三峡三级配混凝土轴向拉伸应力-变形全曲线

采用自行组装的轴向拉伸装置成功地测得三峡三级配混凝土轴向拉伸应力变形全曲线 (试件截面尺寸为 2 5 0mm× 2 5 0mm) ,并根据实测资料进行数学拟合 ,建立了形式较为简单、参数求解方便、具有工程实用价值的数学表达式 .

全级配混凝土轴拉应力-变形全曲线试验研究

全级配混凝土拉应力-变形全曲线是大坝非线性反应计算与极限抗震能力分析中的一个重要指标。本文利用先进的全数字化闭环控制大型材料试验机,采用位移控制的加载方式,对最大骨料粒径为150 mm的Ф450 mm×1 300 mm的圆柱体试件进行轴向拉伸试验,研究应变率约为10-7s-1时混凝土试件测距内的受拉变形随拉应力变化的全过程曲线。达到峰值荷载后,在不同的应力水平下对试件进行往复多次加、卸载,研究全级配混凝土软化段加、卸载曲线的特点。拟合全级配混凝土轴拉应力-变形全曲线及加、卸载曲线的计算式,为数值分析中大坝混凝土模型的建立提供可参考的试验依据。

三级配混凝土轴向拉伸应力～变形全曲线的试验研究

通过对三级配混凝土轴向拉伸应力～变形全曲线的试验研究,提出了可以推广应用于全级配混凝土相应试验研究的加载装置和加荷方式.

全级配混凝土轴向拉伸应力-变形全曲线试验研究

混凝土受力破坏过程中的应力-变形全曲线能够宏观地反映混凝土在各个受力阶段的变形、内部微裂缝的发展、损伤积累、最终破坏等一系列过程,同时又是分析和计算混凝土构件承载力和变形的重要参数,因而备受研究者们的重视。但由于受试验条件的限制,国内外对混凝土轴向拉伸全曲线的研究,目前一般限于截面为25cm×25cm及以下尺寸,对大尺寸、全级配混凝土试件的轴向拉伸应力-变形全曲线的试验研究资料还很有限。本文利用自行研制的试验装置,以锦屏拱坝为背景,成功地进行了两组尺寸为450 mm×450 mm×1350mm的全级配混凝土轴向拉伸应力-变形全曲线的测试,根据试验结果拟合出混凝土轴拉应力-变形全曲线经验公式。有关成果可供大坝安全评价和设计部门参考。

水平井封隔器卡瓦的有限元分析及结构改进

在石油钻采中,封隔器卡瓦承受巨大压力易发生断裂,直接影响到封隔器的密封性能,从而影响油井的开采过程及生产安全。运用有限元分析软件ANSYS Workbench对卡瓦进行有限元数值模拟分析。施加140 kN载荷时,卡瓦最大应力为230.11 MPa,超过其材料的最大抗压强度;对卡瓦封隔器试验模型进行压裂试验,试验施加压力为186.33 kN时卡瓦发生断裂,测得抗压强度为233 MPa;对卡瓦进行结构设计,卡瓦牙间距尺寸分别为15 mm、25 mm和30 mm。根据有限元分析结果,卡瓦牙间距为30 mm时卡瓦应力、应变分布趋于均匀,所承受的最大载荷为240 kN,最大应力为230.66 MPa、最大变形量为0.058mm,证明此卡瓦结构尺寸较为合理。

聚丙烯纤维混凝土直接拉伸性能的试验研究

重点研究聚丙烯纤维增强混凝土在单轴直接拉伸荷载下的力学性能和纤维混凝土的单轴拉伸应力变形全曲线。提出单轴拉伸相对应力裂缝宽度曲线的理论方程式。由单轴拉伸全曲线得到了纤维混凝土的应力裂缝宽度曲线、断裂能及特征长度等。试验发现:当纤维体积掺量为0 14%时,纤维混凝土的轴心抗拉强度比基准混凝土提高20%,极限拉伸应变提高49%,断裂能提高68%,临界断裂时的最大裂缝宽度增加55%。聚丙烯纤维具有良好的阻裂性能,增强了硬化混凝土的能量吸收能力。

