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Determining of the Fatigue Crack Growth Rate of HSLA Steel at Room Temperature

Authors: Srđan Bulatović, Vujadin Aleksić, Ljubica Milović, Bojana Zečević

Abstract

Welded joint is a critical region of a welded structure and fracture mechanics analysis is inevitable in the structural integrity assessment of all welded structures. This paper shows the determining of parameters of the fatigue crack for constituents of welded joints produced of high strength low alloyed steel. The applied methodology refers to the Paris relation where the link was established between the variable load quantity or the corresponding stress intensity factor range and crack growth per cycle. Results have shown that the position of the notch and crack initiation affect the values of the stress intensity range of fatigue threshold ΔKth and parameters in the Paris’ equation. This is mostly expressed when determining growth parameters of the fatigue crack in heat affected zone of HSLA steel, where different changes of growth speed of the fatigue crack clearly express differences in structure of the crack pass.

Key words:crack growth rate, welded joint, HSLA steel, welded joint;

DOI: 10.24867/ATM-2022-1-001

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Influence of Palm Kernel Shell Powder on the Mechanical Properties of Inoculated Gray Cast Iron

Authors: *Chukwudike Ukeje, Saliu Seidu, Sheriff Saka, Daniel Patrick, Ubong Essien,

Abstract

The use of agricultural by-products and waste materials as fillers and additives to produce different mix designs with enhanced properties is one of the ways researchers are shifting focus to seek and develop materials that rely on renewable resources. The present research investigates the influence of Palm Kernel Shell Powder (PKSP) on the mechanical properties of inoculated Gray Cast Iron (GCI). Five specimens consisting of sample C0 (0.3%FeSi, 0%PKSP), Sample C3 (0.3%FeSi, 0.3%PKSP), sample C6 (0.3%FeSi, 0.6%PKSP), sample C9 (0.3%FeSi, 0.9%PKSP), and sample C12 (0.3%FeSi, 1.2%PKSP) were developed using sand mold casting method, the chemical analysis, and their mechanical properties (tensile, hardness, and microstructures) were evaluated. The chemical composition shows that the produced gray cast iron solidified within the hypereutectic cast iron range (Carbon Equivalent, CE > 4.5), while the microstructure reveals through the graphite flakes distribution that the produced gray cast iron consists of type A graphite. The highest tensile strength and hardness values were observed in sample C3 with tensile strength and hardness values of 155.97MPa and 156.74 BHN respectively. From the result obtained, an increase in both tensile and hardness values was observed up to 0.3% PKSP addition, beyond this amount, shows a decrease in both tensile strength and hardness values for the developed gray cast iron samples.

Key words:Cast Iron; Tensile Strength; Hardness; Microstructure; Palm Kernel Shell Powder

DOI: 10.24867/ATM-2022-1-002

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Energy input adaptation according to part geometry in selective laser melting through empirical modelling of thermal emission

Authors: Ema Vasileska, Ali Gökhan Demir, Bianca Maria Colosimob, *Valentina Gečevska, Barbara Previtali

Abstract

Common practice in Selective Laser Melting (SLM) is employing a series of fixed process parameters throughout the whole build. However, process thermal conditions strongly depend on the local geometry of the part. Formation of some common defects, including swelling regions and elevated zones, emerges in critical corner areas due to excessive heat accumulation when constant parameters are used. Adaptation of energy input according to the geometry of the processed zone is highly desirable for avoiding defect formation. To assess the processing conditions, observation of the melt pool and its variation as a function of the process parameters with a coaxial camera operating in near infrared (NIR) demonstrated to be a feasible option. This work develops an empirical model that gives the correct amount of energy input to achieve stable melt pool depending on the single vector length, hence the part geometry. The model was validated on a prototype SLM system, and the results showed that controlling the process parameters considerably improves the geometrical accuracy of the parts with sharp edges prone to hot spot formation.

Key words:Additive manufacturing, Geometrical accuracy, Melt pool monitoring, Process modelling, Energy input control;

DOI: 10.24867/ATM-2022-1-003

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Effects of plasma electrolytic polishing on SLM printed microfluidic platform

Authors: Izidor Sabotin, Marko Jerman, Andrej Lebar, Joško Valentinčič, Toni Böttger, Lisa Kühnel, Henning Zeidler

Abstract

Additive manufacturing (AM) of metallic parts is gaining momentum in production industries. In view of producing a metal microproduct using AM the issue of high surface roughness is prominent. Plasma electrolytic Polishing (PeP) is a post processing technology that greatly reduces surface roughness of metallic parts. In this paper the effects of PeP of microfluidic platform, printed with selective laser melting (SLM) technology, is presented. The results show that surface roughness of the specimens was severely reduced. Also, some geometrical defects inherent to SLM technology were partly removed. It is shown, that for smaller geometrical microfeatures (sizes of less than 0.5 mm) the effectiveness of PeP is reduced. Through this investigation it can be concluded that PeP is a promising post-processing technology for SLM printed microparts since it significantly improves the overall part quality. However, further improvements of the process chain need to be implemented in order to render the microfluidic platform functional.

