Articles in press have been peer-reviewed and accepted, which are not yet assigned to volumes /issues, but are citable by Digital Object Identifier (DOI).
Effect of micro-alloying of Ca and Gd on microstructure and mechanical properties of Mg-Zn-Al alloy
Yanxia NIU, Yixuan WANG, Yan SHI
 doi: 10.51393/j.jamst.2023003
Abstract(29) PDF 1612KB(0)
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Mg-2Zn-1Al alloy was used as the matrix, and 0.2wt% Ca, 0.2wt% Gd, and 0.2wt% Ca+0.2wt% Gd were added into it. The target alloys with four components were extruded at 200℃ and extruded bars with good surface quality were obtained. Optical microscope (OM), scanning electron microscope (SEM), X-ray (XRD) and tensile mechanics experiment were adopted to analyze the effect of trace Ca and Gd on the microstructure and mechanical properties of Mg-2Zn-1Al alloy. It is found that the grain size of the as-cast matrix alloy can be refined by adding Ca and Gd, and the effect of grain refinement was the superposition of the two effects added separately. This is due to the heterogeneous nucleation of Al2Ca and the segregation of Gd in front of the solid-liquid interface leads to the inhibition of grain growth. Furthermore, the addition of Ca and Gd can make the extruded micro-structure fine and uniform, which can weak the texture to improve the mechanical properties of the alloy. And the composite addition has the best refinement effect and texture weakening effect. Therefore, the alloy with the composite addition of the two showed the best mechanical properties.
Investigation into temperature and its effects on hole wall quality in rotary ultrasonic countersinking of thin-walled CFRP/Al stacks
Yakun YANG, Kan ZHENG, Song DONG, Lianjun SUN, Zhenwen SUN
 doi: 10.51393/j.jamst.2023002
Abstract(33) PDF 1883KB(2)
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Carbon fiber-reinforcement plastics (CFRP) have been widely applied in modern aerospace industry with aluminum alloy in the form of thin-walled stacks due to their superior mechanical and physical properties. However, for CFRP, the heat accumulation occurs easily during countersinking process in consequence of low thermal conductivity. The surface thermal damage of CFRP caused by excessive heat would affect the fatigue and stealth performance of aircraft. Consequently, the countersinking temperature is an important indicator to judge the feasibility of CFRP countersinking process. In this paper, to investigate temperature of countersinking process, the application of rotary ultrasonic machining technology to CFRP/Al thin-walled stacks countersinking process under different stiffness conditions with drilling-countersinking integrated tool is carried out by FEA (Finite element analysis) and experiments. And the influences of cutting temperature on countersunk wall quality are discussed. The results demonstrate that the maximum countersinking temperature increases with the decrease of axial stiffness, and the ultrasonic vibration can effectively reduce maximum countersinking temperature by 22.9%-26.2%. Furthermore, analysis of the surface quality of countersunk wall shows that the countersunk wall roughness and defects gradually deteriorate with the increase of the maximum countersinking temperature. Meanwhile, the ultrasonic vibration can improve countersunk surface quality by reducing maximum countersinking temperature effectively.
Corner smoothing for CNC machining of linear tool path: A review
Guangwen YAN, Desheng ZHANG, Jinting XU, Yuwen SUN
 doi: 10.51393/j.jamst.2023001
Abstract(104) PDF 2430KB(13)
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Computer numerical control (CNC) machine tools are widely used in various industrial fields ranging from aerospace, automotive, ship building, and the die/mould to manufacture products. However, tool paths of most CNC machine tools are composed of a series of linear motion commands (G01), which will inevitably cause the discontinuity in curvature and feedrate at the junctions between adjacent linear tool path segments, deteriorating the surface quality with unfavorable marks and decreasing the machining efficiency. To solve this problem for obtaining the steady and continuous motions of machine tools, the local corners have to be smoothed. Generally, the existing corner smoothing methods can be classified as the global smoothing and the local corner smoothing, where the specially designed transition curves or the directly planned motion of machine tools are adopted to generate the geometrically corner-free tool path. Moreover, some new methods that focus on developing different transition or rounding strategies are also developed for further improving the kinematics performance of machine tools. In this paper, the recent advances and researches on corner smoothing methods are reviewed from different categories, and the conclusions, remaining challenges and future directions in corner smoothing are also presented.
2023, Volume 3, Issue 1Date of publication:October 09 2022
Abrasive water jet tool passivation: from mechanism to application
Yanbin ZHANG, Wenyi LI, Lizhi TANG, Changhe LI, Xiaoliang LIANG, Shuaiqiang XU, Zafar SAID, Shubham SHARMA, Yun CHEN, Bo LIU, Zongming ZHOU
2023, 3(1): 2022018.   doi: 10.51393/j.jamst.2022018
Abstract(445) PDF 13493KB(59)
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The passivation process of a tool is a necessary step in the manufacturing process, which could improve tool life and machining efficiency by removing microscopic defects of in tool surface (such as burrs and micro cracks) after grinding or polishing. The abrasive water jet passivation (AWJP) is one of the most commonly used processes for carbide, ceramic and steel materials tools. Nevertheless, the complex action law from passivation to machining performance is indistinct, which makes passivation parameters rely on empirical summaries. To fill this gap, this paper concentrates on the detailed review of AWJP and comprehensive assessment between machining performance and AWJP parameters. Firstly, the mechanism of AWJP is analyzed, and the influence law of jet parameters on the tool nose radius is investigated. Secondly, the effect of tool nose radius on the force in turning and milling are summarized and analyzed. The jet pressure, abrasive concentration and jet time are positively correlated with the tool nose radius. Additionally, then the tool nose radius is positively and negatively correlated with cutting force and tool wear, respectively. Finally, future directions regarding the different parameters in AWJP and the machine tool for tool passivation are proposed: to reveal the complex nonlinear relationships between the parameters in AWJP. Develop economical, practical and efficient tool passivation machine tools to improve passivation efficiency and passivation accuracy and apply them to domestic tool passivation technology.

