Running Temperature and Mechanical Stability of Grease as Maintenance Parameters of Railway Bearings

Spherical roller bearings in railway car wheels are critical components whose failure may have catastrophic consequences. The present study aims to analyse the mechanical stability of greases and temperature of bearings as indicators for condition-based bearing maintenance. The performed case study includes nine fully-formulated commercial greases examined in the wheel bearings of five ore cars operated in northern Scandinavia. The studied ore cars travelled a distance of about 300 000 km during a period of three years. Small samples of the greases were taken on eight occasions to test their mechanical stability. In addition, the temperatures of the bearings were continuously recorded. After the test period, the wear, electrical damage, and corrosion of the bearings were examined. One of the findings is that the shear stress of the grease at a certain shear velocity （the certain yieldstress （CEY） value） is a good maintenance indicator and is highly dependent on the grease type. The bearing＇s wear, electrical damage and corrosion also depend on the grease type. However, no oxidation of the greases was identified. The paper also outlines a systematic methodology to determine an overall maintenance indicator for railway roller bearings which is based on the field measurements.

Fabrication of sintering-free flexible copper nanowire/ polymer composite transparent electrodes with enhanced chemical and mechanical stability

The thermal decomposition synthesis of long copper nanowires （CuNWs） was achieved by controlling the synthesis parameters. A detailed study was performed to determine the effect of the molar ratio of copper chloride to nickel acetylacetonate, temperature, and stirring rate on the final shape of the products. Transparent electrodes （TEs） were fabricated by wet treatment with acetic acid （AA）, without using a sintering process. The low oxidation stability and high surface roughness are the main disadvantages of the CuNW TEs, which limit their applications. In order to overcome these issues, we prepared CuNW/polymer composite TEs by partial embedding of the CuNWs into poly（methyl methacrylate） （PMMA） on poly（ethylene terephthalate） （PET） substrates. The CuNW/PMMA composite TEs exhibit excellent optoelectronic performance （91.3% at 100.7 ff2/sq）, low surface roughness （4.6 nm in height）, and good mechanical and chemical stability as compared with CuNW TEs. On the basis of these properties, we believe that CuNW-based composite TEs could serve as low-cost materials for a wide range of new optoelectronic devices.

Effect of volume fraction and mechanical stability of austenite on ductility of medium Mn steel

A hot-rolled medium Mn(0.2C5Mn)steel is annealed at 650℃ to produce an ultrafine-grained duplex microstructure with different austenite volume fractions by austenite reverted transformation(ART)annealing,and the orientation relationship strictly obeys K-S orientation relationship before deformation.Tensile tests are carried out in a temperature range from-196 to 400℃ to examine the effects of the austenite volume fraction and the deformation temperature on the tensile properties and the austenite stability.Microstructural observations reveal that the metastable austenite gradually transformed into a-martensite,which is controlled by the deformation strain,the temperature and the austenite volume fraction.Both strain hardening behavior and ductility of the studied steel are dependent on austenite volume fraction and deformation temperature significantly.The stress-strain curves of ART-annealed 0.2C5Mn steel assume an S shape and a very large work hardening rate of about 10 GPa is obtained at liquid nitrogen deformation temperature.Based on the experimental data,a quantitative relation is proposed to describe the ductility dependence on both the austenite volume fraction and its mechanical stability.

Enhanced mechanical stability of ultrafine grained steel through intercritical annealing cold rolled martensite

The ultrafine grained ferritic steels possess shortage of work hardening. Fine grained high strength but low ductility due to the ferrite-martensite dual phase microstruc- ture was obtained in a microalloyed steel and low carbon steels through intercritical annealing of the cold rolled martensite. The dual phase microstructure was uniform and the ferrite grain size was smaller in the microalloyed steel resulted from the pin- ning effect of microalloyed precipitates. But ferrite grown apparently and the volume fraction of the martensite was much higher without the addition of microalloying el- ements. By introducing martensite into the fine grained ferrite, the work hardening was effectively improved, leading to better mechanical stability. As a result of the fine ferrite grain size as well as uniform distribution of the martensite, the work harden- ing was enhanced, showing better strength-ductility balance in the microalloyed dual phase steel.

