Calculation of thermal stress.

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Discussion Overview

The discussion revolves around the calculation of thermal stress in a simple structure, specifically a cube, that is exposed to different mediums at varying temperatures. Participants explore different formulas for calculating thermal stress and discuss the implications of thermal strain and restraints in the context of metallic structures.

Discussion Character

  • Technical explanation
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • One participant presents four formulas for calculating thermal stress and seeks advice on the most appropriate one to use.
  • Another participant notes that thermal stresses arise from reactions or shears between the cube and its environment, suggesting that these need to be specified for accurate calculations.
  • A participant mentions that the structure can deform due to temperature gradients, leading to strain before stress develops, but expresses uncertainty about quantifying deformation before stress occurs.
  • There is a clarification that thermal strain is stress-free unless there is some restraint, prompting a call to define the restraints involved.
  • A participant poses a question about finding thermal restraints in a metallic structure experiencing a temperature gradient, indicating confusion about the concept.
  • Another participant questions the relationship between temperature gradients, thermal stress, and thermal strain, seeking mathematical methods to calculate these without direct measurement.
  • There is a challenge to the assertion that temperature gradients result in both thermal stress and strain, with a suggestion that the discussion may be conflating these with residual stresses.
  • A participant asks about the term "creap," indicating a potential misunderstanding or need for clarification on related concepts.

Areas of Agreement / Disagreement

Participants express differing views on the definitions and implications of thermal stress, strain, and restraints. There is no consensus on the appropriate formulas or methods for calculation, and the discussion remains unresolved regarding the specifics of thermal restraints and their impact.

Contextual Notes

Participants have not fully defined the assumptions regarding restraints or the specific conditions under which thermal stress and strain are being analyzed. There are also unresolved mathematical steps related to the calculations being discussed.

chetanladha
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Hi.
I am trying to calculate thermal stress in a simple structure (cube) exposed to two different mediums at different temperatures.
I have come across 4 formulaes, can anyone please advice on which one would be most appropriate.
Please see the attached file as the fourth formulae is too big to write here..

thermal stress,
1. σ1= -EαT
2. σ1= -EαT/(1-v)
3. σ1=[-EαT/(1-v)]+ [E(ex + v*ey)/(1 – v2)]
 

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Good morning chetanladha,

Thermal stresses are developed as a result of reactions/shears between your cube and its environment. These need to be specified before your question can be answered.
 
Hey! Very good morning.
Thank you for your response.

the structure (cube) can deform. So the temperature gradient will first result in strain (till the time it can) and thereafter stress. Although i don't know how to find out how much will the structure deform before stresses could develop.
Mathematically i am planning to use some assumptions for the values of thermal strain.
 
Unless there is some restraint thermal strain is stress free.

So I repeat my comment.
Define your restraints.
 
Ohh.. Yes i understand now, and i hve got my answer.

Another question:-
A metallic structure (e.g. a steel table) has got certain temperature gradient. This will result in thermal strain until restrains, followed by thermal stresses induced in it.

How can i find the thermal restrains in such a case?
 
Another question:-
A metallic structure (e.g. a steel table) has got certain temperature gradient. This will result in thermal strain until restrains, followed by thermal stresses induced in it.

How can i find the thermal restrains in such a case?

I'm completely puzzled by this: what on Earth do you mean?
 
Temperature gradient in a body can either result in thermal stress, thermal strain or a combination of both.

Mathematically (not by measuring expansion/ contraction) how can one calculate how much is the stress and strain?

Thanks..
 
Temperature gradient in a body can either result in thermal stress, thermal strain or a combination of both.

What makes you say that?

Are you sure you are not referring to residual stresses?
 
what is creap?
 

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