Changhui Song, Aibing Huang, Yongqiang Yang, Zefeng Xiao and Jia-kuo Yu
This study aims to achieve customized prosthesis for total joint arthroplasty and total hip arthroplasty. Selective laser sintering (SLS) as additive manufacturing could enable…
Abstract
Purpose
This study aims to achieve customized prosthesis for total joint arthroplasty and total hip arthroplasty. Selective laser sintering (SLS) as additive manufacturing could enable small-scale fabrication of customized Ultra High Molecular Weight Polyethylene (UHMWPE) components; however, the processes for SLS of UHMWPE need to be improved.
Design/methodology/approach
This paper begins by improving the preheating system of the SLS fabricating equipment and then fabricating cuboids with the same size and cuboids with same volume and different size to study the warpage, demonstrating the effect of the value and uniformity of the preheating temperature on component fabrication. Warpage, density and tensile properties are investigated from the perspective of energy input density. Finally, complicated industrial parts are produced effectively by using optimized technological parameters.
Findings
The results show that components can be fabricated effectively after the optimization of the SLS technological parameters i.e. the preheating temperature the laser power the scanning interval and the scanning speed. The resulting warpage was found to be less than 0.1 mm along with the density as 83.25 and the tensile strength up to 14.1 Mpa. UHMWPE sample parts with good appearance and strength are obtained after ascertaining the effect of each factor on the fabrication of the sample parts.
Originality/value
It is very challenging to fabricate UHMWPE sample parts by SLS. This is a new step in the fabrication of customized UHMWPE sample parts.
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Mingkang Zhang, Yongqiang Yang, Changhui Song, Yuchao Bai and Zefeng Xiao
This study aims to focus on the heat treatment influence on the corrosion resistance, adhesion of Streptococcus mutans and mechanical properties of CoCrMo alloys manufactured by…
Abstract
Purpose
This study aims to focus on the heat treatment influence on the corrosion resistance, adhesion of Streptococcus mutans and mechanical properties of CoCrMo alloys manufactured by the selective laser melting (SLM).
Design/methodology/approach
CoCrMo alloys were manufactured using the Dimetal-100 machine. X-ray diffraction (XRD), metallographic analysis, scanning electron microscopy (SEM), electrochemical corrosion, Vickers microhardness and tensile tests were used to characterize SLM-produced CoCrMo alloys and compare them with the ones manufactured by casting and with the ASTM F75 standard.
Findings
The electrochemical results showed that SLM900 samples had the best corrosion resistance in artificial saliva. The adhesion results showed least propagation and overall quantity of Streptococcus mutans on the SLM900 sample. The microhardness, tensile and yield strength of As-SLM, SLM900 and SLM1200D samples were measured according to the ASTM F75 standard. The elongation of SLM900 was less than 8 per cent, which does not meet the standard specifications. Analysis of the fracture morphology showed that the fracture mechanisms of As-SLM and SLM1200D belong to the quasi-cleavage fracture type, and the mechanical fracture mechanism of SLM900 can be characterized as brittle fracture.
Originality/value
This paper presents the adhesion properties of Streptococcus mutans on the surface of CoCrMo alloys manufactured by SLM and proposes how to regulate the effect of the heat treatment on the corrosion resistance and mechanical properties of CoCrMo alloys manufactured by SLM.
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Yuchao Bai, Yongqiang Yang, Zefeng Xiao and Di Wang
This paper aims to verify whether selective laser melting (SLM) could be used for manufacturing mold with conformal cooling channels and determine whether the mechanical…
Abstract
Purpose
This paper aims to verify whether selective laser melting (SLM) could be used for manufacturing mold with conformal cooling channels and determine whether the mechanical properties development of SLM manufacturing maraging steel mold would be beneficial to improve the quality of mold.
Design/methodology/approach
A series of block specimens and cylindrical tensile specimens are manufactured by SLM, and then are heat treated by solution treatment (ST) and solution treatment + aging treatment (ST + AT), respectively. The development of microstructure, microhardness and tensile strength of specimens is investigated. Then, a mold with conformal cooling channels is designed and manufactured by SLM and machined after ST with microhardness decreasing.
Findings
The morphology of microstructure varies widely under different heat treatment. The microhardness and tensile strength decrease after ST with cellular structure broken, which is conducive to mechanical finishing for mold to improve surface accuracy. After that, the hardness and strength of the mold increase significantly by AT with the precipitation of Ni3Mo, Fe2Mo and Ni3Ti particles. The maraging steel mold with conformal cooling channels can be manufactured by SLM successfully. And the surface accuracy of mold could be improved easily by machining.
Originality/value
Compared with the traditional mold with simple cooling channels, the mold with conformal cooling channels can be manufactured by SLM directly. The hardness of maraging steel mold manufactured by SLM can be reduced through ST, which is conducive to mechanical finishing for overcoming the defect of low precision of SLM directly manufacturing mold. This provides a new way for manufacturing mold of high quality.
