拉伸试验中测量的不确定度评定

介绍拉伸试验中测量结果的不确定度评定方法。依据测量不确定度的七个评定步骤，按不同的试样形状、尺寸，试验人员、尺寸测量器具、试验机等级、引伸计等级、拉伸速度等影响因素分别给出拉伸试验中的强度指标RP、ReH、ReL、Rt、Rm，与塑性指标A、Z测量结果的不确定度评定。此次给出的拉伸试验中测量结果的不确定度评定适用于本部门拉伸试验，可按试验时所用的试样形状、尺寸、测量器具、试验机、引伸计等条件选用不确定度的评定结果。     

金属材料拉伸试验结果测量不确定度评定研究

为评定金属材料拉伸试验的结果测量不确定度 ,以轧制厚度为 18mm的Q2 3 5B板材矩形带头短比例试样为例 ,建立了不确定度计算的数学模型 ,确定了影响试验结果 (ReL、Rm)的下屈服力FSL、最大力Fm、试样原始厚度a及试样原始宽度b等各项因素 ,计算出了各种因素的标准不确定度 ,得出拉伸试验结果 (ReL、Rm)的扩展不确定度 ,并给出最终测量结果的表达式 :下屈服强度ReL、抗拉强度Rm的最终测量结果分别为 (3 0 5± 5 )MPa和 (4 3 5± 10 )MPa。     

拉伸试验测量不确定度的研究

分析了拉伸试验中抗拉强度Rm的影响因素，对测量不确定度的主要分量进行量化，评定了Rm的相对测量不确定度，作为生产检验中评定测量不确定度的尝试，以便为用户提供钢材性能测量结果的不确定度。     

抗拉强度不确定度的评定与分析

通过使用不同量具测量同一组拉伸样品尺寸进行拉伸试验,对抗拉强度进行了不确定度评定,对各不确定度量进行了分析.     

电工圆铜线抗拉强度的测量不确定度评定研究

阐述测量不确定度的来源、定义及其评定的重要意义。对TY-3．0电工圆铜线的抗拉强度测量不确定度进行分析和评定,计算出各种因素的标准不确定度,得出抗拉强度的扩展不确定度,并给出最终测量结果的表达式。     

对钢板拉伸性能指标的测量不确定度评定方法的新认识

抗拉强度、屈服强度是钢板产品最重要的质量指标,用户验收时通常会自行取样做拉伸试验,对相关的力学性能指标进行验证;从以往的情况看,往往有一些用户和个别第三方实验室出现验收结果与出厂检验结果不一致的问题.为了判断检测结果的可靠性,并查明出厂检测与用户验收检测的结果不一致的原因,需要对相关性能指标和测量不确定度进行比对分析,而此时能被双方接受的一种可科学方便地对相关检测项目的测量不确定度进行可靠评定的方法是进行比对分析的前提.当前,如何科学合理地进行测量不确定度的评定和应用是各类实验室普遍关心的问题,也是近年来检测质量研究的一个热点,相关的文献报道很多.作者目前所看到的众多文献中,对于拉伸试验结果的测量不确定度评定几乎都是用直接校验的结果结合部分重复测量的数据计算拉伸试验相关检测项目的测量不确定度.而有很多实例证明用直接校验的结果往往不能可靠和全面地对测量不确定度进行评定,这主要有两方面的困难1、有些影响试验结果的因素难以定量;2、另一些影响试验结果的因素在评定不确定度时会被遗漏.为了可靠地对拉伸试验相关检测项目的测量不确定度进行评定,本文借鉴国际硬度试验标准草案中测量不确定度评定的方法,建立起一套以标准物质实测结果为基础的计算屈服强度Rp0.2、抗拉强度Rm和最大力下的总伸长率Agt的测量不确定度的方法.     

拉伸试验各性能指标不确定度的评定

用直径为10mm的45钢拉伸试样，在万能材料试验机上进行拉伸试验，对拉伸试验性能指标屈服强度、抗拉强度、断后伸长率、断面收缩率的测量不确定度进行分析并做出具体评定。     

力学测试中的不确定度评定

本文简要介绍了测量不确定度的基本概念，同时对力学测试中测量不确定度的评定过程和基本方法进行了论述。评定了力学测试中钢材拉伸试验的相对不确定度，验证了实验室日常检测结果的可靠程度。     

拉伸试验中测量不确定度的评定

根据实验室认可要求,对拉伸试验测量不确定度的评定过程和基本方法及试样形状、尺寸、试验人员、尺寸测量器具、试验机的影响因素做了简单的讨论.     

