Question

Advance (also called Constantan) has a strain sensitivity SA=2.1 for strain as large as 8%. Determine the amount of contribution due to the change in specific resistance to SA in the elastic region (Poisson's ratio v=0.30) and plastic region (Poisson's ratio v=0.30).

Answer 1

`(dP)/(P) = 6.25`

Step-by-step explanation:

Given data:

Sa = 2.1

`R = (pl)/(A)`

`(dR)/(R) =(dP)/(P) +(dL)/(L) (1_2V)`

`(dR)/(R) =(dP)/(P) +\epsilon (1_2V)`

`Sa = ((dR)/(R))/(\epsilon) =((dP)/(P))/(\epsilon) +(\epsilon (1_2V))/(\epsilon)`

`Sa = (1+2v) + ((dP)/(P))/(\epsilon)`

change in specific resistance is given as
`(dP)/(P)`

`(dP)/(P) = (Sa -(1-2v))/(\epsilon)` ........2

where v is elastic range = 0.30

`\epsilon = 0.08`

`(dP)/(P) = (2.1 -(1-2* 0.30))/(0.08)`

`(dP)/(P) = 6.25`