Calculation of strain amplification matrix for strain invariant failure theory based on representative volume element models with periodical boundary condition

Strain invariant failure theory (SIFT) is a micro-mechanics-based failure theory for multi-scale failure analysis of composite materials originally proposed by Gosse and Christensen. In this paper, the approach for obtaining strain amplification matrix which is a key step for the execution of SIFT is improved by adopting representative volume element (RVE) finite element models considering periodical boundary condition, based on which more actual deformation mode is reflected. The deformation modes and strain data at the characteristic points of the centroid cell of multi-cell RVE model are analyzed and taken as a reference. It can be concluded that more reasonable deformation mode and relationship between the micro-mechanical and macro-mechanical strain states are obtained by employing the new model. Finally, numerical examples are provided to illustrate the determination of strain amplification factors within the RVEs considering periodical boundary condition at the characteristic points.     

CT reconstruction with priori MRI images through multi-group datasets expansion

Computed tomography (CT) reconstruction with a well-registered priori magnetic resonance imaging (MRI) image can improve reconstruction results with low-dose CT, because well-registered CT and MRI images have similar structures. However, in clinical settings, the CT image of patients does not always match the priori MRI image because of breathing and movement of patients during CT scanning. To improve the image quality in this case, multi-group datasets expansion is proposed in this paper. In our method, multi-group CT-MRI datasets are formed by expanding CT-MRI datasets. These expanded datasets can also be used by most existing CT-MRI algorithms and improve the reconstructed image quality when the CT image of a patient is not registered with the priori MRI image. In the experiments, we evaluate the performance of the algorithm by using multi-group CT-MRI datasets in several unregistered situations. Experiments show that when the CT and priori MRI images are not registered, the reconstruction results of using multi-group dataset expansion are better than those obtained without using the expansion.     

预应力混凝土梁超载能力分析

为了验证利用有限元法分析预应力混凝土梁极限承载能力的准确性,对T形预应力混凝土模型梁进行了极限承载力加载破坏试验,采用ANSYS有限元程序,建立了T梁的分离式有限元模型,分析了模型梁从加载到破坏全过程的受力和变形。发现利用实验与有限元法得到T梁的荷载-挠度曲线与荷载-应变曲线的变化趋势一致,并呈现良好的非线性,但是通过荷载试验得到T梁的超载能力为9.07 kN.m,按照有限元分析得到的超载能力为12.48 kN.m,偏差较大,原因是分析模型偏于理想化。分析结果表明:利用有限元法在总体上能够有效地模拟钢筋混凝土梁受力全过程中各个量的非线性变化,对超载能力的求解是可行的。     

新能源公交车辆大数据决策支持平台的研究

新能源汽车具有能源利用效率高、环境污染小、适用清洁能源种类多、噪声低、方便保养、安全性高等优点,成为未来公共交通发展的重点方向。为了实现更高的信息化程度,为国内大型城市的新能源公交车辆的规模化应用提供便利,相关的信息化系统平台的建设非常重要。大数据技术为新能源公交车辆决策支持平台建立了数据分析与应用基础,该大数据决策支持平台能够存储、处理来自不同数据源的多维数据,利用联机分析处理实现多维度数据分析,运用数据挖掘技术利用新能源公交车辆信息,提供新能源车辆充电决策、充电场地建设决策、电池容量及衰退分析等功能。     

轿车车内空腔声学模态试验研究

利用比利时Lms公司的Test_lab模态分析系统测量了某轿车车内空腔声学模态,采用Spectral Ac-quisition模块测量了声传递函数,用PolyMAX(最小二乘复频域法)分析方法进行了模态参数的识别。通过试验分析获得了该轿车车内空腔共鸣频率和三维模态形状。该方法为控制和降低轿车车内低频噪声提供了参考,为轿车车内空腔声学模态提供了简单易行的测试方法。     

天津市滨海新区市政建设简介

该文介绍了天津市滨海新区市政建设的基本情况及建设方案。     

变速比转向器齿轮副的机理分析

本文运用啮合原理分析方法给出了变速比转向器齿条齿扇传动的啮合线方程、齿扇的齿廓方程,导出了锥形齿扇被切削时小端不根切、大端不尖的变位系数和齿扇几何尺寸计算公式。     

水库蓄水后对既有傍山铁路隧道运营安全的影响研究

针对水库蓄水后将对既有傍山铁路隧道的运营安全产生影响的问题,文章通过数值方法,分析了横江干流盐津-杨柳滩五级水库对内昆铁路水(富)-盐(津)段麻石山隧道安全性的影响,对比了水库蓄水前后隧道二次衬砌内力、安全系数的变化规律,给出了隧道结构需要加固或防护的依据,对今后的水库建设有指导作用.     

与液压间隙调节器有关的参数变化对气门机构动力学计算结果的影响

通过模拟计算考察了在有液压间隙调节器的气门机构中,柱塞—柱塞套间隙、机油温度、供油压力以及高压腔机油内混气变化对有直动式HLA的某气门机构的动力学特性的影响。结果表明,柱塞—柱塞套间隙、机油温度和压力变化对模拟计算结果影响很小;凸轮轴低转速时,柱塞—柱塞套间隙、机油温度对计算结果的影响比高转速时略大些;HLA高压腔机油混气对气门机构动力学计算结果有很大影响。     

成都市火车南站斜拉桥的应力监测

通过对预应力混凝土斜拉桥的应力监测分析 ,认为混凝土在加载龄期较早时的收缩徐变较大 ,直接用所测得的钢筋应力通过弹模比法换算求得的混凝土应力值与理论值相差较大。本文提出的在加载龄期较早情况下 ,考虑混凝土的收缩徐变引起的钢筋和混凝土之间的应力重分布 ,通过静力平衡和变形协调条件 ,由实测钢筋应力推得的混凝土应力与理论计算值吻合较好 ,相应的收缩徐变总量与规范计算值较接近。本文方法在成都市火车南站斜拉桥监控中取得了比较满意的结果