显微维氏硬度测量不确定度评定

对显微维氏硬度测量不确定度进行评定，建立了不确定度计算的数学模型，确定了影响实验结果的各项因素，计算出了各因素的标准不确定度，得出结果的扩展不确定度，并给出最终测量结果的表达式。     

钛管TA2室温拉伸试验测量结果不确定度的评定

钛管TA2因其质量轻且强度高的特点被广泛应用于各行各业。本文主要对金属钛管TA2进行了抗拉强度和断后伸长率的检测,并对这两项拉伸试验结果进行不确定度评定。计算得出的不确定度分项值的大小有助于更好的掌握钛管TA2的力学性能。     

Tensile strain-rate sensitivity of

The tensile strain-rate sensitivity of continuous-tungsten-fiber reinforced niobium composites (W/Nb), fabricated by an arc-spray process, was studied in the 1300 to 1600 K temperature range. The tensile properties of the fiber and matrix components, as well as of the composites, were measured and compared to rule of mixtures (ROM) predictions. The deviation from the ROM was found to depend upon the chemistry of the tungsten alloy fibers, with positive deviations for thoria-dispersed W wire (ST300) reinforced Nb composite(i.e., stronger composite strength than the ROM) and negative or zero deviations for lamp-grade W wire (218) reinforced Nb composite. In addition, it was found that the composites tested at higher crosshead speeds exhibited a strain-rate sensitivity greater than that of the free fibers tested at the same crosshead speeds, even though the composite tensile strength is determined mainly by the fiber component.     

Tensile deformation behavior of high strength anti-seismic steel with multi-phase microstructure

To investigate the tensile deformation behavior of high strength anti-seismic steel with multi-phase micro-structure, tensile tests with strains of 0.05, 0.12 and 0.22 were performed at room temperature.Micro-structure of tested steels was observed by means of optical microscopy (OM), transmission electron mi-croscopy (TEM) and scanning electron microscopy (SEM).Tensile mechanical properties of tested steels were obtained, and the influence of bainite content on deformation behavior was also discussed.Mean-while, the deformation mechanism of steel with three kinds of microstructures of bainite, pearlite and fer-rite was analyzed.Results show that tested steel with high volume fraction of bainite exhibits a continuous deformation behavior, and this may be attributed to a higher bainite volume fraction and a lower mobile dislocation density.The morphology of microstructure will influence the mechanical properties of tested steels.An increasing content of bainite can improve the tensile strength, but reduce the plasticity and toughness of the tested steels.In the deformation process of 0.039Nb steel, the ferrite and bainite have priorities to deform, and the deformation exhibits co-deformation of all microstructures in the later stage of deformation.In the deformation process of 0.024Nb-0.032V steel, the ferrite and pearlite have priori-ties to deform, and the deformation exhibits co-deformation of all microstructures in the later stage of de-formation.     

汽车用高强度IF薄钢板

高强度ＩＦ薄钢板是近年来开发的一种兼有高强度和良好深冲性能的汽车用钢板，它是在ＩＦ钢基础上通过添加适量的固溶强化元素来达到高强度的，总结了这种钢中的合金元素对基板性能及热镀锌镀层的影响，另外还介绍了两种新型的高强度ＩＦ钢，结合宝钢设备的情况，分析了高强度ＩＦ薄钢板开发的可行性。     

Application of Weibull Statistics to the Tensile Strength of Rock Aggregates

Rock aggregates forming part of engineering structures such as embankments, rock fills, pile foundations, and pavements are subjected to static and dynamic loads. As a result of these loads crushing occurs in two different forms: abrasion and particle fragmentation. Particle fragmentation takes place when a particle is subjected to a tensile stress greater than its tensile strength. This tensile strength is a highly variable parameter. The work presented in this study shows that Weibull statistics can be used to characterize the variability in tensile strength of rock aggregates by only using one constant called the Weibull modulus. This parameter can be used not only to describe variability in tensile strength but also to describe the effect of size specimen in tensile strength. The higher the modulus, the lower is the influence of the variability of tensile strength and sample size. More than 390 different specimens coming from a red Biotite Gneiss and a grey Quartzite were tested to validate the use of Weibull statistics. The Weibull modulus was found to be equal to 2.75 and 4.23 for the red Biotite Gneiss and the grey Quartzsite respectively.     

