Keywords

These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

1 Introduction

In present, one of the actual and most perspective directions for solution of scientific and applied problems of state diagnostics of construction materials and goods during their lifetime is the laser interferometry. Its methods allow one to study damage processes in novel materials and composites and register displacements of the control object surfaces by using high-accuracy contactless measurement means. This approach increase significantly a quality (accuracy) and information of analysis of the elastic wave fields at ultrasound defectoscopy, state diagnostics of materials and goods by using acoustic emission methods, etc., that is improve a quality and reliability of different machines and equipment.

The aim of this chapter is the development and scientific (calculations and experiments) grounds of perspective methods and means of contactless measurement of displacements of the control object surfaces. The results are directed to R&D of novel high-accuracy optic measurement technologies and corresponding technical means for state diagnostics of construction materials and goods during all stages of their lifetime (in manufacture and operation). These results are reached by using active and passive methods of non-destructive testing on the base of modern methods of the laser interferometry.

As a base device for solution the pointed problems, we select the two-way laser interferometer with combined branches (see Fig. 24.1). This interferometer includes optically coupled and consecutively located source 1 of coherent optical radiation, optical system 2, beam-splitter 3, reflector 4 fastened at surface 5 of a control object 6, and screen 7 on which are stated photo-detectors 10. The beam-splitter 3 and reflector 4 are situated one from other under angle α. Obtained in combination of reference beam 11 and object beam 12 the interference picture 8 presenting itself the set of rings 9 with various intensities projects on the screen 7, and the photo-detectors 10 are located into rings 9 of interference picture 8.

Fig. 24.1
figure 1

Typical schematic of two-way laser interferometer with combined branches

Full size image

The main directions for improvement of above two-way laser interferometer with combined branches were extension of its functional possibilities and using for solution of applied problems in the structure of mobile diagnostic systems.

2 Models, Methods and Measurement Means

2.1 Modeling Intensity of Optic Radiation in Interference Pictures

We have developed new mathematical models and program software for modeling intensity of optic radiation in interference pictures. These pictures are created by optic meter of displacements on the base of two-way laser interferometer with combined branches. In this case, it takes into account features of an optic measurement scheme and kind of beam-splitter, and also a technical solution (measurement device), ensuring the meter application at solution of scientific-technical problems.

Above results allow us to numerically model different optical schemes (defined by specific problem) of interference meters for contactless measurement of small displacements of the control object surfaces by using two-way laser interferometer with combined branches. This technical solution increases an accuracy of the measurement results during diagnostics of construction materials by acoustic non-destructive testing methods up to 30 % in dependence on used method of processing information, obtained from interference picture. It attains taking into account heterogeneities of distribution of the interference picture optical field.

Based on the proposed models and program software, we performed numerical modeling of intensity distributions of the interference picture optical fields. These results (see Figs. 24.2, 24.3, 24.4 and 24.5) have been obtained at registration of small displacements of the control object surfaces for various versions of optical measurement schemes and kinds of beam-splitters. As the beam-splitters, we considered a semitransparent mirror, amplitude sinusoidal grid, amplitude zone plate, phase sinusoidal grid, phase zone plate and amplitude holographic diffraction grid.

Fig. 24.2
figure 2

Distribution of intensity in horizontal section of interference picture (beam-splitter is the amplitude sinusoidal grid with parallel polarization)

Full size image
Fig. 24.3
figure 3

Distribution of intensity in horizontal section of interference picture (beam-splitter is the amplitude sinusoidal grid with perpendicular polarization)

Full size image
Fig. 24.4
figure 4

Distribution of intensity in horizontal section of interference picture (beam-splitter is the phase sinusoidal grid)

Full size image
Fig. 24.5
figure 5

Distribution of intensity in horizontal section of interference picture (beam-splitter is the phase zone plate)

Full size image

The computer simulation results agree well with the test results and operation data.

As an example, Fig. 24.6 presents the computer simulation results of dependencies of variation of the optic field intensity for interference picture in horizontal section for displacements \(h = 0\) (curve 1) and \(h = \lambda /4\) (curve 2) (where λ is the wavelength of optical radiation of the used laser) for beam-splitter in the form of diffraction grid displayed in contrary beams (a), and for beam-splitter in the form of semitransparent mirror (b). Figure 24.7 presents a scheme of meter of the small displacements with pointed area 11 for registration of optic field intensity of the interference picture.

