权益分类	功能权益	普通用户	{{item.name}}会员
{{category.name}}	{{benefitItem.name}}

Simplified determination of elastic-plastic accumulated strain for analytical life assessment of structures by means of the Simplified Theory of Plastic Zones based on Zarka's method

基于 Zarka 方法的塑性区简化理论简化结构分析寿命评估的弹塑性累积应变测定

基本信息

批准号：
286671283
负责人：
Professor Dr.-Ing. Hartwig Hübel
金额：
--
依托单位：
Fachgebiet Statik und Dynamik
依托单位国家：
德国
项目类别：
Research Grants
财政年份：
2015
资助国家：
德国
起止时间：
2014-12-31 至 2019-12-31
项目状态：
已结题

来源：
https://gepris.dfg.de/gepris/projekt/286671283?language=en
关键词：
Simplified determination elastic plastic accumulated

项目摘要

The lifetime of a structure, operated beyond elastic limits and subjected to varying loads, is dependent on whether a ratcheting mechanism causing an accumulation of stress and strain in successive cycles of loading is developing (progressive deformation) until this process possibly ceases when shakedown is attained. In addition, fatigue is to be considered. Accordingly, the maximum elastic-plastic strain accumulated at the end of a ratcheting process needs to be determined for an analytical assessment of life (for comparison with maximum admissible strains), as well as the effective strain range occurring in subsequent cycles (for determination of fatigue usage factors). Usually, these quantities are obtained by means of incremental elastic-plastic analyses of a finite element model of the structure for many cycles of loading until shakedown is at least approximately achieved, usually associated with a huge computational burden. In contrast to this, the Simplified Theory of Plastic Zones (STPZ) makes use of a reformulation of the elastic-plastic constitutive equations including hardening known from Zarkas method, allowing for estimating some special quantities in some suitable manner. Thus, an approximation of accumulated strains and of strain ranges may be obtained at each location in the structure in the condition of shakedown. Few linear elastic analyses are sufficient, reducing the computational burden remarkably compared to incremental elastic-plastic analyses. Although steel was the material of main focus when developing the STPZ up to now, the basics of the STPZ are independent of a particular material. Accordingly, the potential field of application is widespread, including, for example, civil engineering, plant design and mechanical engineering. First applications give rise to the hope that the STPZ, at least with respect to determining the strain range, is a reasonable compromise between exact but costly cyclic incremental analyses on one hand and the simple and thus weakly based knock-down factors widely used in practical design of structures developing cyclic plasticity (e.g. factor Ke, Neuber method) on the other hand. The object of the project applied is to expand the STPZ in order to achieve a good approximation to the accumulated strains at little computational burden as well, by accelerating the calculation process, expanding its range of applicability and increasing its performance. Since no other simplified methods quantifying accumulated strains founded on sound mechanical background are known so far, this aim is considered to be of great value.

结构的寿命，超过弹性极限运行，并受到变化的负载，是取决于是否棘轮机制引起的应力和应变的积累，在连续的加载循环正在发展（渐进变形），直到这个过程可能停止时，安定是实现。此外，还要考虑疲劳。因此，需要确定棘轮过程结束时累积的最大弹塑性应变，以进行寿命分析评估（与最大容许应变进行比较），以及后续循环中出现的有效应变范围（用于确定疲劳使用系数）。通常，这些量是通过对结构的有限元模型进行多次加载循环的增量弹塑性分析来获得的，直到至少近似地实现安定，通常与巨大的计算负担相关联。与此相反，简化塑性区理论（STPZ）利用了Zarkas方法中已知的包括硬化的弹塑性本构方程的重新表述，允许以某种适当的方式估计一些特殊的量。因此，在安定条件下，可以在结构中的每个位置处获得累积应变和应变范围的近似值。很少的线弹性分析是足够的，减少计算负担显着相比，增量弹塑性分析。虽然钢是开发STPZ时的主要焦点材料，但STPZ的基础是独立于特定材料的。因此，潜在的应用领域是广泛的，包括例如土木工程、工厂设计和机械工程。第一个应用程序产生的希望，STPZ，至少在确定应变范围，是一个合理的折衷之间的准确，但昂贵的循环增量分析，一方面和简单的，因此，弱基础的击倒因素广泛用于实际设计的结构发展循环塑性（如系数Ke，Neuber方法）。该项目的目的是扩大STPZ，以实现良好的近似累积应变在很小的计算负担，以及通过加速计算过程，扩大其适用范围，提高其性能。由于没有其他简化的方法量化累积应变建立在良好的力学背景是已知的，迄今为止，这一目标被认为是很有价值的。