Laser cladding is one of the principal means of equipment remanufacturing and the environmental profiles of this technology has become a research focus. This paper examines the environmental impacts ...of cast iron cylinder head block remanufacturing through laser cladding using life cycle assessment (LCA), and compares it with the new cylinder head block manufacturing. Resource and energy consumptions of each manufacturing and remanufacturing processes are collected along the production line and then the results of six selected environmental impact categories are calculated. Consistency and sensitivity analysis is also conducted after life cycle impact assessment. The results reveal that cylinder head remanufacturing by laser cladding will achieve large environmental benefits, which can cut environment impact over the entire life cycle by 63.8% on average. This paper also discusses the trend of changes in environmental impacts using scenario analysis over different remanufacturing levels. By taking characterized global warming potential (GWP) as the assessment index, the result shows that remanufacturing will no longer be the preferred option if it needs to repair more than 16 cracks by laser cladding for the cylinder head.
•Environmental benefits of cylinder head block laser cladding remanufacturing are identified with life cycle assessment (LCA).•The overall environment impact can be reduced by 63.8% on average through laser cladding remanufacturing technology.•Scenario analysis is conducted to figure out the number of cracks which can be repaired.•Consistency and sensitivity analysis is conducted after life cycle impact assessment.
During the start-stop cycle of marine diesel engines, the cylinder head bears the cyclic thermal stress and produces irreversible deformation. Previous studies mainly predicted the thermomechanical ...fatigue life of cylinder heads based on the strain fatigue damage criterion, but the multi-factor damage mechanism and law of thermal cycle load on the structural integrity of cylinder heads are not clear. A transient thermal cycle analysis method of the viscoelastic plastic Chaboche model was developed to quantitatively account for the marine engine cylinder head's local deformation and leakage failure. The Chaboche model combines the temperature-dependent nonlinear kinematic hardening equation and Norton-Bailey creep equation. A thermal cycling test of simulated cylinder head specimen was designed to cautiously verify the inelastic cyclic behavior of the multiaxial thermal and structural coupling effect. The model and numerical method are verified by the deformation and fatigue test of the specimen. Then the permanent deformation and leakage of the cylinder head and water-cooled valve seat are analyzed. The results show that multiaxial thermal cycle simulation verified the deformation prediction with an error of no more than 14%. Inelastic deformation induced by temperature cycling leads to gradual leakage failure in the exhaust nose bridge area of the cylinder head. The irreversible deformation gradually reduces the contact sealing force, and the cyclic loading plasticity that dominates is 8.36 times that of the creep deformation.
•There is a significant inhomogeneity of mechanical properties in cylinder head.•Tensile properties of cylinder head are mainly controlled by the dendrite arm spacing.•SDAS and eutectic Si area are ...the main affecting factors for the fatigue stress limit.•Aluminum cylinder head fatigue fracture is mainly caused by porosity defects.
The microstructure and mechanical properties of top plate, force wall and bottom plate in low-pressure sand-casting aluminum alloy cylinder head were evaluated at room temperature. The results of the comparison study showed that with different positions of the cylinder head, the microstructure and mechanical properties were considerably different. For the convenience of analysis and discussion, the quality index (Q) was used to characterize tensile test data, which equals ultimate tensile strength plus 150 log elongation. The top plate has the best tensile performance with Q of 443.5 MPa, while the Q of the force wall (292 MPa) and bottom plate (355.5 MPa) is only 66% and 80% of that on the top plate. The tensile properties of the cylinder head are mainly controlled by dendrite arm spacing (DAS), including primary dendrite arm spacing (PDAS) and second dendrite arm spacing (SDAS). The influence intensity varies with the value of DAS. In general, the tensile properties decreased with the increase of DAS. When the aluminum alloy specimen has small DAS (PDAS ≤ 46.49 µm, SDAS ≤ 33.64 µm), Q increases rapidly with the decrease of DAS. However, when PDAS ≥ 104.33 µm, SDAS ≥ 49.82 µm, the effect intensity of DAS on tensile properties is partially reduced. When the number of cycles is 2.5 × 107, the fatigue stress limits of the top plate (69.2 MPa) and bottom plate (70.0 MPa) are highly comparable, which is mainly due to the similar SDAS and eutectic Si average area. Porosity defects also have a significant impact on fatigue performance. The presence of porosity defects increases the scatter of fatigue properties. In addition, more than 90% of the fractures are caused by porosity defects, which indicates that porosity defects are the main factor causing fatigue cracking of low-pressure sand-casting aluminum alloy cylinder head. Therefore, the casting process should be optimized to avoid porosity defects as much as possible in order to improve fatigue performance.
