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Ultrasonic scattering of non-metallic inclusions within polycrystalline materials.

机译：多晶材料中非金属夹杂物的超声散射。

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摘要

The work in this dissertation is focused on ultrasonic inspection of bearing components. Roller bearings sustain the heavy loads railcars can often encounter in the rail industry and consist of an inner and outer ring with rollers transferring the load between the two. Rollers in smaller bearings are typically spherical with the contours of the rings conforming closely to this spherical geometry. Tapered roller bearings were designed to increase this load capacity by increasing the contact area between the rollers and raceways by using rollers of cylindrical shape. This design allows for the support of heavier railcars but introduces a higher likelihood of encountering a defect below the contact surfaces due to increased contact area between rollers and rings.;In this work, metrics for ultrasonic quantification of inclusion content are described and applied to railcar bearings. An analysis program is then developed to quantify inclusion content in a consistent manner regardless of the part geometry such that meaningful comparisons between different steels can be made. Ultrasonic scanning methods and reference parts for equipment setup and calibration are also described.;In a similar manner, an alternative mode of defect detection is employed to detect inclusions in this critical region utilizing surface waves which propagate only near the surface of the part. The analysis code developed also characterizes these defects in terms of similar metrics for comparison between steels. Inspection routines and novel reference parts for verification of experimental setup and parameters are developed.;Predictions of the ultrasonic attenuation of waves in the presence of several types of defects are presented as a result of the analysis and theoretical development. The work presents predictions of detection limits in terms of both defect size and type, as well as the incorporation of steel characteristics such as the average grain size.;Bulk inspection of defects is modeled considering backscattered signals as a function of defect size and type, as well as the grain size of the steel used. Predictions of backscattered amplitude are given for defects with sizes and types that are of concern for fatigue considerations. Previous studies utilize an approach that models grain noise and defect backscatter independently. This work presents a unified approach to this problem that has not been performed previously.
机译：本文的工作主要集中在轴承部件的超声检查上。滚子轴承承受铁路车辆在铁路行业中经常遇到的重负荷，它由一个内圈和一个外圈组成，滚子在两者之间传递负荷。较小轴承中的滚子通常是球形的，其环的轮廓与该球形几何形状非常吻合。圆锥滚子轴承的设计旨在通过使用圆柱滚子来增加滚子与滚道之间的接触面积，从而增加这种负载能力。这种设计可以支撑较重的轨道车，但由于滚子和环之间的接触面积增加，因此在接触表面下方出现缺陷的可能性更高。;在这项工作中，描述了将夹杂物含量进行超声波量化的指标并将其应用于轨道车轴承。然后开发分析程序，以一致的方式量化夹杂物含量，而不管零件的几何形状如何，从而可以在不同的钢之间进行有意义的比较。还描述了用于设备设置和校准的超声波扫描方法和参考零件。以类似的方式，采用缺陷检测的替代方式，利用仅在零件表面附近传播的表面波来检测此关键区域中的夹杂物。所开发的分析代码还根据相似的度量标准对这些缺陷进行了表征，以进行钢之间的比较。分析程序和理论发展的结果，提出了在几种缺陷存在下波的超声波衰减的预测。这项工作提出了根据缺陷尺寸和类型以及钢特性（例如平均晶粒尺寸）在内的检测极限的预测;对缺陷的批量检查进行了建模，考虑了反向散射信号与缺陷尺寸和类型的关系，以及所用钢的晶粒度。对于具有疲劳考虑因素的尺寸和类型的缺陷，给出了后向散射幅度的预测。先前的研究采用了一种独立模拟颗粒噪声和缺陷反向散射的方法。这项工作为以前没有执行过的此问题提出了一种统一的方法。

著录项

  • 作者

    Koester, Lucas William.;

  • 作者单位

    The University of Nebraska - Lincoln.;

  • 授予单位 The University of Nebraska - Lincoln.;
  • 学科 Engineering Mechanical.;Applied Mechanics.;Engineering Materials Science.
  • 学位 Ph.D.
  • 年度 2013
  • 页码 126 p.
  • 总页数 126
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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