Materials Science Forum Vol. 1046

Abstract: The fracture response of macro polypropylene fiber reinforced concrete (PPFRC) and hybrid blend of macro and micro polypropylene fiber reinforced concrete (HyFRC) are evaluated at 1, 3, 7 and 28 days. There is an improvement in the early-age fracture response of HyFRC compared to PPFRC. The changing cohesive stress-crack separation relationship produced by ageing of the concrete matrix is determined from the fracture test responses. An improved early-age cohesive stress response is obtained from the hybrid blend containing micro and macro fibers. The hybrid fiber blend also has a higher tensile strength at early age when compared to an identical volume fraction of macro polypropylene fibers.

Abstract: The present paper analyzes the influence of creep on longitudinal fracture in continuously inhomogeneous rod of circular cross-section loaded in torsion and bending. The rod exhibits continuous material inhomogeneity in both radial and longitudinal directions. The creep is described by using non-linear time-dependent relations between the principle stresses and strains. A time-dependent solution to the strain energy release rate is derived by analyzing the complementary strain energy. The time-dependent strain energy release rate is found also by considering the energy balance for verification. The solutions are applied to perform a parametric study of the strain energy release rate under creep.

Abstract: Over the past years, two-dimensional lattices have attracted the attention of several researchers because they are lightweight compared with their full-solid counterparts, which can be used in various engineering applications. Nevertheless, since lattices are manufactured by reducing the base material, their stiffnesses then become lower. This study presents the weight efficiency of the lattices defined by relations between the elastic modulus and the weight density of the lattices. In this study, the mechanical behavior of 2D lattices is described by the in-plane elastic modulus. Experimental studies on the elastic modulus of the 2D lattices made of steel are performed. Three lattices having different unit cells, including square, body-centered, and triangular unit cells, are considered. The elastic modulus of each lattice is investigated by tensile testing. All specimens of the lattices are made of steel and manufactured by waterjet cutting. The experimental results of the elastic modulus of the lattices with the considered unit-cell patterns are validated with those obtained from finite element simulations. The results obtained in this study are also compared with the closed-form solutions founded in the literature. Moreover, the unit-cell pattern yielding the best elastic modulus for the lattice is discussed through weight efficiency.

Abstract: The present paper deals with an analytical study of the time-dependent delamination in a multilayered inhomogeneous cantilever beam with considering of the loading history. The multilayered beam exhibits creep behaviour that is treated by using a non-linear stress-strain-time relationship. The material properties are continuously distributed along the thickness and length of the layers. The external loading is applied in steps in order to describe the loading history. The analysis reveals that during each step of the loading, the strain energy release rate increases with time. The influences of crack length and location on the time-dependent strain energy release rate are also investigated.

Abstract: This paper presents a study of the screw extrusion parameters that affect on the appearance of clay filament for a clay printing machine. Traditionally, pottery models are formed by using paster mold or hand throwing, which require experienced and proficient workers to form the complex pottery models. Therefore, the clay printing machine has been developed to improve manual pottery fabrication to automatic construction. This machine has been modified based on the additive manufacturing (AM). To assess a capability material deposition of the clay printing machine, nozzle diameter, screw extruder velocity, and screw pitch were investigated as the printing parameters to evaluate a quality of clay filament. Analysis of variance (ANOVA) is used to analyze main effect parameters. The experimental results showed that the 6 mm nozzle diameter, 19 mm/s screw extruder velocity and 24 mm screw pitch were the suitable printing parameters for providing an appropriate appearance of clay filament. A mathematical model was formulated to propose the relationship between response and main effects with their interactions.

Abstract: The present work is concerned with analysis of the dissipated energy in viscoelastic multilayered inhomogeneous beam structure. The layers of the beam are continuously inhomogeneous along the thickness. The Maxwell mechanical model is used for treating the viscoelastic behaviour of the beam. The moduli of elasticity and the coefficients of viscosity vary continuously along the thickness of each layer. The dissipated energy is obtained by integrating of the unit dissipated energy in the volume of the beam. A parametric investigation of the dissipated energy is carried-out by applying the solution derived in order to evaluate the influence of various factors.

Abstract: The use of cold-formed steel (CFS) shapes in steel-concrete composite sections has increased over the past 20 years in the construction industry worldwide. This system has constructive advantages such as high load-bearing capacity, high stiffness and ductility, ease of transportation and assembly, and full usage of the capacity of the materials. Additionally, CFS sections are considered a sustainable alternative in construction.The capacity of the system depends on the effectiveness of shear connectors during the transfer of stress between materials. Currently, the push-out experimental test follows a standardized procedure to evaluate the capacity of shear connectors in composite sections, but CFS shapes have demonstrated premature failures by local buckling, thus questioning the applicability of the experimental test for such configurations.In this research, the capacity of the proposed confined shear connectors (CSC) is evaluated in composite systems, through the alternative pry-out test methodology. From numerical models, the effects of the steel shape thickness, the thickness of concrete slabs, the compressive strength of concrete and the separation between connectors in composite systems are studied. The analysis concluded that, under this test methodology, the separation between connectors does not represent statistically significant changes in the final capacity of the composite system.

Abstract: This paper describes an analytical approach for analyzing of the total damping energy for a continuously inhomogeneous elastic-plastic beam structure subjected to cyclic axial forces. The mechanical behaviour of the material is treated by using a cyclic stress-strain curve of the Ramberg-Osgood form. The beam cross-section is a rectangle. The material properties are distributed continuously along the height of the beam cross-section. The unit damping energy is integrated in the beam volume in order to derive the total damping energy. The analytical solution obtained is applied to carry-out a parametric study of the total damping energy in the beam structure.

Abstract: Directed energy deposition (DED) is an Additive Manufacturing process deposing fused metal powder on a preexisting substrate. This document shows the influence of heat treatment on P295GH deposit made by DED, for hybridization process. The heat treatment must reduce the macroscopic differences between the rolled substrate and the deposited DED material. The experimental plan has been defined around AC₃ temperature, according to P295GH existing literature. XRD analysis, hardness measurements and metallographic inspections have been performed on samples before and after heat treatment. XRD analysis and hardness measurements have shown an isotropic material. The as-built microstructure is ferritic and acicular, but coarsens after the heat treatment. The study promotes a heat treatment at 800°C during 3 hours to obtain the best compromise between properties, impact on the substrate and differences with the rolled substrate.