Preparation of Photoresponsive PAN-NH_(2)@EPESP Fiber Films with Mechanical Stability for Regulating Wettability and Micro-environment Humidity

In view of the current living micro-environment and requirements of green economy,intelligent light-responsive humidification materials have become a hot spot in intelligent polymer materials.In this work,reversible photoresponsive films with a mechanical stability and an excellent humidity adjustment performance are developed by modifying epoxy-ether-spiropyran(EPESP)on amino-nanofibers(PAN-NH2),which was produced through electrospinning.Such smart films for regulating wettability and micro-environment humidity can be reversibly manipulated by the simple switch of UV and visible light irradiation because of the unique transformation between polar ring-opened status and nonpolar ring-closed status of the spiropyran units.The effects of EPESP modification amount on the morphology,wettability,tensile strength and the ability to regulate humidity were investigated in detail.The results show that with the increase of modification amount of EPESP,both the humidity regulation and tensile strength increased;when the modification amount exceeds 7 mg,the range of regulating humidity increases slowly.

Mechanical and thermodynamical stability of BiVO4 polymorphs using first-principles study

First principles calculations of structural, electronic, mechanical, and thermodynamic properties of different poly- morphs of BiVO4 are performed using Bender-type plane/wave ultrasoft pseudopotentials within the generalized gradient approximation （GGA） in the flame of density functional theory （DFT）. The calculated structural and electronic properties are consistent with the previous theoretical and experimental results. The electronic structures reveal that m-BiVO4, op- BiVO4, and st-BiVO4 have indirect band gaps, on the other hand, zt-BiVO4 has a direct band gap. From the DOS and Mulliken＇s charge analysis, it is observed that only m-BiVO4 has 6s2 Bi lone pair. Bond population analysis indicates that st-BiVO4 shows a more ionic nature and a similar result is obtained from the elastic properties. From the elastic prop- erties, it is observed that st-BiVO4 is more mechanically stable than the others, st-BiVO4 is more ductile and useful for high electro-optical and electro-mechanical coupling devices. Our calculated thermodynamic properties confirm the similar characteristics found from electronic and elastic properties, m-BiVO4 is useful as photocatalysts, solid state electrolyte, and electrode and other polymorphs are applicable in electronic device fabrications.

An ab Initio Study of Mechanical and Electronic Properties of Stable Phases of CsXBr3 (X = Ge, Si) Compounds for Solar Cell Applications

Utilising the density functional theory, the mechanical and electrical characteristics of Cesium Germanium Bromide, CsGeBr3 and Cesium Silicon Bromide CsSiBr3 compounds were computed. The complicated and unique physical and chemical properties of these materials include the ideal geometric property, a limited electronic band structure, a charge density distribution, and specific van Hove singularities in the electronic density of states. With the use of the quantum espresso code and pseudo-potentials taken from the quantum espresso data repository, we have applied density functional theory. Plane Wave (PW) basis set and Projector Augmented Wave (PAW) pseudo potentials were used to compute the ground state energy. For the exchange correlation, where plane wave basis sets are used to expand the electronic structure wave function, the Generalised Gradient Approximation (GGA) was employed. For the computation of mechanical behaviour, including the bulk modulus and elastic constants with their derivatives, Thermo_pw was used as a post-processing algorithm. The theoretical framework that is being taught gives a thorough understanding of the many qualities and possible uses for solar cells and other opto-electronic devices. Both the cubic (high-temperature) and tetragonal (low-temperature) phases of CsGeBr3 were discovered to have an appropriate gap for solar cells. The edge-sharing monoclinic phase exhibits a greater distortion of the band structure than the cubic phase, which has a lower total energy and a somewhat bigger electronic gap. Although our estimations are less definite because the matching silicon-based compounds have not yet been created, they nonetheless point to a small gap for cubic CsGeBr3 of about 0.2 - 0.8 eV.

