Computed tomography

Industrial X-ray computed tomography emerged as a reflection of the fabulous success of medical computer tomography, invented by British engineer GN Hounsfield, who published the first description of a computer tomograph in 1972 [1]. Within 7 years, incomplete opening of this remarkable era of the computer revolution had won the Nobel Prize. Since then, the dignity of the medical tomographic diagnosis is not outdated, and it continues to help people to be treated in thousands of hospitals around the world. The unprecedented scale of the success of the medical X-ray tomography — a consequence of the happy coincidence of the unique features of the method of information, adequate diagnostic tasks, size and physical properties of the human body, as well as the presence of multi-billion dollar market for expensive medical equipment.

Inspired by the ideas of imaging, dozens of companies Universities UK, the US, France, Germany, Japan and the USSR Rb7] actively set about creating X-ray CT scanners for industrial and scientific purposes, the development of standards [8611, 26629] and the search for the most important areas of application. From the domestic achievements of that period may be mentioned micro desktop scanners VT650, developed in the laboratory of EI Weinberg, who already in 1990 had been delivered to Italy and the United States with great success presented at a conference in Milan (1990) and San Diego (1991).

Over the past thirty years of development, industrial computed tomography has become a standard tool for development of the technology and reliability of critical industrial products of many innovative industries leading industrial nations [12618].

They are used for quantitative non-destructive quality control of the internal spatial structure of one of the spectrum critical automotive and aerospace components and parts: a complex casting of light alloys, titanium and special steels, cooled turbine blades made of heat-resistant steel, solid rocket motors, large-size fan blade turbofan engines, heat exchangers, transmission, injectors, sensors and valves, complex welded and brazed joints; cylinder heads, pistons, catalytic converters, the brake discs and pads, automatic gearboxes, small engines of cruise missiles and unmanned aerial vehicles; the body in charge of casting and fuel distribution units; carbon seals and bearings, complex ceramics; articles made of composite materials, multilayer structures, adhesive joints, honeycomb structures, thermal protection, sound-absorbing panels and fairings; ammunition, electric motors, batteries, insulators, high-current high-voltage circuit breakers and other electrical products; large tires, geological core samples, etc. at all stages of "life" products from incoming inspection of materials, the completion of process technology, monitoring serial process discipline to the diagnosis during the tests, maintenance and repair.

Despite the complexity, high cost and problems of protection certainly competitive industrial computed tomography is still due to the traditional methods and means of not destroying the middle and measuring quantitatively investigate the complex internal structure of critical parts and assemblies that are critical to ensure the reliability of aerospace, stably, energy and defense systems . For example, the geometry of the cooling system in a cast turbine forehead of heat-resistant steel? How to quantify one of the density distribution and dimensions of the inhomogeneities in the brake disc, the blades or rocket nozzles? How to evaluate the quality of welded and brazed joints within a complex heat exchanger or radionuclide sources current spacecraft? How to determine the correct assembly of the complex, the disposable valve or ammunition to measure gaps and density of the internal structural elements? Similar problems are exceptional and application areas of industrial imaging, in which information may tomographic method is have no equal.

At the same time, if we compare the current level of technology and market industrial computer tomography with its success "forefather" medical tomography, it is inevitable more modest assessment of long-term industrial imaging. Three main reasons:

1. "Uncomfortable" for multi-angle X-physical properties of industrial objects control (high density and effective atomic number materials, large size and weight) and mismatch characteristics of modern sources of bremsstrahlung (of penetrating ability of radiation [19, 20, Tab. 1], the focal spot size [6 14] and the level of exposure dose);

2. Substantially smaller local defects to be detected [4, 5] and increased demands on the resolution, precision measurement of the size and internal structure [4, 14];

3. Low market capacity tomographic equipment for innovative technologies in charge of industrial products of aerospace, automotive and defense applications.

These are the fundamental factors that determine the status and prospects of development of industrial computer tomography.

Today, about 30 companies and research centers in the USA, Germany, UK, Belgium, Japan, Russia, Italy, China and India on their websites offer or describe industrial scanners variety of models for different applications:

"customs" Inspection and Inspection tomographic systems; scanners for industrial control research; coordinate measuring machines using X-ray computed tomography; and the actual universal computer tomography intentional products for testing and certification technologies Deb hoists and components and aircraft engines and automotive industry [15618 21].

In recent years, the ratio of these subspecies of technical diagnostics significantly changed under the influence of demand and economic conditions, rapid technological development, the arrival of a new generation of developers and companies, as well as the growing popularity of automated technologies to minimize "human fakb torus".

In particular, in response to the continued growth of destructive terrorism, drug and arms smuggling, in the first place came the most capacious market of specialized diagnostic radiation for inspection and examination (Fig. 3).

