Test Material Research Articles

An interplay between cross-cultural and psychometric factors in the Montreal Cognitive Assessment: Experience from the language of a small nation

The present study aimed to test the hypothesis that the total word length on the Memory subtest of the Czech version of the MoCA, which is 12 syllables compared to the English version of 7 syllables, would have a significant effect on Delayed Recall scores compared to the newly created well-balanced version of the test (further MoCA-WLE). In the original Czech version of MoCA, we replaced the 12-syllable word list in the Memory subtest with a 7-syllable list (MoCA-WLE) to make it equivalent to the standard English version in this respect. We analyzed data from 83 participants in the original MoCA group (70.63 ± 7.01 years old, 14.61 ± 3.17 years of education, 30.12% males) and 83 participants in the MoCA-WLE group (70.72 ± 6.95 years old, 14.93 ± 3.48 years of education, 30.12% males). We did not find evidence for a significant word-length effect in the original MoCA versus MoCA-WLE Delayed Recall in either the Mann–Whitney U test (W = 3418.0, p = .932) or multilevel binomial regression (b = 0.10, 95% posterior probability interval [−0.46, 0.68]). The present study shows cross-cultural limits in the adaptation of the test material. The results underline the caveats of such an approach to test adaptation. Fortunately, 12-syllables in the MoCA Memory Czech version versus the original 7-syllable list did not show a detectable word-length effect. We did not find evidence for differential item functioning or cultural item bias. The original MoCA Czech version is psychometrically comparable to the original English version.

One-Port Coaxial Line Sample Holder Characterisation Method of Dielectric Spectra.

A technique for solving the one-port closed coaxial transmission line sample holder scattering equation for complex permittivity inversion for lossy materials is presented. A non-linear least-squares procedure is used for the determination of parameters for the specification of the spectral functional form of the complex permittivity. The method allows for accurate retrieval of many low- and high-permittivity dielectric materials in the frequency range of 1 GHz to 3 GHz inserted into the coaxial cell. Using this method, the complex permittivity of a number of liquids and a Maltese soil known as Bajjad soil have been extracted by measurements using a short terminated coaxial transmission line sample holder. The proposed novel inversion method is mainly based on the reflection coefficient of the test material. The measured results of the complex permittivity of liquid dielectrics such as ethanol, methanol, and TX100 are validated and compared with previously published data obtained from measurements made by the National Physical Laboratory (NPL) using a two-port measurement setup made with the same commercial coaxial transmission line sample holder used in the one-port setup. Since the technique allows broadband measurements, it has been used to characterise the soil dielectric spectrum in the frequency range of 1-3 GHz, which is also compared with results from a two-port setup of the same coaxial line. The experimental results are a validation of the proposed approach for different types of materials.

Studying the effect of Cr content on microstructure and deformation behavior of (NiCo)88-xCrxAl10Ta2 medium-entropy alloy through L-DED gradient material

Optimization of Cr content is crucial for γ'-strengthened NiCoCr-based medium entropy alloys, influencing the stacking fault energy, deformation behavior and the precipitation of brittle σ phase. In this study, (NiCo)88-xCrxAl10Ta2 gradient materials were prepared by L-DED, and the influence of Cr content on the phase precipitation and tensile deformation behavior was investigated. As the Cr content decreases from 24.1 at% to 13.9 at%, the aging time for σ phase precipitation at the grain boundaries at 750°C increases from 100 hours to 215 hours. Meanwhile, the coarsening rate of γ' phase at 750°C are found to be 7.84×10−28 m3/s and 13.6×10−28 m3/s for the Cr content of 24.1 at% and 18.7 at%, respectively. It suggests that the reduction in Cr content notably suppresses the precipitation of σ phase, and accelerates the coarsening rate of γ' phase. Tensile testing of the gradient material reveals that the lower Cr content region exhibits fewer and shorter stacking faults during tensile deformation due to its higher stacking fault energy, leading to the rapid development of local strain, subsequent necking, and eventual fracture. Taking into account the evolution of microstructure, hardness, and deformation substructure with varying Cr content, the appropriate Cr content in (NiCo)88-xCrxAl10Ta2 medium entropy alloy is 17–24 at%.

