Zhongxin Wanghai, 5 May -- Topic: Making "coats" for airplanes and rockets They "carved" on "eggshells"

Reporter Zheng Yingying

Large domestic aircraft, "Chinese-made" launch vehicles ... People see the overall rise of China's high-end manufacturing, and rarely pay attention to the process breakthroughs and technological iterations hidden behind it.

In Shanghai, there is such a team, they are co-created by university academics "going to the sea" with enterprises. This team "carved" on the "eggshell", broke through technical problems, and provided a solid and environmentally friendly "coat" for aircraft and rockets.

In the 26 Shanghai Science and Technology Award announced on the 2022th, the project named "Aerospace Large Surface Skin/Box Bottom Double Five-axis Mirror Milling Technology and Equipment" won the special prize of the Technical Invention Award.

Expensive "tunic": one gram of weight, one gram of gold

"Airplanes, launch vehicles, these aircraft have very strict requirements for weight, we describe: one gram of weight, one gram of gold." Wang Yuhan, professor of the School of Mechanical and Power Engineering of Shanghai Jiao Tong University and chairman of Shanghai Tuopu CNC Technology Co., Ltd., said.

After more than 10 years of hard work, his team has solved the processing problem of oversized and ultra-thin "coats" for aircraft and rockets.

Skin, described as the "coat" of the aircraft, is the main load-bearing part that determines the fatigue life of the aircraft, accounting for 80% of the fuselage area and 21% of the fuselage weight.

The skin of the new aircraft is about as thick as an eggshell at its thinnest point, equivalent to the thickness of 8 sheets of A4 paper superimposed, or the diameter of 8 strands of hair combined.

The precision processing of skin is an important technological breakthrough in the mass production of large passenger aircraft. Wang Yuhan introduced that in order to ensure safety, the aircraft uses a very expensive aluminum alloy skin, and most of the weight of the skin must be removed during the processing process (for example, the "coat" of China's domestic large aircraft must remove 90% of the weight of the skin blank), and then the aircraft can be "draped".

"Machining is most afraid of touching soft things, and the tool will be deformed as soon as it touches. How soft is the airplane skin? One finger will deform when pressed, so in the past, chemical corrosion was used to remove excess material. Wang Yuhan said.

However, the traditional chemical corrosion method is very polluted, requiring more than two dozen processes, occupying a lot of manpower, and there will be a variety of manufacturing defects, poor accuracy, which hinders the development of high-performance aircraft. According to reports, the project uses the "mirror milling" method instead of the "chemical corrosion" method, which improves the product accuracy by 5 times and the fatigue life of the product by 10%, which greatly improves the performance of the aircraft.

Wang Yuhan said that the team is currently the only team in China that has mastered mirror milling technology, "We have now provided 12 sets of equipment for domestic large aircraft, and also provided a complete equipment production line for the mass production of regional passenger aircraft." ”

This product is used in aerospace. In terms of rockets, China's new generation of launch vehicles has put forward new demand for processing technology. The bottom of the box is the main bearing part of the rocket launch load, and the new generation of launch vehicles uses liquid hydrogen liquid oxygen fuel, which needs to ensure the carrying capacity of the tank under extreme low temperature conditions, and must use the whole box bottom instead of the traditional tailor welded box bottom.

This leads to a big problem: how to remove excess material from the skin? At this time, traditional chemical methods are no longer possible. The application of the "mirror milling" method breaks through this problem, and the mirror-like milling technology can cut off excess materials as a whole, which raises the manufacturing technology of rockets to another level.

Academics "go to the sea": persist in seeking and helping "Made in China" to be more tenacious

Shanghai Tuopu CNC Technology Co., Ltd. (hereinafter referred to as: Tuopu) is composed of 5 doctors from Shanghai Jiao Tong University and some entrepreneurs in the machine tool industry.

It is not easy for those with academic backgrounds to "go to sea" to become enterprises.

Wang Yuhan said that as a professor, he is good at long-term strategy and knows how to gain insight into technological development, but at the beginning, he did not have a deep understanding of products.

He also remembers that a product raised 1500 million yuan when it was first financed, and because he did not understand the product research and development system, the team spent all this money in three months, "We encountered a financial crisis in the Spring Festival of the year we just raised money. ”

This is a very painful process, and later he understood that even if the core accuracy of the product meets the requirements, it does not mean that the product is qualified, just like "the mobile phone cannot have a single scratch".

After years of exploration, Wang Yuhan summed up two experiences of academic people who "go to the sea" to run enterprises:

1. Transformation. Those who come from an academic background need to understand the product in running a business. Technology and products are far apart, and teams need to think hard to turn technology into products and "sell" globally.

Second, focus. Running a business will inevitably encounter a crisis every year, whether it is a financial crisis or a crisis of product quality, the team must focus on its own direction, do not "run" where to make money.

Scientific research achievements from the "birth" of universities to the "growth" of entering the society are inseparable from the support of all parties. There is also such a story behind the application of mirror milling technology.

"There is a demand for land for high-end equipment, but at that time we had no money, we made some money to invest in research and development, and there was no money to buy land and build factories." Wang Yuhan said.

At that time, in order to support the development of the enterprise, the relevant departments in Shanghai wanted to give Tuopu land, but Wang Yuhan refused, "Many of my friends said, you are stupid, you don't want land in Shanghai." I said no, I'm going to do R&D, I'm going to do products. ”

Later, the factory building was built by the local government, and all the decoration facilities were funded by the government. "The whole investment is more than 2 million yuan, and our company only spent 200 million yuan to relocate, all of which are under construction by the government and are 'tailor-made' for us." Wang Yuhan said.

This kind of support has allowed these enterprises to grow. It is also this kind of support that makes "Wang Yuhan" willing to continue to seek in research and development, persist in fighting in the market, and make "Made in China" more tenacious. (End)

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