Author: Mahadeo Ratilal Patel
Publisher:
ISBN:
Category :
Languages : en
Pages : 138

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Author: A. Rosen
Publisher:
ISBN:
Category :
Languages : en
Pages : 43

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Tensile tests on annealed, commercially pure aluminum specimens were performed in a hard machine at different temperatures for a number of constant strain rates. The results show that a range of strain, strain rate, and temperature exists for which the flow stress decreases with strain rate. This material property, when coupled with suitable mechanical conditions, is believed to be cause of discontinuous, repeated yielding. Various experiments, especially relaxation and reloading tests, show that the decrease of flow stress with strain rate can be directly attributed to rapid strain aging due to impurity diffusion. Other experiments indicate the same effect for different loading histories. An analytical representation of the strain rate and strain aging of the material is developed which predicts results in very good agreement with the experiments.

Author: A. M. Eleiche
Publisher:
ISBN:
Category :
Languages : en
Pages : 76

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A series of tests is described in which tubular specimens of a commercially pure polycrystalline aluminum were loaded in torsion up to shear strains of about 2 and 4% respectively, over the temperature range -180C to 250C. The experimental results give the flow stress in shear, the strain and the strain rate against time. They also give stress-strain curves which are compared to the corrresponding static curves obtained by testing similar specimens in torsion at about 0.001/sec. A graph showing the dependence of flow stress on temperature indicates that there are three different temperature ranges for polycrystalline aluminum within each of which a different deformation mechanism presumably dominates the flow process. (Modified author abstract).

Author: James Richard Cady
Publisher:
ISBN:
Category : Aluminum
Languages : en
Pages : 326

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Author: Jerry Lee Chiddister
Publisher:
ISBN:
Category : Aluminum
Languages : en
Pages : 270

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Author: Abraham Rosen
Publisher:
ISBN:
Category :
Languages : en
Pages :

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Author: Bryan Zuanetti
Publisher:
ISBN:
Category : Aluminum
Languages : en
Pages : 243

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The mechanical properties of materials are known to be rate- and temperature-dependent. Owing to this, investigations aimed towards the exploration of material behavior (i.e. plasticity, strength, and failure) under thermomechanical extremes has been a subject of sustained interest. The extreme temporal and precise nature of these studies produces special experimental challenges, and as a consequence, knowledge regarding the dynamic response of materials, especially in thermomechanical extremes, is still limited by the deficiency of experimental data. The main objectives of the current study are to 1) develop a reliable experimental scheme for investigating the dynamic inelasticity of metals under thermomechanical extremes. In particular, the focus is on elevated temperature dynamic compressive and shearing resistance of metals at plastic strain rates in excess of one-million/sec and sample temperatures approaching melt. And, 2) to address the need for experimental data on the dynamic response of FCC metals in previously unexplored but important thermomechanical regimes, such as elevated temperatures and plastic strain-rates on the order of 10^5 – 10^9 /s. In order to conduct this research, the single-stage gas-gun facility at CWRU was modified to include a breech-end sabot heater system and a novel fully fiber-optics based normal and transverse motion diagnostics system, which enabled reverse geometry normal and pressure-shear plate impact experiments to be conducted on pure aluminum at elevated temperatures. Additionally, a full characterization of the WC anvil plates was performed. Using these capabilities, elevated temperature normal and combined pressure-shear plate impact experiments were carried out to better understand the high temperature dynamic compressive and shearing resistance of aluminum. These experiments were used to shed light on the temperature-dependence of the shock impedance of aluminum at pressures of around 1.0 – 1.6 GPa, and the temperature-dependence of shear flow stress at levels of strain approaching 50% and strain-rates in the order of 4 – 8 x 10^5 /s. The results showed an overall decrease in the shear flow stress with temperatures in the range of 23 – 593 ̊C, showing that temperature facilitates plastic flow of aluminum when deforming at strain-rates approaching 10^6 /s. Additionally, in an effort to better understand the relaxation behavior of this material at incipient plasticity at ultra-high strain-rates, a series of laser-driven shock compression experiments are carried out on pure aluminum films at temperatures ranging from 23 – 400 ̊C. The results are used to correlate the temperature-dependence of the rate-sensitivity of the Hugoniot elastic limit (HEL) of pure aluminum at strain-rates up to 10^9 /s. In contrast to the previous case (i.e. large plastic strains, and lower strain-rates), the results reveal a monotonic increase in the HEL with temperature for strain-rates in the range of 10^4 – 10^9 /s. This effect is shown to decrease with increasing strain-rate.

Author: Waldemar Alfredo Monteiro
Publisher: BoD – Books on Demand
ISBN: 953511588X
Category : Technology & Engineering
Languages : en
Pages : 254

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Lightweight alloys have become of great importance in engineering for construction of transportation equipment. At present, the metals that serve as the base of the principal light alloys are aluminum and magnesium. One of the most important lightweight alloys are the aluminum alloys in use for several applications (structural components wrought aluminum alloys, parts and plates). However, some casting parts that have low cost of production play important role in aircraft parts. Magnesium and its alloys are among the lightest of all metals and the sixth most abundant metal on earth. Magnesium is ductile and the most machinable of all metals. Many of these light weight alloys have appropriately high strength to warrant their use for structural purposes, and as a result of their use, the total weight of transportation equipment has been considerably decreased.

Author: J. E. Hackett
Publisher:
ISBN:
Category :
Languages : en
Pages :

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Author: Gary Tod Meissner
Publisher:
ISBN:
Category : Aluminum crystals
Languages : en
Pages : 24

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