Applied Mechanics and Materials Vol. 471

Abstract: Fuel injector in automotive engine is a very important component in injecting the correct amount of fuel into the combustion chamber. The injection system need to be in a very safe and optimum condition during the engine operation. The mulfunction of the injection system can be avoided if the current working condition is known and a proper maintenence procedure is implemented. This paper proposes the development of a fuel injector monitoring method using strain signals captured by a single-channel strain gage attached on the fuel injector body. The fuel injector was operated under three main sets of parameters; pulse width (ms), frequency (Hz) and pressure (bar) which were varried from 5 ms to 15 ms, 17 Hz to 25 Hz and 10 bar to 70 bar respectively. The settings produce 27 different engine operations and the strain signal will be captured at each operation. The captured strain signals will be analyzed using I-kaz^TM Multilevel technique and will be correlated with the main parameters. The relationship between the I-kaz^TM Multilevel coefficient and the main parameters indicate good correlations which can be used as the guidance for fuel injector monitoring during actual operation. The I-kaz Multilevel technique was found to be very suitable in this study since it is capable of showing consistence pattern change at every parameter change during the engine operation. This monitoring system has a big potential to be developed and improved for the optimization of fuel injector system performance in the automotive industry.

Abstract: This paper describes the correlation between fatigue life with the I-kaz coefficients. Fatigue tests were performed according to the ASTM E466-96 standard with a strain gauge attached to the specimen being tested. AISI 1045 carbon steel was used as the material for this test due to its wide applications in the automotive and machinery industry. Fatigue tests were carried out at several constant loading stresses of 610 MPa, 650 MPa and 690 MPa at the sampling frequency of 8 Hz. A set of data acquisition system was used to collect the fatigue strain signals. The integrated Kurtosis-based algorithm for Z-filter (I-kaz) technique had been used to find the I-kaz coefficient. The I-kaz coefficient is found to have a good correlation with fatigue life, other than can represent fatigue damage.

Abstract: . The utilization of spectral analysis for the purpose of investigating machining parameters in frequency domain has been widely practiced by group of researchers in engineering field. In this case the machining parameters involved are the cutting force parameter. By adapting spectral analysis to the cutting forces data, the researcher will have the access to identify the specific cutting forces exerted to the surface of the workpiece at each particular frequency under a set of frequency content. This paper is paying attention on the essential aspect on how to analyze the cutting forces data appropriately. It is recommended that those data need to be transformed first from the original form of cutting force data in time domain into the form of cutting force data in frequency domain. The outcome from this paper is in the form of graphical representation of cutting force data in frequency domain. It is obtained by applying Fast Fourier Transform (FFT) technique. To be more clear-cut, the result from this research work shows that the cutting force is directly proportional to the depth of cut and inversely proportional to the spindle speed of the end mill machine. The cutting force data later on will be used as an input disturbance for XY table ball screw drive system during the simulation process in the Matlab simulink diagram.

Abstract: The main goal of using mechatronic suspensions is to improve the ride comfort and handling performance. In this work, a robust linear controller for such a system was designed based on the μ synthesis method. The performance of a model two degree of freedom quarter car with parameter perturbations, subjected to road disturbances, was simulated and the time domain responses were analyzed. The simulation results indicate that the robust controller improved the vibration isolation performance of the mechatronic suspension system, despite the presence of parameter perturbations and exogenous disturbances. When compared to both LQG active control and to a passive suspension system, the μ synthesis controller also showed super or performance.

Abstract: Micro-perforated panel (MPP) is well known as the alternative green sound absorbing material replacing the synthetic porous absorber. Several works have been established which model the sound absorption performance of the MPP with various arrangements. However, most existing models are for MPP with rigid condition and rarely discuss the effect of vibration due to the impinging sound. In this paper, a simple approach using wave propagation technique is proposed to take into account the effect of flexural wave in the MPP on its sound absorption. The model begins with an MPP coupled with a solid panel separated by an air gap. The impedance of the back solid panel can then be adjusted to a very large value to simulate a rigid wall.

