Papers by Keyword: Field Theory

Abstract: The transition from elastic behaviour to plastic ow of technical materials under the inuence of increasing mechanical load is obviously of major technical importance. Nevertheless it is a challenge to formalize this transition in terms of consistent eld theories. We adopt here the beautiful theoretical work of Kröner [1], Bilby [2], and Kunin [3], who have shown how this formalization can be done. We shall go beyond their results by assuming energy dissipation if dislocations are moved through surfaces as suggested earlier [4] due to the energy density contribution from inner curved surfaces. Sometimes the mutual movement of adhering planes is described in terms of a stick-slip movement, meaning that the solid switches between elastic and plastic, possibly (and in fact in most experimental cases) showing a hysteresis between the two. Earthquake shear waves, e.g., are a dramatic example. Classical eld theories can hardly account for this eect. We shall try to describe the solid deformations as dislocations in two dierent phases, allowing for transitions between these phases. The tool is the Ginzburg-Landau-formalism in the form Haken [5] used for selforganizing quantized systems. We are aware of the fact that this procedure is consequent only after the above mentioned classical eld theories have been quantized, a still open task for theoretical physicists, but we feel that the practical benet is worth the cavalier assumptions.

Abstract: Physical interpretations of the incompatibility tensor are extensively discussed and applied to model several practically-important dislocation substructures in metallic materials. This paper firstly performs a tangible decomposition of the incompatibility tensor into the two types of defects by introducing Nye’s contortion tensor, and also clarifies the interrelationship with expressions given based on differential geometry. The effects on the evolutions of intra-granular substructures like cells and geometrically-necessary type bands are examined based on finite element simulations on multi-grain models under tension and simple shear with several representative orientations.

Abstract: The conventional concept of dental implants completely lacks odontology. Therefore, the dental implant system is quite different from the gompholic mammalian tooth system. Developmental research on artificial dental roots of the mammalian gompholic system has been carried out by the author successfully for the first time in the world from the viewpoint of odontology. Characteristics of the mammalian tooth system are gompholic and heterodontia with tribosphenic tritubercular molars. The meaning of heterodontia in morphology, i.e., several variations in crown and root shapes in different sites of mammalian jawbones are optimal shapes according to the different tooth functions, i.e., sphenic incisors and canines, and tribosphenic-tritubercular molars. For the optimal shapes of teeth adapted to their functions, the gompholic joint system is inevitable, i.e., fibrous articulation with cementoblasts, ligaments with capillaries, and the alveolar bone proper (socket bone). From this viewpoint, the author has developed artificial dental roots of the heterodontia gompholic system. Integrated research on animal experiments, biomechanical research as well as clinical research, have been carried out. It has been proved by microanalyses, microscopy, and scanning electromicroscopy (SEM) that cementoblasts, the cementum, periodontal ligaments, and the alveolar bone proper (socket bone), develop around artificial roots.