Browsing by Subject "Laser powder bed fusion"
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Item Effect of laser polishing on fatigue behavior of additively manufactured IN718(2022) Lee, Seungjong; Bureš, Martin; Shao, Shuai; Wells, Douglas N.; Zetek, Miroslav; Kepka, Miloslav; Shamsaei, NimaThis study investigates the effect of laser-polishing on the fatigue behavior of Inconel 718 fabricated using laser powder bed fusion process. Three different conditions including as-built and laser-polished using two different process parameters are considered. Uniaxial tension- compression fatigue tests are conducted in strain-controlled mode to examine the fatigue behavior for each condition. In addition, surface roughness measurements and fractography using optical microscopy and porosity measurements using the X-ray computed tomography are also performed for all conditions. The results indicate that laser-polishing alone does not improve fatigue performance, even though it can significantly reduce surface roughness. The beneficial effects of the smoother surfaces may have been countered by the volumetric defects close to the surface induced by laser-polishing. The fracture surfaces also reveal that fatigue cracks are initiated from the defects close to the surface, and therefore, fatigue behavior is not improved.Item Evaluating Concepts for the Integration of Milled Components into the Additive Manufacturing Process(2022) Reichwein, J.; Geis, J.; Kirchner, E.Laser Powder Bed Fusion (L-PBF) has specific advantages over conventional manufacturing processes. These include high freedom in the design of components and cost- efficient production of small quantities. However, the surface quality of components is low compared to milling and the production of large components is often associated with high costs. These challenges are addressed by integrating milled components into the L-PBF process. Therefore, various concepts are presented for positioning, aligning, and fastening machined components in the build space of the L-PBF system with the goal to provide a reliable way to start the L-PBF process on top of these components. Thus, allowing the potential of additive and subtractive manufacturing to be exploited without requiring an additional joining operation. Finally, these concepts are applied to a steering shaft bracket and the costs for manufacturing are evaluated. A 25% reduction in manufacturing costs was achieved compared to the purely additively manufactured component.Item Evaluation of Functionally Graded Lattice Properties of Laser Powder Bed Fused Stainless Steel 316L(2022) Ravichander, Bharath Bhushan; Jagdale, Shweta Hanmant; Theeda, Sumanth; Kumar, GoldenThe development of metal Additive Manufacturing (AM) techniques, in particular the laser powder bed fusion (LPBF) process, has led to an increase in the innovative design and fabrication of lightweight and complex porous metal structures. Despite the limitations of the LPBF process which limits the geometric accuracy of the porous structures, it eliminates the difficulties presented by conventional manufacturing techniques in the fabrication of highly complex structures. The properties of as-built porous structures depend on the unit cell design and porosity level. These lightweight metal structures have applications in medical and aerospace fields. The relationships between the lattice geometry and performance must be determined to successfully implement the functional lattice designs. In this study, functionally graded lattice structures are fabricated from steel using SLM technique and the effect of different lattice types on the manufacturability, density and mechanical properties are investigated.Item Evaluation of Functionally Graded Lattice Properties of Laser Powder Bed Fused Stainless Steel 316L(2022) Ravichander, B.B.; Jagdale, S.H.; Theeda, S.; Kumar, G.The development of metal Additive Manufacturing (AM) techniques, in particular the laser powder bed fusion (LPBF) process, has led to an increase in the innovative design and fabrication of lightweight and complex porous metal structures. Despite the limitations of the LPBF process which limits the geometric accuracy of the porous structures, it eliminates the difficulties presented by conventional manufacturing techniques in the fabrication of highly complex structures. The properties of as-built porous structures depend on the unit cell design and porosity level. These lightweight metal structures have applications in medical and aerospace fields. The relationships between the lattice geometry and performance must be determined to successfully implement the functional lattice designs. In this study, functionally graded lattice structures are fabricated from steel using SLM technique and the effect of different lattice types on the manufacturability, density and mechanical properties are investigated.Item Evaluation of the Ecological Footprint for Parts from AlSi10Mg manufactured by Laser Powder Bed Fusion(2022) Weiss, C.; Boedger, C.; Schiefer, E.; Heussen, D.; Haefner, C.L.The manufacturing industry contributes immensely to the global emissions and therefore is a key factor that has to be addressed when a more sustainable production is desired. Laser Powder Bed Fusion (LPBF) is an AM technique that offers the possibility to manufacture metal parts in a more material efficient way due to the layer-by-layer build-up. Nevertheless, the processing chain for parts from LPBF contains additional steps like powder atomization, which also influence the ecological footprint of the production chain. Within this work, a life-cycle model for the production step of parts from AlSi10Mg powder material is developed. The model is supplied with data from the powder atomization up to the production step, either by literature, database or experimental measurements during production. The footprint in terms of CO2 emissions is then analyzed and emission-intense steps are identified. Two manufacturing scenarios are considered to evaluate the sensitivity on the emissions.Item Fatigue strength prediction through defects-based analysis of L-PBF 17-4 PH stainless steel(2022) Nandi, Indrajit; Welsh, Jade; Simsiriwong, Jutima; Shao, Shuai; Shamsaei, NimaMurakami’s approach has been used in the high cycle fatigue regime to