Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
  • G01N29/04—Analysing solids
  • G01N29/12—Analysing solids by measuring frequency or resonance of acoustic waves
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01H—MEASUREMENT OF MECHANICAL VIBRATIONS OR ULTRASONIC, SONIC OR INFRASONIC WAVES
  • G01H13/00—Measuring resonant frequency

Definitions

• the present invention relates to a device for controlling defects in parts, in particular in foundry parts, metallurgy, etc., enabling the sorting of parts with excessively large defects at the end of production.
• the device controls material defects which have an influence on the elasticity of the material such as variations in the nodularity rate of spheroidal graphite cast irons or heat treatments, global geometry defects due for example to openings, wear or off-center molds, localized faults such as cracks, shrinkage, etc.
• resonance part control systems which use a hammer which strikes the part, the sound picked up by a microphone or by induction in a solenoid is then filtered to select one of the resonant frequencies from the set of frequencies. characteristics of the room, this frequency is then compared to a determined threshold.
• the resonant frequencies are a function of variables such as the characteristics of the material (coefficient of elasticity and density), the shapes or dimensions of the part and the point defects, a method like the one just described which n using only one of the resonance frequencies does not allow the different variables to be determined, since we obtain a single equation with several unknowns.
• the method which consists in exciting the part by shock to analyze its spectrum has the disadvantage of being difficult to implement in a workshop because the signal to be analyzed is greatly disturbed by words and ambient noises, and it is difficult to measure the frequencies of resonances at low overvoltage, because this technique would require an analysis of the signal by Fourier transform for example which would be long and expensive to obtain the required precision.
• the invention aims to provide an apparatus which overcomes the various aforementioned drawbacks, by successively exciting the different characteristic resonances of the part in order to measure the frequency and possibly the overvoltage and by processing the data collected which leads to obtaining the different characteristics of the part.
• the invention relates more specifically to a device for controlling defects in parts, in particular in foundry or metallurgical parts comprising a plurality of pairs of vibration exciter and vibration sensor emitted from a part whose frequencies it is appropriate to measure. sound resonance to assess the quality.
• FIG. 1 illustrates schematically an apparatus according to the invention
• FIG. 2 is a diagram illustrating a measurement generation circuit and treatment according to the invention.
• exciter and vibration sensor couples arranged near the part (1) to be checked, for example (EAl, M1 and EA2, M2).
• the exciters EA1, EA2 and the sensors M1, M2 are connected to a circuit (2) for generating measurement and processing.
• a circuit (2) for generating measurement and processing.
• only two exciter and sensor pairs are shown, which make it possible, for example, to measure the vertical vibration modes for EA2 and horizontal for EA1, but it is possible to extend the process by adding other couples to obtain rotational resonance modes for example.
• the part (1) is placed on a support (not shown), and preferably chosen from an elastic material which does not dampen vibrations, so that the position of the support with respect to the vibration nodes becomes less critical.
• the exciter EA1 and or EA2 is an electromagnet whose coil (3) is traversed by a current
• the vibration sensor M1 and or M2 is a microphone
• any other mechanical excitation device and any sensor vibration are suitable, especially since the exciter and the sensor do not use the same physical phenomenon to avoid direct coupling between the exciter and the sensor.
• a magnetic exciter and an electret microphone can be used.
• Each sensor M1 and or M2 is placed as close as possible to the exciter with which it is associated and in the same direction.
• the part (1) is used as an element for controlling the frequency of an oscillator whose frequency is measured.
• Two couples (EA1, M1) and (EA2, M2) are described here, but as already indicated above, this number of couples can be increased.
• this oscillator consists of the part (1) to be controlled (not shown in Figure 1), which behaves like a set of narrow bandwidth filters, which are stimulated in vibration at a given time at one of its frequencies, the vibration is picked up by one of the sensors (M1 or M2) selected by a selector SELE input (10) depending on whether the input terminal (a) where terminal (b) is selected.
• the output (50) of the SELE selector (10) is connected to a programmable FILT filter (20) whose bandwidth is sufficiently large compared to that of the part (1) so as not to influence the measurement.
• the output (51) of the filter (20) is connected to the input terminal (a) of the selector SELO (11) whose output (52) is connected to the input of a FILT filter (21) of the same type than that of the FILT filter (20).
• the output (53) of the FILT filter (21) is connected to the input of a DEPH programmable phase shifter (30), the output (54) of which is connected to an AMPL power amplifier (40) programmable in level.
• the output (55) of this amplifier is connected to the input of an SELS output selector (12) whose output terminal (a) is connected to the exciter EA1, the second output terminal (b) is connected to exciter EA2.
• a microcomputer (60) or microprocessor is connected in a conventional manner to the commands of the selectors SELE (10) and SELS (12) to choose one of the resonance modes, in our described example it allows to choose between the horizontal and vertical modes according to that the contacts (a) or (b) are closed.
• the microcomputer (60) is also connected to the programming commands of the FILT (20) and FILT (21) filters by the link (71), which makes it possible to select one of the frequencies from the set of frequencies in the room (1).
• the microcomputer (60) is connected to the phase control of the DEPH programmable phase shifter (30), by the control (72) which makes it possible to compensate for the phase shifts of the various elements of the chain, phase shifts caused in particular by the propagation time of the sound in the air, by the sensor and by the exciter concerned.
• a frequency meter (80) has its input connected for example to the output of the FILT filter (21) and its output (73) connected to the microcomputer (60).
• the microcaiculator (60) is connected (link 75) on the one hand to a digital analog DAC converter (90) whose output (74) is connected to the level control of the amplifier AMPL (40).
• this microcomputer (60) is connected to the output of an analog digital CAN converter (71) by the link (76), the input of which is connected to the output (51) of the first FILT filter (20). , which allows on the one hand to program a rapid rise in the vibration level by programming at the start of a measurement cycle a high amplitude of excitation, then when the vibration level of the part (1) measured by the CAN (91) is sufficient, the microcomputer (60) decreases the level of excitation.
• the command (77) of the SELO selector (11) is connected to the microcomputer (60). In Figure 2 this selector (11) is shown in closed position on the input terminal (a) which allows a looped chain to be obtained during the frequency measurement.
• the input terminal (b) of the SELO selector (11) is connected during this start-up phase to the output (53) of the filter.
• FILT (21) while terminal (a) is disconnected. Due to this operation the FILT filter (21) thus constitutes an oscillator whose amplified output signal will excite the part (1) and help the start of the oscillation. As soon as the level measured by the analog digital ADC converter (91) is sufficiently high, SELO (11) is returned to its first position. This operation avoids the use of an auxiliary generator. Both solutions can be both envisaged.
• the microcomputer (60) programs the successive frequencies as a function of the previously chosen modes of the FILT filters (20) and (21), the phase of the DEPH phase shifter (30) and makes the entry of the different resonance frequencies by the frequency counter (80) for the different pairs of exciter and sensor concerned. All the measurement results are then processed by the calculator using a mathematical model which is specific to each type or series of parts.
• This mathematical model was previously determined on a first batch of parts, the characteristic parameters of which are measured by usual methods, for example the elasticity coefficient, the weight, the localized defects.
• df1 to df4 represent the frequency deviations from the nominal frequencies of four resonance modes
• dE, dP, dD1, dD2 represent the deviations of the characteristics of a room
• the differences in the elastic modulus, the weight differences, a first localized defect, a second localized defect, all at a44 represent the coefficients of sensitivity of each characteristic of the part (1) for one resonant frequencies.
• the control device measures for each part (1), the resonance frequencies or the deviations df1 to df4, it uses the equation system (3) to obtain the characteristics dE, dP, dD1, dD2 which are compared to thresholds established at the request of the user to accept or refuse the part (1).

