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C M Sonsino - One of the best experts on this subject based on the ideXlab platform.
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multiaxial fatigue life response depending on proportionality grade between normal and shear strains stresses and Material Ductility
International Journal of Fatigue, 2020Co-Authors: C M SonsinoAbstract:Abstract Current experiences show that a non-proportional loading of ductile Materials such as wrought steels, wrought aluminium or wrought magnesium alloys, not welded or welded, causes a significant fatigue life reduction under an out-of-phase shear strain or shear stress superimposed on a normal strain or normal stress compared with proportional in-phase loading. But when Ductility, here characterised by tensile elongation, is reduced by a heat treatment or by another manufacturing technology such as casting or sintering, the afore-mentioned life reduction is compensated or even inversed, i.e. longer fatigue life results compared with proportional loading. However, some Materials reveal even despite good elongation values a neutral behaviour or a prolongation of life. Responsible for these observations are not only the overall Material ductilities or matrix-ductilities, but also the interaction between matrix and microstructural features such as manufacturing-dependent nodules, pores, internal defects like microporosities. They cause by local constraints a hindrance of deformations despite good overall ductilities. This complex life behaviour under non-proportional loading cannot always be estimated. Therefore, not only in strength hypotheses, but also in experimental proofs of multiaxial loaded parts, especially safety-critical components or structures, with real or service-like signals, emphasis must be placed on retaining non-proportionalities between loads and stresses/strains, respectively.
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Multiaxial fatigue life response depending on proportionality grade between normal and shear strains/stresses and Material Ductility
International Journal of Fatigue, 2020Co-Authors: C M SonsinoAbstract:Abstract Current experiences show that a non-proportional loading of ductile Materials such as wrought steels, wrought aluminium or wrought magnesium alloys, not welded or welded, causes a significant fatigue life reduction under an out-of-phase shear strain or shear stress superimposed on a normal strain or normal stress compared with proportional in-phase loading. But when Ductility, here characterised by tensile elongation, is reduced by a heat treatment or by another manufacturing technology such as casting or sintering, the afore-mentioned life reduction is compensated or even inversed, i.e. longer fatigue life results compared with proportional loading. However, some Materials reveal even despite good elongation values a neutral behaviour or a prolongation of life. Responsible for these observations are not only the overall Material ductilities or matrix-ductilities, but also the interaction between matrix and microstructural features such as manufacturing-dependent nodules, pores, internal defects like microporosities. They cause by local constraints a hindrance of deformations despite good overall ductilities. This complex life behaviour under non-proportional loading cannot always be estimated. Therefore, not only in strength hypotheses, but also in experimental proofs of multiaxial loaded parts, especially safety-critical components or structures, with real or service-like signals, emphasis must be placed on retaining non-proportionalities between loads and stresses/strains, respectively.
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Influence of Material Ductility on Fatigue Life under Multiaxial Proportional and Non-Proportional Normal and Shear Stresses
MATEC Web of Conferences, 2019Co-Authors: C M SonsinoAbstract:Current experiences show that a non-proportional loading of ductile Materials such as wrought steels, wrought aluminium or magnesium alloys, not welded or welded, causes a significant fatigue life reduction under an out-of-phase shear strain or shear stress superimposed on a normal strain or normal stress compared with proportional in-phase loading. However, when Ductility, here characterised by tensile elongation, is reduced by a heat treatment or by another manufacturing technology such as casting or sintering, the afore-mentioned life reduction is compensated or even inversed, i. e. longer fatigue life results compared with proportional loading. Some actual results, determined with additive manufactured titanium, suggest that microstructural features such as manufacturing-dependent internal defects like microporosities should be considered in addition to the Ductility level. This complex life behaviour under non-proportional loading cannot always be estimated. Therefore, in experimental proofs of multiaxial loaded parts, especially safety-critical components or structures, with real or service-like signals, emphasis must be placed on retaining non-proportionalities between loads and stresses/strains, respectively.
