The Experts below are selected from a list of 7956 Experts worldwide ranked by ideXlab platform
R O Ritchie - One of the best experts on this subject based on the ideXlab platform.
-
corrigendum to mixed mode toughness of human cortical bone containing a Longitudinal Crack in far field compression bone 50 2012 331 336
Bone, 2012Co-Authors: Diana Olvera, Elizabeth A Zimmermann, R O RitchieAbstract:This work was supported by the Laboratory Directed Research and Development Program of Lawrence Berkeley National Laboratory (LBNL), funded by the U.S. Department of Energy under contract no. DE AC02 05CH11231. The authors wish to thank Dr. Tony Tomsia and Brian Panganiban for their assistance with the study, and Professor Tony Keaveny and Mike Jekir, of the Mechanical Engineering Department at the University of California, Berkeley, for allowing us to use their bone machining facilities.
-
mixed mode toughness of human cortical bone containing a Longitudinal Crack in far field compression
Bone, 2012Co-Authors: Diana Olvera, Elizabeth A Zimmermann, R O RitchieAbstract:Abstract Bone is generally loaded under multiaxial conditions in vivo ; as it invariably contains microCracks, this leads to complex mixed-mode stress-states involving combinations of tension, compression and shear. In previous work on the mixed-mode loading of human cortical bone (using an asymmetric bend test geometry), we found that the bone toughness was lower when loaded in far-field shear than in tension (opposite to the trend in most brittle materials), although only for the transverse orientation. This is a consequence of the competition between preferred mechanical vs . microstructural Crack-path directions, the former dictated by the direction of the maximum mechanical “driving force” (which changes with the mode-mixity), and the latter by the “weakest” microstructural path (which in human bone is along the osteonal interfaces or cement lines). As most microCracks are oriented Longitudinally, we investigate here the corresponding mixed-mode toughness of human cortical bone in the Longitudinal (proximal–distal) orientation using a “double cleavage drilled compression” test geometry, which provides a physiologically-relevant loading condition for bone in that it characterizes the toughness of a Longitudinal Crack loaded in far-field compression. In contrast to the transverse toughness, results show that the Longitudinal toughness, measured using the strain-energy release rate, is significantly higher in shear (mode II) than in tension (mode I). This is consistent, however, with the individual criteria of preferred mechanical vs . microstructural Crack paths being commensurate in this orientation.
James H Starnes - One of the best experts on this subject based on the ideXlab platform.
-
Residual Strength Pressure Tests and Nonlinear Analyses of Stringer- and Frame-Stiffened Aluminum Fuselage Panels with Longitudinal Cracks
1998Co-Authors: Richard D. Young, Marshall Rouse, Damodar R. Ambur, James H StarnesAbstract:The results of residual strength pressure tests and nonlinear analyses of stringer- and frame-stiffened aluminum fuselage panels with Longitudinal Cracks are presented. Two types of damage are considered: a Longitudinal Crack located midway between stringers, and a Longitudinal Crack adjacent to a stringer and along a row of fasteners in a lap joint that has multiple-site damage (MSD). In both cases, the Longitudinal Crack is centered on a severed frame. The panels are subjected to internal pressure plus axial tension loads. The axial tension loads are equivalent to a bulkhead pressure load. Nonlinear elastic-plastic residual strength analyses of the fuselage panels are conducted using a finite element program and the Crack-tip-opening-angle (CTOA) fracture criterion. Predicted Crack growth and residual strength results from nonlinear analyses of the stiffened fuselage panels are compared with experimental measurements and observations. Both the test and analysis results indicate that ..
-
nonlinear response of thin cylindrical shells with Longitudinal Cracks and subjected to internal pressure and axial compression loads
Nonlinear Response of Thin Cylindrical Shells With Longitudinal Cracks and Subjected to Internal Pressure and Axial Compression Loads, 1997Co-Authors: James H Starnes, Rose A CherylAbstract:The results of an analytical study of the nonlinear response of a thin unstiffened aluminum cylindrical shell with a Longitudinal Crack are presented. The shell is analyzed with a nonlinear shell analysis code that maintains the shell in a nonlinear equilibrium state while the Crack is grown. The analysis accurately accounts for global and local structural response phenomena. Results are presented for internal pressure, axial compression, and combined internal pressure and axial compression loads. The effects of varying Crack length on the nonlinear response of the shell subjected to internal pressure are described. The effects of varying Crack length on the prebuckling, buckling and postbuclking responses of the shell subjected to axial compression, and subjected to combined internal pressure and axial compression are also described. The results indicate that the nonlinear interaction between the in-plane stress results and the out-of-plane displacements near a Crack can significantly affect the structural response of the shell. The results also indicate that Crack growth instabilities and shell buckling instabilities can both affect the response of the shell as the Crack length is increased.
