Device for measuring the median radius of bubbles in a batch of foamed plaster

Abstract

The present invention relates to a method for determining the median radius R0 of a collection of bubbles contained in a foamed liquid medium suitable for curing and, after curing, for forming a solid construction material or a solid polymer foam. The method comprises the steps of transporting the foamed medium into a cavity, emitting an ultrasonic wave pulse towards the cavity, detecting the pulse, measuring a component selected from an amplitude of the detected pulse and a phase of the pulse, and then determining the median radius R0 of the bubbles in the foamed medium within the cavity from the determined component. Figure for the abstract: Fig. 1

Description

Title of the invention: Device for measuring the median radius of bubbles in a batch of foamed plaster. FIELD OF THE INVENTION

[0001] The present invention relates to the manufacture of a mix, more particularly a mix of foamed plaster. In particular, it relates to a method for determining the median radius of bubbles in a mix of foamed plaster, and a device for implementing such a method. STATE OF THE ART

[0002] The manufacture of plaster is energy-intensive, and it is desirable to reduce the energy required for this manufacture. To this end, it is known to increase the air volume fraction in the plaster by introducing air into a plaster mix in the form of bubbles. Thus, it is possible to reduce the amount of water used to produce a predetermined volume of plaster, and thereby reduce the total energy used to produce the mix.

[0003] However, since plaster is an opaque material, it is impossible to optically control the median radius of the bubbles formed inside the mix in a non-destructive manner. Nevertheless, it is necessary to control this median radius of the bubbles: indeed, this radius controls the mechanical characteristics of the plaster after the mix has set.

[0004] For this purpose, it is known to measure the median radius of air bubbles in a plaster mix or in plaster that has already set by X-ray tomography. However, this method is complex, expensive and does not allow for online measurements. Description of the invention

[0005] An object of the invention is to propose a solution to simplify a measurement of a median radius of a set of bubbles formed in a liquid medium with regard to a measurement carried out by X-ray tomography.

[0006] This objective is achieved within the framework of the present invention by means of a method for determining a median radius R0 of a collection of bubbles contained in a liquid foamed medium adapted to be hardened and to form, after hardening, a solid material for construction or a solid polymer foam, the foamed medium having a liquid phase and a gaseous phase formed by the collection of bubbles, and having a predetermined gas volume fraction q> of between 0.05 and 0.8 inclusive, the method comprising the steps of: a) transporting the foamed medium into a cavity, b) emission of an ultrasonic wave pulse towards the cavity by an ultrasonic wave pulse emitter, c) detection of the pulse by an ultrasonic wave pulse detector, d) determination from the pulse detected during step c) and a reference pulse of at least one element chosen from a transmission T of the pulse through the cavity and a reflection R of the pulse on a surface delimiting the cavity, e) Determination of the median radius R of the set of bubbles from the one(s) element(s) determined during step d) and the predetermined gas volume fraction q>.

[0007] The present invention is advantageously complemented by the following features, taken individually or in any of their technically possible combinations: - the foamed medium is non-transparent, - a predetermined gas volume fraction q> is in particular between 0.1 and 0.8 inclusive, and preferably between 0.15 and 0.7, - the cavity has a width l, and the emitter and detector are arranged on either side of the width l of the cavity so that the pulse propagates in the foamed medium along the width l of the cavity, and, in step d), the transmission T of the pulse through the cavity is determined, the method is adapted to determine a predetermined maximum median radius R Omax of the bubble set, and, during step b), the pulse is emitted at an emission frequency strictly greater than an allowed propagation frequency fpp equal to )' c° being the speed of the pulse in the liquid phase of the foamed medium, - the cavity has a width l, the emitter and the detector are arranged on either side of the width l of the cavity so that the pulse propagates in the foamed medium along the width l of the cavity, in step d), the transmission T of the pulse through the cavity is determined, the method is adapted to determine a predetermined maximum median radius R Omax of the bubble set, and, in step b), the pulse is emitted at an emission frequency strictly lower than a limiting sensitivity frequency / / s between 4.^q^ {IjtR} . and 10f / >r0) / (2,^^^et of “mPrise ““ 4^-0)cl 6- - the process lacks a step in which a pulse with a frequency lower than the allowed propagation frequency fpp is emitted, - the emission frequency is between 0.4 MHz and 56 MHz, - the cavity has a width l, and the emitter and detector are arranged on either side of the width l of the cavity so that the pulse propagates in the foamed medium along the width l of the cavity, during step d), the transmission T of the pulse through the cavity is determined, the width l being less than 5 mm, in particular 2 mm, and more preferably 0.8 mm, - in step e), the median radius R is determined from the gas volume fraction q, the component and the width l, - during step e), the median radius R is determined from an attenuation factor a representative of the attenuation of the pulse amplitude in the foamed medium along the width l, - during step a), a flow of the foamed medium is drawn into a channel comprising the cavity, and step b) emission and step c) detection are implemented during the flow, - the foamed medium comprises at least one element chosen from a foam and a mix, preferably at least one element chosen from a mix of plaster, a mix of cement, a mix of lime, a mix of mortar, a polyurethane foam and a polyisocyanurate foam, - in step b), the pulse has a duration between 0.03 ps and 10 ps, ​​- in step d), the component is determined from the beginning of the pulse up to a predetermined duration, the predetermined duration being preferably less than 5 ps, - the cavity has a width l, and the emitter and detector are arranged on either side of the width l of the cavity such that the pulse propagates along the width l of the cavity and in which the pulse is a longitudinal ultrasonic wave pulse, - the cavity has a width l, and the emitter and detector are arranged on either side of the width l of the cavity so that the pulse propagates in the foamed medium along the width l of the cavity. In step d), the transmission T of the pulse through the cavity is determined, and in step e), a magnitude of a complex transmission ITI of the pulse through the cavity is determined at least from the transmission T, and the median radius R0 is determined from the ratio defined by:

