基于实验的钢筋混凝土梁受弯变形分析

通过对钢筋混凝土简支梁进行加载,测试梁纯弯曲段不同高度处的混凝土应变、梁底部钢筋应变以及梁的挠度值。研究分析了混凝土应变随荷载变化过程中,混凝土梁中性轴变化规律。根据实测应变结果,计算不同荷载等级下梁的弯曲曲率,推导出梁的挠度。分析结果表明:通过应变推导出的梁挠度随荷载变化规律与实验测试规律一致,计算结果精度较高。     

耐火材料高温弯曲应力-应变关系测试方法及影响因素

介绍了耐火材料弯曲应力-应变测试仪的基本构成以及对试验炉、加荷装置、变形量测量装置和计算机控制系统等各构件的要求;重点介绍了使用该仪器研究耐火材料应力-应变关系的方法以及影响测试结果的相关的因素。该方法可以用来研究耐火材料在高温下承受弯曲应力时的变形问题,确定耐火材料在各温度下的应力-应变关系,测试和判断耐火材料的弹性、塑性和粘滞流动的温度范围,并根据应力-应变关系计算耐火材料在不同温度下的弹性模量。     

玻璃钢/混凝土梁试验研究

本文介绍了对玻璃钢/混凝土复合梁进行的基本力学性能测试工作,论述了在弯曲应力作用下,复合梁正截面的应力分布、受力变化过程、弯曲挠度分布规律及破坏机理。说明在混凝土表面包覆玻璃钢的方法是提高混凝土结构抗弯能力的合理途径。     

基于石油射孔电机驱动方式的定方位方法与性能测试研究

本文依据油气井用定方位射孔技术使用原理,设计开发出一种电机驱动方式的定方位性能测试方法,并设计出试验装置,该试验装置可测试常温、高温环境下电机旋转弹架性能测试,为石油射孔驱动弹架定方位的装置提供一套新型测试方法与试验装置,经过测试试验,该装置满足性能测试要求。     

高速铣削加工切削参数的优化选择

基于数控机床动力学测试分析和仿真系统,利用X-cut软件获取加工时的切削稳定域,确定加工参数的范围,再依据弯曲应力和挠度变形理论筛选切削参数,进一步缩小实验参数范围。最终经实验得到合适的切削参数,切削后经三坐标测量,零件满足设计尺寸要求和表面粗糙度要求,从而验证了软件优化参数的合理性和有效性。     

小冲杆蠕变试验微试样的应变分析

在假设以弹塑性薄膜变形分析所获得的试样中心挠度与非蠕变中心应变之间的关系近似等于蠕变时试样中心挠度与中心蠕变应变之间的关系的基础上 ,使用塑性薄膜伸张变形模型模拟小冲杆试样的蠕变变形过程 ,设计了以小冲杆试验实测中心挠度数据估算试样中心蠕变应变以至材料蠕变性能的方法 ,并具体推导得到了特定小冲杆试验装置和试样尺寸对应的蠕变应变工程估算方程     

小冲杆蠕变试样中心挠度-蠕变应变关系的有限元分析

利用有限元数值方法分析了小冲杆试样中心挠度δ与中心蠕变应变ε之间的关系 ,指出该δ ε关系与蠕变时间、载荷大小和材料性能等条件均无关。计算结果还表明 ,在薄膜变形分析的基础上 ,非蠕变条件下试样中心挠度 中心弹塑性应变函数关系和蠕变状态下试样中心挠度 中心蠕变应变函数关系等价     

内定向斜井定方位定射角射孔技术用可测量方位的自旋转起爆装置研究与应用

本文针对油田中后期薄层井、剩余油井、油水同层等复杂井开采常使用的定方位定射角射孔技术测量方位问题,设计开发出自旋转起爆装置,该装置通过旋转起爆机构与内定向斜井定方位定射角射孔器弹架相连,采用重力自定向技术,弹架与旋转起爆机构在射孔枪内自由旋转,通过陀螺仪测试旋转起爆机构中方位键的方位,测量整支弹架的方位。通过对比试验验证,自旋转起爆装置能够满足定方位定射角射孔技术中的方位测量要求,为内定向斜井定方位定射角射孔技术提供一套可测量方位的自旋转起爆装置。     

异形压力管道的应力分析及评价

以有限元法和分析设计准则为基础,分析了某异形压力管道复杂的应力分布情况。针对有限元计算的准确性问题,通过应变测试与有限元计算相比较的方法研究了该压力管道在0.43和0.55 MPa压力下一些特殊部位的应力强度,发现有限元结果与实际应变测试一致。研究表明该异形压力管道在0.8 MPa内压下时,虽然在三角区肋板尖端处的薄膜应力和弯曲应力较大,但均在JB4732-1995《钢制压力容器-分析设计标准》允许范围内,对管道运行基本没有影响,及能保证其安全稳定的运行。     

