Análise do uso de escalas nas simulações de processos de estampagem

The purpose of using software based on numerical approximations for metal forming is given by the need to ensure process efficiency in order to get high quality products at lowest cost and shortest time. This study uses the theory of similitude in order to develop a technique capable of simulating the stamping process of a metal sheet, obtaining results close to the real values, with shorter processing times. The results are obtained through simulations performed in the finite element software STAMPACK®. This software uses the explicit integration method in time, which is usually applied to solve nonlinear problems involving contact, such as the metal forming processes. The technique was developed from a stamping model of a square box, simulated with four different scale factors, two higher and two smaller than the real scale. The technique was validated with a bending model of a welded plate, which had a high simulation time. The application of the technique allowed over 50% of decrease in the time of simulation. The results for the application of the scale technique for forming plates were satisfactory, showing good quantitative results related to the decrease of the total time of simulation. Finally, it is noted that the decrease in simulation time is only possible with the use of two related scales, the geometric and kinematic scale. The kinematic scale factors should be used with caution, because the high speeds can cause dynamic problems and could influence the results of the simulations.

Influência das alturas iniciais de pasto diferido na recria de cordeiros sobre o desempenho na terminação em confinamento

The objective of this study was to evaluate the productive performance, metabolic and feeding behavior of sheep after ninety days deferred pasture at different heights. The experiment was conducted at Capim Branco experimental farm of the Universidade Federal de Uberlândia. During the period of 90 days, from June to September 2013, forty-eight crossbred lambs Santa Inês x Dorper, divided into groups of four animals, occupied twelve pickets deferred pasture with four initial heights (15 cm, 25 cm, 35 cm and 45 cm). During this period we evaluated the structural characteristics of pasture. For confinement, from September to December 2013, 32 of these animals were used (16 males and 16 females), divided into four bays, separated as pasture were using. The consumption was assessed daily, while biometric measurements were made every 21 days. In relation to gender, there were differences in average daily gain weight. Reviews of feeding behavior occurred at the beginning, middle and end of the experiment for 24 hours. The rumination and leisure activities do not present statistical differences, both initial height of pasture and by period. The time spent on intake was higher during the daytime both treatments starting height as the experimental periods, however, rumination activity was more intense at night. Blood glucose was achieved in five periods of the day, while other metabolites have been obtained with a collection made fortnightly. The different initial heights not promoted effects on blood glucose. The harvesting times were not affected. However, there was a reduction of basal blood glucose of animals throughout the experimental period. There was a significant interaction between the initial pasture heights and periods of evaluation of basal glucose. Cholesterol and triglyceride levels were below recommended levels, however the final phase of confinement cholesterol level increased significantly. The values of VLDL and GGT were above the reference range. FA and AST showed average values within the recommended values. Total protein was influenced by different initial heights of pasture. The creatinine and albumin had values below the recommended range. Moreover, the albumin decreased during the confinement time. Uric acid showed close to the recommended maximum. There was stabilization of compensatory growth, with modification of consumption and weight gain at 45 days of experiment.