Biomechanical Analysis of Sheep Oesophagus Subjected to Biaxial Testing Including Hyperelastic Constitutive Model Fitting

2021 ◽  
Author(s):  
Harry Ngwangwa ◽  
Thanyani Pandelani ◽  
Makhosasana Msibi ◽  
Israel Mabuda ◽  
Letlhogonolo Semakane ◽  
...  
Keyword(s):  
Constitutive Model ◽  
Model Fitting ◽  
Biomechanical Analysis ◽  
Biaxial Testing

scholarly journals Hip Capsular Closure: A Biomechanical Analysis of Failure Torque

2016 ◽  
Vol 45 (2) ◽  
pp. 434-439 ◽  
Author(s):  
Jorge Chahla ◽  
Jacob D. Mikula ◽  
Jason M. Schon ◽  
Chase S. Dean ◽  
Kimi D. Dahl ◽  
...  
Keyword(s):  
External Rotation ◽  
Arthroscopic Surgery ◽  
Testing Machine ◽  
Biomechanical Analysis ◽  
Biaxial Testing ◽  
Improved Outcomes ◽  
Significant Difference ◽  
Fresh Frozen ◽  
Hip Capsule ◽  
Optimal Quantity

Background: Hip capsulotomy is routinely performed during arthroscopic surgery to achieve adequate exposure of the joint. Iatrogenic instability can result after hip arthroscopic surgery because of capsular insufficiency, which can be avoided with effective closure of the hip capsule. There is currently no consensus in the literature regarding the optimal quantity of sutures upon capsular closure to achieve maximal stability postoperatively. Purpose/Hypothesis: The purpose of this study was to determine the failure torques of 1-, 2-, and 3-suture constructs for hip capsular closure to resist external rotation and extension after standard anterosuperior interportal capsulotomy (12 to 3 o’clock). Additionally, the degree of external rotation at which the suture constructs failed was recorded. The null hypothesis of this study was that no significant differences with respect to the failure torque would be found between the 3 repair constructs. Study Design: Controlled laboratory study. Methods: Nine pairs (n = 18) of fresh-frozen human cadaveric hemipelvises underwent anterosuperior interportal capsulotomy, which were repaired with 1, 2, or 3 side-to-side sutures. Each hip was secured in a dynamic biaxial testing machine and underwent a cyclic external rotation preconditioning protocol, followed by external rotation to failure. Results: The failure torque of the 1-suture hip capsular closure construct was significantly less than that of the 3-suture construct. The median failure torque for the 1-suture construct was 67.4 N·m (range, 47.4-73.6 N·m). The median failure torque was 85.7 N·m (range, 56.9-99.1 N·m) for the 2-suture construct and 91.7 N·m (range, 74.7-99.0 N·m) for the 3-suture construct. All 3 repair constructs exhibited a median 36° (range, 22°-64°) of external rotation at the failure torque. Conclusion: The most important finding of this study was that the 2- and 3-suture constructs resulted in comparable biomechanical failure torques when external rotation forces were applied to conventional hip capsulotomy in a cadaveric model. The 3-suture construct was significantly stronger than the 1-suture construct; however, there was not a significant difference between the 2- and 3-suture constructs. Additionally, all constructs failed at approximately 36° of external rotation. Clinical Relevance: Re-establishing the native anatomy of the hip capsule after hip arthroscopic surgery has been reported to result in improved outcomes and reduce the risk of iatrogenic instability. Therefore, adequate capsular closure is important to restore proper hip biomechanics, and postoperative precautions limiting external rotation should be utilized to protect the repair.

scholarly journals Constitutive Modeling of Time-Dependent Response of Human Plantar Aponeurosis

2014 ◽  
Vol 2014 ◽  
pp. 1-8 ◽  
Author(s):  
P. G. Pavan ◽  
P. Pachera ◽  
C. Stecco ◽  
A. N. Natali
Keyword(s):  
Experimental Data ◽  
Stress Relaxation ◽  
Constitutive Model ◽  
Transverse Isotropy ◽  
Model Fitting ◽  
Viscoelastic Behavior ◽  
Time Dependent ◽  
Plantar Aponeurosis ◽  
Structural Conformation ◽  
Dependent Behavior

The attention is focused on the viscoelastic behavior of human plantar aponeurosis tissue. At this purpose, stress relaxation tests were developed on samples taken from the plantar aponeurosis of frozen adult donors with age ranging from 67 to 78 years, imposing three levels of strain in the physiological range (4%, 6%, and 8%) and observing stress decay for 240 s. A viscohyperelastic fiber-reinforced constitutive model with transverse isotropy was assumed to describe the time-dependent behavior of the aponeurotic tissue. This model is consistent with the structural conformation of the tissue where collagen fibers are mainly aligned with the proximal-distal direction. Constitutive model fitting to experimental data was made by implementing a stochastic-deterministic procedure. The stress relaxation was found close to 40%, independently of the level of strain applied. The agreement between experimental data and numerical results confirms the suitability of the constitutive model to describe the viscoelastic behaviour of the plantar aponeurosis.

