scholarly journals Increasing fatigue performance in AHSS thick sheet by surface treatments

2018 ◽  
Vol 165 ◽  
pp. 22015
Author(s):  
Sergi Parareda ◽  
Antoni Lara ◽  
Henrik Sieurin ◽  
Héber D´Armas ◽  
Daniel Casellas
Keyword(s):  
Surface Roughness ◽  
Fatigue Life ◽  
Residual Stresses ◽  
High Strength Steels ◽  
High Strength ◽  
Fatigue Tests ◽  
Surface Treatments ◽  
Thick Sheet ◽  
Steel Grades ◽  
Mechanical Surface

Advanced High Strength Steels (AHSS) have been widely applied in the automotive industry as an affordable solution for car lightweighting, mainly in parts subjected to crash requirements. Heavy duty vehicle (HDV) can also benefit from the expertise learned in cars, but parts must be designed considering fatigue resistance, especially on trimmed areas, and stiffness. Mechanical surface treatments, as blasting or shot peening, help increasing fatigue life of AHSS in trimmed areas and will allow weight reduction in HDV through gauge downsizing. The expected decrease in stiffness through thickness reduction can be improved by design changes. However, scarce information about the effect of mechanical surface treatments on AHSS are available. Thus, the aim of this work is to evaluate the increment in fatigue life of two different steel grades (350 MPa, and 500MPa of yield strength) in thick sheet by means of mechanical surface treatment – sandblasting. High Cycle Fatigue [HCF] tests were conducted at alternating load [R=-1]. Residual stresses were measured by an X-ray tensometry prior fatigue tests. Also the surface roughness [Rz] and form is measured using an optical non-contact 3D microscope. On the other hand, the fracture surfaces of the test specimens were observed via scanning electron microscope (SEM) in order to determine the crack initiation points. The evaluation of fatigue life in terms of SN curves is also discussed, analysing how the sandblasting process modifies the surface roughness and introduce compressive residual stresses on the external layer of the material. Both phenomena enhance the fatigue strength of the evaluated steel grades.

scholarly journals Fatigue Life Prediction of Machined Specimens with the Consideration of Surface Roughness

Materials ◽  
2021 ◽  
Vol 14 (18) ◽  
pp. 5420
Author(s):  
Xiaochun Zhu ◽  
Zhurong Dong ◽  
Yachen Zhang ◽  
Zhengkun Cheng
Keyword(s):  
Surface Roughness ◽  
Fatigue Life ◽  
Surface Topography ◽  
High Strength Steels ◽  
High Strength ◽  
Fatigue Tests ◽  
Analytical Formulas ◽  
Fatigue Notch Factor ◽  
Underlying Mechanisms ◽  
Effect Of Surface

The fatigue strength and fatigue life of high-strength steels are greatly affected by their surface roughness. This study investigates the underlying mechanisms responsible for fatigue failure of the high-strength steel 42CrMo. Bending fatigue tests of stepped shafts with different levels of surface roughness were conducted to observe the fatigue live reduction affected by surface topography. Besides, the mechanical properties of 42CrMo and its strain–life relationship were established. Moreover, the analytical formulas to describe the stress concentration factor (SCF) and fatigue notch factor (FNF) induced by surface topography were introduced. To estimate the fatigue life of machined specimens with the consideration of surface roughness, the elastic portion of the total strain–life curve of the material was revised with the proposed analytical FNF imposed by surface topography. Comparisons between the estimated fatigue lives and experimentally obtained fatigue lives show that the effect of surface roughness on fatigue lives could be estimated effectively and conveniently by the proposed procedure.

scholarly journals Mechanical surface treatments to optimize the fatigue behavior of quenched and tempered high strength steels

2018 ◽  
Vol 96 (1-4) ◽  
pp. 1225-1235 ◽  
Author(s):  
E. Segurado ◽  
F. J. Belzunce ◽  
I. Fernández Pariente
Keyword(s):  
Fatigue Behavior ◽  
High Strength Steels ◽  
High Strength ◽  
Surface Treatments ◽  
Mechanical Surface

scholarly journals An enhancement of the current design concepts for the improved consideration of residual stresses in fatigue-loaded welds

