RU2069362C1 - Acoustic impedance method of inspection of soldered and adhesive joints of coverings with butt of honeycombs in single-side honeycomb structures - Google Patents

Abstract

FIELD: aerospace industry. SUBSTANCE: converter with contact tip which length of rod is found from condition $$$ is connected to known flaw detector. Configuration of tip of rod is made similar to configuration of cell of honeycomb unit but at angle to axis of rod. EFFECT: increased reliability of inspection of joints. 3 dwg

Description

 The invention relates to non-destructive testing methods and relates to quality control of soldered and adhesive fine-meshed honeycomb structures.

A known method of controlling the quality of soldered and adhesive joints of complex skin with the ends of the cells in one-sided honeycomb structures is that the cells are completely filled with a liquid having wettability with respect to the material of the walls of the cells, excite ultrasonic vibrations from the ends of the cells, take reflected vibrations, analyze them according to the results of the analysis of the quality of the compound [1]
The known solution has the following disadvantages.

 1. When controlling the quality of soldering according to this technical solution, the presence of a meniscus in the cellular capillaries is determined. In the absence of a meniscus, the amplitude of the reflected echo signals increases and non-drift is recorded, which leads to repacking of the products.

 2. In the process of soldering the honeycomb seals, it is possible to disconnect the walls of the honeycomb with solder while maintaining the meniscus in the cell capillaries. Thus, there is a violation of adhesion between the honeycomb and the substrate and the passage of poor-quality products into operation is possible.

A known impedance method for controlling the quality of soldered and adhesive joints of the skin with the ends of the cells in one-sided honeycomb structures is that the combined impedance transducer is pressed against the controlled object from the side of the honeycomb, excite elastic vibrations in the transducer-object system, measure the amplitudes or phase of the received signal and its value determines the defectiveness of the product [2]
The known solution has the following disadvantages.

 1. When controlling soldered honeycomb seals, the maximum thickness of the skin for an aluminum alloy can be 2 microns, for steel 1.5 mm. In this case, the minimum diameter of the detected defect is 30 mm, which significantly limits the scope of use of this technical solution.

 2. It is impossible to control honeycomb seals with complex geometry of the skin, since in order to perform the control, the working surface of the transducer must fit snugly against the skin.

 The objective of the present invention is to enable quality control of the connection of honeycomb structures with complex skin of any shape.

относительно плоскости сотоблока, возбуждают в системе преобразователь-объект упругие колебания, которые создают в сотоблоке возмущающие силы в двух взаимно перпендикулярных направлениях, измеряют амплитуду принятого сигнала и по ее величине определяют дефектность изделия.The problem is solved by implementing the proposed method, which consists in the fact that in the impedance method of controlling the quality of soldered and adhesive joints of the skin with the ends of the cells in homogeneous honeycomb structures, the combined impedance converter is pressed at an angle to the controlled object from the side of the honeycomb

relative to the plane of the honeycomb, elastic oscillations are excited in the transducer-object system, which create disturbing forces in the honeycomb in two mutually perpendicular directions, measure the amplitude of the received signal and determine the defectiveness of the product from its value.

 Compared with the known solutions, the proposed technical solution provides the ability to control the quality of the connection of honeycomb structures with complex skin of any section by creating disturbing forces in the honeycomb block in two mutually perpendicular directions and making it possible to measure the mechanical impedance from the cell block side.

на сотоблок 3 с обшивкой 4 таким образом, чтобы наконечник стержня был погружен в одну из ячеек сотоблока, и прижимается с силой

. Генератор импульсов импедансного дефектоскопа вырабатывает непрерывные синусоидальные электрические импульсы, которые при помощи излучающего пьезоэлемента преобразователя 1 преобразуются в акустические, вследствие чего в системе преобразователь-объект возникают упругие колебания, действующие на сотоблок с силой

.In FIG. 1 shows the implementation of the proposed control method using the proposed Converter. The converter 1, equipped with a contact tip 2, is installed at an angle

on the honeycomb 3 with the casing 4 so that the tip of the rod is immersed in one of the cells of the honeycomb, and is pressed with force

. An impedance flaw detector pulse generator generates continuous sinusoidal electrical pulses, which are converted into acoustic pulses by means of a transducing piezoelectric transducer 1 into acoustic pulses, as a result of which elastic vibrations arise in the transducer-object system, acting on the cell block with force

.