不同应变率下聚甲醛纤维机场道面混凝土弯曲性能研究

机场道面混凝土结构在不同性质荷载作用下的力学行为受应变率的影响较大。为研究应变率对聚甲醛纤维机场道面混凝土(PFAPC)弯曲性能的影响,通过四点弯曲试验,分析不同应变率(10^-5～10^-1 s^-1)下PFAPC抗弯挠度、弯曲模量、弯曲强度及韧性指数的变化规律,并观察断口纤维的微观形貌,总结不同应变率下的纤维失效模式。结果表明：PFAPC的弯曲峰值强度、极限抗弯挠度及弯曲模量随应变率的增加呈上升趋势;与峰值强度相比,应变率对PFAPC残余强度影响较小,但随应变率增大总体呈上升趋势;与极限抗弯挠度相比,峰值挠度随应变率的增加波动上升;聚甲醛纤维在各应变率作用下主要为拔出破坏模式;PFAPC在车辆及飞机冲击作用下能吸收较大能量,呈现出一定的延性破坏特征,具有良好的弯曲韧性。     

The onset of cracking and ductility of steel fiber concrete

The influence of steel fiber reinforcement on the onset of cracking, ductility and energy absorption capacity in flexure is reported. The automatic load-deflection curve predicts a consistently higher load for the onset of cracking than those obtained from strain, pulse velocity and deflection measurements. Fiber reinforcement increases the onset of flexural cracking. However, there is a minimum fiber volume below which only the onset of cracking is increased without any increase in the ultimate flexural strength. The most significant role of fiber reinforcement lies in increasing the post-cracking properties of ductility, tensile strain capability and energy absorption capacity. The increase in flexural modulus is nominal but the resulting crack control and strain capability can be used in design to enhance the serviceability behavior of conventional structural members by the provision of a fiber tensile skin.     

Preparation and characterization of modified starch‐based plastic film reinforced with short pulp fiber. II. Mechanical properties

Native corn starch‐ and hydroxypropylated starch (HPS‐) based plastic films were prepared using the short pulp fiber as the reinforcement and the glycerol as the plasticizer. The results of tensile test showed that the strain and stress at break and elastic modulus increased with pulp content. With glycerol content, the strain at break increased considerably, but the breaking stress and elastic modulus decreased. And the stress–strain curves showed that the brittleness problem of films was overcome by the pulp, glycerol, and water content. The hydroxypropyl starch films showed results similar to those of the native starch films. The results of the three‐point bending test showed that maximum deflection, flexural strength, and specific work increased with pulp content, but the flexural modulus was the highest at a pulp content of 20%. And with the glycerol content, the maximum deflection and specific work of rupture increased, but the bending elastic modulus decreased. The hydroxypropyl starch films showed results similar to those of native starch films as far as the maximum deflection and flexural strength were concerned, but the bending elastic modulus and specific work of the hydroxypropyl starch films were considerably lower than those of starch films. So it was concluded that the flexibility of films was improved by the hydroxypropylation. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2108–2117, 2003     

BFRP筋再生混凝土梁抗弯性能试验研究

通过7根玄武岩纤维(BFRP)筋再生混凝土梁和1根钢筋再生混凝土梁的抗弯性能试验,研究了不同纵筋配筋率与再生骨料取代率对BFRP筋再生混凝土梁受弯性能的影响,分析其承载力变化过程、破坏形态、挠度变形与裂缝发展情况,并与钢筋再生混凝土梁进行对比。结果表明,BFRP筋再生混凝土梁的破坏形式有少筋和超筋破坏两种,分别由BFRP筋拉断和受压区再生混凝土压碎控制。合理配筋的BFRP筋再生混凝土梁破坏前产生的挠度较大,且受拉BFRP筋的应变也较大,说明合理配筋的BRPP筋再生混凝土梁具有一定的延性,能较好地发挥两种材料的性能。BFRP筋再生混凝土梁的裂缝宽度和裂缝条数受再生骨料取代率影响较小,而受配筋率影响较大。此外,BFRP筋再生混凝土梁的初裂荷载相比钢筋再生混凝土梁略低,但极限荷载却有明显提高。     

Self-sensing of flexural damage and strain in carbon fiber reinforced cement and effect of embedded steel reinforcing bars

Self-sensing of flexural damage and strain in carbon fiber reinforced cement is attained by measuring the volume or surface resistance with the four-probe method and electrical contacts on the compression and/or tension surfaces. The oblique resistance (volume resistance in a direction between the longitudinal and through-thickness directions) increases upon loading and is a good indicator of damage and strain in combination. The surface resistance on the compression side decreases upon loading and is a good indicator of strain. The surface resistance on the tension side increases upon loading and is a good indicator of damage. The effectiveness for the self-sensing of flexural strain in carbon fiber reinforced cement is enhanced by the presence of embedded steel rebars on the tension side. For the same midspan deflection, the fractional change in surface electrical resistance is increased in magnitude, whether the surface resistance is that of the tension side or the compression side. The fractional change in resistance of the tension surface is increased by 40%, while the magnitude of the fractional change in resistance of the compression surface is increased by 70%, due to the steel.     

