关于地铁轴流风机叶片发生断裂和出现裂纹的分析

叶片断裂和裂纹是旋转机械中普遍存在的一种安全隐患。对其发生规律进行分析是十分重要的。笔者针对地铁通风系统的某型号 18#轴流式风机发生断裂和出现裂纹的情况 ,采用Star—CD流体计算软件和ANSYS有限元软件计算了有、无软连接两种情况下的风机内流场和风机叶片的内应力。结果表明 ,软连接结构虽然对风机的内流场和叶片内应力有影响 ,但不足以对风机安全运行构成威胁。同时 ,分析了导致叶片断裂和出现裂纹的多种因素 ,并提出了避免类似现象发生的若干建议。     

筛选试验中振动应力量值剪裁方法

目前,筛选试验中振动应力量值选取大多采用GJB推荐值,而不同产品有其不同动力学特性,从而很难保证各类产品都达到强筛选效果.针对这种不足,本文提出一种根据产品实测响应而确定振动量级的新方法,并以电子组件为例,给出具体的实施方法及操作过程中诸多问题的解决办法.实践证明本方法具有推广价值.     

换热器不锈钢换热管束开裂原因分析

一台换热器换热管束发生了开裂泄漏.采取全面检验的方式,通过宏观检查、化学成分分析、断口微观形貌和能谱分析、金相分析等方法,对换热管开裂原因进行了分析.结果表明:该换热管开裂为氯化物应力腐蚀开裂.壳程介质循环冷却水中CI元素含量是应力腐蚀开裂的主要因素,结构缺陷、敏感的工作温度区间、水中溶解氧和含S杂质导致了应力腐蚀的快速发展.     

The early warning of aquatic organophosphorus pesticide contamination by on-line monitoring behavioral changes of Daphnia magna

In this paper, the movement behavior of Daphnia magna was studied as a bio-indicator of organophosphorous pesticide (OP) contamination, using an on-line bio-monitoring method, the Multispecies Freshwater Biomonitor. A static test of acute toxicity test revealed the 24-h and 48-h LC(50) values (95% confidence limit) for Daphnia magna to be respectively 0.45 microg/l and 0.21 microg/l for dipterex 3.80 microg/l and 0.90 microg/l for malathion, and 1.25 microg/l and 0.38 microg/l for parathion. The behavior strength of Daphnia magna was a sensitive indicator of sublethal OP stress and resulted in significant concentration-response relationships for the three OPs. Increasing OP concentration will result in more intensive behavioral responses of Daphnia magna and shorter response time, which could be described by the Stepwise Stress Model (SSM). Therefore movement behavior can be effectively applied in early warning of environment quality by on-line bio-monitoring. The intensive changes in behavior strength of Daphnia magna over a short time follow the SSM concept and can be used as an indicator of early stress response to OP accidental contamination.     

Evaluation of biotargeting and ecotoxicity of Co²⁺-containing nanoscale polymeric complex by applying multi-marker approach in bivalve mollusk Anodonta cygnea

Cobalt (Co²⁺) is present in many nanoscaled materials created for various applications. The key goal of our study was to develop sensitive approaches for assessing the bio-risks associated with using novel Co²⁺-containing nanoscaled polymeric complex (Co-NC). Freshwater bivalve mollusk Anodonta cygnea (Unionidae) was subjected to 14 d action of the developed Co-NC, as well as of Co²⁺ applied in the corresponding concentration (50 μg L⁻¹) or polymeric substance (PS). All experimental groups under study have demonstrated signs of toxic targeting, notably changes in DNA characteristics, oxidative stress (with particularities in each exposed group) and activation of anaerobiosis (Co²⁺ and Co-NC). However, the group exposed to Co-NC showed some advantages that can be related to the activation of metallothionein (MT) function (increase in the level of MT-related SH-groups (MT-SH)): low level of oxyradical formation, no increase in protein carbonylation and vitellogenin-like proteins concentration unlike in Co²⁺ and PS exposed groups. On the other hand, Co²⁺ increased metal (Co, Cu, Zn and Cd) binding to MT (MT-Me) without changes in MT-SH level jointly with activation of oxyradical formation and apoptosis and decreasing of lysosomal membrane stability. PS per se initiated unbalanced changes in activities of the biotransformation enzymes ethoxyresorufin-O-deethylase and glutathione-S-transferase. Thus, Co²⁺ complexing with the developed PS prevented bio-toxic effects of free Co²⁺ ions and PS per se, at least in the studied hydrobiont. The MT-SH was the main distinguishing index of Co-NC group selected by classification and regression tree analysis.     

