Refine Your Search

Topic

Author

Affiliation

Search Results

Training / Education

Introduction to Advanced High Strength Steel Applications and Manufacturing

2019-10-08
Advanced High Strength Steels (AHSS) are now commonly used in automotive body structural applications. The high strength of this grade classification is attractive to help reduce mass in the automotive body through reduction in thickness. Strength also supports improvements in safety requirements so that mass increases are minimized. In some specific grades of AHSS, energy absorption is possible in addition to the high strength. This course will review the definition and properties of AHSS and cover several common applications in automotive body structures.
Technical Paper

The History of Laminated Steel

2019-06-05
2019-01-1578
This paper will discuss the background and history of "laminated steel" (commonly called "noiseless steel" or "MPM". It will provide the early development, where it came from and how it was introduced to North America as a new tool for engineering acoustical solutions. A progressive timeline will show laminated steel from its earliest inception and application in Europe to its current role in today's global market. Case histories along with examples of successful applications will detail its important contribution in advancing the technology for component damping. Many manufacturing sources as well as end-users have been impacted over the the decades since it was introduced. Many of these companies will be highlighted.The background information for this paper is provided by many of the individuates who were involved in the very early stages of its introduction as well as those who are currently working to utilize the technology of "laminated steel".
Technical Paper

Thermal analysis of steel and aluminium pistons in a light duty diesel engine

2019-04-02
2019-01-0546
Chromium-molybdenum alloy steel pistons, which have been used in commercial vehicle applications for some time, have more recently been proposed as a means of improving thermal efficiency in light-duty applications. This work reports a comparison of the effects of geometrically similar aluminium and steel pistons on the combustion characteristics and energy flows on a single cylinder high-speed direct injection diesel research engine tested at two speed / load conditions (1500 rpm / 6.9 bar nIMEP and 2000 rpm / 25.8 bar nIMEP) both with and without EGR. The results indicate that changing to an alloy steel piston can provide a significant benefit in brake thermal efficiency at part-load and a reduced (but non-negligible) benefit at the high-load condition and also a reduction in fuel consumption. These benefits were attributed primarily to a reduction in friction losses.  
Technical Paper

Predicting FLCs of Hot Stamping Boron Steel by Z’-DFC

2019-04-02
2019-01-1089
In this study, combined with an improved Zener-Hollomon parameter (Z’), a previously proposed ductile failure criterion (DFC) is used to predict forming limit curves (FLCs) of Boron steel at hot stamping temperatures. The ductile failure criterion takes into account the critical damage at localized necking or fracture as a function of strain path and initial sheet thickness. The improved Zener-Hollomon equation accounts for the strain rate sensitivity of the material at high temperatures. Compared with published experimental result, the criterion is able to provide accurate prediction of FLCs of different thick Boron sheet steel at different hot stamping temperatures.
Technical Paper

Estimates of the Convective Heat-Transfer Coefficients for Under-Hood and Under-Body Components

2019-04-02
2019-01-0149
In this paper we investigate the application of time constant to estimate the external heat transfer coefficient (h) around specific vehicle components. Using this approach, a test sample in the form of a steel plate is placed around the component of interest. A step change is applied to air temperature surrounding the sample. The response of the sample temperature can be analyzed and the heat transfer coefficient can therefore be calculated. Several test samples were installed at several locations in the vehicle under-hood and underbody. A series of vehicle tests were designed to measure the time constant around each component at various vehicle speeds. A correlation between estimated heat transfer coefficients and vehicle speed was generated. The developed correlations and the measured component ambient temperatures can be readily used as input for thermal simulation tools. This approach can be very helpful whenever CFD resources may not be available.
Technical Paper

Applying Advanced High Strength Steels (AHSS) on Door Outer Panel for Lightweighting and Dent Resistance Performance

