CN103994923A - Suspension electromagnetic incentive resonant type fatigue test method - Google Patents

Abstract

The invention discloses a suspension electromagnetic incentive resonant type fatigue test method. An electro-hydraulic servo type test method has low test frequency, and an electromagnetic type fatigue test method has large noise. The suspension electromagnetic incentive resonant type test method comprises the following specific steps: two specimen clamping arms are hanged on a machine frame by slings, and two ends of a specimen are respectively fixed on the two specimen clamping arms; according to a specimen material and geometrical shape parameters, dynamic calculation is carried out by using two-degree-of-freedom analytical model of a resonant system, and an estimation value of a resonance angular frequency is obtained; a frequency scanning test is carried out, a precise resonance angular frequency rho of the resonant system is obtained, and at the same time by using a half power point method, a damping ratio xi of the system is obtained; according to the frequency scanning test result and test bending moment requirements, fatigue tests are carried out; after each 200000-250000 times of the fatigue tests are carried out, the frequency scanning test is repeated, when the obtained resonance angular frequency of the resonant system is decreased by 5-8% compared with a resonance angular frequency of an initial state rho, the specimen is affirmed to be failed, and the test is completed. The fatigue test method is low in noise, high in frequency and high in precision.

Description

A kind of suspension electric magnetization resonant mode fatigue test method

Technical field

The invention belongs to torture test technical field, relate to fatigue test method, be specifically related to a kind of suspension electric magnetization resonant mode fatigue test method.

Background technology

Fatigue reliability is the important parameter of weighing all kinds of dynamoelectric equipment qualities.The design of fatigue reliability needs the anti-fatigue performance of Knowing material or force structure, and torture test is at present the Main Means that obtains material or Anti-Fatigue performance.

The key technical indexes of fatigue tester comprises test load precision, test frequency etc.At present, fatigue tester mainly contains three kinds of pure mechanical load formula, electro-hydraulic servo loaded type and electromagnetism loaded types etc., there is the deficiencies such as complex structure, precision is low, automaticity is low in the pure mechanical load method occurring the earliest, is replaced gradually by the higher electro-hydraulic servo formula of automaticity and electromagnetism loaded type.Wherein electro-hydraulic servo formula test method precision is high, but test frequency is lower.The test frequency of electromagnetic type fatigue test method is high, but noise is large, and precision is lower slightly.

Summary of the invention

The object of the invention is for the deficiencies in the prior art, a kind of suspension electric magnetization resonant mode fatigue test method is provided, noise is little, frequency is high, precision is high, energy consumption is low.

The device that the present invention uses comprises test specimen clamping limb, permanent magnetism can, permanent magnet, electromagnet and control system.The bottom of described two test specimen clamping limbs is fixed with a permanent magnetism can respectively; The inside of two permanent magnetism cans is equipped with permanent magnet; Two blocks of described electromagnet be separately positioned on two permanent magnetism cans under.

Described control system comprises acceleration transducer, power sensor, signal picker, host computer, signal generator and power amplifier.Two described acceleration transducers are separately fixed at the lateral wall of two permanent magnetism cans, and the top of two power sensors is fixed with the bottom of an electromagnet respectively; The signal input part of the signal output part access in parallel signal picker of described two acceleration transducers and two power sensors; Signal picker is by USB mouth access host computer, and host computer exports signal generator to by USB mouth; The instruction that signal generator is sent according to host computer and parameter generate modulated-analog signal, pass to the input end of power amplifier; Described modulated-analog signal comprises positive phase current signal and negative-phase sequence curent signal; The positive current output terminal of power amplifier is connected with the current input terminal of an electromagnet, and negative-phase sequence curent output terminal is connected with the current input terminal of another electromagnet.

Concrete steps of the present invention are as follows:

Step 1, two test specimen clamping limbs are suspended in frame with hoist cable, guarantee that two test specimen clamping limbs are parallel; The two ends of test specimen are separately fixed on two test specimen clamping limbs.

Step 2, according to the material parameter of test specimen and geometric shape parameters, utilize the two degrees of freedom analytic model of resonator system to do dynamics calculation, obtain the estimated value of resonant angular frequency:

$p^{\′}=\sqrt{\frac{2\mathrm{EI}}{\mathrm{Jl}}}$

Wherein, J is the moment of inertia of test specimen clamping limb, the elastic modulus that E is material for test, and I is the moment of inertia of test specimen smallest cross-sectional, the effective length that l is test specimen.

