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。     

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。     

拉伸试验测量不确定度的评定

对测量不确定度的基本概念作了简单介绍．介绍了测最不确定度A类和B类评定的评定方法，井具体计算出拉伸试验的测罱不确定度．为实验室的检测项目进行测量不确定度的评定提供了参考。     

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。     

拉伸试验机抗拉强度测量结果不确定度的评定

重点论述拉伸试验机抗拉强度测量结果不确定度的来源，并对拉伸试验机抗拉强度测量结果的不确定度进行分析与计算。     

分析测试中的测量不确定度及评定 第二部分 测量不确定度评定的基本方法

本文叙述了测量不确定度评定的基本程序,A类和B类标准不确定度、合成标准不确定度和扩展不确定度评定的基本方法。     

拉伸试验测量不确定度评定

结合本部门仪器特点和检测人员实际水平，按照测量不确定度评定的基本步骤，给出了用于本室拉伸试验测量不确定度评定的通用公式和速查表。一般工程技术人员对具体检测参数的试验结果仅需按照指定的公式进行计算即可求得其测量不确定度，节省了时间，提高了效率，也使得本部门拉伸试验测量不确定度评定变得简单了。     

热轧中板拉伸试验测量不确定度评定

本文以热轧中板拉伸试验为例，阐述拉伸试验测量不确定度的评定方法，对其它金属材料的拉伸试验测量不确定度评定具有通用性。     

分析测试中的测量不确定度及评定第二部分测量不确定评定的基本方法

本文叙述了测量不确定度评定的基本程序,A类和B类标准不确定度、合成标准不确定度和扩展不确定度评定的基本方法.     

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。     

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.     

Anisotropic strain localization in tensile prestrained sheet steel

Multiple forming operations are often needed to stamp complex shapes out of sheet metal. Large changes in strain path can occur from such operations. This study examined the effects of a particular strain path change, tensile-tensile, on the mechanical properties of an aluminum-killed steel. Large tensile specimens were prestrained various amounts in one direction followed by machining smaller tensile specimens at 0, 45, and/or 90 deg to the prestrain direction. The smaller samples were then pulled to failure. For samples pulled in the same direction as the prestrain, the residual strength and ductility were equivalent to those obtained from an interrupted tensile test. In contrast, both the 45 and the 90 deg prestrained specimens showed a larger than expected flow stress and an abrupt change in the nature of the residual ductility at prestrains of 7.5 pct and larger. At 7.5 pct prestrain, the uniform strain, as measured by the maximum-load point on the load vs elongation tensile curve, decreased abruptly. The decrease was accompanied by a corresponding increase in the post-uniform strain. This unusual behavior is explained in terms of a rapid increase in strain-hardening with strain.     

高强IF钢的高速应变行为

利用拉伸实验装置研究了高强IF钢在高应变速率下的变形特性。结果表明：高强IF钢是应变速率敏感性材料,在应变速率10-4～103/s的范围内,应变速率对高强IF钢的应变硬化率与屈服强度的影响具有2阶段性。在第一阶段,应变速率较低,应变硬化率与屈服强度对应变速率的敏感性较小;在第二阶段,应变速率较高,随应变速率的增加,应变硬化率迅速降低,屈服强度迅速增加。     

钢绞线偏斜拉伸系数的不确定度评定

根据测量不确定度原理及国家计量技术规范JJF1059,对钢绞线偏斜拉伸试验测量结果的不确定度进行了详细的评定。此评定方法适用于检测实验室的铜绞线偏斜拉仲检验测量领域。     

Comparison of plane-strain and tensile work hardening in two sheet steel alloys

Extended tensile tests and newly-devised plane-strain tests have been performed on two commercial sheet steels: an aluminum-killed (A-K) steel and a cold-rolled, dual-phase (D-P) steel. Up to uniform strain in uniaxial tension, the average work-hardening rate of both steels was found to be independent of strain state (isotropic hardening). The planestrain behavior of both steels was in good agreement with predictions of Hill’s old theory of normal anisotropic plasticity. At larger strains, the work-hardening rate in tension is greater than in plane strain. All of the tests were adjusted to reflect constant strain rates and all results were well represented by work hardening of the Hollomon type.     

