Browsing by Subject "lattice structures"
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Item Additive Manufactured Lightweight Vehicle Door Hinge with Hybrid Lattice Structure(University of Texas at Austin, 2019) Aydin, I.; Akarcay, E.; Gumus, O.F.; Yelek, H.; Engin, C.B.Item Bimetallic Castings for Wear Performance through Infiltration of Additive Manufactured Metal Lattice Structures(University of Texas at Austin, 2021) Liggett, J.C.; Snelling, D.A.; Xu, M.; Myers, O.J.; Thompson, S.M.High chromium white iron is an alloy frequently employed in the production of abrasion resistive wear components. Ground engaging components for mining or earthmoving frequently require such materials, as well as slurry pumps for mining applications. Although high chromium white iron alloy demonstrates excellent wear performance due to the formation of chromium carbides, it is brittle and lacks toughness. Impact resistance is often of great importance for ground engaging wear components; hence, this study will investigate a method by which high chromium white iron wear components may be reinforced by the formation of a bimetallic composite. In this research, an additively manufactured lattice structure of 316L stainless steel is infiltrated with high chromium white iron via the metal casting process. This procedure results in a bimetallic casting of reinforced white iron. Complete infiltration and metallurgical diffusion bonding were observed between the two alloys, validating this method as a means of reinforcing high chromium white iron castings for applications requiring high abrasion and impact resistance.Item A CAD-Based Workflow and Mechanical Characterization for Additive Manufacturing of Tailored Lattice Structures(University of Texas at Austin, 2018) Koch, P.; Korn, H.; Kordass, R.; Holtzhausen, S.; Schoene, C.; Mueller, B.; Stelzer, R.Lattice structures are highly recommended for lightweight applications and cost reduction in additive manufacturing (AM). Currently, parts with lattice structures are still mainly used for illustrative purposes and rarely in industrial products. One important reason is that, due to their high dependency on macro- and micro-geometry, the mechanical properties of manufactured structures are difficult to predict. Thus, even and precise struts are needed. In this paper, a workflow for fabrication of lattice structures with strut-diameters from 150 µm to 400 µm on commercial laser beam melting (LBM) systems is presented. Based on a CAD-integrated user-interface for lattice design, a customized slicing algorithm determines database-aided suitable exposure parameters which ensure that the properties of the manufactured struts will just be as specified upon design. Subsequently, compression tests are performed in order to verify the established workflow. The developed tool enables designers to integrate AM-specific geometries into their components with little specific experience in AM.Item Comparing Mechanical and Geometrical Properties of Lattice Structure Fabricated Using Electron Beam Melting(University of Texas at Austin, 2014) Park, Sang-in; Rosen, David W.; Duty, Chad E.To design lattice structure, a uniform voxel based approach is widely used which divides a part into unit volumes (e.g., cubes) and maps lattice topology into those volumes. In contrast, conformal lattice structures represent a second design method for constructing lattices in which unit cells are constructed parallel to the surface to be reinforced and are deformed in a manner that enables them to conform to the surface. In this paper, the strength of lattice structures designed using these two methods (uniform voxel based and conformal) are compared based on additive manufacturing (AM) process effects. For this purpose, spheres filled with three types of lattice structure are fabricated using electron beam melting technology and tested in compression. Effects of AM processes are studied in two ways – volumetric and structural performance equivalence. Struts in lattice structures are observed through a microscope to examine volume-equivalence and tests are simulated numerically and compared to identify structural equivalence.Item A Comparison of Synthesis Methods for Cellular Structures with Application to Additive Manufacturing(2008-09-10) Chu, Jane; Engelbrecht, Sarah; Graf, Greg; Rosen, David W.Cellular material structures, such as honeycombs and lattice structures, have been engineered at the mesoscale for high performance and multifunctional capabilities. We desire efficient algorithms for searching the large, complex design spaces associated with cellular structures. In this paper, we present a comparison of two synthesis methods, Particle Swarm