Curing Kinetics, Mechanical Properties and Thermal Stability of Epoxy/Graphene Nanoplatelets(GNPs) Powder Coatings

Epoxy/graphene nanoplatelets（GNPs） powder coatings were fabricated using ultrasonic predispersion of GNPs and melt-blend extrusion method. The isothermal curing kinetics of epoxy/GNPs powder coating were monitored by means of real-time Fourier transform infrared spectroscopy（FT-IR） with a heating cell. The mechanical properties of the epoxy/GNPs cured coatings had been investigated, by evaluating their fracture surfaces with field-emission scanning electron microscopy（FE-SEM） after three-point-bending tests. The thermal stability of the epoxy/GNPs cured coatings was studied by thermo-gravimetric analysis（TGA）. The isothermal curing kinetics result showed that the GNPs would not affect the autocatalytic reaction mechanism, but the loading of GNPs below 1.0 wt % additive played a prompting role in the curing of the epoxy/GNPs powder coatings. The fracture strain, fracture toughness and impact resistance of the epoxy/GNPs cured coatings increased dramatically at low levels of GNPs loading（1 wt %）, indicating that the GNPs could improve the toughness of the epoxy/GNPs powder coatings. Furthermore, from FE-SEM studies of the fracture surfaces, the possible toughening mechanisms of the epoxy/GNPs cured coatings were proposed. TGA result showed that the incorporation of GNPs improved the thermal stability of the cured coatings. Hence, the GNPs modified epoxy can be an efficient approach to toughen epoxy powder coating along with improving their thermal stability.

Mechanical Property Stability of Cu-Mo-Ni Alloyed Austempered Ductile Iron

The aim of present work is to investigate the influencing factors on mechanical property stability of Cu-Mo-Ni alloyed austempered ductile iron （ADI）. The results show that after austenitized at 900℃ for 2 h followed by austempered at 370℃for another 2 h, the mechanical property of the alloyed ADI can reach the Germanite GGG-100 standard, i.e. σb≮1000 MPa,δ≮5%, at 95% confidence level. And the satisfactory mechanical properties were obtained when the alloyed ADI was austenitized at 850℃ to 1 000 ℃ for 1-4 h, and austempered at 355℃ to 400℃ for another 1 h to 4 h. The microstructures, including nodule number, white bright zone content （martensite-containing interdendritic segregation zone） and retained austenite content, can significantly influence the mechanical properties of the ADI. In order to obtain the good combinations of strength and ductility, the volume fraction of white bright zone should he less than 5%, and the retained austenite contents maintain hetween 30 % and 40%. The application of inoculation techniques to increase graphite nodule number can effectively reduce the white bright zone content in the structure.

Unraveling the Fundamental Mechanism of Interface Conductive Network Influence on the Fast‑Charging Performance of SiO‑Based Anode for Lithium‑Ion Batteries

Progress in the fast charging of high-capacity silicon monoxide(SiO)-based anode is currently hindered by insufficient conductivity and notable volume expansion.The construction of an interface conductive network effectively addresses the aforementioned problems;however,the impact of its quality on lithium-ion transfer and structure durability is yet to be explored.Herein,the influence of an interface conductive network on ionic transport and mechanical stability under fast charging is explored for the first time.2D modeling simulation and Cryo-transmission electron microscopy precisely reveal the mitigation of interface polarization owing to a higher fraction of conductive inorganic species formation in bilayer solid electrolyte interphase is mainly responsible for a linear decrease in ionic diffusion energy barrier.Furthermore,atomic force microscopy and Raman shift exhibit substantial stress dissipation generated by a complete conductive network,which is critical to the linear reduction of electrode residual stress.This study provides insights into the rational design of optimized interface SiO-based anodes with reinforced fast-charging performance.

Single-molecule mechanical folding and unfolding kinetics of armless mitochondrial tRNA^(Arg) from Romanomermis culicivorax

The mechanical stability of tRNAs contributes to their biological activities.The mitochondrial tRNAArg from Romanomermis culicivorax is the shortest tRNA ever known.This tRNA lacks D-and T-arms,represents a stem-bulge-stem architecture but still folds into a stable tertiary structure.Although its structure had been reported,studies on its mechanical folding and unfolding kinetic characteristics are lacking.Here,we directly measured the single-molecule mechanical folding and unfolding kinetics of the armless mt tRNAArg by using optical tweezers in different solution conditions.We revealed a two-step reversible unfolding pathway:the first and large transition corresponds to the unfolding of acceptor stem and bulge below 11 pN,and the second and small transition corresponds to the unfolding of anticodon arm at 12 pN-14 pN.Moreover,the free energy landscapes of the unfolding pathways were reconstructed.We also demonstrated that amino acid-chelated Mg^(2+)(aaCM),which mimics the intracellular solution condition,stabilizes the bulge of mitochondrial tRNAArg possibly by reducing the topological constraints or stabilizing the possible local non-canonical base pairings within the bulge region.Our study revealed the solution-dependent mechanical stability of an armless mt tRNA,which may shed light on future mt tRNA studies.

