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RISS 인기검색어
- 검색키워드
- 저자 : Yunhui Mei (검색결과 4 건)
- 무료
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- 유료
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In Situ X-Ray Observation and Simulation of Ratcheting-Fatigue Interactions in Solder Joints
Liting Shi,Yunhui Mei,Gang Chen,Xu Chen 대한금속·재료학회 2017 ELECTRONIC MATERIALS LETTERS Vol.13 No.1
Reflow voids created by solder oxidation reduce thereliability of lap joints. In situ visualization of reflow voids inSn-3Ag-0.5Cu (SAC305) lap-shear solder joints undercyclic stressing was realized by X-ray computed tomography(CT), while the ratcheting deformation of the solder jointswas monitored by a non-contact displacement detectingsystem (NDDS). The results revealed that the shapeevolution of reflow voids in solder joints, as characterized bythe sphericity of the voids, can be divided into three stages:i.e., the initial stage with a sharp drop, a stable stage, and arapidly declining stage. A new evolution law for describingthe progress of sphericity was proposed, and was furtherintroduced into a viscoplastic constitutive model based onthe OW-AF nonlinear kinematic hardening rule. Thedamage-coupled OW-AF model yielded an accurateestimation of the whole-life ratcheting behavior of Sn-3Ag-0.5Cu (SAC305) lap-shear solder joints.
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Shoucheng Huang,Xinhua Guo,Rongkun Wang,Yunhui Mei 전력전자학회 2021 JOURNAL OF POWER ELECTRONICS Vol.21 No.12
In a four-switch three-phase inverter-powered permanent magnet synchronous motor system, the capacitor voltage fluctuates due to the unequal capacitance and the charging and discharging of the bus capacitor. As such, the accuracy of motor vector control becomes significantly affected and even causes the shutdown of the motor drive system. Therefore, this study proposed a space vector PWM (SVPWM) algorithm that considers capacitor voltage imbalance. In the case of voltage basic vector offset, this algorithm first constructs a new orthogonal voltage basic vector and takes the offset modulation range as the constraint condition to synthesize a new target voltage vector. Compared with the traditional SVPWM algorithm, the proposed SVPWM algorithm controls the capacitor voltage fluctuation range in a reasonable range, simplifies the calculation, improves the three-phase stator current asymmetry, and reduces the current harmonic content. Simulation and experimental results demonstrate the effectiveness and feasibility of the proposed SVPWM algorithm.
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Bending ratcheting behavior of pressurized straight Z2CND18.12N stainless steel pipe
Lei Wang,Gang Chen,Jianbei Zhu,Xiuhu Sun,Yunhui Mei,Xiang Ling,Xu Chen 국제구조공학회 2014 Structural Engineering and Mechanics, An Int'l Jou Vol.52 No.6
The ratcheting effect greatly challenges the design of piping components. With the assistance of the quasi-three point bending apparatus, ratcheting and the ratcheting boundary of pressurized straight Z2CND18.12N stainless steel pipe under bending loading and vertical displacement control were studiedexperimentally. The characteristics of progressive inelastic deformation in axial and hoop directions of the Z2CND18.12N stainless steel pipes were investigated. The experiment results show that the ratcheting strainoccurs mainly in the hoop direction while there is less ratcheting strain in the axial direction. Thecharacteristics of the bending ratcheting behavior of the pressure pipes were derived and compared under load control and displacement control, respectively. The results show that the cyclic bending loading and the internal pressure affect the ratcheting behavior of the pressurized straight pipe significantly under loadcontrol. In the meantime, the ratcheting characteristics are also highly associated with the cyclicdisplacement and the internal pressure under displacement control. All these factors affect not only the saturation of the ratcheting strain but the ratcheting strain rate. A series of multi-step bending ratcheting experiments were conducted under both control modes. It was found that the hardening effect of Z2CND18.12N stainless steel pipe under previous cyclic loadings no matter with high or low displacement amplitudes is significant, and the prior loading histories greatly retard the ratcheting strain and its rate under subsequent loadings. Finally, the ratcheting boundaries of the pressurized straight Z2CND18.12N stainless steel pipe were determined and compared based on KTA/ASME, RCC-MR and the experimental results.
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Bending ratcheting behavior of pressurized straight Z2CND18.12N stainless steel pipe
Wang, Lei,Chen, Gang,Zhu, Jianbei,Sun, Xiuhu,Mei, Yunhui,Ling, Xiang,Chen, Xu Techno-Press 2014 Structural Engineering and Mechanics, An Int'l Jou Vol.52 No.6
The ratcheting effect greatly challenges the design of piping components. With the assistance of the quasi-three point bending apparatus, ratcheting and the ratcheting boundary of pressurized straight Z2CND18.12N stainless steel pipe under bending loading and vertical displacement control were studied experimentally. The characteristics of progressive inelastic deformation in axial and hoop directions of the Z2CND18.12N stainless steel pipes were investigated. The experiment results show that the ratcheting strain occurs mainly in the hoop direction while there is less ratcheting strain in the axial direction. The characteristics of the bending ratcheting behavior of the pressure pipes were derived and compared under load control and displacement control, respectively. The results show that the cyclic bending loading and the internal pressure affect the ratcheting behavior of the pressurized straight pipe significantly under load control. In the meantime, the ratcheting characteristics are also highly associated with the cyclic displacement and the internal pressure under displacement control. All these factors affect not only the saturation of the ratcheting strain but the ratcheting strain rate. A series of multi-step bending ratcheting experiments were conducted under both control modes. It was found that the hardening effect of Z2CND18.12N stainless steel pipe under previous cyclic loadings no matter with high or low displacement amplitudes is significant, and the prior loading histories greatly retard the ratcheting strain and its rate under subsequent loadings. Finally, the ratcheting boundaries of the pressurized straight Z2CND18.12N stainless steel pipe were determined and compared based on KTA/ASME, RCC-MR and the experimental results.
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