Deep Indentation Tests of Soft Materials Using Mobile and Stationary Devices.

Measurements of the properties of soft materials are important from the point of view of medical diagnostics of soft tissues as well as testing the quality of food products and many technical materials. One of the frequently used techniques for testing such materials, attractive due to its non-invasive nature, is the indentation technique, which does not puncture the material. The difficulty of testing soft materials, which affects the objectivity of the results, is related to the problems of stable positioning of the studied material in relation to the indentation apparatus, especially with a device held by the operator. This work concerns the comparison of test results using an indentation apparatus mounted on mobile and stationary handles. The tested materials are cylindrical samples of polyurethane foams with three different stiffnesses and the same samples with a 0.5 or 1 mm thick silicone layer. The study presented uses an apparatus with a flat cylindrical indenter, with a surface area of 1 cm2, pressed to a depth of 10 mm (so-called deep tests). Based on the recorded force changes over time, five descriptors of the indentation test were determined and compared for both types of handles. The tests performed showed that the elastic properties of foam materials alone and with a silicone layer can be effectively characterized by the maximum forces during recessing and retraction and the slopes of the recessing and retraction curves. In the case of two-layer materials, these descriptors reflect both the characteristics of the foams and the silicone layer. The results show that the above property of the deep indentation method distinguishes it from the shallow indentation method. The repeatability of the tests performed in the mobile and stationary holders were determined to be comparable.

Developing advanced CrSi coatings for combatting surface degradation of N-type (Zr,Ti)Ni(Sn,Sb) and P-type (Zr,Ti)Co(Sn,Sb) half Heusler thermoelectric materials

In this study, advanced oxidation-protective CrSi coatings were developed and deposited on N-type (Zr,Ti)Ni(Sn,Sb) and P-type (Zr,Ti)Co(Sn,Sb) thermoelectric (TE) materials using an environmentally friendly closed field unbalanced magnetron sputtering PVD system. The oxidation behaviour of the CrSi-coated and uncoated samples was evaluated through static oxidation tests at 500 °C and 600 °C for 10h and 50 h, respectively. In addition, the samples were exposed to cyclic oxidation tests between 25 °C and 500 °C for 10, 30 and 50 cycles, with each cycle consisting of 1h of oxidation at 500 °C, to examine the coating ability to withstand thermal shock, which is involved in the service of TE devices. The surface morphology, cross-section layer structure, elemental distribution and phase constitution were analysed using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDX) and X-ray diffraction (XRD). The mass gain after the oxidation tests was measured and calculated for each sample to study the oxidation kinetics. The uncoated samples exhibited a considerable amount of oxidation, leading to change in the surface morphologies, and the formation of alternated layers including oxide products (Zr(Ti)O2, SnO2) and Ni3Sn4 compound for the N-type and (Zr(Ti)O2, SnO2, Sb2O4) and CoSb compound for the P-type material, after static and cyclic oxidation tests. The experimental work in this study has, for the first time, demonstrated that the CrSi coatings developed with very high thermal stability and oxidation resistance can effectively protect both the N-type and P-type materials from oxidation and sublimation even during cyclic oxidation tests. The strong affinity of Cr and Si to oxygen can trap oxygen, retard its inward diffusion and thus protect the TE material substrate from oxidation. This finding could pave the way towards the further development of long-life high-performance TE generators and devices, thus contributing to the net zero target.

