Simulation and experiment study of burrs in micro-milling Zr-based metallic glass

Jiachun Wang,Zhenhong Zhang,Chuang Zhang,Jiabin Fu,Jianchao Chen 대한기계학회 2020 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.34 No.7

Metallic glass has been widely used in making micro parts and equipment due to its excellent physical and chemical performance. A large quantity of burrs is produced in the micro-milling process that is hard to remove and seriously affects the quality and precision of the parts. Burrs should be effectively restrained; however, the burrs’ type, position and the effect of milling parameters on burrs’ generation in micro-milling metallic glass have not been systematically studied. In this paper, by using 3-D FEM simulation and taking micro-milling experiments of Zr-based metallic glass (Vit1), the burrs in flat-end milling and ball-end milling micro grooves were investigated. The burrs’ type and position were observed and summarized, the formation process of various burrs was analyzed in detail, and the influence of cutting parameters on burrs was clarified. Comparing the simulation and experiment result, we could confirm that the top burr and the entrance burr were produced during the processing of the flatend milling cutter, and ball-end milling cutter effectively inhibits the production of the top burr but takes no actions on burrs’ generation at the entrance and the bottom of the groove. The main cause of the top burr is the extrusion of the tool, and the extrusion of the cutting layer metal and chip accumulation were the main reason for entrance and exit burrs. Reducing the axial cutting depth could effectively restrain the generation of burrs for both two kinds of milling tools.

Evaluation of early age mechanical properties of concrete in real structure

Jiachun Wang,Peiyu Yan 사단법인 한국계산역학회 2013 Computers and Concrete, An International Journal Vol.12 No.1

The curing temperature is known to influence the rate of mechanical properties development of early age concrete. In realistic sites the temperature of concrete is not isothermal 20˚C, so the paper measured adiabatic temperature increases of four different concretes to understand heat emission during hydration at early age. The temperature-matching curing schedule in accordance with adiabatic temperature increase is adopted to simulate the situation in real massive concrete. The specimens under temperature-matching curing are subjected to realistic temperature for first few days as well as adiabatic condition. The mechanical properties including compressive strength, splitting strength and modulus of elasticity of concretes cured under both temperature-matching curing and isothermal 20˚C curing are investigated. The results denote that comparing temperature-matching curing with isothermal 20˚C curing, the early age concretes mechanical properties are obviously improved, but the later mechanical properties of concretes with pure Portland and containing silica fume are decreased a little and still increased for concretes containing fly ash and slag. On this basement using an equivalent age approach evaluates mechanical properties of early age concrete in real structures, the model parameters are defined by the compressive strength test, and can predict the compressive strength, splitting strength and elasticity modulus through measuring or calculating by finite element method the concreted temperature at early age, and the method is valid, which is applied in a concrete wall for evaluation of crack risking.

Influence of microgroove cutting tool on cutting energy and cutting performance during turning of Inconel 718

Jiachun Li,Zhongfei Zou 대한기계학회 2023 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.37 No.4

In this study, an original cutting tool (OCT) for machining nickel-based superalloy Inconel 718 is selected, and a microgroove is designed on its rake face based on the temperature field contour. Hence, we present a new microgroove cutting tool (MCT). Through experimental and simulation trials, the cutting force, cutting energy, cutting temperature, tool life, and tool wear of MCT and OCT are compared and analyzed. The results indicate that cutting temperature and the forces with OCT are greater than that of MCT. Compared with OCT, the shear energy and total cutting energy of MCT are reduced, and the ratio of the shear energy to the total cutting energy (R s-T ) is greater than that of OCT. In addition, the tool life of MCT is 23 % longer than that of OCT under the equivalent machining conditions. The results indicate that the microgroove structure not only changes the balance force relationship but also reduces the generation, and optimizes the distribution of the cutting energy, resulting in extending the tool life.

Antioxidant properties of a vegetable–fruit beverage fermented with two Lactobacillus plantarum strains

Xiaoxing Yang,Jiachun Zhou,Liqiang Fan,Zhen Qin,Qiming Chen,Liming Zhao 한국식품과학회 2018 Food Science and Biotechnology Vol.27 No.6

Fermented vegetable–fruit beverages are a popular fermented food, with many potential health benefits. In this study, two commercial Lactobacillus plantarum strains were selected to ferment a beverage containing apples, pears, and carrots. The metabolites and antioxidant activities were examined during the fermentation process. Results showed that lactic acid and acetic acid accumulated gradually, whereas malic acid decreased. Glucose and fructose increased from 0.48 and 14.8 g/L to 7.7 and 20.8 g/L, respectively, while sucrose decreased slightly. Ascorbic acid also increased continuously during the fermentation to 90.74 mg/100 mL. DPPH and ABTS radical scavenging activity and FRAP reached their maximum value after 4–8 days. The accumulation of TPC, TFC, and SOD reached their maximum value on the 8th day of fermentation. Our study revealed that the L. plantarum-fermented vegetable–fruit beverage showed significant antioxidant activity, which is helpful in evaluating the fermentation end-point and developing a high-quality fermented beverage.

