rus
Issue #4/2021
O. A. Kryuchina, A. B. Lyukhter, V. I. Krivorotov, I. E. Sadovnikov, P. V. Beznosov, A. V. Lukonin
Comprehensive Assessment of the Operational Reliability of a Modular Cabin With Laser Radiation Active Protection
Comprehensive Assessment of the Operational Reliability of a Modular Cabin With Laser Radiation Active Protection
DOI: 10.22184/1993-7296.FRos.2021.15.4.282.295
The results of a comprehensive assessment of the operational reliability of a modular cabin with active protection against the effects of laser radiation are presented. The work was carried out in two stages. At the initial stage, a computational and experimental two-level technique was developed and implemented in practice, including, at the first level, determining the response time of the emergency protection system against laser radiation in a modular cabin with a continuous laser generator with a fiber optic system operating with a maximum power of 6 kW. At the second level, the stress state and bearing capacity of the elements of the modular cabin were assessed. The advantages of a modular cabin in terms of equipping with protection means are shown over protective cabins of a conventional (without active protection) design. At the final stage, after two-level studies, the reliability of the protection of the modular cabin from reflected and scattered radiation during laser technological processes was assessed.
The results of a comprehensive assessment of the operational reliability of a modular cabin with active protection against the effects of laser radiation are presented. The work was carried out in two stages. At the initial stage, a computational and experimental two-level technique was developed and implemented in practice, including, at the first level, determining the response time of the emergency protection system against laser radiation in a modular cabin with a continuous laser generator with a fiber optic system operating with a maximum power of 6 kW. At the second level, the stress state and bearing capacity of the elements of the modular cabin were assessed. The advantages of a modular cabin in terms of equipping with protection means are shown over protective cabins of a conventional (without active protection) design. At the final stage, after two-level studies, the reliability of the protection of the modular cabin from reflected and scattered radiation during laser technological processes was assessed.
Теги: diffusely scattered and reflected laser radiation; stressful con laser technological installations; modular cabins with active pr диффузно-рассеянное и отраженное лазерное излучение; напряженно лазерные технологические установки; модульные кабины с активной
Comprehensive Assessment of the Operational Reliability of a Modular Cabin With Laser Radiation Active Protection
O. A. Kryuchina1, A. B. Lyukhter2, V. I. Krivorotov1, I. E. Sadovnikov1, P. V. Beznosov1, A. V. Lukonin1
NTO IRE-Polyus LLC, Fryazino, Moscow region, Russia
Vladimir State University named after Alexander and Nikolay Stoletovs, Vladimir, Russia
The results of a comprehensive assessment of the operational reliability of a modular cabin with active protection against the effects of laser radiation are presented. The work was carried out in two stages. At the initial stage, a computational and experimental two-level technique was developed and implemented in practice, including, at the first level, determining the response time of the emergency protection system against laser radiation in a modular cabin with a continuous laser generator with a fiber optic system operating with a maximum power of 6 kW. At the second level, the stress state and bearing capacity of the elements of the modular cabin were assessed. The advantages of a modular cabin in terms of equipping with protection means are shown over protective cabins of a conventional (without active protection) design. At the final stage, after two-level studies, the reliability of the protection of the modular cabin from reflected and scattered radiation during laser technological processes was assessed.
Keywords: laser technological installations; modular cabins with active protection (MCAP); two-level research methodology; laser radiation emergency protection system (LREPS); high-power fiber lasers; direct, diffusely scattered and reflected laser radiation; stressful condition; load bearing capacity; reliability of cabin elements; protection against reflected and scattered radiation during laser technological processes; exposure from laser radiation; parameters of the light environment.
Received on: 20.03.2021
Accepted on: 24.05.2021
Introduction
One of the factors for the successful implementation of laser technological complexes and laser processing technologies in industrial production is the fulfillment of laser safety (LS) requirements prescribed by (domestic and world) regulatory documents. After the abolition of SN No. 5804-91 “Sanitary norms and rules for the construction and operation of lasers”, SanPiN 2.2.4.3359-16 “Sanitary and epidemiological requirements for physical factors at workplaces” and SP 2.2.2.1327-03 “Hygienic requirements for the organization of technological processes, production equipment and working tools “entered into force two new documents SanPiN 1.2.3685-21 “Hygienic standards and requirements for ensuring the safety and (or) harmlessness to humans of environmental factors” and SP 2.2.3670-20 “Sanitary and epidemiological requirements to working conditions”.