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Numerical measures of the degree of non-proportionality of multiaxial fatigue loadings
Fracture and Structural Integrity, 2015Co-Authors: A. Bolchoun, Heinz Kaufmann, C M SonsinoAbstract:The influence of the non-proportional loadings on the fatigue life depends on the Material Ductility. Ductile Materials react with a shortening of lifetime compared to proportional loading conditions. For a semiductile Material there is almost no difference between proportional and non-proportional loadings with respect to the fatigue life. Brittle Materials show an increase of the lifetime under non-proportional loadings. If fatigue life assessment is performed using stress-based hypotheses, it is a rather difficult task to take into account Material Ductility correctly, especially the fatigue life reduction as displayed by ductile Materials. Most stress-based hypotheses will compute a longer fatigue life under non-proportional loading conditions. There are also hypotheses, which already include quantitative evaluation of the non-proportionality (e.g. EESH, SSCH and MWCM). Anyway in order to improve assessment for ductile Materials, some sort of numerical measure for the degree of non-proportionality of the fatigue loading is required. A number of measures of this kind (or non-proportionality factors) were proposed in the literature and are discussed here: - the factor used in EESH is a quotient of stress amplitudes integrals, - the factor according to Gaier, which works with a discrete stress tensor values in a scaled stress space, - the factor according to Kanazawa, which makes use of plane-based stress values, - the factor used in MWCM, which exploits stress values in the plane with the highest shear stress amplitude, a new non-proportionality factor, which is based on the correlation between individual stress tensor components, is proposed. General requirements imposed on the non-proportionality factors are discussed and each of the factors is evaluated with respect to these requirements. Also application with the stress-based hypotheses is discussed and illustrated using the experimental data for aluminum and magnesium welded joints under constant and variable amplitude loadings.
Kikuo Kishimoto - One of the best experts on this subject based on the ideXlab platform.
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Material Ductility and toughening mechanism of polypropylene blended with bimodal distributed particle size of styrene ethylene butadiene styrene triblock copolymer at high strain rate
Journal of Applied Polymer Science, 2008Co-Authors: Masaki Omiya, Kikuo KishimotoAbstract:The Material Ductility and toughening mechanisms under high strain rate are characterized in the polypropylene (PP) blended with two different styrene–ethylene–butadiene–styrene triblock copolymer (SEBS) by the tensile tests at the nominal strain rates from 0.3 to 100 s−1, fracture surface observations, interparticle distances, and the morphological finite element (FE) analyses. It is found that the bimodal-distributed SEBS particle morphology enhances the impact Material Ductility by craze bands formation, which is caused by the stress interaction between large rubber particles with the highly elongated small rubber particles inside the fibrils of the craze. It is found that there are three conditions for craze bands formation. The first condition is that the total SEBS content is larger than 15 wt %. Second condition is that the weight ratio of small SEBS particles against total SEBS particles should be larger than 0.06. Third condition is that the interparticle distance of large SEBS particles should be larger than 100 nm. In the numerical aspects, the present constitutive law with the craze nucleation and growth can successfully predict the craze bands in the microstructural FE models, leading to the useful procedure for identifying the ductile brittle transition based on the microstructure. The synergistic effect of these rubber particles gives rise to a strong increase in the Ductility of these bimodal rubber particle distributed PP systems. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
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Material Ductility and toughening mechanism of polypropylene blended with bimodal distributed particle size of styrene–ethylene–butadiene–styrene triblock copolymer at high strain rate
Journal of Applied Polymer Science, 2008Co-Authors: Masaki Omiya, Kikuo KishimotoAbstract:The Material Ductility and toughening mechanisms under high strain rate are characterized in the polypropylene (PP) blended with two different styrene–ethylene–butadiene–styrene triblock copolymer (SEBS) by the tensile tests at the nominal strain rates from 0.3 to 100 s−1, fracture surface observations, interparticle distances, and the morphological finite element (FE) analyses. It is found that the bimodal-distributed SEBS particle morphology enhances the impact Material Ductility by craze bands formation, which is caused by the stress interaction between large rubber particles with the highly elongated small rubber particles inside the fibrils of the craze. It is found that there are three conditions for craze bands formation. The first condition is that the total SEBS content is larger than 15 wt %. Second condition is that the weight ratio of small SEBS particles against total SEBS particles should be larger than 0.06. Third condition is that the interparticle distance of large SEBS particles should be larger than 100 nm. In the numerical aspects, the present constitutive law with the craze nucleation and growth can successfully predict the craze bands in the microstructural FE models, leading to the useful procedure for identifying the ductile brittle transition based on the microstructure. The synergistic effect of these rubber particles gives rise to a strong increase in the Ductility of these bimodal rubber particle distributed PP systems. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Victor C Li - One of the best experts on this subject based on the ideXlab platform.
