00Cr17Ni14Mo2不锈钢的性能研究

本文研究了00C r17N i14Mo2不锈钢材料的的性能,证明其具有很好的机械性能、焊接性能和耐腐蚀性能,从用户和研究开发的角度探讨了其在压力容器、化工装置等领域的应用。     

激光选区熔化成型316L不锈钢工艺参数研究

针对激光选区熔化成型316L不锈钢工艺参数选择问题,采用单因素条件变量分析法,在激光选区熔化过程中,分析了激光功率、扫描速度对316L不锈钢成型零件表面粗糙度、致密度、硬度和尺寸偏差的影响规律。结果表明：当激光功率降低或者扫描速度提高时,内部能量密度减小,粉末熔化量减少,试样表面球化效应增强,孔隙缺陷增多,试样致密度减小、硬度降低;当激光功率提高或者扫描速度降低时,内部能量密度增大,粉末被过度烧蚀,产生较大的尺寸偏差,所形成熔道易塌陷,导致层间结合较差,试样性能降低。当激光功率为300 W、扫描速度为1000 mm/s时,能量密度适中,形成了较好的冶金结合,抗拉强度可达753 MPa,上表面硬度HRB能达到97.22。该项研究为316L不锈钢激光选区熔化工艺参数的合理选择提供了参考。     

A methodology for constructing the aircraft design schema

Aircraft collaboration design is based on a unified set of schemas containing data and model representations and interfaces across disciplines. The aircraft design schema is a central data model that specifies the paradigm for the representation of a full lifecycle model of aircraft design. The construction of the schema currently lacks theoretical guidance. This paper designs a novel methodology to construct the aircraft design schema, a fully functional, logical, and self-consistent methodology. The methodology defines a schema matrix that includes implementation strategies, principles, processes, meta-object facility, views, scenarios, and products. The aircraft conceptual design schema is constructed according to the methodology, which is a hands-on approach to help understand the concept and implementation. The features of the methodology are analyzed, and the methodology and the aircraft conceptual design schema are presented to address the pain points of multiple solution trade-offs, multiple iterations, and multidisciplinary coupling in aircraft conceptual collaboration design.     

航空发动机典型材料超高周疲劳试验技术研究综述

航空发动机作为飞行器最关键、最核心的部位，长期服役于高温、高载等极端环境，疲劳失效是导致发动机结构破坏的主要原因之一。随着工业的发展，发动机材料的超高周疲劳问题日益凸显。本文总结了发动机典型材料超高周疲劳关注领域的研究现状，对当前超高周疲劳试验技术的应用情况进行了阐述，包括超高周轴向振动疲劳、弯曲振动疲劳、扭转振动疲劳、复合振动疲劳等试验加载技术以及温度控制技术、损伤监测技术，并对我国航空发动机典型材料超高周疲劳试验技术的发展做出展望。     

Martian Buildings: Design loading

Multiplanetary life has been studied by scientists as a way to supply energy or sustain human life in the future. Mars is likely to be man’s first destination, colonization using onsite structural construction would be one of the main options. The first step to designing a reliable building is to know the applied structural loads and to have an accurate design load combination. Due to lack of complete knowledge, short span of recorded data, Martian environment, and hazardous environment that Martian structures face, constructed Martian structures should behave appropriately under the highest likely live, dead and environmental loads either simultaneously or as a worst-case scenario. The present study evaluated and calculated probable Martian structural loads, including live, internal pressure, snow, gravity (dead), dust accumulation, thermal stress, wind, marsquake, asteroid, and meteoroid impact loads and their effects. Information was gathered from previous studies and valid data from Martian landers, rovers and orbiters. Wind loads were calculated based on the over 6.5 years of data recorded by Vikings 1 and 2, temperature and winds for InSight (TWINS) sensor. A wind shear exponent and wind profile have been proposed for a Martian flat terrain construction site. Marsquake lateral loads, frequency content and seismicity were assessed using data from the seismic experiment for interior structure (SEIS) and the Viking 2 seismometer. Considering the high influx of micrometeoroids, their penetration distance, impact loads and their effects on structures were calculated. The annual probability of an asteroid impact on a settlement was assessed for a 30-year mission. A load map for Martian residential buildings that considers the worst-case scenario in which a Martian structure should be designed based on them has been proposed.     

