Revistas
Autores:
Cumbicus, W. E. (Autor de correspondencia); Estrems, M.; Arizmendi, Miguel; et al.
Revista:
INTERNATIONAL JOURNAL OF ADVANCED MANUFACTURING TECHNOLOGY
ISSN:
0268-3768
Año:
2023
Vol.:
126
N°:
11-12
Págs.:
5163 - 5178
This article presents a study of the joining of polyetherimide (PEI) polymer parts reinforced with fibre glass which has great application in the automotive sector. A simulation model based on the finite element method is proposed. For the modelling of the polymeric material, the three-network viscoplastic (TNV) rheological model was used, with very adequate results and producing a good fit with the experimental data. In addition, a methodology is proposed that allows simplifying a three-dimensional to an axisymmetric model, which implies a notable reduction in computational cost. In addition, the work includes an experimental analysis that evaluates the tightening torque under conditions of assembly repetitiveness, relaxation over time and influence of thermal cycles. These scenarios have a different influence depending on the geometry of the self-tapping screw used. Regarding repetitiveness, it has been verified that PF-30 (CELOspArk (R)) loses 17.16% while in Delta-PT (DELTA PT (R)) it loses up to 41.93% in the tenth repetition. In contrast, in the relaxation over time scenario, the PF-30 loses 13.38% and the Delta-PT loses 17.82%. Finally, regarding the thermal cycles, cooling allows to slightly delay the loss of tightening torque in both screws in a similar way; however, in the heating stage, 36.89% is lost with PF-30 and only 14.66% with Delta-PT. This study represents an improvement in the knowledge of the joining processes of self-tapping screws with polymeric materials of an engineering nature. The simulation model can be easily adapted to other materials and other geometries, and the experimental study offers a vision of the evolution of tightening conditions in realistic operating scenarios.
Revista:
MATERIALS TODAY COMMUNICATIONS
ISSN:
2352-4928
Año:
2023
Vol.:
37
Págs.:
107042
Heat accumulation along the deposited layers in AM is an important issue that may lead to shape distortions. In this context, the present paper is aimed at analysing the feasibility of interlayer post-processing of depositions to improve interlayer bonding and process performance. Concretely, the use of interlayer machining and laser remelting is tested and their effect on the porosity, mechanical properties and component distortion is analysed. Additionally, the results obtained after each interlayer post-processing technique were compared with an asdeposited sample to analyse the benefits of the hybrid additive manufacturing approach on the generated parts. Samples post-treated through machining showed the lowest deformation. As for the porosity, laser remelting post-processing led to best results. Hardness was also tested along the height of samples and it was observed that it increases in build direction for all the cases tested. Highest hardness values were obtained for the samples post-processed through machining.
Revista:
CIRP - JOURNAL OF MANUFACTURING SCIENCE AND TECHNOLOGY
ISSN:
1755-5817
Año:
2023
Vol.:
40
Págs.:
199 - 212
A hybrid approach combining the laser powder bed fusion (LPBF) process and post-processing operations through 5-axis milling was employed to manufacture a Ti6Al4V aerospace component. From the design step, the requirements and needs in all the stages of the Hybrid Additive Manufacturing process were taken into account. A numerical simulation of distortions promoted by residual stresses during the additive process was employed to consider material allowance. The status of the as-built and post-processed component was analysed through scanning and CMM inspection and roughness measurements. The 3D scanned model of the as-built LPBF-ed component was used to understand the distortion behaviour of the component and compared to the numerical simulation. Finally, 5-axis milling operations were conducted in some critical surfaces in order to improve surface quality and dimensional accuracy of the as-built com-ponent. The inspection of the as-built and post-processed component showed the improvement achieved through the proposed hybrid approach. The work aims to provide the baselines needed to enable the metal Hybrid Additive Manufacturing of components with complex geometries where mandatory precision is required by integrating high accuracy machining operations as post-processing technique.(c) 2022 The Author(s). This is an open access article under the CC BY license (http://creativecommons.org/ licenses/by/4.0/).
Autores:
Ardila-Tellez, L. C. (Autor de correspondencia); Jiménez, A.; Moreno-Tellez, C. M.; et al.
