scholarly journals Influence of the Fatigue Load Level and the Hole Diameter on the Laminate Structure’s Fatigue Performance

2018 ◽  
Vol 2018 (10) ◽  
pp. 21-30
Author(s):  
Małgorzata Zalewska
Keyword(s):  
Fatigue Testing ◽  
Damage Tolerance ◽  
Fatigue Tests ◽  
Load Level ◽  
Hole Diameter ◽  
Test Results ◽  
Fatigue Load ◽  
Loading Mode ◽  
Load Limit ◽  
Two Parameters

Abstract Damage tolerance of composite aircraft structure is one of the main areas of research, important when a new product is being developed. There are a number of variables, such as damage characteristics (dent depth, delamination area) and loading parameters (load type, amplitude of cyclic loading, load sequence) that need to be investigated experimentally [1]. These tests of composite materials are usually performed at an element level and are carried out in order to validate the analytical model, developed to predict the full-scale component’s behaviour. The paper presents the results of compression testing of the [36/55/9] carbon fibre/epoxy laminate, manufactured with the Automated Fibre Placement technology (AFP) and subjected to static and fatigue loads. The laminate compression loading mode was achieved through sandwich 4-point flexure. At the stage of fatigue testing, two parameters were investigated: the damage size, simulated by the hole diameter and the fatigue load level. Based on the test results, the laminate fatigue load limit equal to 75% of the OHC failure load was evaluated. By collating the static and fatigue tests results, the damage tolerance characteristic of the considered laminate was created.

scholarly journals Long-Life Fatigue Test Results for Two Nickel-Base Structural Alloys

1981 ◽  
Vol 103 (2) ◽  
pp. 126-132 ◽  
Author(s):  
D. F. Mowbray ◽  
E. V. Giaquinto ◽  
F. J. Mehringer
Keyword(s):  
Fatigue Test ◽  
Closed Loop ◽  
Iron Alloy ◽  
Fatigue Tests ◽  
Alloy 600 ◽  
Test Results ◽  
Loading Mode ◽  
Long Life ◽  
Cold Worked ◽  
Nickel Base

This paper reports the results of fatigue tests on two nickel-base alloys, hot-cold-worked and stress-relieved nickel-chrome-iron Alloy 600 and mill-annealed nickel-chrome-moly-iron Alloy 625 in which S-N data were obtained in the life range of 106 to 1010 cycles. The tests were conducted in air at 600°F, in the reversed membrane loading mode, at a frequency of ~ 1850 Hz. An electromagnetic, closed loop servo-controlled machine was built to perform the tests. A description of the machine is given.

scholarly journals EXPERIMENTAL STUDY ON POST-BUCKLED COMPOSITE SINGLE-STRINGER SPECIMENS WITH INITIAL DELAMINATION UNDER FATIGUE LOADS

2021 ◽  
Author(s):  
ANTONIO RAIMONDO ◽  
JAVIER PAZ MENDEZ ◽  
CHIARA BISAGNI
Keyword(s):  
Static Load ◽  
Compressive Load ◽  
Fatigue Tests ◽  
Load Level ◽  
Image Correlation ◽  
Compressive Behavior ◽  
Fatigue Load ◽  
Out Of Plane ◽  
Post Buckling ◽  
Correlation System

The fatigue damage tolerance of a composite stiffened structure in post-buckling conditions is experimentally investigated in this work. Single-stringer specimens with an initial delamination, artificially created during the manufacturing process, are tested under cyclic compressive load. Six nominally identical specimens are manufactured: two tested under quasi-static load to understand the compressive behavior of the structure and four under fatigue load cycling between pre- and post-buckling conditions at two different maximum loads. During the tests, digital image correlation system and ultrasonic C-scan are adopted to follow the evolution of the out-of-plane displacements and the propagation of the delamination. Depending on the load level, the delamination starts to grow already in the first cycle or after a few thousand cycles, but in both cases the propagation is fast at the beginning, then slows down gradually. The fatigue tests are interrupted after 150,000 cycles and the specimens are subjected to quasi-static compressive load to evaluate the residual strength of the structure.

