清晨好,您是今天最早来到科研通的研友!由于当前在线用户较少,发布求助请尽量完整的填写文献信息,科研通机器人24小时在线,伴您科研之路漫漫前行!

Multiaxial fatigue criteria for offshore mooring chains subjected to out-of-plane bending

系泊 结构工程 弯曲 有限元法 平面(几何) 弯矩 海底管道 梁(结构) 变形(气象学) 计算机科学 材料科学 工程类 数学 几何学 复合材料 海洋工程 岩土工程
作者
I.J. Calf
摘要

The out-of-plane bending of offshore mooring chains leads to a rapid deterioration of the chain, ultimately leading to failure in a period that is a fraction of the design-life. The deformation of the contact surface of the chainlinks leads to the interlocking of the link. This in turn causes the chain to behave like a bending beam. The combination of the chains behaving in this manner and the vessel movement leads to a bending moment in the chain link, especially in the top section, where the tensions are high. Due to the alternating nature of the loading, multiaxial fatigue effects cause chain failure. In this thesis, a literature study is performed, forming an introduction to the general concept of fatigue and the exploration of available methods. For multiaxial loadings, so-called critical plane methods are widely accepted as the most effective approach. This critical plane method search for the material plane experiencing most damage, according to the damage criterion that is assessed. Furthermore, a number of methods for the cycle decomposition are present. For uniaxial methods, the rainflow method is most used. Applying this method to multiaxial fatigue problems can lead to problems, which leads to the formation of alternative approaches. The other approaches being discussed are the Wang & Brown method and the Modified Wang & Brown method. The Bannantine & Socie method is discussed too, but could be classified as a critical plane search algorithm, instead of a novel cycle counting method. After the exploration of the problem, a finite element model is created. This model consists of multiple chain links, that are proofloaded while plastic deformation is allowed. This leads to the aforementioned deformation of the contact surfaces on the links. After the proofloading step is completed, three different cases are performed with an elastic material formulation. These cases comprise of varying angle ranges; Case 1 only induces an out-of-plane bending in the analysed link, Case 2 induces an out-of-plane and in-plane load, while Case 3 is similar to Case 2, apart from an added phase difference between the two angles. The stress and strain results from the finite element analyses are input in the Pragtic fatigue software. For each case, a number of fatigue criteria are calculated. These criteria are, named after the author, the following: McDiarmid, Dang Van, Matake, Liu & Mahadevan, Carpinteri & Spagnoli, Findley, Wang & Brown & Miller, Smith & Watson & Topper and Socie. Different critical plane search algorithms and/or cycle counting methods have been explored. Some of these criteria lead to a Fatigue Index, while others lead to an Accumulated Damage formulation. From the results it is clear that the cases combining two angles lead to higher damages, leading to the believe that the multiaxial behaviour should be taken into account when assessing fatigue damage of mooring chains. Furthermore, it seems that for the different cases, the SWT criterion gives either the highest or the lowest damage. As this is originally a multiaxial parameter, it shows that the use of traditional uniaxial methods could either over- or underestimate the damage, depending on the specific loading. Furthermore, results show that the criterion that is suggested by Bureau Veritas' Guidance Note on OPB, namely the Dang Van criterion, often gives the lowest fatigue index. This suggests that this criterion might not be conservative enough. This statement needs to be validated with the help of experiments. Furthermore, the method specifically aimed at multiaxial problems, the Wang & Brown method (including the multiaxial cycle counting method), leads to highest accumulated damage. As this method was aimed for multiaxial and non-proportional loading, it can be reasoned that this method makes a conservative, proper prediction. As for the critical plane orientation, it seems that the most damaging plane, likely the location of crack growth, is often close to the shear plane. This fuels the believe that the shear stress is the factor driving the OPB failure mode. However, since this problem inherently involves a mean stress (the tension on the mooring chain), the critical plane does not need to be the shear plane. When exploring this with the globe plane search algorithm, it seems that the critical plane is often a plane oriented at some angle in between the shear and normal plane. The results and statements made in this report are at this point mathematical. As the OPB concept is relatively newly discovered, more experiments are needed to be able to back up any statements that can be made. Furthermore, the research presented here could benefit from a larger group of cases, and added detail on the loading part of the analyses. Furthermore, as material fatigue parameters are limited, a sensitivity anayses on these parameters could shed some light on the influence of parameters used. The parameters used in this report are taken from similar materials and should at least give a very reasonable approximation of the material's fatigue behaviour.

