Chapter 849: Superb Use 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.

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

For example, 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.

But 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 on the quantitative level, it can often still play a guiding role on 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."

The running speed of ordinary PCs these days is limited. If you want to open more 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 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?"

"Well... I've tried it on software."

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

"However, there is no way to conduct experimental control, so it cannot be considered 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 simulations 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, if the R^2 value can reach 0.8, it is already very popular. 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 Chang Haonan had previously estimated.

The error between 10ms and 100ms suddenly becomes 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 removes the material.

If the irradiation time is relatively long and enough carbon fiber conducts heat to the interior, the effect at the macro level will be dominated by thermal effects.

Therefore, 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 whether the principle is a black box, or although it is not a black box, there are multiple mechanisms that interact with each other, and no one is the dominant process.

Then, 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 new 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...

Considering the experimental speed, picosecond or even femtosecond is best——

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

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

It takes a lot of times to stack.

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

...

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

Then he heard a slightly panicked voice next to him:

"Teacher, teacher?"

It was Li Yabo.

"Huh?"

Chang Haonan turned his head and saw his disciple with an anxious 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 stuck to the skin.

It was obviously after a 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 ability, there would be a certain probability of seeing through its essence.

Now thinking back, the sudden inspiration just now should be the "certain probability" that happened to play a role.

It's simply amazing.

"Yabo."

Chang Haonan took a few deep breaths and drank a sip of water to calm himself down:

"I think the thermal effect mechanism of laser ablation can really be written into an article."

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

And the mechanism just speculated by Chang Haonan, even if it was not his original invention, at least it has not received widespread attention.

In this case, why not 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 the future, there is nothing to say -

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 short pause, Chang Haonan continued:

"Although your current data volume is still a little 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, such as 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 just 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 his physical condition does not support frequent activation in a short period of time.

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

But it is not a big problem.

For Chang Haonan now, in materials science, if you want to write a paper, even a high-level paper, as long as you have sufficient funds, it is not difficult.

What's more, there is still real material in it.

It's just that the direction has deviated a little.

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

"Of course, what I said are just a few ideas that I just thought of. You can expand them a little bit, and it would be best if you can come up with a mathematical model."

Chang Haonan put down the paper cup:

"If you can do it well, maybe it will be a Nature article."

"Huh?"

Li Yabo stopped writing and looked up:

"Really publish in Nature?"

"You are going to graduate, too."

Chang Haonan smiled:

"One Nature article is enough."

"Graduation..."

Li Yabo was in a trance.

It has only been a month since he graduated from undergraduate school, why is he already thinking about graduate school graduation...

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

"You mean JCAS..."

Chang Haonan replied:

"By the time that it is officially launched, your article would have been published long ago."

"Besides, I am the editor-in-chief, and you publish articles there...you still have to avoid suspicion..."

In fact, these two reasons are certainly not false.

However, there is a more important reason...

Publishing in Nature has a greater influence, and it is easier to bring colleagues behind to the direction of thermal effects.

It’s just that Li Yabo doesn’t need to know about this kind of operation for the time being...