Modeling of velocity field for vacuum induction melting process

The numerical simulation for the recirculating flow of melting of an electromagnetically stirred alloy in a cylindrical induction furnace crucible was presented. Inductive currents and electromagnetic body forces in the alloy under three different solenoid frequencies and three different melting powers were calculated, and then the forces were adopted in the fluid flow equations to simulate the flow of the alloy and the behavior of the free surface. The relationship between the height of the electromagnetic stirring meniscus, melting power, and solenoid frequency was derived based on the law of mass conservation. The results show that the inductive currents and the electromagnetic forces vary with the frequency, melting power, and the physical properties of metal. The velocity and the height of the meniscus increase with the increase of the melting power and the decrease of the solenoid frequency.     

图像增强算法在车牌图像预处理中的研究与应用

雾天场景下摄像头采集到的车牌图像质量较低,在车牌识别系统中对图像预处理产生较大影响,从而造成车牌定位和识别效果较差。以雾天环境下实际采集的车牌图像为例,分别采用带色彩恢复的多尺度Retinex算法和暗原色先验去雾算法对实际图像增强进行仿真实验。实验结果表明,利用暗原色先验去雾算法对图像进行增强处理,能够提高图像的对比度,实现去雾效果,从而使车牌定位和车牌识别达到更好的效果。     

加工中心常见故障图法诊断的建立及应用

本文将机械加工中心常见故障进行合理分类,并建立了人工诊断图法,以作为系统自动故障诊断的辅助方法,并通过液压系统油缸密封泄漏引起的故障诊断维修实例,说明诊断图法在故障诊断中的实用性。     

添加Nb对Ti-48Al-0.7B合金组织和力学性能的影响

研究了离心铸造汽车排气阀用Ti-48Al-0.7B-xNb(x=0,3,5,8;原子分数, %)合金的组织和力学性能.结果表明,不同Nb含量合金均由α2 γ两相组成,不存在β相.添加Nb后,合金的晶粒尺寸受凝固前沿B产生附加的成分过冷和硼化物钉扎晶界两方面的作用.合金的片层间距λ与晶粒尺寸d-1/2符合线性关系. O含量和Nb含量影响合金的断裂强度,晶粒尺寸是影响合金塑性的主要因素.Ti-48Al-0.7B-5Nb合金的晶粒尺寸最小,综合性能最佳(σb=399.6 MPa,δ=0.26%).     

热处理细化铸态Ti46Al8Nb合金晶粒

研究一种热处理制度对细化铸造Ti46Al8Nb合金晶粒所起的作用。结果表明，加热至1360℃于900℃熔融盐淬火一退火一正火处理能够有效地破坏合金稳定、粗大的铸态组织，铸态晶粒尺寸由800μm可细化至200μm。同时该热处理还可显著降低合金的淬火裂纹倾向性，得到细小均匀的γ＋a2全片层组织（FL），提高铸造合金的室温力学性能。     

添加硼对铸造Ti-46.5Al-8Nb合金组织和性能的影响

全片层Ti-46.5Al-8Nb合金中添加硼(≤0.7%,原子分数)的显微组织观察表明,细化组织的临界硼含量约为0.5%(原子分数).细化机制与凝固前沿硼产生了附加的成分过冷和硼化物钉扎晶界双重机制有关.由于硼减小了片层形成所需要的过冷度,片层间距随硼含量的增加而增加,片层间距λ与晶粒尺寸d-1/2符合线性关系.添加硼的Ti-46.5Al-8Nb合金的α2相体积分数越高,硬度也越高.合金的断裂强度和延伸率随硼含量增加而增加.室温断裂强度与晶粒尺寸符合Hall-Petch关系.