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Impression Creep of Lightweight Alloys

SAE International Journal of Materials and Manufacturing

Univ. of Kentucky-Rong Chen, Fuqian Yang, Y Charles Lu
  • Journal Article
  • 2010-01-0226
Published 2010-04-12 by SAE International in United States
Conventional creep testing requires many samples and therefore is time consuming and inconvenient. The impression creep technique is a new creep test wherein a cylindrical, flat-tipped punch is pressed into the material and the displacement recorded as a function of time. Due to the constant contact area between the punch and specimen, a steady-state deformation can be reached underneath the punch, from which the creep parameters can be obtained. In the present study, the creep behaviors of two lightweight magnesium alloys were studied by using impression creep tests in the temperature range of 408-443K and under the punching stress range of 1.68-60.4 MPa. Using a power law between the steady-state impression velocity and the punching stress, it was found that the stress exponent changes with both stress and temperature. In the high temperature range, the stress exponent n for MRI 230 is ~ 6.7 while for AZ91D is ~ 5.5. The activation energy for MRI 230 is 78.9 kJ/mol and for AZ91D is 59.5 kJ/mol.
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Preliminary Evaluation of a Low-Cost Cast Iron for Exhaust Manifold and Turbocharger Applications

SAE International Journal of Materials and Manufacturing

Univ. of Alabama Birmingham-William (Jud) Dunlap, Alan Druschitz
  • Journal Article
  • 2010-01-0657
Published 2010-04-12 by SAE International in United States
Exhaust manifolds and turbocharger housings require good elevated temperature strength, good resistance to thermal fatigue and a stable microstructure. High silicon ductile iron, high silicon-molybdenum ductile iron and Ni-resist (a high nickel ductile iron) are the cast materials of choice. Unfortunately, molybdenum and nickel are expensive. In this study, a lower cost, high silicon-titanium, compacted graphite iron was developed and compared to high silicon ductile iron and higher cost, high silicon-molybdenum ductile iron. Room and elevated temperature strength data is presented.
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Bolt Load Retention and Creep Response of AS41 Alloyed with 0.15 % Ca

SAE International Journal of Materials and Manufacturing

GKSS Research Centre-Okechukwu Anopuo, Yuanding Huang, Norbert Hort, Hajo Dieringa, Karl Ulrich Kainer
  • Journal Article
  • 2010-01-0404
Published 2010-04-12 by SAE International in United States
Understanding the creep and bolt load retention (BLR) behavior of promising Mg-Al alloys are crucial to developing elevated temperature resistance alloys. This is especially true for elevated temperature automotive applications with a prevalence of bolted joints. In this study, creep and fastener clamp load response of Mg-Al alloy AS41 was investigated and compared to that of Mg4Al and AS41 micro-alloyed with 0.15 % Ca. A compliance-creep approach was used to model the response of these Mg-Al alloys at bolted joints. The equation prediction of the BLR response and experimental results are in good agreement. AS41+0.15 Ca shows improved creep and BLR properties up to 175°C. A correlation between the microstructures, creep and BLR results reveal that the formation of a ternary CaMgSi phase is responsible for the improved elevated temperature behavior.
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Ferrous High-Temperature Alloys for Exhaust Component Applications

SAE International Journal of Materials and Manufacturing

Wescast Industries Inc.-Delin Li, Clayton Sloss
  • Journal Article
  • 2010-01-0654
Published 2010-04-12 by SAE International in United States
There is a wide spectrum of cast ferrous heat resistant alloys available for exhaust component applications such as exhaust manifolds and turbocharger housings. Generally speaking, the ferrous alloys can be divided into four groups including: ferritic cast irons, austenitic cast irons, ferritic stainless steels, and austenitic stainless steels. Selection of a suitable alloy usually depends on a number of material properties meeting the requirements of a specific application. Ferritic cast irons continue to be an important alloy for exhaust manifolds and turbocharger housings due to their relatively low cost. A better understanding of the alloying effects and graphite morphologies of ferritic cast irons are discussed and their effect on material behavior such as the brittleness at medium temperatures is provided. The nickel-alloyed austenitic cast irons, also known as Ni-resist, exhibit stable structure and improved high-temperature strength compared to the ferritic cast irons. Austenitic cast irons with varying nickel contents were evaluated in terms of microstructure stability, heat treatment, oxidation and thermal fatigue resistance. For the most demanding applications requiring even higher elevated-temperature strength, creep, and…
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Novel Method for Casting High Quality Aluminum Turbocharger Impellers

SAE International Journal of Materials and Manufacturing

Aluminum Complex Components-Greg Wallace, Andrew P. Jackson
Midson Group-Stephen P. Midson
  • Journal Article
  • 2010-01-0655
Published 2010-04-12 by SAE International in United States
A turbocharger essentially consists of a turbine and an impeller wheel connected on a common shaft. The turbocharger converts waste energy from the exhaust into compressed air, which is pushed into an engine to produce more power and torque, as well as improving the overall efficiency of the combustion process. The compression ratio for modern diesel engines can be up to 5:1, which can be only achieved using a complex impeller design and very high rotation speeds (up to 150,000 rpm for small impellers). The complex geometry and very high running speeds of impellers creates high stresses at locations such as blade roots and around the bore, and so impellers normally fail from fatigue. Therefore, it is vital to minimize defects while fabricating turbocharger impellers.Current methods for producing aluminum turbocharger impellers are plaster casting or by forging + machining. However, both of these current methods have serious drawbacks. Plaster cast impellers tend to have both surface and interior defects that limit performance and life, while forged + machined impellers are expensive.A new technique for producing…
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Locally Austempered Ductile Iron (LADI)

