Prediction of Shearing and Ploughing Constants in Milling of Inconel 718

The present study proposes an integrated prediction model for both shearing and ploughing constants for the peripheral milling of Inconel 718 by using a preidentified mean normal friction coefficient. An equation is presented for the identification of normal mean friction angle of oblique cutting in milling. A simplified oblique cutting model is adopted for obtaining the shear strain and shearing constants for a tool of given helix angle, radial rake angle, and honed edge radius. The shearing and ploughing constants predicted from analytical model using the Merchant’s shear angle formula and the shear flow stress from the selected Johnson–Cook material law are shown to be consistent with the experimental results. The experimentally identified normal friction angles and shearing and edge ploughing constants for the Inconel 718 milling process are demonstrated to have approximately constant values irrespective of the average chip thickness. Moreover, the predicted forces obtained in milling aged Inconel 718 alloy are in good agreement with the experimental force measurements reported in the literature. Without considering the thermal–mechanical coupling effect in the material law, the presented model is demonstrated to work well for milling of both annealed and aged Inconel 718.

Mechanical characteristics of drum shearer with large mining height under oblique cutting

In order to study the dynamic characteristics of the shearer with large mining height of 8.8 m under Oblique cutting, the spatial mechanical model of the Shearer under oblique cutting was established, the angle between the drum and the working face, the load of the drum and the dynamic characteristics of the fuselage are analyzed by discrete element method and dynamics. The results show that the maximum feed rate of the front drum is 1940mm, the maximum feed rate of the back drum is 1570mm, and the angle between the front drum and the coal wall reaches a maximum of 8° at 64s, and the cutting resistance of the front drum reaches a maximum at 80s, and finally fluctuates up and down at 3.5×105N, the cutting resistance of the back drum increases with the cutting depth, and finally fluctuates up and down at 3.0×105N. The load of the front drum is 1.2 times of that of the back drum. In the process of Oblique cutting, the support force on the lower surface of the front sliding shoe increases by 3.5×105N, the support force on the lower surface of the rear sliding shoe decreases by 2.5×105N, the support force on the upper surface of the front guiding sliding shoe increases by 1.1×105N, and the support force on the upper surface of the rear guiding sliding shoe decreases by 2.3×105N, the whole machine has the tendency of forward turning and side turning to the coal wall. The average radial force between the front rocker arm and the fuselage pin is about 1.8×106N, the average radial force between the front cylinder and the fuselage pin is about 2.2×106N, and the average radial force between the rear rocker arm and the fuselage pin is about 8.0×105N, the average radial force between the rear cylinder and the PIN shaft is about 1.3×106N, which shows that the radial force at the front of the fuselage, the rocker arm and the height of the pin shaft is obviously larger than that at the rear of the fuselage. The research results are important for the design and development of large mining height shearer.

An Oblique Cutting Based Mechanical Model For Insertion Torque of Dental Implant

The insertion torque of a dental implant is an important indicator for the primary stability of dental implants. Thus, the preoperative prediction for the insertion torque is crucial to improve the success rate of implantation surgery. In this present research, an alternative method for prediction of implant torque was proposed. First, the mechanical model for the insertion torque was established based on oblique cutting process. In the proposed mechanical model, three factors, including bone quality, implant geometry and surgical methods were considered by defined bone-quality coefficients, chip load and insertion speeds, respectively. Then, the defined bone-quality coefficients for cancellous bone with the computed tomography (CT) value of 235~245, 345~355 and 415~425 Hu were obtained by a series of insertion experiments of IS and ITI implants. Finally, the insertion experiments of DIO implants were carried out to verify the accuracy of developed model. The predicted insertion torques calculated by the mechanical model were compared with that acquired by insertion experiments, which were agreed match with the relative error less than 15%. This method reduces the time consumption on establishing the fitting equations for different implants and enhance the predicted accuracy by considering the effects of implants’ geometries and surgical methods.

Modeling Dynamic Stability and Cutting Forces in Micro Milling of Ti6Al4V Using Intermittent Oblique Cutting Finite Element Method Simulation-Based Force Coefficients

Tool breakage is a significant issue in micro milling owing to the less stiffness of the micro tool. To cope up with such limitation, precise predictions of dynamic stability, and cutting force have the utmost importance to monitor and optimize the process. In this article, dynamic stability and cutting force are predicted precisely for micro milling of Ti6Al4V by obtaining force coefficients from a novel 3D intermittent oblique cutting finite element method (FEM) simulation considering the influence of tool run out. First, the stability model is modified by incorporating the appropriate values of limiting angles obtained analytically accounting the trajectories of the flutes due to tool run out. This stability model is utilized to select chatter-free parametric combinations for micro milling tests. Next, an improved cutting force model is developed by incorporating the force coefficients obtained from oblique cutting simulation in the mechanistic model and differentiating the whole machining region into three distinct region considering size effect. The force model also considers the effect of increased edge radius of the worn tool, run out, elastic recovery, ploughing, minimum undeformed chip thickness (MUCT), and limiting angles, cumulatively. The proposed dynamic stability and cutting force models based on the oblique cutting simulation show their adequacy by predicting the stability limit and cutting force more precisely, respectively, as compared to those obtained by orthogonal cutting simulation. Besides, the proposed force model for the worn tool is found to be viable as it is closer to the experimental forces, whereas force model without the incorporation of tool wear underestimated the experimental forces.