Effect of pre-strain on the fatigue behavior of SAPH440 steel

2019 ◽  
Vol 9 (9) ◽  
pp. 1001-1008 ◽  
Author(s):  
Li-Hui Zhao ◽  
Hong-Chang Cai ◽  
Shuo Weng ◽  
Song-Lin Zheng
Keyword(s):  
Fatigue Strength ◽  
Dislocation Density ◽  
Work Hardening ◽  
Fatigue Behavior ◽  
Static Strength ◽  
Fatigue Properties ◽  
Uniaxial Tensile ◽  
Test Results ◽  
Transmission Electron ◽  
Static Tensile

The present research envisages the effects of different uniaxial tensile pre-strain levels on the fatigue properties of the SAPH440 steel. The S-N curves of different pre-strain levels (0%, 6%, 12%, 18%) were drawn using different load levels, with a stress ratio R = –1. The test results show that the fatigue strength of the SAPH440 steel increased with an increasement in the uniaxial tensile pre-strain levels. The static tensile test was carried out on different uniaxial tensile and different pre-strain levels specimens. The results show that with an increase in the uniaxial tensile pre-strain levels, the degree of work hardening of the SAPH440 steel and the static strength increased. Additionally, the hardening index and the elongation at break reduced, while the tensile strength and yield strength increased. TEM (Transmission Electron Microscopy) observation of the test samples with different pre-strain levels showed that the dislocation density of different pre-strain levels specimens increased with an increasement in the pre-strain levels. This resulted in an increasement in the fatigue strength of the SAPH440 steel, the degree of work hardening, and the static strength. However, compared with fatigue strength, the increase of dislocation density has a more significant effect on static strength.

scholarly journals Fatigue Behavior of Non-Optimized Laser-Cut Medical Grade Ti-6Al-4V-ELI Sheets and the Effects of Mechanical Post-Processing

Metals ◽  
2019 ◽  
Vol 9 (8) ◽  
pp. 843 ◽  
Author(s):  
André Reck ◽  
André Till Zeuner ◽  
Martina Zimmermann
Keyword(s):  
Surface Roughness ◽  
Fatigue Strength ◽  
Surface Quality ◽  
Laser Cutting ◽  
Fatigue Behavior ◽  
Fatigue Cracks ◽  
Surface Condition ◽  
Mechanical Polishing ◽  
Fatigue Properties ◽  
Post Processing

The study presented investigates the fatigue strength of the (α+β) Ti-6Al-4V-ELI titanium alloy processed by laser cutting with and without mechanical post-processing. The surface quality and possible notch effects as a consequence of non-optimized intermediate cutting parameters are characterized and evaluated. The microstructural changes in the heat-affected zone (HAZ) are documented in detail and compared to samples with a mechanically post-processed (barrel grinding, mechanical polishing) surface condition. The obtained results show a significant increase (≈50%) in fatigue strength due to mechanical post-processing correlating with decreased surface roughness and minimized notch effects when compared to the surface quality of the non-optimized laser cutting. The martensitic α’-phase is detected in the HAZ with the formation of distinctive zones compared to the initial equiaxial α+β microstructure. The HAZ could be removed up to 50% by means of barrel grinding and up to 100% through mechanical polishing. A fracture analysis revealed that the fatigue cracks always initiate on the laser-cut edges in the as-cut surface condition, which could be assigned to an irregular macro and micro-notch relief. However, the typical characteristics of the non-optimized laser cutting process (melting drops and significant higher surface roughness) lead to early fatigue failure. The fatigue cracks solely started from the micro-notches of the surface relief and not from the dross. As a consequence, the fatigue properties are dominated by these notches, which lead to significant scatter, as well as decreased fatigue strength compared to the surface conditions with mechanical finishing and better surface quality. With optimized laser-cutting conditions, HAZ will be minimized, and surface roughness strongly decreased, which will lead to significantly improved fatigue strength.

scholarly journals Effects of thermomechanical history and environment on the fatigue behavior of (β)-Ti-Nb implant alloys

