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Research and Application of the metal bar fatigue fracture

Author: DuRuiZuo
Tutor: ZhangLuoMing
School: Zhengzhou University
Course: Mechanical Manufacturing and Automation
Keywords: Material under the bar stress Brittle fracture Fatigue Incision Finite Element Analysis
CLC: TG115.57
Type: Master's thesis
Year: 2008
Downloads: 55
Quote: 0
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Abstract


The technology of materials under stress , fatigue load is applied so that fatigue crack initiation and rapid expansion to break , so as to achieve the purpose of separation of the material of the methods in a predetermined cross - section of the material . This technique is based on the principles of fracture mechanics safety design of the reverse process , in line with modern machining with little or no cutting precision machining direction of development , is a green processing technology has broad application prospects . But you want to make a practical industrial technology, previous research has also not enough . Based on this, the object bar , from theory and experiment under stress mechanism of material involved in the process and the choice of the main parameters for further research , in order to be able to promote stress cutting technology into productive forces . This article first impact from the stress of cutting bar brittle fracture factors , the bar incision at the stress strain state , discussed the incision site of the fatigue crack initiation and its mechanical model , the microscopic mechanism of fatigue crack growth and internal and external factors affecting the fatigue crack growth rate under material fatigue strength under different loading forms bar macro- morphology and bar stress fracture . The choice of the incision type , we use the finite element method for analyzed four typical incision type material stress (U- , V- , semi- V - and anti - semi- V-shaped ) incision at the stress concentration . The choice of parameters of the incision , using the finite element method analysis of the notch depth , cut open angle and notch root fillet radius of the incision stress concentration . The main conclusions from the theoretically : stress material , V - shaped incision formed stress concentration at the incision , the most conducive to the initiation of fatigue crack initiation ; different diameter bars are the relative depth of the incision near 0.1 , the stress concentration factor of the incision peak ; the incision opening angle has little effect on the stress concentration of the incision to take , it is recommended that the incision opening angle between 60 ° to 90 ° ; incision root fillet radius centralized the incision root stress degree larger impact . On the basis of theoretical analysis , the selection of the two materials , and the experimental verification . The test results support the results of the analysis of the finite element method .

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CLC: > Industrial Technology > Metallurgy and Metal Craft > Metallurgy and Heat Treatment > Metallurgy ( Physical Metallurgy ) > Analytical tests of the metal (Metal Testing and Materials ) > Mechanical properties ( mechanical properties ) test > Fatigue and creep tests , the fracture toughness test
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