Long Life Fatigue Behavior of Shot Peened Steels

2014 ◽  
Vol 627 ◽  
pp. 9-12
Author(s):  
Alan Plumtree
Keyword(s):  
Fatigue Life ◽  
Residual Stresses ◽  
Shot Peening ◽  
Fatigue Behavior ◽  
Fatigue Cracks ◽  
Initiation Site ◽  
Cyclic Softening ◽  
Surface Layers ◽  
Long Life ◽  
Effect Of Surface

The fully reversed long life fatigue cycle behaviour of shot peened steels has been investigated. In the case of air cooled forged 0.4%C and 0.7%C steels, shot peening resulted in a relatively small effect on fatigue life (+2.2% and-2.0% respectively) owing to cyclic softening. Fatigue cracks in the shot peened specimens have been observed to initiate in sub-surface layers, reducing the detrimental effect of surface roughness. Neither cyclic softening nor hardening occurred in the smooth non shot peened samples cycled under the same conditions. Shot peening quench and tempered 0.5%C steel samples resulted in a reduced fatigue limit of 12.0% due to cyclic softening. Relaxation of the residual stresses occurred quickly in these steels due to adjustment and rebalancing of the residual stresses caused by the plastic strain. The effect of cyclic softening and shift in crack initiation site rather than the residual peening stresses was significant in determining the fatigue life of these shot peened steels.

Effect of Frequency on the Fatigue Behavior of IN718 Superalloy

2017 ◽  
Vol 1142 ◽  
pp. 23-30 ◽  
Author(s):  
Jin Hui Du ◽  
Xu Dong Lu ◽  
Qun Deng
Keyword(s):  
Grain Size ◽  
Fatigue Life ◽  
Crack Initiation ◽  
Low Cycle Fatigue ◽  
Fatigue Behavior ◽  
Fatigue Cracks ◽  
Low Frequency ◽  
Initiation Site ◽  
Fatigue Properties ◽  
Crack Initiation Site

IN718 alloy possesses excellent mechanical properties at high temperatures, good process ability, therefore, it has been widely used in aero engine turbine disks, compressor disks, and power turbine shafts (i.e., rotating components). The fatigue properties of the alloy are a key factor that determines the safety and reliability of the engine. In this paper, the fatigue properties of IN718 alloy are investigated under low-and middle-frequency conditions at 600 °C and 455 °C, the initiation of fatigue cracks, and the relation between fatigue life and grain size are discussed. The results show that the carbides response as a crack initiation site at low-frequency fatigue condition (1 Hz), and string-type or heap-type carbides distribution promotes crack propagation and shortens fatigue life, the twin boundaries in large grains are act as a crack initiation site at middle-frequency fatigue condition (10 Hz). The grain size is smaller, and the low cycle fatigue properties of the alloy are better.

Effect of Shot Peening on Fatigue Behavior of AISI 4340 in Different Loading Conditions

2016 ◽  
Vol 713 ◽  
pp. 30-33 ◽  
Author(s):  
Marcelo A.S. Torres ◽  
D.T. Harada ◽  
Carlos Antonio Reis Pereira Baptista ◽  
Maria P. Cindra Fonseca
Keyword(s):  
Fatigue Life ◽  
Shot Peening ◽  
Fatigue Behavior ◽  
Fatigue Tests ◽  
Residual Stress Field ◽  
Surface Layers ◽  
Tension Tests ◽  
Rotating Bending Fatigue ◽  
Rotating Bending ◽  
Aisi 4340

Shot peening is a method widely used to improve the fatigue strength of materials, through the creation of a compressive residual stress field (CRSF) in their surface layers. In the present research the gain in fatigue life of AISI 4340 steel, obtained by shot peening treatment, is evaluated under the three different hardnesses used in landing gear. Rotating bending fatigue tests and alternating tension tests were conducted and the CRSF was measured by x-ray tensometry prior and after interrupted fatigue tests. The evaluation of fatigue life after shot peening in relation to the relaxation of CRSF, of the crack initiation sites and surface roughness is done.

