CN102323033B - Device for testing normal dynamic characteristics of junction surface - Google Patents

Abstract

The invention provides a device for testing normal dynamic characteristics of a junction surface, and belongs to the field of mechanical design and manufacture. In the device, a hammer is connected with a testing system, a left test piece (1) is in bolted connection with a right test piece (3) by using two strain bolts (2), external extension lead wires of built-in resistance strain sheets of thestrain bolts (2) are connected with an electrical bridge, the electrical bridge is connected to an input interface of a dynamic strain gauge, the dynamic strain gauge is connected with the testing system, the testing system is connected with a PC (Personal Computer) through a network cable, the dynamic strain gauge is connected to the PC, acceleration sensors (4) are symmetrically arranged at twoends of the left test piece and the right test piece, and are connected with the testing system, the PC is used for acquiring a frequency response function of a tested piece according to an acceleration signal and an exciting force signal of the hammer, and the normal dynamic characteristics of the junction surface between the left test piece and the right test piece can be identified according to the frequency response function. When the device is adopted, the problem of difficulty in testing the dynamic characteristics of the junction surface is solved, and the normal dynamic characteristics of the junction surface can be separated from dynamic characteristics of an experimental device system.

Description

A kind of device of testing faying face normal direction dynamic perfromance

Technical field

The present invention is a kind of device of testing faying face normal direction dynamic perfromance, belongs to Machine Design and manufacturing field.

Background technology

Physical construction be by many parts by the integral body that certain functional requirement combines, the surface that mutually combines between the parts is called " faying face ".The existence of faying face makes physical construction become no longer continuous, causes the complicacy of mechanical oscillatory structure.Faying face can not only storage power, also can consumed energy, namely show contact stiffness and contact damping.Contact stiffness and contact damping are very big to the influence of structure dynamic property, and the mechanism of action is very complicated.The factor that influences the faying face dynamic perfromance is a lot, and very complicated, and these factors mainly contain:

(1) the specific pressure size on the faying face;

(2) homogeneity of pressure distribution;

(3) material of faying face;

(4) area of faying face;

(5) job operation of faying face (common method: car, mill, dig, grind, scrape etc.);

(6) the dynamic loading character of faying face (normal force, moment of torsion, moment of flexure) and size;

(7) error in geometrical form of surface in contact and nao-and micro relief;

(8) lubricating oil property between faying face etc.

Because influence factor is numerous, the influence degree of each factor and rule can't directly be determined with the method that theory is resolved again, can only be the numerical value that them are determined in the basis with the experiment therefore.

In order systematically to study and verify the relation between faying face normal direction dynamic perfromance and its basic influence factor, and grasp faying face dynamic basis characterisitic parameter, need the apparatus and method of the complete test faying face normal direction dynamic perfromance of a cover, and also do not have the device of relevant test faying face normal direction dynamic perfromance at present.

Summary of the invention

The objective of the invention is to design a cover by power hammer exciting, the use test system obtains acceleration signal, and carry out model analysis, obtain the apparatus and method of the test faying face normal direction dynamic perfromance of unit area faying face dynamic perfromance, utilize this device can obtain various dynamic characteristic parameters (normal stiffness and damping) in conjunction with faying face normal direction under the condition (being various basic influence factor), obtain integrally-built inherent characteristic (Mode Shape, natural frequency, damping ratio, frequency response function etc.), utilize frequency response function to pick out the equivalent power mathematic(al) parameter of faying face.

