蒸汽发生器给水环管热分层强度影响因素及缓减措施研究

为研究低功率运行工况下压水堆核电厂蒸汽发生器给水环管热分层强度的影响因素和缓减措施,采用计算流体力学(CFD)方法,对给水环管内部流体的热分层现象进行了数值模拟。研究了功率提升过程中给水运行方式及给水环管结构对热分层强度的影响,从给水环管布置及结构两个方面提出了两种改进结构。结果表明:提高给水流量提升速率对热分层强度几乎没有影响,给水弯头弯曲半径增大能有效减弱给水弯头处的热分层强度,给水弯头向下布置能明显减弱给水环管内的热分层强度,给水管倾斜角度增大能有效减弱给水弯头、给水管的热分层强度,同时使得给水环的热分层强度增强。将给水弯头向下布置且给水管水平段改为多级阶梯渐缩-渐扩结构、多级球形渐缩-渐扩结构后,给水环管内的热分层现象能得到不同程度的缓解,因此提出的两种改进结构是较理想的改进结构。

Experimental investigation of vibration pretreatment-microwave curing process for carbon fiber reinforced resin matrix composites

The vibration pretreatment-microwave curing process is an efficient,low energy consumption,and high-quality out-of-autoclave curing process for carbon fiber resin matrix composites.This study aims to investigate the impact of vibration pretreatment temperature on the fiber weight content,microscopic morphology and mechanical properties of the composite laminates by using optical digital microscopy,universal tensile testing machine and thermo-gravimetric analyzer.Additionally,the combined mode of Bragg fiber grating sensor and temperature measurement fiber was employed to explore the effect of vibration pretreatment on the strain process during microwave curing.The study results revealed that the change in vibration pretreatment temperature had a slight impact on the fiber weight content when the vibration acceleration remained constant.The metallographic and interlaminar strength of the specimen formed at a vibration pretreatment temperature of 80℃ demonstrated a porosity of 0.414% and a 10.69% decrease in interlaminar shear strength compared to autoclave curing.Moreover,the introduction of the vibration energy field during the microwave curing process led to a significant reduction in residual strain in both the 0°and 90°fiber directions,when the laminate was cooled to 60℃.

Cracked elastic substrate strip with functionally graded coating under thermal-mechanical loading

This paper investigates the functionally graded coating bonded to an elastic strip with a crack under thermal- mechanical loading. Considering some new boundary conditions, it is assumed that the temperature drop across the crack surface is the result of the thermal conductivity index which controls heat conduction through the crack region. By the Fourier transforms, the thermal-elastic mixed boundary value problems are reduced to a system of singular integral equations which can be approximately solved by applying the Chebyshev polynomials. The numerical computation methods for the temperature, the displacement field and the thermal stress intensity factors （TSIFs） are presented. The normal temperature distributions （NTD） with different parameters along the crack surface are analyzed by numerical examples. The influence of the crack position and the thermal-elastic non- homogeneous parameters on the TSIFs of modes I and 11 at the crack tip is presented. Results show that the variation of the thickness of the graded coating has a significant effect on the temperature jump across the crack surfaces when keeping the thickness of the substrate constant, and the thickness of functionally graded material （FGM） coating has a significant effect on the crack in the substrate. The results can be expected to be used for the purpose of gaining better understanding of the thermal-mechanical behavior of graded coatings.