Life Of Components Research Articles

Response characteristics of platinum coated titanium bipolar plates for proton exchange membrane water electrolysis under fluctuating conditions

Voltage fluctuations in energy input not only impact the overall hydrogen production efficiency and stability of Proton Exchange Membrane Water Electrolysis (PEMWE) systems but also pose significant challenges to the long-term service life of individual components. This study focuses on the key component − bipolar plates and investigates the response behavior of platinum-coated titanium bipolar plates under simulated fluctuating voltage conditions. By integrating surface phase analysis and electrochemical testing results, this research elucidates the response characteristics of the bipolar plates to different voltage waveforms and frequencies. And the findings hold substantial significance for the upstream energy control in hydrogen production through water electrolysis.

Non-local fatigue criterion based on standard deviation for notches and defects in Ti-6Al-4V

The aim of this study is to propose a non local multiaxial fatigue criterion in order to assess the fatigue limit of stress concentrator such as notches or defects in Ti-6Al-4V. This criterion is based on the standard deviation of the stresses integrated over a given volume around the hot spot point. Up to now, the standard deviation has never been tested as an indicator of stress heterogeneity to assess fatigue life of notch components. Four parameters are necessary to identify the criterion. The criterion is first validated on notched samples based on literature results and shows very good results. A set of experimental tests is conducted on natural and artificial defects including clustering defects and demonstrates the flexibility and accuracy of the criterion.

MXene quantum dots modified pitaya peel-based composite phase change material with excellent thermal properties for building energy efficiency applications

Bio-based materials have attracted much attention because their application in the construction field is conducive to energy saving and emission reduction. In this paper, a bio-based composite phase change material (CPCM) was prepared by utilizing pitaya peel as a bio-based material, MXene quantum dots (MQDs) as a modified material, and polyethylene glycol (PEG) as a phase change medium. MXene quantum dots dispersed in the pitaya peel-based porous carbon skeleton enhanced the three-dimensional thermal conductivity network of the porous carbon skeleton somewhat improved the thermal conductivity (0.676 W/mK) of the polyethylene glycol/MXene quantum dots-modified pitaya peel-based porous carbon foam (PPF) composite phase change material (PEG/PPF@M). It is worth noting that PEG/PPF@M has excellent thermal stability and its enthalpy is basically unchanged after 100 cycles, which proves the recyclable stability of PEG/PPF@M in practical applications. PEG/PPF@M has great potential for thermal management of buildings and electronic components. Overall, a novel multifunctional CPCM was prepared in this study using a simple process method, which can not only be applied in electronic products to improve the service life of electronic components, but also in the field of construction to realize energy saving and emission reduction, as well as the recycling and reuse of waste.

Fatigue damage assessment of a large rail-cum-road steel truss-arch bridge using structural health monitoring dynamic data

Structural health monitoring (SHM) system provides valuable information for the fatigue assessment of existing rail-cum-road bridges. This paper aims to develop an effective fatigue assessment approach for the rail-cum-road bridge, Jiujiang Yangtze River Bridge, by utilising the SHM data, focusing on dynamic modal analysis, finite element model updating and fatigue assessment. First, the traffic load spectrum and modal characteristics of the bridge are investigated from the SHM data. A three-dimensional finite element model is constructed and then updated by using the measured modal data through the proposed regularised model updating method. Then, the updated numerical model is verified with the measured dynamic response data, which can be utilised for calculating stress response at critical structural components of the rail-cum-road bridge. Finally, an improved Corten-Dolan’s model is proposed to analyse the fatigue damage and structural reliability of the critical structural components of the bridge, taking into account the combined effects of train and highway vehicle loads. The results demonstrate that the proposed fatigue assessment method provides more reliable results for the rail-cum-road bridge by considering the combined effect of multi-level traffic loads and the non-linear fatigue damage accumulation. It is concluded that the short H-shaped suspender is identified as the most vulnerable structural member of the rail-cum-road bridge, and the remaining fatigue service life of the typical components of the bridge should meet the design requirement.