Optimization (PSO) and least-squares minimization (LSM), for the design of components comprised of cellular structures. Computational characteristics of the algorithms are reported for design problems with hundreds of variables. Constraints from SLS and direct-metal manufacturing processes are incorporated to ensure that resulting designs are realizable. Two 2- dimensional examples are used to study the characteristics of the proposed synthesis methods.Item Compressive Response of Strut-Reinforced Kagome with Polyurethane Reinforcement(University of Texas at Austin, 2019) Gautam, Rinoj; Sridharan, Vijay Shankar; Teh, Wee Lee; Idapalapati, SridharLattice structures find immense application in lightweight structures for their high specific strength, modulus, and energy absorption. Strut-reinforced Kagome (SRK) structures provide better compressive performance compared to many existing lattice structures. In this study, the performance of acrylonitrile butadiene styrene (ABS) SRK lattice structures, fabricated by fused deposition modeling, under compression loading is investigated. Further, SRK structures were filled with different polyurethane in the empty space and their effect on the compressive performance was examined. The SRK structure demonstrated abrupt failure at the joints in the vicinity of face sheet, thereby reducing the energy absorption of the structure. The SRK with flexible foam (low-density polyurethane foam) had no significant effect on peak failure load and moduli, whereas energy absorption per unit mass was higher by 16.5%. The SRK with the rigid foam (high-density foam) displayed not only the better energy absorption per unit mass (116%) but also different failure behavior than SRK only.Item A Computational and Experimental Investigation into Mechanical Characterizations of Strut-Based Lattice Structures(University of Texas at Austin, 2019) Sereshk, Mohammad Reza Vaziri; Triplett, Kevin; St. John, Christopher; Martin, Keith; Gorin, Shira; Avery, Alec; Byer, Eric; St Pierre, Conner; Soltani-Tehrani, Arash; Shamsaei, NimaStrut-based lattices are widely used in structural components for reducing weight. Additive manufacturing has provided a unique opportunity to fabricate such complex geometries. In addition to the unit cell type, the strut size and shape can significantly affect the mechanical properties achieved. Therefore, furnishing a lattice structure library may help in selecting the appropriate combination of lattice types and dimensions for targeted mechanical performance for a specific application. This study presents a method for determination of mechanical properties, including strength and stiffness, for lattice structures. Finite element (FE) simulations are used as the main tool and the results of which are to be verified by mechanical testing of samples fabricated using the laser beam powder bed fusion (LB-PBF) process. Proper lattices with the stiffness matched with associated bone were determined. However, the result indicated that lattices made from 316L SS are not strong enough for bone implants. The proposed procedure can be used for other unit cells of interest due to its generality.Item Controlling Thermal Expansion with Lattice Structures Using Laser Powder Bed Fusion(University of Texas at Austin, 2017) Milward, S.S.; Swygart, H.; Eccles, L.; Brown, S.G.R.; Lavery, N.P.Tuning the Co-efficient of Thermal Expansion (CTE) of a component is traditionally limited by material choice. Laser Powder Bed Fusion (LPBF) enables the designer to create complex geometries including lattice structures. When combined with a secondary material, these metallic lattice structures can be designed to exhibit different CTE’s whilst retaining stiffness. This allows the designer the freedom to adjust the CTE by changing CAD variables such as lattice angle, and member thicknesses. This paper aims to develop an arrangement for CTE matched components for high precision optical systems. Development pursued using a Static Thermo-Structural Finite Element Analysis model to determine the best arrangements for the required CTE change. The results are incorporated into a new design prototype of a full cylindrical lens system in metal on a Laser Powder Bed Fusion machine.Item Design of Spatially Varying Orientation Lattice Structures Using Triply Periodic Minimal Surfaces(University of Texas at Austin, 2023) Wei, Chongyi; Smith, Douglas E.Interest continues to grow for lattice structures produced by additive manufacturing methods that are described by triply periodic minimal surface (TPMS). Tunable parameters that define the TPMS provide unique design flexibility where prior research has focused on designing hybrid or functionally graded TPMS