Industrial Computed Tomography Research Articles

Research on the Mechanical and Physical Properties of Basalt Fiber-Reinforced Pervious Concrete.

The aim of this study was to investigate the properties of fiber-reinforced pervious concrete. Ordinary cement, silica fume, coarse aggregate, and basalt fibers were used to produce the concrete mix. The fibers were mixed with pervious concrete at the levels of 0 kg/m3, 2 kg/m3, 4 kg/m3, 6 kg/m3, and 8 kg/m3 to the investigate their influence on the mechanical and physical properties of pervious concrete. It could be observed that the cubic compressive strength, axial compressive strength, and flexural strength increased and then decreased as the content of basalt fiber increased, while the permeability and porosity of the pervious concrete decreased with the increase in the basalt fiber content. The mesostructure of pervious concrete was also studied through industrial computed tomography (ICT); the testing phenomenon showed that the fibers had a significant influence on the arrangement of the aggregate, cement paste, and the interfacial transition zone, and excessive basalt fiber resulted in poor characteristics of the interfacial transition zone (ITZ) and inferior strength properties. It was found that incorporating a basalt fiber content of 4 kg/m3 could achieve a balance between the mechanical and physical properties of pervious concrete, which was suitable for structural applications.

Preface Special Issue “11th CONFERENCE ON INDUSTRIAL COMPUTED TOMOGRAPHY”

Preface Special Issue “11th CONFERENCE ON INDUSTRIAL COMPUTED TOMOGRAPHY”

Utilization of molybdenum tailings as fine aggregate in recycled aggregate concrete

The increasing emissions of construction waste and industrial by-products have caused a serious burden on the environment. The shortage of natural coarse aggregate (NCA) and river sand provides the impetus for the reuse of solid waste. This research provides a cleaner option for the production of recycled aggregate concrete (RAC) from industrial by-product molybdenum tailings (MTs). MTs are used as alternative material to river sand (10%, 30%, 50%, 70% and 100%). Three types of concrete natural aggregate concrete (NAC), RAC, and MTs recycled aggregate concrete (MTs-RAC) were prepared. Firstly, the mechanical properties of the specimens were tested, including compressive strength (fcu) and splitting tensile strength (fst), and the digital image correlation (DIC) system was used to evaluate the strain field distribution. Then, the freeze-thaw (F-T) cycle corrosion resistance of concrete was evaluated. Subsequently, the pore structure was visualized and quantitatively analyzed based on industrial CT technology. The evolution of corrosion resistance of MTs-RAC was confirmed by microstructure. Finally, the economic efficiency factor (EEF) and environmental impact (EI) were evaluated. The experimental results showed that the appropriate amount of MTs significantly improved the pore structure and mechanical properties of RAC, and the fcu of RAC with a 50% MTs replacement rate increased by a maximum of 14.4%, which could achieve the same mechanical properties as NAC. However, the combination of excess MTs and recycled coarse aggregate (RCA) increases the porosity of concrete. The F-T cycle resistance of RAC decreased with the increase of MTs replacement rate. The increase in the proportion of large pores (>10 mm3) is the main factor leading to the destruction of F-T cycles. On balance, the replacement rate of MTs for use in RAC should not exceed 50% in salt lakes and cold regions. The results are helpful to understand the influence mechanism of MTs on RAC performance and provide the theoretical basis for the application of MTs in RAC.

Estimation of remaining capacity of lithium-ion batteries based on X-ray computed tomography

Accurate estimation of remaining capacity of Lithium-ion batteries (LIBs) for electric vehicles (EVs) is critical for battery management and second-use. The traditional methods ignore the degradation of the internal architecture of the battery caused by electrochemical reactions and generally fail to be applied to the dynamic operating condition. In this study, a novel estimation method based on X-ray industrial computed tomography (ICT) is developed. First, as the basis of estimation model, the mathematical relationship between the state of charge (SoC) and the content of lithium is obtained through the principles of electrochemistry. Second, according to Faraday's law and Peukert equation, the function of the remaining capacity and the material parameters (i.e. density, thickness, area of active material) and operating conditions is derived. Meanwhile, a new method for detecting the remaining capacity is proposed based on ICT. Third, experiments are conducted on three lithium iron phosphate (LFP) batteries to establish an estimation model. Comparing with the traditional method, the maximum prediction error of this model is 5.2 %, which is lower than that of the traditional method (24.1 %). Therefore, the novel method has great potential in reducing the cost of secondary use and improving the development efficiency.