Step 3, carry out frequency sweep test, PC control signal generator produces the sinusoidal current of frequency by 0.3p '～1.3p ' linear change, and sinusoidal current amplitude is got 30～50mA.According to frequency sweep response, obtain the exact resonance angular frequency p of resonator system.Utilize Half-power points simultaneously, obtain the damping ratio ξ of system.

Step 4, according to the frequency sweep test result of step 3 and test moment of flexure requirement, carry out torture test.By loading force drive current amplitude with electromagnet try to achieve drive current amplitude I _einitial value; Wherein, a be the lower surface of permanent magnetism can to the distance of test specimen center line, value is determined according to the length of the two ends diameter of test specimen and test specimen clamping limb; Live load factor ω is for loading angular frequency, and the span of initial value is 0.7p～0.9p; k _mfor drive current amplitude I _eand the scale-up factor between loading force L, span is 60～100N/A.Host computer carrys out the drive current amplitude I of controlled loading angular frequency and electromagnet by changing the signal waveform of signal generator _e, make the moment of flexure that test specimen is subject to remain consistent with the moment of flexure of testing requirements.

Step 5, often carry out after the torture test of 20～250,000 steps 4, repeating step 3 declines 5～8% time compared with the resonant angular frequency p of the resonator system resonant angular frequency obtaining and original state, assert that test specimen lost efficacy, and completed test.

The beneficial effect that the present invention has is:

The present invention utilizes bending (torsion) resonance principle, loads by suspension electric magnetization mode.Compared with traditional electromagnetism loaded type fatigue test method, remove loading force push rod, adopt the push-and-pull action between electromagnet and permanent magnet to load, it is a kind of contactless loading, thereby system noise is little, energy consumption is low, and loading force can not be subject to the interference of partial structurtes distortion and vibration, loading force is more prone to control, and can improve largely the precision of test.

Brief description of the drawings

Fig. 1 is the device principle of work schematic diagram that the present invention uses;

Fig. 2 is the structural representation of control system in the device that uses of the present invention;

Fig. 3 is the overall assembling stereogram of test specimen clamping limb and permanent magnetism can and test specimen in the device that uses of the present invention;

Fig. 4 is the structural representation of test specimen.

Embodiment

Below in conjunction with drawings and Examples, the invention will be further described.

As shown in Figure 1, the device that a kind of electric magnetization resonant mode fatigue test method that suspends uses comprises test specimen clamping limb 1, permanent magnetism can 2, permanent magnet 3, electromagnet 4 and control system.The bottom of two test specimen clamping limbs 1 is fixing with a permanent magnetism can 2 respectively; The inside of two permanent magnetism cans 2 is equipped with permanent magnet 3; Two blocks of electromagnet 4 be separately positioned on two permanent magnetism cans 2 under.The material of test specimen clamping limb 1 is alloy steel, and the material of permanent magnetism can 2 is aluminium alloy.

As shown in Figure 2, control system comprises acceleration transducer 5, power sensor 6, signal picker 9, host computer 10, signal generator 11 and power amplifier 12.Two acceleration transducers 5 are separately fixed at the lateral wall of two permanent magnetism cans 2, and the top of two power sensors 6 is fixed with the bottom of an electromagnet 4 respectively; The signal input part of the signal output part access in parallel signal picker 9 of two acceleration transducers 5 and two power sensors 6; Signal picker 9 is by USB mouth access host computer 10, and host computer 10 exports signal generator 11 to by USB mouth; The instruction that signal generator 11 is sent according to host computer and parameter generate modulated-analog signal, pass to the input end of power amplifier 12; Modulated-analog signal comprises positive phase current signal and negative-phase sequence curent signal; The positive current output terminal of power amplifier 12 is connected with the current input terminal of an electromagnet 4, and negative-phase sequence curent output terminal is connected with the current input terminal of another electromagnet 4.

