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Chun-fu Chen - One of the best experts on this subject based on the ideXlab platform.
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LINEAR ANALYTICAL STUDY OF LARGE DEFLECTION OF PIEZOELECTRIC LAYERED PLATE UNDER Initial Tension
Journal of Mechanics, 2013Co-Authors: Chun-fu Chen, B.-c. HuangAbstract:The linear problem of large deflection of a clamped and layered piezoelectric circular plate under Initial Tension due to lateral pressure is solved. Von Karman plate theory for large deflection is extended to a symmetrically laminated case including a piezoelectric layer. The thus derived nonlinear governing equations are simplified by neglecting the arising nonlinear terms, yielding a modified Bessel equation or a standard Bessel equation for the lateral slope. These equations are solved analytically by imposing boundary conditions for the clamped edge. For a 3-layered nearly monolithic plate with a low applied voltage upon the piezoelectric layer, the results are in a good agreement with those available in literature for a single-layered plate under pure mechanical loading, thus validates the present approach. Typical 3layered piezoelectric plates are then implemented and the results show that, piezoelectric effect seems to be apparent only up to a moderate Initial Tension. For a relatively high preTension, the effect of Initial Tension appears to be dominant, yielding nearly the same results for the structural responses, regardless of the piezoelectric effect, i.e., the magnitude of voltage applied upon the piezo-electric layer.
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Transition behavior in large deflection of elastically-bossed unsymmetrically layered plate under Initial Tension
2013 8th International Microsystems Packaging Assembly and Circuits Technology Conference (IMPACT), 2013Co-Authors: Chun-fu Chen, Dz-lung TsaiAbstract:The transition behavior of an elastically-bossed un-symmetrically layered plate in large deflection due to lateral load is studied. von Karman plate theory for large deflection is utilized and extended to the case of a pre-stressed un-symmetrically layered plate with an elastic boss. The governing equations are simplified to a modified Bessel equation for the lateral slope, by neglecting the arising nonlinear terms following a linear consideration. Analytical solution is developed by imposing the interface continuity and the clamped-end boundary condition, which is expressible via modified Bessel functions of the first and the second kinds, rather than only the first kind for a flat plate. A subsequent integration is performed to evaluate the deflection at the center of the plate for studying the transition behavior as a function of preTension. For a nearly monolithic plate with a shallow boss, the results agree well with those of a flat plate available in literature, thus validates the presented approach. For two-layered un-symmetric plates made of typical silicon based materials, various radial sizes and thickness for the center boss are implemented. The solutions show that, widening the center boss may appreciably extend the range of preTension for the plate mode and thus enlarge the preTension for transferring to a membrane behavior.
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Nonlinear Analysis of Large Deflection of Elastically-Bossed Sensor Plate under Initial Tension
Applied Mechanics and Materials, 2012Co-Authors: Chun-fu Chen, Nai Di GaoAbstract:The nonlinear problem of large deflection of an elastically-bossed layered plate under preTension due to lateral load is studied. The approach follows von Karman plate theory for large deflection for a symmetrically layered isotropic case. The thus derived nonlinear governing equations are solved using a numerical finite difference method with the aid of an iteration scheme. For a nearly monolithic plate with a thin boss, the obtained solutions correlate well with those available in literature for a single-layered flat plate, thus validates the presented approach. For three layered symmetric plates made of typical silicon based materials, various Initial Tension and lateral pressure are implemented. The results indicate that, edge behavior may appear at both the boss edge and the clamped end of the plate, thereby revealing severe variations for the structural responses. Varying the central boss size and relative thickness may have a sensible influence upon the behavior of the bossed layered plate. Furthermore, lateral pressure appears to have a sensible effect upon the nonlinear behavior of the bossed layered plate. For a relatively large Initial Tension, however, the preTension effect dominates, yielding a total membrane behavior for the bossed plate, regardless of the size of the center boss, except in the vicinity of the clamped edge.
