Papers by Keyword: Mechanical Behavior

Abstract: The structural vulnerability of rural dwellings built with traditional adobe in high Andean areas motivates the search for sustainable solutions that improve their mechanical properties without increasing costs. This study evaluates the mechanical behavior of adobe blocks reinforced with natural fibers such as sheep wool and corn husk, locally available agricultural waste. Five types of blocks were created, varying the wool content (0.2%, 0.4%, and 0.6%) with a fixed proportion of husk (0.6%), while traditional mixtures with ichu as a reference were used. Standardized compressive and flexural strength tests were performed, identifying the mixture with 0.4% wool and 0.6% husk as the most efficient, achieving average values of 1.83 MPa and 0.81 MPa, respectively. These results exceed traditional blocks by more than 47% and 34%, demonstrating a significant improvement in structural performance. Analysis of the mixture confirmed its viability as a low-cost material for rural areas, improving the mechanical properties of adobe and offering an ecological and replicable alternative for housing in extreme climates.

Abstract: This study evaluates the impact of adding metalized plastic waste (MPW) fibers to lightweight concrete that is used as a filler material in building slopes and bridge ramps. The goal is to open up new opportunities for recycling plastic waste and promote a more sustainable and productive construction industry. This study examined the mechanical behavior of lightweight concrete (LC) at 3, 28, and 90 days, both with and without MPW fiber (1%, 2%, and 3%). Compression tests, 3-point bending tests, and pull-out tests were used to measure the fibers' compressive strength, flexural strength, and maximum load-bearing capacity, respectively. According to the results, the compressive strength (CS) and elasticity modulus (MOE) decreased with increasing fiber content when MPW fiber was added. In the long term, the CS and MOE decrease for the LC containing 3% MPW fiber was 8% and 7%, respectively, lower than for the control concrete. At 90 days, the flexural strength of the LC with 1% MPW fiber was marginally higher than that of the control concrete, rising by 2.40%. After this initial rise, however, the flexural strength declined as the fiber concentration increased, eventually reaching an 8% reduction for LC with 3% MPW fiber.The optimum method for determining maximal load-bearing and comprehending the deformation mechanism is hence the fiber pull-out test. The microstructure study of the LC examined how the pull-out test affected the quality of bonding at fiber-matrix interfaces. The tensile and flexural strength of lightweight concrete are enhanced by MPW fiber's ability to bear significant pulling stress.

Abstract: This article presents a study of the mechanical behavior of tuffeau, a porous building limestone. Previous studies were focused on using strain gauges for mechanical monitoring with some limited success due to the size and the local nature of the measurement. The Digital Image Correlation (DIC) method has proven to be a valuable tool for noncontact, full-field strain measurements in various materials, including rocks which are natural and heterogeneous materials. After a prior phase of optimization involving texture acquisition and lighting conditions, this paper compares several DIC software programs to achieve consistent results on soft limestone specimens. Once the DIC program is chosen, a focus is made on detecting heterogeneities in the stone specimens. The occurrence of such heterogeneities explains why strain gauge measurement sometimes fails when applied to soft and natural materials.

Abstract: The present investigation focuses on the implementation of the multi-axial forging process, recognized as a severe plastic deformation (SPD) technique, with the aim of elevating the mechanical features of the widely employed Al 6061 alloy. Specifically utilized in the automotive and aviation industries, this alloy's behavior was meticulously examined through a series of quasi-static and dynamic tests. To achieve this objective, the multi-directional forging (MDF) process was implemented for up to three cycles, involving a total of nine passes, at a raised temperature of 200 °C. Subsequently, the severely deformed material underwent utilizing high strain rate loading for the Split Hopkinson Pressure Bar (SHPB) test system. After MDF, the grain size is refined down to below 11 microns with a starting grain size of 13 microns. This is reflected as increased hardness and yield strength in the quasi-static regime. For SHPB characterization, increased dynamic strength is also observed. However, although the yield strength showed about 60% increase with decent ductility, the maximum dynamic strength increased about 10% after SPD with a relatively brittle behavior.

