scholarly journals Building Block Synthesis of Self-Supported Three-Dimensional Compliant Elements for Metallic Additive Manufacturing

2020 ◽  
Vol 143 (5) ◽  
Author(s):  
Aschraf N. Danun ◽  
Philip D. Palma ◽  
Christoph Klahn ◽  
Mirko Meboldt
Keyword(s):  
Additive Manufacturing ◽  
Mechanical Performance ◽  
Compliant Mechanisms ◽  
Three Dimensional ◽  
Building Blocks ◽  
Small Scale ◽  
Bistable Switch ◽  
Powder Bed ◽  
Switch Mechanism ◽  
Metallic Additive

Abstract Compliant mechanisms gain motion through the elastic deformation of the monolithic flexible elements. The geometric design freedom of metallic additive manufacturing enables the fabrication of complex and three-dimensional (3D) compliant elements within mechanisms previously too complicated to produce. However, the design of metallic additive manufactured mechanisms faces various challenges of manufacturing restrictions, such as avoiding critical overhanging geometries and minimizing the amount of support structure, which has been reported in a few cases. This paper presents a synthesis approach for translational compliant elements, involving building blocks based on leaf-type springs and covering building orientations between 0 deg and 90 deg. In particular, this range is approached by the synthesis of self-supported 3D building blocks with orientations of 0 deg, 45 deg and 90 deg. The compliant elements are built based on linear and circular plane curves and compared numerically according to their mechanical performance to create preferable building blocks. The applicability of the presented procedure and the manufacturability of the compliant mechanisms are proven by printing individual 3D building blocks and their serial aggregation with laser-based powder bed fusion. Consequently, several prototypes are demonstrated, including a bistable switch mechanism and a large displaceable rotational spring joint. In addition, a small-scale highly maneuverable segment of a surgical instrument with a grasping mechanism at the distal end is proposed.

scholarly journals Material Reuse in Laser Powder Bed Fusion: Side Effects of the Laser—Metal Powder Interaction

Metals ◽  
2020 ◽  
Vol 10 (3) ◽  
pp. 341 ◽  
Author(s):  
Eleonora Santecchia ◽  
Stefano Spigarelli ◽  
Marcello Cabibbo
Keyword(s):  
Additive Manufacturing ◽  
Side Effects ◽  
Metal Powder ◽  
Three Dimensional ◽  
High Energy ◽  
Powder Bed Fusion ◽  
Laser Powder Bed Fusion ◽  
Powder Bed ◽  
Metal Additive Manufacturing ◽  
Metal Additive

Metal additive manufacturing is changing the way in which engineers and designers model the production of three-dimensional (3D) objects, with rapid growth seen in recent years. Laser powder bed fusion (LPBF) is the most used metal additive manufacturing technique, and it is based on the efficient interaction between a high-energy laser and a metal powder feedstock. To make LPBF more cost-efficient and environmentally friendly, it is of paramount importance to recycle (reuse) the unfused powder from a build job. However, since the laser–powder interaction involves complex physics phenomena and generates by-products which might affect the integrity of the feedstock and the final build part, a better understanding of the overall process should be attained. The present review paper is focused on the clarification of the interaction between laser and metal powder, with a strong focus on its side effects.

Structure and mechanical behavior of Big Area Additive Manufacturing (BAAM) materials

2017 ◽  
Vol 23 (1) ◽  
pp. 181-189 ◽  
Author(s):  
Chad E. Duty ◽  
Vlastimil Kunc ◽  
Brett Compton ◽  
Brian Post ◽  
Donald Erdman ◽  
...  
Keyword(s):  
Additive Manufacturing ◽  
Mechanical Performance ◽  
Research Effort ◽  
Small Scale ◽  
Second Phase ◽  
Initial Development ◽  
Imperfect Contact ◽  
Content Type ◽  
Oak Ridge ◽  
Printed Materials

Purpose This paper aims to investigate the deposited structure and mechanical performance of printed materials obtained during initial development of the Big Area Additive Manufacturing (BAAM) system at Oak Ridge National Laboratory. Issues unique to large-scale polymer deposition are identified and presented to reduce the learning curve for the development of similar systems. Design/methodology/approach Although the BAAM’s individual extruded bead is 10-20× larger (∼9 mm) than the typical small-scale systems, the overall characteristics of the deposited material are very similar. This study relates the structure of BAAM materials to the material composition, deposition parameters and resulting mechanical performance. Findings Materials investigated during initial trials are suitable for stiffness-limited applications. The strength of printed materials can be significantly reduced by voids and imperfect fusion between layers. Deposited material was found to have voids between adjacent beads and micro-porosity within a given bead. Failure generally occurs at interfaces between adjacent beads and successive layers, indicating imperfect contact area and polymer fusion. Practical implications The incorporation of second-phase reinforcement in printed materials can significantly improve stiffness but can result in notable anisotropy that needs to be accounted for in the design of BAAM-printed structures. Originality/value This initial evaluation of BAAM-deposited structures and mechanical performance will guide the current research effort for improving interlaminar strength and process control.