SanPiN 1.2.3685-21 contains only maximum permissible levels (MPL) for laser radiation. Until recently, the safe use of laser products was coordinated with representatives of Federal Service for the Oversight of Consumer Protection and Welfare (Rospotrebnadzor). SP 2.2.3670-20 give a link to a special assessment of working conditions, which is carried out by accredited organizations. Requirements for lasers in the document are specified in only one paragraph.
Basic requirements − for the design of laser products (interlocks, control panels, etc.), to the placement of laser products in the premises, to commissioning and operation of laser products; to the staff, to the use of personal protective equipment, to markings and warning signs − remained in the standards. In order to ensure safety and protection from possible harmful and dangerous factors at the workplaces of enterprises, organizational; technical; sanitary and hygienic and medical and preventive measures. The technical measures include, among other things, the design of protective equipment [1–7].
This paper presents the results of studies on assessing the effectiveness of means and methods of protection against laser radiation of personnel serving laser equipment when performing specific technological processes of laser processing. The object of this research and testing is a modular cabin with active protection (MCAP), which, in terms of equipping with protection means, has undoubted advantages over protective cabins (PC) of a conventional (without active protection) design.
Assessment of the operational reliability of a modular cabin with active protection
The assessment of the operational reliability of MCAP was carried out according to a specially developed calculation and experimental two-level technique [8]. At the first level of the methodology, by experimentally determining the time of the “actuation” of the laser radiation emergency protection system (LREPS) at the MCAP laser cladding equipment, the effectiveness of the emergency automatic shutdown of laser radiation was evaluated when a continuous laser generator with a fiber optic system with a maximum power of 6 kW was operating. At the second level, the effect of laser radiation on the structural and physicomechanical characteristics of the metal, the stress state, as well as the operational properties of MCAP elements was investigated. The structural technical solutions incorporated in the design and manufacture of MCAP were taken into account (Fig. 1). On one of the MCAP panels, highly sensitive sensors are fixed that react to laser radiation, which are the fundamental highly sensitive devices that determine the functional purpose and principle of operation of the LREPS, which are as follows. In the event of an accidental hit of a laser beam on any element of the cabin, the LREPS provides the formation of an emergency signal for switching off the laser radiation source to prevent the propagation of laser radiation (LR) beyond the safety barrier of the cabin. Sensitive elements of the sensor are embedded in the space between the double wall of the panel. When the LR hits the front wall of the panel, it heats up, followed by burning / destruction of the affected area. Reflected, diffusely scattered (re-reflected) LR, transmitted as a result of exposure to the inner surface of any of the panels, the spectrum of which falls within the sensitivity range of the applied photodiode (λ = 850–1 100 nm), is recorded by the LREPS module (Fig. 1). Thus, LREPS provides the formation of an emergency signal for switching off the laser radiation source, which excludes the propagation of LR outside the cabin [7, 9–11].
The tests were carried out according to the program regulating the order (sequence) of the tests in accordance with the selected experimental modes (table. one).
The criterion for a positive test result is the absence of a through hole in the back wall of the LREPS panel. Additionally, the results of the effect of the thermal effect of LR on the rear wall material were evaluated using an Olimpus GX optical microscope. The test results were documented in the form of a test report.
As a result of research and experiments, it was found that LREPS with a high degree of reliability performs an emergency disconnection of the laser generator from the mains supply for a specified minimum period of time and ensures the effectiveness of the MCAP application on serial laser processing complexes.
Reflected and diffusely scattered laser radiation is capable of penetrating into the space outside the PC through gaps, slots between posts, panels and other elements of it, which significantly reduces the level of protective properties of the cabin. Therefore, at the second stage of the methodology, along with evaluating the effectiveness of the “actuation” of active protection in the form of a LREPS, we studied the features of the impact of LR (direct and reflected) on the metal structural elements of the cabin to assess the degree of influence of thermal effects from LR on the stressed state of the metal structure of the protective door during a given estimated time of operation of the gearbox [12] .The specified assessment is necessary, first of all, to determine the indicators of the stress state, in order to exclude the impact of mechanical and thermal factors that cause the occurrence of residual deformations in the form of “leash”, “warping” and other macro- and micro-dimensional distortions and imperfections, reducing the effectiveness of the protective (operational) properties of individual assembly elements and the cabin as a whole. An increase in the level of stress in the metal structure of the cabin panels contributes to the appearance of shape distortions and loss of dimensions, the formation of gaps, cracks and other defects that significantly reduce the protective properties of the cabin [13–17].
