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1

Reliability analysis of subway sliding plug doors based on improved FMECA and Weibull distribution

Wang Weibo, Liu Wenxiu, Fang Yu, Zheng Yongkang, Lin Chuan, Jiang Yonghua, Liu Dong

Eksploatacja i Niezawodność

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2024

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Vol. 26, no. 2

art. no. 178275

EN

Using traditional failure mode effects and criticality analysis (FMECA) to analyze the hazard of subway sliding plug door system, there are problems such as easy-to-take repetitive values, irrational allocation of expert's weights, and failure to consider the weights of evaluation factors. To address the above problems, this paper proposes an improved FMECA by using linear interpolation to increase the differentiation of the same fault probability occurrence among various fault modes. Apply the dependent uncertain ordered weighted averaging (DUOWA) algorithm to assign weights to different experts dynamically. The analytic hierarchy process (AHP) is used to endow weights to diverse evaluation factors to make them more suitable for engineering needs. We collected 1,836 days of metro train operation records from the Shanghai subway manufacturing plant and studied 17 common faults. Next, use a reliability-centered maintenance (RCM) strategy to determine maintenance periods for different fault modes. Finally, through the Weibull distribution fitting test, the fault rate function of the door is obtained, and the remaining useful life (RUL) of the door is predicted. The consistency between the vulnerable parts obtained by our proposed method and the statistics of the maintenance records of the subway sliding plug door verifies the effectiveness and reliability of our improved FMECA.

2

Strain‑induced grain evolution of pure nickel under warm power torsional rolling process

Zhang Zhe, Lei Yuyao, Liu Dong, Wang Yuxuan, Zou Juntao

Archives of Civil and Mechanical Engineering

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2024

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Vol. 24, no. 2

art. no. e73, 2024

EN

Since the existing severe plastic deformation (SPD) technology cannot be used to prepare bulk ultrafine-grained material (BUGM) with industry size, a novel method entitled power torsional rolling (PTR), is proposed. The material flow, strain components, strain rate, and temperature were explored by finite element simulation, and the strain-induced grain evolution of pure nickel processed by warm PTR was systematically discussed. The simulation results reveal that the combination of radial compression deformation, longitudinal shear deformation and circumferential shear deformation is beneficial to refine grain size, and the continue local loading characteristic requires less forming load, which confirms that the PTR process has the potential to prepare BUGM with industry size. The experiment results indicate that the grain refinement caused by dynamic recrystallization is remarkable within the temperature range of 450-800 ℃, and the average grain size of pure nickel is refined from 110 μm to 10 μm after two passes PTR. The microstructure distribution of obtained bar is uniform and the isotropic microstructure is observed due to the three-dimensional compression-shear deformation. The tensile test results indicate that the yield strength and ultimate tensile strength increase simultaneously due to the grain-boundary strengthening and twin boundary strengthening.

3

Modelling and evaluating piston slap-induced cavitation of cylinder liners in heavy-duty diesel engines

Liu Dong, Sun Nannan, Zhu Guixiang, Cao Hengchao, Wang Tie, Li Guoxing, Gu Fengshou

Eksploatacja i Niezawodność

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2023

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Vol. 25, no. 3

art. no. 169644

EN

Cavitation erosion of cylinder liner seriously affects the operational reliability and service life of heavy-duty diesel engines. The accuracy of the modeling-based cavitation risk evaluation is limited by the unclear correspondence between cylinder liner vibration and coolant cavitation. This report is intended to investigate the correspondence between cylinder liner vibration and coolant pressure by combining vibration cavitation test, pressure gradient calculation, and visualization observation. The cavitation risk of the cylinder liner under the piston slap is quantitatively analyzed based on a nonlinear structural dynamics model that incorporates the piston-cylinder liner nonlinear collision, piston thermal deformation, and preload of cylinder head. The results show that the occurrence of cavitation will cause a nonlinear relationship between the cylinder liner acceleration and the coolant pressure. The engine under study has a high risk of cavitation when the cylinder liner acceleration exceeds 1189 m/s2. The difference in cavitation risk for each cylinder is related to the structural modal characteristics of the crankcase. In addition, the effect of piston-liner clearance and piston pin offset on the cavitation risk is investigated based on the dynamics model.

4

Residual stresses evolution and process route optimization of TC4 profiled rolled rings incorporating thermal bulging

Lv Nan, Liu Dong, Wang Jianguo, Rao Haodong, Nan Jungang

Archives of Civil and Mechanical Engineering

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2023

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Vol. 23, no. 3

art. no. e200, 2023

EN

The thermal processing of rolled rings inevitably generates and accumulates massive residual stresses, as quenching residual stresses produced by water cooling treatment. Non-uniformly distributed residual stresses would seriously affect the structural strength, dimensional stability and service life of the component. In the traditional rolling process of titanium alloy rings, the quenching residual compressive stresses introduced by solution treatment could reach – 400–600 MPa, for which effective control of the stresses is an urgent issue to be solved. In this research, the stress control efficiency of rolling rings under different process routes was explored according to the thermal bulge stress relief technique. The FEM model of the stress evolution in the whole process of the rolled ring was established. The residual stresses on the ring surface are characterized by the hole-drilling method, while the microstructures are characterized by electron backscatter diffraction. The results indicated that the optimized process incorporating the thermal bulging stress relief technique reduced the levels of stress values to within about ± 50 MP and the stress homogenization index by approximately 60–90%.

