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Issue Info: 
  • Year: 

    2008
  • Volume: 

    5
  • Issue: 

    3
  • Pages: 

    1-7
Measures: 
  • Citations: 

    0
  • Views: 

    348
  • Downloads: 

    0
Abstract: 

Thermal fatigue is a stochastic process often showing considerable scatter even in controlled environments. Due to complexity of thermal fatigue, there is no a complete analytical solution for predicting the effect of this property on the life of various components, subjected to severe thermal fluctuations. Among these components, one can mention car cylinder, cylinder head and piston which bear damages due to thermal fatigue. All these components are usually produced by casting techniques. In order to comprehend and compare the thermal fatigue resistance of cast Al alloys 356 and 413, this research was designed and performed. For this purpose, several samples in the form of disc were cast from the two alloys in sand mould. The microstructures of the cast samples were studied by light microscopy in order to choose the samples with the least amounts of defects for thermal fatigue tests. The results of thermal fatigue tests showed that the nucleation of microcracks in Al-356 alloy occurred at shorter time relative to those occurred in Al- 413 alloy under the same test conditions. In addition, the density of micro-cracks in Al-356 alloy was more than that of Al-413 alloy. The results of fractography on 356 alloy indicated that the cracks were generally nucleated from inter-dendritic shrinkage porosities and occasionally from the interface of silicon particles with the matrix. The growth of these micro cracks was along the dendrite arms. Fractography of 413 alloy fracture surfaces showed that nucleation of microcracks was often associated with silicon particles.

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Issue Info: 
  • Year: 

    0
  • Volume: 

    18
  • Issue: 

    57
  • Pages: 

    16-26
Measures: 
  • Citations: 

    0
  • Views: 

    250
  • Downloads: 

    0
Abstract: 

لطفا برای مشاهده چکیده به متن کامل (PDF) مراجعه فرمایید.

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Writer: 

Issue Info: 
  • End Date: 

    1395
Measures: 
  • Citations: 

    6
  • Views: 

    77
  • Downloads: 

    0
Keywords: 
Abstract: 

Yearly Impact:   مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic Resources

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Issue Info: 
  • Year: 

    2000
  • Volume: 

    58
  • Issue: 

    3
  • Pages: 

    35-41
Measures: 
  • Citations: 

    7
  • Views: 

    1233
  • Downloads: 

    0
Abstract: 

Thalassemia is the most prevalent genetic disorder in Iran and around the world and these patient need regular careful care. The Present study reports results of routine examination of patients visited thalassemia clinic of Tehran. Data about clinical and laboratory examinations of 413 thalassemics were extracted and analyzed. The prevalence of heart complications, diabetes, growth retardation, delayed puberty and primary and secondary amenorrhea was 9 %, 8% 21.3%, 3.1% and 6.3 %, respectively. 44 % didn’t have secondary sex characteristics. Splenectomy had been done for 67.2 % of cases. HBsAg, HBsAb and HBcAb were positive in 1.9 %, 57.4% and 43 %, respectively.We concluded that blood transfusion standards in this Clinic was acceptable, whereas because of poor knowledge, iron chelating is unfavorable.

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Issue Info: 
  • End Date: 

    شهریور 1387
Measures: 
  • Citations: 

    0
  • Views: 

    467
  • Downloads: 

    0
Keywords: 
Abstract: 

یکی از مسائل و مشکلات مهم در حوزه نانو تولید قطعه است. در این طرح پودرهای میکرونی SiC به روش آسیاب کاری مکانیکی سنتز شده و به مذاب آلومینیوم اضافه شد. از طریق همزدن مکانیکی پودرهای مذکور در آلیاژ پراکنده شدند. تست های متالوگرافی، SEM و توزیع اندازه ذره و خواص مکانیکی بر روی نمونه ها انجام شد. این روش برای اولین بار برای تهیه نانوکامپوزیت مورد استفاده قرار گرفته و از نظر اقتصادی و انعطاف پذیر بودن نسبت به روش متالورژی پودر بسیار مناسب تر می باشد.

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Issue Info: 
  • Year: 

    2011
  • Volume: 

    23
  • Issue: 

    1
  • Pages: 

    59-70
Measures: 
  • Citations: 

    0
  • Views: 

    844
  • Downloads: 

    0
Abstract: 

Although the solubility of oxygen in molten aluminum alloys is said to be negligible, the fresh surface of the melt oxidizes quickly in the air and an oxide film is formed on the melt surface. Oxide-metal-oxide sandwich technique is a method for the study of short-time surface oxide films. In this research, air was blown at 0.5 atmosphere into the melts of Al-1Mg and Al-6Mg alloys by means of a compressor in order to form air bubbles within the melts. The sandwiches of oxide-metal-oxide were formed at locations where these bubbles reach each other. Some of the characteristics of these films inside the bubbles were evaluated using the scanning electron microscope. In Al-1Mg alloy, the formation of crystalline aluminum oxide as well as the granules of magnesium oxide at the same time was confirmed whereas the magnesium oxide in the form of layer and granule was detected for the case of Al-6Mg alloy.

