Sriharsha Hegde

Basalt fiber, a natural and eco-friendly reinforcement, has demonstrated superior properties compared with conventional synthetic fibers. This study investigates the effect of ageing on the mechanical and vibrational properties of Basalt/Epoxy, Glass/Epoxy, and Basalt-Glass/Epoxy hybrid composites. Laminates were fabricated using vacuum bagging, ensuring uniform fiber-matrix volume fractions, and then exposed to ageing in seawater, tap water, and distilled water for a duration of 80 days. The moisture absorption pattern followed Fickian diffusion, with seawater exhibiting the highest diffusion coefficients owing to matrix breakdown and osmotic influences. Tensile tests demonstrated a decrease in failure stress and modulus for all materials after ageing, with Glass/Epoxy composites experiencing the most notable degradation despite absorbing less moisture, indicating a weakening of the fiber-matrix interfacial bond. The hybrid laminates exhibited moderate tensile and vibrational characteristics and maintained mechanical performance better in harsh environments. Free vibration tests showed that the natural frequency diminished as mass increased due to moisture absorption, while damping factors rose after ageing. Overall, the combination of basalt and glass fibers enhanced environmental resilience, indicating their suitability for structural applications under challenging conditions.

This study presents an integrated investigation of the machinability of heat treated AISI 1040 steel under annealed, normalized, and oil quenched conditions. The effects of heat treatment parameters, namely austenitizing temperature and soaking time, together with machining parameters including cutting speed, feed rate, and depth of cut, were evaluated in terms of tool life and surface roughness. Experiments were designed using a Taguchi L27 orthogonal array, and the responses were analyzed through analysis of variance (ANOVA), regression modeling, and optimization techniques. The results showed that temperature, cutting speed, and feed rate significantly influenced tool life, whereas feed rate was the most dominant factor affecting surface roughness in all heat treatment conditions. Annealed AISI 1040 steel exhibited the highest tool life and the best overall machinability because of its relatively softer ferrite-pearlite microstructure, while oil quenched specimens showed the lowest tool life due to the formation of hard martensitic phases. Normalized specimens displayed intermediate behavior, indicating a balanced combination of strength and machinability. The developed regression models showed good predictive capability for both tool life and surface roughness within the investigated parameter range. SEM analysis further confirmed that the observed variations in machinability were closely associated with microstructural evolution caused by different heat treatment routes. The study provides useful guidance for selecting suitable heat treatment and machining parameters to improve productivity, tool performance, and surface quality during machining of AISI 1040 steel.

Mechanical components subjected to dynamic loading require materials that combine adequate strength with effective vibration-damping capability. Austempered ductile iron (ADI) is a promising candidate for such applications because of its ausferritic matrix, which provides a useful combination of strength, toughness, wear resistance, and energy dissipation. However, the damping behaviour of manganese-alloyed ADI and its dependence on austempering parameters have not been sufficiently clarified. In this study, ductile iron containing 0.3, 0.6, and 0.9 wt% Mn was austempered at 320, 370, and 420 °C for 1, 1.5, and 2 h using a full-factorial experimental design. The damping response was evaluated through impact hammer-based experimental modal analysis and correlated with hardness, ausferritic morphology, and the volume fraction of carbon-enriched/high-carbon austenite. The results showed that manganese content and austempering temperature significantly influenced the loss factor, whereas austempering time had only a minor effect within the selected range. The highest damping performance was obtained for the alloy containing 0.6 wt% Mn austempered at 370 °C, where a favourable balance was achieved between stabilized high-carbon austenite, refined ausferritic morphology, ferrite/austenite interface density, and controlled matrix hardness. At 320 °C, limited austenite stabilization restricted damping improvement, while at 420 °C, ausferritic coarsening reduced the effective interface-related energy dissipation. ANOVA confirmed manganese content and austempering temperature as the dominant factors, contributing approximately 59% and 39%, respectively, to the variation in loss factor. The regression model showed strong predictive capability within the investigated process window. Overall, the study demonstrates that damping behaviour in manganese-alloyed ADI can be effectively tailored through controlled alloy chemistry and austempering temperature, supporting its potential use in vibration-sensitive engineering components.

Austempered ductile iron has gained increased interest as an ideal choice of material for mechanical components exposed to dynamic loading. Apart from strength and ductility, material damping is also one of the important demands imposed on the machine components exposed to noise and vibrations. In the present study, the damping characteristics of austempered ductile iron with varying levels of Mn variations are investigated. Samples were produced with three levels of Mn variations: 0.31 wt%, 0.60 wt%, and 0.92 wt%, and they were subjected to austenitization and austempering heat treatment. Variation in the damping characteristics of austempered ductile iron were studied before and after the heat treatment by performing the impact hammer test. The microstructure and the hardness variations of the samples were studied to interpret the mechanisms associated with variation in the damping characteristics. The studies revealed that Mn addition and heat treatment contribute to the variation in the microstructure and the mechanical properties. These properties have a contribution to the variation in the damping characteristics of ADI. Additionally, the study also revealed the existence of an optimum level of Mn that could yield better damping characteristics.