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Zefeng Xiao, Yongqiang Yang, Di Wang, Changhui Song and Yuchao Bai
This paper aims to summarize design rules based on the process characteristics of selective laser melting (SLM) and structural optimization and apply the design rules in the…
Abstract
Purpose
This paper aims to summarize design rules based on the process characteristics of selective laser melting (SLM) and structural optimization and apply the design rules in the lightweight design of an aluminum alloy antenna bracket. The design goal is to reduce 30 per cent of the weight while maintaining the stress levels in the original part.
Design/methodology/approach
To reduce weight as much as possible, the titanium alloy with higher specific strength was selected during the process of optimization. The material distribution of the bracket was improved by the topology optimization design. The redesign for SLM was used to obtain an optimization model, which was more suitable for SLM. The component performance was improved by shape optimization. The modal analysis data of the structural optimization model were compared with those of the stochastic lightweight model to verify the structural optimization model. The scanning data were compared with those of the original model to verify whether the model was suitable for SLM.
Findings
Structural optimization design for antenna bracket realized the mass decrease of 30.43 per cent and the fundamental frequency increase of 50.18 per cent. The modal analysis data of the stochastic lightweight model and the structural optimization model indicated that the optimization performance of structural optimization method was better than that of the stochastic lightweight method. The comparison results between the scanning data of the forming part and the original data confirmed that the structural optimization design for SLM lightweight component could achieve the desired forming accuracy.
Originality/value
This paper summarizes geometric constraints in SLM and derives design rules of structural optimization based on the process characteristics of SLM. SLM design rules make structural optimization design more reasonable. The combination of structural optimization design and SLM can improve the performance of lightweight antenna bracket significantly.
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Robo-advisory has become an increasingly popular asset management tool in recent decades. This paper studies the association between robo-advisor usage and perceived financial…
Abstract
Purpose
Robo-advisory has become an increasingly popular asset management tool in recent decades. This paper studies the association between robo-advisor usage and perceived financial satisfaction.
Design/methodology/approach
Using data extracted from the National Financial Capability Study 2015 (NFCS2015), the present study carried out a logistic analysis that examines the association between robo-advisory and perceived financial satisfaction. This model also studies the interaction effect of age on this association.
Findings
The present study finds that robo-advisor usage is positively correlated with a person’s perceived financial satisfaction after controlling for covariates related to financial literacy and other demographic factors. Moreover, the present study reveals that age moderates the association between robo-advisory usage and financial satisfaction. The results are robust after regressing financial satisfaction on robo-advisory by different age groups.
Originality/value
This paper extends existing literature on robo-advisory by showing that robo-advisory usage relates to a higher level of financial satisfaction. This finding helps understand the rapidly increasing trend of robo-advisory in the financial industry. Moreover, the present study reveals a moderate effect of age on the association between robo-advisory usage and perceived financial satisfaction.
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Xingwen Wu, Zhenxian Zhang, Wubin Cai, Ningrui Yang, Xuesong Jin, Ping Wang, Zefeng Wen, Maoru Chi, Shuling Liang and Yunhua Huang
This review aims to give a critical view of the wheel/rail high frequency vibration-induced vibration fatigue in railway bogie.
Abstract
Purpose
This review aims to give a critical view of the wheel/rail high frequency vibration-induced vibration fatigue in railway bogie.
Design/methodology/approach
Vibration fatigue of railway bogie arising from the wheel/rail high frequency vibration has become the main concern of railway operators. Previous reviews usually focused on the formation mechanism of wheel/rail high frequency vibration. This paper thus gives a critical review of the vibration fatigue of railway bogie owing to the short-pitch irregularities-induced high frequency vibration, including a brief introduction of short-pitch irregularities, associated high frequency vibration in railway bogie, typical vibration fatigue failure cases of railway bogie and methodologies used for the assessment of vibration fatigue and research gaps.
Findings
The results showed that the resulting excitation frequencies of short-pitch irregularity vary substantially due to different track types and formation mechanisms. The axle box-mounted components are much more vulnerable to vibration fatigue compared with other components. The wheel polygonal wear and rail corrugation-induced high frequency vibration is the main driving force of fatigue failure, and the fatigue crack usually initiates from the defect of the weld seam. Vibration spectrum for attachments of railway bogie defined in the standard underestimates the vibration level arising from the short-pitch irregularities. The current investigations on vibration fatigue mainly focus on the methods to improve the accuracy of fatigue damage assessment, and a systematical design method for vibration fatigue remains a huge gap to improve the survival probability when the rail vehicle is subjected to vibration fatigue.
Originality/value
The research can facilitate the development of a new methodology to improve the fatigue life of railway vehicles when subjected to wheel/rail high frequency vibration.
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Hongji Xie, Shulin Xu and Zefeng Tong
This study examines the effect of local government debt (LGD) on corporate earnings management using 25,624 firm-year observations from 2007 to 2019.
