The influence of the machining parameters on the dust size and temperature generated during trimming of CFRP has not yet been fully understood. This paper investigates the influence of tool geometry ...and cutting conditions on surface defects and the dust generated during trimming. It was observed that these defects predominantly occurred due to cutting conditions and tool geometry. The defects seemed to increase with an increase in feed speed or decrease of cutting speed in case of burr tool. However, the effects of the cutting parameters were completely different considering the 4 flute end mill. The dust generated during trimming is found to be dependent on tool geometry, cutting conditions and the range of cutting speed. The dust adherence on to the machined surfaces was observed during high speed trimming and this can be attributed to high cutting temperatures around the glass transition temperature.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Cutting forces are critically important in cutting operations because they correlate strongly with cutting performance such as surface accuracy, tool wear, tool breakage, cutting temperature, ...self-excited, and forced vibrations. The drilling operation of titanium alloys is considered by manufactures as complex and difficult in view of the mechanical and thermal properties of this material. In fact, titanium has a very small coefficient of conduction which leaves a high temperature at the area of contact between the tool and the workpiece, which decreases the cutting forces and increases the wear of the tool. For this, more research has focused on the prediction of cutting forces during the drilling of titanium in order to improve the machinability of this material as well as the wear of the tool. Many efforts have been made by researchers to better understand the drilling process and to formulate theoretical cutting forces models to predict and to simulate the phenomenon. This paper presents a numerical model for prediction of cutting forces and torque during a drilling operation including the effect of the regenerative chatter and of the cutting process damping. The corresponding algorithm allows understanding the interaction between the tool and the workpiece and identifying numerically the three-dimensional evolution of the cutting force components and cutting torque generated by the drilling process of a titanium alloy. Verification tests are conducted on a vertical machine for titanium alloy Ti6Al4V and the effectiveness of the model and the algorithm is verified by the good agreement of simulation result with that of cutting tests under different cutting conditions.
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DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, SIK, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
High speed machining is now acknowledged to be one of the key manufacturing technologies to ensure high productivity and throughput. Drilling of CFRP, though a challenging task, is being performed ...successfully at low spindle speeds. However high speed drilling in CFRP thin laminates has not been explored much. This paper reports an experimental investigation of a full factorial design performed on thin CFRP laminates using K20 carbide drill by varying the drilling parameters such as spindle speed and feed rate to determine optimum cutting conditions. The hole quality parameters analyzed include hole diameter, circularity, peel-up delamination and push-out delamination. Analysis of variance (ANOVA) was carried out for hole quality parameters and their contribution rates were determined. Genetic Algorithm (GA) methodology was used in the multiple objective optimization (using MATLAB R2010a software) to find the optimum cutting conditions for defect free drilling. Tool life of the K20 carbide drill was predicted at optimized cutting speed and feed.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Inconel 718 (IN718) is a precipitation hardened nickel-base super-alloy exhibiting high strength and good corrosion resistance at elevated temperatures and on the downside; it is characterized by ...poor machinability. Abrasive water jet (AWJ) process offers a potential method to machining difficult-to-cut materials such as IN718. The present work investigates the influence of AWJ parameters on surface roughness, topography, depth of cut, and residual stress when milling IN718. Surface characterization was conducted through 3D optical microscopy and SEM techniques. Residual stresses were measured in longitudinal and transverse directions with respect to the machining path using X-ray diffraction (XRD) technique. The obtained results showed that milled surfaces have a homogeneous texture with embedded abrasive particles and high surface roughness. AWJ process introduced high compressive residual stresses with similar order of level in both directions (
X
and
Y
). In addition, it was observed that jet pressure is the most influencing parameter on roughness and depth of cut, whilst traverse speed and step-over distance had a significant effect on the residual stress. Based on the experimental analysis, an empirical model to predict the depth of cut was proposed. The validation of the proposed model has shown around 5% error in the predicted and actual pocket depth.
