Issue1. Vol.1 (April, 2013) - IIT Mandi

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ESSENT Society for Collaborative Research and Innovation, IIT MandiMaterial Selection forEngineering DesignDr. Rahul Vaish, Assistant Professor,School of Engineering, IIT Mandi.Dr. Vaish received his Ph.D. from the IndianInstitute of Science, Bangalore, India andrecieved Ph.D. Best Thesis Award (SudboroughMedal). He has also received Inspire FacultyFellowship-2011.His research interests includepiezoelectric devices, glasses for energy and bioapplications, electroceramic simulations andmodeling.andAditya Chauhan,Mr. Chauhan is M.S. Scholar at IIT Mandi.His research interests include advanced andsmart materials.Materials play an important role in engineeringdesign. Engineer needs to find materials withspecific properties, which can be used toachieve the required system performance and/orother requirements. To this end, the design taskis often focused on comparing the properties ofa finite set of materials and selecting the best. Itis important to note that more than 160,000useful materials including metallic alloys,nonmetallic engineering materials such asplastics, ceramics and glasses, compositematerials, and semiconductors are exist. Thislarge number of materials and enormous numberof manufacturing processes available to theengineers, coupled with the complexrelationships between different selectionparameters, often make the selection ofmaterials for a given component a difficult task.In selecting materials, engineers have to takeinto account a large number of properties. Thesematerial properties include mechanicalproperties (Young’s modulus, strength, yieldstress, elasticity, fatigue, creep resistance,ductility, hardness and toughness), physicalproperties (crystal structure, density, meltingpoint, vapor pressure, viscosity, porosity,permeability, reflectivity, transparency, opticalproperties, dimensional stability), magneticproperties, electrical (resistivity, permittivity,dielectric strength), thermal and radiation(specific heat, conductivity, expansively,diffusivity, transmissivity, reflectivity,emissivity), surface (texture, corrosivity, wearresist), manufacturing properties (machinability,formability, weld ability, cast ability, heattreatability, etc.), material cost, reliability,durability, recycle ability, material impact onenvironment, performance characteristics,availability, fashion, market trends, culturalaspects, aesthetics, etc. Beside these aspects,recently user-interaction aspects such asappearance, perceptions and emotions areconsidered in material selection.Fig. 1 shows systematic approach for materialselection. It is clear that material selection is adecision that has to be made based on severalconsiderations. Such a decision making process30 ESSENT|Issue1|Vol1
ESSENT Society for Collaborative Research and Innovation, IIT Mandican be classified and solved by Multiple CriteriaDecision Making (MCDM) technique. MCDMtechniques have been used for decision makingsince a long time but found their way to materialselection only recently. MCDM techniques maybe further divided into two techniques namelyMultiple Objective Decision Making (MODM)and Multiple Attribute Decision Making(MADM). Various material selectionmethodologies are shown in Fig. 2. MODMtechniques rely on the functionalinterdependency between the various attributesassociated with the material and based on designconstraints. These functional requirements arethen used to formulate figures of merits (FOMs)based on one or more goals of the design thatthe designer wants to achieve or maximize, itcan be minimum weight, highest strength orlowest cost. Thus, these FOMs provide a scaleof comparison for various material candidates.Alternatives with higher value of FOMs arepreferred. Pioneer work in this field has beendone by M. F. Ashby. Ashby dividedperformance index P of any engineeringcomponent as P = f(F,G,M), where ‘f’ denotesfunction of functional (F), geometric (G) andmaterials (M) parameters, respectively. Theseparameters are independent of each other andtheir collective output determines the overallperformance of the component [1].MADM technique on the other hand relies onpredetermined mathematical models to rank andcompare the materials based on their attributes[3-5]. Some of these techniques are data drivenwhile others are method driven. NumerousMADM methods have been reported and foundto be promising for the purpose of materialselection [2]. However, as is with any method,every selection and ranking technique has itsown shortcomings and drawbacks. Ashbytechnique is an efficient method and directlycorrelates the effect of various physicalparameters on the overall performance of adeviceFig. 1: Material selection strategy [1]Fig.2: Material selection methods [2]However, the formulation of indices can be acumbersome and difficult task based on the factthat each application is inherently different fromanother application and also, exact functionalrelation between the parameters must be knownand require expert decision. The constraintsimposed on different category of similarcomponents could be different and hencedifferent indices are supposed to be used in it.Also, Ashby approach requires the componentto be approximated to a near simple object forwhich a standard index may either be present or31 ESSENT|Issue1|Vol1
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Issue1. Vol.1 (April, 2013) - IIT Mandi

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