Non-destructive method of stress measurement in object surface layer and stress gauge

FIELD: measurement technology.

SUBSTANCE: invention refers to measurement equipment and is applied to determine mechanical stress in surface layer of an object. Method involves direction of unfocused visible range radiation flow of any intensity onto the test surface and registration of reflected flow by photodetector, comparison of the result with reference value obtained with known mechanical stress, temperature and surface layer roughness values for this radiation source. Stress gauge includes laser, defocusing devices for beam directed onto the test surface and focusing devices for flow reflected by the surface; photodetector of reflected signal; photodetector signal amplifier; comparator comparing voltage supplied by the amplifier with variable voltage of generator and generating voltage pulse; AND circuit encoding comparator pulse to short pulse string of reference frequency generator; temperature measurement unit; test surface roughness measurement unit; reference code storage device; digital comparator comparing signal obtained from the test surface with reference signals obtained with definite temperature and roughness; indicator displaying stress value for the test surface.

EFFECT: voltage determination in surface layer of examination object.

2 cl, 2 dwg

 

The invention relates to the measurement of mechanical stress in the surface layer of the product.

A known method for determining residual stresses [1], consisting in the comparison of the amplitude-frequency characteristics of the reference and sample. This eddy current non-destructive method.

The disadvantage of this method is that it can be used only for ferromagnetic materials.

The known method of determining the stresses in steel structures [2], consisting of multiple measuring microhardness of the surface of the product and comparing it with the microhardness of the standard.

The disadvantage of this method is the damage to the surface, which is determined by the voltage.

A known method of determining the mechanical stresses in the material of the acoustic strain measurement [3], which consists in the registration of the change of velocity of propagation of elastic (usually ultrasound) waves under the influence of tension.

The disadvantages of this method are: the complexity of the survey, the use of complex equipment, the limited implementation in the conditions of production and operation, this contact method.

Known x-ray method of determining the stresses, based on the phenomenon of scattering of monochromatic x-rays when passing through the regular crystal lattice is of the material [4]. This scattering is the interference of rays.

The disadvantage of this method is that it can only be determined voltage 2 and 3 genera in the surface layer of the material of the workpiece without its destruction. When defining the same voltage of the first kind (most important) this method gives large errors.

A known method for the determination of mechanical stresses on the basis of tenzometricheskie, in particular electrosensitive. This method is based on the fact that the deformable surface is fixed wire strain gauge (DMS [4], which treats the deformation of the object and changes its electrical resistance. And deformation is calculated and the voltage, which happened this warp.

The disadvantage of this method is that it needs contact with the surface of the measurement that determines its stationarity. Use it for moving objects is difficult.

A known method for the determination of mechanical stresses by the method of photo-elasticity [5], which consists in the fact that the refractive index of light changes its value when power is applied.

The disadvantage of this method is that it is well to measure voltage in transparent materials. For opaque (e.g., metal) objects this method allows to get only the reasonable price is accurate. For this method, you need to test the item to paste a thin plate made of a photoelastic material (thickness 1-2 mm) special glue, ensuring good contact. And to do it hard enough, especially on large parts or parts with complex shape.

The closest technical solution is the method of holographic interferometry to determine the mechanical stresses [6]. This method consists in obtaining holograms from test items. To obtain an image of this part of the hologram Shine a beam of light. When the stress (strain) occurs the phase distortion of the scattered wave, which affects the form of the observed pattern: there are interference fringes.

The disadvantages of this method are: the multi-stage process, the complexity of the voltage detection requires high qualification of operators, the complexity and awkwardness of the equipment, the difficulty of its use in production and operation.

An object of the invention is to develop a method for determining the mechanical stresses in the surface layer of the product, which allows you to create a compact device for determining the voltage in all conditions, including field, with disassembly and without disassembly of the product.

The technical result of the invention is achieved by the fact that h is about the method of determining the mechanical stress in the surface layer of the product based on the direction of the radiation flux on the test surface and the Desk reflected from her stream.

On the test surface goes all rasfokusirovka stream of radiation, for example laser, visible range and intensity, preferably small, and register values of the reflected stream using photovoltaic receiver such as a phototransistor, a comparison of this value with the reference value, obtained in advance for known values of mechanical stress, temperature and roughness in the surface layer, for a given radiation source. As used rasfokusirovka on some area of the test surface flow, the resulting voltage will be averaged square of the fall of the luminous flux voltage. If strictly, the adjacent areas on the surface have different voltage: though small, but the voltage in the adjacent areas will be different. Therefore, the use of blurred light beam will give a more accurate value of the voltage on the tested surface.

