Changes In Structure Of Material Research Articles

PENGARUH REPAIR LAS GMAW TERHADAP KEKUATAN TARIK, KEKERASAN, DAN STRUKTUR MIKRO PADA MATERIAL BAJA A36

Welding is a technique of joining metal materials that has a detrimental impact in the form of defects in the material, especially welded joints, in the weld joint area with improper welding procedures resulting in weld defects in the material, changes in the crystal structure and mechanical properties of material. This research method is carried out by re-welding or repairing the defective material. The purpose of this study is to analyze and compare the mechanical properties of repair results with welded joints without repair. The repair process uses a variety of repair 2 times, repair 3 times, and repair 4 times by welding GMAW on A36 steel material. The results of the study were mechanical properties of the material in the form of the crystal structure of the specimen, the value of the hardness test and the ultimate tensile strength, microstructure testing there is a crystal structure of perlite and ferrite. The highest hardness test value is repair 2 times 170 HV, without repair 166 HV, repair 3 times 163.3 HV, and repair 4 times 162.8 HV on weld metal. The result of ultimate strength variation without repair 485 N/mm2, repair 2 times 466.5 N/mm2, repair 3 times 466.5 N/mm2, repair 4 times 468 N/mm2 with tensile test fracture located in the base metal area, the result of ultimate tensile strength repair 2 times, repair 3 times, repair 4 times is still within the minimum tensile provision of ASTM A36 steel material of 452 N/mm2 so that welded joints that are made up to 4 times repair can be used.

Investigation of Post-weld Heat Treatment of Laser Welded Ti6Al4V Materials

In this study, the changes in the internal structure and mechanical properties of laser-welded Ti6Al4V material after heat treatment were experimentally investigated. The transformation temperatures of the α and β phase structures of the Ti6Al4V material influenced the heat treatment temperatures. Optical microscopes, XRD, and SEM experiments were performed to detect the microstructural change. Hardness and tensile tests were also carried out to determine the change in mechanical properties. The experimental study determined that the mechanical properties of laser-welded Ti6Al4V material improved after heat treatment. It was observed that ductility and strength increased significantly at heat treatment temperatures above the β phase temperature. It was determined that the Widmanstatten morphology visible in the weld area increased the hardness.

Molecular Dynamics Study on the Mechanism of Gallium Nitride Radiation Damage by Alpha Particles.

In special applications in nuclear reactors and deep space environments, gallium nitride detectors are subject to irradiation by α-particles. Therefore, this work aims to explore the mechanism of the property change of GaN material, which is closely related to the application of semiconductor materials in detectors. This study applied molecular dynamics methods to the displacement damage of GaN under α-particle irradiation. A single α-particle-induced cascade collision at two incident energies (0.1 and 0.5 MeV) and multiple α-particle injections (by five and ten incident α-particles with injection doses of 2 × 1012 and 4 × 1012 ions/cm2, respectively) at room temperature (300 K) were simulated by LAMMPS code. The results show that the recombination efficiency of the material is about 32% under 0.1 MeV, and most of the defect clusters are located within 125 Å, while the recombination efficiency of 0.5 MeV is about 26%, and most of the defect clusters are outside 125 Å. However, under multiple α-particle injections, the material structure changes, the amorphous regions become larger and more numerous, the proportion of amorphous area is about 27.3% to 31.9%, while the material's self-repair ability is mostly exhausted.