scholarly journals Adaptive Honeycomb Based on Additive Manufacturing: Research on Rapid Generation Algorithm, Manufacturing Process, and Mechanical Characteristics

2021 ◽  
Author(s):  
Bo Qian ◽  
Hongri Fan
Keyword(s):  
Additive Manufacturing ◽  
Mechanical Performance ◽  
Dimensional Space ◽  
Three Dimensional ◽  
Absorption Efficiency ◽  
Generation Algorithm ◽  
Steel Material ◽  
Rapid Generation ◽  
Low Efficiency ◽  
Critical Yield

Abstract In order to solve the problems of low efficiency and complex process in the current generation algorithm and process verification of hexagonal honeycomb structures for complex spatial shapes and arbitrarily curved surfaces, this paper proposes an adaptive hexagonal grid calculation method based on the intracellular splitting iteration method for the first time. This method can better adapt to the complex spatial shape and arbitrary curved surface structure in the three-dimensional space, and it can also achieve the purpose of enhancing the mechanical performance while maintaining the lightweight structure. According to the principle of the above algorithm, different structural models including honeycomb cells are calculated and generated. 316L Stainless Steel material and Selective Laser Melting additive manufacturing processes are also used for printing actual samples. The printed samples are mechanically compressed. According to the results of the compression curve, the critical yield force of the honeycomb grid parts with iteration is higher than that of the homogeneous honeycomb grid parts, and the value is basically greater than 30%-40%. Finally, the energy absorption efficiency can be increased by more than 20% according to the compression characteristics of the adaptive iterative honeycomb analyzed.

scholarly journals Review of Powder Bed Fusion Additive Manufacturing for Metals

Metals ◽  
2021 ◽  
Vol 11 (9) ◽  
pp. 1391
Author(s):  
Leila Ladani ◽  
Maryam Sadeghilaridjani
Keyword(s):  
Additive Manufacturing ◽  
Three Dimensional ◽  
Disruptive Technology ◽  
Powder Bed ◽  
Powder Particles ◽  
Metallic Parts ◽  
The Cost ◽  
Scientific Questions ◽  
Metal Additive

Additive manufacturing (AM) as a disruptive technology has received much attention in recent years. In practice, however, much effort is focused on the AM of polymers. It is comparatively more expensive and more challenging to additively manufacture metallic parts due to their high temperature, the cost of producing powders, and capital outlays for metal additive manufacturing equipment. The main technology currently used by numerous companies in the aerospace and biomedical sectors to fabricate metallic parts is powder bed technology, in which either electron or laser beams are used to melt and fuse the powder particles line by line to make a three-dimensional part. Since this technology is new and also sought by manufacturers, many scientific questions have arisen that need to be answered. This manuscript gives an introduction to the technology and common materials and applications. Furthermore, the microstructure and quality of parts made using powder bed technology for several materials that are commonly fabricated using this technology are reviewed and the effects of several process parameters investigated in the literature are examined. New advances in fabricating highly conductive metals such as copper and aluminum are discussed and potential for future improvements is explored.

Numerical Prediction of Residual Deformation and Failure for Powder Bed Fusion Additive Manufacturing of Metal Parts

2020 ◽  
Vol 36 (5) ◽  
pp. 623-636
Author(s):  
D.D. Lyu ◽  
W. Hu ◽  
B. Ren ◽  
X.F. Pan ◽  
C. T. Wu
Keyword(s):  
Additive Manufacturing ◽  
Process Simulation ◽  
Residual Deformation ◽  
Numerical Approach ◽  
Small Scale ◽  
Powder Bed Fusion ◽  
Failure Characteristics ◽  
Deformation And Failure ◽  
Powder Bed ◽  
Inherent Strain Method

ABSTRACTResidual deformation and failure are two critical issues in powder bed fusion (PBF) additive manufacturing (AM) of metal products. Residual deformation caused by the non-uniform residual stress distribution dramatically affects the quality of AM product and can result in catastrophic failure in operation. Therefore, the development of an effective numerical approach to predict residual deformation and failure characteristics of AM product is always a major concern in industrial applications.In this paper, a numerical approach in predicting residual distortion, stress and failure in AM products is presented. The conventional inherent strain method used in welding process is modified to consider the specific characteristic of AM process, such as the influences of reheating and scanning pattern. This approach consists of three simulation steps including a detailed process simulation in small-scale, a onetime static mechanical finite element analysis in part-scale, and a material failure analysis. First, the inherent strains are calculated from a thermo-mechanical process simulation in small-scale, which considers AM process parameters, such as laser power, scanning speed and path. The physical state in deposited materials including powder, liquid and solid states are taken into account in the simulation by specifying the solidus and liquidus temperature and corresponding material properties. Then the inherent strains are applied layer by layer to the part-scale simulation, where the residual distortion and stress can be predicted efficiently. Finally, a Lagrange particle method is utilized to study the failure characteristics of AM products. Numerical examples are studied to investigate the effectiveness and applicability of present approach.