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Repair and retrofit with engineered cementitious composites
Engineering Fracture Mechanics, 2020Co-Authors: Victor C Li, Hideyuki Horii, Petr Kabele, Tetsushi KandaAbstract:Abstract This article presents the novel use of a super ductile fiber reinforced cementitious composite for repair and retrofit of concrete structures. Research in repair and retrofit demands immediate attention because of rapidly deteriorating and heightened safety requirements of civil infrastructures worldwide. The strain-hardening Engineered Cementitious Composites have been developed with the aid of fracture mechanics and micromechanics. It is emphasized that Material Ductility, and not just strength, can translate into strong and ductile structural performance. This article is extended from an original version presented as a Principal Lecture at the FRAMCOS-3 Conference at Gifu, Japan in October, 1998.
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influence of Material Ductility on performance of concrete repair
Aci Materials Journal, 2009Co-Authors: Mo Li, Victor C LiAbstract:The lack of durability in concrete repairs induces premature repair deterioration. Drying shrinkage of "new" repair Material restrained by "old" concrete substrate results in repair layer cracking, and interface delamination between the repair and the concrete substrate. This paper investigates a Material solution to these common repair failures. A high-early-strength engineered cementitious composite (HES-ECC) developed for concrete repair is employed for this study. The HES-ECC possesses high early-age strength (over 47 MPa [6885 psi] in 7 days) and high tensile strain capacity several hundred times that of normal concrete or fiber-reinforced concrete (FRC). Experimental and numerical studies on a layered repair system were conducted to verify that the high Ductility of HES-ECC can relieve shrinkage-induced stresses in the repair layer and at the repairlold concrete interface, thereby simultaneously suppressing large repair surface cracks and interface delamination. Detailed results of these studies are reported in this paper.
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influence of concrete Material Ductility on headed anchor pullout performance
Aci Materials Journal, 2009Co-Authors: Shunzhi Qian, Victor C LiAbstract:There has not been full resolution of anchor/concrete connection fracture failure problems associated with the inherent brittleness of concrete, despite the wide use of steel anchors in the construction industry. There is systematic investigation of Material Ductility's influence on anchor pullout performance in this paper by replacing normal concrete with engineered cementitious composites (ECCs), a relatively new ductile concrete Material. ECC strain hardens to several percent tensile strain capacity, which is also known as tensile Ductility, or a Material's maximum sustainable tensile strain before fracture failure-induced load drop. That when compared with connections with regular concrete Materials, anchor/ECC connections exhibit higher energy absorption, higher displacement capacity, higher ultimate strength, and more ductile failure mode, is shown in experimental results. In concrete Materials, distributed inelastic damage made of microcracking over a volume of Material near the anchor heads replaces the typically observed cone-shaped brittle fracture. Improved steel anchor connection load response results through ECC Material use's significant effectiveness in load redistribution among anchors in a group is suggested through this significant enhancement of Ductility.
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influence of concrete Material Ductility on shear response of stud connections
Aci Materials Journal, 2006Co-Authors: Shunzhi Qian, Victor C LiAbstract:The authors investigate the use of Material Ductility to overcome brittle concrete fracture failure in steel/concrete interaction zones. An experimental study was performed on the influence of concrete Material Ductility on the shear response of stud connections. Using a unique strain-hardening fiber-reinforced engineered cementitious composite (ECC), a series of pushout specimens were tested. Results show that, in addition to improved structural integrity, the stud connections with ECC exhibit a higher ultimate strength and slip capacity and a more ductile failure mode when compared with connections of other concrete Materials. The large enhancement of Ductility suggests that using an ECC Material could be effective in redistributing loads among the shear studs and in improving composite action between concrete bridge decks and steel girders.
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elevating frc Material Ductility to infrastructure durability
2004Co-Authors: Victor C Li, Henrik StangAbstract:Concrete is a brittle Material. The lack of durability of concrete infrastructure has been a recognized concern. Research in fiber reinforced concrete (FRC) often addresses the issue of Material brittleness. However, the translation of improved Ductility of FRC into infrastructure durability is often overlooked. This paper explores the concept of elevating the Ductility of high performance fiber reinforced concretes (HPFRCC) Material to the improved durability of reinforced HPFRCC (R/HPFRCC) structural elements. Special focus is placed on two levels of protection of R/HPFRCC elements. The first level involves the control of ingress of aggressive agents through the HPFRCC cover via crack width control, thereby reducing the rate of corrosion of the rebar. The second level involves the resistance to spalling associated with expansion of corroding steel reinforcing bars. Experimental results supporting both levels of protection are presented. It is suggested that the unique characteristics of certain HPFRCC with high Ductility several hundred times that of normal concrete can serve to effectively enhance infrastructure durability.