Cu-BTC derived CuO and CuO/Cu2O composite: an efficient adsorption material to iodide ions

The copper benzene tricarboxylic acid (Cu-BTC) cannot be used as an adsorbent in water due to hydrophilicity. However, the calcination process can destroy the benzene ring structure to lose hydrophilicity and retains carbon structure skeleton. The CuO composite and CuO/Cu2O composite based on cubical Cu-BTC (C-Cu-BTC) and dodecahedral Cu-BTC (D-Cu-BTC) are successfully manufactured to absorb radioactive iodine ion from water. Before and after calcination, the SEM and XRD were used to characterize the changes of morphology and material structure. The adsorption experiment for iodine ion showed that their saturated adsorption capacities can reach 28.64 mg g−1 (for C–CuO), 49.63 mg g−1 (for D-CuO), 49.84 mg g−1 (for C–CuO/Cu2O) and 91.91 mg g−1 (for D-CuO/Cu2O), respectively. The iodine ion adsorption of adsorbent is an exothermic reaction as shown thermodynamic curves. Through results of adsorption kinetics it is proved that the iodide ion adsorption of CuO composite is physical adsorption and the iodide ion adsorption of CuO/Cu2O composite is chemical adsorption. Compared with CuO composite, CuO/Cu2O composite had better absorption capacity for iodide ions. Furthermore, the interference of common ion on iodide absorption has also been studied. The different types of ion, such as Cl−, SO4 2− and CO3 2−, have effects on the iodine ions absorption capacity for two types of adsorbent. These ions have a slightly effect on iodine ions adsorption of CuO composite. However, these ions have greater influences on iodine ions absorption capacity of the CuO/Cu2O composite. The biggest influence is CO3 2−, and the CO3 2− reduces the adsorption capacity by 44% iodine ion absorption capacity for the CuO/Cu2O composite.

Experimental Study on Mechanism, Aging and Fatigue Performance of Warm Mixing Speed Melting SBS Modified Asphalt Binders

In this study, two kinds of quick melting modifier SBS-T and SBS-W, as well as the traditional SBS modifier, were used in the optimization design of asphalt binders. The changes in material structure and fatigue properties of three polymer-modified asphalt after adding 3% Sasobit to warm mix agent were investigated. The feasibility of SBS-T and SBS-W in asphalt binder was discussed from the modification mechanism and fatigue properties. In order to reveal the modification mechanism, the interaction mechanism between the fast-melting SBS modifier and the base asphalt was characterized by Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). The temperature sensitivity and viscoelastic properties of SBS-T and SBS-W modified binders were determined by frequency scanning (FS). The fatigue properties of SBS-T and SBS-W modified binders were tested by linear amplitude scanning (LAS). The results of FTIR showed that there was no chemical reaction between the SBS-T and SBS-W and the base asphalt. XRD results showed that SBS-W-modified asphalt has stronger fluidity. The results of FS and LAS showed that the asphalt binder with Sasobit has good stiffness and elastic recovery ability, and the same SBS-T and SBS-W have better temperature sensitivity and deformation resistance. In addition, the fatigue life of asphalt binder under the linear viscoelastic continuous damage theory is increased 3.9 times by SBS-W.

Investigation of the Biocompatibility of Laser Treated 316L Stainless Steel Materials

In this study, 316L stainless steel materials, which are widely used in the industry, were produced by investment casting management. Depending on the microstructure, the hardness values constitute an important stage of the properties that can be developed and controlled. For this purpose, the differences between the microstructure and hardness properties of 316L stainless steel, which is produced by the investment casting method, and 316L stainless steel, which is currently used commercially, were examined. The changes caused by the fiber laser on the surface of 316L materials produced with two different production methods were examined. It was observed that the laser used made different changes in the surface structure of the 316L material produced by both methods. Since the surface of the material is a buffer between body fluids and biomaterial, it is known that there is a relationship between surface properties and biocompatibility. In this study, the L929 cell growth test, one of the cytotoxicity tests, was applied and thus, how laser surface treatment affects the biocompatibility of 316L materials produced by both methods was comparatively examined.