2021 ◽  
Vol 65 (4) ◽  
pp. 643-651
Author(s):  
Th. Nitschke-Pagel ◽  
J. Hensel
Keyword(s):  
Residual Stresses ◽  
State Of The Art ◽  
High Strength Steels ◽  
High Strength ◽  
Design Tools ◽  
Design Concepts ◽  
Treatment Processes ◽  
Real Distribution ◽  
Current Design ◽  
Reliable Knowledge

AbstractThe consideration of residual stresses in fatigue-loaded welds is currently done only qualitatively without reliable knowledge about their real distribution, amount and prefix. Therefore, the tools which enable a more or less unsafe consideration in design concepts are mainly based on unsafe experiences and doubtful assumptions. Since the use of explicitly determined residual stresses outside the welding community is state of the art, the target of the presented paper is to show a practicable way for an enhanced consideration of residual stresses in the current design tools. This is not only limited on residual stresses induced by welding, but also on post-weld treatment processes like HFMI or shot peening. Results of extended experiments with longitudinal fillet welds and butt welds of low and high strength steels evidently show that an improved use of residual stresses in fatigue strength approximation enables a better evaluation of peening processes as well as of material adjusted welding procedures or post-weld stress relief treatments. The concept shows that it is generally possible to overcome the existing extremely conservative but although unsafe rules and regulations and may also enable the improved use of high strength steels.

scholarly journals Residual stress effects on fatigue life prediction using hardness measurements for butt-welded joints made of high strength steels

2021 ◽  
Vol 147 ◽  
pp. 106175
Author(s):  
Haohui Xin ◽  
José A.F.O. Correia ◽  
Milan Veljkovic ◽  
Filippo Berto ◽  
Lance Manuel
Keyword(s):  
Residual Stress ◽  
Fatigue Life ◽  
Welded Joints ◽  
Life Prediction ◽  
High Strength Steels ◽  
High Strength ◽  
Fatigue Life Prediction ◽  
Stress Effects

Fatigue and Burst Analysis of Hy-140(T) Steel Pressure Vessels

1970 ◽  
Vol 92 (1) ◽  
pp. 11-16 ◽  
Author(s):  
J. M. Barsom ◽  
S. T. Rolfe
Keyword(s):  
Yield Strength ◽  
Pressure Vessel ◽  
Low Cycle Fatigue ◽  
High Strength Steels ◽  
High Strength ◽  
Fatigue Tests ◽  
Pressure Vessels ◽  
High Yield ◽  
Corrosion Properties ◽  
Burst Analysis

Increasing use of high-strength steels in pressure-vessel design has resulted from emphasis on decreasing the weight of pressure vessels for certain applications. To demonstrate the suitability of a 140-ksi yield strength steel for use in unwelded pressure vessels, HY-140(T)—a quenched and tempered 5Ni-Cr-Mo-V steel—was fabricated and subjected to various burst and fatigue tests, as well as to various laboratory tests. In general, results of the investigation indicated very good tensile, Charpy, Nil Ductility Transition Temperature (NDT), low-cycle fatigue, and stress-corrosion properties of HY-140(T) steels, as well as very good burst tests results, in comparison with existing high-yield strength pressure-vessel steels. The results also indicate that the HY-140(T) steel should be an excellent material for its originally designed purpose, Naval hull applications.

scholarly journals Multiaxial fatigue study on steel transversal attachments under constant amplitude proportional and non-proportional loadings

2018 ◽  
Vol 165 ◽  
pp. 16007
Author(s):  
Martin Garcia ◽  
Claudio A. Pereira Baptista ◽  
Alain Nussbaumer
Keyword(s):  
Fatigue Life ◽  
High Strength ◽  
Fatigue Tests ◽  
Multiaxial Fatigue ◽  
Life Assessment ◽  
Experimental Program ◽  
Proportional Loading ◽  
Load Carrying ◽  
Stress States ◽  
Experimental Values

In this study, the multiaxial fatigue strength of full-scale transversal attachment is assessed and compared to original experimental results and others found in the literature. Mild strength S235JR steel is used and an exploratory investigation on the use of high strength S690QL steel and the effect of non-proportional loading is presented. The study focuses on non-load carrying fillet welds as commonly used in bridge design and more generally between main girders and struts. The experimental program includes 33 uniaxial and multiaxial fatigue tests and was partially carried out on a new multiaxial setup that allows proportional and non-proportional tests in a typical welded detail. The fatigue life is then compared with estimations obtained from local approaches with the help of 3D finite element models. The multiaxial fatigue life assessment with some of the well-known local approaches is shown to be suited to the analysis under multiaxial stress states. The accuracy of each models and approaches is compared to the experimental values considering all the previously cited parameters.