[0008] ___4___

[0009] A being a distance between 20 pm and 500 pm and in particular between 100 pm and 150 pm, B being a dimensionless number between 0.1 and 1 and in particular between 0.2 and 0.6, and gj being a function having variables the width l expressed in mm, the gas volume fraction q> and the modulus of the complex transmission ITl, the function g 7 is equal to

[0010] fyn\T\

[0011] E being a constant value preferably between 0.01 mm and 0.5 mm.

[0012] Another aspect of the invention is a device for determining a median radius Ro of a collection of bubbles contained in a liquid foam medium adapted to be cured and, after curing, to form a solid construction material or a solid polymer foam, the foam medium having a liquid phase and a gaseous phase formed by the collection of bubbles, and having a predetermined gas volume fraction q of between 0.05 and 0.8 inclusive, the device comprising: - a cavity adapted to receive the foam medium, - an ultrasonic wave pulse emitter arranged to emit an ultrasonic wave towards the cavity, - an ultrasonic wave pulse detector arranged to detect an ultrasonic wave pulse, and - a control unit configured to: determine, from a pulse detected by the detector and a reference pulse,at least one element chosen from a transmission T of the impulse through the cavity and a reflection R of the impulse on a surface delimiting the cavity, and to determine the median radius R of the set of bubbles from the determined element(s) and the predetermined gas volume fraction q.

[0013] Advantageously, the cavity has a width l, the transmitter and receiver are arranged on either side of the width l of the cavity so that the pulse propagates through the width l of the cavity, and the width l is preferably less than 5 mm, in particular 2 mm, and more preferably 0.8 mm.

[0014] Advantageously, the device includes a channel adapted for the flow of the foamed medium, the channel comprising the cavity.

[0015] Advantageously, the device is configured to measure a predetermined maximum median radius ROmax of the set of bubbles, the emitter comprising a first transducer extending along a length L in a direction perpendicular to a direction of pulse emission by the emitter, the length L being greater than 30.7 ROmax, preferably greater than 50. DESCRIPTION OF FIGURES

[0016] Other features, objectives and advantages of the invention will become apparent from the following description, which is purely illustrative and not limiting, and which should be read in conjunction with the accompanying drawings on which:

[0017] [Fig.1] - [Fig.1] schematically illustrates a process according to one embodiment of the invention,

[0018] [Fig.2] - [Fig.2] schematically illustrates a device according to one embodiment of the invention,

[0019] [Fig.3] - [Fig.3] illustrates a variation in the attenuation of an ultrasonic wave pulse transmitted through a cavity of a device, as a function of the pulse frequency,

[0020] [Fig.4] - [Fig.4] illustrates a variation of the real part of the natural logarithm of the transmission of a pulse through a cavity filled with a foamed medium comprising bubbles, as a function of the median radius of the bubbles,

[0021] [Fig.5] - [Fig.5] illustrates a device according to an embodiment of the invention adapted to allow the flow of the liquid medium into the cavity,

[0022] [Fig.6] - [Fig.6] illustrates a calibration of a device according to an embodiment of the invention.

