Introduction

ZVUK devices are used for measuring the quality of grinding tools consisting of all types of abrasive materials, all types of adhesive binders, and all types of common structures. The devices can be utilized within other fields too: for example, during the production of heat resistant products, selected direct castings, etc.

Overview of basic characteristics

Two instruments are available and they provide the utilization of method and principle of control within the entire range of dimensions and shapes of measured products.
The ZVUK 130 instrument, which can be labelled as a "Desk-Top", is designated for the quality inspection of products from Ø 3 mm up to Ø 250 mm; the upper diameter for the cutting disc is unlimited.
The ZVUK 203M instrument is a portable, hand-held device, which is designated for the quality inspection of products from Ø 250 mm for straight discs, but is usable up to the dimension of 50 mm, for instance, with cylindrical or dished disks, stones, blocks of heat-resistant moulded bricks, etc.
Both instruments utilize the electronic elements to within the maximum range, and the built-in software has been developed using more than 30 years of tradition and experience of the authors and users of these instruments
After the initial parameters set-up, the actual measuring is the task of a few seconds
The ZVUK 130 can be directly connected to any PC (with the Windows 2000 or Windows XP operating system), and the measurement results can be directly saved and are available for further analysis (measuring protocols, data analysis during serial manufacture, etc.).

Instrument mode of operation - a theoretical method base

For the analysis of materials, ZVUK instruments utilize the correlation relationship existing between the frequencies of oscillations of the material itself and its physical-mechanical functional characteristics. The frequency of inherent oscillations is affected by the input material characteristics, and also by the hardness of individual components and by the whole product, and by porosity and other physical material parameters. Generally, it is possible to define the correlation between the material inherent oscillations and the structural constants and dimensions by this equation:

f_i = F_i x C_l

where:	fi - frequency of inherent oscillations that corresponds to the selected "i" frequency types
	Fi - shape coefficient that is dependent on the shape of a specific material element, its dimensions, type of selected frequency, and on the Poisson number
	Cl - propagation velocity of sonic waves through the measured material. The velocity of the measured material emanates from the equation and represents the velocity of longitudinal propagation of the sonic waves on the axis of the rod infinite in its length In the equation, the "E" is the value of E-Module elasticity (Yang's Elasticity Module), and ρ is the value of the bulk specific gravity of the measured material element

Types of measured frequencies

The following schematic figure shows the characteristics of oscillations within individual material elements during an evaluation of various frequency types. The dashed lines represent the nodal lines that remain inactive with the specific frequency type.

f₁ and f₂ frequencies correspond to the in-plane deflection of the disc perpendicular to the disc axis with two nodal diameters and nodal circular rings (see the dots marked "a" and "b" on the figure below).

"Plus" and "Minus" represents the motion of material element components in the perpendicular plane in the direction upward and downward. The motion direction of these components is changed halfway through each period.

f_d frequency corresponds to the direction of oscillation movements inside the disc diagonally towards its diameter, with two nodal plains (see the dot marked "c" on the figure above). The movements of the material element towards the hole in the disc within the various parts of the period are marked by a dashed line pattern.

f_torz frequency represents the torque frequency of oscillations inside the rod with the nodal plain in the centre of the rod (see the dot "d" on the figure above); the direction of torque is marked by the arrow-tips.

f_pl frequency corresponds to the longitudinal oscillations of the rod with two nodal plains (see the dot marked "e"); the dashed lines represent the arithmetic averages of oscillations for each half of the period. The "f_pl", another type of longitudinal oscillation (see the dot marked "f" in the figure above), corresponds to the rod oscillations with one nodal plain that crosses the centre of the rod. The directions of oscillations are marked by the arrow-tips.