The role of microstructure and its stability in performance of wheels in heavy haul service

Thermal or thermo-mechanical loading is one of the major causes of wheel surface damage in Australian heavy haul operations.In addition,multi-wear wheels appear to be particularly sensitive to thermo-mechanical damage during their first service life.Such damage can incur heavy machining penalties or even premature scrapping of wheels.The combination of high contact stresses as well as substantial thermal loading(such as during prolonged periods of tread braking) can lead to severe plastic deformation,thermal fatigue and microstructural deterioration.For some high-strength wheel grades,the increased sensitivity to thermo-mechanical damage observed during the first service period may be attributed to the presence of a near-surface region in which the microstructure is more sensitive to these loading conditions than the underlying material.The standards applicable to wheels used in Australian heavy haul operations are based on the Association of American Railroads(AAR) specification M-107/M-208,which does not include any requirements for microstructure.The implementation of acceptance criteria for the microstructure,in particular that in the near-surface region of the wheel,may be necessary when new wheels are purchased.The stability of wheel microstructures during thermo-mechanical loading and the effects of alloying elements commonly used in wheel manufacturing are reviewed.A brief guide to improving thermal/mechanical stability of the microstructure is also provided.

MECHANICAL STABILIZATION OF DEFORMED AUSTENITEDURING CONTINUOUS COOLING TRANSFORMATION IN AC-Mn-Cr-Ni-Mo PLASTIC DIE STEEL

The influence of prior austenite deformed at different temperature on the subsequent continuous cooling bainitic transformation has been investigated in an C-Ma-Cr-Ni-Mo plastic die steel. The results show that the prior deformation in low temperature region of austenite retards significantly the bainitic transformation. For the same continuous cooling schedule, as austenite deformed at lower temperature, the quantity of the classical sheaf-like bainite becomes less. The present results show that severe deformation leads to mechanical stabilization of austenite and causes the difficulty of bainitic ferrite propagation into the austenite.

Experimental evaluation of mechanically stabilized earth walls with recycled crumb rubbers

Traditional techniques for treatment of waste rubber, such as burning, generate some highly non- degradable synthetic materials that cause unrepairable environmental damages by releasing heavy metals, such as arsenic, chromium, lead, manganese and nickel. For this, scrap tires are used as light- weight alternative materials in many engineering applications, such as retaining wall backfilling. In the present study, 90 laboratory models were prepared to evaluate the stability of mechanically stabilized earth （MSE） walls with plate anchors. Then, the bearing capacity and horizontal displacements of the retaining walls were monitored by exerting a static loading to investigate the effects of adding different contents （5 wt%, 10 wt%, 15 wt% and 20 wt%） of recycled crumb rubber （RCR） to the fill of a mechanically stabilized retaining wall with plate anchors. To visualize the critical slip surface of the wall, the particle image velocimetry （PIV） technique was employed. Results showed that the circular anchor plates almost continually provided a higher bearing capacity and wall stability than the square plates. Moreover, the backfill with 15 wt% RCR provided the maximum bearing capacity of the wall. Increasing the weight percentage of RCR to 20 wt% resulted in a significant reduction in horizontal displacement of the wall, which occurred due to the decrease in lateral earth pressure against the whole walls. An increase in RCR content resulted in the decrease in the formation of failure wedge and the expansion of the wall slip surface, and the failure wedge did not form in the sand mixtures with 15 wt% and 20 wt% RCRs.

