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RISS 인기검색어
- 검색키워드
- 저자 : Junbo Shi (검색결과 3 건)
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Junbo Zhang,Shuanghong Yin,Fei Guo,Ren Meng,Chuangfu Chen,Hui Zhang,Zhi-qiang Li,Qiang Fu,Huijun Shi,Shengwei Hu,Wei Ni,Tiansen Li,Ke Zhang 한국미생물학회 2014 The journal of microbiology Vol.52 No.8
Brucellosis is a globally distributed zoonotic disease that causes animal and human diseases. However, the current Brucella abortus vaccines (S19 and RB51) are deficient; they can cause abortion in pregnant animals. Moreover, when the vaccine S19 is used, tests cannot differentiate natural from vaccinated infection. Therefore, a safer and more potent vaccine is needed. A Brucella abortus 2308 ery promoter mutant (Δery) was constructed to overcome these drawbacks. The growth of the Δery mutant was significantly attenuated in macrophages and mice and induced high protective immunity in mice. Moreover, Δery induced an anti-Brucellaspecific IgG (immunoglobulin G) response and stimulated the expression of interferon-gamma (INF-γ) and interleukin-4 (IL-4). Furthermore, the expression of EryA antigen allowed for the serological differentiation between natural and vaccinated infection in mice. These results indicate that the Δery mutant is a potential attenuated live vaccine candidate against virulent Brucella abortus 2308 (S2308) infection.
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Fracture analysis of a welded front axle tube structure from a mini-truck
Weimin Guo,Ning Ding,Na Xu,Long Liu,Nan Li,Junbo Shi,Chi-Man Lawrence Wu 대한기계학회 2020 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.34 No.1
The failure (fracture) mechanism of a welded front axle tube structure made of C45E4 steel from a mini truck was analyzed. The fracture occurred on the right side of the right support frame with the fracture surface perpendicular to the tube axis. SEM examination showed that the fracture surface could be divided into three areas: intergranular area, cleavage area and dimple area. Crack initiation site of the failed front axle tube was at the front weld joint fixing the right support frame on the axle tube. The crack propagated in two opposite directions along the circumference of the tube and converged at the dimple area. Intergranular fracture was found to be in heat affected zone (HAZ). With higher magnification, fine dimples, intergranular and trans-granular fracture characteristics were observed in the crack initiation site. By metallurgical examination, Widmanstätten ferrites, which could decrease the toughness and strength of the weld joint, were observed in the columnar grains. The hardness of HAZ coarse grain area (623 VHN) was far higher than HAZ fine grain area (310 VHN) and base metal (225 VHN). As the weld process indicates, neither pre-weld nor post-weld treatment was carried out. A non-uniform temperature distribution around the weld joint could generate large thermal residual tensile stress in HAZ; thus, the material was very unstable. It could fracture for very small or even no external stress. Hydrogen atoms would be released during welding and microstructures with the highest hardness are the most susceptible of hydrogen assisted cracking. It is concluded that the fracture was caused by hydrogen assisted brittleness under the induction of weld residual stress. Post-weld aging treatment (PWAT) is recommended to release the residual stress generated during welding process. In this case, PWAT was carried out on the failed weld joint and Vickers hardness of HAZ coarse grain area, HAZ fine grain area and base metal decreased to 232 VHN, 205 VHN and 125 VHN, respectively. That indicates that the PWAT procedure could effectively soften the material and relieve residual stress.
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Weimin Guo,Zuocheng Wang,Na Xu,Ning Ding,Junbo Shi 대한기계학회 2018 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.32 No.7
A 0.085 wt% P micro - alloyed and Ti-stabilized high strength IF (interstitial free) steel was warm rolled under two conditions: One with lubrication and the other without. The results show that lubrication has a significant effect on texture evolution during warm rolling and the subsequent annealing process. Without lubrication, severe shear deformation occurs in the surface layer, which results in recrystallization and the formation of a <110>//ND (normal direction) texture, while the central layer undergoes plane strain deformation and forms a weak <111>//ND deformation texture (typical of bcc iron). With good lubrication, both the surface and central layer experience plane strain deformation and a strong <111>//ND texture is normally formed. The warm rolling texture (which contains both recrystallized and deformed grains) has a profound effect on the subsequent annealing texture. The final textures influence the draw - ability of the plates, i.e. the r - value (r-value: The ratio of the true width strain to the true thickness strain in a sheet tensile test) and |Dr|-value (planar anisotropy coefficient). After annealing, the lubricated plates are characterized by a higher r - value (1.27) and a much lower |Dr|-value (0.075) than those rolled without lubrication (i.e. 0.96 for the r - value and 0.465 for the |Dr|-value).
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