Multi-Material Composition Optimization vs Software-Based Single-Material Topology Optimization of a Rectangular Sample under Flexural Load for Fused Deposition Modeling Process

Additive manufacturing (AM) technologies have been evolved over the last decade, enabling engineers and researchers to improve functionalities of parts by introducing a growing technology known as multi-material AM. In this context, fused deposition modeling (FDM) process has been modified to create multi-material 3D printed objects with higher functionality. The new technology enables it to combine several types of polymers with hard and soft constituents to make a 3D printed part with improved mechanical properties and functionalities. Knowing this capability, this paper aims to present a parametric optimization method using a genetic algorithm (GA) to find the optimum composition of hard polymer as polylactic acid (PLA) and soft polymer as thermoplastic polyurethane (TPU 95A) used in Ultimaker 3D printer for making a rectangular sample under flexural load in order to minimize the von Mises stress as an objective function. These samples are initially presented in four deferent forms in terms of composition of hard and soft polymers and then, after the optimization process, the final ratio of each type of material will be achieved. Based on the volume fraction of soft polymers in each sample, the equivalent topologically-optimized samples will be obtained that are solely made of single-material PLA as hard polymer under the same flexural load as applied to multi-material samples. Finally, the structural results and manufacturability in terms of the generated support structures, as key element of some AM processes, will be compared for the resultant samples created by two methods of optimization.

Buckling strength of additively manufactured cylindrical shells: An exploratory study of as-printed and reinforced ABS and PLA cases

Additively-manufactured (AM) materials have a defined mesostructure and natural voids which impact their structural stability; thin shells which so not have bulk to support or absorb the effects of the variances in properties are particularly affected. Thin shells are a common feature in many designs, providing good strength-to-weight ratios for many applications, particularly in the aerospace and structural design domains. The use of AM processes to produce thin structures could both expand the use of AM and improve the application space for thin structures in design, but this problem has not yet been widely explored for buckling cases. The brief exploratory study presented in this paper examined the characteristics and critical buckling load of thin-walled ABS and PLA cylinders under static axial and angled radial loading. A designed 2(4-1) factorial experiment was used to explore the buckling behavior, examining the impact of wall thickness, material, and two kinds of internal reinforcement (soft infill and polyurethane foam). Analysis of variance (ANOVA) (including model adequacy testing and proof of Fisher Assumption validity) was completed on data from two replications (32 total tests), providing useful information on the significance of the factors and their interactions. The data is provided in full, along with a discussion of the experimental design and testing method, the results, and the importance of this problem in further research efforts. The results of the tests showed a dramatic variance in the performance based on the characteristics of the cylinders. The data collected can be used to drive future work toward the modeling and design of hard polymer AM thin structures, as well as developing efficient and low-cost methods for testing and exploring these structures for practical design problems.

Utilization of coconut shells in the manufacture of appropriate goods

Coconut shell inside is hard or very hard polymer, because of the composition of lignin > cellulose, such material s not good as a TV antenna. Because if given electromagnetic waves there will be vibrations of molecules >> ure rotation. To overcome this, the lignin concentration is reduced so that the concentration of lignin <cellulose can be used as a TV antenna, HP, because such material has become soft material. This combination of soft> hard polymers can theoretically be used for the purpose of detecting earthquakes, satellite etc. If the coconut is shaken, there will be ripples of coconut water to the ears, facts thus showing that the coconut shell has gaps or pores which carries waves of coconut water to the ears, which come out through the interface of lignin cellulose. The initial symptoms thus mean that the coconut shell can reflect and absorb waves. The advantages of this antenna can close up more clear, clear, cool clearer eyes and reception, can be used in the lowlands, highlands and at the bottom sea, this antenna is very good performance for high frequencies, can close up clearer, clear, cool in the eyes and voice reception clearer.