structures. In this paper, a new strategy is proposed to include an orientation angle and volume fraction of each lattice cell simultaneously when defining structures derived from TPMS. The algorithm iteratively solves an underlying partial differential equation with the finite difference method to obtain a smooth, continuous lattice structure with a spatially varying orientation angle. The resulting lattice structure can be combined with other types of TPMS models using Gaussian radial basis and distance functions to achieve multi-TPMS lattice designs. The spatially varying lattice structures can also take the advantage of the directional effective modulus of TPMS to improve the strength the performance of lattice design.Item The Effect of Cell Size and Surface Roughness on the Compressive Properties of ABS Lattice Structures Fabricated by Fused Deposition Modeling(University of Texas at Austin, 2019) Mason, L.; Leu, M.C.Researchers looking to improve the surface roughness of acrylonitrile butadiene styrene (ABS) parts fabricated by fused deposition modeling (FDM) have determined that acetone smoothing not only achieves improved surface roughness but increases compressive strength as well. However, the sensitivity of ABS parts to acetone smoothing has not been explored. In this study we investigated FDM-fabricated ABS lattice structures of various cell sizes subjected to cold acetone vapor smoothing to determine the combined effect of cell size and acetone smoothing on the compressive properties of the lattice structures. The acetone-smoothed specimens performed better than the as-built specimens in both compression modulus and maximum load, and there was a decrease in those compressive properties with decreasing cell size. The difference between as-built and acetone-smoothed specimens was found to increase with decreasing cell size for the maximum load.Item Effect of Wall Thickness and Build Quality on the Compressive Properties of 304L Thin-Walled Structures Fabricated by SLM(University of Texas at Austin, 2018) Spratt, Myranda; Anandan, Sudharshan; Hussein, Rafid M.; Newkirk, Joseph W.; Chandrashekhara, K.; Misak, Heath; Walker, MichaelThe specific strength of lightweight lattice structures built with SLM is of interest to the aerospace industry. Honeycombs were manufactured with increasing wall thicknesses (which increases density) and tested under compression. The optimal strength to density ratio was determined from the resulting data. The build quality was also evaluated to determine how/if the results were influenced by the specimen quality. Differences between the nominal and as-built geometry were identified, but considered to be minimal. Microstructural evaluation of the specimens revealed a possible dependence on the ‘border scan’ properties, as the thickness of the specimens was such that the board scan made up most of the part. This work was used to validate the results of a finite element analysis of this geometry.Item Effective Elastic Properties of Additively Manufactured Metallic Lattice Structures: Unit-Cell Modeling(University of Texas at Austin, 2019) Fashanu, O.; Murphy, D.; Spratt, M.; Newkirk, J.; Chandrashekhara, K.Lattice structures are lightweight materials, which exhibit a unique combination of properties such as air and water permeability, energy and acoustic absorption, low thermal conductivity, and electrical insulation. In this work, unit-cell homogenization was used to predict the effective elastic moduli of octet-truss (OT) lattice structures manufactured using selective laser melting (SLM). OT structures were manufactured using a Renishaw AM 250 SLM machine with various relative densities. Compression test was carried out at strain rate 5 × 10-3 m-1 using an MTS frame. Finite element analysis was used in the determination of the OT’s effective elastic properties. Results from the finite element analysis were validated using experiments. It was observed that the finite element predictions were in good agreement with the experimental results.Item Effects of Unit Cell Size on the Mechanical Performance of Additive Manufactured Lattice Structures(University of Texas at Austin, 2019) Soltani-Tehrani, Arash; Lee, Seungjong; Sereshk, Mohammad Reza Vaziri; Shamsaei, NimaLattice structures are generated through the repetition of smaller structures, defined as unit cells. These structures are popular alternatives for bone implants due to the potential to adjust the stiffness. However, in some applications, there are volume and mass constraints that cannot be exceeded. Therefore, to match the lattice structure’s stiffness to that of the natural bone, unit cell sizes should be altered. In this study, the effects of different unit