Fig. 24.6
figure 6

Distribution of intensity in horizontal section of interference picture (beam-splitter is the phase zone plate)

Full size image
Fig. 24.7
figure 7

Scheme of meter of small displacements

Full size image

Above results have been published in necessary details in [1–17].

2.2 Method of Contactless Measurement of Small Linear and Angular Displacements

We have developed a novel method of contactless measurement of small linear and angular displacements of the control object surfaces, its theoretical and experimental grounds (mathematical model, program software, results of computer simulation, experimental means, test results, etc.) and technological solution (measurement method), ensuring its realization in solution of scientific-technical problems.

Essence of the proposed solutions consists in that as beam-splitter, it is used sinusoidal diffraction grid; maxima of +1 and −1 orders of interference picture are projected at the screen; the photo-detectors are divided into two groups and placed in areas of the maxima of +1 and −1 orders of the interference picture. The components of small displacement are defined on the base of two values of intensity, measured by using the photo-detector groups, applying dependencies known for each of the maximum. These dependencies couple the intensity with linear and angular displacements. As a result, there are used the values of linear and angular components of displacement, which satisfy simultaneously to the measured intensity at the maxima of +1 and −1 orders.

Significant difference of the technological solution, compared with known analogues, consists in ensuring of possibility of the simultaneous contactless registration of small linear and angular displacements of the control object surface by using only one optical meter. This allows one to extend considerably its functional possibilities.

Figure 24.8 presents optical scheme of the proposed technological solution, and Fig. 24.9 shows dependencies of intensity on linear and angular displacements of the control object surface at −1 (a) and +1 (b) maxima of interference picture (solid lines correspond to results of computer simulation and dotted lines show experimental results).

Fig. 24.8
figure 8

Optical scheme of the proposed technological solution

Full size image
Fig. 24.9
figure 9

Dependencies of intensity on linear and angular displacements of the control object surface at −1 (a) and +1 (b) maxima of interference picture (solid lines correspond to results of computer simulation and dotted lines show experimental results)

Full size image

Above results have been published in necessary details in [1, 13, 14, 16–22].

2.3 Under-Shining Method of Control Object Surface by Laser Interferometer

We have developed a novel method of contactless measurement of displacements of the control object surfaces, consisting in under-shining these surfaces by laser interferometer, its scientific theoretical and experimental grounds (mathematical model, program software, results of computer simulation, experimental means, test results, etc.) and technical solution (measurement device), ensuring its realization in solution of scientific-technical problems.

Essence of the proposed results consists in that the control object is placed after optical scheme, focusing optical radiation on the object surface in the form of a lighting point; beam-splitter, reflector and photo-detector are rigidly fasten on common base, supplied by the displacement mechanism. This mechanism is made with a possibility to increase (decrease) distance between the control object surface and external surface of beam-splitter at increasing (decreasing) a range of measured displacements.

Significant difference of the proposed solution from known analogues is a possibility to change a range of measured values of displacements of the control object surface during experiment without change a measurement scheme by way of alteration of the wave front curvature of the optical radiation reflected from the control object surface. This allows one to extend functional possibilities of the optical interference meter of displacements.

Figure 24.10 presents scheme of the proposed measurement device, and Fig. 24.11 demonstrate the obtained experimental dependence of sensitivity alteration on distance between surfaces of the control object and beam-splitter.

Fig. 24.10
figure 10

Scheme of the proposed measurement device

Full size image
Fig. 24.11
figure 11

Dependence of sensitivity on distance between surfaces of control object and beam-splitter

Full size image

Above results have been published in necessary details in [1, 23–28].

2.4 Method of Complex Correction of the Measurement Results of Displacements

We have developed a novel method of complex correction of the measurement results of displacements by using optical interference means, its scientific theoretical and experimental grounds (mathematical model, program software, results of computer simulation, experimental means, test results, etc.) and technical solution (measurement method), ensuring its realization in solution of scientific-technical problems.

The proposed results differ from known analogues that during measurement of displacements of the control object surface, it is registered simultaneously and continuously a summary intensity of optical field by using a square of interference picture, value of which introduces a correction to the measurement results. This allows one to carry out a correction of the measurement results, immediately during controlling process (in the same time scale) and increase an accuracy of the measurement results up to 20 % in dependence on excitation amplitude.