Nowadays, each industrial process like installation, manufacturing and service industries process possesses the risk of process failure. The risk of process failure is collected from initial supply ...chain to final supply chain and the potential failure can affect the supply chain from one to another which is considered as a major problem in industries. In automotive motorcycle industry, the spare parts supply chain supports to generate the automotive vehicle spare parts that require the integration of a supply chain system to avoid delay from one supply chain to another supply chain. The installation process failure occurred due to the damage of one cylinder head product namely perforated cap camshaft so the assembly mechanism is used in the cylinder head for removing cracks on the torque. To overcome the failure and cracks in Cap Camshaft process, the Process Failure Modes and Effects analysis based Automotive Industry Action Group-Verband der Automobilindustrie (PFMEA-AIAG-VDA) version is proposed. The objective of this proposed method is to analyze the casting process and failure of cap camshaft on the cylinder head assembly parts such as camshaft and bolt flange. The optimization result improves the casting process over the porous camshaft cap by using casting process parameters and design of engineering factor analysis. The proposed method shows a positive impact on product output, wherefrom the monitoring is done by casting production for 20,000 shot castings, and there are no spray holes and cracks found in the suspect cap camshaft area so the production targets are achieved.
•The failure behavior of the cylinder head is analyzed from the material and working load.•The heat transfer boundary and mechanical load boundary are considered in the finite element model.•The ...relationship between the thermal load and the gas pressure are both introduced in the fatigue strength analysis.•The structure optimization design is proposed to improve the fatigue reliability of the cylinder head.
Crack and failure are often captured in the cylinder head of diesel engine during high cycle fatigue test. In order to study the cause and improve the fatigue resistance, tensile test, metallographic observation and fracture analysis were carried out. In addition, the finite element method was applied to simulate the stress distribution and fatigue strength of the cylinder head. Meanwhile, the influence of load factors on the fatigue strength was analyzed. The structure was optimized on the finite element analysis. The results show that the material properties are not the main cause of cylinder head failure. High cycle fatigue failure of cylinder head is identified by the reason of working loads. Among the causes affect fatigue strength, gas force was determined as the dominant factor by changing stress amplitude, while thermal load as the secondary factor by changing mean stress. Additionally, the structural optimization measures for the cylinder head were put forward according to the failure causes, and the safety coefficient of the vulnerable parts was increased from 0.88 to 1.04, meeting the design requirements. This study can provide a reference for the engine reliability analysis.
The continuous drive towards higher specific power and lower displacement engines in recent years place increasingly higher loads on the internal combustion engine materials. This necessitates a more ...robust collection of reliable material data for computational fatigue life prediction to develop reliable engines and reduce developmental costs. Monotonic tensile testing and cyclic stress and strain-controlled testing of A356-T7 + 0.5 wt.% Cu cast aluminium alloys have been performed. The uniaxial tests were performed on polished test bars extracted from highly loaded areas of cast cylinder heads. The monotonic deformation tests indicate that the material has an elastic-plastic monotonic response with plastic hardening. The strain controlled uniaxial low cycle fatigue tests were run at multiple load levels to capture the cyclic deformation behaviour and the corresponding fatigue lives. The equivalent stress-controlled fatigue tests were performed to study the influence of the loading mode on the cyclic deformation and fatigue lives. The two types of tests exhibit similar fatigue lives and stress-strain responses indicating minimal influence of the mode of loading in fatigue testing of A356 + T7 alloys. The material exhibits a non-linear deformation behaviour with a mixed isotropic and kinematic hardening behaviour that saturates after the initial few cycles. There exists significant scatter in the tested replicas for both monotonic and cyclic loading.
