عنوان مقاله :
مقايسه ي نظريه هاي مختلف پيش بيني شكست خستگي نمونه هاي فاق دار فولاد CK45
عنوان به زبان ديگر :
COMPARISON OF DIFFERENT THEORIES OF PREDICTING FATIGUE FAILURE OF NOTCHED CK45 CYLINDRICAL SPECIMENS
پديد آورندگان :
اميريان، جواد دانشگاه صنعتي اصفهان - دانشكده مهندسي مكانيك , شيراني، مهدي دانشگاه صنعتي اصفهان - پژوهشكده علوم و فنون زير دريا
اطلاعات موجودي :
دوفصلنامه سال 1396
كليدواژه :
فاق , عمر خستگي , شكست خستگي , فولاد CK45
چكيده فارسي :
شكست خستگي معمولاً در فاق موجود در سطح ماده - جايي كه به علت تمركز تنش، مقدار تنش افزايش يافته استٓ- رخ مي دهد. نظريه هاي مختلفي براي پيش بيني شكست خستگي نمونه هاي فلزي فاق دار ارائه شده است. اين نوشتار به ارزيابي نظريه هاي مختلف پيش بيني شكست خستگي نمونه هاي فاق دار فولادي براساس قابليت پيش بيني آنها مي پردازد. آزمايش هاي تجربي كششي ساده و خستگي از نوع خمش چرخان روي نمونه هاي استوانه يي ساده و فاق دار فولاد 45C K انجام شده و مشخصات مكانيكي و هم چنين نمودار تنشٓـ عمر نمونه ي ساده و نمونه هاي فاق دار به دست آمده اند. نظريه هاي بيشينه تنش، نيوبر، پترسون، تغييرات تنش، فاصله ي بحراني و ضعيف ترين اتصال براي پيش بيني ضريب كاهش استحكام خستگي نمونه هاي فاق دار فولاد CK45 استفاده شده اند و نتايج اين نظريه ها با نتايج آزمايش مقايسه شده است. مقايسه ي نتايج نظري و آزمايشگاهي نشان داده كه نظريه ي ضعيف ترين اتصال نسبت به نظريه هاي كلاسيك از دقت بهتري برخوردار است.
چكيده لاتين :
Typically، fatigue failure of a component happens at a notch where the stress level rises because of the stress concentration effect. Notch is usually defined as a geometric discontinuity. Notch may be introduced either by design or by the manufacturing process. A hole in a component is an example of a design notch. Material and fabrication defects، such as weld defects، inclusions، casting defects، or machining marks، are notches which are introduced due to the manufacturing process. A variety of methods are available to predict fatigue failure of notched specimens. The purpose of the present investigation is to rank such methods according to their predictive capability. Tensile tests were conducted on CK45 steel specimens and mechanical properties and stress-strain curve were obtained. Rotating bending fatigue tests were performed at room temperature on smooth and notched cylindrical specimens، and S-N curves were obtained. To better investigate the notch-size effect on fatigue life of the cylindrical specimens، two different notch geometries were used. Based on the obtained experimental S-N curve for smooth specimens، fatigue strength reduction factor or fatigue life for notched specimens were predicted by Neuber، Peterson، maximum stress، critical distance (Point method، Line method، Area method) and weakest-link (Area method، Volume method) theories and comparison of experimental results were considered. The predictions by maximum stress and stress gradient methods were conservative، which is some consolation to engineering designers; nevertheless، the errors were high. Neuber، Peterson and critical distance methods are based on stress gradient in notch root radius and predictions by these methods were not accurate. Also، Peterson، Neuber and Stress gradient methods are not consistent with finite element results. The predicted fatigue strength reduction factors by weakest-link methods were the closest to the experimental results. Finally، the weakest-link theory is recommended in terms of predictive capability، availability of the required materials data، and the compatibility with FEA stresses to predict fatigue strength factor among the studied methods in this research
عنوان نشريه :
مهندسي مكانيك شريف
عنوان نشريه :
مهندسي مكانيك شريف
اطلاعات موجودي :
دوفصلنامه با شماره پیاپی سال 1396