[0023] Throughout the figures, similar elements bear identical reference numerals. DEFINITIONS

[0024] The term "non-transparent" means a foamed medium, arranged in a cavity of predetermined geometry, having a blur factor greater than 1%, in particular greater than 5% and preferably greater than 10%.

[0025] The term "blur factor" refers to the ratio between the intensity of a light beam scattered by passing through the medium (diffuse fraction) at an angle greater than 2.5° and the intensity of a light beam transmitted through the medium. The blur factor can be measured using spectroscopic techniques. Integrating the intensity over the entire visible range (from 380 nm to 780 nm) allows the determination of the normal transmission TL and the diffuse transmission Td. Such a measurement can also be obtained using a hazemeter.

[0026] The median radius R 0 of a set of bubbles is understood to be the median radius R 0 determined from a distribution of rays, the distribution being formed by the rays of each bubble in the set of bubbles.

[0027] Transmission T of a pulse is defined as a quantity determined from a pulse detected after propagation of the pulse through a predetermined quantity of a foamed medium in a cavity and from a reference pulse. Reflection R of a pulse is defined as a quantity determined from a pulse detected after reflection of the pulse on a surface delimiting the cavity and from a reference pulse.

[0028] Preferably, "complex transmission T" of a pulse transmitted through a predetermined quantity of a foamed medium in a cavity is understood to mean the ratio between the complex Fourier transform, at the emission frequency / , of the pulse transmitted through a cavity, for a cavity filled with the foamed medium, and between the Fourier transform at the frequency / ,, for a cavity filled with water. The transmission T and / or the reflection R of a pulse can be determined at 25°C.

[0029] In a system formed by a cavity of width Z, formed by a first material, and comprising the medium to be measured, the complex transmission T of a pulse can be the quantity defined by the formula described in the following equation (1): [°03°] T z &^ T = y---rf'W (z^+z)"

[0031] in which Z is the acoustic impedance of the measured medium, Zp is the acoustic impedance of the first material, Z0 is the impedance of the water in the cavity, k is the wavenumber for propagation of the pulse in the measured medium and k0 is the wavenumber for propagation of the pulse in the liquid phase of the measured medium.

[0032] The term "attenuation a" of a pulse propagating through a cavity of width l means the linear attenuation defined by a - -IM / / . Preferably, the attenuation is measured for a pulse propagating in the cavity filled with a bubble-free liquid medium identical to the liquid phase of the foamed medium.

[0033] The term "solid construction material" means any solid material suitable for the implementation of a construction project. A solid construction material may be plaster, mortar, lime, cement, concrete and / or render. DETAILED DESCRIPTION OF THE INVENTION

[0034] General principle for determining a median radius R0 of a set of bubbles 1

[0035] With reference to [Fig. 1] and [Fig. 2], one aspect of the invention is a method 100 for determining a median radius R0 of a set of bubbles 1 contained in a liquid foamed medium 2 suitable for hardening and for forming, after hardening, a solid construction material or a solid polymer foam. The foamed medium 2 may be a non-transparent medium, and in particular an opaque medium.

[0036] The foamed medium 2 has a liquid phase and a gaseous phase formed by the collection of bubbles. The foamed medium 2 has a predetermined gas volume fraction q> between 0.05 and 0.8 inclusive. It is possible to predetermine the gas volume fraction q> by mixing a predetermined volume of bubble-free liquid and a predetermined volume of gas. The predetermined gas volume fraction q> can be confirmed or determined by weighing the foamed medium after the gas has been introduced into the liquid.

[0037] The process 100 includes a step 101 of transporting the foamed medium 2 into a cavity 3. The cavity 3 is filled with the foamed medium 2. It is possible to take a sample of the foamed medium 2 and pour it into a cavity 3 so as to fill the cavity 3.

[0038] The method 100 includes a step 102 of emitting an ultrasonic wave pulse towards the cavity 3 by an ultrasonic wave pulse emitter 4. The ultrasonic wave pulse can then be transmitted through the cavity 3 or reflected by the cavity 3.

[0039] The method 100 includes a step 103 of detecting the pulse by an ultrasonic wave pulse detector 5.

[0040] The method 100 includes a determination step 104 from the pulse detected during step 103 and a reference pulse of at least one element chosen from a transmission T of the pulse through the cavity 3 and a reflection R of the pulse on a surface delimiting the cavity 3.

[0041] Following the determination step 104 of at least one element, the process 100 includes a determination step 105 of the median radius R of the bubble set 1 from the element(s) determined in step 104 and the predetermined gas volume fraction q>.

