Finite Element Modeling Of 3D Printed Partial-infill Stamp .
18th Annual SPE & Automotive Composites Conference ExhibitionSeptember 5-7, 2018Finite element modeling of 3D printedpartial-infill stamp forming moldsSunil Bhandari and Roberto Lopez-AnidoAdvanced Structures and Composites CenterUniversity of Maine
Introduction– 3D printed molds – Quick to production and rapid design changes RTM, Compression molding, injection molding Stamp forming – Fast process, molds for R&D purposes– Infill and outer shell Optimize infill and gap parametersYZXXZ plane (orthogonal tomachine bed)XY plane (parallel tomachine bed)X2
Introduction Create a mold with complex geometry for a part that is relativelydifficult to stamp form.Male MoldPP/GF prepreg tapesFemale Mold3
Introduction Mold FeaturesEdge walls blended with parabolic profile to reduce frictionBlended edges to reducefriction with forming tapesSolid reinforcement to minimizebending at the centerRelease pin holesSlot for transparent Polycarbonate sheet
Finite element model Two models– Coupon level lattice FEM– Part level homogenized continuum FEM5
Introduction - Process6
Coupon level lattice FEA materialcharacterizationShear tabsFilamentASTM ig: Tension test of filamentFig: Compression test of 3D printed specimen7
Finite element model – coupon level lattice A space frame lattice and shell finite element model can be used to predictthe linearly elastic response of a 3D printed part that has cellular internalstructure.The internal structure is modeled as a space frame and the outer perimeteris modeled as a shell.Fig: Space frame and shell model8
.Lattice FEA - ValidationD638 Tension specimenD6641 Compression specimenGauge AreaD7078 Shear specimenFig: ASTM Quasi-static test specimens and the gage area used for strain calculation.9
Lattice FEA - ResultsCompression inElasticElastic ModulusModulus fromfrom ExperimentsModelingwith range in(MPa)parenthesis (MPa)11601090the Z-directionCompression in909925(835 - 1030)Tension in the X 12001140-direction(1060 -1220)903Z-directionShear in the XYplane921726789-1.8796(738 – 872)Poisson’s%Ratio fromRatio fromdiffModelingExperiments0.2480.246 0.800.2350.286-17.80.3500.376-6.90.1890.235-19.6on test)υXZ 5.5-2.0(compression test)υXZ-8.0(693 – 838)785υXYPoisson’s(compressi(888– 962)PlaneShear in the XZ 5.2(990 -1370)the X-directionTension in the% difference(tension)υXY-1.4(tension)10
Finite element model – homogenizedcontinuum model As the size of the part grows larger, the lattice model grows bigger withincreasing number of DOF. The maximum size of element in the latticemodel is limited by geometry of the cellular structure.A homogenized model with smeared properties can be used to overcomethis limitation.Eg - DOF with lattice model : 26,763,264DOF with continuum model : 793,978Analysis time (T) is usually for linear static analysis O(n 2) T O(n 3)Virtual experiments can be carried out on finite element models of the latticestructure to generate material properties for an equivalent homogenouscontinuum solid.11
Continuum FEM - material characterizationShear tabsFilamentASTM : Tension test of filamentFig: Compression test of 3D printed specimen12
Continuum FEM Modelled as orthotropic solid.Infill pattern of -45 degrees gives rise to transverse isotropy.Material constants derived form virtual experiments Ex Ey, Ez, νxy, νxz νyz, Gxy, Gyz Gxz.The outer boundary layer modelled as shell (skin of the orthrotropic solidpart).13
Continuum FEM – virtual experiments for homogenizedpropertiesFig: Finite element model of virtual experiments to determinematerial properties for continuum model.14
Continuum FEM – material propertiesMechanical PropertyValueEx132 MPaEy132 MPaEz186 MPaνxy0.824νxz0νyz0Gxy5.27 MPaGxz34.3 MPaGyz34.3 MPa15
Continuum FEM – analysis16
Continuum FEM results17
