Depth Of Workpiece Research Articles

Temperature measurement methods in an experimental setup during bone drilling: A brief review on the comparison of thermocouple and infrared thermography

Predicting thermal response in orthopedic surgery or dental implantation remains a significant challenge. This study aims to find an effective approach for measuring temperature elevation during a bone drilling experiment by analyzing the existing methods. Traditionally thermocouple has frequently been used to predict the bone temperature in the drilling process. However, several experimental studies demonstrate that the invasive method using thermocouple is impractical in medical conditions and preferred the thermal infrared (IR) camera as a non-invasive method. This work proposes a simplified experimental model that uses the thermocouple to determine temperature rise coupled with the thermal image source approach. Furthermore, our new method provides a significant opportunity to calibrate the thermal IR camera by finding out the undetected heat elevation in a workpiece depth.

Numerical modelling of residual stresses during orthogonal cutting of Ti6Al4V using internally cooled cutting inserts

Residual stress has an adverse effect on the fatigue strength of machined components. The parts used in high end industries like aerospace and automobile sector needs to be carefully examined for the residual stress development during machining process. In this paper, both thermal and mechanical effects have been taken into account to predict the residual stress in workpiece while machining using internal cooled cutting inserts. The internal cooling system has now a days being used as an advanced cooling system for Ti and Ni based materials. In the present paper, Oxley’s model for slip line theory and contact theory using McDowell’s hybrid method have been used to predict the forces and residual stress respectively. The effect of change in the flow of lubricant from laminar to turbulent in internal channel of cutting insert has also been analysed. It has been found analytically that the cutting force of 761 N during dry turning is decreased to 511 N and 494 N in case of laminar and turbulent flow respectively. Besides this, the generation of compressive residual stress is found at the surface layer of machined specimen for internally cooled cutting inserts. The maximum compressive stress of 150 MPa at 0.03 mm depth of work piece has been found in case of laminar flow and 100 MPa for the turbulent flow.

Estimation of Frictional Coefficient between Punch and Billet at Back-Stroke in Backward Can Extrusion Test of Steel

A backward can extrusion test provides severe tribological conditions because high pressure, high temperature, and large surface expansion ratio affect the lubricant. During the forward stroke these conditions intensify with increasing cup depth of the extruded workpiece; additionally, the back-stroke force during retraction of the punch rises to a significant level under a poor-lubricated condition. This study estimates the coefficient of friction μp between punch and workpiece during the back-stroke by combining experiments using conventional soap-phosphate coated steel and numerical analysis by FEM. The values of μp were estimated to be 0.09 and 0.03 in case of small and large workpiece depth, respectively. Friction decreased with elevating temperature.

Study of Metal Strained State During Workpiece Reduction in a Three-Roll Screw-Rolling Mill

Results are given for a study of metal deformation state with screw rolling in a three-roll mill by means of computer modeling. Quantitative characteristics are obtained for the unequal distribution of degree of deformation through a workpiece cross section. Features are established for the use of screw line pitch length, partial reduction, and penetration index for the plastic deformation zone to workpiece axis in relation to screw line pitch number. Recommendations are given according to which in calculating roll calibration the roll profi le should be selected so that deformation penetrates the whole workpiece depth over the whole deformation site length.

Discrete Element Method Simulation of Residual Stresses in Grinding of Granite with Single Diamond Grain

The discrete element model and the model of single diamond grain grinding process of granite were constructed through numerical simulation and calibration of mechanical properties. Based on the models, the grinding processes of granite was dynamically simulated, and the effects of different rank angles, grinding speeds and cutting depths on the distribution of residual stresses as the depth of workpiece were also analyzed. The results show that the residual stress in the workpiece is relatively small after grinding when the tool rank angle lays in a small negative (-200 to 00). Otherwise, when the tool rank angle is too large or too small, there is a significant residual stress. The residual stresses in the workpiece increase with the increase of grinding speed and cutting depth. The residual stress nephogram was accomplished and the generated mechanism of residual stress was also analyzed. The results proved that the discrete element method (DEM) is an effective way to analyze the residual stress

Research on Thin Aspheric Surface Machining Using Elastic Deformation Molding Method

A novel aspheric surface machining method, elastic deformation molding method, is proposed. Based on the linear elasticity of optical glass and the optical replication mechanism, the new method can convert complicate aspheric surface machining to simply flat surface machining, which is suitable for the machining of thin aspherical component with large curvature radius. The basic principle of the new method is described. Then taking a paraboloid with a diameter of 40 mm and a curvature radius of 2 500mm as the target machining profile, the minimum material removal depth of workpiece that ensures the close attachment between workpiece and mold is determined by finite element simulation. The material removal model of the proposed method is established and the machining time is calculated. A machining experiment is then carried out on a built elastic deformation molding machining system, and the validation of established material removal model is verified. A parabolic surface with form accuracy of PV 0.62 μm is obtained. The influencing factors of machining form accuracy are analyzed and measures to improve the machining form accuracy in the future work are put forward.

Influence of Worn Tool on Polishability and Wear Resistance of VP20ISO Mold Steel

The aim of this study was to evaluate the influence of tool flank wear on polishability and wear resistance of mold steel. Two surfaces of Villares VP20ISO steel were machined, one was roughed with worn tools (VB>0.3 mm) and another one with new tools (0.05 mm<VB<0.1 mm), followed by the finishing process of both surfaces by machining with new tools. The surface residual stresses were then measured using the X-ray diffraction method. Surfaces were etched down to different depths in order to monitor the residual stresses in the total affected depth of workpiece deformed layer. The results show that the cutting and passive forces provided the major differences between two machining conditions. The micro-hardness in the cross section did not show significant differences. Moreover, the residual stress measurements showed that after the finishing process, the surface roughed with new tools exhibited 100 MPa compressive stresses at 35 mm below the surface, while the surface roughed with worn tools provided a valley of tensile stress from the surface. Tests conducted on a pin-on-disk tribometer showed that the wear rates of the surface roughed with new tools were lower than the one roughed with worn tools and, after the polishing process, that the surface finishing of the surface roughed with new tools was better.