To determine the stress state of the elements and MCAP as a whole, modern methods of non-destructive magnetometric testing, metallographic and structural analysis, statistical data processing, together with mechanical tests, hardness measurements, etc., were used [18–21]. The chemical composition of the metal of the MCAP panels was determined by the optical emission method on a Magellan Q‑8 analyzer.
To determine the localization of the laser action, the Hc values were measured on the inner (from the side of the sensor) and outer sides of the panel at pre-marked areas. The Hc values were used as a primary and reliable information parameter for the subsequent assessment of the stress state of the MCAP metal. After Hc measurements, samples were taken from the panel for further studies of the metallographic structure and stress state of the MCAP panels. The results of determining the chemical composition of the panel samples are presented in table. 2.
To determine the stress state and physical and mechanical properties of the rolled metal of the protective panel, the magnetometric method of measuring the values of the coercive force was used. It is known that there is a fairly stable relationship between the chemical composition of a ferromagnetic material, its mechanical properties, stress state and coercive force (Hc) [18, 22–25]. This makes it possible to carry out preliminary calculations of Нс and use the results obtained in the future as a reliable primary information parameter of the stressed state of elements and MCAP as a whole. Based on the results of mechanical tests for static tension of samples of thin-sheet metal rolling, a calibration graph was built (Fig. 2) for the subsequent determination of the stress state of panels and other elements of MCAP.
After the experiments on the operation of the LREPS, the values of Нс were measured for the elements of the cabin (panels, racks, etc.) and using a calibration schedule (Fig. 2) the level of acting stresses from thermal loads was determined. As a result, it was found that repeated exposure to laser radiation (direct, reflected and diffusely scattered) does not change the stress state of the elements, cabin panels and MCAP as a whole, to a critical value, at which the geometric dimensions of the cabin panels may be distorted, the formation of gaps, gaps between the panels, which means a decrease in its protective properties.
As a result of the studies carried out at the first stage, it was established by calculation and experiment:
LREPS provides “triggering” of sensors configured for emergency disconnection of the laser generator from the mains supply for a specified minimum period of time;
The thermal effect of LR on the structure, physical and mechanical properties of the metal and the stressed state of the investigated element of the protective cabin with the installed sensor sensitive to the LR effect does not reduce the performance of the sensor itself and the metal structure of the panel, which indicates the reliability of the cab protection system as a whole.
This testifies to the high functional reliability of the MCAP.
Evaluation of the efficiency of a modular cabin with active protection against reflected and scattered radiation
Any laser technological process is accompanied by concomitant factors arising from the interaction of LR with the material, for example, reflected and diffusely scattered LR; secondary radiation (SR) from the steam-plasma torch and the processed material; products of LR interaction with the processed material (vapors, aerosols), etc.
Therefore, at the final stage of research aimed at ensuring the requirements of the LS, the effectiveness of the protection of the MCAP from the factors arising from the laser technological process and the compliance with the fulfillment of these requirements was evaluated. This, in turn, necessitates the creation of an appropriate regulatory framework, harmonized with the standards of the European Union, with the introduction of mechanisms for the mutual recognition of certification results by national laboratories and certification centers. Currently, on the territory of the Russian Federation there are interstate standards (ie, standards in force in the CIS countries, etc.), the main object of standardization of which is LB [26–35].
In this work, a practical assessment of the protective properties of MCAP from accompanying laser and secondary radiation is carried out, which seems to be one of the important steps aimed at providing conditions for the industrial implementation of laser equipment and laser processing technologies.
