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Research on Fretting Fatigue of Tungsten Carbide Coating Based on Strain Energy Density Methods

Zeng Xin, Wang Xiaoxiao, Ping Xuecheng, Wang Renjie, Hu Tao

Archives of Metallurgy and Materials

2023

Vol. 68, iss. 1

21--30

The numerical solutions of stress and strain components on the critical plane of tungsten carbide coating were solved based on the critical plane method in three-dimensional coordinate system, and accordingly three strain energy density parameters (Smith-Watson-Topper, Nita-Ogatta-Kuwabara and Chen parameters) were determined to reveal the fretting fatigue characteristics of tungsten carbide coating. In order to predict the fretting fatigue life based on the strain energy density criterion, the expressions between the strain energy density parameter and the fretting fatigue life was obtained experimentally. After the comparison of the three strain energy parameters, it was found that all three parameters could accurately predict the crack initiation position, but only the Smith-Watson-Topper parameters could accurately predict the crack initiation angle. The effects of cyclic load, normal load and friction coefficient on fretting fatigue damage behaviors were discussed by using the Smith-Watson-Topper criterion. The results show that the fretting fatigue life decreases with the increase of cyclic load; an increase in the normal contact load will cause the Smith-Watson-Topper damage parameters more concentrated at the outer edge of the bridge foot; a decrease in the friction coefficient will increase the Smith-Watson-Topper damage parameters in the middle of the contact surface.

Diversity and Composition of Rhizosphere Fungal Community in Pure and Mixed Forests of South China

Wen Xinmiao, Wang Renjie, Jiang Yi, Deng Xiaojun, Wei Shuoxin, Liu Xiongsheng, Wang Yong

Polish Journal of Ecology

2021

Vol. 69, nr 2

111--123

Rhizosphere fungal communities are of critical importance for forest health. Microbial diversity varies with forest types due to tree species. In order to examine the influence of forest types and species composition on fungal community diversity in rhizosphere soil, the field sampling was conducted in the pure and mixed forest stands of Castanopsis hystrix in a subtropical region of China. Soil samples were taken from four forest types: Castanopsis hystrix pure forests (CH), Castanopsis hystrix × Pinus elliottii mixed forests (CHPE), Castanopsis hystrix × Michelia macclurei mixed forests (CHMM), and Castanopsis hystrix × Mytilaria laosensis mixed forests (CHML), and the species composition and structure of rhizosphere fungal community were examined by using high-throughput sequencing approach for 18S rRNA genes. The results showed that the amount of OTUs (operational taxonomic units) were 288, 331, 334 and 293 in CHML, CHMM, CHPE and CH stands, respectively, and these fungal communities were affiliated with 13 phyla, 28 classes, 85 orders, 87 families, and 131 genera. The fungal diversity was greater in CHMM and CHPE stands than in CH stands. The compositions were similar in CHMM and CHPE stands while those were significantly different in CHML and CH stands. The cladograms and co-expression network analysis showed that Ascomycota, Basidiomycota, Mortierellomycota and Rozellomycota were the dominant phyla. The study results implied that mixed forests might have a high potential for improving the microbial community diversity with formation of key species of microbial taxa due to the favorable microclimate and quality of litter composition occuring in mixed forests.