تحلیل تجربی و عددی رشد ترک خستگی در پیچ‏ های کربونیزه شده سرسیلندر موتور بنزینی

نوع مقاله : پژوهشی کامل

نویسنده

استادیار، دپارتمان مهندسی مکانیک، دانشکده منتظری، دانشگاه فنی و حرفه‏ای استان خراسان رضوی، مشهد، ایران

چکیده

مطالعه در مورد رشد ترک خستگی پیچ‏های کربونیزه شده سرسیلندر موتور بنزینی در دو بخش تجربی و عددی انجام گردید. بخش تجربی مطالعه شامل تعیین ترکیب شیمیایی، خصوصیات کششی، سختی‏سنجی، بررسی ریزساختاری و بررسی سطح شکست بود. مشاهدات میکروسکوپی الکترونی روبشی (SEM) از سطح شکست، خستگی را به عنوان ‏‏عامل‏ اصلی شکست زودرس پیچ‏ها با عمر تقریبی 8^10×1.44 سیکل معرفی نمود. ترک از ناحیه لایه سطحی کربونیزه پیچ‏ها شروع شده است که ناخالصی‏ها‏ی ترکیبات اکسیدی و حفره به انتشار ترک تا شکست نهایی کمک کرده است. بخش عددی مطالعه شامل تحلیل تنش و رشد ترک خستگی بود. تحلیل تنش نشان داد که حداکثر تنش ایجاد شده در پیچ‏ها حدود 4% بیشتر از مقدار استاندارد می‏باشد. تمرکز تنش بالا در ناحیه رزوه یکی از عوامل جوانه‏زنی ترک می‏باشد که نیروی سیکلی فشار احتراق باعث گسترش ترک خستگی می‏گردد. همچنین تحلیل عددی خستگی نشان داد که وجود ترک به عمق 0.12 میلی‏متر منشاء شکست زودرس می‏شود. مقایسه دو بخش تجربی و عددی نشان داد که عمق ترک محاسبه شده با مشاهدات لایه اکسیدی میکروسکوپ‏های نوری و الکترونی روبشی مطابقت قابل قبولی دارند.

کلیدواژه‌ها

موضوعات


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