数字样机区域检查流程及其在直升机研制中的应用

为提升直升机产品的市场竞争力,提高数字样机协同设计的效率与质量,提出了数字样机的区域化协调思想以及区域划分原则,建立了规范的数字样机区域检查流程。应用于某民用直升机协同设计,缩短了区域内数字模型加载时间,提高了区域级数字样机干涉检查与维护性分析的效率,验证了区域划分方法及检查流程的有效性。     

Three-dimensional temperature prediction in cylindrical turning with large-chamfer insert based on a modified slip-line field approach

Chamfered inserts have found broader applications in metal cutting process especially in high-performance machining of hard-to-cut materials for their excellent edge resistance and cutting toughness. However, excessive heat generation and resulting high cutting temperature eventually cause severe tool wear and poor surface integrity, which simultaneously limits the optimal selection of machining parameters. In the present study, an analytical thermal–mechanical model is proposed for the prediction of the three-dimensional (3-D) temperature field in cylindrical turning with chamfered round insert based on a modified slip-line field approach. First, an innovative discretization method is introduced in a general 3-D coordinate system to provide a comprehensive demonstration of the irregular cutting geometry and heat generation zones. Then, a plasticity-theory-based slip-line field model is developed and employed to determine the intensities and geometries of every elementary heat sources in Primary Deformation Zones (PDZ), Secondary Deformation Zones (SDZ) and Dead Metal Zones (DMZ). At last, a 3-D analytical model is suggested to calculate the temperature increases caused by the entire heat sources and associated images. The maximum cutting temperature region predicted is found existing upon the chip-tool contact area rather than the tool edge. Moreover, the rationalities of cutting parameters employed are analyzed along with theoretical material removal rates and ensuing maximum cutting temperatures. The results indicate that the cutting conditions with large depth of cut and high cutting speed are more desirable than those with high feed rates. The proposed models are respectively verified through a series of 3-D Finite Element (FE) simulations and dry cutting experiments of Inconel 718 with chamfered round insert. Satisfactory agreement has been reached between the predictions and simulations as well as the measurements, which confirms the correctness and effectiveness of the presented analytical model.     

直角切削6061-T6铝合金剪切区力学行为及微观结构演化预测

力学行为是塑性变形微观过程的宏观表现,早期的金属切削理论模型没有考虑微观结构对切削力的影响。在考虑热力耦合效应的基础上建立了基于位错密度材料模型的6061-T6铝合金直角切削力预测模型,分析了不同切削参数下基于位错运动的塑性变形机制对切削力的影响。结合等分剪切区和非等分剪切区模型,构建了第一变形区多物理场计算方法,提出一种切屑形成过程中由塑性变形引起的微观结构演化解析模型。通过测量切削力和切屑内晶粒尺寸对模型的可行性进行了初步验证。结果表明：剪切区长度变长引起参与位错滑移的材料增多是切削深度增大导致切削力增大的主要原因。增大切削速度导致切削力的降低不是单一变量影响的结果,而是应变降低引起位错增殖数量减少和温度升高引起位错湮灭作用增加的共同作用结果。非等分剪切区模型正确反映了第一变形区温度和应力的分布特征,且与二维有限元模型分布相一致,建立的第一变形区微观结构演化解析模型能够预测切屑内位错密度和晶粒尺寸。     

斜切径向旋流燃烧室主燃区光学测量与特性分析

针对斜切径向旋流环形燃烧室模型,采用可调谐二极管激光吸收光谱(TDLAS)、相干反斯托克斯喇曼光谱(CARS)光学测量手段,在模化状态(Case 2)下,对燃烧室主燃区进行温度测量,分别得到了主燃区内12个点的温度和沿两条路径的积分温度.使用Fluent 12.0对Case 2进行数值模拟,分别使用两种非预混燃烧模型:平衡化学反应模型(EM)和稳态层流小火焰(SLF)模型.通过将两种不同燃烧模型的计算结果与TDLAS,CARS试验测量数据作对比验证,发现EM计算得到的温度更高,并与试验测量温度更符合,其中与CARS测量的误差小于6%.在试验验证的基础上,完成燃烧室在冷流状态(Case 1)下的计算,分析主燃区的气流组织和主燃孔射流对回流区的影响;利用EM计算分析燃烧室主燃区在全压状态(Case 3)下燃料分布、温度场、组分分布和性能参数,如燃烧室的燃烧效率为0.97、出口温度分布系数为0.312等,较为全面反映了燃烧室内气流流动换热和燃烧现象.      