Study of the fuel irradiation capsule using NEPTUNE_CFD software

The Fuel Irradiation Capsule (FUICA) is an experimental device designed to irradiate fuel elements in a Material Testing Reactor (MTR) during long period. This component is being studied for implementation in the Jules Horowitz reactor (RJH) under construction in France (1).Its function is to irradiate and to cool fuel sample on a passive way by transferring the thermal energy generated to the device periphery, through an annular zone of confined and pressure-regulated water (2). Its external wall, kept cold by the reactor cooling circuit, allows for the heat extraction. Natural convection is the driving force for the heat transfer between the fuel element and the cold wall of the device. By eliminating any internal forced convection cooling system, the device becomes relatively simple and cost-effective.This paper describes the device modeling carried out using the NEPTUNE_CFD software (3). The present work, in its first part, focuses on the behavior of the device depending on the heat flux, and in its second part, the sensitivity to boundary conditions. The objective is to provide a way to design and optimize the fuel capsule thermal characteristics. For that, an arbitrary size of fuel capsule is chosen in order to analyze the physics involved. A sensitivity study is then presented in order to highlight the influence of the physical parameters on the fuel capsule performance.Three operating ranges for the heat transfer are exhibited in this study: moderate in the liquid phase, the heat transfer becomes optimal in the two-phase regime, and even improves with the level of heat flux before deteriorating abruptly for high flux called Critical Heat Flux (CHF). Two observations also arise to improve thermal transfer: in the liquid phase, it is necessary to reduce the water thickness to improve convection, and in the two-phase regime, the heat transfer increases proportionally to the heat flux. In the end, the irradiation capsule is capable of extracting very high heat flux.

Analysis of the Suitability of Ultrasonic Testing for Verification of Nonuniform Welded Joints of Austenitic-Ferritic Sheets.

The purpose of the presented research was to determine the suitability of using ultrasonic testing (UT) to inspect heterogeneous, from a material point of view, welded joints on the example of the joints of a ferritic steel element with elements made of an austenitic steel. The echo technique with transverse (SEK) and longitudinal wave heads (SEL) addressed this issue. Due to the widespread use of 13CrMo4-5 and X2CrNiMo17-12-2 steel grades in the energy industry, they were selected as the test materials for the study. The objects of the presented research were welded joint specimens with thicknesses of 8, 12, and 16 mm and dimensions of 300 × 300 mm, made using the 135 metal active gas (MAG) process with the use of the Lincoln 309LSi wire-a ferritic-austenitic filler material. The stages of the research task were (1) making distance-amplitude curve (DAC) patterns from the test materials; (2) preparation of specimens of welded joints with artificial discontinuities in the form of through-holes; (3) performing UT tests on welded joints with artificial discontinuities using heads with 60° and 70° angles for the transverse wave and angle heads for longitudinal waves with similar beam insertion angles; (4) selection, by radiographic testing (RT), of welded joint specimens with natural discontinuities in the form of a lack of sidewall fusion; (5) performing UT tests on welded joints with natural discontinuities, using heads as welded joints with artificial discontinuities. It was found that (1) the highest sensitivity of discontinuity detection was obtained by performing tests on the ferritic steel side, which is due to the lower attenuation of the ultrasonic wave propagating in ferritic steel compared to austenitic steel; (2) the best detection of discontinuities could be obtained using a longitudinal ultrasonic wave; (3) there is a relationship between the thickness of the welded elements, the angle of the ultrasonic beam introduction, and the effectiveness of discontinuity detection.

Toxicological Assessment of Biodegradable Poli-ε-Caprolactone Polymer Composite Materials Containing Hydroxyapatite, Bioglass, and Chitosan as Potential Biomaterials for Bone Regeneration Scaffolds.

Polycaprolactone (PCL) is a biodegradable polyester that might be used in tissue engineering to obtain scaffolds for bone reconstruction using 3D-printing technologies. New material compositions based on PCL, with improved physicochemical properties and excellent biocompatibility, would improve its applicability in bone regeneration. The aim of this study was to assess the potential toxic effects of PCL-based composite materials containing 5% hydroxyapatite (PCL/SHAP), 5% bioglass (PCL/BIO), or 5% chitosan (PCL/CH) on MG-63 human fibroblast-like cells in vitro. Material tests were carried out using X-ray diffraction, differential thermal analysis/thermal gravimetry, BET specific surface analysis, and scanning electron microscopy. The effect of the biomaterials on the MG-63 cells was then assessed based on toxicity tests using indirect and direct contact methods. The analysis showed that the tested biomaterials did not significantly affect cell morphology, viability, proliferation, or migration. We concluded that biodegradable PCL-based scaffolds may be suitable for tissue scaffold production, and the addition of bioglass improves the growth of cultured cells.

