Journal of Research and Applications in Mechanical Engineering

A Comparative Investigation on Friction and Wear Behavior of Green Lubricants

G. S. Gahir, S. P. S. Matharu — Sun, 20 Sep 2026 00:00:00 +0700

Green lubricants are gaining increased attention due to the rising demand for environmentally friendly and sustainable solutions. To evaluate their suitability as base oils for lubricants in local automobile and power plant engines, the tribological performance of refined, bleached, and deodorized palm and jojoba oils was assessed and compared. The tests were conducted using a four-ball tester. The bio-based oils’ performance was evaluated under various load and temperature conditions using a tribological testing system. The results showed that unprocessed palm oil outperformed jojoba oil in terms of load-bearing capacity and friction reduction in its raw state. Additionally, palm oil exhibited wear protection performance similar to jojoba oil. With the radical incorporation of suitable anti-wear agents, palm oil can be transformed into a highly effective alternative to mineral oils, offering advantages in terms of tribology, environmental impact, and non-food competition.

Effect of Pouring and Mold Shell Temperatures on Porosity in Complex Investment Castings of Stainless Steel 304

T. T. Nguyen, H. G. Le, M. T. Ho, V. T. Nguyen — Sun, 20 Sep 2026 00:00:00 +0700

Investment casting offers a powerful combination of precision, design freedom, material versatility, and potential cost savings, making it an ideal choice for demanding applications across various industries. However, this technology also faces significant challenges that affect part quality, primarily due to the formation of porosity and air entrainment. These defects originate from inadequate solidification control and turbulent flow behavior during the mold filling process. This study aimed to investigate the effect of pouring and firing temperatures on the appearance of porosity in stainless steel 304 complex casting parts, to minimize casting defects. The casting geometry is characterized by intricate features and thin cross-sections, making it highly sensitive to thermal and flow behaviors. Six pouring temperatures (1580 °C, 1600 °C, 1620 °C, 1640 °C, 1660 °C and 1680 °C) and six firing temperatures (950 °C, 1000 °C, 1020 °C, 1040 °C, 1060 °C and 1080 °C) were evaluated. ProCAST software was used to analyze porosity formation and air entrainment, revealing that a pouring temperature of 1640 °C and shell temperature of 1040 °C achieved a minimal porosity (0.01 cm³) while reducing the air entrainment (0.5 mg/cm³). Additionally, the study also clarified that the relationship between pouring/shell temperature and casting defects is non-linear, with “trade-off” effects always happening in casting. Experimental validation via X-ray and microscopy inspection confirmed the simulation trends. The study recommends minimizing defects in thin-walled investment casting parts through precise thermal control, enhancing product quality and manufacturing efficiency.

Hydrodynamic Analysis of a Two-Lobe Bearing Lubricated with a non-Newtonian Fluid: Effects of Geometric and Rheological Parameters on Operating Characteristics

H. Bennaceur, B. Chetti — Sun, 20 Sep 2026 00:00:00 +0700

In the context of hydrodynamic lubrication, this paper investigates the contribution of the aspect ratio R/L to the static performance of two-lobe bearings, by incorporating the non-Newtonian rheological response of the lubricant modeled by the power law. The Reynolds equation is reformulated to incorporate fluid rheology and solved numerically using the finite difference method to determine the pressure profile within the lubricant film. The analysis focuses on the cross-impact of the aspect ratio, the power law index n, and the eccentricity ratio ε, on key parameters such as film thickness, pressure, load-carrying capacity, attitude angle, frictional force and coefficient, as well as the side leakage. The results indicate that film thickness is only marginally affected by the R/L ratio, but is highly sensitive to the lubricant's rheological properties, especially in high shear zones. A reduction of R/L or an increase of n improves the hydrodynamic support. Furthermore, shear-thickening fluids promote the load-carrying capacity and tribological efficiency, while long bearings exhibit increased sensitivity to leakage effects.

