Property of corroded concrete under compressive uniaxial loads

In order to study the compressive property of corroded concrete, accelerated corrosion test were performed on concrete C30.6 corrosive solutions, including hydraulic acid solution （pH=2）, hydraulic acid solution （pH=3） were applied as the corrosive medium. 6 series of corrosion tests, including 111 specimens, were carried out. Mechanical properties of all the corroded specimens were tested respectively. Compressive properties of the corroded specimens （e.g. compressive strength, stress-strain relation, elastic modulus etc.） were achieved. Taking the strength degradation ratio and strain energy loss as damage index, effects of the corrosion solution on the compressive property of corroded concrete were discussed in detail. Relationship between the damage index and corrosion state of specimens were achieved.     

双向等比例加载下的混凝土动态抗压性能

为了研究混凝土试件在多轴受力、不同应力途径下的动态力学性能,采用大型静动态电液伺服试验系统,对混凝土试件进行双轴应力状态下等比例加载的动态抗压试验.双轴加载比例为1∶0、1∶05、1∶1,应变速率分别为10^-5/s、10^-4/s、10^-3/s、10^-2/s 4个量级.通过试验,研究了在不同应变速率、不同应力比情况下,混凝土抗压强度、弹性模量、峰值应变、应力应变曲线的性能.试验结果表明,随着应变速率的提高,各种应力比下混凝土的抗压强度、弹性模量均有提高.在相同应变速率下,与单轴动态受压相比,1∶0.5的应力比其抗压强度提高幅度大.     

Bonding strength in carbon steel sandwich panels under condition of diffusion-rolling with small reduction

One of the key problems by diffusion-rolling bonding with small reduction for carbon steel plates is the bonding assistant coat. Abonding assitant coat used below 850℃ was developed. It contained copper as basic element and zinc as main alloy element. Other small elements and rear metals were added to decrease the melting point and to obtain a better clouding and bigh plasticity. Based on the theory of brazing and transient liquid diffusion welding, two carbon steel plates were rolled with small reduction by using self-made bonding assistant coat. Temperature, pressure and holding time are the main technology parameters for controlling the process of diffusion-rolling. The results show that the bonding strength is the greatest when the bonding temperature is 830℃, holding time is 3 min and the reduction rate is 9%.     

偏高岭土高性能混凝土的轴压应力-应变关系

采用美国产MTS试验机,研究了掺偏高岭土(Melakaolin,MK)的混凝土轴压应力-应变关系．试验结果表明,随着MK掺量的增加,混凝土的抗压强度随之提高,特别是早期强度提高更为显著．弹性模量略有提高,但幅度明显小于强度提高值．混凝土的韧性得到改善．此外,MK对混凝土的流动性影响较小,且能显著改善粘聚性和保水性．因此,偏高岭土是一种优异的高强高性能混凝土掺合料．     

卫星振动试验中频漂现象分析

对卫星在振动试验中经常发生频率漂移现象产生的原因、机理和危害进行了分析,认为卫星结构的非线性或损伤扩展是频率漂移现象产生的主要原因,并针对卫星结构中常用的蜂窝夹层板进行了非线性动力学参数试验,验证了本文可恢复频漂现象机理分析的正确性.     

Structural-acoustic coupling characteristics of honeycomb sandwich plate based on parameter sensitivity analysis简

The structural-acoustic coupling model for isotropic thin elastic plate was extended to honeycomb sandwich plate （HSP） by applying Green function method. Then an equivalent circuit model of the weakly-strongly coupled system was proposed. Based on that, the estimation formulae of the coupled eigenfrequency were derived. The accuracy of the theoretical predictions was checked against experimental data, with good agreement achieved. Finally, the effects of HSP design parameters on the system coupling degree, the acoustic cavity eigenfrequency, and sound pressure response were analyzed. The results show that mechanical and acoustical characteristics of HSP can be improved by increasing the thickness of face sheet and reducing the mass density of material.     

金属蜂窝夹芯板辐射导热耦合问题

针对金属蜂窝夹芯板,研究了其在气动加热条件下的非稳态传热行为.基于高温传热学原理,通过传热机制分析,建立了蜂窝夹芯板的导热-辐射一维瞬态耦合传热数学物理模型.在此基础上,采用控制容积法,结合蒙特卡罗法,发展形成了求解该类辐射导热耦合传热问题的数值方法,并给出了蜂窝夹芯板当量热导率和典型边界条件下金属蜂窝夹芯板瞬态温度场、非加热面热响应的计算方法,进行了典型算例计算和实验验证.结果表明,所建立的数值计算模型在预报蜂窝结构热响应方面是有效的,而且较之Swann-Pittman半经验关系式,提高了计算精度.     

