STATIC AND MODAL ANALYSIS OF COMPOSITE SHIP PROPELLER USING FEM

Transcription

1 STATIC AND MODAL ANALYSIS OF COMPOSITE SHIP PROPELLER USING FEM Nagarjun Kannoju 1,P. Ravikanth Raju 2, Dr. P.HV. Sesha Talpa Sai 3 1 M.Tech Student, Malla Reddy College of Engineering & Technology, Secunderabad ,, India 2 Dept of Mechanical Engineering, Malla Reddy College of Engineering & Technology, Secunderabad ,, India 3 HOD, Dept of Mechanical Engineering, Malla Reddy College of Engineering & Technology, Secunderabad ,, India Abstract - Ships and underwater vehicles like submarine and torpedoes use for propulsion. In general, s are used as propulsors and they are also used to develop significant thrust to propel the vehicle at its operational speed and RPM. The blade geometry and design are more complex involving many controlling parameters. Propeller with conventional isotropic materials creates more vibration and noise in its rotation. In current years the increased need for light weight structural element with acoustic insulation has led to use of fiber reinforced multi layered composite. In this paper static and model analysis of aluminum, composite has been carried out. The composite which is a combination of GFRP (Glass Fiber Reinforced Plastics) and CFRP (Carbon Fiber Reinforced Plastics) materials. In this paper modeling and analyzing the blade of a underwater vehicle for their strength. A is a complex geometry which requires high end modeling software. The solid model of is developed in CATIA V5 R19. Tetrahedral mesh is generated for the model using HYPER MESH. Static and model analysis of both aluminum and composite are carried out in ANSYS. Interlaminar shear stresses are calculated for composite by varying the number of layers. The stresses obtained are well within the limit of elastic property of the materials. The results were compared with Tsai-Wu failure theory and found they were within the safe limits. Keywords: Propeller; Propulsion; Vibration; Composite. 1. INTRODUCTION The study of action and design is complex especially the manufacturing of marine s is a highly specialized procedure, On the experimental side, Froude developed a method for studying the action of a behind a ship. The conditions under which the model experiments can be used to determine ship performance and model s may be derived by dimensional analysis. It is not practicable to fulfil all these conditions exactly, and therefore some empirical corrections are necessary in determining ship performance and model s from experiments with models. First approach to strength problem was made by Taylor [1] considered a blade as a cantilever rigidly fixed at the boss. The stresses are evaluated by him using the theory of simple bending and section of the blade by a cylinder. The method used by the author is simplest of all is still widely used for simple and conventional geometries, with narrow blades. But the method is suspect when used for s with wide blades and width comparable ton length. J E Connolly [2] addresses the problem of wide blades, tried to combine both theoretical and experimental investigations. The author carried out the measurements of deflection and stresses on model blades subjected to simulated loads with an aim to develop a theoretical model calibrated against the laboratory experiments. It was pointed out the accuracy of the predication from the model depends on the accuracy of working load determined. Terje sonntvedt [3] studied the application of finite element methods for frequency response and improve to the frozen type of hydrodynamic loading. The thin shell element of the triangular type and the super parametric shell element are used in the finite element model it presents the realistic and dynamic stresses in marine blades. Stresses and deformation calculated for ordinary geometry and highly skewed s are co mpared with experimental results. Changsup lee [4] et.al investigated the main sources of blade failures and resolved the problem systematically. An FEM analysis is carried out to determine the blade strength in model and full scale condition and the range of safety factor for the under study is determined. The radial stresses have been chosen as typical for the stress situation at each point. G. H. M. Beek [5] the interference between the stress conditions in both parts. Strong tools are available to shift the disturbing boundary conditions for the blade root to the hub-shaft interface and obtain reliable information about the blade root loading an its resolution in the hub. George [6] used the distribution of thrust and torque along the radius to compare actual performance of a with calculated performance. The energy losses in the wake of the as obtained from experimental measurements are discussed. The proposed method permits an analysis of the effects of solidity on the axial and rotational losses of the to be made from the total thrust and torque. P. Castellini [7] describes the vibration measurements on blades of a rotting in water with tracking laser vibrometer. In a number of cases IJCSIET-ISSUE5-VOLUME2-SERIES3 Page 1

