industrial overlord

Chapter 29 Finite Element Analysis

The welding sparks that people see every day are also called electric arcs. If a layer of flux is used to cover the welding point during welding, the arc will be buried under the flux and cannot be seen. This welding process is called submerged arc welding.This feature of submerged arc welding makes the welding pool protected by flux, and there are fewer impurities in the weld, so the welding quality is higher.Submerged arc welding is rarely done manually, but is done automatically by a special submerged arc welding machine, so it is also called automatic submerged arc welding.For the second-class pressure vessel manufacturing enterprises, having a submerged arc welding machine is one of the important inspection indicators.

Fan Shibin, the technical section chief, and Feng Xu, the director of the container workshop, have both visited submerged arc welding in a petrochemical machine. They have some perceptual understanding of the working principle of the submerged arc welding machine, but they can't explain how it works inside. .

Lin Zhenhua, as a graduate student majoring in mechanical engineering, is naturally very familiar with the working principle of submerged arc welding.Submerged arc welding was considered a relatively new technology at that time, but it was a very common technology when Lin Zhenhua lived. There will be a schematic diagram of the welding machine in any welding process tutorial.Zhu Tiejun accidentally mentioned submerged arc welding to Lin Zhenhua, originally he just wanted to ask Lin Zhenhua if he had heard of this technology, but a few days later, Lin Zhenhua actually handed over the drawings of a set of welding machines to him hand.

With the drawings, it does not mean that a submerged arc welding machine can be manufactured immediately. Many related technical parameters, such as welding current, arc voltage, welding wire diameter, welding wire inclination, welding speed, etc., need to be determined through experiments.Of course, these parameters are also included in the textbooks of later generations, but it is impossible for Lin Zhenhua to remember them so clearly.What's more, some parameters need to be adjusted according to the actual situation. Different components of flux and different types of steel will affect the selection of parameters. These problems can only be solved through repeated experiments.

The research team was established under the leadership of Zhu Tiejun. The first thing Lin Zhenhua did was to give lessons to everyone, explaining the principles and technological essentials of submerged arc welding. Listening to the class, including Yang Chunshan, Lin Zhenhua's prospective father-in-law.Zhu Tiejun also took a notebook and sat on the side to record. Although this little old man was born in the army, he also has a deep interest in industrial technology.

"Xiao Lin, after listening to your introduction, I feel that I have figured it out. However, you said that so many parameters need to be tested, so don't we have to do thousands of experiments?" Fan Shibin questioned.

"Thousands of experiments? When will it be done?" Hao Songlin, a welder, muttered.

"Thousands of experiments are not too many." Hu Yang interjected, "To master a technology, thousands of experiments are very normal. When our country introduced a certain torpedo technology from the Soviet Union in the past, in order to master the torpedo track , and fired hundreds of torpedoes, each costing tens of thousands of dollars."

"Since Master Hu has said so, let's start to try. Xiaohua, you issue a work order, and we will do it according to your requirements. There are a dozen of us welders, and we work together thousands of times. The experiment is also very fast." Yang Chunshan said briskly, he is Lin Zhenhua's hardcore backer.

Zhu Tiejun hesitated and said, "How much will it cost for thousands of experiments? Xiao Lin, is there a better way, it is best to do fewer experiments."

Lin Zhenhua sighed, and said, "Well, actually, it is not necessary to do so many experiments. If you can construct the variation curves of several parameters, then it is enough to select a few nodes for experiments."

Zhu Tiejun asked: "Xiao Lin, I don't understand what kind of curve you are talking about. However, how can you construct a curve like what you said?"

Lin Zhenhua said: "Constructing these curves requires some calculations. If you have a computer, these calculations are quite easy. But where can I get a computer now?"

Fan Shibin clicked his tongue and said, "Let's forget about it. I just heard that there is a computer in the Provincial Computing Center, which costs hundreds of dollars an hour, and you need a letter of introduction to use it. How can we afford it?"

Hu Yang asked: "Xiao Lin, what kind of knowledge do you need to use for the calculation you mentioned. We don't have a computer. If we mobilize the educated workers in the whole factory to do the calculation together, is it okay?"

Lin Zhenhua shook his head: "Old Hu, this calculation is not the four arithmetic operations, I am going to do a finite element analysis..."

