scholarly journals Fatigue strength and failure mechanism for the aluminium wrought alloy EN AW 6056 in the VHCF-region and influence of notches and compressive residual stresses

2010 ◽  
Vol 2 (1) ◽  
pp. 1505-1514 ◽  
Author(s):  
Daniela Schwerdt ◽  
Brita Pyttel ◽  
Christina Berger
Keyword(s):  
Fatigue Strength ◽  
Residual Stresses ◽  
Failure Mechanism ◽  
Compressive Residual Stresses

Influence of Residual Stresses and of Mean Stress on the Fatigue Strength of Specimens with Longitudinal Non-Load-Carrying Fillet Welds

1970 ◽  
Vol 12 (6) ◽  
pp. 381-390
Author(s):  
T. R. Gurney
Keyword(s):  
Fatigue Strength ◽  
Residual Stresses ◽  
Stress Ratio ◽  
Fillet Welds ◽  
Direct Result ◽  
Mean Stress ◽  
Test Results ◽  
Load Carrying ◽  
Quantitative Explanation ◽  
Compressive Residual Stresses

Using results obtained in work on fatigue crack propagation in unwelded sheet specimens, an analysis has been made of fatigue test results for specimens with longitudinal non-load-carrying fillet welds tested in the as-welded and stress relieved conditions and also after treatment by local compression and by spot heating. It is shown that, by this means, it is possible to provide a quantitative explanation of the effect of residual stresses and applied stress ratio on fatigue strength, since all the results can be normalized on the basis of an effective stress range. In the course of the work it has been shown that the gross stress concentration factor for this type of joint is approximately 2·57. It has also again been demonstrated that the beneficial effect of spot heating on fatigue strength is a direct result of induced compressive residual stresses.

Characteristics of High Frequency Peening Methods and their Effects on the Fatigue Strength of Welded Details

2007 ◽  
Vol 348-349 ◽  
pp. 429-432
Author(s):  
Imke Weich ◽  
Thomas Ummenhofer
Keyword(s):  
Fatigue Strength ◽  
Residual Stresses ◽  
High Frequency ◽  
Crack Detection ◽  
Surface Hardness ◽  
Detection Methods ◽  
Laser Measurements ◽  
Mechanical Effects ◽  
Weld Toe ◽  
Compressive Residual Stresses

Research has been initiated on the effects of high frequency peening methods on the fatigue strength. These methods combine an improvement of weld toe profile with an initiation of compressive residual stresses and surface hardening. The effects of two techniques, High Frequency Impact Treatment (HiFIT) and Ultrasonic Impact Treatemnt (UIT) are compared. Laser measurements of the weld seam prove that both methods increase the overall weld toe radii. Further, residual stress measurements verify the introduction of compressive residual stresses at least up to a depth of 1 mm. The values meet the yield strength combined with an increase of the surface hardness. These material mechanical effects cause an increased crack resistance. Crack detection methods prove that the material mechanical effects yield to a retarded crack initiation. Experimental results show that these effects lead to a significant increase of the fatigue strength and reduced slopes of the SN-curves.

Fatigue Life Improvement Using Mechanical Post Treatment for Weldment

2008 ◽  
Vol 580-582 ◽  
pp. 97-100
Author(s):  
Seung Ho Han ◽  
Jeong Woo Han ◽  
Yong Yun Nam
Keyword(s):  
Fatigue Life ◽  
Fatigue Strength ◽  
Residual Stresses ◽  
Quantitative Measure ◽  
Fatigue Strength Improvement ◽  
Weld Profile ◽  
Weld Toe ◽  
Life Improvement ◽  
Hammer Peening ◽  
Compressive Residual Stresses

Mechanical post treatments for welded structures have been applied in various industrial fields and, in most cases, have been found to cause substantial increase in their fatigue strength. These methods, generally, consist of the modification of weld toe geometry and the introduction of compressive residual stresses. In hammer peening, the weld profile is modified due to removal or reduction of minute crack-like flaws; compressive residual stresses are also induced by repeated hammering of the weld toe region with blunt-nosed chisel. In this study, a hammer peening procedure, using commercial pneumatic chipping hammer, was developed; a quantitative measure of fatigue strength improvement was performed. The fatigue life of hammer-peened specimen was prolonged by approximately 10 times in S=240MPa, and was doubled for the as-welded specimen.

Influence of the Abrasive on Fatigue in Precision Grinding

1987 ◽  
Vol 109 (3) ◽  
pp. 203-205 ◽  
Author(s):  
H. K. To¨nshoff ◽  
F. Hetz
Keyword(s):  
Fatigue Strength ◽  
Residual Stresses ◽  
Strong Influence ◽  
Cubic Boron Nitride ◽  
Fatigue Tests ◽  
Machining Parameters ◽  
Precision Grinding ◽  
Surface Residual Stresses ◽  
Alternating Bending ◽  
Compressive Residual Stresses

