Study On Measurement Techniques And Evaluation Methods For Micro-sized Valve Seal

The valve seal as one of the common types of parts, has many types of structure, and plays a key role in all walks of life. In the aerospace field, we even propose more strict requirements on sealing part of the engines. With the development of extreme manufacturing technology, the valve seals are getting more miniature and precise, and that puts forward higher requirements on its processing and detecting techniques.At present, there are two difficulties in the measurement of micro-sized valve sales: the first one is how to get the information of the inner surface in cavity with a high deapth, and the other is the measurement of the micro-sized structures with high curvature. In addition, there are few research on the evaluation of the micro-sized valve seals, and in practice, the evaluation results of the parameter Ra is far from expection.About the measurement method of the micro-sized valve seals, this paper put forward a new contact measurement method using the high-aspect-ratio sensor with variable probes. The rod of the probe has a high aspect ratio, and the sensor can be connected with different kind of probes to satisfy the measurement requirements in different conditions, on the other hand, we should provide a high precision rotary shaft and a movement platform to realize the measurement of the form error of the parts.In order to verify the validity of the method, we use the TESA TT80 probe to establish a simple measurement platform, and we use this to get the roudness error of each sample. In addition, we use the Form Talysurf PGI 1240 surface profilers to take the measurement of the roughness and the micro size, and get a lot of experiment results.As for the evaluation method of the valve seals, based on the leakage rate the users provides and relationship between the fractal parameters and the sealing performance, we use Matlab to analysis the validity of the roughness parameters when they are used to evaluate the sealing performance of the seals. It is demonstrated that the Ra has many defects in its numerical stability and the relationship between the sealing performance, and we take the the Root mean square slope R△q for the better evaluation parameter.At last, this paper analysis the uncertainty in measurement of the results, and it is discussed in detail about the process of the small-size torus. And we finish the analysis of the uncertainty in measurement of the results of roundness error, the results of Ra, the results of micro size, and the results of the R△q, the coverage probability in this paper is 3, the accuracy of the measurent of roughness is better than 10 nm, and the accuracy of the measurement of shape and size is better than 10μm.