Sensitivity analysis and parameter interval optimization for residual stress in polishing process of GH4169 blisk blade

Xiaojun Lin,Xiaopeng Xin,Rui Yang,Zhaozhao Lei,Luzhou Sun,Bao Yang,Changyou Bai,Yangwei Yan 대한기계학회 2021 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.35 No.2

Surface integrity has a significant impact on the performance and life cycle of the blisk blade. Residual stress, as one of the important characterization parameters of surface integrity, is closely related to the performance of the aeroengine blisk blade. A certain interval of residual compressive stress can significantly inhibit the generation of microcracks. This paper proposes an optimization method of polishing process parameter interval based on sensitivity analysis. This research studied the effect of polishing parameters of the alumina ACW (abrasive cloth wheel) on the surface residual stress of the GH4169 superalloy blisk blade. Firstly, the experiment was designed by four factors and three levels response surface method, the multiple regression of the experimental data based on Minitab software was used to get a prediction model of polished surface residual stress. And an analysis of variance was performed on the model. Subsequently, the model of relative sensitivity was got based on this model. The sensitivity order of polishing surface residual stress to each polishing parameter was obtained. And the judging method of stable interval and instable interval was put forward. Then, a parameter interval optimization method was proposed, and the optimal interval of process parameters was obtained. Finally, a polishing verification experiment was performed. The results show that: for the polishing of GH4169 superalloy blades, the surface residual stress is most sensitive to the feed rate vf of the ACW, followed by the granularity p and the rotation rate ω, and the compression depth ap is the least sensitive. The optimal interval of polishing process parameters is: the rotation rate ω is [11000 r/min, 11500 r/min], the feed rate vf is [100 mm/min, 200 mm/min], the compression depth ap is [0.6 mm, 1.0 mm], and the granularity p is [400 #, 600 #]. The optimized polishing process parameters can obtain a large and stable surface residual compressive stress, which is helpful to increase fatigue strength of the blisk blade.

Towards Achieving the Maximum Capacity in Large Mobile Wireless Networks under Delay Constraints

Xiaojun Lin,Ness B. Shroff 한국통신학회 2004 Journal of communications and networks Vol.6 No.4

Towards Achieving the Maximum Capacity in Large Mobile Wireless Networks under Delay Constraints

Lin, Xiaojun,Shroff, Ness B. The Korea Institute of Information and Commucation 2004 Journal of communications and networks Vol.6 No.4

In this paper, we study how to achieve the maximum capacity under delay constraints for large mobile wireless networks. We develop a systematic methodology for studying this problem in the asymptotic region when the number of nodes n in the network is large. We first identify a number of key parameters for a large class of scheduling schemes, and investigate the inherent tradeoffs among the capacity, the delay, and these scheduling parameters. Based on these inherent tradeoffs, we are able to compute the upper bound on the maximum per-node capacity of a large mobile wireless network under given delay constraints. Further, in the process of proving the upper bound, we are able to identify the optimal values of the key scheduling parameters. Knowing these optimal values, we can then develop scheduling schemes that achieve the upper bound up to some logarithmic factor, which suggests that our upper bound is fairly tight. We have applied this methodology to both the i.i.d. mobility model and the random way-point mobility model. In both cases, our methodology allows us to develop new scheduling schemes that can achieve larger capacity than previous proposals under the same delay constraints. In particular, for the i.i.d. mobility model, our scheme can achieve (n-1/3/log3/2 n) per-node capacity with constant delay. This demonstrates that, under the i.i.d. mobility model, mobility increases the capacity even with constant delays. Our methodology can also be extended to incorporate additional scheduling constraints.