Key words:Selective laser melting, Plasma electrolytic polishing, Microfluidics, Additive manufacturing;

DOI: 10.24867/ATM-2022-1-004

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3D Printing of parts using metal extrusion: an overview of shaping debinding and sintering technology

Authors: Luigi Maria Galantucci, Alessandro Pellegrini, Maria Grazia Guerra, Fulvio Lavecchia

Abstract

Additive Manufacturing (AM) is the fabrication of real three-dimensional objects from plastics and metals by adding material, layer by layer. One of the most common AM processes is the Material Extrusion (ME) based on different approaches: plunger, filament and screw. Material Extrusion technologies of metal-polymer composites is expanding and it mainly uses the filament or plunger-based approaches. The feedstock used is a mixture of metal powder (from 55 vol% to about 80 vol%) dispersed in a thermoplastic matrix, as the Metal Injection Molding (MIM) materials. The process consists of three steps: shaping, debinding and sintering. The first step provides the extrusion of filament to realize a primary piece called “green part”; subsequent steps, debinding and sintering, allow to obtain a full metal part by dissolving the polymeric binder. The latter can be carried out using solvents, heat and the combination of them. The interest toward this technology is driven by the possibility to replace other Metal AM technologies, such as Selective Laser Melting or Direct Energy Deposition, in sectors like rapid-tooling or mass production, with several benefits: simplicity, safety to use and saving material and energy. The aim of this keynote is to provide a general overview of the main metal ME technologies considering the more technical aspects such as process methodologies, 3D printing strategy, process parameters, materials and possible applications for the manufacturing of samples on a 3D consumer printer.

Key words:Fused Filament Fabrication, Metal Extrusion, SDS process;

DOI: 10.24867/ATM-2022-1-005

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Verification of inverse kinematic equations for a five-axis machine tool with a spindle tilting configuration

Authors: Julija Maletić, Saša Živanović

Abstract

In this paper, the methodology for verifying inverse kinematic equations is presented. Analysis of the kinematic structure of the machine is shown, which results in the kinematic equations needed for the configuration of the machine's postprocessor. The machine proposed in this paper is a five-axis machine tool with two rotating axes on the spindle. The machine's configuration is X'OYZBA. The derived equations are used to transform the CL data for a test model into a G code used on a virtual model of the machine tool. A simplified model of the machine is developed using the PTC Creo software, in which the initial testing of the equations was performed. The inverse kinematic equations were implemented in a postprocessing program using the Matlab software. Generated G-code for multi-axis machining process was tested on a virtual machine tool in the Vericut software.

Key words: Verification; Inverse kinematics; Simulation; Virtual machine tools;

DOI: 10.24867/ATM-2022-1-006

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Feasibility of additive manufacturing processes for lunar soil simulants

Authors: Danijela Ignjatović Stupar, Grégoire Robert Chabrol, Abdoul Razak Ibrahim Baraze, Sylvain Leclerc, Alexandre Tessier, Thierry Cutard, Jocelyne Brendle

Abstract

Combination of In-situ Resource Utilization (ISRU) and on-site Additive Manufacturing (AM) is one of the “outer space applied technologies” candidates where free shape fabrication from micro (e.g., tools) to mega scale (e.g. lunar habitats) will allow in coming future to settle the Moon or potentially other celestial bodies. Within this research, Selected Laser Melting (SLM) of lunar soil (regolith) simulants (LHS-1 LMS-1 and JSC-2A) using a continuous wave 100 W 1090 nm fiber laser was applied. The resulting samples were mechanically and optically characterized. A numerical multiphysics model was developed to understand the heat transfer and optimize the SLM process. Results obtained are in good agreement with the numerical model. The physical and chemical characteristics of the various materials (granulometry, density, composition, and thermal properties) have a strong impact on the AM parameters.

Key words: Additive manufacturing, Laser, Multiphysics modelling, Lunar soil simulant, Regolith;

DOI: 10.24867/ATM-2022-1-007

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