The differences of tension-tension fatigue and tensile creep characters of 2D-C/SiC and 3D-C/SiC composites have been scrutinized to meet the engineering needs. Experiments of tension-tension fatigue and tensile creep...The differences of tension-tension fatigue and tensile creep characters of 2D-C/SiC and 3D-C/SiC composites have been scrutinized to meet the engineering needs. Experiments of tension-tension fatigue and tensile creep are carried out under vacuum high temperature condition. All of the high temperature fatigue curves are flat; the fatigue curves of the 2D-C/SiC are flatter and even parallel to the horizontal axis. While the tension-tension fatigue limit of the 3D-C/SiC is higher than that of the 2D-C/SiC, the fiber pullout length of the fatigue fracture surface of the 3D-C/SiC is longer than that of the 2D-C/SiC, and fracture morphology of the 3D-C/SiC is rougher, and pullout length of the fiber tows is longer. At the same time the 3D-C/SiC has higher tensile creep resistance. The tensile curve and the tensile creep curve of both materials consist of a series of flat step. These phenomena can be explained by the non-continuity of the damage.展开更多
Based on the energy conservation, the elastic energy linked to the compliance change, non-elastic energy dissipated by irreversible deformation and the resistance for crack propagation were quantitatively characterize...Based on the energy conservation, the elastic energy linked to the compliance change, non-elastic energy dissipated by irreversible deformation and the resistance for crack propagation were quantitatively characterized by evaluation the load/load point displacement curves tested by three points bend experiment with single notch beam at 1300℃. The cracks length was determined by compliance calibration curves. It is shown by experimental results that the compliance of 3D-C/SiC composites changes with the cracks can be described by third order polynomial. The variation of crack advancing resistance with non-dimensional equivalent crack length presents a convex curve. The crack advancing resistance increases firstly and then decreases with the non-dimensional equivalent crack length, finally is in comparatively low level. The maximum values of crack advancing resistance are 269.73kJ/m2 for non-dimensional equivalent crack length of 0.318 and original notch length of 0.35mm, and 138.65kJ/m2 for non-dimensional equivalent crack length of 0.381 and original notch length of 2.06mm, respectively.展开更多
The root system is critical for the survival of nearly all land plants and a key target for improving abiotic stress tolerance,nutrient accumulation,and yield in crop species.Although many methods of root phenotyping ...The root system is critical for the survival of nearly all land plants and a key target for improving abiotic stress tolerance,nutrient accumulation,and yield in crop species.Although many methods of root phenotyping exist,within field studies,one of the most popular methods is the extraction and measurement of the upper portion of the root system,known as the root crown,followed by trait quantification based on manual measurements or 2D imaging.However,2D techniques are inherently limited by the information available from single points of view.Here,we used X-ray computed tomography to generate highly accurate 3D models of maize root crowns and created computational pipelines capable of measuring 71 features from each sample.This approach improves estimates of the genetic contribution to root system architecture and is refined enough to detect various changes in global root system architecture over developmental time as well as more subtle changes in root distributions as a result of environmental differences.We demonstrate that root pulling force,a high-throughput method of root extraction that provides an estimate of root mass,is associated with multiple 3D traits from our pipeline.Our combined methodology can therefore be used to calibrate and interpret root pulling force measurements across a range of experimental contexts or scaled up as a stand-alone approach in large genetic studies of root system architecture.展开更多
基金the support of Chinese Defense Foundation for Science
文摘The differences of tension-tension fatigue and tensile creep characters of 2D-C/SiC and 3D-C/SiC composites have been scrutinized to meet the engineering needs. Experiments of tension-tension fatigue and tensile creep are carried out under vacuum high temperature condition. All of the high temperature fatigue curves are flat; the fatigue curves of the 2D-C/SiC are flatter and even parallel to the horizontal axis. While the tension-tension fatigue limit of the 3D-C/SiC is higher than that of the 2D-C/SiC, the fiber pullout length of the fatigue fracture surface of the 3D-C/SiC is longer than that of the 2D-C/SiC, and fracture morphology of the 3D-C/SiC is rougher, and pullout length of the fiber tows is longer. At the same time the 3D-C/SiC has higher tensile creep resistance. The tensile curve and the tensile creep curve of both materials consist of a series of flat step. These phenomena can be explained by the non-continuity of the damage.
文摘Based on the energy conservation, the elastic energy linked to the compliance change, non-elastic energy dissipated by irreversible deformation and the resistance for crack propagation were quantitatively characterized by evaluation the load/load point displacement curves tested by three points bend experiment with single notch beam at 1300℃. The cracks length was determined by compliance calibration curves. It is shown by experimental results that the compliance of 3D-C/SiC composites changes with the cracks can be described by third order polynomial. The variation of crack advancing resistance with non-dimensional equivalent crack length presents a convex curve. The crack advancing resistance increases firstly and then decreases with the non-dimensional equivalent crack length, finally is in comparatively low level. The maximum values of crack advancing resistance are 269.73kJ/m2 for non-dimensional equivalent crack length of 0.318 and original notch length of 0.35mm, and 138.65kJ/m2 for non-dimensional equivalent crack length of 0.381 and original notch length of 2.06mm, respectively.
基金the Department of Energy under Award number:DE-AR0000826 to J.K.M.and C.N.T.the National Science Foundation under Award number:(PGRP)IOS-1638507 to C.N.T.the U.S.Department of Agriculture under Award number:2018-67012-28084 to M.R.S.
文摘The root system is critical for the survival of nearly all land plants and a key target for improving abiotic stress tolerance,nutrient accumulation,and yield in crop species.Although many methods of root phenotyping exist,within field studies,one of the most popular methods is the extraction and measurement of the upper portion of the root system,known as the root crown,followed by trait quantification based on manual measurements or 2D imaging.However,2D techniques are inherently limited by the information available from single points of view.Here,we used X-ray computed tomography to generate highly accurate 3D models of maize root crowns and created computational pipelines capable of measuring 71 features from each sample.This approach improves estimates of the genetic contribution to root system architecture and is refined enough to detect various changes in global root system architecture over developmental time as well as more subtle changes in root distributions as a result of environmental differences.We demonstrate that root pulling force,a high-throughput method of root extraction that provides an estimate of root mass,is associated with multiple 3D traits from our pipeline.Our combined methodology can therefore be used to calibrate and interpret root pulling force measurements across a range of experimental contexts or scaled up as a stand-alone approach in large genetic studies of root system architecture.
