Cijun Shuai, Jingyu Zhuang, Shuping Peng and Xuejun Wen
The paper aims to fabricate an α-tricalcium phosphate (TCP) scaffold with an interconnected porous structure via selective laser sintering (SLS). To inhibit the phase…
Abstract
Purpose
The paper aims to fabricate an α-tricalcium phosphate (TCP) scaffold with an interconnected porous structure via selective laser sintering (SLS). To inhibit the phase transformation from β- to α-TCP in fabrication process of porous scaffolds, a small amount (1 weight per cent) of poly (L-lactic acid) (PLLA) is added into β-TCP powder to introduce the transient liquid phase.
Design/methodology/approach
The paper opted for the transient liquid phase of melting PLLA to decrease the sintering temperature in SLS. Meanwhile, the densification of β-TCP is enhanced with a combined effect of the capillary force caused by melting PLLA and the surface energy of β-TCP particles. Moreover, the PLLA will gradually decompose and completely disappear with laser irradiation.
Findings
The testing results show the addition of PLLA enables the scaffolds to achieve a higher β-TCP content of 77 ± 1.49 weight per cent compared with the scaffold sintered from β-TCP powder (60 ± 1.65 weight per cent), when the laser energy density is 0.4 J/mm2. The paper provides the mechanism of PLLA inhibition on the phase transformation from β- to α-TCP. And the optimum sintering parameters are obtained based on experimental results, which are used to prepare a TCP scaffold with an interconnected porous structure via SLS.
Research limitations/implications
This paper shows that the laser energy density is an important sintering parameter that can provide the means to control the micro-porous structure of the scaffold. If the laser energy density is too low, the densification is not enough. On the other hand, if the laser energy density is too high, the microcracks are observed which are attributed to the volume expansion during the phase transformation from β- to α-TCP. Therefore, the laser energy density must be optimized.
Originality/value
The paper provides a feasible method for fabricating TCP artificial bone scaffold with good biological and mechanical properties.
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Yanli Feng, Ke Zhang, Haoyu Li and Jingyu Wang
Due to dynamic model is the basis of realizing various robot control functions, and it determines the robot control performance to a large extent, this paper aims to improve the…
Abstract
Purpose
Due to dynamic model is the basis of realizing various robot control functions, and it determines the robot control performance to a large extent, this paper aims to improve the accuracy of dynamic model for n-Degree of Freedom (DOF) serial robot.
Design/methodology/approach
This paper exploits a combination of the link dynamical system and the friction model to create robot dynamic behaviors. A practical approach to identify the nonlinear joint friction parameters including the slip properties in sliding phase and the stick characteristics in presliding phase is presented. Afterward, an adaptive variable-step moving average method is proposed to effectively reduce the noise impact on the collected data. Furthermore, a radial basis function neural network-based friction estimator for varying loads is trained to compensate the nonlinear effects of load on friction during robot joint moving.
Findings
Experiment validations are carried out on all the joints of a 6-DOF industrial robot. The experimental results of joint torque estimation demonstrate that the proposed strategy significantly improves the accuracy of the robot dynamic model, and the prediction effect of the proposed method is better than that of existing methods.
Originality/value
The proposed method extends the robot dynamic model with friction compensation, which includes the nonlinear effects of joint stick motion, joint sliding motion and load attached to the end-effector.
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Shunsuke Managi, Jingyu Wang and Lulu Zhang
The purpose of this paper is to provide the extensive review on dynamic monitoring of forestry area in China.
Abstract
Purpose
The purpose of this paper is to provide the extensive review on dynamic monitoring of forestry area in China.
Design/methodology/approach
Countermeasure and suggestions were proposed for three aspects including the establishment of data sets with unified standards, top-level design of monitoring and assessment and analysis models, and establishment of the decision support platform with multiple scenario simulation.
Findings
Finally, the authors proposed key research area in this field, i.e., improving the systematic and optimal forest management through integrating and improving the data, models and simulation platforms and coupling the data integration system, assessment system and decision support system.
Originality/value
The authors explored the limitation of dynamic monitoring and state of the art research on data accumulation, professional model development and the analytical platform.
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The purpose of this paper is to investigate the process parameters and optimise the machining input parameter of powder mixed electric discharge machining for high carbon high…
Abstract
Purpose
The purpose of this paper is to investigate the process parameters and optimise the machining input parameter of powder mixed electric discharge machining for high carbon high chromium alloy steel (D2 steel) for the industrial application. Grey relational analysis approach has been used to obtain the multiple performance output response.
Design/methodology/approach
In this experimental work, input parameters, namely, pulse on-time, discharge current, tool material and grit size, are selected. The design of the experiment has been constructed with the help of MINITAB 7 Software, in which L16 orthogonal array has been preferred for the experimentation. The effect of input parameters, namely, material removal rate, tool wear rate and surface roughness, is investigated. Grey relational analysis and analysis of variance are performed to optimise the input parameters and better output results.
Findings
In this experimentation, there is an increment of tool wear rate by 64.49 per cent, material removal rate by 47.14 per cent and surface roughness by 35.82 per cent.
Practical implications
A lot of practical applications have been found in many different material processing industries like metallurgy, machinery, electronics, transportation, military science, agricultural machinery, etc. These practical applications have brought forward definite and noticeable economic benefits.
Originality/value
The reader is given a general overview on the machining investigation and optimisation of processes parameters through the grey theory approach. It gives a new framework to investigate the problems where multiple input machining variable and various output responses are obtained in single optimised parameters.