Thermofluid Properties of Ti-6Al-4V Melt Pool in Powder-Bed Electron Beam Additive Manufacturing

2019 ◽  
Vol 141 (4) ◽  
Author(s):  
M Shafiqur Rahman ◽  
Paul J. Schilling ◽  
Paul D. Herrington ◽  
Uttam K. Chakravarty
Keyword(s):  
Electron Beam ◽  
Additive Manufacturing ◽  
Heat Source ◽  
Thermal Behavior ◽  
Source Parameters ◽  
Three Dimensional ◽  
Full Density ◽  
Layer By Layer ◽  
Powder Bed ◽  
Melt Pool

Electron beam additive manufacturing (EBAM) is a powder-bed fusion additive manufacturing (AM) technology that can make full density metallic components using a layer-by-layer fabrication method. To build each layer, the EBAM process includes powder spreading, preheating, melting, and solidification. The quality of the build part, process reliability, and energy efficiency depends typically on the thermal behavior, material properties, and heat source parameters involved in the EBAM process. Therefore, characterizing those properties and understanding the correlations among the process parameters are essential to evaluate the performance of the EBAM process. In this study, a three-dimensional computational fluid dynamics (CFD) model with Ti-6Al-4V powder was developed incorporating the temperature-dependent thermal properties and a moving conical volumetric heat source with Gaussian distribution to conduct the simulations of the EBAM process. The melt pool dynamics and its thermal behavior were investigated numerically, and results for temperature profile, melt pool geometry, cooling rate and variation in density, thermal conductivity, specific heat capacity, and enthalpy were obtained for several sets of electron beam specifications. Validation of the model was performed by comparing the simulation results with the experimental results for the size of the melt pool.

Microstructure of In738Lc Fabricated Using Laser Powder Bed Fusion Additive Manufacturing

2021 ◽  
pp. 1-19
Author(s):  
Nandana Menon ◽  
Tanjheel Hasan Mahdi ◽  
Amrita Basak
Keyword(s):  
Additive Manufacturing ◽  
Electron Backscatter Diffraction ◽  
Small Scale ◽  
Second Phase ◽  
Face Centered Cubic ◽  
Powder Bed Fusion ◽  
Laser Powder Bed Fusion ◽  
Powder Bed ◽  
Nickel Base Superalloys ◽  
Nickel Base

Abstract Nickel-base superalloys are extensively used in the production of gas turbine hot-section components as they offer exceptional creep strength and superior fatigue resistance at high temperatures. Such improved properties are due to the presence of precipitate-strengthening phases such as Ni3Ti or Ni3Al (gγ phases) in the normally face-centered cubic (FCC) structure of the solidified nickel. Although this second phase is the main reason for the improvements in properties, the presence of such phases also results in increased processing difficulties as these alloys are prone to crack formation. In this work, specimens of IN738LC are fabricated on a Coherent Creator laser powder bed fusion (L-PBF) additive manufacturing (AM) equipment. Optical microscopy (OM), scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), and X-Ray diffraction (XRD) are carried out to characterize the deposit region. Metallurgical continuity is achieved in the entire deposit region and the specimens do not show any warpage. However, the specimens show voids (e.g., pores and cracks) in the deposit region. The results show that the percentage void area decreases along the build height direction. The deposited IN738LC shows polycrystalline grains in the entire deposit region as confirmed by XRD and EBSD. The grain size also shows variations along the build direction. In summary, the results open opportunities for academic researchers and small scale businesses in fabricating high-gγ nickel-base superalloys on a desktop laser powder bed fusion AM equipment

Thermal Analysis of Electron Beam Additive Manufacturing Using Ti-6Al-4V Powder-Bed

2017 ◽  
Author(s):  
M. Shafiqur Rahman ◽  
Paul J. Schilling ◽  
Paul D. Herrington ◽  
Uttam K. Chakravarty
Keyword(s):  
Electron Beam ◽  
Additive Manufacturing ◽  
Three Dimensional ◽  
Vital Role ◽  
Full Density ◽  
Rate Variation ◽  
Layer By Layer ◽  
Powder Bed ◽  
Part Quality ◽  
Melt Pool

Electron Beam Additive Manufacturing (EBAM) is one of the emerging additive manufacturing (AM) technologies that is uniquely capable of making full density metallic components using layer-by-layer fabrication method. To build each layer, the process includes powder spreading, pre-heating, melting, and solidification. The thermal and material properties involved in the EBAM process play a vital role to determine the part quality, reliability, and energy efficiency. Therefore, characterizing the properties and understanding the correlations among the process parameters are incumbent to evaluate the performance of the EBAM process. In this study, a three dimensional computational fluid dynamics (CFD) model with Ti-6Al-4V powder has been developed incorporating the temperature-dependent thermal properties and a moving conical volumetric heat source with Gaussian distribution to conduct the simulations of the EBAM process. The melt-pool dynamics and its thermal behavior have been investigated numerically using a CFD solver and results for temperature profile, cooling rate, variation in density, thermal conductivity, specific heat capacity, and enthalpy have been obtained for a particular set of electron beam specifications.

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