Some Observations On Damage Tolerance Analyses in Pressure Vessels

In order to unravel the damage mechanisms occurring in composite-overwrapped pressure vessels (COPVs) subjected to crash conditions, a combined experimental-numerical study has been performed. For the purpose of generality and simplicity, quasi-static contacts on filament-wound cylinders are considered in this paper, as a precursor for geometrically complex impacts on COPVs. Rings with different wall thicknesses are tested to assess how failure mechanisms change when transitioning from thin-wall to thick-wall cylinders. The experimental results are used to identify, which mechanisms occur, and the numerical model is subsequently exploited to analyze the corresponding mechanisms. Based on the understanding of the mechanisms, a method to improve the damage tolerance of thick cylinders is presented. The rings are locally pre-delaminated during manufacturing to promote the growth of these pre-delaminations instead of the initiation of fiber failure.

Download Full-text

Design of Horizontal Pressure Vessels Using the Decision Support Problem Technique

Journal of Mechanisms Transmissions and Automation in Design ◽

10.1115/1.3260803 ◽

1986 ◽

Vol 108 (2) ◽

pp. 203-210 ◽

Cited By ~ 5

Author(s):

N. Nguyen ◽

F. Mistree

Keyword(s):

Decision Support ◽

Damage Tolerance ◽

Design Method ◽

Pressure Vessels ◽

General Application ◽

Wide Range ◽

Conflicting Objectives ◽

Horizontal Pressure ◽

Computer Based ◽

System Variables

A design method has been developed to determine systematically the system variables that will best achieve multiple design objectives involving both cost and damage tolerance of horizontal vessel design. The method is computer based, and is particularly suited for designing pressure vessels using multiple (conflicting) objectives. The method has been tested and validated against a computer program used extensively in industry. Better results by the new design method are demonstrated through case studies. The results indicate a wide range of vessel dimensions to which the design method can be applied. In general, application of the method will increase the efficiency of the design of horizontal pressure vessels.

Download Full-text

Fatigue-Life Assessment

10.31399/asm.hb.v11a.a0006819 ◽

2021 ◽

pp. 98-133

Author(s):

Phillip E. Prueter

Keyword(s):

Fatigue Life ◽

Damage Tolerance ◽

Pressure Vessels ◽

Life Assessment ◽

Cyclic Plasticity ◽

Fatigue Assessment ◽

Fatigue Life Assessment ◽

Component Design ◽

Engineering Mechanics ◽

Growth Approach

Abstract This article offers an overview of fatigue fundamentals, common fatigue terminology, and examples of damage morphology. It presents a summary of relevant engineering mechanics, cyclic plasticity principles, and perspective on the modern design by analysis (DBA) techniques. The article reviews fatigue assessment methods incorporated in international design and post construction codes and standards, with special emphasis on evaluating welds. Specifically, the stress-life approach, the strain-life approach, and the fracture mechanics (crack growth) approach are described. An overview of high-cycle welded fatigue methods, cycle-counting techniques, and a discussion on ratcheting are also offered. A historical synopsis of fatigue technology advancements and commentary on component design and fabrication strategies to mitigate fatigue damage and improve damage tolerance are provided. Finally, the article presents practical fatigue assessment case studies of in-service equipment (pressure vessels) that employ DBA methods.

Download Full-text

1250-kilovolt scanning transmission electron microscope

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100113007 ◽

1984 ◽

Vol 42 ◽

pp. 624-625

Author(s):

T. Imura ◽

S. Maruse ◽

K. Mihama ◽

M. Iseki ◽

M. Hibino ◽

...

Keyword(s):

High Voltage ◽

Electron Probe ◽

Scanning Transmission Electron Microscope ◽

Pressure Vessels ◽

Practical Applications ◽

Voltage Generator ◽

Transmission Electron ◽

Scanning Transmission ◽

New Applications ◽

High Voltage Generator

Ultra high voltage STEM has many inherent technical advantages over CTEM. These advantages include better signal detectability and signal processing capability. It is hoped that it will explore some new applications which were previously not possible. Conventional STEM (including CTEM with STEM attachment), however, has been unable to provide these inherent advantages due to insufficient performance and engineering problems. Recently we have developed a new 1250 kV STEM and completed installation at Nagoya University in Japan. It has been designed to break through conventional engineering limitations and bring about theoretical advantage in practical applications.In the design of this instrument, we exercised maximum care in providing a stable electron probe. A high voltage generator and an accelerator are housed in two separate pressure vessels and they are connected with a high voltage resistor cable.(Fig. 1) This design minimized induction generated from the high voltage generator, which is a high frequency Cockcroft-Walton type, being transmitted to the electron probe.

Download Full-text

Probabilistic evaluation of detection capability of eddy current testing to inspect pitting on a stainless steel clad using multiple signal features

International Journal of Applied Electromagnetics and Mechanics ◽

10.3233/jae-209306 ◽

2020 ◽

Vol 64 (1-4) ◽

pp. 47-55

Author(s):

Takuma Tomizawa ◽

Haicheng Song ◽

Noritaka Yusa

Keyword(s):

Stainless Steel ◽

Eddy Current ◽

Pressure Vessels ◽

Eddy Current Testing ◽

Probability Of Detection ◽

Current Testing ◽

Multiple Signal ◽

Signal Features ◽

Inner Surface ◽

Drill Holes

This study proposes a probability of detection (POD) model to quantitatively evaluate the capability of eddy current testing to detect flaws on the inner surface of pressure vessels cladded by stainless steel and in the presence of high noise level. Welded plate samples with drill holes were prepared to simulate corrosion that typically appears on the inner surface of large-scale pressure vessels. The signals generated by the drill holes and the noise caused by the weld were examined using eddy current testing. A hit/miss-based POD model with multiple flaw parameters and multiple signal features was proposed to analyze the measured signals. It is shown that the proposed model is able to more reasonably characterize the detectability of eddy current signals compared to conventional models that consider a single signal feature.

Download Full-text