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为了提高小孔松弛法的灵敏度,就应使电阻应变计尽可能地靠近孔的边缘。然而,愈是靠近孔的边缘,其压缩塑性应变也就愈大,愈不利于提高测量精度。本文对使用0°、45°、90°应变花(3×2×3-45°型),钻φ3×3的平底盲孔,进行了较深人的研究。我们发现,由于钻削所引起的压缩塑性应变量是不容忽视的;不同的钻孔方法所引起的钻削塑性应变也不同。我们认为,对低碳钢而言,钻削塑性应变最小的钻孔方法是,先用φ2的麻花钻头,钻孔深为3mm,然后再用中φ3的鍵槽铣刀,加工出合乎尺寸要求的φ3×3平底盲孔。平均应变量为-123该数值应当从实測的释放应变量中除去。本文列出了修正残余应力分布的例子,从理论上或实践上看都是合理的。另外,还对小孔松弛法中常用的单片法和应变花法进行了对比。试验结果表明,採用单片法测定板条结构中的纵向焊接残余应力是足够精确的。应变花法适于测定复杂应力场的残餘应力分布,但其计算工作量十分繁杂。
In order to improve the sensitivity of the hole relaxation method, the strain gauge should be as close as possible to the edge of the hole. However, the more close to the edge of the hole, the greater its compressive plastic strain, the less conducive to improve the measurement accuracy. In this paper, the use of 0 °, 45 °, 90 ° strain flower (3 × 2 × 3-45 ° type), drilled φ3 × 3 flat-bottomed blind hole, conducted a more in-depth study. We find that the compressive plastic strain caused by drilling can not be ignored; the drilling plastic strain caused by different drilling methods is also different. In our opinion, for low-carbon steels, the drilling method with the lowest plastic strain on the drilling is to use a φ2 twist drill first to drill a depth of 3mm and then use a key-flute milling cutter of φ3 to produce a size- φ3 × 3 flat bottom blind hole. The average amount of strain should be -123 This value should be removed from the measured amount of strain released. This article lists examples of modifying residual stress distributions, both theoretically and practically. In addition, we compare the single-chip method and the strain method which are commonly used in pinhole relaxation method. The test results show that it is sufficiently accurate to measure the longitudinal welding residual stress in the slat structure by the monolithic method. Strain flower method is suitable for the determination of residual stress distribution in complex stress field, but its computational workload is very complicated.