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Article
Publication date: 30 September 2013

Bin He, Dichen Li, Anfeng Zhang, Zhongliang Lu, Jiangbo Ge and Doan Tat Khoa

The purpose of this paper is to investigate the influence of the oxidation on the cracks of DZ125L nickel-based superalloy thin-walled parts in laser metal direct forming (LMDF)…

488

Abstract

Purpose

The purpose of this paper is to investigate the influence of the oxidation on the cracks of DZ125L nickel-based superalloy thin-walled parts in laser metal direct forming (LMDF).

Design/methodology/approach

Thin-walled cylinders were fabricated in protective atmosphere with different oxygen contents in order to reveal the influence of oxidation on the morphology of cracks. The influence of oxidation on the cracks was investigated in detail by measuring the wall thicknesses of cylinders, the residual stress in the top surface of the cylinders and the composition of the cracks. Finally, the validity of the results was verified by fabricating a thin-walled turbine blade in protective atmosphere.

Findings

The experimental results showed that wall thickness fluctuation of cylinders, unequal residual stress distribution of cylinders and the oxides in the crack were all the critical factors which led to crack of DZ125L thin-walled parts. Thin-walled turbine blades with no cracks can be fabricated when the oxygen content was about less than 150 ppm in protective atmosphere.

Research limitations/implications

The appropriate oxygen content in protective atmosphere is helpful for fabricating thin-walled parts of nickel-based superalloy like DZ125L, and the results can show what will happen at different oxygen levels. Moreover, the results show that the cracks can be eliminated as the oxygen content reduce to less than 150 ppm rather less than 10 ppm or even less, which can reduce the cost of protective gas as forming thin-walled parts of nickel-based superalloy such as DZ125L.

Practical implications

The appropriate oxygen content in protective atmosphere is helpful for fabricating thin-walled parts of nickel-based superalloy like DZ125L. However, when heavy solid parts of some other material other than DZ125L were fabricated, the oxygen content of less than 150 ppm may be not suitable.

Originality/value

The influence of oxidation on the cracks of DZ125L thin-walled parts in LMDF was investigated in detail, and a DZ125L thin-walled turbine blade with no cracks was fabricated by adjusting the oxygen content in protective atmosphere.

Details

Rapid Prototyping Journal, vol. 19 no. 6
Type: Research Article
ISSN: 1355-2546

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Article
Publication date: 11 April 2016

Zhongliang Xie, Zhu-shi Rao, Na Ta and Ling Liu

As the companion paper of Part I, this paper aims to get more insight into the essence of lambda and to reveal its nature and role in the transition of lubrication states. Mixed…

502

Abstract

Purpose

As the companion paper of Part I, this paper aims to get more insight into the essence of lambda and to reveal its nature and role in the transition of lubrication states. Mixed lubrication (ML) model with micro-asperities contacts has been discussed in details in Part I.

Design/methodology/approach

Mimetic algorithm is used to get numerical solutions. Relationships between film thickness ratios and lubrication states transition with different external loads, rotating speeds, radial clearances, elastic modulus, surface hardness and roughness parameters are obtained.

Findings

The characteristic parameters of transitions from boundary lubrication (BL) to ML and ML to hydrodynamic lubrication (HL) are studied to determine how these parameters change with above factors. Finally, the essence and major influencing factors of lambda are summarized for such bearings.

Originality/value

In Part II, the authors believe that the paper presents for the first time: further insight into the essence of the lambda ratio, and its role in the lubrication states transition are given; the determinations of the characteristic parameters of transition from BL to ML and ML to HL are investigated for the first time; the characteristic parameters of transitions from BL to ML and ML to HL are also studied to determine how parameters (external load, rotating speed, radial clearance, elastic modulus, surface hardness and roughness parameter) change with above factors; a summary of the essence and major influencing factors of lambda for such bearings is given.

Details

Industrial Lubrication and Tribology, vol. 68 no. 3
Type: Research Article
ISSN: 0036-8792

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Article
Publication date: 11 April 2016

Zhongliang Xie, Zhu-shi Rao, Na Ta and Ling Liu

This paper aims to provide efficient methods to calculate the friction coefficients and film thickness ratios in mixed lubrication (ML) regime for water lubricated bearings…

483

Abstract

Purpose

This paper aims to provide efficient methods to calculate the friction coefficients and film thickness ratios in mixed lubrication (ML) regime for water lubricated bearings. Mathematical models consider influence of micro-asperities contacts which is based on the Gauss random distribution.

