On the existence and convergence of the solution of PML equations

In this article we study the mesh termination method in computational scattering theory known as the method of Perfectly Matched Layer (PML). This method is based on the idea of surrounding the scatterer and its immediate vicinity with a fictitious absorbing non-reflecting layer to damp the echoes coming from the mesh termination surface. The method can be formulated equivalently as a complex stretching of the exterior domain. The article is devoted to the existence and convergence questions of the solutions of the resulting equations. We show that with a special choice of the fictitious absorbing coefficient, the PML equations are solvable for all wave numbers, and as the PML layer is made thicker, the PML solution converge exponentially towards the actual scattering solution. The proofs are based on boundary integral methods and a new type of near-field version of the radiation condition, called here the double surface radiation condition. Partly supported by the Finnish Academy, project 37692.     

矩形坯连铸生产40MnB钢试验研究

借鉴国内钢厂生产40MnB钢的成功经验，设计出首钢连铸生产40MnB钢的内控成分和各工序关键工艺，利用BOF-LF—CC工艺批量生产汽车用优质钢40MnB。     

调质状态下 4 0 C r钢的焊接

在合理制定焊接工艺的基础上,采用R307珠光体耐热钢焊条成功地进行了40Cr钢在调质状态下的焊接,解决了通常采用25-13型奥氏体焊条焊接时出现的焊缝强度低、焊接接头性能差的问题。     

CrNiMo钢在高速干滑动条件下摩擦表面的组织变化研究

在MMS-1G型高速干滑动摩擦磨损试验机上,采用CrNiMo钢作为销试样,与H96黄铜盘配副,进行了高速干滑动摩擦磨损试验,研究其高速干滑动摩擦磨损性能。对试验后的试样沿纵切面进行微观组织分析,探讨摩擦表面在试验前后及不同试验参数条件下的组织变化。结果表明,在高速干滑动条件下,CrNiMo钢材料的摩擦磨损性能随滑动速度的增加存在突变,其微观组织摩擦后沿纵切面发生了较大变化,且摩擦表面组织随滑动速度增加,发生了回复再结晶及碳化物的析出和长大。     

HP40Nb合金钢高温劣化的非线性超声评价

耐高温合金材料在服役过程中会发生高温劣化,主要表现为微观组织结构的变化,从而导致在其中传播的超声波能产生显著的高次谐波.针对HP40Nb合金钢材料高温劣化的检测及评价,提出采用归一化超声纵波非线性参量来表征材料的高温损伤状态.对HP40Nb损伤试样进行了非线性超声信号的测量结果显示,归一化超声纵波的非线性参量随着材料高温加载时间呈现出显著的上升-平稳-下降趋势.对材料微观组织演化过程进行了扫描电镜(SEM)的观察和分析,结果表明,超声非线性参量在早期阶段的上升与HP40Nb材料高温加载过程中η相等第二相的析出和聚集密切相关;其在后期阶段的下降归因于析出相的减少和脱落以及微孔洞的产生.由此可见,非线性超声对HP40Nb材料高温劣化后微观组织的变化非常敏感.     

EH40高强度船板Z向拉伸性能分析

利用扫描电镜及能谱仪对EH40的断口形貌、夹杂进行分析,结果表明：硫化物对钢板厚度方向抗层状撕裂性能的影响较大。为满足钢材Z向性能的要求,冶炼过程中应尽量控制硫的含量。     

Influence of T5 heat treatment on the microstructure and lubricated wear behavior of ternary ZnAl40Cu2 and quaternary ZnAl40Cu2Si2.5 alloys

A ternary ZnAl40Cu2 and a quaternary ZnAl40Cu2Si2.5 alloys were produced by permanent mold casting and subjected to T5 heat treatment at a temperature of 150 °C for 24 hours. The structural, mechanical and lubricated wear properties of these alloys were investigated in the as-cast and heat-treated conditions and the results were compared with those of SAE 65 (CuSn12) plain bearing bronze. Microstructure of the ternary alloy consisted of aluminum-rich α, eutectoid conversion product of α+η and ϵ phase located in the interdendritic channels. In addition to these phases, silicon particles were observed in the microstructure of the quaternary alloy. T5 heat treatment caused a considerable amount of reduction in the hardness, tensile strength and wear resistance of ZnAl40-based ternary and quaternary alloys, but improved their ductility and stability. These alloys in the as-cast and heat-treated conditions exhibited lower wear volume or higher wear resistance than SAE 65 bearing bronze. Among the experimental alloys, the optimum mechanical properties and wear performance were obtained from ZnAl40Cu2Si2.5 alloy in both as-cast and heat-treated conditions. Adhesion appeared to be the main wear mechanism for the ZnAl40-based alloys, but abrasion dominated the wear of SAE 65 bronze.     

改善40Mn2钢低倍质量的实践

介绍了40Mn2钢的特性及用途。结合石钢3#连铸机设备的实际情况,分析了导致40Mn2铸坯低倍内裂的原因。通过优化电磁搅拌参数和振动参数,基本消除了40Mn2钢材低倍内裂的缺陷问题,为连铸设备出现变化时如何保证生产提供了思路。     

三种植物叶片类胡萝卜素含量的比较分析

以红继木、红苋和七彩扶桑的叶片为材料,采用丙酮-乙醇法提取,利用紫外-可见分光光度计对三种植物叶片中胡萝卜素、叶黄素和总类胡萝卜素的含量进行了测定。结果表明,胡萝卜素含量:红苋>红继木>七彩扶桑;叶黄素含量:七彩扶桑>红苋>红继木;总类胡萝卜素含量:红苋>红继木>七彩扶桑。