Low Cycle Fatigue Behavior of CP-Ti at Different Temperatures

2019 ◽  
Vol 795 ◽  
pp. 29-34
Author(s):  
Tian Hao Ma ◽  
Le Chang ◽  
Chang Yu Zhou
Keyword(s):  
Fatigue Life ◽  
Low Cycle Fatigue ◽  
Fatigue Behavior ◽  
Fatigue Cracks ◽  
Cyclic Softening ◽  
Cycle Fatigue ◽  
Different Temperatures ◽  
Cp Ti ◽  
The Relationship ◽  
Life Prediction Model

Low cycle fatigue (LCF) tests are performed on CP-Tiat different temperatures (293K,423K and 523K). It is found that the fatigue life of CP-Tidecreases with temperature. A short cycle hardening phenomenon occurs at the beginning of cyclic deformationat 293K and 423K, followed by cyclic softening untilfailure. At 523K, cycle hardening isexhibited throughout the entire cycle until thefracture. The fatigue-life curves obtained from the tests are constructed using Coffin-Manson-Basquin model. According to the relationship between the four parameters of Coffin-Manson-Basquin model and temperature, the temperature-based life prediction model is further proposed. Scanning electron microscopy observation of fatigue fractures showsthat the fatigue cracks of CP-Tiat 423K and 523K under different strain amplitudes initiate on the surface of fatigue specimens and extend to the fracture zone by the transgranular mode.

The Analysis on the Low Cycle Fatigue Behavior of a Directionally Solidified Superalloy with Recrystallized Surface Layers

2008 ◽  
Vol 44-46 ◽  
pp. 43-50 ◽  
Author(s):  
Hui Ji Shi ◽  
Xian Feng Ma ◽  
Da Wei Jia ◽  
Hai Feng Zhang ◽  
Li Sha Niu
Keyword(s):  
Fatigue Life ◽  
Shot Peening ◽  
Low Cycle Fatigue ◽  
Fatigue Behavior ◽  
Turbine Blades ◽  
Fatigue Tests ◽  
Cycle Fatigue ◽  
Directionally Solidified ◽  
Surface Layers ◽  
Time Observation

Specimens of a directionally solidified superalloy with different shot peening pressure were annealed at 1220oC in vacuum condition to get recrystallized surface layers with different micro-structures. Low cycle fatigue tests of these specimens were performed at room temperature and 400oC by using an electrohydraulic load frame in the SEM system for real-time observation. The initiation and propagation of cracks were inspected and the influence of the micro-structure of the recrystallized layer on the material fatigue behavior was analyzed. The low cycle fatigue life of the specimens depends mainly on the characteristics of the recrystallized layer. When the shot peening pressure is lower, the recrystallized layer is thin and not integrated, and the fatigue life decreases obviously in comparison with that of the specimen without recrystallized surface layer. When the shot peening pressure increases, the recrystal grains are more integrated, and the fatigue life rises. A comparison of the recrystallized layers between the blade surface and the specimen surface has been done and it points that the incompact surface recrystal layer is very dangerous to gas turbine blades.

Effects of Shot-Peening on Fretting-Fatigue Behavior of Ti-6Al-4V

2002 ◽  
Vol 124 (2) ◽  
pp. 222-228 ◽  
Author(s):  
S. A. Namjoshi ◽  
V. K. Jain ◽  
S. Mall
Keyword(s):  
Fatigue Life ◽  
Shot Peening ◽  
Fatigue Behavior ◽  
Contact Region ◽  
Fretting Fatigue ◽  
Initiation Site ◽  
Fatigue Tests ◽  
Residual Tensile Stress ◽  
X Ray Diffraction ◽  
Element Analysis