Effect of Pad and Liner Material Properties on the Static Load Performance of a Tilting Pad Thrust Bearing

Tilting pad thrust bearings (TPTBs) control rotor axial placement in rotating machinery, and their main advantages include low drag power loss, simple installation, and low-cost maintenance. The paper details a novel thermo-elasto-hydrodynamic (TEHD) analysis predictive tool for TPTBs that considers a three-dimensional (3D) thermal energy transport equation in the fluid film, coupled with heat conduction equations in the pads, and a generalized Reynolds equation with cross-film viscosity variation. The predicted pressure field and temperature rise are employed in a finite element (FE) structural model to produce 3D elastic deformation fields in the bearing pads. Solutions of the governing equations delivers the operating film thickness, required flowrate, and shear drag power loss, and the pad and lubricant temperature rises as a function of an applied load and shaft speed. To verify the model, predictions of pad subsurface temperature are benchmarked against published test data for a centrally pivoted eight-pad TPTB with 267 mm in outer diameter (OD) operating at 4–13 krpm (maximum surface speed = 175 m/s) and under a specific load ranging from 0.69 to 3.44 MPa. The current TEHD temperature predictions match well the test data with a maximum difference of 4 °C and 11 °C (<10%) at laminar and turbulent flow conditions, receptively. Next, the TEHD predictive tool is used to study the influence of both pad and liner material properties on the performance of a TPTB. The analysis takes a whole steel pad (without a liner or babbitt), a steel pad with a 2-mm-thick babbitt layer (common usage), a steel pad with a 2-mm-thick hard-polymer (polyether ether ketone, e.g., PEEK®) liner, and a pad entirely made of hard-polymer material, whose elastic modulus is just 12.5 GPa, only 6% that of steel. The bare steel pad reveals the poorest performance among all the pads as it produces the smallest fluid film thickness and consumes the largest drag power loss. For laminar flow operations (Reynolds number Re < 580), the babbitted-steel pad operates with the thickest fluid film and the lowest film temperature rise. For turbulent flow conditions Re > 800, the solid hard-polymer pad, however, shows a 23% thicker film than that in the babbitted pad and produces up to 25% lesser drag power loss. In general, the solid hard-polymer TPTB is found to be a good fit for operation at a turbulent flow condition as it shows a lower drag power loss and a larger film thickness; however, its demand for a too large supply flowrate is significant. Predictions for steel pads with various hard-polymer liner and babbitt thicknesses demonstrate that using a hard-polymer liner, instead of white metal, isolates the pad from the fluid film and results in an up to 30 °C (50%) lower temperature rise in the pads than that for a babbitted-steel pad. For operations under a heavy specific load (>3.0 MPa), however, a thick hard-polymer liner extensively deforms and results in a small film thickness.

Effect of Pad and Liner Material Properties on the Static Load Performance of a Tilting Pad Thrust Bearing