Design/methodology/approach

Effects of external loads, rotating speeds and radial clearances are obtained. Algorithm shown here is applied to a class of common industrial problems. Calculated Stribeck values are given and evaluated. The calculated and experimental results agree well which proves the correctness of the model.

Findings

In Part I, the authors believe that the paper presents the following for the first time: universal methods are developed for the calculation of friction coefficients and film thickness ratios (lambda) in ML regime; effects of different external loads, rotating speeds and radial clearances on friction coefficients and film thickness ratios are presented in detail; comparisons are made between the results predicted by the model and experimental results, and they agree rather well which proves the correctness of the model.

Originality/value

Present work successfully develops universal methods for predicting the friction coefficients and film thickness ratios.

Details

Industrial Lubrication and Tribology, vol. 68 no. 3
Type: Research Article
ISSN: 0036-8792

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Article
Publication date: 7 September 2015

Yumiao Chen, Jianping Wang and Zhongliang Yang

– The purpose of this paper is to provide an overview of the human factors/ergonomics (HFE) studies for respirator.

792

Abstract

Purpose

The purpose of this paper is to provide an overview of the human factors/ergonomics (HFE) studies for respirator.

Design/methodology/approach

This review paper describes and discusses the various factors and methodologies of HFE, for the purpose of better considering human factors, used in respirator studies and further human-centered product development.

Findings

Many attempts have been made to study human factors for respirators mainly including fit, human performance, comfort, and mood. Physical, psychological, and physiological indices of people are extremely valuable to HFE studies for respirator. Objective and subjective measures were methodologies widely used. Quantitative and qualitative approaches were adopted to illustrate the human performance and well-being influenced by respirators. A summary table presented with major methods used for indices of respirators in the field of HFE. According to the current researches, this review indicated three particular challenges facing HFE studies of respirators now.

Practical implications

With the ever increasing role of protection from air pollution in society, respirator has become an increasingly important part of our daily lives. HFE intervene in optimizing the relationships between respirators and the human using them. Plenty of efforts have been dedicated for the development of protection capability, but HFE studies for respirators are lacking. In recent years, there has been a tremendous interest in introducing HFE research methods that can evaluate respirators from the perspective of human and translate them into constraints for designing human-centered respirators.

Originality/value

This is a first paper in the field of HFE studies for respirator, which will remain helpful to the scientific community to start further human-centered research work and product development.

Details

International Journal of Clothing Science and Technology, vol. 27 no. 5
Type: Research Article
ISSN: 0955-6222

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Article
Publication date: 5 June 2019

Yumiao Chen and Zhongliang Yang

Breathing resistance is the main factor that influences the wearing comfort of respirators. This paper aims to demonstrate the feasibility of using the gene expression programming…

109

Abstract

Purpose

Breathing resistance is the main factor that influences the wearing comfort of respirators. This paper aims to demonstrate the feasibility of using the gene expression programming (GEP) for the purpose of predicting subjective perceptions of breathing resistances of wearing respirators via surface electromyography (sEMG) and respiratory signals (RSP) sensors.

Design/methodology/approach

The authors developed a physiological signal monitoring system with a specific garment. The inputs included seven physical measures extracted from (RSP) and (sEMG) signals. The output was the subjective index of breathing resistances of wearing respirators derived from the category partitioning-100 scale with proven levels of reliability and validity. The prediction model was developed and validated using data collected from 30 subjects and 24 test combinations (12 respirator conditions × 2 motion conditions). The subjects evaluated 24 conditions of breathing resistances in repeated measures fashion.

Findings

The results show that the GEP model can provide good prediction performance (R2 = 0.71, RMSE = 0.11). This study demonstrates that subjective perceptions of breathing resistance of wearing respirators on the human body can be predicted using the GEP via sEMG and RSP in real-time, at little cost, non-invasively and automatically.

Originality/value

This is the first paper suggesting that subjective perceptions of subjective breathing resistances can be predicted from sEMG and RSP sensors using a GEP model, which will remain helpful to the scientific community to start further human-centered research work and product development using wearable biosensors and evolutionary algorithms.

Details

Sensor Review, vol. 39 no. 4
Type: Research Article
ISSN: 0260-2288

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Article
Publication date: 23 October 2018

Yumiao Chen and Zhongliang Yang

Investigating the subjective breathing resistance of wearing respirators requires a valid and reliable technique to measure breathing resistance. The purpose of this study is to…

166

Abstract

Purpose

Investigating the subjective breathing resistance of wearing respirators requires a valid and reliable technique to measure breathing resistance. The purpose of this study is to test the validity and reliability of several rating scales and select the best for investigation of breathing resistance.