The effects of shot-peening on the fretting fatigue behavior of titanium alloy, Ti-6Al-4V were investigated. Specimens were shot-peened as per AMS 2432 standard. X-ray diffraction analysis measured a maximum compressive stress of 800 MPa at the specimen surface, which reduced to zero at a depth of 188 μm. The compensatory residual tensile stress in the specimen was estimated using a curve fitting technique, the maximum value of which was found to be 260 MPa at a depth of 255 μm. Fretting fatigue tests were conducted at room temperature at a cyclic frequency of 200 Hz. Scanning electron microscopy of the shot-peened fretting fatigue specimens showed that the crack initiated at a point below the contact surface, the depth of which was in the range of 200–300 μm. Finite element analysis of the fretting fatigue specimens was also conducted. Fatigue life diagrams were established for the fretting fatigue specimens with and without shot-peening, and were compared to those under the plain fatigue condition, i.e. without fretting. Shot-peening improved the fretting fatigue life of Ti-6Al-4V; furthermore, it moved the crack initiation site from the fretting contact region to a region inside the specimen. Moreover, stress analysis showed that the fatigue failure of shot-peened specimens was caused by the compensatory tensile residual stress.

scholarly journals Effect of Oil – Corrosion on Tensile and Fatigue S-N Curve Properties of AA6061-T6

2021 ◽  
Vol 39 (3A) ◽  
pp. 407-414
Author(s):  
Hussain J.M. Al-Alkawi ◽  
Ghgada A. Aziz ◽  
Shmoos R. Mazel
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Fatigue Life ◽  
Fatigue Strength ◽  
Corrosion Fatigue ◽  
Shot Peening ◽  
Fatigue Behavior ◽  
Surface Layers ◽  
Compressive Residual Stresses ◽  
Behavior Strength

The present study described the effect of shot peening on mechanical properties and rotating corrosion –fatigue behavior (strength and life) of AA6061-T6. Ultimate tensile strength (UTS) and yield stress (YS) were reduced by 4.6% and 1.24% when immersing the tensile samples in crude oil for 60 days. The values of (UTS) and (YS) were raised from 307 to 316 MPa and from 248 to 254 MPa respectively when treated for 10 min. shot peening (SP). Hardness of oil corrosion samples dropped due to pitting corrosion and slightly raised for SP prior to corrosion samples. Oil corrosion reduced the fatigue strength by (-1.25%). This percentage was enhanced due to SP to 2.377%. SP significantly increased the rotating fatigue life by a factor of 1.19 and 1.3 at (UTS) and (Ys) loads respectively. (SP) technique improved corrosion-fatigue resistance due to producing compressive residual stresses at surface layers.

scholarly journals Influence of Shot Peening on the Isothermal Fatigue Behavior of the Gamma Titanium Aluminide Ti-48Al-2Cr-2Nb at 750 °C

Metals ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 1083
Author(s):  
Christoph Breuner ◽  
Stefan Guth ◽  
Elias Gall ◽  
Radosław Swadźba ◽  
Jens Gibmeier ◽  
...  
Keyword(s):  
Residual Stresses ◽  
Shot Peening ◽  
Elevated Temperatures ◽  
Stress Amplitude ◽  
Negative Impact ◽  
Fatigue Behavior ◽  
Surface Hardness ◽  
Fatigue Tests ◽  
Positive Effects ◽  
Isothermal Fatigue

One possibility to improve the fatigue life and strength of metallic materials is shot peening. However, at elevated temperatures, the induced residual stresses may relax. To investigate the influence of shot peening on high-temperature fatigue behavior, isothermal fatigue tests were conducted on shot-peened and untreated samples of gamma TiAl 48-2-2 at 750 °C in air. The shot-peened material was characterized using EBSD, microhardness, and residual stress analyses. Shot peening leads to a significant increase in surface hardness and high compressive residual stresses near the surface. Both effects may have a positive influence on lifetime. However, it also leads to surface notches and tensile residual stresses in the bulk material with a negative impact on cyclic lifetime. During fully reversed uniaxial tension-compression fatigue tests (R = −1) at a stress amplitude of 260 MPa, the positive effects dominate, and the fatigue lifetime increases. At a lower stress amplitude of 230 MPa, the negative effect of internal tensile residual stresses dominates, and the lifetime decreases. Shot peening leads to a transition from surface to volume crack initiation if the surface is not damaged by the shots.

scholarly journals Quantitative Analysis of Inclusion Engineering on the Fatigue Property Improvement of Bearing Steel