A Constitutive Model Fitting Methodology for Ductile Metals Using Cold Upsetting Tests and Numeric Optimization Techniques

2018 ◽  
Vol 141 (1) ◽  
Author(s):  
Devon C. Hartlen ◽  
Darrel A. Doman
Keyword(s):  
Constitutive Model ◽  
Model Fitting ◽  
Frictional Coefficient ◽  
Optimization Techniques ◽  
Model Parameters ◽  
Plastic Behavior ◽  
Radial Deformation ◽  
Plasticity Model ◽  
Cold Upsetting ◽  
Hardening Rule

This work documents the development of a tool to perform automated parameter fitting of constitutive material models. Specific to this work is the fitting of a Swift hardening rule and isotropic linear plasticity model to aluminum 2024-T351, C36000 brass, and C10100 copper. Material characterization was conducted through the use of compressive, cold upsetting tests. A noncontact, optical displacement measurement system was applied to measure the axial and radial deformation of the test specimens. Nonlinear optimization techniques were then applied to tune a finite element model to match experimental results through the optimization of material model parameters as well as frictional coefficient. The result is a system, which can determine constitutive model parameters rapidly and without user interaction. While this tool provided material parameters for each material and model tested, the quality of the fit varied depending on how appropriate the constitutive model was to the material's actual plastic behavior. Aluminum's behavior proved to be an excellent match to the Swift hardening rule while the behavior of brass and copper was described better by the linear plasticity model.

Anisotropic elasto-damage constitutive model for the biomechanical analysis of tendons

2005 ◽  
Vol 27 (3) ◽  
pp. 209-214 ◽  
Author(s):  
A.N. Natali ◽  
P.G. Pavan ◽  
E.L. Carniel ◽  
M.E. Lucisano ◽  
G. Taglialavoro
Keyword(s):  
Constitutive Model ◽  
Biomechanical Analysis ◽  
Damage Constitutive Model

Three Conceptual Impediments to Developing Scale Theory for Formative Scales

Methodology ◽  
2018 ◽  
Vol 14 (4) ◽  
pp. 156-164 ◽  
Author(s):  
Keith A. Markus
Keyword(s):  
Scale Development ◽  
Item Analysis ◽  
Model Fitting ◽  
Item Bias ◽  
Validity Evidence ◽  
Scale Theory ◽  
Underlying Theory ◽  
Standard Scale ◽  
Item Scores

Abstract. Bollen and colleagues have advocated the use of formative scales despite the fact that formative scales lack an adequate underlying theory to guide development or validation such as that which underlies reflective scales. Three conceptual impediments impede the development of such theory: the redefinition of measurement restricted to the context of model fitting, the inscrutable notion of conceptual unity, and a systematic conflation of item scores with attributes. Setting aside these impediments opens the door to progress in developing the needed theory to support formative scale use. A broader perspective facilitates consideration of standard scale development concerns as applied to formative scales including scale development, item analysis, reliability, and item bias. While formative scales require a different pattern of emphasis, all five of the traditional sources of validity evidence apply to formative scales. Responsible use of formative scales requires greater attention to developing the requisite underlying theory.

Biomechanical Analysis of Tool Use

2012 ◽  
Vol 220 (1) ◽  
pp. 53-54 ◽  
Author(s):  
Elena Biryukova ◽  
Blandine Bril
Keyword(s):  
Tool Use ◽  
Biomechanical Analysis

Statistical Model Fitting: A State-of-the-Art Review

1978 ◽  
Vol 23 (11) ◽  
pp. 937-938
Author(s):  
JAMES R. KLUEGEL
Keyword(s):  
Statistical Model ◽  
State Of The Art ◽  
Model Fitting

IMPLICATIONS OF A CONSTITUTIVE MODEL FOR STRAIN LOCALIZATION

1988 ◽  
Vol 49 (C3) ◽  
pp. C3-489-C3-496
Author(s):  
B. D. COLEMAN ◽  
M. L. HODGDON
Keyword(s):  
Constitutive Model ◽  
Strain Localization
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