The passivation process of a tool is a necessary step in the manufacturing process, which could improve tool life and machining efficiency by removing microscopic defects of in tool surface (such as burrs and micro cracks) after grinding or polishing. The abrasive water jet passivation (AWJP) is one of the most commonly used processes for carbide, ceramic and steel materials tools. Nevertheless, the complex action law from passivation to machining performance is indistinct, which makes passivation parameters rely on empirical summaries. To fill this gap, this paper concentrates on the detailed review of AWJP and comprehensive assessment between machining performance and AWJP parameters. Firstly, the mechanism of AWJP is analyzed, and the influence law of jet parameters on the tool nose radius is investigated. Secondly, the effect of tool nose radius on the force in turning and milling are summarized and analyzed. The jet pressure, abrasive concentration and jet time are positively correlated with the tool nose radius. Additionally, then the tool nose radius is positively and negatively correlated with cutting force and tool wear, respectively. Finally, future directions regarding the different parameters in AWJP and the machine tool for tool passivation are proposed: to reveal the complex nonlinear relationships between the parameters in AWJP. Develop economical, practical and efficient tool passivation machine tools to improve passivation efficiency and passivation accuracy and apply them to domestic tool passivation technology.

Methods on error-modeling, detection and compensation in gear hobbing process: A short review
Weisen ZHAO, Qiang GUO, Changlin SHU, Zhixi ZHEN, Wenbo WANG
2023, 3(1): 2022019.   doi: 10.51393/j.jamst.2022019
Abstract(935) PDF 10272KB(7)
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Gear is one of important transmission components in mechanical devices.How to correctly produce gears that meets the transmission requirements has always been the research focus in the mechanical industry.Among processing methods of gears,gear hobbing is the one of the most important processing methods because of its high production efficiency and strong universality.However,due to the influence of machining process,various errors will inevitably appear in the gear hobbing process.Therefore,the analysis of hobbing error modeling,detection and compensation are very vital to improve gear accuracy.This paper summarizes researches and developments of the above three aspects,and puts forward the direction and content that need to be further studied:constructing a closed-loop hobbing machining system of "tooth surface error modeling-tooth surface error tracing-error compensation".