Abstract: The effect of tempforming on strength and fracture toughness of a 0.4%C-2%Si-1%Cr- 1%Mo-VNb steel was examined. Tempering at a temperature of 600°C followed by plate rolling at the same temperature results in the formation of lamellar structure with a spacing of 72 nm between longitudinal boundaries and a lattice dislocation density of ~10¹⁵ m⁻² that enhances fracture toughness in normal direction of tempformed plate. The increase in the absorbed impact energy is attributed to delamination, which occurs in plains intersecting the propagation path of main crack that blunts crack tip.

Abstract: In the current paper, the effect of two different coating techniques of boronizing and tungsten carbide (WC) coating on the room and high temperature tensile behavior of the AISI 321 stainless steel were investigated. Consequently, the fracture morphology observations were conducted via scanning electron microscopy (SEM) to inspect the variation of fracture mechanisms after implementing different coating methods. The results of tensile tests at room temperature revealed that despite boronizing reduced the yield strength of the sample due to the softening and grain growth at high coating temperature, the dispersion of boron particles improved the work hardening and ductility of boronized AISI 321. In contrast, the strain to failure of the WC coated sample was decreased due to the fast fracture of the ceramic WC layer at both room and high tensile tests. Furthermore, results of SEM revealed that particle decomposition occured on the fracture surface of the boronized 321 stainless steel represented by dispersed boron particles on the edges of the dimples after failure at high temperature.

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 study of the shear strength parameters of mixtures comprising tire-derived aggregates (TDA) and clay was the main objective of this experimental work. The tests were performed using the direct shear box. First, the test was performed on specimens comprising only clay in its natural state and then on mixtures consisting of clay and TDA in increasing contents. A total of four samples (natural clay and natural clay with 2, 4, and 6% tire-derived aggregates)) were made and tested at three normal stress levels (100, 200, and 300 kPa). Then, Mohr-Coulomb failure envelopes were drawn to determine the internal friction angle and cohesion for all mixes. The results were compared to find the optimum TDA content and to study the stress-strain behavior of the mixtures. It was observed that mixing TDA up to 6% by weight with clay significantly changes the shear strength, and the internal friction angle increases from 27.47 to 59.39º (an increase of 46.25%). However, the cohesion significantly decreases from 45 to 26 kPa (a decrease of 57.77%). On the other hand, it was observed that increasing the TDA content reduces the density and increases the shear strength of the mixtures. Also, the addition of TDA increases the mixture consolidation and deformation level at failure.

Abstract: This paper presents an experimental investigation of the mechanical response and failure mode of magnesium alloy-based Fibre Metal Laminates (FMLs) having different surface pretreatments under axial compression loading conditions. To improve the interfacial bonding strength between the metal and composite layers, three categories of samples were fabricated by hot pressing using sandblasted, annealed and both sandblasted and annealed AZ31B magnesium alloy sheets. To evaluate the bonding strength along the shear and normal directions, single lap shear tests and T-peel tests were conducted. It was found that the combination of sandblasting and annealing can greatly enhance the shear and normal interfacial bonding strength compared with only sandblasting and annealing, separately. To assess the effect of the interfacial bonding strength on the FML compressive performance, quasi-static buckling tests were performed at varying surface treatments of the magnesium alloy sheets. The analysis of the load-stroke curves and failure modes indicates that delamination can significantly reduce the buckling capability and structural stability, and that the improvement of interfacial bonding strength can dramatically strengthen the FML compressive capability.

Abstract: Over the recent years, Nitinol (Ni-Ti) shape memory alloys have gained popularity in the medical, aerospace and energy sectors, due to their superelasticity, shape memory effect, low stiffness, good biocompatibility and corrosion resistance. Compared to steels and other common metallic materials, it is difficult to model the mechanical behavior of Ni-Ti due to the inherent functional properties caused by the diffusion-less solid-state phase transformations. With the help of Laser Powder Bed Fusion (L-PBF) process, these transformational characteristics can be controlled. This will ultimately lead to controlling the mechanical and thermal properties for specific applications. In this work, Finite Element Analysis (FEA) was conducted to replicate the actual mechanical phenomenon occurring in Nitinol. Models were generated for simulating the superelastic and plastic behaviors, and were validated against actual experimental data. The ability to model the complex mechanical response of Nitinol will enable exploration into the sensitivity of material response to phase volumes, material composition, and strain rate. Robust models of these phenomenal also provide the potential for tailoring in-silico the microstructure required for specified desired macroscopic material properties.