Due to the lack of currently rigorous and standardized methods for measuring the irradiance of scattered and reflected LR in the process of laser processing, in practice, one has to face a number of questions and problems [36, 37]. This applies equally to not only methodological, but also metrological support of measurements [38,39]. Therefore, measurements of the scattered and reflected LR were carried out according to a program specially developed for this case. A laser dosimeter (LD) of the “LD‑07” model was used as the main device (Fig. 3). The dosimeter LD‑07 is included in the State Register of Measuring Instruments and is a portable device consisting of a photodetector unit (FPU) (Fig. 3–1) and a control and display unit (CUI) (Fig. 3–2). Measurement data are processed and displayed on the CUI liquid crystal display. The device provides:
Measurements of the maximum irradiance Emax from LR with a wavelength of λ = 1.07 μm can be carried out both when using FPU1 (Fig. 3–3) and using FPU2 (Fig. 3–4). To carry out measurements in real operating conditions of laser technological installations, the FPU2 device was selected.
The ARGUS series of devices allows measuring the energy characteristics of radiation in the range from 180 to 1 100 nm, as well as such parameters of the light environment as illumination and brightness.
To study UV radiation, radiometers are used: ARGUS‑04-1 (UV-A 315–400 nm) (Fig. 4); ARGUS‑05-1 (UV-B 280–315 nm); ARGUS‑06 / 1 (UV-C 180–280 nm). The measuring units of the instruments include ultraviolet photodetectors with a bias voltage supply device and specially designed light filters.
The increased brightness of the light and the blinding effect of the steam-plasma torch can also be attributed to the factors accompanying the laser technological process. To measure illumination and brightness, a luxmeter and a brightness meter are used, respectively [40].
Measurements of the energy characteristics of laser and secondary radiation in the framework of this study were carried out at the laser robotic complex No. 1 of the Laser Engineering Center (EC). In accordance with a specially developed test program, the following was carried out:
production control of the energy parameters of the reflected and scattered radiation during the development of laser welding technology;
determination of points with the maximum value of energy parameters.
The parameters (factors) measured in this study and their values are shown in Table 3.
Within the scope of the study, 9 series of measurements were carried out. As an example, this work presents the results of the first series of measurements. The measurements were carried out at an operating laser power of 2 500, 3 000, 4 000 and 5 000 W, three experiments for each power mode. The linear dimensions of the position of the control points were determined with a PLR25 laser rangefinder. When performing all experiments, we used individual (protective absorbing goggles (OZP)) and collective (protective cabin with active protection) protective equipment. The measurement scheme with indication of control points is shown in Fig. 5. The characteristics of the control points are presented in Table 4.
The values of the maximum permissible levels (MPL) of exposure from laser radiation in accordance with regulatory documents (with a duration of exposure tв нп = 8.5 s) are presented in Table 5.
The results of measurements of the maximum irradiance from laser radiation and comparison with the remote control are presented in table 6, the readings of ARGUS devices are presented in Table 7.
From the data table. 6–7 it follows that when the laser robotic complex No. 1, equipped with a protective cabin, operates in the studied power range (2 500, 3 000, 4 000 and 5 000 W), LR is safe with a single exposure to the eyes and skin. However, the use of personal protective equipment (glasses and overalls) for the personnel serving the laser complex is a mandatory requirement to ensure safe work at the complex.
Conclusion
As a result of a computational and experimental study of the data obtained in this work on assessing the effectiveness of protection of MCAP equipped with LREPS, as well as determining the degree of danger of LR during the operation of the laser robotic complex No. 1, it was established:
LREPS provides “triggering” of sensors configured for emergency disconnection of the laser generator from the mains supply for a specified minimum period of time;
The thermal effect of LR on the structure, physical and mechanical properties of the metal and the stressed state of the investigated element of the protective cabin with the installed sensor sensitive to the LR effect does not reduce the performance of the sensor itself and the metal structure of the panel, which indicates the reliability of the cab protection system as a whole.
When operating the laser robotic complex No. 1, equipped with a protective cabin in the studied power range (2 500, 3 000, 4 000 and 5 000 W), LR is safe with a single exposure to the eyes and skin.
The use of personal protective equipment (glasses and overalls) for personnel serving the laser complex is a mandatory requirement to ensure safe work at the complex.
