Necking

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

A mathematical relation between volume strain, elongational strain and stress in homogeneous deformation

Abstract: A model is presented for the volume strain of a two-phase blend which elongates homogeneously in a tensile test apparatus. In the case when only elastic deformation and crazing take place the volume strain against elongation curve can be constructed and calculated from the data of the stress-strain curve alone. When, as well as crazing and elastic deformation, shearing takes place, the data of the stress against elongation curve and the volume strain against elongation curve can be used to calculate the separate contributions of the three deformation mechanisms at any elongation. In principle, the model can be also used for any homogeneous system which deforms without necking and where one or more deformation mechanism is present.

Effect of cryorolling on the microstructure and tensile properties of bulk nano-austenitic stainless steel

Abstract: We report the synthesis of nanostructured austenitic AISI 304L stainless steel (SS) through cryorolling (CR) and reversion annealing in the temperature range of 700–800 °C. Severe CR at sub-zero temperature promotes twinning in γ-austenite, which transform into α׳-martensite with lath thickness of 50–100 nm. Whereas, 50–300 nm size γ-grains recrystallize in nano-twinned α׳ through reversion annealing as confirmed by transmission electron microscopy (TEM) and electron back scattered diffraction (EBSD) imaging. The evolution of highly processable bulk nano-austenitic SS with bimodal grain size distribution on achieving high strength (~1295 MPa), large tensile ductility (~0.47), and true necking strain of 0.59, have been discussed.

Mechanical anisotropy in injection‐molded polypropylene

Abstract: By use of a mod with a film gate, two straight polypropylenes (PP) with different melt flow index (MFI) and a glass fiber-reinforced polypropylene (FRPP) were injection molded at various molded at various temperatures into square plates with orientational anisotropy. The anisotropies of tensile property, tensile impact strength, and flexural property were studied on the molded sample cut mainly in the machine direction (MD), 45°-direction (45°), and transverse direction (TD). Both the orders of the yield strength and tensile impact strength of the FRPP, and those of the necking stress and tensile impact strength of the straight PP, were MD >45° >TD, which are reasonable tendencies. The orders of the yield strength and flexural modulus of the straight PP were MD > TD > 45°, which suggests the presence of shear deformation between the lamellae in the skin layer. The variation of the flexural modulus with the angle to the MD fitted well to Hearmon's equation. Generally, for straight PP, the anisotropy of various properties increased as the MFI and cylinder temperature became lower, or as the skin layer became thicker. For the FRPP, the anisotropy increased as the cylinder temperature became higher, or as the degree of the orientation of glass fibers became higher.

Possible explanation for unexpected departures in hydrostatic tension-fracture strain relations

Abstract: For materials which fail by void coalescence and growth, and possibly for solids failing by other mechanisms, it is commonly held that increasing tensile hydrostatic stress states at fracture produce lower strains to fracture. In tests on sheet material there is a marked change in strain ratio before fracture if plane-strain necking occurs. Then it may be shown that at the instant of fracture the current hydrostatic stress is most tensile for the greatest strains to fracture. These contrary observations may be explained by means of, path-dependent damage functions which involve not only the hydrostatic stress and effective strain but also the current strain ratio.