科研通智能强力驱动
Strongly Powered by AbleSci AI
更新
大幅提高文件上传限制,最高150M (2024-4-1)

科研通是完全免费的文献互助平台,具备全网最快的应助速度,最高的求助完成率。 对每一个文献求助,科研通都将尽心尽力,给求助人一个满意的交代。
实时播报
STAR完成签到 ,获得积分10
31秒前
Will完成签到 ,获得积分10
35秒前
游01完成签到 ,获得积分10
47秒前
上官若男应助榴莲咖啡采纳,获得10
53秒前
john完成签到,获得积分10
57秒前
1分钟前
榴莲咖啡发布了新的文献求助10
1分钟前
南风完成签到 ,获得积分10
1分钟前
属实有点拉胯完成签到 ,获得积分10
1分钟前
小强完成签到 ,获得积分10
1分钟前
汉堡包应助科研通管家采纳,获得10
1分钟前
在水一方应助科研通管家采纳,获得10
1分钟前
科研通AI2S应助榴莲咖啡采纳,获得30
2分钟前
Lotus完成签到 ,获得积分10
2分钟前
fatcat完成签到,获得积分10
2分钟前
日暮炊烟完成签到 ,获得积分0
2分钟前
白菜完成签到 ,获得积分10
2分钟前
胖胖猪完成签到,获得积分10
2分钟前
慕青应助junhan采纳,获得10
2分钟前
3分钟前
yujie完成签到 ,获得积分10
3分钟前
Adi完成签到,获得积分10
3分钟前
3分钟前
秋夜临完成签到,获得积分10
3分钟前
junhan发布了新的文献求助10
3分钟前
Hiaoliem完成签到 ,获得积分10
3分钟前
3分钟前
充电宝应助冷傲士萧采纳,获得10
3分钟前
开心夏旋完成签到 ,获得积分10
4分钟前
4分钟前
4分钟前
咯咯咯完成签到 ,获得积分10
4分钟前
摆渡人发布了新的文献求助10
4分钟前
chcmy完成签到 ,获得积分0
4分钟前
摆渡人完成签到,获得积分10
4分钟前
科研通AI2S应助mariawang采纳,获得10
4分钟前
xxiao完成签到 ,获得积分10
4分钟前
4分钟前
April完成签到 ,获得积分10
5分钟前
5分钟前
高分求助中
The late Devonian Standard Conodont Zonation 2000
Nickel superalloy market size, share, growth, trends, and forecast 2023-2030 2000
The Lali Section: An Excellent Reference Section for Upper - Devonian in South China 1500
Very-high-order BVD Schemes Using β-variable THINC Method 890
Mantiden: Faszinierende Lauerjäger Faszinierende Lauerjäger 800
PraxisRatgeber: Mantiden: Faszinierende Lauerjäger 800
A new species of Coccus (Homoptera: Coccoidea) from Malawi 500
热门求助领域 (近24小时)
化学 医学 生物 材料科学 工程类 有机化学 生物化学 物理 内科学 纳米技术 计算机科学 化学工程 复合材料 基因 遗传学 催化作用 物理化学 免疫学 量子力学 细胞生物学
热门帖子
关注 科研通微信公众号,转发送积分 3257066
求助须知:如何正确求助?哪些是违规求助? 2899025
关于积分的说明 8303390
捐赠科研通 2568282
什么是DOI,文献DOI怎么找? 1395014
科研通“疑难数据库(出版商)”最低求助积分说明 652929
邀请新用户注册赠送积分活动 630664