共查询到19条相似文献,搜索用时 234 毫秒
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通过比较几种旋压封头与标准椭圆封头的形状,并在理解JB4732、ASME、AD等规范关于凸形封头的设计计算方法的基础上,认为只要能满足GB150-98规定的标准椭圆封头的允许形状偏差,不论封头的成形方法如何,都应属于标准椭圆封头,故在材料、厚度相同时可以等效代替标准椭圆封头。 相似文献
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通过对不锈钢锥体封头在拉延过程中的应力应变受力分析,成功地设计了拉延成形摸具,使锥体封头由原来多道工序成形,变为一次拉延成形。工人劳动强度小,生产周期短,零件质量高。 相似文献
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封头在旋压过程中因加工硬化及磨削应力导致裂纹产生,这些残余应力如不及时进行去应力退火,造成封头表面在残余应力作用下产生延迟裂纹 相似文献
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一台反应釜两端所采用的椭圆封头因加工工艺不当,封头壁厚在小圆弧的过渡段出现严重减薄。依据压力容器分析设计原理,采用有限元方法确定减薄后椭圆封头的承载能力,给出满足安全要求的使用条件。 相似文献
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封头形状尺寸总体偏差要求由必不可少的 7个要素组成。内样板严格按被测封头的规定形状制作成带直边段的完整弓形 ,同时检测曲面过渡、转角半径及最大偏差值就可证明 ,近似椭圆形封头根本不存在等效代替 2∶1椭圆形封头的可能性 相似文献
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不锈钢复合钢板由较薄的复层及较厚的基层通过轧制或爆炸等方法复合而成。其中复层满足了耐腐蚀性的要求,而基层是利用相对复层成本低得多的碳素钢或低合金钢来满足强度方面的要求。由于其良好的经济性而被广泛用于石油化工和海水淡化等行业的压力容器制造。压力容器不锈钢复合钢板封头压制分为冷压和热压。因设备条件的限制,对于基层厚度大于8mm的不锈钢复合钢板封头的压制,我公司一般采用热压成型。由于奥氏体不锈钢在550~850℃缓慢冷却时,晶界有高铬的碳化物Cr23C6析出,造成碳化物邻近部分贫铬,引起晶间腐蚀的倾向。因此,压制过程中工… 相似文献
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《Food Control》2016
Salmonella biofilm is recognized as a frequent source of cross-contamination and has been associated with food-borne outbreaks. It is more meaningful for evaluating biofilm formation in food-based medium than in laboratory-growth medium. In the present study, the expression of functional genes during biofilm formation of Salmonella Typhimurium grown in meat-based and standard growth substrates were determined by RT-qPCR assays. The number of viable cells and the expression of tested genes during biofilm formation displayed a specific behavior according to the growth conditions. When biofilm was grown for 7 days in a laboratory trypticase soy broth (TSB), the expression of the tested genes increased, but when grown in a meat thawing loss broth (MTLB), gene expression was inhibited as compared to corresponding planktonic cells. Relative gene expression of biofilm in MTLB was lower than that in TSB. Positive relationships were found between each gene tested in biofilm cells grown in TSB and MTLB at 3, 5 and 7 days incubation, their correlation did not changed with the variation of growth media of biofilm. A preliminary positive relationship was also observed between growth days and the expression levels of some tested genes. Our results suggested that biofilm formation was coordinately governed by a highly complex regulatory network, where the genes tested in this study (adrA, bapA, csgB, csgD, csrA, rpoS, invA, sipB-C, sdiA and luxS) played important roles. 相似文献
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LNG天然气处理管线广泛采用奥氏体不锈钢。本文作者应用三维设计和应力分析对中海油渤西油气处理厂改造项目低温不锈钢管线设计和施工进行了优化,确保了工程进度和施工质量。 相似文献
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