金属蜂窝结构有效热导率的预报与实验研究

建立了蜂窝夹芯结构有效热导率的数值计算模型,算例表明预报结果与实际值吻合很好.设计并制造了有效热导率的测试设备,对A l蜂窝样件进行了稳态热传导实验测试,结果表明,在平均温度高于150℃时与数值结果的相对误差不超过7%,所建立的分析和实验方法能够实现对蜂窝结构热性能的评价分析.     

含初始缺陷的蜂窝夹芯板疲劳行为

借助四点弯曲装置,对含有初始芯面脱焊缺陷的钢质蜂窝夹芯板开展了室温疲劳行为研究.载荷比为0.20,载荷水平在15％ ～90％.通过考虑不同脱焊尺寸研究该类结构的失效,得到疲劳寿命S-N曲线和疲劳极限.利用曲线拟合和外推技术,得到疲劳阈值为105次不发生破坏的临界缺陷尺寸为7.04 mm.失效模式分析表明:当芯子和面层脱焊缺陷尺寸为30 ～40 mm时,较易发生脱焊区的整体横向断裂;缺陷尺寸为15 ～20 mm时,主要以脱焊尖端的蜂窝芯壁撕裂和坍塌为主.     

勾缝加固砖砌体墙的抗压性能试验

为研究勾缝加固方法对砌体墙抗压性能的影响及加固效果,根据不同勾缝深度和加固砂浆强度,设计12个勾缝加固砌体构件和3个未加固构件,并对其进行了轴压试验,分析了勾缝深度和加固砂浆强度对加固砌体墙的开裂荷载、破坏荷载、应力-应变曲线和弹性模量的影响.试验及分析结果表明,相比未加固构件,勾缝加固构件的破坏形态和破坏过程相似,但其开裂荷载降低,而破坏荷载和弹性模量提高,提高的幅度与勾缝深度、加固砂浆强度有关,最大达到30%.根据试验数据和理论分析,基于砌体结构设计规范中的公式,提出了考虑勾缝深度和加固砂浆强度影响的勾缝加固砌体墙的抗压强度、应力-应变曲线和弹性模量的计算公式,且公式的计算结果与试验结果吻合较好.因此,勾缝方法可以用于砌体墙的加固,特别是近现代历史建筑.     

彩钢岩棉夹芯屋面板、墙面板节点性能研究

为了掌握彩钢岩棉夹芯屋面板、墙面板与檩条的螺钉连接节点抗拉破坏机理,采用理论分析、试验验证及有限元模拟相结合的方法研究了不同钢板厚度及芯材厚度时节点破坏情况.分析结果表明:屋面板节点连接破坏是由于钢板局部屈曲引起的,墙面板则是钢板被冲剪破坏造成的,同时,结合对有限元模拟结果的回归,提出了节点承载力设计公式,可为以后节点设计提供参考.增加岩棉刚度及其与侧向钢板的粘结,或增加钢板厚度对提高屋面板节点极限承载力起着重要作用.     

Experimental and theoretical research on residual strength of plain concrete under compressive fatigue loading

To investigate the residual strength of concrete under fatigue loading, experiments were conducted to determine the functional relation between residual strength and the number of cycles. 80 100mm × 100mm × 100mm specimens of plain concrete were tested under uniaxial compressive fatigue loading. Based on probabili- ty distribution of the residual strength of concrete under fatigue loading, the empirical expressions of the residual strength corresponding to the number of cycles were obtained. There is a good correlation between residual strength and residual secant elastic modulus. Thus the relationship between residual secant elastic modulus and the number of cycles is established. A damage variable based on the longitudinal maximum strain is defined, and a good linearity relationship between residual strength and damage is found out.     

Predicting test data of aluminum honeycomb sandwich board based on volterra adaptive filters

Random vibration test was done on aluminum honeycomb sandwich board.The result suggested that chaotic behavior is found in the test data.The Volterra expression can not be gained from the input and output data directly in this paper.The state space reconstruction was used to convert the system observed data into the quasi-input/output pairs,and the second-order Volterra adaptive filter was used to predict the test data.It is shown that combining the state space reconstruction with the Volterra adaptive filter,these chaotic series could be accurately predicted.     

