Fatigue failures of driveline and suspension notched components for ground vehicles under multiaxial loading conditions are common, since most of those components are subjected to complex multiaxial loadings in servic...Fatigue failures of driveline and suspension notched components for ground vehicles under multiaxial loading conditions are common, since most of those components are subjected to complex multiaxial loadings in service. A computational fatigue analysis methodology has been proposed here for performing multiaxial fatigue life prediction for notched components using analytical and numerical methods. The proposed multiaxial fatigue analysis methodology consists of an elastic-plastic stress/strain model and a multiaxial fatigue damage parameter. Results of the proposed multiaxial fatigue analysis methodology are compared to sets of experimental data published in the literature to verify the prediction capability of the elastic-plastic stress/strain model and the multiaxial fatigue damage parameter. Based on the comparison between calculated results and experimental data, it is found that the multiaxial elastic-plastic stress/strain model correlates well with experimental strain data for SAE 1070 steel notched shafts subjected to several non-proportional load paths. In addition, the proposed fatigue damage parameter is found to correlate reasonably well with experimental fatigue data of SAE 1045 steel notched shafts subjected to proportional and non-proportional loadings.展开更多
A series of low cycle fatigue and creepfatigue tests on smooth specimens and notched specimens were performed with a high temperature alloy used in the manufacture of aeroengine turbine discs. The cyclic stressstrain ...A series of low cycle fatigue and creepfatigue tests on smooth specimens and notched specimens were performed with a high temperature alloy used in the manufacture of aeroengine turbine discs. The cyclic stressstrain behavior and fracture characteristics of the notched specimens were emphatically investigated. A comparison of fatigue behavior between smooth and notched specimens was done and lifetime of notched specimens was evaluated. At the same temperature, the fatiguecreep lives of the smooth specimens are far greater than that of the notched specimens.展开更多
The effective notch stress approach for evaluating the fatigue strength of rib-deck welds requires notch stress concentration factors obtained from complex finite element analysis.To improve the efficiency of the appr...The effective notch stress approach for evaluating the fatigue strength of rib-deck welds requires notch stress concentration factors obtained from complex finite element analysis.To improve the efficiency of the approach,the notch stress concentration factors for three typical fatigue-cracking modes(i.e.,root-toe,root-deck,and toe-deck cracking modes)were thoroughly investigated in this study.First,we developed a model for investigating the effective notch stress in rib-deck welds.Then,we performed a parametric analysis to investigate the effects of multiple geometric parameters of a rib-deck weld on the notch stress concentration factors.On this basis,the multiple linear stepwise regression analysis was performed to obtain the optimal regression functions for predicting the notch stress concentration factors.Finally,we employed the proposed formulas in a case study.The notch stress concentration factors estimated from the developed formulas show agree well with the finite element analysis results.The results of the case study demonstrate the feasibility and reliability of the proposed formulas.It also shows that the fatigue design curve of FAT225 seems to be conservative for evaluating the fatigue strength of rib-deck welds.展开更多
In the actual engineering of the structure, mechanical notch is inevitable, which will significantly reduce the fatigue life of the structure. In order to ensure the application of notch structures in engineering, the...In the actual engineering of the structure, mechanical notch is inevitable, which will significantly reduce the fatigue life of the structure. In order to ensure the application of notch structures in engineering, the accurate evaluation of the impact of notch on fatigue life has become the basis of fatigue reliability design of structures. To investigate the influence of the concave structure on the overall fatigue life in practical engineering, three different sizes of V-notch parts and concave structure simulation parts were designed, and the life prediction was carried out by using the critical distance method. The results show that the stress gradient of the concave structure with the same stress concentration coefficient is much greater than that of the V-notch structure. Considering the notch effect, the S-T model in the critical distance method is modified by the stress concentration coefficient and stress gradient, and it is found that the life prediction accuracy reaches the ideal.展开更多
By using the finite element method,three-dimensional models of a number of periodic blunt and sharp notches subjected to tension loading are investigated.The aim of this research is to investigate the thickness effect...By using the finite element method,three-dimensional models of a number of periodic blunt and sharp notches subjected to tension loading are investigated.The aim of this research is to investigate the thickness effect on the location of maximum stress and notch stress intensity factor(NSIF)of corresponding blunt and sharp periodic notches respectively.With this aim,different number of periodic notches as well as different notch opening angles are examined.While for two-dimensional plates weakened by periodic notches some results are available in the literature,this paper first faces the problem of three-dimensional cases.A total of about 100 geometrical configurations are investigated.It is found that,the effect of plate thickness of periodic notched components can be characterized by the relative value with respect to the depth of the notch(H/t).For the blunt periodic notches with relatively higher values of H/t ratio,the value of the maximum tensile stress is located near the free surface.On the contrary for lower values of H/t,it is placed at the middle plane.The same behaviour is observed for sharp periodic notches in terms of notch stress intensity factors.展开更多
文摘Fatigue failures of driveline and suspension notched components for ground vehicles under multiaxial loading conditions are common, since most of those components are subjected to complex multiaxial loadings in service. A computational fatigue analysis methodology has been proposed here for performing multiaxial fatigue life prediction for notched components using analytical and numerical methods. The proposed multiaxial fatigue analysis methodology consists of an elastic-plastic stress/strain model and a multiaxial fatigue damage parameter. Results of the proposed multiaxial fatigue analysis methodology are compared to sets of experimental data published in the literature to verify the prediction capability of the elastic-plastic stress/strain model and the multiaxial fatigue damage parameter. Based on the comparison between calculated results and experimental data, it is found that the multiaxial elastic-plastic stress/strain model correlates well with experimental strain data for SAE 1070 steel notched shafts subjected to several non-proportional load paths. In addition, the proposed fatigue damage parameter is found to correlate reasonably well with experimental fatigue data of SAE 1045 steel notched shafts subjected to proportional and non-proportional loadings.
