Post-processing of FDM 3D-printed polylactic acid parts by laser beam cutting

In this paper, the post-processing of 3D-printed poly lactic acid (PLA) parts is investigated. Workpieces are manufactured by fused deposition modeling (FDM) 3D printing, while they may have defects in some areas such as edges. A post-processing is introduced here for 3D-printed samples by low power CO2 laser. The thickness of the FDM samples are 3.2 mm and printed by optimum conditions. Effects of process parameters such as focal plane position (−3.2–3.2 mm), laser power (20–40 W), and laser cutting speed (1–13 mm/s) are examined based on the design of experiments (DOE). Geometrical features of the kerf; top and bottom kerf; taper; ratio of top to the bottom kerf are considered as output responses. An analysis of the experimental results by statistical software is conducted to survey the effects of process parameters and to obtain regression equations. By optimizing of the laser cutting process; an appropriate kerf quality is obtained and also optimum input parameters are suggested. Experimental verification tests show a good agreement between empirical results and statistical predictions. The best optimum sample with 1.19 mm/s cutting speed, 36.49 W power and 0.53 mm focal plane position shows excellent physical features after the laser cutting process when 276.9 μm top and 261.5 μm bottom kerf width is cut by laser

on the improvement of mechanical and tribological response

This work deals mechanical and tribological properties of pure copper, reinforced by various weight percentages of tin, before and after the application of equal channel angular pressing. It is found that the hardness, yield, and ultimate shear strengths are considerably improved through ECAP due to grain refinement. The effect of ECAP process on mechanical properties of dilute copper alloys is more significant than that of the pure condition. Also, the strengthening behavior is slightly intensified by increasing the amount of tin content in pure copper. Additionally, work-hardening potential of CP-Cu is restricted due to the ECAP process and also, through the production of dilute copper alloys. The results showed that the effect of ECAP on friction coefficient reduction is more sizeable than making the dilute alloys. Furthermore, the reduction of electrical conductivity in the deformed materials relies on the lattice distortion increase of copper due to the addition of Sn to Cu and the increment of dislocations density. Finally, ECAP procedure and alloying together, terminate to the better wear response of the materials.C1 [Ebrahimi, M.] Univ Maragheh, Fac Engn, Dept Mech Engn, POB 55136-533, Maragheh, Iran.[Shaeri, M. H.; Armoon, H.] IKIU, Dept Mat Sci & Engn, Qazvin, Iran.[Gode, C.] Pamukkale Univ, Program Machine, Sch Denizli Vocat Technol, Denizli, Turkey.[Shamsborhan, M.] Islamic Azad Univ, Mahabad Branch, Dept Engn, Mahabad, Iran

Acoustic characterization of hydraulic systems: application to POGO Phenomenon

International audienceThis paper presents an experimental methodology for the evaluation of dynamic transfer matrices using three pressure sensors. The experimental study was carried out at the CREMHyG’s acoustic test rig. The speed of sound in the pipe, as well as discharge fluctuations were evaluated from the pressure fluctuations measured during tests carried out under excitation of a modulator (piston). The method applied to reconstitute flow rate fluctuations from pressure sensors were validated by comparisons with piston displacement measurements. The transfer matrices for straight pipes and POGO corrective devices were identified based on electrical analogy. The identification method was validated by comparing the transfer matrix components to theoretical values. The results can be applied in the future, in the case of space rocket