Applied Mechanics and Materials Vols. 592-594

Abstract: The failure of valve affects the engine performance and as a result importance is given to the failure analysis of internal combustion engine valves. The valve may fail by valve face recession, wear failure, fatigue failure, thermal fatigue, erosion / corrosion of valves, overheating of valves and carbon deposits on valves. Mostly valves fail due to high pressure and temperature. This paper presents a failure analysis of diesel engine exhaust valve used in a passenger car. The analyzed exhaust valve failed after a very short period of usage of the car. To determine the cause of failure stress analysis is carried out by finite element method which shows the highly stressed region on the valve. A proper CAD model is developed by using CATIA software and saved in 'iges' format. It is then imported into ANSYS 14 software which gives the von mises stress, strain and deformation. The stress analysis shows that maximum stress is developed near the head of valve when piston crashed to the valve and material analysis shows that the strength of valve decreases due to decarburization of material and as a result the valve was bent.

Abstract: Fused Deposition Modeling (FDM) is one of the efficient rapid prototyping (RP) technologies that forms 3D objects by adding material layer by layer from CAD generated solid models. However, the FDM built part is hardly anisotropic in nature due to layer-by-layer build mechanism. Literature suggests that mechanical property, especially tensile strength, of FDM built part is severely affected by process parameters. Among all the parameters, contour number happens to be an important parameter because it reduces stress concentration resulting in avoidance of premature breakdown. Therefore, in this work contour number along with five important process parameters such as layer thickness, raster width, part orientation, raster angle and air gap are considered and their effect on tensile strength of FDM built parts is studied. Experiments are conducted using Face Centred Central Composite Design (FCCCD) in order to reduce the experimental runs. An optimal parameter setting has been suggested for the maximisation of tensile strength of the FDM built parts.

Abstract: The deflection and natural frequency of a 3 – Dimensional Timoshenko Beam (TB) is analyzed using Finite Element (FE) method. Significant improvement in computational time can be obtained when new shape functions are used. The results obtained from existing software packages and the new FE model are compared and good improvement is observed.

Abstract: The fighter aircraft transmission system consists of a light weight, High Speed Flexible Coupling (HSFC), used to transmit power from engine gear box to accessory gear box at speed ranging from 10,000 to 18,000 rpm. The HSFC accommodates larger parallel and axial misalignment resulting from differential thermal expansion of the aircraft engine and mounting arrangement. As the HSFC operates at higher rotational speeds close to critical velocities, it is important to analyze, the unbalance exciting forces considering the misalignment. In the present work, prediction of critical speed by camp bell diagram and unbalance response of the HSFC has been carried out using FEA. An experimental investigation also been carried out to study the influence of applied misalignment on a bi-plane dynamically balanced HSFC. The study shows that lower reaction forces are transmitted to HSFC end supports with the applied misalignments, as they are accommodated by the elastic material flexure of flexible plates.

Abstract: The changing magnetic field will induce eddy currents in the conductor. These currents will dissipate energy in the conductor and generate drag force. It is found that Aluminium is the best material as conductor compared to Copper and Zinc. Also, it is found that the larger thickness of disc, more number of turns of electromagnet and higher electrical conductivity of conductor influences the generation of greater braking torque. Conventional braking system relies on adhesion force between rail and wheel. It is found that a brake built up from permanent magnet pieces that combine both magnetic rail brake and eddy current brake permits the most profitable braking action through the whole range of acceptable speeds. Permanent magnet eddy current brake uses Neodymium - Iron - Boron (NdFeB) magnets. The analysis of permanent magnet eddy current shows that the parallel magnetised eddy current topology has the superior braking torque capability. In electrically controlled eddy current braking system subjected to time varying fields in different wave forms, the triangular wave field application resulted in highest braking torque. Electromagnetic brakes were found to interfere with the signalling and train control system. Permanent magnet eddy current brakes are a simple and reliable alternative to mechanical or electromagnetic brakes in transportation applications. Greater the speed greater is the eddy current braking efficiency. Hence, author intends to work on the development and investigation of permanent magnet eddy current braking system.

Abstract: This paper focuses on the kinematic analysis of rectangular path generating adjustable four-bar crank rocker linkage. One of the ground pivots of rocker side of the adjustable mechanism is subjected to continuous adjustment while the crank arm is given uniform angular velocity. Variations of coupler and rocker position, velocity and acceleration are computed for continuously changing phases of the adjustable four bar linkage. These kinematic parameters are compared with non-adjustable four-bar mechanism. Effect of the continuous adjustment on transmission angle and torque ratio are presented. The above procedures are implemented successfully in MATLAB environment and graphical results are presented.

Abstract: External load in a bearing is transferred from one race to another race through the rolling elements. In the present work, an investigation has been made to estimate the load on a rolling element in a bearing subjected to dynamic loading. The dynamic loading, in the present study, included harmonic and periodic loadings which are deterministic functions of time. The roller load is also investigated under random loading with known statistical values of mean and variance. Numerical values have been obtained for NJ204 bearing with known radial clearance. These results show the variation in the spectra obtained for different nature of external loadings. These results can be expected to satisfy the difference in theoretical and experimental spectra obtained by earlier researchers.

Abstract: Cyclic thermal loading causes cyclic thermal stress and thermal fatigue in the component. The goal of this paper is to characterize the thermal fatigue behavior of after-treatment (AT) device, i.e. Exhaust Gas Processor (EGP) and prediction of crack initiation cycles. The paper contains transient thermal analysis to map temperature on EGP model. By taking temperature distribution as input, Elasto-plastic structural analysis is done. Based on stress-strain data and fatigue material property, crack initiation cycles are estimated. For low cycle fatigue analysis, strain based approach, i.e. Brown-Miller Criteria with Morrow mean stress correction factor [1] is used. The von-Mises stress and crack initiation cycles are investigated and S-N curve and Ɛ-N curve are compared with standard graphs.

Abstract: The focus of this paper is to study the energy absorption characteristics of aluminium foam filled sections. The energy absorption capability of square mild steel foam filled and empty samples to absorbed mechanical energy have been estimated according to the results from the compressive tests. The tests were performed on the universal testing machine .The experimental results shows that aluminium foam filled sections feature have good energy absorption at various strain rates from 10^-3/s to 10/s.

Abstract: The performance of a high speed spindle is mainly attributed to the thermal behavior of spindle bearings. Hence, it is very significant to simulate the thermal behavior of spindle bearings. Finite element analysis is carried out for a typical high speed spindle by considering bearing and motor heat generation under various loading conditions to investigate the transient temperature rise of the spindle assembly. The influence of different cooling arrangements on the thermal behaviour of spindle bearings is then investigated with the objective of minimization of transient temperature fluctuations.