粉煤灰掺量对PVA-ECC性能的影响

采用粉煤灰替代部分水泥(40%、50%、60%和70%(质量分数))进行聚乙烯醇纤维增强水泥基复合材料(PVA-ECC)的力学性能、韧性、抗渗性能研究;建立了PVA-ECC抗压强度与其极限拉伸强度、弯曲荷载、弯曲韧性指数、挠度及抗渗性能之间的相关性;同时还进行了PVA-ECC渗水高度的统计数据概率分布分析。结果表明,随粉煤灰含量增加,强度逐渐下降,极限拉伸应变逐渐增大,韧性指数、能量吸收能力及跨中挠度逐渐增大,各组别抗渗性能相对于粉煤灰40%含量组别均有所提升。建立抗压强度与其余指标之间相关性,得到一套完整的强度、韧性、抗渗性的相关性理论体系。对PVA-ECC的渗水高度的频率分布直方图采用正态分布进行统计分析,得到渗水高度概率分布,同时计算出平均渗水高度95％置信区间。     

CFRP加固初始受载钢筋砼梁弯曲性能的试验研究

在对一组采用CFRP进行抗弯加固的初始受载钢筋混凝土梁土梁试验的基础上。研究了这些梁的裂纹扩展。载荷-挠度曲线。纵向钢筋和碳纤维布的应变，破坏载荷和破坏特征。     

Flexural behavior of fiber and nanoparticle reinforced concrete at high temperatures

In this study, the flexural tests were conducted to investigate the effects of temperature, steel fiber, nano‐SiO₂, and nano‐CaCO₃ on flexural behavior of concrete at high temperatures. The load‐deflection curves of fiber and nanoparticle reinforced concrete (FNRC) were measured both at room and high temperatures. Test results show that the load‐deflection curves become flatter, and the flexural strength, peak deflection, and energy absorption capacity decrease seriously with the increase of temperature. Both steel fiber and nanoparticles could significantly improve the flexural behavior of the concrete at room and high temperatures. The energy absorption capacity of FNRC before the peak point increases with the increase of steel fiber volume fraction. The improvement of nano‐SiO₂ on flexural strength of FNRC at high temperature is better than that at room temperature, but the enhancement on energy absorption capacity is reverse. Nano‐SiO₂ is more effective than nano‐CaCO₃ in improving flexural behavior of concrete both at room and high temperatures.     

超高性能轻质混凝土的弯曲性能研究

本文主要以漂珠作为轻集料,制备出密度在1700-1950kg/m~3的超高性能轻质混凝土(Ultra High Performance Light-weight Concrete,简称UHPLC),对其进行四点弯曲试验,并根据ASTM C1609标准研究其弯曲性能。研究表明:密度范围在1700~1950kg/m~3的UHPLC,其抗压强度在78.8~114.2MPa;2%体积率钢纤维掺量的UHPLC在开裂后有明显的挠度硬化行为,表现出优异的抗弯性能;根据ASTM C1609测试指标,随着密度的增加,UHPLC的初裂强度、0.5mm挠度下的残余强度、2mm挠度下的残余强度、峰值强度、弯曲韧性均增加;U1900抗压强度、抗弯强度比抗弯强度分别为114.2MPa、22.4MPa、11.7k Pa/kg·m-3,其抗弯性能可达国家标准《活性粉末混凝土》RPC160水平,比抗弯强度超过RPC最高等级RPC180。     

梁压区边缘设置碳纤维板抗弯承载力试验研究

对2根受压区设置CFRP板的钢筋混凝土适筋梁进行静载四点弯曲试验,分别为在受压区设置一层CFRP板和二层CFRP板.实测轴向荷载-挠度关系曲线,分析加固梁的受压破坏形式、受压区设置CFRP板对适筋梁抗弯承载力、挠度以及应变的影响规律,同时进行1根普通钢筋混凝土适筋梁的静载试验,与受压区设置CFRP板的适筋梁进行比较,最后验证CFRP板加固混凝土构件应考虑CFRP板受压性能对构件承载力的提高作用,并推导出受拉面和受压面粘贴CFRP板加固的矩形截面受弯构件的正截面承载力计算公式.     

Deflection behaviors of polymer mortar sandwich panels reinforced with GFRP

This study prepared sandwich panel specimens composed of methyl methacrylate (MMA)‐modified polymer mortar at the core and reinforced with high‐tensile GFRP on both faces to propose a method to predict the deflection of polymer mortar sandwich panels under flexural load. Nine experimental specimens of different thickness at the core and face were prepared for the flexural load test to determine the moment‐deflection relationship, and the experimental results were compared with existing theoretical models. The comparison study revealed that the deflection behavior of the specimens in response to the variation in the thickness of the specimens at the core and face could be well predicted. Additionally, an analytical model, which revised a bilinear method, to explain the tension stiffening effect of the prepared sandwich panel specimens under the influence of flexural load is proposed. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008