Configuration de test
Cheveux
Hair is a fine thread, usually cylindrical, growth from the skin of humans or animals.
À propos de ce matériau
Le cheveux est un fil fin, généralement cylindrique, dont on peut observer la croissance sur la peau des humains ou des animaux. Le cheveu est un biomatériau hautement organisé, composé principalement de kératine. Au niveau moléculaire, il s’agit d’une structure très rigide qui offre à la fois une bonne résistance mécanique et une grande flexibilité. Les propriétés mécaniques des cheveux sont étudiées pour en apprendre davantage sur: leur fonction structurale dans le corps, les effets des pathologies sur la mécanique des cheveux et les questions cliniques connexes. Différents tests peuvent mesurer la fibre capillaire, sa résistance aux étirements, son élasticité, etc. Certains tests peuvent valider l’efficacité de produits cosmétiques et de produits capillaires.
Configurations de test (3)
Études de cas (1)
Vidéothèque
Voir : Cheveux : traction et torsionTissue testing · 0:44
Cheveux : traction et torsion
Essais de traction et de torsion sur des cheveux avec le Mach-1.
Ressources associées (3)
FAQ
Qu'est-ce que le module d'Young E?
Propriété mécanique intrinsèque d'un matériau indépendant de sa géométrie. Correspond à la pente du stress par rapport à la contrainte pendant une compression non-confiné lorsqu'on tiens compte de la géométrie de l'échantillon.
Module de laboratoire — Compression non confinée de disques d’hydrogel
Qu'est-ce que l'allongement à la rupture?
La quantité de la déformation uniaxiale à la fracture, y compris la déformation élastique et plastique.
Comment fonctionne le modèle "Sinusoid"?
(En anglais seulement) This feature is used to obtain the Frequency, Amplitude and Offset of a sinusoidal signal. A blue line displays the theoretical sinusoid with the Frequency, Amplitude and Offset obtained (Figure 1). The values of the Frequency, Amplitude and Offset are indicated in the "Results" field. The units vary according to the graph’s axes.
This feature can also be used for sinusoidal stimulus-response analysis. Sinusoidal stimulus shall be selected on the x-axis and the sinusoidal response on the y-axis. The Modulus is the ratio of the response Amplitude over the stimulus Amplitude. The Phase is the phase difference between the response and the stimulus. The Modulus’ is computed as the Modulus*Cos(Phase) and the Modulus” is computed as the Modulus*Sin(Phase). A blue line displays the theoretical sinusoidal stimulus-response with the Frequency, Modulus and Phase obtained (Figure 2). The values of the Modulus and Phase are indicated in the “Results” field. The units vary according to the graph’s axes.
One use for this feature would be to compute material properties by multiplying the Modulus obtained by the appropriate geometric factors. For example, the Young’s Modulus can be obtained during uniaxial compression or tension on cylindrical sample with t/pi*r2 as the geometric factor, t is the thickness and r is the radius of the sample.
Mach-1 Analysis – Sinusoid – Exemple d’analyse stimulus-réponse
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.
Qu'est-ce que la résistance ultime à la traction (résistance à la traction)?
La résistance ultime est la contrainte maximale développée dans un matériau avant la rupture durant un test de tension.
Qu'est-ce que la limite élastique de la rigidité?
La contrainte à laquelle un matériau commence à montrer une déformation plastique.
Qu'est-ce que l'élasticité?
Propriété d'un matériau à déformer sous déformation ou contrainte et revenir à sa forme originale lorsque la contrainte est relâché.
Module de laboratoire — Torsion de l’os
LAB MODULE – Unconfined Compression of Hydrogel Disks – Student Version