Faculty Publications
Permanent URI for this communityhttps://idr.nitk.ac.in/handle/123456789/18736
Publications by NITK Faculty
Browse
4 results
Search Results
Item Effect of axial compression on dynamic response of concurrently printed sandwich(Elsevier Ltd, 2021) Bharath, H.S.; Waddar, S.; Bekinal, S.I.; Jeyaraj, J.; Doddamani, M.In this work, the sandwich is concurrently realized using high density polyethylene (HDPE) skins and syntactic foam core through three-dimensional printing (3DP). Syntactic foam core is printed using lightweight feedstock filaments having glass microballoons (GMBs) by 20–60 vol% embedded in HDPE. These lightweight filaments are used as feed material in FFF (fused filament fabrication) based three-dimensional printer. The concurrently printed sandwich is loaded axially in a compressive mode for investigating the influence of GMB loading on buckling and natural frequency. The experimental load–deflection data and modal analysis are utilized for estimating critical buckling load and natural frequencies, respectively, under axial compression. Increasing GMB content enhances load to buckle and frequency of the printed sandwiches. The natural frequency decrease with higher compressive loads. Furthermore, the fundamental natural frequency increases exponentially when these printed sandwiches are subjected to axial compression loads that are higher than the load required for critical buckling. The load–deflection data and frequency obtained experimentally are compared with numerical predictions deduced using finite element analysis (FEA), which are noted to match well. © 2020 Elsevier LtdItem Flexural response of 3D printed sandwich composite(Elsevier Ltd, 2021) Bharath, H.S.; Bonthu, D.; Gururaja, S.; Prabhakar, P.; Doddamani, M.Among many lightweight materials used in marine applications, sandwich structures with syntactic foam core are promising because of lower water uptake in foam core amid face-sheets damage. HDPE (high-density polyethylene) filament is used to 3D print sandwich skin, and glass microballoon (GMB) reinforced HDPE syntactic foam filaments are used for the core. The optimized parameters are used to prepare blends of 20, 40, and 60 vol% of GMB in HDPE. These foamed blends are extruded in filament form to be subsequently used in commercially available fused filament fabrication (FFF) based 3D printers. The defect-free syntactic foam core sandwich composites are 3D printed all at once (skin-core-skin printing in sequence at once) using optimized printing parameters and characterized for the flexural behavior. The result reveals that the addition of GMB increases both specific modulus and strength in sandwich composites and is highest for the sandwich having a core with 60 vol% of GMB. The measured properties of sandwiches are compared with a respective core to study the effect of the sandwich. It is observed that flexural strength, fracture strength, and strain of foam core sandwiches registered superior response than their respective cores. The experimental results are found in good agreement with theoretical predictions. Finally, the failure mode of the printed sandwich is also discussed, and it is observed that none of the 3D printed syntactic foam core sandwiches fractured due to shear failure. © 2021 Elsevier LtdItem Dynamic behavior of concurrently printed functionally graded closed cell foams(Elsevier Ltd, 2021) Dileep, B.; Prakash, R.; Bharath, H.S.; Jeyaraj, J.; Doddamani, M.In this work, functionally graded foams (FGFs) of closed cell types are three-dimensionally printed (3DP) concurrently. These closed cell syntactic foams are manufactured by reinforcing 20, 40, and 60 vol% hollow glass microballoons (GMBs) in the high density polyethylene (HDPE) matrix and are investigated for their mechanical buckling and free vibration response. The critical buckling load (Pcr) of the FGFs are evaluated using the Double Tangent Method (DTM), Modified Budiansky Criteria (MBC), and Vibration Correlation Technique (VCT). It is observed that Pcr evaluated by all three methods are in good agreement. Among all FGFs, FGF-2 exhibited higher buckling strength with 22–26% higher than FGF-1 and FGF-3. Under no-load and uniaxial compressive loads, the first three natural frequency of FGFs and their corresponding damping factors are evaluated. At first mode, the natural frequency of FGFs decreases in the pre-buckling zone and started increasing in the post-buckling zone. Damping factor exhibited reverse trend compared to the trend shown by the natural frequencies. Among all FGFs, FGF-2 (20-40-60 GMB gradation) exhibited better natural frequency. Experimental results are compared with a finite element based simulation results. © 2021 Elsevier LtdItem Mechanical response of additively manufactured foam: A machine learning approach(Elsevier B.V., 2022) Neelam, R.; Kulkarni, S.A.; Bharath, H.S.; Powar, S.; Doddamani, M.This paper uses ensemble and automated machine learning algorithms to predict the mechanical properties (tensile and flexural strength) of a three-dimensionally printed (3DP) foamed structure. The closed cell foams were made from the most commonly used thermoplastic, High-Density Polyethylene (HDPE). The hollow glass microspheres are infused in HDPE at varying volume %. The available data on these foams' mechanical properties are used by the chosen machine learning (ML) algorithms to propose the best suited algorithm for such a three-phased microstructure as these closed cell foams exhibit. Finally, the strength predictions from the models were validated using experimental data. The models were trained with nozzle temperature, bed temperature, and force values as input parameters. The output parameters predicted were the tensile and flexural strength. LightGBM outperforms all other models in terms of performance among ensemble-based models, while H2OAutoML outperforms all other models. All the ML algorithms produced models with greater than 95% accuracy. Finally, memory and time consumption for each model are presented. © 2022 The Authors