检定几何量仪器标准器组测量不确定度评定

以标准线纹尺、小量块组、多面棱体、刻线样板、标准半圆球、渐开线样板检定／校准几何量光学仪器时,标准器组的测量不确定度评定。     

热量表示值误差不确定度评定

本文结合实际检定工作、热能表检定规程及不确定度评定方法的步骤,分析与阐述了大口径热能表检定装置示值误差测量不确定度评定。     

光切显微镜示值误差检定方法及误差分析

JJG76—80光切显微镜检定规程指出:用单刻线样板检定光切显微镜示值误差时,先将该样板置于被检仪器工作台上,并调整仪器使样板在视场出现清晰的像,借助仪器手轮移动该样板,使其应用段连同两个记号一起呈现在狭缝清晰像一边,且其刻线方向与狭缝像的长边垂直,转动测微目镜的十字线,使其水平线平行狭缝像的边缘后,与样板刻线表面像重合,并得到第一次读数a1,然后转动测微目镜之水平线与样板刻线底部的像重合,得到第二次读数a_2,所测得深度应为:     

电阻箱检定时测量不确定度的评价

介绍了用QJ48型直流比较电桥装置检定电阻箱时，测量标准不确定度的分析和评价过程；讨论了影响评价结果不确定度的几个主要来源；通过一组实例，给出了电阻箱检定不确定度的分析和评价结果，该过程和结论可应用在对于计量标准进行相应指标的不确定度分析上，也可用于估计电阻箱检定本身的不确定度。     

扭矩扳子检定装置测量不确定度评定

结合扭矩扳子检定装置的建标工作,依据JJG707-2003《扭矩扳子检定规程》、GJB2749A-2009《军事计量测量标准建立与保持通用要求》、GJB3756-99《测量不确定度表示及评定》,对扭矩扳子检定装置的测量标准不确定度以及利用该装置检定4级扭矩扳子的测量结果不确定度进行了评定。     

经纬仪检定装置测量不确定度分析

不确定度是测量工作的质量和测量结果可信赖程度和评价。利用JSJ-ⅡZ型精密水准仪经纬仪综合检验仪作为标准器,通过对经纬仪检定装置测量不确定度来源的分析,评定经纬仪检定装置测量不确定度的大小,分析得到的结果可满足目前国内外各等级经纬仪室内检定要求。     

0.01级活塞式压力计检定装置测量值的不确定度评定

本文分析了用0.01级活塞压力计检定装置测量值的不确定度的来源,对各项测量不确定度进行了评定,最后给出了一台压力变送器3MPa点电流信号测量值的扩展不确定度。并对检定结果进行了验证,验证结果表明,装置测量不确定度符合要求     

压力传感器静态检定装置的测量不确定度

本文根据压力传感器（静态）国家计量检定规程，对压力传感器静态检定装置进行误差分析，得出该装置的测量不确定度。最后，通过实例说明实际测量不确定度与理论分析相符合。     

水表检测装置不确定度评定

随着JJG164－2000《液体流量标准装置》的实施,对装置已经不再采用误差的概念来评定,虽然液体流量标准装置对不确定度有一个分析,但由于其未考虑到系统效应带来的不确定度,同时,也未给出自由度,因而是不完全的。本文以我院建立的静态容积法水表检定装置为例,试图对水表检定装置的不确定度进行评定。     

经纬仪检定装置测角不确定度评定

着重介绍了用有基准的检定装置检定经纬仪水平度盘和竖直度盘时,测角不确定度分量的组成和不确定度评定。     

Effects of side‐groove depth on creep crack‐tip constraint and creep crack growth rate in C(T) specimens

The effects of side‐groove depth on creep crack‐tip constraint and creep crack growth (CCG) rate in C(T) specimens have been quantitatively studied. The results indicate that with increasing side‐groove depth, the constraint level and CCG rate increase and constraint distribution along crack front (specimen thickness) becomes more uniform. The constraint and CCG rate of thinner specimen are more sensitive to side‐groove depth. Two new creep constraint parameters (namely R^* and A_c) both can quantify constraint levels of the specimens with and without side‐grooves, and the quantitative correlations of CCG rate with constraint have been established. The mechanism of the side‐groove depth effect on the CCG rate has also been analyzed.     

Integrated MD simulation of scratching and shearing of 3D nanostructure

An integrated MD simulation of scratching and shearing with one specimen is conducted to analyze the nanomachining mechanism and mechanics properties of nanostructures. Simulation results indicate that during scratching the onset and propagation of dislocations depend on the scratch depths; during shearing, the yielding stress of a small-size nanostructure is more sensitive to nanomachining imperfection and residual defects. Dislocations nucleate first near the burr in a scratched specimen. In an ideal nanostructure or a nanostructure with shallow scratched groove, the distribution of stress is generally lower and flatter. As the depth of groove increases, high stresses transit from the corner to either end of groove, especially near the burr or around the location of tool withdraw. During the deformation of nanostructures, shear stress plays a leading role in the elastic stage, and both normal stress gradients and shear stress determine the onset and evolvement of defects in the plastic stage. When the ratio of the depth of groove to the height of specimen is up to one third, the scratched groove determines the breakpoint of a nanostructure. The fluctuation of shear stress during the plastic deformation of specimen is caused by the competition between atoms which form new atomic planes and slip on different slip planes.     