Fatigue performance of a fastener hole treated by a novel electromagnetic strengthening process

In this study, a novel non-contacting electromagnetic cold expansion process was proposed to improve the fatigue performance of hole component using a single power supply and a single coil. The stress state and deformation of the 6063-T6 aluminum alloy hole component during the electromagnetic strengthening process were investigated through numerical simulation. The residual stress around the hole edge was measured using XRD. Fatigue testing was performed to verify the effectiveness of the process on improving the fatigue life of the hole component. Results showed that the proposed electromagnetic strengthening process could effectively improve the fatigue life of the hole component. Fatigue life of the specimen via electromagnetic treatment is 3.42 times of that of the original specimen at a maximum stress of 120 MPa. Simulation results indicated that the generation of compressive residual stress was attributed to the falling stage of the pulse current, and the maximum compressive residual stress was −102 MPa.

Large Eddy Simulations of a Francis Turbine Operating at Ultra-Low Load to Overload Conditions

Due to the increasing global power demand, hydropower plants face the challenge of operating at flow rates far from their best efficiency point to comply with the electrical grid. Consequently, turbine units experience unstable high swirling flows under different load conditions, reducing the life of system components. Understanding the mechanisms behind the onset and sustenance of these instabilities in the swirling flow leaving the turbine runner is crucial for improving turbine performance. To achieve this, large-eddy simulations (LES) were conducted to characterize the unsteady flow inside an industrial-sized Francis turbine. The turbine was studied under a wide range of flow rates, 100, 80, 60, 40, and 120% of the design flow rate. A high swirl velocity was introduced as the flow rate deviated from 100% load, causing significant changes in the flow structure. An organized structure of vortex filaments in a helical pattern is seen inside the draft tube at 80 and 60% load, and the 40% load case showed an unorganized collection of small-scale vortices. A straight vortex cavity is seen in the draft tube center at 120% excess load. At the best design point, the magnitude of the swirl velocity was 0.1 times the tip speed. However, as the flow rate dropped to 40% of the design flow rate, the magnitude increased to 0.4 times the tip speed near the wall. In addition, the 40% load case had the highest magnitude of pressure fluctuations, over 25 times the peak design case near the runner. This showed a very unsteady flow field could damage the system or cause unstable operation at ultra-low partial loads. Generated power dropped dramatically as the flow rate decreased, and more noise was present in the power signal.

Surface integrity and high-cycle fatigue life of direct laser metal deposited AISI 431 alloys modified by plasticity ball burnishing

Laser metal deposition (LMD) as an additive manufacturing (AM) is widely used to repair and extend wear and fatigue life of the critical components. This paper has investigated the application of ball burnishing (BB) to improve surface integrity and high-cycle fatigue resistance of LMDed AISI 431 alloys. Results showed that the BB treated samples exhibited significant surface finish improvement by lowering roughness by 91 %. Microhardness increased from 490 to 530 HV0.1, an increase by 10 % with a modified depth of 400 µm from the top surface. XRD results showed a peak shift and increase in FWHM by up to 17 %. This had been corroborated by EBSD exhibiting a 20 % increase in dislocation density and 24 % increase in localised misorientation within microstructure. As a result, the overall high cycle fatigue strength of the burnished sample increased by 50 %, and the cracks initiated from sub-surface level defects at a depth of 350 μm below the top surface, delaying the crack propagation and fracture failure. The findings clearly highlight that the burnishing treatment can be a plausible approach in improving the dynamic fatigue resistance and the overall service life of LMDed AISI 431 steel alloys components in engineering applications.

Reliability analysis of 50000 kN hydraulic support test bench under shrinkage test conditions

The large mining-height hydraulic support test-bed serves as a crucial tool for heavy hydraulic support factory inspections and type testing. With the successful development of the ZY29000/45/100D hydraulic support, the need for a large high-mining hydraulic support test-bed has become evident. This paper combines the theory of rigid-flexible coupling in virtual prototypes and ADAMS multi-body dynamic simulation technology to analyze the strength of the 50,000 kN hydraulic support test-bed. ANSYS classic modules were employed to address the flexibility of key components within the test-bed. The fatigue life of the test-bed was analyzed using NSOFT software, the von Mises yield criterion, and the Goodman modified curve. The S-N curve of material parameters for the test-bed components was used to conduct a shrinkage test. The results indicate that the lowest position is the most vulnerable during the shrinkage test. Among the key components, the stress on the pin bearing is 356.6 MPa, which is 167.9 %, 123.3 %, and 41.6 % higher than that of the pillar, movable beam, and base, respectively. The fatigue life of the base under low, medium, and high shrinkage conditions is1.1×107, 4.0×108, and 1.7×108, with damage values of 8.8×10-8, 2.5×10-9, and 5.7×10-9, respectively. The base’s life under low shrinkage conditions is the shortest, followed by that under high shrinkage conditions. These research findings provide technical guidance and an optimization foundation for the successful development of a 50000 kN hydraulic support test-bed. They also offer a new method and approach for analyzing and predicting the fatigue life of key components in large-scale industrial and mining equipment operating under complex conditions, with promising practical applications.