Abstract
Purpose
This study examines the effect of local government debt (LGD) on corporate earnings management using 25,624 firm-year observations from 2007 to 2019.
Design/methodology/approach
Pooled ordinary least squares (OLS) regression is used to examine the impact of LGD on earnings management. A difference-in-differences (DID) method is also used to alleviate potential endogeneity.
Findings
Results show that LGD motivates firms to increase earnings management, especially income-decreasing earnings management. Findings are robust to DID method and robustness tests. Heterogeneity analyses show that the positive effect of LGD on earnings management is pronounced in firms with political dependence and moderated by external governance mechanisms. Further discussions indicate that tax enforcement is an underlying channel for LGD to affect earnings management. Firms engage in downward real earnings management by increasing their abnormal discretionary expenditures and higher LGD leads to a greater book-tax difference in those firms that manipulate income-decreasing earnings management.
Originality/value
This study contributes towards examining the political costs hypothesis, the microeconomic effects of LGD and the determinants of earnings management.
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Wei Li, Xiaoxuan Yang, Peng Wang, Zefeng Wen and Jian Han
This study aims to investigate the cause of high-order wheel polygonization in a plateau high-speed electric multiple unit (EMU) train.
Abstract
Purpose
This study aims to investigate the cause of high-order wheel polygonization in a plateau high-speed electric multiple unit (EMU) train.
Design/methodology/approach
A series of field tests were conducted to measure the vibration accelerations of the axle box and bogie when the wheels of the EMU train passed through tracks with normal rail roughness after re-profiling. Additionally, the dynamic characteristics of the track, wheelset and bogie were also measured. These measurements provided insights into the mechanisms that lead to wheel polygonization.
Findings
The results of the field tests indicate that wheel polygonal wear in the EMU train primarily exhibits 14–16 and 25–27 harmonic orders. The passing frequencies of wheel polygonization were approximately 283–323 Hz and 505–545 Hz, which closely match the dominated frequencies of axle box and bogie vibrations. These findings suggest that the fixed-frequency vibrations originate from the natural modes of the wheelset and bogie, which can be excited by wheel/rail irregularities.
Originality/value
The study provides novel insights into the mechanisms of high-order wheel polygonization in plateau high-speed EMU trains. Futher, the results indicate that operating the EMU train on mixed lines at variable speeds could potentially mitigate high-order polygonal wear, providing practical value for improving the safety, performance and maintenance efficiency of high-speed EMU trains.
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Zefeng Bai, Pengcheng Wang and Miaoqing Jia
In this paper, we empirically investigate how crypto investments in times of economic downturn would affect credit card usage, a widely used payment method that has a significant…
Abstract
Purpose
In this paper, we empirically investigate how crypto investments in times of economic downturn would affect credit card usage, a widely used payment method that has a significant impact on individual financial well-being.
Design/methodology/approach
We carry out an ordinary least squares regression analysis and an instrumental variable design on data from the most recent National Financial Capability Study 2021 (NFCS2021). The NFCS2021 collects information about various demographic and financial backgrounds of US adults.
Findings
We find that crypto investments are associated with a significantly higher likelihood of credit card misuse, as indicated by making only the minim um payments, late payments and using credit cards for cash advances. Meanwhile, social media use is a strong predictor of crypto investments. Results from our analysis are robust after accounting for endogeneity concerns using an instrumental variable design.
Originality/value
Our findings provide new insights into the influence of emerging financial instruments on delinquent credit card behaviors, which can further intensify individual and household financial instability during periods of market stress. Furthermore, our findings underscore the necessity of improving individual awareness of the high-risk characteristics of cryptocurrencies, despite their increasing popularity in the financial marketplace in the current financial marketplace.
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Shuliang Zhao and Li Liu
The impact of environmental regulations on ecological innovation is a contested issue in current research. However, there is no uniform consensus on existing conclusions. It is…
Abstract
Purpose
The impact of environmental regulations on ecological innovation is a contested issue in current research. However, there is no uniform consensus on existing conclusions. It is commonly accepted among scholars that external environment and organizational characteristics are key factors affecting ecological innovation. However, these are often analyzed in isolation, without consideration of the interaction between leadership and external environment. So this study aims to explore the impact of environmental regulation on ecological innovation by combining internal and external factors.
Design/methodology/approach
Based on institutional theory and leadership theory, this paper takes environmental regulation as the independent variable, environmental leadership as the intermediary variable and intellectual property protection level as the regulating variable to explore the impact mechanism of environmental regulation on ecological innovation.
Findings
The findings indicate an inverted U-shaped relationship between environmental regulation and ecological innovation. Additionally, there is a positive correlation between environmental leadership and intellectual property protection level with ecological innovation. Furthermore, environmental leadership partially mediates the relationship between environmental regulation and ecological innovation. However, the level of intellectual property protection does not have a significant moderating effect on the relationship between environmental leadership and ecological innovation.
Originality/value
This paper proposes suggestions for regional ecological innovation based on the current policy and research situation to promote its development.