2018 ◽  
Vol 165 ◽  
pp. 06001 ◽  
Author(s):  
André Reck ◽  
Stefan Pilz ◽  
Ulrich Thormann ◽  
Volker Alt ◽  
Annett Gebert ◽  
...  
Keyword(s):  
Fatigue Strength ◽  
Cyclic Loading ◽  
Fatigue Behavior ◽  
Fatigue Tests ◽  
Grain Structure ◽  
Fatigue Properties ◽  
Β Phase ◽  
Α Phase ◽  
Nb Content ◽  
Implant Alloys

This study examined the fatigue properties of a newly developed cast and thermomechanical processed (β)-Ti-40Nb alloy for a possible application as biomedical alloy due to exceptional low Young’s modulus (64-73 GPa), high corrosion resistance and ductility (20-26%). Focusing on the influence of two microstructural states with fully recrystallized β-grain structure as well as an aged condition with nanometer-sized ω-precipitates, tension-compression fatigue tests (R=-1) were carried out under lab-air and showed significant differences depending on the β-phase stability under cyclic loading. Present ω- precipitates stabilized the β-phase against martensitic α’’ phase transformations leading to an increased fatigue limit of 288 MPa compared to the recrystallized state (225 MPa), where mechanical polishing and subsequent cyclic loading led to formation of α’’-phase due to the metastability of the β-phase. Additional studied commercially available (β)-Ti-45Nb alloy revealed slightly higher fatigue strength (300 MPa) and suggest a change in the dominating cyclic deformation mechanisms according to the sensitive dependence on the Nb-content. Further tests in simulated body fluid (SBF) at 37°C showed no decrease in fatigue strength due to the effect of corrosion and prove the excellent corrosion fatigue resistance of this alloy type under given test conditions.

scholarly journals Relationships among the Microstructure, Mechanical Properties, and Fatigue Behavior in Thin Ti6Al4V

2016 ◽  
Vol 2016 ◽  
pp. 1-9 ◽  
Author(s):  
Y. Fan ◽  
W. Tian ◽  
Y. Guo ◽  
Z. Sun ◽  
J. Xu
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
Fatigue Strength ◽  
Laser Welding ◽  
Fracture Strength ◽  
Fatigue Behavior ◽  
Fatigue Properties ◽  
Proof Stress ◽  
Martensite Microstructure

The microstructures of Ti6Al4V are complex and strongly affect its mechanical properties and fatigue behavior. This paper investigates the role of microstructure on mechanical and fatigue properties of thin-section Ti6Al4V sheets, with the aim of reviewing the effects of microstructure on fatigue properties where suboptimal microstructures might result following heat treatment of assemblies that may not be suited to further annealing, for example, following laser welding. Samples of Ti6Al4V sheet were subjected to a range of heat treatments, including annealing and water quenching from temperatures ranging from 650°C to 1050°C. Micrographs of these samples were inspected for microstructure, and hardness, 0.2% proof stress, elongation, and fracture strength were measured and attributed back to microstructure. Fractography was used to support the findings from microstructure and mechanical analyses. The strength ranking from high to low for the microstructures of thin Ti6Al4V sheets observed in this study is as follows: acicularα′martensite, Widmanstätten, bimodal, and equiaxed microstructure. The fatigue strength ranking from high to low is as follows: equiaxed, bimodal, Widmanstätten, and acicularα′martensite microstructure.

The Effects of Specimen Size on the Very High Cycle Fatigue Properties of FV520B-I

2015 ◽  
Author(s):  
Ming Zhang ◽  
Weiqiang Wang ◽  
Aiju Li
Keyword(s):  
Fatigue Life ◽  
Fatigue Strength ◽  
High Cycle Fatigue ◽  
Specimen Size ◽  
Fatigue Properties ◽  
Test Results ◽  
Cycle Fatigue ◽  
Very High Cycle Fatigue ◽  
Heat Effects ◽  
Very High

The authors researched the effects of specimen size on the very high cycle fatigue properties of FV520B-I through ultrasonic fatigue testing. The test results showed that the very high cycle fatigue mechanism was not changed and the fatigue properties declined as the specimen size increased. The S-N curve moved downward and the fatigue life decreased under the same stress level maybe due to the heat effects of large specimens in tests. The fatigue strength and the fatigue life were predicted by relevant models. The prediction of fatigue strength was close to test result, and the prediction of fatigue life was less effective compared with the previous prediction of small size specimen test results.

