The Military-industrial Scientific Research System of the Academic Master Chapter 849

Chapter 849: Super performance of passive skills

Li Yabo's guess can be regarded as a common phenomenon in molecular dynamics and even in the entire field of microphysics.

Due to the existence of irregular thermal motion, the motion characteristics of a single molecule in a very short time cannot be accurately predicted.

Once a large number of molecules form a macroscopic substance, it will have relatively stable apparent physical characteristics.

Just like the molecular simulation mentioned by Chang Haonan just now.

If you only focus on one or ten molecules and study it or their actions in the next lattice relaxation time, then even if the whole process is completely correct, the results will most likely be irrelevant to the experimental results.

However, if the scale of the research object and the research time are increased by a few orders of magnitude, even if it is still very outrageous at the quantitative level, it can often provide guidance at the qualitative level.

However, when it comes to the phenomenon that the two men just discussed, this explanation seems a bit far-fetched.

Because 10 ms is already a long "macroscopic time" for molecular motion, and the research object is also a multi-layered 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 again and returned behind Li Yabo:

“Let me take a look at the simulation results.”

Ordinary PCs these days have limited running speeds. If you want to open more complex numerical calculation software such as TORC 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 good habits and has the habit of sorting out 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.

“It feels like...the 10ms results are not completely irregular...”

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

“Have you ever tried a shorter exposure time, such as 1ms?”

“Hmm… I've tried it on software.”

Li Yabo said and clicked on another worksheet in the Excel file:

“However, there is no way to carry out experimental control, so it cannot be regarded as valid data.”

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

“In addition, according to the literature I have collected before, laser irradiation of 2ms or lower cannot produce sufficient thermal conductivity for CFRP boards, and effective processing cannot be achieved at all.”

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

It was found that indeed in the simulation of 1000ms or longer, the results fit the experimental data quite well.

Of course, it's “not bad” in the physical sense.

In molecular physics, an R^2 value of 0.8 is already a high value. As for results starting with 9, or even several 9s, it is something that one would never dare to dream of.

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

The errors between 10ms and 100ms suddenly become larger, which may be explained by...

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

If the irradiation time is relatively long and the carbon fiber is enough to conduct heat to the interior, the effect at the macro level will be mainly thermal effect.

So the numerical calculation results fit well.

When the irradiation time is very short, the thermal effect has not had time to be reflected, or it has not been fully reflected, so the effect of another mechanism is reflected.

As a result, numerical calculation results fitted based on pure thermal effects begin to deviate.

The shorter the time, the fewer components of the thermal effect, and the worse the fitting results.

Reasonable.

Very reasonable.

This is also the main weakness of numerical calculation methods.

There is nothing we can do about the principle being a black box, or even though it is not a black box, there are multiple mechanisms that interact with each other and no one is the dominant process.

So, the next work is to find this mechanism that coexists with the thermal effect.

Considering that it can show its effect in a very short time of 10ms, Chang Haonan boldly speculated that it is likely to be a real instant effect.

That is to say, it produces an effect every time a high-energy ray is irradiated on the material surface, regardless of the subsequent irradiation time...

“Then we need to get a new piece of equipment...”

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

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

So before the thermal effect shows obvious effects, to observe the new mechanism alone, at best, a pulse laser with a period of less than nanoseconds is needed...

Taking into account the experimental speed, it is best to use picoseconds or even femtoseconds—

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

That means that the single action effect of this new mechanism is very poor.

It takes a number of times to pile up.

In the same period of time, the number of irradiations of the picosecond laser will be 500 million times that of the 2ms laser...

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

Then I heard a slightly panicked voice next to me:

“Teacher, teacher?” It's Li Yabo.

"Um?"

Chang Haonan turned his head and saw his disciple looking anxious, 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 already sweating.

The shirt stuck to my skin.

Apparently it has undergone intensive heat dissipation.

“Oh…I just thought about something.”

Chang Haonan took the toilet paper, pulled off a few pieces and wiped 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 of being able to see through its essence.

Looking back now, the sudden wave of inspiration just now should be due to this "certain probability" happening to play 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 really write an article on the thermal effect mechanism of laser ablation.”

Laser processing should be considered a popular direction in the field of materials science at this time, but the research focus is mainly on thermal effects.

The mechanism just speculated by Chang Haonan, even if he was not the first to do so, at least has not received widespread attention.

In this case, it's better to just go with the flow.

Let everyone continue to go a little further in the direction of thermal effects.

Even if someone discovers the secret in this in the future, there is nothing that can be said—

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

Can you still blame me for studying too deeply?

After a brief pause, Chang Haonan continued:

"Although your current data volume is still a bit small, I think you can add the effects of different wavelengths, different laser beam incidence methods, and different gas environments on the processing effect later, and then explain the reasons for this effect from a microscopic mechanism, such as Epoxy resin molecules must have different absorption rates for different wavelengths of laser light.”

“Also, the chemical bond energy between CFPR molecules should be exactly within the energy range of visible light, so infrared incidence cannot directly break the bond, and 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, it is not difficult to write a paper in materials science, even a high-level paper, as long as there is sufficient funds.

What's more, there are real materials in it.

It's just a slight deviation in the direction.

Li Yabo next to him was holding a small notebook and taking notes while listening.

“Of course, what I'm talking about are just a few ideas that I just thought of. You can expand some more, and it's best to come up with a mathematical model.”

Chang Haonan put down the paper cup:

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

"ah?"

Li Yabo stopped writing and raised his head:

“Is it really Nature?”

“You're going to graduate too.”

Chang Haonan smiled:

“One Nature article is enough.”

"graduate…"

Li Yabo was in a trance for a while.

He has only graduated from undergraduate degree one month ago, so why is he already thinking about graduating from graduate school...

"What I mean is...didn't you say before that we have a domestic journal that is under preparation? You are the editor-in-chief."

“You said JCAS…”

Chang Haonan replied:

“By the time it's officially done, your article will have been published long ago.”

“Besides, I'm the editor-in-chief, so when you publish articles on it… you still have to avoid suspicion…”

In fact, these two reasons certainly cannot be said to be false.

It's just that there is a more important reason…

The influence of Nature is greater, and it is easier to lead subsequent colleagues to the direction of thermal effects.

It's just this kind of operation that Li Yabo doesn't need to know yet…

(End of this chapter)

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