文摘A series of low cycle fatigue and creepfatigue tests on smooth specimens and notched specimens were performed with a high temperature alloy used in the manufacture of aeroengine turbine discs. The cyclic stressstrain behavior and fracture characteristics of the notched specimens were emphatically investigated. A comparison of fatigue behavior between smooth and notched specimens was done and lifetime of notched specimens was evaluated. At the same temperature, the fatiguecreep lives of the smooth specimens are far greater than that of the notched specimens.
基金This study was sponsored by the National Key Research and Development Project(No.2017YFE0128700)the Fundamental Research Funds for the Central Universities(B200203006).
文摘The effective notch stress approach for evaluating the fatigue strength of rib-deck welds requires notch stress concentration factors obtained from complex finite element analysis.To improve the efficiency of the approach,the notch stress concentration factors for three typical fatigue-cracking modes(i.e.,root-toe,root-deck,and toe-deck cracking modes)were thoroughly investigated in this study.First,we developed a model for investigating the effective notch stress in rib-deck welds.Then,we performed a parametric analysis to investigate the effects of multiple geometric parameters of a rib-deck weld on the notch stress concentration factors.On this basis,the multiple linear stepwise regression analysis was performed to obtain the optimal regression functions for predicting the notch stress concentration factors.Finally,we employed the proposed formulas in a case study.The notch stress concentration factors estimated from the developed formulas show agree well with the finite element analysis results.The results of the case study demonstrate the feasibility and reliability of the proposed formulas.It also shows that the fatigue design curve of FAT225 seems to be conservative for evaluating the fatigue strength of rib-deck welds.
文摘In the actual engineering of the structure, mechanical notch is inevitable, which will significantly reduce the fatigue life of the structure. In order to ensure the application of notch structures in engineering, the accurate evaluation of the impact of notch on fatigue life has become the basis of fatigue reliability design of structures. To investigate the influence of the concave structure on the overall fatigue life in practical engineering, three different sizes of V-notch parts and concave structure simulation parts were designed, and the life prediction was carried out by using the critical distance method. The results show that the stress gradient of the concave structure with the same stress concentration coefficient is much greater than that of the V-notch structure. Considering the notch effect, the S-T model in the critical distance method is modified by the stress concentration coefficient and stress gradient, and it is found that the life prediction accuracy reaches the ideal.
文摘By using the finite element method,three-dimensional models of a number of periodic blunt and sharp notches subjected to tension loading are investigated.The aim of this research is to investigate the thickness effect on the location of maximum stress and notch stress intensity factor(NSIF)of corresponding blunt and sharp periodic notches respectively.With this aim,different number of periodic notches as well as different notch opening angles are examined.While for two-dimensional plates weakened by periodic notches some results are available in the literature,this paper first faces the problem of three-dimensional cases.A total of about 100 geometrical configurations are investigated.It is found that,the effect of plate thickness of periodic notched components can be characterized by the relative value with respect to the depth of the notch(H/t).For the blunt periodic notches with relatively higher values of H/t ratio,the value of the maximum tensile stress is located near the free surface.On the contrary for lower values of H/t,it is placed at the middle plane.The same behaviour is observed for sharp periodic notches in terms of notch stress intensity factors.