Effects of dioxin exposure in Eisenia andrei: integration of biomarker data by an Expert System to rank the development of pollutant-induced stress syndrome in earthworms

A battery of biomarkers has recently been developed in the earthworm Eisenia andrei. In this study, different biomarkers (i.e. Ca²⁺-ATPase activity, lysosomal membrane stability-LMS, lysosomal lipofuscin and neutral lipid content) were utilized to evaluate the alterations in the physiological status of animals, induced by exposure for 3 d to different sublethal concentrations of TCDD (2,3,7,8-tetrachlorodibenzo-p-dioxin) (1.5 × 10⁻³, 1.5 × 10⁻², 1.5 × 10⁻¹ ng mL⁻¹) utilizing the paper contact toxicity test. Lysosome/cytoplasm volume ratio and DNA damage were also evaluated as a biomarker at the tissue level and as a biomarker of genotoxicity, respectively. Moreover, the NR retention time assay conditions were optimized for the determination of in vivo LMS in earthworm coelomocytes. The results demonstrate that LMS and Ca²⁺-ATPase activity were early warning biomarkers able to detect the effects of minimal amounts of TCDD and that biomarkers evaluated at the tissue level are important for following the evolution of the stress syndrome in earthworms. To evaluate the health status of the animals, an Earthworm Expert System (EES) for biomarker data integration and interpretation was developed. The EES proved to be a suitable tool able to rank, objectively, the different levels of the stress syndrome in E. andrei induced by the different concentrations of TCDD.     

Individual differences in reactions towards color in simulated healthcare environments: The role of stimulus screening ability

The notion that the physical healthcare environment can affect our mood and behavior is well established. Despite this, individual differences in sensitivity to environmental stimuli have not received much attention. With the current research showing the importance of individual differences in sensitivity towards color, these may explain the contradictory effects found in color research. Two experiments focused on differences in environmental sensitivity, measured with stimulus screening ability. In both experiments, participants were presented with a scenario describing hospitalization with appendicitis and were exposed to a photo of a hospital room. The experiments tested the effects of environmental coloring of the hospital room (green and orange, both contrasted with white as a control condition), and the moderating role of stimulus screening ability (high-screeners vs. low-screeners) on stress (study 1) and arousal (study 2), and cognitive appraisals of the room (study 2). Stress-reducing effects of green and arousal-inducing effects of orange were both more pronounced for people scoring low on stimulus screening ability than for those who are able to effectively screen out complexity in the environment (high-screeners).     

Stress-70 as indicator of heavy metals accumulation in blue mussel Mytilus edulis

The induction of stress-70 (Hsp70) in the blue mussels Mytilus edulis from southern Baltic after exposure to cadmium, lead and copper, administrated individually and/or as a mixture, was investigated by means of standard Western blotting using a clone 3A3 monoclonal antibody. The general course of the stress-70 induction was found to be similar for all tested metals. It could be characterised by three main features: (1) The induction of stress-70 proteins was only slightly increased at low metal concentration. (2) Strong induction of stress-70 occurred at high concentration of metals. Combination of metals (Cd+Cu) was found to increase the stress-70 level more intensely than related concentrations of singularly applied metals. (3) Five weeks of long depuration had no effect on stress-70 levels. Experiments revealed different induction of stress-70 as a response to cadmium, lead and copper exposure and confirm that the applied technique might serve as a versatile tool to assess invertebrate stress reaction to environmentally relevant heavy metals.     

不锈钢波纹管应力腐蚀防护方法研究

不锈钢波纹管是现代工业广泛使用的金属弹性元件,长期应用实践表明,在特殊环境条件下,波纹管常常发生因应力腐蚀引发的爆炸失效事故,对环境、安全构成极大威胁。本文详细阐述了固溶处理不锈钢波纹管组形变马氏体含量分布、残余应力分布。不锈钢波纹管在加工、成型过程中,波峰波谷会发生塑性变形,一部分奥氏体组织转变为马氏体组织。试验研究结果表明,固溶处理后残余应力变为压应力,残余应力比未固溶处理波纹管的大大减小;固溶处理后形变马氏体含量较少,且分布均匀,约占0.25%;残余应力越大,马氏体含量越高,不锈钢SCC敏感性大。对固溶处理前后波纹管应力腐蚀开裂进行实验研究,研究表明,固溶处理可提高波纹管抗SCC性能;喷丸强化可提高波纹管抗SCC能力,表面硬度、强度增大,也可延长疲劳寿命。     

再沸器管箱封头环焊缝裂纹形成机理研究

某化工厂的一分塔再沸器在定期检验过程中,发现材质为奥氏体不锈钢的管箱封头环焊缝存在穿透性纵向裂纹缺陷。为了进一步了解裂纹形成的原因,避免类似缺陷再次产生。本文通过对案例背景介绍,在定期检验结果的基础上,通过对缺陷部位进行取样,在实验室采用理化检验方法,结合设计和使用参数,对裂纹的形成机理进行分析并得出结论。