A digital-twin driven Split Hopkinson bar layout for the tensile characterization of thin, low impedance, sheet-like materials

The Split Hopkinson or Kolsky bar is one of the most popular devices when it comes to the mechanical characterization of material samples under high strain-rates. While testing of high impedance materials, such as metal alloys, is relatively straight forward, samples with low impedance pose certain challenges. The present work focuses on the detailed implementation of a high strain-rate tensile testing method for thin, low impedance, sheet-like materials by using the Split Hopkinson test principle. In order to find a suitable Split Hopkinson setup a digital twin was created using explicit finite element methods. With the help of the digital twin, the design of the transmission bar and the sample holders including the friction liners were explored. The numerical model indicated, that a hollow transmission bar with a moderate tapering (hollow bar 1.0) is suited for the characterization of low impedance materials over a wide strain-rate range. Furthermore, this setup has to be combined with an asymmetrical sample holder configuration (heavier on the incident side and lighter on the transmission side) and aluminum friction liners to return accurate results. This numerically derived setup was validated against experimental tests on paper, representative of low impedance, sheet-like materials.

Development of Independent Curriculum IPAS Teaching Materials Using a Project-Based Learning Approach Assisted with the Kvisoft Flipbook Maker Application to Increase the Learning Motivation of Class IV Primary School Students

This research aims to develop IPAS teaching materials using a Project Learning approach assisted by the Kvisoft Flipbook Maker application to increase the learning motivation of fourth-grade elementary school students. This type of research is Research and Development (R&D) research using a 4-D development model consisting of four stages: analysis, design, development, and implementation. The media developed is science and technology teaching materials using a Project Learning approach assisted by the Kvisoft Flipbook Maker application to increase the learning motivation of fourth-grade elementary school students. The results of the research show that: the validity test of IPAS teaching materials obtained an overall validity value of 91.80 % in the very valid category; The teacher's practicality results were 93.30 % in the convenient category and the students' practicality results obtained a percentage of 93.50 % in the convenient category; the effectiveness used in increasing the learning motivation of fourth-grade elementary school students received an N-gain value of 0.73 in the high category. From the results of this research, it can be concluded that the IPAS teaching materials using the Project Based Learning approach assisted by the Kvisoft Flipbook Maker application to increase the learning motivation of fourth-grade elementary school students are valid, practical and effective and can increase the learning motivation of fourth-grade elementary school students.

Effects of Carbon Fiber Content on the Crystallization and Rheological Properties of Carbon Fiber-Reinforced Polyamide 6.

Carbon fiber (CF)-reinforced polyamide 6 (PA6) composites have an excellent performance, attributed to properties such as light quality, high strength, and vibration reduction, and they are widely used in fields such as aerospace and transportation. Four kinds of carbon fiber-reinforced polyamide 6 (CF/PA6) composite pellets with carbon fiber contents of 20, 30, 40, and 50 wt.% were prepared using twin screw extrusion. The results were characterized using a simultaneous thermal analyzer, capillary rheometer, electronic universal material testing machine, and scanning electron microscope (SEM); their crystallization, rheological behavior, mechanical properties, surface structure, etc., were studied. DSC results indicate that an increase in carbon fiber content enhances the thermal stability of CF/PA6 and narrows the crystallization window but has a minor effect on the molecular chain diffusion time. The crystallinity reaches its maximum at a carbon fiber content of 40 wt.%, reaching 55.16%. The steady-state rheological behavior reveals that CF/PA6 behaves as a pseudoplastic fluid, exhibiting shear-thinning behavior. When the carbon fiber content is 40 wt.%, the power law exponent (n) reaches its maximum, and the consistency coefficient (K) decreases by 300 Pa⋅sn compared to the 30 wt.% content. With increasing temperature, n increases while K decreases. SEM observations reveal that samples with carbon fiber contents of 20 wt.% and 40 wt.% exhibit better fiber dispersion and orientation. However, the interfacial bonding strength is superior in the 40 wt.% sample. When the carbon fiber content reaches 50 wt.%, significant injection molding defects occur at the clamping end, leading to extensive matrix tearing during tension testing.