Conclusions A space frame and lattice model can be used to predict effective propertiesof a 3D printed part that has cellular internal structure.A continuum model based on homogenization of lattice FEM can be usedanalyze 3D printed part that has cellular internal structure.Since a continuum model based on homogenization of lattice structure canbe modelled with smaller number of element, the finite element analysis canbe faster compared to space frame and shell lattice model.Future work : Iterative design optimization problems might be sped up ifhomogenized continuum model is used instead of lattice model.18
Questions ?19
References Sunil Bhandari, Roberto Lopez-Anido, Finite element analysis ofthermoplastic polymer extrusion 3D printed material for mechanical propertyprediction, Additive Manufacturing, Volume 22, August 2018, Pages 187196, ISSN 2214-8604, https://doi.org/10.1016/j.addma.2018.05.009.Sunil Bhandari, Roberto Lopez-Anido, Finite element modeling of 3Dprinted part with cellular internal structure using homogenized properties (Inreview)20
Fig: ASTM Quasi-static test specimens and the gage area used for strain calculation. D7078 Shear specimen. Elastic Modulus from Modeling (MPa) Elastic Modulus from Experiments with range in parenthesis (MPa) % difference
Finite element analysis DNV GL AS 1.7 Finite element types All calculation methods described in this class guideline are based on linear finite element analysis of three dimensional structural models. The general types of finite elements to be used in the finite element analysis are given in Table 2. Table 2 Types of finite element Type of .
element type. This paper presents a comprehensive study of finite element modeling techniques for solder joint fatigue life prediction. Several guidelines are recommended to obtain consistent and accurate finite element results. Introduction Finite element method has been used for a long time to study the solder joint fatigue life in thermal .
1 Overview of Finite Element Method 3 1.1 Basic Concept 3 1.2 Historical Background 3 1.3 General Applicability of the Method 7 1.4 Engineering Applications of the Finite Element Method 10 1.5 General Description of the Finite Element Method 10 1.6 Comparison of Finite Element Method with Other Methods of Analysis
Finite Element Method Partial Differential Equations arise in the mathematical modelling of many engineering problems Analytical solution or exact solution is very complicated Alternative: Numerical Solution – Finite element method, finite difference method, finite volume method, boundary element method, discrete element method, etc. 9
3.2 Finite Element Equations 23 3.3 Stiffness Matrix of a Triangular Element 26 3.4 Assembly of the Global Equation System 27 3.5 Example of the Global Matrix Assembly 29 Problems 30 4 Finite Element Program 33 4.1 Object-oriented Approach to Finite Element Programming 33 4.2 Requirements for the Finite Element Application 34 4.2.1 Overall .
2.7 The solution of the finite element equation 35 2.8 Time for solution 37 2.9 The finite element software systems 37 2.9.1 Selection of the finite element softwaresystem 38 2.9.2 Training 38 2.9.3 LUSAS finite element system 39 CHAPTER 3: THEORETICAL PREDICTION OF THE DESIGN ANALYSIS OF THE HYDRAULIC PRESS MACHINE 3.1 Introduction 52
Figure 3.5. Baseline finite element mesh for C-141 analysis 3-8 Figure 3.6. Baseline finite element mesh for B-727 analysis 3-9 Figure 3.7. Baseline finite element mesh for F-15 analysis 3-9 Figure 3.8. Uniform bias finite element mesh for C-141 analysis 3-14 Figure 3.9. Uniform bias finite element mesh for B-727 analysis 3-15 Figure 3.10.
The Finite Element Method: Linear Static and Dynamic Finite Element Analysis by T. J. R. Hughes, Dover Publications, 2000 The Finite Element Method Vol. 2 Solid Mechanics by O.C. Zienkiewicz and R.L. Taylor, Oxford : Butterworth Heinemann, 2000 Institute of Structural Engineering Method of Finite Elements II 2
