scholarly journals Aluminum Foams as Permanent Cores in Casting

2021 ◽  
Vol 3 (1) ◽  
pp. 3
Author(s):  
Sara Ferraris ◽  
Graziano Ubertalli ◽  
Antonio Santostefano ◽  
Antonio Barbato
Keyword(s):  
Molten Metal ◽  
Metal Foams ◽  
Skin Thickness ◽  
Foam Core ◽  
Aluminum Foams ◽  
Vibration Absorption ◽  
Before And After ◽  
Al Foam ◽  
Casting Experiment ◽  
Casting Porosity

Their low density and high specific stiffness and impact energy/vibration absorption ability make Al-based metal foams promising materials in applications for which a light weight and energy/vibration absorption abilities are crucial. In view of these properties, Al-based foams can be extremely interesting as cores in cast components in order to improve their performances and simplify their whole technological process. However, both in the scientific literature and in technological application, this topic is still poorly explored. In the present work, Al-based metal foams (Cymat foams and Havel metal foams in the form of rectangular bars) are used in a gravity casting experiment of an Al-Si-Cu-Mg alloy (EN AB-46400). The foams were fully characterized before and after insertion in casting. Porosity, cell wall and external skin thickness, microstructure, infiltration degree, and the quality of the interface between the foam core and the dense cast shell, have been investigated by means of optical microscopy and scanning electron microscopy equipped with energy dispersive spectroscopy (SEM-EDS). The analyses evidenced that a continuous and thick external skin protect the foam from infiltration by molten metal, preserving the initial porosity and insert shape. A detailed analysis of the foam’s external skin highlights that the composition of this external skin is crucial for the obtaining of a good joining between the molten metal and the Al foam core. In fact, the presence of Mg oxides on the foam surface prevents bonding, and maintains a gap between the core and the shell. This point opens up the opportunity to design innovative surface modifications for this external skin as promising strategies for the optimization of cast components with a foam core.

scholarly journals Magnetic Resonance Imaging Evaluation in Patients with Linear Morphea Treated with Methotrexate and High-Dose Corticosteroid

2018 ◽  
Vol 2018 ◽  
pp. 1-6 ◽  
Author(s):  
Mohammad Shahidi-Dadras ◽  
Fahimeh Abdollahimajd ◽  
Razieh Jahangard ◽  
Ali Javinani ◽  
Amir Ashraf-Ganjouei ◽  
...  
Keyword(s):  
Magnetic Resonance Imaging ◽  
Magnetic Resonance ◽  
High Dose ◽  
Skin Thickness ◽  
Resonance Imaging ◽  
High Dose Corticosteroid ◽  
Before And After ◽  
Lesion Extension ◽  
Dose Corticosteroid ◽  
Mri Changes

Background. Morphea is an inflammatory disease of the connective tissue that may lead to thickening and hardening of the skin due to fibrosis. The aim of this study was to document magnetic resonance imaging (MRI) changes in patients with linear morphea who were treated with methotrexate (MTX) and high-dose corticosteroid. Methods. This study was conducted on 33 patients from the outpatient’s dermatology clinic of our institute, who fulfilled the inclusion criteria. Patients received 15 mg/week of MTX and monthly pulses of methylprednisolone for three days in six months. The effectiveness of the treatment was evaluated by MRI, modified LS skin severity index (mLoSSI), and localized scleroderma damage index (LoSDI). Results. All parameters of mLoSSI and LoSDI including erythema, skin thickness, new lesion/lesion extension, dermal atrophy, subcutaneous atrophy, and dyspigmentation were also noticeably improved after treatment. Subcutaneous fat enhancement was the most common finding in MRI. MRI scores were significantly associated with clinical markers both before and after the treatment with the exception of skin thickness and new lesion/lesion extension which were not associated with MRI scores before and after the treatment, respectively. Limitations. The lack of correlative laboratory disease activity markers, control group, and clearly defined criteria to judge the MRI changes. Conclusion. MRI could be a promising tool for the assessment of musculoskeletal and dermal involvement and also monitoring treatment response in patients with morphea.

Heat Transfer Performance of Aluminum Foams

2011 ◽  
Vol 133 (6) ◽  
Author(s):  
Simone Mancin ◽  
Claudio Zilio ◽  
Luisa Rossetto ◽  
Alberto Cavallini
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Pressure Drop ◽  
Fluid Dynamic ◽  
Foam Core ◽  
Aluminum Foams ◽  
Experimental Heat ◽  
High Heat Transfer ◽  
Experimental Heat Transfer ◽  
Core Height