Energy Harvesting Using One-Way Bearing for Vehicle Suspension Applications

S. Chanayuth, K. Thoatsanope, S. Szathys — Sun, 20 Sep 2026 00:00:00 +0700

Road degradation amplifies suspension energy dissipation due to factors like vehicle mass, speed, and surface roughness. Harvesting energy from suspension motion is challenging, requiring the conversion of irregular mechanical energy into electrical power. The energy harvesting device must operate effectively under ISO 8608 Class C and D conditions. An indirect-drive system converts linear motion into rotational motion to power a generator, with the 'two-leg mechanism' and one-way bearing rectifying motion direction. This research combines simulation and experimentation to assess power generation under sinusoidal wave conditions (10–20 mm amplitude, 1–3 Hz frequency). Maximum power occurs at 10–20 Ω resistance, increasing with frequency and amplitude. With 88.15% accuracy, the simulation model provides valuable insights for optimizing real-world performance.

Rotational Effects on Heat Transfer for In-Line Jet Impingement Array in a Mid-Span Turbine Channel: An Experimental Study

C. Sathiravorakul, C. Nuntadusit — Sun, 20 Sep 2026 00:00:00 +0700

This study examined heat transfer for a 3x11 inline impinging jet array within a rotating channel that simulates the turbine blade cooling in mid-span region. The heat transfer on the impingement surface was investigated using Thermochromic Liquid Crystals and a thin-foil heater under steady-state conditions. The influence of impingement distance (L/D=2, 4, 6) and Rotation number (Ro=0.0-0.0083) was examined at a constant Reynolds number of Re=10,000. Results indicate intricate relationships between impingement distance, Coriolis forces, and crossflow. Increased rotation numbers generally diminish heat transfer on both of leading and trailing sides relative to the stationary condition. At a small L/D of 2, crossflow effects predominated over rotational effects, resulting in gradual decrease in downstream region. In contrast to distances L/D=4 and 6, the Nusselt number declined rapidly in the upstream region, whereas the influence of rotation lessened in the downstream region.

A Digital Twin and Probabilistic Optimization Framework for Resistance Spot-Welded Joints in Automotive Applications

P. P. Kulkarni, P. R. Kulkarni — Sun, 20 Sep 2026 00:00:00 +0700

This study formulates a digital twin–driven probabilistic model to forecast and optimize the tensile behavior of resistance spot-welded (RSW) galvanized steel auto-body joints. Experimental experimentation was performed on multi-spot cross-tension specimens by a Taguchi L27 design with the considerations of welding current (8959–9554 A), sheet thickness (0.19–0.30 mm), electrode force (350–497 N), weld spot number (2–8), and radial distance (12–16 mm). Tensile strength varied from 4.08 Kgf to 150.91 Kgf. A linear regression model accomplished ±5% prediction accuracy in this range, with thickness and number of welds as the most significant parameters, and radial distance as having a significantly negative effect on strength. To offset the weakness of regression, finite element analysis (FEA) was systematically incorporated, allowing for a mechanistic understanding of stress concentrations due to off-center weld placement and to confirm the observed empirical trends. The FEA also showed predictive validity, with calculations at an unseen parameter set (9554 A, 0.27 mm, 350 N, 8 spots) approximating tensile strength to 145.2 Kgf versus the tested 150.9 Kgf (3.7% error). Parameter uncertainty was quantified using Monte Carlo simulations with Latin Hypercube Sampling (170 runs), and Global Sensitivity Analysis indicated sheet thickness and weld radius as overall factors on strength variability. Dynamic tensile testing (1.32–2.00 m/min) validated the model's insensitivity to service-relevant strain rates. Together, the synergy from the combination of regression, FEA, and probabilistic simulations provides a predictive digital twin approach that is both statistically sound and mechanistically interpretable. The approach improves weld performance assessment reliability and provides scalable applicability towards lightweight and safe automotive structures.