(см. фиг. 1). Очевидно, что если длина стержня обеспечивает его максимальный изгиб, то он осуществляется через время, соответствующее четверти периода распространения изгибных колебаний, т.е. τ₁= T/4=1/4f, где Т период распространения изгибных колебаний, f частота генерируемых звуковых колебаний. Тогда изгиб в противоположную сторону будет осуществляться позже на полупериод, т.е.

. С другой стороны, излучающий пьезоэлемент преобразователя в процессе генерации звуковых колебаний испытывает деформации растяжения-сжатия, т.к. генератор дефектоскопа вырабатывает синусоидальные сигналы. Благодаря возникающим колебаниям на сотоблок воздействуют упругие колебания в направлении оси преобразователя оси стержня контактного наконечника, которые в идеальном случае через некоторый промежуток времени τ_o совпадают по фазе с колебаниями стержня, и система преобразователь-сотоблок входит в автоколебательный режим. Таким образом, на сотоблок воздействует дополнительная сила

. Максимальной амплитуда колебаний, создаваемая этой силой, будет при максимальной деформации растяжения излучающего пьезоэлемента преобразователя, которая возникает через время Т/4. Значит, в момент времени τ₁ на сотоблок воздействуют силы

и

. Через полупериод на пьезоэлементе осуществляется деформация сжатия, что соответствует времени 3Т/4. Следовательно, в момент времени τ₁ и τ₂ на сотоблок воздействуют силы

.In addition, when sound waves pass through the rod of the contact tip 2, four types of waves appear in the rod: tensile-compression, torsional, longitudinal, radial and bending (see Bergman L. Ultrasound and its use in science and technology. M. Foreign literature, 1957, p. 342). It is obvious that the vibrations created in the rod by waves, the propagation of which is associated with a change in the size of the rod, have a relatively small amplitude, therefore it is proposed to consider only the bending vibrations of the rod. It is proposed to consider the perturbing forces arising in the block at different time instants τ. If we assume that at time t ₁ , the rod bends in one of the directions, it acts on the honeycomb with force

(see Fig. 1). Obviously, if the length of the rod provides its maximum bending, then it is carried out after a time corresponding to a quarter of the period of propagation of bending vibrations, i.e. τ ₁ = T / 4 = 1 / 4f, where T is the period of propagation of bending vibrations, f is the frequency of the generated sound vibrations. Then the bend in the opposite direction will be carried out later for a half-period, i.e.

. On the other hand, the transducer piezoelectric element in the process of generating sound vibrations experiences tensile-compression strains, because the flaw detector generator generates sinusoidal signals. Due to the vibrations that arise, the honeycomb is affected by elastic vibrations in the direction of the axis of the transducer of the axis of the rod of the contact tip, which ideally after a certain period of time τ _o coincide in phase with the vibrations of the rod, and the transducer-honeycomb system goes into self-oscillating mode. Thus, additional force acts on the honeycomb

. The maximum oscillation amplitude created by this force will be at the maximum tensile strain of the transducer emitting piezoelectric element, which occurs after T / 4. Hence, at time τ ₁ , forces act on the honeycomb

and

. After a half period, a compression deformation is carried out on the piezoelectric element, which corresponds to a time of 3T / 4. Therefore, at time τ ₁ and τ ₂ on the sotoblock forces act

.

, которые можно представить соответственно в виде горизонтальной и тангенциальной составляющих: в момент

, в момент

Таким образом, в моменты времени τ₁ и τ₂ на сотоблок воздействуют сдвиговые и тангенциальные колебательные силы. Очевидно, что при возможных других сочетаниях сил, действующих на сотоблок со стороны преобразователя, изменяется только абсолютная величина или направление колебательных сил. Погружение сотоблока под углом α = 90^° выбирается с целью устранения плотного прилегания сотоблока к обшивке за счет прижима преобразователя с силой

