Damage mechanics is one of the most important parts of mechanical engineering that determines the time life for different mechanical elements. The most various models that have been provided so far in damage mechanics, are related to ductile or brittle damage. Nowadays, the investigation of materials by ductile-brittle damage behavior has been considered by researchers. Kintzel quasi-brittle damage model is one of the best damage models in this field. Therefore, in this paper, due to the application of 2024 Al alloy in different industries especially aerospace and the ductile-brittle damage behavior of this alloy, the implementation of the Kintzel quasi-brittle damage model is presented. For this purpose, by writing an explicit user subroutine VUMAT in finite element software (ABAQUS), a test sample under periodic loading has been modeled. The results of this research showed that the complete failure occurs after the 12th cycle under a periodic loading. Also, 2024 Al alloy showed a good ultimate tensile strength (about 400 MPa) under periodic loading. The magnitude of ductile and brittle damage variables are 0.23 and 0.38, respectively. Manuscript profile

Nowadays, different industries are using sheets, plates, and shells as important parts of their components. Because of their small thickness compare to other dimensions, their structural safety requires more attention. Therefore, increasing their strength and intensifying their resistance against any kind of failure type could be introduced as an important problem for enhancing the structural safety. Buckling is one of the most significant failure type that should be considered in the stability of any parts such as sheet metals. Thus, investigation of the buckling capacity of the sheet metals is remarkable. On the other hand, the existence of discontinuity like holes and notches in sheet metals can decrease their buckling capacity, significantly. In current study, based on Finite Element Method (FEM), ABAQUS/Explicit has been employed to determine the elastic buckling capacity in a perforated rectangular sheet metal with different boundary conditions on its edges. Afterward, the effect of the hole position and the plate aspect ratios (plate length/plate width) on the buckling capacity of sheet metal was studied. Finally, in order to enhance the sheet metal buckling capacity, two different types of stiffeners were used. The outcomes showed that the maximum buckling coefficient is related to the sheet metal which have four clamped edges. Moreover, For all boundary conditions, the buckling coefficient does not change significantly for the sheet metals with aspect ratio of more than 4. Also, stiffener type 2 increased the buckling capacity of sheet metal up to 83%. Manuscript profile

Joints are considered the weakest part of an engineering structure and failure usually occurs in this region, firstly. One of the main factors in the rupture of adhesive joints is the normal stresses between the layers created by the presence of an out-of-center load and bending moment. The present research work has focused on the influence of parameters including the adhesive zone length, adhesive and adherend layer thickness on reducing the amount of normal interlayer stress in a single-lap adhesive joint. Optimization of parameters have been done using BA and PSO optimization algorithm. The distribution of normal and shear stresses are based on two-dimensional elasticity theory that includes the complete stress-strain and strain-displacement relations for the adhesive and adherends. The results obtained from current research revealed that by optimization of mentioned parameters, the value of peeling stress is significantly reduced. Although increasing in Young’s modulus of adhesive layer leads to an increase in normal stress of the joint, it creates a more uniform stress distribution at the edges. The outcomes also revealed that increasing the length of the joint zone and the thickness of adherends can improve the interlayer normal stress in the adhesive joint. Manuscript profile

در این تحقیق، کمک فنر الکترومغناطیسی به مدل یک چهارم خودرو با دو درجه آزادی و مدل یک دوم خودرو با چهار درجه آزادی اضافه شده است. در ادامه، با استفاده از الگوریتم بهینه‎سازی زنبورعسل در دو مرحله، مدل شبیه سازی شده، بهینه شده است. در مرحله اول، فقط ثوابت کمک فنر الکترومغناطیسی بهینه شده و پارامترهای سیستم تعلیق ثابت فرض گردیده است. در مرحله دوم، علاوه بر ثوابت کمک فنر الکترومغناطیسی، پارامترهای سیستم تعلیق نیز مورد بهینه سازی قرار گرفته که در هر دو مرحله، مقادیر پارامترهای بهینه شده از اعمال ورودی ترکیبی شامل ده ورودی سینوسی با دامنه های مختلف و یک ورودی پله واحد به دست آمده و در نهایت با استفاده از این مقادیر، میزان انتگرال قدر مطلق خطا نسبت به چند حالت ورودی محاسبه شده است. برای تعیین تابع هدف در بهینه سازی انجام شده از انتگرال قدر مطلق خطا استفاده شده که هدف، کمینه سازی سطح زیر نمودار (جابه جایی خودرو) می باشد. نتایج نشان داد که مقادیر تابع هدف در حالت دوم بهینه سازی نسبت به حالت اول کمتر بوده، به گونه ای که به عنوان نمونه در اثر اعمال ورودی سینوسی با دامنه 5 مقدار این تابع برای مدل یک چهارم و یک دوم خودرو در حالت اول بهینه سازی به ترتیب برابر 293/0 و 283/0 و در حالت دوم بهینه سازی به ترتیب برابر 261/0 و 255/0 است. Manuscript profile