共查询到20条相似文献,搜索用时 250 毫秒
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数字射线检测技术是获得数字检测图像的射线检测技术。它与胶片射线照相检验技术的不同有二个方面:一是用探测器替代胶片探测射线检测信号;二是采用了图像数字化技术。图像数字化理论是数字射线检测技术的基本理论。数字射线检测技术系统由探测器系统、透照技术、图像数字化技术、图像显示与评定和技术稳定性控制构成。 相似文献
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射线照相检测固体发射机装药质量时,是将缺陷的三维尺寸投影到两组平面的胶片上,难以对缺陷尺寸的精确测量和深度的准确定位。射线实时成像的检测原理虽与其大致相同,但可充分利用其动态观察和较先进的图像处理技术,使其检测准确性大大提高,利用固体发动机在转台上的旋转,在切向照相对,使其界面脱粘检出率大大提高;准确测定缺陷的最大尺寸和缺陷间的最短距离;利于判断缺陷性质;利用固体发动机的不停转动,使其裂纹的检出率 相似文献
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目前高密度电阻率法所采用的数据处理方法主要是将地质结构体视为二度体进行二维处理,因而二维数据资料处理结果只是一种近似解释,其计算精度与反演效果达不到精确反演的要求。设计两种典型的电阻率异常地质体模型,利用有限单元法进行正演计算。为更真实地模拟实测数据并分析二维、三维反演算法对噪声的敏感度,在正演剖面中加入1%的高斯随机误差,然后再分别利用最小二乘法进行高密度电阻率法二维、三维反演。对比二维和三维高密度电阻率法的反演水平切片及垂直切片图可知,三维反演受高斯随机误差的影响更小,反演结果在模型异常位置、形态和电阻率特性反映上都比二维反演的效果更好,与实际地质模型更接近。 相似文献
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基于聚焦合成的砂轮表面三维重构方法 总被引:4,自引:1,他引:4
提出一种基于聚焦合成的重构砂轮三维地貌的新方法。利用显微镜物镜焦深范围有限,观察砂轮样本时不能聚焦清晰图像的特点,先采集同一区域的一系列聚焦在不同深度的图像,用图像聚焦评价函数进行图像叠合、比较,得到图像中不同位置的深度信息,最后通过高斯插值法得到砂轮表面的三维地貌。并根据所得到的三维地貌数据,对砂轮磨刃高度分布进行了计算。 相似文献
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D. J. Rowenhorst A. C. Lewis 《JOM Journal of the Minerals, Metals and Materials Society》2011,63(3):53-57
While there are many microstructural parameters that can be measured from a planar two-dimensional (2-D) section through a
material, there are many measurements that require knowledge of the full three-dimensional (3-D) microstructure, such as true
size and shape of individual objects, connectivity and interfacial curvatures. Serial sectioning and reconstruction can reveal
the 3-D microstructure but are often considered to be time consuming and labor intensive. However, what is not often realized
is that the majority of the time invested in serial sectioning is spent in the image segmentation, wherein individual objects
are digitally identified. This article reviews the current state of image segmentation and novel analysis within 3-D materials
science. We will also briefly discuss the future possibilities for more efficient segmentation of digital images for a broader
range of materials. 相似文献
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三维椭圆振动切削被认为是目前最具潜力的机械加工方式,但是加工过程中的控制问题还未被很好的解决,特别是加工过程中对于外界干扰的自适应问题,为了在三维椭圆振动切削过程中实现控制方法的鲁棒性,根据所研制的一种三维椭圆振动切削装置独特的结构方式,首先分析了各个运动之间的串扰情况,并根据装置柔性铰链的特征建立了三维椭圆振动切削装置的动力学模型。提出了三维椭圆振动切削模糊自适应滑模控制的滑模函数与滑模控制律,并通过李雅普诺夫稳定性条件证明了所设计的滑模控制器系统稳定性,采用正弦信号数字实现模糊自适应滑模控制,位置跟踪在3 s内误差控制在0.005范围内,速度跟踪在0.4 s内控制在±0.05之内,能够达到满意的精度,系统模糊自适应滑模控制的模糊逼近也能在0.2 s内收敛,证明了三维椭圆振动切削系统采用模糊自适应滑模控制可以实现较强的鲁棒性。 相似文献
