Fatigue Life Test of Metal Bellows for Electric Vacuum Devices
Metal bellows play an important role as elastic sensitive components, compensation components, and sealing elements in instruments, meters, valves, and electric vacuum devices. When instruments, meters, mesh doors, and electric vacuum devices are working, the bellows often In the working state of reciprocating tension and compression, in order to assess the number of times that the bellows can withstand reciprocating tension and compression without failure, the mechanical fatigue life test of metal bellows is introduced. This article combines specific examples to introduce the influence of the mechanical fatigue life of the bellows The parameters and the reasonable choice of these parameters in practice
With the increasing use of vacuum interrupters to connect and cut off circuits in power systems and places requiring explosion protection, metal bellows as sealing and connecting components are also widely used in vacuum interrupters to isolate the outside air. , It is a very important part to isolate the arc and connect the movable guide rod. It must meet the mechanical life and airtight reliability requirements of various arc extinguishing chambers, so the mechanical fatigue life of the metal bellows directly affects The life of the vacuum interrupter. The metal bellows used in the vacuum interrupter are now more and more made of non-magnetic stainless steel. This is mainly because it has a long operating life, is not affected by heat treatment during the manufacturing process and loses its elasticity and is not easy to oxidize. And corrosion resistance and other advantages. There are many types of bellows. Generally, only hydroformed bellows and sheet welded bellows are used in the vacuum interrupter.
According to the national professional standard ZB Y-352-85, the metal bellows has the following basic parameters: effective area, recommended inner diameter, recommended outer diameter, recommended wave distance, recommended wave thickness, single wave stiffness, single wave maximum allowable displacement, The maximum pressure resistance (external pressure), etc., these parameters will affect the mechanical fatigue life of the bellows to varying degrees.
Although there are as many as eight basic parameters of the bellows, the basic parameters of the manufactured bellows have been determined. The main factor affecting the mechanical fatigue life of the bellows is the maximum displacement of a single wave applied during use. In order to ensure that the product can reach the specified service life, we must sample each batch of corrugated pipes for mechanical fatigue life test. The specific test method is: the corrugated pipe is welded to the structure shown in Figure 2. Vacuum the space formed with the shell and install the titanium pump. The vacuum degree should reach 1×10-4Pa. Fix the device on the testing machine, and carry out the test according to the specified test frequency and displacement alternating range. The test frequency is determined by the crank connecting rod mechanism. The rotation speed of the bellows is determined, and the displacement alternating amplitude of the bellows is determined by the length of the crank. 2 times the crank length is the displacement alternating amplitude of the bellows. The number of times the bellows is stretched and compressed is automatically recorded by the counter.