Practical Part-Specific Trajectory Optimization for Robot-Guided Inspection via Computed Tomography

Robot-guided computed tomography enables the inspection of parts that are too large for conventional systems and allows, for instance, the non-destructive and volumetric evaluation of mechanical joining components within already assembled cars in the automotive industry. However, the typical scan time required by such setups is still significant and represents a major barrier for its industrial large-scale application. As an approach to mitigate the necessary time demand, we propose a part-specific adjustment of the acquisition trajectory. Common circular standard trajectories are inherently inefficient, since they are applied independently of the considered inspection task, while the use of acquisition orbits tailored particularly to the investigated object effectively allows a reduction of the required number of projections, which in turn has the potential to directly decrease the scan time significantly. In contrast to former simulation-guided approaches, this work is considered to be the first successful task-specific trajectory optimization being performed on a robot-based industrial CT platform and aims towards providing a first proof of concept that such methods can be practically applied in a shop floor environment. Based on representative results, a reduction of the number of required projections by approx. 55 % or an image quality improvement according to the root-mean squared error by approx. 40 % compared to the conventionally applied planar acquisition trajectory was achieved.

Study on the fast measurement method of fine-pitch hourglass worm tooth surface based on industrial CT

The accuracy of fine-pitch hourglass worm directly affects the working performance and service life of the mechanisms. To satisfy the increasing requirements, a fast measurement method of fine-pitch hourglass worm tooth surface is demonstrated based on the industrial computer tomography. An accurate matching method between the theoretical tooth surface and the real tooth surface is analyzed through designing the search iteration method based on the golden section method. This paper performs the sample detection and the deviation analysis, and verifies the accuracy of the measurement method through the detection by using coordinate measuring machine. The maximum difference of the average deviation of the tooth surface is 0.0034 mm, the error is less than 10%. For this experiment, the measurement efficiency can be improved by 81.5%. The results turn out that this fast measurement method is feasible.

Experimental Study on Hydraulic Fracturing of Laminated Sandstone Combined with Industrial CT and L-NMR

Hydraulic fracturing in the immediate roof is a suitable method to increase the permeability of soft outburst coal seam. In this work, the propagation law of hydraulic fractures in laminated virgin sandstone and the change of microstructure after hydraulic fracturing were revealed. The results show that the hydraulic fracturing pressure of sandstone with different bedding angles is 15.69~22.17 MPa. In the experiments, the hydraulic fractures extend through the bedding planes when the bedding angle is 45°. When the bedding angle is 0°, 15°, 30°, or 60°, the hydraulic fracture is prone to extend along a bedding plane. The hydraulic fracture in sandstone is jointly determined by the internal fractures and the cementation strengths of the bedding planes. The internal fractures may not necessarily guide the extension of the hydraulic fractures. The hydraulic fracturing pressures of the samples affected by the bedding plane and internal fractures are significantly lower than that of samples with uniform strength. Besides, hydraulic fracturing cannot change the connectivity between pores. The hydraulic fractures are the main channel for gas migration. The results can provide some guidance for the design and application of hydraulic fracturing in the immediate roof of the soft outburst coal seam.

Study on Performance of Retarded Composite Semi-Rigid Base Mixed with Rubber Powder.

In order to solve the problem of poor crack resistance and frost resistance of semi-rigid base, rubber powder and retarder were added to a semi-rigid base mixture. First, 61 mixing ratios were determined. Then, through the unconfined compressive strength, splitting strength, and other tests, the mechanical, crack, and frost resistance properties of the retarded composite semi-rigid base coarse mixture with rubber powder were studied. Finally, the macro and micro properties of the two kinds of admixture composite semi-rigid base coarse mixtures were studied by means of SEM and industrial CT. The results show that rubber powder and retarder can effectively improve the cracking and freezing resistance of the mixture. After five freeze–thaw cycle tests, the strength of the retarded composite semi-rigid base material mixed with rubber powder decreased slightly compared with the mixture without additives. It can be seen that rubber powder improved the frost resistance of the mixture. When the content of rubber powder was 1.5%, the BDR value of the mixture increased by 8.8%. With the increase of unconfined compressive strength, splitting strength, and flexural tensile strength at 28 d and 90 d, it was found that the retarder improved the middle and late strength of the mixture. When the content of retarder was 0.09%, the increase of unconfined compressive strength at 28 d reached 3.9%. The addition of rubber powder and retarder improved the distribution of internal pores, the proportion of large pores decreased, and the proportion of small pores increased. The retarder changed the morphology of hydration products, formed a dense network supporting structure, further refined the pores, and reduced the porosity of the mixture. The proportion of pores with a volume greater than 100 mm3 in the total pore volume decreased by 26.01%, and the proportion of medium pores increased by 13.07%, thereby improving the mechanical properties of the mixture.

