Cast Iron Cylinder Head Research Articles

Prediction of thermomechanical fatigue life in RuT450 compacted graphite cast iron cylinder heads using the Neu/Sehitoglu model

The increase in engine power has resulted in a significant rise in both thermal and mechanical loads on cylinder heads, leading to the emergence of thermomechanical fatigue (TMF) as one of the significant issues. This paper proposed a parameter identification method for the Neu/Sehitoglu model, utilizing multi-objective optimization (MOO), and applied it to predict the TMF life of compacted graphite cast iron (CGI) material used in cylinder heads. The study assessed the TMF behavior of RuT450 material through various experiments, including tensile, low cycle fatigue (LCF), creep, TMF, and oxidation experiments. Employing the MOO, the unknown model parameters are estimated and optimized to predict the TMF life of RuT450 materials. Results demonstrated that over 95% of the predicted TMF life falls within twice the error band of experimental values. Furthermore, plastic strain amplitude, temperature, and strain rate significantly influenced the damage mechanism and life prediction. The TMF life under out-of-phase (OP) loading conditions was found to be smaller than that of in-phase (IP) loading. Notably, under out-of-phase thermomechanical fatigue (OP TMF), oxidation damage and fatigue damage together contributed to over 95% of the total damage in RuT450 materials. Moreover, variations in oxidation damage parameters had a considerable impact on the predicted life. This study might offer an effective method for determining Neu/Sehitoglu model parameters and establish material boundaries for TMF life assessment of cylinder heads.

Experimental and numerical studies of thermal-structural behavior based on cast iron scaled cylinder head specimen

In order to clarify the thermal deformation and failure mechanism of the nodular cast iron cylinder head of marine diesel engines during long-term service, a high-efficiency thermal cycling experiment was conducted on scaled cylinder head specimen based on the similarity principle, and the thermal cycling load was simulated by flame heating and water spray cooling method. Then the Chaboche combined hardening model considering temperature and cumulative effect was established. The cyclic plastic behavior of the scaled specimen model during non-uniform thermal cycling was verified from transient temperature, cumulative out-of-round deformation and crack failure. Subsequently, the law of cyclic plastic deformation of specimens under thermal cycling was studied. The results showed that with the increase of the cycle number, the plastic strain of the valve bridge region of the scaled specimens accumulated gradually, showing a large amount of permanent strain of the circular hole within a maximum of 20.3 μm out-of-round deformation. The difference between the calculated and tested deformation is 1.9 μm (10.5%), which shows the excellent predictability of the numerical model. The research findings are valuable for predicting and evaluating the thermal-structural behavior of the prototype cylinder head.

Research on Creep Test of Compacted Graphite Cast Iron and Parameter Identification of Constitutive Model under Wide Range of Temperature and Stress

With the increase in engine power density, the temperature and stress carried by the cylinder head during operation also increase. The thermal engine fatigue life prediction of the cylinder head needs to consider accurate and reasonable creep-constitutive models and parameters. In view of the wide range of temperature and stress working conditions of the compacted graphite cast iron (CGI) cylinder head, the creep test of CGI under the conditions of temperature 450~550 °C and stress 100~300 MPa was carried out, and CGI under the conditions of wide temperature and stress was proposed to characterize a creep-constitutive model for minimum creep rate. Research indicated that under wide temperature and stress conditions, CGI was more prone to creep damage than under low load, and creep deformation was dominated by grain boundary sliding (GBS), intragranular dislocation glide (IDG), and dislocation climb (IDC). With the deformation mechanism-based true stress (DMTS) creep model, combined with the multiobjective optimization method, a creep-constitutive model of CGI was constructed, and 73% of the predicted values of the model were within twice the error range. Compared with the linear regression method, the multiobjective optimization method could still fit the accurate model parameters in the case of small samples.

