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Studies On Fatigue Life Prediction Of 15-5PH High Strength Steel Specimens With Center-hole Subjected To Shot Peening

Posted on:2016-11-27Degree:MasterType:Thesis
Country:ChinaCandidate:L F ZhouFull Text:PDF
GTID:2191330464969907Subject:Power Engineering
Abstract/Summary:PDF Full Text Request
Fatigue failure is one of the most common failure forms in structures of aeronautical engineering, mechanical engineering, shipbuilding engineering and other fields of industry. Fatigue damage occurs in stress concentration position of structures, such as rivet holes, fasteners,keyways and so on.Therefore,shot peening technology is often used to increase the fatigue strength and fatigue life of the stress concentration position. In many practical applications, the mechanical structures often work under random loading condition, random fatigue damage is the main failure form. Therefore, it is of practical significant to study the fatigue life prediction of shot-peened notched components under both constant and variable loading.In this paper,fatigue tests of 15-5ph center-hole shot peening specimens under constant amplitude loading were carried out, and the fatigue life under two kinds of stress ratio(R=-1 and R=0.06) were obtained. Using the normal distribution assumption, the p-S-N curves of the notched specimens different survival rates were determined. At mean time, the capacity of the prediction of six mean stress correction models were checked. The results showed that the SWT model can well describe the influence of mean stress on the fatigue test performance of the specimen.On the basis of FKM method, we studied the coefficient of surface strengthening factor in detail, and the specimen’s fatigue limits under two kinds of stress ratio were calculated. Calculated results showed that when R=-1, the calculated value and experimental value is very closed, the error is only 5.55%; When R=0.06,the error between the calculated result and experimental result is a little larger, it is about 21.46%, so using FKM method to calculate component fatigue limit can get a reasonable prediction results.We further carried out the test of 15-5ph center-hole shot peening specimens under variable amplitude loading, and fatigue life of specimens in three different stress level were obtained. And we used FKM to predict fatigue life of specimen under random loading spectrum. Calculated results showed that under low stress levels, predicted values and experimental values is very closed,the error is no more than 1 times; Under high stress level, the difference between predicted values and experimental values is a little larger, the biggest difference is closed to 4 times. We also analysed the causes of error, and thinked unreasonable mean stress correction model of FKM method is the main cause of the error. Further calculated results showed that the modified FKM method can significantly improve the accuracy of fatigue life prediction of specimen, the error between the predicted results and the experimental results is less than 10%.So, we can use the modified FKM model for the fatigue design of shot-peening notch components of 15-5ph high-strength steel.
Keywords/Search Tags:high-strength steel, shot peened, center-hole components, fatigue limit, fatigue life prediction, variable amplitude load
PDF Full Text Request
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