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Indenter, Flat (D = 31.75 mm)

MA263

A flat-ended indenter

SKU: MA263 Categories: ,

This versatile indenter can be used in several test configuration and is a very popular accessory for the mechanical tester.

  • This accessory has been designed to facilitate cleaning and desinfection.
  • This part has a robust design and will keep its integrity for years
  • Designed to be used in contact with physiological saline solution
  • Easy to assemble and mount on the tester
  • A knurling facilitates assembly
  • Compatible with multiaxial load cells
  • Compatible with single axis load cells
Material

Stainless Steel 316L

Diameter

31.75 mm

Upper Attachment

1/4-28 Male Thread

Test configurations (5)

FAQ

How does the "Elastic Model on Spherical Sample" feature works?
This tool allows for the computing and visualizing of the shear modulus (MPa) from an unconfined compression test performed using a flat indenter on a spherical sample (Figure 1).

Results analysis is performed considering small deformation of a perfectly spherical sample (with uniform elastic material properties) tested in unconfined compression between two flat platens. Curve fitting is based on Gauthier et al., 2004 who used the Hertz model predicting the force exerted by a rigid spherical body under small deformation (less than 10%) which is given by the equation (attached), where F(r) is the force exerted by the sphere when the distance separating the compressing platen surface from the bottom platen is r (and r ˂ 2 R0), u is the shear modulus and R0 is the bead's initial radius.

The radius of the spherical sample has to be specified in order to calculate the material properties. The error on the estimation of the best curve representing the compression curve is calculated using the root of the mean squares (RMS) method and is displayed under “RMSE”. For example, (Figure 2) shows parameters used for the “Stress Relaxation” (Mach-1 Motion) function in an unconfined compression protocol on a single spherical bead. Corresponding results are shown in (Figure 1).

Mach-1 Analysis – Elastic Model on Spherical Sample – parameters

Mach-1 Analysis – Elastic Model on Spherical Sample – Equation

Mach-1 Analysis – Elastic Model on Spherical Sample – Example

How does the "Poroelastic Model in Unconfined Compression" feature works?
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).

Mach-1 Analysis – Poroelastic Model in Unconfined Compression – Parameters

Mach-1 Analysis – Poroelastic Model in Unconfined Compression – Cartilage

Mach-1 Analysis – Poroelastic Model in Unconfined Compression – Example

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

Mach-1 Analysis – Sinusoid – Example for signals analysis

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