تحلیل ارتعاشات اجباری تیر ویسکوالاستیک تحت اعمال ناگهانی نیروی متحرک هارمونیک و جریان جرمی متحرک

نویسندگان

دانشکده مهندسی مکانیک دانشگاه صنعتی سیرجان

چکیده

در مقاله حاضر، رفتار دینامیکی تیر ویسکوالاستیک تحت تأثیر نیروی متحرک هارمونیک و جریان جرمی بررسی شده است. معادله حاکم بر حرکت، به­صورت نیمه­تحلیلی و با استفاده از روش گالرکین و رانگ­کوتای مرتبه چهار تحلیل شده است. نتایج این بررسی برای چهار شرایط مرزی مختلف، دوسرمفصل، دوسرگیردار، گیردار- مفصل و گیردار- آزاد به­دست آمده است. نیروی متحرک به­صورت سرعت یکنواخت، شتاب تندشونده و کندشونده و جریان جرمی با سرعت یکنواخت در نظر گرفته شده است. در این بررسی ابتدا تیر مستقیم بوده و در یک زمان خاص به یک­باره جریان جرمی و همچنین نیرو به­طور همزمان و غیرهمزمان بر تیر اثر می­گذارند و بعد از عبور نیرو از انتهای آن، تأثیر نیرو خارجی بر تیر حذف می­شود. در این بررسی تأثیر تغییرات پارامترهای مختلف از جمله نسبت جرمی، حالت­های مختلف حرکت، تأثیر زمان اعمال نیرو و جریان جرمی و تأثیر شرایط مرزی مختلف بر تغییر مکان تیر مورد مطالعه قرار می­گیرد. برای اعتبارسنجی مسئله از مقایسه پاسخ به­دست­آمده در غیاب جریان جرمی با پژوهش­های قبلی اسـتفاده شده است. همچنین، به­عنوان مقایسه­ای دیگر، نتـایج تغییر مکان به­دست­آمده در اینجا با نتایج حاصل از روش تربیع دیفرانسیلی تعمیم یافته (GDQ)، مقایسه شده و انطباق خوب جـواب­هـا مشاهده گردید.

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