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Nonlinear geometrical responses in large deflection of un-symmetrically layered piezo-electric plate under Initial Tension
2011 6th International Microsystems Packaging Assembly and Circuits Technology Conference (IMPACT), 2011Co-Authors: Chun-fu ChenAbstract:The nonlinear geometrical responses in large deflection of an un-symmetrically piezo-electric layered plate under Initial Tension are studied. von Karman plate theory for large deflection is utilized and extended to an un-symmetrically layered plate including a piezoelectric layer. The nonlinear governing equations are derived, first, in a non-dimensional form in terms of lateral slope and radial force resultant. These equations are solved u sin g a numerical finite difference method with the aid of the clamped-ended boundary conditions of the problem and an iteration procedure, by taking the associated linear analytical solution of lateral slope as the Initial guess. For an early monolithic plate under a very low applied voltage, the results agree well with available solutions for a single-layered case due to uniform lateral load in literature and thus the present approach is validated. For a two-layered un-symmetric plate made of typical silicon-based materials, the results show that piezoelectric effect seems to be apparent only up to a moderate Initial Tension and a moderate lateral pressure. Under this circumstance, the higher the applied voltage, the greater the central deflection; and hence the plate may transit to a membrane in a relatively low preTension condition. For a relatively high preTension or a severe lateral load, however, the piezoelectric effect becomes insignificant. Moreover, the effects of Initial Tension and lateral load may merge to become dominant, yielding nearly the same responses, regardless of the magnitude of the applied voltage.
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Nonlinear study of large deflection of simply supported piezoelectric layered-plate under Initial Tension
International Journal of Mechanical Sciences, 2011Co-Authors: Chun-fu Chen, John-han ChenAbstract:Abstract The nonlinear problem of large deflection of a simply supported piezoelectric layered plate under Initial Tension is studied. The approach follows von Karman’s plate theory for large deflection for a symmetrically layered isotropic case including a piezoelectric layer. The nonlinear governing equations are solved using a finite difference method, by taking the associated linear analytical solution as an Initial guess in the numerical iteration procedure. The results for a nearly monolithic plate under a very low applied voltage are found to correlate well with available solutions for a single-layered case under pure mechanical loading and thus the present approach is validated. For three-layered plates made of typical silicon based materials, various Initial Tension and lateral pressure are considered, and different applied voltages up to a moderate magnitude are implemented. No edge effect was observed, in contrast to the cases of clamped plates in literature. In additions, varying the layer moduli seems to have an insignificant effect upon the structural responses of the layered plate. On the other hand, the piezoelectric effect tends to be apparent only in a low preTension condition. For a relatively large preTension, the effect of Initial Tension becomes dominant, yielding nearly unique solutions for the structural responses, regardless of the magnitudes of the applied voltage and the lateral pressure.
Stephe M Howell - One of the best experts on this subject based on the ideXlab platform.
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Initial Tension and anterior load displacement behavior of high stiffness anterior cruciate ligament graft constructs
Journal of Bone and Joint Surgery American Volume, 2004Co-Authors: Ari Karchi, M L Hull, Stephe M HowellAbstract:Background: Because the Tension that exists in an anterior cruciate ligament graft when the knee is unloaded (the Initial Tension) affects the surgical outcome and because high Initial Tension has a number of adverse consequences, the primary purpose of this study was to determine quantitatively how much less Initial Tension was required for a high-stiffness construct than for a low-stiffness construct. A secondary purpose was to determine how the stiffness of the graft construct affects the anterior load-displacement behavior of the knee from 0° to 90° of flexion. Methods: Anterior-posterior load-displacement was measured in each of ten intact cadaveric knee specimens, the anterior cruciate ligament was excised, and the anterior cruciate ligament was reconstructed with a double-loop bovine tendon graft. Graft constructs of different stiffness were created with use of six springs, ranging in stiffness from 25 to 275 N/mm to simulate the fixation stiffness. After adjusting the Initial Tension of the graft so that the anterior-posterior laxity of the reconstructed knee matched that of the intact knee, the 0-N posterior limit and the 225-N anterior limit were measured at 0°, 30°, 60°, and 90° of flexion. Results: The highest stiffness fixation (275 N/mm) required an average of 73 N of Initial Tension, which was more than three times less than the average of 242 N of Initial Tension required by the lowest stiffness fixation (25 N/mm). The 225-N anterior limit was overconstrained an average of 1.0 mm with the highest stiffness fixation (275 N/mm), which was 3.6 mm less than the overconstraint with the lowest stiffness fixation (25 N/mm). Likewise, the posterior limit was overconstrained an average of 2.6 mm with the highest stiffness fixation (275 N/mm), which was 3.8 mm less than the overconstraint with the lowest stiffness fixation (25 N/mm). Conclusions: The Initial Tension for a high-stiffness graft construct is more than three times less than that for a low-stiffness construct. The Initial Tension for a high-stiffness graft construct better restores both the 225-N anterior limit and the 0-N posterior limit to normal than the Initial Tension for a low-stiffness graft construct over the range of flexion from 0° to 90°. Clinical Relevance: Because a high-stiffness graft construct requires substantially less Initial Tension than a low-stiffness graft construct, the Tension pattern in a high-stiffness graft construct better matches the pattern in the intact anterior cruciate ligament. This Tension pattern may avoid adverse consequences to both the knee joint function and the graft, which have been linked to high Initial graft Tension when the Initial Tension is maintained postoperatively. When the Initial Tension is not maintained postoperatively, a high-stiffness construct may be advantageous in avoiding a recurrence of knee instability.