Characterisation of Fibre Bundle Deformation Behaviour—Test Rig, Results and Conclusions

Deformation of continuous fibre reinforced plastics during thermally-assisted forming or joining processes leads to a change of the initial material structure. The load behaviour of composite parts strongly depends on the resultant material structure. The prediction of this material structure is a challenging task and requires a deep knowledge of the material behaviour above melting temperature and the occurring complex forming phenomena. Through this knowledge, the optimisation of manufacturing parameters for a more efficient and reproducible process can be enabled and are in the focus of many investigations. In the present paper, a simplified pultrusion test rig is developed and presented to investigate the deformation behaviour of a thermoplastic semi-finished fiber product in a forming element. Therefore, different process parameters, like forming element temperature, pulling velocity as well as the forming element geometry, are varied. The deformation behaviour in the forming zone of the thermoplastic preimpregnated continuous glass fibre-reinforced material is investigated by computed tomography and the resultant pulling forces are measured. The results clearly show the correlation between the forming element temperature and the resulting forces due to a change in the viscosity of the thermoplastic matrix and the resulting fiber matrix interaction. In addition, the evaluation of the measurement data shows which forming forces are required to change the shape of the thermoplastic unidirectional material with a rectangular cross-section to a round one.

Valorization of forestry residues by thermal methods. The effect of temperature on gradual degradation of structural components in bark from silver fir (Abies alba Mill.)

Thermal treatments are largely used for valorization of biomass resources. However, thorough knowledge on gradual degradation of chemical and structural components of biomass are still needed to allow selection of best procedures and operation conditions that lead to desired properties according to target applications. In this paper we studied thermal degradation of silver fir bark by torrefaction at 240–310 °C and pyrolysis at 550 °C. Detailed characterization of products and hierarchical clustering analysis was performed to obtain an overview on the relation between the severity of thermal treatment, the compositional and structural changes of material and the properties of final products. Hemicelluloses started to degrade around 250 °C into furans, acids and linear ketones. Part of volatile terpenes remained embedded in the unaffected lignin and cellulose. Degradation of lignin became significant around 270 °C, producing phenol derivatives, especially at higher temperatures. Cellulose was apparently not affected by torrefaction but was degraded by pyrolysis. Color gradually changed towards black with increasing temperature, O/C and H/C atomic ratios decreasing close to those of coals. Compressibility was maintained after torrefaction but was lost by pyrolysis while wettability changed to the hydrophobic side, even reaching highly hydrophobic character. Porosity increased, solids having complex structured morphology due to slow release of volatiles during torrefaction pretreatment step.

Battery Materials Characterization Workflow for Effective Battery Electrode Manufacturing Processes

A lithium-ion battery’s performance characteristics demand the highest performing materials in the anode, cathode, electrolyte, and separator. Materials characterization is an essential set of analytical techniques for ensuring optimal battery performance during the stages of material selection, development, and manufacturing. Key material characterization technologies for ensuring that batteries achieve their performance characteristics include thermal analysis, rheology, mechanical analysis and isothermal microcalorimetry. Thermal analysis provides insights into material thermal stability and structure change under different temperature ranges. Rheology provides insights into battery slurry storage, mixing, coating, and drying for more uniform and defect free electrode manufacturing. Mechanical testing provides insights into structure-property relationship such as verifying whether the polymer material in a separator will shut down safely without melting. Isothermal microcalorimetry allows researchers to study the electrochemistry of a working battery cell by enabling direct heat flow measurements that provide insights into battery lifetime. This presentation will focus on the electrode manufacturing with thermal analysis and rheology characterization to highlight how advanced material characterization can help battery researchers, developers, and production specialists develop better analytical material characterization and quality control procedures.

