RU2009479C1 - Non-destructive control method - Google Patents

Abstract

FIELD: non-destructive control. SUBSTANCE: relation between strength parameters and parameters of electric or sonic fields is chosen in form of coefficient of k-level of destruction; this coefficient is calculated according to equation given in the description of the invention. EFFECT: improved precision of measurement of carrying capacity of the item depending on level of destructions in the item. 1 cl, 4 cl, 2 dwg

Description

 The invention relates to non-destructive testing of the physical parameters of materials and can be used to determine the magnitude of the voltage in long rods or pipes such as cable cables or umbilicals, as well as for calibration of samples when assessing damage to materials during fatigue testing and for monitoring products in the process of perceiving dynamic loads .

 A known method of monitoring the product in the process of its production (implemented in the device) (1), based on non-destructive testing by the method of acoustic emission.

 Its disadvantages are the weakness of the emission signals compared with other noise levels in the deformable material, i.e., the poor noise immunity of the method, unreliable electro-acoustic contact of the sensors with the controlled product, i.e., a decrease in the reliability of control and the high complexity due to the need to use instead of one, several sensors to determine the coordinates of defects.

 A known method for detecting cracks in products (2), based on vibro-acoustic control of products having a reference plane. The method consists in securing the product along a plane of symmetry, exciting elastic vibrations in one part of the product with a shock, measuring the attenuation decrement of elastic vibrations, similar measurements are carried out at a symmetric point in the second part of the product, and decrements are compared.

 The disadvantages of this method are the mechanical excitation of vibrations in the product by impact, which is not always acceptable, can lead to surface violations of the products and the inability to establish the dependence of the bearing capacity of the product (or tensile strength) on the level of damage accumulated in it.

 A known method for determining the mechanical figure of merit of samples using ultrasonic vibrations (3), in which excite oscillations in the sample through the air layer, measure the after-sound time of the sample, select the thickness of the air layer, measure the decay time of the oscillations, which determine the mechanical figure of merit of the sample.

 The disadvantage of this method is the inability to accurately determine the location of the defect and identify the dependence of the bearing capacity of the sample on the level of damage accumulated in it.

 Closest to the invention is a method of non-destructive testing of products or samples (4), which consists in the fact that the strength properties are determined by a group of products or samples from a series, destroying some of them and applying mechanical load to the others, strength properties are determined before and after loading, simultaneously affect them with an acoustic field, measure parameter A (amplitude of echo pulses per loading cycle) corresponding to a specific load, establish the type of connection of the parameters of non-destructive testing and products Strength parameters or sample from the group is carried out non-destructive testing of a series of products by means of electric or acoustic fields, compared with the results of the control value calculated by the group of products, and by comparing the judge the controlled condition of the product or sample.

 In FIG. 1 and 2 show a diagram of the implementation of the method, respectively, by the echo method and the shadow method.

 The circuit contains a sample 1 with identified defects 2, ultrasonic transducers 3.4, a probe pulse generator 5, a synchronizer 6, a generator 7, an amplifier 8, and a recorder 9.

 The method is as follows.

Strength properties are determined by a group of products or samples from a series, in particular, the bearing capacity of a flat sample or tensile strength σ _{b are} determined from the level of damage accumulated in it.

, где Р_max - максимальное усилие, вызывающее разрыв образца,
F_о - начальная площадь поперечного сечения образца.σ $\genfrac{}{}{0ex}{}{\text{o}}{\text{b}}$ =

where P _max - the maximum force causing the rupture of the sample,
F _about - the initial cross-sectional area of the sample.

Then, a mechanical load (cyclic bending) is applied to the remaining samples and the strength is determined as a parameter A, for example, the amplitude of an ultrasonic signal with an echo or shadow control method:
σ _b = f (A).

 The specific nature of this relationship can be obtained in the test process.

k =

.In the simplest form, we obtain a linear dependence:
σ _b = σ _о - kA, where k is the coefficient determined experimentally

k =

.

Typically, the destruction of the samples is carried out after receiving σ _b .