cell sizes, on the compression behavior of lattice structures fabricated from 316L stainless steel (SS) via laser beam powder bed fusion (LB-PBF) are studied through finite element analysis (FEA) while the volume and mass are kept constant and results of which, are validated by experiments. It was found that energy absorption capability and stiffness of lattice structures can increase with decreasing the size while the volume and mass are kept constant. The lattice structure with smaller unit cell dimensions tolerated a relatively higher maximum force for the same amount of displacement.Item Experimental and Numerical Investigations on Dynamic Mechanical Properties of TPMS Structures(University of Texas at Austin, 2023) Pokkalla, Deepak Kumar; Turner White, Brandon; Wang, Jier; Spencer, Ryan; Panesar, Ajit; Kim, Seokpum; Vaidya, UdayTriply Periodic Minimal Surface (TPMS) lattice structures have been of increasing interest due to their light weighting, enhanced mechanical properties, and energy absorption characteristics for automotive and biomedical applications. With the advent of additive manufacturing and geometric modeling software, TPMS lattices with complex geometries can be realized. In this work, TPMS lattice structures were fabricated with PLA using fused filament fabrication (FFF) and their dynamic properties are characterized through drop tower experiments. Although lightweight TPMS lattices are beneficial for their impact absorption capability, most of the existing works are limited to quasi-static compression, and dynamic impact tests are rarely performed. The current study investigates the stress-strain and energy absorption characteristics of TPMS lattices through drop tower testing and numerical modeling. Finite element modeling for TPMS lattices is carried out to validate the experimental responses. The mechanical properties, deformation, and failure mechanisms of TPMS lattices under dynamic impact are summarized for potential future applications.Item Fabrication of Support-Less Engineered Lattice Structures via Jetting of Molten Aluminum Droplets(University of Texas at Austin, 2018) Jayabal, Dinesh Krishna Kumar; Zope, Khushbu; Cormier, DenisMagneto Hydro Dynamic (MHD) jetting is a promising new metal additive manufacturing technique that employs on-demand jetting of molten metal droplets onto a moving substrate. A particularly unique aspect of the process is its potential to print down-facing features without the need for support structures. Under suitable droplet jetting conditions affecting time and temperature, each droplet at least partially solidifies prior to impact of the next incoming molten metal droplet. The combination of droplet jetting frequency and substrate velocity dictates the stepover distance between incoming droplets. With relatively large droplet step-over distances (or equivalently small percentage of droplet overlap), it is possible to print unsupported down-facing features that are nearly parallel to the X-Y build platform. In this paper, we describe initial results in which engineered lattice structures have been printed using 4043 aluminum using this approach. A parametric study that maps jetting frequency and droplet step-over distance with the resulting lattice strut angle is presented. With careful control of jetting parameters, we show that it is possible to print nearly horizontal lines without any support.Item Improving the Mechanical Response of the IWP Exo-skeletal Lattice Through Shape Optimization(University of Texas at Austin, 2023) Fisher, Joseph W.; Miller, Simon W.; Bartolai, Joseph; Simpson, Timothy W.Triply Periodic Minimal Surfaces have been identified as good candidates for the generation of lattice structures produced with additive manufacturing. These TPMS-based lattice structures avoid sharp features that are characteristic of strut-based lattice structures because of their constant zero mean curvature. Although studies have explored part-scale optimization using TPMS-based lattice structures, they have only varied the volume fraction by changing the level set in the approximate surface equations. By defining new parameterizations in the approximate surface equation, we can redistribute volume within the lattice structure at any volume fraction. In this paper, we introduce an approach for optimization of this new parameterization of TPMS equations using the Borg multi-objective evolutionary algorithm. We demonstrate this framework on the IWP exo-skeletal lattice under uniaxial compression. A relationship between the new parameters and the level set is derived for designs on the Pareto frontier of the optimized IWP TPxS. The performance of the Pareto optimal designs and the efficacy