The test surface may be stationary or mobile. This surface will absorb some of the energy of the incident flow, and the higher the temperature of the surface being examined, the greater the absorption of the incident flow will occur [7]. The remaining part of the incident energy is scattered and reflected, and the bol the higher will be the temperature of the test surface, the smaller will be the impact of the incident energy. The same can be said about the roughness of the surface: the higher the class of purity, i.e., the smaller the roughness, the more value will be reflected flux. Photoelectric receiver registers the magnitude of the reflected flux incident into it, in the form of a signal: electrical voltage or current. Depending on the magnitude of the voltage in the surface layer to vary the intensity of the reflected flux, and hence the magnitude of the signal in the photodetector (e.g., current): may increase or decrease. This dependence will also be connected with tension: tension compression or tensile strength. When the voltage compression of the reflected luminous flux will increase (absorption of light energy decreases), while the tensile strength of the opposite - decrease (absorption of light energy increases). Depending on the magnitude of the reflected luminous flux will be generated and the magnitude of the electrical signal in the receiver, such as a phototransistor.

The inventive method is implemented in the detection voltage, which contains a light emitter in the form of a laser, and the identifier further comprises a device defocus incident on the test surface of the beam and focusing reflected by this surface sweat the spacecraft; the photodetector of the reflected signal, which is applied by the phototransistor; power signal from the phototransistor; a comparator that compares entering the voltage from the amplifier with a linearly changing voltage generator generating a voltage pulse; the scheme And encoding coming at it from a comparator pulse in a pack of short pulse generator model frequency; a binary pulse counter that counts pulses in a packet; a decoder pulses, and the unit for determining the temperature of the test surface, and the unit for determining the roughness of the test surface; the device memory reference code, where pre-recorded signals from known mechanical stresses, temperature and roughness of the test surface; digital comparator performing a comparison of results obtained with the sample surface signal with the reference signals received at a known temperature and roughness; a display device, where the displayed voltage value of the test surface, and formed in the phototransistor signal enters the amplifier and simultaneously to the inputs of the blocks determine the temperature and roughness, from the output of the amplifier to the input of the comparator, and the comparator output to a schema And then to the input of binary counter pulses, d is over - to the input of the decoder, the output of the decoder is input to a digital comparator, where simultaneously the signal receives signals from the memory device reference codes, which receives signals from blocks of determining the temperature and roughness, providing for the issuance of reference codes for certain in this test the temperature and surface roughness, and the output of the digital comparator is input to the display unit.

New features with significant differences according to the method are:

1. The use of electromagnetic radiation of the visible range of frequencies and intensity, preferably small.

2. The use of blurred beam for irradiation of the test surface.

3. Determination of stresses in the surface layer according to the intensity of the reflected her light stream.

The essential distinguishing characteristics of the device are:

- the presence of rasfokusirovka and focusing systems;

photodetector such as a phototransistor;

- system for processing signals from the photodetector.

Using new features in conjunction with the known, and new connections between them ensures the achievement of the technical result of the invention, namely the method of irradiation of the sample surface by any range izlucheniya any energy level of this radiation to determine the mechanical stress on this surface; the ability to create a compact device that can be used in any environment, including field, as with disassembly and without disassembly (in working position).

In Fig.1 is a diagram of the use of the proposed method of measuring the stress in the surface layer of the product and the structural diagram of the detection voltage, and Fig.2 - generation of signals in the elements of the processing system reflected from the examined surface of the light stream.

In the proposed method is used (Fig.1) the source of radiation, for example laser 1, refocusing device, such as a lens 2, the analyzed surface 8, a focusing device, such as a lens 3, the receiver of the reflected signal, for example a phototransistor 4.

As the voltage of the test surface is determined by the voltage areas with uneven size, so is the defocusing of the incident on the testing surface of the beam to average the portion of this beam with some surface area. It should be noted that position associated with surface temperature and roughness. Each site on the surface will reflect an incident beam individually. However, if you take a certain area of the sample surface (the area of the incident beam), the reflectivity will determine the impact the positive capacity of the whole sample surface. In this case, a sample of the whole population, where all the test surface has researched population areas, and the area of the incident surface of the beam - sample of the population. Therefore, the incident beam refocused. And, Vice versa, to collect the photodetector as much energy reflected from the sample surface flow, the reflected beam is focused on a photodetector such as a phototransistor, which under the action of the beam a signal in the form of electrical voltage or current. The more stress in the surface layer, the more (or less, depending on the type of voltage: compression or tension) in value will be reflected flux and resulting in the photodetector signal.