人工骨料全级配大坝混凝土的拉压力学性能

用大尺寸试件试验研究了全级配大坝混凝土在单轴拉伸与压缩荷载下的力学性能,并研究了龄期对混凝土性能的影响,给出了单轴拉伸和压缩的应力-应变全曲线及相对拉应力与相对裂缝宽度曲线。试验发现,龄期增加,混凝土的强度、弹性模量及断裂能提高,龄期对极限应变和最大裂缝宽度的影响不明显。双曲线方程可以用于表述混凝土强度、弹性模量及断裂能等力学参数与龄期的关系。

高速铁路轨道-路基列车移动荷载模拟的全比尺加速加载试验

介绍了一种全比尺的高速铁路加速试验装置,以重现轮轴移动荷载下轨道路基的动力响应和长期性能。根据列车移动过程中扣件承受荷载的模拟要求,提出高速铁路路基加速试验的设计准则。在此基础上自行建造完成时序式动力加载系统,由8个动态液压激振器、1套控制系统和1套反力框架构成,在室内实现最高速度360km/h列车移动荷载的有效模拟。同时在室内建设完成1∶1比尺的I型板式轨道-路基模型,通过控制填料级配、目标密度和目标含水量来保证路基的压实系数、地基系数和变形模量等指标满足规范的设计要求。前期试验表明,随着列车荷载的逐层传递,其叠加效应愈加显著。轨道结构荷载峰值对应列车轮轴,路基动土压力峰值对应列车转向架。路基横断面方向,基床顶面的动土压力呈马鞍形分布,两侧应力最大,轨道中心应力最小;地基顶面的动应力分布较为均匀。路基土体应力-变形呈现出明显的滞回特征,从长期加载过程看,土体残余变形逐渐累积,表现出明显的塑性特征;但对于每一次加卸载过程,土体的应力-应变可近似为非线性弹性行为。

Hot deformation behavior and constitutive relationship of Q420qE steel

Isothermal compression tests at temperatures from 1 273 to l 423 K and strain rates from 0.1 to 10 s-q were carried out to investigate the flow behaviors of Q420qE steel. Stress-strain data collected from the tests were employed to establish the constitutive equation, in which the influence of strain was incorporated by considering the effect of strain on material constants Q, n, a, and lnA. The results show that the flow stress curves are dependent on the strain, strain rate and deformation temperature. They display typical dynamic recrystallization behavior and consist of three stages, i.e., hardening stage, softening stage and steady stage. The flow stress decreases with increasing the deformation temperature and decreasing the strain rate. In addition, the flow stress data predicted by the proposed constitutive model agree well with the corresponding experimental results, and the correlation coefficient and the average absolute relative error between them are 0.990 3 and 3.686%, respectively.

耐碱玻璃纤维混凝土的单轴拉伸特性研究

试验研究了耐碱玻璃纤维混凝土的单轴拉伸力学特性,研究了纤维掺量对混凝土单轴拉伸力学性能的影响规律。测定了耐碱玻璃纤维混凝土的拉伸应力-变形全曲线,由全曲线得到了纤维混凝土的抗拉强度、弹性模量、最大拉应变及断裂能等力学指标。试验发现:耐碱玻璃纤维掺量为1.6、2.0、2.7kg/m3时,纤维混凝土的抗拉强度比基准混凝土分别提高了5.6%、9.0%和14.5%,最大拉应变分别提高了19.5%、18.9%和41.9%,断裂能分别提高了33.7%、51.1%、69.2%。结论表明耐碱玻璃纤维对硬化混凝土具有一定阻裂增韧作用。

