Work of Adhesion Analysis for Metal-Substituted W₄C₄ Carbides in a Cobalt Matrix

The density of WC, which is greater than that of metals, can be reduced by partially substituting heavy W with metals, e.g., Mo and Cr, while retaining the desired strength. This makes them effective as reinforcements for hard-facing overlays and tool alloys, as they can be homogeneously dispersed in the metal matrix. Since it is unclear if the modified WC has good interfacial bonding with metals such as cobalt, one of the typical metal matrixes for hardfacing overlays, the interfacial bonding between cobalt and WC doped with Mo and Cr, respectively, was investigated via first principle calculations. The selected interfaces having the lowest interfacial mismatches with both HCP and FCC cobalt are (1120)Carbide//(001)Co, (1010)Carbide//(100)Co, (1010)Carbide//(110)Co, and (0001)Carbide//(110)Co. The characteristics of created interfacial connections were analyzed using methods such as the electron localization function, electronic density of states, bond order, and net charge. It is demonstrated that WC carbides partially substituted with Mo and Cr (called (W4–x, M)C4, M = Mo or Cr) are adherent to Co as strong as or even better than that of mono-WC. The metal-substituted or doped W4C4 carbides are promising candidates as reinforcements for hardfacing overlays, cutting tools, and bearings without interfacial bonding concerns

Vibrational analysis of double-walled silicon carbide nano-cones: a finite element investigation

Abstract A three-dimensional finite element model is used to investigate the vibrational properties of double-walled silicon carbide nano-cones with various dimensions. The dependence of the vibrational properties of double-walled silicon carbide nano-cones on their length, apex angles and boundary conditions are evaluated. Current model consists a combination of beam and spring elements that simulates the interatomic interactions of bonding and nonbonding. The Lennard–Jones potential is employed to model the interactions between two non-bonding atoms. The fundamental frequency and mode shape of the double-walled silicon carbide nano-cones are calculated

Highly compressible concrete: The effect of reinforcement design on concrete’s compressive behavior at high strains

In squeezing ground tunnel construction, yielding elements must absorb the large tunnel deformation without damaging the tunnel lining. Various designs for these highly compressible structures exist. Still, they all share one commonality: they are complicated to manufacture, and it is difficult to alter their design to match desired compressive properties. A new yielding element design is presented here, consisting of corrugated metal plates embedded within fiber-reinforced concrete. As this yielding element is compressed, the corrugated plates are gradually flattened, increasing the plates’ stiffness. This mechanism enables the engineering of structures with monotonically increasing compressive stress–strain curves and matches the target compressive properties. When compared against alternate reinforcement schemes, including fiber reinforcement, flat plate reinforcement, and polymeric lattice reinforcement, compression results indicate that only the corrugated metal plate reinforcement produced monotonically increasing stress–strain curves while keeping stress levels below a prescribed limit. Additionally, the corrugated metal plate-reinforced specimens began densification at a strain 280% larger than the strain at which the fiber-reinforced samples began densification, indicating that the corrugated metal plates extended the yield plateau. Fiber-reinforced concrete in conjunction with corrugated metal plates shows promise for use as a yielding element

Polymer lattice-reinforcement for enhancing ductility of concrete

Concrete is the most widely used engineering material. While strong in compression, concrete is weak in tension and exhibits low ductility due to its low crack growth resistance. With increasingcompressive strength, concrete becomes even more brittle, hence requiring appropriate reinforcement to enhance its ductility. This paper presents a new method for increasing the ductility of ultra-high-performance concrete by reinforcing it with 3D printed polymeric lattices made of either polylactic acid (PLA) or acrylonitrile butadiene styrene (ABS). These latticereinforced concrete specimens were then tested in compression and four-point bending. The effect of polymeric reinforcement ratios on mechanical properties was investigated by testing two lattice configurations. The lattices were very successful in transforming the brittle ultrahigh-performance concrete (UHPC) into a ductile material with strain hardening behavior; all flexural specimens revealed multiple cracking and strain hardening behavior up to peak load. Increasing the ABS reinforcing ratio from 19.2% to 33.7% resulted in a 22% reduction in average compressive strength. However, in flexure, increasing the PLA reinforcing ratio from 19.2% to 33.7% resulted in a 38% increase in average peak load. The compression results of all specimens independent of their reinforcement ratio revealed smooth softening behavior incompression

Polymer lattice-reinforcement for enhancing ductility of concrete

Concrete is the most widely used engineering material. While strong in compression, concrete is weak in tension and exhibits low ductility due to its low crack growth resistance. With increasingcompressive strength, concrete becomes even more brittle, hence requiring appropriate reinforcement to enhance its ductility. This paper presents a new method for increasing the ductility of ultra-high-performance concrete by reinforcing it with 3D printed polymeric lattices made of either polylactic acid (PLA) or acrylonitrile butadiene styrene (ABS). These latticereinforced concrete specimens were then tested in compression and four-point bending. The effect of polymeric reinforcement ratios on mechanical properties was investigated by testing two lattice configurations. The lattices were very successful in transforming the brittle ultrahigh-performance concrete (UHPC) into a ductile material with strain hardening behavior; all flexural specimens revealed multiple cracking and strain hardening behavior up to peak load. Increasing the ABS reinforcing ratio from 19.2% to 33.7% resulted in a 22% reduction in average compressive strength. However, in flexure, increasing the PLA reinforcing ratio from 19.2% to 33.7% resulted in a 38% increase in average peak load. The compression results of all specimens independent of their reinforcement ratio revealed smooth softening behavior incompression

An Octet-Truss Engineered Concrete (OTEC) for lightweight structures

Recent advances in the development of Ultra-High Performance Fiber-Reinforced Concrete (UHP-FRC) with very high compressive strength has inspired the development of a lightweight structure by engineering the void spaces in the material, thus taking advantage of porous concrete’s thermal insulating properties while maintaining strength and stiffness. This paper refers to this engineered material as Octet-Truss Engineered Concrete (OTEC). To make OTEC structures, UHP-FRC and “green” UHP-FRC (G-UHP-FRC) mixtures were developed. 50.8-mm side-length OTEC unit cell specimens with various element diameters as well as 5×1×1-cell OTEC flexural specimens with 8 mm-diameter elements were cast and tested under uniaxial compression and four-point bending, respectively. The compressive strength of the OTEC unit cell specimens with various element diameters is mainly stretching-dominated, and hence considerably surpasses that of the control foam Green Ultra-High Performance Concrete specimens with random pore orientations. These results indicate a promising application of UHP-FRC and G-UHP-FRC OTECs for lightweight structures

An Octet-Truss Engineered Concrete (OTEC) for lightweight structures

Recent advances in the development of Ultra-High Performance Fiber-Reinforced Concrete (UHP-FRC) with very high compressive strength has inspired the development of a lightweight structure by engineering the void spaces in the material, thus taking advantage of porous concrete’s thermal insulating properties while maintaining strength and stiffness. This paper refers to this engineered material as Octet-Truss Engineered Concrete (OTEC). To make OTEC structures, UHP-FRC and “green” UHP-FRC (G-UHP-FRC) mixtures were developed. 50.8-mm side-length OTEC unit cell specimens with various element diameters as well as 5×1×1-cell OTEC flexural specimens with 8 mm-diameter elements were cast and tested under uniaxial compression and four-point bending, respectively. The compressive strength of the OTEC unit cell specimens with various element diameters is mainly stretching-dominated, and hence considerably surpasses that of the control foam Green Ultra-High Performance Concrete specimens with random pore orientations. These results indicate a promising application of UHP-FRC and G-UHP-FRC OTECs for lightweight structures