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A 2016 study of the genomes of a set of bacteria and archaea suggested that the last universal common ancestor (LUCA) of all cells was using an ancient Wood–Ljungdahl pathway in a hydrothermal setting, [10] but more recent work challenges this conclusion as they argued that the previous study had "undersampled protein families, resulting in incomplete phylogenetic trees which do not reflect ...
The two primary methods of deformation in metals are slip and twinning. Slip occurs by dislocation glide of either screw or edge dislocations within a slip plane. Slip is by far the most common mechanism. Twinning is less common but readily occurs under some circumstances. Twinning occurs when there are not enough slip systems to accommodate ...
The slip systems are described by the Schmid tensor, which is tensor product of the Burgers vector and the slip plane normal, and the Schmid tensor is used to obtain the resolved shear stress in each slip system. Each slip system can undergo different amounts of shearing, and obtaining these shear rates lies at the crux of crystal plasticity.
Unit cell of an fcc material. Lattice configuration of the close packed slip plane in an fcc material. The arrow represents the Burgers vector in this dislocation glide system. Slip in face centered cubic (fcc) crystals occurs along the close packed plane. Specifically, the slip plane is of type , and the direction is of type < 1 10>.
Sample deformation mechanism map for a hypothetical material. Here there are three main regions: plasticity, power law creep, and diffusional flow. A deformation mechanism map is a way of representing the dominant deformation mechanism in a material loaded under a given set of conditions. The technique is applicable to all crystalline materials ...
Mechanical deformation of hard tissues (like wood, shell and bone) may be analysed with the theory of linear elasticity. On the other hand, soft tissues (like skin , tendon , muscle , and cartilage ) usually undergo large deformations, and thus, their analysis relies on the finite strain theory and computer simulations .
Dislocation creep is a deformation mechanism in crystalline materials.Dislocation creep involves the movement of dislocations through the crystal lattice of the material, in contrast to diffusion creep, in which diffusion (of vacancies) is the dominant creep mechanism.
While undergoing deformation, slip motion will take place. Grain boundaries act as an impediment to dislocation motion for the following two reasons: 1. Dislocation must change its direction of motion due to the differing orientation of grains. [4] 2. Discontinuity of slip planes from grain one to grain two. [4]