5

Simultaneous determination of eight antiepileptic drugs and two metabolites in human plasma by liquid chromatography/tandem mass spectrometry

Yu Hengyi, Ren Xiuhua, Liu Lu, Xiang Dong, Li Xiping, Li Juan, Liu Dong, Gong Xuepeng

Acta Chromatographica

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2023

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Vol. 35, no. 2

161--169

EN

Epilepsy is one of the most prevalent neurological conditions and antiepileptic drugs are the mainstay of epilepsy treatment. High variation in pharmacokinetic profiles of several antiepileptic drugs highlights the importance of therapeutic drug monitoring to estimate pharmacokinetic properties and consequently individualize drug posology. In this work, a simple, rapid and robust liquid chromatography-tandem mass spectrometry method was developed for simultaneous quantification of carbamazepine and its metabolite carbamazepine-10,11-epoxide, gabapentin, levetiracetam, lamotrigine, oxcarbazepine and its metabolite mono-hydroxy-derivative metabolite, phenytoin, topiramate, and valproic acid in human plasma for therapeutic drug monitoring. d6-Levetiracetam, d4-gabapentin and d6-valproic acid were used as internal standards. After addition of internal standards along with two-step protein precipitation and dilution sample preparation, plasma samples were analyzed on a C18 column using a gradient elution in 5 min without interference. The calibration curves were linear over a 100-fold concentration range, with determination coefficients (r2) greater than 0.99 for all analytes. The limit of quantification was 0.5 μg mL⁻¹ (0.1 μg mL⁻¹ for oxcarbazepine, 2 μg mL⁻¹ for levetiracetam, and 10 μg mL⁻¹ for valproic acid) with precision and accuracy ranging from 3% to 9% and from 94% to 112%, respectively. Intra- and inter-day precision and accuracy values were within 15% at low, medium and high quality control levels. No significant matrix effect was observed in the normal, hemolyzed, lipemic, and hyperbilirubin blood samples. This method was successfully used in the identification and quantitation of antiepileptic drugs in patients undergoing mono- or polytherapy for epilepsy.

6

Numerical and experimental investigations on Mannesmann effect of nickel‑based superalloy

Zhang Zhe, Liu Dong, Man Tongchi, Li Nan, Yang Yanhui, Pang Yuhua, Wang Jianguo

Archives of Civil and Mechanical Engineering

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2022

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Vol. 22, no. 3

art. no. e133

EN

The preparation of nickel-based superalloy tubes by rotary tube piercing (RTP) process is still difficult due to the Mannesmann effect (central cracking phenomenon) has not been clarified. The combinations of numerical analysis and experiment verifications method were adopted in the study. The critical parameters for central cracking were determined by experiments. It was found that the evolution process of central cracking for nickel-based superalloy includes voids nucleation, growth and aggregation. Based on the obtained critical parameters, the evolutions of stress, strain, strain rate, temperature and damage were discussed by numerical simulation. By comparing the experiment results and simulation results, the Normalized Cockcroft and Latham (NCL) model was determined as the most suitable model. Considering the influences of temperature and strain rate on the damage threshold, the NCL model of Inconel 718 alloy was established by high-temperature tensile test. Based on the above results, it is found that the maximum shear stress promotes the plastic deformation, which provides necessary conditions for the generation of defects, and the maximum principal stress induces the generation of voids and expansion of micro-cracks, which directly leads to the central cracking. The essence of central cracking is ductile fracture under tensile stress.

7

Experimental and numerical analyses of 45 steel during three dimensional severe plastic deformation (3D-SPD)

Pang Yuhua, Lin Pengcheng, Sun Qi, Zhang Zhe, Liu Dong

Archives of Civil and Mechanical Engineering

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2020

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Vol. 20, no. 4

71--81

EN

Due to the limitation of huge forming load, inhomogeneity of plastic deformation, and small volume of deformation region, it is difficult to prepare bulk ultra-fine grains material (UFGM) with industry size by the existing severe plastic deformation (SPD) methods. In this study, a novel SPD method, namely 3D-SPD, was proposed. By establishing finite element model, the distribution of material flow, restraining to Mannesmann effect, and comparison of load were discussed. Based on the self-developed rolling mill, the corresponding experiments were conducted. The experimental results reveal that the buck ultra-fine grains material of 45 steel was obtained under the condition of feed angle 21°, cross angle 15°, cone angle 5°, reduction rate 50%, and roll speed 30 rpm. The average grain size was refined from 46 to 0.8–4 μm. The tensile test results indicate that the yield strength and tensile strength of the rolled bar were significantly improved.