Mixed-mode (I/II) rupture assessment of rubber-like materials weakened by cracks using the averaged strain energy density criterion

In the present study, the application of the averaged strain energy density (ASED) criterion is extended from pure mode-I to mixed-mode (I/II) loading for hyperelastic materials. Indeed, the use of a recently proposed method by the present authors for determination of the critical values of strain energy density and radius of control volume in mode-I loading has been generalized to the mixed-mode loading conditions. The key point in the generalization is the almost uniaxial state of stress fields near the crack tip in rubber-like materials. To validate the accuracy of the criterion in mixed-mode (I/II) loading, a new set of experiments on rubbers weakened by cracks has been carried out. The experimental results confirm the accuracy of the ASED criterion in the case of cracked rubbers under mixed-mode (I/II) loading.submittedVersionThis is a submitted manuscript of an article published by Elsevier Ltd in Theoretical and applied fracture mechanics, 25 May 2017

Rupture analysis of rubber in the presence of a sharp V-shape notch under pure mode-I loading

The rupture behavior of styrene-butadiene rubbers (SBR) in the presence of a V-shape notch is investigated for the first time both experimentally and theoretically. In the experiments, V-notched samples of SBR are tested under tensile loading and their rupture displacements are determined. Afterwards and in the analytical field, the rupture loads of tested rubbers are predicted using the averaged strain energy density (ASED) criterion. The key idea of this criterion (i.e. the almost uniaxial state of stress field near the notch tip) is verified through non-linear finite element modeling. It is shown that good agreement exists between the predictions of the ASED criterion and the experimental results obtained for SBR. Moreover, the microscopic study of the ruptured surfaces of the notched SBR demonstrates its high roughness which can be attributed to the resistance of the rubber chains against the crack growth

Mixed-mode (I/II) rupture assessment of rubber-like materials weakened by cracks using the averaged strain energy density criterion

In the present study, the application of the averaged strain energy density (ASED) criterion is extended from pure mode-I to mixed-mode (I/II) loading for hyperelastic materials. Indeed, the use of a recently proposed method by the present authors for determination of the critical values of strain energy density and radius of control volume in mode-I loading has been generalized to the mixed-mode loading conditions. The key point in the generalization is the almost uniaxial state of stress fields near the crack tip in rubber-like materials. To validate the accuracy of the criterion in mixed-mode (I/II) loading, a new set of experiments on rubbers weakened by cracks has been carried out. The experimental results confirm the accuracy of the ASED criterion in the case of cracked rubbers under mixed-mode (I/II) loading

Rupture analysis of rubber in the presence of a sharp V-shape notch under pure mode-I loading

The rupture behavior of styrene-butadiene rubbers (SBR) in the presence of a V-shape notch is investigated for the first time both experimentally and theoretically. In the experiments, V-notched samples of SBR are tested under tensile loading and their rupture displacements are determined. Afterwards and in the analytical field, the rupture loads of tested rubbers are predicted using the averaged strain energy density (ASED) criterion. The key idea of this criterion (i.e. the almost uniaxial state of stress field near the notch tip) is verified through non-linear finite element modeling. It is shown that good agreement exists between the predictions of the ASED criterion and the experimental results obtained for SBR. Moreover, the microscopic study of the ruptured surfaces of the notched SBR demonstrates its high roughness which can be attributed to the resistance of the rubber chains against the crack growth.submittedVersionThis is a submitted manuscript of an article published by Elsevier Ltd in International Journal of Mechanical Sciences, 13 August 2018

Osteoporosis in Iran, Overview and Management

Osteoporosis is the most common metabolic bone disease. It is characterized by low bone mass and micro-architectural deteriora¬tion of bone tissue, leading to enhanced bone fragility and a consequent increase in fracture risk. Osteoporosis is an as¬ymptomatic disease and is an important public health issue because of its clinical expression in age-related fractures. In Iran it is estimated that the prevalence of osteoporosis among women who older than 50 years old is 6 percent which is less than other countries such as Canada and Japan. The estimated lifetime risk of hip fracture for white women at age 50 years is about 16 percent (versus five percent for men). The incidence of fall related hip fracture in Iran in 2003 in male and fe¬male was respectively 20.6 and 17.5 per 100,000 person-year which is increased significantly in old people. Nowadays, sev¬eral treatments are available and more are being developed. Currently available drugs are anti-resorptive which focus on decreas¬ing bone turnover. Newer therapies with the aim of increasing bone formation are being studied. This document out¬lines all aspects of osteoporosis "especially in Iran "including risk factors, diagnosis, prevention and treatment

Waist Circumference, Weight, and Body Mass Index of Iranians Based on National Non-Communicable Disease Risk Factors Surveillance

Background: Obesity is an important and life-threatening disease, associated with different chronic conditions such as cardiovascular disease, diabetes, and dyslipidemia. We sought to address the paucity of information on the trends of anthropometric indices such as weight, waist circumference, and body mass index in the adult population of Iran. Methods: We drew upon data from the First Non-communicable Disease Survey in Iran in 2005. In total, 79,611 participants between 20 and 64 years old were selected via the random multistage cluster sampling. The Lambda Median Scale method was applied to construct normal curves for anthropometric indices.Results: The mean of waist circumference in both genders increased with age and in all the age groups except those between 20 and 24 years old was higher in the women. The mean of body mass index was higher in all the age brackets in the women, but the means of weight and height were higher in the men. The association of theses indices with diabetes, hypertension, and dyslipidemia was stronger in men. Conclusion: The ranges of waist circumference and body mass index in Iranian population are different from those of other countries. The higher body mass index and waist circumference in females and the direct association between obesity and chronic diseases, is advisable that the effects of this phenomenon be fully investigated and due heed be paid to the importance of lifestyle modification

Learning Automata-Based Solutions to the Single Elevator Problem

The field of AI has been a topic of interest for the better part of a century, where the goal is to have computers mimic human behaviour. Researchers have incorporated AI in different problem domains, such as autonomous driving, game playing, diagnosis and security. This paper concentrates on a subfield of AI, i.e., the field of Learning Automata (LA), and to use its tools to tackle a problem that has not been tackled before using AI, namely the problem of the optimally scheduling and parking of elevators. In particular, we are concerned with determining the Elevators’ optimal “parking” location. In this paper, we specifically work with the Single (We consider the more complicated multi-elevator problem in a forthcoming paper.) Elevator Problem (SEP), and show how it can be extended to the solution to Elevator-like Problems (ELPs), which are a family of problems with similar characteristics. Here, the objective is to find the optimal parking floors for the single elevator scenario so as to minimize the passengers’ Average Waiting Time (AWT). Apart from proposing benchmark solutions, we have provided two different novel LA-based solutions for the single-elevator scenario. The first solution is based on the well-known LRI scheme, and the second solution incorporates the Pursuit concept to improve the performance and the convergence speed of the former, leading to the LRI scheme. The simulation results presented demonstrate that our solutions performed much better than those used in modern-day elevators, and provided results that are near-optimal, yielding a performance increase of up to 80%