African Nationhood

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When the technicians and engineers gathered in the large conference room of the workshop, they found Zheng Tingxiang writing on the blackboard in the conference room.

Everyone found a seat and sat down. Some silently read the content on the blackboard, while others exchanged questions with others in a low voice. Shi Min sat in the corner very consciously.

Even Tingyu and Huo Zhiying didn't speak, and sat silently waiting.

When the entire blackboard was filled with writing, Zheng Tingxiang stopped writing on the blackboard, turned around, picked up the wooden pole and tapped on the blackboard.

"Everyone, please pay attention. What we are going to hold now is the 'Artillery Barrel Fastening Technical Meeting'. You should listen carefully. If there is anything you don't understand, please ask it and we will solve it together."

After finishing speaking, Zheng Tingxiang pointed to the beginning of the writing on the blackboard with a wooden pole: "The beginning of body tube fastening technology."

"Because everyone started working at different times, I will start from the beginning. Skip the ones you already know about, and listen carefully to those who have never been exposed to it."

"Yes."

"Everyone knows about the explosion, but why does it happen?
Someone will definitely answer me that it is because the charge is inappropriate or it expands due to thermal expansion and contraction. Yes, this is the correct answer.

But what we want to discuss today is the barrel fastening technology, which does not involve the issue of powder charging.

Everyone knows that when a cannonball is fired, the inner ring of the barrel will produce a high-temperature and high-pressure environment in a short period of time due to the friction of the cannonball and the explosion of gunpowder. These heat and pressure will cause the inner chamber of the barrel to rapidly expand in a short period of time.

However, the outer surface of the barrel receives almost no heat and no high pressure acts on it.

Therefore, every time a shell is fired, the force of the expansion of the barrel's inner chamber will tear the outer ring. Over time, cracks will appear in the barrel, and the cracks will continue to expand during use and eventually become an explosion.

Bore explosion is a situation that none of our military technicians and soldiers want to encounter.

How can we avoid chamber explosion and effectively extend the life of the barrel?
Gun barrel fastening technology came into being.

Since the 19th century, European countries, led by the United Kingdom, have discovered that square-section steel wires are tightly wound around the gun barrel. The steel wire tension resists the shooting stress of the gun barrel, enhances the performance of the gun barrel, and effectively extends the life of the gun barrel.

This technology is the "wire wrapping fastening" technology. The wire wrapping technology is simple and the steel wire is easy to control. It has been used on many battleships and guns.

However, it has a fatal shortcoming: the longitudinal strength of the gun barrel is insufficient, and the processing technology is complicated and takes too long.

Later, the British invented the "sleeve fastening" technology. The British Armstrong cannon sleeved two or more round tubes together.

The outer tube is heated first and then put on the inner tube. The outer tube shrinks after cooling, and the inner and outer tubes are tightly put together.

This process is currently the most mainstream barrel fastening process in the UK. We introduced this processing technology when negotiating with the UK.

Jianye Metal Processing Factory also used this technology to successfully produce a 305mm caliber coastal defense cannon.

But we heard that the British are building a larger caliber cannon, and it is said that they plan to build a 405mm caliber cannon.

The disadvantage of this technology is that the cannons produced are very heavy.

A giant cannon like the one manufactured by our Jianye Metal Processing Plant weighs dozens or hundreds of tons. Such a giant cannon can only be used as a coastal defense gun and cannot move quickly at all.

We often wonder if we can find a way to make a lightweight barrel.

We have found this method today. This is the idea provided by our great Chairman Shi. This idea is excellent.

The principle of this technology is to use supercharging equipment to create a pressure on the inner surface of the barrel that exceeds the yield strength of the barrel material, which will cause permanent plastic deformation of part of the inner tube material section that cannot be recovered.

Due to the different degrees of plastic deformation inside and outside the body tube, the inner layer of the body tube will produce compressive prestress, and the outside will be subject to tensile prestress. One tends to expand outward and the other tends to compress inward.

To put it simply, a body tube is used to create a structure similar to a multi-layer body tube. The layers are interlocked. Not only can the compressive strength and fatigue resistance be greatly improved, but the weight of the body tube can also be effectively reduced, making it The maneuverability of large-caliber artillery has also increased rapidly. "

"Chairman Shi has provided several ideas for the self-tightening method of the body tube based on this principle, namely air pressure, hydraulic pressure and mechanical pressure. 'Pneumatic pressure', as the name suggests, uses some explosions to generate high-pressure gas to increase pressure on the inner wall of the body tube, but this The method is difficult to control and very difficult to control.

'Hydraulic' uses water as a high-pressure body to pressurize the inner wall of the body tube. This method has many advantages. The only problem is the leakage of the liquid. If it leaks halfway, it will cause failure.

'Mechanical pressing' uses a harder metal rod to pressurize the inner wall of the barrel. However, this method can easily cause irreversible damage to the inner wall of the barrel. Overall, hydraulic pressure is the most effective method. "

Now let me talk about this new gun barrel fastening method provided by Chairman Shi (France adopted this method in 1913, and later the Japanese learned it and started the Great Leap Forward in armaments).

Chairman Shi named this new technology 'hydraulic body tube self-tightening' technology. "

After saying this, Zheng Tingxiang pointed the wooden pole at the diagram he drew.

"This is the core schematic diagram of the 'hydraulic body tube self-tightening' technology."

Having said this, Zheng Tingxiang looked down. The many engineers and technicians participating in the meeting were all taking notes silently, and no one expressed any objection to this.

“The body tube self-tightening technology was derived from Chairman Shi’s detailed mathematical deductions, and I wrote down the entire deduction process on the blackboard.

If you have any questions or something you don’t understand, you can ask them. "

Shi Min sat down and watched carefully. Everyone in the conference room was silently copying the deduction process on the blackboard, and there was a rustle in the conference room.

Shi Min had no choice but to follow Da Liu and start copying. At this time, he was completely new to military research and didn't understand many things.

There were many mathematical symbols and calculation formulas on the blackboard. As he read it, he marveled at how long his brain was and how he knew so much.

His best strategy at present is to write down what he doesn't understand first, and then slowly understand it later.

I also learned many new concepts during the copying process, such as:
Artillery barrel thick-walled cylinder formula, tangential and radial equivalent stresses;

Radial and tangential stress and strain are linearly related to chamber pressure;
The maximum values ​​of tangential and radial stress appear on the inner wall of the barrel;
Tangential stress is greater than radial stress…

These new concepts made him realize that he, a graduate student, still had a long way to go if he wanted to catch up with everyone else's progress.

……

After he finished writing the contents on the blackboard and drew the curve diagram of the outer radius of the body tube and the elastic strength of the body tube, everyone in the conference room came to life, and everyone was whispering about the derivation process of these mathematical formulas.

Shi Min listened attentively, and in the end, he actually understood part of it.

When the wall thickness of the artillery barrel is small, the tangential equivalent stresses on the inner and outer surfaces are not much different, that is, the stress distribution within the wall is relatively uniform.

As the wall thickness increases, the difference in tangential equivalent stress between the inner and outer surfaces becomes larger and larger.

……

"Okay, do you have any questions that you want to discuss?"

Lian Tingyu saw that the people present were still thinking and did not fully understand it. It would probably take some time to digest it.

He explained directly: "I think everyone can't digest it completely so quickly. Why don't we let everyone digest it for a few more days and we can have a meeting to discuss it later?"

Zheng Tingxiang smiled when he heard this, "I'm too impatient, okay, let's go back and digest it ourselves.

Ten days later, we held another technical discussion meeting. "(End of chapter)