Effect of side grooves on the elastic-plastic stress state of fracture toughness specimens—three-dimensional finite element analysis

Elastic-plastic stress states on double-edge-notched tensile specimens are analyzed by the three-dimensional finite element method. Effect of side grooves on the stress state around the crack tip are discussed on specimens about 30% side-grooved in U, V and slit types comparing with a regular flat specimen. On the flat specimen, the plastic zone develops extensively near the free surface but the dilatant stress there does not increase so much as at middle region. Accordingly, differences of the plastic zone size and the stress through the thickness increase with increasing the load. Although the side groove promotes the severe plastic deformation over limited region near the root of the groove, practically even distributions of the plastic zone and the dilatant stress can be resulted on V-grooved and slitted specimens.     

水平阵列方微柱表面自然对流的结霜特性研究

本文制作了微机械加工的阵列方微柱金属表面,实验研究了其在环境温度Tatm=24℃,相对湿度RH=17%,不同冷表面温度(Tw=-5.2、-10.1、-15.2℃)及不同试件尺寸时,自然对流条件下的结霜特性,分析了表面温度和持续时间对霜层厚度和霜重量的影响,提出了阵列方微柱表面的抗结霜机理,并通过仿真模拟进行了验证。结果表明:当冷表面温度为-10℃时,阵列方微柱表面的霜层质量比平表面降低了约32%;自然对流使微柱之间产生了空气涡旋,水蒸气会随着空气涡旋流动而无法在凹槽内停留,霜仅形成在微柱顶部,凹槽内不结霜,从而显著减少了有效结霜面积;当微柱间距L过大时,凹槽内会形成冷凝液滴并结霜。     

X射线粉末衍射少量试样的试样板制作

从对参与衍射的试样体积(宽度)、入射X射线在试样表面的总光量和亮度及X射线被试样吸收三个方面在扫描过程中的变化的分析出发,讨论了在试样量少到不能以薄层填满整个试样槽时,如何制作试样板以得到衍射强度高的高质量衍射谱的方法.在固定发散狭缝宽度的条件下,为使参与衍射的试样面积大,使长度方向的试样尺寸与X射线管中线焦点的长度相...     

Evaluation of corrosion fatigue crack propagation life at low-pressure steam turbine rotor groove

The corrosion fatigue crack propagation life of Christmas-tree type rotor groove with three hooks is studied. Each corner of the hook can be a candidate for crack initiation site therefore the condition where cracks initiate and propagate simultaneously at several hook corners must be considered. When a blade is inserted in the rotor groove, narrow gap is introduced unavoidably between the rotor groove and the blade root. The effect of this narrow gap on the crack behavior must also be considered. A procedure was presented to assess the crack initiation and propagation behavior under such a condition. Using the procedure, crack initiation and propagation behavior was evaluated for several gap conditions. It was revealed that the gap condition had little effect on the relation between crack depth at the third hook corner and life consumption ratio (ratio of loading cycle to final failure life). A corrosion fatigue test was performed using a rotor groove model specimen, and the results were compared with the evaluation results.     

Numerical prediction of notch bluntness effect on fracture resistance of SM490A carbon steel

The present work investigates the notch radius effect on fracture resistance using the finite element (FE) damage analysis based on the multiaxial fracture strain model. The damage model was determined from experimental data of notched bar tensile and fracture toughness test data using a sharp‐cracked compact tension specimen. Then, the FE damage analysis was applied to simulate fracture resistance tests of SM490A carbon steel specimens with different notch radii. Comparison of simulated results with experimental data showed good agreement. Further simulation was then performed to see effects of the specimen size, thickness, and side groove on J‐R curves for different notch radii. It was found that effects of the specimen size and thickness became more pronounced for the larger notch radius. Furthermore, it was found that without side groove, tearing modulus for notched specimens was similar to that for cracked specimens, regardless of the notch radius.     

Research on fatigue behavior and residual stress of large-scale cruciform welding joint with groove

Fatigue fracture behavior of the 30 mm thick Q460C-Z steel cruciform welded joint with groove was investigated. The fatigue test results indicated that fatigue strength of 30 mm thick Q460C-Z steel cruciform welded joint with groove can reach fatigue level of 80 MPa (FAT80). Fatigue crack source of the failure specimen initiated from weld toe. Meanwhile, the microcrack was also found in the fusion zones of the fatigue failure specimen, which was caused by weld quality and weld metal integrity resulting from the multi-pass welds. Two-dimensional map of the longitudinal residual stress of 30 mm thick Q460C-Z steel cruciform welded joint with groove was obtained by using the contour method. The stress nephogram of Two-dimensional map indicated that longitudinal residual stress in the welding center is the largest.     

Evaluation on toughness degradation of Cr–Mo–V steel using miniaturized impact specimen technology

Miniaturized specimen technology is inevitable when the amount of available material for test is limited. In this study, miniaturized Charpy V-notched specimens of 1Cr–1Mo–0.25 V rotor steel with five different aging periods were artificially prepared by an isothermal aging heat treatment at 630°C and tested. For the miniaturized specimens, two different types of specimens with or without side groove were utilized. A correlation between the ductile brittle transition temperature (DBTT) obtained by the miniaturized specimen and that by the standard specimen was investigated. In addition, the relationship between fracture toughness and DBTT by the miniaturized specimen of degraded 1Cr–1Mo–0.25 V rotor steels was proposed.