丁羟推进剂定载破坏试验探索研究

研究了丁羟推进剂在定载荷下断裂所需时间与推进剂本身抗拉强度的关系，并且给出了环境温度和湿度，试件大小，形状和制作方法对推进剂断裂所需时间的影响，为固体火箭发动机药柱设计提供了参考数据。     

水分对碳－环氧复合材料Ⅱ型分层韧性的影响

通过研究不同湿热条件下Ｔ３００／９１４Ｃ和Ｔ３００／Ｍ１０两种复合材料的玻璃化转变温度、层间剪切强度和分层断口形貌，分析了水分影响复合材料Ⅱ型分层韧性的机理。结果表明，水分对强界面和弱界面基体体系的作用机理不同，对两类复合材料的分层韧性也有不同的影响。对强界面纤维－基体体系，水分的增塑作用使得其分层韧性增强，而对弱界面体系这种韧性降低。而水分的溶胀作用对两类复合材料的分层韧性都不利。     

固体发动机壳体用D406A钢锻件的断裂韧度KIC测试研究

对固体发动机壳体用D406A超高强度锅锻件,进行了平面应变断裂韧度K_(IC)测试研究,获得了壳体重要部位实用锻件的K_(IC)值;找到了材料强度和断裂韧度合理匹配的碳含量范围,为壳体设计与安全使用及断裂分析提供了试验依据。     

铝合金薄板K_c测试新方法的探讨

通过用圆(或椭圆)孔试件测量金属薄板平面应力断裂韧性Kc的方法,与通过用中心穿透裂纹试件Kc的标准方法相比较之后,将Whitney和Nuismer用于复合层压板中的点应力破坏准则,推广到铝合金薄板Kc的测量。 在理论和实验分析的基础上,拟合出与实验结果相一致的经验公式。     

用奇异有限元法计算正交各向异性复合材料平面断裂的应力强度因子

将复合材料平板视为正交各向异性平板，把正交各向异性平板裂纹顶点附近的位移展开式迭加在一般的等参数单元上，建立了用于复合材料平板应力强度因子计算的奇异元。并以所做出的公式，对正交各向异性板含单边裂纹和双边裂纹问题进行了计算分析，取得了较好的效果。     

A new approach on necking constitutive relationships of ductile materials at elevated temperatures

A new method is presented to determine the full-range, uniaxial constitutive relationship of materials by tensile tests on funnel specimens with small curvature radius and finite element anal-ysis (FEA). An iteration method using FEA APDL (ANSYS parametric design language) program-ming has been developed to approach the necking constitutive relationship of materials. Test results from SAE 304 stainless steel at room temperature show that simulated load vs displacement curve, diameter at funnel root vs displacement curve, and funnel deformation contours are close to mod-eled results. Due to this new method, full-range constitutive relationships and true stress and effec-tive true strain at failure are found for 316L stainless steel, TA17 titanium alloy and A508-III stainless steel at room temperature, and 316L stainless steel at various elevated temperatures.     

时效工艺对高强度Al-Cu-Li合金断裂韧性的影响

采用Kahn撕裂法测试了高强度Al-Cu-Li合金2090在不同时效制度下的断裂韧性及其变化规律,并借助TEM和SEM对相应微观组织形貌及断口形貌进行了观察。结果表明:双级时效和应变时效均可促进T_1相析出,改善合金的断裂韧性,但这种促进作用在过时效状态下减弱;晶界PFZ的宽化和粗大晶界平衡相的析出降低合金的断裂韧性,并对时效工艺、微观组织及断裂韧性之间的关系进行了讨论。     

航天飞行器的两大数学问题

本文考虑火箭燃烧室燃烧不稳定性,固体推进剂不稳定燃烧,液体火箭贮箱推进剂晃动引起火箭系统不稳定性以及航天飞行不稳定性等问题的偏微分方程组定解问题。并指明航天飞行器的断裂问题是断裂力学的时代问题之一,研究它的数学方法如奇异积分方程法,J积分方法,研究复合材料的线性断裂力学原理以及处理边缘断裂问题的边界单元法都是值得探讨的。     

Experimental study of effect of post processing on fracture toughness and fatigue crack growth performance of selective laser melting Ti-6Al-4V

For Ti-6Al-4V, a titanium alloy increasingly used in aerospace structure, selective laser melting (SLM) is an attractive additive manufacturing technology, which is attributed to its complex construction capability with high accuracy and good surface quality. In order to obtain qualified mechanical properties, SLM parameters and post processing should be tailored for diverse service conditions. Fracture toughness and fatigue crack growth (FCG) behavior are critical characteristics for damage tolerance evaluation of such metallic structures, and they are affected by post processing technologies significantly. The objective of this study is to obtain the fracture toughness and fatigue crack growth behavior of Ti-6Al-4V manufactured by SLM, and to evaluate the influence of post-SLM thermomechanical treatment and surface machining. Fracture toughness and FCG tests were performed for SLM Ti-6Al-4V in three types of post processing status: as-built, heat treated and hot isostatically pressed (HIPed), respectively. Specimens with as-built and machined surface were tested. The microstructure and fractography were analyzed as well in order to investigate the relevance among manufacture process, microstructure and mechanical properties. The results demonstrate that as-built SLM Ti-6Al-4V presents poor ductility and FCG behavior due to martensitic microstructure and residual stresses. Both heat treatment and hot isostatic pressing improve the plane-stress fracture toughness and FCG performance considerably, while surface machining shows slight effect.     

航空发动机高速锥齿轮瞬态动力学分析与试验研究

针对航空发动机中央传动锥齿轮由行波共振引起的掉块故障,采用瞬态接触动力学分析方法与试验验证相结合的手段,对行波共振发生时从动锥齿轮的共振特性和应力分布开展研究。基于声测法开展了航空发动机中央传动锥齿轮行波共振试验,研究中央传动锥齿轮行波共振特性,获取了从动锥齿轮行波共振动频、危险转速以及破坏断裂特征。仿真计算结果与试验结果对比分析表明:试验中出现三节径共振皆是前行波共振,四节径共振是后行波共振;三节径共振危险转速范围为74.2%～76.2%,四节径共振危险转速范围为102.8%～104.2%。数值仿真与试验测试中结构静频值具有一致性,三节径误差小于2%,四节径误差小于5%,验证了仿真计算模型的准确性。仿真计算四节径行波共振时从动锥齿轮齿根处和辐板应力集中,应力分布形式与齿轮故障复现试验断裂形式基本一致,辐板正面应力值大小与试验结果基本吻合,误差在0.5%～9.5%,满足工程级应力预测要求,验证了瞬态接触动力学分析方法对齿轮行波共振应力预测的有效性。试验表明该齿轮结构是否存在初始缺陷是发生齿轮断裂故障的重要因素之一。