In Ukrainian

In this paper, changes in the porous structure of carbon material are investigated during chemical activation of apricot pit at different temperatures. The main purpose of the research has been to study the features of the internal micro- and mesostructure of the carbon surface, as well as to find patterns in the size distribution of pores dependent on the carbonization temperature of plant raw materials and subsequent chemical activation. The object of the study is porous carbon material, obtained from dried apricot fruit pits, pre-crushing, and cleaned from the core. This raw material has been carbonized at 300–900 °C with an interval of 100 °C and subjected to chemical activation by potassium hydroxide in the weight ratio XК, where ХК = m(KOH)/m(C). Thereby, a series of samples C3÷C9 has been obtained. The porous structure characteristics (specific surface area and total pore volume) of porous carbon material have been determined based on the analysis of nitrogen adsorption / desorption isotherms. It has been found that these materials have a frame structure with a large number of micropores. The analysis of literature data has revealed that the experimental curves belong to the isotherms that are characteristic of multilayer adsorption in micro- and mesopores of materials of organic origin. The hysteresis loop observed on these isotherms is related to the sorption processes in narrow pores. It has been found that carbonization of raw materials and chemical activation contribute to the cleaning of the frame structure, and there are acceptable modes of heat treatment of raw materials of plant origin, which determine the optimal pore size distribution and have a specific surface area S = (1042–1313) m2/g. With the help of scanning electron microscopy, the peculiarities of the formation of impurities on the surface of the original samples have been studied and their nature has been elucidated. It has been found that the largest total pore area has a sample carbonized at 600 ºC, and the largest pore volume Vtotal = 0.68 cm3/g for sample C3 is associated with a significant number of mesopores in the porous structure. As the carbonation temperature increases to 800-900 °C, narrow micropores degenerate and the carbon matrix transforms, resulting in a decrease in both the total pore area and the total porous volume.

Effect of ATR sample holder on the FT-IR spectrum of polypropylene foil

Pressing by ATR (Attenuate Total Reflection) accessory on the sample can cause reversible or irreversible material structure changes in the plastics. In the successive ATR- FT-IR spectra of the PP (polypropylene) film under constant compression, the shift of the baseline and the changes in the peak intensities can be observed, respectively. To interpret the changes in IR absorbances of the PP foil sample, a semi-empirical model is proposed by us. To separate the wavenumber-dependent and independent factors influencing the spectra, a spectrum pre-processing method consisting of baseline correction (rubber band correction) and SNV1-Anti-SNV2 transformation (SAS; SNV = standard normal variate) has been developed. With this spectrum pretreatment, the wavenumber-independent effect of the ATR sample holder on the IR spectrum can be compensated. As a result, the wavenumber-dependent effect can be uncovered. The feature of our spectrum pretreatment strategy to eliminate the wavenumber-independent effect is also supported by a mathematical deduction. The significant absorbance change induced by continuous clamping to PP foil has been confirmed by regression analysis. Correlation analysis among the spectral peaks shows strong correlations separately for both the primary and for the transformed spectra. Any peak combination of the primary spectra results in positive correlations. For the transformed spectra reflecting back only the wavenumber-dependent factor effect, the correlations between the peak intensities of the stretching and the bending vibrations are all negative. These negative correlations suggest that the compression applied in the ATR sample holder is give a rise to steric hindrance in deformation vibrations and affects the polarities of C-H valence bonds.

Assessing the fracture and fatigue resistance of nanostructured thin films

Fatigue failure through sustained loading of ductile materials manifests in irreversible motion of dislocations, followed by crack initiation and growth. This contrasts with the mechanisms associated with brittle ceramics, such as nanostructured physical vapor deposited thin films, where inhibited dislocation mobility typically leads to interface-controlled damage. Hence, understanding the fatigue response of thin films from a fundamental viewpoint – including altered atomic bonds, crystal structures, and deformation mechanisms – holds the key to improved durability of coated engineering components. Here, a novel method utilizing quasi-static and cyclic-bending of pre-notched, unstrained microcantilever beams coupled with in situ synchrotron X-ray diffraction is presented to study the fracture toughness and fatigue properties of thin films under various loading conditions. Investigating a model system of sputter-deposited Cr and Cr-based ceramic compounds (CrN, CrB2, and Cr2O3) demonstrates that the fatigue resistance of such thin films is limited by the inherent fracture toughness. In fact, cantilever cycling close to the critical stress intensity is sustained up to 107 load cycles on all materials, without inducing noticeable material damage, structural or stress-state changes. The observed variation in fracture toughness is put into context with linear-elastic fracture theory and complementary micro-pillar compression, thereby elucidating the wide range of values from as low as 1.6±0.2 MPa√m for Cr1.79O3 up to 4.3±0.3 MPa√m for Cr1.03B2, respectively. Moreover, possible mechanisms governing the elastic-plastic deformation response of all coatings, both in quasi-static and cyclic-loading conditions, are discussed. Our findings contribute key-insights into the underlying mechanisms dictating the damage tolerance of PVD coated components by relating fatigue strength limits to fundamental material properties.

