Hybrid casting as 3D printing solution
Mohamed EL MANSORI
Ecole Nationale Supérieure d’Arts et Métiers, France
Casting has been successful in creating complex industrial parts for thousands of years. While the process has significant advantages, the traditionally high cost and time involved in the creation of tooling and mould have limited the casting industry. 3D printing may offer an opportunity for the foundry industry to rethink old casting approaches and to revive this manufacturing approach, allowing high-quality parts to be produced more quickly and cheaply. One of the major concerns in sand moulding using 3D printing is the proper characterization of the local density and permeability of the mould for assessment quality without its destroying. Moulding sand compaction and liquid binder jetting bonding play crucial role on the mould quality and hence the quality of manufacturing casting. The air in the mould cavity can escape through the interstices of the porous 3D printed mould during metal casting, limiting casting defects caused by gas trapping in the melt. This keynote is designed to introduce the power of hybrid casting (3D printing combined to conventional metal casting) as rapid process to produce many types of mechanical parts and other objects requiring complex and exact geometries.
In-situ thermal cycle induced graded structure in 3D printed Ti–7.5Mo alloy a new insight in 4D printing
Key Laboratory of Metal High Performance Additive Manufacturing and Innovative Design, MIIT China, Northwestern Polytechnical University, Xi’an, Shaanxi 710072, P. R. China
Functionally graded materials (FGMs), which consists by multifunctional parts with different mechanical or physical properties, presents great potential application to tailor the microstructure to specific operating conditions with minimizing the interfacial problem. Laser solid forming (LSF), or direct energy deposition, is one kind of co-axial powder feeding laser additive manufacturing, which can fabricate near-net-shaped components with full density and fine microstructure. From the point of this work, using LSF process to produce FGMs can be considered as one kind of near 4D printing technology. The almost dense Ti-7.5Mo alloy (over 99.5%), which is thermal sensible, was manufactured by LSF from powder mixture of pure Ti and pure Mo. The as-fabricated sample presents a gradient microstructure along the building direction, which can be attributed to the thermal accumulation and in-situ thermal cycles during LSF process. Then, microstructure was determined by using XRD, SEM, EBSD and TEM with focus on grain size, phase, residual stress and dislocation. The gradient feature of mechanical properties was investigated by tensile tests, in which the tensile sample is prepared in sheet form at several altitude position. As the deposited altitude increase, the yield strength and ultimate tensile strength decreases from 681 Pa and 791 MPa to 579 MPa and 686 MPa, respectively. In contrast, the elongation of as-deposited sample increases from 10% to 25 %. Compared with LSF processed commercial pure Ti and Ti-6Al-4V, it is worth to note that the Young’s modulus of Ti-7.5Mo shows low value of 105 GPa for the entire sample. This work gives indication about a possible way to build complex shapes with strength and ductility graded Ti-Mo alloy for medical implant application.
Damage modeling and design of manufacturing materials considering structural features
Roberto M. Souzaa *, Newton K. Fukumasua, Izabel F. Machadoa
Escola Politécnica da Universidade de São Paulo, Brazil
The alternatives of metallic part production using additive manufacturing (AM) have increased significantly over the past few years. A wide range of compositions, structures and properties are available through options that are not limited to the type of process but include materials selection and melt strategies. Such an extensive set of possibilities discourage the use of traditional design of experiments approaches, especially those with the actual manufacturing of components for a given mechanical application. Alternatively, materials development may rely on the evaluation of component performance, combining real-time observations with physical and mathematical modeling of operation, such that damage phenomena are recorded as a function of the mechanical loads acting on the component. In this case, many conditions may be simulated in advance, reducing the number of options to manufacture to the most promising ones identified during the modeling step. However, in many cases, the effects of mechanical loadings must be modeled both at macroscopic and microscopic scales. At macroscopic scale, one must determine how the loads distribute in the component as a whole, considering the overall dimensions and bulk properties. Analysis at the microscopic scale aims to calculate how stresses are distributed over the material structure, considering both the macroscopic loads and the characteristics of the micro constituents.
This work describes an example were the concepts above were applied to study the wear behavior of hot forming tools used in rolling and forging. The example describes modeling of the progressive damage of the tools based on physical and mechanical properties of the micro-constituents of the tool material, thus allowing the design of materials with “engineered microstructure” for high performance. The correspondent experimental validation was conducted based on pilot operations. Possibilities of using these concepts in the design of AM components are discussed.
Identifying the Anisotropic and Cyclic Inelastic Characteristics of the Ti-6Al-4V and Maraging Steel 300 fabricated via Additive Manufacturing
Kyriakos I. Kourousis
School of Engineering, University of Limerick, Limerick Ireland.
