Stress Relaxation Behavior of GH4169 Superalloy

GH4169 superalloy stress relaxation test was investigated to study its characteristics of stress relaxation curves at various temperatures( 550,650,and 750 ℃). These curves presented jointly two distinct stages,the stage of inner stress relaxing quickly,and the stage of inner stress relaxing slowly and closing to the stress relaxation limit. And these curves obtained could be fitted by second order exponential decay function well. Based on the experimental stress relaxation curves,the relationship between stress relaxation rate and time were derived, which showed that the higher relaxation temperature and the greater initial rate of stress relaxation. The whole process presented two different stages,the stage of stress relaxation rate falling rapidly and the stage of stress relaxation rate slowing down and tending to be constant. The relation curve between creep strain rate and stress of GH4169 superalloy can be divided into three stages,low stress stage,transition stage,and high stress stage.Both the high stage and the low stage present linear correlation.     

中国美丽休闲乡村时空分异与影响机制

选取2010—2020年1 216处美丽休闲乡村地作为研究样本,运用ArcGIS 10.5中的最邻近点指数、核密度分析、标准差椭圆等方法从空间分布类型、均衡度与方向3个角度探究美丽休闲乡村的时空发展演化过程;最后采用地理探测器揭示其影响因素并归纳影响机制.研究结果表明:(1)根据其数量变化,可以将其发展分为起步期、迅速增长期和平稳发展期.(2)美丽休闲乡村在空间上总体呈现集聚、不均衡的分布态势.空间分布类型从随机分布转变为集聚态势;均衡度从差距悬殊逐渐转化为比较平均分布,长远朝“绝对平均”类型发展;分布密度呈现明显的“点—簇—面”发展演化模式;分布中心由山西省晋中市先向西南迁移,后向东南迁移至河南省南阳市,分布方向从“东—西”方向分布逐渐转向“东北—西南”方向.(3)美丽休闲乡村空间特征影响机制是自然因素、社会因素和人文因素综合作用的结果.