Research on rotary forming mechanism of cartridge bottom by FEM

0　ＩＮＴＲＯＤＵＣＴＩＯＮＣａｒｔｒｉｄｇｅｂｏｔｔｏｍｉｓａｄｉｓｋｗｉｔｈａｈｏｌｅｒｉｇｈｔｉｎｔｈｅｍｉｄｄｌｅａｓｓｈｏｗｎｉｎＦｉｇ .1,ｗｈｉｃｈｃａｎｂｅｍａｎｕｆａｃ ｔｕｒｅｄｂｙｒｏｔａｒｙｆｏｒｇｉｎｇｆｒｏｍａｒｉｎｇｂｉｌｌｅｔ .Ｔｈｉｓｋｉｎｄｏｆｐａｒｔｉｓｕｓｕａｌｌｙｆｏｒｍｅｄｂｙｈｏｔｆｏｒｇｉｎｇｏｒｅｘｔｒｕｄｉｎｇｆｒｏｍａｃｙｌｉｎｄｅｒｂｉｌｌｅｔａｎｄｔｈｅｎｂｏｒｉｎｇａｔｔｈｅｃｅｎｔｅｒ .Ｔｈｅｃｏｎｖｅｎｔｉｏｎａｌｐｒｏｃｅｓｓｎｅｅｄ…     

Prevention of thinning at disc center during rotary forging

0　ＩＮＴＲＯＤＵＣＴＩＯＮＲｏｔａｒｙｆｏｒｇｉｎｇｈａｓｓｕｃｈａｄｖａｎｔａｇｅｓａｓｅｎｅｒｇｙｓａｖｉｎｇ ,ｈｉｇｈｐｒｅｃｉｓｉｏｎｗｏｒｋｐｉｅｃｅ ,ｌｏｗｅｒｌｅｖｅｌｓｏｆｎｏｉｓｅａｎｄｖｉｂｒａ ｔｉｏｎ .Ｔｈｅｒｏｔａｒｙｄｉｅｓｐｉｒａｌｌｙｃｏｍｐｒｅｓｓｅｓｐａｒｔｏｆｔｈｅｗｏｒｋ ｐｉｅｃｅｕｎｔｉｌｔｈｅｆｉｎａｌｓｈａｐｅｉｓｆｏｒｍｅｄ .Ｉｔｉｓｅｓｐｅｃｉａｌｌｙｓｕｉｔ ａｂｌｅｆｏｒｔｈｅｆｏｒｍｉｎｇｏｆａｘｉｓｙｍｍｅｔｒｉｃａｌｐａｒｔｓ[1] .Ｎｏ…     

Characteristics of thickness distribution of tailor-welded tube hydroforming

Both experimental and mechanical analyses were carried out to investigate the characteristics of thickness distribution for tailor-welded tube (TWT) hydroforming with dissimilar thickness. Then, the effects of weld-seam position and thickness difference were also revealed. A multiple-diameter tube was formed to reveal the characteristics and the regularity of thickness distribution during TWT hydroforming. It is indicated that there are obvious fluctuations in thickness distribution though the TWTs have the same expansion ratio. The thinning ratio of thinner tube is bigger than that of thicker tube especially in the zone closed to the weld-seam. The difference in thinning ratio between two tube segments can reach 9%. Consequently, sudden and large fluctuation of thickness appears in the zone nearby the weld-seam. The difference in thinning ratio between thinner and thicker tubes enlarges as the thickness difference increases, but improves as length ratio increases. Different strain states are the main reason to induce nonuniform thickness distribution. The difference in thickness is the main reason to induce different strain states on thinner and thicker tubes.     

管件外压成形的数值模拟及屈曲特征分析

对采用液体介质在管坯外部施加压力,使坯料横截面缩小并成形到置于其内部的芯模上的外压成形方法进行了有限元数值模拟研究.分析了影响管件屈曲变形特征和成形过程的主要因素.研究表明:随着管坯长度的增加,环向屈曲波数减少,临界屈曲压力降低;随着管坯厚度的增加,环向屈曲波数减少,临界屈曲压力升高;带有一定不圆缺陷的管坯的临界屈曲压力与理想管坯相比降低很多,但在成形后期对壁厚和成形效果无明显影响.     

基于单元结构填土模型试验确定累积变形状态阈值的方法

设计了一套利用单元填土模型试验确定累积变形状态阈值的方法。通过有限元计算确定主要受力区作为模型填土空间,以砖墙和砂袋组合形成模型填土非完全侧限边界约束,结合变形测试和循环加载设备构成试验系统。在填土空间内填筑相应压实状态的模型进行循环加载试验,获得累积变形随加载次数的变化曲线,运用"幂次判别法"确定循环荷载作用下累积变形演化状态阈值。选用级配碎石填料进行循环加载试验,验证了基于单元填土模型试验确定累积变形状态阈值的可行性。     

一箱“磨砂”烟 全是废纸壳

3月5日中午,贵州省都匀市平浪镇香烟销售个体户韦成科（右）来到都匀市墨冲镇工商所平浪镇约时定点便民服务站投诉。前不久,贵州省都匀市烟草公司专车配送来的一箱“磨砂”牌黄果树香烟,每条香烟里面全是废纸壳。韦成科找到都匀市烟草公司负责人肖某和烟草公司专门配送香烟的杨某,要求赔偿损失,肖某和杨某都称烟被掉包了,与公司无关。     

基于多视角属性散射中心的风电机动态叶片雷达回波模拟

模拟高保真的动态风电机叶片雷达回波并提取其多普勒特征,是解决风电场对雷达台站无源干扰的关键问题.针对现有算法均无法准确且实时模拟动态叶片回波的问题,突破采用单一视角的静态散射中心模拟叶片回波的传统思路,将雷达视线下叶片整个旋转周期大转角划分为多个子视角,提出一种基于多视角属性散射中心的动态风电机叶片雷达回波模拟算法.考...     

基于无功-频率下垂特性的无功扰动法在孤岛检测中的应用

孤岛检测是光伏并网研究的难点,特别在光伏并网逆变器输出与负载功率平衡时难以有效检测出孤岛,为此提出一种基于无功-频率下垂特性的无功扰动孤岛检测方法。该方法通过引入一个与负载无功-频率特性相关的线性函数作为无功扰动的输入量,打破功率平衡情况下发生孤岛时所存在的孤岛稳定运行点。再将实时检测到公共耦合点频率的偏差,引入到无功扰动的函数中形成正反馈回路,加速频率的偏移,使并网逆变器输出电压频率超出限定阈值,从而实现孤岛检测。仿真结果表明,该方法具有无检测盲区、响应快速、对电能质量影响小的特点。