Accurate knowledge of the mechanical behaviour of metals fabricated via additive manufacturing (AM) methods is of critical importance for engineering design. Adopters of the powder bed fusion (PBF) AM technology face challenges in obtaining the fabricated parts’ elastic and inelastic anisotropy and cyclic elastoplastic characteristics. This is attributed mainly to the lack of existing data and the sensitivity of the obtained mechanical properties to the various PBF build parameters and post-processing heat treatment. Commonly used PBF-fabricated metals in a range of biomedical, aerospace and manufacturing applications include Ti-6Al-4V and Maraging Steel 300. This talk presents the research findings on the anisotropic and cyclic plasticity response of the as-built SLM Ti-6Al-4V and the heat treated EOS Maraging Steel 300 [1-4]. Three primary build orientations (0º, 45º and 90 º relative to the horizontal build plate platform) have been examined for both alloys. The as-built SLM Ti-6Al-4V was subjected to an array of strain-controlled cyclic tests, while for the EOS Maraging Steel 300 a tensile test campaign was conducted on specimens undergone various heat treatment plans. The as-built SLM Ti-6Al-4V test results have shown substantial differences in the mechanical performance in relation to the wrought material, due to differences in the microstructure and the impact of the (non-relieved) residual stresses. In the case of the EOS Maraging Steel 300, the results included both tensile stress-strain curves and strain measurements, with data obtained via a digital image correlation (DIC) method, along the longitudinal and transverse dimension of the test specimens relative to the loading direction. The material’s strength, ductility and plastic anisotropy values and variations occurring from the various heat treatment plans were examined via a comprehensive visual representation (contour maps). Overall, both research studies contribute valuable data and insight to the open literature, focusing on mechanical performance beyond the commonly reported tensile properties for both AM metals.
Post Processing Strategies for AM parts
Satish T. S. Bukkapatnam
Texas A&M University, Texas, U.S.A
Surface finishing processes consume 20–70% of the cycle time of the emerging additive manufacturing (AM) process chains. This talk presents two different post processing strategies developed at the Institute for Manufacturing Systems at Texas A&M Engineering Experiment Station (TEES). These post-processing strategies include coupling traditional machining processes with non-traditional fine abrasive finishing (FAF) methods, as well as a novel magnetic fluidic polishing setup for localized finishing of freeform AM surfaces based on employing electro-permanent magnet arrays configured using a recently developed magnetic concentration principle. We demonstrate that the proposed post-processing strategies can be used to (a) selectively impart surface finish Sa < 25 nm on 316 L stainless steel and Ti64 components fabricated via laser powder-bed fusion, (b) reduce the surface porosity by ∼89% when compared to the as-fabricated sample, (c) polish hard-to-access local (up to 1.5 cm2) regions of freeform workpiece surfaces. We also present the results from characterization studies on the mechanics of surface modification resulting from these finishing processes.
Solid Freeform Fabrication of a Conceptual Artificial Photosynthesis Device
Jack G. Zhou
Department of Mechanical Engineering, Drexel University, Philadelphia, U.S.A
Additive manufacturing has brought a revolutionary change on traditional industrial production methods and people’s understanding of fabrication concepts. Tissue and Energy Engineering are multi-discipline researches which involves biomaterials science and engineering, biomedical engineering, precision design and manufacturing, and micro/nano technology. In this presentation I will introduce several research projects we have developed by using additive manufacturing, advanced bio, micro and nano technology in tissue and energy engineering applications and the detailed topics are:
- Biomimetic Structured Porogen Freeform Fabrication System for Tissue and Surgical Engineering; the project developed a new manufacturing process and a machine for three-dimensional bone scaffold using biomaterials, Solid Freeform Fabrication and biomimetic bone structure modeling. The scaffold can have the exact shape and similar internal structure of the bone tissue, and sufficient mechanical strength.
- Additive Manufacturing of a highly efficient artificial photosynthesis device with multi-layer interconnected channels and micro-porous structures; the project will fabricate an artificial photosynthesis device that is capable of receiving and then converting sunlight, CO2 and water into sugars/glucose for the production of biofuels. Additive manufacturing (AM) enhanced by high-resolution heterogeneous material printing technology and multi-function nozzle array will be investigated to design and build the innovative device with multi-layer interconnected channels and micro-porous structures.
The promise and risk of metal 3D printing
Brad L. Boyce
Sandia National Laboratories, Center for Integrated Nanotechnology
Additive manufacturing of metallic components offers new opportunities for rapid, low-cost, agile production of complex components. Moreover the manufacturing method enables an alternative approach to design via topology optimization, and an ability to produce lattice metamaterials with effective properties that are not achievable in monolithic materials. Agile qualification of additively manufactured (AM) structural components requires rapid, high-throughput post-process measurements of material properties. To this end, Sandia is developing automated robotic inspection platforms for additive materials. As an early demonstration, high-throughput tensile testing has been automated to enable hundreds of tests per day by a single operator and test machine. This method has revealed rare stochastic defects associated with network porosity that would have likely been missed by conventional test methods. Ultimately, high-throughput material property measurements can be integrated with the printers and post-print processing to enable automated process-structure-property optimization.
