Thermal stresses occur when two materials connected at one end experience different temperatures. At room temperature, there is no stress. But at higher temperatures, like 150 degrees Celsius, each material would expand a different amount if not connected. Being connected causes them to experience opposing stresses - one in compression from being pulled and one in tension from being pushed beyond its free expansion limit. The change in length of each material can be calculated from the difference between its free expansion and the forced contraction or expansion caused by the other material. Understanding these thermal stress concepts is important.

1. Thermal Stresses
Mandar Jagtap

2. At Room
Temperature
(Normal Life)
I’m so
happy..
Nothing is
beautiful than
this!!

3. If I wasn’t with her I would have been here… 😒
If I wasn’t with him I would have been here… 😒
At elevated
temperature than
room temp., say
150 deg. Celsius.
(Life under stress)
It’s Free Expansion
length of Blue if it
was alone.
It’s Free Expansion length of Red,
if it was alone.

4. So.. Finally we’re together.
Different capabilities ended
with same results..
That’s how it works.. We’re
metals. And when we’re
brazed or connected rigidly at
ends together, we can expect
such a result only.

5. But can’t you see? I should have
been ended and where I’m? It’s
so stressful !
How mean! Don’t you see I’m
also affected due to this. I
have crossed my limit. Me
too equally stressed.
Materials
experiencing
equal forces, but
opposite in
direction.
Blue one under
compressive stress
since it has been pulled
due to force applied by
Red one.
Similarly Red one under
tensile stress since it has
been pushed further it’s
limits due to force applied by
Blue one.

6. So what about strain and change
in length of both?
It was a little misunderstanding.!
It's temperature causing stress in
us.
It’s my Forced Contraction.
Yes… and for me
it’s Forced
Expansion. Isn’t it?
Pos. at Room Temp.
Pos. at Elevated Temp.

7. Free Expansion
(Blue)
Free Expansion
(Red)
Pos. at Room Temp.
Pos. at Elevated Temp.
Forced Expansion
(Red)
Forced Contraction
(Blue)
So, We can see…
at elevated temp.
For Blue one
Change in Length =
Free Expansion –
Forced Contraction
For Red one
Change in Length =
Free Expansion +
Forced Expansion
Convincing!!
Whatever it’s..
We’re together!
Change in
length

8. And we know obviously
Forced contraction or Forced expansion = (nothing but) Normal change in length (∂L)
And ∂L = PL/AE
Similarly Free expansion = α.Δt.L
So, how important
understanding is!!
Yes.. wasn’t that
much difficult 
Change in length =
(Free Expansion – Forced Contraction) = (Free Expansion + Forced Expansion)

9. And they lived happily together….
Thank You.. !!!