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Effect of dimensional conformance of threaded product on yield and tensile strength.

机译：螺纹产品的尺寸一致性对屈服强度和拉伸强度的影响。

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摘要

This dissertation presents experimental and simulation results from tests that investigate the effect of thread dimensional conformance of fasteners on mechanical performance. The experimental part includes test specimen combinations of bolts and nuts within conformance as specified by ASME Standard B1.1-1992, as well as bolts with undersized pitch and major diameters and nuts with oversized pitch and minor diameters. Tensile tests were performed in accordance with ASTM F606-95b. Data from the tests show reduced yield and tensile strength for the fastener combinations with undersized pitch and major bolt diameters or oversized pitch and minor nut diameters, compared to fastener combinations within conformance. Variations in bolt pitch diameter were found to affect the yield and tensile strength by about an order of magnitude more than variations in bolt major diameter or nut pitch and minor diameters. The mean yield strength for conforming product was found to be as much as 17% greater than the mean yield strength for nonconforming product.; The numerical approach consisted of creating 2D axisymmetric and 3D finite element (FE) models of a bolt and nut assembly. Those models resulted from multiple tests regarding geometry, materials, friction, boundary conditions, loading, mesh distribution and mesh density. Highly dense meshes for 2D models and medium dense meshes (due to computational limitations) for 3D models were evaluated. Numerical results for both models provided excellent qualitative correlation by matching the types of failures found experimentally. Quantitatively, for the axisymmetric models, the mean yield strength for conforming product was found to be at most 6% greater than the yield strength for nonconforming product. The numerical results for yield strength obtained from the relatively coarse 3D models were at most 9% greater for the conforming product. Advantages of the 3D FE models over the 2D axisymmetric models were identified and include: ability to model lead and pitch variations, plastic deformation along the helix of the thread, asymmetric load and stress distribution and associated bending, rotational tightening and loosening, bolt and nut misalignment, thread jumping, and thread jamming.
机译：本文给出了试验和仿真结果，这些试验研究了紧固件的螺纹尺寸一致性对机械性能的影响。实验部分包括符合ASME标准B1.1-1992规定的螺栓和螺母的测试样本组合，以及节距和直径较大的螺栓以及节距和直径较小的螺母。根据ASTM F606-95b进行拉伸测试。测试数据表明，与合格组合内的紧固件组合相比，螺距过小且螺栓直径较大，螺距过大且螺母直径较小的紧固件组合的屈服强度和抗拉强度降低。发现螺栓螺距直径的变化比螺栓大直径或螺母螺距和次直径的变化对屈服强度和抗拉强度的影响大约大一个数量级。已发现，合格品的平均屈服强度比不合格品的平均屈服强度高出17％。数值方法包括创建螺栓和螺母组件的2D轴对称和3D有限元（FE）模型。这些模型来自于关于几何形状，材料，摩擦，边界条件，载荷，网格分布和网格密度的多次测试。对2D模型的高密度网格和3D模型的中密度网格（由于计算限制）进行了评估。通过匹配实验发现的故障类型，两个模型的数值结果都提供了极好的定性相关性。定量地，对于轴对称模型，发现合格品的平均屈服强度比不合格品的平均屈服强度高最多6％。从合格的3D模型获得的屈服强度的数值结果最多比合格产品大9％。确定了3D FE模型相对于2D轴对称模型的优势，包括：对引线和螺距变化进行建模的能力，沿螺纹螺旋的塑性变形，不对称的载荷和应力分布以及相关的弯曲，旋转拧紧和松动，螺栓和螺母错位，跳线和卡线。

著录项

  • 作者

    Leon-Oviedo, Francisco Manuel.;

  • 作者单位

    University of South Florida.;

  • 授予单位 University of South Florida.;
  • 学科 Engineering Mechanical.
  • 学位 Ph.D.
  • 年度 2002
  • 页码 144 p.
  • 总页数 144
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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