или k =

П р и м е р. Металлические образцы по ГОСТ 1497-61 изготовленные для испытаний на растяжение или усталостные испытания сначала испытывают на разрыв и определяют при этом предел прочностиσ_b ^о усталостных дефектов. Например, берут пять образцов и один из них на разрывной машине разрывают, причем готовят к испытаниям и изготавливают четыре группы таких образцов из разных партий одного и того же материала (или из одной партии). Сечение образца должно быть плоским. На всех образцах размечают базу прозвучивания, длиной l, одинаковую для всех 20 штук образцов. Один из целых образцов в каждой из четырех групп используют для начальной настройки прибора ультразвукового контроля. Длина прозвучивания l была выбрана равной 100 мм. Полезный сигнал (амплитуда А) в пределах выбранного строб-импульса на этом образце равен нулю. В других образцах создаются усталостные дефекты, например, на машине ГМС-50 за пределами упругости образцов в средней части, в пределах базы прозвучивания при растяжении или испытании на усталость. Статической или циклической нагрузки подвергаются все 4 группы из 4 образцов, определенной для каждой группы базой циклов нагружения. В результате в одной и той же группе все образцы имеют одинаковый уровень повреждаемости. Образцы прозвучивают ультразвуковым дефектоскопом УД-10 на той же постоянной базе прозвучивания, где образуются усталостные дефекты. Образцы прозвучивают, определяется амплитуда А для каждого образца, затем они испытываются на разрыв и определяется σ_b. Результаты испытаний усредняются. По одному образцу из каждой группы (желательно со средним значением амплитуды) оставляют в качестве эталонных. При линейной зависимости, например: σ_b= σ_b ^о-kA коэффициент k для каждой группы образцов с разным уровнем повреждаемости должен быть одинаков. Геометрические размеры выявляемых дефектов определялись по искусственным дефектам (эталонным) с использованием АРД-диаграмм. Экспериментально находился закон изменения амплитуды в зависимости от роста дефектов.With a linear relationship, the coefficient k for each group of samples with different levels of damage should be the same. If not, then another dependence is sought - a parabola, for example: k =

or k =

PRI me R. Metal samples according to GOST 1497-61 made for tensile tests or fatigue tests are first tested for tensile strength and the tensile strength σ _b ^of fatigue defects is determined in this case. For example, five samples are taken and one of them is torn on a tensile testing machine, and they are prepared for testing and four groups of such samples are made from different batches of the same material (or from one batch). The cross section of the sample should be flat. On all samples, a sounding base, length l, is the same for all 20 pieces of samples. One of the whole samples in each of the four groups is used for initial tuning of the ultrasonic testing device. The sounding length l was chosen equal to 100 mm. The useful signal (amplitude A) within the selected strobe pulse on this sample is zero. In other samples, fatigue defects are created, for example, on a GMS-50 machine beyond the elasticity of the samples in the middle part, within the sounding base during tensile or fatigue tests. Static or cyclic loads are exposed to all 4 groups of 4 samples, defined for each group by the basis of loading cycles. As a result, in the same group, all samples have the same level of damage. Samples are sounded by an ultrasonic flaw detector UD-10 on the same constant sounding base, where fatigue defects are formed. Samples are sounded, amplitude A is determined for each sample, then they are tested for breaking and σ _{b is} determined. Test results are averaged. One sample from each group (preferably with an average amplitude) is left as a reference. With a linear relationship, for example: σ _b = σ _b ^о -kA, the coefficient k for each group of samples with different levels of damage should be the same. The geometric dimensions of the detected defects were determined by artificial defects (reference) using ARD diagrams. The law of amplitude variation was experimentally determined depending on the growth of defects.

 Similarly, tests are carried out using changes in the electrical resistance of the sample during deformation. In this case, it is possible to measure both the resistance by the direct method and the voltage based on the measurement using an E6-12 electronic milliometer.

 The method increases the accuracy of establishing the bearing capacity (or tensile strength) from the level of damage accumulated in it, allows you to determine the location of the defect, as well as to observe the sequence of development and the transition of one stage of destruction to another, to fix the threshold of destruction, that is, to predict the resource of products. (56) 1. USSR author's certificate N 1206685, cl. G 01 N 29/04, 1984.

 2. USSR author's certificate N 1228008, G 01 N 29/04, 1983.

 3. Copyright certificate of the USSR N 1229680, G 01 N 29/04, 1984.

 4. Proceedings of the 10th annual conference, vol. 3B, London New York, Santa Cruz, 1984, 1243-1250, translation of the MCP N M-33040 (prototype).

Claims (4)

1. The method of non-destructive testing of products or samples, which consists in the fact that the strength properties are determined by a group of products or samples with a flat section from a series, destroying some of them and applying a mechanical load to the others, strength properties are determined before and after loading, at the same time they affect them with an electric or acoustic field, measure the parameter A corresponding to a specific load, establish the type of connection of the parameters of non-destructive testing and strength parameters of the product or sample from g groups, conduct non-destructive testing of products from the series using an electric or acoustic field, compare the results of this control with the value calculated by the group of products, and according to the results of comparison judge the state of the controlled product or sample, characterized in that the relationship between the strength parameters and electric parameters or the acoustic field is selected in the form of a coefficient K of the damage level, which is calculated by the formulas
K =

, K =

or K =

/
where σ _in ^o -σ _in - the initial tensile strength and tensile strength after cyclic loading, respectively;
n = 1, 2, 3 - exponent.  2. The method according to p. 1, characterized in that a static load is applied to the samples or products.  3. The method according to claim 1, characterized in that a dynamic load is applied to the samples or products.  4. The method according to p. 1, characterized in that a cyclic load is applied to the samples or products.

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