Effect of Nb and Ti on second-phase precipitation and mechanical properties of 430 ferritic stainless steel

The influence of Ti and Nb on the microstructure,mechanical properties,and second-phase precipitation of 430 ferritic stainless steel was investigated.In addition to optical microscopy,transmission electron microscopy and X-ray diffraction analyses,tensile tests,and carbonitride extraction experiments were conducted to investigate the microscopic mechanisms.The results showed that the primary precipitates in SUS 430 ferritic stainless steel were Cr_（23）C_6,Mn_（23）C_6,and Cr_7C_3,and the primary strengthening mechanism was precipitation strengthening.When Ti was added separately,the main precipitates were TiC and TiN.However,coarse TiC adversely affected the mechanical properties of steel.When double-stabilized with Ti and Nb,coarse TiC was replaced by fine NbC.The type of precipitation was altered,and precipitation and solid solution strengthening occurred.Therefore,the tensile strength and plastic strain ratio（r-value） improved to 433.60 MPa and 1.37,respectively.

An upgraded polymeric composite with interparticle chemical bonding microstructure toward lithium-ion battery separators with enhanced safety and electrochemical performances

A composite separator of SiC/PVDF-HFP was synthesized for lithium-ion batteries with high thermal and mechanical stabilities.Benefiting from the nanoscale,high hardness,and melting point of SiC,SiC/PVDFHFP with highly uniform microstructure was obtained.This polarization caused by barrier penetration was significantly restrained.Due to the Si-F bond between SiC and PVDF-HFP,the structural stability has been obviously enhanced,which could suppress the growth of lithium(Li) dendrite.Furthermore,some 3D reticulated Si nanowires are found on the surface of Li anode,which also greatly inhibit Li dendrites and result in irregular flakes of Li metal.Especially,the shrinkage of 6% SiC/PVDF-HFP at 150℃ is only 5%,which is notably lower than those of PVDF-HFP and Celgard2500.The commercial LiFePO_(4) cell assembled with 6% SiC/PVDF-HFP possesses a specific capacity of 157.8 mA h g^(-1) and coulomb efficiency of 98% at 80℃.In addition,the tensile strength and modulus of 6% SiC/PVDF-HFP could reach 14.6 and 562 MPa,respectively.And a small deformation(1000 nm) and strong deformation recovery are obtained under a high additional load(2.3 mN).Compared with PVDF-HFP and Celgard2500,the symmetric Li cell assembled with 6% SiC/PVDF-HFP has not polarized after 900 cycles due to its excellent mechanical stabilities.This strategy provides a feasible solution for the composite separator of high-safety batteries with a high temperature and impact resistance.

Utilizing hybrid faradaic mechanism via catalytic and surface interactions for high-performance flexible energy storage system

Improving the capacitance and energy density is a significant challenge while developing practical and flexible energy storage system(ESS).Redox mediators(RMs),as redox-active electrolyte additives,can provide additional energy storing capability via electrochemical faradaic contribution on electrodes for high-performance flexible ESSs.Particularly,determining effective material combinations between electrodes and RMs is essential for maximizing surface faradaic redox reactions for energy-storage performance.In this study,an electrode-RM system comprising heterostructured hybrid(carbon fiber(CF)/MnO_(2)) faradaic electrodes and iodine RMs(I-RMs) in a redox-active electrolyte is investigated.The CF/MnO_(2)with the 1-RMs(CF/MnO_(2)-I) induces dominant catalytic faradaic interaction with the I-RMs,significantly enhancing the surface faradaic kinetics and increasing the overall energy-storage performance.The CF/MnO_(2)-I ESSs show a 12.6-fold(or higher) increased volumetric energy density of 793.81 mWh L^(-1)at a current of 10 μA relative to ESSs using CF/MnO_(2)without I-RMs(CF/MnO_(2)).Moreover,the CF/MnO_(2)-I retains 93.1% of its initial capacitance after 10,000 cycles,validating the excellent cyclability.Finally,the flexibility of the ESSs is tested at different bending angles(180° to 0°),demonstrating its feasibility for flexible and high-wear environments.Therefore,CF/MnO_(2)electrodes present a practical material combination for high-performance flexible energy-storage devices owing to the catalytic faradaic interaction with I-RMs.