铝蜂窝夹层板模态密度参数实验辨识

模态密度是应用统计能量分析方法研究振动噪声问题的基本参数,对于梁、板等简单结构,模态密度可以通过理论解析获得,但对于复杂结构或者具有复合材料特性的结构的模态密度很难通过理论解析法和数值法获得,或者获得的模态密度值不准确.因此,需要通过实验辨识模态密度.本文采用激励点导纳法对铝蜂窝夹层板进行悬挂振动实验研究.通过对比实验结果与文献资料的经验值发现有良好的吻合性,验证了该方法在新型复合材料领域的适用性.     

早龄期混凝土力学性能试验及其单轴本构模型

为了研究早龄期混凝土的立方体抗压强度、轴心抗压强度、劈裂抗拉强度、静力受压弹性模量以及单轴受压应力应变曲线的规律,进行了系统的加载试验和试验数据分析.总结了早龄期阶段力学指标随龄期的变化规律以及与立方体抗压强度之间的换算关系,通过拟合相关参数,提出了分段式的受压应力应变全曲线拟合公式,拟合结果与试验数据吻合较好.试验结果表明,早龄期C40混凝土的强度和弹性模量随着龄期非线性增长,7 d是增长变化的分界时点;随着龄期的增长,峰值应变减少,脆性变大;早龄期C40混凝土的单轴受压应力应变曲线与充分养护龄期混凝土形状相似.     

双轴受压状态下混凝土动态抗压特性试验研究

由于多轴试验装置的高技术性,混凝土在复杂应力状态下的动力研究相对偏少。为研究双轴受压状态下混凝土的动态抗压特性,采用真三轴静动综合加载试验系统,进行了5种双轴受压状态下混凝土立方体试件的冲击压缩试验,分别从应力-应变曲线特征、强度特性和变形特性等方面分析双轴受压状态对混凝土动力响应的影响规律。结果表明：双轴受压状态下,混凝土承受冲击荷载时呈现典型的脆性破坏,应力-应变曲线初期无明显压实挤密阶段;主轴压比一定时,随单侧压比的增大,混凝土的动态抗压强度呈现出先升高后降低的趋势,峰值应变和平均应变率皆呈现出先减小后增大的趋势;双轴受压对混凝土有加固约束作用,因而提高了其动态抗压强度和抗变形能力,主轴压比：单侧压比为0.4：0.4时作用效果最佳。     

正方形蜂窝纸板面内压缩力学性能仿真分析

采用SolidWorks软件仿真分析结构性能的功能,研究了正方形蜂窝结构面内压缩力学性能。结果表明,当蜂窝厚度一定时,蜂窝边长越大,屈服强度迅速下降;当蜂窝边长一定时,随着蜂窝厚度增加,屈服强度逐渐增加。通过有限元分析方法能有效地降低实际测试费用。     

Experimental study on mechanical behavior of high performance concrete under multi-axial compressive stress

Experimental investigation was conducted to characterize the responses of high performance concrete(HPC) subjected to multiaxial compressive stresses. The HPC specimens were prepared with three different mix proportions, which corresponds to three different uniaxial compressive strengths. The cubic specimens with size of 100 mm for each edge were tested with servo-hydraulic actuators at different stress ratios. The principal stresses and strains of the specimens were recorded, and the failure of the cubic specimens under various stress states was examined. The experimental results indicated that the stress states and stress ratios had significant influence on the strength and deformation of HPC under biaxial and triaxial compression, especially under triaxial compression. Failure criteria were proposed for the HPC specimens under biaxial and triaxial compressive loading. The test results provided a valuable reference for obtaining multi-axial constitutive law for HPC.     

夹芯板弯曲屈曲试验研究

由二个金属面层和泡沫芯层组成的夹芯板，芯层有效地抵抗受压面层的屈曲，而压型槽又增加了面层的抗压强度。但是，当压型金属板受压翼缘较宽时，易于发生局部屈曲，并出现皱折而破坏。对冷弯薄壁型钢压型表面泡沫夹芯板进行弯曲屈曲试验研究，测得了夹芯板受压面层板屈曲时的临界应力、屈曲荷载及屈曲半波长，并与有限条－棱方法计算结果进行了对比，理论值与试验值吻合较好。     

一种确定六边形蜂窝芯材共异面弹性模量的简单有限元法

参照相关实验标准,通过模拟实验载荷条件的方法建立了用来求解六边形蜂窝芯材共异面弹性模量的有限元方法.通过改变参数,利用该方法进行了大量模拟计算.将计算结果与已有理论计算结果进行比较分析,发现两者吻合较好,验证了该有限元模拟方法的正确性.