The stress distribution of notched specimen of brittle material under a plane pressure was studied using a photoelastic meth- od,When elastic deformation appeared inside the specimen,the force transferred by dowel par...The stress distribution of notched specimen of brittle material under a plane pressure was studied using a photoelastic meth- od,When elastic deformation appeared inside the specimen,the force transferred by dowel part was triangular transverse force and frictional force on the upper surface of the sample.The quantity of the frictional force was about 31 percent of transverse force.The stress inside the sample was linear along the central cross section of the sample and there was maximum tensile stress σ_y at the tip of the notch.Basing on shearing stress deviation method,the tensile stress σ_y,σ_x and shearing stress τ_(xy) at the cen- tral sections and four adjacent cross sections were calculated.The result pointed out that σ_x and τ_(xy) were smaller than σ_y.There- fore,σ_y was the main factor for crack formation and propagation.展开更多
To compare finite element analysis(FEA)predictions and stereovision digital image correlation(StereoDIC)strain measurements at the same spatial positions throughout a region of interest,a field comparison procedure is...To compare finite element analysis(FEA)predictions and stereovision digital image correlation(StereoDIC)strain measurements at the same spatial positions throughout a region of interest,a field comparison procedure is developed.The procedure includes(a)conversion of the finite element data into a triangular mesh,(b)selection of a common coordinate system,(c)determination of the rigid body transformation to place both measurements and FEA data in the same system and(d)interpolation of the FEA nodal information to the same spatial locations as the StereoDIC measurements using barycentric coordinates.For an aluminum Al-6061 double edge notched tensile specimen,FEA results are obtained using both the von Mises isotropic yield criterion and Hill’s quadratic anisotropic yield criterion,with the unknown Hill model parameters determined using full-field specimen strain measurements for the nominally plane stress specimen.Using Hill’s quadratic anisotropic yield criterion,the point-by-point comparison of experimentally based full-field strains and stresses to finite element predictions are shown to be in excellent agreement,confirming the effectiveness of the field comparison process.展开更多
Based on the theory of damage mechanics, a method for fatigue crack initiation life prediction of notched components is proposed in this paper. The damage evolution equation of notched specimen under tensioncompressio...Based on the theory of damage mechanics, a method for fatigue crack initiation life prediction of notched components is proposed in this paper. The damage evolution equation of notched specimen under tensioncompression loading is obtained in term of closed-form solution. The crack initiation life of notched specimen is estimated by the proposed method even when material and stress concentration factor are different. It has been verified that the result calculated by the proposed method agrees with the experimental result. The proposed method is concise, effective and feasible to practical application.展开更多
In this context,four specimens,i.e.(i)circumferentially notched cylindrical torsion(CNCT),(ii)circum-ferentially notched cylindrical direct tension(CNCDT),(iii)edge notch disc bend(ENDB)and(iv)three-point bend beam(3P...In this context,four specimens,i.e.(i)circumferentially notched cylindrical torsion(CNCT),(ii)circum-ferentially notched cylindrical direct tension(CNCDT),(iii)edge notch disc bend(ENDB)and(iv)three-point bend beam(3PBB),were utilized to measure the modesⅠandⅢfracture toughness values of gypsum.While the CNCT specimen provides pure modeⅢloading in a direct manner,this pure mode condition is indirectly produced by the ENDB specimen.The ENDB specimen provided lower KⅢc and a non-coplanar(i.e.twisted)fracture surface compared with the CNCT specimen,which showed a planar modeⅢfracture surface.The ENDB specimen is also employed for conducting pure modeⅠ(with different crack depths)and mixed modeⅠ/Ⅲtests.KIc value was independent of the notch depth,and it was consistent with the RILEM and ASTM standard methods.But the modeⅢfracture results were highly sensitive to the notch depth.While the fracture resistance against modeⅢwas significantly lower than that of modeⅠ,the greater work of fracture under modeⅢwas noticeable.展开更多
Numerical calculations of creep damage development and life behavior of circular notched specimens of nickel-base single crystal had been performed. The creep stress distributions depend on the specimen geometry. For ...Numerical calculations of creep damage development and life behavior of circular notched specimens of nickel-base single crystal had been performed. The creep stress distributions depend on the specimen geometry. For a small notch radius, von Mises stress has an especial distribution. The damage distribution is greatly influenced by the notch depth, notch radius as well as notch type. The creep crack initiation place is different for each notched specimen. The characteristics of notch strengthening and notch weakening depend on the notch radius and notch type. For the same notch type, the creep rupture lives decrease with the decreasing of notch radius. A creep life model has been presented for the multiaxial stress states based on the crystallographic slip system theory.展开更多
文摘The stress distribution of notched specimen of brittle material under a plane pressure was studied using a photoelastic meth- od,When elastic deformation appeared inside the specimen,the force transferred by dowel part was triangular transverse force and frictional force on the upper surface of the sample.The quantity of the frictional force was about 31 percent of transverse force.The stress inside the sample was linear along the central cross section of the sample and there was maximum tensile stress σ_y at the tip of the notch.Basing on shearing stress deviation method,the tensile stress σ_y,σ_x and shearing stress τ_(xy) at the cen- tral sections and four adjacent cross sections were calculated.The result pointed out that σ_x and τ_(xy) were smaller than σ_y.There- fore,σ_y was the main factor for crack formation and propagation.
