1,721,028 research outputs found
Experimental analysis of laser assisted joining of Al-Mg aluminium alloy with Polyetheretherketone (PEEK)
No full textThe work is aimed at understanding the influence of process parameters of Laser Assisted Joining of Al-Mg alloy with Polyetheretherketone (PEEK) on the mechanical behavior of the joints. Experimental joining tests were performed by means of a diode laser, with maximum power of 200 W. Laser texturing was performed on the aluminium substrate before joining. These joints exploited the penetration of the aluminium teeth (produced by texturing) into the polymer surface. Laser spot joints were produced by varying the laser beam power and supplied energy. The temperature distribution was monitored during the joining process by means of IR camera. Mechanical characterization tests, based on single lap shear tests, were conducted. Fracture surface analysis was carried out by means of optical microscopy. Different fracture modes were observed depending on the amount of penetration and the presence of bubbles at the substrates interface. The maximum strength of the joints was obtained for P = 200 W and E = 2000 J. Under these conditions, the average strength reached 30 MPa, corresponding to 53% of the PEEK shear strength
Homogenization of temperature distribution at metal-polymer interface during Laser Direct Joining
No full textThe strength of joints produced by Laser Direct Joining depends on several factors and it is greatly influenced by the temperature at the metal-polymer interface. The temperature should be kept within a certain processing window to increase the overall strength of the joint to enable enough polymer melting and avoid detrimental phenomena such as polymer degradation. The influence of laser beam defocusing, and laser beam position has been investigated. To this end, a FE model of the process was developed to predict the thermal field during the joining process. Measurements of experimental tests were used to calibrate and validate the numerical model. Particularly, the peak temperature measurements were used for determination of absorption coefficient by means of inverse analysis technique. On the other hand, the model validation was performed by comparing the thermal field predicted by the model with the morphology of the joints. Once validated, the numerical model was used to understand how laser beam defocusing and laser beam position affect the temperature gradients at the metal-polymer interface. In addition, energy efficiency issue was also investigated. The results indicated that laser beam defocusing can be mainly exploited to reduce the temperature peaks within a narrow region (beam spot). On the other hand, the laser beam position enabled to modify the thermal field over a wider region, but it involved lower energy efficiency
Moisture-induced defects produced by direct laser joining of AA7075 aluminum and PEEK
No full textThe present investigation aims to determine how polymer moisture and volatile compounds influence the mechanical behavior of hybrid metal-polymer joints made by Laser-Assisted Joining. Experimental laser joining tests were performed on AA7075 aluminum alloy and Polyetheretherketone (PEEK). Some polymer samples were pre-treated through drying to remove the moisture stored in the PEEK before joining. Laser spot joints were produced with dried and as-received samples at different heating times. Different characterization techniques were adopted to determine the influence of moisture on the performance of the joints. Single lap shear tests were performed to assess the mechanical behavior of the joints. Fracture surface analysis was carried out through Optical Microscopy to determine the influence of the moisture content on the mechanical behavior. The results indicated a significant influence of moisture on the mechanical behavior of the joints. This led to the formation and coalescence of voids at the metal-polymer interface that affected the mechanical behavior of the joints. Dried samples were characterized by higher shear force (up to 33 %) and higher toughness (up to 130 %) compared to as-received samples
Laser assisted joining of AA5053 aluminum alloy with polyvinyl chloride (PVC)
No full textLaser Assisted Joining (LAJ) of Aluminum AA5053 sheets with Polyvinyl chloride (PVC) is investigated. The process was performed by means of a diode laser with a maximum power of 200 W. The materials did not show good chemical affinity. Thus, laser sculpturing was performed on the aluminum substrate before joining. This enabled to produce teeth features on the aluminum surface. Thus, the main joining mechanism was based on the penetration of the teeth throughout in PVC surface. The influence of the scanning speed and laser beam power used during the LAJ process on the mechanical strength of the joints was investigated. Single lap shear tests were conducted. Morphological analysis was carried out by means of optical microscopy. Thermal analysis was also conducted to measure the thermal field and the thermal history of the specimen during LAJ process. The results indicated the presence of two opposite phenomena: poor penetration of the teeth (due to insufficient heating) and polymer degradation (due to excessive heating). Both these conditions affected severely the mechanical strength of the joints. Great variation of the temperature and the morphology was observed on the joints. Under optimal conditions (P = 200 W and Ss = 100 mm/min), the average joint strength reached 71% (15.3 MPa) of the base material shear strength. (C) 2018 Elsevier Ltd. All rights reserved
Error introduced by direct 3D printing of compression samples of PLA made by FDM process