Joining Processes for Fibre-Reinforced Thermoplastics: Phenomena and Characterisation.

Thermoplastic composites (TPCs) are predestined for use in lightweight structures, especially for high-volume applications. In many cases, joining is a key factor for the successful application of TPCs in multi-material systems. Many joining processes for this material group are based on warm forming the joining zone. This results in a change of the local material structure characterised by modified fibre paths, as well as varying fibre contents, which significantly influences the load-bearing behaviour. During the forming process, many different phenomena occur simultaneously at different scales. In this paper, the deformation modes and flow mechanisms of TPCs during forming described in the literature are first analysed. Based on this, three different joining processes are investigated: embedding of inserts, moulding of contour joints, and hotclinching. In order to identify the phenomena occurring in each process and to describe the characteristic resulting material structure in the joining zones, micrographs as well as computed tomography (CT) analyses are performed for both individual process stages and final joining zones.

Polymer Electrolyte Fuel Cell Degradation Investigations Using X-Ray Computed Tomography

On-going research is aimed at commercializing low temperature fuel cell technology systems as zero emission alternatives for automotive applications in order to reduce greenhouse gas emissions and air pollution. These systems use polymer electrolyte fuel cells (PEFCs) to generate electricity via an electrochemical process using hydrogen and ambient air (oxygen) to produce water. Advantages of PEFCs include quick start-up time, low operating temperature, low weight, high efficiency, and relatively simple design. An important area of current research is the identification of factors which affect fuel cell performance degradation during operation and ultimately, its durability. A technique that has yielded new insights in the investigation and identification of failure modes in fuel cells is lab-based X-ray computed tomography (XCT), which is most advantageous due to its on-demand availability. The Fuel Cell Research Laboratory (FCReL) at Simon Fraser University currently operates Canada’s only facility for multi-length scale XCT, comprising of two state-of-the-art laboratory-based XCT scanners from Carl Zeiss X-ray Microscopy (Zeiss Xradia 520 Versa and 810 Ultra) with complementary resolution and field of view capabilities. This unique combination offers unprecedented access to investigations at multi length scales; with an ability to probe fuel cell components at the micro as well as the nano scale. Figure 1 illustrates the fuel cell holder and its orientation with respect to the X-ray beam as well as an exploded view of the miniature fuel cell design.An overview of recent fuel cell degradation investigations at FCReL using the XCT technique will be shown. The XCT based workflow facilitates determination and quantification of material structure and properties changes resulting from degradation stresses associated with operational parameters such as temperature, relative humidity, and voltage. The non-destructive nature of lab-based XCT visualization coupled with the ability to scan the same fuel cell multiple times without inducing damage [1] has enabled detailed studies of fuel cell degradation evolution in four dimensions (3D space, 1D time) [2 - 4]. The new knowledge gained from this procedure has led to root cause identification with respect to membrane and catalyst layer crack initiation and propagation [5 - 7], sealing issues [8,9], and subsequent mitigation toward enhanced fuel cell durability. Acknowledgement This research was supported by the Natural Sciences and Engineering Research Council of Canada, Canada Foundation for Innovation, British Columbia Knowledge Development Fund, Western Economic Diversification Canada, Canada Research Chairs, and Ballard Power Systems.