基金Financial support provided by Correlated Solutions Incorporated to perform StereoDIC experimentsthe Department of Mechanical Engineering at the University of South Carolina for simulation studies is deeply appreciated.
文摘To compare finite element analysis(FEA)predictions and stereovision digital image correlation(StereoDIC)strain measurements at the same spatial positions throughout a region of interest,a field comparison procedure is developed.The procedure includes(a)conversion of the finite element data into a triangular mesh,(b)selection of a common coordinate system,(c)determination of the rigid body transformation to place both measurements and FEA data in the same system and(d)interpolation of the FEA nodal information to the same spatial locations as the StereoDIC measurements using barycentric coordinates.For an aluminum Al-6061 double edge notched tensile specimen,FEA results are obtained using both the von Mises isotropic yield criterion and Hill’s quadratic anisotropic yield criterion,with the unknown Hill model parameters determined using full-field specimen strain measurements for the nominally plane stress specimen.Using Hill’s quadratic anisotropic yield criterion,the point-by-point comparison of experimentally based full-field strains and stresses to finite element predictions are shown to be in excellent agreement,confirming the effectiveness of the field comparison process.
基金the National Natural Science Foundation of China(Nos.51605212 and 51665028)the Natural Science Foundation of Gansu Province(No.17JR5RA122)
文摘Based on the theory of damage mechanics, a method for fatigue crack initiation life prediction of notched components is proposed in this paper. The damage evolution equation of notched specimen under tensioncompression loading is obtained in term of closed-form solution. The crack initiation life of notched specimen is estimated by the proposed method even when material and stress concentration factor are different. It has been verified that the result calculated by the proposed method agrees with the experimental result. The proposed method is concise, effective and feasible to practical application.
文摘In this context,four specimens,i.e.(i)circumferentially notched cylindrical torsion(CNCT),(ii)circum-ferentially notched cylindrical direct tension(CNCDT),(iii)edge notch disc bend(ENDB)and(iv)three-point bend beam(3PBB),were utilized to measure the modesⅠandⅢfracture toughness values of gypsum.While the CNCT specimen provides pure modeⅢloading in a direct manner,this pure mode condition is indirectly produced by the ENDB specimen.The ENDB specimen provided lower KⅢc and a non-coplanar(i.e.twisted)fracture surface compared with the CNCT specimen,which showed a planar modeⅢfracture surface.The ENDB specimen is also employed for conducting pure modeⅠ(with different crack depths)and mixed modeⅠ/Ⅲtests.KIc value was independent of the notch depth,and it was consistent with the RILEM and ASTM standard methods.But the modeⅢfracture results were highly sensitive to the notch depth.While the fracture resistance against modeⅢwas significantly lower than that of modeⅠ,the greater work of fracture under modeⅢwas noticeable.
基金supported by the National Natural Science Foundation of China(50005016,50375124)Natural Science Foundation of Shaanxi Province and China Aviation Foundation(02C53011,03B53003)as well as the Yangtze River Foundation
文摘Numerical calculations of creep damage development and life behavior of circular notched specimens of nickel-base single crystal had been performed. The creep stress distributions depend on the specimen geometry. For a small notch radius, von Mises stress has an especial distribution. The damage distribution is greatly influenced by the notch depth, notch radius as well as notch type. The creep crack initiation place is different for each notched specimen. The characteristics of notch strengthening and notch weakening depend on the notch radius and notch type. For the same notch type, the creep rupture lives decrease with the decreasing of notch radius. A creep life model has been presented for the multiaxial stress states based on the crystallographic slip system theory.