Ⅰ型载荷下缺口前端氢浓度分布的研究

采用离子探针微分析仪,对Ⅰ型载荷下21Cr9Ni9MnN奥氏体钢缺口前端氢浓度分布进行了研究。结果表明,缺口前端存在两个氢浓度的富集峰,一个位于缺口顶端,另一个距缺口稍远。缺口顶端的氢富集峰是位错对氢陷阱作用结果,而静水应力导致远离缺口的氢富集峰。对缺口前端氢的富集过程以及应力强度因子对氢浓度分布的影响进行了讨论。     

低碳钢冷脆特性参量——临界缺口(裂缝)尺寸的研究

本文研究了缺口尺寸对低碳钢低温断裂行为的影响,分析了断裂载荷谷值所对应的温度T_C~*(称为冷脆特征温度)附近的断裂特征,结合工程设计特点,提出了冷脆临界缺口(裂缝)尺寸α_C及其特征值α_C~*的概念,推荐作为控制冷脆的一个基本特性参量。文中推导出了α_C及α_C~*的数学表达式,该式的可行性得到了静载及疲劳载荷条件下模拟试验数据的验证。     

微波传感技术在智能马桶上的应用

介绍了一种应用于智能马桶,可以穿透陶瓷和塑料来检测人体运动的微波传感技术。该技术利用多普勒原理实现对人体运动的检测。当微波传感器检测到人体移动后,会输出多普勒信号,该信号经过滤波、放大后送给PIC单片机进行处理。实际应用证明,该设计具有很好的检测效果。     

材料性质和试样几何形状对应力三维度的影响

为研究应力三维度和塑性应变对金属材料微孔聚合型损伤发展和延性断裂过程的影响,用有限元法计算16Mn钢和两种铝合金材料不同缺口根半径拉伸试样的应力、应变分布. 结果表明:缺口根半径越小,最小横截面上周向和径向应变相差越大且越不均匀,并导致最小横截面上的应力三维度与Bridgman公式预测结果不一样. 材料性质和试样几何形状对应力三维度的影响很大:缺口根半径相同的3种材料试样最小横截面的应力三维度分布形态相似,但应力三维度峰值及其所处位置有所不同;同种材料的试样缺口根半径不同,应力三维度分布形态也不同.     

基于DDPG的柔性伺服系统级联陷波器设计

针对柔性伺服系统的多频谐振抑制问题,提出一种基于DDPG的级联陷波器参数整定方法。以系统速度环开环bode图及陷波器bode图预处理结果作为训练数据,并以相位裕度作为奖励函数训练神经网络,实现所设计的伺服系统级联陷波器深度及宽度参数优化训练。搭建了三质量柔性伺服系统实验平台,并开展了多频谐振抑制实验,实验结果表明所提出的参数选择方法能够 找到具有最大相位裕度的陷波器参数,并有效地抑制系统多频谐振。     

砖烟囱爆破拆除不同切口形状的数值模拟

针对烟囱爆破拆除时爆破切口形状的确定往往按经验确定,没有重视烟囱倒塌过程中一些问题很难通过理论预见的情况,利用ANSYS/LS-DYNA软件数值模拟了常见的长方形切口、正梯形切口、倒梯形切口这3种爆破切口形状对烟囱倒塌拆除过程并进行了对比和分析,研究结果表明:首先从爆破切口闭合时间看到,倒梯形切口闭合时间最长,正梯形切口闭合时间次之,长方形切口闭合时间最短。其次从烟囱顶端着地时间分析,正梯形切口烟囱顶端着地时间最长,而其它两种切口方案次之,并且这两种方案对烟囱倒塌时间差不多相等。再从模拟烟囱倒塌的过程分析,正梯形切口及长方形切口烟囱倒塌过程出现"后座"现象。最后从烟囱倒塌顶端速度变化曲线中看出正梯形切口烟囱倒塌方案对地面的冲击力最小,引起地面的振动强度最小。     

Fracture investigation of U‐notch made of tungsten–copper functionally graded materials by means of strain energy density

The averaged strain energy density over a well‐defined control volume was employed to assess the fracture of U‐notched specimens made of tungsten–copper functionally graded materials under prevalent mode II loading. The boundary of control volume was evaluated by using a numerical method. Power law function was employed to describe the mechanical properties (elasticity modulus, Poisson's ratio, fracture toughness and ultimate tensile stress) through the specimen width. The effect of notch tip radius and notch depth on notch stress intensity factors and mode mixity parameter χ were assessed. In addition, a comparison based on fracture load between functionally graded and homogeneous W–Cu was made. Furthermore, in this research, it was shown that the mean value of the strain energy density over the control volume can be accurately determined using coarse meshes for functionally graded materials.     

Non-local line method for notched elements with use of effective length calculated in an elasto-plastic condition

The paper presents a non-local line method used to the fatigue life calculation of notched elements. The presented method is based on the concept of an effective length which determines the size of the equivalent fatigue zone. Effective values of normal stress calculated in the critical plane with a weight function were applied when determining the equivalent fatigue zone. Simulation studies were performed for two types of steel and two types of loading. Five different series of tests and simulations were used. Experimental studies were carried out for 40 HM-T and EA4T steels. These materials are used in railway industry, including the manufacturing of coupling bars. The notched test specimens contained notches with a tip radius of 0.2, 0.5, 0.8 and 1 mm. Stress calculations were performed using the finite element method by adopting cyclic material properties described by the model of a multi-linear hardening. Non-local calculations were performed in a defined critical plane for normal stress distribution and a weight function. As a result, the function of variation of the effective length depending on the loading level and geometry of the notch has been determined.     

复杂环境下12层框剪结构楼房爆破拆除

介绍了复杂环境下一栋12层框剪结构楼房的爆破拆除工程实例。采用10.4m高的复合梯形爆破切口、楔形半秒孔内延时,分3个爆区三响总延时1 020ms,实现了楼房的整体定向倒塌;通过确定合理的爆破参数、充分的预处理、间隔装药结构、双回路起爆网路等技术措施确保了安全准爆和精确定向倒塌;通过铺设缓冲垫层、炮孔包裹防护、搭设防护屏障等措施有效控制了爆破塌落振动及飞石的危害。楼房按照设计方向倒塌在设计范围内,周围建(构)筑物均没受到影响。该爆破拆除工程在精确定向,控制塌落振动及飞石等方面取得了较好的效果,可为同类工程爆破施工提供参考。     

基于陷波器参数自调整的伺服系统谐振抑制

针对永磁交流伺服系统中的柔性传动环节,建立电机——负载二质量模型,通过对模型的Simulink仿真分析阐述系统机械谐振发生的机理。为抑制伺服系统的机械谐振,根据对伺服系统谐振的定量分析,结合对电机速度误差信号的快速傅里叶变换（FFT）分析,设计自动调整参数的陷波滤波器,并进行仿真实验与实际实验。实验结果证实理论分析的正确性和所设计陷波器的有效性,在传动环节的刚度、阻尼和负载惯量不尽准确的情况下,相关仿真结果验证所设计陷波器依旧有效。