Intelligent recognition of defects in vermicular graphite cast iron engine cylinder head by ultrasonic testing

To detect and intelligently identify the defects of the vermicular cast iron cylinder head, defective casting samples were made corresponding to each type of the actual defects. We setup the ultrasonic testing system to examine the defective samples. The detected defect signals were processed to obtain the characteristic spectrograms of the defects, which were further sorted and classified into a sample database. An algorithm based on a convolutional neural network was proposed to identify the defects intelligently. A convolutional neural network model was established. The network structure and parameters were optimized. It shows that a neural network with 3×3 convolution kernel dimension, 3 convolution layers, 20 convolution kernels in each layer and a learning rate of 0.0005 can effectively identify the spectrograms of the defects. The results show that the identification accuracy of the proposed algorithm is 97.14%. The model meets the practical requirements of cylinder head defect detection. The detection efficiency has improved significantly.

Simulation-driven product development of cast components with allowance for process-induced material behaviour

Abstract This paper presents a methodology that can be used to consider local variations in thermomechanical and thermophysical material properties, residual stresses, and strength-differential effects in finite element analyses of cast components. The methodology is based on applying process simulations and structural analyses together with experimentally established, or already available literature data, in order to describe element-specific material variations. A cast-iron cylinder head was used in order to evaluate the influence of several simplifications that are commonly performed in computer aided engineering. It is shown that non-trivial errors of a potentially large magnitude are introduced by not considering residual stresses, compressive behaviour, temperature dependence, and process-induced material property variations. By providing design engineers with tools that allow them to consider the complex relationships between these aspects early in the development phase, cast components have the potential to be further optimized with respect to both weight and performance.

On the use of heterogeneous thermomechanical and thermophysical material properties in finite element analyses of cast components

Cast components generally show a heterogeneous distribution of material properties, caused by variations in the microstructure that forms during solidification. Variations caused by the casting process are not commonly considered in structural analyses, which might result in manufacturing of sub-optimised components with unexpected in-use behaviour. In this paper, we present a methodology which can be used to consider both thermomechanical and thermophysical variations using finite element analyses in cast components. The methodology is based on process simulations including microstructure modelling and correlations between microstructural features and material properties. Local material data are generated from the process simulation results, which are integrated into subsequent structural analyses. In order to demonstrate the methodology, it is applied to a cast iron cylinder head. The heterogeneous distribution of material properties in this component is investigated using experimental methods, demonstrating local variations in both mechanical and physical behaviour. In addition, the strength-differential effect on tensile and compressive behaviour of cast iron is considered in the modelling. The integrated simulation methodology presented in this work is relevant to both design engineers, production engineers as well as material scientists, in order to study and better understand how local variations in microstructure might influence the performance and behaviour of cast components under in-use conditions.

Experimental study on repairing of damaged cast iron cylinder heads by 3D printing arc welding system

To realize repairing of damaged cast iron cylinder heads by 3D printing arc welding system mainly composed of an industrial robot and an arc welding machine, the remanufacturing process flow of 3D printing arc welding system was introduced, and a single straight wall stacking experiment was designed. The effects of process parameters on the appearance quality and mechanical properties of welding pieces were studied. The forming laws of welding piece were obtained. The main conclusions include: The higher the preheating temperature, and interlayer temperature, the more obvious the effects of process parameters on the hardness of welding pieces, and the effects of preheating temperature are more evident than that of interlayer temperature. With the increase of layer number, the hardness of welding pieces decreases gradually. When welding piece is lower than eight layers, the rise of width and height of the welding piece is approximately proportional to the increase of layers. Those conclusions of this paper provide general guidance and technical support for the repairing of cast iron cylinder heads and welding of other cast iron parts.

Investigation into diesel engine cylinder head failure

Abstract 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.

Comparative study on the fatigue criteria for the prediction of failure in engine structure

Abstract Recently, authors have developed a numerical procedure in order to predict the fatigue failure of the cast iron cylinder head [Three dimensional analysis of low cycle fatigue failure in engine part subjected to multi-axial variable amplitude thermo-mechanical load, Engineering Failure Analysis 62 (2016) 128–141]. The aim of the present study is a comparative investigation on the application of the different equivalent stress and strain approaches and critical plane fatigue theories in order to accurately determine the critical zone and life cycle in the failed cylinder head. The experimental observations in engine durability test ISO 8178 E5 and some multi-axial fatigue criteria are explained in detail. Then the fatigue life predictions obtained through the developed numerical procedure are compared with the observations. Results reveal that Morrow and SWT as equivalent strain-based criteria and Fatemi-Socie as critical plane criterion would lead to more accurate predictions in comparison with others. However, in the case of engine structure analysis, there is no considerable superiority between the two last groups of multi-axial fatigue models.

