scispace - formally typeset
Search or ask a question
Journal ArticleDOI

Post-forming monotonic and cyclic behavior in a HSLA steel sheet after large deformations by in-plane compression

01 Oct 2015-International Journal of Fatigue (Elsevier)-Vol. 79, pp 54-64
TL;DR: In this article, the effects of large prestrains on the asymmetry and anisotropy of the stress response and on the fatigue life were investigated under fully reversed axial strain for a 345 MPa yield strength V-N high strength low alloy steel sheet.
About: This article is published in International Journal of Fatigue.The article was published on 2015-10-01. It has received 6 citations till now. The article focuses on the topics: Bauschinger effect & Compression (physics).
Citations
More filters
Journal ArticleDOI
TL;DR: In this article , the cyclic deformation in association with bulk texture evolution in HSLA steel is studied in an X-ray diffraction analysis and the results exhibit an increase in strain accumulation from 0.23 to 30.61%.
Abstract: Ratcheting deformation in association with bulk texture evolution in HSLA steel is studied in this investigation. The cyclic deformation behaviors and damage modes of the specimens are obtained at room temperature, employing asymmetric stress-controlled tests under various combinations of mean stress and stress amplitudes. Bulk texture measurements of the specimens are done adopting an X-ray diffraction analysis. The results exhibit an increase in strain accumulation from 0.23 to 30.61% associated with a sharp reduction in ratcheting life from 3320 to 880 cycles by the increment in mean stress/stress amplitude. A continuous cyclic softening until the final failure is observed for all the ratcheting tests. It is noticed that variation of mean stress is more detrimental than stress amplitude in controlling strain accumulation while the effect of stress amplitude is more pronounced than mean stress for the reduction of ratcheting life. The fracture surface morphology indicates typical striation formation in the crack propagation region along with overload failure. The bulk texture studies indicate that there is a transition between ‘ϒ’ fiber and ‘ζ’ fiber during all loading conditions. The texture intensity is increased from 5.71 to 11.68 with progressive ratcheting strain accumulation. Here also, influence of stress amplitude is more significant than the mean stress.

6 citations

Dissertation
04 Feb 2016
TL;DR: In this paper, the authors propose a polycristallin de comportement and d'endommagement en fatigue for acier ferritique with a haute limite d'elasticite HC360LA.
Abstract: Cette these, realisee dans le cadre du projet APSTRAM (Allegement et Performance des STRuctures Acier Marine) de l’IRT Jules Verne, s’interesse a l’endommagement en fatigue a grand nombre de cycles d’un acier ferritique a haute limite d’elasticite HC360LA. La premiere partie de ce travail est dediee a la realisation d’essais de fatigue a contrainte imposee avec differents rapports de charge et differentes conditions initiales (fixees a partir d’un eventuel pre-ecrouissage). Ces essais montrent que le pre-ecrouissage, obtenu par traction uniaxiale, permet d’augmenter significativement la resistance a la fatigue. Aussi, un effort experimental est fait pour estimer a partir des mesures de force, d’elongation et de temperature comment l’energie de deformation est soit dissipee en chaleur, soit stockee dans le materiau par ecrouissage. Les resultats ainsi obtenus montrent qu’il existe a l’echelle macroscopique une correlation entre l’energie dissipee et le nombre de cycles a rupture independamment des conditions initiales et des conditions de chargement. Cela souligne donc l’importance de la plasticite dans le processus d’endommagement en fatigue de l’acier HC360LA. Un modele polycristallin de comportement et d’endommagement en fatigue est ensuite propose. Il repose sur la formulation d’une loi de comportement a l’echelle cristalline qui utilise les ingredients de la mecanique de l’endommagement pour decrire la degradation progressive des proprietes mecaniques. La loi de comportement est etablie de sorte a considerer le couplage de l’endommagement avec la plasticite, le caractere anisotrope de l’endommagement et l’influence de l’anisotropie des proprietes elastiques. Elle est ensuite implementee dans un modele d’homogeneisation afin de prendre en compte le caractere polycristallin de l’acier HC360LA. Le modele propose est finalement utilise pour etudier le comportement en fatigue a l’echelle microscopique. Il permet d’abord de montrer que l’endommagement de fatigue est un processus extremement localise qui ne concerne que quelques cristaux d’orientation particuliere. De ce fait, si une diminution de la rigidite est localement observee, les proprietes elastiques macroscopiques sont peu influencees par l’endommagement. Aussi, le modele permet de souligner que la contribution de l’endommagement a la dissipation de chaleur est negligeable devant celle de la plasticite. La correlation entre le nombre de cycles a rupture et l’energie dissipee n’existe donc que parce que l’endommagement de fatigue est le resultat de l’accumulation de deformation plastique.

5 citations


Cites background from "Post-forming monotonic and cyclic b..."

