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, Wentao Qin, Shibiao Wu, Jie Chen and Changhui Song
This study aims to focus on the optimized design and mechanical properties of gradient triply periodic minimal surface cellular structures manufactured by selective laser melting.
Abstract
Purpose
This study aims to focus on the optimized design and mechanical properties of gradient triply periodic minimal surface cellular structures manufactured by selective laser melting.
Design/methodology/approach
Uniform and gradient IWP and primitive cellular structures have been designed by the optimized function in MATLAB, and selective laser melting technology was applied to manufacture these cellular structures. Finite element analysis was applied to optimize the pinch-off problem, and compressive tests were carried out for the evaluation of mechanical properties of gradient cellular structures.
Findings
Finite element analysis shows that the elastic modulus of IWP increased as design parameter b increased, and then decreased when parameter b is higher than 5.5. The highest elastic modulus of primitive increased by 89.2% when parameter b is 6. The compressive behavior of gradient IWP and primitive shows a layer-by-layer way, and elastic modulus and first maximum compressive strength of gradient primitive are higher than that of gradient IWP. The effective energy absorption of gradient cellular structures increased as the average porosity decreased, and the effective energy absorption of gradient primitive is about twice than that of gradient IWP.
Originality/value
This paper presents an optimized design method for the pinch-off problem of gradient triply periodic minimal surface cellular structures.
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Jie Chen, Yongqiang Yang, Shibiao Wu, Mingkang Zhang, Shuzhen Mai, Changhui Song and Di Wang
In this paper, the mechanical properties and corrosion resistance of CoCr alloy fabricated by selective laser melting (SLM) were studied, and the changes of performance after…
Abstract
Purpose
In this paper, the mechanical properties and corrosion resistance of CoCr alloy fabricated by selective laser melting (SLM) were studied, and the changes of performance after porcelain sintering process were also analysed. This study is to point out the relationship between the microstructure, mechanical properties and corrosion resistance of CoCr alloys prepared by SLM after porcelain sintering process. In addition, the biosafety of the sintered CoCr alloy was evaluated.
Design/methodology/approach
The microscopic feature changes of CoCr alloy samples after porcelain sintering process were observed by DMI 5000 M inverted metallographic microscope and Nova Nano430 FE-SEM. Moreover, phase identification and determination were conducted by X-ray diffraction (XRD) using Smartlab X-ray diffractometer. The Vickers microhardness was measured on the HVS-30 microhardness tester, and tensile tests were carried out on a CM3505 electronic universal testing machine. The corrosion resistance was tested by a classical three-point electrode system electrochemical method, then the ion precipitation was measured by using an atomic absorption spectrometer of Z2000 7JQ8024.
Findings
The XRD results indicate that the transition of γ phase (FCC) to e phase (HCP) occurs during the porcelain sintering processing of CoCr alloy. Moreover, the Vickers microhardness of the upper surface and the side surface of the CoCr alloy sample was improved by more than 36%. In addition, the ultimate strength of CoCr alloy via porcelain sintering treatment was increase to 1,395.3 ± 53.0 MPa compared to 1,282.7 ± 10.1 MPa of unprocessed CoCr alloy. However, the corrosion resistance of CoCr alloy samples decreases after porcelain sintering process.
Originality/value
There are few studies on the relationship of microstructure, mechanical properties and corrosion resistance of CoCr alloys prepared by SLM after porcelain sintering process. In this study, the microstructure, mechanical properties and corrosion resistance of CoCr alloy after porcelain sintering process were studied, and the biosafety of the alloy was evaluated. The research found that it is feasible to apply CoCr alloy fabricated by SLM to dental medicine after porcelain sintering process.
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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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Changhui Song, Junfei Huang, Linqing Liu, Zehua Hu, Yongqiang Yang, Di Wang and Chao Yang
This paper aims to better control the mechanical properties and functional properties of NiTi alloy.
Abstract
Purpose
This paper aims to better control the mechanical properties and functional properties of NiTi alloy.
Design/methodology/approach
NiTi alloy samples with equal atomic ratio were formed by selective laser melting (SLM). X-ray diffraction (XRD), differential scanning calorimetry (DSC), scanning electron microscopy and tensile testing methods were used to study the effects of different laser power and scanning speed on the densification behavior, phase transformation characteristics and mechanical properties of NiTi alloy.
Findings
Compared with the laser power, the variation of the keyhole effect caused by the change of scanning speed is more intense, which has a greater effect on the densification behavior of SLM NiTi alloy. The effect of the laser power on the phase transition temperature is small. The increase of scanning speed weakens the burning degree of Ni element, so phase transition temperature decreases. The results of DSC test and tensile test show that the scanning velocity can significantly change the phase transition temperature, martensite twins reorientation and stress–strain behavior of SLM NiTi alloy.
Originality/value
This study provides a potential method to regulate the mechanical properties and functional properties of NiTi shape memory alloy in the future and NiTi alloys formed by SLM with good elongation were obtained because the Supercellular crystal structure formed during the nonequilibrium solidification of SLM and the superfine precipitates dispersed in the alloy prevented the dislocation formation.
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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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Zixin Liu, Yongqiang Yang, Di Wang, Jie Chen, Yunmian Xiao, Hanxiang Zhou, Ziyu Chen and Changhui Song
This study aims to investigate the influence of the gas-flow field distribution and design on the parts quality of 316L stainless steel and the vapor–spatter behavior.
Abstract
Purpose
This study aims to investigate the influence of the gas-flow field distribution and design on the parts quality of 316L stainless steel and the vapor–spatter behavior.
