Mesomechanical numerical modeling of the stress-strain localization and fracture in an aluminum alloy with a composite coating

The organic-inorganic hybrid sol was prepared using an alkaline silica sol modified by acid-catalyzed hydrolytic polycondensation of methyltrimethoxysilane (MTMS) in a water-bath condition of 60oC, and then the water-based primer and topcoat were prepared through adding the pigments and nano-TiO2 suspension respectively. Through spraying and baking, the organicinorganic composite coating on the treated aluminum alloy was obtained. The optimum range of P/B (weight ratio of the pigment/binder) is determined between 1:1 and 1.5:1 by investigating the influence of the P/B of the primer on the adhesion and impact resistance of the coating. The microstructure of the coating was characterized by optical microscopy and scanning electron microscopy. The results show that there are lots of holes and lamellar structure in the primer coating and the obtained topcoat coating is uniform, smooth and dense. The coating of ~30 μm in thickness is mainly composed of three elements of silicon, aluminum and titanium, in which transition layer of ~10 μm is included. The physicochemical properties suggest that the coatings on aluminum alloy can meet the needs of finishing coating very well.

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Simulation on Flexible Thixo-Extrusion of Variable Cross-Section Part Based on DEFORM-3D Software

Solid State Phenomena ◽

10.4028/www.scientific.net/ssp.217-218.201 ◽

2014 ◽

Vol 217-218 ◽

pp. 201-207

Author(s):

Chun Fang Wang ◽

Kai Kun Wang ◽

Zhe Luo

Keyword(s):

Aluminum Alloy ◽

Control Method ◽

Complex Geometry ◽

Variable Cross Section ◽

Extrusion Process ◽

Simulation Software ◽

Variable Cross ◽

Stress Strain ◽

Different Temperatures ◽

Deform 3D

Flexible thixo-extrusion, as an innovative near-net-shape forming method, has huge advantages in processing the components with complex geometry. However, it should keep in mind that conventional liquid casting still represents the dominant mean of aluminum alloys production. One of the obstacles the thixo-extrusion has to overcome is lack of proof that can live up to the claim that thixo-extruded components have better mechanical properties. The main aim of this paper is to simulate the flexible thixo-extrusion process of aluminum alloy A356 and investigate the control method of materials flow front. An isothermal compression test of aluminum alloy A356 is first conducted to obtain the true stress-strain curves at different temperatures and strain rates. A constitutive equation describing the relationship of stress, strain, strain rate and temperature is fitted by Origin and then imported to the DEFORM-3D simulation software. The results show that the quality of final component is enormously influenced by the radius of the arcs and the flexible thixo-extruded components has less defects compared with the conventional extruded ones.

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Combined-Stress Tests on 24S-T Aluminum-Alloy Tubes

Journal of Applied Mechanics ◽

10.1115/1.4009666 ◽

1947 ◽

Vol 14 (2) ◽

pp. A147-A153

Author(s):

W. R. Osgood

Keyword(s):

Aluminum Alloy ◽

Hoop Stress ◽

Axial Stress ◽

Axial Strain ◽

Maximum Deviation ◽

Shearing Stress ◽

Stress Tests ◽

Combined Stress ◽

Stress Strain ◽

Shearing Strain

Abstract Combined-stress tests were made on five 24S-T aluminum-alloy tubes, 1 3/4 in. ID × 0.05 in. thick. The ratios of circumferential (hoop) stress to axial stress were 0, 1/2, 1, 2, and ∞. The tubes were tested to failure and sufficient measurements of circumferential strain and axial strain were taken to plot stress-strain curves almost up to rupture. The results are presented in the form of two sets of stress-strain curves for each ratio of stresses, namely, maximum shearing stress plotted against maximum shearing strain, and octahedral shearing stress plotted against octahedral shearing strain. In each plot the maximum deviation of the curves is about ± 5 per cent. A method of evaluating small octahedral shearing strains from the data is given which does not assume Poisson’s ratio to be 1/2.

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