2019-04-02
2019-01-0520
The lightweighting potential of applying advanced high strength steels (AHSS) was studied on door outer panel. The dent resistance performance is considered in this study, which is most crucial for exterior panels on vehicles like door outer. NEXMET®440EX and NEXMET®490EX, which are exposed quality AHSS products, are evaluated together with several other bake hardening grades. The door outer panel was chosen from a public domain vehicle model, and dent resistance analysis was conducted using ABAQUS at critical locations. The minimum gauge required to meet the dent resistance performance was obtained for these steels at each dent location. The gauge reduction offered by NEXMET® grades is evaluated based on the results from all dent locations.
Technical Paper

Accounting for Geometry and Residual Stresses in Weld Fatigue: A Strain Energy Density Approach to Total Life of Welded T-Specimens

2019-04-02
2019-01-0523
Although many practical examinations of metal fatigue focus on crack initiation or crack growth, in practice many fatigue failures begin by initiating a crack which then grows until the part fractures completely or can no longer support the loads for which it was designed. This two-phase view of fatigue, called “total life”, is intended to aid engineers in designing parts that will meet design requirement while reducing unnecessary weight and cost. The challenge of using the total life to predict component life is magnified when components are welded together. This work, as a part of a larger project, examines the influence of the welding process on fatigue life predictability by predicting the life of welded specimens made from A36 steel as well as specimens machined from the same material using a geometry designed to develop a nearly identical stress distribution when loaded in the same way and comparing the predictions to measurements.
Technical Paper

Strain Rate Effect on Martensitic Transformation in a TRIP Steel Containing Carbide-Free Bainite

2019-04-02
2019-01-0521
Adiabatic heating during plastic straining can slow the diffusionless shear transformation of austenite to martensite in steels that exhibit transformation induced plasticity (TRIP). However, the extent to which the transformation is affected over a strain rate range of relevance to automotive stamping and vehicle impact events is unclear for most third-generation advanced high strength TRIP steels. In this study, an 1180MPa minimum tensile strength TRIP steel with carbide-free bainite is evaluated by measuring the variation of retained austenite volume fraction (RAVF) in fractured tensile specimens with position and strain. This requires a combination of servo-hydraulic load frame instrumented with high speed stereo digital image correlation for measurement of strains and ex-situ synchrotron x-ray diffraction for determination of RAVF in fractured tensile specimens.
Technical Paper

Fatigue Behavior of Large Cast Components under Variable Amplitude Loading with Overloads

2019-04-02
2019-01-0526
To reduce the weight and to increase the power as well as to enable the utilization of nodular cast iron components, e.g. for wind turbines and heavy industry parts, locally higher stresses need to be withstood by the material. This becomes crucial, when additional overloads influence the structure of thick-walled components causing high local elastic-plastic deformations. In this case, the cyclic, elastic-plastic material behavior and its development under cyclic loading are important points to be considered during component design. To assess the material’s local elastic-plastic material behavior, strain-controlled fatigue tests were performed under alternating loading, Rε = -1, with unnotched specimens removed from cast blocks as well as from a hub and a planet carrier of wind turbines, made of EN-GJS-400-18U-LT, EN-GJS-700-2, ADI-800 and ADI-900.
Technical Paper

Tempered Wire Fatigue Testing

2019-04-02
2019-01-0532
A new bench for the rotating bending fatigue tests of tempered steel wires is presented. The new bench is used to check the spring wire just before it is finally winded to realize a spring. The bench is basically a four-point bending machine. There are two main differences with respect to current bending machines. The first one is that the focus is on semi-finished components (more than 1 meter long), rather than standard small-scale specimens. The second one is that there is a non-linear configuration of the tested component due to its length. The bench design has provided some unreferenced features that make the bench quite accurate and effective in producing quick fatigue assessments. A rotor-dynamic study has allowed to perform tests at 50 Hz. As a preliminary application, some fatigue bending tests of tempered steel wires are described and discussed.
Technical Paper

Comparison of Total Fatigue Life Predictions of Welded and Machined A36 Steel T-Joints