The surface residual stresses produced by grinding may have a strong influence on the life of highly stressed components. Different abrasives such as aluminum oxide (Al2O3) and cubic boron nitride (CBN) may lead to very different results. While CBN produces compressive residual stresses in nearly all combinations of machining parameters, the use of Al2O3 normally leads to tensile residual stresses. Fatigue tests carried out in alternating bending showed a remarkable increase in fatigue strength for CBN ground specimens compared with Al2O3 ground ones.

scholarly journals X-ray Determination of Compressive Residual Stresses in Spring Steel Generated by High-Speed Water Quenching

Materials ◽  
2019 ◽  
Vol 12 (7) ◽  
pp. 1154
Author(s):  
Diego E. Lozano ◽  
George E. Totten ◽  
Yaneth Bedolla-Gil ◽  
Martha Guerrero-Mata ◽  
Marcel Carpio ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Residual Stresses ◽  
High Speed ◽  
Spring Steel ◽  
X Ray Diffraction ◽  
Laboratory Equipment ◽  
X Ray ◽  
Water Chamber ◽  
Hardened Case ◽  
Compressive Residual Stresses

Automotive components manufacturers use the 5160 steel in leaf and coil springs. The industrial heat treatment process consists in austenitizing followed by the oil quenching and tempering process. Typically, compressive residual stresses are induced by shot peening on the surface of automotive springs to bestow compressive residual stresses that improve the fatigue resistance and increase the service life of the parts after heat treatment. In this work, a high-speed quenching was used to achieve compressive residual stresses on the surface of AISI/SAE 5160 steel samples by producing high thermal gradients and interrupting the cooling in order to generate a case-core microstructure. A special laboratory equipment was designed and built, which uses water as the quenching media in a high-speed water chamber. The severity of the cooling was characterized with embedded thermocouples to obtain the cooling curves at different depths from the surface. Samples were cooled for various times to produce different hardened case depths. The microstructure of specimens was observed with a scanning electron microscope (SEM). X-ray diffraction (XRD) was used to estimate the magnitude of residual stresses on the surface of the specimens. Compressive residual stresses at the surface and sub-surface of about −700 MPa were obtained.

scholarly journals Thermal Effects on Surface and Subsurface Modifications in Laser-Combined Deep Rolling

2021 ◽  
Vol 5 (2) ◽  
pp. 55
Author(s):  
Robert Zmich ◽  
Daniel Meyer
Keyword(s):  
Surface Layer ◽  
Residual Stresses ◽  
Thermal Loads ◽  
Deep Rolling ◽  
Mechanical Loads ◽  
Thermomechanical Process ◽  
Compressive Stresses ◽  
New Process ◽  
Negative Effect ◽  
Compressive Residual Stresses

Knowledge of the relationships between thermomechanical process loads and the resulting modifications in the surface layer enables targeted adjustments of the required surface integrity independent of the manufacturing process. In various processes with thermomechanical impact, thermal and mechanical loads act simultaneously and affect each other. Thus, the effects on the modifications are interdependent. To gain a better understanding of the interactions of the two loads, it is necessary to vary thermal and mechanical loads independently. A new process of laser-combined deep rolling can fulfil exactly this requirement. The presented findings demonstrate that thermal loads can support the generation of residual compressive stresses to a certain extent. If the thermal loads are increased further, this has a negative effect on the surface layer and the residual stresses are shifted in the direction of tension. The results show the optimum range of thermal loads to further increase the compressive residual stresses in the surface layer and allow to gain a better understanding of the interactions between thermal and mechanical loads.

scholarly journals Additive Manufactured 316L Stainless-Steel Samples: Microstructure, Residual Stress and Corrosion Characteristics after Post-Processing

Metals ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 182
Author(s):  
Suvi Santa-aho ◽  
Mika Kiviluoma ◽  
Tuomas Jokiaho ◽  
Tejas Gundgire ◽  
Mari Honkanen ◽  
...  
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Sample Surface ◽  
Post Processing ◽  
Magnesium Chloride Solution ◽  
Manufacturing Method ◽  
Four Point Bending ◽  
Traditional Manufacturing ◽  
Processing Steps ◽  
Compressive Residual Stresses

Additive manufacturing (AM) is a relatively new manufacturing method that can produce complex geometries and optimized shapes with less process steps. In addition to distinct microstructural features, residual stresses and their formation are also inherent to AM components. AM components require several post-processing steps before they are ready for use. To change the traditional manufacturing method to AM, comprehensive characterization is needed to verify the suitability of AM components. On very demanding corrosion atmospheres, the question is does AM lower or eliminate the risk of stress corrosion cracking (SCC) compared to welded 316L components? This work concentrates on post-processing and its influence on the microstructure and surface and subsurface residual stresses. The shot peening (SP) post-processing levelled out the residual stress differences, producing compressive residual stresses of more than −400 MPa in the AM samples and the effect exceeded an over 100 µm layer below the surface. Post-processing caused grain refinement and low-angle boundary formation on the sample surface layer and silicon carbide (SiC) residue adhesion, which should be taken into account when using the components. Immersion tests with four-point-bending in the heated 80 °C magnesium chloride solution for SCC showed no difference between AM and reference samples even after a 674 h immersion.

Sign in / Sign up

Export Citation Format

Share Document