Heating upon sudden elastic compression of material

In summary: Your Name]In summary, Gabriele asks about the expected heating of an elastic material upon sudden compression and shares their calculations, which show a higher temperature change than observed in dynamic simulations. The expert suggests that the discrepancy may be due to the system not being in equilibrium, other factors such as electronic energy not being accounted for, and the limitations of classical MD simulations. They recommend further investigation and comparison to experimental data for validation.
  • #1
g_mogni
48
0
Hello,

I would expect the heating of an elastic material upon sudden elastic compression to be given simply by the first law of thermodynamics, i.e. Delta Q=Delta U + P Delta V where P is constant since the compression is applied suddenly as in a square-wave pressure pulse (this is equivalent to the change in enthalpy). This heat released by the material upon elastic compression should then be re-absorbed entirely by the material assuming periodic boundary conditions, and this is what gives rise to the rise in temperature of the material after the compression. If I'm not wrong then this heat released is basically converted entirely into thermal vibrational energy upon re-absorption (3NkbT in the classical limit). I tried calculating (using classical MD codes) the thermal energy of iron for example from static zero-temperature energy surface calculations and phonon vibrational calculations, however my predictions for the rise in temperature upon elastic compression from these static calculations according to the above reasoning is much higher than the one I observe in the actual dynamic simulations. Can you see anything wrong with my reasoning?

Many thanks,

Gabriele
 
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  • #2


Dear Gabriele,

Thank you for your question and for sharing your calculations. Your reasoning is correct in that the heat released by the elastic material upon compression should be re-absorbed by the material, resulting in a rise in temperature. However, there are a few factors that may be contributing to the discrepancy between your predicted and observed results.

Firstly, the first law of thermodynamics assumes that the system is in equilibrium, which may not be the case in your dynamic simulations. The sudden compression may cause the system to deviate from equilibrium, leading to a different temperature change than predicted.

Secondly, the thermal energy of a material is not solely determined by its vibrational energy. Other factors such as electronic energy and interatomic interactions also play a role. It is possible that these factors are not fully accounted for in your calculations, leading to a difference in the predicted and observed temperature change.

Lastly, it is important to consider the limitations of classical MD simulations. These simulations do not account for quantum effects, which may be significant in the case of iron at high temperatures. This could also contribute to the difference in your results.

I would suggest further investigating these factors and possibly refining your calculations to better account for them. It may also be helpful to compare your results to experimental data for validation. I hope this helps and good luck with your research.

 

1. What is heating upon sudden elastic compression of material?

Heating upon sudden elastic compression of material is a phenomenon that occurs when a material is rapidly compressed, causing its temperature to increase. This is due to the conversion of mechanical energy into heat energy.

2. What causes heating upon sudden elastic compression of material?

The heating is caused by the sudden increase in pressure on the material, which leads to an increase in the kinetic energy of the molecules. This increase in energy results in an increase in temperature.

3. How does heating upon sudden elastic compression of material affect the material?

The increase in temperature can cause changes in the material's properties, such as its strength and conductivity. It can also lead to thermal expansion, which can cause dimensional changes in the material.

4. Is heating upon sudden elastic compression of material reversible?

In most cases, yes, the heating is reversible. Once the compression is released, the material will return to its original temperature. However, in some materials, such as rubber, the heating can cause permanent changes in the material's properties.

5. How is heating upon sudden elastic compression of material used in practical applications?

This phenomenon is utilized in various applications, such as in the production of heat by compressing gases, in the operation of diesel engines, and in the creation of high temperatures in materials processing. It is also used in shockwave research and in the design of shock-absorbing materials.

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