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DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, SIK, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Carbon fiber reinforced polymers (CFRPs) have found wide-ranging applications in numerous industrial fields such as aerospace, automotive, and shipping industries due to their excellent mechanical ...properties that lead to enhanced functional performance. In this paper, an experimental study on edge trimming of CFRP was done with various cutting conditions and different geometry of tools such as helical-, fluted-, and burr-type tools. The investigation involves the measurement of cutting forces for the different machining conditions and its effect on the surface quality of the trimmed edges. The modern cutting tools (router tools or burr tools) selected for machining CFRPs, have complex geometries in cutting edges and surfaces, and therefore a traditional method of direct tool wear evaluation is not applicable. An acoustic emission (AE) sensing was employed for on-line monitoring of the performance of router tools to determine the relationship between AE signal and length of machining for different kinds of geometry of tools. The investigation showed that the router tool with a flat cutting edge has better performance by generating lower cutting force and better surface finish with no delamination on trimmed edges. The mathematical modeling for the prediction of cutting forces was also done using Artificial Neural Network and Regression Analysis.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
In aerospace industry, polymers reinforced with carbon fibre offer several advantages, such as weight/strength ratio and corrosion resistance. However, the manufacturing process is complex, ...especially the machining of composite materials, due to their specific properties and characteristics. The detection and prediction of surface finishing and occurrence of defects during manufacturing using non-destructive techniques is industrially useful, in terms of fomenting automated manufacturing systems to increase productivity and quality control. Acoustic emission signal processing is being successful in mechanical tests for determining material defects, more recently used as a method for manufacturing evaluation of machined parts. This paper focused in the machining process of CFRP plate, in terms of surface finishing evaluation with comprehension of process phenomenology using analyses of temperature and acoustic emission signal features. The aim of this paper is to show the possibility of online monitoring of the cutting process and to understand mechanism behind variables of control, with comparisons of different milling parameters and focusing in their impacts in acoustic emission signals and surface finishing, with suggestions of evaluation and prediction methods of machined surface quality using mainly acoustic emission signals.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
This article presents a comprehensive thermomechanical analysis and failure assessment in the drilling of glass fiber-reinforced polymer (GFRP) composites with different thicknesses using a CNC ...machine and cemented carbide drill with a diameter of 6 mm and point angles of ϕ = 118°. The temperature distribution through drilling was measured using two techniques. The first technique was based on contactless measurements using an IR Fluke camera. The second was based on contact measurements using two thermocouples inserted inside the drill bit. A Kistler dynamometer was used to measure the cutting forces. The delamination factors at the hole exit and hole entry were quantified by using the image processing technique. Multi-variable regression analysis and surface plots were performed to illustrate the significant coefficients and contribution of the machining variables (i.e., feed, speed, and laminate thickness) on machinability parameters (i.e., the thrust force, torque, temperatures, and delamination). It is concluded that the cutting time, as a function of machining variables, has significant control over the induced temperature and, thus, the force, torque, and delamination factor in drilling GFRP composites. The maximum temperature recorded by the IR camera is lower than that of the instrumented drill because the IR camera cannot directly measure the tool–work interaction zone during the drilling process. At the same cutting condition, it is observed that by increasing the thickness of the specimen, the temperature increased. Increasing the thickness from 2.6 to 7.7 had a significant effect on the heat distribution of the HAZ. At a smaller thickness, increasing the cutting speed from 400 to 1600 rpm decreased the maximum thrust force by 15%. The push-out delaminations of the GFRP laminate were accompanied by edge chipping, spalling, and uncut fibers, which were higher than those of the peel-up delaminations.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
Cement production is among the most important contributors to global CO
2
emissions. Partial replacement of cement with waste cork granules in mortars simultaneously enables the reduction of CO
2
...emissions and cork waste while achieving some improved material properties. Therefore, in the current study, cement content in the mortar formulations was partially replaced with waste cork particles. The produced mortars with 0.5, 1, 1.5, and 2% of waste cork (wt%) with two different cork granulometry were investigated for normal consistency, setting time, density, compressive and bending strengths, and thermal conductivity properties. The results show that mortar density decreases up to 8% with cork additions. Mortar strength in bending and compression decreases 11% and 42%, respectively, for 2% cork incorporation in mortars. Microscopic analysis by scanning electron microscopy (SEM) revealed a good adhesion between cork particles and cement. Cement-cork replacement had the greatest impact on the thermal conductivity of the mortars which was reduced up to 61%, showing that mortars with improved thermal insulation properties were produced.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
The influence of in-situ cutting temperature on machining induced damage and machining forces during drilling of multi-directional carbon fiber reinforced polymer (MD-CFRP) composites has been ...examined using a coupled thermo-mechanical finite element (FE) framework. The MD-CFRP laminate has been modeled ply-by-ply as an equivalent homogeneous anisotropic material (EHM) using temperature dependent laminate elastic and fracture properties. Stress-based criteria has been adopted for element deletion simulating the drilling process. The intralaminar damage model for simulating various composite machining induced damage modes was implemented in the FE framework via a user material subroutine. A new composite damage criterion is proposed that accounts for the out-of-plane drilling damage behavior along tool feed direction. Additionally, a fracture mechanics approach has been used to simulate interlaminar delamination onset using surface based cohesive elements at the drill exit plies. The current numerical model predictions show a good agreement with drilling experiments for thrust force, delamination damage, and in-situ cutting temperature.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZRSKP
In this paper, a numerical FE analysis is proposed to calculate the thrust forces responsible for the defect at the exit of the hole during the drilling phase of long-fibre composite structures, ...within a quasi-static framework. This numerical model – compared with the analytical models studied in the literature – takes into account the tool point geometry as well as the shear force effects in the laminate. The validation of this numerical model is carried out thanks to punching tests conducted at low speed on two types of semi products in carbon/epoxy long fibre manufactured by Hexcel composites. The numerical results provide the right correlation with the experimental values. Moreover, the comparison between the numerical thrust forces and those provided by the analytical models of the literature is called into question.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
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