Abstract
The capacity to damp mechanical vibrations is one of the most important properties of granite-epoxy composites, even superior to the cast iron one. For this reason, these materials have been adopted for manufacturing of tool machine foundations and precision instruments. This work presents a study concerning the behavior of particulate composite beams, based on granite powder and epoxy, subjected to mechanical vibrations. Composite samples were prepared with different combinations of processing variables, like the weight fraction of epoxy in the mixture and size distributions of granite particles. The damping behavior of the material was investigated adopting the logarithmic decrement method. Samples, in the form of prismatic beams, were excited in the middle point and the output signal was measured in a point located at the extremity. The obtained results showed that composite samples, with weight fractions of about 80% of granite and 20% of epoxy, presented damping properties approximately three times greater than gray cast iron.
Highlights
The precision of Machine Tools (MT) and Coordinate Measuring Machines (CMM), used in metal-mechanical industry, is directly related with the materials used in their construction
Cast iron presents high thermal expansion and conductivity, which allow errors in the manufacturing, due to dimensional changes caused by thermal expansion and contraction and structure distortions induced by the variations in the room temperature[1]
That cast iron presents a decrease in amplitude after 0.015 seconds, and, later, an increase of this amplitude, reaching larger values than that obtained for the granite‐epoxy samples after 0.022 seconds
Summary
The precision of Machine Tools (MT) and Coordinate Measuring Machines (CMM), used in metal-mechanical industry, is directly related with the materials used in their construction. The materials specified for its manufacture must have high values of elastic modulus, yield strength, mechanical as well as wearing resistance and toughness, due to the machine intense mechanical demands. Added to these properties, it is desirable that these materials present reduced thermal expansion coefficient and high vibrations damping capacity to perform their tasks with the required precision, subject to the less possible variations in response to the requirements of the operation environment. Cast iron presents high thermal expansion and conductivity, which allow errors in the manufacturing, due to dimensional changes caused by thermal expansion and contraction and structure distortions induced by the variations in the room temperature[1]. An additional choice mentioned in the literature is the use of concrete structures, but the reduced dimensional stability associated to water absorption makes its use unfeasible[2]
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