Flexible CNC polishing process and surface integrity of blades

Xiaojun Lin,Dongbo Wu,Xiufeng Shan,Gang Wu,Tong Cui,Yun Zhang,Liangyi Hu,Jie Yu 대한기계학회 2018 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.32 No.6

The surface integrity of aero-engine blades directly affects its mechanical behavior. To improve the surface integrity and address the problem, that is, the blade is mainly polished manually, a flexible polishing process was proposed and surface integrity was investigated. First, flexible polishing technology and the machine tool that the authors researched and developed were introduced. Second, a polishing experiment was conducted on a TC4 titanium alloy blade. Finally, the surface integrity before and after polishing was measured and the results were compared and analyzed. Results showed that the knife marks, pits, unevenness, and other defects of the blade surface were effectively removed through flexible polishing; the surface residual compressive stress was reduced from 483 MPa to 397 MPa; the surface roughness was reduced to Ra 0.4 μm; the surface micro-hardness increased by 18 HV; and the surface metamorphic layer caused by milling was removed. Flexible polishing effectively improved the surface quality without affecting the depth layer quality of the workpiece.

Important Role of Immunological Responses to Environmental Exposure in the Development of Allergic Asthma

Xinliu Lin,Xia Ren,Xiaojun Xiao,Zhaowei Yang,Siyang Yao,Gary WK Wong,Zhigang Liu,Charles Wang,Zhong Su,Jing Li 대한천식알레르기학회 2020 Allergy, Asthma & Immunology Research Vol.12 No.6

Allergic asthma is a public health problem that affects human health and socioeconomic development. Studies have found that the prevalence of asthma has significantly increased in recent years, which has become particularly pronounced in developed countries. With rapid urbanization in China in the last 3 decades, the prevalence of asthma has increased significantly in urban areas. As changes in genetic backgrounds of human populations are limited, environmental exposure may be a major factor that is responsible for the increased prevalence of asthma. This review focuses on environmental components of farms and rural areas that may have protective effects in reducing the development of asthma. Farm and rural related microorganism- and pathogen-associated molecular patterns are considered to be important environmental factors that modulate host's innate and adaptive immune system to induce protection effects later in life. Environmental microbial-related immunotherapy will also be discussed as the future research direction for the prevention of allergic asthma.

Distributed Greedy Approximation to Maximum Weighted Independent Set for Scheduling With Fading Channels

Joo, Changhee,Lin, Xiaojun,Ryu, Jiho,Shroff, Ness B. Institute of Electrical and Electronics Engineers, 2016 IEEE/ACM transactions on networking Vol.24 No.3

<P>It has been known that scheduling algorithms designed to achieve throughput optimality and good delay performance often require solving the Maximum Weighted Independent Set (MWIS) problem. However, under most realistic network settings, the MWIS problem is known to be NP-hard. In non-fading environments, low-complexity scheduling algorithms have been provided that converge either to the MWIS solution in time or to a solution that achieves at least a provable fraction of the achievable throughput. However, in more practical systems the channel conditions can vary at faster time-scales than convergence occurs in these lower-complexity algorithms. Hence, these algorithms cannot take advantage of opportunistic gains, and may no longer result in achieving good performance. In this paper, we propose a low-complexity scheduling scheme that performs provably well under fading channels and is amenable to implement in a distributed manner. To the best of our knowledge, this is the first scheduling scheme under fading environments that requires only local information, has a low complexity that grows logarithmically with the network size (provided that the conflict graph has bounded maximum vertex degree), and achieves provable performance guarantees (arbitrarily close to that of the well-known centralized Greedy Maximal Scheduler). We verify that the throughput and the delay of our proposed scheme are close to those of the optimal MaxWeight that solves MWIS at each time. Further, we implement our algorithm in a testbed by modifying the existing IEEE 802.11 DCF. The experiment results show that our implementation successfully accounts for wireless fading, attains the short-term opportunistic gains in practice, and hence substantially outperforms IEEE 802.11 DCF.</P>

Dexmedetomidine promotes the progression of hepatocellular carcinoma through hepatic stellate cell activation

