RU2051351C1 - Electrodynamic vibration-testing machine - Google Patents

Abstract

FIELD: electrodynamics. SUBSTANCE: working table of electrodynamic vibration-testing machine has round-shaped adjusting plate, provided with members for fixing article under test. The plate is supported by six radial ribs of rigidity, which have constant heights. Working table also has shell, which embraces ribs of rigidity along their heights. Table is made as a unit of magnesium or beryllium alloy. Relations are given for determining thickness of the shell, ribs of rigidity and adjusting plate, and heights of the ribs depending on frequency of cut-on of working range of vibration-testing machine, internal diameter of the table, modulus of elasticity and density of table material. EFFECT: maximal resonant frequency; minimized table weight. 3 dwg

Description

 The invention relates to test equipment and can be used to test products for vibration.

Known electrodynamic vibrator equipped with a desktop made of fusible alloy. The table is a round mounting plate, equipped with elements for mounting the test product [1]
Due to the absence of stiffeners, the large mass table has a relatively low resonant frequency, which leads to a decrease in the acceleration developed by the vibration bench and a reduction in the working frequency range.

Known electrodynamic vibrostand equipped with a worktable made of light alloy, equipped with radial stiffeners with decreasing height to the center of the table [2]
Reducing the height of the ribs towards the center of the table leads to a significant decrease in the bending stiffness of the structure and a sharp decrease in its resonant frequency, which means a reduction in the operating frequency range.

A known electrodynamic vibrostand equipped with a working table made of beryllium alloy and representing a round mounting plate attached by six radial stiffening ribs of constant height, equipped with elements for attaching the test product. Stiffeners are glued with an installation plate and between themselves with epoxy glue [3]
The disadvantage of the desktop is the lack of a shell covering the stiffening ribs and the mounting plate, which reduces the bending stiffness of the structure and the uniformity of the transfer of forces from the power coil to the table.

The closest in technical essence to the invention is an electrodynamic vibrostand containing a magnetic circuit with a magnetizing coil and an elastically suspended moving system consisting of a power coil located in the working gap of the magnetic circuit, and a working table made in one piece of magnesium alloy, including a mounting plate with elements for mounting the test object, supported by six radial stiffeners of constant height, and covering their shell, and the shell covers t ribs not over their entire height. In addition, the work table of the vibrating stand is equipped with an additional annular rib located concentrically between the center of the table and the shell, the height of which is much less than the height of the radial stiffeners [4]
Insufficiently rigid fastening of the ends of the ribs when using a shell of a lower height than the height of the ribs leads to a decrease in the bending stiffness of the table, and hence its resonant frequency. In addition, the additional annular rib does not absorb the load when the table is bent and only increases its mass, which leads to a decrease in both the resonant frequency and acceleration.

 The problem to which the invention is directed, is to achieve the maximum resonant frequency with a minimum mass of the desktop vibrostand.

где f_в частота верхней границы рабочего диапазона частот;
D_in внутренний диаметр стола;
Е модуль упругости материала стола;
ρ плотность материала стола, толщина установочной пластины составляет
h_п=

а высота ребер жесткости определяется по формуле
H_р=

На фиг. 1 изображен вибростенд, разрез; на фиг.2 разрез стола в аксонометрии; на фиг. 3 рабочий стол, разрез.To do this, in an electrodynamic vibrostand containing a magnetic circuit with a magnetizing coil and an elastically suspended moving system consisting of a power coil located in the working gap of the magnetic circuit, and a working table made in one piece of magnesium or beryllium alloy, including a round mounting plate with elements for mounting of the test object, supported by six radial stiffeners of constant height, and covering their shell, the shell covers the stiffeners over their entire heights , The mantle thickness is and stiffeners
h _p =

where f _{is the} frequency of the upper limit of the working frequency range;
D _{in the} inner diameter of the table;
E is the modulus of elasticity of the table material;
ρ is the density of the table material, the thickness of the mounting plate is
h _p =

and the height of the stiffeners is determined by the formula
H _p =

In FIG. 1 shows a vibration stand, section; figure 2 is a section of a table in a perspective view; in FIG. 3 desktop, cut.

 The vibrostand contains a magnetic circuit 1 with a magnetization system 2 and a movable system consisting of a power coil 3 rigidly connected to the work table 4. The mobile system is suspended on elastic suspensions 5. The round mounting plate 6 of the work table is supported by six radial stiffening ribs 7 and is surrounded by a shell 8. To connect the table 4 with the power coil 3 are threaded holes 9. On the table 4 there is an object 10 of the test, connected to the table by means of bolts included in the screw plugs 11 of the table 4.

 The device operates as follows.

 When a constant voltage is applied to the magnetization system 2, a constant magnetic flux appears, penetrating the power coil 3. When a voltage 3 is applied to the coil 3 with the necessary frequency under the influence of the forces of interaction of the constant magnetic flux and current in its turns, the coil 3 comes into reciprocating motion with a frequency alternating current. Table 4, rigidly connected to the power coil 3, also performs translational motion. As the frequency of the alternating current increases, the bending resonance of the table occurs. It has been experimentally established that, provided that the resonant frequencies of the bending vibrations of the table elements are equal, the table oscillates as a whole in the entire frequency range. If the resonance frequency of a single part of the table resonance is exceeded, the mass of the part as a whole is overstated.

где f_в частота верхней границы рабочего диапазона частот;
D_in внутренний диаметр стола;
Е модуль упругости материала стола;
ρ плотность материала стола;
h_п=

где h_n толщина установочной пластины,
H_р=

где Н_р высота ребра жесткости.In order to obtain the maximum resonant frequency with the minimum weight of the desktop of the vibration bench, it is necessary to design a table whose dimensions (plates, ribs, shells) will be calculated in accordance with the following mathematical expressions:
h _p =

where f _{is the} frequency of the upper limit of the working frequency range;
D _{in the} inner diameter of the table;
E is the modulus of elasticity of the table material;
ρ is the density of the table material;
h _p =

where h _{n the} thickness of the mounting plate,
H _p =

where H _{p the} height of the ribs.

 Mathematical expressions establish a relationship between the resonant frequency of the table elements, which is equal to the upper boundary of the operating frequency range of the vibration bench, the modulus of elasticity of the table material, the density of the table material and the dimensions of the table elements. The resonant frequency depends on the rigidity of the table design, and therefore, on the elastic modulus E and density ρ. The more E and less ρ, the higher the resonance frequency.

 Numerical coefficients of mathematical expressions are established experimentally.

 When designing desktops of vibration stands without taking into account the mathematical expressions, most of the details can have an overestimated resonance frequency, as well as a mass, and a lower underestimated frequency. As a result, the table has a low resonant frequency with a large mass.

 The tests showed that the workstations of vibration stands, the element sizes of which are calculated according to the given mathematical formulas, significantly increase the upper limit of the working frequency range and increase the acceleration developed, and the mass of these tables is much lower than the mass of known tables.

Claims (1)

ELECTRODYNAMIC VIBROSTEND, containing a magnetic circuit with a magnetizing coil and an elastically suspended movable system consisting of a power coil placed in the working gap of the magnetic circuit, and a working table made in one piece from a magnesium or beryllium alloy and including a round mounting plate with elements for mounting the test object, reinforced by six radial stiffeners of constant height, and covering their shell, characterized in that the shell covers the stiffeners in all their height, while the thickness of the shell and stiffeners is

where f _{b is the} frequency of the upper limit of the operating frequency range;
D _{i n the} inner diameter of the table;
E is the modulus of elasticity of the table material;
r is the density of the table material,
the thickness of the mounting plate is

and the height of the ribs is determined by the formula

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