Effect of Plastic Working on Fatigue Properties of Ti-6Al-4V Alloy with Notch

2005 ◽  
Vol 297-300 ◽  
pp. 2513-2518
Author(s):  
Nobusuke Hattori ◽  
Shinichi Nishida ◽  
Masahiro Hara ◽  
Sun Young Son
Keyword(s):  
Fatigue Strength ◽  
Fatigue Limit ◽  
Work Hardening ◽  
Fatigue Cracks ◽  
Fatigue Properties ◽  
Plastic Working

This study is focused to the effects of plastic working on the fatigue strength of Ti-6Al-4V alloy with notch. In general, the fatigue strength of plastic worked specimen is higher than that of non-worked one. However, the potential of hardening ability of Ti-6Al-4V alloy is very limited. Accordingly, the effect of work hardening on fatigue strength about this material is very small. In addition, the surface of the worked part becomes rougher with increasing plastic deformed value and the fatigue cracks initiate at this part. Consequently, the fatigue limit of the plastic worked specimen is lower than that of the non-plastic-worked one.

The Relationship Between Tensile and Fatigue Strength of Friction Welded Steel Joints

2015 ◽  
Author(s):  
S. T. Selvamani ◽  
K. Palanikumar ◽  
K. Shanmugam ◽  
S. Divagar ◽  
M. Vigneshwar
Keyword(s):  
Fatigue Strength ◽  
Fatigue Testing ◽  
High Carbon Steel ◽  
Testing Machine ◽  
Fatigue Properties ◽  
Uniaxial Tensile ◽  
Sensitivity Factor ◽  
Welded Steel ◽  
Steel Joints ◽  
The Relationship

The friction welding of AISI 52100 grade low chromium and high carbon steel joints are investigated in this work to evaluate the fatigue life of the joints by conducting the experiments using servo hydraulic fatigue testing machine at different stress levels. All the experiments are conducted under uniaxial tensile loading condition (stress ratio=0). Fatigue strength, fatigue notch factor (Kf) and notch sensitivity factor (q) are evaluated for the optimized joints and the relationship between tensile and fatigue properties of Fully Deformed None (FDZ) is established. Finally, the Characteristics of friction welded joint is investigated with the help of Scanning Electron Microscope and Optical Microscopy under optimized condition.

EVALUATION OF CRACK INITIATION AND FATIGUE BEHAVIOR OF CrN FILM DEPOSITED ON Ti-6Al-4V ALLOY

2010 ◽  
Vol 24 (15n16) ◽  
pp. 2502-2505 ◽  
Author(s):  
MD. SHAMIMUR RAHMAN ◽  
TAKESHI KATSUMA ◽  
DAISUKE YONEKURA ◽  
RI-ICHI MURAKAMI
Keyword(s):  
Wear Resistance ◽  
Titanium Alloy ◽  
Fatigue Strength ◽  
Tensile Test ◽  
Fatigue Test ◽  
Bias Voltage ◽  
Fatigue Behavior ◽  
Fatigue Properties ◽  
Negative Bias ◽  
Negative Bias Voltage

Titanium alloy has an attractive strength-to-weight ratio and good fatigue properties. However, the titanium alloy has very poor wear resistance, therefore, surface treatments must be considered in order to make the contact parts. Hard thin film deposited by PVD technique is well-known to improve the wear resistance. In this study, chromium nitride ( CrN ) film was applied to titanium alloy and its effect on the fatigue behavior was investigated. Ti -6 Al -4 V alloy was used as a substrate material. The CrN film was deposited by arc ion plating (AIP) method at two different negative bias voltages because the film hardness, crystal orientation and surface morphology were strongly depended on the bias voltage during the deposition. Tension-tension fatigue test and tensile test were carried out to investigate the fatigue properties. As the result, the fatigue strength was influenced by the deposition of the CrN film, especially, the fatigue strength was remarkable decreased by the deposition of the CrN film at high negative bias voltage compared to the uncoated specimen and the deposition of the CrN at low negative bias voltage. The difference of the fatigue strength was also investigated on the basis of crack initiating behavior during fatigue test and tensile test.