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ABOUT AUTHORS
O. A. Kryuchina, NTO IRE-Polyus LLC, oKryuchina@ntoire-polus.ru, Fryazino, Moscow region, Russia.
ORCID ID No. 0000-0001-7592-0790
A. B. Lyukhter, Vladimir State University named after Alexander and Nikolay Stoletovs, 3699137@mail.ru, Vladimir, Russia
V. I. Krivorotov, NTO IRE-Polyus LLC, vKrivorotov@ntoire-polus.ru, Fryazino, Moscow region, Russia.
I. E. Sadovnikov, NTO IRE-Polyus LLC, iSadovnikov@ntoire-polus.ru, Fryazino, Moscow region, Russia.
ORCID ID No. 0000-0002-7576-6591
P. V. Beznosov, NTO IRE-Polyus LLC, pbeznosov@ntoire-polus.ru, Fryazino, Moscow region, Russia.
A. V. Lukonin, NTO IRE-Polyus LLC, aLukonin@ntoire-polus.ru, Fryazino, Moscow region, Russia.
Contribution by the members
of the team of authors
The article was prepared on the basis of many years of work by all members of the team of authors.
Conflict of interest
The authors claim that they have no conflict of interest. All authors took part in writing the article and supplemented the manuscript in part of their work.
O. A. Kryuchina1, A. B. Lyukhter2, V. I. Krivorotov1, I. E. Sadovnikov1, P. V. Beznosov1, A. V. Lukonin1
NTO IRE-Polyus LLC, Fryazino, Moscow region, Russia
Vladimir State University named after Alexander and Nikolay Stoletovs, Vladimir, Russia
The results of a comprehensive assessment of the operational reliability of a modular cabin with active protection against the effects of laser radiation are presented. The work was carried out in two stages. At the initial stage, a computational and experimental two-level technique was developed and implemented in practice, including, at the first level, determining the response time of the emergency protection system against laser radiation in a modular cabin with a continuous laser generator with a fiber optic system operating with a maximum power of 6 kW. At the second level, the stress state and bearing capacity of the elements of the modular cabin were assessed. The advantages of a modular cabin in terms of equipping with protection means are shown over protective cabins of a conventional (without active protection) design. At the final stage, after two-level studies, the reliability of the protection of the modular cabin from reflected and scattered radiation during laser technological processes was assessed.
Keywords: laser technological installations; modular cabins with active protection (MCAP); two-level research methodology; laser radiation emergency protection system (LREPS); high-power fiber lasers; direct, diffusely scattered and reflected laser radiation; stressful condition; load bearing capacity; reliability of cabin elements; protection against reflected and scattered radiation during laser technological processes; exposure from laser radiation; parameters of the light environment.
Received on: 20.03.2021
Accepted on: 24.05.2021
Introduction
One of the factors for the successful implementation of laser technological complexes and laser processing technologies in industrial production is the fulfillment of laser safety (LS) requirements prescribed by (domestic and world) regulatory documents. After the abolition of SN No. 5804-91 “Sanitary norms and rules for the construction and operation of lasers”, SanPiN 2.2.4.3359-16 “Sanitary and epidemiological requirements for physical factors at workplaces” and SP 2.2.2.1327-03 “Hygienic requirements for the organization of technological processes, production equipment and working tools “entered into force two new documents SanPiN 1.2.3685-21 “Hygienic standards and requirements for ensuring the safety and (or) harmlessness to humans of environmental factors” and SP 2.2.3670-20 “Sanitary and epidemiological requirements to working conditions”.
SanPiN 1.2.3685-21 contains only maximum permissible levels (MPL) for laser radiation. Until recently, the safe use of laser products was coordinated with representatives of Federal Service for the Oversight of Consumer Protection and Welfare (Rospotrebnadzor). SP 2.2.3670-20 give a link to a special assessment of working conditions, which is carried out by accredited organizations. Requirements for lasers in the document are specified in only one paragraph.
Basic requirements − for the design of laser products (interlocks, control panels, etc.), to the placement of laser products in the premises, to commissioning and operation of laser products; to the staff, to the use of personal protective equipment, to markings and warning signs − remained in the standards. In order to ensure safety and protection from possible harmful and dangerous factors at the workplaces of enterprises, organizational; technical; sanitary and hygienic and medical and preventive measures. The technical measures include, among other things, the design of protective equipment [1–7].
This paper presents the results of studies on assessing the effectiveness of means and methods of protection against laser radiation of personnel serving laser equipment when performing specific technological processes of laser processing. The object of this research and testing is a modular cabin with active protection (MCAP), which, in terms of equipping with protection means, has undoubted advantages over protective cabins (PC) of a conventional (without active protection) design.
