Search Results (142)

Nodular Cast Iron (NCI, also known as ductile iron) is widely used in important components such as crankshafts for automotive engines and internal combustion engines, as well as storage and transportation containers for spent fuel in nuclear power plants, due to its good comprehensive mechanical properties such as strength, toughness, and wear resistance. The effect of temperature on the fracture behavior of NCI was investigated using compact tensile (CT) specimens at different temperatures. The results showed that the conditional fracture toughness parameter (K_Q) of the NCI specimens firstly increased and then decreased with decreasing temperature. The crack tip opening displacement δ_m shows a significant ductile–brittle transition behavior with the decreasing of temperature. δ_m remains constant in the upper plateau region but sharply decreases in the ductile–brittle region (−60 °C to −100 °C) and stabilizes at a smaller value in the lower plateau region. Multiscale fractographic analysis indicated that the fracture mechanism changed from ductile fracture (above −60 °C) to ductile–brittle mixed (−60 °C to −100 °C) and then to completely brittle fracture (below −100 °C). As the temperature decreased, the fracture characteristics changed from ductile dimples to dimple and cleavage mixed and then to brittle cleavage. Full article

The piston, as one of the main components of the crankshaft mechanism, is subjected to significant mechanical and thermal loads. The mechanical properties of the alloy from which it is made and the technology of its manufacture are related to the maximum allowable value of the combustion pressure. The purpose of this paper is to determine the maximum value of the boost pressure of an existing gasoline engine, without causing damage to its piston. To achieve this goal, the stress and strain state of the piston was determined using finite element analysis (FEA) with consideration of the influence of temperature at different values of the boost (intake) pressure. The temperature distribution of the piston was determined using transient thermal analysis. The analyses were performed using SolidWorks Simulation. The obtained results were compared and analyzed. Full article

The precise measurement of crankshaft torsional vibration is critical for diesel engine reliability, yet it is often compromised by systematic errors from toothed disc runout. To address this challenge, this paper elucidates the dual mechanism of these errors, which manifest as micro-level voltage fluctuations in signal and macro-level time-domain deviations. Based on this understanding, a composite compensation method is proposed. First, a dual-line approximation method is presented for preprocessing the raw sensor signals, aiming to eliminate the distortion in rotational speed calculations caused by anomalous voltages. Second, a synchronous sampling scheme based on the differential measurement principle is developed. This scheme utilizes a symmetrically arranged dual-sensor structure to suppress runout errors and is combined with a time-domain feature reconstruction technique to restore the true rotational speed signal. Validation on a custom-built universal joint torsional vibration test rig demonstrates that the proposed method can effectively eliminate systematic deviations arising from toothed disc runout, thereby significantly enhancing the accuracy of torsional vibration measurements. The measurement method presented in this paper offers a valuable reference for the high-precision measurement of engine torsional vibration characteristics. Full article

Torsional vibration dampers effectively mitigate torsional oscillations and additional stresses in diesel engine crankshaft systems, ensuring operational safety and reliability. Traditional damper selection principles, grounded in dual-pendulum dynamic models, focus on minimizing maximum torsional angles but fail to accurately characterize vibration behaviors in multi-cylinder engines. This study addresses this limitation by investigating dynamic modeling and numerical methods for an eight-cylinder diesel crankshaft system. A torsional vibration model was developed using Cholesky decomposition and the Jacobi sweep method for free vibration analysis, followed by dynamic response calculations through model decoupling and modal superposition. Parameter optimization of the damper was achieved via the NSGA-II multi-objective algorithm combined with a Bayesian-hyperparameter-optimized BP neural network. The results show that high-inertia-ratio dampers effectively suppress vibration and stress, while low-inertia-ratio configurations require approximately 20% elevated tuning ratios beyond theoretical parameters to achieve an additional 5% stress reduction, albeit with amplified torsional oscillations. Additionally, the study critically evaluates the numerical reliability of conventional dual-pendulum-based tuning ratio selection methods. This integrated approach enhances the precision of damper parameter matching for multi-cylinder engine applications. Full article