Source Apportionment of Lead and Cadmium in Cropland Near a Contaminated Site: A Combined Approach of Positive Matrix Factorization and Geostatisticalanalysis

Jianlong Xue,Yuyou Zhi,Jiachun Shi,Laosheng Wu,Lingzao Zeng 한국토양비료학회 2014 한국토양비료학회 학술발표회 초록집 Vol.2014 No.6

Intensity of Intraoperative Spinal Cord Hyperechogenicity as a Novel Potential Predictive Indicator of Neurological Recovery for Degenerative Cervical Myelopathy

Chen Guoliang,Wei Fuxin,Li Jiachun,Shi Liangyu,Zhang Wei,Wang Xianxiang,Xu Zuofeng,Liu Xizhe,Zou Xuenong,Liu Shaoyu 대한영상의학회 2021 Korean Journal of Radiology Vol.22 No.7

Objective: To analyze the correlations between intraoperative ultrasound and MRI metrics of the spinal cord in degenerative cervical myelopathy and identify novel potential predictive ultrasonic indicators of neurological recovery for degenerative cervical myelopathy. Materials and Methods: Twenty-two patients who underwent French-door laminoplasty for multilevel degenerative cervical myelopathy were followed up for 12 months. The Japanese Orthopedic Association (JOA) scores were assessed preoperatively and 12 months postoperatively. Maximum spinal cord compression and compression rates were measured and calculated using both intraoperative ultrasound imaging and preoperative T2-weight (T2W) MRI. Signal change rates of the spinal cord on preoperative T2W MRI and gray value ratios of dorsal and ventral spinal cord hyperechogenicity on intraoperative ultrasound imaging were measured and calculated. Correlations between intraoperative ultrasound metrics, MRI metrics, and the recovery rate JOA scores were analyzed using Spearman correlation analysis. Results: The postoperative JOA scores improved significantly, with a mean recovery rate of 65.0 ± 20.3% (p < 0.001). No significant correlations were found between the operative ultrasound metrics and MRI metrics. The gray value ratios of the spinal cord hyperechogenicity was negatively correlated with the recovery rate of JOA scores (ρ = -0.638, p = 0.001), while the ventral and dorsal gray value ratios of spinal cord hyperechogenicity were negatively correlated with the recovery rate of JOA-motor scores (ρ = -0.582, p = 0.004) and JOA-sensory scores (ρ = -0.452, p = 0.035), respectively. The dorsal gray value ratio was significantly higher than the ventral gray value ratio (p < 0.001), while the recovery rate of JOA-motor scores was better than that of JOA-sensory scores at 12 months post-surgery (p = 0.028). Conclusion: For degenerative cervical myelopathy, the correlations between intraoperative ultrasound and preoperative T2W MRI metrics were not significant. Gray value ratios of the spinal cord hyperechogenicity and dorsal and ventral spinal cord hyperechogenicity were significantly correlated with neurological recovery at 12 months postoperatively.

A comparative study on population development patterns of Sogatella furcifera between tropical and subtropical areas

Yang Hu,Jia-An CHENG,Zengrong Zhu,Kong Luen Heong,Qiang Fu,Jiachun He 한국응용곤충학회 2014 Journal of Asia-Pacific Entomology Vol.17 No.4

The White-backed Planthopper (WBPH), Sogatella furcifera (Horváth (Hemiptera: Delphacidae)) has been the most serious pest threatening rice production in Asia since the late 1970s. A series of field experiments using the same research protocol was carried out to compare the effects of main environmental factors on population development of WBPH in tropical (Philippines) and subtropical (China) areas in 2010–2012 and to provide further evidences of ecological mechanisms involved that cause frequent outbreak in subtropical rice. Outcomes showed that WBPH population in subtropical area could be characterized as the higher population growth rates and higher peak densities. The average growth rate (116.60 ± 46.16) in subtropical area was significantly higher than that in tropical area (24.02± 11.25). The higher realized fecundity in subtropical area indicated that the higher growth rates and higher peak densities were mainly related to the poor natural regulating forces in subtropical area. Our results showed that resistant variety could significantly reduce the peak density in subtropical areas, but not in tropical areas. We inferred that the reason for not detecting the effect of resistant variety in tropical area was due to the dominant controlling effects provided by natural enemies,which means that the natural regulating effect in tropical areawas strong enough to disguise the effects of resistant variety. The significant interactions between plant resistance and location demonstrated that integration of natural enemies and use of plant resistance could play important roles for reducing outbreak frequency of WBPH effectively in subtropical rice.