scholarly journals Reliability Analysis of a Mono-Tower Platform

1990 ◽  
Vol 112 (3) ◽  
pp. 237-243 ◽  
Author(s):  
P. H. Kirkegaard ◽  
I. Enevoldsen ◽  
J. D. So̸rensen ◽  
R. Brincker
Keyword(s):  
Fatigue Strength ◽  
Reliability Analysis ◽  
Failure Mode ◽  
Fatigue Failure ◽  
Cross Sections ◽  
Failure Modes ◽  
Damping Ratio ◽  
Limit State ◽  
Cumulative Fatigue Damage ◽  
Fatigue Limit State

In this paper, a reliability analysis of a Mono-tower platform is presented. The failure modes considered are yielding in the tube cross sections and fatigue failure in the butt welds. The fatigue failure mode is investigated with a fatigue model, where the fatigue strength is expressed through SN relations. In determining the cumulative fatigue damage, Palmgren-Miner’s rule is applied. Element reliability, as well as systems reliability, is estimated using first-order reliability methods (FORM). The sensitivity of the systems reliability to various parameters is investigated. It is shown that the fatigue limit state is a significant failure mode for the Mono-tower platform. Further, it is shown for the fatigue failure mode that the largest contributions to the overall uncertainty are due to the damping ratio, the inertia coefficient, the stress concentration factor, the model uncertainties, and the parameters describing the fatigue strength.

Reliability analysis of wood I-joists

1993 ◽  
Vol 20 (4) ◽  
pp. 564-573 ◽  
Author(s):  
R. O. Foschi ◽  
F. Z. Yao
Keyword(s):  
Reliability Analysis ◽  
Carrying Capacity ◽  
Failure Modes ◽  
Limit State ◽  
Load Carrying Capacity ◽  
Limit States ◽  
Element Analysis ◽  
Strength Limit ◽  
Reliability Method ◽  
Load Carrying

This paper presents a reliability analysis of wood I-joists for both strength and serviceability limit states. Results are obtained from a finite element analysis coupled with a first-order reliability method. For the strength limit state of load-carrying capacity, multiple failure modes are considered, each involving the interaction of several random variables. Good agreement is achieved between the test results and the theoretical prediction of variability in load-carrying capacity. Finally, a procedure is given to obtain load-sharing adjustment factors applicable to repetitive member systems such as floors and flat roofs. Key words: reliability, limit state design, wood composites, I-joist, structural analysis.

Tooth Flank Breakage: Influences on Subsurface Initiated Fatigue Failures of Case Hardened Gears

2013 ◽  
Author(s):  
Karsten Stahl ◽  
Bernd-Robert Höhn ◽  
Thomas Tobie
Keyword(s):  
Failure Mode ◽  
Fatigue Failure ◽  
Failure Modes ◽  
Calculation Model ◽  
Operating Conditions ◽  
Material Strength ◽  
Gear Design ◽  
Increased Risk ◽  
Tooth Flank ◽  
Flank Surface

Pitting and tooth root breakage are typical fatigue failure modes of case hardened gears. Both failure types are usually initiated at the surface or close to the surface. General trends in modern gear industry, such as improved gear design with adequate flank modifications, high-quality gear materials and high-performance lubricants, modern manufacturing processes with additional post-processes as shot peening and superfinishing as well as advanced calculation methods, have allowed an optimized utilization of the allowable pitting and bending stress numbers in recent years. As a result of the increased power density, however, the stresses below the surface rise with the consequence of an increased risk of fatigue failure initiation in the material below the surface. This paper describes main characteristics of a failure mode characterized by tooth breakages which start in the area of the active flank from cracks that are typically initiated at a considerable depth beneath the loaded flank surface. Based on theoretical and experimental investigations, relevant influence parameters related to gear design, operating conditions and material strength on the failure mode “Tooth Flank Breakage” will be discussed and basic principles of a developed calculation model to evaluate the risk of such failures presented. Finally, exemplarily experimental results from gear running tests, which failed due to flank breakage, are compared to the results of the new calculation model.

