In-situ experiments were carried out using the powder metallurgy superalloy FGH96 to observe the evolution of small fatigue cracks under different thermal and mechanical loading scenarios.Electron backscatter diffract...In-situ experiments were carried out using the powder metallurgy superalloy FGH96 to observe the evolution of small fatigue cracks under different thermal and mechanical loading scenarios.Electron backscatter diffraction was subsequently employed to assist in the analysis of how changes in temperature and stress levels influence the growth behavior of small fatigue cracks.The influence mechanisms of crystallographic parameters(Schmid factor and geometric compatibility factor)on small fatigue crack propagation were quantitatively examined.During the study,a temperature-induced transition in the dominant crack propagation mode was observed in FGH96,occurring between 600 and 700℃.Specifically,the dominant mode changed from transgranular to intergranular propagation.Within the temperature range from room temperature to 600℃,neither temperature nor applied stress level showed a noticeable effect on the relationship between the Schmid factor of the activated slip system and the maximum Schmid factor.Under these conditions,small fatigue cracks followed a consistent propagation mechanism governed by the Schmid factor.The Schmid factor emerged as a key parameter in controlling the transgranular propagation behavior of small fatigue cracks in FGH96,whereas the role of the geometric compatibility factor appeared to be limited.展开更多
In this article,a grinding force model,which is on the basis of cutting process of single abrasive grains combined with the method of theoretical derivation and empirical formula by analyzing the formation mechanism o...In this article,a grinding force model,which is on the basis of cutting process of single abrasive grains combined with the method of theoretical derivation and empirical formula by analyzing the formation mechanism of grinding force,was established.Three key factors have been taken into accounts in this model,such as the contact friction force between abrasive grains and materials,the plastic deformation of material in the process of abrasive plowing,and the shear strain effect of material during the process of cutting chips formation.The model was finally validated by the orthogonal grinding experiment of powder metallurgy nickel-based superalloy FGH96 by using the electroplated CBN abrasive wheel.Grinding force values of prediction and experiment were in good consistency.The errors of tangential grinding force and normal grinding force were 9.8%and 13.6%,respectively.The contributions of sliding force,plowing force and chip formation force were also analyzed.In addition,the tangential forces of sliding,plowing and chip formation are 14%,19%and 11%of the normal forces on average,respectively.The pro-posed grinding forcemodel is not only in favor of optimizing the grinding parameters and improving grinding efficiency,but also contributes to study some other grinding subjects(e.g.abrasive wheel wear,grinding heat,residual stress).展开更多
基金supported by the National Natural Science Foundation of China(Grant No.U2233213).
摘要In-situ experiments were carried out using the powder metallurgy superalloy FGH96 to observe the evolution of small fatigue cracks under different thermal and mechanical loading scenarios.Electron backscatter diffraction was subsequently employed to assist in the analysis of how changes in temperature and stress levels influence the growth behavior of small fatigue cracks.The influence mechanisms of crystallographic parameters(Schmid factor and geometric compatibility factor)on small fatigue crack propagation were quantitatively examined.During the study,a temperature-induced transition in the dominant crack propagation mode was observed in FGH96,occurring between 600 and 700℃.Specifically,the dominant mode changed from transgranular to intergranular propagation.Within the temperature range from room temperature to 600℃,neither temperature nor applied stress level showed a noticeable effect on the relationship between the Schmid factor of the activated slip system and the maximum Schmid factor.Under these conditions,small fatigue cracks followed a consistent propagation mechanism governed by the Schmid factor.The Schmid factor emerged as a key parameter in controlling the transgranular propagation behavior of small fatigue cracks in FGH96,whereas the role of the geometric compatibility factor appeared to be limited.
基金financial support for this work by the National Natural Science Foundation of China(Nos.51775275,51921003 and 51905363)the Funding for Outstanding Doctoral Dissertation in NUAA of China(No.BCXJ19-06)+1 种基金the Natural Science Foundation of Jiangsu Province of China(No.BK20190940)the Natural Science Foundation of the Jiangsu Higher Education Institutions of China(No.19KJB460008)。
摘要In this article,a grinding force model,which is on the basis of cutting process of single abrasive grains combined with the method of theoretical derivation and empirical formula by analyzing the formation mechanism of grinding force,was established.Three key factors have been taken into accounts in this model,such as the contact friction force between abrasive grains and materials,the plastic deformation of material in the process of abrasive plowing,and the shear strain effect of material during the process of cutting chips formation.The model was finally validated by the orthogonal grinding experiment of powder metallurgy nickel-based superalloy FGH96 by using the electroplated CBN abrasive wheel.Grinding force values of prediction and experiment were in good consistency.The errors of tangential grinding force and normal grinding force were 9.8%and 13.6%,respectively.The contributions of sliding force,plowing force and chip formation force were also analyzed.In addition,the tangential forces of sliding,plowing and chip formation are 14%,19%and 11%of the normal forces on average,respectively.The pro-posed grinding forcemodel is not only in favor of optimizing the grinding parameters and improving grinding efficiency,but also contributes to study some other grinding subjects(e.g.abrasive wheel wear,grinding heat,residual stress).