  • ...Figure I.24 : Comportement à l’écrouissage cyclique d’un acier HSLA soumis à une pré-déformation dans le plan de la tôle de −0,58 (IPC : in-plane compression)....

    [...]

  • ...Charpentier (Charpentier, 2015) a récemment étudié les effets d’une pré-déformation plastique sur les comportements mécaniques monotone et cyclique d’un acier HSLA (AISI 50XF) avec une limite d’écoulement plastique minimale de 345 MPa....

    [...]

  • ...Les essais sont conduits à déformation totale imposée parallèlement ou perpendiculairement à la direction de compression IPC (Charpentier, 2015) ....

    [...]

  • ...Les essais sont conduits à déformation totale imposée parallèlement ou perpendiculairement à la direction de compression IPC (Charpentier, 2015) ...................................................................................................................................................... 25 Figure I.25 : Comportement en fatigue d’un acier HSLA 420, (a) Courbes d’auto-échauffement obtenus pour trois niveaux de pré-déformation plastique en traction, (b) Courbes de Wöhler pour le matériau vierge et le matériau pré-déformé à 10% (Munier, 2012) ...................................................... 26 Figure I.26 : Evolution de la limite d’endurance (normalisée par rapport au cas non-déformé) d’un acier HSLA 420, pour plusieurs modes et niveaux de pré-déformation (Munier, 2012) (AE : Autoéchauffement, TU : Traction Uniaxiale, TP SL-ST : Pré-déformation en traction plane dans le sens Long, essai de fatigue dans le sens travers, Fatigue : données de fatigue avec des essais « classiques ») ............................................................................................................................................................... 27 Figure I.27 : Effet de moyenne en fatigue dans un acier HSLA 420, (a) Courbes d’auto-échauffement obtenues pour trois rapports de charge R=−1, −0,3, 0,1, (b) Courbes de Wöhler pour le matériau prédéformé à 10% et deux niveaux moyens 0 et 200 MPa (Munier, 2012) ............................................... 28 Figure I.28 : Évolution de la surface des bandes de glissement en fonction de l’échauffement dans un acier ferritique (Galtier, et al., 2002) ........................................................................................................

    [...]

  • ...Les essais sont conduits à déformation totale imposée parallèlement ou perpendiculairement à la direction de compression IPC (Charpentier, 2015) L’étude la plus complète de la littérature sur l’influence des modes de pré-déformation est sans nul doute celle conduite par Munier dans sa thèse de doctorat (Munier, 2012)....

    [...]

Journal Article
TL;DR: In this article, the effects of rolling parameters on the mechanical properties of the experimental steels are analyzed by means of thermal simulation, controlling rolling and cold control in the laboratory, and the fatigue performance of different high strength steel is studied by drawing the fatigue life curve.
Abstract: In this paper, the effects of rolling parameters on the mechanical properties of the experimental steels are analyzed by means of thermal simulation, controlling rolling and cold control in the laboratory. As the wheel’s work under random loads, the failure modes of the wheels are mainly caused by the damages of strength and fatigue, in which more than 80% are caused by fatigue damage. So that the life of wheel's fatigue is the most important performance index of the wheel. At present, the domestic research on the fatigue performance is automobile wheel steel, especially for different organizations of automotive wheels with high strength steel fatigue performance differences are still relatively less. On the basis of hot rolling experiment, the fatigue test of high strength steel for different wheels is carried out by using high frequency fatigue testing machine. The fatigue performance of different high strength steel is studied by drawing the fatigue life curve. The main conclusion is as the following. The final cooling temperature is 630°C, the Rm increases from 766°C to 820°C, Rm increases from 720MPa to 748MPa, Rp0.2 increases from 463MPa to 525MPa, and the elongation reaches 20.0%. The change is not obvious. When the finishing temperature is 870°C, Rm is lower, 655MPa, Rp0.2 is 415MPa, but the elongation that is 26.98% is higher.

