Abstract
The aim of this work is to evaluate the effect of different densities of hybrid aluminum polymer foam on the frequency behavior of a foam filled steel structure with different ratios between steel and foam masses. The foam filled structure is composed of three steel tubes with a welded flange at both ends bolted together to form a portal grounded by its free ends. Structure, internal and ground constraints have been designed and manufactured in order to minimize nonlinear effects and to guarantee optimal constraint conditions. Mode shapes and frequencies were verified with finite elements models (FEM) to be in the range of experimental modal analysis, considering the frequency measurement range limits for instrumented hammer and accelerometer. Selected modes have been identified with suitable modal parameters extraction techniques. Each structure has been tested before and after filling, in order to compute the percentage variation of modal parameters. Two different densities of hybrid aluminum polymer foam have been tested and compared with structures filled with aluminum foams produced using the powder compact melting technique. All the foam fillings were able to suppress high frequency membrane modes which results in a reduction of environmental noise and an increase in performance of the components. Low frequency modes show an increase in damping ratio only when small thickness steel frames are filled with either Hybrid APM or Alulight foam.
Highlights
The use of aluminum foam as a filling for structural components is intended to improve their dynamic behavior, increase impact energy absorption, etc. [1]
In the mid-frequency mode for the same tubes thickness, it is possible to see that Alulight foam filling strongly increases the damping ratio, while hybrid APM reduce the ratio
The lack of documentation on the design of structural components in order to maximize the effect of foam filling was the pivotal reason for this work
Summary
The use of aluminum foam as a filling for structural components is intended to improve their dynamic behavior, increase impact energy absorption, etc. [1]. The use of aluminum foam as a filling for structural components is intended to improve their dynamic behavior, increase impact energy absorption, etc. In the machine tools field, the structures are generally designed by means of finite elements models (FEM) of the whole machine (basement, ram, spindle, etc.) to obtain the desired dynamic behavior, the desired material savings and to avoid unwanted vibrations [2]. If the virtual model is taken as a starting point (as in the work here described), the technological problems for the realization of the designed structure must be solved. In the realization of a ram with aluminum foam filling [3], as an example, the component must be grinded and heat-treated. The use of aluminum foam fillings adds a degree of freedom to the structure design and introduces some technological issues
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