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1 64 International Jornal of Physical and Mathematical Sciences Vol 2, No 1 (2011) ISSN: International Jornal of Physical and Mathematical Sciences jornal homepage: PRELIMINARY STUDY ANALYTICAL APPROACH IN EXPERIMENTAL RIG OF AUTOMOTIVE FLEXIBLE WIPER SYSTEM M.A.Salim*, N.A.I.H.Nik Ab Rashid, F.A.Mnir, M.R.Mansor, N.Razali, M.N.N.Rashid, M.R.M.Zin, M.I.M.Azmi Faclty of Mechanical Engineering, Universiti Teknikal MalaysiA Melaka, Hang Tah Jaya, Drian Tnggal, Melaka, Malaysia azli@tem.ed.my RECEIVED DATE ( ) Abstract In this stdy, experimental rig of atomotive wiper System is designed and analyzed sing nmerical tool. Generally, this rig tilizes different types of electric motor as a power assist. In addition, a sitable dimension and material for each part was chose for the rig. There are two main considerations in order to design the experimental rig. The first consideration is the selection of power assist (electric motor) and the second is the consideration made pertaining to the criteria the design method. In research methodology, the design and materials sed in this stdy is needed to be strctrally analyzed sing analytical calclation. After the calclation is complete and the desired reslts is obtained, then only the experimental rig of atomotive wiper system can be fabricated and tested. The platform of the rig was analyzed to identify the external forces acting on the rig. Strctral finite element analysis is condcted on the completed a best design. It is to ensre the rig has a safety factor dring the experiment going on. Key words: Wiper system, finite element, analytical, nmerical. Introdction Windscreen wipers are the essential components to a vehicle. It fnction is to provide good vision to the driver dring rains. Nowadays, almost all atomobiles are eqipped with windscreen wiper which is one of the legal reqirements. Clear vision for the car driver is an important safety aspect in road traffic. A conventional wiper is shown in Figre 1. A wiper system is consists of an arm which rotating at a pivot point at one end. This arm is has a long rbber or silicone blade attached together. The fnction of the blade is to swing back and forth over the windscreen which conseqently removes water drops from windscreen srface. The mechanical strctre of the wiper blades is attached to the arm tips, holds the rbber blade, which drains the water off the windscreen or to smooth the water on the srface of the windscreen in order to create a thin film that allows light to pass throgh it withot refracting or bending as shown in Figre 2. Wiper Blade Wiper Arm Wiper Link Wiper Motor Figre 1: Wiper system on a windscreen

