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.

Effect of Pre-Strain and Roller Working on Torsional Fatigue Properties of a Structural Steel

2011 ◽  
Vol 295-297 ◽  
pp. 2227-2230
Author(s):  
Cong Ling Zhou
Keyword(s):  
Residual Stress ◽  
Fatigue Limit ◽  
Work Hardening ◽  
Compressive Residual Stress ◽  
Strain Ratio ◽  
Fatigue Tests ◽  
The Other ◽  
Fatigue Properties ◽  
Torsional Fatigue ◽  
Stress Work

In this study, fatigue tests have been performed using two kinds of specimens made of 25 steel. One is pre-strained specimen with pre-strain ratio changing from 2% to 8% by tension, the other is roller worked with deformation of 0.5 mm and 1.0 mm in diameter direction. In the case of pre-strained specimen, the fatigue limit increases according to increase of tensile pre-strain, the fatigue limit of 8% pre-strained specimen is 25% higher than that of non-pre-strained one; in the case of roller worked specimen, the fatigue limit of R05 and R10 is 126% and 143% to that of non-roller worked specimen, respectively. These remarkable improvements of fatigue limit would be caused by the existence of compressive residual stress, work-hardening and the elongated microscopic structures.

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 Effect of Ultrasonic Surface Impact on the Fatigue Properties of Ti3Zr2Sn3Mo25Nb

Materials ◽  
2020 ◽  
Vol 13 (9) ◽  
pp. 2107
Author(s):  
Zhangjianing Cheng ◽  
Xiaojian Cao ◽  
Xiaoli Xu ◽  
Qiangru Shen ◽  
Tianchong Yu ◽  
...  
Keyword(s):  
Titanium Alloy ◽  
Fatigue Strength ◽  
Fatigue Cracks ◽  
Dislocation Motion ◽  
Fatigue Properties ◽  
Surface Residual Stress ◽  
Initiation Zone ◽  
Rotating Bending Fatigue ◽  
Average Size ◽  
Grain Surface

The effect of nano grain surface layer generated by ultrasonic impact on the fatigue behaviors of a titanium alloy Ti3Zr2Sn3Mo25Nb (TLM) was investigated. Three vibration strike-numbers of 24,000 times, 36,000 times and 48,000 times per unit are chosen to treat the surface of TLM specimens. Nanocrystals with an average size of 30 nm are generated. The dislocation motion plays an important role in the transformation of nanograins. Ultrasonic surface impact improves the mechanical properties of TLM, such as hardness, surface residual stress, tensile strength and fatigue strength. More vibration strike numbers will cause a higher enhancement. With a vibration strike number of 48,000 times per square millimeter the rotating-bending fatigue strength of TLM at 107 cycles is improved by 23.7%. All the fatigue cracks initiate from the surface of untreated specimens, while inner cracks appear after the fatigue life of 106 cycles with the ultrasonic surface impact. The crystal slip in the crack initiation zone is the main way of growth for microcracks. Crack cores are usually formed at the junction of crystals. The stress intensity factor of TLM titanium alloy is approximately 7.0 MPa·m1/2.

THE EFFECT OF COATING THICKNESS ON FATIGUE PROPERTIES OF STEEL THERMALLY SPRAYED WITH Ni-BASED SELF-FLUXING ALLOY

2006 ◽  
Vol 20 (25n27) ◽  
pp. 3599-3604 ◽  
Author(s):  
HIROYUKI AKEBONO ◽  
JUN KOMOTORI ◽  
HIDETO SUZUKI
Keyword(s):  
Fatigue Strength ◽  
Thermal Spray ◽  
Coating Thickness ◽  
Volume Fraction ◽  
Steel Substrate ◽  
Fatigue Cracks ◽  
Spray Coating ◽  
Maximum Size ◽  
Thermal Spray Coating ◽  
Fatigue Properties

The Thermal spraying is one of the most popular surface coating techniques. To achieve the most efficient use of this technique in practice, it is very important to clarify the fatigue properties of steel coated with a thermal spray coating. In this study, to clarify the effects of coating thickness on the fatigue properties of the steel substrate, three types of sprayed specimens with different coating thickness (0.2, 0.5 and 1.0mm) were prepared and fatigue tests were carried out. Coating thickness strongly affected the fatigue properties; the thinner the coating thickness, the higher the fatigue strength. Fatigue crack propagation behaviors were observed. Accordingly the fatigue cracks propagated through many defects on the coated surface. The sizes and number of the coating defects were determined by coating thickness; the thicker the coating thickness, the larger the defect and number. Therefore, the sprayed specimens with thinner coatings indicated higher fatigue strength. Furthermore, estimations of the fatigue strength were performed by using Murakami's equation. The fatigue strengths of thermal spray coated specimens were estimated by three parameters; (i) maximum size of coating defects estimated by statistics of extreme value, (ii) hardness of the matrix and (iii) volume fraction of coating defects.

Effect of Pre-Strain on Fatigue Properties of NHH Rail

2004 ◽  
Vol 261-263 ◽  
pp. 1239-1244
Author(s):  
Wen Xian Sun ◽  
S. Nishida ◽  
Nobusuke Hattori ◽  
X.L. Yue
Keyword(s):  
Fatigue Crack ◽  
Fatigue Strength ◽  
Fatigue Test ◽  
Fatigue Cracks ◽  
Fatigue Tests ◽  
Fatigue Properties ◽  
Slip Lines ◽  
Propagation Behavior ◽  
Strain Process ◽  
Initiation And Propagation

In the present study, fatigue tests have been performed to study the effect of pre-strain on fatigue properties of NHH (New Head-Hardened) rail. The objectives of this study were: (1) to observe the microscopic behavior of specimens during pre-strain process, (2) to research the influence of pre-strain on fatigue strength of NHH rail and (3) to investigate initiation and propagation behavior of the fatigue crack. The results showed that plastic pre-strain decreased the fatigue strength of NHH rail; fatigue limits had no obvious variation among the different pre-strain ratios. Fatigue cracks initiated in the microscopic cracking or slip lines that were originated in the pre-strain process and propagated from these sites in the later fatigue test.

