Analysis for inversion load and energy absorption of a circular tube
Analysis for inversion load and energy absorption of a circular tube
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DOI：
10.1243/03093247v183177
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发表时间：
1983-07
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影响因子：
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通讯作者：
A. Kinkead
中科院分区：
文献类型：
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作者：
A. Kinkead
摘要通过引入两个以前未被发现的附加子结构机制，对圆管外部或内部到外部反转力学的基本理论方法进行了研究和扩展。结果表明，这些改进时，适用于已发表的结果，在非摩擦过程中，韧性铝管倒置，提供非常令人鼓舞的相关性。由于这种分析是在“工程塑性应变”的基础上进行的，因此在主要的子结构过程中采用“纯塑性应变”或“自然应变”进行补充计算。由此产生的比较表明，对于刚性/塑性材料特性，在使用工程应变时推导出的简化在反演载荷的评估中不会引入严重的误差。这里可能要提到的是，在许多引用的关于外部反演的论文中，虽然初始方程是以纯塑性应变项建立的，但随后的分析常常通过将对数应变表示为一个级数并消除除第一项以外的所有项来简化。这会将分析恢复为工程应变类型。因此，在这方面所描述的工作验证了这些先前采用的简化。鉴于通过对管外反演过程引入上述理论改进而获得的令人满意的相关性，同样的过程也被应用于管内或管外-管内反演的情况。已发表的内部反转过程的分析，以前忽略了明显的增厚效应清楚地表明，在所有的实验结果。（管壁厚度变化在外部反转期间根本不明显，事实上这也有助于简化分析）。在本方法中的摩擦和加工硬化的影响，在压缩模具过程中的内部反转已被列入在其他研究中已经推导出的方式，但此外，进一步的子结构过程的解释和量化的相关增厚的管壁已制定。这里应该提到的是，在基于平均塑性应变的应变硬化应用方面存在一些不确定性。然而，由于四个已公布的实验结果已与材料表现出应变硬化特性，总的新开发的和以前演变的分析已经结合起来，使一些相关性。在三种不同材料中，两组独立结果的预测内部反转载荷与实验值非常吻合。
Abstract The basic theoretical approach in the mechanics of external or inside-to-outside inversion of circular tubes is examined and extended by the introduction of two additional and previously unperceived sub-structural mechanisms. It is shown that these refinements when applied to published results for ductile aluminium tubing inverted, in a non-frictional process, furnish very encouraging correlations. Since this analysis is made on an ‘engineering plastic strain’ basis a supplementary calculation is made employing ‘pure plastic strain’ or ‘natural strain’ in the predominant sub-structural processes. The resulting comparisons have shown that for rigid/plastic material characteristics the simplification derived in the use of engineering strain does not introduce serious errors in the evaluation of the inversion load. Here it might be mentioned that in many of the cited papers on external inversion, although the initial equations are set up in pure plastic strain terms, frequently the ensuing analysis is simplified by expressing the logarithmic strain as a series and eliminating all but the first term. This reverts the analysis to an engineering strain type. Hence the work described in this connection validates these previously adopted simplifications. In view of the satisfactory correlations achieved by introducing the above theoretical refinements for the external inversion process, the same procedure has also been applied to the case of internal or outside-to-inside tube inversion. Published analysis of the internal inversion process has previously neglected the pronounced thickening effect clearly demonstrated in all experimental results. (Tube-wall thickness change is not at all evident during external inversion and in fact this also assists in simplifying that analysis). In the present approach the effects of friction and work hardening in a compressive die process of internal inversion have been included in the manner already deduced in other research but in addition a further sub-structural process explaining and quantifying the associated thickening of the tube wall has been formulated. Here it should be mentioned that some uncertainty exists in relation to the application of strain hardening based on average plastic strains. However, since the four published experimental results available have been made with materials exhibiting strain hardening characteristics, the total newly developed and previously evolved analyses have been combined to enable some correlation to be made. The predicted internal inversion loads for two separate sets of results in three different materials are in very reasonable agreement with experimental values.