OBJECTIVE Physical activity is positively related to improved student behaviors. Stability balls have been used as interventions to affect student behavior. The objective of this study was to determine whether the use of stability balls elicits more physical activity than the use of regular chairs and whether stability balls positively influence behavior. METHOD Participants (n = 43 fourth gr...

On the basis of metallographic studies, authors determined characteristic defects grinding balls rolled from rejects continuously cast billets K76F rail steel. Relationship presence internal with their impact resistance was established. Defects in form cracks accumulations non-metallic inclusions area localization and flocks have greatest on reduction resistance. Such are cause destruction duri...

Abstract The main objective of this work is to model wear a disc which was subjected dry contact with ball in unidirectional sliding. Tribological tests sliding pairs were carried out using tribological tester T-11 ball-on configuration. Stationary balls made 100Cr6 steel hardness 62 ± 2 HRC co-acted rotating discs 42CrMo4 40 2HRC. Discs machined by lapping, grinding, milling, and vapour blasti...

This article studies the evolution of microstructure and wear resistance in tantalum processed by a newly developed Severe Plastic Deformation (SPD) technique called Indirect Extrusion Angular Pressing (IEAP). The tribological behavior nanostructured IEAP were analyzed this work. samples extruded for two, five, twelve passes then exposed to ball-on-disk testing dry sliding conditions. It was sh...