Self-Diffusion of Iron in Molten Fe-C Alloys

Self-diffusion coefficients of iron in molten Fe-C alloys have been measured by using the capillary method. In addition, the samples have been autoradiographed and sectioned to insure that no significant convection has occurred during the diffusion. The results can be represented by the equation D = 4.3×10^?3 exp (—12.200/RT) for carbon = 4.6 pct and T = 1513° to 1633°K; and D = 1.0×10^?2 exp (—15,700/RT) for carbon = 2.5 pct and T = 1613° to 1673°K. The D values are higher and the heat of activation for diffusion lower in alloys containing more carbon. Calculation based on the Einstein-Stokes equation indicates that the diffusing species is iron ion.     

新颖的绕线拉紧装置

本文介绍一种新型适用的线圈绕制中的线材拉紧装置，并将其与传统的拉紧装置进行比较，得出各自的优缺点。     

冰箱门堵盖零件工艺分析和注射模设计

通过对冰箱门堵盖的工艺性分析,设计出结构合理的注射模,满足了堵盖零件的各项技术要求。     

30CrMnSiNi2A钢件镀硬铬的氢脆分析

本文叙述了用延迟破坏法试验超高强度钢(υb=1700MPa)不超过三次镀硬铬的氢脆情况。     

Investigation into the thermo-viscoplastic finite element analysis of square die extrusion of square section with Lagrangian description

An analysis of three-dimensional hot extrusion through landless square dies is carried out as a nonsteady-state problem. In the problem, difficulties arise from the severe distortion and die interference of elements at the aperture rim of the die, even with a small punch travel. Finite element simulation is impossible without intermittent remeshing procedures. To overcome these difficulties, an automatic remeshing technique is proposed by employing a modular conceptual mesh structure. In the analysis of temperature distribution, conduction, convection and radiation are considered in connection with a deformation analysis of a visco-plastic material. The effect of the mesh structure on the present scheme as well as material properties and temperatures associated with punch travel is discussed. As an example, an extrusion of a square section is simulated. In order to confirm the present scheme, experiments are carved out using aluminium at the elevated temperature.     

大型精密机械设备的验收与管理

对学院使用的大型精密机械设备——五轴加工中心和数控铣床等设备的安装条件、验收指标、技术管理和日常维护进行了阐述,确保设备到位后及时安装和有效使用。     

谈谈水泥土挡墙的合理计算

阐述了水泥土挡墙在工程基坑支护中的作用,并结合工程实例,对水泥土挡墙的合理计算模型进行了探讨。     

压铸模的热流量与温度梯度

提出用型壁和界面层的温度梯度度量压铸模热流量的观点和方法。通过实测和计算 ,研究不同冷却条件对型壁温度、合金释放的热量、型壁增加的热量的影响。计算机凝固过程数值模拟 ,得到试验的系统热阻为 2 .6cm2 ·K·s/J。     

Evaluation of the coupled multielectrode array sensor as a real-time corrosion monitor

Coupled multielectrode array sensors made of carbon steel and stainless steels were evaluated and compared with electrochemical noise (EN) sensors. Good correlations between sensor signals and solution corrosivity were observed for all multielectrode array sensors. Some correlation between the average pit index and solution corrosivity was observed for the carbon steel EN sensors, but not for the stainless steel EN sensors. The time-average noise resistances from the stainless steel EN sensors correlate well with solution corrosivity. There were, however, large random fluctuations and drifting for all EN signals, which make the EN sensors unreliable as real-time monitors.     

粘土砂旧砂再生效果与其含水量的关系

在影响粘土砂旧砂再生效果的诸多因素中,旧砂中水分含量是最重要的因素。本文就水分含量对再生效果的影响规律、再生效果最佳的水分含量等进行了研究和分析,得出了如下结论:并非含水量越低再生效果就越好,而是存在一个去泥率低谷区;再生效果最佳的适宜水分含量为1～2%。