Remineralizing effect of NSF on artificial enamel caries

IntroductionNanotechnology offers new approaches and endless opportunities for remineralizing tooth decay without being toxic or causing allergies. This study aimed to determine the effect of nanosilver fluoride (NSF) on the remineralization potential of enamel caries-like lesions compared to 5% sodium fluoride varnish in permanent teeth.MethodsFifteen teeth (molars and premolars) were gathered, cleaned, and polished using a scaler. After sectioning the teeth mesiodistally and removing the roots, the thirty specimens were subjected to a demineralized solution to induce early enamel lesions and then assigned randomly into two equal groups. The test materials were applied, and then all the specimens were subjected to a pH cycling model for 30 days. DIAGNOdent and surface roughness were investigated, and an evaluation of the enamel Ca and P weight% for Ca/P ratio calculation was done using SEM-EDX to analyze the specimens at the end of the study. The data were analyzed using an independent t-test.ResultsThe mean values for the DIAGNOdent measurements for NSF and NaF at baseline and after demineralization were not significantly different (p > 0.05). After treatment, NaF varnish showed a significantly higher mean DIAGNOdent measurement (11.8 ± 5.80) than NSF (4.7 ± 1.6). The mean surface roughness of the NaF group (1.64 ± 0.39) was much higher than NSF’s mean surface roughness (1.07 ± 0.21). Specimens treated with NSF had statistically significant smoother surfaces (p < 0.001). The NSF group had a higher mean Ca/P ratio (2.9 ± 0.35) than NaF (2.2 ± 0.11). This difference was statistically significant (p = 0.012).ConclusionThe study reveals that nano silver fluoride is a more effective treatment than sodium fluoride varnish in enhancing teeth’s clinical characteristics, particularly in terms of mineral content and surface roughness, suggesting it could be an improved strategy to prevent dental caries and maintain enamel integrity.

The effects of setup parameters on the measured kinetic output of cervical disc prostheses

Mechanical testing machines are used to evaluate kinematics, kinetics, wear, and efficacy of spinal implants. The simulation of "physiological" spinal loading conditions necessitates the simultaneous use of multiple actuators. The challenge in achieving a desired loading profile lies in achieving close synchronization of these actuators. Errors in load application can be attributed to both the control system and the intrinsic sample response. Moreover, the presence of friction in the setup can have an impact on the measured outcome. The optimization of setup parameters can substantially improve the ability to simulate spinal loading conditions and obtain reliable data on implant performance. In this study, a reproducible kinematic test protocol was developed to evaluate the sensitivity of the kinetic response (i.e., measured loads, moments, and stiffnesses) of a cervical disc prosthesis to several testing parameters. In this context, five ceramic ball and socket sample implants were mounted in a 6 DOF material testing machine and tested with a constant axial compressive force of 100 N in two motion modes: 1) flexion-extension (±7.5°) and 2) lateral bending (±6°). Parameters including rotation rate, slider friction, friction between the samples' articulating surfaces, and moment arm were considered to determine their effects on measured kinetic parameters. The sensitivity analysis indicated that all setup parameters except friction between the samples' articulating surfaces had a substantial effect on the results. The findings were then compared to predictions from a free body diagram to determine the optimal setup parameters. Consequently, the setup with the lowest rotation rate and employing passive sliders yielded results that were consistent with the free body diagram. This study demonstrated the significance of a comprehensive setup evaluation for reliable and reproducible testing of spinal implants, also for comparison between labs.

Tensile Specimen Circular Grid Pattern and AI-Based Strain Calculation Method

During tensile testing of materials, strain measurement is conducted using either contact or non-contact methods. Contact methods offer high accuracy and precision but are limited by the specimen’s thickness and dimensions, whereas non-contact methods minimize damage to thin specimens and allow measurements in various environments, though they require longer preparation and calculation times. This paper proposes a circular grid marking pattern and a strain prediction algorithm using artificial intelligence (AI), which simplifies the preparation process and allows strain prediction without additional equipment. The circular grid pattern can be arranged in various configurations from 1 × 5 to 5 × 7, and a laser marker, which requires minimal time, was used to engrave the pattern on the specimen to shorten the preparation time. The AI model, trained on image-based data, enables strain calculation regardless of the specimen’s gauge length and size, and allows measurement of local strain as well as gauge-length strain. The reliability of this concept was verified by applying it to tensile testing.