Gear is one of important transmission components in mechanical devices.How to correctly produce gears that meets the transmission requirements has always been the research focus in the mechanical industry.Among processing methods of gears,gear hobbing is the one of the most important processing methods because of its high production efficiency and strong universality.However,due to the influence of machining process,various errors will inevitably appear in the gear hobbing process.Therefore,the analysis of hobbing error modeling,detection and compensation are very vital to improve gear accuracy.This paper summarizes researches and developments of the above three aspects,and puts forward the direction and content that need to be further studied:constructing a closed-loop hobbing machining system of "tooth surface error modeling-tooth surface error tracing-error compensation".

Rolling bearing condition monitoring method based on multi-feature information fusion
Yanfei ZHANG, Yunhao LI, Lingfei KONG, Wenchao LI, Yanjing Yi
2023, 3(1): 2022020.   doi: 10.51393/j.jamst.2022020
Abstract(622) PDF 11946KB(13)
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In machining operations, the misalignment of the bearing assembly or imbalanced load often leads to deflection and failure of the tool spindle. The use of single feature information does not accurately monitor the complex working conditions. Considering this, this paper proposes a rolling bearing running condition monitoring method which is based on multiple feature information. Firstly, a multi-dimensional feature matrix is obtained by extracting the features of a single type of raw data in the time domain, frequency domain, and time-frequency domain, and then the dimensionality of the matrix is reduced by principal component analysis (PCA). An entropy weight improved the D-S(EWID-S) evidence theory is proposed. By updating the initial evidence source, and applying the Euclidean distance of the spatial centroid, the fusion results were evaluated. Finally, a test rig for eccentric bearing load operation is developed to obtain the vibration signals at two distinct locations and to confirm the proposed method. The test results show that the condition monitoring method based on the PCA and EWID-S evidence theory can effectively identify the bearing operating at different degrees of deflection. At the same time, by comparing with other improved D-S evidence theory methods, it is verified that this method has more advantages in information fusion and bearing condition monitoring.

In machining operations, the misalignment of the bearing assembly or imbalanced load often leads to deflection and failure of the tool spindle. The use of single feature information does not accurately monitor the complex working conditions. Considering this, this paper proposes a rolling bearing running condition monitoring method which is based on multiple feature information. Firstly, a multi-dimensional feature matrix is obtained by extracting the features of a single type of raw data in the time domain, frequency domain, and time-frequency domain, and then the dimensionality of the matrix is reduced by principal component analysis (PCA). An entropy weight improved the D-S(EWID-S) evidence theory is proposed. By updating the initial evidence source, and applying the Euclidean distance of the spatial centroid, the fusion results were evaluated. Finally, a test rig for eccentric bearing load operation is developed to obtain the vibration signals at two distinct locations and to confirm the proposed method. The test results show that the condition monitoring method based on the PCA and EWID-S evidence theory can effectively identify the bearing operating at different degrees of deflection. At the same time, by comparing with other improved D-S evidence theory methods, it is verified that this method has more advantages in information fusion and bearing condition monitoring.

An accuracy control strategy for micro-milling process of folded waveguide slow wave structure
Xiguang LI, Chuangqiang GUO, Henan LIU, Chang LIU, Zhiyuan MA, Mingjun CHEN, Chunya WU
2023, 3(1): 2022021.   doi: 10.51393/j.jamst.2022021
Abstract(219) PDF 26978KB(20)
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The slow-wave structure (SWS) working in the terahertz frequency band features large aspect ratio and long span with characteristic dimensions of tens of microns. The development of micro-manufacturing technology for the high-quality fabrication of terahertz SWS is technically essential to promote the advancement of terahertz radiation source devices. In this work, micro-milling approaches were devised to process the 0.34 THz folded waveguide SWS with particle-reinforced metal matrix composite material. The causes of shape error and position error, especially within the arc-shape region, were analyzed in detail, considering the influence from the following error of machine tool and the unfavorable rigidity of milling tools. The optimization of regionalized cutting parameters was achieved, and two productive tool-path-planning schemes were conceived according to the structural features within the processing areas, attempting to minimize the external impact on the shape accuracy of SWS. A practical tool replacement scheme with the orthometric setting slots as a reference for resetting after tool replacement was determined, in order to avoid misalignment at the junction of adjacent units. In consideration of the structural complexity of SWS and the position specificity of burrs, the tool path in the horizontal plane was designed in the way of alternately milling of S-shape slot and straight slot, with cutting parameters adaptable to the depth of the processing subregion, which shows excellent suppression effect of burrs. The proposed micro-milling process strategy offers promises to improve the fabrication quality of high-aspect-ratio SWSs with the minimum structure size of ~50μm.

