Fatigue-Life Prediction Method Based on Small-Crack Theory in an Engine Material

2011 ◽  
Vol 134 (3) ◽  
Author(s):  
James C. Newman ◽  
Balkrishna S. Annigeri
Keyword(s):  
Crack Closure ◽  
Test Data ◽  
High Cycle Fatigue ◽  
Fatigue Cracks ◽  
Loading Conditions ◽  
Cycle Fatigue ◽  
Constant Amplitude ◽  
Notched Specimens ◽  
Wide Range ◽  
Stress Ratios

Plasticity effects and crack-closure modeling of small fatigue cracks were used on a Ti-6Al-4V alloy to calculate fatigue lives under various constant-amplitude loading conditions (negative to positive stress ratios, R) on notched and un-notched specimens. Fatigue test data came from a high-cycle-fatigue study by the U.S. Air Force and a metallic materials properties handbook. A crack-closure model with a cyclic-plastic-zone-corrected effective stress-intensity factor range and equivalent-initial-flaw-sizes (EIFS) were used to calculate fatigue lives using only crack-growth-rate data. For un-notched specimens, EIFS values were 25-μm; while for notched specimens, the EIFS values ranged from 6 to 12 μm for positive stress ratios and 25-μm for R = −1 loading. Calculated fatigue lives under a wide-range of constant-amplitude loading conditions agreed fairly well with the test data from low- to high-cycle fatigue conditions.

Fatigue-Life Prediction Method Based on Small-Crack Theory in an Engine Material

2011 ◽  
Author(s):  
James C. Newman ◽  
Balkrishna S. Annigeri
Keyword(s):  
Crack Closure ◽  
Test Data ◽  
High Cycle Fatigue ◽  
Fatigue Cracks ◽  
Loading Conditions ◽  
Cycle Fatigue ◽  
Constant Amplitude ◽  
Notched Specimens ◽  
Wide Range ◽  
Stress Ratios

Plasticity effects and crack-closure modeling of small fatigue cracks were used on a Ti-6Al-4V alloy to calculate fatigue lives under various constant-amplitude loading conditions (negative to positive stress ratios, R) on notched and un-notched specimens. Fatigue test data came from a high-cycle-fatigue study by the U.S. Air Force and a metallic materials properties handbook. A crack-closure model with a cyclic-plastic-zone-corrected effective stress-intensity factor range and equivalent-initial-flaw-sizes (EIFS) were used to calculate fatigue lives using only crack-growth-rate data. For un-notched specimens, EIFS values were 25-μm; while for notched specimens, the EIFS values ranged from 6 to 12 μm for positive stress ratios and 25-μm for R = −1 loading. Calculated fatigue lives under a wide-range of constant-amplitude loading conditions agreed fairly well with the test data from low- to high-cycle fatigue conditions.

scholarly journals Characterization and modelling of both high-cycle hightemperature fatigue behaviour of Stainless Steel Grades

2018 ◽  
Vol 165 ◽  
pp. 19008
Author(s):  
Pierre-Olivier Santacreu ◽  
Cloé Prudhomme ◽  
Benoit Proult ◽  
Isabelle Evenepoel
Keyword(s):  
Stainless Steel ◽  
High Temperature ◽  
High Temperatures ◽  
High Cycle Fatigue ◽  
Fatigue Cracks ◽  
Fatigue Behaviour ◽  
Cycle Fatigue ◽  
Vibration Fatigue ◽  
Steel Grades ◽  
Stress Ratios

In the same context of thermo-mechanical fatigue and high temperature applications of stainless steel, high-frequency vibration fatigue at high temperatures should be considered, in particular for automotive exhaust gas applications. In fact one of the most frequent incidents that can happen on exhaust components is an accumulation of low-cycle thermal fatigue and high-cycle fatigue. The prediction of the lifetime of a structure under such complex thermal and mechanical loading is therefore a constant challenge at high temperature due to the coupling of metallurgical, oxidation or creep effects. In order to better understand in a first approach, the high cycle fatigue of stainless steels at high temperatures, tractioncompression tests were performed on flat specimens at 25Hz, under air and in isothermal conditions from ambient temperature to 850°C. Two different stress ratios, R=-1 and 0.1, are characterized with the objective to assess a multiaxial model for high temperature. Different criteria are used to predict the ruin of a structure under high-cycle fatigue but in general for ambient-around temperatures. In particular, multiaxial and stress-based DangVan criterion is today widely used to evaluate the risk of fatigue cracks initiation and it has been implemented recently in our fatigue life processor Xhaust_Life®. Therefore the Dang Van criterion was identified from the isothermal high cycle fatigue using the 2 stress ratio and its validity is discussed especially for temperatures higher than 500°C where strain rate and creep effects have increasing influence. Results are presented for two ferritic stainless steel grades used in high temperature exhaust applications: K41X (AISI 441, EN 1.4509) and K44X (AISI 444Nb, EN 1.4521).

scholarly journals High Temperature, High Cycle Fatigue Demeanor of 10wt% cr Steel and Unlike Metal Weld