Fatigue strength assessment of ship structures accounting for a coating life and corrosion degradation

2016 ◽  
Vol 7 (2) ◽  
Author(s):  
Yordan Garbatov
Keyword(s):  
Finite Element ◽  
Fatigue Strength ◽  
Fatigue Damage ◽  
Hot Spot ◽  
Limit State ◽  
State Function ◽  
Fatigue Reliability ◽  
Hot Spot Stress ◽  
Notch Stress ◽  
Fatigue Limit State

Purpose Fatigue strength and reliability assessment of complex double hull oil tanker structures, based on different local structural finite element approaches, is performed accounting for the uncertainties originating from load, nominal stresses, hot spot stress calculations, weld quality estimations and misalignments and fatigue S-N parameters including the correlation between load cases and the coating life and corrosion degradation. Design/methodology/approach Ship hull wave-induced vertical and horizontal bending moments and pressure are considered in the analysis. Stress analyses are performed based on the nominal, local hot spot and notch stress approaches. A linear elastic finite element analysis is used to determine the stress distribution around the welded details and to estimate structural stresses of all critical locations. Fatigue damage is estimated by employing the Palmgren-Miner approach. The importance of the contribution of each random variable to the uncertainty of the fatigue limit state function is also estimated. The probability of fatigue damage of hot spots is evaluated taking into account random coating life and corrosion wastage. Fatigue reliability, during the service life, is modelled as a system of correlated events. Findings The fatigue analysis showed that the fatigue damage at the hotspot, located at the flange of the stiffener close to the cut-out, is always highest in the cases of the structural hot spot stress and effective notch stress approaches, except for the one of the nominal stress approach. The sensitivities of the fatigue limit state function with respect to changes in the random variables were demonstrated showing that the uncertainty in the fatigue stress estimation and fatigue damage are the most important. Fatigue reliability, modelled as a parallel system of structural hot spots and as a serial system of correlated events (load cases) was evaluated based on the Ditlevsen bounds. As a result of the performed analysis, reliability and Beta reliability indexes of lower and upper bounds were estimated, which are very similar to the ones adopted for ultimate strength collapse as reported in literature. Originality/value This paper develops a very complex fatigue strength and reliability assessment model for analysing a double hull oil tanker structure using different local structural finite element approaches accounting for the associated uncertainties and the correlation between load cases and the coating life and corrosion degradation. The developed model is flexible enough to be applied for analysing different structural failure modes.

Studies on Fatigue Properties of Steel with Co-Based Alloy Hardfacing Coating

2010 ◽  
Vol 118-120 ◽  
pp. 161-165
Author(s):  
Hong Xia Deng ◽  
Hui Ji Shi ◽  
Seiji Tsuruoka ◽  
Hui Chen Yu ◽  
Bin Zhong
Keyword(s):  
Fatigue Strength ◽  
Failure Mode ◽  
Failure Modes ◽  
Fatigue Tests ◽  
Fatigue Properties ◽  
Main Task ◽  
Interface Failure ◽  
Coating Failure ◽  
Rotating Bending Fatigue ◽  
Stellite 12

The main task of this paper was to evaluate the influence of hardfacing technique and service temperature on the fatigue properties of heat-resistant steel X45CrSi9-3 coated with Co-based alloy Stellite 12. The results of rotating bending fatigue tests showed that at room temperature (RT), the fatigue strength of specimens welded by the acetylene gas welding (AGW) was lower than that of specimens welded by the plasma transferred arc welding (PTAW). For PTAW specimens, the fatigue strength at 500oC was much higher than that at RT. Two failure modes were presented, one was termed as the coating failure mode at RT and the other was termed as coating-interface failure mode at 500oC. The fatigue life prediction was conducted by using a modified Murakami’s model.

scholarly journals Reliability Analysis of Anchored Geotechnical Structures for the Design Limit States

2020 ◽  
Vol 8 (2) ◽  
pp. 35-47
Author(s):  
Sohaib K Al-Mamoori ◽  
Laheab A. Al-Maliki ◽  
Khaled El-Tawel
Keyword(s):  
Reliability Analysis ◽  
Reliability Index ◽  
Failure Modes ◽  
Limit State ◽  
Tensile Failure ◽  
Limit States ◽  
Geotechnical Parameters ◽  
Retaining Structure ◽  
Geotechnical Structures ◽  
Bending Failure

Reliability has been considered of magnificent importance in engineering design specially in geotechnical engineering due to the unpredictable conditions of soil layers. It is essential to establish well- designed failure modes that could guarantee safety and durability of the proposed structure. This study aims to suggest a reliability analyses procedure for retaining walls by the mean of a reliability index β using the specifications of AASHTO Bridge Design 2002, Eurocode 7, and DIN EN 1993-5 norms. Two failure modes; Tensile failure of tendon (G1) and Failure by bending (G2) were studied and compared by using equation of the Design Limit State (DLS) and by taking some basic geotechnical parameters as Random Variables RV. The analyses demonstrated that the reliability index β and probability of failure Pf are the most important parameter in the reliability analysis. Also, the suitable height (H) for the retaining structure (for all angles ϴ) equals to 6 m and the most critical angle is ϴ= 45º to prevent the failure by tensile of tendon. While the bending failure reliability analysis shows that all heights of retaining structure are suitable. After comparing the two cases it was found that (G1) is more dangerous than (G2).