Tensile Strength of Unsaturated Sand

A theory that accurately describes tensile strength of wet sand is presented. A closed form expression for tensile strength unifies tensile strength characteristics in all three water retention regimes: pendular, funicular, and capillary. Tensile strength characteristically increases as soil water content increases in the pendular regime, reaches a peak in the funicular regime, and reduces with a continuing water content increase in the capillary regime. Three parameters are employed in the theory: internal friction angle (at low normal stress) ?t, the inverse value of the air-entry pressure α, and the pore size spectrum parameter n. The magnitude of peak tensile strength is dominantly controlled by the α parameter. The saturation at which peak tensile strength occurs only depends on the pore size spectrum parameter n. The closed form expression accords well with experimental water retention and tensile strength data for different sands.     

Tensile Deformation Behavior of Fe-Mn-Al-C Low Density Steels

Room temperature tensile tests of Fe-Mn-Al-C low density steels with four different chemical compositions were conducted to clarify the dominant deformation mechanisms.Parameters like product of strength and elongation,as well as specific strength and curves of stress-strain relations were calculated.The microstructures and tensile fracture morphologies were observed by optical microscope,scanning electron microscope and transmission electron microscope.The tensile behavior of low density steel was correlated to the microstructural evolution during plastic deformation,and the effects of elements,cooling process and heat treatment temperature on the mechanical properties of the steels were analyzed.The results show that the tensile strength of steels with different cooling modes is more than 1 000 MPa.The highest tensile strength of 28Mn-12Al alloy reached 1 230 MPa,with corresponding specific strength of 189.16 MPa·cm~3·g~(-1),while the specific strength of 28Mn-10 Al alloy was 178.98 MPa·cm~3·g~(-1),and the excellent product of strength and elongation of 28Mn-8Al alloy was over 69.2 GPa·%.A large number of ferrite reduced the ductility and strain hardening rate of the alloy,while the existence of κ carbides may improve the strength but weaken the plasticity.Some fine κ carbides appeared in the water-quenched specimen,while coarse κ carbides were observed in the air-cooled specimen.High temperature heat treatment improved the decomposition kinetics of γ phase and the diffusion rate of carbon,thus speeded up the precipitation of fine κ carbides.The dominant deformation mechanism of low density steel was planar glide,including shear-band-induced plasticity and microbandinduced plasticity.     

Tensile Strength Characteristics of Unsaturated Sands

Tensile strength characteristics of unsaturated sands are examined through a combined theoretical and experimental study. The characteristics of tensile strength in all three water retention regimes of pendular, funicular, and capillary are examined. A simple direct tensile strength apparatus is employed to determine tensile strength for sands with a broad range of particle sizes from silty sand to fine sand and medium sand over a full range of degree of saturation. Tensile strength characteristic curves (TSCC) are established experimentally for these sands and are used to validate the existing theories for tensile strength in the pendular regime. The TSCC for sand characteristically exhibits two zeros at 0 and near 100% saturation, and two peak values occurring in the pendular and capillary regimes, respectively. A minimum tensile strength is observed in the dense fine sand, indicating that either water bridges or pore pressure contributes exclusively to the tensile strength in the funicular regime of this sand. The maximum tensile strength for the silty sand is 1,448?Pa, the fine sand is 1,416?Pa, and the medium sand is 890?Pa. Comparison between the soil–water characteristic curves obtained for these sands indicates that the peak tensile strength in the capillary regime is highly correlated to the air-entry pressure. Photographs of the failure surfaces clearly delineate distinct geometric characteristics for different water retention regimes. Analysis of the patterns of failure surfaces in different water retention regimes indicates that the effective stress principle is valid for tensile stress failure in unsaturated sands.