2021 ◽  
Vol 9 (VI) ◽  
pp. 1113-1128
Author(s):  
Hilal Ahmad Shah
Keyword(s):  
Fatigue Life ◽  
Ferritic Steel ◽  
High Cycle Fatigue ◽  
Stress Amplitude ◽  
Fatigue Behavior ◽  
Strong Dependence ◽  
Cycle Fatigue ◽  
Wide Range ◽  
Stress Ratios ◽  
Metal Weld

The present study primarily focuses on understanding the high cycle fatigue behavior (HCF) of alloy 10wt%Cr Ferritic Steel and Dissimilar metal weld (DMW) joint between 617M and 10wt%Cr Ferritic Steel. For assessing the HCF behavior, tests were conducted under stress controlled cycling, by employing dissimilar stress ratios (R) and wide range of temperatures (300 K – 853 K). The S-N curves plotted at R= -1 and temperatures (300 K,673 K,853 K) for 10wt%Cr Ferritic Steel shows that fatigue life decreased with increase in stress amplitude. It is also observed that fatigue life of 10wt%Cr Ferritic Steel falls with increase in the temperature regardless of the stress amplitude, clearly showing the strong dependence of fatigue life on the temperature. An effort has been made to find out the fatigue parameters at 300 K and 853 K using Basquin equation. These fatigue parameters were used for life prediction, showed that predicted life is in good agreement with experimental life with in a scatter band of 2. At 853 K, Goodman diagram shows that limiting alternating stress decreases with increase in the mean stress. The results were linked with the detailed scanning electron microscope investigation where it is analyzed that at 300 K, the fatigue failure was by trans-granular mode, characterized by striations while at 673 K and 853 K, intergranular mode and strong oxidation is seen, thus lowering the life at said temperatures. The standard S-N behavior for DMW at R= -1 and at temperature of 853 K showed that the welding reduces the number of cycles to failure. Vicker’s hardness measurements show that there is softening in the 10wt%Cr side & hardening in the butter layer resulting in failure of all non-defective samples on the 10wt%Cr side. HCF test was also showed on damaged samples at 230 MPa and 200 MPa, found, that crack initiates & propagates near the damage at 230 MPa while at 200MPa crack initiates and propagates in the 10wt%Cr side irrespective of the damage.

Effect of Plasma Nitriding on Ultra-High Cycle Fatigue Behaviors of Ti-6Al-4V

2011 ◽  
Vol 295-297 ◽  
pp. 2386-2389 ◽  
Author(s):  
Ren Hui Tian ◽  
Qiao Lin Ouyang ◽  
Qing Yuan Wang
Keyword(s):  
High Cycle Fatigue ◽  
Plasma Nitriding ◽  
Fatigue Behavior ◽  
Fatigue Crack Initiation ◽  
Fatigue Tests ◽  
Fatigue Properties ◽  
Cycle Fatigue ◽  
Ultrasonic Fatigue ◽  
Ultra High Cycle Fatigue ◽  
Stress Ratios

In order to investigate the effect of plasma nitriding treatment on fatigue behavior of titanium alloys, very high cycle fatigue tests were carried out for Ti-6Al-4V alloy using an ultrasonic fatigue machine under load control conditions for stress ratios of R=-1 at frequency of ƒ=20KHz. Experiment results showed that plasma nitriding treatment played the principal role in the internal fatigue crack initiation. More importantly, plasma nitriding treatment had a detrimental effect on fatigue properties of the investigated Ti-6Al-4V alloy, and the fatigue strength of material after plasma nitriding treatment appeared to be significantly reduced about 17% over the untreated material.

Influence of Reinforcement Geometry on the Very High-Cycle Fatigue Behavior of Aluminium-Matrix-Composites

2015 ◽  
Vol 825-826 ◽  
pp. 150-157 ◽  
Author(s):  
Alexandra Müller ◽  
Anja Weidner ◽  
Horst Biermann
Keyword(s):  
High Cycle Fatigue ◽  
Fatigue Testing ◽  
Fatigue Behavior ◽  
Aluminum Matrix ◽  
Aluminum Matrix Composites ◽  
Matrix Composites ◽  
Loading Conditions ◽  
Cycle Fatigue ◽  
Very High Cycle Fatigue ◽  
Very High

During technical operation, high performance materials are partially exposed to high frequency cyclic loading conditions. Furthermore, the small strains in the very high cycle fatigue (VHCF)-regime lead to accumulative damage which causes crack initiation related to an appropriate local deformation leading to final fatal fracture. At the same time, quite high requirements with regard to high number of cycles without any damage are demanded for many applications. Fields of application of these light-weight, but expensive materials, are e.g. in the automobile industry (e.g. engine blocks, cylinder heads, brakes).The fatigue behavior of Al-matrix composites (Al-MMCs) reinforced by alumina particles (15 vol.% Al2O3) or short fibers (20 vol.% Saffil), respectively, was already intensively studied in the LCF and HCF range. The present study is focusing on investigations in the very high cycle fatigue regime at stress amplitudes up to 140 MPa to reach fatigue life of about 1010 cycles. All experiments were carried out using an ultrasonic fatigue testing device under symmetric loading conditions (R=-1). Fatigue tests were accompanied by in situ thermography measurements to record the temperature of the whole specimen and to find “hot spots” indicating changes in microstructure and therefore the initiation or growth of cracks. Moreover, the resonant frequency as well as the damage parameter were evaluated to determine the beginning of damage. For a better understanding of the damage mechanism (matrix decohesion, matrix failure or failure of reinforcement) all fractured surfaces were investigated by scanning electron microscopy. The combination of these methods contributes to a better understanding of the underlying mechanism of damage in aluminum-matrix-composites.

