Design Evaluation Method for Random Fatigue Based on Spectrum Characteristics

2012 ◽  
Vol 134 (3) ◽  
Author(s):  
Shinsuke Sakai ◽  
Satoshi Okajima ◽  
Satoshi Izumi ◽  
Naoto Kasahara
Keyword(s):  
Fatigue Damage ◽  
Design Process ◽  
Upper Bound ◽  
Stress Amplitude ◽  
Extreme Values ◽  
Spectral Characteristics ◽  
Evaluation Procedure ◽  
Design Evaluation ◽  
Random Waves ◽  
Random Fatigue

This paper shows a new design approach for random fatigue evaluation based on spectral characteristics. Fatigue damage under random loading is usually evaluated by first, decomposing random waves to stress amplitudes using the rainflow-cycle counting (RFC) method; then, evaluating fatigue damage using Palmgren–Miner’s linear summation rule. In the design process, the fluctuation of load is usually characterized through power spectral density (PSD). Therefore, the design process is expected to be generalized, if the fatigue damage is directly evaluated from the PSD together with the S-N diagram of the material. In fact, many properties related to fatigue damage, such as distribution of extreme values, can be derived theoretically from the geometrical properties of PSD. However, it is rather difficult to derive the distribution of stress amplitude counted by RFC theoretically due to its complicated procedure. In this paper, the upper bound of stress amplitude distribution is confirmed for many random waves generated by numerical simulation for many types of PSDs. Expressing the upper-bound distribution by a closed form function using PSD characteristics leads us to the direct evaluation of fatigue damage with a safety margin if the fatigue damage by a particular stress amplitude is approximated using a series expansion form. A simple procedure for approximating high-cycle fatigue damage for austenitic stainless steel and ferritic steel is proposed in this paper. Finally, a design evaluation procedure based on the fatigue-damage evaluation from PSD together with an S-N diagram is summarized.

Design Evaluation Method for Random Fatigue Based on Spectrum Characteristics

2009 ◽  
Author(s):  
Shinsuke Sakai ◽  
Satoshi Okajima ◽  
Satoshi Izumi ◽  
Naoto Kasahara
Keyword(s):  
Fatigue Damage ◽  
Design Process ◽  
Upper Bound ◽  
Stress Amplitude ◽  
Extreme Values ◽  
Spectral Characteristics ◽  
Evaluation Procedure ◽  
Design Evaluation ◽  
Approximation Procedure ◽  
Random Fatigue

This paper shows the new design approach for random fatigue evaluation based on spectral characteristics. Fatigue damage under random loading is usually evaluated according to the following steps: 1. decomposition of random wave to stress amplitude using the rainflow cycle counting method (RFC) 2. evaluation of fatigue damage using Palmgren-Miner’s linear summation rule. In design process, the fluctuation of load is usually characterized through power spectral density (PSD). Therefore, the design process is expected to be generalized if the fatigue damage is directly evaluated from the PSD together with S-N diagram of the material. In fact many properties related to fatigue damage, such as distribution of extreme values, can be derived theoretically from geometrical properties of PSD. However, concerning the distribution of stress amplitude counted by RFC, it is rather difficult to derive it theoretically due to its complicated procedure. In this paper, upper bound of stress amplitude distribution is confirmed for many random waves generated by numerical simulation for many types of PSD. Expressing the upper bound distribution by closed form function using PSD characteristics leads us to the direct evaluation of fatigue damage with safety margin if the fatigue damage by particular stress amplitude is approximated using some series expansion form. Simple approximation procedure of high cycle fatigue damage for austenitic stainless steel and ferritic steel will be proposed in the paper. Finally, design evaluation procedure for the fatigue damage evaluation from PSD together with S-N diagram is summarized.