Revista:
SURFACE AND COATINGS TECHNOLOGY
ISSN:
0257-8972
Año:
2023
Vol.:
471
Págs.:
129892 - *
The reactivity of Al0.66Ti0.33N, Al0.31Ti0.62Si0.07N, Al0.60Cr0.40N, and Al0.38Cr0.54Si0.07N cathodic arc-coated hardmetal tools with Inconel 718 has been evaluated by using diffusion couple experiments at 900 degrees C and 1100 degrees C. As expected, a strong reaction occurs at these temperatures between Inconel 718 and uncoated hard-metal samples leading to the formation of & eta; phases; mainly M12C and M6C carbides. PVD coatings act as diffusion barriers limiting the presence of such reactions as long as they maintain their structure in contact with Inconel 718 at high temperatures. Diffusion couple experiments confirm that Cr-containing coatings are significantly more unstable than Al0.66Ti0.33N or Al0.31Ti0.62Si0.07N materials, thus leading to notable differences in cutting performance. The relation between diffusion couple results and drill wear mechanisms in drilling Inconel 718 with different coating materials are also analysed. The best results are obtained either with Al0.66Ti0.33N or Al0.31Ti0.62Si0.07N coated drills, where the coating remains longer time at the cutting edge leading to more efficient protection, especially at the drill corner.
Autores:
Bidare, P. (Autor de correspondencia); Mehmeti, A.; Jiménez, A.; et al.
Revista:
INTERNATIONAL JOURNAL OF ADVANCED MANUFACTURING TECHNOLOGY
ISSN:
0268-3768
Año:
2022
Vol.:
120
N°:
11-12
Págs.:
8063 - 8074
Nickel-based alloys are known as non-weldable materials due to their complex characteristics. Consequently, additive manufacturing of these alloys is particularly challenging. In this paper, the influence of process parameters on the porosity, crack formation and microstructure of additively manufactured CM247LC nickel-based alloy is analysed. The feasibility of the direct laser deposition (DLD) process to manufacture crack-free and low-porosity CM247LC samples is studied. CM247LC samples were built on Inconel 718 that has similar chemical composition, to form hybrid superalloy parts. It was shown that crack-free and high-density CM247LC samples can be obtained through DLD without significant substrate preheating for certain parameter combinations: laser power in the range of 800-1000 W and powder feed rates between 6 and 8 g/min. High-cost and complex preheating was avoided that was commonly reported as necessary to achieve similar densities. For hybrid parts, a large beam diameter and slow scan speeds were employed to achieve optimal conditions as it was evident from the achieved bonding between the Inconel 718 substrate and the deposited layers. It was observed that good bonding between the two materials can be obtained with laser power values between 800 and 1000 W, scanning speed higher than 300 mm/min and powder flow rates of 6-8 g/min.
Revista:
NUMERICAL HEAT TRANSFER PART A-APPLICATIONS
ISSN:
1040-7782
Año:
2022
Vol.:
82
N°:
11
Págs.:
743 - 764
In this article, an analytical solution is developed to determine the transient temperature distribution in a rotating finite cylinder subject to a heat source acting on its flat surface with convective cooling. The resolution of the heat conduction problem for the cylinder temperature is carried out by means of the successive application of one-dimensional integral transforms: the finite Fourier transform and the finite Hankel transform. The solution can be applied in different engineering applications such as turning, pin-on-disk devices, bearings and braking systems. Taking this solution into account, a numerical analysis of the transient temperature distribution generated in a rotating cylinder subject to a heat source is performed. In this analysis the effect of the rotation speed and of the convective cooling on the transient temperature distribution of the cylinder and on the time required to reach the quasi-steady state is studied by means of two dimensionless parameters: the Peclet number and the Biot number, which depend on the rotation speed and on the convective heat transfer coefficient, respectively. Finally, different heat source geometries (circular, square and circular trapezoid) are considered.
