Start-stop Tests Research Articles

Observation of wear around surface crack of PEEK thrust bearing under rolling contact fatigue in water

Abstract Rolling bearings are important mechanical elements for machines. Poly-ether-ether-ketone (PEEK) polymer is a suitable material for bearings in water and corrosive conditions because of its excellent water and chemical resistance. Some study had been examining rolling contact fatigue (RCF) tests in water; however, the competition between cracks propagation and wear on the surface of PEEK bearing in water was not clear. In the present study, in order to evaluate the crack propagation and wear process, RCF test with PEEK thrust bearings at 3750 [N] in water was carried out. The lengths of the surface cracks and the profiles of the grooves were observed at different number of cycles. In addition, so as to identify the cracks which cause the flaking, start-stop test was carried out. We found the surface crack, which was initially observed at 4.62×105 cycles, were gradually worn down and completely disappeared at 6.32×105 cycles. We concluded that rolling contact fatigue caused some surface cracks of PEEK to wear down in water condition.

Theoretical and experimental research on static stiffness, performance, and lift-off characteristics of multi-layer gas foil thrust bearings

In this study, a new comprehensive fully coupled elastic-hydrodynamic model is developed for a multi-layer gas foil thrust bearing (GFTB). The interaction effects among the top foil, back board, middle foil, and bottom foil, as well as the Coulomb friction effect, are considered. The stiffness and static characteristics obtained by the experimental and theoretical approaches are in good agreement, which verifies the accuracy of the model. The contribution of each foil layer to the overall stiffness and the load-carrying mechanism are analyzed. Interaction effects of the load, preload, and rotational speed on the static performance are investigated comprehensively. Furthermore, start-stop tests are performed to achieve the lift-off speed, start-up torque, and shut-down torque under various operating conditions.

Highly Durable Membrane–Electrode-Assemblies Using High M w and Ether-Free Polyfluorene-Based Electrolytes for Anion Exchange Membrane Water Electrolyzer

Water electrolysis technology, which produces hydrogen through electrolysis of water using electricity derived from renewable energy, is attracting attention as a way to realize a carbon-neutral society. Among water electrolysis systems, anion exchange membrane water electrolysis (AEMWE) can achieve high energy conversion efficiency and quick response to fluctuating power supplies by using thin polymer electrolyte membranes, and operates in an alkaline environment, allowing the use of inexpensive non-precious metals for bipolar plates and electrodes. However, conventional AEMs and ionomers exhibit low durability in high-temperature and alkaline environments, which is a critical issue in realizing high-performance and highly durable membrane–electrode assemblies (MEAs) for AEMWE.Our group developed high-molecular-weight (M w) and ether-free, polyfluorene-based anion conducting polyelectrolyte (PFT-Cx-TMA, Cx represent the number of carbon atoms in the alkyl side chain) as shown in Fig. 1a.1 These polyelectrolytes show high OH− conductivity over 100 mS cm− 1, high chemical durability (stable in 8 M NaOH at 80 °C for 168 h), and high tensile strength (25–42 MPa, comparable to a Nafion membrane). This study applied PFT-Cx-TMA to AEMs and ionomers in MEAs to evaluate the durability against various AEMWE operations (constant current operation and start-stop operation in different voltage ranges), demonstrating MEAs with both high performance and high durability.Fig. 1b shows the constant current durability of the MEA with PFT-C8-TMA as AEM and ionomer.2 This test was performed at the constant current density of 0.2 A cm− 2 and 80 °C using a 1 M KOH aqueous solution fed to the anode. Here, to investigate the effects of AEMs and ionomers on MEA durability, conventional precious metal catalysts (anode: IrO2, cathode: Pt/C or PtRu/C) were used in the MEA. The MEA with PFT-C8-TMA exhibited a current density of 1.0 A cm− 2 at 1.79 V and there was almost no voltage change even after the constant current operation for over 100 h. It is noteworthy that the MEAs using PFT-C8-TMA and PFT-C10-TMA demonstrated high performance and high durability not only in the alkaline-fed operation but also in the pure-water-fed operation.Next, this study investigated the start-stop durability of MEAs using voltage cycles simulating the start-stop operation of water electrolyzer. Here, square-wave voltage cycling of holding at 1.8 V and 0.1 V for 1 min each was used for the start-stop test at 80 °C with a 1 M KOH solution fed to the anode. As a comparison, the MEA was prepared using a commercial AEM (Sustainion X37-50, 50 μm in thickness) and ionomer (Sustaionion XB-7). As shown in Fig. 1c, the MEA using a PFT-C10-TMA AEM (56 μm in thickness) and ionomer was highly durable in the start-stop test compared to the MEA using commercial Sustaionion. During the test, the elution of black solid particles from the catalyst layer and the increase in charge transfer resistance (Rct) were observed in the MEA with Sustaionion, whereas no elution of catalyst materials and no change in Rct were confirmed in the MEA with PFT-C10-TMA. These results suggest that nonlinear mechanical stress via rapid bubble formation and shutdown during start-stop cycles caused the leaching of catalysts, resulting in the performance loss of the MEA with Sustainion. The commercial ionomer (Sustainion XB-7) exhibits a large dimensional change (156%) compared to the PFT-C10-TMA membrane (34%) at 80 °C in a 1 M KOH aqueous solution. Catalyst particles covered with a highly swollen ionomer are easily detached from a catalyst layer by the nonlinear mechanical stress. On the other hand, the PFT-C10-TMA ionomer has a high molecular weight (M w = 240000 g mol−1), low swelling degree, and well-entangled polymer chains, hence preventing leaching of the catalyst particles.In summary, this study demonstrates that MEAs using high M w and ether-free polyfluorene-based electrolytes with both high chemical and mechanical durability have excellent durability for AEMWE operations including constant and dynamic (start-stop voltage cycling) operations. Acknowledgement This presentation is based on results obtained from a project, JPNP14021, commissioned by the New Energy and Industrial Technology Development Organization (NEDO). References (1) S. Miyanishi and T. Yamaguchi, Polym. Chem., 2020, 11, 3812–3820.(2) R. Soni, S. Miyanishi, H. Kuroki, and T. Yamaguchi, ACS Appl. Energy Mater., 2021, 4, 1053–1058. Figure 1