Assessment of the operational reliability of a modular cabin with active protection
The assessment of the operational reliability of MCAP was carried out according to a specially developed calculation and experimental two-level technique [8]. At the first level of the methodology, by experimentally determining the time of the “actuation” of the laser radiation emergency protection system (LREPS) at the MCAP laser cladding equipment, the effectiveness of the emergency automatic shutdown of laser radiation was evaluated when a continuous laser generator with a fiber optic system with a maximum power of 6 kW was operating. At the second level, the effect of laser radiation on the structural and physicomechanical characteristics of the metal, the stress state, as well as the operational properties of MCAP elements was investigated. The structural technical solutions incorporated in the design and manufacture of MCAP were taken into account (Fig. 1). On one of the MCAP panels, highly sensitive sensors are fixed that react to laser radiation, which are the fundamental highly sensitive devices that determine the functional purpose and principle of operation of the LREPS, which are as follows. In the event of an accidental hit of a laser beam on any element of the cabin, the LREPS provides the formation of an emergency signal for switching off the laser radiation source to prevent the propagation of laser radiation (LR) beyond the safety barrier of the cabin. Sensitive elements of the sensor are embedded in the space between the double wall of the panel. When the LR hits the front wall of the panel, it heats up, followed by burning / destruction of the affected area. Reflected, diffusely scattered (re-reflected) LR, transmitted as a result of exposure to the inner surface of any of the panels, the spectrum of which falls within the sensitivity range of the applied photodiode (λ = 850–1 100 nm), is recorded by the LREPS module (Fig. 1). Thus, LREPS provides the formation of an emergency signal for switching off the laser radiation source, which excludes the propagation of LR outside the cabin [7, 9–11].
The tests were carried out according to the program regulating the order (sequence) of the tests in accordance with the selected experimental modes (table. one).
The criterion for a positive test result is the absence of a through hole in the back wall of the LREPS panel. Additionally, the results of the effect of the thermal effect of LR on the rear wall material were evaluated using an Olimpus GX optical microscope. The test results were documented in the form of a test report.
As a result of research and experiments, it was found that LREPS with a high degree of reliability performs an emergency disconnection of the laser generator from the mains supply for a specified minimum period of time and ensures the effectiveness of the MCAP application on serial laser processing complexes.
Reflected and diffusely scattered laser radiation is capable of penetrating into the space outside the PC through gaps, slots between posts, panels and other elements of it, which significantly reduces the level of protective properties of the cabin. Therefore, at the second stage of the methodology, along with evaluating the effectiveness of the “actuation” of active protection in the form of a LREPS, we studied the features of the impact of LR (direct and reflected) on the metal structural elements of the cabin to assess the degree of influence of thermal effects from LR on the stressed state of the metal structure of the protective door during a given estimated time of operation of the gearbox [12] .The specified assessment is necessary, first of all, to determine the indicators of the stress state, in order to exclude the impact of mechanical and thermal factors that cause the occurrence of residual deformations in the form of “leash”, “warping” and other macro- and micro-dimensional distortions and imperfections, reducing the effectiveness of the protective (operational) properties of individual assembly elements and the cabin as a whole. An increase in the level of stress in the metal structure of the cabin panels contributes to the appearance of shape distortions and loss of dimensions, the formation of gaps, cracks and other defects that significantly reduce the protective properties of the cabin [13–17].
To determine the stress state of the elements and MCAP as a whole, modern methods of non-destructive magnetometric testing, metallographic and structural analysis, statistical data processing, together with mechanical tests, hardness measurements, etc., were used [18–21]. The chemical composition of the metal of the MCAP panels was determined by the optical emission method on a Magellan Q‑8 analyzer.
To determine the localization of the laser action, the Hc values were measured on the inner (from the side of the sensor) and outer sides of the panel at pre-marked areas. The Hc values were used as a primary and reliable information parameter for the subsequent assessment of the stress state of the MCAP metal. After Hc measurements, samples were taken from the panel for further studies of the metallographic structure and stress state of the MCAP panels. The results of determining the chemical composition of the panel samples are presented in table. 2.