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how the fixation method stiffness and Initial Tension affect anterior load displacement of the knee and Tension in anterior cruciate ligament grafts a study in cadaveric knees using a double loop hamstrings graft
Journal of Orthopaedic Research, 2004Co-Authors: Paul Eaga, M L Hull, Stephe M HowellAbstract:There were two objectives to this study. The first was to investigate the relationship of graft fixation stiffness and graft Initial Tension on the anterior load–displacement behavior of knees reconstructed with a double-loop hamstrings tendon graft. The second was to determine the corresponding graft Tensions at 225 N of anterior force applied to the knee. To satisfy these objectives, the anterior-load displacement curves were measured for seven cadaveric knees with the ACL intact at flexion angles ranging from 0� to 90� . The ACL was reconstructed in the same knees using a double-loop hamstrings graft. A/P load–displacement curves of the knee and graft Tension were measured as the fixation method stiffness and the Initial Tension applied at full exTension were varied (25–326 N/mm and 25–300 N). The 0 N posterior limit (unloaded position of tibia) and the anterior laxity (difference between the 0 N posterior limit and 225 N anterior limit) were computed to characterize the A/P load–displacement of the intact and reconstructed knees. The key results were that the 0 N posterior limit of the tibia was insensitive to changes in stiffness (p > 0:6503) but that increasing Initial Tension caused increasing posterior subluxation of the tibia with respect to the femur (p ¼ 0:0001). The tibia was subluxed posteriorly by 5–6 mm on average at high levels of Initial Tension. Both Initial Tension and stiffness significantly affected the anterior laxity (p ¼ 0:0001 for both factors). Anterior laxity was restored closely to normal (i.e. <1 mm difference) by relatively high Initial Tension of 200 N in combination with low stiffness of 25 N/mm and by low Initial Tension of 25 N in combination with higher stiffness ranging between 94 and 326 N/mm. When anterior laxity is restored to normal using a high Initial Tension–low stiffness combination however, the tibia undergoes a large posterior subluxation with respect to the femur in the unloaded state (approximately 5 mm) and a relatively high graft Tension of 275 N is developed at 225 N of anterior force. Both the tibial subluxation and graft Tension are reduced substantially with low Initial Tension–higher stiffness combinations because the amount of Initial Tension
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How the fixation method stiffness and Initial Tension affect anterior load–displacement of the knee and Tension in anterior cruciate ligament grafts: a study in cadaveric knees using a double-loop hamstrings graft
Journal of Orthopaedic Research, 2004Co-Authors: Paul Eagar, M L Hull, Stephe M HowellAbstract:There were two objectives to this study. The first was to investigate the relationship of graft fixation stiffness and graft Initial Tension on the anterior load–displacement behavior of knees reconstructed with a double-loop hamstrings tendon graft. The second was to determine the corresponding graft Tensions at 225 N of anterior force applied to the knee. To satisfy these objectives, the anterior-load displacement curves were measured for seven cadaveric knees with the ACL intact at flexion angles ranging from 0� to 90� . The ACL was reconstructed in the same knees using a double-loop hamstrings graft. A/P load–displacement curves of the knee and graft Tension were measured as the fixation method stiffness and the Initial Tension applied at full exTension were varied (25–326 N/mm and 25–300 N). The 0 N posterior limit (unloaded position of tibia) and the anterior laxity (difference between the 0 N posterior limit and 225 N anterior limit) were computed to characterize the A/P load–displacement of the intact and reconstructed knees. The key results were that the 0 N posterior limit of the tibia was insensitive to changes in stiffness (p > 0:6503) but that increasing Initial Tension caused increasing posterior subluxation of the tibia with respect to the femur (p ¼ 0:0001). The tibia was subluxed posteriorly by 5–6 mm on average at high levels of Initial Tension. Both Initial Tension and stiffness significantly affected the anterior laxity (p ¼ 0:0001 for both factors). Anterior laxity was restored closely to normal (i.e.
John-han Chen - One of the best experts on this subject based on the ideXlab platform.
