جستجوی مقالات مرتبط با کلیدواژه « rotational speed » در نشریات گروه « مکانیک »

To fix the femoral neck fracture using screws, there are different opinions among orthopedic surgeons about screw placement. Also, the parameters of bone drilling, including the angle of the drill tip and the rotational speed of the drill, can also have an effect on the fixation strength. In this research, experimentally and with the help of simulation, the effect of three types of arrangement including triangle, inverted triangle and linear, and parameters of rotational speed and angle of the drill tip on the strength of femoral neck fracture fixation has been investigated for the first time. In experimental tests, the maximum force tolerated by for the inverted triangle arrangement is 25% and 37% higher than the triangle and linear arrangements, respectively. The rotational speed of the drill 2000 rpm compared to 1000 rpm and the tip angle of the drill 60° compared to 118° have increased the connection strength by 11 and 7.5 percent, respectively. The analysis of variance showed that the effect of the type of screw arrangement, respectively. the rotational speed of the drill and the angle of the drill tip on the fixation strength is 83.26, 6.98 and 3.24%, respectively. The results obtained from the numerical simulation showed that the proper arrangement is the inverted triangle with the drilling parameters of the rotational speed of the 2000 rpm and the tip angle of the 60°, which has endured N4782 force.

In general, rotating objects always produce different rotational torques according to different dimensions and rotational speeds. In some cases, it can cause a lot of damage to equipment, so it is necessary to be aware of the amount of torque that rotating objects produce at different rotational speeds, as well as in the presence or absence of air flow. in this study, numerical and experimental analysis of non-continuous flow around a cylindrical model with vertical plates under forced rotation is performed and its main purpose is to measure the torque of rotating objects in the presence of wind current also to stabilize rotation. Rotational speeds are constant. First, an aerodynamic torque measuring device was built and then a 3-fin cylindrical model was tested in a wind tunnel, and numerical simulations of 3 and 2 fin models were performed in the same laboratory conditions by Ensys Fluent software. A good agreement was observed between the experimental and numerical results and the maximum error between them was less than 10%, which is acceptable. From the simulation results, it was observed that in every 180 degrees of rotation that the maximum cross section of the models is exposed to direct wind flow, the maximum torque produced by the 2-blade cylindrical model is 30% higher than the maximum torque produced by the 3-blade model. As the wind speed increases from 20 to 60 meters per second, the torque of the 3-fin model increases from 0.4 to 1.2 Nm, which is equivalent to 200%.

Polishing using nanoscale magnetic field (NMAF) is a new method for surface coating with nanoscale roughness as a mechanical process and is done by abrasive powder abrasion as a tool. The force required to move the abrasive particles is provided by a magnetic field that has a relative motion to the workpiece. This method can be used for polishing non-magnetic metal parts or non-metallic parts. One of the special features of this method is the reduction of thermal stresses to the workpiece and the lack of restrictions on polishing surfaces of the workpiece, which due to their geometric shape, the ability to work with conventional tools is difficult. Such as polishing of superalloys and hard metals, as well as for surfaces with special forms that can not be achieved by other methods to an acceptable level of smoothness. In this paper, using the nano-polishing mechanism, the polishing of cylindrical external surfaces of Inconel superalloy is investigated, so that the surface quality is improved at the nanoscale. To create a magnetic field, variable magnets with the ability to adjust the current intensity of the magnetic field have been used. In this research, aluminum oxide and silicon-carbide abrasive particles have been used and their combination.

Single point incremental forming is one of the novel processes in forming of metallic sheets that has created high forming levels in sheet by local plastic deformation. In this paper, new tool based on incremental forming principles is introduced for production of cylindrical flange. Using this tool for forming of the flange, the manual milling machine is used instead of milling machine equipped with computer numerical control (CNC). Forming of flange wall is accomplished by a new tool that includes two forming punches. Tool shank is fixed on milling machine spindle and the value of eccentricity determines the final diameter of flange. Movement of rotary tool is simple and downward with defined step. The results show that flanges with specified diameters can be formed by using this method very fast. Increasing the diameter of the primary hole created on the sheet increases the flange height but also increases the thinning. Increasing rotational speed results in forming flanges with higher height but increasing vertical feed rate of tool decreases the flange height.