scholarly journals Changing in Fatigue Life of 300 M Bainitic Steel After Laser Carburizing and Plasma Nitriding

2018 ◽  
Vol 165 ◽  
pp. 21002 ◽  
Author(s):  
Antonio J. Abdalla ◽  
Douglas Santos ◽  
Getúlio Vasconcelos ◽  
Vladimir H. Baggio-Scheid ◽  
Deivid F. Silva
Keyword(s):  
Mechanical Properties ◽  
Fatigue Life ◽  
Plasma Nitriding ◽  
Fatigue Behavior ◽  
High Strength ◽  
Tensile Tests ◽  
Steel Sample ◽  
Fatigue Tests ◽  
300M Steel ◽  
Structural Applications

In this work 300M steel samples is used. This high-strength steel is used in aeronautic and aerospace industry and other structural applications. Initially the 300 M steel sample was submitted to a heat treatment to obtain a bainític structure. It was heated at 850 °C for 30 minutes and after that, cooled at 300 °C for 60 minutes. Afterwards two types of surface treatments have been employed: (a) using low-power laser CO2 (125 W) for introducing carbon into the surface and (b) plasma nitriding at a temperature of 500° C for 3 hours. After surface treatment, the metallographic preparation was carried out and the observations with optical and electronic microscopy have been made. The analysis of the coating showed an increase in the hardness of layer formed on the surface, mainly, among the nitriding layers. The mechanical properties were analyzed using tensile and fatigue tests. The results showed that the mechanical properties in tensile tests were strongly affected by the bainitic microstructure. The steel that received the nitriding surface by plasma treatment showed better fatigue behavior. The results are very promising because the layer formed on steel surface, in addition to improving the fatigue life, still improves protection against corrosion and wear.

The Effect of Several Finishing Processes on the Fatigue Resistance of Hole Surfaces

1989 ◽  
Vol 111 (1) ◽  
pp. 71-73 ◽  
Author(s):  
M. O. Lai ◽  
A. Y. C. Nee
Keyword(s):  
Surface Roughness ◽  
Plastic Deformation ◽  
Fatigue Life ◽  
Residual Stresses ◽  
Fatigue Resistance ◽  
Radial Direction ◽  
Fatigue Loading ◽  
Steel Plates ◽  
Finishing Processes ◽  
Compressive Residual Stresses

This investigation examines the effects of different finishing processes on the fatigue life of premachined holes in Assab 760 steel plates. The finishing processes studied were reaming, ballizing, and emery polishing. A general decrease in fatigue life with increase in surface roughness is observed for all the processes employed. In comparing the different processes, for a constant surface roughness, polishing is generally found to give the longest fatigue life while ballizing, in spite of the greater compressive residual stresses induced on the surface of the finished hole, the shortest. The surprising phenomenon was found to be attributed to the amount of plastic deformation occurred before fatigue loading. For Assab 760 steel, a prestrain in the radial direction of less than about 2.5 percent appeared to reduce the fatigue resistance of the material.

Short Crack Propagation Model Applied to Shot Peened Aluminium Alloys

2009 ◽  
Vol 65 ◽  
pp. 53-61 ◽  
Author(s):  
J. Solis ◽  
J. Oseguera-Peña ◽  
I. Betancourt
Keyword(s):  
Surface Roughness ◽  
Residual Stresses ◽  
Crack Propagation ◽  
Aluminium Alloys ◽  
Micromechanical Model ◽  
High Strength ◽  
Crack Arrest ◽  
Propagation Model ◽  
Safe Load ◽  
Compressive Residual Stresses

The Navarro-Rios micromechanical model was used to assess the bounds of two different damage zones: crack arrest region and crack propagation region of controlled shot peening (CSP) of high strength aluminium alloys. Performance of CSP in terms of fatigue resistance was investigated. This comparison indicated that CSP in terms of fatigue depends on the competition between its beneficial and detrimental products, i.e. surface roughness and compressive residual stresses respectively. The gathered information can be used for safe load determinations in design.

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