Multi-Frequency Broadband Vibration Mitigation of a Beam Under Tensile Load

The vibration characterization is directly associated with the system’s physical properties, such as mass, damping, and stiffness. For over a century, vibration resonator or dynamic absorber has been used for vibration control and mitigation in many sectors of engineering. A limitation of this device is that it acts as a notch filter, which is only effective over a narrow band of frequencies. Therefore, researchers have designed the call metamaterial, which in this case, targets the improvement of vibration attenuation and induces locally resonant bandgaps. This work investigates the broadband vibration mitigation of a beam under tensile load with periodically attached dynamic absorbers. The study uses the modal analysis approach, a simple formulation that only depends on the resonator target frequency and total mass ratio to investigate single and multiple-frequency bandgap formation. Metamaterial and rainbow metamaterial beam under tensile load are employed to widen the gap. In practical designs, a finite number of resonators is required for the open bandgap, and this ideal number is explored in the paper. Additionally, a tensiled beam (cable) virtual twin is built from a physical system to forecast its broadband vibration mitigation with the metamaterial approach. Numerical investigations are conducted regarding the effects of mass ratio and the ideal mass ratio on the open and on the gap convergence, as well as resonators in single and multiple arrangements inducing multiple gaps.

Pengaruh Penambahan Serat Kawat Bendrat Terhadap Kuat Lentur Beton Geopolimer

Currently, innovation continues to be developed to replace cement with other materials so that the use of cement as a building material can be reduced. Utilization of coal waste (fly ash) is an alternative to subtitude cement. From previous studies, fly ash mixed with alkaline materials in the form of NaOH and Na2SiO3 in a ratio of 1:5 can produce geopolymer concrete. This geopolymer concrete research was continued by adding bendrat wire fibers into the geopolymer concrete mixture. The method used in testing the aggregate, testing the compressive strength of normal concrete K225, testing the flexural strength of normal concrete and geopolymer concrete refers to SNI. Another additional material that is mixed is bendrat wire fiber. The research was carried out in the form of making flexible beams of 10 cm x 10 cm x 50 cm with fiber variations of 0%, 0.5%, and 1,0% at the age of 14 and 28 days. The results of the flexural strength test of the BN beam at the age of 28 days can withstand loads than BG. The average flexural strength obtained with variations of BN, BN+SB 0.5% and BN+SB 1.0% respectively were 2.796 MPa, 3.113 MPa, and 3.879 MPa. The results of testing the average flexural strength of geopolymer concrete beams at 28 days, obtained variations of BG, BG+SB 0.5%, and BG+SB 1.0% respectively were 0 MPa, 0.055 MPa and 0.104 MPa. In addition, geopolymer concrete cannot be used as a beam and the addition of bendrat wire fiber to geopolymer concrete cannot withstand the tensile load on the concrete.

A Study on Tensile Behavior According to the Design Method for the CFRP/GFRP Grid for Reinforced Concrete

In the present study, fiber-reinforced plastics (FRP) grid-reinforced concrete with very rapid hardening polymer (VRHP) mortar composites were fabricated using three types of design methods for the FRP grid (hand lay-up method, resin infusion method, and prepreg oven vacuum bagging method), along with two types of fibers (carbon fiber and glass fiber) and two types of sheets (fabric and prepreg). The FRP grid was prepared by cutting the FRP laminates into a 10 mm thick, 50 mm × 50 mm grid. The tensile behavior of the FRP grid embedded in composites was systematically analyzed in terms of the load extension, fracture mode, partial tensile strain, and load-bearing rate. The CFRP grid manufactured by the prepreg OVB method showed the best tensile behavior compared to the CFRP grid manufactured by the hand lay-up and resin infusion methods. The load-bearing of each grid point was proportional to the height from the load-bearing part when reaching the maximum tensile load. In addition, finite element analysis was conducted to compare the experimental and analysis results.

