Necking

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

Investigation on microstructure and mechanical properties of Al/Al-Zn-Mg–Cu laminated composite fabricated by accumulative roll bonding (ARB) process

Abstract: In this study, an Al/Al-Zn-Mg-Cu laminated composite was successfully produced for the first time by using Al 1050 and a super high strength 7xxx aluminum alloy sheets through accumulative roll bonding (ARB) process at an elevated temperature. In this process after sandwich preparation, in per cycle applied 50% reduction in total thickness. The microstructural investigations after different ARB cycles showed that ARB process led to a fine distribution of the secondary phases and also a relatively remarkable decrease in their particle size in the Al-Zn-Mg-Cu (AZMC) layer. Furthermore, it was observed that all the layers of the ARBed sheets remained relatively straight without any necking or fracture during the plastic deformation in the first two cycles. Also, the macrostructure showed elongated and ultra-fine grains after the fourth cycle in the AZMC and pure Al (PA) layers, respectively. In addition, computer simulation demonstrated strain and stress gradients in the ARBed sheet. The mechanical examinations displayed a significant improvement of elongation and ultimate tensile strength (UTS) values and also microhardness values of the AZMC layer with increasing the ARB cycles. However, the microhardness variations were so slight (

Deformation and fracture of Ti/439 stainless steel clad composite at intermediate temperatures

Abstract: Deformation and fracture of Ti/439 stainless steel (STS) were studied. Activation energy for elongation minimum in Ti/STS 439 is close to that of carbon diffusion in iron, suggesting ductility loss is caused by dynamic strain aging in STS 439. Wavy surface in Ti-layer is caused by multiple necking in titanium.

Cold Drawn Steel Wires-Processing, Residual Stresses and Ductility-Part I: Metallography and Finite Element Analyses

Abstract: Cold drawing steel wires lead to an increase of their mechanical strength and to a drop of their ductility. The increase of their mechanical strength has long been related to the reduction of the various material scales by plastic deformation, but the mechanisms controlling their elongation to failure have received relatively little attention. It is usually found that heavily deformed materials show a tendency to plastic strain localization and necking. However, in this paper it is shown that, though the steel wires are plastically deformed up to strain levels as high as 3.5, a significant capability of plastic deformation is preserved in as-drawn wires. This apparent contradiction is resolved by the existence of residual stresses inside the wire. Finite element analyses have been conducted in order to show that residual stresses, inherited from the drawing process, are sufficient to produce a significant hardening effect during a post-drawing tensile test, without introducing any hardening in the local material behaviour. The main conclusion of this paper is that once the material has lost its hardening capabilities, residual stresses, inherited from the process, control the elongation of cold drawn wires. The finite element method allowed also the determination of the residual stress field that would lead to the best agreement between the simulated and the experimental stress strain curve of as-drawn wires.

Self-oscillation mechanism of necking on extension of polymers

Abstract: A new phenomenon in necking of some polymers, including poly(ethylene terephthalate) (PETP) was detected It was found that extension of PETP films under certain conditions results in periodic stress oscillations and a periodic change in appearance of the sample The conditions at which self-oscillations appear have been determined, and the principal regularities of this regime of deformation are described The following factors are critical for the appearance of self-oscillation: speed of straining and compliance of the sample The self-oscillation of stress and formation of the periodic transverse bands is attributed to heat dissipation during necking corresponding to local temperature jumps and periodic strong variation of elasticity modulus due to poor heat conductivity of the polymer Changing the external conditions of heat transfer influences the possibility and development of the effect The phenomenon is common for various crystallizing polymers, being dependent on physical properties of the polymer and conditions of deformation