Sub-pixel high precision dimensional measurement method for aero-engine hollow turbine blade based on industrial computed tomography image

Aero-engine hollow turbine blades are work under prolonged high temperature, requiring high dimensional accuracy. Blade profile and wall thickness are important parameters to ensure the comprehensive performance of blades, which need to be measured accurately during manufacturing process. In this study, a high accuracy industrial computed tomography (ICT) measuring method was developed based on standard cylindrical pin and ring workpieces of different sizes. Combining ICT with cubic spline interpolation, a sub-pixel accuracy was achieved in measuring the dimension of component. Compared with the traditional and whole-pixel level image measurement method, the cubic spline interpolation algorithm has the advantages of high accuracy in image edge detection and thus high accuracy of dimensional measurement. Further, the technique was employed to measure the profile and wall thickness of a typical aerospace engine turbine blade, and an accuracy higher than 0.015 mm was obtained.

Evaluation of molybdenum tailings as replacement for fine aggregate in concrete: Mechanical, corrosion resistance, and pore microstructural characteristics

This study explored the feasibility of molybdenum tailings (MTs) as an alternative to natural river sand for concrete production. Firstly, the compressive (fcu) and splitting tensile strengths (fsts) of molybdenum tailings concrete (MTs-C) and the relationship between the two were evaluated. Then, the corrosion resistance of MTs-C was investigated. This includes fcu loss, relative dynamic elastic modulus (RDEM) loss, and mass loss. Subsequently, the pore distribution under the sulfate freeze–thaw (F-T) cycle was tested by nuclear magnetic resonance (NMR). Besides, the pore evolution characteristics were visualized and quantified using industrial computed tomography (CT) techniques. Finally, the corrosion products were identified by X-ray diffraction (XRD). The results showed that the mechanical properties of concrete with 60% MTs only decreased by less than 10%. In the sulfate F-T environment, the corrosion resistance of MTs-C decreases as the replacement ratio of MTs increases, and it decreases significantly when the replacement ratio exceeds 60%. The porosity of MTs-C was the first to decrease and then increase with the F-T cycle, while the proportion of large pores gradually increased. Based on industrial CT scanning, it was further verified that the evolution of small pores to large pores is the main degradation mechanism of sulfate F-T cycles for the pore structure of MTs-C. Taking into account the mechanical properties, durability, and pore evolution, it was determined that 60% MTs replacement of natural sand for concrete production would be feasible.

Quantitative assessment of a beam hole scatter correction in industrial computed tomography

Abstract In industrial Computed Tomography (CT), scattered radiation causes a loss of quality of the reconstructed 3D volume. Scatter is caused by photon-matter interaction, whereby a photon is deflected from its initial propagation direction. The most prominent contributor to scattered radiation in the scope of photon energies occurring in industrial CT is Compton Scattering. With the used Beam Hole Array (BHA) technology for scatter correction, scatter intensities are determined by subtracting the primary intensities, which are gathered behind small apertures from the total intensities, which are gathered in the absence of the apertures. Intensities measured behind the apertures are assumed to be scatter free, since the transversal components of the radiation are strongly reduced. The scatter correction is performed by subtracting scatter intensities from primary intensities in the projection image. Improvements are evaluated for a newly developed test specimen considering image quality metrics and dimensional accuracy. The contrast could be improved especially for small structures. Cupping artifacts that express as systematic offset of grey values rising with the penetration length were reduced. Measurement deviations towards tactile references were decreased.

Effect of Graphene Oxide and Fly Ash on Frost Resistance of the Steel Fiber Reinforced Concrete

The addition of graphene oxide (GO) and fly ash (FA) to SFRC (steel fiber reinforced concrete) increases frost resistance. Based on the analysis of the amelioration of GO on the frost resistance of SFRC, the improvement mechanism and the effects of GO and FA on the durability of SFRC were studied in depth. The test blocks’ compressive strength, relative dynamic modulus of elasticity, and mass-loss rate were tested through experiments. The pore distribution and morphological characteristics of concrete were captured by industrial CT scanning technology. The effects of GO and FA on the pore distribution and morphology of the SFRC are discussed. The results show that the compressive strength of GO-SFRC(graphene oxide and steel fiber reinforced concrete)with GO proportion of 0.03% is 28.20% higher than that of ordinary SFRC without freezing and thawing; after 100 freeze-thaw cycles, the compressive strength of the G0.03S25 increased by 31.70% compared with the compressive strength of the G0.00S25, and pore shape of G0.03S25 presents a spherical shape and an elliptical spherical shape; based on the data analysis of the strength loss, relative dynamic elastic modulus loss and mass-loss rate, it is considered that the properties of ordinary SFRC are the worst under freezing and thawing; as FA admixture increases, the porosity decreases; with FA of 30% and GO of 0.03%, the GO-FA-SFRC has the best frost resistance, as well as most of the pores are closed which resemble spheres and ellipsoids.

