33 research outputs found
Application of the continuum damage mechanics model in the three point bending test of Ti-6Al-4V titanium alloy specimens
One of the most important and challenging activities in the simulation of the mechanical behaviour of materials is the prediction of the failure phenomena. If well calibrated, damage models can simulate and predict the failure of materials in a generalized way allowing the replication of not only the calibration tests themselves but also of different loading cases. Generally damage models can be categorized into three different groups including phenomenological models, porosity models and continuum damage mechanics (CDM) models. Different CDM models have been proposed by researchers and these models have been applied in diverse loading conditions, geometries and materials. However the limitations and advantages of the CDM models are still not completely explored in the application areas. In this paper, a CDM model, (previously calibrated with round smooth specimen) has been applied in a three-point bending test model in order to simulate the correlated experiment. Specifically, the CDM framework has been applied in a finite element model and the obtained results have been compared with the experimental data. The tested material is Ti-6Al-4V titanium alloy, which is a widely used material in the aerospace industry because of its high strength and low density. Load-displacement data in the experiments and numerical simulations are the main results, which have been compared. Therefore, the ability of the CDM model to simulate the three point bending test has been investigated and the results are discussed
Higher dimensional slowly rotating dilaton black holes in AdS spacetime
In this paper, with an appropriate combination of three Liouville-type
dilaton potentials, we obtain the higher dimensional charged slowly rotating
dilaton black hole solution for asymptotically anti-de Sitter spacetime. The
angular momentum and the gyromagnetic ratio of such a black hole are determined
for the arbitrary values of the dilaton coupling constant. It is shown that the
dilaton field modifies the gyromagnetic ratio of the rotating dilaton black
holes.Comment: 11 pages, 1 figure, the version to appear in Phys. Rev.
A Case Study on Influence of Utilizing Hill-type Muscles on Mechanical Efficiency of Biped Running Gait
The presence of compliant elements in biped running mechanisms generates a smoother motion and decreases impact forces. Biological creatures that have a complicated actuation system with parallel and series elastic elements in their muscles demonstrate very efficient and robust bipedal gaits. The main difficulty of implementing these systems is duplicating their complicated dynamics and control. This paper studies the effects of an actuation system, including Hill-type muscles on the running efficiency of a kneed biped robot model with point feet. In this research, we implement arbitrary trajectories compatible with the initial condition of the robot, and we calculate the necessary muscle forces using an analytical inverse dynamics model. To verify the results, we execute the direct dynamics of the robot with the calculated control inputs to generate the robot’s trajectory. Finally, we calculate the contractile element force of the muscles and its cost of transport, and we investigate the effects of the muscles’ elements on reducing or increasing the cost of transport of the gait and maximum actuating forces.Наявність податливих елементів у механізмах виконання двоногої ходи породжує плавність руху і зменшує сили удару. Біологічні істоти, які мають складну систему спрацьовування з паралельними і серіями еластичних елементів в м'язах, демонструють дуже ефективну і надійну двоногу ходу. Основними труднощами реалізації цих систем є дублювання їх складної динаміки і контролю. Вивчаються наслідки спрацьовування системи, в тому числі м'язів типу Хілла на ефективність роботи коліна у моделі двоногої ходи. У цьому дослідженні введено довільні траєкторії, сумісні з початковим станом робота, і розраховано необхідні сили м'язів за допомогою аналітичної зворотної моделі динаміки. Для перевірки результатів виконано пряму динаміку робота з обчисленням імпульсів управління для генерації траєкторії робота. Розраховано скорочувальну силу елемента м'язів і вартість його передачі для робота, і досліджено вплив елементів м'язів на зменшення або збільшення витрат на ходу і максимальні виконавчі сили
Asymptotically flat charged rotating dilaton black holes in higher dimensions
We find a class of asymptotically flat slowly rotating charged black hole
solutions of Einstein-Maxwell-dilaton theory with arbitrary dilaton coupling
constant in higher dimensions. Our solution is the correct one generalizing the
four-dimensional case of Horne and Horowitz \cite{Hor1}. In the absence of a
dilaton field, our solution reduces to the higher dimensional slowly rotating
Kerr-Newman black hole solution. The angular momentum and the gyromagnetic
ratio of these rotating dilaton black holes are computed. It is shown that the
dilaton field modifies the gyromagnetic ratio of the black holes.Comment: 9 pages, 1 figur
Hawking emission from quantum gravity black holes
We address the issue of modelling quantum gravity effects in the evaporation
of higher dimensional black holes in order to go beyond the usual
semi-classical approximation. After reviewing the existing six families of
quantum gravity corrected black hole geometries, we focus our work on
non-commutative geometry inspired black holes, which encode model independent
characteristics, are unaffected by the quantum back reaction and have an
analytical form compact enough for numerical simulations. We consider the
higher dimensional, spherically symmetric case and we proceed with a complete
analysis of the brane/bulk emission for scalar fields. The key feature which
makes the evaporation of non-commutative black holes so peculiar is the
possibility of having a maximum temperature. Contrary to what happens with
classical Schwarzschild black holes, the emission is dominated by low frequency
field modes on the brane. This is a distinctive and potentially testable
signature which might disclose further features about the nature of quantum
gravity.Comment: 36 pages, 18 figures, v2: updated reference list, minor corrections,
version matching that published on JHE
Higher Dimensional Charged Rotating Dilaton Black Holes
In this paper, we present the metric for the -dimensional charged slowly
rotating dilaton black hole with independent rotation
parameters, associated with orthogonal planes of rotation in the background
of asymptotically flat and asymptotically (anti)-de Sitter spacetime. The mass,
angular momentum and the gyromagnetic ratio of such a black hole are determined
for the arbitrary values of the dilaton coupling constant. We find that the
gyromagnetic ratio crucially depends on the dilaton coupling constant,
, and decreases with increasing in any dimension.Comment: 15 pages, 1 figur
Application of the continuum damage mechanics model in the three point bending test of Ti-6Al-4V titanium alloy specimens
One of the most important and challenging activities in the simulation of the mechanical behaviour of materials is the prediction of the failure phenomena. If well calibrated, damage models can simulate and predict the failure of materials in a generalized way allowing the replication of not only the calibration tests themselves but also of different loading cases. Generally damage models can be categorized into three different groups including phenomenological models, porosity models and continuum damage mechanics (CDM) models. Different CDM models have been proposed by researchers and these models have been applied in diverse loading conditions, geometries and materials. However the limitations and advantages of the CDM models are still not completely explored in the application areas. In this paper, a CDM model, (previously calibrated with round smooth specimen) has been applied in a three-point bending test model in order to simulate the correlated experiment. Specifically, the CDM framework has been applied in a finite element model and the obtained results have been compared with the experimental data. The tested material is Ti-6Al-4V titanium alloy, which is a widely used material in the aerospace industry because of its high strength and low density. Load-displacement data in the experiments and numerical simulations are the main results, which have been compared. Therefore, the ability of the CDM model to simulate the three point bending test has been investigated and the results are discussed