Analysis of the vibration characteristics of a strongly coupled liquid-structure-gas system

This thesis describes an investigation of the vibration of a system comprising a thin elastic plate, acting as a separator, between a fluid and gas column contained in a cylindrical container. The intention is that the plate will constrain the movement of the liquid to one end of the container, preventing it from splashing around the container enclosure, hence improving the stability of the system. However in general systems involving fluid-structural vibration interaction, it has been shown by previous researchers that there exists a critical condition where the fluid and structure are strongly coupled together. At this critical condition the levels of vibration induced kinetic energy of the plate and fluid are comparable. This strong couple characteristic may affect the stability and structural health of the whole coupled system especially the thin elastic plate. In this thesis, critical vibration characteristics of such system are studied. The theoretical analysis of vibration interaction of liquid-structure-gas system is presented. The values of natural frequencies and relative energy distribution throughout the system obtained theoretically have been verified with the values obtained by finite element analysis and by laboratory experiment where appropriate. Then, the characteristics of strong coupled vibration interaction of liquid-structuregas system are investigated around three possible strong coupled conditions. Results have shown that for a liquid-structure-gas system, strong couple vibration occurs if the system fulfills either of the following conditions

Vibration Characteristics of Beam Structure Attached with Vibration Absorbers at its Vibrational Node and Antinode by Finite Element Analysis

In this study, the vibration characteristics of fixed ends beam are analysed after attached with dynamic vibration absorbers at vibrational node and antinode by simulation using ANSYS APDL. This study aim to obtain the best location and optimum number of DVAs placed on the fixed ends beam in order to reduce vibration of beam. The dynamic vibration absorber were attached to the fixed ends beam vibrational node and antinode for a total of three modes of vibration. The 0.84 m long beam is modelled by ANSYS and divided into 21 elements where each element is 0.04 m. A harmonic force, Fo of 28.84 N is exerted at node 3 of beam element. Modal analysis and harmonic analysis are carried out in this study to obtain the natural frequency and frequency response of the beam respectively. The vibration characteristics of fixed ends beam without DVA and beam attached with DVAs were compared. The simulation results show reduction of vibration amplitude of the beam especially when the DVA were attached at the vibrational antinode. The DVA amplitude increase when amplitude of beam decreases. From this study, it is proved that DVAs absorb vibration of the beam structure. The best position to attach DVAs is the vibrational antinode based on the modes of vibration. The increment of DVAs number will not affect the percentage reduction of vibration amplitude as long as the DVAs are placed at optimum location. &nbsp

Lepironia articulata as a sustainable acoustic absorber

Lepironia articulata is found abundant in a swamp and along streams in West Malaysia and it is commonly used for grey water treatment, numerous traditional craft and now commercialise as an organic straw. However, there is a scarcity of knowledge on the physical and acoustical properties of this natural fibre. Therefore, this study was to determine the potential of Lepironia articulata as acoustic absorber. The absorption coefficient was tested using the impedance tube method (ASTM E1050-98) for four different structure arrangements, namely “axial”, “horizontal”, “crossed” and “combination” made up of Lepironia articulata with the diameter ranging from 2 to 4 mm and 4 to 7 mm respectively and the thickness remains at 50 mm. The influence of air gap of 0 to 25 mm, in 5 mm increment was introduced in each sample and other physical properties such as density, porosity and tortuosity were investigated. The results revealed that the Lepironia articulata in horizontal, crossed and combination arrangements showed greatest absorption performance especially in the low frequency range compared to the axial arrangement. If compared between samples with the range diameter of 4 to 7 mm and 2 to 4 mm, bigger stalks diameter in axial arrangement exhibits the least NRC value. Next, air gaps have great influence at low frequency range whereby it shifted the peaks and sound absorption coefficient curve toward lower frequency. Sound absorption coefficient increases as porosity increase and decrease as density�tortuosity increase. Overall, Lepironia articulata has the potential to be used as a sustainable acoustic absorber as all the samples has the NRC value more than or equal to 0.20