Full text linkThis study delves into the crucial aspect of sample preparation methodology and its profound impact on characterizing the physical and mechanical properties of components fabricated through the material extrusion (fused deposition modeling—FDM) process. Two distinct manufacturing approaches, direct printing and sample extraction from a plate, were employed to produce samples. To assess the influence of artifacts introduced by direct printing, compression tests were conducted under various loading directions. The investigation extends to density measurements and comprehensive morphological analysis, which plays a pivotal role in understanding the ramifications of different manufacturing approaches and principal sample directions. Notably, the research findings reveal that direct printing inflicts significant artifacts within the samples, fundamentally altering the properties obtained during testing. These artifacts substantially affect density measurements and mechanical behavior, indicating a potential avenue for future research and applications. Besides, the printing direction also significantly influenced the extent of the artifacts and differences in mechanical behavior. The maximum difference in density measurement was − 5.3%, while Young’s modulus reached − 29%, and yield strength ranged between − 12% (for vertical samples) and + 18% for horizontal samples with filaments arranged along the loading path. These findings underscore the necessity for meticulously crafted quality assessment protocols when utilizing functional parts manufactured through the material extrusion process. Such protocols should also consider the influence of sample dimensions on the mechanical characteristics of the components
Laser finishing of 3D printed parts produced by material extrusion
No full textLaser surface finishing of 3D printed components made by material extrusion is investigated. A 30W CO2 laser source, working in continuous wave (CW) mode, was employed to treat the surface of components made of Polylactic acid (PLA) obtained by material extrusion (ME). The mechanism of surface finishing was investigated and the influence of the laser treatment parameters (scanning speed, energy density and hatch distance) on the surface morphology was determined. The surface of treated samples was characterized by means of roughness measurements and optical microscopy. The results indicated that laser finishing was capable to improve significantly the surface roughness (more than ten times). However, interaction mechanisms involve surface ablation. ANalysis of VAriance (ANoVA) was performed to determine the influence of the process parameters on the surface characteristics. In addition, Response Surface Method (RSM) and Multi-Response Optimization (MRO) were adopted to determine the optimum process conditions. Thus, process conditions that enabled to enhance the surface roughness (form Ra = 16 μm for untreated surface to Ra = 0.3 μm under optimal process conditions) and minimize the surface recession (0.1 mm) were determined
Defects formation during Friction Assisted Joining of metals and semi crystalline polymers
No full textThe work aims to identify the key factors (KFs) influencing the product quality in the Friction Assisted Joining process and how these depend on the process parameters. Experimental tests were performed under low and high-speed conditions. The tests were conducted on hybrid joints made of aluminum alloy AA7075 alloy and semicrystalline Polyamide PA66. Friction Assisted Joining experiments were conducted using an instrumented CNC machine equipped with load and position sensors. The temperature variation and distribution were measured through an Infrared Camera. The influence of plunging load, tool rotation speed, plunging rate and dwell time on the quality of the joints was investigated. Single lap shear tests were conducted to determine the mechanical behavior of the joints. The results indicated that the quality of the joints is mainly determined by the processing temperature reached during the joining process. The processability window along with the onset of main adverse phenomena affecting the mechanical behavior of the joints was determined
Determination of local density in components made by fused deposition modeling through indentation test
Full text linkThe present study is aimed at determining the local density of components made by fused deposition modeling (FDM) through non-destructive indentation tests. An experimental campaign was performed to assess such a relationship. Specimens were made varying the amount of material flow and the direction of deposition. The specimen’s dimension and weight were measured to determine the average density. The internal porosity due to uncomplete filling produced due to the deposition process was also assessed through cross-sectioning. Instrumented indentation tests were conducted on the samples to determine a relationship between the density and the slopes during the loading and unloading phases. The tests were performed using flat cylindrical indenters of different diameters. The results indicated that the density of the specimens was strongly influenced by the adopted material flow and the orientation during deposition. An empirical relationship was determined between the slopes measured during indentation tests and the density. Such a relationship is independent of the deposition orientation. The optimized procedure represents a valuable tool to determine the local density of components made by fused deposition modeling through non-destructive indentation tests
An automated procedure for machines distribution among plants based on genetic algorithm approach
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