2 65 International Jornal of Physical and Mathematical Sciences Vol 2, No 1 (2011) ISSN: Figre 2: Load distribtion of a wiper blade (Denso, 2008) It is very often that the windscreen wiper generates nwanted and annoying noise and vibration. As stated by Goto et al. (2001), the noise and vibration can be categorized into three types [1]. The categories are sqeal noise, chattering and reversal noise. The first type which is sqeal noise has a high freqency of vibration p to 1000 Hz. On the other hand, chattering or beep noise is noise occrs at lowfreqency vibration of 100Hz or less. Fthermore, an impact sond with a freqency of 500 Hz is defined as reversal noise. Impact sond is prodced when the wiper reverses. Goto et al. (2001) also added that these types of noise and vibration can lead to visal and adible annoyance for the driver and passengers [1]. There are nmeros stdies condcted to investigate noise and vibration of an atomotive wiper system. Those stdies were condcted by sing analytical, nmerical and experimental approaches. Okra et al. (2000) in his stdy had performed dynamic analysis of blade reversal behaviors by sing a 2-dimensional (2D) mechanical model of a wiper system and a spring-mass model of an arm and blade [2]. Apart from that, in their different works, frther stdies of the dynamic analysis by sing a complete 3-dimensional (3D) model were sccessflly delivered. Okra et al. (2000) had made comparison between the 2- and 3- dimensional model for the arm and blade [2]. They have sggested in the reslts that the 3D model cold simlate the reversal behavior of the wiper system more accrately than the 2D model. Investigation to minimize sqeal noise by sing a mathematical model had been proposed in (Goto et al, 2001a; Goto et al, 2001b) [1], [3]. In their stdies, physical properties and design of the blade were varied. In order to validate the simlated reslts, experiments on sqeal noise were also carried ot to verify the effectiveness of the proposed material and design changes. Moreover, an excellent work had been done by Grenoillat et al. (2002) who combined approach [4]. In their work, wiper motion tests were carried ot on a developed test rig. Different attack angles and pressre were sed and their effect on the wiper motion was observed. Grenoillat et al. (2002) also developed a 2D mathematical model to demonstrate the inflence of the geometrical configration of the wiper system on the generation of nstable motion [5]. The application of dither control to stabilize sqeal noise in the wiper system has been introdced in Stallaert et al. (2006) [6]. A finite element (FE) model was developed in order to spport the optimization of the control configration. The stdy showed that with a proposed dither control, wiper sqeal noise was effectively sppressed. Finite Element (FE) model is developed to stdy dynamic instability of a flexible wiper system. Different vales of arm forces and attack angles of a rbber blade were selected and simlated to examine their effects on the vibration response of the wiper. The predicted reslts were close to those obtained in the experiments. 1. Windscreen Wiper System Windscreen wiper can be defined as a mechanical device that cleans the windshield dring raining. The first invented windscreen wipers were operated manally. The driver needs to move a lever inside the car back and forth and this redces the driver attention and maneverability. In crrent design, most vehicles are eqipped with electric windscreen wipers. The wipers withot fail keep the windscreen clear, moving back and forth across the windscreen in contless times to remove the water away. Fig. 3 Wiper system (Porsche-parts, Agst 3, 2010) The wiper blades are important part in wiper system. They are made of a rbber compond and are held on to the windshield wiper glass by a spring in the wiper arm. The wiper blade and its parts showed in Figre 4.

3 66 International Jornal of Physical and Mathematical Sciences Vol 2, No 1 (2011) ISSN: Sperstrctre Pivot pin Latch release Element Pivot block Flexor Figre 4: Wiper blade The aerodynamic properties of the wiper blades have become increasingly important de to the design of the vehicle as different air crrents flow on and arond the screen area. The strip on top of the rbber element is often perforated to redce air drag. A good qality blade will have a contact width of abot 0.1mm. The lip wipes the srface of the screen at an angle of abot 45. The pressre of the blade on the screen is also important as the coefficient of friction between the rbber and glass can vary from 0.8 to 2.5 when dry and 0.1 to 0.6 when wet condition. There are two types of wiper blade which is rbber and silicone. Wiper blades fnction like sqeegees. A thin rbber strip is dragged by the arms of the wiper across the windscreen to remove away the rain water. The rbber strip is clean withot element of crack or nicks when it is new. Hence, it able to remove water withot prodcing streaks. However, as the wiper blades getting older, there will be formation of nicks or cracks. Conseqently, road grime bilds p on the edge as it does not make as tight a seal against the windscreen. This will lead to the wiper leaves streaks. The lifetime of the rbber wiper blade can be prolonged a little bit by wiping the edge with a cloth soaked in window cleaner ntil no more dirt comes off the blade. Claw 2. Research Methodology i. Design Specifications Design specifications are very important in a design process becase it provides precise and explicit information abot reqirements for a prodct design. Besides that, it consist the best soltion to prodce this project or design. Throgh design specifications, it will help engineers and researchers to nderstand the problem and demerits of the existing design before the design is improved. There are several aspects in design specifications which are: i. Appearance ii. Geometry limitation iii. Dimension iv. Prodct v. Endrance ii. Parts Selection A material or part selection is an important aspect of design for mechanical, electrical, thermal, chemical or other applications. Systematically, selection of the best material for any application begins with properties, cost of materials and specifications needed. Ths, comparison between each material and part is important step to be considered. For this stdy, there are three parts that needed to be considers before the right part and material sage will be choose. There are: i. Strength Strength can be related to the crash worthiness or general drability of the platform table. However, strength has no effect on the wiper system properties. Apart from that, strength is determined by a property of the material which is called yield strength. The factors that affects the yield strength property is the qality, heat treatment and alloying elements sed in a particlar brand of tbing. ii. Stiffness Stiffness affects the strength of the stand to spport the wiper system inclding windscreen. Elastic modls is the determinant of stiffness. In a particlar metal, elastic modls is an independent property that can affect the qality or alloying elements. Nevertheless, all kind of steel has the same modls of elasticity. iii. Weight (specific gravity) Specific gravity is an indication how mch the strength and stiffness of a material is affected if the volme is added. The specific weight of a given metal is not significantly affected by the addition of different alloying elements.

