Search

Determining the mechanical characteristics of additively manufactured materials has been an active topic of research in recent years. Many studies have been performed analyzing the impact of different 3D print parameters on the tensile properties of the printed material. However, compared to typical metals and polymers, there is no widely adopted standard for testing additively manufactured polymers. Consequently, the test results reported by the researchers in this field exhibit high amounts of variability between studies. A set of consistent experiments across five different printing parameters including build orientation, raster orientation, infill type, infill density, and layer thickness was carried out in the present paper. The results were analyzed to look at trends between the tested variables and the yield strength and elastic modulus of the resultant additively manufactured polyethylene terephthalate-glycol (PETG). Build orientation, raster orientation, infill type, and infill density all showed strong relationships with the tensile properties. Layer thickness showed little variation across the typical range for a given extrusion width. Previously developed experimental models were also checked and showed that even small variations in other parameters such as raster gap or extrusion factor could create significant enough variation to make the model inaccurate for a specific scenario. [ABSTRACT FROM AUTHOR]

The spread of 3D printing in many different fields has become eminent. This paper aims to improve the mechanical properties of parts printed by fused deposition modeling technique. Acrylonitrile butadiene styrene (ABS) specimens are printed with custom printing parameters. These parameters give a tensile strength that is 86% of the injection- molded ABS strength, and give one of the best recorded results for 100% infill printed ABS tensile specimens. Furthermore, a post filling technique has been studied. Specimens are printed with inner voids and different densities using slicing software. Void shape is precisely selected to conform to the filling process. High-strength, low-cost thermoset resin is injected through specimens to fill those voids. A tensile test has been performed after the full curing of the resin. A morphology analysis is done. Using this technique strength to printed weight ratio is improved by 151% and the cost is reduced by 51%. [ABSTRACT FROM AUTHOR]

Hybrid manufacturing approaches with additive and subtractive manufacturing is a promising technology for many sectors from personal care goods to aerospace. When it comes to the residual stresses, there are hardly about the additive manufacturing (AM). Although some researches have been conducted for the hybrid laser additive manufacturing and subtractive manufacturing (SM) processes, only the machining parameters, material properties, and surface quality were analyzed; there were a few experiments about the residual stresses. Taking this into account, this paper aims to analyze the surface residual stresses in hybrid manufacturing approaches. Additive machining process, electrochemical corrosion, and surface residual stresses testing were described in detail. The main results of the research would be references for the surface residual stresses when 316L stainless steel specimens are manufactured with laser metal deposition and milling after AM immediately. The oxidation is much serious in additive manufacturing, and the surface tensile stresses are quite small. Both the electrochemical corrosion and milling at high temperature will affect the distribution of the surface residual stresses. The residual tensile stresses are distributed symmetrically after milling process while they are asymmetric after electrochemical corrosion. [ABSTRACT FROM AUTHOR]

This paper presents a comprehensive study of the tensile performance, heat treatment, fracture, decrease of residual stress, second-phase particle and microstructures of a 316L stainless steel fabricated by directed laser deposition (DLD) and thermal milling (starting milling temperature at 250 ± 50 °C), a typical hybrid additive and subtractive manufacturing process. Experiments of different post-heat treatment temperatures and tensile tests at room temperature were performed. The residual stress was eliminated with heat treatment at 400 °C for 2 h, and the average residual stress decreased 53.7% while the yield strength and ultimate strength decreased slightly. The fracture surfaces of different heat treatment temperatures were observed. The typical ductile fracture microstructures of dimples were seen in almost all specimens whenever the heat treatment temperature was low or high. The evolution of dimples from formation to destruction by heat treatment was analyzed. The different morphology and composition of the second-phase particles of different heat treatment temperatures were compared. The yield strength of 427.5 MPa, the ultimate strength of 599.27 MPa, and the elongation of 36.48% showed the new hybrid manufacturing technology could be used for further fabrication of components. [ABSTRACT FROM AUTHOR]

Additive manufacturing (AM) has various independent parameters that affect the mechanical properties and quality of the produced parts that are not linearly the function of each other. Process parameters in metal AM are very hard to control, analyse and optimise because they affect each other even though they can be independently changed. Changing process parameters in a wide range is not possible due to the formation of problems such as cracks, balling, unmelted powders, porosity and distortion. In this paper, a numerical model to predict the value of tensile strength of selective laser melting (SLM) Ti-6Al-4V parts and analyse the effect of process parameters on the results has been proposed. Taguchi L25 Design of Experiment (DOE) across 125 samples to create a comprehensive and general overview of influential parameters on the build process was investigated. Specifically, parameters included laser power, scan speed, hatch spacing, laser pattern angle and heat treatment (HT). To evaluate and analyse the build process according to established statistical variances, a minimum of five samples based on ASTM standard (for tensile test) were prepared. Heat treatment was added to the DOE to analyse the combined process and post-process effects. Results were compared (cross-validated) against existing values found in the literature and were found to effectively predict and explain the behaviour of tensile strength when changing process parameters. [ABSTRACT FROM AUTHOR]

