مهندسی مکانیک مدرس

مهندسی مکانیک مدرس

بررسی تجربی و عددی خواص کششی و شکل‌پذیری ورق فولادی St14 در شکل‌دهی ضربه‌ای با نرخ کرنش متوسط

نوع مقاله : پژوهشی اصیل

نویسندگان
گروه مهندسی مکانیک، دانشکده مهندسی، دانشگاه بوعلی‌سینا، همدان، ایران
چکیده
با توجه به گسترش روزافزون استفاده از پرس‌های پرسرعت مثل سروو پرس‌های سرعت بالا در صنعت خودروسازی، بررسی شکل‌پذیری ورق‌های فلزی در این محدوده سرعت شکل‌دهی ضروری به‌نظر می‌رسد. بنابراین، این تحقیق با هدف بررسی اثر شکل‌دهی در نرخ کرنش متوسط بر شکل‌پذیری ورق فولادی St14 انجام شده‌است. آزمایش کشش در نرخ‌های کرنش مختلف انجام شد و آزمایشهای شکل‌پذیری برای ایجاد منحنی‌های حد شکل‌دهی، در شکل‌دهی شبه‌‌استاتیک و شکل‌دهی ضربه‌ای صورت گرفت. جهت استخراج منحنی حد شکل‌دهی عددی، از شبیه‌سازی اجزای محدود استفاده شد. مدل مادی با در نظر گرفتن اثر نرخ کرنش توسط زیربرنامه ویوهارد وارد شبیه‌سازی شد. نتایج آزمایش کشش نشان داد که با افزایش نرخ کرنش، چند شاخص مهم کرنش سختی کاهش می‌یابد. هم‌چنین، رفتار کششی در نرخ‌های کرنش مختلف توسط مدل مادی با دقت خوبی پیشبینی شد. در شکل‌دهی ضربه‌ای، به‌دلیل تغییر شرایط اصطکاکی، شکست و تمرکز کرنش به مرکز گنبد منتقل شد و ارتفاع گنبد در حالت کشش دومحوره 17/1% نسبت به شکل‌دهی شبه‌استاتیکی کاهش یافت. منحنی حد شکل‌دهی در شکل‌دهی ضربه‌ای در مقایسه با شکل‌دهی شبه‌استاتیک به‌طرف پایین و سمت راست نمودار حد شکل‌دهی جابجا شد. در شکل‌دهی ضربه‌ای، حد شکل‌دهی در حالت کرنش صفحه‌ای در مقایسه با شکل‌دهی شبه‌استاتیکی، 8/1% کاهش یافت. هم‌چنین، نتایج شبیه­‌سازی شامل موقعیت شکست، منحنی حد شکل‌دهی و ارتفاع گنبد در هر دو روش شکل‌دهی انطباق خوبی با نتایج تجربی داشت.
کلیدواژه‌ها

موضوعات


عنوان مقاله English

Experimental and numerical investigation of tensile properties and formability of St14 steel sheet at medium strain rate via impact forming

نویسندگان English

Ahmad Amini
َََAli Alavi Nia
Department of Mechanical Engineering, Bu-Ali Sina University, Hamedan, Iran
چکیده English

Considering the increasing use of high-speed presses, such as high-speed servo presses, in the automotive industry, it seems necessary to investigate the formability of sheet metals in this range of forming speed. Therefore, this study has been conducted to investigate the effect of medium strain rate forming on the formability of the St14 steel sheet. Tensile tests were done at various strain rates, and formability tests were performed to create forming limit curves at the quasi-static and impact forming. Finite element simulation was used to extract the numerical forming limit curves. The material model was entered into the simulation by considering the strain rate effect using the VUHARD subroutine. The results of tensile tests showed that some influential strain-hardening indicators reduce with strain rate enhancement. Also, using the material model, the tensile behavior was predicted with good accuracy at each strain rate. In impact forming, fracture and strain concentration was transferred to the dome center, and the dome height in biaxial stretching was reduced by 17.1% compared to quasi-static forming due to the variation of frictional conditions. The forming limit curve of impact forming was shifted to the lower values and right side of the forming limit diagram compared to quasi-static forming. In impact forming, the forming limit in plane-strain condition was reduced by 8.1% compared to quasi-static forming. Also, the simulation results, including fracture position, forming limit curve, and dome height in both forming processes, were in good agreement with the experimental results.

کلیدواژه‌ها English

Tensile properties
formability
Forming limit curve
Medium strain rate
Impact forming
St14 steel
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