The major air terminals of the world dozens of such expensive, and the total number of air passengers in the world every 15 years and is already more than three billion people (and Cheb Madanov), which corresponds to the needs of three thousand Inspection CT scanners, for which passengers pay! This growing market scanners "Name 2001" an order prevyb creases needs tomographic control in manufacturing.

Among high (from 600 to 1,800 suitcases per hour) CT scanners for the screening of air baggage explosives detection scanners investments more competitive North American firms Rapiscan Systems /, Morpho Detection (Safran Group) /, L63 Communica6 tion / Security Detection Systems (partner of Analogic) /www.L6, SAIC Security and Transportation Technology /, and European manufacturer Smiths Heimann / Smiths Detection /www.smithdetection .com /.

This technically advanced and economically most advantageous subspecies of industrial X-ray tomography deserves attention of developers, but due to the low power (10 mm steel, 90 … 180 kW) and spatial resolution (~ 5 … 10 per / cm), adequate specificity control objects, "luggage" scanners, even less than the mass medical tomography, are not effective for tomographic control of the internal structure of industrial products from dense metals. At the same time the design of conveyor "luggage" (with the modernization of the source of radiation detectors and protection) can be used as a basis for high-performance 100% responsible tomographic control serial products "on stream" moderate metrology.

We note in passing new and large market of high-energy (MeV 3/4/6/9) digital radiographic inspection longer vehicles, railcars and sea containers, which is achieved through the use of accelerators increased penetrating power (up to 200 mm steel) objects to control 4x5x20 m (Figure . 4), but the idea of ​​multi-angle-through with the implementation of kompyuterb tomography remain at the level of advanced design study. Among the successful manufacturers of various models can be specified screening equipment US firm Rapiscan Systems / and American Science and Engineering (AS&E) /, Smiths Heimann / Smiths Detection (Germany) / and NUCTECH (PRC) / This equipment is currently the main consumer of industrial accelerators (mainly linear) with the energy of the accelerated electrons from 3 to 9 MeV and a multi-element detector arrays with large scintillation crystal.

In recent years significantly increased the number of X-ray micro tomography for non-destructive inspection of the internal structure of small articles (1, 0 … 100 mm), materials, imaging and electronic components and research [23]. Today, the market for industrial scanners presented a large number of models of micro and nano toomografov scanners using sealed and gasketed tubes (0.2 … 6 m at a power on the target of 0.2 … 6 W) with a voltage from 80 to 225 kW. For multi-angle tomography monitoring of steel products voltage 225 kB (15 mm steel) is certainly not enough, but a further increase in the anode voltage microfocus X-ray tubes is technologically difficult and dramatically increase the weight of an autonomous biological protection. However, the European company Nikon Metrology NV (HbGek)

/ www. UE by microfocus tube at 225 kV (3 micron) uses in its original microtomography collapsible tube with a focal length and voltage of 320 kV (20 m) and 450 kV (80 microns). While the tube (Fig. 5) at 450 kV best achievement in penetrating power of industrial micro tomography, although umeb cussed with extreme resolution at 100 cycles / cm.

Fig. 6 shows the appearance of two models of well-known manufacturers: mikrotomograficheskoy coordinate&measuring machine METRO TOM 1500 the company Carl Zeiss / a collapsible tube at 225 kV and nano tomography phoenix nanotom s&m company GE Sensing & Inspection Technologies (Phoenix | x6ay) /, www.phoö nanofokusnoy tube with 180 kB.

Among manufacturers microbe nano and scanners, in addition to the three mentioned above, it should be noted: European firms Yxlon International (Comet Group) /, RayScan Technologies /, MatriX Technologies / , Bruker microCT (SkyScan) /, RX Solutions / www.rxsolu6, Viscom /, Procon Hbpu /www.procon6c6 /, Shake /www.shake6gmbh .de /, Scanco Medical /www.scan6; American company North Star Imaging (XVIEWCT) /, Xradia / and IRIS Systems /, Japanese Shimadzu / ndi /, Yamato Scientific / and Toshiba IT & Control Systems /

Most of these companies offers customers several models of micro tomography, provides maximum control object, penetrating radiation, the limit of the spatial resolution, the type used by the X-ray tube (operating voltage and spot size), the type of multi-channel detector (sampling interval, number of elements, geometrical dimensions, bit ADC design features: Two-dimensional panels, single-row or multi-row detector line), the range of the scanning system dimensions and weight X-ray box, as well as the features of the software package.

In most cases, manufacturers of original programs for the control and the same type of the purchase, software packages, reconstruction, processing, visualization, transformation and automatic interpretation of the results. For example, software firms Volume Graphics /, Visualization Sciences Group /, InnovMetric Software / and Fraunhofer IIS / for a conical beam and SPIBA General tomography.