Probing phonon dynamics with multidimensional high harmonic carrier-envelope-phase spectroscopy

We explore pump-probe high harmonic generation (HHG) from monolayer hexagonal-boron-nitride, where a terahertz pump excites coherent optical phonons that are subsequently probed by an intense infrared pulse that drives HHG. We find, through state-of-the-art ab initio calculations, that the structure of the emission spectrum is attenuated by the presence of coherent phonons and no longer comprises discrete harmonic orders, but rather a continuous emission in the plateau region. The HHG yield strongly oscillates as a function of the pump-probe delay, corresponding to ultrafast changes in the lattice such as specific bond compression or stretching dynamics. We further show that in the regime where the excited phonon period and the pulse duration are of the same order of magnitude, the HHG process becomes sensitive to the carrier-envelope phase (CEP) of the driving field, even though the pulse duration is so long that no such sensitivity is observed in the absence of coherent phonons. The degree of CEP sensitivity versus pump-probe delay is shown to be a highly selective measure for instantaneous structural changes in the lattice, providing an approach for ultrafast multidimensional HHG spectroscopy. Remarkably, the obtained temporal resolution for phonon dynamics is ∼1 femtosecond, which is much shorter than the probe pulse duration because of the inherent subcycle contrast mechanism. Our work paves the way toward routes of probing phonons and ultrafast material structural changes with subcycle temporal resolution and provides a mechanism for controlling the HHG spectrum.

Modelling and Analysis of CNC Milling Machine Bed with UHM CFRP composite Material

Abstract: Structural materials are used in a machine tool have a key role in defining the productivity, accuracy and Size proportions of the part manufactured by machine tool. The conventional structural materials like cast iron and Stainless or carbon steel at high operating speeds but used in precision machine tools grow positional errors due to the vibrations transferred into the Machine tool structure. Faster cutting speeds can be achieve only by structure which has good damping characteristics and high stiffness. Clearly the life of a machine tool is proportional to the levels of vibration Produce by machine. The further Work is carried out to Study the deformation and natural frequency using Static analysis and Modal analysis respectively. The bed in machine tool Took Major role in the precision in components. It is one of the greatest vital tool structures which is absorb the vibrations resultant from the cutting operation. To analyse the bed for possible material changes and Structure changes that could increase stiffness, decrease weight, expand damping characteristics and segregate natural frequency at the operating range. So main enthusiasm behind the impression to go for a composite Material in model involving ultra-High Modulus Carbon Fibre Reinforced Polymer Composite Material (UHM CFRP). In a carbon has good stiffness and strength properties but its absences in damping requirements. On the other hand, polymers, though its deficiencies in strength but, good damping in characteristics and it is easily holding the carbon fibres. So, this is makes greatest combination of materials in an appropriate manner. In this work, a machine tool’s bed is selected for the analysis static loads. Then study is carried out to decrease the weight of the machine tool’s bed without affecting its structural rigidity. The 3D CAD model of the bed has been created by using commercial 3D modelling software and analyses were carried out using ANSYS 2021 R2. Keywords: Composite material, hybrid structures, Milling machine bed, UHM CFRP.

Tunable Thermochromic Graphene Metamaterials with Iridescent Color.

Thermochromic materials have been widely applied in energy-efficient buildings, aerospace, textiles, and sensors. Conventional thermochromic materials rely on material phase or structure changes upon thermal stimuli, which only enable a few colors, greatly limiting their applicability. Here, we propose and demonstrate the concept of dynamically tunable thermochromic graphene metamaterials (TGMs), which can achieve continuous color tunability (380-800 nm) with fast (<100 ms) response times. The TGMs are composed of an ultrathin graphene oxide (GO) film on a flexible metal substrate. We demonstrated that external thermal energy can dynamically adjust the water contents in the GO film to manipulate the color of TGMs. An impressive thermochromic sensitivity of 1.11 nm/°C covering a large percentage of the color space has been achieved. Prototype applications for a cup and smartphone have been demonstrated. The reversible TGMs promise great potential for practical applications of temperature sensing in optoelectronic devices, environmental monitoring, and dynamic color modulation.

