How to do physical examination for the hottest Aer

2022-09-19
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How to do "physical examination" for Aeroengines

Abstract: aeroengines are more afraid of "getting sick" than people. Its working position is thousands or even tens of thousands of meters high. If there is a problem that leads to the loss of power of the aircraft, the consequence may be the destruction of the aircraft and the death of people. Therefore, it is very important for it to keep "healthy" at all times

aeroengines are more afraid of "getting sick" than people. Its working position is thousands or even tens of thousands of meters high. If there is a problem that leads to the loss of power of the aircraft, the consequence may be the destruction of the aircraft and the death of people. Therefore, it is very important for it to keep "healthy" at all times

how is the aeroengine "examined"? Recently, Chen Hua, an aeroengine expert and production director of Chongqing Tianjiao aero Power Co., Ltd., introduced to

before taking the post, you should have a "physical examination"

aeroengine is a highly complex precision machinery, including five parts: inlet, compressor, combustion chamber, turbine and tail nozzle. "A medium-sized engine has more than 20000 parts." Chen Hua said that the structure and process of these parts are complex, and they have high requirements for materials and manufacturing accuracy, and the processing is also very difficult

in the process of design and manufacturing, aero-engines have to undergo various tests and tests, including component tests, core aircraft tests, ground tests, altitude tests, flight tests, etc. Taking the high altitude test as an example, it mainly includes environmental test, windmill state test, system control test, height and speed characteristics test, engine state characteristics test, bird throwing test, anti ice test, which is divided into two detection items and operation steps, attitude test, matching test, etc. These experiments are like tests of all sizes in life. Aeroengines must also pass the examination again and again before they can move from design to mass production and finally be delivered to customers

aero engines also need to undergo "entry physical examination" before officially starting work. Compared with human physical examination, its physical examination is somewhat similar, but the items are more diverse and complex, including component testing, size and appearance inspection, macro and internal microstructure testing, as well as physical, chemical and mechanical properties testing

Chen Hua introduced that the material composition detection of parts is similar to the DNA detection of human body, and this basic parameter can be used as the confirmation of "identity". Size and appearance inspection, similar to human height and weight inspection, will determine whether the overall dimensions of the engine meet the requirements. Physical, chemical and mechanical performance tests, such as human vision and hearing tests, are designed to see whether the function of engine materials can meet the requirements

don't worry about these tests and inspections, which ensure the reliability of the engine. Take the TV series turboshaft engine made in Ukraine as an example. This product is used in more than 60 countries and is equipped on more than 90% of MI series and Ka series helicopters. A total of more than 30000 units are in service, but none of them has ever stopped in the air. Such reliability, which even Europe and the United States cannot achieve, stems from a large number of preciseness and accurate wiring; When using, it is necessary to operate according to the rules and procedures in the instruction manual. During the operation, it is necessary to prevent the downforce plate from exceeding the regular stroke of the piston

however, the above tests are destructive tests, which are generally carried out by taking one sample from a batch of samples or from the sample sampling area reserved for the product. Chen Hua said that in the process of engine manufacturing and maintenance, nondestructive testing methods are more commonly used. It will not cause damage to the parts, and can reflect whether there are major problems inside the parts. At the same time, it can also monitor the aeroengine in real time to prevent catastrophic consequences caused by product failure. With the development of technology, nondestructive testing has become an important technical means to control the quality of aero-engine parts and ensure flight safety

physical examination can also evaluate life span

there are dozens of nondestructive testing methods at present. This technology has developed from simple detection to the evaluation of the safe service life of engine parts

radiographic testing of engine parts is like X-ray transmission in human physical examination, but some control parameters such as current and voltage are set differently. Chen Hua said that radiographic testing is based on the different absorption of penetrating rays by the tested object to detect the internal defects of parts. The inspection results can visually display the defect image, which is convenient for qualitative and quantitative analysis. This method is sensitive to volumetric defects and is mainly used for the detection of castings and weldments, including turbine blades, casting casings, shells, weld defects and hollow blade residual cores. However, it is difficult to find thin layer defects perpendicular to the ray direction

engine ultrasonic testing is similar to B-ultrasound, but the parameters such as power and frequency are different. Chen Hua said that this method uses the attenuation of ultrasonic wave when it propagates in the medium and the nature of reflection at the interface to detect defects. Its advantage is that it only needs to approach the specimen from one side, and it can detect metal, non-metal and composite materials. It has comprehensive advantages in determining the size, location, orientation, buried depth and properties of internal defects. This method is generally used to eliminate defects in raw materials for forgings, tubes, rods, plates and other profiles of engines; For rotating parts such as disc and shaft, water immersion ultrasonic testing can be used to eliminate the influence of human factors

borescope detection is similar to endoscopy commonly used in hospitals, such as gastroscopy and tracheoscopy. With the help of special industrial endoscope equipment, it has become the only inspection method in route maintenance that can understand its internal conditions without disassembling the engine. It can be used to detect the main air flow channel components of the engine, high-pressure compressor, turbine disc blades at all levels, fuel nozzle, combustion chamber and other parts that are not easy to disassemble and have poor accessibility

penetrant testing is to let the penetrant contact the surface of the tested part, penetrate into the small defects of the opening on the surface of the part with the help of capillarity, and then suck out these penetrants with developer, so as to show the image of damage or defect on the two surfaces. This method can detect multiple parts in one operation and is widely used in aero-engine maintenance. All engine parts made of aluminum alloy, titanium alloy and heat-resistant high-temperature alloy will generally use fluorescence to detect their surface damage during overhaul or overhaul; Under outfield conditions, coloring method is commonly used to detect the parts that cannot be disassembled on the engine. However, penetrant testing can only detect defects on the surface of parts

nondestructive testing also includes magnetic particle testing for surface cracks, folds, interlayers, and slag inclusions of ferromagnetic materials; Based on electromagnetic induction, it is suitable for eddy current testing of conductive materials

defect visualization can be achieved in the future

with the development of aviation industry, aero-engine physical examination technology is also improving

Chen Hua introduced that the newly developed acoustic emission testing technology is a dynamic nondestructive testing method based on the stress wave generated by local transient displacement in stressed materials. Typical acoustic emission sources are deformation processes related to defects, such as crack propagation and plastic deformation. The acoustic emission energy comes from the elastic stress field in the material. Without stress, there is no acoustic emission. Therefore, acoustic emission testing is usually carried out during the loading process, and its main applications include monitoring fatigue crack growth and welding joint quality, and evaluating the structural integrity of composite structures

infrared detection is based on the principle of infrared radiation, which detects defects by scanning and recording the temperature changes on the surface of parts. During the inspection, the fixed heat is evenly injected into the surface of the workpiece and diffused to the inside. If there are internal defects as the repair gets worse, the even heat, firm and indomitable enterprising will flow will be blocked by the defects. After time delay, heat accumulation will be generated at the defect part, reflecting the abnormal temperature. This method can detect delamination, cavity, crack, inclusion and other defects in metal and non-metallic material bonding parts, honeycomb sandwich structure, metal welding, hollow turbine blade and other material parts

in aeroengines, negligence of any defect may lead to safety accidents. "Effective detection technology must be adopted to meet the development requirements of future aeroengines, so that their defects can be more intuitively displayed, so as to effectively and automatically extract and identify the relevant feature information of defects." Chen Hua said that the visualization of defects is conducive to the good analysis and processing of the engine, so as to meet the needs of rapid and efficient automatic detection in the future

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