Chapter 849: Superb Use of Passive Skills

Li Yabo's conjecture is a relatively common phenomenon in molecular dynamics and even in the entire field of microscopic physics.

Due to the existence of random thermal motion, the motion characteristics of a single molecule in an extremely short period of time cannot be accurately predicted.

But when a large number of molecules form macroscopic matter, they have relatively stable apparent physical characteristics.

For example, the molecular simulation mentioned by Chang Haonan just now.

If we only focus on one or ten molecules and study their behavior during the next lattice relaxation time, then even if the whole process is completely correct, the results will most likely be completely unrelated to the experimental results.

However, if the scale of the research object and the order of magnitude of the research time are increased, even if it is still very outrageous at the quantitative level, it can often play a guiding role at the qualitative level.

However, specifically speaking of the phenomenon the two just discussed, this explanation seems a bit far-fetched.

Because 10ms is a very long "macroscopic time" for molecular motion, and the research object is also a multi-layer molecule near the surface, it should be enough to offset the error caused by Brownian motion.

Thinking of this, Chang Haonan put down the briefcase he had picked up and returned to Li Yabo:

"Let me take a look at the simulation results."

The running speed of ordinary PCs these days is limited. If you want to open complex numerical calculation software such as TORCH Multiphysics or Materials Studio, which even has a graphical interface, you have to wait for a while.

Fortunately, although Li Yabo has not been in the laboratory for a long time, he has developed good habits and has the habit of organizing data after each work.

So soon, an Excel data sheet appeared in front of Chang Haonan.

There are even screenshots of simulation results at key locations.

"I feel like... the 10ms result isn't completely irregular..."

Chang Haonan looked at the densely packed table in front of him and felt that it was not as exaggerated as he thought, so he asked:

"Have you tried shorter exposure times, such as 1ms?"

"Well...I interviewed on software."

Li Yabo said as he clicked into another worksheet in the Excel file:

"But there is no way to conduct experimental control, so it cannot be considered valid data."

"Our device is a continuous laser source and does not support a single irradiation time of less than 10ms. The manual says that if the setting value is less than 5, the time error will become larger and it will cause an unnecessary high load on the laser."

"In addition, according to the literature I have collected before, laser irradiation of 2ms or less cannot produce sufficient heat conduction effect on CFRP plates, and effective processing cannot be achieved at all."

Chang Haonan did not answer immediately, but clicked on several other worksheets in sequence.

It is found that in simulations of 1000ms or longer, the results are already quite good fit with the experimental data.

Of course, it is "good" in the sense of physics.

In molecular physics, an R^2 value of 0.8 is already a blessing. As for results starting with 9 or even several 9s, they are something you wouldn't even dare to dream of.

In short, at least in terms of hot processing, the accuracy of numerical calculations is much better than Chang Haonan had previously estimated.

The sudden increase in the error between 10ms and 100ms may be explained by...

When high-energy rays irradiate the surface of a material, in addition to the thermal effect, there is another mechanism that simultaneously produces a removal effect on the material.

If the irradiation time is long enough for the carbon fiber to conduct heat to the inside, the effect presented at the macro level will be mainly thermal effect.

Therefore, the numerical calculation results are well fitted.

However, when the irradiation time is very short, the thermal effect has not had time to manifest itself, or has not had time to fully manifest itself. In this way, as one mechanism weakens while the other one increases, the effect of another mechanism will manifest itself.

This causes the numerical calculation results based on the pure thermal effect to begin to deviate.

The shorter the time is, the smaller the thermal effect is and the worse the fitting result is.

reasonable.

Very reasonable.

This is also the main weakness of numerical calculation methods.

There is no way to deal with processes whose principles are black boxes, or although they are not black boxes, there are multiple mechanisms that influence each other and no one mechanism is dominant.

So, the next step is to find the mechanism that exists simultaneously with the thermal effect.

Considering that the effect can be shown in an extremely short time of 10ms, Chang Haonan boldly speculated that it is likely to be a truly instantaneous effect.