To determine the stress state and physical and mechanical properties of the rolled metal of the protective panel, the magnetometric method of measuring the values of the coercive force was used. It is known that there is a fairly stable relationship between the chemical composition of a ferromagnetic material, its mechanical properties, stress state and coercive force (Hc) [18, 22–25]. This makes it possible to carry out preliminary calculations of Нс and use the results obtained in the future as a reliable primary information parameter of the stressed state of elements and MCAP as a whole. Based on the results of mechanical tests for static tension of samples of thin-sheet metal rolling, a calibration graph was built (Fig. 2) for the subsequent determination of the stress state of panels and other elements of MCAP.
After the experiments on the operation of the LREPS, the values of Нс were measured for the elements of the cabin (panels, racks, etc.) and using a calibration schedule (Fig. 2) the level of acting stresses from thermal loads was determined. As a result, it was found that repeated exposure to laser radiation (direct, reflected and diffusely scattered) does not change the stress state of the elements, cabin panels and MCAP as a whole, to a critical value, at which the geometric dimensions of the cabin panels may be distorted, the formation of gaps, gaps between the panels, which means a decrease in its protective properties.
As a result of the studies carried out at the first stage, it was established by calculation and experiment:
LREPS provides “triggering” of sensors configured for emergency disconnection of the laser generator from the mains supply for a specified minimum period of time;
The thermal effect of LR on the structure, physical and mechanical properties of the metal and the stressed state of the investigated element of the protective cabin with the installed sensor sensitive to the LR effect does not reduce the performance of the sensor itself and the metal structure of the panel, which indicates the reliability of the cab protection system as a whole.
This testifies to the high functional reliability of the MCAP.
Evaluation of the efficiency of a modular cabin with active protection against reflected and scattered radiation
Any laser technological process is accompanied by concomitant factors arising from the interaction of LR with the material, for example, reflected and diffusely scattered LR; secondary radiation (SR) from the steam-plasma torch and the processed material; products of LR interaction with the processed material (vapors, aerosols), etc.
Therefore, at the final stage of research aimed at ensuring the requirements of the LS, the effectiveness of the protection of the MCAP from the factors arising from the laser technological process and the compliance with the fulfillment of these requirements was evaluated. This, in turn, necessitates the creation of an appropriate regulatory framework, harmonized with the standards of the European Union, with the introduction of mechanisms for the mutual recognition of certification results by national laboratories and certification centers. Currently, on the territory of the Russian Federation there are interstate standards (ie, standards in force in the CIS countries, etc.), the main object of standardization of which is LB [26–35].
In this work, a practical assessment of the protective properties of MCAP from accompanying laser and secondary radiation is carried out, which seems to be one of the important steps aimed at providing conditions for the industrial implementation of laser equipment and laser processing technologies.
Due to the lack of currently rigorous and standardized methods for measuring the irradiance of scattered and reflected LR in the process of laser processing, in practice, one has to face a number of questions and problems [36, 37]. This applies equally to not only methodological, but also metrological support of measurements [38,39]. Therefore, measurements of the scattered and reflected LR were carried out according to a program specially developed for this case. A laser dosimeter (LD) of the “LD‑07” model was used as the main device (Fig. 3). The dosimeter LD‑07 is included in the State Register of Measuring Instruments and is a portable device consisting of a photodetector unit (FPU) (Fig. 3–1) and a control and display unit (CUI) (Fig. 3–2). Measurement data are processed and displayed on the CUI liquid crystal display. The device provides:
- registration and accounting of background indicators (irradiance (Eb, W / cm2), energy exposure (Nb, J / cm2));
- registration of the highest value of the measured parameter (irradiance (Emax, W / cm2), energy exposure (Hmax, J / cm2) LR) during the measurement cycle;
- measurement of the current values of parameters (irradiance (E, W / cm2), energy exposure (H, J / cm2) LR) scattered or reflected laser radiation [39].
Measurements of the maximum irradiance Emax from LR with a wavelength of λ = 1.07 μm can be carried out both when using FPU1 (Fig. 3–3) and using FPU2 (Fig. 3–4). To carry out measurements in real operating conditions of laser technological installations, the FPU2 device was selected.
The ARGUS series of devices allows measuring the energy characteristics of radiation in the range from 180 to 1 100 nm, as well as such parameters of the light environment as illumination and brightness.