To achieve these goals, the present invention has taked following technical scheme.A kind of device of testing faying face normal direction dynamic perfromance comprises power hammer, left test specimen 1, right test specimen 3, acceleration transducer 4, dynamic strain indicator, strain bolt 2, electric bridge, test macro and PC; It is characterized in that: left test specimen 1 is placed on the same straight line with right test specimen 3 symmetries, left side test specimen 1 all becomes T font and staggered relatively with right test specimen 3, be equipped with along the bolt hole of test specimen axis direction on the lower convexity on the T font of left side test specimen 1 and right test specimen 3, upper bolt hole on test specimen 1 projection of a left side contacts with the upper bolt hole on right test specimen 3 projectioies and aligns, the following bolt hole of left side test specimen 1 projection contacts with the following bolt hole of right test specimen 3 projectioies and aligns, with left test specimen 1 and right test specimen 3 bolts, left test specimen 1 forms a normal direction faying face with the projection contact site of right test specimen 3 by two strain bolts 2; Described strain bolt 2 is that resistance strain plate is embedded bolt in the high-strength bolt screw rod; When bolt is applied pretightning force, because the compression of screw rod causes foil gauge to deform synchronously.The distortion of foil gauge just causes the self-resistance value to change.The outer extension lead of the foil gauge in the strain bolt 2 is connected with electric bridge, electric bridge is connected with the input interface of dynamic strain indicator by output plug, change the resistance change of foil gauge into the magnitude of voltage variation, the output terminal of dynamic strain indicator is connected to the signal sampling channel of test macro, test macro is connected with PC, and dynamic strain indicator links to each other with computer; Power hammer, left test specimen 1, right test specimen 3 linearly dispose; Acceleration transducer 4 is arranged in the end of left test specimen 1 and right test specimen 3; Power hammer for the left test specimen of vertical drive 1 end links to each other with the signal sampling channel of test macro, is used for measuring the acceleration transducer 4 of response signal and arriving test macro, and test macro is connected to PC.

Acceleration transducer 4 is fixed on the two ends, the left and right sides of test specimen by magnetic sheet.

The material of described left test specimen 1 and right test specimen 3 adopts Q235-Q235 or HT250-HT250 or QT600-QT600.

The surfaceness of described left test specimen 1 and right test specimen 3 is finish-milling-finish-milling or mill-mill.

3 of described left test specimen 1 and right test specimens add machinery oil No. 30.

It is the modal forces hammer of PCB-086C03 that described power hammer adopts model; It is the acceleration transducer of PCB-333B30 that described acceleration transducer adopts model; Dynamic strain indicator adopts the BZ2668 dynamic strain indicator.

Of the present inventionly can obtain following beneficial effect:

(Fig. 1) can find out from experimental provision, and the characterisitic parameter that tests out only is the faying face part characteristic between the test specimen of the left and right sides, reduced the number of the physical quantity of measuring, and employing is the direct method of measurement.

For the ease of each the basic influence factor that influences the faying face dynamic perfromance is studied, this experimental provision guarantees that test specimen is easy to change, be easy to the location.

Owing to only be the normal direction dynamic perfromance of faying face between the test specimen of the test left and right sides, be easier to separate from the dynamic perfromance of experimental provision system so can guarantee the faying face dynamic perfromance.

Description of drawings

Fig. 1 is the structural representation that the present invention tests faying face normal direction dynamic perfromance;

Fig. 2 is the front view (left and right test specimen is identical) of left test specimen.

Fig. 3 is the left view (left and right test specimen is identical) of left test specimen.

Among the figure: 1, left test specimen, 2, the strain bolt, 3, right test specimen, 4, acceleration transducer.

Embodiment

Below in conjunction with principle of work and structure accompanying drawing method of testing is described in further detail to closing face dynamic perfromance device.

As Figure 1-3, left test specimen 1 is by bolt hole strain bolt 2 and right test specimen 3 bolts, and left test specimen 1 and right test specimen 3 are identical, thereby have guaranteed the contact of left and right test specimen faying face, have also guaranteed the linearity of left and right sides test specimen.Left and right test specimen is used after strain bolt 2 bolts, freely is suspended on the double ladder with the spring rope.

Acceleration transducer 4 is adsorbed on the end of left and right test specimen respectively with magnetic sheet, the power hammer is done vertical drive in the end of left test specimen 1.The output signal of power hammer pumping signal, acceleration transducer 4 is transferred to test macro, and PC is delivered in the data output of test macro.

During use, measure the size of strain bolt 2 pretightning forces on the faying face by dynamic strain indicator.When firmly hammer encourages left test specimen 1 end, should exert all one's strength and hammer the vertical drive end surface into shape, the power sensor in hammering into shape by power obtains the size of exciting force, obtains the acceleration signal of test block by the acceleration transducer 4 of test piece end absorption.After obtaining the response under the different excitation signal, use the frequency response function identification method can obtain the faying face dynamic characteristic parameter.The big I of pretightning force of adjusting strain bolt 2 on the test specimen faying face repeatedly changes the face pressure value of faying face, namely presses to study the influence that the faying face normal stiffness is pressed by face by coplanar not.

Utilize this device can do following a few class experiment:

(1) certain in conjunction with (material of the area of faying face, roughness, processing mode, faying face, the medium between the faying face etc. certain situation under) under the condition, the face that changes faying face is pressed (namely by changing the face pressure that bolt pretightening changes faying face), the amplitude of the exciting force of power hammer keeps stable, and the change that the face of probing into is pressed is to the influence of faying face normal stiffness.

