Probabilistic Fatigue Life Assessment of a Titanium Alloy Impeller for Turbo Shaft Engine Application

2015 ◽  
Author(s):  
Esakki Muthu Shanmugam ◽  
Raghu V. Prakash ◽  
Sakthivel Ammaiappan
Keyword(s):  
Titanium Alloy ◽  
Fatigue Life ◽  
Equivalent Strain ◽  
Life Assessment ◽  
Centrifugal Impeller ◽  
Test Results ◽  
Distribution Method ◽  
Reliability Improvement ◽  
Fatigue Life Assessment ◽  
Strain Method

The fatigue life of the titanium alloy centrifugal impeller is estimated based on strain life method. a) Equivalent Strain Method and b) Smith Watson Topper Method are used. The probabilistic analysis of fatigue life is carried out by Weibull distribution method. The fatigue life of the impeller is assessed through cyclic spin test. The results are compared. The Equivalent Strain Method is found non conservative. The average fatigue life of the impeller is estimated as 12000 cycles by SWT method, which is found more closer to test results. The reliability improvement from 95% to 99% reduces the fatigue life around 18%.

Fatigue Life Analysis of Polyurethane Bending Stiffeners

2005 ◽  
Author(s):  
Fre´de´ric Demanze ◽  
Didier Hanonge ◽  
Alain Chalumeau ◽  
Olivier Leclerc
Keyword(s):  
Fatigue Life ◽  
Effective Strain ◽  
Fatigue Behaviour ◽  
Life Assessment ◽  
Test Results ◽  
Critical Areas ◽  
Fatigue Life Assessment ◽  
Fatigue Data ◽  
Life Analysis ◽  
Fatigue Life Analysis

Following some experiences of bending stiffeners fatigue failures during full scale tests performed at Flexi France on flexible pipe and stiffener assemblies, Technip decided to launch in 1999 a major research program on fatigue life analysis of bending stiffeners made of Polyurethane material. This fatigue life assessment is now systematically performed by Technip for all new design of flexible riser bending stiffeners. This totally innovative method comprises a number of features as follows: Firstly fatigue behaviour of polyurethane material is described. The theoretical background, based on effective strain intensity factor, is detailed, together with experimental results on laboratory notched samples, solicited under strain control for various strain ratios, to obtain fatigue data. These fatigue data are well fitted by a power law defining the total number of cycles at break as a function of the effective strain intensity factor. The notion of fatigue threshold, below which no propagation is observed, is also demonstrated. Secondly the design used by Technip for its bending stiffeners, and most of all the critical areas regarding fatigue for these massive polyurethane structures are presented. Thirdly the methodology for fatigue life assessment of bending stiffeners in the critical areas defined above is discussed. Calibration of the strain calculation principle is presented versus finite element analysis. Based on all fatigue test results, the size of the equivalent notch to be considered at design stage, in the same critical areas, is discussed. Finally, a comprehensive calibration of the methodology according to full and middle scale test results is presented. The present paper is therefore a step forward in the knowledge of fatigue behaviour of massive polyurethane bending stiffener structures, which are critical items for flexible risers integrity, and widely used in the offshore industry. The confidence in bending stiffeners reliability is greatly enhanced by the introduction of this innovative methodology developed by Technip.

Blade Fatigue Life Assessment of an Axial Compressor Rotor Through Probabilistic Method

2017 ◽  
Author(s):  
Esakki Muthu Shanmugam ◽  
Raghu V. Prakash ◽  
Shakthivel Ammaiappan
Keyword(s):  
Fatigue Life ◽  
Probabilistic Method ◽  
Axial Compressor ◽  
Test Methods ◽  
Test Method ◽  
Life Assessment ◽  
Distribution Method ◽  
Compressor Rotor ◽  
Fatigue Life Assessment ◽  
Cumulative Fatigue Damage

The fatigue life of the titanium alloy axial compressor rotor blade was estimated based on stress based life method. The fatigue life of the compressor blade was evaluated through incremental amplitude test method. The incremental amplitude test method involves cumulative fatigue damage at different stress levels by using Miner’s Hypothesis. The probabilistic analysis of fatigue life was carried out by Weibull distribution method. The analytical and test methods results were compared and found satisfactory.

scholarly journals Unified Principal S–N Equation for Friction Stir Welding of 5083 and 6061 Aluminum Alloys

2021 ◽  
Vol 34 (1) ◽  
Author(s):  
Xiangwei Li ◽  
Ji Fang ◽  
Xiaoli Guan
Keyword(s):  
Aluminum Alloy ◽  
Fatigue Life ◽  
Friction Stir Welding ◽  
Test Data ◽  
Fatigue Tests ◽  
Life Assessment ◽  
Test Results ◽  
Friction Stir ◽  
Fatigue Life Assessment ◽  
Curve Equation

AbstractWith the popularization of friction stir welding (FSW), 5083-H321 and 6061-T6 aluminum alloy materials are widely used during the FSW process. In this study, the fatigue life of friction stir welding with two materials, i.e., 5083-H321 and 6061-T6 aluminum alloy, are studied. Fatigue tests were carried out on the base metal of these two materials as well as on the butt joints and overlapping FSW samples. The principle of the equivalent structural stress method is used to analyze the FSW test data of these two materials. The fatigue resistances of these two materials were compared and a unified principal S–N curve equation was fitted. Two key parameters of the unified principal S–N curve obtained by fitting, Cd is 4222.5, and h is 0.2693. A new method for an FSW fatigue life assessment was developed in this study and can be used to calculate the fatigue life of different welding forms with a single S–N curve. Two main fatigue tests of bending and tension were used to verify the unified principal S–N curve equation. The results show that the fatigue life calculated by the unified mean 50% master S–N curve parameters are the closest to the fatigue test results. The reliability, practicability, and generality of the master S–N curve fitting parameters were verified using the test data. The unified principal S–N curve acquired in this study can not only be used in aluminum alloy materials but can also be applied to other materials.

scholarly journals Mapping of scatter in fatigue life assessment of welded structures—a round-robin study

2021 ◽  
Author(s):  
Gustav Hultgren ◽  
Mansoor Khurshid ◽  
Peter Haglund ◽  
Zuheir Barsoum
Keyword(s):  
Fatigue Life ◽  
Round Robin ◽  
Life Assessment ◽  
Fatigue Life Assessment ◽  
Fatigue Life Estimation ◽  
Box Structures ◽  
Load Carrying ◽  
Local Stresses ◽  
Sources Of Variation ◽  
Global And Local

AbstractA round-robin study has been carried out within a national project in Sweden with the addition of an international participant, where several industrial partners and universities are participating. The project aims to identify variation and sources of variation in welding production, map scatter in fatigue life estimation, and define and develop concepts to reduce these, in all steps of product development. The participating organisations were asked to carry out fatigue life assessment of welded box structures, which is a component in load-carrying structures. The estimations of fatigue life have also been compared with fatigue test results. Detailed drawings, loads and material data were also given to the participants. The participants were supposed to use assessment methods based on global and local stresses using the design codes or recommendations they currently use in-house. Differences were identified between both methods and participants using the same codes/recommendations. Applicability and conditions from the cases in the codes were also identified to be differently evaluated between the participants. It could be concluded that for the applied cases the nominal stress method often overestimated the fatigue life and had a high scatter in the estimations by different participants. The effective notch method is conservative in comparison to the life of tested components with little scatter between the results derived by the participants.

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