Revista:
INTERNATIONAL JOURNAL OF MECHANICAL SCIENCES
ISSN:
0020-7403
Año:
2021
Vol.:
204
Págs.:
106524
High temperatures generated in cutting processes significantly affect the surface integrity of machined parts and tool wear, leading to workpiece thermal damage, tensile residual stresses in the workpiece and a reduction in tool life. In recent years, different analytical thermal models to predict cutting temperatures have been developed in literature based on 2D modeling of the cutting process and the assumption that thermal conductivities of work piece and chip are not dependent on temperature. However, this dependence of conductivity on temperature may have a significant influence on predicted temperatures and must be taken into account. In this paper, a thermal model of the orthogonal cutting process that considers thermal conductivity of materials (chip and tool) to be dependent on temperature is developed. A linear variation of thermal conductivity with temperature is assumed for chip (workpiece) and tool materials. The model is based on application of: (1) the Kirchhoff transformation in order to convert the nonlinear heat conduction problem into a linear one, (2) the theory of moving and stationary heat sources in semi-infinite and infinite mediums in order to model primary and secondary deformation zones and (3) imaginary heat sources to meet adiabatic boundary conditions in the chip and tool. Imaginary heat sources were defined in the thermal model proposed in this paper in such a way that the effect of the tool-chip interface dimensions and of cutting tool width on
Revista:
INTERNATIONAL JOURNAL OF ADVANCED MANUFACTURING TECHNOLOGY
ISSN:
0268-3768
Año:
2021
Vol.:
114
N°:
9 - 10
Págs.:
2711 - 2720
This paper presents an experimental method for predicting tool wear in drilling Inconel 718 superalloy. The method combines analysis of drilling force signals and tool wear progress. Force characteristics were studied both in time and frequency domains (power spectrum and wavelet decomposition) in order to find best correlation with tool wear progress. These analyses show that the mean value of the thrust force component, the high frequency component of the force, the frequencies that arise during drilling, and the evolution of the wavelet decomposition details are all sensitive to tool wear progress. Therefore, these characteristics can be employed as indicators for drill failure prediction. Among all those indicators, the mean value of the thrust force and the standard deviation of high frequency components of that force have shown the greatest sensitivity to drill wear.
Revista:
INTERNATIONAL JOURNAL OF MATERIAL FORMING
ISSN:
1960-6206
Año:
2021
Vol.:
14
N°:
4
Págs.:
777 - 798
Revista:
INTERNATIONAL JOURNAL OF ADVANCED MANUFACTURING TECHNOLOGY
ISSN:
0268-3768
Año:
2019
Vol.:
100
N°:
9-12
Págs.:
2831 - 2855
In this work, a model for the prediction of drilling stability against low-frequency lateral vibrations, named as whirling in the literature, is proposed. These vibrations are lateral displacements of the tool that arise at frequencies near multiples of the rotation frequency of the drill. The appearance of whirling vibrations leads to the generation of lobe-shaped holes. In order to predict whirling vibrations, the motion equation of the drill is deduced taking into account the modal characteristics of the drill and the cutting and process damping forces that act on it. In this paper, forces that arise in two different regions of the drill are considered: (1) forces on the main cutting edges and (2) forces on the chisel edge. Different force models are presented for each region that include both the regenerative effect of the vibration on the cutting area and the process damping. An oblique cutting model and an orthogonal model are employed for the calculation of cutting forces acting on the main cutting edges and on the chisel edge, respectively. The cutting force model for the main cutting edges takes into account the cutting angle (inclination angle, rake angle, and chip flow angle) variation along the main cutting edges. For the chisel edge region, where the feed speed is no longer negligible with respect to the cutting speed, the dynamic cutting angles are employed for the force model development. Concerning the process damping force model, previous works in the literature consider a constant value of the clearance angle for the calculation of the process damping coefficient. However, in this work, the variation of the normal clearance angle along the main cutting edges is considered. It is shown that, depending on the clearance face grinding parameters employed, the clearance angle can double its value along the main cutting edges. Considering the force models and through the semi-discretization of the motion equation of the drill, the appearance of low-frequency lateral vibrations is predicted regarding the drill geometry and cutting conditions such as drill rotation speed and feed. In addition, given cutting conditions at which whirling vibrations are expected to occur, the model is able to predict the vibration frequencies that are excited. The drilling model and the stability predictions are experimentally validated by means of drilling tests with different drill diameters and cutting conditions. In comparing the experimentally obtained results and the predictions obtained by the model, it is concluded that the model can reasonably predict the appearance of whirling vibrations as a function of drill geometry and cutting conditions. Generated hole shape is also analyzed through the measurement of hole roundness and bottom surface geometry. It is observed that, when drilling in the presence of whirling vibrations, holes with lobed shape and polygonal bottom surface are generated. It is also noticed that both the number of lobes and the number of sides of the polygonal bottom surface are directly related to the vibration frequencies that arise.