Fatigue damage accumulation in a bolted joint subjected to the random loading

Fatigue damage in structures, which escalates with cyclic loading, is traditionally analyzed using blocks of constant amplitude. This study aims to derive the fatigue loading spectrum for the Cirrus SR20 multipurpose airplane and predict the fatigue life of its main spar connection. Using available reference loading data from acrobatic and training aircraft, the loading spectrum was established, and constant amplitude loading blocks were determined through the Rainflow cycle counting and statistical methods. Fatigue damage in the bolted joint was assessed using both linear and nonlinear Miner rules, revealing that results from nonlinear criteria tend to converge towards those from linear predictions as loading blocks increase. This approach provides a robust predictive framework for assessing the fatigue life of airplane components under variable amplitude loadings, potentially enhancing maintenance protocols and structural design durability.

Phase-field modeling of crack growth under coupled creep-fatigue

Crack growth under coupled creep-fatigue strongly influences service life of metallic components operating at high temperatures. However, there lack numerical models that enable direct simulations of crack growth and plasticity development under coupled creep-fatigue. In this study, a unified phase-field model is developed for simulating crack growth under fatigue, creep, and coupled creep-fatigue. This model is able to reproduce the Paris laws for both brittle and ductile materials in pure fatigue mode, which shows that the degradation rate due to cyclic stress in ductile materials is generally larger than that in brittle materials. Fatigue simulations with different yield strengths demonstrate that plasticity facilitates crack growth in typical ductile materials. High-throughput simulations are performed under coupled creep-fatigue conditions, with varying hold-stress levels and hold-time. By analyzing crack growth rate under different hold-time, a creep-fatigue interaction term is obtained. Simulation results demonstrate that the creep-fatigue interaction is caused by smaller stress gradient and enhanced degradation rate ahead of the crack tips under coupled creep-fatigue, compared to the situation of pure fatigue. This work reveals the origin of different Paris-law exponents in brittle and ductile materials and demonstrates how the interplay between creep and fatigue affects crack growth.

Fatigue performance and damage of partially prestressed concrete beam with fiber reinforcement

Ordinary concrete exhibits low strength and a propensity for cracking. Carbon fibers and aramid fibers, as materials characterized by high strength, high toughness, and excellent fatigue resistance, can effectively limit the propagation of micro-cracks and enhance the strength of concrete. To explore the influence of different fiber types on the fatigue performance of prestressed concrete beams, this study initiates from the perspective of beam components. Employing a combination of experimental research and theoretical analysis, it conducts bending and constant-amplitude fatigue tests on 12 prestressed concrete beams with various fiber types. Based on the stiffness of the beam section and residual strain, the damage evolution patterns of the tested beams were described. The results indicated that the utilization of fiber-reinforced concrete significantly improves the fatigue life and residual bearing capacity of the beam components. Specifically, the residual bearing capacities of beams reinforced with carbon fibers, aramid fibers, and hybrid fibers increased by 58.6 %, 49.5 %, and 64.9 %, respectively. The analysis revealed that residual strain is a suitable indicator for describing fatigue damage in specimens and recommends prioritizing the concrete residual strain index. These findings provided a theoretical basis for the application of fiber-reinforced concrete in practical engineering projects and lifespan assessment.

Uncertainty quantification in residual stress affected fatigue crack growth life

In recent years a number of studies have been performed in which the impact of residual stress on structural performance, especially fatigue performance, has been evaluated both experimentally and analytically. These efforts are leading to an emerging paradigm in which residual stresses are represented explicitly in structural design, analysis, manufacturing and sustainment calculations. In order for this new approach to be become minimally viable, it is necessary to be able to quantify both the residual stresses in the structural component in question, and the impact that those residual stresses have on component strength and life. However, to achieve general acceptance, especially for critical applications in which the presence of the residual stress directly impacts whether or not the component will meet its design requirements, deterministic quantification alone may not be sufficient. Thus, it may be necessary to quantify the uncertainties in both the residual stresses and the resulting fatigue lives.