Tilting Pad Thrust Bearings (TPTBs) control rotor axial placement in rotating machinery and their main advantages include low drag power loss, simple installation, and low-cost maintenance. The paper details a novel thermo-elasto-hydrodynamic (TEHD) analysis predictive tool for TPTBs that considers a 3D thermal energy transport equation in the fluid film, coupled with heat conduction equations in the pads, and a generalized Reynolds equation with cross-film viscosity variation. The predicted pressure field and temperature rise are employed in a finite element structural model to produce 3D elastic deformation fields in the bearing pads. Solutions of the governing equations delivers the operating film thickness, required flow rate, shear drag power loss, and the pad and lubricant temperature rises as a function of an applied load and shaft speed. To verify the model, predictions of pad sub-surface temperature are benchmarked against published test data for a centrally pivoted eight-pad TPTB with 267 mm in outer diameter operating at 4–13 krpm (maximum surface speed = 175 m/s) and under a specific load ranging from 0.69 to 3.44 MPa. The current TEHD temperature predictions match well the test data with a maximum difference of 4°C and 11°C (< 10%) at laminar and turbulent flow conditions, receptively. Next, the TEHD predictive tool is used to study the influence of both pad and liner material properties on the performance of a TPTB. The analysis takes a whole steel pad (without a liner or babbitt), a steel pad with a 2 mm thick babbitt layer (common usage), a steel pad with a 2 mm thick hard-polymer (polyether ether ketone, e.g PEEK®) liner, and a pad entirely made of hard-polymer material, whose elastic modulus is just 12.5 GPa, only 6% that of steel. The bare steel pad reveals the poorest performance among all the pads as it produces the smallest fluid film thickness and consumes the largest drag power loss. For laminar flow operations (Reynolds number Re < 580), the babbitted-steel pad operates with the thickest fluid film and the lowest film temperature rise. For turbulent flow conditions Re > 800, the solid hard-polymer pad, however, shows a 23% thicker film than that in the babbitted pad and produces up to 25% lesser drag power loss. In general, the solid hard-polymer TPTB is found to be a good fit for operation at a turbulent flow condition as it shows a lower drag power loss and a larger film thickness, however, its demand for a too large supply flow rate is significant. Predictions for steel pads with various hard-polymer liner and babbitt thicknesses demonstrate that using a hard-polymer liner, instead of white metal, isolates the pad from the fluid film and results in an up to 30°C (50%) lower temperature rise in the pads than that for a babbitted-steel pad. For operations under a heavy specific load (> 3.0 MPa), however, a thick hard-polymer liner extensively deforms and results in a small film thickness.

Feasibility of Utilization of Industrial Polyurethane (PU) Rubber Waste in Geopolymer Concrete.

Concrete being most widely used construction material across the world need to be sustainable. This study aims at feasibility study the effects of addition of PU rubber in geopolymer concrete for its strength. PU rubber is formed by polymerization process. A long and low crosslinking chain gives stretchy polymer and a short and high crosslinking chain gives hard polymer. High amounts of crosslinking give tough or rigid polymers. Geopolymer concrete includes an alternate material i.e Fly ash in replacement of cement, as a binding material . Fly ash reacts with the alkaline activated solution i.e mixture of Sodium Hydroxide (NaOH) and Sodium Silicate (Na2SiO3) forming a gel which binds the aggregates thoroughly. Cubes of size 150mm x 150mm x 150mm were casted and oven curing was done for 24 hour at 100°C. Compression test was performed in hardened state, for different proportions of replacing the aggregate with PU rubber i.e. 5%, 10%, 15%, 20%. Compressive strength test was performed at 7 &amp; 28 days. Results were obtained and compared. Optimum mixes are Fly ash Coarse aggregate, Fine aggregate, Solution of NaOH and Na2SiO3 combined. Decrease in strength was observed at 7 &amp; 28 days.

Sustainable and Eco-Friendly Vege Roofing Tiles: An Innovative Bio-Composite

This paper presents a research study conducted on the usage of vegetable oil for the production of eco-friendly Vege roofing tiles. Conventional roofing tiles which constitute of concrete and clay are considered as environmentally unfriendly because of the significant amount of greenhouse gas emission during their production. An entirely novel methodology of utilizing catalyzed vegetable oil is proposed which can totally replace the use of traditional binders like cement and clay. Limited trails conducted on prototypes samples revealed that when catalyzed vegetable oil mixed with aggregates, properly compacted and heat cured at 190oC for 24 hours, have shown flexural strength up to 9.5 MPa. The superior strength gain of these prototype samples was considered due to the use of the catalyst with vegetable oil, which resulted in the initiation of catalytic oxy-polymerization set of reactions during heat curing, converting vegetable oil to solid, hard polymer which is considered responsible for strength achievement factor for these novel Vege roofing tiles. All prototypes samples were tested for performance indicators like water absorption, permeability, and flexural strength according to ASTM standards. Moreover, the susceptibility of oil leachate from the tiles oil, when tested using electrical conductivity method showed a negligible amount of the electrical conductivity. Moreover, the estimated embodied energy requirements for these tiles were found quite less when compared to conventional tiles.