Papers by Keyword: Drilling

Abstract: The demand for mechanical fastening in composite materials is increasing due to their potential in large assemblies, aerospace and automotive industries. In practice, small components are integrated into large assemblies drilling holes in composite materials. Drilling defect free holes in composite presents many challenges during part assembly and services. This study presents the effects of cutting parameters used for drilling holes in glass fiber reinforced polymeric (GFRP) composites and hybrid fiber reinforced polymeric (HFRP) composites. Both the composites plates of 3 mm thickness were fabricated using a hand lay-up technique for the purpose of evaluating the effects of parameters on the quality of drilled holes. The holes were drilled using a 5 mm solid carbide twist drill at different spindle speed and feed rate. The quality of holes was assessed with respect to damage factor (F_d) and surface roughness (Ra) of the drilled holes. Results showed that the HFRP composite experienced lower damage factor (F_d) as compared to GFRP composite at lower feed rate or spindle speed. Scanning electron microscopic (SEM) examination revealed that the occurrence of delamination, fiber pull-out and matrix cracking was accelerated in the drilled holes at high spindle speed and feed rate.

Abstract: The purpose of this study was to find experimentally the effects of concave and convex major cutting edge (Helical & Recon point) and chisel point on the drilling composite. Due to composite materials are natural orthotropic, so gradually these materials are substituted by some metals such as steel that are used in manufacturing automobile and aerospace and other industris. Because of increasing composites utilization in industries, it is necessary to stabilize and set standards of machining parameters. Drilling is the main machining operation in producing process for assembled the composite work piece. So the quality of drilling hole should be considered to avoid snapping mechanical structure. Tool geometry is one of the most important factors in the drilling process. If it is neglected, the thrust forced increase, and it causes damage around the hole such as delamination, large entrance and exit burr, and induced cracks. The most damaging in drilling FRP is delamination of the composites lamina that occurs when drill bit is entered and exited. In the other hand, this study used ANSYS finite element software to determine the value of stress in composite plate and use to analyze for designing the jig & fixture in this drilling process. In conclusion, with comparing delamination, the best geometry tool introduced for the lowest amount of damage.

Abstract: Surface integrity of machined component is of major importance for the reliability and safety requirements during in service especially for the aerospace applications. This paper presents an investigation on the effect of drill geometry on the surface integrity of drilled hole of Ti-6AL-4V during drilling operation. Drilling experiments were conducted under the MQL using a special vegetable oil known as Jatropha oil. Experimental results revealed that drill point angle and coolant-lubricant conditions significantly influence the surface integrity which include surface roughness, micorhardness and microstructure defects. The surface roughness decreased with greater drill point angle. The subsurface deformation layer thickness was approximately 9 - 15 μm from the top of the machined surface. Microhardness profiles of the last hole indicated that the subsurface deformation extend up to a 150 to 200 μm until it reaches to the average hardness.

Abstract: Various kinds of damage may occur during the drilling of carbon fiber reinforced polymer composite (CFRP). To review the mechanism of CFRP drilling, a three-dimensional macro-mechanical finite element (FE) model was constructed for CFRP drilling based on FE software tool Abaqus. The workpiece was modeled as equivalent homogenous anisotropic material (EHAM) with elastic-failure behavior. Three-dimensional Hashin criterion was used to predict the material failure. The material was implemented in user subroutine VUMAT. The drilling process was analyzed and the thrust force with respect to cutting conditions was evaluated. The simulation shows that thrust force increase with feed rates while decrease with spindle speed, as agrees with experiment.

Abstract: In the specialized literature the cost of the machining process has been analyzed using a number of approaches and varying degrees of simplification to determine the optimum tool life and the tool speed. The accuracy of prediction is dependent on the degree of sophistication of the model. The purpose of this paper is the optimization of the cutting tool life and the cutting speed at the drilling of the stainless steels in terms of the minimum machining cost. A more comprehensive nonlinear programming model to minimize the total cost at the drilling of a stainless steel is developed in this paper. The optimum tool life and the associated tool speed are obtained by solving this model. The results can be taken into consideration in the educational studies and in the theoretical technical research. They can be implemented in the manufacturing activity.

Abstract: The research in the last decade regarding their cutting machinability have highlighted the insufficiency of the data for establishing of the optimum cutting processing conditions and the optimum cutting regime. The purpose of this paper is the optimization of the tool life and the cutting speed at the drilling of the stainless steels in terms of the maximum productivity. A nonlinear programming model to maximize the productivity at the drilling of a stainless steel is developed in this paper. The optimum cutting tool life and the associated cutting tool speed are obtained by solving the proposed mathematical model. The use of this productivity model allows greater accuracy in the prediction of the productivity for the drilling of a certain stainless steel and getting the optimum tool life and the optimum cutting speed for the maximum productivity. The obtained results can be used in production activity, in order to increase the productivity of the stainless steels machining. Finally the paper suggests new research directions for the specialists interested in this field.

Abstract: This paper presents a study on the influence of cutting parameters (Cutting speed and Feed rate) on drilling multi walled carbon nanotubes (MWCNTs) filled epoxy / glass fabric hybrid polymeric nanocomposite. For comparison neat epoxy / glass fabric polymeric composite was also fabricated. Drilling tests were carried out on these materials with HSS twist drill of diameter 6mm. Optimal cutting conditions were found using grey relational analysis by simultaneously considering the surface delaminations of the drilled holes at the entrance and exit sides. Surface delaminations of the drilled holes were quantified in terms of delamination factor. From the mean grey relational grades, it is observed that the multi walled carbon nanotubes (MWCNTs) has significant effect in improving the drilled hole quality. Mean grey relational grades of MWCNTs filled epoxy composite was found to be better than that of neat epoxy composite.

Abstract: The basic hypothesis of this article focuses on the study changes in deformation under the machined surface of stainless steels and steel C45 when drilling. The problem of drilling holes with diameter D=5 to 12.5 mm resides in the fact that 25 to 30% of these holes do not comply with prescribed requested requirements. This article presents the results of experiments focusing on the study of the damage process in helical drills with diameter d=8.0 mm when drilling into austenitic stainless steel DIN 1.4301 and steel C45. This study also includes an analysis of accompanying phenomena in the cutting zone by measuring some selected parameters.

Abstract: The content of this article also focuses on the analysis of the tool life of screw drills. This paper presents the conclusions of tests on a stainless steel DIN 1.4301.The results of the article are conclusions for working theory and practice for drilling of stainless steels. Based on the cutting tests, cutting speeds of 30 to 60 m/min, feed rate of 0.04to0.1 mm and screw drill carbide monolite.

Abstract: The paper shows an adaptive system for drilling. To drill diameter measure video optical method with USB camera was used. Rotation of drill tool was controlled using an inverter. Adaptive system was controlled by PC using special software made in C++.