The presence of the autonomous biological protection is a standard that allows them to operate under normal laboratory premises and promotes higher education. This expansion of the range of sizes and density of objects of control is inevitable due to the increase in anode X-ray tube voltage and even more weight gain X-ray box.

Despite the optimism of advertising leaflets, buying, and even more nano tomography is necessary to show a certain caution, trusting only the experimental results. For example, the spatial effect is not rated, and the total size of the focal spot, taking into account the contribution of afocal light and changes a position of the focal spot in the process under the influence of mechanical strain, variations of the electromagnetic focusing system and the target values ​​of the accelerating voltage or vibrations. In addition, the spatial resolution is important for the interval detector channels, the focal length used and the increase in [6]. Therefore reducible in the prospectuses of the small value of the nominal focal spot x-ray tube does not guarantee adequately high yield space scanner.

Similarly, with the competition of advertising values ​​of power microfocus tubes, as it corresponds to the maximum size of the focal spot, and for the minimum tube almost all equal, because have limiting thermal load on the target mobile palates of ~ 1 W / mK (kW / mm), and the difference is 10 … 50% of this level significant, since leveled statistics quantum noise proportional to the square root of the number of registered photons.

Using industrial scanners collapsible tubes with continuous pumping and replaceable electrodes creates inconvenience and performance is a clear indication of imperfection technology industrial equipment. For comparison, in the mass imaging uses only e sealed-off tube. And the modern design of serial medical imaging tubes used cooling oil sealed-off vacuum chamber with a short tepb Cretaceous load distributed on a rotating target 100 … 200 kW / mm, which is two orders of magnitude higher than in the industrial imaging.

With regard to the choice of detector design should pay attention to long-term stability chuvstvitelb of channels and the problem of physical weakening contribution rasseb yannogo radiation dominates the Compton scattering Rusby at a higher voltage. The latter problem is not Reb Shen panels for two-dimensional detector, resulting in quality and metrology microtomography collimated with a linear array of detectors (while reducing the volume of the object obluchaeb direct control) bsuschestvenno above.

Regarding synchrotron microtomography on ondulyab Thorne and emission free electron lasers [24]. Podobb nye work is carried out in ten accelerator centers with drives with stations of synchrotron radiation, such as the Novosibirsk Institute of Nuclear Physics, the Kurchatov Institute, the Argonne and Brookhaven National Laboratory, Stanford labob Laboratory of Synchrotron Light (USA), in Grenoble and Melburb not in the Japanese national KEK laboratory in Barcelona, ​​etc. Izbza disappointingly low energy synchrotron radiation (10 … 40 keV) for industrial facilities they lose control microtomography on bremsstrahlung X-ray tubes. Significant research facilities for kotob ryh high intensity and polarization expensive sinhb rotronnogo radiation appeared to a decisive extent, is not revealed.

The metrological support of modern production complex spatial development of products play an important role high-precision computerized machines koordinatno6-13meritel6 nye, passed in its development a long way ottyab zhelovesnyh portal to portable portable usb tings contact and non-contact laser measuring instruments outdoor geometb Rhee products of any complexity and scale (Fig. 7).

Not stopping there, leading manufacturers koordinatnobomeritelnyh cars in recent years, we decided peb reschedule developed and standardized [23] principles besb kontaktnyhtrehkoordinatnyh meters from the outer surface of industrial izdeb ly on their internal structure by zameb us mechanical schub Brokers and optical huts radiation on mnogorab kursnoe rentgenovsb something translucence and reconstruction trehb dimensional tomograms of the measured product (Fig. 6, 8).

Among the most advanced izgotob sentatives of this subspecies industrial tomographic oborub ment should highlight European firms Werth Messtechnik /, Carl Zeiss /, Nikon Metrology NV (HbGek) / www. and North Star Imaging (XVIEWCT) / From the euphoria of initial OPB timizma meters of electronic components, these companies have already doshb whether to understanding the limited penetrating power nizb-energy radiation microfocus tubes napryazheb niem225 kV and now, in addition to measuring mikrotob tomography, company Werth Messtechnik and Nikon Metrology NV (HbGek) developed a more informative models for voltage of 450 kB with penetrating steel up to 50 mm. And the trend is to further enhance the energy of the radiation tomographic koordib natnobomeritelnyh machines undeniable.

Finally a proper universal scanners promyshb PARTICULAR products for the non-destructive testing of internal strukb tours, development of the technology and the certification of critical parts and components of aerospace, automotive and defense mashinob structure.

The development of this subspecies of industrial scanners printsipib cially difficult and does not adequately progress of digital technology and software.

The basic fundamental physical limitation bkonechb tion penetrating power bremsstrahlung [19620]. Although reducing consumption of materials in modern mashinostrob enii widely used thin-walled structures, light splab you (on the basis of "P, A1 or Mg) and composites, the most loaded and SEL-temperature pobprezhnemu parts are made of steel and high-temperature alloys with a density of 7.6 to 8.6 g / cm3. This probb Lem is reflected in the standards.