Internal deformation monitoring of granular material using intelligent aggregate

Particle motion is the critical factor leading to the internal deformation of granular materials. However, relying on conventional techniques to monitor particle motion in internal deformation of granular materials has limitations. This study presents a novel method to monitor the internal movement of granular materials using intelligent aggregate. The intelligent aggregate packaging structure is fabricated through industrial CT technology and 3D printing. The six position method and fast fourier transform method are used to eliminate the measurement error caused by the packaging structure and the rutting tester vibration noise respectively. The results show that intelligent aggregate could maintain good linkage with surrounding aggregates under load, and the fine aggregates have a greater impact on the stability of the coarse aggregate skeleton. This method based on intelligent aggregates provides a basic technology for further real-time monitoring of granular material properties.

The quantitative characterization of hydraulic fracture connectivity from a postmortem investigation

AbstractTwo bio-siliceous Onnagawa (ONG I and ONG II) shale samples have been hydraulically fractured under two constant differential stresses (60 and 85 MPa, respectively) to investigate the fracture network's connectivity evolution by a postmortem analysis. The pressure inside the drilled borehole in a cylindrical core sample is increased above the confining pressure (10 MPa) until failure by hydraulic fracture. The two samples failed at two different borehole pressures (ONG I: 42 MPa, ONG II: 16 MPa). Fractured samples were scanned in an industrial X-ray CT machine and the tomographic images of the fracture network were extracted for a postmortem investigation. From the fracture volume segments, obtained by thresholding the frequency distribution of the fracture network's voxel values, a quantitative estimation of fracture connectivity was carried out. The connectivity was quantified based on the relative entropy of size distribution of fractures (${H_r}$), a method adapted from information theory. Fracture connectivity estimation shows that ${H_r}$ is at a maximum value when the fractures show a significant distribution with very limited connectivity. The value of ${H_r}$ is at a minimum and close to 0 when a well-linked fracture network is formed. In both samples, this minimum was attained at the threshold of 43k indicating the highest connectivity and the best representation of the fracture network. The extracted fracture network of ONG I showed a multi-winged hydraulic fracture network while a planar conventional two-winged hydraulic fracture network had been generated in ONG II with a lower fracture volume.

An analysis of the meso-structural damage evolution of coal using X-ray CT and a gray-scale level co-occurrence matrix method

To study the meso-damage evolution in coal under loading conditions, the industrial CT scanning tests under the uniaxial compression condition were carried out using an industrial CT scanner equipped with a loading control system. The gray level co-occurrence matrix (GLCM) theory was applied to quantitatively analyze the meso-damage evolution and the fracturing characteristics using the acquired CT images at each scanning stage. Four statistical features (i.e., contrast, energy, correlation, and homogeneity) of the CT images were extracted to evaluate the internal damage evolution in coal. The results show that the contrast generally took a changing trend of first decreasing and then increasing with the closure, initiation, and expansion of the fractures, that is, it decreased slowly at the compaction stage, slightly increased at the elasticity stage, and drastically increased at the post-peak stage. On the contrary, the energy, correlation, and homogeneity showed a changing trend opposite to that of the contrast. The changing tendency of mean values of the four statistical features could be depicted by the Boltzmann function, and in addition, the statistical features followed Gaussian distribution during the complete stress-strain process. The maximum damage cross-section of the coal sample could be transferred with the increase of deformation in the coal sample, indicating that the final failure location may not be the maximum initial damage location. The fracture ratio measured by the binarization and K-Means clustering algorithm methods typical showed three changing stages (i.e., a slow reduction process, a slight increase process, and a dramatic increase process) and could be used to reflect the meso-damage development process in coal at different deformation stages.