2019-04-02
2019-01-0527
A new total fatigue life methodology was utilized to make fatigue life predictions, where total fatigue life is defined as crack initiation and subsequent crack propagation to a crack of known size or the component’s inability to carry load. Fatigue life predictions of an A36 steel T-joint geometry were calculated using the same total fatigue life methodology for both welded and machined test specimens that have the same geometry. The only significant difference between the two analyses was the inclusion of the measured weld residual stresses in the welded specimen life predictions. Constant amplitude tests at several load levels and R ratios were analyzed along with block cycle and variable amplitude loading tests. The accuracy of the life predictions relative to experimental test lives was excellent, with most within a factor of +/- two.
Technical Paper

Testing of Welded and Machined A36 Steel T-Joint Configuration Specimens

2019-04-02
2019-01-0535
For this latest SAE Fatigue Design and Evaluation project, fatigue tests were run by loading, in bending, both welded and machined T-Joint specimens that have the same geometry. The test rig setup consisted of a horizontally mounted actuator, with pinned joints at both ends, where the load is applied to the top of the vertical leg of the “upside down T” of a T-Joint specimen, while the horizontal legs of the “upside down T” were clamped to the bedplate. Specimens were tested until failure or until the specimen was unable to carry the commanded load. They were cycled under constant amplitude (at several load levels and R ratios), block cycle, and variable amplitude loadings. Welded and machined T-Joint specimens of the same geometry were included in the test plan such that fatigue life predictions could be compared to test lives for each case. Those comparisons would demonstrate the methodology’s relative predictive ability to manage welds, residual stress, etc...
Technical Paper

Crack Initiation and Propagation Fatigue Life Prediction for an A36 Steel Welded Plate Specimen

2019-04-02
2019-01-0538
Fatigue crack initiation and propagation models predict the fatigue life of welded "T" specimens tested by the Fatigue Design and Evaluation (FDE) Committee of SAE under constant and variable amplitude load histories. The crack propagation equations stipulated by British Standard BS-7910 have been incorporated in a material memory model for cyclic deformation. The simulations begin with the crack initiation model and show how it is used to account for cyclic mean stress relaxation and the effects of periodic overloads. After the cracks initiate the BS-7910 model is applied to predict the crack advance due to either constant or variable amplitude histories. Simulation results correspond to the experimental results with good accuracy.
Technical Paper

Composite Components for Vehicle Lightweight: Springs, Wishbones, Low-Cost Hydrogen Tanks, Demise of Astronautic Composite Overwrapped Pressure Vessel

2019-04-02
2019-01-1276
SARDOU SAS has invented in 1992 composite “C” springs (patented in 1993), these springs where offering a high energy density of 1350 joules per kilogram (compared to 300 for steel springs). This huge energy density means a potential 78% weight savings! But in the last century, weight saving was less important and platform managers were reluctant to use anything other than coil springs. So, in 2002, in order to comply with their wishes, SARDOU SAS invented composite coils springs. Easy to fit in standard suspensions, Composite coils springs are the optimum choice for McPherson-strut suspensions. As weight saving is now mandatory, composite springs, are the best choice for automotive suspensions, offering a 50% weight saving compared to steel. A Joint Venture, between SARDOU and SOGEFI Suspensions SA called S.ARA, was created in 2008 in order to mass produce composite coils springs; the official Start Of Production happen in 2014 for AUDI.
Technical Paper

Experimental Study of Sliding Wear Behavior of the Casted Lead Bronze Journal Bearing Material

2019-04-02
2019-01-0824
Lead (Pb) bronze material is used for the manufacturing of bearings. Lead provides less friction and wear-related properties to bronze. During working of the bearings the lead contained micro-chips mixes with the lubricant oil and makes its disposal difficult. Rotational speed and applied load are the two main parameters on which the working and amount of wear from the bearing depend. So it is important to find out an optimum set of speed and pressure on which a particular bearing should operate to minimize the wear and hence minimize the lead-contaminated lubricating oil. In the present work, Taguchi technique has been used to find out the optimum values of speed and pressure. To measure the specific wear rate (SWR) and coefficient of friction (COF) of the leaded bronze material, it is made to slide on a mild steel material and amount of wear and coefficient of friction has been recorded using a pin on disc machine using ASTM-G99 standards.
Technical Paper

