High-Cycle Fatigue Strength and Residual Stress in Welded Joints of Structural Steels

2004 ◽  
Author(s):  
Masahito Mochizuki ◽  
Masao Toyoda
Keyword(s):  
Residual Stress ◽  
Phase Transformation ◽  
Fatigue Strength ◽  
Low Temperature ◽  
Weld Metal ◽  
Welded Joints ◽  
Compressive Residual Stress ◽  
High Cycle Fatigue ◽  
Temperature Phase ◽  
Cycle Fatigue

Improvement of high-cycle fatigue strength by reducing residual stress in welded joints is studied in this paper. 10% Nickel and 10% Chromium are involved in the developed welding material for producing the property of thermal shrinkage by martensitic phase transformation at a low temperature and for generating compressive residual stress during cooling process. A cruciform fillet-welded joint is used for the numerical simulation of the thermal elastic-plastic finite-element analysis with coupling phase transformation effect. Distribution of the computed residual stress agrees with the measuring values by strain gauge. Compressive residual stress mostly distributes in the weld metal for both longitudinal and transverse directions with weld line. Fatigue test is also performed in order to clarify the effect of the developed weld material on fatigue strength. Developed weld metal has much higher characteristics for high-cycle fatigue strength than a conventional one. Increase effect of fatigue strength is shown by the modified Goodman diagram when residual stress is treated as mean stress. Weld metal with the property of low-temperature phase transformation is effective to reduce residual stress and to improve fatigue strength.

Residual Stress Redcution by Using Weld Metal With Property of Low-Temperature Phase Transformation

2004 ◽  
Author(s):  
Masahito Mochizuki ◽  
Masao Toyoda ◽  
Takahiro Kubo ◽  
Yasushi Morikage
Keyword(s):  
Residual Stress ◽  
Finite Element ◽  
Phase Transformation ◽  
Low Temperature ◽  
Weld Metal ◽  
Compressive Residual Stress ◽  
Weld Line ◽  
Temperature Phase ◽  
Element Analysis ◽  
Low Temperature Phase

Residual stress in welded joints by using a new weld metal with the property of low-temperature phase transformation is numerically analyzed. 10 % Nickel and 10 % Chromium are involved in the developed welding material for producing the property of martensitic phase transformation at a low temperature and for generating compressive residual stress. A fillet-welded joint between plate and stiffener is used for the numerical simulation of the thermal elastic-plastic finite-element analysis with coupling phase transformation effect. Moving heat source is considered by using the gradual deposition of the finite-element during welding. Distribution of the computed residual stress mostly agrees with the measuring values by strain gauge. Compressive residual stress distributes in the weld metal for both longitudinal and transverse directions with weld line. The effects of the material of weld metal and welding pass sequence on residual stress are investigated. Residual stresses on the weld toe and root are improved lower by using the low-temperature transformation weld wire than the conventional one, regardless of the sequence of welding deposition. It is found that the weld metal with property of low-temperature phase transformation is effective to reduce residual stress near weld metal.

Effects of Laser Peening Treatment on High Cycle Fatigue and Crack Propagation Behaviors in Austenitic Stainless Steel

2009 ◽  
Author(s):  
Yasuo Ochi ◽  
Kiyotaka Masaki ◽  
Takashi Matsumura ◽  
Takaaki Ikarashi ◽  
Yuji Sano
Keyword(s):  
Residual Stress ◽  
Stainless Steel ◽  
Surface Layer ◽  
Fatigue Crack ◽  
Fatigue Strength ◽  
Crack Propagation ◽  
Compressive Residual Stress ◽  
High Cycle Fatigue ◽  
Laser Peening ◽  
Cycle Fatigue

