Sylvatest

Sylvatest is an ultrasonic measuring device that provides an overall diagnosis of a wooden component to test its mechanical strength. This is a specific non-destructive testing tool for wooden beams.

Description

Sylvatest is an acousto-ultrasonic measuring device that provides an overall diagnosis of the wood element, based on the speed and energy absorption of the transmitted ultrasonic wave. The result given reflects the residual health of the wood in the trunk of the tree tested or the beam measured. These are non-destructive tests.

The technology was developed by Professor Jean-Luc Sandoz as part of his thesis at EPFL in 1984.

Characterization of wood by ultrasound

Non-destructive ultrasonic testing of wood is a method used to assess its mechanical properties, particularly the modulus of elasticity in different directions. It is based on measuring the propagation velocity of sound waves through the material and the density of the wood.

Principle

An ultrasonic wave is emitted through a wood specimen using a transducer (sender) placed at one end. It is received by a second transducer (receiver) at the opposite end. The transit time is used to calculate the propagation velocity V of the wave through the material. This velocity is directly related to the mechanical properties of the wood.

Fundamental Equations

The propagation velocities of ultrasonic waves in a material, such as wood, are directly related to its mechanical properties and density.

Longitudinal (VL) and radial (VR) wave speeds can be expressed as:

$V_L = \sqrt = \sqrt$

$V_R = \sqrt = \sqrt$

* density is the material’s mass per unit volume.

These relationships are commonly used in non-destructive testing (NDT), particularly in ultrasonic transmission techniques, to assess the internal mechanical condition of wood and other materials.

Applications

This method is widely used for:

* assessing the quality of structural and construction timber,
* inspecting historical structures (e.g., heritage roof trusses),
* detecting internal defects such as cracks or decay,
* reuse wood structural diagnostic,
* scientific studies on the anisotropic mechanical behavior of wood.

It was notably applied in the structural assessment of the spire of Notre-Dame Cathedral in Paris, to evaluate the mechanical condition of oak beams without destructive sampling.

The sylvatest is used in many countries (Brazil, Europe and Asia).

It has been used on historic buildings such as the Entrepôts des magasins généraux in Paris, the Forbidden City in Beijing, and the beams of Notre-Dame de Paris or even the Château de Valère.

It is also used to certify the quality of wood for registered designations of origin such as Bois des Alpes or Bois de Chatreuse.

Bibliography

* Research seminar: Diagnosing century-old reclaimed timber with a view to its reuse;
* Nondestructive Techniques for Determination of Wood Mechanical Properties of Urban Trees in Madrid;
* CMechanical strength of structural timber. Taking account of singularities when modelling mechanical behaviour.
* Rita Bütler, Lita Patty, Renée-Claire Le Bayon et Claire Guenat, ''Forest Ecology and Management'', , avril 2007,
* Document de travail Interreg France-Suisse de 2019
* Probe-wood contact and gauge pressure with Sylvatest-Duo for precision ultrasonic measurements of wood
* Evaluation of two acoustic methods for determining the modulus of elasticity of young hybrid larch wood (Larix x eurolepis Henry) - comparison with a standard static bending method
* Classification of Guyanese structural timbers. Comparison of three non-destructive techniques: visual, ultrasonic and modal analysis.
* Evaluation of modulus of elasticity of date palm sandwich panels using ultrasonic wave velocity and experimental models

References

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