Fatigue Reliability Method Research Of High-stress Valve Springs

The springs are important components of various types of mechanical equipmentsand devices. In recent years, with the improvement of main engine to spring’sperformance requirements, the high-stress spring appears. Generally high-stress springis more than800MPa for service stress, its main application fields and products contain:high-stress spring in vehicles, high-stress elastic component of the high-speedlocomotive, shock absorption and buffer spring in large-scale engineering machine,balancing spring of electrical equipment and piping system, valve spring and so on.High-stress spring is an important fundamental component for national medium andlong-term scientific and technological development programs. the pros and cons of theirquality directly affects the overall system property and safety. With the rapiddevelopment of Chinese economy and technology, These fields present increasinglyhigh demand for lightweight, high reliability, high fatigue life to high-stress spring.High-stress spring possess design of high bearing stress, the wide stress amplitude,change difficult, complex work environment, high requirement for fatigue life andanti-relaxation properties and so on. Among them, high fatigue life is the most centralrequirement of all. The high fatigue life should meet the normal operation of mainengine in the life period.With the further improvement of design and manufacturing level for high-stressvalve spring, which the requirement of fatigue life, fatigue reliability has drawnincreasing attention. As a result, this paper focused on the study of fatigue reliability onhigh-stress valve spring.Based on the study of domestic and foreign high-stress valve spring fatigueanalysis，combined with the current state of Chinese high-stress valve spring industryand fatigue requirements, focused on the performance testing of fatigue, the methodstudy of fatigue reliability’s calculation model, put high-stress valve spring as the mainresearch object, in this paper the following aspects were discussed:1) Based on the research of the spring’s stress and the internal residual stress, the characteristics of high-stress valve spring’s fatigue and the key factors that affect thefatigue properties of the high-stress valve spring were studied.2）Based on the analysis of the characteristics of high-stress spring’s fatigue, thestrengthening principle of the high-stress valve spring’s shot peening was studied. Alsothe two different strengthening mechanisms of shot peening were analyzed withexperimental verifications.3）The high stress valve spring was selected to study the fatigue performance testmethods. The fatigue failure criteria and data processing methods of the fatigue testwere studied based on the fatigue test.4) The mathematical model and drawing methods for P-S-N curves based onWeibull distribution with the fatigue test data.5）In this dissertation, a fatigue residual life distribution model of the high-stressvalve spring is established based on a three-parameter Weibull distribution and priorprobability theory.