The slow-wave structure (SWS) working in the terahertz frequency band features large aspect ratio and long span with characteristic dimensions of tens of microns. The development of micro-manufacturing technology for the high-quality fabrication of terahertz SWS is technically essential to promote the advancement of terahertz radiation source devices. In this work, micro-milling approaches were devised to process the 0.34 THz folded waveguide SWS with particle-reinforced metal matrix composite material. The causes of shape error and position error, especially within the arc-shape region, were analyzed in detail, considering the influence from the following error of machine tool and the unfavorable rigidity of milling tools. The optimization of regionalized cutting parameters was achieved, and two productive tool-path-planning schemes were conceived according to the structural features within the processing areas, attempting to minimize the external impact on the shape accuracy of SWS. A practical tool replacement scheme with the orthometric setting slots as a reference for resetting after tool replacement was determined, in order to avoid misalignment at the junction of adjacent units. In consideration of the structural complexity of SWS and the position specificity of burrs, the tool path in the horizontal plane was designed in the way of alternately milling of S-shape slot and straight slot, with cutting parameters adaptable to the depth of the processing subregion, which shows excellent suppression effect of burrs. The proposed micro-milling process strategy offers promises to improve the fabrication quality of high-aspect-ratio SWSs with the minimum structure size of ~50μm.

Topologically optimized electrodes for electroosmotic actuation
Jianwen SUN, Jianyu ZHANG, Ce GUAN, Teng ZHOU, Shizhi QIAN, Yongbo DENG
2023, 3(1): 2022022.   doi: 10.51393/j.jamst.2022022
Abstract(259) PDF 9975KB(27)
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Electroosmosis is one of the most used actuation mechanisms for the microfluidics in the current active lab-on-chip devices. It is generated on the induced charged microchannel walls in contact with an electrolyte solution. Electrode distribution plays the key role on providing the external electric field for electroosmosis, and determines the performance of electroosmotic microfluidics. Therefore, this paper proposes a topology optimization approach for the electrodes of electroosmotic microfluidics, where the electrode layout on the microchannel wall can be determined to achieve designer desired microfluidic performance. This topology optimization is carried out by implementing the interpolation of electric insulation and electric potential on the specified walls of microchannels. To demonstrate the capability of this approach, one typical electroosmotic device, i.e., electroosmotic micropump, is modeled with several electrode layouts derived. And this approach permits potential applications in chemicals and biochemistry due to its outstanding capability on determining the performance of electrokinetic microfluidics.

Electroosmosis is one of the most used actuation mechanisms for the microfluidics in the current active lab-on-chip devices. It is generated on the induced charged microchannel walls in contact with an electrolyte solution. Electrode distribution plays the key role on providing the external electric field for electroosmosis, and determines the performance of electroosmotic microfluidics. Therefore, this paper proposes a topology optimization approach for the electrodes of electroosmotic microfluidics, where the electrode layout on the microchannel wall can be determined to achieve designer desired microfluidic performance. This topology optimization is carried out by implementing the interpolation of electric insulation and electric potential on the specified walls of microchannels. To demonstrate the capability of this approach, one typical electroosmotic device, i.e., electroosmotic micropump, is modeled with several electrode layouts derived. And this approach permits potential applications in chemicals and biochemistry due to its outstanding capability on determining the performance of electrokinetic microfluidics.