Because of their interesting heat transfer and mechanical properties, metal foams have been proposed for several different applications, thermal and structural. This paper aims at pointing out the effective thermal fluid dynamic behavior of these new enhanced surfaces, which present high heat transfer area per unit of volume at the expense of high pressure drop. The paper presents the experimental heat transfer and pressure drop measurements relative to air flowing in forced convection through four different aluminum foams, when electrically heated. The tested aluminum foams present 5, 10, 20 and 40 PPI (pores per inch), porosity around 0.92–0.93, and 0.02 m of foam core height. The experimental heat transfer coefficients and pressure drops have been obtained by varying the air mass flow rate and the electrical power, which has been set at 25.0 kW m−2, 32.5 kW m−2, and 40.0 kW m−2. The results have been compared against those measured for 40 mm high samples, in order to study the effects of the foam core height on the heat transfer. Moreover, predictions from two recent models are compared with heat transfer coefficient and pressure drop experimental data. The predictions are in good agreement with experimental data.

scholarly journals Energy Absorption of Different Cell Structures for Closed-Cell Foam-Filled Tubes Subject to Uniaxial Compression

Metals ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 1579 ◽  
Author(s):  
Yang Yu ◽  
Zhuokun Cao ◽  
Ganfeng Tu ◽  
Yongliang Mu
Keyword(s):  
Energy Absorption ◽  
Absorption Efficiency ◽  
Foam Core ◽  
Aluminum Foams ◽  
Static Compression ◽  
Cell Structures ◽  
Closed Cell ◽  
Energy Absorption Efficiency ◽  
Foam Filled ◽  
Quasi Static Compression

The energy absorption of different cell structures for closed-cell aluminum foam-filled Al tubes are investigated through quasi-static compression testing. Aluminum foams are fabricated under different pressures, obtaining aluminum foams with different cell sizes. It is found that the deformation of the foam core is close to the overall deformation, and the deformation band is seriously expanded when the cell size is fined, which leads to the increase of interaction. Results confirm that the foam-filled tubes absorb more energy due to the increase of interaction between the foam core and tube wall when the foaming pressure increases. The energy absorption efficiency of foam-filled tubes can reach a maximum value of 90% when the foam core is fabricated under 0.30 MPa, which demonstrates that aluminum foams fabricated under increased pressure give a new way for the applications of foam-filled tubes in the automotive industry.

The Effects of Compression and Pore Size Variations on the Liquid Flow Characteristics in Metal Foams

2001 ◽  
Vol 124 (1) ◽  
pp. 263-272 ◽  
Author(s):  
K. Boomsma ◽  
D. Poulikakos
Keyword(s):  
Flow Characteristics ◽  
Maximum Flow ◽  
Metal Foams ◽  
Heat Sinks ◽  
Convection Heat ◽  
Hydraulic Characteristics ◽  
Aluminum Foams ◽  
Transitional Regime ◽  
Open Cell ◽  
Flow Velocities

Open-cell aluminum foams were investigated using water to determine their hydraulic characteristics. Maximum fluid flow velocities achieved were 1.042 m/s. The permeability and form coefficient varied from 2.46×10−10 m2 and 8701 m−1 to 3529×10−10 m2 and 120 m−1, respectively. It was determined that the flowrate range influenced these calculated parameters, especially in the transitional regime where the permeability based Reynolds number varied between unity and 26.5. Beyond the transition regime where ReK≳30, the permeability and form coefficient monotonically approached values which were reported as being calculated at the maximum flow velocities attained. The results obtained in this study are relevant to engineering applications employing metal foams ranging from convection heat sinks to filters and flow straightening devices.

Application of Superplastic Flow to Manufacturing of Microcellular Aluminum Foams

2005 ◽  
Vol 475-479 ◽  
pp. 3021-3024 ◽  
Author(s):  
Shinya Kamimura ◽  
Koichi Kitazono ◽  
Eiichi Sato ◽  
Kazuhiko Kuribayashi
Keyword(s):  
Thermal Conductivity ◽  
Cell Shape ◽  
Aluminum Foam ◽  
Oblate Spheroid ◽  
Metal Foams ◽  
Aluminum Foams ◽  
Roll Bonding ◽  
Heat Insulator ◽  
5083 Aluminum Alloy ◽  
Superplastic Condition

A new application of superplasticity was proposed in the manufacturing process of metal foams. Preform sheets were manufactured using superplastic 5083 aluminum alloy sheets through accumulative roll-bonding (ARB) process. Microcellular aluminum foam plates with 50% porosity were produced through solid-state foaming under the superplastic condition. The cell shape was oblate spheroid, which is effective to reduce the thermal conductivity. The present aluminum foam plates have a potential as an excellent heat insulator.

scholarly journals Al-Based Foams as Permanent Cores in Al Castings: Effect of Surface Skin Thickness and Composition on Infiltration and Core-Shell Bonding

