Papers by Keyword: Interface

Abstract: An additively manufactured M789 steel was deposited on wrought precipitation-hardening N709 steel to form a hybrid alloy using the laser powder bed fusion (LPBF) process. After tensile testing, failure in the as-printed (AP) state was detected in the M789 section with a peak strength of 1019 MPa, consistent with the nanoindentation measurement across the M789-N709 interface. The application of heat treatment of the hybrid alloy shifted the failure zone to the N709 alloy with a peak strength of 1600 MPa. The high strength of M789 after heat treatment was due to the formation of the η-phase during aging. A robust metallurgical bond was successfully formed between the two alloys since the fracture did not occur in the interface for both the AP and heat treated (HT) states during tensile testing.

Abstract: Reinforced geopolymeric mortars were manufactured by mixing mining tailings, fine sand, Ichu fibers (in variable percentages), sodium hydroxide and water. The microstructure of the obtained mortars consisted of a continuous geopolymer binder phase with sand particles and Ichu fibers dispersed within the binder phase. The real density and average porosity of the reinforced mortars was 2.74 g/cm3 and 34%, respectively. It was possible to verify the influence of the addition of Ichu fibers on the mechanical response in uniaxial compression of the studied mortars, due to the poor interface between the geopolymer and the fibers. The mechanical results revealed a systematic reduction of the maximum compressive strength when the volume of Ichu fibers in the mortar mixtures was increased. On the other hand, a higher degree of deformation was evidenced in mortar mixtures containing a greater amount of Ichu fibers, reaching deformation values ​​of up to 5%. The maximum resistance values ​​found were from 2.87 to 20.76 MPa for samples with 8 and 0 vol.% of Ichu fibers added, respectively.

Abstract: The motion of a rigid sphere located at tissue-mimicking material interface in response to a dynamic force of short duration for the purpose of the determination of material viscoelastic properties was investigated in this study. The experiments were performed using a rigid sphere located at tissue-like material (gelatin phantom) interfaces. An electromagnet was used to apply the desired dynamic force to the sphere and a high-speed camera was used to track the movement of the sphere. Using the experimentally measured response of the sphere and the dynamic response of the sphere predicted by a sophisticated analytical model of the sphere located at a medium interface, the shear modulus, density and damping of the tissue-mimicking material were determined. The procedure followed in this study successfully produced the shear modulus, density and viscous damping ratio of the 20% (and 30%) gelation phantom as 1320 Pa, 1040 kg/m³ and 0.12 (and 2580 Pa, 1180 kg/m³ and 0.2), respectively. As the sophisticated theoretical model that is valid for small and large sphere displacements includes many parameters for the system such as the mass and size of the sphere, the inertia force of the medium involved in motion and the radiation damping due to shear waves and the experimental setup is very straightforward, it is believed that the procedure proposed in this study can be widely exploited to identify accurate material viscoelastic properties in practice.

Abstract: Masonry existing buildings are subjected to significant structural damages when seismic events occur. Over the last decades, innovative techniques like composite materials based on inorganic mortar (FRCM – Fiber Reinforced Cementitious Matrices) have emerged as attractive solutions for the strengthening of civil structures. FRCM shows better compatibility with masonry substrates with respect to Fiber Reinforced Polymers. The effectiveness of FRCM reinforcement systems relies on the composite-substrate bond behavior which is affected by many parameters, leading to different failure mechanisms. Although numerous studies investigate the FRCM-substrate bond, few attentions have been paid to the study of fiber grid-matrix interface behavior. In this study, the preliminary results of a wider experimental campaign aimed at investigating the interface behavior between fiber and mortar accounting for the contribution of transversal grid wires are presented. Different typologies of fiber and mortar were tested and the results are compared and discussed.