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• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Acoustics & Sound (AREA)
• Health & Medical Sciences (AREA)
• Life Sciences & Earth Sciences (AREA)
• Chemical & Material Sciences (AREA)
• Analytical Chemistry (AREA)
• Biochemistry (AREA)
• General Health & Medical Sciences (AREA)
• Immunology (AREA)
• Pathology (AREA)
• Measurement Of Mechanical Vibrations Or Ultrasonic Waves (AREA)
• Investigating Or Analyzing Materials By The Use Of Ultrasonic Waves (AREA)
• Testing Electric Properties And Detecting Electric Faults (AREA)
• Catching Or Destruction (AREA)
• Disinfection, Sterilisation Or Deodorisation Of Air (AREA)

Applications Claiming Priority (2)

Publications (1)

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• 1985
  • 1985-12-27 FR FR8519454A patent/FR2592481B1/fr not_active Expired
• 1986
  • 1986-12-26 JP JP62500404A patent/JPS63502137A/ja active Pending
  • 1986-12-26 WO PCT/FR1986/000447 patent/WO1987004250A1/fr not_active Ceased
  • 1986-12-26 US US07/098,622 patent/US4829823A/en not_active Expired - Lifetime
  • 1986-12-26 EP EP87900175A patent/EP0253829A1/fr not_active Withdrawn
• 1987
  • 1987-08-26 DK DK445187A patent/DK445187D0/da not_active Application Discontinuation

Non-Patent Citations (1)

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