Current-carrying tribological behavior and wear mechanism of CuW composites with different W content

CuW composites are widely used in the field of electrical contacts, such as high-voltage switch and microelectronic devices, and the service life of the key components is directly affected by its wear resistance and corrosion resistance. In this paper, the effects of loading current on the tribological behavior of CuW composites with different W content were studied, focusing on the variation of friction coefficient during friction, wear rate and the wear topography of the surface after friction, and the wear mechanism was discussed. The results indicate that the friction coefficient of CuW composites was larger under energized conditions than under dry friction conditions, and that the friction coefficient first increases and then decreases with the increasing current. The main reason for the decrease in friction coefficient is that the heat generated by increasing current creates a layer of molten lubricant on the contact surface. In addition, the wear rate of the CuW composites decreased as the W content increased. When loaded with a current of 15 A, the CuW80 composites exhibited the lowest wear rate of 8 × 10−3 mg/m, which was attributed to the improved wear resistance due to the ability of the high W content to resist plastic deformation. The wear forms of CuW composites under current loading include adhesion, abrasive wear and arc erosion, and fatigue wear was also associated with long-term high current conditions.

Use of mobile metallography to assess the extent of damage to high temperature components in power plants

Abstract Microstructural replicas are used in recurrent testing of hot, pressuriszed components to detect creep damage. The test location must be representative of the damage development and subsequent component failure. Poor preparation leads to the formation of artefacts which are considered in the damage assessment. The assessment is subject to method and operator variability. When assessing the life of components based on microstructure replicas, these must be taken into account and, if necessary, extended stress calculations for the component must be used.

Development of High Temperature Materials for Aero Engine Hot End Components: An Overview

The present paper overviews the development of materials and superalloys for aero engine hot end components to meet the increasing trend of turbine inlet temperature. Requirement of higher and higher thrust is steadily increasing the turbine inlet temperature and the development of nickel-chromium superalloys in early 1940s could not fulfil the material capability for long. Various nickel-base superalloys developed in 1950s and 1960s could increase the life of hot end components by retaining strength and resisting oxidation at extreme temperatures. In the 1960s and 1970s, with almost stagnation in high temperature alloy development, metallurgists changed focus from alloy chemistry to alloy processing which evolved the directional solidification and single crystal casting technologies. At present, almost all fighter class engines and high bypass commercial engines are using nickel and cobalt base superalloys for hot end components and single crystal superalloys particularly for turbine blades. This paper covers the developmental phases of superalloys and casting technologies for engine hot end components. This paper will be an invaluable asset for the researchers as well as for designers of future gas turbine engines.

Predicting fatigue failure in five‐axis machined ball‐end milled components through FKM local stress approach

AbstractComponents created with five‐axis machining show a multi‐scale surface character due to cusps created on the surface and feed and tool marks within the cusps. Therefore, it becomes difficult to incorporate the effects of surface character on fatigue life for such components. In this work, an Forschungskuratorium Maschinenbau (FKM) guideline is adapted to develop a fatigue prediction model which considers cusps as notches and marks within the cusps as surface roughness (characterized by parameter R10z). The assessment uses stresses obtained from an finite element analysis model to predict the fatigue life of components whilst considering stress concentration, stress gradient, mean stress, and surface roughness effects. When cusps are regarded as surface roughness within the conventional FKM approach, fatigue life is considerably underestimated. In comparison, fatigue life predictions that take into consideration the roughness within cusps and treat cusps as stress‐raising notches are closer to experimental life.

Sustainable Battery Lifecycle: Non-Destructive Separation of Batteries and Potential Second Life Applications

Large quantities of battery systems will be discarded from electric vehicles in the future. Non-destructive separation of used electric vehicle (EV) traction batteries enables a second life of battery components, extraction of high value secondary materials, and reduces the environmental footprint of recycling and separation processes. In this study, the key performance indicators (KPIs) for the second life application of spent EV batteries are identified. Three battery packs are analyzed in terms of the joining techniques used—and possible separation techniques—considering only direct recycling methods. The components that can be recovered from these batteries are evaluated against the KPIs. This study shows that all the batteries analyzed allow a second life in stationary and semi-stationary electrical storage systems and marine applications when used at the pack and module levels. Two packs can be reused in electric vehicles such as forklifts. However, the feasibility of re-use in micro-mobility and consumer electronics is very limited. This study shows that technically feasible separation methods are dictated and constrained by the joining techniques used. As welding and adhesive bonding pose challenges to separation processes, future efforts should prioritize ‘design for disassembly’ to ensure sustainable battery life cycle management.

