TECHNOLOGY

MEASUREMENT TECHNIQUE

Measuring with GrindoSonic® SA is surprisingly simple.
As soon as the instrument is switched on, it is ready to operate. There is never any adjustment or warming up required. 
The measurement itself is executed in just a few seconds.

TOUCH

In the majority of cases, a vibrator detector is used to capture the vibrations, and to convert it into an electrical signal. The point of the detector is simply brought into contact with the sample

TAP

The sample is excited into vibration through the means of a light tap. Very little energy is required.

READ

Almost immediately the numerical result is displayed on the front panel. A few moments later the display is cleared and the instrument is ready for the next measurement.

BACKGROUND

Most materials show a property known as elasticity. This means that they will deform under an externally applied load and return to their original shape once the load is removed. 

The amount of strain (deformation) is linearly proportional to the applied stress (load), hence the material is said to be linearly elastic. This proportionality between stress and strain was first described by Robert Hooke and is known as Hooke’s law:

Stress
--------- = constant
Strain


In this equation, the constant is a factor of proportionality known as the modulus of elasticity of the material.
This material characteristic is extremely important in engineering, because most structures are designed to function at low levels of stress in order to avoid permanent deformation.
 
The GrindoSonic® system has been designed to measure the elastic properties of a wide range of materials. It is based on the “impulse excitation technique”, because the object under test is subjected to an initial deformation by means of a light mechanical impulse. Immediately, the object will act as a spring-mass system and produce a transient mechanical vibration. The frequency of this vibration depends on the mass of the object and its stiffness, which is determined by its shape and dimensions and the modulus of elasticity of the material. 

The GrindoSonic® instrument records this vibration, makes an analysis in the time domain and measures the natural frequency of the dominant vibration mode against a precision reference oscillator. This measurement technique is non-destructive, highly accurate and very simple. Elastic moduli have been measured over a range extending from some 50 Mpa to over 1000 Gpa. Samples ranged from 0.1 g to over a ton in weight and measurements have been performed over a temperature range from –200 ºC to over 1200 ºC.