"What did you say? Finite element?" A strange light appeared in Hu Yang's eyes.

"Well, it's just a calculation method anyway, it doesn't matter what it's called." Lin Zhenhua hurriedly looked at it sloppily. The word finite element is really too difficult for the people of Hanhua Factory.

Unexpectedly, Hu Yang insisted on it: "Xiao Lin, I have seen the concept of finite element in a mechanical magazine, but I don't know what it is. Could it be that you know it?"

Lin Zhenhua bit the bullet and said: "I barely know something, but to do the simplest finite element analysis, it also involves calculations such as matrices and differential equations. I'm afraid..."

Hu Yang turned to Zhu Tiejun and Fan Shibin and said: "Director Zhu, Section Chief Fan, you all know that I have a high school degree, and I like to read some books these years. I understand the matrix and differential equations mentioned by Xiaolin. One point. How about I take the initiative to invite Ying to cooperate with Xiaolin in the finite element analysis, do you think it is okay?"

"Of course." Fan Shibin and Zhu Tiejun looked at each other, and immediately expressed their opinion: "Speaking of which, I also learned these things when I was in college, but they have been useless for more than ten or twenty years, and I have almost forgotten them." Yes. I did some calculations just now. Those in our factory who can do matrix calculations can probably do it with a single slap. Their situation is similar to mine. If Master Hu can still remember and help Xiaolin do this calculation, that would be great But that's all."

Zhu Tiejun stood up and said: "Okay, let's stop here today, Master Hu, you and Xiao Lin discuss what this yuan is called, and see if you can help Xiao Lin do it. Submerged arc welding is a matter of ours. What to do. It would be the best if you can do fewer experiments through calculations. If it is not possible, just a few thousand experiments. If we can get the second-class container certificate, it is worthwhile for us to spend some money of."

Everyone left with admiration for Lin Zhenhua, only Hu Yang remained.Lin Zhenhua looked at Populus euphratica, and said with a sad face: "Master Hu, are you really going to do the finite element analysis by hand?"

Hu Yang nodded and said: "That's right, what a computer can do, a human can do. But, I haven't studied finite element analysis. I don't know exactly what's going on. Can you tell me about it?"

Lin Zhenhua said: "Master Hu, tell me first, how much do you know about matrices and differential equations? You say you have a high school education, these things are not high school knowledge."

Hu Yang smiled and said: "Xiao Lin, I don't have any other hobbies, but I prefer to learn new things. Although I only have a high school degree, I have taught myself advanced mathematics. Let me talk big, matrix and Differential equations and other general topics will definitely not be difficult for me."

"Well, let me tell you about finite element analysis." Lin Zhenhua said, "The so-called finite element analysis is to replace complex problems with some relatively simple problems and then solve them. Its core idea is to solve complex problems. The solution domain is regarded as composed of many small interconnected sub-domains called finite elements, assuming a suitable and relatively simple approximate solution for each unit, and then deriving and solving the total satisfaction conditions of this domain, so as to obtain the solution of the problem untie."

Hu Yang listened to Lin Zhenhua's explanation carefully, repeating the words in his mouth, as if he wanted to force the knowledge into his mind.

After Lin Zhenhua finished speaking, he asked a little worriedly: "Master Hu, can you understand what I said?"

Hu Yang nodded: "I roughly understand that this idea should have a long history. Isn't that the way of thinking about calculus?"

"That's right." Lin Zhenhua said, "However, it was in the 60s that the finite element method was formally proposed. In just over ten years, this method has been widely used in western engineering circles, involving almost all technology field."

A haze flashed in Hu Yang's eyes: "Oh, look at us, we have been tossing around in the past ten years, and we don't know how far we have traveled abroad."

Lin Zhenhua quickly comforted him and said: "Master Hu, don't worry, we can catch up now. Hasn't the Party Central Committee proposed the spring of science? A self-taught engineer like you will definitely be of great use."

"Let's not talk about this." Hu Yang waved his hand, "Xiao Lin, you still tell me how to do finite element analysis."

"Okay, let's start with a simple example..." Lin Zhenhua spread out a piece of paper, wrote a model for Hu Yang, and then began to introduce the basic ideas of finite element analysis to Hu Yang step by step.

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(End of this chapter)