SAE International Journal of Materials and Manufacturing

Ajax TOCCO Magnethermic-George Pfaffmann
Applied Process Inc.-Christopher A. Bixler, Kathy L. Hayrynen, John Keough
  • Journal Article
  • 2010-01-0652
Published 2010-04-12 by SAE International in United States
There are numerous component applications that would benefit from localized austempering (heat treating only a portion of the component) for either improved wear properties or fatigue strength. Currently available methods for “surface austempering” of ductile iron are often expensive and not as well controlled as would be desired. This study was undertaken to find a better process. Locally Austempered Ductile Iron (LADI) is the result of those efforts.LADI is a surface hardening heat treatment process that will produce a localized case depth of an ausferrite microstructure (ADI) in a desired area of a component. This process has been jointly developed by Ajax Tocco Magnethermic Corporation (ATM) and Applied Process, Inc.- Technologies Division (AP) with support and collaboration from ThyssenKrupp Waupaca, Inc. (TKW). This paper describes the outcome of using this patent pending process (US #65/195,131).
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Determination of the Cylinder Head Valve Bridge Temperatures in the Concept Phase Using a Novel 1D Calculation Approach

SAE International Journal of Materials and Manufacturing

FEV Motorentechnik GmbH-Sven Lauer
Institute for Combustion Engines, RWTH Aachen Univ.-Taner Gocmez, Ozen Ozdemir
  • Journal Article
  • 2010-01-0499
Published 2010-04-12 by SAE International in United States
The steady increase of engine power and the demand of lightweight design along with enhanced reliability require an optimized dimensioning process, especially in cylinder head valve bridge, which is progressively prone to cracking. The problems leading to valve bridge cracking are high temperatures and temperature gradients on one hand and high mechanical restraining on the other hand. The accurate temperature estimation at the valve bridge center has significant outcomes for valve bridge thickness and width optimization.This paper presents a 1D heat transfer model, which is constructed through the cross section of the valve bridge center by the use of well known quasi-stationary heat convection and conduction equations and reduced from 3D to 1D via regression and empirical weighting coefficients. Several diesel engine cylinder heads with different application types and materials are used for model setup and verification. Calculated values with the 1D model are compared with the 3D finite element analysis results for exhaust-exhaust and exhaust-intake valve bridges, where estimated results lie in a +/- 6°C error interval showing a reasonable approximation. The proposed calculation…
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AHSS Shear Fracture Predictions Based on a Recently Developed Fracture Criterion

SAE International Journal of Materials and Manufacturing

Meng Luo
Massachusetts Institute of Technology-Tomasz Wierzbicki
  • Journal Article
  • 2010-01-0988
Published 2010-04-12 by SAE International in United States
One of the issues in stamping of advanced high strength steels (AHSS) is the stretch bending fracture on a sharp radius (commonly referred to as shear fracture). Shear fracture typically occurs at a strain level below the conventional forming limit curve (FLC). Therefore it is difficult to predict in computer simulations using the FLC as the failure criterion. A modified Mohr-Coulomb (M-C) fracture criterion has been developed to predict shear fracture. The model parameters for several AHSS have been calibrated using various tests including the butter-fly shaped shear test. In this paper, validation simulations are conducted using the modified (M-C) fracture criterion for a dual phase (DP) 780 steel to predict fracture in the stretch forming simulator (SFS) test and the bending under tension (BUT) test. Various deformation fracture modes are analyzed, and the range of usability of the criterion is identified. Good correlations have been found for failure prediction for tight radius stretch bending.
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Development of Flax Fiber/Soy-Based Polyurethane Composites for Mass Transit Flooring Application

SAE International Journal of Materials and Manufacturing

North Dakota State Univ.-Michael Fuqua, Shanshan Huo, Venkata S. Chevali, Chad A. Ulven
  • Journal Article
  • 2010-01-0428
Published 2010-04-12 by SAE International in United States
In this study, soy-based polyurethane foam was reinforced with randomly oriented flax fiber to create green composite paneling. This paneling can be used as replacement for plywood in mass transit flooring. To establish optimal material properties, the flax/foam composite's density was modified through manipulation of both fiber volume fraction and foam void content in order to determine processing modification upon mechanical performance. Both static flexural testing and dynamic low velocity impact were performed. Mechanical characterization was performed by both flexural testing and screw fastener pullout studies. Resultant properties demonstrate the feasibility of lower maintenance renewable composite materials as replacement for current transit flooring.
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Lean Design for Integrated Product Realization

SAE International Journal of Materials and Manufacturing

Kettering Univ.-Mohamed El-Sayed
  • Journal Article
  • 2010-01-0400
Published 2010-04-12 by SAE International in United States
Implementing the lean principles and tools in manufacturing has been successful in many companies. This success has led to different implementations, of these principles, in other organizational activities such as design and management. While these implementations can produce some improvements, the segmentation of the product development processes in most company limits the potential for achieving the desired goals and in some cases the success of the implementation process itself. In other words, full success of lean principles implementation cannot be achieved when applied to isolated segments of the product development process. This paper addresses lean design, in the context of a fully integrated product realization process. The paper discusses the integrated nature of any product realization process and its flow from concept to production. It also addresses the effect of this integrated nature of the process on the implementation of the different lean principles such as value, value streaming, flow, pull, and perfection.
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