, что позволяет увеличить амплитуду колебаний сотоблока. Настройка дефектоскопа и контроль качества соединения сотоблока в обшивкой осуществляются по известной технологии (см. Ланге Ю.В. Контроль клеевых и паяных соединений в многослойных конструкциях акустическим импедансным дефектоскопом АД-40И. М. НИИинтроскопии, 1976, с. 9-15). Контроль проводится путем отдельных перестановок преобразователя вдоль поверхности сотоблока с шагом сканирования, который определяется в соответствии с минимальными размерами допустимого единичного дефекта. Для сравнения на фиг. 4 представлено аналогичное нагружение сотоблока известным совмещенным преобразователем. В этом случае воздействие на сотоблок осуществляется только за счет деформации растяжения-сжатия пьезоэлемента и в момент времени τ₁= T/4 представлено колебательной силой

, которую можно разложить на горизонтальную составляющую

и тангенциальную составляющую

. В момент времени

действие на сотоблок со стороны преобразователя осуществляется только за счет прижима с силой

. Далее предлагается сравнить амплитуды внешних сил, действующих на сотоблок, учитывая, что система преобразователь-сотоблок является автоколебательной. Со стороны преобразователя на сотоблок в общем случае действует внешняя сила

, изменяющаяся со временем по синусоидальному закону с частотой ω:

,
где F_o амплитуда внешней силы,
t время
(см. Кузмичев В.Е. Законы и формулы физики. Киев: Наукова думка, Киев, с. 354-355). Малые вынуждающие колебания описываются следующим дифференциальным уравнением:

где 2β=r/m, ω $\genfrac{}{}{0ex}{}{\text{2}}{\text{o}}$ = k/m, f_o= F_o/m,
r коэффициент сопротивления (вязкого трения) системы,
m масса колебательной системы,
К коэффициент квазиупругой силы (жесткость системы),
Х смещение,

скорость,

ускорение.In FIG. Figures 2 and 3 show the projections of the forces acting on the honeycomb at times τ ₁ and τ ₂ , as a result of which the resulting forces

which can be represented respectively in the form of horizontal and tangential components: at the moment

, in the moment

Thus, at time instants τ ₁ and τ _2, shear and tangential vibrational forces act on the honeycomb. Obviously, with other possible combinations of forces acting on the sotoblock from the converter side, only the absolute value or direction of the vibrational forces changes. The immersion of the honeycomb block at an angle α = 90 ^° is selected in order to eliminate the tight fit of the honeycomb block to the skin due to the pressure of the transducer with force

, which allows to increase the amplitude of the oscillations of the honeycomb. The flaw detector is set up and the quality control of the honeycomb connection in the casing is carried out according to the known technology (see Lange Yu.V. Adhesive and soldered joints in multilayer structures are controlled by the AD-40I acoustic impedance flaw detector. M. NIIintroskopiya, 1976, p. 9-15). The control is carried out by separate permutations of the transducer along the surface of the honeycomb with a scanning step, which is determined in accordance with the minimum dimensions of an allowable single defect. For comparison, in FIG. 4 shows a similar loading of a honeycomb block by a known combined transducer. In this case, the impact on the honeycomb is carried out only due to the tensile-compression strain of the piezoelectric element and at the time point τ ₁ = T / 4 is represented by the vibrational force

which can be decomposed into a horizontal component

and tangential component

. At time

the action on the sotoblock from the converter side is carried out only by pressing with force

. Further, it is proposed to compare the amplitudes of external forces acting on the honeycomb, given that the converter-honeycomb system is self-oscillating. On the converter side, an external force acts in general on the honeycomb

, which varies with time according to a sinusoidal law with a frequency ω:

,
where F _{o the} amplitude of the external force,
t time
(see Kuzmichev V.E. Laws and formulas of physics. Kiev: Naukova Dumka, Kiev, p. 354-355). Small driving vibrations are described by the following differential equation:

where 2β = r / m, ω $\genfrac{}{}{0ex}{}{\text{2}}{\text{o}}$ = k / m, f _o = F _o / m,
r coefficient of resistance (viscous friction) of the system,
m is the mass of the oscillatory system,
K coefficient of quasi-elastic force (system stiffness),
X offset

speed,

acceleration.

The solution of equation (1) has the form:
X = Acos (ωt-α) (2),
where A is the amplitude of the oscillatory system,
α is the angle by which the forced oscillations of the system lag behind the disturbing force in phase.