A Study of Topology Optimization for Spot-Welding Locations in Automotive Body by Using Driving Simulation

2019-04-02
2019-01-0830
An automotive body is made by joining over 500 components made from steel sheets. Since the joining locations for spot-welding are decided by the designer of each component, the number of spot-welding points tends to be either excessive or inadequate for the required automotive body stiffness. In this study, a topology method which is able to select effectively from design space was applied to optimization of spot-welding locations for vehicle stiffness performance by using a full vehicle model. Static stiffness using constraint of nodes cannot sufficiently express deformation during driving. Torsional deformation occurred in all parts of the body in the mode in which one point of the front bilateral suspension parts was forced and the other three points were constrained in the general static stiffness mode.
Technical Paper

Development of Detection Method for Clamped Part Stiffness in Bolted Joint

2019-04-02
2019-01-1113
If a bolted joint is subjected to axial vibration, the internal force the bolt receives is determined based on the load factor that is a function expressed by bolt stiffness and clamped part stiffness. The stiffness of the bolt and clamped part are generally calculated based on VDI2230, but if the structure of the clamped parts is complicated or made of multiple materials, we have to calculate the clamped part stiffness using FE analysis. FE analysis is very useful for calculations of clamped part stiffness. However it is not easy to conduct FE analysis for all parts and structures. A new method to detect clamped part stiffness of bolted joints was developed in this study. The proposed method is based on a clamp force detection method that we had already proposed. In the method, a protruding bolt thread portion is first pulled while holding down the nut’s upper surface and the displacement at the pulling point is measured.
Technical Paper

Comparative Study of Dissimilar Materials Joints

2019-04-02
2019-01-1115
The presenting work tends to compare the dynamic effect of the self-piercing riveted (SPR) connection with mechanical clinched connection of the same material combination. The substrates used in this investigation are aluminum alloy AA5182-O and deep drawing steel DX51D+Z. The static, dynamic behaviors and the failure modes of the SPR and the clinching connections are characterized by lap-shear, cross-tensions and coach-peel tests. Influence of the strain-rate dependent mechanical behavior of the substrates on the joints is examined, which helps improve the prediction of energy absorption of the joints under impact loading. Considering the realistic baking process in painting shop, the deforming and hardening effects on the SPR and the clinching joints induced by baking are also studied. The specimens are heated to 180°C for 30 minutes in the oven and cooled down in the air.
Technical Paper

Development of Plastic Region Tightening 1.6-GPa Ultra-High Strength Bolt with High Delayed Fracture Resistance

2019-04-02
2019-01-1116
A new variable compression turbo (VC-Turbo) engine, which has a multi-link system for controlling the compression ratio from 8:1 to 14:1, requires high axial force for fastening the multi-links because of high input loads and the downsizing requirement. Therefore, it was necessary to develop a 1.6-GPa tensile strength bolt with plastic region tightening. One of the biggest technical concerns is delayed fracture. In this study, quenched and tempered alloy steels were chosen for the 1.6-GPa tensile strength bolt.
Technical Paper

Lumped Parameter Transient Thermal Model of Motor Considering Temperature and Flow Rate of Cooling Water

2019-04-02
2019-01-0890
The influence of heat flow and cooling water characteristics on motor temperature cannot be accurately reflected by the traditional motor temperature analysis method. In order to study the motor and its key components’ temperature characteristics under different temperatures and flow rates of cooling water, this paper establishes the lumped parameter transient thermal model which includes cooling water module, based on a 50kW permanent magnet synchronous motor. The transient and steady temperature is calculated through this model together with the motor loss calculation module in the electric drive system model. The influence of different temperature and flow rate of cooling water on motor and its key components’ temperature characteristics is compared. During the modeling process, the motor body is divided into 14 parts, based on the internal heat flow path of the motor. The thermal resistance of each key component and cooling water is calculated.
X