The complex structure of a diesel engine crankshaft, combined with diverse and dynamically changing loads, leads to the interaction of torsional, bending, and longitudinal vibrations. These complexities present challenges in achieving comprehensive and efficient dynamic modelling and analysis. This paper presents a dynamic modelling and numerical computation method for the crankshaft system based on the substructure dynamic model to address this. Specifically, the primary degrees of freedom (DOFs) of the crankshaft system are transformed through coupling between master and slave node DOFs and DOF condensation. A numerical method for free vibration analysis is developed using Cholesky decomposition and Jacobi iteration, while a dynamic response is computed based on the Newmark-β implicit integration algorithm. Additionally, an adaptive step-size control strategy based on the energy gradient criterion was proposed by introducing a dynamic relaxation factor, significantly enhancing computational efficiency. The study further examines the influence of primary DOF selection, coupling region size between master and finite element nodes, bearing support stiffness, and integration step size on the dynamic response. Numerical case studies demonstrate that the substructure model, with fewer DOFs, accurately characterizes the dynamic behaviour of the crankshaft by appropriately selecting primary DOFs and computational parameters, thereby enabling efficient dynamic analysis. Full article

The Free Double-Piston Composite Cycle Engine (FDP-CCE) integrates the turbofan engine architecture with the characteristics of piston engines with the aim of improving engine efficiency and decreasing CO₂ emissions. The FDP-CCE features a free-piston design, providing a lighter and more compact structure compared to conventional crankshaft-connected piston engines due to the elimination of mechanical transmissions and lubrication systems. Innovations like air lubrication and increased piston velocities contribute to higher cylinder temperatures, underscoring the need for advanced thermal management strategies. For this reason, in the present work, a heat transfer model to address the thermal management challenges in this innovative engine design is developed. More specifically, a novel filling–discharge model for a two-stroke compression ignition engine is developed, dividing the operational cycle into phases handled by the piston engine and the piston compressor. Special emphasis is given to the implementation of various geometric zones for each piston to optimize the heat transfer between the combustion chamber and the cylinder walls and heads. The final step of this research work involves the integration of piston temperatures into the boundary conditions of an equivalent computational domain to conduct a detailed heat transfer and fluid flow analysis around and on the FDP cylinder. By focusing on these critical aspects, this study establishes a fundamental framework for future aeroengine designs, promoting sustainable propulsion solutions with reduced fuel consumption and emissions. Full article

The aim of this study is to design and analyze a variable compression ratio (VCR) technology gasoline engine variable compression ratio connecting rod set and to verify its kinematic properties through numerical simulations. This study first constructs a mathematical model of the VCR connecting rod set and derives its kinematic equations. Numerical simulations were carried out using MATLAB R2022b software to analyze the kinematic state of the piston under different compression ratio conditions. The results show that the equations of motion of the VCR mechanism realize continuously variable compression ratios from 8 to 14, which provides a valuable reference for the study of overall engine performance control. This study also verified the accuracy of the theoretical model through the multibody dynamics software ADAMS 2020 to ensure the reliability of the model. The results of this study show that the piston position is jointly influenced by the crankshaft angle and the control shaft angle, and a change in the control shaft angle leads to a change in the piston upper and lower stop positions and stroke. With the increase in the control shaft angle, the maximum velocity (absolute value) of the piston gradually decreases, while the maximum acceleration (absolute value) gradually increases. The results of this study provide important reference data for the development of variable compression ratio engines. Full article

