The military-industrial scientific research system of the academic master

Thinking of this, Chang Haonan suddenly felt that the name Wei Yongming seemed familiar.

He was very sure that this was the first time he had contact with Qinghua University since his rebirth.

Then it should be someone who has heard it in the previous life.

"Casting process testing requires a lot of financial resources and time, and as you know, these two things are what we lack most now. At present, the United States, Japan and Russia, the pioneer countries, have been researching titanium-aluminum alloys for many years. We rely on traditional means to It is difficult to catch up with them in a short period of time, but the decoupling methods we are currently using have basically reached a dead end, and the project team has great differences in the subsequent route selection."

After briefly introducing the current situation and the difficulties he faced, Wei Yongming asked Chang Haonan with expectant eyes:

"So, I am here to ask you this. With the current technical means, is it possible to simulate the casting process on a computer through numerical calculations like fluid mechanics or structural mechanics? "

Although he is only a master's student, his summary ideas are clear and organized, and he is definitely deeply involved in the entire project, rather than a simple starter.

His question even stumped Chang Haonan for a while.

In fact, this is not the first time the latter has faced similar problems.

Yan Zhongcheng mentioned before at the celebration party of Sanmen that Liming Factory plans to use 1Cr16Ni2MoN martensitic stainless steel to produce aeroderivative gas turbine blades through hot forging, but there is a gap between the deformation, heat transfer and organizational evolution of the material. The interaction greatly limits the application of the finite element method in hot forging processes that need to fully consider the influence of microstructure.

In the discussion about the Star of the Sea radar some time ago, Guo Lin also mentioned that a big problem faced by 14 is that the large-diameter active phased array antenna on the ship is exposed to sunlight, wind load, salt spray erosion, etc. Under the influence of environmental loads, the antenna array will inevitably undergo structural deformation, deteriorating the antenna radiation performance, and requiring more power to be consumed to achieve the same transmit power.

However, increasing the input power will bring greater thermal power consumption. In addition to wasting the already precious electric energy on the warship, temperature-sensitive T/R components and array power supplies will also cause performance temperature drift, resulting in T The excitation current output by the /R component changes, further deteriorating the radiation performance of the antenna.

Although these issues may seem unrelated and involve completely different fields, the dilemmas faced by everyone are the same——

Compared with aircraft aerodynamics and structural design, which basically only need to consider the influence of mechanics, they are designed to involve more physical fields, and they have a very close impact on each other. For the currently popular calculation and analysis methods, there is no way to simultaneously Calculate and optimize so many physical quantities.

In traditional calculation methods, when nonlinear conditions are introduced, the calculation needs to iterate among multiple sets of partial differential equations many times in order to obtain convergence. However, casting problems involve material nonlinearity, geometric nonlinearity, and boundary nonlinearity at the same time. Iteration The extremely low efficiency means that the calculation time needs to be measured in months or even years, and there is a high probability that the final result will be divergent.

However, if these physical fields are separated and calculated separately, the coupling effect is ignored, causing the simulation results to be completely unable to fit the actual situation.

As far as existing technical means are concerned, there is no solution to this problem.

Therefore, what Chang Haonan has always wanted to do during this period is to write a new, comprehensive multi-physics simulation modeling software.

But this requires high theoretical support, at least beyond the current era.

This is also the reason why he urgently wants to upgrade the system's theoretical ability level to LV3.

After taking some time to summarize the language, Chang Haonan gave his answer in a cautiously optimistic manner:

"Traditional decoupling methods, including the recently developed indirect coupling methods, can only deal with weak coupling problems between multiple physics fields. Strong coupling problems cannot be directly decoupled, so it is meaningful to continue to try in this direction. It’s really not big.”

"For example, the casting process you just mentioned involves a fluid-solid coupling. Only under the assumption of small deformation, this is a weak coupling problem, because the flow channel will affect the fluid, but in turn the fluid will affect the flow channel. The effect can be ignored, and such problems can be solved by decoupling.”

"But the casting process doesn't fit that hypothesis..."

Wei Yongming's eyes dimmed slightly. Obviously, he hoped to continue using numerical calculations.

Because this is the only way China can achieve technological leaps.

"Yes, but it's not completely hopeless."

Chang Haonan nodded:

"I'm developing a fully coupled solution method. If it goes well, then..."

If multiphysics simulation is reduced to a mathematical problem, it is actually solving a system of partial differential equations with a high degree of nonlinearity. However, since engineering only requires numerical solutions and does not require analytical solutions, the overall difficulty should be okay.

In addition, in the original timeline, FEMlab was renamed COMSOL Multiphysics in 2005 and officially entered the field of multiphysics simulation. The time span is 8-10 years, and LV3 level theory should be enough to cope with it.

What's more, things like engineering software always need to collect data for version iteration. It is impossible to expect that the first release will be perfect. Even if only the most basic force-thermal coupling can be done at this stage, for almost all industries, It can be called a huge help.

"If everything goes well, there may be some phased results in the second half of the year."

He still didn't choose to open the champagne at halftime.

Wei Yongming, who was still a little disappointed just now, suddenly became excited:

"So, can we continue to use numerical analysis to shorten the research cycle?"

If someone else drew such a big picture, he probably wouldn't look at it seriously.

But who’s to say will score.

Before coming on this trip, Wei Yongming had certainly done some homework.

Judging from past experience, the "phased results" mentioned by the general counsel are generally not phased.

It is the kind that can be directly solved by putting it in one topic.

“Of course, or rather, this is my ultimate goal in studying algorithms and control theory.”

Chang Haonan smiled and nodded.

Life sometimes has some wonderful symmetries.

For example, he just told three students from Yenching University a few days ago about something similar.

Now I said it again to a student of Qinghua University.

"If you want to do your job well, you must first sharpen your tools. Although waiting for about half a year may cost you some time, it is worth it in exchange for higher efficiency in the end."

As a scientific research dog doing projects in his previous life, Chang Haonan chose the second half of this year as the time node, naturally taking into account the actual situation Wei Yongming and the others faced——

Scientific research projects must submit periodic summary reports at the end of the year.

If he supports the software until next year, the project team is likely to choose to return to the traditional route under schedule pressure to ensure that the report at least has content that is easy to write.

Experiments are of course necessary, but the cost of experiments lacking theoretical guidance is indeed too high for today's China.