scholarly journals Fatigue Life Testing of Locally Additive Manufactured AlSilOMg Test Specimens

R&D Journal ◽  
2021 ◽  
Vol 37 ◽  
Author(s):  
N. Agenbag ◽  
C. McDuling
Keyword(s):  
Surface Roughness ◽  
Fatigue Life ◽  
Additive Manufacturing ◽  
Surface Finish ◽  
Material Properties ◽  
Fatigue Testing ◽  
Fatigue Tests ◽  
Surface Finishing ◽  
Test Results ◽  
Static Testing

ABSTRACT In order for additive manufacturing to become a viable manufacturing methodfor aerospace engineering, it is required that exhaustive static and fatigue testing be performed. The testing is required in order to describe material properties in a statistical manner. Fatigue tests were performed on standard additive manufactured ASTM E466 test specimens in order to obtain the low (1000 cycles) to high cycle (1E6 cycles) behaviour of AlSi10Mg. The specimens were manufactured using non-heat treated, but stress relieved specimens. Specimens were printed in three build directions, namely the XY (parallel with build plate), 45 degree and vertical direction as measured with respect to the build baseplate. The three different directions were chosen to investigate the sensitivity of the material properties to the build direction. The specimens were stress relieved on the baseplate. Static testing was also performed on specimens according to ASTM E8/E8M. The specimens were produced to have a surface finish representative of standard deburring techniques used in the aerospace industry. The surface roughness on the specimens were measured. The scatter in test data as a result of the surface finish on material properties is quantified. It is a requirement to quantify the effect of the surface roughness on fatigue failure allowable values since a machined type finish (less than 3.2 micrometer) is not always practically possible to achieve with additive manufactured structures. This is because the organic shapes produced with additive manufacturing makes some surfaces inaccessible to normal surface finishing techniques. Furthermore, some internal structures such as lattice structures are completely inaccessible to surface finishing techniques such as polishing or lapping. In addition to the surface roughness the roundness of the test section was also measured using inspection equipment. This was required since the industrial deburring techniques did not yield a completely concentric test section as a lathe operation would produce. Once again this is representative of an additive manufactured structure. The fatigue tests were performed at an R-ratio of 0.1. The test results were used to produce Wöhler or S-N curves for the material in all three material directions. The scatter was quantified using industry accepted methods. The results were compared with fatigue test results from literature of specimens produced with a lathe in order to compare a practical industrial surface finish on an additive manufactured component with a machined surface finish. It was found that the build support structures of the additive manufacturing process causes stress concentrations in the fatigue test specimens. This leads to a reduction in fatigue life and an increase in the scatter of the results. Additional keywords: Additive manufacturing, fatigue testing, static testing, aluminium, AlSi10Mg.

scholarly journals Experimental and Analytical Study on Deformation Behavior in Hogging Moment Regions of Composite Beams

2020 ◽  
Vol 2020 ◽  
pp. 1-10
Author(s):  
Aiming Song ◽  
Qi Luo ◽  
Shui Wan ◽  
Zhicong Li
Keyword(s):  
Analytical Study ◽  
Fatigue Behavior ◽  
Residual Deformation ◽  
Composite Beams ◽  
Fatigue Tests ◽  
Structural Deformation ◽  
Test Results ◽  
Fatigue Load ◽  
Deformation Curves ◽  
Good Agreement

The results of an experimental and analytical study on the static and fatigue behavior in steel-concrete composite beams under the hogging moment were presented in this paper, and the structural deformation was discussed cautiously and emphatically. Firstly, the static and fatigue tests on three inverted simply supported beams were conducted. The development of cracks under static loading, the load-deformation curves, and the values of residual deformation under fatigue load were recorded and analyzed in detail. Several meaningful conclusions were obtained from the analysis of experimental results. To study the development laws of residual deformation under fatigue load, the analytical methods of residual midspan deflection and residual rebar strain were proposed, respectively. The limitation and accuracy of the presented models were studied according to the comparison between the prediction and measured results. The calculation values of the proposed models showed good agreement with the test results. Finally, the design recommendations of fatigue deformation were proposed according to the experimental and analytical study on steel-concrete composite beams subjected to hogging moment.

