The present study was envisaged to address the problem of poor reconstruction of associated images of the inner wall of cylinder head caused due to changes in the thermal field gradients. By ...introducing the idea of multiscale in this study, a method for the associated reconstruction of inner wall of the cylinder head based on hybrid thermal field pattern was proposed. Initially, the characteristics of the thermal field distribution in the inner wall of the cylinder head were analyzed. The inner wall of cylinder head was divided into 7 areas based on each nose bridge area, the surrounding areas of the nozzle and the cylinder head, and then subdivided according to the shape of the area. Subsequently, numerical simulation was performed on the thermal field using finite element software to calculate the variation range and gradient of the thermal field in each area, and the minimum interval of the thermal field and its thermal field resolution was determined according to the area. Further, the thermal field at some positions of the inner wall of cylinder head was measured by thermocouple thermometry. Thermal field pattern was constructed in this procedure based on the study of filling method of thermal field on different resolutions. Finally, the constructed thermal field pattern was correlated with the thermal radiant energy of outer wall of the cylinder head, and the inner wall image was reconstructed. The reconstruction results of the single-scale thermal field pattern were compared and analyzed. The experimental results show that the structural similarity of the reconstructed image obtained using hybrid thermal field pattern constructed based on the multiscale idea was 12.5–77.01% higher than that of the single-scale thermal field pattern with same correlation algorithm. The results indicated that the proposed method was more appropriate for discriminating the cracks and other defects caused by the thermal fatigue damage.
•Simulated component of cylinder head is established based on the equivalent model of flame deck.•The simulation method of thermo-mechanical fatigue is developed by the Sehitoglu theory and loading ...spectrums.•Damage characteristics at typical working condition are predicted from three damage types.
As the vulnerable component of diesel engine, cylinder head is subjected to the thermo-mechanical coupling loads more and more heavily. For establishing a simple and effective technology to evaluate the damage degree, a prediction method based on simulated component is developed in the present work. By the comparison of temperature and stress at measured points, it shows that the simulation and testing results have a good agreement, verifying the effectiveness of simulated component. Applying Sehitoglu theory and loading spectrums, the failure locations are predicted successfully. Then damage characteristics of thermo-mechanical fatigue are analyzed at failure locations. It indicates that mechanical damage takes a leading role compared with oxidative damage and creep damage, and thermal load is more sensitive to mechanical damage in three damage types. This study may provide an effective way to estimate the service life of cylinder head.
In the present study, the effect of the T6 heat treatment on high-cycle bending fatigue properties of the A380 (AlSiCu) aluminum alloy has been investigated. The fracture behavior of materials was ...also examined under stress-controlled cyclic loadings. For such an objective, standard specimens were prepared and tested by a rotating bending fatigue machine. In addition, the microstructural characterization and the fracture surface analysis were performed by the scanning electron microscopy. Using the T6 heat treatment, the solution treatment was performed at 510°C for 5 hrs and after quenching in the air, the ageing treatment was carried out at 200°C for 3 hrs. The main aim of this work is to investigate the heat treatment effect on fatigue properties of AlSiCu alloys. Moreover, the roughness influence was also studied on the fatigue lifetime. Based on experimental results, the heat treatment changed the distribution and the size of silicon phases and enhanced the microhardness. Under the highest and lowest stress levels, the heat treatment increased the high-cycle bending fatigue lifetime by 26% and 85%, respectively. Samples with low roughness had a greater fatigue lifetime than those with high roughness. The fracture surface analysis demonstrated that in both as-cast and heat-treated specimens, several microcracks occurred through intermetallic compounds. The heat-treated and as-cast materials showed a brittle fracture behavior due to cleavage planes on the fracture surface of specimens. However, some dimples and quasi-cleavages were also observed on the fracture surface of as-cast samples.
•T6 treatment increased fatigue lifetimes of A380 aluminum alloy between 26% and 85%.•Fatigue lifetimes were 124.5% and 156.2% greater in low roughness samples, respectively for T0 and T6 specimens.•Fracture surfaces demonstrated that microcracks initiated in intermetallic compounds.
