Arif Gok

Three-dimensional finite element model of friction drilling process in hot forming processes:

Friction drilling processes are used commonly in hot forming operations. This process is similar to drilling processes but without using chip. This process is used especially for joining thin-walled metal components. In this study, the drilling process using centerdrill is investigated both experimentally and numerically. The finite element analyses (FEA) were conducted using deform-3D software based on finite element method (FEM). In this study, an analytic model is developed, which calculate the process parameters as torque and axial power, heat transfer coefficient. A comparison was also made for temperature, torque and axial force obtained from experimental and numerical analyses. At the end of the study, while the torque and axial force values decrease with increasing of spindle speed, temperature values of centerdrill and workpiece increase with increasing of spindle speed. A good consistency between both experimental and FEA simulations was found during the centerdrill process.

Three-dimensional finite element modeling of effect on the cutting forces of rake angle and approach angle in milling

In this study, milling operations were carried out using AISI 1040 specimens steel in dry cutting conditions. The cutting tools used in the experiment include P20 tool steel and they also have three different approach angles (45°, 60°, 75°) and rake angles (0°, −6°, −12°). In milling experiments, cutting parameters with a depth of cut of 1.5 mm, cutting speed of 193 m/min, and feed rate of 313 mm/min were selected. A comparison was presented between the force values which were obtained by measured value and predicted with numerical simulations, and then a good agreement was found between measured and predicted force values. As result of, it was observed that the rake and approach angles were effective in milling operations.

Comparison of effects of different screw materials in the triangle fixation of femoral neck fractures

In this study, biomechanical behaviors of three different screw materials (stainless steel, titanium and cobalt–chromium) have analyzed to fix with triangle fixation under axial loading in femoral neck fracture and which material is best has been investigated. Point cloud obtained after scanning the human femoral model with the three dimensional (3D) scanner and this point cloud has been converted to 3D femoral model by Geomagic Studio software. Femoral neck fracture was modeled by SolidWorks software for only triangle configuration and computer-aided numerical analyses of three different materials have been carried out by AnsysWorkbench finite element analysis (FEA) software. The loading, boundary conditions and material properties have prepared for FEA and Von-Misses stress values on upper and lower proximity of the femur and screws have been calculated. At the end of numerical analyses, the best advantageous screw material has calculated as titanium because it creates minimum stress at the upper and lower proximity of the fracture line.Graphical Abstract

The Effect on the Cemented Carbide Cutting Tool of Austempering Process

Austempered ductile irons (ADI) have been developed for an increasing number of the engineering applications such as crankshaft, gears, and other mechanic equipments because of its combination of strength and toughness. Therefore, austempering process has important effects on the mechanical properties of ADI. In this study, we have investigated the effect of austempering process on the cutting tool stresses. The cutting forces (main cutting force, feed force and thrust force) obtained from experimental studies have been applied to rake face, main cutting edge, auxiliary cutting edge on the cutting tool, and then the stresses (von-Mises, shear stress, normal stresses in the X, Y and Z directions) occurred on the cutting tool has been analyzed based on finite element method using ANSYS Workbench commercial software. It is also observed that analytical process of Frocht for the stresses on cutting tool tip. The results obtained show that the austempering process is the significant factor affecting cutting tool stresses.

NUMERICAL ANALYSIS OF TEMPERATURE, SCREWING MOMENT AND THRUST FORCE USING FINITE ELEMENT METHOD IN BONE SCREWING PROCESS

In this study, the bone screwing process carried out with M3.5 cortex screw for stabilization after reduction of femur shaft fracture was investigated both experimentally and numerically. The numerical analyses were performed based on the finite element method using Deform-3D software. The friction, material model, the loading and boundary conditions were exactly identified for finite element analyses. An analytic model and software were developed, which calculate the process parameters such as screwing power and thrust power, heat transfer coefficients in order to determine the temperature distributions occurring in the screw and bone material (sawbones) during screwing process. As a result, the screwing moment and thrust force values decrease with increasing of spindle speed. On the contrary, temperature values of screw and sawbones increase with increasing of spindle speed. A good consistence between the results obtained from both experimental and numeric simulations was found during the bone screwing process.

Response concerning ‘Letter to editor’ by Ni et al. (2017), Arch Orthop Trauma Surg. DOI 10.1007/s00402-017-2710-2

1. Gok K, Inal S, Gok A, Gulbandilar E (2017) Comparison of effects of different screw materials in the triangle fixation of femoral neck fractures. J Mater Sci Mater Med 28(5):81 2. Ni J, Wang X, Yuang Y, Liu H, Zhou L (2017) Letter to the editor concerning ‘‘Femoral neck fracture osteosynthesis by the biplane double-supported screw fixation method (BDSF) reduces the risk of fixation failure: clinical outcomes in 207 patients’’ by Filipov O, Sommer C et al (2017). Arch Orthop Trauma Surg. doi:10.1007/s00402-017-2710-2 3. Gok K, Inal S (2015) Biomechanical comparison using finite element analysis of different screw configurations in the fixation of femoral neck fractures. Mech Sci. 6(2):173–179. doi:10.5194/ ms-6-173-2015 Dear Editor,

Determination of experimental, analytical, and numerical values of tool deflection at ball end milling of inclined surfaces

The deflections appeared by cutting forces in ball end milling of inclined surfaces can result in defects in workpiece. Finding deflection values has a significant importance for keeping the production within the appropriate tolerances and in lessening production costs. The aim of this study was to evaluate tool deflection values experimentally, analytically, and numerically depending on cutting force in ball end milling of inclined convex and concave surfaces of DIN 1.2344 using TiN-coated cutting tool. The experiments were conducted with different cutting tools strategies and cutting parameters at related parameter levels. During machining, real time cutting tool deflections were recorded by inductive sensors for the experiments. In analytical studies, tool deflections were calculated depending on cutting force using cantilever beam method. In numerical studies, the solution was made with the finite element method. In the implementation of this method, commercial finite element software ANSYS was used. As a result, the values of tool deflections measured experimentally were found to match closely with analytical and numerical studies. The most effective parameters within the selected cutting parameters for both inclined surfaces were found step over and feed rate. At the same time, the measurement of dynamic deflection with inductive sensors was found to be beneficial for three-axis milling operations.