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Assessment of Various Ductile Damage Criteria in Numerical Simulations of Machining Processes
Mojtaba Hejazi,Farhad Haji Aboutalebi 한국정밀공학회 2024 International Journal of Precision Engineering and Vol.25 No.1
In the machining processes, chip removal can be performed by the applied forces. Therefore, predicting the required forces and energy is an essential challenge to reach the efficient processes. In this research, employing various ductile damage models of the continuum damage mechanics (CDM), a few machining processes such as 3D plane machining, 3D drilling, and turning are numerically simulated. Using the numerical simulations of finite element method (FEM), variations of the applied forces on the workpiece and the maximum force as well as the mechanism of chip formation during the machining processes are estimated. Besides, to assess the ductile damage models, the numerical simulation results are compared with the experimental results. The comparison reveals that the Ayada, Ayada negative, and Johnson–Cook damage criteria can accurately predict the required forces and respectively are the reliable models for numerical simulations of chip removal in the machining processes.
Majid Emadi,Hamid Beheshti,Mohammad Heidari-Rarani,Farhad Haji Aboutalebi 대한기계학회 2019 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.33 No.5
Thin-walled aluminum tubes have been widely used in engineering structures, aerospace and transportation industries due to their excellent properties. In this paper, the effect of tempering and annealing on the crushing behavior of aluminum alloy tubes, in brittle or ductile manner, under quasi-static compression were investigated. The chemical composition, the Brinell hardness number and the tensile stress-strain curves of various types of Al alloys, i.e., Al 2024, Al 7075 and Al 6061 were obtained in both tempered and annealed state. Then, the axial compression tests were performed on the tubes by a universal testing machine at a controlled displacement rate of 5 mm/min. The crushing mode, load-displacement curve, and crashworthiness characteristics were achieved to obtain specifications of mentioned aluminum tubes. Annealing process, apart from changing the deformation mode and material strength, has often reduced energy absorption in the ductile alloy, Al 6061, and increased in brittle alloys, Al 2024-T3, T4 and Al 7075-T651. This process could also be used as a triggering mechanism to decrease the initial peak force. These experimental results give useful information regarding the material behavior of aluminum alloys to be utilized in the design process of crashworthy components.
Multi crack detection in helical gear teeth using transmission error ratio
Mohsen Rezaei,Mehrdad Poursina,Shahram Hadian Jazi,Farhad Haji Aboutalebi 대한기계학회 2019 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.33 No.3
Gear systems are used to transmit power in the industry when accuracy and synchrony are needed and helical gear systems are used in more accurate and high-speed industries. It is important to ensure that these systems work faultlessly, therefore the detection of the crack location and situation is very efficient in the gear systems. In this research, a new approach is proposed to detect the multi crack location and length in the helical gear teeth. To this end, after giving an explanation of helical gear mesh stiffness and demonstrating the helical gear pair dynamic modeling, the transmission error ratio method is used to detect the cracks locations and lengths. Then, according to solved examples, when the cracks locations are far enough that their effects on the transmission error are completely separated, the cracked teeth and the lengths of cracks can be detected exactly, and when the cracks are in adjacent teeth, according to the cracks lengths and depths and their effects overlap, the number of cracks and their lengths can be detected exactly, approximately or absolutely undetectable.
Mohsen Rezaei,Mehrdad Poursina,Shahram Hadian Jazi,Farhad Haji Aboutalebi 대한기계학회 2018 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.32 No.8
Time-dependent mesh stiffness is a most important reason of vibration and dynamic excitation in gear sets. In this research, analytical formulas of the helical gear set and the planetary gear system are combined to calculate the time-dependent mesh stiffness of the helical planetary gear system. For this purpose, at the first step, the analytical equations are derived for the spur gear pair. Then by dividing a helical tooth into the several independent thin spur tooth slices, the helical gear pair mesh stiffness is extracted. Finally, these equations are extended to the helical planetary gear system. The suggested analytical results and those which obtained by the finite element method (FEM) are compared and are in good agreement when the helix angle is less than 15 degrees. Also, the helical planetary gear system mesh stiffness in different cases such as fixed carrier, fixed sun gear and fixed ring gears is calculated. These results show that the value of mesh frequency ratio in each case scales the mesh stiffness shapes in the rotation angle direction. In other words, mesh frequency ratio parameter determines the number of meshing period in each rotation of planets.