Study Of Very-High Cycle Fatigue Life Prediction And Remanufacturability Judgment Based On Fatigue Defect For Impeller Material FV520B-I

Centrifugal compressor is an important measure of industrial development in a country.The core component is the impeller blade manufactured by high-strength steel FV520B-?.The remanufacturing of used impeller can effectively save resource,reduce energy consumption and avoid environmental pollution,and it is an important way to achieve the sustainable development.According to the defect degree of the used blade and its remaining life,it is the key problem for the used impeller remanufacturing to explore the new remanufacturability judgment method based on the fatigue defect and the fatigue life.At present,the evaluation system for the remanufacturability of used impeller at home and abroad is still not perfect.Supported by the National 973 project(Basic Scientific Problem of Mechanical Equipment Remanufacturing,No.2011CB013401),this research is carried out based on the classic fatigue theory to reveal the mechanism of very-high cycle fatigue failure competition,establish the residual life prediction model of FV520B-I impeller based on different fatigue defect,propose a method for judging the remanufacturability based on the fatigue defect,and realize a quantitative characterization of compressor blade remanufacturability evaluation.This paper mainly carries out the following work:1.Analysis on surface and internal fatigue failure competition.Based on the fracture mechanics,surface and internal fatigue failure competition mechanism of high-strength steel is revealed by combining the fatigue strength models of different fatigue defect under different surface roughness conditions.The main factors of fatigue failure of the impeller under different defect conditions are analyzed,and the competition model of surface and internal fatigue failure is proposed.2.The fatigue life prediction for FV520B-? based on internal inclusion.The FV520B-?very-high cycle internal fatigue failure mechanism is analyzed.Based on the Murakami model,the actual working condition parameters of the blade are integrated,and the fatigue strength calculation model suitable for FV520B-? is proposed.By employing the Paris formula and energy dissipation theory,the material performance model parameters related to FV520B-? were obtained with the very-high cycle fatigue test data,and the very-high cycle fatigue life prediction model based on internal inclusions for FV520B-? impeller is proposed.3.The fatigue life prediction for FV520B-? based on surface microscopic defect.The FV520B-? very-high cycle fatigue test based on different roughness is carried out to analyze the influence of surface microscopic defects on the very-high cycle fatigue life of the material FV520B-?,and the surface microscopic defects are quantitatively characterized by surface roughness Ra.Combined with the ultrasonic fatigue test,the fatigue life prediction model of FV520B-? based on surface microscopic defects is established with reference to the classical Paris formula.4.The modified FV520B-? fatigue life prediction model affected by the ultrasonic loading frequency.A comparative study of ultrasonic fatigue test and conventional fatigue test is carried out.Based on the Basquin formula,the conversion model between ultrasonic fatigue test data and conventional fatigue test data is proposed,and the FV520B-I very-high cycle fatigue life model is modified.5.The remanufacturability judgment besed on the fatigue defect for FV520B-I.Based on the FV520B-? very-high cycle fatigue life prediction model and the existing remanufacturability evaluation system,the critical threshold of remanufacturing based on fatigue defect and the remanufacturability judgment index are obtained according to the logical relationship between residual fatigue life and remanufacturability.The method of judging remanufacturability based on fatigue defect is proposed.The method of judging remanufacturability based on fatigue defect is proposed.In this paper,the combination of fatigue failure mechanism,fatigue life prediction and remanufacturability judgment has opened up a new way for FV520B-? blade fatigue life prediction and remanufacturability judgment research,which has important theoretical and practical significance.