4 67 International Jornal of Physical and Mathematical Sciences Vol 2, No 1 (2011) ISSN: Material Alminm (Alloy 1100-H14) Table 1: Material properties Modls of Yield Elasticity Strength (GPa) (MPa) Specific Gravity (SG) Steel (ASTM A36) Titanim According to Table 1, there are three common materials for platform of the rig. The common material for table of rig is alminm, steel and titanim. The selections of this material are based on material properties as shown in the table. The alminm frame will be only 1/3 as stiff as steel and the titanim only half as stiff compare to steel. If the strength were considers, the yield strength is very important. Finally, the specific gravity vales show that the alminm frames wold only weight 1/3 compares to steel and titanim frame. However, any of these materials is qite sitable for table of rig bt if we consider the cost, titanim is not sitable becase it costly compare to steel and alminm. Ths, the comparison between all this materials is analyzed to get the best design and material se. The final material selected is alminm becase of cost and the modls of elasticity and yield strength still cover the load. iii. Design With Compter Aided Design (CAD) It is important to nderstand the sages, fnctions, commands, featres and many more of nmerical tools. This tool is a state of the art 3-dimensional (3D) mechanical CAD program that rns on high processor. CAD is sed to design and develop prodcts, which can be goods sed by end consmers or intermediate goods sed in other prodcts. CAD is also extensively sed in the design of tools and machinery sed in the manfactre of components. CAD is also sed in the d r a f t i n g and design of all types of b i l d i n g s, from small residential types (hoses) to the largest commercial and indstrial types (hospitals and factories). It is sed throghot the engineering process from conceptal design and layot, throgh detailed engineering and analysis of components to definition of manfactring method. Each of the different types of CAD systems reqires the operator to think differently abot how he will se them and he mst design his virtal components in a different manner for each. Ths, based on conceptal design and brain sketching, the final design will be drawing by sing CAD software. i. Finite Element Method (FE) The procedre is shown as follows: a. Discretization of the domain b. Selection of a proper interpolation model c. Derivation of elements stiffness matrices and load vectors d. Assemblage of elements eqation to obtain the overall eqilibrim eqations e. Soltion for nknown field variable (integration of bondary condition) f. Comptation of elements strain and stresses. For comptation of element of beam, the formla sed: Where, F = Internal force A = Area acting on the force E = Yong Modls L = Length between nodes U = Deflection 3. Reslts and Discssion The design concept is a method where early sketching is involved for designing a new prodct. This sketch is based on the design specification that is mentioned in previos section. There are several sketches that need to be done before the final design is finalized. For this stdy, there are three sketched designs have completed. The best design is selected as the final design and shown in Figre 5.