基于红外热成像的TC4钛合金光纤激光焊接接头拉伸力学性能研究

对光纤激光焊接2.5mm厚TC4对接接头的拉伸力学性能进行研究,其研究方法为在常规的拉伸试验中,附加同步的红外热像测量,实时记录拉伸全过程中试样在力作用下温度场的变化。常规测试结果表明:接头与母材的强度相当,延伸率只达到母材的59.53%。试样温度场测试结果表明:当接头和母材受到的轴向载荷低于屈服强度对应载荷时,接头在热影响区部位会产生较大的应力集中,但接头和母材均未产生明显的塑性变形;当载荷等于屈服强度对应载荷时,均在宏观屈服点之前发生了微观的塑性变形;当载荷等于抗拉强度对应载荷时,接头发生剧烈塑性变形区域的长度只达到母材的35%,且接头与母材发生剧烈塑性变形区域的长度随拉伸过程的进行逐渐增加。     

壁湍流等动量区对惯性颗粒分布的影响

对摩擦雷诺数为1000、颗粒Stokes数为1.0的含颗粒槽道湍流进行了直接数值模拟,采用高斯函数叠加法提取了等动量区的模态速度,对各等动量区内的颗粒分布进行了分析。发现在高动量的核心区,颗粒平均浓度高于非核心区,而浓度脉动低于非核心区。在等动量区界面上,流体速度和颗粒浓度变化剧烈,展向涡结构的出现导致了局部颗粒浓度较低。在等动量区的界面以下,在较高的壁面法向位置,存在大尺度的浓度幅值低而浓度脉动高的结构,其等值线分布与核心区/非核心区界面一致。     

基于ANSYS Workbench的压接修理民机液压管路振动特性分析

探究振动环境中管径为1/4 in的民机液压直管的最佳压接修理尺寸。首先，建立压接修理民机液压直管与流体的有限元模型，在ANSYS Workbench中对该模型进行有限元仿真分析得到其前6阶固有频率；然后，用三综合振动试验台对压接修理民机液压直管进行扫频振动试验，得到其前6阶固有频率，将试验结果平均值与仿真结果进行对比，结果误差较小且曲线拟合良好，验证了有限元仿真分析的合理性；最后，对压接修理民机液压管路进行受力分析，并以压制区域公差和压接长度为变量分别对压接修理民机液压直管进行固有频率、最大应力以及沿Y、Z轴方向的最大位移响应进行分析。结果表明：压制区域公差为4 mm、压接长度为39 mm时，管路的固有频率较大，应力及位移响应较小，此时，最大应力及位移响应集中分布于压接接头处，且与受力分析结果一致。     

Design and analysis of a hypersonic inlet with an integrated bump/forebody

Numerical simulations and experiments showed that bump inlet had a remarkable effect on boundary layer diversion of supersonic flow.However, the design and analysis of bump in hypersonic flow was still few.In this paper, the mechanism of a supersonic bump inlet is introduced to the design of hypersonic forebody.A hypersonic inlet with an integrated bump/forebody is obtained by the Method Of Characteristics(MOC) based on a chin inlet.Numerical simulations show that the modified inlet achieves diversion of low-speed flow.Besides, the integrated bump/-forebody is also beneficial to inlet start.During the starting process, the shape of the separation zone is rebuilt by the modified forebody surface which makes spillage much easier.This new design leads to a reduction of the self-start Mach number by 0.95.     

短周期谱载荷作用下的疲劳裂纹扩展估算

本文公式系由线性累积损伤寿命公式乘以一个考虑超载迟滞效应的修正系数而构成的。 1.公式推导 Walker裂纹扩展方程为 da/dN=c(ZK_(max))~n (1)式中c,n,q及u为材料常数;R为应力比。 应力强度因子可以表示成式中,σ_(max)为垂直于裂纹的外加毛应力;Y为构型系数,它与裂纹长度有关。 当考虑超载迟滞效应时,Wheeler模型可以表示为     

空中环境谱编制中的假设检验方法

 在依据空测环境数据通过模糊聚类分析确定空中环境谱区域划分中，提出了对分类的各类数据总体分布齐次性检验加以判别和归类的方法。通过对典型应用实例中3种检验方法（t分布假设检验、秩和检验、斯米尔诺夫检验）检验结果的分析，确定使用秩和检验与斯米尔诺夫检验相结合的方法进行空中环境谱模糊聚类分析的假设检验，使空中环境谱的区域划分更为科学合理。