2 component failures are caused principally by vibrating related fatigue stress. Monitoring of component vibration can play an important role in preventing failures due to fatigue. J. G. Russel [8] developed a method of blade construction employing CFRP in a basic load carrying spar with a GFRP outer shell of aerofoil form. Full scale blade specimens have been fatigue tested in various modes. Other tests such as bird impact trails have been carried out. Comparisons have been made between the measured vibratory strains and the fatigue test results. Gau-Feng Lin [9] et.al, carried out stress calculations for a fiber reinforced composite thruster blade. The composite blade is constructed using multiple layers of braided fiber in a thick shell skin layer. The core is filled with foam type material and uses shear webs for internal supports. The objective of this work is to explore the rotating blade hydrodynamic design constraints of a typical composite blade by performing a 3-D element- stress analysis. Shigeki nitbiyama [10] et.al, mainly concentrated on the development of contra- rotating s to bulk carrier. The Contra Rotating Propeller (CRP) has been practical use on torpedoes small boats and airplane but it is has not been adopted for large merchant ships. 2. MODELING OF PROPELLER The following are the properties of the Aluminum and EPOXY+CFRP which are used for manufacturing of the. The is modelled in CATIA V 5 software and is shown in Fig. 1. The meshing of the is carried out in HYPERMESH 10.0 software and the model in loading condition is shown in Fig. 2. Mechanical properties of aluminum: Young s modulus, E x : 70 Gpa Rigidity modulus: 2.71 x 10 4 N/sq.mm Poisson s ratio: 0.29 Density: 2.7g/cc Hardness: 105 BHN Mechanical properties of EPOXY+CFRP: E x = 180Gpa E y = 10Gpa E z = 10Gpa Poisson s ratio nu xy = 0.28 Shear modulus G xy = 7.1 Gpa Mass density = 1600kg/m 3 Damping co-efficient =0.018 Fig. 1: Propeller model Fig. 2: Meshed model in loading condition 3. STATIC ANALYS IS OF ALUMINUM & ALUMINUM PROPELLER: The thrust of 4000N is applied on face side of the blade in the region between 0.7R and 0.75R. The intersection of hub and shaft point s deformations in all directions are fixed. The thrust is produced because of the pressure difference between the face and back sides of blades. The blade is considered as cantilever beam i.e. fixed at one end and free at other end. The deformation pattern for aluminum. The maximu m deflect ion was found as mm in y- direction. Similar to the cantilever beam the deflection is maximum at free end. The maximum von mises stress induced for aluminum blade is N/mm 2.The stresses are greatest near to the mid chord of the blade-hub intersection with s maller stress magnitude toward the tip and edges of the blade. Fig.3: Deformation of aluminum Fig.4: Max von mises stress of aluminum IJCSIET-ISSUE5-VOLUME2-SERIES3 Page 2

3 Two cases are considered for static analysis of composite by varying the number of layers to check the bonding strength. Interlaminar shear stresses are calculated for 4 and 8 layered composite plates. Analysis results of 4 layers: Maximum deflection for composite with 4 layers was found to be mm of the blade. The maximum von mises stress was found to be N/mm 2. The maximum interlaminar shear stress was found to be N/mm 2 for 4 layered composite plates. Fig.11: Deformation of composite with 8 layer Fig.9: Deformation of composite with 4 layer Fig.12: Max. Von mises stress of composite with 8 layers Table.1: Static analysis results of both aluminum and composite Static analysis results Maximum deflection (mm) Maximum von mises stress (N/mm 2 ) Aluminum Composite with 4 layers Composite with 8 layers Fig.10: Max. Von mises stress of composite with 4 layers Analysis results of 8 layers: Deformation for composite with 8 layers was found to be mm of the blade. The maximum von mises stress was found to be N/mm 2. The maximum interlaminar shear stress was found to be N/mm 2 for 8 layered composite plates. The deflection for composite blade was found to be decrease by increasing no. of layers i.e, 1.104mm to mm which is much less than that of aluminum i.e mm, which shows composite materials, is much stiffer than aluminum. 4. MODAL ANALYS IS OF ALUMINUM & COMPOS ITE PROPELLER ALUMINUM PROPELLER: This analysis does not represents the response due to any loading but yields by natural frequencies and IJCSIET-ISSUE5-VOLUME2-SERIES3 Page 3