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Nonlinear study of large deflection of simply supported piezoelectric layered-plate under Initial Tension
International Journal of Mechanical Sciences, 2011Co-Authors: Chun-fu Chen, John-han ChenAbstract:Abstract The nonlinear problem of large deflection of a simply supported piezoelectric layered plate under Initial Tension is studied. The approach follows von Karman’s plate theory for large deflection for a symmetrically layered isotropic case including a piezoelectric layer. The nonlinear governing equations are solved using a finite difference method, by taking the associated linear analytical solution as an Initial guess in the numerical iteration procedure. The results for a nearly monolithic plate under a very low applied voltage are found to correlate well with available solutions for a single-layered case under pure mechanical loading and thus the present approach is validated. For three-layered plates made of typical silicon based materials, various Initial Tension and lateral pressure are considered, and different applied voltages up to a moderate magnitude are implemented. No edge effect was observed, in contrast to the cases of clamped plates in literature. In additions, varying the layer moduli seems to have an insignificant effect upon the structural responses of the layered plate. On the other hand, the piezoelectric effect tends to be apparent only in a low preTension condition. For a relatively large preTension, the effect of Initial Tension becomes dominant, yielding nearly unique solutions for the structural responses, regardless of the magnitudes of the applied voltage and the lateral pressure.
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analytical geometrical responses in large deflection of simply supported piezoelectric layered plate under Initial Tension
Journal of The Chinese Institute of Engineers, 2010Co-Authors: Chun-fu Chen, John-han ChenAbstract:Abstract The analytical geometrical responses in large deflection of a simply supported and layered piezoelectric circular plate under Initial Tension due to lateral pressure are presented. The approach follows von Karman plate theory for large deflection with a consideration of a symmetrically laminated case including a piezoelectric layer. The related nonlinear governing equations are derived in a non‐dimensional form and are simplified by neglecting the arising nonlinear terms, yielding a modified Bessel equation or a standard Bessel equation for the lateral slope. The associated analytical solutions are developed by imposing the simply supported edge conditions of the problem. For a 3‐layered nearly monolithic plate under a low preTension and a low applied voltage upon the piezoelectric layer, the results agree well with those obtained by using the classical plate theory for a single‐layered plate under pure mechanical loading, and thus the developed approach is validated. Typical 3‐layered piezoelect...
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Nonlinear study of large deflection of simply supported piezoelectric layered-plate under Initial Tension
2009 4th International Microsystems Packaging Assembly and Circuits Technology Conference, 2009Co-Authors: Chun-fu Chen, John-han ChenAbstract:The nonlinear problem of large deflection of a simply supported piezoelectric layered plate under Initial Tension is studied. The approach follows von Karman plate theory for large deflection for a symmetrically layered isotropic case including a piezoelectric layer. The thus derived nonlinear governing equations for the lateral slope and radial force resultant are solved using a numerical finite difference method with the aid of an iteration scheme, by taking the associated linear analytical solution as an Initial guess. The case of a nearly monolithic plate under a very low applied voltage across the piezoelectric layer was implemented, first. The results for are found to correlate well with available solutions for a single-layered case under pure mechanical loading and thus the present approach is validated. For three layered symmetric plates made of typical silicon based materials, various Initial Tension and lateral pressure are considered, and different applied voltages up to a moderate magnitude are implemented. No edge effect was observed, in contrast to the cases of clamped plates in literature. In additions, varying the layer moduli seems to have an insignificant effect upon the structural responses of the layered plate. On the other hand, the piezoelectric effect tends to be apparent only in a low preTension condition. For a relatively large preTension, the effect of Initial Tension becomes dominant, yielding nearly unique solutions for the structural responses, regardless of the magnitudes of the applied voltage and the lateral pressure.
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Analytical Linear study of Large Deflection of Simply Supported Layered-Plate under Initial Tension
2008 3rd International Microsystems Packaging Assembly & Circuits Technology Conference, 2008Co-Authors: Chun-fu Chen, John-han ChenAbstract:The problem of large deflection of a simply supported layered plate under Initial Tension is studied. The approach is based on von Karman plate theory for large deflection in deriving the nonlinear governing equations for the lateral slope and radial force resultant, followed by a non-dimensional scheme. To have a preliminary insight, however, only the linear problem is considered by neglecting the arising nonlinear terms, yielding a modified Bessel equation for the lateral slope. This equation is solved analytically by considering the boundary conditions of simply supported ends along the edge. The related geometrical responses are then obtained by utilizing the re-occurrence relationships between the modified Bessel functions. Emphasis is placed upon the investigation of the effects of Initial Tension and deviation in layer moduli upon the transition behavior between a plate and a membrane as well as the deviation in the edge zone behavior near the boundary of the plate, between a simply supported case and a clamped one, for typical micro-plates made of common silicon-based materials.
