Configuration de test
Cartilage articulaire (osteoarthrite)
Articular cartilage is the thin layer of tissue which lines the bony ends of all diarthrodial joints.
À propos de ce matériau
(En angalis seulement) Articular cartilage is the thin layer of tissue which lines the bony ends of all diarthrodial joints. Healthy cartilage in our joints makes it easier to move. It allows the bones to glide over each other with very little friction and improves the load transfer between bones. Articular cartilage degeneration is characterized by structural and biochemical changes leading to the clinical syndrome of Osteoarthritis (OA). These changes will lead to a significant loss of mechanical function and be the source of pain. In their efforts to find treatments and drugs to alleviate the symptoms or to eventually cure OA, doctors and researchers need to study the disease evolution and the effect of treatments in humans and in animal models. Either by the time of total knee replacement in humans or at necropsy in animal models, ex vivo mechanical indentation mapping of entire articular surface or mechanical testing of biopsies samples can generate a huge amount of useful information about degradation patterns and tissue biochemical composition.
Configurations de test (13)
Configuration de test
Compression Non-Confinée
Configuration de test
Indentation (Raideur)
Configuration de test
Friction
Configuration de test
Cartographie 3D d'épaisseur
Configuration de test
Cisaillement
Configuration de test
Impact
Configuration de test
Compression confinée
Configuration de test
Contrôle de la temperature
Configuration de test
Mesure électromécanique
Configuration de test
Capteurs analogues externes
Configuration de test
Flux de caméra
Configuration de test
Positionnement (manuel)
Études de cas (5)
Ressources associées (15)
FAQ
Qu'est-ce que la poroelasticité?
Propriété d'un matériau élastique ou viscoélastique avec une phase fluide libre incompressible. Lorsqu'un tel matériau est mis sous le stress, le fluide interstitiel est relâché de la matrice solide. La friction générée par le mouvement du fluide à travers la matrice poreuse affecte le comportement mécanique d'un tel matériau. Ces matériaux sont normalement testés dans un bain de fluide.
Mach-1 Analysis – Modèle poroélastique en compression non-confinée – Paramètres
Mach-1 Analysis – Modèle poroélastique en compression confinée – Paramètres
Mach-1 Analysis – Modèle poroélastique en compression confinée – Exemple
Mach-1 Analysis – Modèle poroélastique en compression non-confinée – Cartilage
Mach-1 Analysis – Modèle poroélastique en compression non-confinée – Exemple
LAB MODULE – Torsion of Disk-Shaped Samples – Student Version
Comment fonctionne le modèle poroélastique en compression confinée "Poroelastic Model in Confined Compression"?
(En anglais seulement) This tool allows for the computing and visualizing of the aggregate modulus (MPa), the permeability (mm2/MPa·s) and the mean square error (RMSE) of the fit calculated from a “Stress Relaxation” curve (load or force vs. time) in confined compression (Figure 1) on a disk sample. The curve is fitted to the linear biphasic model (Mow et al., 1980 or Bursać et al., 1999) in order to obtain the mechanical properties of the disk. Sample radius, strain and sample thickness need to be specified.
This model is well adapted for the mechanical characterization of samples containing a liquid fraction and a solid matrix, for example: cartilage or gel samples. A user license is required in order to obtain the results of the poroelastic model in confined compression (Software Add-On, contact Biomomentum to obtain your license).
Mechanical properties can be obtained from the stress relaxation curves obtained under confined compression such as the aggregate modulus (HA) and the hydraulic permeability (k). The aggregate modulus is a measure of stiffness of the sample at equilibrium while the hydraulic permeability is the ability of the fluid to flow through the cartilage matrix.
For example, (Figure 2) shows parameters used for the “Stress Relaxation” function in a confined compression testing protocol on human cartilage disks. Corresponding results are shown in (Figure 1).
This model is well adapted for the mechanical characterization of samples containing a liquid fraction and a solid matrix, for example: cartilage or gel samples. A user license is required in order to obtain the results of the poroelastic model in confined compression (Software Add-On, contact Biomomentum to obtain your license).
Mechanical properties can be obtained from the stress relaxation curves obtained under confined compression such as the aggregate modulus (HA) and the hydraulic permeability (k). The aggregate modulus is a measure of stiffness of the sample at equilibrium while the hydraulic permeability is the ability of the fluid to flow through the cartilage matrix.
For example, (Figure 2) shows parameters used for the “Stress Relaxation” function in a confined compression testing protocol on human cartilage disks. Corresponding results are shown in (Figure 1).
Mach-1 Analysis – Modèle poroélastique en compression confinée – Paramètres
Mach-1 Analysis – Modèle poroélastique en compression confinée – Exemple
Comment fonctionne le modèle poroélastique en compression non-confinée "Poroelastic Model in Unconfined Compression"?
(En anglais seulement) This tool allows for the computing and visualizing of the fibril network modulus (MPa), the equilibrium modulus (MPa), the permeability (mm2/MPa·s), and the mean square error (RMSE) of the fit calculated from a “Stress Relaxation” curve (load or force vs. time) in unconfined compression (Figure 1) on a disk or osteochondral core sample. The curve is fitted to the linear fibril-network-reinforced biphasic model (Soulhat et al. 1999) in order to obtain the mechanical properties of the disk. Sample radius, strain, and Poisson’s ratio need to be specified. This model is well adapted for the mechanical description of samples containing a liquid fraction and a fibril network, for example: cartilage or gel samples. A user license is required in order to obtain the results of the poroelastic model in unconfined compression (Software Add-On, contact Biomomentum to obtain your license).