[0042] Thus, transmission of the pulse through cavity 3 or reflection of the pulse on cavity 3 stimulates the bubbles of the foamed medium 2, each bubble acting as a local acoustic diffuser. The detected pulse includes the contributions of each of the local diffusers formed by the bubbles, and the detection of the transmitted or reflected pulse allows the median radius Ro to be determined within the volume fraction range of 0.05 to 0.8. The measurement of the median radius of the bubbles is therefore simplified compared to a measurement performed by X-ray tomography.

[0043] Pulse emission frequency f T

[0044] The method 100 can be adapted to determine a predetermined maximum median radius ROmax of the bubble assembly. The cavity 3 can have a width l. The emitter 4 and the detector 5 can be arranged on either side of the width l of the cavity 3 so that the pulse propagates in the foamed medium 2 along the width l of the cavity 3. This configuration allows detection of the pulse by pulse transmission. With reference to Figure 3, during the emission step 102, the pulse can be emitted at an emission frequency fpp strictly greater than an allowed propagation frequency fpp. The frequency fpp is equal to fc0, where fp is the speed of the pulse in the liquid phase of the foamed medium 2, notably free of bubbles. Thus, it is possible to transmit The pulse is transmitted by propagation through the cavity. Indeed, for frequencies θ, lower than the allowed propagation frequency fpp, the pulse transmission is due to an evanescent regime in cavity 3. In the evanescent regime, the attenuation is very high compared to the attenuation in the propagation regime, making pulse detection impossible. For this reason, the frequency θ, can be higher than the frequency fpp.

[0045] The method 100 can be adapted to determine a maximum median radius less than 700 pm, in particular equal to 250 pm. For a maximum median radius ROmax equal to 250 pm and a gas volume fraction q > equal to 0.05, the permissible propagation frequency fpp is equal to 0.4 MHz. The emission frequency fpp can be greater than 0.4 MHz, in particular when the foamed medium 2 is a mix, in particular greater than 1 MHz and preferably greater than 4 MHz.

[0046] The method 100 can be adapted to determine a minimum median radius R Omm greater than 20 pm.

[0047] Fig. 3 illustrates the attenuation a of a pulse transmitted through the cavity 3 comprising a foamed medium 2 having a gaseous volume fraction q > equal to 0.35 and bubbles having a median radius R 0 equal to 75 pm.

[0048] With reference to Figure 4, the method 100 can be adapted to determine a predetermined maximum median radius R Omax of the bubble set 1. During the emission step 102, the pulse can be emitted at an emission frequency strictly lower than a sensitivity limit frequency, between ) e' J * preference between J and l(p7r.R{ )' Thus, it is possible to increase the sensitivity of the Determination of median radius R0 as the median radius R0 tends towards R0max. Indeed, the sensitivity of the detection of the median radius R0 is significantly higher for / , less than fL, than for / , greater than fis.

[0049] The sensitivity limit frequency / / can be between 2.5 MHz and 140 MHz and preferably between 3 MHz and 10 MHz.

[0050] The method 100 may be devoid of a frequency sweep. Indeed, detection of the pulse at a single frequency can allow the median radius R0 to be determined. The emitted pulse may exhibit a frequency spectrum centered on the emission frequency. The method 100 may be devoid of a step in which a pulse with a frequency lower than the allowed propagation frequency is emitted. Thus, the determination of the resonance frequency of the bubbles in a foamed medium can be avoided to determine the median radius R0, which makes it possible to accelerate and simplify the determination of the median radius R0 with respect to a process in which the acquisition of a frequency spectrum covering the resonance frequency of the foamed medium would be necessary.

[0051] Determination of the median radius R 0 from the element

[0052] The cavity 3 may have a width l, and the emitter 4 and the detector 5 may be arranged on either side of the width l of the cavity 3 so that the pulse propagates in the foamed medium 2 along the width l of the cavity. In step d), the transmission T of the pulse through the cavity 3 can be determined. In the determination step 105, the median radius R0 can be determined from the gas volume fraction q, the component, and the width l.

[0053] Preferably, the median radius R 0 can be determined by evaluating a radius determination function g dr having as variables the gas volume fraction q>, the width l, and the complex transmission T. The radius determination function g dr can have as a variable the modulus ITIdc the complex transmission.

[0054] The known independent scattering approximation model (ISA, described in the document Sheng P., 2006, Introduction to wave scattering, localization and mesoscopic phenomena, Vol. 88, Springer Science & Business Media) does not allow the determination of the median radius R 0 for a gas volume fraction q> greater than 2%.

[0055] To this end, the inventors have developed a phenomenological model from data comprising pairs associating the complex transmission T with the median radius R 0.

