فهرس المقالات Young&rsquo

• حرية الوصول المقاله
  • صفحة الملخص
  • نص كامل
  
  1 - Determination of Material Properties Components used in FEM Modeling of Ultrasonic Piezoelectric Transducer
  Abbas Pak
  Ultrasonic transducers have found new applications such as ultrasonic assisted micromachining, micro forming, surface treatment, welding, etc. Apart from the transducer’s shape and size, the resonant frequencies and amplitude are seriously affected by materials pr أکثر

  Ultrasonic transducers have found new applications such as ultrasonic assisted micromachining, micro forming, surface treatment, welding, etc. Apart from the transducer’s shape and size, the resonant frequencies and amplitude are seriously affected by materials properties used for transducer components. A further problem with the material is that their properties may vary from batch to batch and may also depend on the size of the raw stock. In this work using modal analysis, the material properties are calculated based on the frequency response method, which is more accurate than the nominal one. The finite element modelling was employed for both 2D and 3D FEM analysis to observe the behaviour of the cylindrical test rods and two sandwich-type piezoelectric transducers with the nominal frequency of 20 kHz and 30 kHz to find the validity of these properties. The obtained results showed that the modal analysis method could accurately determine the bar speed, Poisson's ratio and elastic modulus of the ultrasonic transducer components. The accuracy of this method increases by considering more vibration mode. Based on the results, obtained errors for FEM modelling of two ultrasonic transducers with the frequency of 20 kHz and 30 kHz are 0.15% and 0.33%, respectively. تفاصيل المقالة
• حرية الوصول المقاله
  • صفحة الملخص
  • نص كامل
  
  2 - The Molecular Mechanics Model of Carbon Allotropes
  Mohsen Motamedi AMIRHOSSEIN NAGHDI
  10.22034/jna.2017.543209.1030
  Due to its valency, carbon can form too many allotropes. A number of well-known forms of carbon include graphene, carbon nanotubes, capped carbon nanotubes, buckyballs, and nanocones. The remarkable mechanical properties of these carbons have attracted researchers. Nume أکثر

  Due to its valency, carbon can form too many allotropes. A number of well-known forms of carbon include graphene, carbon nanotubes, capped carbon nanotubes, buckyballs, and nanocones. The remarkable mechanical properties of these carbons have attracted researchers. Numerous studies have been conducted on carbon nanotubes or graphene. In the present study, however, we applied the molecular mechanic method in order to model five forms of carbon with a uniform approach and draw a detailed comparison between the allotropes of carbon. Furthermore, we obtained Young’s modulus and natural frequencies for every form of carbon, which can be useful for researchers. The results show that increasing the diameter of the carbon nanotube will decrease its strength (decreases the Young’s modulus). Also, the capped carbon nanotube is stronger than the non-capped nanotube. This is because of the end bonds of the carbon nanotube. Also, the results show that Buckyball has extraordinary properties. Its strength is three times more than that of the carbon nanotube with the same diameter. تفاصيل المقالة
• حرية الوصول المقاله
  • صفحة الملخص
  • نص كامل
  
  3 - The Molecular Mechanics Model of Carbon Allotropes
  Mohsen Motamedi Amirhossein Naghdi
  10.22034/jna.2017.540019
  Carbon can form numerous allotropes because of its valency. Graphene, carbon nanotubes,capped carbon nanotubes, buckyballs, and nanocones are well-known polymorphs of carbon.Remarkable mechanical properties of these carbon atoms have made them the subject of intenserese أکثر

  Carbon can form numerous allotropes because of its valency. Graphene, carbon nanotubes,capped carbon nanotubes, buckyballs, and nanocones are well-known polymorphs of carbon.Remarkable mechanical properties of these carbon atoms have made them the subject of intenseresearch. Several studies have been conducted on carbon nanotubes or graphene. In the presentstudy, the molecular mechanics method was applied to model five polymorphs of carbon witha uniform approach and compare the allotropes of carbon in detail. Also, we obtained Young’smodulus and natural frequencies for every form of carbon, which can be useful for researchers.We found that an increase in the diameter of the carbon nanotube would accompany with adrop in its strength and Young’s modulus. Moreover, our results show that the capped carbonnanotube has a higher strength compared to that of the non-capped nanotube, which might bedue to the end bonds of the carbon nanotube. Finally, we identified extraordinary properties ofBuckyball including its strength, which is three times more than that of the carbon nanotubewith the same diameter تفاصيل المقالة