Friction Coefficient during Five-Phased Start-Stop Tests of PEEK-PTFE Hybrid Radial Ball Bearings Reaching 50 c° under 487N at 600rpm in Air

Start-stop rolling contact fatigue tests of PEEK-PTFE hybrid radial bearings were carried out, to investigate the influence of start-stop heat cycle on the friction coefficient of PEEK-PTFE hybrid radial bearings. It was found in all start-stop tests, the temperature of sample side increased as the friction coefficient increased. RCF cycles to reach 50 °C of the third start-stop phase clearly increased from the second start-stop tests, and then kept constant value.

Effects of Foil Bearing Load on Working Foil Wear

The article presents issues related to the study on the impact of high-speed foil bearing service loads on the wear of working foils. The work includes a brief introduction, test methodology and a description of the test stand for testing the wear on working foil bearings under simulated operating conditions. The test stand was located in the Machinery Design Fundamentals laboratory at the Faculty of Technical Sciences of the University of Warmia and Mazury in Olsztyn (Poland), where it is used for start-stop tests. The article describes the course of the tests and the results, providing relevant conclusions and a better understanding of the phenomena occurring during work with foil bearings.

Durability Studies on PBI Based High Temperature PEMFC

HT-PEMFC based on phosphoric acid-doped polybenzimidazole membranes are a technology characterized by simplified construction and operation along with methanol reformers. Durability issues including acid loss, platinum sintering and carbon corrosion are recognized for both steady state and start-stop cycling operations. This work reports experimental studies on the degradation of PBI-based fuel cells operating with synthetic reformate fuel and air. Degradation stressors include elevated temperatures, pressures, current densities, and start-stop cycles. An average degradation rate of 9.3 mV/h is observed for continuous operation at 0.4 A/cm2 and 160 ˚C for 12,000 hours. High pressure (1.5 bara) operation at 170 oC and 0.8 A/cm2 shows an average degradation rate of 12.6 µV/h during a period of 2,000 hours. A start-stop test from 50 oC consisting of 240 cycles between temperatures of 165 and 175 oC and current density of 0.31 and 0.55 A/cm2 reveals a performance decay by 0.48-0.58 mV/cycle.

(Invited) HT-PEM Fuel Cell Development for Product Definition and Scaleup

“High Temperature” Proton conducting Electrolyte Membrane (HT-PEM) fuel cells offer an attractive method of converting renewable energy carriers (e.g. methanol) to electricity, especially remotely and in transportation. A particular advantage is their ability to digest reformates containing a few % CO, thus not requiring high purity hydrogen.Membranes of polybenzimidazole (PBI) allow for operation in the 150-200 °C range, as they do not require liquid water for continuous moisturizing as do fluorinated polymer membranes. This temperature range is advantageous for the typically used Pt catalyst, as the passivation by CO is limited.A central challenge is cost reduction, with particular focus on Pt loading of electrodes. The critical trade-off is against lifetime and electrode performance while maintaining adequate tolerance to CO and fuel trace impurities. These limitations are sensitive to system and customer parameters via selection of fuel, reformer characteristics and operation mode.Results will be presented and discussed on single cell lifetime in the 10.000 h range; objectives and results in electrode development and Pt loading, as well as results on methanol slip testing, start-stop testing and testing at elevated pressure. Lessons from early upscaling will be shared.