Aggressive downsizing of the internal combustion engines used as part of electrified powertrains in recent years have resulted in increasing thermal loads on the cylinder heads and consequently, the ...susceptibility to premature thermo-mechanical fatigue failures. To enable a reliable computer aided engineering (CAE) prediction of the component lives, we need more reliable material deformation and fatigue performance data. Material for testing was extracted from the highly loaded valve bridge area of specially cast cylinder heads to study the monotonic and cyclic deformation behaviour of the A356-T7 + 0.5% Cu alloy at various temperatures. Monotonic tensile tests performed at different temperatures indicate decreasing strength from 211 MPa at room temperature to 73 MPa at 300 °C and a corresponding increase in ductility. Completely reversed, strain controlled, uniaxial fatigue tests were carried out at 150, 200 and 250 °C. A dilatometric study carried out to study the thermal expansion behaviour of the alloy in the temperature range 25-360 °C shows a thermal expansion coefficient of (25-30) × 10
°C
. Under cyclic loading, increasing plastic strains are observed with increasing temperatures for similar load levels. The experimental data of the cyclic deformation behaviour are calibrated against a nonlinear combined kinematic-isotropic hardening model with both a linear and non-linear backstress.
The electrification of automotive powertrains in recent years has been driving the development of internal combustion engines towards reduced volumes with higher power outputs. These changes place ...extreme demands on engine materials. Engineers employ the computer-aided engineering approach to design reliable and cost-effective engines. However, this approach relies on accurate knowledge of the material deformation and fatigue characteristics during service-like loading. The present study seeks to investigate the effect of dwell times on the deformation and fatigue behaviour of the A356-T7 + 0.5 wt.% Cu alloy used to cast cylinder heads. In particular, we study the effect of dwell time duration at various temperatures. A combined fatigue-dwell testing procedure, with the dwell at the maximum compressive strain, replicates the service conditions. It is found that the material exhibits a stress relaxation behaviour with a decreasing relaxation rate. At lower temperatures, the load level influences the relaxation more than at elevated temperatures. However, the dwell does not significantly affect the hardening behaviour or the life of the tested alloy. Finally, we model the time-dependent material behaviour numerically. The Chaboche model, combined with a Cowper–Symonds power-law, is found to capture the visco-plastic deformation behaviour accurately.
The research work was carried out on the mechanical performance testing and characterization of an engine cylinder head material,and the prediction of the cylinder head thermal engine fatigue life. ...The fluid-solid coupling method was used to obtain accurate results of the thermal boundary and temperature field of the cylinder head. The calculated temperature field is consistent with the measured results. According to the thermal shock test specifications of the whole machine,the Sehitoglu model was used to predict the thermal fatigue life of the cylinder head. The simulation results show that the minimum life of the cylinder head occurs in the nose bridge area on the exhaust side of the second cylinder fire surface,which is mainly caused by environmental damage. The service life is 6 860,which meets the design requirements. At the same time,the cylinder head has successfully passed the heat engine fatigue bench test of the whole machine.
When alloys are exposed to elevated temperatures they experience a decrement in their mechanical properties that leads to material failure. However, the use of thixoforming, an alternative metal ...processing method, could enhance mechanical properties by minimising the defects that exist in as-received alloys. Therefore, this study aimed to determine the tensile strength of thixoformed A319 under elevated temperatures by taking into account its intended use in vehicle cylinder head components. Thixoformed A319 was compared with as-received alloy manufactured by permanent mould casting. The cooling slope method was used to prepare the feedstock for thixoforming. The feedstock was reheated by induction heating until it reached 574 °C and was then formed in a mould. Afterwards, the as-received and thixoformed samples underwent T6 heat treatment. The resulting samples were characterised by using optical microscopy, scanning electron microscopy equipped with energy dispersive X-ray, X-ray diffraction analysis and a tensile test. Elevated temperature tensile tests were performed at 250 °C, in line with the temperature condition experienced by cylinder head components during operation. The ultimate tensile strength of the thixoformed samples was 30% higher than that of the as-received samples under elevated temperatures. Also, the analyses of the fracture surfaces showed that porosity, intermetallic compounds and impurities were amongst the failure factors for both alloys.
Graphic Abstract
PDF