That is, each time the high-energy rays hit the surface of the material, they have an effect, regardless of the subsequent exposure time...

"Then we need a new device..."

Chang Haonan turned his eyes to the continuous laser processing equipment not far away.

It is known that the relaxation time of electrons to the lattice is approximately in the order of picoseconds (10^-12 seconds).

So to observe the new mechanism alone before the thermal effect becomes apparent, at the very least, a pulsed laser with a period of less than nanoseconds is required...

Considering the experimental speed, picoseconds or even femtoseconds are best.

Li Yabo has said before that according to past research, the effect of continuous laser processing below 2ms is very poor.

That is to say, the single-action effect of this new mechanism is very poor.

Need times to stack.

In the same period of time, the number of irradiation of picosecond laser will be 2 million times that of 5ms laser...

……

About ten minutes later, Chang Haonan finally came out of his thoughts.

Then I heard a slightly panicked voice next to me:

"Teacher, teacher?"

It’s Li Yabo.

"Ok?"

Chang Haonan turned around and saw his disciple with an anxious look on his face, holding a roll of toilet paper and a glass of water in his hand.

"Teacher, you..."

At this time, Chang Haonan realized that he was sweating all over.

The shirt was sticking to my skin.

Obviously it has undergone some high-intensity heat dissipation.

"Oh...I just thought of something."

Chang Haonan took the toilet paper and tore off a few pieces to wipe himself.

He quickly remembered that when his theoretical level was promoted to LV4, the system had reminded him that when studying an unknown phenomenon within the scope of his ability, there would be a certain probability that he would be able to see through its essence.

Looking back now, the sudden inspiration just now should be the result of this "certain probability" playing a role.

It's simply amazing.

"Abo."

Chang Haonan took a few deep breaths and drank some water to calm himself down a little:

"I think we can write an article on the thermal effect mechanism of laser ablation."

At present, laser processing should be considered a hot direction in the field of materials science, but the research focus is on thermal effects.

The mechanism that Chang Haonan just speculated, even if it was not his original idea, at least has not received widespread attention.

In that case, why not just go with the flow?

Let us continue to go a little further in the direction of thermal effect.

Even if someone discovers the secret in the future, there is nothing they can say.

I didn't falsify any data, I just revealed the mechanism of laser thermal effect.

Can you blame me for going too far in my research?

After a brief pause, Chang Haonan continued:

"Although the amount of data you have now is a bit small, I think you can add the effects of different wavelengths, different laser beam incident methods, and different gas environments on the processing effect, and then explain the reasons for this effect from a microscopic mechanism. For example, the absorption rate of epoxy resin molecules to lasers of different wavelengths must be different."

"Also, the chemical bond energy between CFPR molecules should be within the energy range of visible light, so infrared radiation cannot directly break the bonds. It can only promote thermal melting through the photothermal effect..."

This time, he did not activate the passive skill.

It is estimated that the physical condition does not support frequent activation in a short period of time.

After all, the amount of sweating just now was indeed a bit abnormal.

But it's not a big problem.

For Chang Haonan now, in materials science, it is not difficult to write a paper, even a high-level paper, as long as there is sufficient funding.

What's more, there is real stuff in it.

It's just that the direction is slightly off.

Li Yabo next to him was holding a small notebook and taking notes as he listened.

"Of course, what I've said are just a few ideas that I just thought of. You can expand on them. It would be best if you could come up with a mathematical model."

Chang Haonan put down the paper cup:

“If we can do it well, it might be a Nature article.”

"what?"

Li Yabo stopped writing and raised his head:

“Is it really published in Nature?”

“You’re going to graduate, too.”

Chang Haonan smiled:

"One article in Nature is enough."

"graduate……"

Li Yabo was in a trance.

He had only graduated from undergraduate school for a month, so why was he already thinking about graduating from graduate school...

"I mean... didn't you say before that we have a domestic journal in the works? You're the editor-in-chief."