Metals ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 1715
Author(s):  
Sara Ferraris ◽  
Antonio Santostefano ◽  
Antonio Barbato ◽  
Roberto Molina ◽  
Graziano Ubertalli
Keyword(s):  
Skin Thickness ◽  
Al Alloy ◽  
Strength Increase ◽  
Aluminum Foams ◽  
Gravity Casting ◽  
Acoustic Insulation ◽  
Metallurgical Bonding ◽  
Compression Resistance ◽  
Effect Of Surface ◽  
Al Foams

An emerging and still poorly explored application of aluminum foams is their potential use as permanent cores (inserts) in the casting of aluminum alloys. In this context, Al-based foams can introduce a weight reduction, the obtainment of cavities, a strength increase, the ability to absorb impact energy and vibration, acoustic insulation ability, the possibility to simplify the technological processes (no removal/recycling of traditional sand cores), and finally, they can be fully recyclable. Cymat-type Al foams with thin outer skin were used as permanent cores in Al-alloy gravity casting in the present research. Al-foams were characterized in terms of porosity, density, cell wall and skin thickness, surface chemical composition and morphology, and compression resistance. Cast objects with foam inserts were characterized by means of optical microscopy. The preservation of up to 50% of the initial porosity was observed for foam inserts with higher density. Metallurgical bonding between the foam core and the cast metal was observed in some regions.

Structure and Deformation of Gradient Metal Foams Produced by Machining

2019 ◽  
Author(s):  
H. Qiao ◽  
T. G. Murthy ◽  
C. Saldana
Keyword(s):  
Aluminum Foam ◽  
Mechanical Performance ◽  
Metal Foams ◽  
Aluminum Foams ◽  
Open Cell ◽  
Computed Tomographic ◽  
Surface Gradient ◽  
Structure Changes

Abstract The effects of surface structure on mechanical performance for open-cell aluminum foam specimens was investigated in the present study. A surface gradient for pore structure and diameter was introduced into open cell aluminum foams by machining-based processing. The structure changes in the strut and pore network were evaluated by computed tomography characterization. The role of structure gradients in affecting mechanical performance was determined using digital volume correlation and in situ compression within the computed tomographic scanner. These preliminary results show that the strength of these materials may be enhanced through surface structural gradients.

Tensile properties of composite metal foam and composite metal foam core sandwich panels

2020 ◽  
pp. 109963622094288
Author(s):  
Jacob Marx ◽  
Afsaneh Rabiei
Keyword(s):  
Tensile Strength ◽  
Ultimate Tensile Strength ◽  
Metal Foam ◽  
Failure Strain ◽  
Sandwich Panels ◽  
Metal Foams ◽  
Bond Line ◽  
Upper And Lower Bounds ◽  
Foam Core ◽  
The Face

Steel-steel composite metal foam (SS-CMF) and composite metal foam core sandwich panels (SS-CMF-CSP) were manufactured and tested under quasi-static tension. The SS-CMF-CSP were manufactured by attaching stainless steel face sheets to a SS-CMF core using solid-state diffusion bonding. SEM imaging was used to inspect the microstructure of SS-CMF and compare it to that of SS-CMF-CSP. The results indicate a cohesive bond line at the interface of the core and the face sheets. The bare SS-CMF samples had an ultimate tensile strength between 75–85 MPa and a failure strain between 7.5–8%. The normalized tensile strength of the SS-CMF was approximately 24 MPa/(g/cm3), 410% higher than other comparable metal foams, with a specific energy absorption of 0.95 J/g under tension. The uniform porosities and strong bonding between the sphere wall and matrix seem to be the strengthening factor of SS-CMF under tension when compared to other metal foams. The ultimate tensile strength of the SS-CMF-CSP was 115% stronger than the bare SS-CMF at 165 MPa with an average failure strain of 23%. The normalized strength of the SS-CMF-CSP was 52% higher than the bare SS-CMF. The modulus of elasticity was approximated using the rule of mixtures for the SS-CMF and the SS-CMF-CSP and the experimental results were found to lie within the calculated upper and lower bounds.

Structure and Deformation of Gradient Metal Foams Produced by Machining

2019 ◽  
Vol 141 (7) ◽  
Author(s):  
Haipeng Qiao ◽  
Tejas G. Murthy ◽  
Christopher Saldana
Keyword(s):  
Aluminum Foam ◽  
Mechanical Performance ◽  
Metal Foams ◽  
Aluminum Foams ◽  
Open Cell ◽  
Computed Tomographic ◽  
Surface Gradient ◽  
Structure Changes

The effects of surface structure on mechanical performance for open-cell aluminum foam specimens were investigated in the present study. A surface gradient for pore structure and diameter was introduced into open-cell aluminum foams by machining-based processing. The structure changes in the strut and pore network were evaluated by computed tomography characterization. The role of structure gradients in affecting mechanical performance was determined using digital volume correlation and in situ compression within the computed tomographic scanner. These preliminary results show that the strength of these materials may be enhanced through surface structural gradients.

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