Fatigue Strength Reliability Analysis of Diesel Connecting Rod Based on Stochastic Finite Element Method

1999 ◽  
Vol 121 (4) ◽  
pp. 741-745 ◽  
Author(s):  
C. Yi ◽  
W. Mingwu ◽  
T. Ling
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Fatigue Strength ◽  
Stress Analysis ◽  
Reliability Analysis ◽  
Fatigue Failure ◽  
Failure Criterion ◽  
Stochastic Finite Element Method ◽  
Stochastic Finite Element ◽  
Connecting Rod

In this paper, stress of a diesel connecting rod (CR) is analyzed by the perturbation stochastic finite element method (PSFEM). A fatigue failure criterion of a diesel CR is also put forward with Corten-Dolan fatigue cumulative damage theory. Based on fatigue failure criterion and the results of stochastic stress analysis, the advanced first order second moment (AFOSM) method is used for fatigue strength reliability analysis. It is shown that PSFEM is efficient and accurate in stochastic stress analysis by comparing with Monte-Carlo simulation. The analysis shows that the reliability of a certain type of diesel CR is 0.99917, which coincides with the statistical data from the factory. It is also found that operating parameters such as combustion peak pressure and engine rotary speed have the greatest influence on CR reliability because of the large variances and high stress response sensitivity.

Propagation of Contact Fatigue From Surface and Subsurface Origins

1966 ◽  
Vol 88 (3) ◽  
pp. 624-635 ◽  
Author(s):  
W. E. Littmann ◽  
R. L. Widner
Keyword(s):  
Fatigue Life ◽  
Fatigue Strength ◽  
Fatigue Failure ◽  
Contact Stress ◽  
Environmental Conditions ◽  
Failure Modes ◽  
Contact Fatigue ◽  
Initiation And Propagation ◽  
Tapered Roller ◽  
Tapered Roller Bearings

Fatigue life of tapered roller bearings and other elements subject to cyclic contact stress reflects the fatigue strength of the selected material under given environmental conditions. The various modes of contact-fatigue failure have been classified according to their appearance and the factors which promote their initiation and propagation. Illustrations of the various failure modes include rig test specimens and bearings representing normal catalog-rated life under laboratory and application environments. Evidence is presented for the propagation of contact fatigue from surface and subsurface origins.

Passive System Reliability Modeling of the Combination of Failure Modes

2016 ◽  
Author(s):  
Luciano Burgazzi
Keyword(s):  
Reliability Analysis ◽  
Failure Mode ◽  
System Reliability ◽  
Probabilistic Models ◽  
Failure Modes ◽  
Natural Circulation ◽  
Heat Transfer Process ◽  
Passive System ◽  
Modes Of Failure ◽  
Degradation Failure

Innovative probabilistic models to extend the reliability analysis of passive systems under different modes of failure are proposed. The prevailing failure mode on the system can be predicted through the failure probability assessment on each specific mode. A realistic case is presented to analyze a passive system with two kinds of major failure modes — natural circulation stoppage due to e.g., isolation valve closure (a catastrophic failure) and heat transfer process degradation due to e.g., deposit thickness on component surfaces (a degradation failure). Modeling of each individual failure mode together with system reliability analysis is presented and results are discussed.

Mechanical Component’s Dimension Design With Required Reliability by the Monte Carlo Method

2020 ◽  
Author(s):  
Xiaobin Le
Keyword(s):  
Monte Carlo ◽  
Monte Carlo Method ◽  
Failure Mode ◽  
Failure Modes ◽  
Limit State ◽  
Design Parameters ◽  
Mechanical Component ◽  
Component Design ◽  
The Monte Carlo Method ◽  
State Functions

Abstract Since the main design parameters in a mechanical component design have some uncertainties and should be treated as random variables, the reliability of a component is a better measurement of the safe status of a component. A component will not be reliable unless it is designed with specified reliability. Therefore, the mechanical component design should be a dimension design with the required reliability. The fundamental concept of the Monte Carlo method is to plug-in randomly generated numerical values into the governing equation of a design problem to get a trial result. The Monte Carlo method has become so powerful numerical simulation approach in almost every field such as optimization, numerical integration, and reliability calculation. But for reliability engineering, most of the literature shows how to use the Monte Carlo method to calculate the reliability of a component. This paper will propose the modified Monte Carlo method to determine a component dimension with required reliability. This paper first discusses and establishes typical limit state functions of a component under static loads. These limit state functions cover two failure modes including the failure mode due to strength and the failure mode due to excessive deformation. Then, the procedure and the flowchart of the modified Monte Carlo method will be explained in detail. The provided procedure and the flowchart are easy to be followed for compiling a MATLAB program to conduct a dimension design with required reliability. Two examples will show how to implement the proposed new method for conducting a dimension design with required reliability.

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