Bifurcation analysis based on a material model with stress-rate dependency and non-associated flow rule for fracture prediction in metal forming

Recent increasing application of advanced high-strength metals causes grow-ing demand for accurate fracture prediction in metal forming simulation. However, since the construction of objective and reliable fracture prediction method is generally difficult, essential progress in fundamental theory that supports evolution of fracture rediction framework is required. In this study, a fracture prediction framework based on the bifurcation theory is pre- sented. The main achievement is a novel material model based on stress-rate dependency related with non-associate flow rule. This model is based on non-associated flow rule with independent arbitrary higher-order yield function and plastic potential function for any anisotropic materials. And this formulation is combined with the stress-rate depen- dency plastic constitutive equation, which is known as Ito-Goya model, to construct a generalized plastic constitutive model in which non-normality and non-associativity are reasonably considered. Then, by adopting the three-dimensional bifurcation theory, which is known as the 3D localized bifurcation theory, more accurate prediction of the initiation of shear band is realized, leading to general and reliable construction of forming limit dia- gram. Then, by using virtual material data, numerical simulation is carried out to exhibit fracture limit diagram for demonstrating the generality and reliability of the proposed methodology. In particular, the effect of stress-rate dependency on the bifurcation analy- sis is investigated, and the order of the yield function is used to investigate the influence on the forming limit prediction

Dynamic Stresses Induced within Rock in Case of Blasting with One Free Face

In this study, the behaviour of the dynamic principal stresses induced within rock by an explosion under confined condition was analyzed in case of blasting with one free face by applying the values of measured radial displacement, particle velocity and so on to equations derived from the theory of elasticity, and at the same time, the dynamic stresses on the free face were also calculated from the strain measured by the wire strain gauges affixed on the free face. The results obtained are briefly shown below. 1) The maximum stress on the free face appeared at the intersection between the free face and the burden, and its magnitude was about twice as large as the magnitude of the tangential tensile stress imparted by the incident stress wave within the range related to the breakage by blasting. 2) The maximum value of the compressive stress near the free face was decreased due to the existence of the free face, while that of the tensile stress was increased. 3) Let us consider the spherical coordinate of which origin is the center of a spherical charge. Then, at any point near the free face, the directions of the principal stresses in the γθ plane changed with time except in the direction of the burden, but at another point near an explosion point where the principal stresses were mainly composed of the stresses caused by the initial longitudinal wave, the directions of the principal stresses coincided with those of the coordinate used. 4) The maximum value of the tensile stress in φ direction was larger than those in the γθ plane on and near the free face. 5) The tensile stress caused by the Hopkinson effect appeared only near the burden. 6) It is presumed from the results of stress analysis that radial cracks will be produced in the rock mass near an explosion point, but with the approach of the free face the directions of the cracks will be curved towards the direction parallel to the free face. 7) The appearance of the breakage deduced from this investigation agrees fairly well with the practical observations

Preliminary Study of Coagulation Monitoring by Antenna for Treatment during Microwave Coagulation Therapy

Microwave coagulation therapy (MCT) has been employed mainly for treatment of small size tumors. In the treatment, thin microwave antenna is inserted into the tumor and microwave energy heats up the tumor up to at least 60°C for generation of enough coagulated volume including the target tumor. During the microwave radiation, reflection coefficient of treatment antenna changes significantly. In this paper, possibility of coagulation monitoring was found observing the reflection coefficient change of the antenna by numerical calculations and measurements

WTC rat has unique characteristics such as resistant to streptozotocin

AbstractBecause we found that WTC rats might be resistant to streptozotocin (STZ), we have elucidated the mechanisms of resistant to the diabetogenic effects of STZ in the WTC rats. Dose response to STZ was evaluated with glucose levels. No significant changes in glucose level to STZ administration were observed in WTC rats. Insulin secretion by suppling glucose was preserved in WTC rats even after STZ administration. Although there was no significant difference in gene expression of both GLUT2 and Kir6.2, which were involved in STZ resistance, between WTC rats and Wistar rats, the expression of metallothionein 2a in pancreas and liver to STZ administration of WTC rats was significantly higher than that of Wistar rats. Moreover, alloxan did not induce diabetes in WTC rats as same as STZ. These results suggest that WTC rats might have powerful antioxidant property to protect β cells in pancreas. Because the STZ-resistant property is very close characteristics to human beings, WTC rats will become a useful animal model in diabetic researches

Leptonic CP asymmetry and Light flavored scalar

We consider a situation where right-handed neutrinos couple to a light scalar which is possibly a Nambu-Goldstone boson resulting from high-energy symmetry breaking. Its coupling is typically complex-valued and flavor-dependent. In this work, we investigate the possibility of the leptonic asymmetry generation in the Universe from tree-level right-handed neutrino decay to flavorful light scalar. Furthermore a new source of asymmetry generation from a single decay process is pointed out, which is characteristic of the present setting.Comment: 28 pages, 10 figure