基于柔顺机构的新型可变形机翼设计方法研究

机翼翼型变体技术可以根据任务和环境自适应地改变机翼形状、厚度、弯度等重要参数,使飞机在不同飞行状态下都能取得较理想的气动特性。柔顺机构是实现机翼蒙皮光滑变形的驱动装置,相比传统液压机构具备质量特性好的优势。采用鱼骨型柔性钢架与四连杆机构实现了机翼前缘上下蒙皮向内收缩、前缘形状由钝变尖的弹性变形过程。通过设计“撞块”机构实现驱动行程的有效分解,解决了前缘尖端开口处蒙皮回收与机翼变形控制所需的驱动行程不一致的内在矛盾。变形后翼型与目标翼型误差最大位置不超过4 mm,变形过程中结构最大应力小于材料许用应力值。相比传统采用纯液压机构驱动的变形机翼设计方案,该基于柔顺机构的变体机翼结构减质14.1%。     

激光熔化沉积15-5PH沉淀硬化不锈钢组织及拉伸性能

利用激光熔化沉积技术制备15-5PH沉淀硬化不锈钢板,利用金相显微镜(OM)、扫描电镜(SEM)、透射电镜(TEM)、电子探针(EPMA)技术,对沉积态组织进行分析,测试沉积态组织的室温拉伸性能。结果表明:激光熔化沉积15-5PH不锈钢沉积态组织由沿沉积增高方向贯穿多层外延生长的柱状晶组成,柱状晶内包含多个细长整齐排列的胞状树枝晶,枝晶内为马氏体组织,枝晶间为铁素体;沉积态组织中弥散分布大量细小的NbC析出相,尺寸12～20 nm;15-5PH不锈钢沉积态组织具有良好的力学性能,纵向抗拉强度和延伸率分别为1 128.5 MPa和14.0%,横向抗拉强度和延伸率分别为1 101 MPa和12.25%。     

航空用不锈钢磨粒流光整加工表面完整性研究

为研究磨粒流光整加工不锈钢闭式整体叶环的表面完整性，通过对电火花制备的不锈钢试样进行加工时间、加工压强及磨料目数的单因素试验，研究3个因素对加工后表面完整性的影响。结果表明：表面粗糙度Ra随着加工时间的增加而降低，从初始时的1.459μm降至60 min时的0.193μm，降低速率越来越慢，最后趋于稳定。磨粒流加工有效去除了加工表面再铸层。显微硬度在加工后明显降低，由450～950 HV降至270～350 HV且分布均匀性得到改善。显微硬度随着加工时间的增加整体上呈降低趋势，并出现了一定的加工硬化现象。在使用不同目数的磨料进行磨粒流加工后，残余应力由拉应力变为压应力。随着加工时间和加工压强的增加，试样表面越平整，抛光效果越好。     

推进剂管理装置的可靠性增长及试验验证

采用原始的焊接方式焊接筛网式推进剂管理装置的收集器合格率低、可靠性差。为此,采用纯钛箔作为过渡层进行了不锈钢筛网与钛合金支压板的电阻缝焊试验以及随后这两者与钛合金骨架的电子束焊试验,然后进行了地面力学环境下的振动试验,以验证焊接方式改进后收集器的可靠性。焊接试验结果表明,纯钛箔过渡层一方面可以大幅降低筛网在电阻缝焊时的焊接热量,有效地减小筛网的热变形;另一方面可以在电阻缝焊后形成牢固、封闭的纯钛/不锈钢筛网焊缝过渡区,有效地增加电子束焊时筛网的变形抗力,从而使得焊接后试样的合格率和性能大幅提高。振动试验结果表明,焊接方式改进后收集器的可靠度置信下限从0.90增加到了0.96。     

超大规格300M钢棒超声波探伤及缺陷分析

对Φ450 mm规格的300M钢棒材进行了超声波探伤,采用2.5 MHz软膜探头可以保证探伤的灵敏度并降低噪声水平。通过宏观、显微观察和能谱分析等手段对探伤缺陷进行了分析。结果表明:探伤缺陷处存在氧化铝、氧化镁和氧化钙复合夹杂物,单个夹杂物最大尺寸可达100μm。该缺陷属于熔炼过程中引入的外来夹杂物,对材料性能有不利的影响。