Lifetime Assessment of Cylinder Heads for Efficient Heavy Duty Engines Part II: Component-Level Application of Advanced Models for Thermomechanical Fatigue Life Prediction of Lamellar Graphite Cast Iron GJL250 and Vermicular Graphite Cast Iron GJV450 Cylinder Heads

A complete thermomechanical fatigue (TMF) life prediction methodology is developed for predicting the TMF life of cast iron cylinder heads for efficient heavy duty internal combustion engines. The methodology uses transient temperature fields as thermal loads for the non-linear structural finite-element analysis (FEA). To obtain reliable stress and strain histories in the FEA for cast iron materials, a time and temperature dependent plasticity model which accounts for viscous effects, non-linear kinematic hardening and tensioncompression asymmetry is required. For this purpose a unified elasto-viscoplastic Chaboche model coupled with damage is developed and implemented as a user material model (USERMAT) in the general purpose FEA program ANSYS. In addition, the mechanismbased DTMF model for TMF life prediction developed in Part I of the paper is extended to three-dimensional stress states under transient non-proportional loading conditions. The material properties of the plasticity model are determined for lamellar graphite cast iron GJL250 and vermicular graphite cast iron GJV450 from isothermal and non-isothermal uniaxial tests. The methodology is applied to obtain a TMF life prediction on two cast iron cylinder heads for heavy duty diesel engine applications made from both cast iron materials. It is shown that the life predictions using the developed methodology correlate very well with observed lives from two bench tests in terms of location as well as number of cycles to failure.

Environmental benefits of remanufacturing: A case study of cylinder heads remanufactured through laser cladding

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.

Three dimensional analysis of low cycle fatigue failure in engine part subjected to multi-axial variable amplitude thermo-mechanical load

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.

Lifetime Prediction of EN-GJV 450 Cast Iron Cylinder Heads under Combined Thermo-Mechanical and High Cycle Fatigue Loading

Lifetime Prediction of EN-GJV 450 Cast Iron Cylinder Heads under Combined Thermo-Mechanical and High Cycle Fatigue Loading

Cast Iron Solidification Structure and how it is Related to Defect Formation

In this work, the meaning of the solidification structure and how it is related to defect formation in grey cast iron will be discussed. The work also confirms observations made earlier. In previous work the formation of shrinkage porosity in grey cast iron cylinder heads was investigated. It was found that the defect is located around solidification units resembling primary austenite grains. The solidification of grey cast iron starts with the formation of primary austenite grains, followed by the eutectic solidification. The primary grains nucleate and grow either as columnar or equiaxed grains, creating a columnar to equiaxed transition between the two zones. Based on the presence of a migrating hot spot, and other characteristics found on the cylinder heads, a geometry was developed that promote the formation of shrinkage porosity. The primary solidification structure, normally transformed during the solid state transformation, was preserved using a technique called Direct Austempering After Solidification (DAAS). After solidification, the samples were cut and prepared for investigation using a Scanning Electron Microscope (SEM) equipped with a detector for Electron Back Scattered Diffraction (EBSD). Individual grains were identified and the primary solidification structure around the defects was revealed. The investigation shows how shrinkage porosity is formed and located between primary austenite grains. This confirms that the primary solidification structure has a large influence on the formation of defects in grey cast iron. The investigation also confirms the correctness of earlier results as well as the validity of the DAAS technique.