Micro-structural Characterization and Mechanical Properties of Two Copper Alloys Fabricated by the Selective Laser Melting (SLM) Process
Wojciech Z. Misiolek1
Loewy Institute, Lehigh University, Bethlehem, PA
Selective Laser Melting (SLM) is an additive manufacturing technique based on powder bed fusion technology that can produce near fully dense metal components. The additive processes are based on various approaches, however the SLM process is one of the leading candidates from the group of powder-based processes. The presented research results are addressing fabrication process optimization of selected two copper alloys, Cu-Sn and Cu-Ni-Si, with different level of metallurgical complexity. Mechanical properties as well as microstructure characterization were performed on the as printed and heat-treated samples. Discussion of existing engineering challenges, such as surface quality, remaining porosity and residual stresses within the printed parts is presented. Initial analysis of the residual stresses in the as printed and removed from the base plate parts are discussed
Tuning Biological Cell Responses: Additive Manufacturing 3D Biomaterial Substrates
Melt electrowriting (MEW) is an advanced polymer-based manufacturing process for fabricating structured 3D biomaterial substrates, and in conjunction with a machine-learning algorithm to classify cell shapes, it can be applied to produce a substrate with high cell shape homogeneity. Specifically, tuning the biophysical properties of the precision-stacked biomaterial substrates on which cells operate is a potential way to control cellular morphology and function. Our working premise is that there exists an unexplored dimensional scale window of 3D biomaterial substrates with geometrical feature sizes at the cell’s operating length scales (10 – 100 μm). Specifically, there exists a missing quantitative link between manufacturing process-enabled structured biomaterials and the single-cell biological performance outcomes for the fabricated substrates. To methodically address this knowledge gap, we advance an electrohydrodynamics-based 3D printing process to produce high-fidelity microscale fibrous substrates with consistent, welldefined pore microarchitectures and cellular-relevant dimensional characteristics. Furthermore, we compare the resultant biological outcomes on the 3D microscale fibrous substrates with 2D surface and nonwoven fiber meshes with optical measurements certified with a dimensional metrology framework. We implement Individual cell shapes to train a classifier to distinguish single cell confinement states that are induced by the prescribed substrate dimensionalities and topographies. In summary, we will report on a novel bioinformatics-guided AM technology platform, one that promises insight into cell-material interactions beyond the reach of current phenotypic control and analysis. Moreover, we will describe how the combination of AM and metrology tools can pave a new avenue for the systematic engineering of functional biomaterial systems to reliably guide distinct, uniform, and predictable cell responses, including fundamental mechanobiology studies and 3D printing of tissue constructs to meet specific biological designs at the single-cell level. Finally, we will comment on how design principles and metrology workflows advanced by way of the polymeric printing process described herein may have a prospective role in the printing and biological qualification of porous metal constructs.
Integrated Computational Materials Engineering Approach to Design Aerospace Parts
A. Kontsos and A. Najafi
Drexel University and Boeing Philadelphia are investigating the technology readiness level (TRL) of advanced manufacturing (AM) in relation to aerospace parts. A specific part has been identified which is replaced by a new part that is 3D printed. To obtain a new design, we define an optimization problem subjected to some design objective and constraint functions. To perform the optimization, we use topology optimization (TO) combined with lattice and skin optimization (LSO). We also study available additive manufacturing equipment to produce the part with the optimal design. Finally, mechanical testing, as well as characterization of the printed part, are used to select the appropriate metal to allow the manufacturing of the new part so that the design criteria are met.
Design of Materials using Shape and Topology Optimization
A. Najafi and A. Kontsos
Motivated by key advances in manufacturing techniques, the tailoring of materials with specific macroscopic properties has been the focus of active research in mechanical engineering and materials science over the past decade. The key challenge in this line of work is how to optimize the material microstructure to achieve a desired macroscopic constitutive response. The overwhelming majority of this type of inverse design work relies on topology and shape optimization based on linear and nonlinear theory. We develop and implement a method to design materials at the mesoscale using a shape optimization scheme to minimize or maximize a nonlinear cost function at the macroscale while satisfying a set of constraints associated, for example, with the volume fraction of inclusions or with the manufacturing technique. We apply the proposed shape optimization scheme in this work to several 2D and 3D structural problems including some benchmark and application examples to demonstrate the performance and accuracy of the method.