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Showing 5 results for Finite Element Analysis

A. Khalkhali, M. Afroosheh, M.r. Seyedi,
Volume 4, Issue 1 (3-2014)
Abstract

In this paper, numerical simulation of FRP composite cylinder tubes progressive crushing processes is conducted using LS-Dyna. Details on the numerical modeling strategy are given and discussed. It is found that triggers introduced in the numerical simulation can effectively model the bevel trigger at the end of the tubular specimens. It is also found that two-layer finite element model based on the TsaiWu failure criteria is effective in representing the crushing failure mode of the tubular composite specimens and energy absorption characteristics. Employing GEvoM software, two meta-models are then obtained for modeling of both the absorbed energy (E) and the peak crushing force (Fmax) with respect to geometrical design variables using input output data obtained from the finite element modeling. Comparison between obtained meta-models and numerical results in both of training and testing sets show good approximation by using obtained polynomial models.


H. Ashuri,
Volume 5, Issue 2 (6-2015)
Abstract

Loading conditions and complex geometry have led the cylinder heads to become the most challenging parts of diesel engines. One of the most important durability problems in diesel engines is due to the cracks valves bridge area. The purpose of this study is a thermo-mechanical analysis of cylinder heads of diesel engines using a two-layer viscoelasticity model. The results of the thermo-mechanical analysis indicated that the maximum temperature and stress occurred in the valves bridge. The results of the finite element analysis correspond with the experimental tests, carried out by researchers, and illustrated the cylinder heads cracked in this region. The results of the thermo-mechanical analysis showed that when the engine is running the stress in the region is compressive caused by the thermal loading and combustion pressure. When the engine shut off the compressive stress turned into the tensile stress because of assembly loads. The valves bridge was under the cyclic tensile and compressive stress and then is under low cycle fatigue. After several cycles the fatigue cracks will appear in this region. The lifetime of this part can be determined through finite element analysis instead of experimental tests. Viscous strain was more than the plastic strain which is not negligible.
H. Ashouri,
Volume 5, Issue 4 (12-2015)
Abstract

Loading conditions and complex geometry have led the cylinder heads to become the most challenging parts of diesel engines. One of the most important durability problems in diesel engines is due to the cracks valves bridge area. The purpose of this study is a thermo-mechanical analysis of cylinder heads of diesel engines using a two-layer viscoplasticity model. In this article, mechanical properties of A356.0 alloy, obtained by tensile tests at 25 and 200°C. The results of the thermo-mechanical analysis indicated that the maximum temperature and stress occurred in the valves bridge. The results of the finite element analysis of cylinder heads correspond with the simulation results, carried out by researchers.


H. Ashuri,
Volume 7, Issue 2 (6-2017)
Abstract

This paper presents finite element analysis (FEA) of a coated and uncoated cylinder heads of a diesel engine to examine the distribution of temperature and stress. A thermal barrier coating system was applied on the combustion chamber of the cylinder heads, consists of two-layer systems: a ceramic top coat (TC), made of yttria stabilized zirconia (YSZ), ZrO2-8%Y2O3 and also a metallic bond coat (BC), made of Ni-Cr-Al-Y. The coating system in this research comprises 300 μm zirconium oxide TC and 150 μm BC. The three-dimensional model of the cylinder heads was simulated in abaqus software and a two-layer viscoplasticity model was utilized to investigate the elastic, plastic and viscous behavior of the cylinder heads. The elastic and plastic properties of BC and TC layers were considered and the effect of thermal barrier coatings on distribution of temperature and stress was investigated. The aim of this study is to compare the distribution of temperature and stress in the coated and uncoated cylinder heads under thermo-mechanical loads. The results of FEA showed that the thermal barrier coating system reduces the temperature about 53°C because of its lower thermal conductivity. As a result, the cylinder head tolerates lower temperature and fatigue life will increase. The results of thermo-mechanical analysis indicated that the stress in the coated cylinder head decreased approximately 24 MPa for the sake of depletion of temperature gradient which can lead to higher fatigue lifetime. Viscous strain was significant and its amount is not negligible.
Hamed Saeidi Googarchin, Ali Qasemian, Mohammad Rouhi Moghanlou,
Volume 10, Issue 4 (12-2020)
Abstract

The primary objective of a brake disc is to absorb frictional heat during braking and dissipated it immediately by convection and radiation. However, during hard and repetitive brakings, thermal coning on brake disc generates surface hot spots which are responsible for the undesired accumulation of compressive stresses on the surface of the brake disc. These stresses would lead to disc cracking and finally failure of it. In the current paper, a coupled transient thermo-mechanical FE analysis of a heavy vehicle braking system is carried out in a way that thermal coning of the disc and surface hot spots and bands are recognizable. Braking condition is chosen from a standard for hard braking in trucks. Moreover, five additional braking actions with different severities are investigated to study the effects of braking severity on thermo-mechanical instability of brake discs. Comparison of numerical results of transient temperature during braking and cooling phases with experiment reveal a high accuracy of thermal prediction of this model. Also, the results show that thermal coning of brake disc is varied between 0.05 to 0.7 mm depending on braking severity and tangential location of the disc. Additionally, surface hot spots experience higher temperature gradients in higher decelerations. Finally, results show that circumferential compressive stresses during braking are the major component of thermal stresses and should be taken into account for life estimation analysis.

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