Laser peening without protective coating (LPwC) treatment is one of surface enhancement techniques using impact wave of high pressure plasma induced by laser pulse irradiation. One of the effects of the LPwC treatment is expected to reduce the tensile residual stress and to induce the compressive residual stress in the surface layer of metallic materials. As a laser has no reaction force due to irradiation and also it has easy characteristics for remote control, the LPwC treatment is practically used as a technique for preventing the stress corrosion cracking (SCC) and for improving the fatigue strength of some structural materials. In this study, high cycle fatigue tests with four-points rotating bending loading were carried out on the non-peened and the LPwC treated low-carbon type austenitic stainless steel 316L in order to investigate the effects of the LPwC treatment on the high cycle fatigue strength and the surface fatigue crack propagation behavior. Two types of specimens were prepared; one was a smooth specimen, the other was a specimen with a pre-crack by the fatigue loading from a small artificial hole. As the results of the LPwC treatment, the high compressive residual stress was induced in the surface layer on the specimens, and the region of the compressive residual stress was about 1mm depth from the surface. The fatigue strength of the LPwC treated SUS316L was remarkably improved during the whole regime of the fatigue life up to the 108 cycles compared with the non-peened materials. Through the fracture mechanics investigation of the pre-cracked materials after the LPwC treatment, it became clear that the fatigue crack propagation was restrained by the LPwC treatment on the pre-cracked region, when the stress intensity factor range ΔK on the crack tip was under the value of 7.6 MPa√m.

scholarly journals Influence of Preaging Temperature on the Indentation Strength of 3Y-TZP Aged in Ambient Atmosphere

Materials ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 2767
Author(s):  
Ki-Won Jeong ◽  
Jung-Suk Han ◽  
Gi-Uk Yang ◽  
Dae-Joon Kim
Keyword(s):  
Residual Stress ◽  
Phase Transformation ◽  
Low Temperature ◽  
Compressive Residual Stress ◽  
Yttria Stabilized Zirconia ◽  
Ambient Atmosphere ◽  
Aged Specimen ◽  
Stabilized Zirconia ◽  
M Phase ◽  
The Relationship

Yttria-stabilized zirconia (3Y-TZP) containing 0.25% Al2O3, which is resistant to low temperature degradation (LTD), was aged for 10 h at 130–220 °C in air. The aged specimens were subsequently indented at loads ranging from 9.8 to 490 N using a Vickers indenter. The influence of preaging temperature on the biaxial strength of the specimens was investigated to elucidate the relationship between the extent of LTD and the strength of zirconia restorations that underwent LTD. The indented strength of the specimens increased as the preaging temperature was increased higher than 160 °C, which was accompanied by extensive t-ZrO2 (t) to m-ZrO2 (m) and c-ZrO2 (c) to r-ZrO2 (r) phase transformations. The influence of preaging temperature on the indented strength was rationalized by the residual stresses raised by the t→m transformation and the reversal of tensile residual stress on the aged specimen surface due to the indentation. The results suggested that the longevity of restorations would not be deteriorated if the aged restorations retain compressive residual stress on the surface, which corresponds to the extent of t→m phase transformation less than 52% in ambient environment.

scholarly journals High cycle fatigue analysis in the presence of autofrettage compressive residual stress

2018 ◽  
Vol 41 (11) ◽  
pp. 2305-2320
Author(s):  
V. Okorokov ◽  
D. MacKenzie ◽  
Y. Gorash ◽  
M. Morgantini ◽  
R. van Rijswick ◽  
...  
Keyword(s):  
Residual Stress ◽  
Compressive Residual Stress ◽  
High Cycle Fatigue ◽  
Fatigue Analysis ◽  
Cycle Fatigue

Effect of Hammer Peening Processing on Fatigue Property of Welded Joints After Overload

2013 ◽  
Author(s):  
Yasushi Morikage ◽  
Satoshi Igi ◽  
Kenji Oi
Keyword(s):  
Residual Stress ◽  
Fatigue Strength ◽  
Compressive Stress ◽  
Welded Joints ◽  
Compressive Residual Stress ◽  
Welded Joint ◽  
Fatigue Property ◽  
Weld Toe ◽  
Hammer Peening ◽  
General Method

One general method for improving the fatigue strength of welded joints is introduction of compressive residual stress by peening. However, there is concern that the fatigue strength of the welded joint may decrease if excessive preloading is applied after peening. It has been found that fatigue strength decreased after applying compressive preloading to a welded joint due to cancellation of the compressive stress at the weld toe. In the present research, the influence of excessive preloading on the fatigue strength of welded joints with compressive residual stress at the weld toe was clarified by experiments using hammer peening with an improved pin. When hammer peening was applied to welded joints, increasing the radius of the weld toe reduced the decrease of compressive residual stress due to excessive preloading. As a result, the decrease of the fatigue strength of the welded joint was also reduced.

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