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In this paper the capability of a 3-D point reconstruction algorithm based on multiple hypothesis tracking is experimentally explored on a setup consisting of a microfocus X-ray source and a digital detector array. The algorithm is verified to detect and 3-D position steel particles with diameters 0.16–0.26 mm radiographed behind 4.7 mm Inconel 718 at two to ten times magnification. At ten times magnification the algorithm is verified to detect and 3-D position with an average error of 0.1 mm pore defects with diameters 0.05–0.25 mm in 4.7 mm thick titanium alloy laser welds. 相似文献
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在采用非接触式三维扫描技术对硬质合金可转位刀片槽型复杂曲面扫描的过程中,通过修正相机镜头畸变提高扫描精度,运用Geomagic Studio软件对点云数据进行噪声去除、点云拼接和特征提取等系列处理保证重构模型的准确性。重构刀片的三维模型经过与原始点云数据的误差比较,大部分的偏差值在(-0.011,0.011)区间内,满足精度要求。在扫描过程中,应选择刀片主要特征表面进行扫描,以减少扫描角度及扫描次数。同时,根据重建模型的曲面特征对数据块进行曲面修改,可以更有效、快捷的优化该刀片槽型的设计。 相似文献
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建立了一种改进的元胞自动机模型来模拟熔体对流条件下的二元合金三维枝晶的生长。模型中考虑了界面能各向异性和溶质扩散对固/液界面推移的影响,在同一套网格中耦合求解质量传输和液相流动方程,从而可以模拟溶质扩散和熔体对流之间的相互作用。使用该模型模拟了一定过冷度条件下,强制对流对Al-7%Si(质量分数,下同)合金三维枝晶生长形貌的影响。模拟结果表明,熔体强制对流导致迎流侧尖端溶质富集层减薄,枝晶生长出现了迎流生长现象。将模拟得到的溶质过饱和度与Oseen-Ivantsov解析解进行对比,当流速较大时两者吻合较好。同时模拟了三维和二维强制对流作用下枝晶生长形貌的演化,由于三维条件下对流使得熔体能够绕过垂直于对流方向的一次枝晶臂主干将溶质带到背流侧,而二维条件下只能绕过垂直方向一次臂的尖端,因此三维MCA模型能更准确地反映强制对流对枝晶生长的影响。 相似文献
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The growth behavior of ferrite allotriomorphs nucleated on grain boundary faces in a low carbon steel was revealed by means
of serial sectioning and three-dimensional (3-D) computer-aided reconstruction techniques. The length, width and thickness
of ferrite allotriomorphs were measured on the basis of 3-D reconstructed images. The measurements indicated that the lengthening
of ferrite allotriomorphs was much larger than that of widening and thickening. As isothermal holding time prolonged, adjacent
ferrite allotriomorphs impinged against each other and gradually coalesced and finally covered grain boundary faces. The measured
growth rate constant was smaller than that calculated, which was probably attributed to solute drag-like effect of manganese
in the alloy. 相似文献
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Nathalie Limodin Julien Réthoré Jean-Yves Buffière Anthony Gravouil François Hild Stéphane Roux 《Acta Materialia》2009,57(14):4090-4101
Three-dimensional (3-D) tomographic images of a nodular graphite cast iron obtained using a laboratory X-ray source were used to analyze the opening of a fatigue crack during in situ mechanical loading. Direct image analysis and digital image correlation are utilized to obtain the 3-D morphology and front location of the crack, as well as the displacement fields in the bulk of the specimen. From digital image correlation results it is possible to extract the crack opening displacement (COD) map in the whole sample cross-section and to compute stress intensity factors (SIFs) all along the crack front, even for COD values that are less than the image resolution. The comparison of COD maps with local values of the SIF enabled for an estimation of the opening SIF (Kop) equal to 6 MPa m1/2. 相似文献