20g钢焊接接头冷弯开裂及断裂行为的研究

本文考察了一侧经手弧焊,另一侧经埋弧自动焊焊接接头的显微组织,并用扫描电镜对断口进行了分析。在此基础上,研究了接头的冷弯开裂及断裂行为。结果表明:只有埋弧焊一侧产生冷弯开裂或断裂现象。冷弯初期,在过热区出现裂纹,但在随后的弯曲过程中无明显扩展,这是由于裂纹周围的显微组织具有较大的抗裂纹扩展阻力。冷弯后期,焊缝产生裂纹并迅速扩展而断裂,这主要是由于条虫状气孔的存在所致,而显微气孔及少量的球状显微夹杂对断裂仅起着促进作用。     

可调角度弯钻杆的研制

在处理井下事故特别是藏鱼头事故时,由于鱼头不居中,甚至贴在井径变化较大处,因此很难实施普通打捞。现场普遍采用可弯肘节和折弯钻杆的方式进行寻找落鱼,实施打捞,有可能多次折弯钻杆,造成浪费,甚至造成井下更复杂情况的发生。根据这一情况,设计了可调角度弯钻杆。可调角度弯钻杆由上接头、花键体、调整套、下接头等组成,通过调节调整套和花键体等机构,可实现弯钻杆0°~4°调节。已完成可调角度弯钻杆的样机制造,并在多口井中进行应用。结果表明,采用可调角度弯钻杆可有效实施藏鱼头打捞,井口调节方便,应用取得了成功;单井可节约近30万元。     

矩形磁极线圈弯曲半径的选择

通过生产实践观察和理论分析，阐述了矩形磁极线圈弯曲半径对弯角部位形状尺寸的影响．并从理论上对弯曲半径进行探讨，介绍了一种实用的弯曲半径的设计选择方法．     

基于SFS-SVM的V形件弯曲工艺参数优化研究

影响V形工件弯曲回弹的工件尺寸、力学性能、负载条件和材料各向异性等众多因素相互耦合,表现出高度复杂的非线性,从而导致回弹预测结果的不确定性.把板料回弹后的张开角和圆角半径作为目标优化函数,将支持向量机模型部署到顺序向前筛选算法中以高效筛选出最优的特征变量参数子集,从而提高弯曲回弹模型预测结果的精度与可靠性.有限元分析和...     

内压作用下含内表面环向裂纹弯管的应力强度因子和极限载荷

应用大型有限元软件ANSYS对在内压作用下合内拱内表面环向裂纹弯管的应力强度因子和极限栽荷进行研究.计算出不同尺寸弯管的应力强度因子和极限载荷并加以分析,其结果可供工程安全评定使用.     

冰期河流弯道冰水动力学行为研究

以黄河什四份子弯道为研究对象,基于2019-2020年度的凌情监测影像及现场试验数据,分析了河流弯道冰水动力学行为特征。结果表明:上宽下窄的河道形态是造成弯道卡冰的主要原因,流凌-封河阶段,弯顶节点工程对水流的顶托作用促进了上游回流区的形成;受弯道离心力作用,河冰聚集于河道凹岸一侧,并在回流区堆积形成冰桥,从而缩小了断面过冰面积,河道逐渐封冻;弯顶下游流速大且来冰量少,形成清沟,主流向河中发展;冰塞堆积于弯顶上游凹岸主河槽内,水流被挤压至凸岸非冰塞区,弯道主流易位;在稳封期,河道冰水动力特征基本不再变化,在解冻开河期,凸岸非冰塞区流速较大,主流区冰盖优先解冻且沿主流输移,回流区冰盖最后消融,河道主流逐渐恢复至畅流阶段,整体呈复归式。     

魏氏组织TC17钛合金绝热剪切带(ASB)的组织与织构

利用热模拟试验机对原始组织为魏氏组织的TC17钛合金进行了热压缩试验,采用电子背散射衍射技术(EBSD)研究了不同变形参数对魏氏组织TC17钛合金材料显微组织与结构的影响。结果表明:在700℃以上进行热压缩变形时,魏氏组织TC17钛合金的材料均发生绝热剪切行为,所形成的ASB中心区域组织主要由动态再结晶形成的等轴状β相晶粒和少量α相组成。随变形温度升高,残余α相略有增加,β相晶粒尺寸增大。不同变形参数对于ASB中心区域β相的取向分布影响甚微,在β相中主要形成高斯织构。同时绝热剪切敏感性的研究表明,魏氏组织TC17钛合金具有较高的绝热剪切敏感性,且随变形温度升高,绝热剪切敏感性增强。     

An experimental investigation of a new method for protecting bends from erosion in gas-particle flows

This paper intends to introduce a new way of bend erosion protection: the ribbed bend erosion protection method. Experimental research has come out fixing ribs on the outer-wall of the inside bend as well as on the wall of the straight pipe extending behind the bend in order to decrease the erosion damage caused by the “bend effect”. The experiment shows that ribbed bend technology is a simple and efficient erosion protection method, which can greatly enhance bend erosion protection ability. It also shows that the rib relative height and the rib gap between two adjacent ribs are two important parameters in the ribbed bend erosion protection ability. The same result can be reached on the straight pipe extending from the bend.     

Development and characterization of hot-pressed matrices for engineered ceramic matrix composites (E-CMCs)

The present research effort was undertaken to develop a new generation of SiC fiber- reinforced engineered ceramic matrix composites (E-CMCs). In contrast to traditional CMCs with a brittle SiC matrix, an E-CMC is designed to consist of a matrix engineered to possess sufficient high temperature plasticity to minimize crack propagation, relatively high fracture toughness, and self-healing capabilities to prevent oxygen ingress to the BN-coated fibers through surface-connected cracks. The present paper discusses the bend strength, isothermal oxidation, microstructures and self-healing properties of several silicide-behaved engineered matrices. Based on the oxidation tests, where it was observed that some of the matrices exhibited either catastrophic oxidation (“pesting”) or spalling of the oxide scale, two engineered matrices, CrSi₂/SiC/Si₃N₄ and a CrMoSi/SiC/Si₃N₄, were down-selected for further investigation. Four-point bend tests were conducted on these two engineered matrices between room temperature and 1698 K. Although these matrices were brittle at low temperatures, it was observed that the bend strengths and bend ductility increased at high temperatures as the silicide particles became more ductile, which was qualitatively consistent with the theoretically expected behavior that crack blunting at these particles should increase the matrix strength. Additional studies were conducted to study the effects of different additives on the self-healing properties of the engineered matrices, which helped to identify the most effective additives.