Figure 24.12 shows a device scheme realizing the proposed technological solution. Figure 24.13 demonstrates an experimental dependence of summary intensity of optical field of the interference picture during measurement of displacement of the control object surface (a) and results of direct measurement of displacement of the control object surface (b). The dotted line shows measurement results, and solid line corresponds to measurements after introducing the correction.

Fig. 24.12
figure 12

Scheme of device realizing the proposed method

Full size image
Fig. 24.13
figure 13

Results of measurements and processing

Full size image

Above results have been published in necessary details in [1, 29, 30].

2.5 Method of Increasing Vibro-stability of the Optical Interference Meter

We have developed a novel method of increasing vibro-stability of the optical interference meter based on using its own measurement possibilities, its scientific theoretical and experimental grounds (experimental means, test results, etc.) and technical solution (measurement device), ensuring its realization in solution of scientific-technical problems.

The proposed results differ from known analogues by continuous during measurement of displacements of the control object surface, the registration and compensation of influence of the external destabilizing effect (vibrations, impacts, etc.) on the measurement results. They allow increasing an accuracy of the measurement results up to 40 % in dependence of kind of the destabilizing influence.

Figure 24.14 presents a scheme of the proposed technical solution.

Fig. 24.14
figure 14

Scheme of device for measurement of small displacements of the control object surfaces, protected of external destabilizing influences

Full size image

Above results have been published in necessary details in [1, 31–33].

2.6 Measurement Devices Realizing the Optical Interference Measurement Methods

We have developed new scientific-grounded technical solutions (measurement devices), realizing the optical interference measurement methods of displacements of the control object surfaces (see Sects. 24.2.1–24.2.5), adapted for using in the structure of stationary and mobile diagnostic complexes.

These measurement devices allow us to ensure solution of measurement problems both as in laboratory conditions, as in “wild” conditions (mobile diagnostic complexes). By this, we reach complete preservation of functional possibilities of the methods, presented in Sects. 24.2.1–24.2.5, decreasing labor and time expenses on mounting and tuning at preparation of measurements and also during testing.

Figure 24.15 presents scheme of device for measurement of small displacements of the control object surfaces for mobile diagnostic complexes. Figure 24.16 shows scheme of device for measurement of small displacements of the control object surfaces for mobile diagnostic complexes with regulated range. Figure 24.17 demonstrates common form of experimental sample for measurement of small displacements of the control object surfaces.

Fig. 24.15
figure 15

Scheme of device for measurement of small displacements of the control object surfaces for mobile diagnostic complexes

Full size image
Fig. 24.16
figure 16

Scheme of device for measurement of small displacements of the control object surfaces for mobile diagnostic complexes with regulated range

Full size image
Fig. 24.17
figure 17

Common form of experimental sample of measurement device

Full size image

Above results have been published in necessary details in [9, 10, 31, 34–37].

3 Conclusions

The technical and technological solutions have been manufactured in the form of full-scale measurement means, experimental-measurement laboratory devices, demonstration models and used in solution of actual scientific and industrial problems for study of strength characteristics of construction materials, developments of novel methods for quality control of construction materials and goods. Moreover, the obtained results have been used for study of damage processes in high-temperature superconductive tapes [38–41].

These technical and technological solutions and also program software, presented in the chapter, have been awarded by 13 medals and main prizes of the following international salons and exhibitions: “Concours Lepine International Paris 2014”, “Inventions Geneva—2014”, “INVENTICA 2013–2015”, “TunisInnov—2014”, “Tesla Fest—2014”, “Archemede 2013–2014”.

Scientific novelty and significance of the obtained results are confirmed by the Russian patents and certificates on Russian state registration of programs for computer. Reliability of the obtained results is based on the performed modeling and study of functional characteristics of the technical and technological solutions, compared with known analogues.

The obtained results may be applied in high-accuracy measurements of small linear and angular displacements of the control object surfaces at experimental studies of perspective constructions, estimation of their state and diagnostics, investigation of acoustic-emission processes in solids, research of damage in novel materials, consideration of wave processes in layered constructions and anisotropic materials applied in different branches of industry.