Chapter 849 The Superpower 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 a macroscopic substance, it 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 order of magnitude of the research time are increased, even if it is still very outrageous at the quantitative level, it can often still play a guiding role 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 10ms is already a very long "macroscopic time" for molecular motion. In addition, the research object is also a multi-layered molecule near the surface, which should be enough to offset the error caused by Brownian motion. Lose.
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 TORC Multiphysics or Materials Studio, which even has a graphical interface, you have to wait. some time.
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.
"I feel... 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 irradiation time, such as 1ms?"
"Well... I tried it on the software."
Li Yabo clicked on the Excel file as he spoke in another worksheet:
"However, there is no way to conduct experimental comparison, 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. Then the time error will become larger and it will cause unnecessary high load on the laser. "
"In addition, according to the literature I collected before, there is no solution for laser irradiation of 2ms or lower. There is insufficient thermal conductivity for the CFRP board, and effective processing cannot be achieved at all."
Chang Haonan did not answer immediately, but clicked on several other worksheets in sequence.
I 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, if the R^2 value reaches 0.8, it is enough to burn high incense. As for the result 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 sudden increase in the errors between 10ms and 100ms may be explained by...
When high-energy rays irradiate the surface of the material, in addition to the thermal effect, there is another mechanism at the same time Produces a removal effect on 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.
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 is too late to be fully reflected. In this way, the effect of another mechanism is reflected.
As a result, the numerical calculation results fitted based on pure thermal effects began to deviate.
The shorter the time, the fewer components of the thermal effect, and the worse the fitting results will be.
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 none of them 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, every time a high-energy ray is irradiated on the surface of the material, it has an effect, regardless of the subsequent irradiation time...
"Then we need to build a 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 worst, a pulse laser with a period below nanoseconds is needed...
Considering the experimental speed, it is best to Picosecond or even femtosecond——
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 number of times to pile.
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 was Li Yabo.
"Huh?"
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.
My shirt stuck to my skin.
Obviously it has undergone intense 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 work.
It is simply amazing.
"Yabo."
Chang Haonan took a few deep breaths and drank some water to calm himself down a little:
"I think laser burning The thermal effect mechanism of corrosion can really be written in an article. ”
At this time, laser processing should be regarded as a popular direction in the field of materials science, but the research focus is mainly on thermal effects.
As for the mechanism that Chang Haonan just speculated, even if he was not the first to create it, at least it has not received widespread attention.
In this case, it’s better to 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, nothing 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 different wavelengths, different laser beam incident methods, and different The impact of the gas environment on the processing effect, and then explain the reasons for this impact from the microscopic mechanism. For example, the absorption rates of epoxy resin molecules for lasers of different wavelengths are definitely different."
"There are also CFPR molecules. The chemical bond energy between them should be exactly within the energy range of visible light, so infrared incidence cannot directly break the bond. 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 sweat 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 are sufficient funds.
What's more, there is still real material in it.
There is just a slight deviation in the direction.
Li Yabo next to him was holding a small notebook, listening and taking notes.
"Of course, what I said is just a few ideas that I just thought of. You can expand some more, and it is best to come up with a mathematical model."
Chang Haonan put down the paper cup:< br>
"If it can be done well, it might be a Nature article."
"Huh?"
Li Yabo stopped writing and raised his head:
"Is it really a Nature?" ”
“You want to graduate too.”
Chang Haonan smiled:
"One article in Nature is enough."
"Graduation..."
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...
"I mean...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 Said:
“By the time it’s officially done, your article will probably have been published already.”
“Besides, I’m the editor-in-chief, so if you publish an article on it... you still have to avoid suspicion. …”
In fact, these two reasons certainly cannot be said to be false.
However, there is a more important reason...
Nature has a greater influence, and it is easier to lead subsequent colleagues to the direction of thermal effects.
It’s just this kind of operation, Li Yabo doesn’t need to know about it yet...
(End of this chapter)