Tensile properties of 3D printed INCONEL 718 cellular specimens

The aim of the presented research by the authors was to compare the behaviour of four types of cellular structures under quasi-static tensile stress, while two samples were formed by mono-structures Gyroid 10 % and Diamond 10 %, and the other two types were bi-structures, which were created by combining two single structures (Gyroid 5 % + Gyroid 5 %) and (Gyroid 5 % + Diamond 5 %). The samples were made of Inconel 718 by Direct Metal Laser Sintering technology on an EOS EOSINT M270 machine, and they were heat treated according to AMS 5664 procedure. Tensile tests were performed on an Instron 8802 servo-hydraulic testing machine with a maximum capacity of 250 kN at ambient temperature. The results showed that the maximum load corresponded to the diamond (D) cellular structure (approximately 48 kN), while the minimum load was observed for the gyroid-gyroid (GG) structure (approximately 32 kN)

Effect of crosshead speed and volume ratio on compressive mechanical properties of mono- and double-gyroid structures made of Inconel 718

The current development of additive technologies brings not only new possibilities but also new challenges. One of them is the use of regular cellular materials in various components and constructions so that they fully utilize the potential of porous structures and their advantages related to weight reduction and material-saving while maintaining the required safety and operational reliability of devices containing such components. It is therefore very important to know the properties of such materials and their behavior under different types of loads. The article deals with the investigation of the mechanical properties of porous structures made by the Direct Metal Laser Sintering (DMLS) of Inconel 718. Two types of basic cell topology, mono-structure Gyroid (G) and double-structure Gyroid + Gyroid (GG), with material volume ratios of 10, 15 and 20 %, were studied within our research to compare their properties under quasi-static compressive loading. The testing procedure was performed at ambient temperature with a servo-hydraulic testing machine at three different crosshead testing speeds. The recorded data were processed, while the stress–strain curves were plotted, and Young’s modulus, the yield strength Re0.2, and the stress at the first peak of the local maximum σLocMax were identified. The results showed the best behavior under compression load among the studied structures displayed by mono-structure Gyroid at 10 %. At the same time, it can be concluded that the wall thickness of the structure plays an important role in the compressive properties but on the other hand, crosshead speed doesn´t influence results significantly.Ministerstvo školstva, vedy, výskumu a športu Slovenskej republiky, (APVV-19-0550); Kultúrna a Edukacná Grantová Agentúra MŠVVaŠ SR, KEGA, (005TUKE-4/2021, 032TUKE-4/2022, SK-CN-21-0046)ELKEME S.A [APVV-19-0550, KEGA 005TUKE-4/2021, KEGA 032TUKE-4/2022

Final Heat Treatment as a Possible Solution for the Improvement of Machinability of Pb-Free Brass Alloys

Heat treatment was performed in order to improve the machinability of three lead-free extruded and drawn brasses, namely CuZn42 (CW510L), CuZn38As (CW511L), and CuZn36 (C27450), based on the concept of microstructural modification. The examined machinability criteria were the following: chip morphology, power consumption, cutting force, and surface roughness. All the above quality characteristics were studied in turning mode in “as received” and “heat treated” conditions for comparison purposes. The selected heat treatment conditions were set for CW510L (775 °C for 60 min), CW511L (850 °C for 120 min), and C27450 (850 °C for 120 min) lead-free brass alloys, according to standard specification and customer requirement criteria. The results are very promising concerning the chip breaking performance, since the heat treatment contributed to the drastic improvement of chip morphology for every studied lead-free brass. Regarding power consumption, heat treatment seems beneficial only for the CW511L brass, where a reduction by 180 W (from 1600 to 1420 W), in relation to the as-received condition, was achieved. Furthermore, heat treatment resulted in a marginal reduction by 10 N and 15 N in cutting forces for CW510L (from 540 to 530 N) and CW511L (from 446 to 431 N), respectively. Finally, surface roughness, expressed in terms of the average roughness value (Ra), seems that it is not affected by heat treatment, as it remains almost at the same order of magnitude. On the contrary, there is a significant improvement of maximum height (Rt) value of CW511L brass by 14.1 μm (from 40.1 to 26.0 μm), after heat treatment process performed at 850 °C for 120 min