Bionic Riblet Impeller for a Centrifugal Pump: CFD and Experimental Performance Analysis

R. J. Pawar, M. P. Ray, S. R. Suryawanshi — Sun, 20 Sep 2026 00:00:00 +0700

This study adopts a novel bionic approach to evaluate the performance of a centrifugal pump using numerical simulations and validates the findings through experimental analysis. The centrifugal pump, featuring six backward-curved blades, was modeled by incorporating shark-skin-inspired riblet structures into the impeller design. The flow inside the pump was studied using k-epsilon (k-ε) turbulence models. The k-ε model gave results that were closest to the real experimental data. In most studies, only design parameters considered during computational fluid dynamics (CFD) analyses without consideration of experimental result. Here new bio inspired technique called bionics is applied to impeller of pump. The experiments were carried out using a computer-controlled pump testing setup. The pump's head, hydraulic efficiency, and power were analyzed using both CFD simulations and experimental tests on the duty point as per manufacturer’s catalog, having the revolution of 2,900 rpm, The bionic impeller achieves a best efficiency point (BEP) at a discharge rate of 12 m³/hr., with a head of 32.75 m and an efficiency of 39.21%. The CFD results closely matched the experimental results at the design flow rate and at all other tested flow rates as per duty points. In addition, by integrating nature-inspired design with testing, this study contributes to the development of high-performance, sustainable pumps. The results may help advance efficient industrial fluid transport systems. This research bridges biomimetic innovation with practical engineering, paving the way for future pump advancements.

Heat Transfer Characteristics of Filmwise and Dropwise Condensation on Vertical Tubes in the Presence of Air: An Experimental Study

M. S. Baba, N. K. Surisetty, B. P. Maddilety, K. Talari — Sun, 20 Sep 2026 00:00:00 +0700

Condensers are essential to many industrial processes, such as desalination, refrigeration, and power generation. The condenser performance largely depends on the mode of condensation (filmwise or dropwise) which significantly affects heat transfer rates. In this paper, An experimental investigation has been made on filmwise condensation (FWC) & dropwise condensation (DWC) to determine) the heat flux and heat transfer coefficient (HTC) for three steam temperatures of 100^oC, 80^oC and 60^oC. The results are compared with predicted values. It is observed that HTC of DWC is more than FWC. Experimental calculations of the influence of non-condensable gas (air) on heat flux and HTC have also been done and it was proved that the effect of air (1% and 2%) has a very detrimental effect on both FWC and DWC. The experimental values of HTC in presence of air are compared with predicted values obtained by two latest empirical correlations and deviation is identified in FWC. A satisfactory relation is obtained between actual and predicted values.

CFD and Experimental Study of Cavitation Behavior in Three-Lobe Journal Bearings Lubricated with TiO₂-Based Nanofluids

N. Ahire, D. Deshmukh — Sun, 20 Sep 2026 00:00:00 +0700

Three-lobe journal bearings are widely used in high-speed rotating machinery due to their superior stability and load-carrying capacity. However, they are susceptible to vapor cavitation in the diverging region, which weakens the lubricant film and degrades performance. This study presents a combined numerical and experimental investigation of pressure distribution in three-lobe journal bearings under cavitating conditions, comparing a base oil (Mobil DTE 24) with a TiO₂-enhanced nanolubricant. Simulations were performed using the Zwart–Gerber–Belamri (ZGB) cavitation model within a multiphase CFD framework in ANSYS Workbench 2024R1 at operating speeds of 500- 1000 rpm. Results were validated against experimental pressure measurements at twelve angular positions using a custom-built test rig. For the base lubricant, CFD accurately predicted peak pressure near 210° and vapor cavitation between 240° and 330°, with deviations within ±0.06 MPa. The addition of TiO₂ nanoparticles increased peak pressure by up to 36% and raised the minimum pressure from –0.52 MPa to +0.50 MPa, indicating over 60% cavitation suppression. These improvements confirm enhanced film stability, greater load capacity, and close agreement between simulation and experiment. Furthermore, the TiO₂ nanolubricant reduced friction losses, minimized lubricant degradation, and supports the development of energy-efficient and sustainable tribological systems.