[0056] With reference to [Fig. 4], the median radius R0 can be determined from a predetermined function by a defined fit based on a set of element series, each element series comprising at least one predetermined median radius R0i and a complex transmission T associated with the median radius R0. Each series may also include a gas volume fraction q0 associated with the median radius R0i, and / or a width l associated with the median radius R0i. The predetermined median radius R0i can be obtained by various known types of measurements, such as optical measurement or X-ray tomography.

[0057] The median radius R 0 can be determined from the formula defined in the following equation 2:

[0058] Æ __A (2) 0

[0059] in which A is a distance between 20 pm and 500 pm, and in particular between 100 pm and 150 pm, B is a dimensionless number between 0.1 and 1, and in particular between 0.2 and 0.6, and gj is a function having variables the width l expressed in mm, the gas volume fraction q> and the modulus of the complex transmission ITI.

[0060] The function g can be defined as described in the following equation 3: [°061]

[0062] in which E is a constant value homogeneous to a distance, and preferably between 0.01 mm and 0.5 mm, and in particular between 0.070 mm and 0.090 mm.

[0063] The method 100 can be adapted to measure a median radius R0 between 20 pm and 120 pm, where A is equal to 120 pm, B is equal to 0.5 mm, and E is equal to 0.072 mm. Curve (a) in [Fig. 4] illustrates the variation of ILI for a model including these parameters.

[0064] The method 100 can be adapted to measure a median radius R0 between 50 pm and 200 pm, where A is equal to 110 pm, B is equal to 0.25 mm, and E is equal to 0.072 mm. Curve (b) in [Fig. 4] illustrates the variation of In ITI for a model including these parameters.

[0065] The determination of the median radius R0 can be implemented using an attenuation factor α representative of the linear attenuation of the pulse amplitude in the foamed medium 2. The phenomenological model developed can take into account the attenuation α of the pulse during its propagation in the cavity 3 filled with a bubble-free liquid medium identical to the liquid phase of the foamed medium. Each series used for determining the function predetermined by a fit can include the attenuation α. ​​The median radius R0 can be determined from the formula defined in the following equation 4:

[0066] R---A--- (4) U B-gJfpiTty

[0067] The function g 2 can be defined by the following equation 5:

[0068] g =^ln\T\+al

[0069] Architecture of the device 6 for determining the median radius R 0

[0070] With reference to [Fig.2], another aspect of the invention is a device 6 for determining the median radius R 0 of the set of bubbles 1 included in the foamed medium 2. The device 6 is adapted to implement the method 100.

[0071] Foamed medium 2

[0072] The foamed medium 2 is liquid and suitable for curing and, after curing, for forming a solid construction material or a solid polymer foam. The foamed medium 2 may be non-transparent, and preferably opaque. Indeed, the process 100 makes it possible to determine the median radius R0 of the set of bubbles 1 without that it is necessary to use the optical transmission properties of the foamed medium 2.

[0073] The predetermined gas volume fraction q> of the foamed medium 2 is between 0.05 and 0.8 inclusive, in particular between 0.1 and 0.8 inclusive and preferably between 0.3 and 0.8. Indeed, the process 100 makes it possible to measure media having very high predetermined gas volume fractions q> compared to the state of the art.

[0074] The foamed medium 2 may comprise a cement mix, a plaster mix, a lime mix, or a mortar mix. Thus, it is possible to control the median radius R0 of the bubbles 1 introduced into a mix so as to lighten the material formed by the solidified mix without degrading the mechanical performance of this material.

[0075] The foamed medium 2 can be produced by mixing water in a proportion of 3 / 7 and plaster in a proportion of 4 / 7 in a mechanical mixer (for example a Tefal brand blender, model BL305801), adjusting the volume of water and plaster relative to the total volume of the mixer so that the gaseous fraction is between 0.05 and 0.8.

[0076] The foamed medium 2 may comprise a polyurethane foam and a polyisocyanurate foam.

[0077] Cavity 3

[0078] The device 6 includes a cavity 3 adapted to receive the foamed medium 2. The cavity 3 may have a width l. The width l can be measured according to the direction of pulse propagation.

[0079] The emitter 4 and the receiver 5 can be arranged on either side of the width l of the cavity 3, so that the pulse propagates through the width l of the cavity 3, preferably in the foamed medium 2. The emitter 4 can include a first transducer 11. The receiver 5 can include a second transducer 12. The first transducer 11 can be arranged to emit a pulse in the direction of the second transducer 12.

