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By 袁春凤 (Tiffany)
Hydrogen induced wear: hydrogen is released during the friction due to mechanical and chemical action. Hydrogen diffuses into the deformed layer of metal surface, causing a large number of crack sources in the deformed layer. The generation and development of cracks make the surface material fall off, which is called hydrogen-induced wear. Oxygen may come from material itself or environmental medium, such as lubricating oil and water.
By 袁春凤 (Tiffany)
The mechanism of cavitation is surface fatigue damage caused by impact force, but the chemical and electrochemical action of liquid and abrasive inclusion in liquid may accelerate cavitation damage. For example, the cylinder liner cavitation is caused by the action of piston lateral thrust because the combustion pressure in cylinder varies with crankshaft angle. The elastic deformation and high-frequency vibration of bubbles produce great impact force (tens or even tens of thousands of high pressure) and high temperature (hundreds of degrees) at the instant of collapse, and the collapse speed can reach 250m/s.
Feilong jiangli will update analysis of more auto parts failure models.
By 袁春凤 (Tiffany)
What is an automobile shock absorber?
In order to accelerate the vibration attenuation of the frame and body and improve the ride comfort of the vehicle, vibration absorbers are installed in the suspension system of most automobiles. Both the shock absorber and the elastic element are installed in parallel.
Hydraulic shock absorbers are widely used in vehicle suspension systems. The principle of the hydraulic shock absorber is that the oil in the shock absorber shell flows repeatedly from one cavity to another through some narrow cavities when the piston moves in the cylinder cylinder when the driver and the bridge move reciprocating relative to each other. At this time, the friction between the hole wall and the oil and the internal friction of the liquid molecule form a damping force to the vibration, so that the vibration energy of the body and the frame is converted into heat energy, which is absorbed by the oil and shock absorber shell, and then emitted into the air. The damping force of the shock absorber increases or decreases with the relative velocity of the frame and the axle, and is related to the viscosity of the oil. Therefore, it is required that the viscosity of the oil used in the shock absorber should be as little as possible affected by the temperature change, and has the properties of anti-vaporization, anti-oxidation and non-corrosion to various metal and non-metal parts.
By 袁春凤 (Tiffany)
Automotive engine bracket
Automobile engine bracket is a safe and functional part of powertrain mounting system. It must satisfy the strength of automobile under various driving conditions and the restraint mode of mounting bracket has a great influence on the noise inside the vehicle. If the design is unreasonable, the natural frequency of the mounting bracket I is too low and in the range of engine operating speed, the mounting bracket will produce resonance, which will increase the noise inside the vehicle. Therefore, modal is one of the important design indexes of mounting bracket. Taking the four-cylinder engine of passenger car as an example, according to the resonance theory, it is required that the natural frequency of the engine mounting bracket should be greater than 500 Hz, and the lowest should be greater than 400 Hz. In fact, due to the limitation of the layout space, the above requirements can not be met. The first order natural frequency should be increased as much as possible. Feilong Jiangli,40 years specialize in engine bracket, through the optimization design and modal analysis of the suspension bracket practice, summed up to improve the modal method, to provide a theoretical basis for design.
By 袁春凤 (Tiffany)
The phenomenon that two objects move relative to each other to produce motion resistance between their contact surfaces is called friction, which is called friction. The existence of friction not only increases the power consumption, but also causes the wear of parts' contact surfaces. Therefore, lubricating oil is usually used between the relative moving surfaces of automobile parts to reduce friction. Failure of automotive parts 75% is caused by friction.
Friction can be divided into dry friction, liquid friction, boundary friction and mixed friction according to the lubrication state of the parts.
(1) dry friction
The friction between the frictional surfaces without any lubricating medium is called dry friction.
When the parts are in the state of dry friction, the surface of the parts is abraded sharply, so the surface of the moving parts of the automobile should avoid the occurrence of dry friction as far as possible.
Dry friction and boundary friction are the main friction between the upper part of cylinder wall and piston ring. Dry friction will occur when the journal and bearing are subjected to impact load in the working process.
(2) liquid friction
Two the friction of the friction surface when the lubricant is completely separated is called liquid friction.
In liquid friction, the two friction surfaces are completely separated by a layer of lubricating oil film with a thickness of 1.5-2.0um, which avoids direct contact between the working surfaces of the two parts. Friction only occurs between the lubricating fluid molecules, so the friction resistance is very small, and the wear of the parts is very slight.
Most of the relative motion parts of a car are carried out under the condition of liquid friction (for example, crankshaft and bearing).
(3) boundary friction
Two friction surface separated by a very thin boundary film is called boundary friction.
The oil film thickness is usually below 0.1um. Friction only occurs between the outer molecules of the boundary film, reducing the friction and wear of the parts. But its thickness is very small, and it is easy to be destroyed by impact and high temperature, so it is not as reliable as liquid friction.
For example: between cylinder wall and piston ring; if the work crankshaft and journal between the insufficient supply of lubricant, easy to produce boundary friction.
(4) Mixed friction
The friction between two friction surfaces in the presence of dry friction, liquid friction and boundary friction is called mixed friction.
In the actual working state, the parts usually work under the mixed friction state, and the friction state varies with the working conditions.