Test configuration
Ligament and Tendon
Ligaments and tendons are soft collagenous tissues.
About this material
Ligaments and tendons are soft collagenous tissues. Ligaments connect bones together while tendons attach muscle to bone. Both ligaments and tendons are viscoelastic tissues. Together, tendons serve to sustain high tensile loads by being flexible in allowing changes in the direction of muscle pull, while ligaments serve to guide movements and resist applied forces. Mechanical properties of the ligaments and tendons are studied to learn about: their structural function in the body, the effects of pathologies in ligament and tendon mechanics and related clinical issues and development of engineered constructs of tendons and ligaments.
Test configurations (8)
Test configuration
Unconfined Compression
Test configuration
Indentation (Stiffness)
Test configuration
Simultaneous Compression and Torsion
Test configuration
Dynamic Mechanical Analysis
Test configuration
Temperature Control
Test configuration
External Analog Sensors
Test configuration
Camera Feed
Related resources (1)
FAQ
What is Young's modulus E?
Intrinsic mechanical property of a material independent of its geometry. From the slope of the stress vs. strain graph during an unconfined compression and considering the geometry of the sample, we can calculate the Young's modulus.
What is the elongation at rupture?
The amount of uniaxial strain at fracture including both elastic and plastic deformation.
How does the "Sinusoid" model works?
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 – Example for stimulus-response analysis
How does the creep function works?
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.
What is the ultimate tensile strength (tensile strength)?
Ultimate tensile strength is the maximum stress developed in a material before rupture in a tension test.
What is the yield strength?
The stress at which a material starts to show plastic deformation.
What is the elasticity?
Property of a material to deform under load or strain and to return to its original shape when the stress is released.
LAB MODULE – Unconfined Compression of Hydrogel Disks – Student Version
What is the toe region?
Region of a stress-strain curve prior to the elastic region. The shape of the toe region is different from that of the elastic region due to the primary realignment of the sample in the grip, the straightening of slack fibers and the rotation of collagen fibers to align with the direction of elongation.