Study of Plastic Deformation of Pressure Chamber and the Effect on Fatigue Strength

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Project title

Code/計畫編號

MOST108-2218-E019-003

Translated Name/計畫中文名

壓力艙結構塑性變形對疲勞強度影響之評估

Project Coordinator/計畫主持人

Pai-Chen Guan

Funding Organization/主管機關

National Science and Technology Council

Department/Unit

Department of Systems Engineering and Naval Architecture

Website

https://www.grb.gov.tw/search/planDetail?id=13176651

Year

2019

Start date/計畫起

01-09-2019

Expected Completion/計畫迄

31-08-2020

Bugetid/研究經費

700千元

ResearchField/研究領域

土木水利工程

本計畫主要目標為利用計算與實驗，建立高降伏強度金屬在歷史塑性變形作用過後，塑性應變累積對疲勞強度的影響，並提出可供參考的SN曲線修正建議。這項計畫的緣由主要是因為壓力艙結構中，調節船重的水櫃分為經常性與非經常性使用櫃，在載具操作過程中必須承受所謂的工作壓力與潛深壓力，經常性水櫃用在一般運作狀態需要經常性承受任何操作所需要的水壓，所以強度上有很高的要求。而非經常性水櫃僅需在調節重量與姿態時使用，也不需要直接承受外部的水壓，所以此種結構一般強度設計上可以較低，也是結構優化時可以利用的部分。但是非經常性水櫃在完成建造後，仍然需要經過最極端狀況下之水壓測試，這種較高的測試載重在後續操作中比較不常遇到，僅在緊急狀態下會達到，但是由於次數很少，比較類似極端強度估算時。所以，如果可以在第一次測試時使用部分降伏後的應變硬化，可以在符合極端強度與疲勞強度估算的情況下，大幅度降低結構重量。為了瞭解結構行為，本計畫詳細任務包含：1.模擬水櫃在工作與潛深壓力情況下塑性變形與應變硬化累積程度；2.設計並進行高強度鋼材在經歷塑性變形後的疲勞實驗；3.找出可能的疲勞強度與歷史塑性變形關係 The objective of this project is to use numerical modeling and experiment to establish the effect of historical strain when high strength metal under cyclic loading conditions and to offer references of how we should adjust the SN curve. When pressure vessel is operating underwater, water tanks, which are usually used to adjust the gravitational center and the lifting center, suffer two type of loading conditions. They are the operation loading and the deep diving loading. Some of the water tanks usually doesn’t experience the real deep diving water pressure during operation except for the emergency scenario and its structure can be optimized to reduce overall weight. However, when the construction of the pressure vessel is complete, all water tanks still need to go through testing conditions which represent the deep diving condition. If plastic deformation occurs, those strength-reduced water tanks may have less fatigue life and affect the performance of the ship.To understand the structural behavior, this project will perform the following tasks: 1. Numerical modeling of water tanks under operation and deep diving loading conditions to obtain the strain hardening behavior; 2. Design and perform fatigue experiment of high strength metal with plastic deformation history; 3. Possible relation between fatigue strength and historical plastic deformation.

Keyword(s)

疲勞
塑性力學
應變硬化
循環加載
fatigue
plasticity
strain hardening
cyclic loading

DSpace CRIS

Study of Plastic Deformation of Pressure Chamber and the Effect on Fatigue Strength

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