# Thermal Stress (Thermodynamics)

1. Sep 20, 2009

### Luongo

1. Equation F/A=-Y$$\alpha$$$$\Delta$$T (thermal stress) gives the stress required to keep the length of a rod constant as its temperature changes. Show that if the length is permitted to change by an amount $$\Delta$$L when its temperature changes by $$\Delta$$T, the stress is equal to F/A = Y(($$\Delta$$L/L$$_{}0$$)-$$\alpha\Delta$$T) where F is the tension on the rod, L(naut) is the original length of the rod, A its cross-sectional area, alpha its coefficient of linear expansion, and Y its Young's modulus.

i don't know where to start can somebody help? this thermal stress is stressing me out

Last edited: Sep 20, 2009
2. Sep 20, 2009

### Luongo

3. Sep 20, 2009

### Andrew Mason

If the length changes by dL what does the volume change by? So what does the area, A, change by? How does this affect the stress, F/A?

AM

4. Sep 20, 2009

### Luongo

if the length changes the area would increase and the pressure would decrease. i'm not sure how you "Show This" though