Obtained from the reflected beam at the photodetector signal is compared with a reference signal obtained in advance from arduous surfaces with known size and type of voltage at a known temperature and roughness), and which of them matches the value of this voltage and will have a test surface.

The determinant voltage (Fig.1) contains a light emitter such as a laser 1, refocusing device, such as a lens 2, a focusing device, such as a lens 3, a sensor 4, for example a phototransistor, photoshotel 5, a comparator 6, a diagram And 7, ASC is Adamou surface 8, the oscillator ramp voltage 9, the pulse generator model frequency 10, the binary pulse counter 11, a decoder 12, the block determining the temperature of the investigated surface 16, the block determining the roughness of the sample surface 17, the device memory reference code 14, the comparator 13 (digital), indicating unit 15.

The detection voltage is as follows.

The emitter 1, such as a laser, produces an incident beam and sends it to refocusing device 2, for example the lens (if the laser beam is out of focus, the device 2 is not required). Then the laser (or any other) beam falls on the analyzed surface 8 at any angle, providing a reflection of the incident radiation (the angle of incidence must be always the same and equal to the angle of incidence at the formation of the reference codes). With square incident on the surface of the beam is a reflection of the energy of the beam (the shape of the cross section of the reflected beam follows the shape of the spot incident on the surface of the beam, whether elliptical or any other). The energy of the reflected flux can be very small, the radiation source 1 may comprise a light source with very low energy dissipation in space. So on the path of the reflected flux is set to a focusing device 3, provide the its collection dispersed in the reflected beam energy in focus where is the sensor 4, such as a phototransistor. However, in this case, the value generated under the action of the energy of the reflected and focused light flux of the electric voltage (or current) may be small, so after the photodetector in the determinant voltage installed power 5 this voltage (or current)that provides all the subsequent elements of the device. With the photodetector signal is simultaneously supplied, in addition to the amplifier 5, the blocks determine the temperature 16 and roughness 17 (their structure, see, for example, respectively, in [8, 9]). The proposed detection voltage is used the principle of time-pulse conversion based on the conversion value of the measured voltage Ux from the output of the amplifier 5 in the time interval, with subsequent encoding of this interval by the method of successive bills in a bundle of impulses. The voltage Ux, by comparing its comparator 6 with linearly varying voltage U1 generator 9 (see Fig.2, oblique line; the horizontal line is the Ux)is converted into a pulse voltage U2 of duration ∆t, which is supplied to the circuit "And" 7, which is encoded in the bundle of short pulses of the pulse generator 10 is an exemplary frequency U3. Counting the number of pulses "n" in the stack is in LW the ranks of the pulse counter 11, where schemes "And" 7 signal U4:

n=∆t/To=Ux/CTo=foUo/C,

where C is the coefficient describing the rate of change of the voltage U(t), i.e. U1 in the oscillator ramp voltage 9;

Then, fo - period and frequency of the output voltage U3 of the pulse generator model frequency 10.

The equation shows that the number of pulses "n" is proportional to the voltage Ux from the amplifier 5. Choosing the proportionality coefficient fo/C=10m(m is an integer), you can get the readings of the voltages Ux in the required units of measure (V, mV, and so on). Then, in the decoder 12 this signal is detectable and supplied to the comparator (digital) 13, where at the same time with this signal receives signals from the device memory reference code 14 (previously removed from the standards of mechanical stress at different temperatures and the roughness of their surface). But before that, in the memory device 14 receives signals from blocks temperature 16 and roughness 17, which provide the comparator 13 reference signals obtained for the roughness and temperature, which has currently studied the surface. In the device 13 compares these signals, and when the signal from the decoder 12 will be equal or close to one of the reference signals from the memory device reference codes, the output of the comparator 13 on istwo indicating signal in the form of a voltage value indicating its type, for example, "10 PA compression" or "10 PA stretch" is displayed on the indicator.

The use of the claimed invention allows the use of the method of exposure of the surface being examined to determine the stress in its surface layer, and the area of this surface and any any range of measured voltages, with improved working conditions and increased productivity, you can create compact and light detection voltage, which could be used in any environment, including in the field, with disassembly and without disassembly of products (in working position).

Sources of information

1. A. C. the USSR №1566234 "Method of determination of residual stresses".

2. RF patent for the invention №2389988 "method of determining the mechanical stresses in steel structures".

3. GOST R 52731 - 2007. Non-destructive testing. Acoustic control method mechanical stresses. General requirements.

4. Lectures on FOPI file Fur e.g. power point, doc

5. I. C. Saveliev. The physics course. Tutorial in three volumes. Volume 2: Electricity. Oscillations and waves. Wave optics, third edition, stereotyped. - SPb.: DOE, 2007. - 480 S.

