414: Chapter 864 You think you can figure out the problem with math? You must be kidding!

Zhao Yang asked, somewhat puzzled.

"What happened? Is it urgent?"

"I can't explain it in a few words over the phone. You'll know once you get here!"

Hearing this tone, Zhao Yang knew it was a serious matter. He didn't ask any more questions, hung up the phone, and immediately had Wang Hai drive to the address General Li had given him.

Upon arriving, General Li was already waiting at the entrance. Zhao Yang got out of the car, walked over quickly, and asked with curious eyes, "What exactly is the situation?"

"There's a problem with the test bench. Chief Engineer Li suspects that there's a deviation in the structural design scheme you provided earlier. You'll understand once you go inside and take a look."

General Li's expression was very serious as he led Zhao Yang into the laboratory.

Entering the laboratory, Chief Engineer Li and several engineers were gathered around the test bench, the atmosphere somewhat oppressive. General Li briefly introduced the people present. Chief Engineer Li shook hands with Zhao Yang, skipped the unnecessary pleasantries, and led him directly to the test bench, pointing at the engine cavity with its casing partially removed, and said.

"Professor Zhao, we discovered abnormal engine vibrations during the test run this morning. There are several new peaks on the vibration spectrum data that weren't there before. We shut down and checked the external pipelines and sensors, and everything is fine. The source of the anomaly must be inside the cavity, but we haven't determined exactly which part it is yet."

After he finished speaking, he glanced at Zhao Yang, his tone carrying a hint of hesitation: "Our preliminary investigation hasn't ruled out the possibility that it's due to the overall structural design."

This was said tactfully, but everyone present understood the implication. If there really was an issue with the overall structural design, the mathematical model Zhao Yang had established would need to be re-verified.

The engineers nearby all had their eyes on Zhao Yang; some looked worried, others had complex expressions, but no one spoke. A young engineer muttered softly, "I told you that model was too idealistic," only to be glared at by an older engineer beside him.

Zhao Yang didn't offer any explanation, only saying, "Let me take a look first."

He walked over to the console next to the test bench, sat down, and pulled up the real-time vibration spectrum data from the test run and the flow field parameters inside the cavity, then called up his structural design model for comparison.

Several sets of data were laid out side-by-side on the screen. Zhao Yang's fingers slid rapidly across the trackpad, occasionally pausing at a certain data point to zoom in on the local curve to check the details.

The engineers nearby, who had initially been whispering and discussing, grew quieter and quieter as they watched Zhao Yang's movements.

The speed at which he accessed the data was too fast; it didn't look like he was verifying them one by one, but rather that he had already re-simulated the entire internal structure of the engine in his mind. Chief Engineer Li stood behind him, watching the rapidly switching data windows on the screen, his brows furrowing tighter and tighter, but he didn't say anything.

After reviewing the data, Zhao Yang stood up, walked to the test bench, pressed his fingers against the engine casing, and slowly moved them along the outer wall of the cavity.

He stopped at three locations, tapped the casing with his fingers, listened to the frequency of the echoes for a few seconds, then turned to Chief Engineer Li and said, "There is a manufacturing flaw on the inside of the fourth section of the cavity. It's not a design issue; it's a localized defect created during the manufacturing process. The location is roughly here."

He drew a simple diagram on a piece of scratch paper, marking the specific coordinates.

Chief Engineer Li was stunned: "We tested this location before the test run and didn't find any problems."

"You used standard X-ray inspection, but this flaw is inside the cavity, and the ray projection angle happened to be blocked by the stiffener. When you took the images from this angle, there was obstruction; this slight angle easily hides problems."

Zhao Yang looked at Chief Engineer Li and said, his tone very certain.

Hearing Zhao Yang's explanation, Chief Engineer Li and the other engineers nearby looked at each other, their eyes filled with hesitation, unsure if what Zhao Yang said was correct.

"Whether it's like this or not, we'll know once we re-test it."

Zhao Yang saw the hesitation in the eyes of Chief Engineer Li and the others, and he smiled.

He had the operator adjust a set of ultrasonic testing parameters according to his requirements and conduct a second probe of the engine cavity at the angle and frequency range he specified.

The waveform graph on the screen scrolled for quite a while, and at the location Zhao Yang had marked, a very faint, abnormal echo indeed appeared.

After zooming in, one could see a very small internal crack; it wasn't very long or deep, but it was located exactly in the high-stress zone of the combustion chamber exit section. The vibration frequency this location endured during the test run happened to match the engine's operating frequency, creating resonance, which was why those abnormal peaks appeared on the spectrum.

The entire laboratory was silent for several seconds. The young engineer who had been muttering earlier stared at the waveform graph on the screen, the expression on his face changing from suspicion to disbelief. He opened his mouth as if to say something, but in the end, he only managed to blurt out, "Holy crap! It really is this spot."

Another slightly older engineer took off his glasses, wiped the lenses, put them back on to look at the waveform graph carefully, then turned to look at Zhao Yang, asking him in shock.

"Professor Zhao, how did you pinpoint it? The casing wasn't removed, you didn't look at the internal structure, and just by relying on external vibration data and flow field parameters, you were able to calculate the location of such a small internal flaw?"

"The abnormal peak frequency on the vibration spectrum basically matches the characteristic frequency of the combustion chamber exit section, and the flow field pressure data shows an extremely weak attenuation at that location. By using the finite element model to reverse-calculate and then substituting it into the structural design model for parameter comparison, I could roughly lock onto the location."

Zhao Yang said calmly.

Chief Engineer Li stood to the side, listening to this, and was silent for a long while before saying, "Professor Zhao, this is a problem that occurred in our own manufacturing process; it has nothing to do with your design scheme. It's fortunate you came today; otherwise, our entire team might have wasted a lot of time in the wrong direction."

The entire laboratory quickly sprang into action. After confirming the location of the flaw, several engineers carefully removed part of the casing according to the location Zhao Yang had marked, exposing the inner wall of the cavity. They used an endoscope to confirm the specific form of the crack, then performed localized grinding and repair welding.

After quite a bit of work, the repair was completed, and it was re-tested; the waveform graph returned to normal.

General Li had been silent the whole time, but after the repair results came out, he patted Zhao Yang's shoulder heavily: "It's a good thing you came. This batch of materials is the top-tier in the country; the cost of this engine used for the test run alone is not a small sum. If it had been scrapped directly, the loss would have been too great. Previously, in order to gather this set of materials, I personally made several trips to the Materials Institute, and the director almost fell out with me."

"Don't rush to put it back on the test bench yet. Have the engineers run an ultrasonic scan on all cavity sections according to these parameters, and make sure there are no problems before proceeding."

Zhao Yang said directly.

"Similar problems aren't easy to detect!"

"You're right!"

Hearing Zhao Yang's words, Chief Engineer Li nodded hurriedly and ordered his subordinates to execute it immediately.

General Li kept Zhao Yang for a meal. In the private room of the experimental design bureau's cafeteria, Chief Engineer Li looked at Zhao Yang with a bitter smile and said helplessly, "Professor Zhao, to be honest, I've spent more than half my life working on aero-engines, and what gives me the biggest headache is materials. Sometimes there's clearly no problem with the design, and the calculated data is beautiful, but the actual manufactured product just doesn't meet the design standards. The flaw today, ultimately, boils down to insufficient machining precision and the stability of the material itself."