The Iraqi Journal For Mechanical And Material Engineering, Vol.15, No1, 2015 31 EFFECT OF HOLE SHAPE ON FREE VIBRATION CHARACTERISTICS OF UNIDIRECTIONAL COMPOSITE PLATES. Dr. Mohsin Abdullah Al-Shammari Mechanical Engineering Department College of Engineering/Baghdad University dr.alshammari@uobaghdad.edu.iq ABSTRACT In this research, a free vibration of unidirectional composite laminated plate with different holes shape effect investigation is done experimentally and numerically. The natural frequency and deflection response of a unidirectional composite plate are studied with different holes shape effect as (rectangular or triangular or square or ellipse or circular shape, for simply supported and clamped composite laminated plate boundary conditions. This effect is studied for different shape cutout with the same area of different cutout shapes. The results of natural frequency evaluated by experimental work are compared with those evaluated by numerical method using a finite element method, (ANSYS program Ver. 14). The deflection of composite laminated plate with different holes effect is evaluated using finite element method. The results showed that the maximum natural frequency of unidirectional composite plate occurs at the clamped supported boundary composite plate with circular cutout. The experimental results of natural frequency of composite plate with different cutout shape are compared with those obtained using FEM. The comparison of results showed that the maximum discrepancy between experimental and numerical natural frequency is about (14.85%). ﺍﻟﺨﻼﺻﺔ: ﻓﻲ ﻫﺬﺍ ﺍﻟﺒﺤﺚ ﺗﻢ ﺩﺭﺍﺳﺔ ﺍﻻﻫﺘﺰﺍﺯ ﺍﻟﺤﺮ ﻟﻠﺼﻔﺎﺋﺢ ﺍﻟﻤﺮﻛﺒﺔ ﺍﻟﻐﻴﺮ ﻣﺘﻤﺎﺛﻠﺔ ﺍﻟﺨﻮﺍﺹ ﺍﻟﻤﻜﻮﻧﺔ ﻣﻦ ﻋﺪﺓ ﻁﺒﻘﺎﺕ ﺑﺘﺄﺛﻴﺮ ﺗﻢ ﺩﺭﺍﺳﺔ ﺍﻟﺘﺮﺩﺩ ﺍﻟﻄﺒﻴﻌﻲ ﻭﺍﻻﻧﻬﻴﺎﺭ ﻟﻠﺼﻔﺎﺋﺢ ﺍﻟﻤﺮﻛﺒﺔ ﺍﻟﻨﺎﺗﺞ ﺑﺴﺒﺐ ﻭﺟﻮﺩ ﺛﻘﺐ ﻭﺳﻂ. ﺷﻜﻞ ﺍﻟﺜﻘﺐ ﺑﺎﻷﺳﻠﻮﺑﻴﻦ ﺍﻟﻌﻤﻠﻲ ﻭﺍﻟﻌﺪﺩﻱ ﻟﻠﺼﻔﺎﺋﺢ ﺍﻟﻤﺜﺒﺘﺔ ﺑﻄﺮﻳﻘﺔ ﺍﻹﺳﻨﺎﺩ ﺍﻟﺤﺮ ﺃﻭ ﺍﻹﺳﻨﺎﺩ(ﻣﺴﺘﻄﻴﻞ ﺃﻭ ﻣﺜﻠﺚ ﺃﻭ ﻣﺮﺑﻊ ﺃﻭ ﺑﻴﻀﻮﻱ ﺃﻭ ﺩﺍﺋﺮﻱ) ﺍﻟﺼﻔﻴﺤﺔ ﺑﺄﺣﺪ ﺍﻷﺷﻜﺎﻝ ﺍﻟﻨﺘﺎﺋﺞ ﺍﻟﻌﻤﻠﻴﺔ ﻟﻠﺘﺮﺩﺩ ﺗﻢ ﻣﻘﺎﺭﻧﺔ. ﺃﺟﺮﻳﺖ ﻫﺬﻩ ﺍﻟﺪﺭﺍﺳﺔ ﺑﺘﺄﺛﻴﺮ ﻧﻔﺲ ﺍﻟﻤﺴﺎﺣﺔ ﻟﻠﺜﻘﺐ ﺍﻟﻤﻘﻄﻮﻉ ﻣﻦ ﺍﻟﺼﻔﺎﺋﺢ. ﺍﻟﺜﺎﺑﺖ ﻟﻠﺼﻔﺎﺋﺢ ِ ﺍﻟﻄﺒﻴﻌﻲ ﻣﻊ ﺍﻟﻨﺘﺎﺋﺞ ﺍﻟﺘﻲ ﺗﻢ ﺍﻳﺠﺎﺩﻫﺎ ﺑﺎﻷﺳﻠﻮﺏ ﺍﻟﻌﺪﺩﻱ ﺑﺎﺳﺘﺨﺪﺍﻡ ﻁﺮﻳﻘﺔ ﺍﻟﻌﻨﺎﺻﺮ ﺍﻟﻤﺤﺪﺩﺓ ﺑﺎﺳﺘﺨﺪﺍﻡ ﺑﺮﻧﺎﻣﺞANSYS ﺍﻻﺻﺪﺍﺭ14 ﺃﻣﺎ ﺣﺴﺎﺑﺎﺕ ﻧﺘﺎﺋﺞ ﺍﻻﻧﻬﻴﺎﺭ ﻟﻠﺼﻔﺎﺋﺢ ﺍﻟﻤﺮﻛﺒﺔ ﺑﺘﺄﺛﻴﺮ ﺷﻜﻞ ﺍﻟﺜﻘﺐ ﺃﺟﺮﻳﺖ ﺑﺎﺳﺘﺨﺪﺍﻡ ﻁﺮﻳﻘﺔ ﺍﻟﻌﻨﺎﺻﺮ ﺍﻟﻤﺤﺪﺩﺓ. . ﻓﻘﻂ ﺑﻴﻨﺖ ﺍﻟﻨﺘﺎﺋﺞ ﺍﻟﺘﻲ ﺗﻢ ﺍﻟﺤﺼﻮﻝ ﻋﻠﻴﻬﺎ ﺍﻥ ﺍﻋﻠﻰ ﻗﻴﻤﺔ ﻟﻠﺘﺮﺩﺩ ﺍﻟﻄﺒﻴﻌﻲ ﺗﺤﺪﺙ ﻟﻠﺼﻔﻴﺤﺔ ﺍﻟﻤﺮﻛﺒﺔ ﺍﻟﻐﻴﺮ ﻣﺘﻤﺎﺛﻠﺔ ﺍﻟﺨﻮﺍﺹ ﺍﺟﺮﻳﺖ ﻋﻤﻠﻴﺔ ﻣﻘﺎﺭﻧﺔ ﺑﻴﻦ ﺍﻟﻨﺘﺎﺋﺞ ﺍﻟﻌﻤﻠﻴﺔ ﻟﻠﺘﺮﺩﺩ ﺍﻟﻄﺒﻴﻌﻲ. ﺍﻟﻤﺜﺒﺘﺔ ﺑﺼﻮﺭﺓ ﺍﺳﻨﺎﺩ ﺛﺎﺑﺖ ﻭﺍﻟﻤﺤﺘﻮﻳﺔ ﻋﻠﻰ ﺛﻘﺐ ﻋﻠﻰ ﺷﻜﻞ ﺩﺍﺋﺮﻱ ﻟﻠﺼﻔﺎﺋﺢ ﺍﻟﻤﺮﻛﺒﺔ ﻣﻊ ﺍﻟﻨﺘﺎﺋﺞ ﺍﻟﻌﺪﺩﻳﺔ ﺍﻟﺘﻲ ﺗﻢ ﺍﻟﺤﺼﻮﻝ ﻋﻠﻴﻬﺎ ﺑﺎﻷﺳﻠﻮﺏ ﺍﻟﻌﺪﺩﻱ ﺑﺎﺳﺘﺨﺪﺍﻡ ﻁﺮﻳﻘﺔ ﺍﻟﻌﻨﺎﺻﺮ ﺍﻟﻤﺤﺪﺩﺓ، ﻭﻗﺪ ﺑﻴﻨﺖ ) ﺍﻟﻤﻘﺎﺭﻧﺔ ﺑﺎﻥ ﺍﻋﻠﻰ ﻗﻴﻤﺔ ﻟﻠﺘﻔﺎﻭﺕ ﺑﻴﻦ ﻧﺘﺎﺋﺞ ﺍﻷﺳﻠﻮﺏ ﺍﻟﻌﺪﺩﻱ ﻭﺍﻷﺳﻠﻮﺏ ﺍﻟﻌﻤﻠﻲ ﻛﺎﻧﺖ ﺑﺤﺪﻭﺩ14.85 .(% KEYWORDS Holes, Plates, Vibration, FEM.