Multi-Objective Optimization of Crashworthiness of Shrink Tube Energy Absorption Structure

By means of material testing, truck testing and numerical simulation, the structural parameters of the shrink tube anti-climb device for high-speed trains were determined. The effects of cone angle, tube thickness, friction coefficient and axial length of the friction cone on the crashworthiness of the shrink tube were studied, and the main causes were analyzed. Using cone angle and tube wall thickness as input variables, and peak crush force, mean crash force and specific energy absorption as crashworthiness indexes, a proxy model was constructed using a radial basis function. The global response surface methodology was adopted to optimize the design of the shrink tube’s structural parameters. The results showed that the crashworthiness of the shrink tube was positively correlated with the cone angle, the thickness of the shrink tube and the friction coefficient, and the influence decreased successively, while the influence was negatively correlated with the axial length of the friction cone, which had the least influence. Through the optimized design, the peak force of the shrink tube increased by only 5.41%, while the specific energy absorption increased by 31.03%. Additionally, the mean force was closer to the technical requirements of 600 kN, and the crashworthiness was optimized.

The Process of Steam Oxidation Degradation of High Cr Steel after 125 000 Hours at 568 °C under 16.5 MPa

AbstractThe aim of this work was to analyze the effect of steam oxidation when TP347HFG grade steel was exposed to industrial conditions for 125 000 hrs at 568 °C under 16.5 MPa pressure. The testing material was acquired from one of the coal power plants operating in Poland. Comprehensive investigations were carried out on the outer surface and cross section of the exposed sample using XRD, SEM/EDS and TEM. The analysis revealed the development of a fine grain oxide scale thickness spanning from 20 to 200 µm, consisting Fe2NiO4 (78 %), Cr1.3Fe0.7O3, Fe2O3 (0.8 %) and Fe3Co (0.8 %). Cross-sectional observations showed the formation of grains rich in Nb precipitates type MX carbonitrides surrounded by M23C6 carbides developed as a continuous net at the grain boundaries. The extent of material degradation under the influence of temperature, pressure and exposure time has been meticulously discussed. Graphical Abstract

Modular Open Chamber Stand for Biomass Densification Using the Example of Miscanthus × Giganteus Greef Et Deu

This article presents a modular open chamber stand which simulates the densification process that occurs in a single channel of a pelletising die. The results of the verification tests confirmed the suitability of this stand for determining the optimal geometry of the channel. The test material was the biomass of Miscanthus × giganteus which is considered to be a difficult material for pressure densification; therefore, it was decided that it would be a good material for verifying the stand. The stand consists of four modules: an introductory section with a diameter of D = 12 and 10 mm, a conical part with an angle of α = 10°, 20°, 30°, 40°, a cylindrical part with lengths L = 5, 15, 25, 35, 45 mm and diameter d= 8 mm and a pellet receiving module. The stand is able to heat the densification channel. Individual modules can be assembled into test combinations; this results in a change in channel geometry without the necessity to manufacture many singular channels. The optimum geometry of the channel for miscanthus with a moisture content of 13%, densified at 100 °C was determined. It should be a channel with D = 10 mm, α = 40° and L = 18 mm.