1 citations

Journal ArticleDOI
TL;DR: In this paper , the use of laser shock peening (LSP) to improve back stress in additively manufactured 316L parts was studied and it was shown that LSPed samples exhibit a reduction to back stress that varies for differing build directions.
Abstract: This work studies the use of laser shock peening (LSP) to improve back stress in additively manufactured 316L parts. Grain morphologies and irregular dislocation distribution resulting from crystallization schemes that occur during printing cause anisotropic mechanical properties in additively manufactured metal. Tension-compression asymmetry caused by back stress has been observed as one of these anisotropic properties. Such asymmetry complicates application of 3D-printed metal for mechanical design because 3D-printed parts will behave differently than traditionally manufactured parts under the same loading conditions. While heat treatments such as annealing and hot-isostatic pressing are shown to eliminate back stress, they do not also impart additional beneficial properties such as compressive residual stress. LSP is known to improve fatigue life by inducing compressive residual stress and has been applied with promising results to additive manufactured metal parts. It is here demonstrated that LSP may also be used as a tool for mitigating tensile back stress in 3D printed parts. Hysteresis tensile testing measures the back stress from additively manufactured dog bone samples built in both XY and XZ directions. Both LSPed and as-built conditions are tested and compared, showing that LSPed samples exhibit a reduction to back stress that varies for differing build directions. Electron backscatter diffraction performed under these conditions elucidates how grain morphologies and texture contribute to the observed improvement in back stress. Crystal plasticity finite element modelling develops insights as to the mechanisms by which this reduction is achieved in comparison with EBSD results.
References
More filters
Journal ArticleDOI
TL;DR: The authors showed that the difference between the tensile and compressive strengths of tempered martensites is primarily a manifestation of the general pressure dependence of flow stress in these materials and that the volume expansion after deformation was much smaller than that predicted by the normality flow rule of plasticity theory for materials with such pressure dependence.
Abstract: Earlier results showed that the difference between the tensile and compressive strengths of tempered martensites is primarily a manifestation of the general pressure dependence of flow stress in these materials. However, the same results also showed that the volume expansion after deformation was much smaller than that predicted by the normality flow rule of plasticity theory for materials with such pressure dependence. Additional results now obtained on maraging and HY-80 steels support these conclusions. The results for all these materials exhibit a strong, but not perfect, correlation between pressure dependence, yield stress, and volume expansion. The volume expansion, however, which is believed to result primarily from the generation of new dislocations, is very small and does not appear to be essential to the pressure dependence. Most of the pressure dependence, the portion responsible for the discrepancy with the normality flow rule, may be an effect on dislocation motion. The results suggest that an appropriate plasticity model would be one in which the octahedral shear yield stress is linearly dependent on the mean pressure, but the volume change is negligible in violation of the normality flow rule. Such a model has been proposed previously for the plastic deformation of soils. However, unlike that model, the present theory includes strain hardening.

230 citations

Journal ArticleDOI
TL;DR: In this paper, the authors proposed two types of automotive steels, namely, extra-and ultra-AHSSs, which are designed to utilize nano-scale retained austenite embedded in fine bainite and martensite.
Abstract: The body design with light weight and enhanced safety is a key issue in the car industry. Corresponding to this trend, POSCO is developing various automotive steel products with advanced performance. Conventional advanced high strength steels such as DP and TRIP steels are now expanding their application since the steels exhibit higher strength and ductility than those of conventional solution and precipitation strengthened high strength steels. Efforts have been made to enhance the mechanical performance of these steels such as ductility, hole expansion ratio, deep drawability, etc. Current research is focused on development of extra- and ultra-AHSS. Extra-AHSS are designed to utilize nano-scale retained austenite embedded in fine bainite and martensite. Ultra-AHSS are designed to have austenite as the major phase, and the ductility is enhanced primarily by continuous strain hardening generated during forming. These steels including extra- and ultra-AHSS are believed to be the next generation automotive steels which will replace the existing high strength steels due to their extremely high strength and ductility combinations.

113 citations

Journal ArticleDOI
A. M. Sherman1
TL;DR: In this article, the effects on fatigue behavior of two types of plastic prestrains were determined, and it was found that tensile pre-strains are more detrimental to fatigue resistance than compressive pre strains, and that HSLA steel has a higher fatigue notch sensitivity than HRLC steel.
Abstract: High strength-low alloy (HSLA) steels are a relatively new group of alloys similar to hot rolled low carbon steel (HRLC) but having higher strengths as a result of composition and processing variations. Because these steels are of potential use in a variety of structural applications involving cyclic loading a knowledge of their fatigue behavior is important. Fatigue experiments were performed on several 80 ksi yield strength HSLA steels and on conventional HRLC steel for comparison. The HSLA steels were all found to exhibit similar fatigue resistance, and were superior to HRLC steel at longer lives. The effects on fatigue behavior of two types of plastic prestrain were determined. While prestrains caused large increases in monotonic strength properties, such improvements were largely lost in fatigue due to cyclic softening. Tensile prestrains are more detrimental to fatigue resistance than compressive prestrains. Finally, it was found that HSLA steel has a higher fatigue notch sensitivity than HRLC steel, however its notch fatigue resistance is still superior to that of HRLC steel.

69 citations

Journal ArticleDOI
TL;DR: In this article, the effects of plane strain prestrain, induced via cold-rolling, and subsequent automotive paint bake hardening cycle on both tensile and fatigue properties of a hot-rolled TRIP780 multiphase steel were examined.

67 citations

Journal ArticleDOI
TL;DR: In this article, a linear relation was found between the fatigue strength at fixed life and the ultimate tensile strength, and the ranking of the steels with respect to fatigue life was sensitive to the choice of characteristic parameter.

52 citations