Damage constitutive model of gas-bearing coal using industrial CT scanning technology

Determining the deformation characteristics and mechanical behavior of gas-bearing coal is beneficial to understanding the phenomena and rules of dynamic disasters during coal mining. In this study, a computed tomography (CT) scanner and a triaxial loading seepage system were used to perform CT scanning tests on gas-bearing coal under triaxial compressive conditions. We processed the CT images in different deformation stages of the gas-bearing coal and analyzed them with a digital image processing technology to depict dynamic evolution damage trend. In addition, we employed a fracture area projection method to propose a new damage variable and theoretically constructed a new damage constitutive model. The results showed that the coal specimens became prone to increased instability and damage as gas pressure increased. The growth and expansion of fissures in gas-bearing coal were heterogeneous and anisotropic and mainly experienced three processes, that is, closure in the compaction stage and elasticity stage, expansion in the strain-hardening stage, and sharp propagation and interconnection in the post-peak stage. With the progression of fracture propagation, the degree of damage gradually decreased then increased. The proposed new damage variable was more suitable than the traditional damage variable for depicting the damage degree and damage evolution process. Furthermore, the proposed new damage constitutive model well mirrored the deformation behavior of gas-bearing coal under triaxial compressive loads.

Characterization of Porous Titanium-Hydroxyapatite Composite Biological Coating on Polyetheretherketone (PEEK) by Vacuum Plasma Spraying

Titanium powders and hydroxyapatite powders were used to fabricate the titanium and hydroxyapatite composite coating (Ti/Ti/HA) on the Polyetheretherketone (PEEK) by vacuum plasma spraying (VPS). The phase composition and morphology of the Ti/Ti/HA coating were analyzed by XRD, SEM, industrial CT, and three-dimensional contour profiler (DEKTAK XT). The results showed that the phase composition of the Ti/Ti/HA coating was dominated by the HA phase and a small amount of the Ti phase. The Ti/Ti/HA composite coating presented an obvious three-layer structure with different roughness and porosity. The bottom was Ti coating with a porosity less than 10%; the middle was porous Ti coating with a porosity of 35% ± 10%; the surface coating was HA coating with the crystallinity near 95%, a porosity of 32% ± 10%, a roughness Ra = 30 ± 10 μm. Moreover, the TG-DSC and ATR-FTIR results showed that VPS coating has no effect on thermochemical properties of PEEK material. The average bond strength of the composite coating was achieved 32 MPa.

Benchmarking of different reconstruction algorithms for industrial cone-beam CT

In the field of industrial computed tomography, there have been a lot of interests in different reconstruction algorithms which could perform better than the standard FDK algorithm in non-ideal conditions leading to faster CT acquisitions. However, the computation efforts required by iterative algorithms are quite high, which makes them less practical in industrial environments. In this work, we propose a benchmark of the performances of various reconstruction algorithms using Tomographic Iterative GPU-based Reconstruction (TIGRE) toolbox; the benchmarking criteria used include both image quality metrics and taskoriented post-reconstruction results (measurements, porosity, etc.). Furthermore, we have also tested their performances with limited projections and limited angular range to facilitate faster CT acquisitions. The preliminary results indicate several improvements in the reconstructions (better feature definitions) with one of the iterative algorithms (CGLS: conjugate gradient least squares) as compared to FDK.

The CTSimU software toolbox for CT-related image processing and quality assessment

A software toolbox is introduced that addresses several needs common to computed tomography (CT). Built for the WIPANO CTSimU project [1] to serve as the reference implementation for its image processing and evaluation tasks, it provides a Python 3 interface that is adaptable to many conceivable applications. Foremost, the toolbox features a pipeline architecture for sequential 2D image processing tasks, such as flat field corrections and image binning, and enables the user to create their own processing modules. Beyond that, it provides means to measure line profiles and image quality assessment algorithms to calculate modulation transfer functions (MTF) or to determine the interpolated basic spatial resolution (iSRb) using a duplex wire image [2]. It can also be used to calculate projection matrices for the reconstruction of scans with arbitrary industrial CT geometries and trajectories. The CTSimU project defined a framework of projection- and volume-based test scenarios [3] for the qualification of radiographic simulation software towards its use in dimensional metrology. The toolbox implements the necessary evaluation routines and generates reports for all projection-based tests.

Preface and Program

The relevance of Industrial X-ray computed tomography (CT) is continuously increasing – mainly due to its great advantages in the non-destructive testing (NDT) of materials and components. In contrast to other NDT methods, CT is able to provide three-dimensional representations of a component´s internal structure. The biggest advantage of CT is that the part is represented in three dimensions facilitating the detection of hidden, internal features and defects (e.g. shrink-holes, cracks, inclusions, and pores). Using CT it is possible to determine physical variables like porosity and density using high-resolution, 3D image data. Even after decades of progress in the advancement of industrial CT systems, new products, methods, and applications are constantly developed. The industry and scientific presentations during the iCT Conference 2022 will give insight into the latest developments as well as established methods.