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Issue Info: 
  • Year: 

    2013
  • Volume: 

    13
  • Issue: 

    2
  • Pages: 

    295-304
Measures: 
  • Citations: 

    0
  • Views: 

    1003
  • Downloads: 

    145
Abstract: 

In this research work nano porous silicon layers with different porosity were prepared by using electrochemical etching. Surface morphology and size of pores were investigated by scanning electron microscopy (SEM). TiO2 thin films with EBPVD method have been deposited on the surface of PSi layers. The influence of anodization conditions such as anodization time interval and current density on electrical properties and surface morphology of sandwich devices were carried out using I-V measurements .The results showed that, electrical properties were influenced by changes of current density and anodization time interval. We also investigated the AC electrical conductivity of Al/TiO2/PSi/Al sandwich devices over the range of frequency 102 to 105 Hz and temperature range 300 to 378 K. It is known that, over the range of frequency<103Hz the band theory and over the range of frequency>103Hz hopping mechanism is applicable in explaining the conductivity of TiO2/PSi thin films nano structures with aluminum electrodes.

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Author(s): 

ARAM M.R.

Journal: 

SAFINEH

Issue Info: 
  • Year: 

    2004
  • Volume: 

    1
  • Issue: 

    3 (SPECIAL ISSUE ON THE HADITH)
  • Pages: 

    49-58
Measures: 
  • Citations: 

    0
  • Views: 

    2429
  • Downloads: 

    0
Keywords: 
Abstract: 

One of the narrations attributed to the holy prophet of allah (p.b.u.h) is, "We, the prophets, do not leave inheritance: what we leave is charity." Many of the Shia and Sunny scholars have discussed the truth of attribution, and the content of this tradition.In this essay, the viewpoints and explanations given by shaikh Mofid, the well - Known Shia scholar, jurisprudent and philosopher of the 4th and 5th centuries are surveyed.A.H. shaikh Mofid just talked about the guidelines of the tradition. He believed that if we consider it as a true tradition, we can read it in 2 ways, and then he preferred the second type of reading, which meant, "We, the prophets, do not leave inheritance as charity." This short treatise, is a sample of comparative jurisprudence.

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Issue Info: 
  • Year: 

    2021
  • Volume: 

    5
  • Issue: 

    1
  • Pages: 

    51-62
Measures: 
  • Citations: 

    0
  • Views: 

    47
  • Downloads: 

    2
Abstract: 

In the current study the microstructure and mechanical properties of Al-2Ni-xMn alloys was investigated as a substitute for Al-4Ni alloys. To this end, different melts containing 2 wt. % Ni and 1, 2, and 4 wt. % Mn were solidified at two cooling rates of 3.5 and 10.4 C/s. According to the results, under the low solidification rate, the tensile strength, fracture strain, and toughness of Al-2Ni-1Mn alloy are lower than those of Al-4Ni alloy by 26, 115, and 137%, respectively. However, further Mn addition impaired the tensile properties. Increasing the solidification cooling rate decreases the size and improves the distribution of Ni(Mn)-rich compounds and porosities within the microstructure and reduces the sizes of secondary dendrite arm spacing and grains. This substantially improved the mechanical properties of Mn-rich alloys. For instance, compared to Al-4Ni alloy solidified at 3.5 C/s, the tensile strength, fracture strain, and toughness of copper mold cast Al-2Ni-1Mn alloy increased by 50, 200, and 330%, respectively.

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Issue Info: 
  • Year: 

    2018
  • Volume: 

    20
  • Issue: 

    1
  • Pages: 

    77-91
Measures: 
  • Citations: 

    0
  • Views: 

    661
  • Downloads: 

    0
Abstract: 

Incremental sheet metal forming is one of methods more innovation in science and industrial zone. The purpose of this research is the study of influence of factors such as tool diameter, step down, rotation speed and feed rate on metallurgical properties of explosive-welded Al/Cu/Al multilayer. In order to this purpose, a sample of explosive-welded Al/Cu/Al multilayer was produced. Then, a statistical model (RSM) was used for the experimental plan (with these variables) to determine the runs of experiment (or selected points). Next, forces and times values of sheet metal forming were measured. The experimental results showed that force and time forming of Al/Cu/Al multilayer is highly sensitive to factors like step down and feed rate. Also the most effective coefficient on the incremental forming is belonged to step down factor that showed it is very important in machining parameters. Finally, by using coefficient estimates of (RSM) model, relation between input variables and response was obtained. Finally, this model was predicted the optimum design points of machining parameters.

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