Methodology of Testing Foil Bearings in the Start-Stop Cycle in the Presence of a Working Medium - Stabilization of Temperature in the Test Chamber

Abstract The article presents the methodology of testing sliding bearings with a flexible shell, focusing on the issue of temperature increase during experiments for a specific time interval of the START-STOP test cycle. Selected material pairs, used in previous studies, were used in the experiment. The stand used for tests in the start-stop cycle was developed under the project POIG.01.03.01-00-027 / 08-00 at the Faculty of Technical Sciences UWM in Olsztyn.

Comprehensive fatigue estimation and fault diagnosis based on Refined Generalized Multi-Scale Entropy method of centrifugal fan blades

Fan is widely used in industry as a very important component of pressure transmission and system cooling. Fan blade is the key part which decides the service life of fan and the whole system. In this paper, the research focuses on the centrifugal fan of high-speed train cooling system and the blades on it. The experimental system and research method of fatigue analysis and fault diagnosis are built. The fan can work in both steady and unsteady state conditions controlled and driven by the test system. At the same time, the signals of strain and acceleration at different positions can be obtained accurately. Based on the static tension and dynamic fatigue test of the material, the accurate simulation of the fan is carried out. By simulation analysis, steady-state test, long-time start-stop test and metallographic test, the prediction of fatigue life of fan blades is conducted with in-depth analysis and comprehensive evaluation. The results show that fan meets the requirements of actual working life. As the actual working state is more diverse and severe than the above test process, some phenomena of damage also appear in the blades after service. Based on real situation, the blade faults are classified. After determination of measuring point position, the vibration signals of four fault states of blade under rated speed are collected. This paper proposes a new fault feature extraction method – the Refined Generalized Multi-Scale Entropy (RMSEσ2) combined with Support Vector Machine (SVM). According to the results of the empirical mode decomposition (EMD), the effective intrinsic mode function (IMF) components are selected by energy distribution and correlation coefficient. The comparative analysis of multi-scale entropy (MSE), generalized multi-scale entropy (MSEσ2) and RMSEσ2 between the original signal and 1–8 IMF components are carried out. Results show the RMSEσ2 of IMF1 component of Z direction of point 1 is the best choice. And it is imported into SVM for pattern recognition with scale factor 20. The optimal SVM model is obtained by choosing kernel function and parameters that are optimized by Particle Swarm Optimization (PSO) method. The results show the faults of centrifugal fan blades can be classified accurately. A set of research flow and method is set up, which provides important reference for fatigue and fault pattern recognition of fan blades in the future.

Frequent Start-Stop Test Study of Graphene Coatings on Journal Bearings

In this study, the graphene was prepared by chemical vapor deposition (CVD) method, and then through thermal annealing technique it was firmly coated on and partly diffused into the inner surfaces of journal bearings made from aluminum bronze CuAl10Fe3. The journal bearings without graphene coatings were also prepared with made from aluminum bronze CuAl10Fe3 and tested under the same conditions as the references of comparison. Through frequent start-stop test, the changing laws of coefficient of friction (COF), power consumption, and back temperature rise and wear loss for each journal bearing with or without graphene coating were obtained. The test results showed that graphene coating could significantly reduce the power consumption and wear loss during the start and stop phases.

(Invited) HT-PEM Fuel Cell Development for Product Definition and Scaleup

“High Temperature” proton conducting electrolyte membrane (HT-PEM) fuel cells offer an attractive method of converting renewable energy carriers (e.g. methanol) to electricity, especially remotely and in transportation. A particular advantage is their ability to digest reformates containing a few % CO, thus not requiring high purity hydrogen.Membranes of polybenzimidazole (PBI) allow for operation in the 150-200 °C range, as they do not require liquid-water for continuous moisturizing as do classical fluorinated polymer membranes. This temperature range is advantageous for the typically used Pt catalyst, as passivation by CO is limited.A central challenge is cost reduction, with particular focus on Pt loading of electrodes. The critical trade-off is against lifetime and electrode performance while maintaining adequate tolerance to CO and fuel trace impurities. These limitations are sensitive to system and customer parameters via selection of fuel, reformer characteristics and operation mode.Results will be presented and discussed on single cell lifetime in the 10.000 h range; objectives and results in electrode development and Pt loading, as well as results on methanol slip testing, start-stop testing and testing at elevated pressure. Lessons from early upscaling will be shared.