George Y. Laflamme - One of the best experts on this subject based on the ideXlab platform.
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Initial Tension loss in cerclage cables
Journal of Arthroplasty, 2013Co-Authors: Jérémie Ménard, Maxime Émard, Fanny Canet, Vladimir Brailovski, Yvan Petit, George Y. LaflammeAbstract:Cerclage cables, frequently used in the management of fractures and osteotomies, are associated with a high failure rate and significant loosening during surgery. This study compared the capacity to maintain Tension of different types of orthopaedic cable systems. Multifilament Cobalt-Chrome (CoCr) cables with four different crimp/clamp devices (DePuy, Stryker, Zimmer and Smith&Nephew) and one non-metallic Nylon (Ny) cable from Kinamed were instrumented with a load cell to measure Tension during insertion. Significant Tension loss was observed with crimping for all cables (P<0.05). Removing the Tensioner led to an additional unexpected Tension loss (CoCr-DePuy: 18%, CoCr-Stryker: 29%, CoCr-Smith&Nephew: 33%, Ny: 46%, and CoCr-Zimmer: 52%). The simple CoCr (DePuy) cable system outperformed the more sophisticated locking devices due to its significantly better ability to prevent Tension loss.
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Initial Tension loss in cerclage cables.
Journal of Arthroplasty, 2013Co-Authors: Jérémie Ménard, Maxime Émard, Fanny Canet, Vladimir Brailovski, Yvan Petit, George Y. LaflammeAbstract:Cerclage cables, frequently used in the management of fractures and osteotomies, are associated with a high failure rate and significant loosening during surgery. This study compared the capacity to maintain Tension of different types of orthopaedic cable systems. Multifilament Cobalt-Chrome (CoCr) cables with four different crimp/clamp devices (DePuy, Stryker, Zimmer and Smith&Nephew) and one non-metallic Nylon (Ny) cable from Kinamed were instrumented with a load cell to measure Tension during insertion. Significant Tension loss was observed with crimping for all cables (P
M L Hull - One of the best experts on this subject based on the ideXlab platform.
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Initial Tension and anterior load displacement behavior of high stiffness anterior cruciate ligament graft constructs
Journal of Bone and Joint Surgery American Volume, 2004Co-Authors: Ari Karchi, M L Hull, Stephe M HowellAbstract:Background: Because the Tension that exists in an anterior cruciate ligament graft when the knee is unloaded (the Initial Tension) affects the surgical outcome and because high Initial Tension has a number of adverse consequences, the primary purpose of this study was to determine quantitatively how much less Initial Tension was required for a high-stiffness construct than for a low-stiffness construct. A secondary purpose was to determine how the stiffness of the graft construct affects the anterior load-displacement behavior of the knee from 0° to 90° of flexion. Methods: Anterior-posterior load-displacement was measured in each of ten intact cadaveric knee specimens, the anterior cruciate ligament was excised, and the anterior cruciate ligament was reconstructed with a double-loop bovine tendon graft. Graft constructs of different stiffness were created with use of six springs, ranging in stiffness from 25 to 275 N/mm to simulate the fixation stiffness. After adjusting the Initial Tension of the graft so that the anterior-posterior laxity of the reconstructed knee matched that of the intact knee, the 0-N posterior limit and the 225-N anterior limit were measured at 0°, 30°, 60°, and 90° of flexion. Results: The highest stiffness fixation (275 N/mm) required an average of 73 N of Initial Tension, which was more than three times less than the average of 242 N of Initial Tension required by the lowest stiffness fixation (25 N/mm). The 225-N anterior limit was overconstrained an average of 1.0 mm with the highest stiffness fixation (275 N/mm), which was 3.6 mm less than the overconstraint with the lowest stiffness fixation (25 N/mm). Likewise, the posterior limit was overconstrained an average of 2.6 mm with the highest stiffness fixation (275 N/mm), which was 3.8 mm less than the overconstraint with the lowest stiffness fixation (25 N/mm). Conclusions: The Initial Tension for a high-stiffness graft construct is more than three times less than that for a low-stiffness construct. The Initial Tension for a high-stiffness graft construct better restores both the 225-N anterior limit and the 0-N posterior limit to normal than the Initial Tension for a low-stiffness graft construct over the range of flexion from 0° to 90°. Clinical Relevance: Because a high-stiffness graft construct requires substantially less Initial Tension than a low-stiffness graft construct, the Tension pattern in a high-stiffness graft construct better matches the pattern in the intact anterior cruciate ligament. This Tension pattern may avoid adverse consequences to both the knee joint function and the graft, which have been linked to high Initial graft Tension when the Initial Tension is maintained postoperatively. When the Initial Tension is not maintained postoperatively, a high-stiffness construct may be advantageous in avoiding a recurrence of knee instability.