Ceramic Panel for Sound Insulation Application

In order to reduce noise nowadays, many researcher find different way to solve this problem. One of the ways to reduce noise is by using a sound insulation. This research has been conducted in order to produce high density sound insulation panel made from ceramic. The fabrication of ceramic panel undergo several processes which are milling, mixing, forming, drying and sintering process. The ceramic panel of different  types of forming were developed as square plate 110mm x 110 mm with a constant thickness of 5 mm. Type of forming were used for this particular study are slip casting and uniaxial press. The composition used were 100 % clay and 90% + 10 % clay cement. The transmission loss were determined by using acoustic insulation test. The apparatus consists of sound level meter, portable speaker and computer. The Sound Pressure Levels (SPL) were taken at 250 Hz, 500 Hz, 1000 Hz, 2000 Hz and 4000 Hz which based on 1 octave frequency bands. The analysis shown that the sample 90 % + 10 % clay cement casting has the higher transmission loss in the lower frequency region, the sample 90 % + 10 % clay cement uniaxial press has the higher transmission loss in the middle frequency region and lastly the sample 100 % clay uniaxial press has the higher transmission loss in higher frequency region. The sample also were tested using Charpy impact test in order to gain their impact energy and impact strength. The tests were according to ASTM-D256. Charpy impact test can determines the amount of energy absorbed by a material during fracture. The analysis shown that the impact energy of the ceramic panel have a small percentage different. It can be concluded that uniaxial press is better than the slip casting in forming ceramic insulation panel

A Review on The Development of Panel and Membrane Sound Absorbers

Noise pollution has become one of the most serious environmental problems, especially in developing countries. Noise pollution caused discomfort, dizziness, and continuous exposure to an excessive amount of it affects human health both physically and psychologically. The utilization of sound absorption material has become an effective solution in reducing or controlling this noise pollution problem. Panel and membrane material getting more attention because of its effectiveness in absorbing low-frequency sounds, more hygienic and safer to human health compared to the porous material. Therefore, the panel and membrane absorbers have been developed rapidly in various fields and also have evolved to become more designable, advanced, and efficient in absorbing sound. However, combinations of membrane or panel absorber with porous materials are still advantageous in term of sound absorption performance and even worth considering. This paper aims to provide an information and literature study on panel and membrane absorbers evolution in the past decades in terms of improving the sound quality. This paper also covers the introduction of panel and membrane sound absorption system, variations of panel and membrane absorber concepts, and factors affecting the absorption performance of the materials. From the review, material properties such as mass density, air cavity, thickness, and perforation found to influence sound absorption performances. By looking at the intensity of research and progress of panel or membrane absorber, it is predicted that there will be more development and improvement of panel and membrane absorbers. Therefore, it is essential to review the progress and development of the panel and membrane absorbers to give a better understanding of their absorption characteristics and to seek new research opportunities in the future

Mechanical Performances of Twill Kenaf Woven Fiber Reinforced Polyester Composites

Natural fibres have been explored by many researchers. Natural fibres have the potential aspect to replace glass fibre in fibre-reinforced composites application. Kenaf is also one of the selected natural fibres that have bio resource profit regarding on their capability to absorb energy absorption especially. This study focused on the twill yarn kenaf woven composite structure. Composites were prepared using the hand lay-up method with different type of orientation each layered arrangement by Taguchi. The hardened composites were cured for 24 hours before it was shaped according to ASTM D3039. Taguchi method is used in this study for optimization which can reduce the time consumed rather than using experimental approach. The result shows orientations were significant on tensile and modulus strength performances. After optimizations, the values of tensile and modulus strength was 55.738 MPa and 5761.704 Joule, which is increasing 3.77% for tensile strength and 4.23% for Young modulus. By comparing fracture mechanism before and after optimizations, there was clear decreasing fracture surface. It indicated that, the mechanical behavior performances of the twill woven kenaf reinforced composites can be effectively improved by this method