Methods of Research of Foil Bearings in START-STOP Cycle in the Presence of Working Medium

Abstract A method for testing sliding bearings with an elastic bearing liner was presented in the paper with a focus on the issue of selection of particular time intervals of the START-STOP test cycle. Then, results of the tests carried out according to the selected material combinations were presented. The working cycle of foil bearings tested on the test stand was performed in an automatic mode at the set number of sequences start-work-rundown-stop. Due to the highest use of sliding bearings during start and rundown of a machine, this type of tests is essential for selection of relevant sets of material for bearing elements. The article also presents the use of a thermo-visual camera for identification of additional thermal loads and manners of temperature stabilization in the test chamber.

Methodologies to Compare IC Engine Power Assembly Interface Materials

To meet the needs of higher power, lower weight and better emissions IC engines, component manufacturers develop new materials, coatings and surface technologies (e.g. surface texture). In this paper methodologies have been developed for comparing & ranking interface materials with custom-built rigs built in GE Global Research, Bangalore for large sized IC engines. This work will discuss the three methodologies developed using: i) Journal Bearing Rig ii) Piston-Liner Rig and the iii) Valve-seat rig. The Journal bearing Rig can be spun to engine linear speeds with lubricant heated to engine oil temperature. The loading is performed using a hydraulic system. Seizure, steady state wear and start stop tests can be performed on this rig. The piston liner rig can accommodate a section of the liner and ring from an actual engine. The combination of the pneumatic mechanism and the 2-axis load cell can load and measure the normal load & frictional load. The piston ring-liner simulates interface hot engine temperatures and contact pressures at TDC/BDC. Scuffing & wear tests can be performed with this test rig to compare scuffing limits and steady state wear rates. The valve-seat rig fixture is built within a MTS frame and can accommodate small sections of the actual engine valve and seat. Normal load and the fretting stroke is simulated using MTS hydraulic system A furnace is used around the fixture to simulate higher temperatures. Case studies comparing & ranking different coatings/repair coatings and oil additives etc. will be presented in this work to showcase the effectiveness of the methodology. Tests using this methodology can be typically performed in 10 % of time & cost of actual engine test.

Preparation and Experimental Study of Graphite Material for Water Lubricated Thrust Bearing of Nuclear Main Pump

Based on technical difficulties of graphite water-lubricated thrust bearing such as preparation and properties detection, this paper investigated graphite bearing systematically from preparation and property testing, three different types of graphite (#1, #2 and #3) were carried out. The result indicated the tribological properties are poor if the graphitization of graphite is too high or low. The pads of water-lubricated thrust bearing are manufactured by the three kinds of graphite, and the start-stop test were carried out on a test platform for half-size bearing of nuclear primary pump. The result of start-stop test were indicated the graphitization have a visible influence on the wear loss mass of graphite pad.

Experimental and direct numerical analysis of hard-disk drive

The purpose of this paper is to study methods for enhancing the reliability and performance of hard-disk drives (HDD) because it is essential for improving recording density, speed of data access, and output signal. This study also investigates various techniques that can be used for head/disk contact detection. The acoustic emission (AE) and friction signal characteristics were observed with respect to the durability of the head/disk interface (HDI) under various operating conditions using a contact start-stop (CSS) test. In addition, to study the influence of surface topography on the stiction performance of the HDI, a modified and polished laser pump was proposed and CSS investigations were accomplished. Moreover, the static and dynamic properties of an HDD air slider were studied using a finite element method (FEM).

立位乗車式買い物用電動車の開発

We are proposing a small electric vehicle which uses a low powered battery (7.2 V, approximately 2 Ah) to be used for shopping by the elderly. For this study, we have developed a standing position ride-type electric vehicle with an easy operation system in terms of easy shopping. Furthermore, steady running tests and repeated start-stop tests were conducted simulating actual vehicle use. Then, power consumption on various acceleration time are investigated to determine suitable acceleration slope. And, voltage history while getting on-off the vehicle were investigated using electromyograph. This paper will present the design with respect to easy shopping and running performance and present the experimental results.

