Thermomechanical Analysis of Diesel Engine Exhaust Manifold (original) (raw)
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Design and Analysis of an Exhaust Manifold subjected to Thermo-Mechanical Loading
SAE International journal of engines, 2017
ARTICLE INFO The exhaust manifold is mounted on the cylinder head of an engine which collects exhaust gases. It is subjected to thermo-mechanical loading. A finite element (FE) thermo-structural analysis is carried on the manifold and yield margins are calculated. Most of the manifolds yield due to material behaviour at high temperatures. Conventionally linear elastic analysis approach is followed. Linear elastic approach considers linear stress-strain relationship even beyond the yield limit. So the objective is to develop a new approach (elasto-plastic) which is more accurate and captures the actual material behavior beyond the yield limit. Finding the temperature dependent material properties is to be undertaken. Correlation of the yield margins by both the approaches is done. It is observed that the Von Mises stresses are reduced by 57.9% and the yield margins are improved by 58.18% by using the Elastic-Plastic analysis approach.
Design and Analysis of Exhaust Manifold Subjected to Thermo-Mechanical Loading
2015
Designers follow iterative methodology for exhaust manifold design, in which designer makes a design based on his experience and intuition for given operating conditions and other input data. This design is analyzed in FEA software by analyst. If design is found to be failing then the designer makes modifications accordingly. New design is again checked in FEA software. This procedure is continued till all constraints are satisfied. Generally such a procedure takes many iterations and hence time, and as an output we get a feasible solution but not an optimal solution. The exhaust manifold is mounted on the cylinder head of an engine which collects exhausted gases. It is subjected to thermo-mechanical loading. A FE thermo-structural analysis is carried on the manifold and yield margins are calculated. Most of the Manifolds yield due to material behaviour at high temperatures. Conventionally linear elastic analysis approach is followed. Linear elastic approach considers linear stress-...
Thermal and Modal Analysis of Engine Exhaust Manifold for Different Materials
International Journal of Engineering Research and, 2017
The ultimate goal of this project is to investigate the thermal and modal analysis of multi cylinder engine exhaust manifold used in TATA tipper BS-II. The manifold has been analyzed for different materials such as Grey cast iron, Carbon steel and Stainless steel using finite element analysis. The most commonly used material in manifold is Grey cast iron which is less costly but the weight of the material is much higher than the other materials. The exhaust manifold is designed by using Creo 3.0 and analyzed in ANSYS 17.0. The heat flux, temperature distribution and modal analysis are investigated for different materials. Finally, the results were compared with the existing material. By this comparison it shows that Stainless steel has better heat flux and temperature distribution compared to other materials. It also shows that the modal deformation of Carbon steel and Stainless steel have better than the Grey cast iron.
Effect of Constitutive Model on Thermomechanical Fatigue Life Prediction
Procedia Engineering, 2015
In this paper, thermomechanical fatigue life (TMF) prediction is performed on an automotive exhaust manifold using in-house postprocessor code (Hotlife) with four different constitutive models: elastoplastic model with kinematic hardening, two-layer viscoplastic model, and two unified elasto-viscoplastic models based on the equations proposed by Sehitoglu and Chaboche, respectively. Commercial FEA software Abaqus has been used for the analysis. The first two models are already available in Abaqus; the Chaboche and Sehitoglu models were implemented using a user material subroutine (UMAT, available in Abaqus). The stress and strain histories calculated by these four models are output to Hotlife for post-processing. The results from the prediction are then compared to the experimental TMF life obtained from a component thermal fatigue bench test. Result show the Hotlife calculations based on the two implemented elasto-viscoplastic models yield better correlation with test results.
Thermomechanical Fatigue Analysis of Cast Aluminum Engine Components
Cast aluminum engine components are increasingly being used in the automobile industry. Due to high engine operating temperature, thermal fatigue during start-stop cycles is a very important design consideration. In this paper we will describe the application of newly developed analysis methods to analyze these complex problems. A user material subroutine for viseoplasticity stress analysis using the commercial FEA code ABAQUS has been developed. Stress and strain of engine heads during thermal cycle are thus analyzed and this code verified. The thermomechanical fatigue model developed by Neu and Sehitoglu, a damage accumulation model including fatigue, oxidation and fatigue damage, has been extended to three-dimensional state of stress by using the concept of critical planes. The enhanced damage model has been implemented in a FEA postprocessor for engine component life analysis. The predictions of thermal strains and fatigue life based on 3D FEA analysis are compared with measurements of engine component tests. Three different thermal loading cycles are considered. The thermal fatigue life predictions are within 30% error of actual component test data.
Fatigue design of structures under thermomechanical loadings
Fatigue & Fracture of Engineering Materials & Structures, 2002
A B S T R A C T This paper presents a global approach to the design of structures that experience thermomechanical fatigue loading, which has been applied successfully in the case of cast-iron exhaust manifolds. After a presentation of the design context in the automotive industry, the important hypotheses and choices of this approach, based on a thermal 3D computation, an elastoviscoplastic constitutive law and the dissipated energy per cycle as a damage indicator associated with a failure criterion, are first pointed out. Two particular aspects are described in more detail: the viscoplastic constitutive models, which permit a finite element analysis of complex structures and the fatigue criterion based on the dissipated energy per cycle. The FEM results associated with this damage indicator permit the construction of a design curve independent of temperature; an agreement is observed between the predicted durability and the results of isothermal as well as non isothermal tests on specimens and thermomechanical fatigue tests on real components on an engine bench. These results show that thermomechanical fatigue design of complex structures can be performed in an industrial context.
Engineering Failure Analysis, 2016
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 2600 rpm. 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.
Thermo-mechanical Analysis of a section of an exhaust manifold for automobile applications
International Journal of Innovative Research in Engineering & Multidisciplinary Physical Sciences, 2018
In the present work, a sectional model of the exhaust manifold has been studied to reduce the heat loss by insulating the pipe with different insulating materials. Four different insulating materials were used to increase the thermal resistance of the exhaust manifold so that there would be less heat loss in the manifold. The model with the insulating materials was modeled and discretized. The thermal and structural properties have been assigned to the discretized model and processed for analysis. The heat flux from the exhaust gas is taken as input to the analysis model. Heat loss and temperature difference were taken as output. From the present analysis, it can be said that by using these four materials, the heat loss through the exhaust manifold will be reduced.
Comparison between damage criteria in thermo-mechanical fatigue
2008
ABSTRACT Weight reduction becomes increasingly important in design of engine components, but in the same time designers have to improve engine efficiency increasing in-cylinder pressure and temperature. The paper presents a description of literature damage models and life assessment methods for thermo-mechanical fatigue. The aim is to investigate the life prediction results in the case of a specific load history such as thermal and mechanical loading conditions upon an exhaust manifold.
THERMAL AND STRUCTURAL ANALYSIS OF AN EXHAUST MANIFOLD OF A MULTI CYLINDER ENGINE
The paper deals with the thermal and structural analysis of a multi cylinder engine exhaust manifold, for the given dimensions. The dimensions of the exhaust manifold are taken from the drawing. The 3D model is prepared using NX-CAD software. Thermal and Coupled Field analysis are performed. Critical frequencies in the operating range are obtained by performing Modal analysis. Harmonic analysis is performed and the deflections and stresses at the nearest natural frequencies are plotted. The exhaust manifold design’s acceptance is done from the results obtained in different analysis. It is an effort to automate design optimization which would reduce technical, schedule, and cost risks for new engine developments.