scholarly journals On the Influence of Control Type and Strain Rate on the Lifetime of 50CrMo4

Metals ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 1458
Author(s):  
Max Benedikt Geilen ◽  
Josef Arthur Schönherr ◽  
Marcus Klein ◽  
Dominik Sebastian Leininger ◽  
Alexander Giertler ◽  
...  
Keyword(s):  
Strain Rate ◽  
Fatigue Testing ◽  
Cyclic Stress ◽  
Fatigue Tests ◽  
Carbon Steels ◽  
Cyclic Test ◽  
Test Results ◽  
Strain Rate Effects ◽  
Rate Dependent ◽  
Ultrasonic Fatigue

In this study, we investigate the influence of control type and strain rate on the lifetime of specimens manufactured from 50CrMo4. This influence is described by a strain rate dependent method that uses cyclic stress strain curves to correct displacement-controlled cyclic test results. The objective of this correction is to eliminate the stress related differences between displacement-controlled cyclic test results and force-controlled cyclic test results. The method is applied to the results of ultrasonic fatigue tests of six different combinations of heat treatment, specimen geometry (notch factor) and atmosphere. In a statistical analysis, the corrected results show an improved agreement with test results obtained on conventional fatigue testing equipment with similar specimens: the standard deviation in combined data sets is significantly reduced (p = 4.1%). We discuss the literature on intrinsic and extrinsic strain rate effects in carbon steels.

A New Tool for Design and Certification of Aircraft Turbine Rotors

2002 ◽  
Author(s):  
Gerald R. Leverant ◽  
R. Craig McClung ◽  
Harry R. Millwater ◽  
Michael P. Enright
Keyword(s):  
Damage Tolerance ◽  
Fatigue Tests ◽  
Test Results ◽  
Time Efficiency ◽  
Jet Engine ◽  
Software Code ◽  
Turbine Rotors

This paper summarizes recent enhancements to a probabilistic damage tolerance software code, DARWIN™, that can be used for design certification of aircraft jet engine titanium disks/rotors that may contain melt-related anomalies. Evaluations of DARWIN™ by engine manufacturers are also discussed, including comparisons with existing codes for accuracy and time efficiency. In addition, relevant test results, including various fatigue tests on material containing melt-related anomalies, are summarized.

scholarly journals Comments on Linear Summation Hypothesis of Fatigue Failures

2014 ◽  
Vol 21 (3) ◽  
pp. 77-85 ◽  
Author(s):  
Grzegorz Szala
Keyword(s):  
High Cycle Fatigue ◽  
Low Cycle Fatigue ◽  
Fatigue Tests ◽  
Load Level ◽  
Test Results ◽  
Cycle Fatigue ◽  
Load Spectrum ◽  
Linear Summation ◽  
Analysis Of Results ◽  
Fatigue Failures

Abstract This paper presents a comparative analysis of results of fatigue life calculations with the u se of the linear summation hypothesis of fatigue failures (LHSUZ), confronted with experimental test results. Te calculations and fatigue tests were performed for variable amplitude(VA), two-step and ten-step loading conditions, both in the low-cycle fatigue (LCF) and high-cycle fatigue (HCF) range, for the case of C45 steel as an example. Experimental verification of the hypothesis LHSUZ did not revealed any significant influence of load level and form of load spectrum on conformity of results of the calculation by using the LHSUZ, to results of fatigue tests on C45 steel. However, it enabled to assess magnitude of a correction factor which appears in the considered linear hypothesis.