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.

Effect of Plating Thickness on Fatigue Strength of Galvanized Steel

2020 ◽  
Vol 841 ◽  
pp. 3-8
Author(s):  
Kayo Hasegawa ◽  
Tatsuo Hayashi ◽  
Motoaki Morita ◽  
Shinichi Motoda
Keyword(s):  
Tensile Strength ◽  
Fatigue Strength ◽  
Fatigue Limit ◽  
Main Crack ◽  
Immersion Time ◽  
Room Temperature ◽  
Columnar Structure ◽  
Galvanized Steel ◽  
Fatigue Properties ◽  
Plating Layer

Effect of the plating thicknesses on tensile and fatigue properties of hot-dip galvanized steel at room temperature was evaluated. The galvanized steel with thickness of 100 μm and 200 μm were prepared. Both microstructures of η-phase and δ1-phase were similar with each other. In the comparison with the galvanized steel with thickness of 100 μm, the microstructure of ζ-phase for the galvanized steel with thickness of 200 μm was blunt columnar structure due to long immersion time. Tensile and fatigue strengths for a galvanized steel are sensitive to the microstructure of the galvanized layer. The tensile strength and the strength of fatigue limit for the galvanized steel with thickness of 200 μm were smaller than that of 100 μm. In the galvanized steel with thickness of 200 μm, the peeling at plating layer easily occurred. The exfoliated sites have the potential to become subcracks. As the result, the main crack may propagate at early cycles.

Effect of Shot Peening on Fatigue Properties of Zr-based Amorphous Matrix Composites

2011 ◽  
Vol 1300 ◽  
Author(s):  
Changwoo Jeon ◽  
Choongnyun Paul Kim ◽  
Sunghak Lee
Keyword(s):  
Residual Stress ◽  
Fatigue Limit ◽  
Shot Peening ◽  
Compressive Residual Stress ◽  
Amorphous Matrix ◽  
Fatigue Cracks ◽  
Microstructural Analysis ◽  
Fatigue Properties ◽  
Composite Surface ◽  
Cast Composite

AbstractEffects of shot peening on fatigue properties of Zr-based amorphous matrix composite containing ductile crystalline particles were investigated, and fatigue processes were analyzed and compared with those of an as-cast composite. The microstructural analysis results of the shot-peened composite surface indicated that the deformation and surface flexion were observed as the shot-peening time or pressure increased. The compressive residual stress formed on the shot-peened surface was about the half of the ultimate tensile strength, and was not varied much with shot-peening time or pressure. The fatigue limit and fatigue ratio of the shot-peened composite were considerably higher than those of the as-cast composite. This was because the compressive residual stress formed by the shot peening induced the initiation of fatigue cracks at the specimen interior, instead of the specimen surface, thereby leading to the enhanced fatigue limit and fatigue life.

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.

High Cycle Fatigue Properties of Modified 9Cr-1Mo Steel at Elevated Temperatures

2012 ◽  
Author(s):  
Yoshiaki Matsumori ◽  
Jumpei Nemoto ◽  
Yuji Ichikawa ◽  
Isamu Nonaka ◽  
Hideo Miura
Keyword(s):  
Fatigue Strength ◽  
Fatigue Limit ◽  
Room Temperature ◽  
Structural Reliability ◽  
High Cycle Fatigue ◽  
Elevated Temperatures ◽  
Fatigue Behavior ◽  
Cyclic Softening ◽  
Fatigue Properties ◽  
Cycle Fatigue

Since high-cycle fatigue loads is applied to the pipes in various energy and chemical plants due to the vibration and frequent temperature change of fluid in the pipes, the high-cycle fatigue behavior of the alloys used for pipes should be understood quantitatively in the structural reliability design of the pipes. The purpose of this study, therefore, is to clarify the high-cycle fatigue strength and fracture mechanism of the modified 9Cr-1Mo steel at temperatures higher than 400°C. This material is one of the effective candidates for the pipes in fast breeder demonstration reactor systems. A rotating bending fatigue test was applied to samples at 50 Hz in air. The stress waveform was sinusoidal and the stress ratio was fixed at −1. The fatigue limit was observed at room temperature and it was about 420 MPa. This value was lower than the 0.2% proof stress of this alloy by about 60 MPa. This decrease can be attributed to the cyclic softening of this material. The limited cycles at knee point was about 8×105 cycles. All fracture was initiated from a single surface crack and no inclusion-induced fracture was observed in the fracture surface by SEM. Thus, the high-cycle fatigue design based on the fatigue limit may be applicable to the modified 9Cr-1Mo steel at room temperature. The fatigue limit of about 350 MPa was also observed at 400°C, and it appeared at about 107 cycles, while it appeared at around 106 cycles at room temperature. Thus, it was confirmed that the fatigue strength of this alloy decrease with temperature. However, the fatigue limit didn’t appear at 550°C up to 108 cycles. The fatigue limit may disappear in this alloy at 550°C. It is very important, therefore, to evaluate the ultra-high cycle fatigue strength of this alloy at temperatures higher than 400°C.

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