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how the fixation method stiffness and Initial Tension affect anterior load displacement of the knee and Tension in anterior cruciate ligament grafts a study in cadaveric knees using a double loop hamstrings graft
Journal of Orthopaedic Research, 2004Co-Authors: Paul Eaga, M L Hull, Stephe M HowellAbstract:There were two objectives to this study. The first was to investigate the relationship of graft fixation stiffness and graft Initial Tension on the anterior load–displacement behavior of knees reconstructed with a double-loop hamstrings tendon graft. The second was to determine the corresponding graft Tensions at 225 N of anterior force applied to the knee. To satisfy these objectives, the anterior-load displacement curves were measured for seven cadaveric knees with the ACL intact at flexion angles ranging from 0� to 90� . The ACL was reconstructed in the same knees using a double-loop hamstrings graft. A/P load–displacement curves of the knee and graft Tension were measured as the fixation method stiffness and the Initial Tension applied at full exTension were varied (25–326 N/mm and 25–300 N). The 0 N posterior limit (unloaded position of tibia) and the anterior laxity (difference between the 0 N posterior limit and 225 N anterior limit) were computed to characterize the A/P load–displacement of the intact and reconstructed knees. The key results were that the 0 N posterior limit of the tibia was insensitive to changes in stiffness (p > 0:6503) but that increasing Initial Tension caused increasing posterior subluxation of the tibia with respect to the femur (p ¼ 0:0001). The tibia was subluxed posteriorly by 5–6 mm on average at high levels of Initial Tension. Both Initial Tension and stiffness significantly affected the anterior laxity (p ¼ 0:0001 for both factors). Anterior laxity was restored closely to normal (i.e. <1 mm difference) by relatively high Initial Tension of 200 N in combination with low stiffness of 25 N/mm and by low Initial Tension of 25 N in combination with higher stiffness ranging between 94 and 326 N/mm. When anterior laxity is restored to normal using a high Initial Tension–low stiffness combination however, the tibia undergoes a large posterior subluxation with respect to the femur in the unloaded state (approximately 5 mm) and a relatively high graft Tension of 275 N is developed at 225 N of anterior force. Both the tibial subluxation and graft Tension are reduced substantially with low Initial Tension–higher stiffness combinations because the amount of Initial Tension
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How the fixation method stiffness and Initial Tension affect anterior load–displacement of the knee and Tension in anterior cruciate ligament grafts: a study in cadaveric knees using a double-loop hamstrings graft
Journal of Orthopaedic Research, 2004Co-Authors: Paul Eagar, M L Hull, Stephe M HowellAbstract:There were two objectives to this study. The first was to investigate the relationship of graft fixation stiffness and graft Initial Tension on the anterior load–displacement behavior of knees reconstructed with a double-loop hamstrings tendon graft. The second was to determine the corresponding graft Tensions at 225 N of anterior force applied to the knee. To satisfy these objectives, the anterior-load displacement curves were measured for seven cadaveric knees with the ACL intact at flexion angles ranging from 0� to 90� . The ACL was reconstructed in the same knees using a double-loop hamstrings graft. A/P load–displacement curves of the knee and graft Tension were measured as the fixation method stiffness and the Initial Tension applied at full exTension were varied (25–326 N/mm and 25–300 N). The 0 N posterior limit (unloaded position of tibia) and the anterior laxity (difference between the 0 N posterior limit and 225 N anterior limit) were computed to characterize the A/P load–displacement of the intact and reconstructed knees. The key results were that the 0 N posterior limit of the tibia was insensitive to changes in stiffness (p > 0:6503) but that increasing Initial Tension caused increasing posterior subluxation of the tibia with respect to the femur (p ¼ 0:0001). The tibia was subluxed posteriorly by 5–6 mm on average at high levels of Initial Tension. Both Initial Tension and stiffness significantly affected the anterior laxity (p ¼ 0:0001 for both factors). Anterior laxity was restored closely to normal (i.e.