[0080] The width l can be less than 5 mm, in particular less than 2 mm, and preferably less than 0.8 mm. Thus, it is possible to determine the median radius R o by acquiring a signal representative of a ballistic portion of the transmitted pulse. Indeed, for widths l greater than 5 mm, the signal acquired by the detector 5 is mainly representative of the superposition of several diffusion paths in the foamed medium 2, which is caused by a gaseous volume fraction between 0.05 and 0.8. This portion of the transmitted signal can be called the "coda". Due to a width l less than 5 mm, it is possible to acquire a portion of the transmitted signal devoid of the coda. This portion is also called the "ballistic portion". of the signal”. Only the ballistic part of the signal can be used to determine the median radius R 0.

[0081] Ultrasonic wave pulse emitter 4

[0082] The device 6 includes an ultrasonic wave pulse emitter 4 arranged to emit an ultrasonic wave towards the cavity 3.

[0083] The emitter 4 can be configured to emit a longitudinal ultrasonic wave pulse and / or a transverse ultrasonic wave pulse. During the pulse emission step 101, when the ultrasonic wave pulse is longitudinal, the method 100 can include a detection step 103 of the pulse propagated through the cavity 3. The detector 5 can then be arranged on the opposite side of the cavity 3 from the emitter 4. When the ultrasonic wave pulse is transverse, the method 100 can include a detection step 103 of the pulse reflected by the cavity 3. The detector 5 can then be arranged on the same side of the cavity 3 as the emitter 4.

[0084] The transmitter 4 may include a voltage generator 10. The first transducer 11 may be an immersion transducer. The first transducer 11 may be focused at infinity. The first transducer 11 may be, for example, a transducer of the V308-SU model from the registered trademark Olympus.

[0085] The device 6 can be configured to measure a predetermined maximum median radius ROmax of the bubble array, and the first transducer 11 can extend along a length L in a direction perpendicular to the direction of pulse emission from the transmitter 4. The length L can be greater than 3Q.ROmax, preferably greater than 50.ROmax. Thus, it is possible to increase the proportion of the ballistic portion of the pulse detected and reduce the proportion of the coda portion of the pulse detected. Indeed, a high length L of the first transducer 11 relative to the maximum radius ROmax of the bubbles allows for the averaging of signals, each carried by an individual scattering on a bubble. The predetermined maximum median radius ROmax can be equal to 300 pm, and the length L can be greater than 9 mm, and preferably greater than 15 mm.

[0086] The voltage generator 10 can be a high-voltage electrical pulse generator, configured to emit an electrical pulse with an amplitude greater than 50 V, in particular greater than 100 V and preferably greater than 400 V. The voltage generator 10 can be configured to emit an electrical pulse with a negative average voltage, so that the voltage of the electrical pulse is always negative. Thus, it is possible to counteract the attenuation of the pulse amplitude caused by transmission through cavity 3 or reflection from cavity 3, and thus enable pulse detection. by detector 5. The voltage generator 10 can be configured to emit an electrical pulse with a duration between 0.03 ps and 10 ps. The voltage generator 10 can be a JSR Ultrasonics DPR300 model generator.

[0087] Ultrasonic wave pulse detector 5 Device 6 includes an ultrasonic wave pulse detector 5 arranged to detect an ultrasonic wave pulse. Detector 5 may include a second transducer 12.

[0088] The emitter 4 and the detector 5 can be arranged on either side of the width l of the cavity 3 so that the pulse propagates in the foamed medium 2 along the width l of the cavity 3. This configuration corresponds to a measurement of the pulse transmitted through the cavity 3. The first transducer 11 and the second transducer 12 can be identical. The second transducer 12 can be a V308-SU model transducer from the registered trademark Olympus. The second transducer 12 can extend over a length L in a direction perpendicular to a direction of pulse emission from the emitter 4. The length L can be at least greater than 30 Ωmax, preferably greater than 50 Ωmax. Thus, it is possible to increase the proportion of the ballistic part of the pulse detected and to reduce the proportion of the coda of the pulse detected.

[0089] The emitter 4 and the detector 5 can be arranged on the same side of the cavity 3, so that the pulse is reflected by the cavity 3. This configuration corresponds to a measurement of the pulse by reflection on the cavity 3. During a measurement by reflection, the pulse does not propagate in the cavity 3, but the foamed medium 2 of the cavity 3 causes a modification of the signal reflected back to the detector 5. In this configuration, the first transducer 11 and the second transducer 12 can be the same transducer. The transducer can be directly connected to the control unit 7.