Abstract: Fabric Reinforced Cementitious Matrix (FRCM) materials are increasingly common for strengthening existing masonry structures. Their popularity is due to their many advantages with respect to resin-based composites, especially when applied to stone supports. The constitutive behaviour of FRCM materials is defined by the combination of their tensile response and the bond behaviour with the masonry support, both depending on complex stress transfer mechanisms between matrix and fabric, especially in the post-cracking stage. This paper presents a numerical study which aims to predict the mechanical behaviour of FRCM systems through simple 2D models of truss elements and non-linear springs to simulate the fabric-to-matrix and composite-to-substrate interaction. The comparisons between results of numerical approach and experimental responses showing that the proposed methodology is an effective and easy tool to predict the mechanical behaviour of FRCM composites.

Abstract: As a novel exploration, the hybrid additive manufacturing (AM) process combining selective laser melting (SLM) and directed energy deposition (DED) was used to produce a copper/steel bimetal structure in this paper. Stainless steel was deposited on the SLMed Cu-Cr alloy substrate successfully by DED. The interfacial phenomena, microstructure, and forming mechanism were investigated systematically. The Cu element of the substrate flowed up due to the Marangoni flow, and liquid phase separation occurred during the process. This work indicates that the microstructure and morphology between the cladding layer of steel and Cu-Cr substrate are significantly influenced by the laser power.

Abstract: In order to predict the effect of the Marangoni convection and the morphology of melted stainless steel powder, during the selective laser melting (SLM) process, a transient three-dimensional numerical model is developed at the mesoscale. The evolution of the temperature and velocity fields’ is then studied. The initial powder bed distribution is obtained by the discrete element method (DEM) calculation, and the temperature distribution and the molten pool shape deformation are calculated and analyzed by the Ansys-Fluent commercial code. The molten pool shape is obtained by considering the influence of Marangoni convection on the internal flow behavior. The recoil force was not considered in our calculation. As main results, a slight deviation between the position of the maximum temperature of the molten pool and the center of the laser spot is observed. The direction of the heat diffusion is more likely to be horizontal and the flow centrifugal, which causes the melt track to be wide. Finally, the Marangoni convection is the main driver of the flow.

Abstract: This work examine the potential of ZrB₂ in the presence of Ni-P-Zn sulphate rich bath coating on mild steel under change in time from 10-25 min. The coating pH of 5, current density of 1 A/cm², and stirring rate of 250 rpm was considered in the fabrication process. The microstructure evolution and properties of the deposited coating was analysed using a scanning electron microscope enhanced with energy dispersive spectroscopy (SEM/EDS). All deposited composite coating was investigated in 0.5 M H₂SO₄ and 3.5% NaCl with the help of linear polarization and open circuit potential. From the result, a solid crystal formation containing zirconium boride was seen from the SEM study. At 25 min a remarkable dispersed and even thin film was noticeable at the interface. From all indication, coating produced with Ni-P-Zn-10ZrB₂ at 25 min provides a passive response against corrosion damage. Keywords: Electrodeposition, interface, nanocrystalline, structure, coating

Abstract: Modeling the processes of forming contact regions (interface) of the multilayer niobium-cobalt nanosystem is carried out. The morphology and composition of a multilayer nanosystem interface is investigated. The layer boundaries morphology is shown to depend on the deposition substrate temperature and, largely, is determined by preparing the surface for deposition. The work considers the deposition surface modification by removing its defects. Simulation showed that surface preparation significantly affects the morphology and composition of a multilayer nanosystem interface, depending on the type of deposited atoms and atoms forming the deposition surface.

Abstract: It is evident that the interface in MMCs plays a crucial role with respect to thermophysical and mechanical properties of the composites. Inert systems like copper/carbon or silver/carbon will have low performance due to a very weak bonding between the constituents, whereas in reactive systems like Al/carbon, Fe(Ni)/WC and WC-Co/diamond the interfacial reaction has to be clearly controlled to avoid uncontrolled reactions. Such reactions may lead to partial or even complete dissolution of the phases and thus can have very detrimental impact on properties. In this contribution, we will summarize and present different approaches and recent results to overcome any interfacial problems. This can be either technological parameters like time, temperature, rate of consolidation, contact time in infiltration or inherent parameters like nominal composition, coatings, and surface terminations. It is of general interest to adjust optimal interfacial conditions for each application to achieve ideal properties in the composites.