Timothy L Norman - One of the best experts on this subject based on the ideXlab platform.
-
calculation of porosity and osteonal cement line effects on the effective fracture toughness of cortical bone in Longitudinal Crack growth
Journal of Biomedical Materials Research, 2000Co-Authors: Y N Yeni, Timothy L NormanAbstract:Based on the microscopic analyses of Cracks and correlational studies demonstrating evidence for a relationship between fracture toughness and microstructure of cortical bone, an equation was derived for bone fracture toughness in Longitudinal Crack growth, using debonding at osteonal cement lines and weakening effect of pores as main Crack mechanisms. The correlation between the measured and predicted values of fracture toughness was highly significant but weak for a single optimal value of matrix to cement line fracture toughness ratio. Using fracture toughness values and histomorphometrical parameters from an available data set, matrix to cement line fracture toughness ratio was calculated for human femoral bone. Based on these calculations it is suggested that the effect of an osteon on fracture toughness will depend on the cement line's ability to compensate for the pore in an osteon. Matrix to cement line fracture toughness ratio significantly increased with increasing age, suggesting that the effectiveness of osteons in energy absorption may be reduced in the elderly due to a change in cement line properties.
Elizabeth A Zimmermann - One of the best experts on this subject based on the ideXlab platform.
-
corrigendum to mixed mode toughness of human cortical bone containing a Longitudinal Crack in far field compression bone 50 2012 331 336
Bone, 2012Co-Authors: Diana Olvera, Elizabeth A Zimmermann, R O RitchieAbstract:This work was supported by the Laboratory Directed Research and Development Program of Lawrence Berkeley National Laboratory (LBNL), funded by the U.S. Department of Energy under contract no. DE AC02 05CH11231. The authors wish to thank Dr. Tony Tomsia and Brian Panganiban for their assistance with the study, and Professor Tony Keaveny and Mike Jekir, of the Mechanical Engineering Department at the University of California, Berkeley, for allowing us to use their bone machining facilities.
-
mixed mode toughness of human cortical bone containing a Longitudinal Crack in far field compression
Bone, 2012Co-Authors: Diana Olvera, Elizabeth A Zimmermann, R O RitchieAbstract:Abstract Bone is generally loaded under multiaxial conditions in vivo ; as it invariably contains microCracks, this leads to complex mixed-mode stress-states involving combinations of tension, compression and shear. In previous work on the mixed-mode loading of human cortical bone (using an asymmetric bend test geometry), we found that the bone toughness was lower when loaded in far-field shear than in tension (opposite to the trend in most brittle materials), although only for the transverse orientation. This is a consequence of the competition between preferred mechanical vs . microstructural Crack-path directions, the former dictated by the direction of the maximum mechanical “driving force” (which changes with the mode-mixity), and the latter by the “weakest” microstructural path (which in human bone is along the osteonal interfaces or cement lines). As most microCracks are oriented Longitudinally, we investigate here the corresponding mixed-mode toughness of human cortical bone in the Longitudinal (proximal–distal) orientation using a “double cleavage drilled compression” test geometry, which provides a physiologically-relevant loading condition for bone in that it characterizes the toughness of a Longitudinal Crack loaded in far-field compression. In contrast to the transverse toughness, results show that the Longitudinal toughness, measured using the strain-energy release rate, is significantly higher in shear (mode II) than in tension (mode I). This is consistent, however, with the individual criteria of preferred mechanical vs . microstructural Crack paths being commensurate in this orientation.
Ambur, Damodar R. - One of the best experts on this subject based on the ideXlab platform.
-
Residual Strength Pressure Tests and Nonlinear Analyses of Stringer-and Frame-Stiffened Aluminum Fuselage Panels with Longitudinal Cracks
1998Co-Authors: Rouse Marshall, Young, Richard D., Starnes, James H., Ambur, Damodar R.Abstract:The results of residual strength pressure tests and nonlinear analyses of stringer- and frame-stiffened aluminum fuselage panels with Longitudinal Cracks are presented. Two types of damage are considered: a Longitudinal Crack located midway between stringers, and a Longitudinal Crack adjacent to a stringer and along a row of fasteners in a lap joint that has multiple-site damage (MSD). In both cases, the Longitudinal Crack is centered on a severed frame. The panels are subjected to internal pressure plus axial tension loads. The axial tension loads are equivalent to a bulkhead pressure load. Nonlinear elastic-plastic residual strength analyses of the fuselage panels are conducted using a finite element program and the Crack-tip-opening-angle (CTOA) fracture criterion. Predicted Crack growth and residual strength results from nonlinear analyses of the stiffened fuselage panels are compared with experimental measurements and observations. Both the test and analysis results indicate that the presence of MSD affects Crack growth stability and reduces the residual strength of stiffened fuselage shells with long Cracks