The aim of this study is to evaluate the effect of printing parameters and their interactions on the mechanical properties of ABS-based specimen, 3D printed by fused deposition modeling (FDM), using the response surface method. The manufacturing direction (X, Y, or Z) and the deposition angle (0°, 30°, or 45°) are analyzed as input factors. The Young modulus, the yield stress, the tensile strength, and the deformation at fracture in tension are considered as responses. An empirical model for each response is built in terms of factors and their interactions. The predicted results are in good coherence with experimental ones. The original contribution of this paper consists in the evaluation of the optimal combination of manufacturing parameters thanks to the MINITAB software. [ABSTRACT FROM AUTHOR]

Additive manufacturing (AM) started as a rapid prototyping (RP) technology to aid in visualizing and validating designs in the design process. However, with the recent improvements in metal AM parts, functional parts can be manufactured using laser-based AM. Currently, metal AM parts have comparable mechanical properties to traditional manufacturing parts. 15-5PH stainless steel and Inconel 718 are two of the most commonly used metals in laser-based AM, and they have a high modulus of elasticity and tensile strength and can be precipitate hardened to increase their strength and hardness by heat treatment. These properties make 15-5PH stainless steel and Inconel 718 suitable for many industrial applications such as aerospace and automotive. However, due to the nature of AM, AM parts usually suffer from anisotropy. In this paper, the mechanical properties such as tensile strength, modulus of elasticity, yield strength, and ductility are investigated at various elevated temperatures up to 350 °C and compared with the mechanical properties at room temperature using specimens printed in three different orientations to capture the effect on the anisotropy. In addition to that, the microstructure of the specimens is studied to investigate the influence of elevated temperature on the specimens. [ABSTRACT FROM AUTHOR]

In this paper, the effect of additive particles on the mechanical properties of ultraviolet (UV)-cured resin was evaluated based on tensile strength and shear strength. The experimental results showed that the tensile strength was improved with proper particle addition, but the shear strength was always decreased. Moreover, the effects of additive particles on the holding force of diamond abrasive, critical exposure energy, and penetration depth of UV-cured resin were elucidated. The holding force of resin with 15 wt.% Al2O3 addition was found to be higher than that of pure UV resin. Based on the experimentally determined critical UV exposure energy and penetration depth, UV-cured resins with and without additive particles were used to fabricate grinding wheels using additive manufacturing technology. Grinding experiment demonstrated the performance of UV resinoid grinding wheels was significantly improved with the addition of 15 wt.% Al2O3 particles. [ABSTRACT FROM AUTHOR]

A new auxetic structure, re-entrant chiral auxetic (RCA) structure, is proposed for the first time in this paper. The RCA structure combines the topological features of hexagonal re-entrant and anti-tetrachiral honeycombs. Additive manufacturing technique, stereolithography (SLA), and traditional waterjet machining (WJM) were employed to fabricate six samples made from photopolymer (VisiJet SL Flex) and aluminum alloy (6061), respectively. Quasi-static uniaxial tensile tests were conducted in the X and Y directions, respectively. Numerical models were developed using ANSYS/LS-DYNA and verified by experimental data. Deformation modes, stress-strain curves, and Poisson’s ratios were considered to examine the effects of loading directions and material types. A comparative study was conducted experimentally and numerically between the well-known hexagonal re-entrant honeycomb, and this newly developed RCA structure. The proposed RCA structure presented here was found to display lower density compared with re-entrant honeycomb. Moreover, it shows higher tensile properties and auxetic effect compared with re-entrant honeycomb when loaded in the X direction. The validated FEA models were employed to investigate the effect of friction on the deformation pattern and mechanical properties of the RCA structure when it is loaded in both directions. [ABSTRACT FROM AUTHOR]

Customized processing and manufacturing is the main constraint in the application of ultra-high-molecular-weight polyethylene (UHMWPE), especially in customized prosthetics, such as tibial inserts. In this study, the enabling of selective laser sintering (SLS) was explored to achieve direct fabrication of customized UHMWPE tibial insert. The mechanical properties and the dimensional accuracy of UHMWPE tibial inserts, fabricated by SLS method, were tested. The results showed that when the customized shape-controlled tibial insert was fabricated, its tensile strength increased from 14.1 to 24.1 MPa and the elongation increased from 5.4 to 390 % by a simple post-heat treatment. In the present paper, UHMWPE tibial insert could be made suitable for femoral component and tibial tray by enlarging the designed size by 10.5 % in the directions of X and Y and 6.5 % in the direction of Z. This study demonstrated that the new manufacturing capabilities for UHMWPE tibial insert will be developed further, which was motivated by the needs of customized manufacture. [ABSTRACT FROM AUTHOR]