(2) certain in conjunction with (material of the area of faying face, roughness, processing mode, faying face, the medium between the faying face etc. certain situation under) under the condition, keep the face of faying face to press constant (namely the strain bolt on the faying face being applied constant pretightning force), the amplitude of the exciting force of change power hammer is probed into different exciting forces to the influence of faying face normal stiffness.

(3) keep the face of faying face to press constant (namely the strain bolt on the faying face being applied constant pretightning force), change (for example changes the roughness of faying face in conjunction with condition, and material of the area of faying face, processing mode, faying face, the medium between the faying face etc. are constant), the amplitude of exciting force of confining force hammer is constant, probes into different from the influence of condition to the faying face normal stiffness.

During experiment, left test specimen 1 and right test specimen 3 can be changed dissimilar, can be as different materials such as Q235-Q235, HT250-HT250, QT600-QT600, can be finish-milling-finish-milling, mill-different surface roughness such as mill.Can also between left test specimen 1 and right test specimen 3, add medium, as No. 30 machinery oil.

Faying face normal direction dynamic characteristic parameter is identified.Normal direction faying face in the test specimen partly is reduced to one group of spring, damping system.Test specimen and faying face are partly carried out Dynamic Modeling, because the axial first natural frequency of test specimen and damping ratio are only used in parameter identification, under this natural frequency, test specimen is done axial symmetrical tension and compression vibration, and intermediate point is node.Test specimen is partly carried out Dynamic Modeling, and modeling process is as follows: left test specimen is reduced to average elastic rod 1, and the length L of elastic rod, cross-sectional area A, elastic modulus E, linear mass μ conform to rod member; Coupling bolt and contact block are reduced to the lumped mass piece, and m is lumped mass piece quality; The normal direction faying face partly is reduced to one group of spring, damping system.The boundary condition of simplified model is consistent with when experiment to be free state.

So, the identification of bolted joint dynamic characteristic parameter is converted into to spring rate K the identification of ratio of damping C.Identifying is as follows:

For average elastic rod 1, the axial free movement Newton's equation of bar 2 is respectively:

$\mathrm{EA}\frac{{\&PartialD;}^{2}U(x,t)}{{\&PartialD;x}^2}=\mathrm{\&mu;}\frac{{\&PartialD;}^{2}U(x,t)}{{\&PartialD;\mathrm{<figure-callout\; id="2"\; label="t"\; filenames="HDA0000064885150000011.png"\; state="\{\{state\}\}">t</figure-callout>}}^2}$

$\mathrm{EA}\frac{{\&PartialD;}^{2}V(z,t)}{{\&PartialD;z}^2}=\mathrm{\&mu;}\frac{{\&PartialD;}^{2}V(z,t)}{{\&PartialD;t}^2}---\left(1\right)$

Wherein (x is that coordinate x position is at t vibration displacement constantly on the bar 1 t) to U, and (z is that coordinate z position is at t vibration displacement constantly on the bar 2 t) to V, and μ is the rod member linear mass.EA is the tension and compression rigidity of rod member, and wherein E is elastic modulus, and A is the rod member cross-sectional area.

We with two bar vibration displacement U (x, t), V (z, t) carry out displacement and separate with the variable of time quantum:

U(x，t)＝U(x)e ^λt

V(z，t)＝V(z)e ^λt (2)

Equation (2) substitution equation (1) is obtained:

$\frac{d^{2}U\left(x\right)}{{\mathrm{dx}}^2}-{\mathrm{\&beta;}}^{2}U\left(x\right)=0$

$\frac{d^{2}V\left(z\right)}{{\mathrm{dz}}^2}-{\mathrm{\&beta;}}^{2}V\left(z\right)=0---\left(3\right)$

Wherein: ${\mathrm{\&beta;}}^2=\frac{{\mathrm{\&mu;\&lambda;}}^2}{\mathrm{EA}}---\left(4\right)$

Equation (3) is asked its general solution.Border coordination condition according to test specimen two ends freedom, middle bolt in the test obtains about a then ₁, a ₂, a ₃, a ₄Matrix equation, that is:

Aa＝0 (5)

Wherein:

a＝[a ₁，a ₂，a ₃，a ₄] ^T

Be the matrix equation (5) of a for unknown number, equation has the condition of solution to be: A=0, so obtain about the secular equation of λ as follows:

-2cλEAβ ³cosh(βL)sinh(βL)+1.6cλ ³β ²cosh ²(βL)-2kEAβ ³cosh(βL)sinh(βL)+1.6kβ ²λ ²cosh ²(βL)+E ²A ²β ⁴(1-cosh ²(βL))+1.6EAβ ³λ ²sinh(βL)cosh(βL)-0.64β ²λ ⁴cosh ²(βL)＝0 (6)

Wherein known by formula (4): ${\mathrm{\&beta;}}^2=\frac{{\mathrm{\&mu;\&lambda;}}^2}{\mathrm{EA}}$

For eigenvalue, we know that its value is under the free state:

$\mathrm{\&lambda;}=-{\mathrm{\&xi;\&omega;}}_n\&PlusMinus;j\sqrt{1-{\mathrm{\&xi;}}^2}{\mathrm{\&omega;}}_n---\left(7\right)$

Natural frequency ω in the formula (7) _nWith damping ratio ξ, obtain by the test specimen axial vibration experiment of above introducing, so formula (6) only contains unknown number K, C.Formula (6) is carried out the arrangement of real part and imaginary part, and make real part, imaginary part be respectively zero according to the condition that equation is set up, the final system of equations that obtains about K, C.Utilize software for calculation that system of equations is resolved and find the solution, finally obtain the exact solution of unknown number K, C, be i.e. rigidity, the damping value of this normal direction bolt faying face.

Claims (6)

1. a device of testing faying face normal direction dynamic perfromance comprises power hammer, left test specimen (1), right test specimen (3), acceleration transducer (4), dynamic strain indicator, strain bolt (2), electric bridge, test macro and PC; It is characterized in that: left test specimen (1) is placed on the same straight line with right test specimen (3) symmetry, left side test specimen (1) all becomes T font and staggered relatively with right test specimen (3), be equipped with along the bolt hole of test specimen axis direction on the lower convexity on the T font of left side test specimen (1) and right test specimen (3), upper bolt hole on test specimen (1) projection of a left side contacts with the upper bolt hole on right test specimen (3) projection and aligns, the following bolt hole of left side test specimen (1) projection contacts with the following bolt hole of right test specimen (3) projection and aligns, with left test specimen (1) and right test specimen (3) bolt, left test specimen (1) forms a normal direction faying face with the projection contact site of right test specimen (3) by two strain bolts (2); Described strain bolt (2) is that resistance strain plate is embedded bolt in the high-strength bolt screw rod; The outer extension lead of the foil gauge in the strain bolt (2) is connected with electric bridge, electric bridge is connected with the input interface of dynamic strain indicator by output plug, change the resistance change of foil gauge into the magnitude of voltage variation, the output terminal of dynamic strain indicator is connected to the signal sampling channel of test macro, test macro is connected with PC, and dynamic strain indicator links to each other with PC; Power hammer, left test specimen (1), right test specimen (3) linearly dispose; Acceleration transducer (4) is arranged in the end of left test specimen (1) and right test specimen (3); The power hammer that is used for test specimen (1) end, a vertical drive left side links to each other with the signal sampling channel of test macro, and the acceleration transducer (4) that is used for the measurement response signal is connected to test macro, and test macro is connected to PC.

2. a kind of device of testing faying face normal direction dynamic perfromance according to claim 1, it is characterized in that: acceleration transducer (4) is fixed on the two ends, the left and right sides of test specimen by magnetic sheet.

3. a kind of device of testing faying face normal direction dynamic perfromance according to claim 1 is characterized in that: material employing Q235-Q235 or HT250-HT250 or the QT600-QT600 of described left test specimen (1) and right test specimen (3).

4. a kind of device of testing faying face normal direction dynamic perfromance according to claim 1, it is characterized in that: the method for surface finish of described left test specimen (1) and right test specimen (3) is finish-milling-finish-milling or mill-mill.

5. a kind of device of testing faying face normal direction dynamic perfromance according to claim 1 is characterized in that: add machinery oil No. 30 between described left test specimen (1) and right test specimen (3).

6. a kind of device of testing faying face normal direction dynamic perfromance according to claim 1 and 2 is characterized in that: the modal forces hammer that described power hammer employing model is PCB-086C03; It is the acceleration transducer of PCB-333B30 that described acceleration transducer adopts model; Dynamic strain indicator adopts the BZ2668 dynamic strain indicator.

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