The influence of laser hardening on wear in the valve and valve seat contact

In internal combustion engines it is important to manage the wear in the valve and valve seat contact in order to minimise emissions and maximise economy. Traditionally wear in this contact has been controlled by the use of a valve seat insert and the careful selection of materials for both the valve and the insert. More recently, due to the increasing demands for both performance and cost, alternative methods of controlling the wear, and the resulting valve recession, have been sought. Using the heating effect of a laser to induce localised phase transformations, to increase hardness and wear resistance, in materials has been used since the 1970s, however it is only in recent years that it has been able to compete with more established surface treatment techniques, particularly in terms of cost, as new laser hardware has been developed. In this work, a laser has been used to treat the valve seat area of a cast iron cylinder head. In order to optimise the laser parameters for use on the head, preliminary tests were carried out to investigate the fundamental wear characteristics of untreated cast iron and also cast iron with a range of laser treatments. Previous work has identified the predominant wear mechanism in the valve and valve seat contact as impact on valve closure. Two bespoke test machines, one for testing basic specimens and one for testing components, were used to identify the laser parameters most likely to yield acceptable results when applied to a cylinder head to be used in a fired dynamometer test.

Thermomechanical Fatigue Life Prediction of Cylinder Heads in Combustion Engines

While the deformation and damage behavior of aluminum cylinder heads under complex thermal mechanical loading has been the subject of numerous studies in the past, cast iron cylinder heads have been in the focus of thermomechanical fatigue (TMF) only to a minor extent. In this paper, a feasible procedure is presented to set up material models and estimate service life of cast iron cylinder heads under variable thermomechanical loading conditions by the use of computer-aided engineering tools. In addition, the influence of thermal load and mechanical constraints on TMF life span is shown. A specimen model is used for parameter identification in material model setup and a cylinder head model is used for correlation with cracking phenomena. Investigation of different thermomechanical load influences is conducted on the cylinder head model. The principal strain and energy based fatigue criteria are used in assessment of TMF lifetime for the cast iron family and material specific evaluation procedures are pointed out. The results highlight the importance of exact definitions of the boundary conditions and underline the sensitivity of TMF lifespan of cast iron cylinder heads with respect to the defined boundary conditions. Considering this sensitivity, an approach conforming to the engine development requirements is proposed. It is shown that both the crack location and fatigue lifetime are predicted with high accuracy.

522 高温用カプセル型ひずみゲージを用いての鋳鉄製シリンダヘッドの熱ひずみ測定に関する一考察(OS-4 熱弾性・等温弾性(2))

522 高温用カプセル型ひずみゲージを用いての鋳鉄製シリンダヘッドの熱ひずみ測定に関する一考察(OS-4 熱弾性・等温弾性(2))

Consideration on Regard to Fatigue Safety Life in Operating Condition of Diesel Engine Cylinder Head

The temperature and thermal strain were examined on the fire surface of the gray cast iron cylinder head. The measurements were carried out by thermo-couple and strain gage during high temperature and high pressure in operating condition. The mechanism generating the strain on the fire surface of the cylinder head in the operating condition was made clear using experimental data and some numerical analyses. The considrations on regard to the temperature distribution and the stiffness distribution of the cylinder head etc. were very important for understanding this mechanism. And also, the calculated results were in good agreement to the measured temperature and strain. The evaluation of the fatigue safety life for the thermal strain was discussed, including the material properties and the operating condition in the fishing boat.The prediction of the reliability would be possible to perform in the design stage of the cylinder head.

Experimental Study on Regard to Stress and Strain in Operating Condition of Diesel Engine Cylinder Head

The temperature and thermal stresses were examined on the fire surface of the gray cast iron cylinder head. The measurements were carried out by thermo-couple and strain gage during high temperature and high pressure in operating condition. The cylinder head temperature was predicted from the engine performance data that is the fuel consumption etc. in the result of the regression analysis. The calculated temperature was good accuracy for the measured temperature. The thermal stress was measured during the engine operating cycles by many improvements of the preparation and data analysis. The thermal load was bigger than the mechanical loads considerably. The compression plastic deformations were occurred on the fire surface by the large compression thermal stresses. As the result of the plastic deformations in engine stop and go cycles, the tensile stresses were observed on the valve bridge of the fire surface after the engine operation.

Quality Control of Induction on Hardened Cast Iron Cylinder Head Valve Seats

Quality Control of Induction on Hardened Cast Iron Cylinder Head Valve Seats