Design/methodology/approach

The authors designed three scales, that is, BRX scale, CP-100 scale and RVAS scale, and 30 subjects were separated into three groups, each group with a different scale. They sat for 5 min and walked for 5 min while wearing three models of respirators. After each trial, subjects were asked to complete subjective ratings of breathing resistance. Reliability was examined by the coefficient of Cronbach’s α, and validity was examined through content validity, discriminant validity and criterion validity. Generally, subjects were capable of reporting their sensation of breathing resistance by using the rating scale technique. However, the accuracy of rating strongly depended upon the properties of the scale.

Findings

The CP-100 scale was found to be highly reliable and most valid for rating subjective breath resistance. The validated CP-100 scale is very sensitive and accurate.

Originality/value

This is the first paper to select the best subjective scale for investigation of breathing resistance of respirators. The CP-100 scale will find wide applications in subjective breathing resistance evaluation for the use of respirators in industrial benchmarking activities. It will introduce the human factor engineering into the respirator manufacturing to improve the comfort of respirators.

Details

Journal of Engineering, Design and Technology, vol. 16 no. 6
Type: Research Article
ISSN: 1726-0531

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Article
Publication date: 10 June 2014

Zhongliang Yu, Yulong Zhao, Lili Li, Cun Li, Xiawei Meng and Bian Tian

The purpose of this study is to develop a piezoresistive absolute micro-pressure sensor for altimetry. For this application, both high sensitivity and high overload resistance are…

343

Abstract

Purpose

The purpose of this study is to develop a piezoresistive absolute micro-pressure sensor for altimetry. For this application, both high sensitivity and high overload resistance are required. To develop a piezoresistive absolute micro-pressure sensor for altimetry, both high sensitivity and high-overload resistance are required. The structure design and optimization are critical for achieving the purpose. Besides, the study of dynamic performances is important for providing a solution to improve the accuracy under vibration environments.

Design/methodology/approach

An improved structure is studied through incorporating sensitive beams into the twin-island-diaphragm structure. Equations about surface stress and deflection of the sensor are established by multivariate fittings based on the ANSYS simulation results. Structure dimensions are determined by MATLAB optimization. The silicon bulk micromachining technology is utilized to fabricate the sensor prototype. The performances under both static and dynamic conditions are tested.

Findings

Compared with flat diaphragm and twin-island-diaphragm structures, the sensor features a relatively high sensitivity with the capacity of suffering atmosphere due to the introduction of sensitive beams and the optimization method used.

Originality/value

An improved sensor prototype is raised and optimized for achieving the high sensitivity and the capacity of suffering atmosphere simultaneously. A general optimization method is proposed based on the multivariate fitting results. To simplify the calculation, a method to linearize the nonlinear fitting and optimization problems is presented. Moreover, a differential readout scheme attempting to decrease the dynamic interference is designed.

Details

Sensor Review, vol. 34 no. 3
Type: Research Article
ISSN: 0260-2288

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Article
Publication date: 7 May 2019

Alireza Ardehshiri, Gholamreza Karimi and Ramin Dehdasht-Heydari

This paper aims to design, optimize and simulate the Radio Frequency (RF) micro electromechanical system (MEMS) Switch which is stimulated by electrostatically voltage.

105

Abstract

Purpose

This paper aims to design, optimize and simulate the Radio Frequency (RF) micro electromechanical system (MEMS) Switch which is stimulated by electrostatically voltage.

Design/methodology/approach

The geometric structure of the switch was extracted based on the design of Taguchi-based experiment using the mathematical programming and obtaining objective function by the genetic meta-heuristic algorithm.

Findings

The RF parameters of the switch were calculated for the design of Taguchi-based S11 = −5.649 dB and S21 = −46.428 dB at the working frequency of 40 GHz. The pull-in voltage of the switch was 2.8 V and the axial residual stress of the proposed design was obtained 28 MPa and the design of Taguchi-based S11 = −4.422 dB and S21 = −48.705dB at the working frequency of 40 GHz. The pull-in voltage of the switch was 2.5 V and the axial residual stress of the proposed design was obtained 25 MPa.

Originality/value

A novel complex strategy in the design and optimization of capacitive RF switch MEMS modeling is proposed.

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