Selection and Properties of Materials

Final Project

Team $3$

Problem $1$: Insulating walls for freezers

Freezers and refrigerated trucks have panel$-$walls that provide thermal insulation, and at the same time are stiff, strong, and light $($stiffness to suppress vibration, strength to tolerate rough usage$).$ To achieve this the panels are usually of sandwich construction, with two skins of steel, aluminum or GFRP $($providing the strength$)$ separated by$,$ and bonded to$,$ a low$-$density insulating core. In choosing the core we seek to minimize thermal conductivity, $,$ and at the same time to maximize stiffness, because this allows thinner steel faces, and thus a lighter panel, while still maintaining the overall panel stiffness.

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A$.$ List the Function, Constraints, Objective and Free variables for this problem.

B$.$ Use a scientific selection procedure $($penalty function, software, charts, documentation $...)$ to propose an alternative material. steps to follow: define the design requirements: Function: What does the component do$?$ Constraints: Essential requirements that must be met: e$.$g$.,$ stiffness, strength, corrosion resistance, forming characteristics, etc. Objective: What is to be maximized or minimized? Free variables: Which are the unconstrained variables of the problem? $2$ List the constraints $($no yield, no fracture, no buckling, etc$)$ and develop an equation for them if necessary. $3$ Develop an equation for the objective in terms of the functional requirements, the geometry, and the material properties $($objective function$).4$ Identify the free $($unspecified$)$ variables. $5$ Substitute the free variables from the constraint equations into the objective function. $6$ Group the variables into three groups: functional requirements F$,$ geometry G$,$ and material properties M; thus Performance metric P fi$$A$$G$$ or performance metric P $$ f$($F$)$ f$2($G$)$ f$($M$)7$ Read off the material index, expressed as a quantity M that optimizes the performance metric P$.$ M is the criterion of excellence.