Fatigue life prediction of rough Hastelloy X specimens fabricated using laser powder bed fusion

Additive manufacturing, especially laser powder bed fusion (L-PBF), is extensively used for fabricating metal parts with intricate geometries. However, parts produced via L-PBF suffer from varied surface roughness, which affects the fatigue properties. Accurate prediction of fatigue properties as a function of surface roughness is a critical requirement for qualifying L-PBF parts. In this work, an analytical methodology was put forth to predict the fatigue life of L-PBF components having heterogeneous surface roughness. Thirty-six Hastelloy X specimens were printed using L-PBF followed by industry-standard heat treatment procedures. Half of these specimens had as-printed gauge sections and the other half were printed as cylinders from which fatigue specimens were extracted via machining. Specimens were printed in a vertical orientation and an orientation of 30° from the vertical axis. The surface roughness of the specimens was measured using computed tomography and parameters such as the maximum valley depth were used to build an extreme value distribution. Fatigue testing was conducted at an isothermal condition of 500 °F. It was observed that the rough specimens failed much earlier than the machined specimens due to the deep valleys present on the surfaces of the former ones. The valleys behaved as notches leading to high strain localization. Based on this observation, an analytical functional relationship was formulated that treated surface valleys as notches and correlated the strain localization around these notches with fatigue life, using the Coffin-Manson-Basquin and Ramberg-Osgood equations. The functional relationship was generated with the average of the extreme value distribution. The mean life curve from the functional relationship showed a maximum difference of 2 % from the experimental mean fatigue life observations for vertically built rough specimens and 10 % for 30⁰-built rough specimens. In conclusion, the proposed analytical model successfully predicted the fatigue life of L-PBF specimens at an elevated temperature undergoing different strain loadings.

Tribocorrosion performance of TC4 anodized/carbon fiber composite in marine environment

The TC4 titanium alloy is extensively utilized in marine engineering due to its exceptional comprehensive performance. However, when subjected to harsh marine environments, the TC4 titanium alloy is susceptible to tribocorrosion, which can shorten the service life of components. This paper employs an electrochemical anodic oxidation treatment of the TC4 titanium alloy and a ceramic adhesive to fabricate a TC4 anodic oxidation/carbon fiber composite (CFCM) to address this challenge. Hence, A systematic study has been conducted on the friction and wear behavior of TC4 titanium alloy in artificial marine and air environments, focusing on exploring the tribocorrosion behavior and their intrinsic mechanisms in marine environments. The corrosion behavior of the TC4 titanium alloy was determined through kinetic potential polarization analysis. The results indicate that the anodized/carbon fiber composite can significantly enhance the tribocorrosion resistance of the material. Two orders of magnitude reduce the passivation corrosion density, and the corrosion potential increases to −0.136 V compared to the TC4 substrate. Furthermore, the wear mechanism is predominantly characterized by abrasive wear. This study offers novel insights for optimizing the selection of anticorrosive materials and designing coatings in marine engineering.

Experimental study on the effect of reaming on the fatigue life of split-sleeve cold-expanded Ti–6Al–4V alloy components

The split-sleeve cold expansion technique has been widely used in the aerospace industry to improve the fatigue life of metal components with holes. Due to the morphology change after the expansion, a reaming process is necessary to improve the machining accuracy of the hole surface. This final reaming process might change the residual stress distribution around the hole significantly but the effect of the reaming ratio has not been fully explored. This paper investigated the effect of reaming depth on the fatigue life of split-sleeve cold-expanded Ti–6Al–4V alloy components using a series of experiments, including the residual stress measurements, uniaxial fatigue tests, and fracture morphology observations. The expectations of the fatigue cycles were estimated using the 2-parameter Weibull distribution and the S-N curves of different components were acquired. Residual stress measuring results and the fracture surface observations explained the effect of cold expansion and reaming on the components. The experimental results showed that the fatigue life of the components decreased with the increase of the reaming ratio, demonstrating that excessive reaming depth is harmful to the fatigue performance of the cold-expanded components.