As shown in Figure 3, the bottom of permanent magnetism can 2 is fixed with bottom 2-1, and permanent magnet 3 is arranged on bottom 2-1.The top sidewall of test specimen clamping limb 1 offers test specimen mounting hole 1-1, and top end face offers hoist cable and stretches into groove 1-2 and test specimen clamp screw pit 1-3; The xsect of test specimen mounting hole 1-1 is square; The bottom that hoist cable stretches into groove 1-2 and test specimen clamp screw pit 1-3 all connects with the hole wall of test specimen mounting hole 1-1.

The attainable major function of device that this suspension electric magnetization resonant mode fatigue test method uses is as follows:

1, exciting: pass into the exchange current of modulating, amplifying through power amplifier 12 by host computer 10 in electromagnet 4, make generation between electromagnet 4 and permanent magnet 3 be modulated the alternation push-and-pull action of signal controlling, the electric current of two blocks of electromagnet 4 is anti-phase each other, acts on the alternate load of test specimen 7 with superimposed.

2, load control: the vibration acceleration to test specimen clamping limb 1 in process of the test and exciting force carry out Real-Time Monitoring.Obtain the dynamics of the resonator system jointly being formed by test specimen 7 and test specimen clamping limb 1 by system dynamic modeling analysis and frequency sweep test.Taking actual measurement vibration acceleration, exciting force and system dynamics parameter as basis, the load that test specimen in process of the test is suffered is carried out to real-time analysis, modulate accordingly frequency, the direction and intensity of drive current, by the stress of testing requirements controlled loading power and test specimen.

3, the loading of combined waveform load: exciting force can be by modulating the direction of current that passes into electromagnet 4 and intensity.According to the dynamics of resonator system, by calculating in real time the time dependent rule of electric current corresponding to combined waveform load, and inputed to driver, realize combined waveform and load.

4, the realization of bending, torsional fatigue test: when repeated bend test, two block permanent magnets 3 are placed on the both sides of test specimen 7; When torsional fatigue test, two block permanent magnets 3 are placed on the front and back position of test specimen 7.

The concrete steps of this suspension electric magnetization resonant mode fatigue test method are as follows:

Two bare terminal ends of step 1, test specimen 7 embed respectively in the test specimen mounting hole 1-1 of two test specimen clamping limbs, in the test specimen clamp screw pit 1-3 of two test specimen clamping limbs, holding screw are all set, and holding screw compresses test specimen 7; Article two, the hoist cable that corresponding test specimen clamping limb is stretched into respectively in the bottom of hoist cable 8 stretches in groove 1-2, and fixes with one end of test specimen 7 respectively; Article two, the top of hoist cable 8 is all fixed with frame.As shown in Figure 4, test specimen 7 is standard specimen, effective diameter d=8mm, effective length l=60mm; The material of test specimen 7 is No. 45 steel.

Step 2, according to the material parameter of test specimen 7 and geometric shape parameters, utilize the two degrees of freedom analytic model of resonator system to do dynamics calculation, obtain the estimated value of resonant angular frequency:

$p^{\′}=\sqrt{\frac{2\mathrm{EI}}{\mathrm{Jl}}}=\sqrt{\frac{2\×210\×{10}^9\mathrm{Pa}\×2\×{10}^{-10}{m}^4}{25.6\×{10}^{-4}\mathrm{kg}{m}^2\×0.06m}}=740(\mathrm{rad}/s)$

Wherein, J is the moment of inertia of test specimen clamping limb, the elastic modulus that E is material for test, and I is the moment of inertia of test specimen smallest cross-sectional, l is the effective length of test specimen 7.

Step 3, carry out frequency sweep test, host computer 10 control signal generators 11 produce the sinusoidal current of frequency by 0.3p '～1.3p ' linear change, and sinusoidal current amplitude is got 50mA, to guarantee that frequency sweep process can not produce extra fatigue damage to test specimen.According to frequency sweep response, obtain the exact resonance angular frequency p=741rad/s of resonator system.Utilize Half-power points simultaneously, obtain damping ratio ξ=0.01 of system.

