multiple constraints and conflicting objectives

trade offs in materials selection

conflicting constriants and balance divergent objectives

conflicting constraints examples

stiffness, fatigue strength, toughness

balance divergent objectives

light but also cheap

if you have many constraints and one objective

-screen using constraints

-identify material index that limits performance

-rank using property or index

many constraints and two objectives

screen, using constraints

identify material index that limits performance

construct trade-off plots for Ms

is necesarry, create and evaluate penalty function Z

many constraints more than two objectives

scree, using constraints

identify material properties

create and evaluate penalty function Z

the screening stage imposes

constraints on properties or on the ability to be processed in a certain way

the candidate materials that survive the screening stage

are ranked using property charts

the analytical method is

evaluating both m1 and m2 for each member of the material population and assigning the larger value of the two to each member than ranking the members by the assigned value, seeking a minimum

for the analytical method you basically

take the given values and plug them into the material indices

for each of the calculated values the larger value is the dominant and controlling value

graphical method

we can plot m1 against m2

each bubble represents a material

the line m1=m2 separates the chart into 2 regions

region 1 is to minimize the larger material index

region 2 is to maximize the smaller material index

this should define an envelope with the corner on the m1=m2 line

the box is pulled ot the bottom left, decreasing the m

the best material value is left in the box

to get the coupling constant what is graphed

M1 against M2

in the M1=M2 equation which one goes in front of the equal sign

what ever index you want on the y axis

when the equations are set equal to each other what comes from it

teh coupling constant

what do you do with the coupling constant

plot it on the chart and then use the box to go to the left and get the material

each objective defines a

performance metric

why does conflict arise

because the choice that optimizes one metric of performance will not do the same for the others