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Necking

About: Necking is a research topic. Over the lifetime, 5280 publications have been published within this topic receiving 113945 citations.


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TL;DR: In this article, a commercial Al-6 pct Mg-0.3 pct Sc alloy subjected to equal-channel angular extrusion (ECAE) at 325 °C to a total strain of about 16 resulted in an average grain size of about 1 µm.
Abstract: A commercial Al-6 pct Mg-0.3 pct Sc-0.3 pct Mn alloy subjected to equal-channel angular extrusion (ECAE) at 325 °C to a total strain of about 16 resulted in an average grain size of about 1 µm. Superplastic properties and microstructural evolution of the alloy were studied in tension at strain rates ranging from 1.4 × 10−5 to 1.4 s−1 in the temperature interval 250 °C to 500 °C. It was shown that this alloy exhibited superior superplastic properties in the wide temperature range 250 °C to 500 °C at strain rates higher than 10−2 s−1. The highest elongation to failure of 2000 pct was attained at a temperature of 450 °C and an initial strain rate of 5.6 × 10−2 s−1 with the corresponding strain rate sensitivity coefficient of 0.46. An increase in temperature from 250 °C to 500 °C resulted in a shift of the optimal strain rate for superplasticity, at which highest ductility appeared, to higher strain rates. Superior superplastic properties of the commercial Al-Mg-Sc alloy are attributed to high stability of ultrafine grain structure under static annealing and superplastic deformation at T ≤ 450 °C. Two different fracture mechanisms were revealed. At temperatures higher than 300 °C or strain rates less than 10−1 s−1, failure took place in a brittle manner almost without necking, and cavitation played a major role in the failure. In contrast, at low temperatures or high strain rates, fracture occurred in a ductile manner by localized necking. The results suggest that the development of ultrafine-grained structure in the commercial Al-Mg-Sc alloy enables superplastic deformation at high strain rates and low temperatures, making the process of superplastic forming commercially attractive for the fabrication of high-volume components.

43 citations

Journal ArticleDOI
TL;DR: In this paper, the effect of rigid particles on the fracture mode of polymers that yield with necking was analyzed theoretically with a model of regularly arrayed spherical particles, where the adhesion between a polymer and particles was assumed to be weak, and particles were assumed to debond from the polymer before necking.
Abstract: The effect of rigid particles on the fracture mode of polymers that yield with necking was analyzed theoretically with a model of regularly arrayed spherical particles. The adhesion between a polymer and particles was assumed to be weak, and particles were assumed to debond from the polymer before necking. A linear decrease in engineering draw stress with an increase in the filler content was derived. An increase in filler content leads to a transition in deformation mechanism. The transition depends on the ability of the polymer to strain-harden. If the ability to strain-harden is insignificant and the engineering fracture stress (strenght) of the polymer is lower than its yield stress, the transition is from ductile to brittle fracture. If the ability to strain-harden is essential and the strength of the unfilled polymer is higher than its yield stress, the transition (ductile-to-ductile) is from neck propagation to uniform ductile yield. The critical filler contents were determined for both transitions from the properties of an unfilled polymer. The ductile-to-ductile transition without embrittlement is possible if the strength of the unfilled polymer is higher than its yield stress. Results for polymers filled by weakly bonded particles were compared with polymers filled by particles that debond after the yield stress.

43 citations

Journal ArticleDOI
TL;DR: A review of the sheet metal formability analysis based on the theory of damage mechanics is presented in this paper, where the damage anisotropy is considered, and several formability analyses are summarized, including the accumulative critical damage method, the damage-coupled vertex theory and the damage coupled acoustic tensor method.
Abstract: This article presents a review of the sheet metal formability analysis based on the theory of damage mechanics. Specifically, the damage anisotropy is considered. Forming limit analyses based on the anisotropic damage are summarized, including the accumulative critical damage method, the damage-coupled vertex theory and the damage-coupled acoustic tensor method. The accumulative critical damage method postulates that the critical damage at the localized necking is strain-path or loading history independent. It can be applied to predict the forming limit diagrams under either proportional or nonproportional loading. The vertex theory considers that localized necking is associated with the vertex developed on yield surface. The theory is applicable to engineering materials exhibiting the strain-hardening and/or strain-rate dependent behaviors. The acoustic tensor method, on the other hand, can only be applied to the strain-softening materials, which are often observed in warm/hot sheet metal forming or hydroforming.

43 citations

Journal ArticleDOI
TL;DR: In this article, an explicit numerical implementation is described, for a constitutive model of glassy polymers, previously proposed and validated, to simulate spontaneous strain localization (necking) occurring during extension of a prismatic bar of a typical glassy polymer.

43 citations

Journal ArticleDOI
TL;DR: In this paper, the problem of necking in metal specimens under uniaxial tension is investigated by means of the mathematical theory of bifurcation and uniqueness due to R. Hill, with particular reference to the maximum load criterion normally used by engineers.
Abstract: T he problem of necking in metal specimens under uniaxial tension is investigated by means of the mathematical theory of bifurcation and uniqueness due to R. Hill, with particular reference to the maximum load criterion normally used by engineers. The difficulties encountered with rigid/plastic materials are demonstrated. It is shown that, for appropriate boundary-value problems, uniqueness certainly holds for specimens of elastic/plastic material until the load reaches an analytic maximum. An exact necking solution of simple form is exhibited for a circular cylinder of incompressible elastic/plastic material. The stress at which this mode is initiated, although of the order of the elastic (shear) rigidity in magnitude, at least serves to bound the critical stress at necking from above.

43 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
2023174
2022351
2021241
2020249
2019213
2018238