针对某直列四缸增压柴油机排气歧管在台架耐久试验中出现开裂现象,应用有限元(finite element analysis,FEA)-计算流体力学(computational fluid dynamics,CFD)耦合方法对排气歧管进行了热应力分析。排气歧管热应力分析模型中的材料性...针对某直列四缸增压柴油机排气歧管在台架耐久试验中出现开裂现象,应用有限元(finite element analysis,FEA)-计算流体力学(computational fluid dynamics,CFD)耦合方法对排气歧管进行了热应力分析。排气歧管热应力分析模型中的材料性质随着温度变化的关系由试验测定;在相应发动机工况下对模型预测的温度场和台架上测量的排气歧管温度进行对比,以对模型进行标定。应用标定后的模型分析排气歧管在给定热负荷条件下的应力-应变分布。FEACFD耦合分析结果表明:发生开裂的区域为高塑性应变区,从而推论导致排气歧管开裂原因为热力耦合应力作用下产生的塑性变形,即失效形式为热机械疲劳。以等效塑性应变作为塑性变形的度量及许可的等效塑性应变经验值为判据对排气歧管进行了设计改进,并从三种改进方案中找出最安全的方案进行试验验证,改进后的排气歧管顺利通过发动机台架耐久试验考核。展开更多
Based on finite element analysis of thermal mechanical behavior, structural optimization design was proposed for a side cooling collimating mirror subjected to high heat load for a beamline at SSRF(Shanghai Synchrotro...Based on finite element analysis of thermal mechanical behavior, structural optimization design was proposed for a side cooling collimating mirror subjected to high heat load for a beamline at SSRF(Shanghai Synchrotron Radiation Facility). The temperature distribution,stress concentration effect, maximum equivalent(vonMises) stress, and slope error of the mirror were analyzed.In particular, the cooling water channels of the traditional structural design were optimized, and the modified designs were further optimized. Although the traditional structural and the improved designs could meet requirements for the temperature and thermal stress, the deformation gradients were relatively large for several structural designs, and this led to larger slope error. The further improved structural designs could be of better performance.展开更多
Cam-followers provide reliable and controlled motions in various mechanical systems. Due to the highly fluctuating load between the cam and follower in operation, the cam-follower may be subjected to a high risk of co...Cam-followers provide reliable and controlled motions in various mechanical systems. Due to the highly fluctuating load between the cam and follower in operation, the cam-follower may be subjected to a high risk of contact fatigue failure. This paper assesses the fatigue life of a cycloidal displacement cam and a flat-faced follower under the defined loads and constraints. Computer-aided design (CAD) model of the cam-follower is developed in CATIA software and imported to ANSYS software for finite element analysis (FEA) of fatigue life. MATLAB programming is developed for determining the appropriate spring constant and pre-load force to always keep the cam and follower in contact. The fatigue life of the cam-follower has been estimated under the specified operating conditions. The analysis method can be applied to investigate the fatigue life of cams with other profiles, including the modified trapezoidal functions, polynomial functions, etc.展开更多
文摘针对某直列四缸增压柴油机排气歧管在台架耐久试验中出现开裂现象,应用有限元(finite element analysis,FEA)-计算流体力学(computational fluid dynamics,CFD)耦合方法对排气歧管进行了热应力分析。排气歧管热应力分析模型中的材料性质随着温度变化的关系由试验测定;在相应发动机工况下对模型预测的温度场和台架上测量的排气歧管温度进行对比,以对模型进行标定。应用标定后的模型分析排气歧管在给定热负荷条件下的应力-应变分布。FEACFD耦合分析结果表明:发生开裂的区域为高塑性应变区,从而推论导致排气歧管开裂原因为热力耦合应力作用下产生的塑性变形,即失效形式为热机械疲劳。以等效塑性应变作为塑性变形的度量及许可的等效塑性应变经验值为判据对排气歧管进行了设计改进,并从三种改进方案中找出最安全的方案进行试验验证,改进后的排气歧管顺利通过发动机台架耐久试验考核。
基金supported by the National Natural Science Foundation of China(No.11175243)
文摘Based on finite element analysis of thermal mechanical behavior, structural optimization design was proposed for a side cooling collimating mirror subjected to high heat load for a beamline at SSRF(Shanghai Synchrotron Radiation Facility). The temperature distribution,stress concentration effect, maximum equivalent(vonMises) stress, and slope error of the mirror were analyzed.In particular, the cooling water channels of the traditional structural design were optimized, and the modified designs were further optimized. Although the traditional structural and the improved designs could meet requirements for the temperature and thermal stress, the deformation gradients were relatively large for several structural designs, and this led to larger slope error. The further improved structural designs could be of better performance.
文摘Cam-followers provide reliable and controlled motions in various mechanical systems. Due to the highly fluctuating load between the cam and follower in operation, the cam-follower may be subjected to a high risk of contact fatigue failure. This paper assesses the fatigue life of a cycloidal displacement cam and a flat-faced follower under the defined loads and constraints. Computer-aided design (CAD) model of the cam-follower is developed in CATIA software and imported to ANSYS software for finite element analysis (FEA) of fatigue life. MATLAB programming is developed for determining the appropriate spring constant and pre-load force to always keep the cam and follower in contact. The fatigue life of the cam-follower has been estimated under the specified operating conditions. The analysis method can be applied to investigate the fatigue life of cams with other profiles, including the modified trapezoidal functions, polynomial functions, etc.