5 68 International Jornal of Physical and Mathematical Sciences Vol 2, No 1 (2011) ISSN: Figre 5: Final design of experimental rig After each part is assigned to its material properties, the parts are then assembled. After the assembly is done the analysis procedres are assigned in step modle. Defining the bondary condition is also done nder the step modle. Next, the interactions between the parts are defined. Then the meshing is done, the 3D stress element type is sed for the whole model. Tetrahedral meshing was sed to most of the parts except the windscreen and the rail spring. These two parts were assigned hexahedron elements. Hexahedron element can only be sed on simple geometry where else tetrahedron element can be sed to mesh complex geometries. Finally the job is created and sbmitted for analysis. Figre 6: Dimension of experimental rig table Figre 7: Free Body Diagram (FBD) of experimental rig table The abrpt change in the distribtion load not really effect to the internal force, then the force is assmed on the center of beam. The strctre also in symmetry and divided by two and force also divided by two.

6 69 International Jornal of Physical and Mathematical Sciences Vol 2, No 1 (2011) ISSN: The bondary conditions of the system are: Figre 8: FBD after consider the distribtion load and symmetry with nmber of nodes Element Nodal 1 2 Table 2: Table of connectivity L Ѳ C S C² S² CS The local stiffness matrix is: 4. C² CS C² CS AE CS S² CS S² L C² CS C² CS CS 1 CS S Area, A for element 1 and 3 = 0.06 x 0.95 = m² Area, A for element 2 and 4 = 0.59 x 0.95 = m² A/L for element 1 and 3 = 0.057/0.345 = A/L for element 2 and 4 = /0.59 = 0.95

7 70 International Jornal of Physical and Mathematical Sciences Vol 2, No 1 (2011) ISSN: For element 1, AE L 3y y 3 x 3 y E For element 2, AE L 2x 2y x 2 y 2x 2y E For element 3, AE L 3y 5x 5y x 5 y 2 x 2 y 5x 5 y E x y x y

8 71 International Jornal of Physical and Mathematical Sciences Vol 2, No 1 (2011) ISSN: For element 4, 4x 4y 3y E x 4y 3y E For global stiffness matrix apply the bondary condition is, By solving the eqation, the reslts are: F F y F 2 y y = E F3 x F y F4 y y According to the reslts in eqation (2) ntil (7), the nknown can be assmed depending on the design criterion made. The force apply on the experimental rig table is consider nknown. That means, the strength of the table 4. Conclsion The design of experimental rig table is completed sing finite element method. There are some problems to get the best design and sitable concept for development of this stdy. However, the problem was sccessflly overcome after a few hand sketching and by the combination of different method of attaching mechanism. The 3D view of this design had been drawn by sing nmerical tool. The dimension of the experimental rig in the drawing is approximated to the real dimensions. Then, the shape and fnctioning method is same. By referring to this design, the prototype and the analysis of this stdy will make to stdy the noise and vibration level on this particlar system for frther stdy. 5. Acknowledgement The athors wold like to acknowledge Faclty of Mechanical Engineering, Universiti Teknikal Malaysia Melaka for spporting this work throgh a short term grant.

9 72 International Jornal of Physical and Mathematical Sciences Vol 2, No 1 (2011) ISSN: References [1] Shinya Goto, Hiroshi Takahashi, Takio Oya, Clarification of Mechanism of Wiper Blade Rbber Sqeal Noise Generation, Jornal of Society of Atomotive Engineers, Review 22, 2001, pp [2] Shigeki Okra, Tohr Sekigchi, Takio Oya, Dynamics analysis of blade reversal behavior in a windshield wiper system, The Engineering Society for Advancing Mobility Land Sea Air and Space (SAE), [3] Shinya Goto, Hiroshi Takahashi, Takio Oya, Investigation of wiper blade sqeal redction measres, Society of Atomotive Engineers, [4] R. Grenoillat, C. Leblanc, Simlation of mechanical pressre in a rbber-glass contact for wiper systems, SAE Technical Paper,2002, [5] Grenoillat, C. Leblanc, Simlation of chatter vibrations for wiper systems, SAE Technical Paper, 2002, [6] B. Stallaert, F.Dacet, J.Rys, Application of dither control for atomotive wiper sqeal, Proceeding of ISMA2006.