Masaki Omiya - One of the best experts on this subject based on the ideXlab platform.
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Material Ductility and toughening mechanism of polypropylene blended with bimodal distributed particle size of styrene ethylene butadiene styrene triblock copolymer at high strain rate
Journal of Applied Polymer Science, 2008Co-Authors: Masaki Omiya, Kikuo KishimotoAbstract:The Material Ductility and toughening mechanisms under high strain rate are characterized in the polypropylene (PP) blended with two different styrene–ethylene–butadiene–styrene triblock copolymer (SEBS) by the tensile tests at the nominal strain rates from 0.3 to 100 s−1, fracture surface observations, interparticle distances, and the morphological finite element (FE) analyses. It is found that the bimodal-distributed SEBS particle morphology enhances the impact Material Ductility by craze bands formation, which is caused by the stress interaction between large rubber particles with the highly elongated small rubber particles inside the fibrils of the craze. It is found that there are three conditions for craze bands formation. The first condition is that the total SEBS content is larger than 15 wt %. Second condition is that the weight ratio of small SEBS particles against total SEBS particles should be larger than 0.06. Third condition is that the interparticle distance of large SEBS particles should be larger than 100 nm. In the numerical aspects, the present constitutive law with the craze nucleation and growth can successfully predict the craze bands in the microstructural FE models, leading to the useful procedure for identifying the ductile brittle transition based on the microstructure. The synergistic effect of these rubber particles gives rise to a strong increase in the Ductility of these bimodal rubber particle distributed PP systems. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
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Material Ductility and toughening mechanism of polypropylene blended with bimodal distributed particle size of styrene–ethylene–butadiene–styrene triblock copolymer at high strain rate
Journal of Applied Polymer Science, 2008Co-Authors: Masaki Omiya, Kikuo KishimotoAbstract:The Material Ductility and toughening mechanisms under high strain rate are characterized in the polypropylene (PP) blended with two different styrene–ethylene–butadiene–styrene triblock copolymer (SEBS) by the tensile tests at the nominal strain rates from 0.3 to 100 s−1, fracture surface observations, interparticle distances, and the morphological finite element (FE) analyses. It is found that the bimodal-distributed SEBS particle morphology enhances the impact Material Ductility by craze bands formation, which is caused by the stress interaction between large rubber particles with the highly elongated small rubber particles inside the fibrils of the craze. It is found that there are three conditions for craze bands formation. The first condition is that the total SEBS content is larger than 15 wt %. Second condition is that the weight ratio of small SEBS particles against total SEBS particles should be larger than 0.06. Third condition is that the interparticle distance of large SEBS particles should be larger than 100 nm. In the numerical aspects, the present constitutive law with the craze nucleation and growth can successfully predict the craze bands in the microstructural FE models, leading to the useful procedure for identifying the ductile brittle transition based on the microstructure. The synergistic effect of these rubber particles gives rise to a strong increase in the Ductility of these bimodal rubber particle distributed PP systems. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Masayoshi Suehiro - One of the best experts on this subject based on the ideXlab platform.
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synergy effect of shear angle and anisotropic Material Ductility on hole expansion ratio of high strength steels
Journal of Materials Processing Technology, 2016Co-Authors: Takashi Matsuno, Koichi Sato, Riki Okamoto, Masaaki Mizumura, Masayoshi SuehiroAbstract:Abstract This study investigated the effect of using a rooftop piercing punch on the hole-expansion ratio of high-strength steels. The holes made using the piercing punch showed very high hole-expansion ratios under certain conditions. Regarding the rooftop-vertical angles, the hole-expansion ratio increased at 80° and decreased at 45°. The sheet bending effect caused by the rooftop shape contributed to these results. The small amount of bending in the case of 80° induced tensile stress around the punch edge without plastic deformation, which accelerated the Material fracture. This acceleration decreased the plastic strain on the pierced surface and led to a high hole-expansion ratio. In the case of 45°, a large amount of bending caused plastic deformation around the punch edge, which deteriorated the hole-expansion ratio. Regarding the Material direction when set on a die face, the hole-expansion ratio increased when the Material direction with the highest Ductility on the pierced surface was at 90° to the rooftop line. In this condition, the Ductility at the weakest position on the pierced surface resulting from piercing using the rooftop punch reaches a maximum in the other Material directions.