Abstract: Excessive exposure to noise is harmful for human health. Noise-induced hearing loss is one prevalent disorder resulted from above case. One root solution that converts the unnecessary sound waves to dissipated heat energy is acoustic absorption panel. Previous studies had looked upon potential sound-absorbing resources corresponding to natural fiber. However, several characteristics of these biodegradable supplies such as stiffness, anti-fungus and flammability are still yet to be improved. Hence, this research was undertaken to enhance the fire retardant performance of coir fiber for the production of high quality yet low cost acoustic absorption panel. Three types of additives, borax, Di-Ammonium Phosphate (DAP), and urea were investigated to perform chemical treatment for coir fiber. Experimental measurements were executed to validate the results by referring standard of ASTM E6902 (Standard Test Method for Combustible Properties of Treated Wood) by using the Fire-Tube Apparatus. Final results showed that DAP-treated fiber has the lowest percentage loss in mass of 6.67% compared to that of borax and urea-treated fiber with values of 7.60% and 9.48% respectively. This outcome clarified that DAP-treated fiber possesses higher self-extinguishing ability. Further evaluations in term of economic values, degree of hazards against health, flammability as well as reactivity supported that DAP is the best choice since its potency was ahead of the other two chemicals.

Abstract: The majority of aircrafts structure cracks due to fatigue are thin gage metallic structures and secondary support structures. Beside lower fatigue strength, they may also occur due to mechanical defects, especially at weak area and for areas exposed to high repetitive force such as vibration, friction, acoustic load and tensile force. Normally, the Original Equipment Manufacturer (OEM) recommended the aircraft operator to repair the crack by typical patch or doublers repair technique which is formally known as Non-Flush Patch Repair Scheme. However, the crack tends to reappear and tend to be more severe. The natural frequency and damping ratio of a structure which is treated with Typical Non-Flush Patch Repair, with and without Passive Damping Treatment (PDT) are studied using impulse based technique. Experimental data are presented to demonstrate the difference of damping ratio (ζ) among the test specimens. The cracked structure which has been treated with PDT on Non-Flush Repair Scheme has a better damping ratio and resonates at a different natural frequency. The experiment data generated from this study can be used as a basis to further the study on aircrafts structural repair scheme.

Abstract: An application of In-Situ method of measuring sound absorption coefficient on the surface of direct piercing carved wood panel using the concept of ensemble averaged is discussed. The method offer an easier way to measure the absorption performance for each individual aperture of carved wood panel with floral pattern which was replicated from one of the oldest mosque, namely Masjid Abidin located in Terengganu, Malaysia. Two pieces of 20 mm thick of cengal wood (Neobalanocarpus heimii) with 30% and 40% perforation ratio were respectively measured in a reverberation room in order to determine the value of . At lower frequencies (0.1 kHz-1.5 kHz), the measured values of for both direct piercing carved wood panel with floral pattern (Daun Sireh motif) are shown that the sound absoption for both direct piercing carved wood panel are in perform level. From the measurements, clearly, the installation of the direct piercing carved wood panel with floral pattern (Daun Sireh motif) in the Masjid Abidin can provide better air circulation and additional natural sunlight, as well as better sound intelligibility inside the building.

Abstract: Statistical Energy Analysis (SEA) is a well-known method to analyze the flow of acoustic and vibration energy in a complex structure. The structure is divided into subsystems where the energy in each of the subsystem is assumed to be reverberant. This study investigates the application of SEA model in a 'damped' acoustic space where the direct field component from the sound source dominates the total sound field rather than a diffuse field in a reverberant space which the SEA model assumption is based on. A measurement was conducted in a scaled room divided into two acoustic spaces separated by a partition with an opening. Absorbent materials were installed on the room walls and the power injection technique was implemented to obtain the coupling loss factor (CLF) of the system. It is found that correction of the direct field component from the subsystem energy improves the prediction of the CLF of the system.

Abstract: This paper presents a study on the sound absorption properties of a single layer date palm fiber based on the flow resistivity. Experimental measurements were carried out to estimate the flow resistivity value using differential pressure tube. The average diameter of the fibers is 0.462 mm. A date palm fiber sample of 25mm thickness is used in this research. The flow resistivity of the date palm fiber sample was found to be 4.26 kPa.s/m². The flow resistivity was used to calculate the sound absorption coefficient using Delany and Bazley model. The simulation showed that the values of absorption coefficient are small at low frequencies and rising with increasing frequency. To check the effect of flow resistivity on the sound absorption coefficient Delany and Bazley model was simulated for three different flow resistivity values. The simulation results showed that the sound absorption coefficient increases with the increase of the flow resistivity.