Decarbonization of the automotive sector is essential to achieve global climate goals, as passenger cars contribute a substantial share of CO₂ emissions. This research project focuses on the preliminary design of an innovative 2-stroke hydrogen-fueled opposed-piston engine, offering a promising solution for reducing emissions from passenger cars. Hydrogen enables clean combustion due to its carbon-free nature and allows the possibility of nearly-zero NOx emissions when burned in an ultra-lean mixture. Although the ultra-lean mixture inevitably leads to a significant drop in performance, the opposed-piston engine architecture offers a potential solution for maintaining power output and overall dimensions comparable to traditional internal combustion engines. The study addressed the global balancing of the engine. Unlike conventional engines, the opposed-piston engine presents non-trivial challenges, such as the interaction between the two crankshafts. Two engine architectures are addressed: 3-cylinder and 4-cylinder. Full article

This research article outlines our aim to perform topology optimization (TO) by reducing the mass of the connecting rod of an internal combustion engine based on static structural and dynamic analyses. The basic components of an internal combustion engine like the connecting rods, pistons, crankshaft, and cylinder liners were designed using Autodesk Inventor Professional 2025. Using topology optimization, we aimed to achieve lesser maximum von Mises stress during static structural analysis and maintain a factor of safety (FOS) above 2.5 during rigid body dynamics. A force of 64,500 N was applied at the small end of the connecting rod while the big end was fixed. Topology optimization was carried out using ANSYS Discovery software at various percentages on a trial-and-error basis to determine better topology with lesser maximum von Mises stress. Target reduction was set to 4%, and as a result, 5.66% mass reduction from the original design and 6.25% reduced maximum von Mises stress was achieved. Later, transient analysis was carried out to evaluate the irregular motion loads and moments acting on the connecting rod at 1000 rpm. The results showed that the FOS remained above 2.5. Finally, the optimized connecting rod was simulated and verified for longevity using Goodman fatigue life analysis. Full article

Crankshafts, present in internal combustion engines, are mechanical parts subject to torsion and bending that vary over time and, if the forcing is close to one of the natural frequencies of the system, they can encounter problems of torsional oscillations. These vibrations can lead to maximum oscillation amplitudes, with consequent fatigue stresses that would compromise the resistance and correct functioning of the shaft. The aim of this work is to indicate a methodology for identifying the natural frequencies of the crankshaft and the decomposition of the torques, due to gases and inertia, to identify the different harmonics; in fact, if one of these harmonics is close to the natural frequency of the crankshaft, the system will go into resonance. Full article

The crankshaft is a critical component in large marine ships, often regarded as the “heart” of the vessel due to its role in transmitting power and motion. This article addresses the technological challenges in the forging of marine crank throws, a key segment of the crankshaft. The study employed finite element simulations to evaluate three Near-Net-Shape (NNS) forming methods: One-Step Extrusion (OSE), Upsetting/Backward Extrusion (U/BE), and Grooving–upsetting/Backward Extrusion (G–U/BE). The results show that the G–U/BE method requires the lowest load. The grooving–upsetting step in the G–U/BE process forms a rigid journal end web shape that influences the subsequent backward extrusion, with the relative groove depth (the ratio of groove depth to width) playing a crucial role in the final forging quality. Optimal crank throw formation occurs when the ratio is 1.5; deeper grooves increase the load required, diminishing the effectiveness of the grooving–upsetting step. Scaled-down experiments validate G–U/BE as a practical and feasible method for producing large marine crank throw forgings, ensuring both the desired shape and microstructural properties. Full article