Fatigue Properties of Titanium Alloy TA11 under Multiaxial Loadings with Tension - Bending Vibration

2014 ◽  
Vol 887-888 ◽  
pp. 873-877
Author(s):  
Bin Li ◽  
Nan Ma ◽  
Xin Ling Liu ◽  
Zhi Wang Qiu ◽  
Hong Ren Li
Keyword(s):  
Titanium Alloy ◽  
Fatigue Behavior ◽  
Fatigue Tests ◽  
Fatigue Properties ◽  
Loading Conditions ◽  
Test Results ◽  
Bending Vibration ◽  
Alpha Titanium ◽  
Vibration Loads ◽  
Multiaxial Loadings

This paper studied the fatigue behavior of the near alpha titanium alloy TA11 under multiaxial loading conditions with tension - bending vibration, to simulate the service stress state applied on the engine blades, where a large centrifugal force is superimposed with bending vibration loads. A plate-like specimen was used in the fatigue tests with different ratios between the tension and bending vibration loads, then, the energy based fatigue criteria were applied for correlation of the test results. The fatigue properties of titanium alloy TA11 under the specialized loading conditions are characterized and discussed.

Tensile Properties and Fatigue Strength in High Humidity in Extruded 7075 Al Alloys with Different Aging Conditions

2013 ◽  
Vol 845 ◽  
pp. 292-296 ◽  
Author(s):  
Y. Nakamura ◽  
Norio Kawagoishi ◽  
K. Kariya
Keyword(s):  
Fatigue Strength ◽  
Dislocation Density ◽  
Tensile Properties ◽  
Extrusion Direction ◽  
Solution Treatment ◽  
Al Alloys ◽  
Fatigue Properties ◽  
X Ray Diffraction ◽  
Aging Conditions ◽  
Resistance To Stress

In the present study, the tensile and fatigue properties of extruded 7075 Al alloys subjected to re-solution treatment and then T6, T73 and retrogression-reaging (RRA) tempers were reassessed based upon the microstructural analyses by means of electron backscattering diffraction (EBSD) and X-ray diffraction (XRD). The microstructural analyses indicated that fibrous grains having orientations close to <111> and <001> were preferentially aligned in the extrusion direction and that re-solution treatment increased the fraction of <111> grains. Further the as-received T6 specimens had very high dislocation density as well as fine subgrains, while the re-solution treatment decreased dislocation density considerably and increased grain size. These characteristics explained tensile properties well, by taking into account the effect of precipitates formed by tempers. On the other hand, fatigue strength decreased prominently in all of the specimens, as the relative humidity (RH) was increased from 25% to 85%. T73 and RRA treatments which improve the resistance to stress corrosion cracking (SCC) in static loading were not effective in the humidity-enhanced deterioration in fatigue strength.

Fatigue Behavior of Type 316L Stainless Steel Coated with Plasma-Sprayed Alumina in Corrosive Environment

1998 ◽  
Author(s):  
H. Kisuki ◽  
M. Sugano ◽  
T. Oshima ◽  
Y. Nasu ◽  
K. Okazaki ◽  
...  
Keyword(s):  
Stainless Steel ◽  
Fatigue Strength ◽  
Plasma Spraying ◽  
Early Stage ◽  
Fatigue Behavior ◽  
Fatigue Cracks ◽  
Fatigue Properties ◽  
Crack Growth Behavior ◽  
Grit Blasting ◽  
Plasma Sprayed

Abstract Fatigue properties of the Al2O3 plasma-sprayed SUS316L stainless steel rod specimens coated on different spraying conditions have been studied in a physiological saline solution (0.9 % NaCl solution) to evaluate the potential of surgical implant application. Fatigue tests were conducted in push-pull loading at the stress ratio of R = -1, and frequency of 2 Hz. Microstructure related with fatigue damage was examined by SEM and TEM. The fatigue strength of Al2O3 plasma-sprayed metals significantly depended on spraying conditions: the effects of spraying on fatigue strength decreased with increasing the applied stress amplitude. As-blasted specimens were higher in fatigue strength than Al2O3 plasma-sprayed specimens. It was found that the plasma spraying had significant effects on fatigue crack growth behavior in the early stage of crack propagation. Fatigue cracks preferentially originated from dents that had been caused on the substrata metal surface subjected to grit-blasting. These results are discussed with both the compressive residual stresses due to the grit blasting which was carried out prior to plasma spraying and the corrosion-resistance of the alumina deposit.

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