电工钢用单片测量方法测量偏差分析

对取向电工钢SST(82)和SST(92)单片测试方法的差异进行分析,并对两者间的测量偏差进行量化评价。结果表明:SST(92)单片测试方法测量比总损耗较SST(82)平均偏高5.03%左右,这主要是因为SST(82)单片测试方法的有效磁路长度不固定,且离散性较大,而有效磁路长度主要跟单片磁轭有关。另外,直接测量试样磁场强度的H线圈方法由于规避了有效磁路长度的影响,可视为一种可靠的替代方法。     

加载方向对TRIP双相不锈钢板带拉伸性能的影响

 为了研究加载方向对一种TRIP型双相不锈钢板带力学性能的影响,利用拉伸试验机研究了加载方向与轧制方向分别成0°、45°和90°条件下试验钢板带的拉伸变形行为。利用EBSD、TEM、XRD等分析手段对比研究了不同加载方向下形变组织演化的特点及形变诱导马氏体相变动力学规律,探讨了作用机理。结果表明,试验钢表现出明显的各向异性,其中各方向塑性和抗拉强度(由高到低)的变化规律为0°＞45°＞90°,但屈服强度对加载方向不敏感。钢中奥氏体相发生了形变诱导马氏体相变,主要演化机制为γ→ε→α′,从而形成TRIP效应。0°加载有助于TRIP效应的发生与发展,而90°加载时,两相间的应变配分延迟了马氏体相变的进程,抑制了TRIP效应。通过回归分析分别建立了不同加载方向下形变诱导马氏体相变动力学模型,可实现各加载方向下不同变形阶段马氏体转变量的预测。     

Thermal gradients,strain rate,and ductility in sheet steel tensile specimens

The effect on ductility of strain rate and thermal gradients arising from deformation is examined in tensile specimens of 1008 AK steel. The total elongatione _tot is taken as the measure of ductility, since it reflects changes in the strain hardeningn and strain-rate sensitivitym. Tensile specimens are pulled to failure in 23 °C air, at initial strain rates from 10⁻³ to 10⁻¹ s⁻¹, with thermocouples recording temperature along the 50.8 mm gauge section. The maximum temperature is ∼110 °C just prior to failure at the highest rate. Thee _tot, however, remains fairly constant with rate at ∼40 pct. When thermal gradients are prevented by immersing the specimens in circulating water at 23 °C,e _tot, increases with rate to a maximum of ∼54 pct at 10⁻¹ s⁻¹. Direct measurements of isothermal values ofm at 23, 60, and 90 °C show thatm increases with rate.e _tot, therefore, would be expected to increase with rate. Since under nonisothermal conditionse _tot does not change, it appears thatm and thermal gradients are competing influences on ductility at higher rates. Enhanced ductility in stampings should be possible by suppressing gradients, either by controlling die temperature or by heat transfer properties of a lubricant.     

In situ observations on the austenite stability in TRIP‐steel during tensile testing

In‐situ deformation tests have been performed on a steel displaying the transformation‐induced plasticity (TRIP) effect, while monitoring the phase transformation by means of X‐ray diffraction. A tensile stress is applied to 0.4 mm thick samples of this steel with mass contents of 0.26 % Si, 1.5 % Mn, and 1.8 % Al in a transmission geometry for a synchrotron‐radiation beam of 25 μm · 25 μm. On the diffraction patterns every grain appears as a discrete spot. The austenite {200} reflections are analysed during this investigation. The diffraction patterns are treated like a powder pattern for five different η‐angles, with η representing the angle between the tensile direction and the normal direction of the diffracting {200} planes. The results of the analysis show that η = 0° and η = 90° are the preferential orientations for the transformation to martensite. The Ludwigson and Burger model [9] is used to gain more information about the stress dependence of the deformation induced martensite formation. The microdiffraction patterns also reveal the changes in carbon concentration in austenite at each retained austenite fraction.     

冷轧薄板试样加工和拉伸试验常见问题浅析

冷轧薄板是莱钢产品的新品种,检验人员对试样加工和拉伸试验没有经验积累,实验中常出现很多导致试验结果不准确的问题.对常见问题进行分析并找出正确方法,以指导实验.