of the optimization approach are shown by comparing to the standard IWP lattice and four other lattices that share the same topology. The optimized designs are implemented and shared in custom nTopology blocks.Item An Investigation on the Definition and Qualification of Form on Lattice Structures(University of Texas at Austin, 2021) Praniewicz, M.; Fox, J.; Saldana, C.The lack of uniform qualification techniques for additively manufactured components throughout industry currently limits their application in high risk environments. This stems from a shortage of proper tolerancing and product definition to convey design intent and required qualification. This definition is particularly difficult for complex lattice geometries. The results of studies in which the form of a lattice component is defined by theoretical supplemental surfaces are summarized, with specific attention to the role of data sampling in the evaluation of form. A new case study is presented where techniques borrowed from surface metrology, namely the construction of a bearing area curve, are used to evaluate the sampling cutoff for form evaluation. This method is first validated on the nominal geometry of three lattice designs. Initial results indicate this as a promising methodology.Item Machine Learning Derived Graded Lattice Structures(University of Texas at Austin, 2021) Wang, J.; Panesar, A.Herein, we propose a new lattice generation strategy that is computationally cheaper and produces high-quality geometric definition based on Machine Learning (ML) when compared to traditional methods. To achieve the design of high-performance unit cells, firstly, the optimal mechanical property for each cell region is derived according to the loading condition and the reference density obtained utilising a conventional topology optimisation result. Next, a Neural Network (NN) is employed as an inverse generator which is responsible for predicting the cell pattern for the optimal mechanical property. Training data (~ 500) were collected from Finite Element (FE) analysis with varied cell parameters and then fed to the NN. With the help of ML, the time spent in building the inverse generator is significantly reduced. Furthermore, the ML-based inverse generator can handle different cell types rather than one specific type which facilitates the diversity and optimality of lattices.Item Manufacturability and Mechanical Characterization of Laser Sintered Lattice Structures(University of Texas at Austin, 2016) Josupeit, Stefan; Delfs, Patrick; Menge, Dennis; Schmid, Hans-JoachimThe implementation of lattice structures into additive manufactured parts is an important method to decrease part weight maintaining a high specific payload. However, the manufacturability of lattice structures and mechanical properties for polymer laser sintering are quite unknown yet. To examine the manufacturability, sandwich structures with different cell types, cell sizes and lattice bar widths were designed, manufactured and evaluated. A decisive criterion is for example a sufficient powder removal. In a second step, manufacturable structures were analyzed using four-point-bending tests. Experimental data is compared to the density of the lattice structures and allows for a direct comparison of different cell types with varied geometrical attributes. The results of this work are guidelines for the design and dimensioning of laser sintered lattice structures.Item Mechanical Behavior of Additively-Manufactured Gyroid Lattice Structure under Different Heat Treatments(University of Texas at Austin, 2019) Sereshk, Mohammad Reza Vaziri; Shrestha, Rakish; Lessel, Brandon; Phan, Nam; Shamsaei, NimaGyroid lattice structures, known for high stiffness and specific strength, are gaining attention for their energy absorption ability. However, energy absorption and strength of the gyroids are two desired properties, which vary contradictory. This study investigates manipulating properties on lattices using post-processing operation instead of modifying dimensions with consequent changes in weight and production cost. The challenge is that a particular post-processing heat treatment may improve one property, while it may be detrimental to other ones. The compressive properties of 17-4 PH stainless steel gyroid lattice structures fabricated using laser beam powder bed fusion (LB-PBF) method is investigated. Compressive properties such as load bearing capacity, crashing strength, and energy absorption are determined and the trends in their variation are discussed. Based on the experimental results, heat treating lattices with CA H900 procedure improves energy absorption and strength considerably, while increases crashing force, as well.