Temperature gradient load application in plate elements

Creation date: 6/4/2021 3:38 PM Updated: 6/4/2021 3:38 PM civil fea temperature temperature gradient

Question:

Hi,

Need a clarification on temperature gradient load application in plate elements.

In the attached model- negative temperature of -7.2 degree Celsius to be applied from top of deck to 300mm below. Can you please let us know if it is applied correctly.

Answer:

Hello,

Greetings.

Thanks for reaching us.

We can only apply linear temperature gradient in plate elements but can't apply non-linear thermal gradient.

So, if deck depth is 300mm, then the temperature gradient can be applied.

If that's not the case, the temperature gradient can't be applied to the plates.

Question: Linear distribution is OKAY.

Now please check the below snap. My deck thickness is 750mm & I want to put the negative temperature of -7.2 degrees at the top & reduce to 0 degree at 300mm from top. Have I correctly applied it? By looking at the snap it looks incorrect. I am seeing -7.2 at the soffit of the deck. Please let me know.

Answer:

Actually, T2z-T1z is temperature difference value between the 2 faces of plate in local z-direction.

So, if the temperature difference value is provided as x, then x/2 is applied at top and -x/2 is applied at bottom. In between temperature varies linearly.

Further, Hz value is used, it will apply gradient from mid depth.

For eg: If plate depth is 1m and Hz value is 0.5 m and temp difference is 5 C, then it will apply 2.5 C at .25m above the centroid and -2.5 C at 0.25 m below centroid and further extrapolate the gradient temperature to surface. So, temperature at top surface will be 5C and bottom surface will be -5C.

So, it is not the correct way of applying the non-linear gradient and we can't apply non-linear gradient to plate.

Question: So there is no other way of applying the temperature gradient in plate elements then!

Answer: Sorry, there is no other possible way.

Question: Can we do this in FEA NX? Please let us know.

Answer: Yes, we can do so in FeaNx, but the plate elements have same limitation in FEANX. Non-linear - thermal gradient can't be applied as such.

But we can model the deck as solid elements. If the depth of deck is 750 mm and 300mm below the deck top, temperature is zero.

We can mesh the solid elements such that nodes are coming at 300 mm below the deck. Choose upper deck solid element depth as 300 mm and lower as 450 mm as one of the possible mesh size.

After that we can provide the nodal temperature.

DataImage62.png

Files
	DataImage62.png 127 KB

Temperature gradient load application in plate elements

Contents