Step 4, according to the frequency sweep test result of step 3 and test moment of flexure requirement, getting test moment is M _b=25Nm, carries out torture test.By loading force drive current amplitude with electromagnet 4 try to achieve drive current amplitude I _einitial value be 0.931A; Wherein, a be the lower surface of permanent magnetism can 2 to the distance between test specimen mounting hole 1-1 center line, value is 0.128m; Live load factor ω is for loading angular frequency, and getting initial value is 0.9p; k _mfor drive current amplitude I _eand the scale-up factor between loading force L, value is 80N/A.Host computer 10 carrys out the drive current amplitude I of controlled loading angular frequency and electromagnet 4 by changing the signal waveform of signal generator 11 _e, it is consistent with the moment of flexure of testing requirements that the moment of flexure that test specimen 7 is subject to remains.In process of the test, loading angular frequency and loading force L can monitor by accelerometer and power sensor respectively in real time, thereby realizes closed-loop control.

Step 5, often carry out after the torture test of 200,000 steps 4, repeating step 3 declines 5% time compared with the resonant angular frequency p=741rad/s of the resonator system resonant angular frequency obtaining and original state, and test specimen 7 lost efficacy, and completed test.

Claims (1)

1. a suspension electric magnetization resonant mode fatigue test method, is characterized in that: the device that the method is used comprises test specimen clamping limb, permanent magnetism can, permanent magnet, electromagnet and control system; The bottom of described two test specimen clamping limbs is fixed with a permanent magnetism can respectively; The inside of two permanent magnetism cans is equipped with permanent magnet; Two blocks of described electromagnet be separately positioned on two permanent magnetism cans under;

Described control system comprises acceleration transducer, power sensor, signal picker, host computer, signal generator and power amplifier; Two described acceleration transducers are separately fixed at the lateral wall of two permanent magnetism cans, and the top of two power sensors is fixed with the bottom of an electromagnet respectively; The signal input part of the signal output part access in parallel signal picker of described two acceleration transducers and two power sensors; Signal picker is by USB mouth access host computer, and host computer exports signal generator to by USB mouth; The instruction that signal generator is sent according to host computer and parameter generate modulated-analog signal, pass to the input end of power amplifier; Described modulated-analog signal comprises positive phase current signal and negative-phase sequence curent signal; The positive current output terminal of power amplifier is connected with the current input terminal of an electromagnet, and negative-phase sequence curent output terminal is connected with the current input terminal of another electromagnet;

The concrete steps of the method are as follows:

Step 1, two test specimen clamping limbs are suspended in frame with hoist cable, guarantee that two test specimen clamping limbs are parallel; The two ends of test specimen are separately fixed on two test specimen clamping limbs;

Step 2, according to the material parameter of test specimen and geometric shape parameters, utilize the two degrees of freedom analytic model of resonator system to do dynamics calculation, obtain the estimated value of resonant angular frequency:

$p^{\′}=\sqrt{\frac{2\mathrm{EI}}{\mathrm{Jl}}}$

Wherein, J is the moment of inertia of test specimen clamping limb, the elastic modulus that E is material for test, and I is the moment of inertia of test specimen smallest cross-sectional, the effective length that l is test specimen;

Step 3, carry out frequency sweep test, PC control signal generator produces the sinusoidal current of frequency by 0.3p '～1.3p ' linear change, and sinusoidal current amplitude is got 30～50mA; According to frequency sweep response, obtain the exact resonance angular frequency p of resonator system; Utilize Half-power points simultaneously, obtain the damping ratio ξ of system;

Step 4, according to the frequency sweep test result of step 3 and test moment of flexure requirement, carry out torture test; By loading force drive current amplitude with electromagnet try to achieve drive current amplitude I _einitial value; Wherein, a be the lower surface of permanent magnetism can to the distance of test specimen center line, value is determined according to the length of the two ends diameter of test specimen and test specimen clamping limb; Live load factor ω is for loading angular frequency, and the span of initial value is 0.7p～0.9p; k _mfor drive current amplitude I _eand the scale-up factor between loading force L, span is 60～100N/A; Host computer carrys out the drive current amplitude I of controlled loading angular frequency and electromagnet by changing the signal waveform of signal generator _e, make the moment of flexure that test specimen is subject to remain consistent with the moment of flexure of testing requirements;

Step 5, often carry out after the torture test of 20～250,000 steps 4, repeating step 3 declines 5～8% time compared with the resonant angular frequency p of the resonator system resonant angular frequency obtaining and original state, assert that test specimen lost efficacy, and completed test.