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Papers by hongqin yang
Icf13, Oct 20, 2013
A three-term crack growth model was developed by adding a creep-fatigue interaction term to the t... more A three-term crack growth model was developed by adding a creep-fatigue interaction term to the traditional linear superposition law. It is based on the hypothesis that the maximal creep-fatigue interaction occurs when creep and fatigue crack growth rates are comparable. Thereby a novel exponential form of interaction intensity factor was proposed. In order to verify the model, the creep-fatigue crack growth behaviour of a nickel-based powder metallurgy superalloy (FGH97) was experimentally investigated. Creep-fatigue crack growth rates were obtained at 750 °C with various dwell times. Comparison of the crack growth rates between fitted and measured values at 0s, 90s, 450s and 1500s dwell times show great agreement. Encouragingly, excellent predictive ability of the model was verified by the experiment at 25s dwell time. Furthermore, to test the applicability of the interaction law on other materials, experimental data of two additional superalloys from references, namely Alloy 718 and Hastelloy® X, were used to fit the model. The results are also satisfactory.
Journal of Composite Materials, 2011
Fatigue delamination growth of multidirectional carbon/bismaleimide composites was investigated t... more Fatigue delamination growth of multidirectional carbon/bismaleimide composites was investigated to disclose the specific role of ply orientations. Both fatigue crack growth rate and threshold values of strain energy release rate in Mode I were studied by double cantilever beam test. For specimens with rising delamination resistance effect, the fatigue crack growth rate was found to be dependent on normalized interlaminar energy, GI/GIC, rather than GI. The experimental data also show that the fatigue threshold Gth is almost proportional to the corresponding GIC, that is Gth /GIC is constant and hardly affected by the midplane-adjacent fiber orientation. Furthermore, fractographs revealed that the rising delamination resistance is dominantly aroused by fiber bridging and intra-ply fracture.
International Journal of Fatigue, 2013
Crack growth experiments at elevated temperature were performed in a nickel-based powder metallur... more Crack growth experiments at elevated temperature were performed in a nickel-based powder metallurgy (PM) superalloy. The crack propagation procedure was monitored by travelling microscope, high temperature extensometer and beachmarking technique. The appropriate creep crack growth relating parameter for the present alloy was discussed. The crack growth behaviours in standard compact tension specimens and side-grooved compact tension specimens were compared. Several crack length measurement techniques including beachmarking, linear correction and compliance measurement were discussed and the results were compared.
International Journal of Fatigue, 2011
Crack growth behaviour of a nickel-based powder metallurgy superalloy has been studied under elev... more Crack growth behaviour of a nickel-based powder metallurgy superalloy has been studied under elevated temperatures. Test results show that there is a turning point for RT, 550°C and 650°C crack growth curves. Above this point, the three curves merge together and influence of elevated temperature disappears. Material characteristic microstructure length (grain size) is considered to be responsible for this phenomenon. However, this turning point is suppressed at 750°C possibly by grain boundary weakening. Dwell tests show that effect of 90 s holding time on the crack growth rate is limited at 650°C but much significant at 750°C due to creep damage.
Icf13, Oct 20, 2013
A three-term crack growth model was developed by adding a creep-fatigue interaction term to the t... more A three-term crack growth model was developed by adding a creep-fatigue interaction term to the traditional linear superposition law. It is based on the hypothesis that the maximal creep-fatigue interaction occurs when creep and fatigue crack growth rates are comparable. Thereby a novel exponential form of interaction intensity factor was proposed. In order to verify the model, the creep-fatigue crack growth behaviour of a nickel-based powder metallurgy superalloy (FGH97) was experimentally investigated. Creep-fatigue crack growth rates were obtained at 750 °C with various dwell times. Comparison of the crack growth rates between fitted and measured values at 0s, 90s, 450s and 1500s dwell times show great agreement. Encouragingly, excellent predictive ability of the model was verified by the experiment at 25s dwell time. Furthermore, to test the applicability of the interaction law on other materials, experimental data of two additional superalloys from references, namely Alloy 718 and Hastelloy® X, were used to fit the model. The results are also satisfactory.
Journal of Composite Materials, 2011
Fatigue delamination growth of multidirectional carbon/bismaleimide composites was investigated t... more Fatigue delamination growth of multidirectional carbon/bismaleimide composites was investigated to disclose the specific role of ply orientations. Both fatigue crack growth rate and threshold values of strain energy release rate in Mode I were studied by double cantilever beam test. For specimens with rising delamination resistance effect, the fatigue crack growth rate was found to be dependent on normalized interlaminar energy, GI/GIC, rather than GI. The experimental data also show that the fatigue threshold Gth is almost proportional to the corresponding GIC, that is Gth /GIC is constant and hardly affected by the midplane-adjacent fiber orientation. Furthermore, fractographs revealed that the rising delamination resistance is dominantly aroused by fiber bridging and intra-ply fracture.
International Journal of Fatigue, 2013
Crack growth experiments at elevated temperature were performed in a nickel-based powder metallur... more Crack growth experiments at elevated temperature were performed in a nickel-based powder metallurgy (PM) superalloy. The crack propagation procedure was monitored by travelling microscope, high temperature extensometer and beachmarking technique. The appropriate creep crack growth relating parameter for the present alloy was discussed. The crack growth behaviours in standard compact tension specimens and side-grooved compact tension specimens were compared. Several crack length measurement techniques including beachmarking, linear correction and compliance measurement were discussed and the results were compared.
International Journal of Fatigue, 2011
Crack growth behaviour of a nickel-based powder metallurgy superalloy has been studied under elev... more Crack growth behaviour of a nickel-based powder metallurgy superalloy has been studied under elevated temperatures. Test results show that there is a turning point for RT, 550°C and 650°C crack growth curves. Above this point, the three curves merge together and influence of elevated temperature disappears. Material characteristic microstructure length (grain size) is considered to be responsible for this phenomenon. However, this turning point is suppressed at 750°C possibly by grain boundary weakening. Dwell tests show that effect of 90 s holding time on the crack growth rate is limited at 650°C but much significant at 750°C due to creep damage.