Microstructure-related fracture toughness and fatigue crack growth behaviour in toughened, anhydride-cured epoxy resins

Fracture toughness and fatigue crack propagation (FCP) of plain and modified anhydride-cured epoxy resin (EP) were studied at ambient temperature. Liquid carboxyl-terminated acrylonitrile-butadiene (CTBN) and silicon (SI) rubber dispersions were used as tougheners for the EP. The morphology of the modified EP was characterized by dynamic mechanical analysis (DMA) and by scanning electron microscopy (SEM). The fracture toughness, K_c, of the compositions decreased with increasing deformation rate. K_c of the EP was slightly improved by CTBN addition and practically unaffected by incorporation of the SI dispersion when tests were performed at low cross-head speed, v. Both modifiers improved K_c at high v, and also the resistance to FCP, by shifting the curves to higher stress intensity factor ranges, ΔK, by comparison with the plain EP. It was established that both fracture and fatigue performance rely on the compliance, J_R, at the rubbery plateau, and thus on the apparent molecular mass between crosslinks, M_c. The failure mechanisms were less dependent upon the loading mode (fracture, fatigue), but differed basically for the various modifiers. Rubber-induced cavitation and shear yielding of the EP were dominant for CTBN, whereas crack bifurcation and branching controlled the cracking in SI-modified EP. The simultaneous use of both modifiers resulted in a synergistic effect for both the fracture toughness at high deformation rate and the FCP behavior.     

20CrMnTi螺旋锥齿轮中出现圆鼓泡问题的分析

在对机车转向架螺旋锥齿轮的粗、精加工中发现其表面鼓起许多小泡，将其剖开酸洗后呈现为小裂纹状，该现象在实际生产中较为罕见，对此进行分析，探讨，查找原因，确定这是钢材内气泡未能焊合的结果，为此制定了改进措施。     

强腐蚀环境下锚索强度指标及表观特性试验研究

利用自行制做的试验装置,以配制出的强腐蚀环境土为介质,对非预应力锚索和预应力锚索的裸筋以及对有注浆缺陷的锚索试件进行了腐蚀试验,从外观腐蚀状况和腐蚀后的钢绞线力学性能的改变特性进行了研究.结果表明:从外观上看,预应力锚索试件的腐蚀程度总体上比非预应力试件的腐蚀程度要重,含注浆缺陷的锚索试件的腐蚀程度比裸筋的腐蚀程度要重...     

硝铵装置降膜蒸发存在问题与改进措施

对我公司硝铵装置降膜蒸发工序存在的问题进行分析 ,并通过技术改进 ,使干燥洗涤液全部返回系统 ,造粒塔粘塔问题得到缓解 ,取得可观的经济效益和环保效益     

湿式储气罐防腐失效原因分析及改进措施

分析了济钢10万m3低压湿式储气罐防腐失效的原因,从防腐涂料的选择、施工过程等环节提出了改进的措施,实施后效果良好。     

Two Modified Semicircle Control Charts for Detecting Process Improvement

A semicircle control chart can be used in detecting both increases and decreases in the mean and/or variance. In this paper, we propose two modified semicircle charts for detecting a reduction in the process variance, a.k.a. process improvement. Each of these modified semicircle charts, namely, SC1 and SC2 has two limits, defined by the inner and outer semicircles. A process improvement is detected by the SC1 scheme if a point is plotted inside the smallest semicircle, or if two successive points are plotted between the inner and outer semicircles and by the SC2 scheme if a point plots inside the smallest semicircle or if two of three successive points plot between the inner and outer semicircles. It will be shown that the two modified semicircle charts have superior average run length (ARL) performances to the basic semicircle chart in the detection of process improvement. The ARL study is conducted by means of a simulation.     

Software Process and Product Improvement: A Historical Perspective

In this paper, a historical overview of significant attempts to get over the software crisis is presented. In particular, we trace the development of lifecycle models and information systems development methodologies during the last four decades. Finally, we explore the role of measurements and outline current and future works leading to process and product improvement.     

冷轧原料库南侧吊车大车轨道固定方式的改进

对热轧板厂冷轧原料库南侧吊车轨道的使用情况进行总结，分析存在问题的原因，提出了改进方案。     

Are Reviews an Alternative to Pair Programming?

From the first presentation of extreme programming on, pair programming has attracted a wide range of programmers to work together in front of one display. The proposed advantages of pair programming are a faster development cycle and code with higher quality. However, the nearly doubled personnel cost when compared to single developers seems to outweigh these advantages. Instead of showing the superiority of pair programming, we seek an alternative. Can a single developer be assisted by an already known technique with which he produces the quality of pairs with only a fraction of the cost? The answer with some restrictions is: yes, he can. Reviews are a reasonable candidate with respect to code quality and cost.     

平凉电厂300MW机组机炉协调控制系统及设备的优化改进

火电机组热控自动化水平的高低,直接反映着企业的安全生产和技术经济水平;同时为满足电网资源优化配置的需要,机组AGC功能的投运也势在必行。作为AGC投运基础的CCS能长期稳定的运行不但能够实现机组的最优控制,提高机组的发电效率而且可以降低运行人员的劳动强度。因此对新投产的机组在运行期间不断对CCS系统及各子系统逻辑组态进行优化完善,对CCS系统测量装置和执行机构进行调整改进,对各系统反复进行扰动试验完全可以使CCS系统长周期稳定投运,同时提高机组运行的可靠性和稳定性。重点介绍平凉电厂300MW机组CCS系统及设备的优化改进。