Static Structural Analysis of Different Materials for Connecting Rod

Connecting Rods are an important and irreplaceable part of IC Engines. It is responsible for converting the reciprocating motion of the piston into the rotary motion of the crankshaft. During this process, the connecting rod is subjected to various loads. Therefore, the materials used for connecting rod are also very important. In this paper, a static structural analysis of a connecting rod made of 5 different materials: Forged Steel, Carbon Steel, Stainless Steel, Grey Cast Iron and Titanium Alloy are compared. The connecting rod is analyzed only for the axial compressive load and not the axial tensile load because the tensile load is very much lesser than the compressive load. The connecting rod’s model is developed in FUSION 360 software and then imported to and analyzed using Finite Element Method in the ANSYS 2021 WORKBENCH software. The equivalent stress, total deformation along with the factor of safety for all the materials is found and compared in the analysis and all the results are shown with the help of images and graphs. Keywords: Connecting Rod, FEA, ANSYS WORKBENCH, Structural Analysis, Forged Steel, Carbon Steel, Stainless Steel, Grey Cast Iron, Titanium Alloy.

A New Specimen Geometry for Evaluation of the Mechanical Orthotropic Properties Presented in Parts Printed by FDM

Additive manufacturing (AM) by FDM (Fused Deposition Modeling) has been increasingly adopted due to the low cost of 3D printers as an option capable of producing parts with complex geometries. Since the FDM process is a layer-by-layer manufacturing method, the characterization of the behavior of parts manufactured by this technology, especially with regard to anisotropic mechanical properties, has led to many works relating printing parameters with tensile strength. However, the use of specimens with the conventional flat "dog bone" and cylindrical geometries specified in the ASTM-638 standards do not perfectly suit the special characteristics of parts produced by FDM, since these standards were created for solid and isotropic materials. A new geometry for specimens printed in FDM to study anisotropy transverse to layer deposition is suggested in this work. Problems such as slippage and crushing in the grips of the test machines due to the fragility of the bound between the beds, as well as the appearance of lateral forces that distort the results due to misalignment of the tensile load, twists and curvature of the specimens, normally observed in the Strain measurements by extensometers, are suppressed with the adoption of the new geometry presented in this work. Keywords: Fused Deposition Modeling, Additive Manufacturing, Mechanical Strength, Tensile Testing, Specimen Geometry

Development of Multi-Scale Carbon Nanofiber and Nanotube-Based Cementitious Composites for Reliable Sensing of Tensile Stresses

In this work, multi-scale cementitious composites containing short carbon fibers (CFs) and carbon nanofibers (CNFs)/multi-walled carbon nanotubes (MWCNTs) were studied for their tensile stress sensing properties. CF-based composites were prepared by mixing 0.25, 0.5 and 0.75 wt.% CFs (of cement) with water using magnetic stirring and Pluronic F-127 surfactant and adding the mixture to the cement paste. In multi-scale composites, CNFs/MWCNTs (0.1 and 0.15 wt.% of cement) were dispersed in water using Pluronic F-127 and ultrasonication and CFs were then added before mixing with the cement paste. All composites showed a reversible change in the electrical resistivity with tensile loading; the electrical resistivity increased and decreased with the increase and decrease in the tensile load/stress, respectively. Although CF-based composites showed the highest stress sensitivity among all specimens at 0.25% CF content, the fractional change in resistivity (FCR) did not show a linear correlation with the tensile load/stress. On the contrary, multi-scale composites containing CNFs (0.15% CNFs with 0.75% CFs) and MWCNTs (0.1% MWCNTs with 0.5% CFs) showed good stress sensitivity, along with a linear correlation between FCR and tensile load/stress. Stress sensitivities of 6.36 and 11.82%/MPa were obtained for the best CNF and MWCNT-based multi-scale composite sensors, respectively.

Experimental study on mechanical property and stone-chip resistance of automotive coatings

The damage of automotive coatings caused by stone impact is a problem that has attracted great attention from automotive companies and users. In this work, experiments were conducted to investigate the dynamic tensile properties and stone-chip resistance of automotive coatings. Four kinds of paint films and three typical coatings (single-layer electrocoat coating, single-layer primer coating, and multilayered coating) were used. Under dynamic tensile load using split Hopkinson tension bar (SHTB), the engineering stress-strain curves of the paint films at medium and high strain rates (from 50 to 600 s-1) were obtained. Results indicated that the mechanical properties of the paint films exhibited strong nonlinearity and strain-rate correlation. A modified anti-impact tester was used to complete repeatable single impact tests. The effects of some key parameters, i.e., impact velocity, impact angle, and paint film thickness, on the stone-chip resistance of coatings were systematically investigated. The influence of contact type under high-speed impact conditions was investigated as well. The surface morphologies of the coatings after impact were examined by scanning electron microscopy (SEM), and the failure mechanism of the coatings under normal/oblique impact was discussed. In all experiments, the paint films showed brittle fracture behavior.