Design/methodology/approach
Based on the hot-wire wind speed test method, the exact value of the gas velocity at different locations was accurately measured to establish the effect on the porosity and the mechanical properties of the parts. The influence of the placement of single or dual blow screens on the performance of the parts quality was also studied. Through scanning electron microscope and energy dispersive spectrometer, high-speed photography and other methods, the influence mechanism was explained.
Findings
It was found that too high or too low gas velocity both play a negative role, for 316L stainless steel, the range of 1.3–2.0 m/s is a suitable gas field velocity during the multilaser powder bed fusion process. And printing quality using dual blow screens is better than single.
Practical implications
The optimization of gas field design and optimal gas velocity (1.3–2.0 m/s) applied during laser melting can improve the quality of ML-PBF of 316L stainless steel.
Originality/value
This study showed the influence of the gas field on the spatter–vapor in the process during ML-PBF, and the unfavorable gas field led to the formation of pores and unmelted powders.
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Changhui Song, Yongqiang Yang, Yunda Wang, Jia-kuo Yu and Di Wang
This paper aims to achieve rapid design and manufacturing of personalized total knee femoral component.
Abstract
Purpose
This paper aims to achieve rapid design and manufacturing of personalized total knee femoral component.
Design/methodology/approach
On the basis of a patient’s bone model, a matching personalized knee femoral component was rapidly designed with the help of computer-aided design method, then manufactured directly and rapidly by selective laser melting (SLM). Considered SLM as manufacturing technology, CoCrMo-alloyed powder that meets ASTM F75 standard is made of femoral component under optimal processing parameters. The feasibility of SLM forming through conducting experimental test of mechanical properties, surface roughness, biological corrosion resistance was analyzed.
Findings
The result showed that the tensile strength, yield strength, hardness and biological corrosion resistance of CoCrMo-alloyed personalized femoral component fulfill knee joint prosthesis standard through post-processing.
Originality/value
Traditional standardized prosthesis implantation manufacturing approach was changed by computer-aided design and personalized SLM direct manufacturing, and provided a new way for personalized implanted prosthesis to response manufacturing rapidly.
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Di Wang, Changhui Song, Yongqiang Yang, Ruicheng Liu, Ziheng Ye, Dongming Xiao and Yang Liu
This paper aims to verify that additive manufacturing technology could be used for the redesign and rapid manufacturing of tools and determine whether the mechanical performance…
Abstract
Purpose
This paper aims to verify that additive manufacturing technology could be used for the redesign and rapid manufacturing of tools and determine whether the mechanical performance of such tools can satisfy the practical operating requirements.
Design/methodology/approach
A special key was selected as the research object in this paper. The special key was innovatively redesigned and manufactured directly using selective laser melting (SLM). The function and critical geometries of the special key were first analysed, which was followed by discussions on the geometrical constraints in the manufacturing of typical geometrical features using SLM technology. Next, the special key was redesigned based on the SLM geometrical constraints and the functional requirements. Finally, the key was manufactured using SLM, and the mechanical performance characteristics of the key were determined.
Findings
The minimal geometrical feature was 0.2 mm when manufacturing thin walls using SLM. The reliable building angle of an overhanging surface was 40°. The top surface quality of the part could be greatly improved through laser surface re-melting. The volume of the redesigned special key based on the SLM process was only one-third to one-fourth of the original key. The mechanical properties, such as tensile strength and micro-hardness, of the samples manufactured using SLM were able to reach the practical operating requirements.
Originality/value
It is completely feasible to redesign and manufacture precision tools based on the innovative approach of SLM. The advantages of the redesigned tools includes the lack of design restrictions that hinder traditional manufacturing methods, material savings, ability to produce tools that cannot be easily copied and rapid production speed for a small number of tools.
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Hao Li and Changhui Cao
This paper investigates the buy online and pick up in-store cooperation (BOPSC) of online and offline retailers. Specifically, this study solves the following questions: (1) What…
Abstract
Purpose
This paper investigates the buy online and pick up in-store cooperation (BOPSC) of online and offline retailers. Specifically, this study solves the following questions: (1) What is the impact of BOPSC on their optimal price and sales volume of products? (2) When should an online retailer and an offline retailer conduct the BOPSC strategy with each other?
Design/methodology/approach
The paper first establishes two game models to explore the equilibriums of online and offline retailers in non-BOPSC and BOPSC. Then the condition for online and offline retailers to implement BOPSC strategy are determined. Furthermore, the applicability of the BOPSC strategy is enhanced by incorporating numerical analysis.
Findings
The study’s findings reveal that BOPSC strategy will not always beneficial to online and offline retailers, which depends on the total cost of online shopping and the product valuation of consumers. BOPSC strategy leads to the increase of prices and online orders, and the demand of offline retailer is eroded. Moreover, BOPS cooperation between different retailers is easier to achieve than omni-channel integration strategy. When the convenience difference between offline shopping and BOPSC pick-up is moderate, the effectiveness of BOPSC strategy can be improved.
Originality/value
This study has the following two main contributions: Firstly, the authors investigate the effects of BOPSC strategy on the prices of online and offline retailers. The study results show that the BOPSC strategy alleviates price competition and promotes a win–win situation between online retailers and offline retailers. Secondly, this paper mainly studies the cooperative behavior between online and offline retailers and reveals the optimal conditions for online and offline retailers to adopt BOPSC strategy. It can help small- and medium-sized online and offline retailers to choose suitable products for BOPSC strategy, so as to achieve the purpose of increasing profit.