4 corresponding mode shapes in the form of Eigen vectors of the blade when there is no dissipation of energy due to damping. In short cut it is the analysis of undamped free vibration of blade in the absence of damping and applied loads. Eigen value analysis is carried out by using Block Lanczos method. First four natural frequencies are obtained for aluminum Modal Results First four natural frequencies are obtained for Composite Modal Results.9: 1 st Mode of composite with 8 layers Fig Fig.5: First mode of Aluminum Fig.6: Second mode of Aluminum Fig.10: 2 nd Mode of composite with 8 layers Fig.7: Third mode of Aluminum Fig.11: 3 rd Mode of composite with 8 layers Fig.12: 4 th Mode of composite with 8 layers Fig.8: Forth mode of Aluminum IJCSIET-ISSUE5-VOLUME2-SERIES3 Page 4

5 Table.2: Natural frequencies comparison of aluminum and composite No. of mode s Natural frequency of aluminum in (Hz) Natural frequency of composite in (Hz) The natural frequencies of composite when comparing to aluminum is much more than aluminum, because of the High strength carbon/epoxy and high modulus carbon/epoxy shafts were approximately 50% weight saving. 5. CONCLUS IONS: After performing simulation for different material and layers the following conclusions are drawn. The deflection for composite blade was found to be around 1.104mm for 4 layers which is much less than that of aluminum i.e 4.402mm, which shows composite materials is much stiffer than aluminum. Inter laminar shear stresses were calculated for composite by incorporating different number of layers viz. 4 and 8 was found that the percentage variation was about 3.147%,which shows that there is strong bonding between the layers and there s no peel-off. Modal analysis results showed that the natural frequencies of composite is much more than aluminum, because of the High strength carbon/epoxy and high modulus carbon/epoxy shafts were approximately 50% weight saving when comparing to Aluminum Propeller The High Strength Carbon/Epoxy and High Modulus Carbon/Epoxy Composite drive shafts have been designed to replace the Aluminum Propeller Future scope of work 1. The present work only consists of static and Modal analysis, which can be extended for transient and spectrum analysis in case of both aluminum and composite materials. 2. There is also a scope of future work to be carried out for different types of materials, which can be extended for CFD analysis. 3. Analysis will do to obtain relat ions between fibre angle orientation and parameters like stresses induced in each layer, deflection in each layer and natural frequencies of the composite shaft. REFRENCES 1. Taylor, D.w, The S peed and Power and Ships, Washington, J.E.Conolly, Strength Of Propellers, reads in London at a meeting of the royal intuition of naval architects on dec ,pp Terje sonntvedt, Propeller Blade Stresses, Application Of Finite Element Methods computers and structures, vol.4,pp Chang-sup lee, yong-jik kim,gun-do kim and in -sik nho. Case Study On The Structural Failure Of Marine Propeller Blades 5. G.H.M.Beek, visitor, lips B.V.,Drunen. Hub-Blade Interaction In Propeller Strength, the socity of naval architects and marine enginers, may 24-25,1978,pp George W.Stickle and John L Crigler. Propeller analysis from experimental data report No.712, pp P.Castellini, C.Santolini. Vibration Measurements On Blades Of A Naval Propeller Rotating In Water With Tracking Laser Vibromneter Dept. of mechanics, university of Ancona, pp J.G.Russel use of reinforced plastics in a composite blade plastics and polymers, Dec 1973 pp Gau-Feng Lin Three Dimensional Stress Analysis of a Fiber Reinforced Composite Thruster Blade the society of naval architects and marine engineers Shigeki nithiyama, yoshitaro sakamoto, shunichi ishida and minoru oshima Development of contra rotating system for juno-a dwt class bulk carrier snname transactions, vol ,Pp27-52 IJCSIET-ISSUE5-VOLUME2-SERIES3 Page 5