Humidification vibration deformation behavior of intact loess

A parameter, known as the parameter of humidification vibration deformation, was proposed, describing quantitatively the impact of water content on vibration settlement deformation, and its relationship with humidification water content, dynamic shear stress peak value, initial consolidation stress and vibration frequency was built. The result shows that 1） the parameter of humidification vibration deformation increases with the vibration shear stress peak value increasing. 2） The humidification water content has significant influence on the curve of the parameter of humidification vibration deformation and the peak vibration shear stress. When the humidification water content is low, the curve increases slowly. However, when the humidification water content is high, the curve increases rapidly. 3） Initial consolidation stress has significant influence on the humidification vibration deformation coefficient. When initial consolidation stress is not large enough to destroy the loess structure, with initial consolidation stress increasing, the humidification vibration deformation coefficient decreases. On the contrary, the humidification vibration deformation coefficient increases with initial consolidation stress increasing. 4） With the increase of vibration time, the parameter of humidification vibration settlement shows an increasing trend overall. The initial dynamic shear stress peak value and humidification water content all have significant effects on the curve of the parameter of humidification vibration settlement and vibration time. However, the humidification water content is even more significant.

High temperature stress–strain curves of MnS and their applications in finite element simulation

A novel method for testing stress–strain curves of non-metallic materials was presented.The high temperature stress-strain curves of MnS were preliminarily obtained and corrected to account for the influence of friction.Using the finite element method,the influence of deformation parameters on the deformation evolution of MnS inclusions was investigated based on the experimental reference data.The corresponding physical experiment was designed for comparative analysis.The results indicate that the experimental high-temperature deformation data of MnS are highly reliable.In the process of matrix deformation,the shapes of MnS inclusions change from spherical to ellipsoidal and even to lamellar.There are some differences in the morphological deformation of MnS inclusions located at different positions.With the increase in the initial size of MnS inclusions,the risk of failing the inclusion-flaw inspection increases and the forging quality further deteriorates.

煤沥青碳纤维增强混凝土的性能研究

本文对煤沥青碳纤维增强混凝土的抗弯冲击性能和轴拉性能进行了试验研究。随着纤维掺量的增加,混凝土冲击性能显著提高,纤维体积掺量为0.076%时,改性煤沥青碳纤维混凝土的初裂冲击次数、破坏冲击次数分别比素混凝土提高1458%、1462%;当掺量大于0.076%时,冲击韧性不再明显提高。当纤维体积掺量为0.1%时,纤维混凝土的抗拉强度比基准混凝土提高11%,极限拉伸应变提高24%,断裂能提高47.8%。试验证明,碳纤维具有良好的阻裂性能,可增强硬化混凝土的抗裂性能。

碳纤维增强混凝土的单轴拉伸特性

试验研究了碳纤维增强混凝土在单轴拉伸荷载下的力学性能。试验发现:当纤维体积掺量为0.1%时,纤维混凝土的抗拉强度比基准混凝土提高11%,极限拉伸应变提高24%,断裂能提高47.8%。纤维混凝土特征长度增加,即纤维混凝土脆性降低。试验证明:碳纤维具有良好的阻裂性能,增强了硬化混凝土的抗裂性能。

Hot deformation behaviour and processing maps of AA6061-10 vol. % SiC composite prepared by spark plasma sintering

AA6061-10 vol.% SiC composite was successfully prepared by spark plasma sintering. The deformation behaviour of this composite was studied using the uniaxial compression test, which was conducted at temperatures between 300 and 500℃ and strain rates between 0.001 and 1 s^-1. Results indicate that the stress-strain curves of the AA6061-10 vol.% SiC composite typically feature dynamic recrystallization. The steady stress can be described by a hyperbolic sine constitutive equation, and the activation energy of the composite is 230.88 kJ/mol. The processing map was established according to the dynamic materials model. The optimum hot deformation temperature is 450-500℃ and the strain rate is 1-0.1 s^-1. The instability zones of flow behaviour can also be identified using the processing map.

A new method to determine the elastoplastic properties of ductile materials by conical indentation

Based on load-displacement curves,indentation is widely used to extract the elastoplastic properties of materials.It is generally believed that such a measure is non-unique and a full stress-strain curve cannot be obtained using plural sharp and deep spherical indenters.In this paper we show that by introducing an additional dimensionless function of A/A (the ratio of residual area to the area of an indenter profile) in the reverse analysis,the elastoplastic properties of several unknown materials that exhibit visually indistinguishable load-displacement curves can be uniquely determined with a sharp indentation.