Revista:
INTERNATIONAL JOURNAL OF MECHANICAL SCIENCES
ISSN:
0020-7403
This paper presents a model for predicting the surface topography generated in face milling operations. In these operations, when the face mill inserts remove the workpiece material, they leave marks on the machined surfaces. The marks depend on the face mill geometry, the geometry and runout of the face mill inserts, and cutting conditions, e.g. feed and step over. In order to predict the surface topography, the geometry of the face mill cutting edges must first be modelled. The modelling of the cutting edge geometry is for round insert face mills and for square shoulder face mills. Due to the influence of insert runout on the final surface topography, axial and radial runouts of the face mill inserts are also taken into account in the modelling of the cutting edge geometry. Next, the equations expressing the trajectory of any cutting edge point are derived as a function of the feed value, the rotation angle of the face mill, its axial position, and its radial position with respect to the face mill axis. Finally, given the cutting edge geometry and the trajectory of cutting edge points, a methodology based on the discretization of the milled surface in a grid with a finite number of points is developed in this paper for the simulation of the surface topography. The methodology is based on the fact that at each grid point, the final height of the topography will be the height of the workpiece material remaining at this point after many face mill revolutions. For this reason, the procedure initially estimates the rotation angles of the face mill for which the face mill cutting edges in their front-cutting and back-cutting motion pass by the grid point being considered. In order to achieve this, a transcendental equation that is only dependent on the rotation angle is derived from the cutting edge trajectory equations. This equation is transformed into an equivalent polynomial equation by means of Chebyshev expansions. The transformed equation is solved for the rotation angle using a standard root finder that does not require a starting value. Then, by means of the estimated rotation angles and the cutting edge trajectory equations, the radial positions of the cutting edge points passing by the grid point are obtained. Finally, based on these radial positions and the cutting edge geometry, the heights of cutting edge points, which can generate the surface topography at this grid point, are estimated. The final height of the surface topography will correspond to the lowest value among the estimated height values. The methodology can be easily extended and applied to face mills with other insert geometries or to face mills with central and peripheral inserts. In addition, the simulation of the surface topography generated by lateral passes in face milling operations is simplified. The procedure allows the influence of the face mill geometry, the feed value and the step over between passes to be analysed and the roughness values to be predicted. In order to validate the model predictions, a series of face milling tests are carried out. Predicted surface topographies are compared with measured topographies and a good agreement between them is observed.
Revista:
INTERNATIONAL JOURNAL OF MACHINE TOOLS AND MANUFACTURE
ISSN:
0890-6955
Año:
2019
Vol.:
137
Págs.:
79 - 95
Revista:
INTERNATIONAL JOURNAL OF ADVANCED MANUFACTURING TECHNOLOGY
ISSN:
0268-3768
Año:
2018
Vol.:
96
Págs.:
1971 - 1990
A model that predicts the appearance of low-frequency lateral vibrations in drilling with pilot hole is proposed in this work. These vibrations, called whirling in the literature, are responsible for the generation of lobe-shaped holes during drilling. The present model considers both the influence of the regenerative effect of vibrations on the cutting forces and the influence of the process damping phenomenon that appears along the main cutting edges. In order to model cutting forces, cutting edges are divided into discrete elements and for each of them oblique cutting model is employed. Specific cutting forces at each cutting edge element are calculated as function of cutting speed and normal rake angle value. A new methodology is developed to analyze the motion equation of the drill in the frequency domain in order to predict the appearance of whirling vibrations during drilling with pilot hole. Regarding the depth of cut and the spindle rotational speed, drilling stability limits against low-frequency lateral vibrations are obtained. Moreover, in the presence of vibrations, the model can predict the whirling frequencies that are excited depending on the established cutting conditions. In addition, the stability model is experimentally validated via drilling tests over pilot holes of different diameters for a wide range of cutting conditions. In order to study the appearance of low-frequency vibrations and to avoid the appearance of other vibrations such as regenerative chatter, the analysis is focused on low spindle speed values. A comparison between predicted vibration frequencies and actual frequencies in measured cutting forces during drilling tests is carried out and a good correlation between them is observed.