Biofuels are the most essential types of alternative fuels, which currently have significant potential to reduce CO₂ emissions compared to fossil fuels. Methanol is a more efficient fuel than petrol due to its physicochemical properties, such as a higher latent heat of vaporization, research octane number, and heat of combustion of the fuel–air mixture. Also, biomethanol is cheaper than traditional petrol and diesel fuel for agricultural countries. The authors have proposed a new approach to improve the characteristics and efficiency of methanol diesel engines by using biomethanol mixed with hydrogen instead of pure biomethanol. Using a hydrogen–biomethanol mixture in modern engines is an effective method because hydrogen is a carbon-free, low-ignition, highest-flame-rate, high-octane fuel. A small quantity of hydrogen added to biomethanol and its combustion in an engine with a heat exchanger increases the combustion temperature and heat release, increases engine power, and reduces fuel consumption. This article presents experimental results of methanol combustion and a hydrogen-in-methanol mixture if hydrogen was retained due to the utilization of the heat of the exhaust gases. The tests were carried on a single-cylinder experimental engine with an injection of liquid methanol and gaseous hydrogen mixtures. The experiments showed that green hydrogen generated onboard the car due to the utilization of heat significantly reduced fuel costs of engines of vehicles and technological installations. It was established a hydrogen gaseous mixture addition of up to 5% by mass to methanol requires a corresponding change in the coefficient of excess air to λ = 1.25. Also, using an additional hydrogen mixture requires adjustment at the ignition moment in the direction of its decrease by 4–5 degrees of the engine crankshaft. Hydrogen gas mixture addition reduced methanol consumption, reaching a maximum reduction of 24%. The maximum increase in power was 30.5% based on experimental data. The reduction in the specified fuel consumption, obtained after experimental tests of the methanol research engine on the stand, can be implemented on the vehicle engines and technological installations equipped with an onboard heat recovery system. Such a system, due to the utilization of heat and the supply of additional hydrogen, can be implemented for engines that work on any alternative or traditional fuels. Full article

This research aims to study the mechanical behavior of the materials most commonly used in crankshaft manufacturing by designing a four-piston crankshaft, analyzing the stresses and displacements resulting from the applied load, and determining vibration frequencies. Additionally, this study examines the thermal behavior of the crankshaft. For this purpose, a three-dimensional model of the crankshaft was designed using CATIA V5 R18 software, and finite element analysis was subsequently performed using ANSYS 2019 R1 software under static, dynamic, and thermal conditions with four different materials in various orientations. To verify the effectiveness of the proposed design, it was compared with a reference design in terms of stresses and displacements. This study also explores improvements in crankshaft geometry and shape. The results indicate that selecting the appropriate material for the working conditions and optimizing the geometry and shape enhance engine performance and reduce the crankshaft’s weight by 20%. The findings were validated by comparing the designs, which support increased productivity and improved durability. Full article

As modern diesel engine design progresses toward higher burst pressure and power density, strict performance indices impose greater demands on the structural strength and reliability of crankshafts. We integrated finite element analysis and strength testing methods to achieve a lightweight crankshaft design. A comparison of the simulated results with the test data revealed that the crankshaft safety factor surpassed the permissible safety factor by 3.5 times, demonstrating significant safety redundancy in the design. We employed topology optimization techniques to create various crankshaft optimization models, yielding near-optimal solutions. Consequently, we identified the crankshaft with the best overall performance following comparative evaluations. We examined the influence of the fillet structure on the safety factor to mitigate stress concentration issues. Through multibody dynamic fatigue analysis, optimizing the crankshaft fillet resulted in a 6~7% increase in the safety factor. The minimum safety factor for the designed crankshaft was 1.6 times higher than the material permissible safety factor, which was 1.15. Utilizing the developed transient dynamics model of the lightweight crankshaft and a backpropagation genetic algorithm, we created a crankshaft fillet design tool to streamline the design process, which holds significant importance for the marine engine sector. Full article

A well-known phenomenon in machinery systems is the easing of a blocked connection of mechanical parts after an impact hit close to the connection. Such impact hits may also arise in shaft–hub connections such as gears, crankshafts, or other parts. The objective of this study is to investigate the influence of local impact loads on the transmittable torque of smooth shaft–hub connections. In a specially designed test rig, it was demonstrated that the transmittable torque of the shaft–hub connection is reduced as a consequence of the impact, resulting in a reduction in the frictional force and slippage of the hub. Increasing the impact load leads to an increase in the reduction in the frictional force as well as the slippage and reduces the transmittable torque. By carrying out a modal analysis of the relevant parts and FE simulations of the impact, two possible reasons have been identified: (i) the impact load excites a vibration mode in the connection which reduces the frictional force and the transmittable torque; and (ii) the impact causes local deformation of the shaft, which results in local slip. Full article