Thermal Fatigue Evaluation Method of Pipes by Equivalent Stress Amplitude

2012 ◽  
Author(s):  
Takafumi Suzuki ◽  
Naoto Kasahara
Keyword(s):  
Fatigue Damage ◽  
Thermal Fatigue ◽  
Evaluation Method ◽  
Stress Amplitude ◽  
Equivalent Stress ◽  
Safety Margin ◽  
Evaluation Procedure ◽  
Fatigue Evaluation ◽  
High Cycle Thermal Fatigue ◽  
Equivalent Stress Amplitude

In recent years, reports have increased which are about failure cases caused by high cycle thermal fatigue both at light water reactors and fast breeder reactors. One of the biggest reasons of the cases is a turbulent mixing at a Tee-junction, where hot and cold temperature fluids are mixed, in a coolant system. In order to prevent thermal fatigue failures at Tee-junctions, The Japan Society of Mechanical Engineers (JSME) published the guideline S017-2003 (or JSME guideline) which is an evaluation method of high cycle thermal fatigue damage at a nuclear piping. It has some limitations in terms of its inconstant safety margin and its complexity in evaluation procedure, however. In order to solve these limitations, this paper proposes a new evaluation method of thermal fatigue damage with use of the “equivalent stress amplitude” which represents random temperature fluctuation effects on thermal fatigue damage. Because this new method makes methodology of evaluation clear and concise, it will contribute to improving the guideline for thermal fatigue evaluation.

A Procedure for Fast Evaluation of High-Cycle Fatigue Under Multiaxial Random Loading

2001 ◽  
Author(s):  
Bin Li ◽  
Manuel de Freitas
Keyword(s):  
Shear Stress ◽  
Fatigue Damage ◽  
High Cycle Fatigue ◽  
Stress Amplitude ◽  
Hydrostatic Stress ◽  
Evaluation Procedure ◽  
Cycle Fatigue ◽  
Random Loading ◽  
Proportional Loading ◽  
Fast Evaluation

Abstract This paper presents a fast evaluation procedure for high-cycle fatigue (HCF) under multiaxial random loading. The recent multiaxial cycle counting method of Wang and Brown is used to identify the loading reversals. For each identified reversal, the effective shear stress amplitude is directly calculated from the component stress ranges by an equation derived from the MCE approach, which is a newly developed method to account for non-proportional loading effect. This shear stress amplitude and the maximum hydrostatic stress during the time period of an identified reversal are used to evaluate the fatigue damage for that reversal by Crossland’s criterion. The fatigue damage of the loading block is then calculated by summing the damages of all the identified reversals by Miner’s rule. Comparisons with other multiaxial HCF approaches show that the procedure is a computationally efficient and conservative engineering approach.

A Procedure for Fast Evaluation of High-Cycle Fatigue Under Multiaxial Random Loading

2002 ◽  
Vol 124 (3) ◽  
pp. 558-563 ◽  
Author(s):  
Bin Li ◽  
Manuel de Freitas
Keyword(s):  
Shear Stress ◽  
Fatigue Damage ◽  
High Cycle Fatigue ◽  
Stress Amplitude ◽  
Hydrostatic Stress ◽  
Evaluation Procedure ◽  
Cycle Fatigue ◽  
Computationally Efficient ◽  
Random Loading ◽  
Fast Evaluation

This paper presents a fast evaluation procedure for high-cycle fatigue (HCF) under multiaxial random loading. The recent multiaxial cycle counting method of Wang and Brown is used to identify the loading reversals. For each identified reversal, the effective shear stress amplitude is directly calculated from the component stress ranges by an equation derived from the MCE approach, which is a newly developed method to account for nonproportional loading effect. This shear stress amplitude and the maximum hydrostatic stress during the time period of an identified reversal are used to evaluate the fatigue damage for that reversal by Crossland’s criterion. The fatigue damage of the loading block is then calculated by summing the damages of all the identified reversals by Miner’s rule. Comparisons with other multiaxial HCF approaches show that the procedure is a computationally efficient and conservative engineering approach.

Optimization Methods for Calculating Design Imprecision

1995 ◽  
Author(s):  
William S. Law ◽  
Erik K. Antonsson
Keyword(s):  
Fuzzy Sets ◽  
Design Process ◽  
Optimization Methods ◽  
Experiment Design ◽  
Design Evaluation ◽  
Preliminary Design ◽  
New Methods ◽  
Evaluation Functions ◽  
Incomplete Design ◽  
Alternative Designs

Abstract The preliminary design process is characterized by imprecision: the vagueness of an incomplete design description. The Method of Imprecision uses the mathematics of fuzzy sets to explicitly represent and manipulate imprecise preliminary design information, enabling the designer to explore the space of alternative designs in the context of the designer and customer’s preferences among alternatives. This paper introduces new methods to perform Method of Imprecision calculations for general non-monotonic design evaluation functions that address the practical necessity to minimize the number of function evaluations. These methods utilize optimization and experiment design.