relate the fatigue limit to the critical defect size and location in additively manufactured (AM) metallic materials. However, the applicability of this model has not yet been thoroughly examined for AM materials in the very high cycle fatigue (VHCF) regime. Therefore, this study investigates the possibility of relating the volumetric defect features to the fatigue strength of 17-4 precipitation hardened (PH) stainless steel (SS) manufactured via laser-powder bed fusion (L-PBF) additive manufacturing technology. The 17-4 PH SS specimens are manufactured using an EOS M290 L-PBF system, heat-treated, machined, polished, and tested in the VHCF regime using an ultrasonic fatigue testing system. Careful fractography has also been performed on all fractured specimens to determine the volumetric defects responsible for the crack initiation.Item In-situ Monitoring of Laser-Powder-Bed-Fusion Using IR and NIR Emissions to Detect Thermal Anomalies(2022) Roach, M.A.; Fowler, B.; Thakkar, D.; Babbitt, C.; Khurana, S.; Jared, B.H.Process monitoring of laser-powder-bed-fusion (L-PBF) has advanced significantly since the beginning of this technology. Many methods exist today for in-situ process monitoring; however, these methods can be costly to implement and provide sub-par image resolutions. This research aims to develop a method of low-cost and high-resolution thermal monitoring system using near-infrared (NIR) wavelength band emission monitoring to detect anomalies. This research will compare more expensive infrared (IR) wavelength band monitoring methods to the cheaper NIR method and other drawbacks brought about by monitoring one wavelength band over the other.Item Investigating the Relationship Between In-Process Quality Metrics and Mechanical Response in the L-PBF Process(2022) Sampson, Bradley J.; Morgan-Barnes, Courtney; Stokes, Ryan; Doude, Haley; Priddy, Matthew W.Laser powder bed fusion (L-PBF) additive manufacturing is a process that utilizes a high- powered laser to build near net-shaped parts in a layer-by-layer fashion using metal powder as the feedstock material. Traditionally, the analysis of L-PBF produced parts has relied solely on post- build characterization to understand the relationship between the printing process and the final mechanical properties. Recent developments of in-process quality assurance systems, such as Sigma Additive Solutions’ PrintRite3D, can measure in-process thermal signatures and melt pool disturbances in real-time. This research aims to examine the relationship between process parameters (e.g., scan strategy, scanning speed, and layer thickness) and in-process quality metrics (IPQMs) captured by the PrintRite3D system on a Renishaw AM400. The mechanical response of multiple part geometries (NIST residual stress bridges, single-arched bridges) and build materials (Ti6Al4V) includes residual stress deflection and hardness; the results are compared with the IPQMs.Item Machine Health Verification Process for Laser Powder Bed Fusion(2022) Hilton, Z.T.; Gray, JameeLaser powder bed fusion (LPBF) machines are complex systems comprised of a number of interconnected subsystems which work in concert during the laser powder bed fusion process. The health, i.e. consistency in performance, of these complex systems must be monitored and verified to ensure consistency in the process during long-term production. If a system is 'unhealthy' the process becomes less controlled and can lead to decreased, unknown, or unverifiable part quality. To monitor and validate whether a machine is healthy, a number of tests were developed, which consist of: power monitoring, multi-laser alignment, laser position, laser caustic, gas flow, elevator accuracy, and machine condition. The methodology and efficacy of each test are discussed along with additional potential tests and next steps.Item A Multiphysics Modeling Approach to Assess the Powder Bed Characteristics of High Strength Steel in Selective Laser Melting(2022) Rangapuram, M.; Yang, M.; Babalola, S.; Newkirk, J.W.; Bartlett, L.N.; Liou, F.F.; Chandrashekhara, K.Selective laser melting (SLM) is a type of additive manufacturing technique which uses a powder bed to form complex metal parts in a layer-by-layer process. The density of the powder bed in SLM affects the mechanical properties of the produced part. Good powder packing results in a higher powder bed density which in turn influences the quality of the produced part. In this work, a computational fluid dynamics (CFD) model was developed for the SLM process using Flow 3D software to study the effect of powder bed density on the melt pool characteristics of high strength steel. Discrete element method (DEM) was used to generate powder beds with realistic powder properties. The realistic powder properties of AF9628 were obtained using JMatPro software. The powder beds were irradiated with a moving laser heat source to study the melt pool characteristics. These models were validated with experimental results.Item Revealing Texture Induced Abnormal Tensile Deformation Behavior in Additively Manufactured Haynes 282 Using Crystal Plasticity Simulations(2022) Nandi, Indrajit; Ahmad, Nabeel; Shamsaei, Nima; Shao, ShuaiA ductile fracture typically features a dimpled surface appearance because of micro-void coalescence and a circular cup-and-cone morphology. Tensile fracture surfaces of additively manufactured Haynes 282, a nickel-base superalloy, in this work exhibit an elliptical shape – an aberration to classic fracture surface. Both microstructural characterization and fractography were performed using scanning electron microscopy (SEM) on the tensile deformed surfaces to assess the fracture behavior. To gain better mechanistic insights into the governing factors of this elliptical shape fracture, crystal plasticity finite element (CPFE) simulations were performed using the experimentally calibrated material parameters. Uniaxial tensile loading simulations were carried out on a polycrystalline aggregate where the initial texture was varied to the CPFE simulation to emulate the experimental microstructure. The mechanical response and shape of the fracture surface obtained from the simulations were compared with the experimental tensile deformed surface to illustrate the texture dependent deformation inhomogeneity.