This study investigates the influence of printing parameters on the tensile properties and void architecture of poly(lactic) acid (PLA) parts fabricated using the fused filament fabrication (FFF) technique. Two Taguchi optimisation methods were employed to identify the optimal parameter combinations for maximising tensile performance. The results revealed a positive correlation between tensile performance and nozzle diameter (ND). Notably, the analysis of the coefficient of variance (COV) studies revealed that both tensile strength and modulus exhibited minimal variation within a tight range of 5.5%, suggesting a high degree of process consistency in achieving desired mechanical properties regardless of the chosen parameters within the investigated range. Micro-computed tomography (micro-CT) analysis was used to quantify void characteristics within the as-printed samples. Micro-CT analysis confirmed the influence of ND and layer thickness (LT) on void architecture. By establishing structure–property relationships, the study revealed that larger NDs paired with finer LTs yielded superior tensile properties due to reduced void content. This work highlights the interplay between printing parameters, void architecture, and the resulting mechanical behaviour of MEX-based PLA parts.

Influence of turbulence on the stability characteristics of a water lubricated journal bearing is analyzed. Locus of the journal centre is plotted using the non – linear transient analysis method for different flow regimes of the bearing subjected to three different types of loading. The bearing groove angles of 18^o and 36^o is considered for the analysis. Turbulent coefficients are incorporated in the modified form of Reynolds equation which is solved using the 4th order Runge-Kutta method. The path traversed by journal centre is generated for different loading conditions and the stability of the bearing is examined. For periodic and fluctuating rotating loads, the journal centre traversed shorter path and reached stable position when the flow regime changed from laminar to turbulent.

Active vibration control designs for journal bearings have improved rotordynamic stability and led to advancements in adjustable bearing types that enable precise control of bearing geometry. In this study, optimized machine learning (ML) algorithms were modeled and implemented to accurately predict the static performance envelope of a four-pad active journal bearing with features of controlling the radial and tilt positions of pads in real time. ML models developed for the adjustable bearing system help predict its behavior as a function of three key input parameters such as the eccentricity ratio and radial and tilt positions of pads. Four supervised regression models, such as Random Forest Regression (RFR), Extreme Gradient Boosting (XGBoost), Light Gradient Boosting Machine (LightGBM), and a feedforward Artificial Neural Network (ANN), were chosen for their demonstrated ability to capture complex nonlinear patterns and their robustness against overfitting in such tribological applications. Hyperparameter tuning for each model was performed using the Optuna framework, which applies Bayesian optimization to efficiently determine the best parameter settings. The Optuna-optimized ensemble and neural network models were used to identify the optimal combinations of input variables that maximize the static performance envelope of the active bearing system with geometric adjustments.

This study examines how adding titanium dioxide (TiO2) and boron nitride (BN) nanoparticles to Jatropha-based biolubricant improves its viscosity and thermal conductivity. The impact of sonication time, concentration of surfactant (oleic acid), nanoparticle type and nanoparticle content on the thermal and rheological behaviour of the biolubricants was assessed. To guarantee homogeneous dispersion, biolubricants containing 0.05 – 0.20 wt. % TiO2 or BN were made using ultrasonic agitation. To determine the importance of the parameters and their interactions, a statistical analysis of thermal conductivity and viscosity was conducted. Because of its higher heat transfer properties and dispersion stability, BN consistently produced significant improvements in the biolubricant's thermal performance when nanoparticles were added. The highest thermal conductivity of 0.262 W/mK was obtained at 0.20 wt. % BN nanoparticle content and a 10X surfactant concentration, while viscosity remained within acceptable limits for lubrication applications. The type of nanoparticle emerged as the most significant factor, followed by nanoparticle content, for both thermal conductivity and viscosity. Overall, the results indicate that optimising formulation parameters can significantly improve heat transfer performance without compromising flow behaviour. Biolubricants filled with BN and TiO2, therefore, show strong potential as environmentally sustainable lubricants for thermal management and industrial applications.

This study focuses on the design of disc brake and dynamic analysis of metal matrix composite (MMC)-based disc brake pads for a small car, using a representative volume element (RVE) approach. The brake caliper for the Formula car was designed based on the principles of vehicle dynamics. Following this, the brake pad was designed to suit the caliper. For the brake pad friction block, a ceramic particle reinforced AA6061 matrix composite was used. B $$_4$$ 4 C particles (5 wt%) served as the ceramic reinforcements. A suitable mesoscale RVE model was developed in ANSYS Design Modeler^® software to compute the material properties, which were then applied to the macro model of the brake pad for dynamic analysis using the Explicit dynamics tool^®. In this analysis, the oppositely positioned brake pads were held against the counter disc under a compressive force equal to the clamping force of the front caliper piston. The brake pad performance in terms of von Mises stress, equivalent elastic strain during the dynamic analysis, the sliding velocity, interface pressure, and frictional heating characteristics were studied in detail. The analysis demonstrated the effectiveness of using an RVE-based approach for accurately predicting the dynamic performance and thermo-mechanical behavior of MMC-based brake pads.

Multi-grooved water-lubricated bearings (MGWLBs) are widely used in marine stern tube applications, where hydrodynamic performance is strongly influenced by groove geometry and operating conditions. This study presents a combined experimental and computational investigation of water film lubrication characteristics in MGWLBs with different groove geometries. An experimental test setup redesigned to replicate the operational behavior of MGWLBs was employed to record the circumferential film pressure variations under varying rotational speeds and applied loads. Detailed experimental tests were performed on a MGWLBs with filleted V-shaped grooves, where the film pressures at the bearing midplane were measured using a flush-mounted diaphragm pressure sensor mounted on a hollow shaft. The experimental results revealed a transition from localized, non-uniform pressure generation at low speeds to stable and circumferentially continuous hydrodynamic pressure fields at higher speeds and loads. CFD simulations were also conducted to analyze the influence of groove geometry on pressure distribution and flow behavior. An increase in rotational speed was shown to significantly enhance pressure magnitude, circumferential continuity, and film stability under moderate to high loading conditions. Filleted V-shaped, semicircular, and short V-shaped groove models were analyzed for a speed range of 400 to 6000 RPM. Filleted V-shaped grooves produced smooth pressure development with moderate gradients, while semicircular grooves improved pressure and velocity uniformity by limiting localized intensification. In contrast, short V-shaped grooves generated higher peak pressures due to enhanced flow acceleration at groove–land interfaces. The findings provide design guidance for selecting groove geometry and operating conditions to enhance the hydrodynamic performance of marine water-lubricated bearings.