Understanding Fatigue Damage Under High-Cycle Random Fatigue on the Basis of the Actual Fatigue Process.

1998 ◽  
Vol 64 (624) ◽  
pp. 2152-2157
Author(s):  
Masahiro MIYAKE ◽  
Shoji HARADA ◽  
Yoshihito KUROSHIMA ◽  
Masao TAKAHARA
Keyword(s):  
Fatigue Damage ◽  
Fatigue Process ◽  
Random Fatigue

Design Aspects of Green Water Loading on FPSOs

2003 ◽  
Author(s):  
Bas Buchner ◽  
Joaqui´n Lopez-Cortijo Garcia
Keyword(s):  
Evaluation Method ◽  
Offshore Structures ◽  
Green Water ◽  
Evaluation Procedure ◽  
Design Evaluation ◽  
Water Impact ◽  
Advantages And Disadvantages ◽  
Water Problem ◽  
Semi Empirical ◽  
Empirical Design

Green water is a significant problem for floating ship-type offshore structures, which needs to be assessed in the early design of the structure. First the present paper summarises a new semi-empirical design evaluation procedure that can assist in this design process. Then the practical design considerations related to the green water problem are discussed. There are different ways to solve the green water problem for a particular structure at a specific location: • Design the vessel and structures on the deck against the predicted green water impact load levels. • Optimise the bow shape (underwater shape and above water bow flare). • Increase the freeboard height such that green water is prevented completely. • Increase the freeboard height such that the green water loads are reduced to acceptable levels and design for these load levels. • Optimise the structures on the deck to minimise the green water impact loads. • Use protecting breakwaters in front of critical structures on the deck. All these options have their advantages and disadvantages. The semi-empirical design evaluation method and the different design options are discussed in a case study, focussing on a new DP FPSO concept.

An Assessment of Industrial Designers Use of Human Factors Criteria in Product Design Evaluation

1988 ◽  
Vol 32 (6) ◽  
pp. 420-424 ◽  
Author(s):  
Kamran Abedini
Keyword(s):  
Human Factors ◽  
Product Design ◽  
Design Process ◽  
Common Sense ◽  
Design Evaluation ◽  
Chi Square ◽  
Cad System ◽  
Actual Application ◽  
Chi Square Test ◽  
Industrial Designers

In order to know the pattern of actual application of human factors criteria by industrial designers an experiment was conducted by asking 87 students of industrial design to evaluate a CAD workstation after completing a course in “human factors in design”. The guidelines chosen for the evaluation were those related to design of visual displays, controls and workstation layout on the CAD system. Since the main objective was to see how many of the principles had become part of their “common sense” they were asked to evaluate the equipment without any reference to any books/notes. The subject's responses were compared with the human factors guidelines using a Chi-square test (0.05 significance). The results pointed out that industrial designers readily accepted general criteria such as visibility, operability, and accessibility but interpretability of the display was frequently unrecognized. Such information could be used by industrial designers and human factors experts to improve their cooperation in the design process and thus increase the acceptance and marketability of the product.

Modification for Fatigue Curves Based on Component Reliability

2012 ◽  
Vol 590 ◽  
pp. 116-121
Author(s):  
Li Juan Cao ◽  
Shou Ju Li ◽  
Yi Jin Shangguan
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Fatigue Life ◽  
Fatigue Damage ◽  
Safety Evaluation ◽  
Evaluation Procedure ◽  
Element Analysis ◽  
Component Reliability ◽  
The Relationship

Based on component reliability and scatter factors of material, a new procedure is proposed to modify fatigue curves. The scatter characteristics of fatigue life and strength are investigated. The relationship between modified S-N curves and scatter factors of material is presented. The safety evaluation procedure for fatigue damage based on finite element analysis is performed.

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