Effect Steel Fibre Content on the Load-Carrying Capacity of Fibre-Reinforced Concrete Expansion Anchor

The article presents the pull-out strength tests carried out on M10 expansion anchors in non-cracked and cracked concrete with a crack width cw = 0.30 mm. The breaking loads and the average pull-out strength of anchors in fibre-reinforced concrete substrates were determined. Fibre content ratios of 15, 30 and 50 kg/m3 were used. In addition, two different classes of concrete (C20/25 and C50/60) were tested. The addition of steel fibres caused a decrease in the pull-out strength by 5% for non-cracked concrete of C20/25 class and fibre content up to 30 kg/m3 and a further 7% for the remaining specified dosage. While for concrete of the C50/60 class, it a decrease in the pull-out strength of up to 20% was observed. For cracked concrete class C20/25 with crack initiation cw = 0.30 mm, the reduction was from 9% to 16% in relation to non-cracked concrete and a maximum of 18% for the fibre content of 50 kg/m3. The difference between the tensile load capacity of C50/60 class cracked and non-cracked concrete was lower than 5% and fell within the measurement error.

Innovative and Sustainable Materials in Architectural Engineering

The advantages of fiber-reinforced polymer (FRP) composite material have attracted architectural engineers as alternative construction materials. FRP materials are noncorrosive, lightweight, exhibit high tensile strength, and stiffness, are easily fabricated and constructed. For architectural applications, FRP materials are fabricated using a polymer matrix, such as epoxy, vinyl ester, or polyester, and reinforced with various grades of carbon, glass, and/or aramid fibers. In this study, FRP coupons have been tested under axial tensile load to evaluate the strength of these materials for architectural application. Coupon specimens were cut from two different types of glass-FRP (GFRP) tubes namely: Type I and II, the two types had constant internal diameter equal to 152 mm. The GFRP tubes Type I consist of six layers with (±60°) fibers angles oriented mainly in the hoop direction with respect to the longitudinal axis of the tubes, the total thickness is 2.65 mm. While GFRP tubes I consist of fourteen layers with different fibers angles (±65, ±45, ±65) and the total thickness are 6.4 mm. The test results were presented and discussed. The strength of the coupon showed an acceptable level to be used for architectural application. Some of the FRP composites successful applications are briefly presented and discussed to provide the appropriate background for the application of FRP composites in architectural engineering. The promising results presented for the GFRP materials represent a further step toward architectural application.

Origins of strain localization in a silver-based flexible ink under tensile load

Flexible electronics often employs composite inks consisting of conductive flakes embedded in a polymer matrix to transmit electrical signal. Recently, localized necking was identified as a cause of a substantial increase in normalized resistance with applied strain thereby adversely impacting electrical performance. The current study explores two possible contributing factors for the formation of such localization – ink surface roughness and local variations in silver flake volume fraction. Uniaxial tension experiments of a DuPont 5025 type ink are used to inform a constitutive model implemented using Finite Element Method (FEM) on different substrates. Surface roughness was modeled by sinusoidal variation in ink height, whose amplitude and wavelength are informed by experimental laser profilometry scan data. Local flake fraction variation obtained from experimental measurements before applying any strain, were modeled as local variations in the elastic modulus according to an inverse rule of mixtures between the silver flake and acrylic binder material properties. The study identified that the ink height roughness is the most impactful contributor to the subsequent strain localization. The substrate elastic properties impact the number and magnitude of localization bands, with the stiffer substrate delocalizing strain and averting catastrophic crack formation seen with a more compliant substrate. The model incorporating surface roughness closely matches experimental measurements of local strain across different substrates. The study can inform designers of the adverse impact of ink surface roughness on localization and subsequent detrimental increase of the resistance.