A F_o•C, где С const, т.к. для случая системы сотоблок-преобразователь k, m, ω, r - const.Equation (3) can be represented as:

AF _o • C, where C const, because for the case of a cell-to-converter system, k, m, ω, r is const.

, амплитуда колебаний сотоблока по вертикали

При нагружении сотоблока с помощью предлагаемого преобразователя в течение периода времени Т (см. фиг. 2, 3) амплитуда колебаний сотоблока в плоскости

амплитуда колебаний сотоблока по вертикали

На основании вышеизложенного можно сделать вывод, что амплитуда вынужденных колебаний сотоблока при его нагружении предлагаемым преобразователем значительно превосходит амплитуду вынужденных колебаний сотоблока при его аналогичном нагружении известным преобразователем. За счет нагружения сотоблока в двух взаимно перпендикулярных направлениях и значительного увеличения амплитуды колебаний сотоблока возрастает разница между амплитудой колебаний в дефектной и бездефектной зонах сотоблока, т.е. чувствительность контроля.When loading the honeycomb with a known transducer (see Fig. 4) during the period T, the amplitude of the oscillations of the honeycomb in the plane,

, the amplitude of the oscillations of the honeycomb vertically

When loading the honeycomb using the proposed Converter for a period of time T (see Fig. 2, 3) the amplitude of the oscillations of the honeycomb in the plane

the amplitude of the oscillations of the honeycomb vertically

Based on the foregoing, we can conclude that the amplitude of the forced oscillations of the honeycomb when it is loaded by the proposed converter significantly exceeds the amplitude of the forced oscillations of the honeycomb when it is similarly loaded by a known converter. Due to loading of the honeycomb in two mutually perpendicular directions and a significant increase in the amplitude of the vibrations of the honeycomb, the difference between the amplitude of vibrations in the defective and defect-free zones of the honeycomb increases, i.e. sensitivity control.

 Example. The study of the proposed technical solution was carried out for small-cell honeycomb seals in the ring blanks. The diameter of the cell was 0.8 mm, the height of the honeycomb was 10 mm, the width was 10 mm, and the cross section of the substrate was 5 mm. A corresponding sample was made on a full-scale part with a number of artificial defects. Defects were obtained as follows.

Before soldering the honeycomb block, through holes with a diameter of 4, 6, 8, 10 mm were drilled to the base in the ring. Nepropay defects were also laid in parallel by applying Ti ₂ C titanium carbide to the surface of the substrate in the form of round spots with a diameter of 4, 6, 8, 10 mm. The distance between single defects was chosen equal to 30 mm. Then, according to the known technology, the honeycomb was soldered in a substrate, and the solder was not filled onto a portion of the substrate free of single defects, the length of which was about 200 mm. The length of the soldered area was about 500 mm.

 For work, an AD-40I impedance acoustic flaw detector and a PADI-5 transducer (as having maximum sensitivity) with a contact tip according to the proposed technical solution were used. The refinement of the converter was carried out as follows.

 The transducer connected to the flaw detector was mounted vertically on the surface of the cell block, and a search was made for the resonant frequency of the system, which amounted to 3.5 kHz. Then, the contact tip made of corundum ceramic was removed from the converter. Weighing showed that its weight is 0.5 g; therefore, the total mass of the new contact tip should be 0.5 g. The diameter of the measuring piezoelectric element was 10 mm. For ease of manufacture, the contact tip was designed from CT20 with a round rod with a diameter of d 1.5 mm (see Fig. 5).

It is known that in round rods, ultrasonic bending vibrations propagate with speed (see Bergman L. Ultrasound and its application in technology. M. Foreign Literature, 1957, p. 342), where d is the diameter of the rod, f is the frequency of ultrasonic vibrations, E Young's model for bar material, ρ _{o the} density of the bar material.