The nonhomogeneous composite model (i.e. linear fibril-network-reinforced biphasic model) is an extension of the previously developed isotropic homogeneous biphasic model, and was achieved by reinforcing the latter with a network of nonlinear fibrils distributed homogeneously in the r, θ, z directions and which resist extension only (Figure 2). The isotropic matrix is described by the drained elastic constants Em (Young’s modulus), vm(Poisson’s ratio) and a hydraulic permeability k. The fibril network is described by the Young’s modulus of individual fibrils ef which, combined with a fibril volume fraction χ (fibrils volume/ total-volume), results in an equivalent tensile modulus of the fibril network, Ef = 1/3 χ ef (since 1/3 of the fibrils are oriented in each of three mutually orthogonal directions).
For example, (Figure 3) shows parameters used for the “Stress Relaxation” function in an unconfined compression testing protocol on ovine cartilage disks. Corresponding results are shown in (Figure 1).
The nonhomogeneous composite model (i.e. linear fibril-network-reinforced biphasic model) is an extension of the previously developed isotropic homogeneous biphasic model, and was achieved by reinforcing the latter with a network of nonlinear fibrils distributed homogeneously in the r, θ, z directions and which resist extension only (Figure 2). The isotropic matrix is described by the drained elastic constants Em (Young’s modulus), vm(Poisson’s ratio) and a hydraulic permeability k. The fibril network is described by the Young’s modulus of individual fibrils ef which, combined with a fibril volume fraction χ (fibrils volume/ total-volume), results in an equivalent tensile modulus of the fibril network, Ef = 1/3 χ ef (since 1/3 of the fibrils are oriented in each of three mutually orthogonal directions).
For example, (Figure 3) shows parameters used for the “Stress Relaxation” function in an unconfined compression testing protocol on ovine cartilage disks. Corresponding results are shown in (Figure 1).
Mach-1 Analysis – Modèle poroélastique en compression non-confinée – Paramètres
Mach-1 Analysis – Modèle poroélastique en compression non-confinée – Cartilage
Mach-1 Analysis – Modèle poroélastique en compression non-confinée – Exemple
Comment le paramètre quantitatif de l'Arthro-BST est-il calculé?
Le paramètre quantitatif de l'Arthro-BST (QP) correspond au nombre de microélectrodes en contact avec le cartilage (voltage inférieur à -2 mV) lorsque la somme de ces potentiels électriques atteint -100mV.
Qu'est-ce que le module aggrégat?
(En anglais seulement) The aggregate modulus (Ha) corresponds to the stiffness of the material at equilibrium when fluid has ceased flowing through it in a confined compression test configuration. The aggregate modulus can be calculated from Young's modulus (E) and the Poisson ratio (v) using the formula Ha=E(1-v)/[(1+v)(1-2v)].
Comment fonctionne la fonction Creep (Fluage)?
(En anglais seulement) The Creep function moves a stage until a predefined load variation (Load Target (relative to initial load)) is reached and maintains this loading through real-time closed-loop PID adjustment of the stage position. This function can be used, for example, to study the deformation of a sample under constant loading. Note that tuning a PID requires a reasonable amount of closed-loop system understanding. A set of PID parameters optimized for a particular experimental configuration will probably be inappropriate for a different configuration and could even create system instabilities (oscillations) that can result in damage to the system.
Parameters:
STAGE AXIS - On multi-axis systems, the user must specify which axis will perform the “Creep”.
DIRECTION - Specify if the stage has to start moving in the positive or negative direction. With a positive displacement, a vertical stage will move down (compression), a horizontal stage will move right, and a rotation stage will move clockwise. Enter a negative value for stage displacements in opposite directions.
STAGE VELOCITY, MM/S - Specify the speed at which the stage will move. Refer to the specifications of your Mach-1™ model to learn about the velocity range allowed. In Mach-1 Motion, the speed is always specified in absolute value terms.
RELATIVE LOAD TARGET, GF OR N - Specify the relative amount of load to be applied and maintained on the sample. When a value is entered, the stage will initiate its movement until a change in load of that magnitude is reached. The value for Relative Load Target is specified in absolute value terms.
CREEP TIME, SEC - This is the time period during which the relative loading will be maintained. Note that after this period, the final stage position will be maintained.
P GAIN - This is the Proportional gain of the PID control loop. This is the main parameter that drives the feedback loop. Our experiments revealed that a good starting point for the optimization of this parameter is given by P = 0.001 (and I = 0), then raising P in logarithmic increments (0.01, 0.1, 1) until a satisfactory amplitude in reached. The higher the P value, the faster the error will be corrected, however if the P is made too large, the error can go negative (actual load > desired load) which may start a process where the stage starts to oscillate between speeding up and slowing down. This oscillation can result in the motor control system going unstable. A simple way to eliminate this instability would be to decrease P until the oscillation stops.
I GAIN - This is the Integral gain of the PID control loop. Integral control sums the error from each position update then multiplies the sum by the Integral gain, I. Our experiments revealed that for most creep tests, best results are achieved with I = 0. If a residual error exists while holding a load, the I value can also be incrementally increased until the error disappears.