Investigation of Temperature and Humidity Control System for Mushroom House

 Abstract: Monitoring and control the mushroom house environment play an important role in mushroom cultivation quality. Assurance of optimal temperature and humidity has a direct influence on the mushroom growth performance. Traditionally, mushroom cultivation has required a great effort to connect and distribute all the sensors and data acquisition systems. Natural environment such as the temperature during the day either on a hot day and the rain is affecting the temperature and moisture in the mushroom house directly. The optimal temperature and humidity for mushroom house is around 20°C and 80% respectively. For this reason, in order to maintain an optimal temperature and humidity, Matlab Simulink was developed to run simulations on the system. Simulink's block diagram is composed of three main parts for this system whereas input, control system and the output temperature and humidity for the mushroom house. Matlab/Simulink tool is use for modeling, simulating and analyzing the performance of the system.   &nbsp

Classification of damage severity in natural fibre composites using principal component analysis

The present paper deals with an approach in predicting the classification of damage in natural fibre reinforced composites (NFC) panel using signal processing procedure as indicative parameters and principle component analysis as a learning tool. An impact event produced strain data and the response signal was investigated. An effective impact damage classification procedure is established using a principal component analysis approach. The system was trained to classify the damage class based on the input from the signal features. It has been observed that, the network can learn and classify effectively the damage size in the panel which is the combination features retained at about 84.5% of the varianc

Mechanical performances of twill kenaf woven fiber reinforced polyester composites

Natural fibres have the potential aspect to replace glass fibre reinforced composites. One of these fibers is kenaf. It is also one of the selected natural fibres that have bio resource profit regarding on their capability to absorb energy absorption especially. In order to prove the application of this fiber for the load-bearing application, the fiber in the form of yarn is weaved into fiber mat and reinforced with the plastic resin. This study focused on the twill yarn kenaf woven composite structure. Composites were prepared using the hand lay-up method with different type of orientation where the orientation is designed using Taguchi method. The hardened composites were cured for 24 hours in an ambient temperature before it was shaped according to ASTM D3039. The samples were then stressed uni-axially to obtain the stress-strain curves. The result shows the fiber orientations were significant factor in determining the performance of tensile strength. In this work, fiber mats are then optimized and the results showed that the values of tensile and modulus strength were 55.738 MPa and 5761.704 Joule, which is increased 3.77% and 4.23% for tensile strength and Young modulus, respectively. By comparing fracture mechanism before and after optimizations, there was clear decreasing fracture surface. It indicated that, the mechanical behavior performances of the twill woven kenaf reinforced composites can be effectively improved by this method

Oil Palm Empty Fruit Bunch (OPEFB) handsheet production from optimized biodelignification of rhynchophorus ferrugineus microbiome’s enzymes

Oil palm plantation generates massive amount of oil palm empty fruit bunch (OPEFB) which source great amount of cellulose. However, wrapping this cellulose is an adhesive compound called lignin. Biodelignification process was applied to remove lignin in pulp and paper industry. Therefore, this study is focused on optimum conditions of delignification process using a combination of bacteria from Rhynchophorus ferrugineus on OPEFB. The composition of chemicals was characterized according to the TAPPI standard method and Kursher-Hoffner method. The Box-Behnken design (BBD) was used to determine the optimum conditions of delignification process based on lignin loss of OPEFB. The optimized fiber was investigated based on mechanical properties according to TAPPI standard methods. From BBD analysis, the finest conditions for delignification were recognized to be at 35 °C in 48 h incubation time with 5 mL of 1% glucose for predicted value 54.3% compared to experimental value 52% of lignin loss as revealed by confirmatory study. The highest result of chemical analysis was recognized at run 12 (1.15%), 10 (12.35%), 4 (48.99%) and 5 (1.28%) for extractive, lignin, cellulose and ash content respectively. The tensile, burst and tear were identified as 9.93 Nm/g, 0.98 kPa.m2/g and 2.57 mN.m2/g respectively for handsheet product at optimum conditions. In conclusion, the results obtained was indicated that the delignification process via bacteria combination from R. ferrugineus is a viable alternative pulping process for pulp and paper-based industry. The delignification process on OPEFB also provides a cleaner technology process and more sustainable development for the country