Promoted electrochemical performance by MOF on MOF composite catalyst of microbial fuel cell: CuCo-MOF@ZIF-8 and the comparison between two-step hydrothermal method and dual-solution method

The microbial fuel cell (MFC) is a device that simultaneously achieves electricity generation and sewage degradation. In this study, a novel cathode catalyst metal-organic frameworks (MOFs) have been fabricated by two-step hydrothermal and dual-solution method (CuCo-MOF@ZIF-8). The synthesized trimetal MOFs exhibited a 3D badminton-like structure morphology and porosity. The results of the characterizations showed that CuCo-MOF@ZIF-8 possesses greater surface area porosity and novel functional groups. The Trimetal MOF-on-MOF mode not only demonstrated the stability of the structure but also enhanced its mechanism. Molecular mechanism analysis revealed changes in the organic ligand and metal binding site due to the transformation of Cu2+ to Cu+, Co2+ to Co3+, and Zn–N to Zn–O organic connection. Furthermore, differences between the two fabrication methods were compared. The solid-state single preparation (CuCo-MOF@ZIF-8-1), was synthesized using the two-step hydrothermal method; the liquid mixed preparation material (CuCo-MOF@ZIF-8-2), was synthesized using the dual-solution method; they exhibited completely different chemical structures and morphologies during material testing and characterization. The maximum output power density of CuCo-MOF@ZIF-8-2-MFC was 246.38 mW/m2, about 2.49 times of ZIF-8 (98.72 mW/m2). The output voltage of CuCo-MOF@ZIF-8-1-MFC was measured at 357 mV over 10 d, while that of CuCo-MOF@ZIF-8-2-MFC reached 365 mV over 12 d.

NEW METHODOLOGIES FOR ASSESSING CAVITATION LOAD AND RESISTANCE OF STRUCTURAL MATERIALS AND PROTECTIVE COATINGS IN NUCLEAR POWER INDUSTRY. PART I. MONOFRACTIONAL APPROACH

The paper presents a new method for assessing the cavitation load and durability of structural materials and protective coatings. To determine the cavitation load on a rotating disk or other test rig, a new method for extracting erosion loads based on tests of reference materials on a reference cavitation rig is proposed. Direct measurements of the cavitation load in a cavitation tunnel with a slot cavitator, performed using piezoelectric sensors, made it possible to obtain information on the spatial distribution of the impact load. As an analytical function for modeling cumulative erosion curves in the monofractional approach, the logarithmic formula of L. Sitnik is used, assuming that cavitation erosion is a stochastic process described using fatigue theory. Armco iron is chosen as a reference material, in view of the weak dependence of its erosion rate on cavitation qualitative features. Therefore the local load value could have been extracted from the eroded surface profile of the Armco iron sample. Using the example of TiN coating analysis on stainless steel and VT3-1 titanium alloy, the time dependencies and threshold characteristics of their resistance were determined depending on the parameter of the density of the supplied energy.

Powder Bed Fusion Techniques in Metal 3D Printing: A Review

The use of 3D printing (additive manufacturing) with metal has grown significantly in demand recently, greatly reducing the time and expense required to produce complex interconnected metal components. This method minimizes material wastage, facilitates material recycling, and eliminates the need for support materials. Among the various Metal Additive Manufacturing techniques, Powder Bed Fusion (PBF) processes stands out as the most prevalent for manufacturing parts. Within the realm of PBF, electron beam melting technique, selective laser sintering technique, and selective laser melting technique are the primary methods employed. Selective laser melting and selective laser sintering operate without the need for any special conditions, unlike EBM, which necessitates a vacuum environment. Regarding the choice of materials, laser melting/sintering processes are suitable for almost all types of metals except those which surpasses beam melting capabilities. While electron beam melting is constrained to a few materials such as titanium alloys, cobalt and chromium alloys, and nickel alloys, whereas selective laser melting and sintering allows for a broad range of materials, including iron and steel alloys. However, electron beam melting exhibit the ability to process brittle materials that would typically be challenging for melting and sintering through laser. Nevertheless, the ductility, yield testing, and ultimate testing of materials created through EBM are inferior to those processed by laser methods. Although all PBF techniques excel at creating complex structures, finishing products to have a smooth surface directly over a rough surface remains a subject of ongoing research. To attain suitable mechanical properties such as hardness, tensile strength, and endurance, critical process factors include power of laser or beam, speed for scanning, density for powder bed, thickness of laser or beam, and material characteristics. Inadequate material selection coupled with incorrect process settings can lead to issues such as porosity, slag formation, and other flaws.