Atomically embedded Ag on transition metal hydroxides triggers the lattice oxygen towards sustained seawater electrolysis

Exploiting highly robust and active electrocatalysts for large-scale (sea)water electrolysis at industrial-level current densities (> 500 mA cm−2) is an increasingly appealing for developing renewable energy technologies. The current researches are limited by the complex synthetic procedures and poor stability of catalysts in practical application. Transition-metal (oxy)hydroxides are promising candidates for oxygen evolution reaction (OER) yet challenging approach to the clean energy by the low electrical conductivity. In this work, we pioneered an atomical-doping engineering strategy for achieving highly efficient and robust electrocatalyst towards large current density. Ag doped NiFe layered double hydroxide (LDH) was prepared by a one-step redox reaction on Ni foam without complex synthetic approach. Benefiting from the increased intrinsic conductivity, abundant active sites, and improved intrinsic surface area, Ag/NiFe LDH present a superior catalytic activity toward large-scale application, requiring low overpotentials of 240 and 276 mV at 100 and 1000 mA cm−2 in 1 M KOH, respectively. More importantly, a low overpotential of 303 mV at 1000 mA cm−2 in alkaline seawater-based electrolyte was attained, which remained 1000 h with long-term operation. Experimental and theoretical calculations demonstrated that the oxidation of Ag triggers the lattice oxygen redox and stabilizes the lattice oxygen, which does not induce significant material structure change and reconstruction during operation, ensuring the OER stability. This work remarkably advances the development of seawater electrolysis for large-scale clean energy.

Development and Verification Experiment of In-Situ Friction Experiment Device for Simulating UV Irradiation in Space.

In order to explore the influence of space ultraviolet radiation on spacecraft lubricating materials, an in-situ friction experimental device simulating space ultraviolet radiation was developed in the laboratory, and the experimental verification was carried out. This paper firstly introduced the design index, structure and working principle of the space ultraviolet irradiation simulation device, and then calibrated and tested the parameters of the whole device, and also conducted a virtual operation of the device’s operation effect by simulation software, and the results showed that it met the design index. Finally, the validation tested of the ultraviolet irradiated in-situ friction experimental device were described in detail. By using the device to irradiate the samples, it was found that the in-situ ultraviolet irradiation device could achieve the expected irradiation effect, and the irradiation would lead to changes in the surface structure and properties of the PTFE material, while also achieving the need for in-situ spatial friction property testing of the material, providing favorable conditions for future testing.

A Study on Early Stages of White Etching Crack Formation under Full Lubrication Conditions

The appearance of White Etching Cracks (WEC), not covered by the ISO 281 modified failure rate calculation, leads to difficulties in predicting bearing reliability. This uncertainty in bearing applications leads to a worldwide activity in order to understand and prevent this situation since the WEC failure mode deviates from the traditional Rolling Contact Fatigue (RCF) mode. Plenty of factors have been found to influence this phenomenon over the years, however the precise initiation of the WEC is still under debate. In order to understand the initiation and analyze the temporal evolution, interrupted tests on the same material were performed under conditions that were known to lead to WEC formation and RCF. To avoid the added complexity of boundary lubrication, a Deep Groove Ball Bearing (DGBB) test rig under full lubrication (Elastohydrodynamic Lubrication, EHL) was chosen. Within a standard operating mode, named Mode 1 (RCF), the bearings are solely subjected to a radial load. By suspending the tests at different time steps, a continuous progress of changes in the subsurface material structure seen as equiaxed grains with low dislocation densities, identified as ferrite, is observed. The bearings did not fail up to load cycles of 109. In contrast, a Mode 2 Electrical Charged Contact Fatigue (ECCF) test provoked the early formation of cracks and crack networks, first without WEA, then later with WEA. It became obvious when comparing Mode 1 (RCF) with Mode 2 (ECCF) that Mode 2 (ECCF) achieves far fewer load cycles until failure occurs.