ﺑﺮرﺳﯽ ﻋﺪدي و ﺗﺠﺮﺑﯽ ﻫﯿﺪروﻓﺮﻣﯿﻨﮓ ﻓﺸﺎر ﭘﺎﯾﯿﻦ ﻟﻮﻟﻪﻫﺎي آﻟﻮﻣﯿﻨﯿﻮﻣﯽ

Numerical and Experimental Investigation of Low Pressure Hydroforming of Aluminum Tubes

ﻓﺮاﯾﻨﺪ ﻫﯿﺪروﻓﺮﻣﯿﻨﮓ ﻟﻮﻟﻪ ﺑﻪﻃﻮر ﮔﺴﺘﺮده در ﺗﻮﻟﯿﺪ ﻗﻄﻌﺎت ﺳﺎﺧﺘﺎري اﺗﻮﻣﺒﯿﻞ اﺳﺘﻔﺎده ﻣﯽﺷﻮد. ﯾﮑﯽ از ﺧﺼﻮﺻﯿﺎت ﻗﻄﻌﺎت ﺗﻮﻟﯿﺪ ﺷﺪه ﺑﺎ اﯾﻦ ﻓﺮاﯾﻨﺪ، ﻧﺴﺒﺖ اﺳﺘﺤﮑﺎم ﺑﻪ وزن ﺑﺎﻻ ﻣﯽﺑﺎﺷﺪ. ﻫﯿﺪروﻓﺮﻣﯿﻨﮓ ﻟﻮﻟﻪ ﻓﺸﺎر ﭘﺎﯾﯿﻦ، ﯾﮑﯽ از روشﻫﺎي ﭘﯿﺸﻨﻬﺎد ﺷﺪه ﺑﺮاي ﺣﻞ ﻣﺸﮑﻼت ﻫﯿﺪروﻓﺮﻣﯿﻨﮓ ﻟﻮﻟﻪ از ﻗﺒﯿﻞ ﻧﯿﺎز ﺑﻪ ﻓﺸﺎر ﺑﺎﻻي ﺳﯿﺎل و ﻣﺸﮑﻼت آب ﺑﻨﺪي ﻣﯽﺑﺎﺷﺪ. روش اﻧﺠﺎم ﻫﯿﺪروﻓﺮﻣﯿﻨﮓ ﻓﺸﺎر ﭘﺎﯾﯿﻦ ﻟﻮﻟﻪ ﺷﺒﯿﻪ ﻓﺸﺮدن ﯾﮏ ﺟﺴﻢ ﺟﺎﻣﺪ ﺗﻮﺧﺎﻟﯽ اﺳﺖ و در آن ﺑﺮﺧﻼف ﻫﯿﺪروﻓﺮﻣﯿﻨﮓ ﻓﺸﺎر ﺑﺎﻻ، ﻗﺎﻟﺐ ﺑﺎﻻﯾﯽ در ﻃﻮل ﻓﺮاﯾﻨﺪ ﺛﺎﺑﺖ ﻧﻤﯽﺑﺎﺷﺪ و ﻫﻢزﻣﺎن ﺑﺎ اﻋﻤﺎل ﻓﺸﺎر داﺧﻠﯽ ﺑﻪ ﻟﻮﻟﻪ ﺣﺮﮐﺖ ﻣﯽﮐﻨﺪ و ﻟﻮﻟﻪ را ﺗﺤﺖ ﻓﺸﺎر ﻗﺮار ﻣﯽدﻫﺪ. ﻧﺎزكﺷﺪﮔﯽ دﯾﻮاره ﻫﺎي ﻟﻮﻟﻪ ﭘﺲ از ﺷﮑﻞدﻫﯽ و ﺧﻄﺎﻫﺎي ﻫﻨﺪﺳﯽ در ﻓﺮم ﻧﻬﺎﯾﯽ ﻗﻄﻌﻪ، از ﻋﯿﻮب ﻣﻬﻢ ﻓﺮاﯾﻨﺪ ﻫﯿﺪروﻓﺮﻣﯿﻨﮓ ﻓﺸﺎر ﭘﺎﯾﯿﻦ ﻣﯽﺑﺎﺷﻨﺪ. در اﯾﻦ ﻣﻘﺎﻟﻪ، ﻓﺮاﯾﻨﺪ ﻫﯿﺪروﻓﺮﻣﯿﻨﮓ ﻓﺸﺎرﭘﺎﯾﯿﻦ ﻟﻮﻟﻪﻫﺎي آﻟﻮﻣﯿﻨﯿﻮﻣﯽ آﻟﯿﺎژ AA6063اﻧﺠﺎم ﺷﺪه و ﻣﻘﻄﻊ ﮔﺮد ﻟﻮﻟﻪ ﺑﻪوﺳﯿﻠﻪ ﻓﺮاﯾﻨﺪ ﻫﯿﺪروﻓﺮﻣﯿﻨﮓ ﺑﻪ ﻣﻘﻄﻊ ﻣﺴﺘﻄﯿﻠﯽ ﺗﻐﯿﯿﺮ ﺷﮑﻞ داده اﺳﺖ. ﺗﻮزﯾﻊ ﺿﺨﺎﻣﺖ، ﻣﻘﺎدﯾﺮ ﺷﻌﺎع ﮔﻮﺷﻪ ﺷﮑﻞ داده ﺷﺪه و ﺗﺨﺘﯽ ﺳﻄﺢ ﺑﺎﻻﯾﯽ ﻗﻄﻌﻪ ﺗﺤﺖ ﻣﺴﯿﺮﻫﺎي ﺑﺎرﮔﺬاري ﻣﺘﻔﺎوت ﺑﺮرﺳﯽ ﺷﺪه اﺳﺖ. ﻧﺘﺎﯾﺞ ﻧﺸﺎن ﻣﯽدﻫﺪ ﮐﻪ ﺑﺎ اﻓﺰاﯾﺶ ﻓﺸﺎر داﺧﻠﯽ ﻣﯽﺗﻮان ﺑﻪ ﺷﻌﺎع ﮔﻮﺷﻪ ﮐﻤﺘﺮي دﺳﺖ ﭘﯿﺪا ﮐﺮد اﻣﺎ ﻧﺎزكﺷﺪﮔﯽ اﻓﺰاﯾﺶ ﭘﯿﺪا ﻣﯽﮐﻨﺪ. ﺑﯿﺸﺘﺮﯾﻦ ﺗﺨﺘﯽ ﺳﻄﺢ ﺑﺎﻻﯾﯽ ﻗﻄﻌﻪ زﻣﺎﻧﯽ ﺣﺎﺻﻞ ﻣﯽﺷﻮد ﮐﻪ ﺟﺎﺑﻪﺟﺎﯾﯽ ﻗﺎﻟﺐ ﺑﺎﻻﯾﯽ ﺑﻌﺪ از رﺳﯿﺪن ﻓﺸﺎر داﺧﻠﯽ ﺑﻪ ﻣﻘﺪار ﻣﺎﮐﺰﯾﻤﻢ ﺧﻮد اﻧﺠﺎم ﺷﻮد. ﺣﺪاﻗﻞ ﺷﻌﺎع ﮔﻮﺷﻪ ﺗﻮﻟﯿﺪ ﺑﺎ ﻓﺸﺎر داﺧﻠﯽ 10 ﻣﮕﺎﭘﺎﺳﮑﺎل در ﮔﻮﺷﻪ ﺑﺎﻻﯾﯽ ﻣﻘﻄﻊ 5 /63mmو در ﮔﻮﺷﻪ ﭘﺎﯾﯿﻨﯽ ﻣﻘﻄﻊ 5 /62mmﺷﮑﻞ داده ﺷﺪه اﺳﺖ. ﺑﺎ اﻋﻤﺎل ﻓﺸﺎر داﺧﻠﯽ 10 ﻣﮕﺎﭘﺎﺳﮑﺎل، ﻓﺮورﻓﺘﮕﯽ ﺳﻄﺢ ﺑﺎﻻﯾﯽ ﻗﻄﻌﻪ ﺑﻪ 0 /2mm رﺳﯿﺪه اﺳﺖ.

Tube hydroforming process is used widely in production of car structural parts. High strength to weight ratio is one of the properties of parts which is produced using this process. Low pressure tube hydroforming (LPTH) is one method recommended for solving problems of tube hydroforming such as requiring high pressure of fluid and sealing problems. LPTH method is similar to crushing a hollow solid body. Unlike high pressure tube hydroforming, upper die is not fixed in this process and it moves at the same time by applying internal pressure and squeezes the tube. Main defects in low pressure hydroforming are tube wall thinning and geometric errors at final form of the part. In this paper, LPTH of AA6063 aluminum tubes was carried out and circular cross section of tube was deformed to rectangular. Thickness distribution, formed corner radius and flatness of top surface of part was investigated under three different loading paths. Results show that lower corner radius can be achieved with higher internal pressure while thinning is increased. Maximum of flatness was obtained when moving of the upper die was carried out after reaching the maximum of internal pressure. Minimum of radius was formed at upper corner equal to 5.63mm and at lower corner equal to 5.62mm under internal pressure of 10MPa. Concavity of upper surface of part was decreased to 0.2mm by applying 10MPa internal pressure.