Chen Peng,Luo Xiaojun,Dai Guanqi,Jiang Yuchuan,Luo Yue,Peng Shuang,Wang Hao,Xie Penghui,Qu Chen,Lin Wenyu,Hong Jian,Ning Xue,Li Aimin 생화학분자생물학회 2020 Experimental and molecular medicine Vol.52 No.-

Dexmedetomidine (DEX) is an anesthetic that is widely used in the clinic, and it has been reported to exhibit paradoxical effects in the progression of multiple solid tumors. In this study, we sought to explore the mechanism by which DEX regulates hepatocellular carcinoma (HCC) progression underlying liver fibrosis. We determined the effects of DEX on tumor progression in an orthotopic HCC mouse model of fibrotic liver. A coculture system and a subcutaneous xenograft model involving coimplantation of mouse hepatoma cells (H22) and primary activated hepatic stellate cells (aHSCs) were used to study the effects of DEX on HCC progression. We found that in the preclinical mouse model of liver fibrosis, DEX treatment significantly shortened median survival time and promoted tumor growth, intrahepatic metastasis and pulmonary metastasis. The DEX receptor (ADRA2A) was mainly expressed in aHSCs but was barely detected in HCC cells. DEX dramatically reinforced HCC malignant behaviors in the presence of aHSCs in both the coculture system and the coimplantation mouse model, but DEX alone exerted no significant effects on the malignancy of HCC. Mechanistically, DEX induced IL-6 secretion from aHSCs and promoted HCC progression via STAT3 activation. Our findings provide evidence that the clinical application of DEX may cause undesirable side effects in HCC patients with liver fibrosis.

Optimization of abrasive flow polishing process parameters for static blade ring based on response surface methodology

Zhao Tao,Shi Yaoyao,Lin Xiaojun,Huang Tianran 대한기계학회 2016 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.30 No.3

Static blade ring process technology is a key part for gas turbine manufacturing, and the surface quality of the static blade ring has great influence on a gas turbine. To improve surface roughness of static blade ring, abrasive flow polishing process technology is studied. First, the range of extrusion pressure is obtained by using ANSYS software to analyze the blade deformation. Then a simplified model of surface roughness is estabalished according to experimental results and ANOVA’s results. At the same time, the optimal polishing parameters are confirmed through the response surface methodology. Finally, the polishing experiment is carried out by using the optimal polishing parameters. The experimental results demonstrate that the surface roughness of static blade ring decreased greatly (nearly 14.7%) compared with result using normal parameters.

Roughness modeling for polishing an aero-engine blade with an abrasive cloth wheel

Chao Xian,Yaoyao Shi,Xiaojun Lin,De Liu 대한기계학회 2020 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.34 No.8

Roughness is a crucial factor that determines workpiece quality. In this paper, the time-domain signals of polishing force for polishing an aero-engine blade with an abrasive cloth wheel were experimentally obtained, and the contact arc lengths were determined based on these signals. A mathematical model for the representative R a of blade surface roughness after polishing was then established, and this model is only related to the contact arc length. This model was experimentally verified, and the prediction results agree well with the measurement results.

Polishing surface integrity of TC17 aeroengine blades

De Liu,Yaoyao Shi,Xiaojun Lin,Chao Xian,Zhiyang Gu 대한기계학회 2020 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.34 No.2

Aeroengine blades have high requirements for surface integrity. Through the flexible polishing of TC17 engine blades, the surface integrity of polished blades is improved. First, the influence of process parameters on polishing force and polishing temperature is analyzed through experiments. The influence of parameters on surface roughness is analyzed, and the relationship between wear debris shape and surface morphology under different process parameters are analyzed from the microscopic level. Second, the influence of process parameters on the residual stress of the polished surface is analyzed in accordance with the polishing force and polishing temperature. Then, the variation of the residual stress of the blade after milling and polishing is analyzed. In addition, the microstructure of the metamorphic layer after milling and polishing is analyzed. Experimental results show that reasonable polishing parameters can effectively improve the surface integrity of the blade.