enough to evaluate the phenomenon. In this study, the new CAE method simulating the fretting fatigue failure on the engine block face is developed and the mechanism of the fretting fatigue on the engine block is investigated.
Technical Paper

A Dynamic Analysis of Rotary Combustion Engine Seals

Real time work cell pressures are incorporated into a dynamic analysis of the gas sealing grid in Rotary Combustion Engines. The analysis which utilizes only first principal concepts accounts for apex seal separation from the trochoidal bore, apex seal shifting between the sides of its restraining channel, and apex seal rotation within the restraining channel. The results predict that apex seals do separate from the trochoidal bore and shift between the sides of their channels. The results also show that these two motions are regularly initiated by a seal rotation. The predicted motion of the apex seals compares favorably with experimental results. Frictional losses associated with the sealing grid are also calculated and compare well with measurements obtained in a similar engine. A comparison of frictional losses when using steel and carbon apex seals has also been made as well as friction losses for single and dual side sealing.
Technical Paper

A Failure Criterion for Stretch Bendability of Advanced High Strength Steels

Studies in an Angular Stretch Bend Test (ASBT) have demonstrated that the failure location moves from the side wall to punch nose area. This occurs as the R/T ratio decreases below a certain limit and applies to most low carbon steels with the exception of Dual Phase (DP) steels. Such behavior in DP steels indicates that bending effects have a severe impact on the formability of DP materials. Therefore, the traditional criterion using the forming limit curve (FLC) is not suitable to assess the formability at punch radius areas for DP steels due in part to its uniqueness of unconventional microstructures. In this paper, a new failure criterion, ‘Bending-modified’ FLC (BFLC), is proposed by extending the traditional FLC using the “Stretch Bendability Index” (SBI) concept for the stretch bendability assessment.
Technical Paper

A Family of Automotive Formable Hot Rolled Strip Steels-Their Properties and Applications

The Australian steel and automotive industries have been cooperating to rationalise automotive hot strip production and usage in Australia. This has permitted a reduction in the number of required grades from 63 to 7. The 4 most critical grades in this rationalized range comprise the Xtraform Family of Formable Strip Steels. These steels are of nominally 200, 300, 400 and 500MPa yield strength with tensile strengths to meet ‘equivalent’ SAE and JIS standards. This paper details the state of development in mid 1935 and describes the composition structure and properties of the Xtraform series. Excellent results have been achieved in comparison with imported steels in the vital areas of Low-cycle Fatigue and Spot Weldability. Applications of the steels in various automotive assemblies are described in three case studies.
Technical Paper

A Fatigue Prediction Method for Spot Welded Joints

Generally linear finite element analysis (FEA) is used to predict fatigue life of spot welded joints in a vehicle body structure. Therefore, the effect of plastic deformation at the vicinity of the spot welded joints is not included on fatigue prediction. This study introduces a simple technique to include the plastic deformation effect without performing elastic-plastic finite element analysis. The S-N curve obtained from fatigue test results is modified to consider this effect. Tensile strength test results of spot welded joint specimens were utilized to find the load range for FEA equivalent to the applied load range for fatigue tests. To demonstrate the proposed approach, fatigue test results of advanced high strength steels (AHSS) for lap-shear and coach peel specimens were used. Both the specimen types were tested at various constant amplitudes with the load ratios of R=0.1 and 0.3.
Technical Paper

A Finite Element and Experimental Study of Sheet Deformation as Influenced by Drawbead End Geometry

Drawbeads have been playing an important role in deep drawing processes. The restraining force exerted by the drawbeads is important in enhancing the part formability. It is found that improper drawbead design will result in defects such as wrinkles and splitting. Thus, the drawbead geometry, especially its end radius, is a critical aspect in the die design. The present investigation focuses on the influence of the drawbead end radius and blankholder force on the sheet deformation patterns. The experimental results reveal that a drawbead with end radius equal to its cross sectional radius will cause severe deformation and wrinkling downstream of its end. With drawbead end radius twice the size of its cross sectional radius, the deformation in the downstream side of the drawbead end becomes smoother, hence improving the severe deformation and wrinkling. A higher blankholding force also suppresses the wrinkling near the drawbead end.
Technical Paper

A Formable-Strengthenable Sheet Steel

High-strength cold-rolled sheet steels offer a potential to accomplish weight savings through gage reductions. However, the reduced formability which accompanies increased strength presents difficulties in the application of these steels for sheet metal stampings which require the formability equivalent of deep-drawing steels. A new deep-drawing sheet steel is being developed which overcomes the formability limitations of high-strength cold-rolled steels. Parts made from this steel can be uniformly strengthened to a high yield strength, up to 120,000 psi (827 MPa). Strengthening is accomplished by a 1200°F (921°K) heat treatment in a controlled atmosphere which results in internal nitridation. The nitrides formed by the alloying elements in the steel provide precipitation hardening. No distortion of the parts results from the heat treatment. The effect of heat-treating variables on tensile properties, weldability, fatigue, and toughness, are discussed.