[0090] The detector 5 can also include an array of second transducers 12. Thus, it is possible to image the pulse propagated through the cavity 3. The array of second transducers can be a linear array in which the second transducers are arranged in a direction perpendicular to the width l.

[0091] Control Unit 7

[0092] The device 6 includes a control unit 7 configured to acquire at least one component selected from an amplitude of the pulse detected by the detector 5 and a phase of the pulse detected by the detector 5.

[0093] The control unit 7 is configured to determine, from a pulse detected by the detector 5 and a reference pulse, at least one element chosen from a transmission T of the pulse through the cavity 3 and a reflection R of the impulse on a surface delimiting cavity 3. The control unit 7 can also be configured to determine the module of the complex ITI transmission.

[0094] The control unit 7 is configured to determine the median radius R of the bubble set 1 from the determined element(s) and the predetermined gas volume fraction q. To this end, the control unit 7 can be configured to calculate the median radius R0 from the model described above. The control unit 7 may include at least one processor and at least one memory, enabling the calculation of the component and / or the median radius R0. The memory may include data representative of the reference pulse(s).

[0095] The control unit 7 can be connected to the detector 5, in particular to the second transducer 12 of the detector 5. The control unit 7 can be configured to control the voltage generator 10 of the transmitter 4. The control unit 7 can include a multiplexer for acquiring a signal associated with a pulse from the first transducer 11 and / or the second transducer 12.

[0096] During the determination step 104, the element can be determined from a signal representative of the beginning of the pulse up to a predetermined pulse duration. The predetermined duration can be less than 2(1 / / ,) and preferably less than (1 / / ,). Thus, it is possible to avoid taking into account any echoes of the pulse when determining the component. The control unit 7 can be configured to determine the median radius R0 from the component determined only from the beginning of the pulse up to the predetermined duration.

[0097] Flow of the foamed medium 2

[0098] With reference to [Fig.5], the device 6 may include a channel 8 adapted for a flow of the foamed medium 2. The channel 8 includes the cavity 3. The channel 8 may have a thinning along the main flow direction of the channel 8, a thinned portion of the channel forming the cavity 3.

[0099] During the transport 101 of the foamed medium 2 in the cavity 3, a flow of the foamed medium 2 can be drawn into the channel 8. Thus, it is possible to control the median radius of the bubbles R 0 of a foamed medium 2 during its production by diverting a sample of this foamed medium 2 towards the channel 8. The flow of the foamed medium 2 can be drawn by a flow generator 9.

[0100] The flow of the foamed medium 2 can be sequential. The flow is then distinct from the emission step 102, detection step 103.

[0101] The flow of the foamed medium 2 can be continuous. The emission 102 and the detection 103 are then implemented during the flow. Thus, it is possible to average the effect of bubbles on the diffusion of the pulse(s), which allows for an increase in the accuracy of the determination of the median radius R 0.

[0102] Calibration of device 6

[0103] With reference to [Fig. 6], the device 6 can be calibrated from median radius measurements Trx implemented by X-ray tomography. [Fig. 6] illustrates a calibration curve determined from the median radius measurements implemented by X-ray tomography and from the determination of the associated median radii for the same liquid media 2. The median radii are determined using the model described by the formulas of equations (2) and (3) previously described.

Claims

Demands

1. A method for determining a median radius R0 of a collection of bubbles (1) contained in a liquid foamed medium (2) suitable for curing and for forming, after curing, a solid construction material or a solid polymer foam, the foamed medium having a liquid phase and a gaseous phase formed by the collection of bubbles, and having a predetermined gas volume fraction q> between 0.05 and 0.8 inclusive, the method comprising the steps of: a) transporting the foamed medium (2) into a cavity (3), b) emitting an ultrasonic wave pulse towards the cavity (3) by an ultrasonic wave pulse emitter (4), c) detecting the pulse by an ultrasonic wave pulse detector (5),d) determination from the pulse detected in step c) and a reference pulse of at least one element chosen from a transmission T of the pulse through the cavity (3) and a reflection R of the pulse on a surface delimiting the cavity (3), e) determination of the median radius R of the set of bubbles (1) from the element(s) determined in step d) and the predetermined gas volume fraction q.

2. A method according to claim 1, wherein the cavity (3) has a width l, and wherein the emitter (4) and the detector (5) are arranged on either side of the width l of the cavity (3) so that the pulse propagates in the foamed medium (2) along the width l of the cavity (3), and wherein, in step d), the transmission T of the pulse through the cavity (3) is determined, the method being adapted to determine a predetermined maximum median radius R omax of the bubble set (1), wherein, in step b), the pulse is emitted at an emission frequency f, strictly greater than an allowed propagation frequency f pp equal to )' c° being the speed of the pulse in the liquid phase of the foamed medium (2).