Так как минимальные потери энергии колебаний стержнем обеспечиваются его минимальной длиной, было выбрано n 0, тогда

, где
d 1,5 мм 0,15 см,
f 3,5 кГц 3500 Гц,
Е 20,4•¹⁰ 2,04•10¹² дин/см²,
ρ_o 7,8 • 10³ кг/м³ 7,8 см³,
(см. Выборнов Б.И. Ультразвуковая дефектоскопия. М. Металлургия, 1985, с, 54).Since the length of the rod l is selected from the condition l = (2n + 1) λ / 4, we can write:

Since the minimum energy loss of vibrations of the rod is provided by its minimum length, n 0 was chosen, then

where
d 1.5 mm 0.15 cm
f 3.5 kHz 3500 Hz,
E 20.4 • ¹⁰ 2.04 • 10 ¹² dyne / cm ² ,
ρ _o 7.8 • 10 ³ kg / m ³ 7.8 cm ³ ,
(see. Vybornov B.I. Ultrasonic flaw detection. M. Metallurgy, 1985, p. 54).

.

.

Given the fact that the honeycomb is a round capillary, and to increase the manufacturability of control, the tip of the rod was designed in the form of a cone with a height of S 2 mm with an angle of inclination relative to the axis of the rod β 45 ^o .

объем конусной части стержня,

объем цилиндрической части стержня

,

С учетом того, что диаметр дискового элемента должен быть равен диаметру измерительного пьезоэлемента, был выбран D 10 мм и определено сечение дискового элемента

где m 0,5 г масса корундового контактного наконечника, которая соответствует массе инерционной нагрузки компенсационного пьезоэлемента.Thus, the mass of the rod was determined from the condition:
m ₁ = (V _к + V _у ) ρ, where, where

the volume of the conical part of the rod,

the volume of the cylindrical part of the rod

,

Considering that the diameter of the disk element must be equal to the diameter of the measuring piezoelectric element, D 10 mm was selected and the cross section of the disk element was determined

where m 0.5 g is the mass of corundum contact tip, which corresponds to the mass of the inertial load of the compensation piezoelectric element.

Изготовленный по соответствующим расчетам контактный наконечник при помощи эпоксидного клея приклеивался к измерительному пьезоэлементу преобразователя ПАДИ-5 взамен корундового наконечника. Затем исследовалась возможность контроля наличия непропая на описанном выше образце при помощи серийного преобразователя ПАДИ-5 (маркировка ПЭПОО) и ПАДИ-5 с контактным наконечником по предлагаемому техническому решению (маркировка ПЭП15) в комплекте с дефектоскопом АД-40И.

The contact tip, made according to the corresponding calculations, was glued to the measuring piezoelectric element of the PADI-5 transducer instead of corundum tip using epoxy glue. Then, the possibility of monitoring the presence of non-solder on the sample described above was investigated using the PADI-5 serial converter (PEPOO marking) and PADI-5 with a contact tip according to the proposed technical solution (PEP15 marking) complete with AD-40I flaw detector.

Flaw detector setup and sample control for each transducer were carried out in resonance mode using known technology. The scanning step was chosen equal to 5 mm. Using PEP00, the sample was controlled from the side of the substrate and the honeycomb with its vertical installation (α = 90 ^° ), as well as from the side of the honeycomb with the installation of PEP00 on its edge at an angle α = 30 ^° . Using PEP15, the sample was monitored from the side of the honeycomb with the PEP15 installation at an angle α = 30 ^° (see Fig. 1).

 Based on the analysis of the results obtained, it can be concluded that the proposed technical solution provides control of cell seals in one-sided honeycomb structures with maximum sensitivity.

Using the proposed technical solution will allow:
1) to control the quality of soldering of honeycomb structures with any cross-section of the substrate due to the creation of disturbing forces in the honeycomb in two mutually perpendicular directions;
2) to carry out quality control of the soldering of honeycomb structures with any configuration of the substrate due to the loading of honeycomb structures from the side of the honeycomb.

Claims (1)

The acoustic impedance method of controlling the quality of soldered and adhesive joints with the ends of the cells in one-sided honeycomb structures is that the combined impedance transducer is pressed against the controlled object, the object oscillates in the transducer system, the amplitude of the received signal is measured, and the defectiveness of the product is determined by its value, characterized in that the transducer is pressed against the part of the honeycomb structure at an angle α <90 ^° relative to its plane and to create a cellular structure zmuschayuschie forces in two mutually perpendicular directions.

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