The effect of printing speed on the tensile strength of acrylonitrile butadiene styrene (ABS) samples fabricated using the fused deposition modelling (FDM) process is addressed in this research. The mechanical performance of FDM-ABS products was evaluated using four different printing speeds (10, 30, 50, and 70 mm/s). A numerical model was developed to simulate the experimental campaign by coupling two computational codes, Abaqus and Digimat. In addition, this article attempts to investigate the impacts of printing parameters on ASTM D638 ABS specimens. A 3D thermomechanical model was implemented to simulate the printing process and evaluate the printed part quality by analysing residual stress, temperature gradient and warpage. Several parts printed in Digimat were analysed and compared numerically. The parametric study allowed us to quantify the effect of 3D printing parameters such as printing speed, printing direction, and the chosen discretisation (layer by layer or filament) on residual stresses, deflection, warpage, and resulting mechanical behaviour. [ABSTRACT FROM AUTHOR]

This experimental study investigates the effects of process parameters for 3D printing polylactic acid (PLA) samples on both the mechanical properties obtained and the energy consumption in the fused deposition modelling (FDM) process. The explained experimental activities provide an in-depth evaluation of all the strategies adopted in different temperatures and scan speed strategies. The results, extracted in tensile strength, ultrasonic inspection (UT), and specific energy consumption (SEC), highlight the printing parameters that mainly affect the mechanical characteristics of the final workpieces and the energy consumption to find an appropriate energy-saving energy strategy for the PLA additive manufacturing process. The results indicate a more excellent uniformity of the molded material, reducing the printing time and total energy consumption at high speeds (V = 110 mm/s) and one level of temperature (T = 215 °C). A new efficiency index has been introduced to release guidelines to pursue the best setup compromise. [ABSTRACT FROM AUTHOR]

An expansion of the high-temperature/high-performance polymer 3D printing feedstock palette is critical for the adoption of the technology in more aerospace applications. Open-source printers are a potential platform for the insertion of new materials to the printing palette. However, as-purchased, they are not capable of printing high-temperature polymers. To address this, we developed an open-source-based 3D printer with increased environment controls. These include an enclosure and part heating using infrared energy focused on the printed part to keep it close to the desired temperature, while the printer components stay within their design operating ranges. This enables printing of high-temperature polymers while preventing damage to the machine. The effectiveness of this approach is demonstrated by printing polyetherimide parts (Tg = 217 °C). The temperature of the part as well as temperatures at various locations in the build chamber is monitored and assessed. We then evaluate the overall success of the approach by showing the relationship between part temperature and final properties such as surface flaws, tensile strength, and interfacial bonding. [ABSTRACT FROM AUTHOR]

Fused deposition modeling (FDM) is the most widespread 3D printing technology. The primary reasons for this are its simplicity in manufacturing and low cost. The common issue of FDM is an anisotropic property of the extruded layer. Therefore, the mechanical strength of traditional machining methods is significantly better than FDM-fabricated parts. Implementation of diode laser (450 nm) with 5 W power for localized heating of the pre-deposition layer is proposed to overcome this problem. The laser power is controlled during the printing process. Thereby, layer interface temperature reached for critical point, where the bonding diffusion process between layers increased for the maximum level. The effect of the pre-deposing heating method is presented at different laser power values and printing speed. Tensile test results on PLA (polylactic acid) plastic specimen indicate a 10.16% increase in ultimate tensile strength at 2.84 W power of the laser. However, crack and hole formations indicate a negative result of intensive laser heating employment. [ABSTRACT FROM AUTHOR]

Fused deposition modelling is an additive manufacturing technology that is widely employed to produce good quality products with complex geometries at a low cost and with efficient manufacturing and delivery logistics. The mechanical properties can be enhanced by studying the numerous FDM parameters and by using new materials. In this work, was studied the mechanical properties tensile strength, flexural strength, and impact energy of 3D printed parts manufactured with FDM technology and PLA-graphene raw material by varying the infill and layer thickness parameters using a statistical technique CCD—central composite design. Due to the layered production process, 3D printed parts exhibit anisotropic behaviour. In the tests, the flat orientation and honeycomb infill pattern were maintained. The results showed that the mechanical properties improve as the linear layer thickness parameter increases. The behaviour was different in each test for the linear infill parameter. The mechanical properties, tensile strength and flexural strength, increased as the infill increased, while impact energy decreased as infill increased. The relationship between mechanical properties and printing time/weight was also evaluated. [ABSTRACT FROM AUTHOR]

By the nature of selective laser melting (SLM) additive manufacturing (AM), property variations are likely to arise in specific structures of parts. The problem here is that it is hard to predict exactly how properties will be affected or conversely, how the mechanical properties in local sections of the built parts can be intentionally changed. There is little known about how build geometry and grain structures unique to SLM affects the mechanical properties of SLM parts. To address this issue, various SLM manufactured parts, created using the Renishaw™ AM 250, were tested for significant variation in mechanical properties. Specifically, the use of both mini tensile tests and Automated Ball Indentation (ABI) is employed to incrementally test localized sections. ABI has the potential to greatly improve the ability to monitor properties. This research advances collective understanding of AM and leads to methods that assure property uniformity or intentional manipulation of mechanical properties. [ABSTRACT FROM AUTHOR]