During the E5 engine durability test, the failure happens in cast iron cylinder head. This is characterized as low cycle fatigue. The macro-scale cracks initiate and propagate in valve bridge region. ...The present investigation focuses on simulating durability test and evaluating low cycle fatigue life of the failed part. The simulation includes one pre-step as a determination of material grid and three steps as fluid, structural and fatigue analyses. In order to cover the durability test, the analysis steps are repeated at five crack speeds, 750, 1650, 2075, 2350, and 2600rpm. The cylinder head is subjected to cyclic multi-axial variable amplitude loads. In fatigue analysis, critical plane and cumulative damage theories are utilized in order to predict fatigue life. A general script is developed and validated so as to calculate fatigue life in the whole model. The numerical results also show that the failure of critical cylinder head can be characterized as low cycle fatigue. The valve bridge region, in which high temperature exists during engine operation, is the critical area in fatigue analysis approach. The simulation results are in a good agreement with the durability test observations.
•Low cycle fatigue failure occurs in valve bridge region of cylinder head.•Critical cylinder head subjected to E5 engine durability test is simulated.•Numerical and Experimental results are in a good agreement.•Graphical life prediction avoids misunderstanding about structural fatigue behavior.•It can provide helpful viewpoints for designers.
Sand casting process is used by man from olden days to manufacture metallic components. Due to various problems of sand, mold and filling, the process is considered not suitable to produce small ...intricate castings having thin geometries. Only huge castings are preferred and sophisticated components are completely ruled out of the process. However, the cost-effectiveness of the process is very attractive. The present work is taken up to investigate the possibility of sand mold casting process to produce intricate components having thin sections like automobile cylinder head castings. The project uses additive layer manufacturing technique for pattern development and computer-aided casting simulation technique to analyze mold filling and solidification aspects. Simulations are performed by varying pouring temperature and gating system design which also reduces shop floor trials and lead time. Based on simulation results, experiments are design and conducted using three types of sand, namely air-set sand, dry sand, and sodium-silicate sand. The produced castings are tested for various parameters and found successful. Results obtained from simulation are validated experimentally proving the methodology adopted is very helpful in producing intricate castings economically.
The failure analyses of the cast iron cylinder head of diesel engine, including the chemical composition, microstructure, mechanical properties, crack initiation and propagation, were studied in this ...paper. Based on the results, it was found that the most dangerous site analyzed by the dye penetrant inspection is the thinnest area of the bridge zone. In high temperature, the oxidation phenomenon becomes severe. The cracks initiate from the interface between the graphite and ferrite matrix in the surface of the cylinder head, and the oxide promotes the crack propagation. Failure of the engine cylinder head is mainly caused by the thermal fatigue, which was proved by the result of finite element method and crack morphology. Furthermore, the improvement of thermal conductivity of material is a useful way to enhance the service life of engine.
•Based on the failure analysis most dangerous site is the thinnest area of the bridge zone.•Failure is caused by the thermal fatigue. The cracks initiate from the boundary of the graphite and ferrite matrix in the surface.•Based on thermal conductivity calculated by the FEM, a useful improvement design was raised.
A one-dimensional model of the diesel engine working process was established, and thermal boundary conditions of gases contacting with a cylinder head were determined by comparing them with the ...results of a routine test. A fluid-structure interaction model between the cooling water and cylinder head passages was established in which boundary conditions of cooling water were obtained by computational fluid dynamics analysis. Simultaneously, considering the pressure mechanical load in the cylinder, temperature and the stress distribution of the cylinder head were analysed by the model with a thermo-mechanical coupling load. The model was validated using the temperature hardness plug method. Four parameters of intake valve opening, exhaust valve opening, fuel supply beginning, and compression ratio were selected as influencing factors, and the thermo-mechanical coupling load of the cylinder head was optimised by the Taguchi and analysis of variance method subsequently. The study indicates that the error of the calculation model for the cylinder head’s thermal-mechanical coupling load is within ±1.5%, and the proportion of the thermal stress in the cylinder head thermal-mechanical coupling stress is above 90%. The fuel supply beginning has the greatest influence on the thermal load of the cylinder head. Based on the optimisation methods within the required power range, the maximum temperature and maximum thermo-structural coupling stress of the cylinder head are decreased by about 10.05 K and 7.13 MPa in the nose bridge area, respectively.
Taking the combustor composite structure of a high-strength diesel engine as the main research object, dedicated tests have been conducted to verify the accuracy of three distinct cylinder gasket ...pressure simulation models. Using the measured cylinder gasket compression rebound curve, a gasket unit has been designed and manufactured. For this unit, the influence of the bolt pretension, cylinder body and cylinder head material on gasket sealing pressure has been investigated systematically in conditions of thermo-mechanical coupling. The results show that the bolt pretension force is one of the most important factors affecting the cylinder gasket sealing pressure. The change of the body material has little effect on this pressure. The cylinder gasket seal pressure decreases progressively with the reduction of the elastic module of the cylinder head material.
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