A New Tool for Design and Certification of Aircraft Turbine Rotors

2004 ◽  
Vol 126 (1) ◽  
pp. 155-159 ◽  
Author(s):  
G. R. Leverant ◽  
H. R. Millwater ◽  
R. C. McClung ◽  
M. P. Enright
Keyword(s):  
Damage Tolerance ◽  
Fatigue Tests ◽  
Test Results ◽  
Time Efficiency ◽  
Jet Engine ◽  
Software Code ◽  
Turbine Rotors

This paper summarizes recent enhancements to a probabilistic damage tolerance software code, DARWINTM, that can be used for design certification of aircraft jet engine titanium disks/rotors that may contain melt-related anomalies. Evaluations of DARWINTM by engine manufacturers are also discussed, including comparisons with existing codes for accuracy and time efficiency. In addition, relevant test results, including various fatigue tests on material containing melt-related anomalies, are summarized.

Mean Load Impact on Mooring Chain Fatigue Capacity: Lessons Learned From Full Scale Fatigue Testing of Used Chains

2019 ◽  
Author(s):  
Øystein Gabrielsen ◽  
Kjell Larsen ◽  
Oddgeir Dalane ◽  
Hans B. Lie ◽  
Svein-Arne Reinholdtsen
Keyword(s):  
Fatigue Test ◽  
Limit State ◽  
Fatigue Tests ◽  
Load Level ◽  
Full Scale ◽  
General Corrosion ◽  
Test Results ◽  
Original Design ◽  
The Mean ◽  
Mooring Chain

Abstract Fatigue of mooring chain is for many floating offshore installations a limiting factor in design. With aging installations and the need for field life extension beyond the original design life, questions on mooring chain endurance are raised. Current SN curves utilized in fatigue limit state (FLS) calculation are based on full scale testing of new chain, performed at a high mean load level (20% of the chains minimum breaking load (MBL)). The high mean load level in the tests do not correspond to the conditions for many chains in operation, as mean load in fatigue relevant seastates are often significantly less than mean load used in the new chain fatigue tests. Mooring chains in operation also experience different degree of corrosion, both general corrosion and pitting. Surface roughness and corrosion pits contribute to crack initiations, and thus reduce fatigue capacity. Fatigue tests with new chain condition cannot be assumed representative for corroded chains. As part of mooring integrity programs, Equinor has been replacing mooring chains since year 2000. To assess actual fatigue capacity, many chain segments have been full scale fatigue tested. First tests started in 2011, and the tests cover different degrees of corrosion. The tests have been performed at typical mean load levels relevant for operation of the installations, which for most cases are less than 20%MBL. From these tests it is observed that fatigue capacity in some cases are better than expected for new chain, even for chain segments with significant corrosion. Fatigue test results show a large effect of the mean load. For test cases with significant corrosion and high mean load (20%MBL), a significant reduction in fatigue capacity compared to new chains is found. This paper presents some of the fatigue test results on used chain, highlighting the effect of the mean load for the given chain conditions. Effect of corrosion at mean load of 20%MBL is also included. The paper discusses some of the underlaying causes for the mean load dependency.

Qualification of S-N Curve by Experiments: Estimation of Survival Probability for a Low Number of Experiments

2015 ◽  
Author(s):  
Philippe Thibaux ◽  
Cristina Tonesi
Keyword(s):  
Confidence Level ◽  
Fatigue Testing ◽  
Probability Of Failure ◽  
Mean Value ◽  
Load Level ◽  
Experimental Results ◽  
Test Results ◽  
Survival Estimation ◽  
The Mean ◽  
The Cost

Due to the cost of fatigue testing, qualification of new weld details or improved welding techniques is often performed by comparing the experimental results with a mean S-N curve. The experimental dataset is considered to qualify for a given S-N curve if the mean of the log of the experimental results is larger than the mean of the chosen S-N curve plus an interval depending on the chosen confidence level. The confidence level is generally chosen arbitrary high, typically 75% or 90%. The survival estimation does not take into account the risk incurred by the fact that the actual mean has a probability of 25% or 10% of being lower than the theoretical S-N curve. In the present paper, we propose a different methodology based on the design S-N curve. The probability of failure for a given load level is computed by combining the probability of failure considering the mean value of the S-N curve, and the probability of this mean value. Thanks to the present method it is possible to estimate the probability of failure without making an assumption on the confidence level, which reduces the arbitrary during the estimation of the test results, particularly when the number of experimental results is limited.

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