It is evident that due to the irrevocable laws of physics promyshb lenny entry-level scanner should have an X-ray tube anode voltage of not less than 450 kW, and promising universal scanner for industrial products should osnab schatsya accelerator at energies of the order of 5 … 9 MeV. This axiom gradually over 20 years have begun to understand the leading manufacturers and today this class of universal high-promyshb PARTICULAR scanners presented a certain number vysokoenergeb cal models from well-known manufacturers: Yxlon International (Comet Group), GE Sensing&lnspection Technologies (Phoenix | x6ny), RayScan Technologies, Nikon Metrology NV (HbGek), MatriX Technologies, North Star Imaging (XVIEWCT) and the Russian company Promintro (Indintro).

Fig. 9 shows the appearance of a universal vysokoeb nergeticheskogo industrial tomograph Russian firm "Promintro" tomograms with diameters from 50 to 800 mm, gruzopodb emnostyu more than 500 kg and a stroke length of the vertical of more than 1 m. Tobe tomography used two sources of light: not folding IIB nifokusnaya X-ray tube at 450 kV (with two focal pyatb us 0.4 and 1 mm) and an electron accelerator with an energy of 5 MeV socheb in Britain with additional collimators, razmerab control of the effective focal spot (0.4 / 0.2 mm), and minimizes the afocal radiation. Penetration of steel Bne less than 150 mm, the limit of the spatial resolution in the whole energy range of 650 cycles / cm, and the measurement accuracy razmeb ditch internal structural elements 60.05 mm. Used meb Tod local tomography [7] with the format of the reconstructed MPS Zorn and local tomograms from 1024×1024 to 2048×2048 with adequate number of projections of a unified point.

If the voltage of 450 kV penetrating 50mm steel manufacturers offer X-ray boxes of various sizes weighing up to 20 tons, for the high-energy industrial CT scanners with the accelerator and penetrating spob lities more than 1 50 mm steel biological protection obespechivab by concrete walls Boxing thickness greater than 1 meter with a maze to protect the front door.

Features available tubes and high-usb koriteley is poor and limited izbza sprob sa do not improve over the years. For example, the only model of sealed minifokusnyh (0.4 mm) tubing for 450 (600) kV MXR6 451 (600) HP / 11, the issue of which carries a Swiss company Comet /, afocal have elevated levels of radiation significantly impairs metrology scanner, but there is no alternative.

Similarly, the available linear accelerators, the energy and the intensity of the radiation which is unstable, significant urob Wen background radiation, and the focal spot size is typically of the order of 2 mm instead of the required 0.4 … 0.2 mm.

The use of accelerators and increase the spatial resolution of universal high-scanners yavb seems important trends in the development of this subspecies promyshb PARTICULAR scanners to increase sensitivity to lokalb nym defects and improve the accuracy of measuring the size of elemenb Comrade complex internal structure. Therefore, modern energy vysokob tomography industrial control object in the best scanners already contain up to 2048×2048 settlement eleb cops. Beyond that, by using the method of local tomography [7], the overall diameter of the object of the control element and a minimum resolution tomography 0 / A1 may ascend Preben 104. This industrial scanners ahead medib Qing X-ray tomography, for which one to yavb standard format 512×512 with the reconstructed tomograms vizuab tion with interpolation up to 024 1024×1.

Due to the continuous increase in the volume of data and three-dimensional tomographic monitoring results inevitable transition from interactive digital decoding of tomograms experienced operator with an automatic diagnosis formirovab tion of the final protocol quantifying compliance Tobe demographic control results and requirements konstruktorsb Coy product documentation. Automation of the complete cycle Koliba-quality tomographic diagnosis is most justified for specialized industrial scanners narrow klasb meat products, increases productivity and reduces dependence on "Human" factor when interpreting the results kontb Rola. Unfortunately, the role of visualization tomogb grammes, the cost of two-dimensional and three-dimensional graphics and even weaken the operator. Beauty tomography gives ratsionalb of digital assessments.

To illustrate the achieved level of informativeness and otkb undermines prospects in Fig. 10 examples vysokoeb nergeticheskih (5 MeV) tomograms of large metal parts AVB cle obtained in an industrial tomograph Russian firm "Promintro".

We see that the industrial imaging alive, branched out into a number of related sub-species, which continue razvib vatsya, though not always as expected.


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27. EN 1601662: 2011 Non destructive testing Radiation methods 6 6 Computed tomography 6Part 2: Principle, equipment and samples.

28. EN 1601663: 2011 Non destructive testing Radiation methods 6 6 Computed tomography 6Part 3: Operation and interpretation.

29. EN 1601664: 2011 Non destructive testing 6 Radiati

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