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
OPEN ACCESSMetals 2012, 2 212 damping ratio only when small thickness steel frames are filled with either Hybrid APM or Alulight foam.
In waterjet/abrasive waterjet (WJ/AWJ) cutting systems, the components of both the ultra high-pressure (UHP) intensifier and the cutting head are subject to faults and performance degradation. Abrasive particles are responsible for focusing tube wear and orifice breakage, whereas challenging pressure conditions are responsible for the wear and cracks of UHP pump components. The impact of these factors on quality and productivity leads to the need for reliable condition-monitoring systems in WJ/AWJ shop floors. This paper investigates a new approach for the online health condition assessment of both UHP pump and cutting head components by using a single type of information source, i.e., the plunger displacement signal. A multivariate analysis of variance (MANOVA) was performed to study the effects of actual faulty components on the acquired signals during AWJ cutting. The results demonstrate that plunger displacement signals are suitable for detecting and identifying critical faults in WJ/AWJ cutting systems
The favorable energy-absorption properties of metal foams have been frequently proposed for damping or anti-crash applications. The aim of this paper is to investigate the endurance of these properties for composite structures, made by a metal or a hybrid metal-polymeric foam used as the core filling of a tubular metal case. The results of experimental tests are shown, run with two types of structures: 1) square steel tubes filled with aluminum or with hybrid aluminum-polymer foams; 2) round titanium tubes filled with aluminum foams. The paper shows that the damping properties of a foam-filled tube change (improve) with the number of cycles, while all other dynamic properties are nearly constant. This result is very important for several potential applications where damping is crucial, e.g., for machine tools.
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