On a plastic instability criterion for ultra-large radial-axial ring rolling process with four guide rolls

A dynamic mechanical model is proposed to describe the complexing actions of all the rolls on the ring during the ultra-large radial-axial ring rolling(RARR) process with four guide rolls. Based on the model, the calculation models for bending moment and normal stress at any section of the ring are deduced by force method. If the maximum section bending normal stress exceeds the yield stress of the ring materials, the ring will be distorted thus leading to the instability of the RARR process. Ac...     

基于电加热膜防冰设计方案的分流环表面换热特性试验研究

分流环表面换热特性对提升防冰设计效能至关重要。针对传统热气防冰方案中试验件与试验方案系统复杂、成本高昂等问题，本文提出了一种新型电加热膜防冰设计方案的分流环表面换热系数的试验方法。根据能量守恒定律，推导出分流环表面换热系数理论公式。试验研究了不同俯仰角、速度、液态水含量（Liqid water content,LWC）以及水滴中位体积直径（Median volumetric diameter, MVD）等对分流环表面换热特性的影响。试验结果表明：前缘区域换热系数随俯仰角先增大后降低，25°俯仰角是明显的转折点；相同喷雾条件下的前缘区域、下表面区域的平均换热系数约是干空气条件下的3倍；分流环前缘的换热系数明显大于上、下表面的换热系数。     

Pressure performance for a thin-walled ring and turbulent-jet orifice modeled elastic squeeze film damper

This paper explores an analytical model for Elastic Ring Squeeze Film Damper (ERSFD) with thin-walled ring and turbulent-jet orifices, and uncovers its Oil Film Pressure Performance (OFPP). Firstly, the ring deformation is addressed by using the Fourier series expansion approach and the orifice outflow rate is characterized with the Prandtl boundary layer theory. Secondly, applying finite difference scheme, the influence of elastic ring flexibility, orifice diameter, and attitude angle on the OFPP is analyzed. Finally, Outer chamber pressure was measured experimentally at different rotor speeds. The results indicate that the outer chamber pressure coats an individual load-carrying region and spreads symmetrically pertaining to the attitude angle. Its amplitude drops as the elastic ring flexibility decreases but boosts with the reduction of the orifice diameter. For inner chamber pressure, the orifice diameter effects a similar trend to the outer cavity, but exhibits more stable distribution regarding the attitude angle. Minimizing the elastic ring flexibility causes an increase in amplitude. The model is validated by the test results giving that the outer chamber pressure shifts synchronously and periodically with the variation of the attitude angle, while the pressure amplitude increases slightly at higher rotor speeds.     

Modelling and analysis of metal flowing behaviors in constraining ring rolling of tapered ring with thin wall and three high ribs

Tapered ring with thin wall and three high ribs(TRTWTHR), showing complicated geometry(wall thickness is less than 4 mm and rib height exceeds 20 mm), is extensively utilized to fabricate the critical structural parts of aerospace equipment such as spacecraft cabin, rocket body and fuel tank because of light weight and high carrying capacity. How to fabricate TRTWTHR with high performance is a critical problem that aerospace area needs to solve. In this work, constraining ring rolling(CRR) techn...     

基于ICA包络增强MEMD的滚动轴承故障诊断

针对多元经验模态分解(MEMD)存在模态混叠、带内噪声干扰导致轴承故障特征信息微弱难提取问题,提出了基于独立分量分析(ICA)包络增强MEMD的滚动轴承故障诊断.采用MEMD对多通道信号进行自适应分解,依据峭度和相关系数选取包含故障信息的本征模态函数(1MF);对所选取IMF分量的包络信号进行ICA分析,抑制模态混叠和...