Lithium nitrate regulated carbonate electrolytes for practical Li-metal batteries: Mechanisms, principles and strategies

Li-metal batteries(LMBs)regain research prominence owing to the ever-increasing high-energy requirements.Commercially available carbonate electrolytes exhibit unfavourable parasitic reactions with Limetal anode(LMA),leading to the formation of unstable solid electrolyte interphase(SEI)and the breed of Li dendrites/dead Li.Significantly,lithium nitrate(LiNO_(3)),an excellent film-forming additive,proves crucial to construct a robust Li_(3)N/Li_(2)O/Li_(x)NO_(y)-rich SEI after combining with ether-based electrolytes.Thus,the given challenge leads to natural ideas which suggest the incorporation of LiNO_(3) into commercial carbonate for practical LMBs.Regrettably,LiNO_(3) demonstrates limited solubility(~800 ppm)in commercial carbonate electrolytes.Thence,developing stable SEI and dendrite-free LMA with the incorporation of LiNO_(3) into carbonate electrolytes is an efficacious strategy to realize robust LMBs via a scalable and cost-effective route.Therefore,this review unravels the grievances between LMA,LiNO_(3)and carbonate electrolytes,and enables a comprehensive analysis of LMA stabilizing mechanism with LiNO_(3),dissolution principle of LiNO_(3) in carbonate electrolytes,and LiNO_(3) introduction strategies.This review converges attention on a point that the LiNO_(3)-introduction into commercial carbonate electrolytes is an imperious choice to realize practical LMBs with commercial 4 V layered cathode.

The geomechanics of Shenhua carbon dioxide capture and storage(CCS) demonstration project in Ordos Basin,China

Carbon dioxide(CO2) capture and storage(CCS) is considered widely as one of promising options for CO2emissions reduction,especially for those countries with coal-dominant energy mix like China.Injecting and storing a huge volume of CO2in deep formations are likely to cause a series of geomechanical issues,including ground surface uplift,damage of caprock integrity,and fault reactivation.The Shenhua CCS demonstration project in Ordos Basin,China,is the first and the largest full-chain saline aquifer storage project of CO2in Asia.The injection started in 2010 and ended in 2015.during which totally 0.3 million tonnes(Mt) CO2was injected.The project is unique in which CO2was injected into 18 sandstone formations simultaneously and the overlying coal seams will be mined after the injection stopped in 2015.Hence,intense geomechanical studies and monitoring works have been conducted in recent years,including possible damage resulting from the temperature difference between injected CO2and formations,injection induced stress and deformation change,potential failure mode and safety factor,interaction between coal mining and CO2geological storage,determination of injection pressure limit,and surface monitoring by the interferometric synthetic aperture radar(InSAR) technology.In this paper,we first described the background and its geological conditions of the Shenhua CCS demonstration project.Then,we gave an introduction to the coupled thermo-hydro-mechano-chemical(THMC) processes in CO2geological storage,and mapped the key geomechanical issues into the THMC processes accordingly.Next,we proposed a generalized geomechanical research flowchart for CO2geological storage projects.After that,we addressed and discussed some typical geomechanical issues,including design of injection pressure limit.CO2injection induced near-field damage,and interaction between CO2geological storage and coal mining,in the Shenhua CCS demonstration project.Finally,we concluded some insights to this CCS project.

Effect and mechanism of reductive polyaniline on the stability of nitrocellulose

The search for new green and efficient stabilizers is of great importance for the stabilization of nitrocellulose(NC). This is due to the shortcomings of traditional stabilizers, such as high toxicity. In this study, reduced polyaniline(r-PANI), which has a similar functional structure to diphenylamine(DPA) but is non-toxic, was prepared from PANI based on the action with N_(2)H_(4) and NH_(3)-H_(2)O, and used for the first time as a potential stabilizer for NC. XPS, FTIR, Raman, and SEM were used to characterize the reduced chemical structure and surface morphology of r-PANI. In addition, the effect of r-PANI on the stabilization of NC was characterized using DSC, VST, isothermal TG, and MMC. Thermal weight loss was reduced by 83% and 68% and gas pressure release by 75% and 49% compared to pure NC and NC&3%DPA, respectively.FTIR and XPS were used to characterize the structural changes of r-PANI before and after reaction with NO_(2). The 1535 cm^(-1) and 1341 cm^(-1) of the FTIR and the 404.98 eV and 406.05 eV of the XPS showed that the -NO_(2) was generated by the absorption of NO_(2). Furthermore, the quantum chemical calculation showed that NO_(2) was directly immobilized on r-PANI by forming -NO_(2) in the neighboring position of the benzene ring.