Real-time Physics Based Simulation for 3D Computer Graphics

Restoration of realistic animation is a critical part in the area of computer graphics. The goal of this sort of simulation is to imitate the behavior of the transformation in real life to the greatest extent. Physics-based simulation provides a solid background and proficient theories that can be applied in the simulation. In this dissertation, I will present real-time simulations which are physics-based in the area of terrain deformation and ship oscillations. When ground vehicles navigate on soft terrains such as sand, snow and mud, they often leave distinctive tracks. The realistic simulation of such vehicle-terrain interaction is important for ground based visual simulations and many video games. However, the existing research in terrain deformation has not addressed this issue effectively. In this dissertation, I present a new terrain deformation algorithm for simulating vehicle-terrain interaction in real time. The algorithm is based on the classic terramechanics theories, and calculates terrain deformation according to the vehicle load, velocity, tire size, and soil concentration. As a result, this algorithm can simulate different vehicle tracks on different types of terrains with different vehicle properties. I demonstrate my algorithm by vehicle tracks on soft terrain. In the field of ship oscillation simulation, I propose a new method for simulating ship motions in waves. Although there have been plenty of previous work on physics based fluid-solid simulation, most of these methods are not suitable for real-time applications. In particular, few methods are designed specifically for simulating ship motion in waves. My method is based on physics theories of ship motion, but with necessary simplifications to ensure real-time performance. My results show that this method is well suited to simulate sophisticated ship motions in real time applications

Investigation of Aerosol Particles Produced from Rapid Failure of Concrete

This work addresses the hypothesis that modern concrete admixtures and inclusions have changed the microstructure mechanical properties sufficiently to result in undocumented concrete response to dynamic loading. The macro-, micro-, and nano- scale fragmentation of concrete as a function of different admixtures and inclusions is studied. This was done by loading them rapidly in a materials testing machine, with air sampling equipment standing by to sample the air, and collect the dust that resulted from the impact event. Four mixes were studied: regular Portland cement concrete for comparison, fly ash and slag admixtures to study effects of micro-scale inclusions, and steel-fiber reinforced concrete to study effects of macro-scale inclusions. Previous studies have shown that concrete fragments follow the Rosin-Rammler distribution as predicted by brittle fracture probabilities. This work concludes that such information is not representative of the aerosol particles that are generated, which are of primary importance for health. It is found that in particular the inclusion of large fibers generates a higher concentration of nanoscale fragments than the other admixtures. An improved analytical formulation for the probability of formulation of small fragments is developed

Aplicação de modelos de quebra de partículas do ambiente de simulação do método dos elementos discretos no estudo de microprocessos de cominuição

In this work one of the comminution microprocesses were studied using three particle breakage models within the DEM simulation environment: The Bonded Particle Model – BPM, the Fast Breakage Model - FBM, and the Particle Replacement Model – PRM. Such models were calibrated on the basis of the median fracture energy of individual particles. The potential of these tools to describe comminution was demonstrated through validation using virtual experiments of impact breakage of unconfined particle beds. They showed that the BPM presents higher resolution in the description of effects as the broken mass and particle capture radius on the bed. However, the poor adherence between experimental and simulated product size distribution suggest the need to improve the model to obtain a better representation of this effect. The PRM demonstrated some potential in the description of broken mass and particle capture, and higher adherence between experimental and simulated product size distribution. The FBM demonstrated potential in the description of both the breakage probability and the t10 parameter of particles, but in a non-simultaneous way. The latter also demonstrated some potential in the description of broken mass and particle capture, and poor resolution in the description of experimental product size distributions.Neste trabalho foram estudados um dos microprocessos de cominuição usando três modelos de quebra de partículas dentro do ambiente de simulação DEM: O modelo de ligação de elementos – BPM, o modelo de elementos tetraédricos – FBM e o modelo de substituição de elementos – PRM. Tais modelos foram calibrados com na base da energia média de fratura de partículas individuais. Foram evidenciados o potencial e as limitações destas ferramentas para descrever a quebra por impacto de partículas em leitos não confinados, a qual é a condição de aplicação de esforços encontrada em moinhos de bolas. Em geral, o BPM apresentou alta resolução na descrição da massa quebrada e do raio de captura de partículas no leito. No entanto, a fraca aderência da distribuição de tamanhos à experimental mostra a necessidade de melhorar o modelo. O PRM mostrou algum potencial na descrição da massa quebrada e captura de partículas, e boa aderência com a distribuição de tamanhos experimental. O FBM demonstrou potencial na descrição da probabilidade de fratura de partículas e o parâmetro t10, embora, de forma não simultânea. Aliás, neste último ainda mostrou algum potencial na descrição da massa quebrada e captura de partículas, embora fraca capacidade de descrever as distribuições de tamanhos experimentais