High-cycle and very-high-cycle fatigue behavior of a stainless steel for air-conditioning compressor valve plates

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Xu Jia ◽  
Yang Ou Xiang ◽  
Hu Yuan Pei ◽  
Song Wei
Keyword(s):  
Stainless Steel ◽  
Cyclic Loading ◽  
Air Conditioning ◽  
High Cycle Fatigue ◽  
Loading Conditions ◽  
Cycle Fatigue ◽  
Content Type ◽  
Very High Cycle Fatigue ◽  
Load Characteristics ◽  
Very High

PurposeThe investigations could guide the structural design and fatigue life prediction of air-conditioning compressor valve plates.Design/methodology/approachThe High-Cycle Fatigue (HCF) and Very-High-Cycle Fatigue (VHCF) behaviors of stainless steel used for air-conditioning compressor valve plates were investigated. Monotonic and cyclic loading conditions were designed to explore the fatigue responses according to the load characteristics of the structure.FindingsThe crack initiation can be observed as the arc-shaped cracks at both sides of specimens and Y-shaped crack bifurcation in the specimens. Moreover, the middle section and the cracks at both ends are not connected to the surface of the specimen. The stress-life results of the materials under two directions (vertical and horizontal) were provided to examine the difference in fatigue strength.Originality/valueMonotonic and cyclic loading conditions were designed to explore the fatigue responses according to the load characteristics of the structure. Based on the experimental data, the results indicate that specimens under cyclic loading conditions could demonstrate better mechanical performance than static loadings.

Very High Cycle Fatigue Testing under Spectrum Loading for Endurance Limit Structural Design

2020 ◽  
Vol 65 (1) ◽  
pp. 1-7
Author(s):  
David T. Rusk ◽  
Robert E. Taylor ◽  
Bruce A. Pregger ◽  
Luis J. Sanchez
Keyword(s):  
Fatigue Test ◽  
Test Data ◽  
High Cycle Fatigue ◽  
Fatigue Testing ◽  
Crack Nucleation ◽  
Peak Stress ◽  
Material Behavior ◽  
Cycle Fatigue ◽  
Very High Cycle Fatigue ◽  
Very High

A program has recently concluded that generated fatigue test data for the influence of a rotorcraft main rotor blade root bending spectrum (Helix) on the crack nucleation mechanisms in 7075-T651 aluminum. High-frequency tests were performed that generated spectrum fatigue failures out to nearly 109 cycles. Fractographic examination showed a distinct change in crack nucleation from slip initiated to inclusion-initiated cracking as the spectrum peak stress level was increased. Spectrum life predictions were made using three different baseline constant-amplitude S-N curves, one using a traditional rotorcraft original equipment manufacturer fitting methodology, one using the high-cycle fatigue (HCF) portion of a strainlife curve, and one that was fitted to S-N data with test lives out to 3×108 cycles. The spectrum life prediction using the S-N curve that properly modeled material behavior in the very high cycle fatigue regime provided a good correlation to the spectrum fatigue test data. Predictions using the other S-N curves were highly conservative.

Smooth and notched fatigue performance of aging treated and shot peened ZK60 magnesium alloy

2010 ◽  
Vol 25 (7) ◽  
pp. 1375-1387 ◽  
Author(s):  
Wen-Cai Liu ◽  
Jie Dong ◽  
Ping Zhang ◽  
Xing-Wei Zheng ◽  
Wen-Jiang Ding ◽  
...  
Keyword(s):  
Magnesium Alloy ◽  
Compressive Residual Stress ◽  
High Cycle Fatigue ◽  
Fatigue Performance ◽  
Fatigue Properties ◽  
Cycle Fatigue ◽  
Notched Specimen ◽  
Notched Specimens ◽  
Zk60 Alloy ◽  
Zk60 Magnesium Alloy

The influence of shot peening (SP) on high cycle fatigue (HCF) performance of smooth and notched specimens of hot-extruded ZK60 magnesium alloy was investigated and compared to that of hot-extruded and T5 aging-treated ZK60 magnesium alloy referred to as ZK60-T5. The increases in fatigue properties at the optimum Almen intensities were found to depend on the material states. In contrast to ZK60 alloy, higher smooth and notched fatigue properties for both unpeened and peened specimens were observed for ZK60-T5 alloy. Meanwhile, the improvement of fatigue life for notched specimen by SP was much more than that for the smooth specimen. The mechanism by which the compressive residual stress induced by SP resulted in the improvement of fatigue performance of smooth and notched specimens for ZK60 and ZK60-T5 alloys was discussed.

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