3. A method according to claim 2, wherein the cavity (3) has a width l, and wherein the emitter (4) and the detector (5) are arranged on either side of the width l of the cavity (3) so that the pulse propagates in the foamed medium (2) the along the width l of the cavity (3), and wherein, in step d), the transmission T of the pulse through the cavity (3) is determined, the method being adapted to determine a predetermined maximum median radius R Omax of the bubble set (1), wherein, in step b), the pulse is emitted at an emission frequency strictly lower than a limiting sensitivity frequency f ls between 10(7^.co) / (2;^ and preferably between 4 and (2^AwJ'

4. A method according to claim 2 or 3, devoid of a step in which a pulse having a frequency lower than the allowed propagation frequency fpp is emitted.

5. A method according to any one of claims 2 to 4, wherein the emission frequency is between 0.4 MHz and 56 MHz.

6. A method according to any one of claims 1 to 5, wherein the cavity (3) has a width l, and wherein the emitter (4) and the detector (5) are arranged on either side of the width l of the cavity (3) so that the pulse propagates in the foamed medium (2) along the width l of the cavity (3), and wherein, at step d), the transmission T of the pulse through the cavity (3) is determined, the width l being less than 5 mm, in particular 2 mm, and more preferably 0.8 mm.

7. A method according to claim 6, wherein, in step e), the median radius R is determined from the gas volume fraction q, the component and the width l.

8. A method according to claim 7, wherein, in step e), the median radius R is determined from an attenuation factor a representative of the attenuation of the pulse amplitude in the foamed medium (2) along the width l.

9. A method according to any one of claims 1 to 8, wherein in step a), a flow of the foamed medium (2) is drawn into a channel (8) comprising the cavity (3), and preferably wherein the emission step b) and the detection step c) are carried out during the flow.

10. A method according to any one of claims 1 to 9, wherein the foamed medium (2) comprises at least one element selected from a foam and a mix, preferably at least one element chosen from a mix of plaster, a mix of cement, a mix of lime, a mix of mortar, a polyurethane foam and a polyisocyanurate foam.

11. A method according to any one of claims 1 to 10, wherein, at step b), the pulse has a duration between 0.03 ps and 10 ps.

12. A method according to any one of claims 1 to 11, wherein, in step d), the component is determined from the beginning of the impulse up to a predetermined duration, the predetermined duration being preferably less than 5 ps.

13. A method according to any one of claims 1 to 12, wherein the cavity (3) has a width l, and wherein the emitter (4) and the detector (5) are arranged on either side of the width l of the cavity (3) so that the pulse propagates along the width l of the cavity (3) and wherein the pulse is a longitudinal ultrasonic wave pulse.

14. Device (6) for determining a median radius R0 of a set of bubbles (1) contained in a liquid foamed medium (2) adapted to be cured and, after curing, to form a solid construction material or a solid polymer foam, the foamed medium having a liquid phase and a gaseous phase formed by the set of bubbles, and having a predetermined gas volume fraction q of between 0.05 and 0.8 inclusive, the device (6) comprising: - a cavity (3) adapted to receive the foamed medium (2), - an ultrasonic wave pulse emitter (4) arranged to emit an ultrasonic wave towards the cavity (3), - an ultrasonic wave pulse detector (5) arranged to detect an ultrasonic wave pulse, and - a control unit (7) configured to: determine, from a pulse detected by the detector (5) and a reference pulse,at least one element chosen from a transmission T of the impulse through the cavity (3) and a reflection R of the impulse on a surface delimiting the cavity (3), and for, determine the median radius R of the set of bubbles (1) from the determined element(s) and the predetermined gas volume fraction q>.

15. Device (6) according to claim 14, wherein the cavity (3) has a width l, the emitter (4) and the receiver (5) being arranged on either side of the width l of the cavity (3) so that the pulse propagates through the width l of the cavity (3), the width l being preferably less than 5 mm, in particular 2 mm, and more preferably 0.8 mm.

16. Device (6) according to claim 14 or 15, comprising a channel (8) adapted for the flow of the foamed medium (2), the channel (8) comprising the cavity (3).

17. Device (6) according to any one of claims 14 to 16, configured to measure a predetermined maximum median radius ROmax of the bubble set, the emitter (4) comprising a first transducer (11) extending along a length L in a direction perpendicular to a direction of pulse emission by the emitter (4), the length L being greater than 30ROmax and preferably greater than 50ROmax.

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