Application of Deep Hole Drilling to the Measurement and Analysis of Residual Stresses in Steel Shrink‐Fitted Assemblies

Abstract: Residual stress measurement of shrink‐fitted assemblies was achieved through finite element simulations and experiments using the deep hole drilling technique. Shrink‐fitted assemblies using stainless steel and cast iron were manufactured and residual stresses measured using a combination of deep hole and centre hole drilling. The results from the finite element simulations demonstrated that modifications to the deep hole drilling method were required to account for plastic relaxation during the measurement process. This was verified through the experimental measurements. The results from both the stainless steel and cast iron assemblies provided a clear demonstration that the final residual stress state was a consequence of the machining and assembly of the components.     

绿色建筑全生命周期增量成本与效益研究

从全生命周期角度对绿色建筑与传统建筑的区别进行分析。进行理论分析的同时,也进行数字化分析。将绿色建筑相较于传统建筑的成本进行细化,并对绿色建筑的效益进行货币化分析,构建全生命周期成本与效益研究评价模型。通过南通检测中心绿色建筑实例对模型进行论证。     

Improving energy efficiency of incremental relay based cooperative communications in wireless body area networks

In this paper, we investigate the energy efficiency of an incremental relay based cooperative communication scheme in wireless body area networks (WBANs). We derive analytical expressions for the energy efficiency of direct and cooperative communication schemes taking into account the effect of packet error rate. The following communication scenarios specific to a WBAN are considered: (i) in‐body communication between an implant sensor node and the gateway, and (ii) on‐body communication between a body surface node and the gateway with line‐of‐sight (LOS) and non‐LOS channels. The results reveal a threshold behavior that separates regions where direct transmission is better from regions where incremental relay cooperation is more useful in terms of energy efficiency. It is observed that, compared with direct communication, incremental relay based cooperative communication schemes improves the energy efficiency significantly. Further, cooperation extends the source‐to‐destination hop length over, which energy efficient communication can be achieved as compared with direct communication. We also observe that, for both direct as well as cooperative transmission schemes in error prone channels, an optimal packet size exists that result in maximum energy efficiency. Copyright © 2013 John Wiley & Sons, Ltd.     

Experimental Study on Springback of Sheet Metal Single Point Incremental Forming

Sheet metal single point incremental forming(SPIF)is a new technology for flexible process.The springback phenomenon in single point incremental forming has been discussed.Effects of forming angle and shape of the part are analysed using simple experimental method.Tool diameter,sheet thickness,step size,material parameters and the interaction of them are also analysed by using orthogonal test.The results show that the primary factor affecting springback is forming angle.In addition,springback is decreased when the specimen has a larger forming angle.The order of the four factors that influence springback is tool diameter,sheet thickness,step size and material parameters.The forming precision will increase if springabck is decreased by optimizing the forming parameters.     

板坯动态二冷增量型PID控制研究

为解决连铸拉速工况变化时因使用一级水表配水控制所引起的铸坯表面温度波动的问题,建立了考虑铸坯纵向导热的板坯传热瞬态模型.通过Gleeble试验获得钢的热塑性,制定了铸坯的目标温度.采用增量型PID控制方法开发了动态二冷控制软件Visual Cast.结果表明:与传统的一级水表相比,当拉速发生变化时VisualCast能...     

样本自选择回归分析算法在转炉炼钢中的应用

针对转炉炼钢静态控制模型广泛采用的常规回归分析算法采用目标炉次的前几炉次冶炼数据作为样本,模型预测准确度低的问题,提出了一种基于样本自选择的回归分析算法。该算法从实际生产数据中自动选取一定数量的合适样本来构建回归分析预测模型,实现吹氧量、冷却剂加入量、终点温度和终点碳含量的预测。通过某钢厂120t转炉Q235B钢种的实...     

工具头大小对板材多点复合渐进成形过程影响的有限元分析

多点渐进成形具有变形均匀、可成形性强、成形效率高且能有效抑制失稳等优势。通过建立金属板材多点复合渐进成形三维有限元模型,对不同尺寸大小的工具头成形典型方锥台制件的多点复合渐进成形过程进行了数值模拟和分析,探讨了工具头大小对成形件的等效塑性应变、成形精度、厚度减薄率等的影响。通过对仿真结果的对比分析表明:工具头直径越小,制件成形区的厚度减薄越严重,越易产生破裂;工具头直径越大,制件变形越均匀、成形精度更高,但法兰区的等效塑性应变更大、越易产生起皱。     

面向数控渐进成形鼓包问题的成形轨迹生成与规划

针对数控渐进成形中鼓包的问题,提出了基于STL(Sterolithography)模型的等高线轮廓扫描、等高线轮廓与底面扫描、各等高层由外向内全扫描和各等高层由内向外全扫描4种挤压工具扫描运动轨迹类型,并给出了基于STL模型顶点偏置算法和多边形边偏置算法的各类型挤压运动轨迹生成方法;同时,采用有限元分析软件对这4种扫描运动轨迹的数控渐进成形效果进行了数字模拟仿真分析。研究结果表明,采用各等高层由内向外全扫描的轨迹进行数控渐进成形时不发生鼓包现象,并且能够减少制件的整体厚度差。     

考虑碰撞效应的相邻框架结构地震易损性分析

针对间距不足和高度不等的相邻钢筋混凝土框架结构,设置考虑碰撞刚度和阻尼非线性的碰撞单元,通过对三维非线性有限元模型的时程分析研究地震碰撞效应,并开展增量动力分析,分别以所有层和碰撞层最大层间位移角为工程需求参数,提出考虑碰撞效应的地震易损性分析方法。以6层和4层、6层和5层、6层和3层相邻钢筋混凝土框架结构为例,对比分析不同周期比下考虑与不考虑碰撞效应的相邻结构地震易损性曲线。结果表明：对于6层和4层相邻结构,考虑碰撞效应后,6层结构所有层的最大层间位移角对应的失效概率略有减小,4层结构的反之,而较低结构的碰撞层及较高结构的碰撞层以上层的最大层间位移角对应的失效概率明显增大,即碰撞效应对结构整体响应影响不明显,而对局部响应影响显著;6层和5层、6层和3层相邻结构地震易损性曲线具有类似规律,且相邻结构自振周期越接近,碰撞对结构地震易损性影响越小。