6. Leonid Baranak, Yuri Nepochatov. A holographic interferometer for determining the deformation fields of displacements in the microelectronics// Tehnologii electronic industry, No. 3, 2007.

7. Grigoryants A., fundamentals of laser material processing. - M.: Mashinostroenie, 1989. - S. 65.

8. RF patent №2445589 C1 "Method for measuring the surface temperature and the meter". Published: 20.03.2012. Bull. No. 8.

9. RF patent №2375677 C1 "roughness Meter". Posted: 10.12.2009. Bulletin no.34.

1. Non-destructive method of determining stress in a surface layer of a product that uses light radiation, characterized in that the test surface is directed emission of visible range in the form of a blurred stream of any radiation intensity and register values of the reflected stream using a photoelectric receiver, a comparison of this value with the reference value, obtained in advance for known values of mechanical stress, temperature and roughness in the surface layer, for a given radiation source.

2. The determinant voltage under item 1, using light radiation, characterized in that it contains a light emitter visible range, while the determiner further comprises a device defocus incident on the test surface of the beam and focusing reflected by this surface flow; a sensor of the reflected signal; the amplifier signal from the photodetector; a comparator that compares entering the voltage from the amplifier if ANO variable voltage generator generating a voltage pulse; scheme And encoding coming at it from a comparator pulse in a pack of short pulse generator model frequency; a binary pulse counter that counts pulses in a packet; a decoder pulses, and the unit for determining the temperature of the test surface, and the unit for determining the roughness of the test surface; the device memory reference code, where pre-recorded signals from known mechanical stresses, temperature and roughness of the test surface; a digital comparator performing a comparison of results obtained with the sample surface signal with the reference signals received at a known temperature and roughness; a display device, where the displayed voltage value of the test surface, and formed in the phototransistor signal enters the amplifier and simultaneously to the inputs of the blocks determine the temperature and roughness, from the output of the amplifier to the input of the comparator, and the comparator output to a schema And then to the input of a binary pulse counter, then to the input of the decoder, the output of the decoder is input to a digital comparator, where simultaneously the signal receives signals from the memory device reference codes, which receives signals from blocks of determining the temperature and roughness, ensuring the e issuance of reference codes for certain at this test temperature and roughness surface, and the output of the digital comparator is input to the display unit.



 

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5 cl, 1 dwg

FIELD: physics.

SUBSTANCE: optical fibre structure with Bragg lattices is put into composite material during production thereof. The spectral position of peaks of the Bragg lattices is measured after making the structure from the composite material and distribution of mechanical and thermal deformations inside the structure of the composite material is determined by solving the system of equations: , where f(T,ε) is the distribution function of mechanical and thermal deformations on the structure made from composite material (T is the temperature value, ε is the deformation value); f(Ex, y, z) is the distribution function of elastic properties of the structure made form composite material, Ex, y, z is the Young 's modulus tensor; f(αx, y, z, vx, y, z) is the distribution function of thermal characteristics of the composite material (αx, y, z is the coefficient of volume expansion tensor, vx, y, z is the thermal conductivity coefficient tensor);f(Fload, FT) is the distribution of mechanical and temperature effects on the structure made from composite material (Fload is the value of the mechanical effect, FT is the value of the temperature effect); fFBG(T,ε) is the function of total deformation on the path of the optical fibre with Bragg lattices (T is the temperature value, ε is the deformation value); fi-FBG(Δλ) is shift transformation function of the position of the i-th peak of the Bragg lattice to the temperature value and deformation (Δλ is the displacement of the peak of the Bragg lattice). The optical fibre contains two or more Bragg lattices which are not more than 5 mm long. The distance between the Bragg lattices and one optical fibre is not less than 5 mm.

EFFECT: high measurement accuracy.

3 cl, 15 dwg

FIELD: process engineering.

SUBSTANCE: glass fibre is introduced in composition used for forming controlled object as a material similar to that used as a filler for forming part carcass matrix, that glass fibre allows channeling light beam there through. Note here that glass fibre intact lengths, longer than said part, are used to be arranged to cross paths of probable defect development in part sections not subjected to processing. Occurrence of defect is detected by light beam passage or decreased in emergent light flux brightness.

EFFECT: efficient detection of defects.

6 cl, 1 dwg

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