Metals ◽  
2019 ◽  
Vol 9 (4) ◽  
pp. 476 ◽  
Author(s):  
Chao Gu ◽  
Min Wang ◽  
Yanping Bao ◽  
Fuming Wang ◽  
Junhe Lian
Keyword(s):  
Fatigue Life ◽  
Quantitative Analysis ◽  
Critical Size ◽  
Fatigue Behavior ◽  
Fatigue Cracks ◽  
Fatigue Property ◽  
Bearing Steel ◽  
Fatigue Properties ◽  
Bearing Steels ◽  
Inclusion Distribution

The fatigue property is significantly affected by the inner inclusions in steel. Due to the inhomogeneity of inclusion distribution in the micro-scale, it is not straightforward to quantify the effect of inclusions on fatigue behavior. Various investigations have been performed to correlate the inclusion characteristics, such as inclusion fraction, size, and composition, with fatigue life. However, these studies are generally based on vast types of steels and even for a similar steel grade, the alloy concept and microstructure information can still be of non-negligible difference. For a quantitative analysis of the fatigue life improvement with respect to the inclusion engineering, a systematic and carefully designed study is still needed to explore the engineering dimensions of inclusions. Therefore, in this study, three types of bearing steels with inclusions of the same types, but different sizes and amounts, were produced with 50 kg hot state experiments. The following forging and heat treatment procedures were kept consistent to ensure that the only controlled variable is inclusion. The fatigue properties were compared and the inclusions that triggered the fatigue cracks were analyzed to deduce the critical sizes of inclusions in terms of fatigue failure. The results show that the critical sizes of different inclusion types vary in bearing steels. The critical size of the spinel is 8.5 μm and the critical size of the calcium aluminate is 13.5 μm under the fatigue stress of 1200 MPa. In addition, with the increase of the cleanliness of bearing steels, the improvement of fatigue properties will reach saturation. Under this condition, further increasing of the cleanliness of the bearing steel will not contribute to the improvement of fatigue property for the investigated alloy and process design.

Fatigue Life Improvement of Welded Elements and Structures by Ultrasonic Impact Treatment

2011 ◽  
Author(s):  
Yuriy Kudryavtsev ◽  
Jacob Kleiman
Keyword(s):  
Mechanical Properties ◽  
Fatigue Life ◽  
Fatigue Strength ◽  
Residual Stresses ◽  
Fatigue Testing ◽  
Highway Bridges ◽  
Surface Layers ◽  
Ultrasonic Impact Treatment ◽  
Stress Relieving ◽  
Life Improvement

The ultrasonic impact treatment (UIT) is relatively new and promising process for fatigue life improvement of welded elements and structures. In most industrial applications this process is known as ultrasonic peening (UP). The beneficial effect of UIT/UP is achieved mainly by relieving of harmful tensile residual stresses and introducing of compressive residual stresses into surface layers of a material, decreasing of stress concentration in weld toe zones and enhancement of mechanical properties of the surface layers of the material. The UP technique is based on the combined effect of high frequency impacts of special strikers and ultrasonic oscillations in treated material. Fatigue testing of welded specimens showed that UP is the most efficient improvement treatment as compared with traditional techniques such as grinding, TIG-dressing, heat treatment, hammer peening and application of LTT electrodes. The developed computerized complex for UP was successfully applied for increasing the fatigue life and corrosion resistance of welded elements, elimination of distortions caused by welding and other technological processes, residual stress relieving, increasing of the hardness of the surface of materials. The UP could be effectively applied for fatigue life improvement during manufacturing, rehabilitation and repair of welded elements and structures. The areas/industries where the UP process was applied successfully include: Shipbuilding, Railway and Highway Bridges, Construction Equipment, Mining, Automotive, Aerospace. The results of fatigue testing of welded elements in as-welded condition and after application of UP are considered in this paper. It is shown that UP is the most effective and economic technique for increasing of fatigue strength of welded elements in materials of different strength. These results also show a strong tendency of increasing of fatigue strength of welded elements after application of UP with the increase in mechanical properties of the material used.

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