Constant Velocity High Force Microactuator for Stick-Slip Testing of Micromachined Interfaces

A chevron thermal actuator has been implemented as a constant velocity puller in a multiasperity frictional test platform. This platform enables a wide variation of puller velocity (1– $3100~\mu \text{m}$ /s, 3.5 decades), normal load (2– $4500~\mu \text{N}$ , 3.4 decades), and spring constant (0.06– $100~\mu \text{N}/\mu \text{m}$ , 3.2 decades). These characteristics are achieved by leveraging the actuator thermal time constant, which is long compared with the mechanical time constant, in combination with iterative learning control. Good thermal isolation between the actuator and the friction block is achieved by shunting heat to the substrate. Uncoated and FOTAS [tridecafluorotris(dimethylamino)silane, CF3(CF2)5(CH2)2Si(N(CH3)2)3]-coated devices were tested, and normal load induced a transition from steady sliding to stick-slip. This platform could have several important uses for mapping microscale kinetic friction phase diagrams, including determining the stick-slip to steady sliding bifurcation line, performing start-stop tests and instantaneous velocity change tests, and inferring information on wear performance of coatings as a function of load and velocity. [2015-0123]

Degradation of Pt/C catalysts in start-stop cycling tests

The stability of highly disperse 50 wt % Pt catalysts deposited on carbon supports with various porosity and morphology is tested in accelerated oxidative experiments in the potential range of 1–1.5 V (RHE) in 0.1 M HClO4 solution. The electrochemically active surface area of platinum (S Pt) is determined based on the charge of adsorbed hydrogen by the cyclic voltammetry (CVA) method. The specific activity per mass unit (the mass catalytic activity (MCA)) and the electrochemically active surface area of the active component (surface catalytic activity (SCA)) are determined in the oxygen electroreduction reaction (OERR) by the method of rotating disk electrode (RDE). It is shown that the catalyst degradation is mainly due to the growth of Pt particles and the corrosion of the carbon support. It is found that under these cycling conditions, the rate of the S Pt decline depends inversely on the cycle number throughout the cycling interval (up to 60000 cycles) for all catalysts, which points to the quadratic dependence of the degradation rate on S Pt. Two regions are revealed in the MCA and SCA dependences on the cycle number, In the first region (from 0 to 8–10 thousand cycles), a sharp decrease in MCA and SCA is observed for all catalysts, which can be associated with the restructuring or passivation of the Pt particle surface due to the oxide formation on oxidative cycling. In the second region, the relative stabilization of MCA and the linear increase in SCA are observed for all catalysts without exception. The linear increase in SCA is due to the growth of Pt particles and the size effect. It is shown that carbonization of the carbon support leads to enhancement of its cycling stability.

Friction and wear behaviors of carbon-based multilayer coatings sliding against different rubbers in water environment

We have addressed the friction and wear behaviors of multilayer Cr/CrN/GLC (graphite-like carbon) coatings sliding against different rubbers in water environment. Stribeck curves and start–stop tests were presented to analyze the water-lubrication mechanism and tribological properties of coating/rubber tribopairs. Results exhibited that applied loads had a minor influence on the tribological performances of coating/rubber tribopairs compared to sliding speeds. The friction coefficients fluctuated during the test process, including in the start–stop process, which related to the viscoelasticity of rubbers. Furthermore, the different tribological performances of tribopairs were attributed to the hardness, surface wettability and tensile strength as well as viscoelasticity.

The Tribological Performances of Multilayer Graphite-Like Carbon (GLC) Coatings Sliding Against Polymers for Mechanical Seals in Water Environments

Graphite-like carbon (GLC) coatings are being increasingly used in mechanical seals, especially under the water-lubricated condition, to improve component durability by providing a low friction coefficient and high wear resistance. We have addressed the friction and wear performances of multilayer Cr/CrN/GLC coatings sliding against polyether–ether–ketone (PEEK), polyimide (PI), and polytetrafluoroethylene (PTFE) in distilled water under various applied loads and sliding speeds using a ring-on-block test rig. Stribeck curves were developed to analyze the water lubrication mechanisms. Start–stop tests were also carried out to evaluate the tribological performances of the coatings. Our results showed that the friction coefficients and wear rates of the polymers decreased with increasing sliding speeds. Compared to the applied load, the sliding speed had a major effect on the friction and wear performance of the polymer. Three coating/polymer tribopairs demonstrated different tribological behaviors, which were attributed to their different molecular structures, the different mechanical properties of the polymers, and the different lubrication mechanisms. The transfer film determined the lubrication mechanism of the three tribopairs and also resulted in the low friction coefficient and wear rate. The initial and steady-state friction coefficient also decreased with increases in the repeated start–stop times. Based on our results, we concluded that the coating/PEEK tribopair presented an excellent tribological performance that we ascribed to the chemical properties of PEEK and the hydrodynamic lubrication regime of the coating/PEEK tribopair at high sliding speeds.