To study UV radiation, radiometers are used: ARGUS‑04-1 (UV-A 315–400 nm) (Fig. 4); ARGUS‑05-1 (UV-B 280–315 nm); ARGUS‑06 / 1 (UV-C 180–280 nm). The measuring units of the instruments include ultraviolet photodetectors with a bias voltage supply device and specially designed light filters.
The increased brightness of the light and the blinding effect of the steam-plasma torch can also be attributed to the factors accompanying the laser technological process. To measure illumination and brightness, a luxmeter and a brightness meter are used, respectively [40].
Measurements of the energy characteristics of laser and secondary radiation in the framework of this study were carried out at the laser robotic complex No. 1 of the Laser Engineering Center (EC). In accordance with a specially developed test program, the following was carried out:
production control of the energy parameters of the reflected and scattered radiation during the development of laser welding technology;
determination of points with the maximum value of energy parameters.
The parameters (factors) measured in this study and their values are shown in Table 3.
Within the scope of the study, 9 series of measurements were carried out. As an example, this work presents the results of the first series of measurements. The measurements were carried out at an operating laser power of 2 500, 3 000, 4 000 and 5 000 W, three experiments for each power mode. The linear dimensions of the position of the control points were determined with a PLR25 laser rangefinder. When performing all experiments, we used individual (protective absorbing goggles (OZP)) and collective (protective cabin with active protection) protective equipment. The measurement scheme with indication of control points is shown in Fig. 5. The characteristics of the control points are presented in Table 4.
The values of the maximum permissible levels (MPL) of exposure from laser radiation in accordance with regulatory documents (with a duration of exposure tв нп = 8.5 s) are presented in Table 5.
The results of measurements of the maximum irradiance from laser radiation and comparison with the remote control are presented in table 6, the readings of ARGUS devices are presented in Table 7.
From the data table. 6–7 it follows that when the laser robotic complex No. 1, equipped with a protective cabin, operates in the studied power range (2 500, 3 000, 4 000 and 5 000 W), LR is safe with a single exposure to the eyes and skin. However, the use of personal protective equipment (glasses and overalls) for the personnel serving the laser complex is a mandatory requirement to ensure safe work at the complex.
Conclusion
As a result of a computational and experimental study of the data obtained in this work on assessing the effectiveness of protection of MCAP equipped with LREPS, as well as determining the degree of danger of LR during the operation of the laser robotic complex No. 1, it was established:
LREPS provides “triggering” of sensors configured for emergency disconnection of the laser generator from the mains supply for a specified minimum period of time;
The thermal effect of LR on the structure, physical and mechanical properties of the metal and the stressed state of the investigated element of the protective cabin with the installed sensor sensitive to the LR effect does not reduce the performance of the sensor itself and the metal structure of the panel, which indicates the reliability of the cab protection system as a whole.
When operating the laser robotic complex No. 1, equipped with a protective cabin in the studied power range (2 500, 3 000, 4 000 and 5 000 W), LR is safe with a single exposure to the eyes and skin.
The use of personal protective equipment (glasses and overalls) for personnel serving the laser complex is a mandatory requirement to ensure safe work at the complex.
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ABOUT AUTHORS
O. A. Kryuchina, NTO IRE-Polyus LLC, oKryuchina@ntoire-polus.ru, Fryazino, Moscow region, Russia.
ORCID ID No. 0000-0001-7592-0790
A. B. Lyukhter, Vladimir State University named after Alexander and Nikolay Stoletovs, 3699137@mail.ru, Vladimir, Russia
V. I. Krivorotov, NTO IRE-Polyus LLC, vKrivorotov@ntoire-polus.ru, Fryazino, Moscow region, Russia.
I. E. Sadovnikov, NTO IRE-Polyus LLC, iSadovnikov@ntoire-polus.ru, Fryazino, Moscow region, Russia.
ORCID ID No. 0000-0002-7576-6591
P. V. Beznosov, NTO IRE-Polyus LLC, pbeznosov@ntoire-polus.ru, Fryazino, Moscow region, Russia.
A. V. Lukonin, NTO IRE-Polyus LLC, aLukonin@ntoire-polus.ru, Fryazino, Moscow region, Russia.
Contribution by the members
of the team of authors
The article was prepared on the basis of many years of work by all members of the team of authors.
Conflict of interest
The authors claim that they have no conflict of interest. All authors took part in writing the article and supplemented the manuscript in part of their work.
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