Effect of wear on the vibrating behaviour of the tool at turning CW724R alloy

The development of new materials and technologies also significantly affects traditional methods of component production, as it forces companies to increase the efficiency of the production process and thus remain competitive. This pressure also brings new challenges in the field of machining. The article deals with the influence of wear on the vibration behaviour of the tool when turning CW724R alloy. The aim of the research is to know the frequency response of the system to different sizes of tool wear, which causes deterioration of the quality of machined parts and instability of the entire cutting process. A specific method of artificial wear of cutting tool was applied to determine the vibration behaviour of a worn tool. To reduce the number of experimental measurements, the methodology of the orthogonal non-rotating composition plan was chosen. The matrix of two independent variables (cutting speed versus artificial wear) was selected to evaluate the relationships between them under conditions of the constant depth of cut and feed, which was processed by the multiple linear regression methodology. Finally, a dependence of vibrations on cutting speed and wear rate for evaluated material was plotted in a spatial graph. © 2022 IEEE

Effect of wear on vibration amplitude and chip shape characteristics during machining of eco-friendly and leaded brass alloys

The dynamic stability of the machining set and the entire cutting process, together with the appropriate form of chips generated during machining under the given conditions, are the basic prerequisites for autonomous machining in accordance with the Industry 4.0 trend. The research, based on a newly designed method, aims to study the frequency response of the machining system to different values of tool wear and cutting speed, which cause the worsening of the machined parts' quality and the instability of the whole cutting process. The new idea is based on the inverse principle, in which the wear with various values of VB was artificially prepared in advance before machining. Consequently, the effect of artificial wear and cutting speed on vibration and chip shape characteristics were studied. Three types of brass alloys were used within the experiments as the machined materials. Measured data were statistically processed and the desired dependencies were plotted. Chips were collected for each combination of machining conditions, while the article presents a database of the obtained chip shapes at individual cutting speeds so that they can be compared and classified. The results showed that brass alloys CW510L and CW614N exhibit an average of three times lower vibration damping compared to the CW724R alloy, while relatively good chip formation was noted in the evaluated machining conditions even without the use of a chip breaker. The problematic chip shape occurred only in some cases at the machining of CW510L and CW724R, which cannot be generalized.Ministerstvo školstva, vedy, výskumu a športu Slovenskej republiky: APVV-19-0550; Kultúrna a Edukacná Grantová Agentúra MŠVVaŠ SR, KEGA: 005TUKE-4/2021, 032TUKE-4/2022, SK-CN-21-0046Ministry of Education, Science, Research and Sport of the Slovak Republic [APVV-19-0550, KEGA 005TUKE-4/2021, KEGA 032TUKE-4/2022, SK-CN-21-0046]; ELKEME S.A

Machinability of Eco-Friendly Lead-Free Brass Alloys: Cutting-Force and Surface-Roughness Optimization

The machinability in turning mode of three lead-free brass alloys, CuZn42 (CW510L), CuZn38As (CW511L) and CuZn36 (C27450) was evaluated in comparison with a reference free-cutting leaded brass CuZn39Pb3 (CW614N), as far as the quality characteristics, i.e., cutting force and surface roughness, were concerned. A design of experiments (DOE) technique, according to the Taguchi L16 orthogonal array (OA) methodology, as well as analysis of variance (ANOVA) were employed in order to identify the critical-to-machinability parameters and to obtain their optimum values for high-performance machining. The experimental design consisted of four factors (cutting speed, depth of cut, feed rate and alloy) with four levels for each factor using the “smaller-the-better” criterion for quality characteristics’ optimization. The data means and signal-to-noise (S/N) responses indicated that the depth of cut and the feed rate were the most influential factors for the cutting force and surface roughness, respectively. The optimized machining parameters for cutting force (34.59 N) and surface roughness (1.22 μm) minimization were determined. Confirmation experiments (cutting force: 39.37 N and surface roughness: 1.71 μm) seem to show that they are in close agreement to the main conclusions, thereby validating the findings of the statistical evaluation performed