The present study investigated the tensile behavior, failure mechanisms and deformation characteristics of glass fiber-reinforced polymer (GFRP) composites with symmetric [0°/90°/90°/0°] and asymmetric [0°/90°/0°/90°] stacking sequences across a temperature range of 30–150 °C. Tensile testing revealed superior mechanical performance in the symmetric lay-up, with higher tensile strength and failure strain sustained across elevated temperatures. Failure mode analysis revealed a transition from ductile failure to brittle failure with increasing temperature, which was more pronounced in the asymmetric lay-up, along with increased delamination and reduced fiber pull-out. Failure surface examination supported these findings, revealing better interfacial bonding and matrix integrity in the symmetric lay-up. Deformation analysis further confirmed a more homogeneous distribution of strain and longer failure time in symmetric laminates. Across all the metrics, including toughness, energy absorption, and strain uniformity, the symmetric configuration outperformed the asymmetric counterpart, underscoring the critical role of balanced stacking in enhancing the thermal durability. The observed temperature-induced degradation and its impact on mechanical and failure behavior emphasize the need for temperature-sensitive design strategies in GFRP-based structures.

The study investigates the transient vibration analysis of two-wheeler handlebar and the optimization of vibration damping using constrained layer Magnetorheological Elastomers (MRE). The research explores how varying magnetic field strengths affect the damping properties of MRE, which is strategically implemented in the handlebar of a two-wheeler with a view to reducing vibrations and improving rider comfort. This study is a combination of numerical simulation and experimental data to highlight the effectiveness of semi-active damping systems under different magnetic fields. A sandwich beam was prepared at the laboratory for the damping material, and it was tested for the variation in damping ratio when the magnetic field was varied. The results demonstrate significant improvements in vibration attenuation when MRE damping ratios are optimized by varying the magnetic field, resulting in enhanced structural integrity and rider comfort.

With the rising need for sustainable and high-performance materials, significant research has been conducted on natural fiber-based composites for various engineering uses. This research examines the acoustic characteristics of composites made from Areca Husk fiber and Coir fiber, using thermoplastic (corn starch) and thermoset (epoxy) matrix materials. The Areca and Coir fibers were extracted and treated with a 1% Sodium Hydroxide (NaOH) solution to improve fiber-matrix bonding and then analyzed through Fourier Transform Infrared Spectroscopy (FTIR). Specimens were created using compression molding and their sound transmission loss was tested with an Impedance Tube across a frequency range of 63 Hz to 6300 Hz, in accordance with ISO 10534-2 standards. The findings reveal that the fiber treatment enhances acoustic performance by increasing the density and roughness of the materials which improves sound wave attenuation. Composites based on corn starch showed better sound absorption than those based on epoxy, due to their higher porosity and viscoelastic properties. Furthermore, increasing the specimen thickness significantly boosted acoustic performance. These results underscore the potential of Areca and Coir fiber composites as environmentally friendly, sustainable and cost-effective options for sound insulation applications.

Natural fiber-reinforced composites have gained significant attention due to their environmental benefits and desirable mechanical properties, including inherently beneficial vibration damping and acoustic characteristics. In this study, untreated, Alkali, Silane and Permanganate-treated Helicteres isora fiber-reinforced Polylactic acid composites were assessed to determine the effect of fiber treatment on the vibration and acoustic behaviour of the composites. Vibrational analysis was conducted to identify natural frequencies and damping ratios of the composites. The results demonstrated that alkali-treated fiber composite significantly enhanced the vibrational properties of the composites, with a 30% increase in damping ratio compared to untreated fiber composites. Acoustic transmission loss (TL) was measured to assess their suitability as soundproofing material using the impedance tube method. The results showed that silane-treated composites offered the highest TL in the frequency range 4000 to 6300 Hz, 35% more than untreated fiber composites, indicating their potential as an effective material in applications requiring soundproofing. In contrast, untreated fibers provided the lowest TL, affirming the impact of fiber modifications on acoustic performance. This study demonstrates that fiber modifications play a significant role in optimizing the vibrational and acoustic behaviour of natural fiber-reinforced bio-composites, making them a viable alternative for lightweight structural and noise-reducing applications.

The vibrations generated in the two-wheeled vehicles like motorcycles due to road irregularities such as cracks, potholes, and bumps on the road cause discomfort for the rider as well as the pillion. These vibrations are reported to cause lower back pains, musculoskeletal effects, fatigue, and long-term health issues. Particularly, electric two-wheelers are more susceptible to these vibrations caused by the road and need attention. This paper presents an innovative technique for the reduction of vibrations at prominent locations in the electric two-wheeler to improve the rider’s comfort. All measured accelerations are about vertical direction (along z-axis as per ISO 2631-1 standard). Passive and Semi-active damping treatments namely, Room temperature vulcanizing Silicone rubber and Magnetorheological elastomer (MRE) were applied on the test vehicle at strategic locations of vibration. Both were compared for their effectiveness in reducing the vibrations. Results showed that MRE based damping technique proved better vibration isolation at the strategic locations. The weighted root mean square acceleration as well as vibration dose values were found to decrease with the help of damping treatments thus improving the rider’s overall comfort level.