Showing papers by "Rashid K. Abu Al-Rub published in 2018"

Topology-mechanical property relationship of 3D printed strut, skeletal, and sheet based periodic metallic cellular materials

Abstract: Recent advances in additive manufacturing facilitated the fabrication of parts with great geometrical complexity and relatively small size, and allowed for the fabrication of topologies that could not have been achieved using traditional fabrication techniques. In this work, we explore the topology-property relationship of several classes of periodic cellular materials; the first class is strut-based structures, while the second and third classes are derived from the mathematically created triply periodic minimal surfaces, namely; the skeletal-TPMS and sheet-TPMS cellular structures. Powder bed fusion technology was employed to fabricate the cellular structures of various relative densities out of Maraging steel. Scanning electron microscope (SEM) was also employed to assess the quality of the printed parts. Compressive testing was performed to deduce the mechanical properties of the considered cellular structures. Results showed that the sheet-TPMS based cellular structures exhibited a near stretching-dominated deformation behavior, while skeletal-TPMS showed a bending-dominated behavior. On the other hand, the Kelvin and Gibson-Ashby strut-based topologies exhibited a mixed mode of deformation while the Octet-truss showed a stretching-dominated behavior. Overall the sheet-TPMS based cellular structures showed superior mechanical properties among all the tested structures. The most interesting observation is that sheet-based Diamond TPMS structure showed the best mechanical performance with nearly independence of relative density. It was also observed that at decreased volume fractions the effect of geometry on the mechanical properties is more pronounced.

The effect of architecture on the mechanical properties of cellular structures based on the IWP minimal surface

Abstract: Architected materials are materials engineered to utilize their topological aspects to enhance the related physical and mechanical properties. With the witnessed progressive advancements in fabrication techniques, obstacles and challenges experienced in manufacturing geometrically complex architected materials are mitigated. Different strut-based architected lattice structures have been investigated for their topology-property relationship. However, the focus on lattice design has recently shifted toward structures with mathematically defined architectures. In this work, we investigate the architecture-property relationship associated with the possible configurations of employing the mathematically attained Schoen’s I-WP (IWP) minimal surface to create lattice structures. Results of mechanical testing showed that sheet-based IWP lattice structures exhibit a stretching-dominated behavior with the highest structural efficiency as compared to other forms of strut-based and skeletal-based lattice structures. This study presents experimental and computational evidence of the robustness and suitability of sheet-based IWP structures for different engineering applications, where strong and lightweight materials with exceptional energy absorption capabilities are required.

Nature-Inspired Lightweight Cellular Co-Continuous Composites with Architected Periodic Gyroidal Structures

Abstract: Shell-core cellular composites are a unique class of cellular materials, where the base constituent is made of a composite material such that the best distinctive physical and/or mechanical properties of each phase of the composite are employed. In this work, the authors demonstrate the additive manufacturing of a nature inspired cellular three-dimensional (3D), periodic, co-continuous, and complex composite materials made of a hard-shell and soft-core system. The architecture of these composites is based on the Schoen's single Gyroidal triply periodic minimal surface. Results of mechanical testing show the possibility of having a wide range of mechanical properties by tuning the composition, volume fraction of core, shell thickness, and internal architecture of the cellular composites. Moreover, a change in deformation and failure mechanism is observed when employing a shell-core composite system, as compared to the pure stiff polymeric standalone cellular material. This shell-core configuration and Gyroidal topology allowed for accessing toughness values that are not realized by the constituent materials independently, showing the suitability of this cellular composite for mechanical energy absorption applications.

Modeling Time and Frequency Domain Viscoelastic Behavior of Architectured Foams

Abstract: The time-dependent behavior of architected lightweight cellular solids or foams is important to investigate for various structural applications. In this paper, the authors studied the linea...

Effect of the Realistic Tire Contact Pressure on the Rutting Performance of Asphaltic Concrete Pavements

Abstract: The effect of different configurations of normal contact stresses on the rutting performance of asphalt concrete overlays on a soft and stiff Crushed Aggregate Base (CAB) layer is investigated. A three-dimensional (3-D) finite element model of a pavement structure is generated. The effect of different types of simplified normal contact stresses and a realistic 3-D normal stress on the rutting performance is investigated. Since the failure mechanism of asphaltic materials at high temperature is mainly related to the flow of the material, the viscoelastic and viscoplastic constitutive relationships coupled with the hardening-relaxation mechanisms are utilized to represent the behavior of asphalt concrete layer. This constitutive relationship is part of the PANDA (Pavement Analysis using Nonlinear Damage Approach) model developed by the authors and their collaborators. As the result of simulation, the magnitude of the rut depth on the asphalt concrete layer is generally determined to be inversely proportional to the stiffness of the CAB layer, and the rut depth on the asphalt concrete layer under the realistic 3-D normal stress is about 1.5 times greater than the rut depth under uniformly distributed normal stress.

Three-dimensional feed spacers with tpms architectures for membrane-based systems

Abstract: A filter element comprises a membrane layer; and a feed spacer on the membrane layer, wherein the feed spacer comprises a plurality of unit cells arranged in three dimensions, wherein each of the plurality of unit cells comprises a cavity defined by a triply periodic minimal surface, and wherein the cavities of the plurality of unit cells are interconnected to allow a fluid to pass through the cavities of the plurality of unit cells.

CFD Modelling of NOx and Soot Formation in Aluminum Anode Baking Furnace

Abstract: The cost and quality of aluminum produced by the reduction process are strongly dependent on heat treated (baked) carbon anodes. A typical aluminum smelter requires more than half a million tons of carbon anodes for producing one million ton of aluminum. The anode baking process is very energy intensive, approximately requires 2GJ of energy per ton of carbon anodes. Moreover, pollutant emissions such as NOx and soot formation are of major concern in the aluminum anode baking furnace. The current study aims at developing an accurate numerical platform for predicting the combustion and emissions characteristics of an anode baking furnace. The Brookes and Moss model, and the extended Zeldovich mechanism are employed to estimate soot and NOx concentration, respectively. Considering a fire group of three burner bridges, one after the other in the fire direction, combustion and emissions features of these three firing sections are interrelated in terms of oxidizer’s concentration and temperature. In the present study, considering this interconnection, the effect of diluted oxygen concentration at elevated oxidizer’s temperature (∼1200°C), which are the key features of the moderate or intense low oxygen dilution (MILD) combustion are analyzed. It is observed that by circulating some of the exhaust gases through the ABF crossovers, oxygen dilution occurs which results in higher fuel efficiency, lower pollutant emissions, and more homogeneous flow and temperature fields.