Crash Analysis Of Car Chassis Frame Using Finite Element Method T. Ananda Babu 1 D. Vijay Praveen 2 Dr.M.Venkateswarao 3

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1 Crash Analysis Of Car Chassis Frame Using Finite Element Methd T. Ananda Babu 1 D. Vijay Praveen 2 Dr.M.Venkateswara 3 1. PG Student, Dept.f mechanical engineering Bapatla engineering cllege, Bapatla, A.P, India 2. Lecturer, Dept.f mechanical engineering Bapatla engineering cllege, Bapatla, A.P, India 3. Prfessr, Dept.f mechanical engineering Bapatla engineering cllege, Bapatla, A.P, India ABSTRACT Vehicle crash is a highly nnlinear transient dynamics phenmenn. The purpse f a crash analysis is t see hw the car will behave in a frntal r sideways cllisin. Crashwrthiness simulatin is ne typical area f applicatin f Finite-Element Analysis (FEA). This is an area in which nn-linear Finite Element simulatins are particularly effective. In this prject impacts and cllisins invlving a car frame mdel are simulated and cycle and can reduce the need fr cstly destructive testing prgram. Intrductin In autmbile design, crash and structural analysis are the tw mst imprtant engineering prcesses in develping a high quality vehicle. Cmputer simulatin technlgies have greatly enhanced the safety, reliability, and cmfrt, envirnmental and analyzed using ANSYS sftware. The chassis frame manufacturing efficiency f tday's frms the backbne f a heavy vehicle; its principle functin is t safely carry the maximum lad fr all the designed perating cnditins. The frame shuld supprt the chassis cmpnents and the bdy. It must autmbiles. This significant achievement was realized with the advanced sftware and pwerful cmputers that have been available in the last twenty years. als withstand static and dynamic lads withut undue The primary cncern fr drivers and deflectin r distrtin. The given mdel is tested under frntal cllisin cnditins and the resultant defrmatin and stresses are determined with respect t a time f 80 Mille sec fr ramp lading using ANSYS sftware. The crash analysis simulatin and results can be used t assess bth the crashwrthiness f current frame and t investigate ways t imprve the design. This type f simulatin is an integral part f the design passengers is safety. Gvernments have respnded t this key cncern and expectatin with an increasing number f regulatins. Althugh the details may vary slightly frm cuntry t cuntry, the fundamental requirements are almst similar. A vehicle is expected t prvide adequate prtectin t drivers and passengers in a nt s serius accident. T prtect the ccupants f a car, there are many new tangible safety features such as airbags; ABS cntrl brakes, tractin 1

2 cntrl. A less tangible feature that cannt easily be seen by drivers and passengers is the crash respnse behavir. In a well designed autmbile, the car bdy and varius cmpnents are the prtective layer fr the ccupants f the vehicle. They serve as the crumpling zne t absrb the energy f impact. The traditinal apprach invlves multiple iteratins f design, prttype and crash tests. The prcess is time cnsuming and expensive. The availability f high perfrmance cmputers and crash simulatin sftware has revlutinized the prcess. Instead f relying n experimental validatins, the safety design prcess is supplemented with cmputer simulatin t evaluate the design. Since the inceptin f crash simulatin, the prduct cycle f a new autmbile has been reduced by half and the resultant vehicle is safer, better and mre cmfrtable. withstand static and dynamic service lads encuntered during the vehicle life cycle. The vehicle bdy prvides mst f the vehicle rigidity in bending and in trsin. In additin, it prvides a specifically designed ccupant cell t minimize injury in the event f crash. The vehicle bdy tgether with the suspensin is designed t minimize rad vibratins and aerdynamic nise transfer t the ccupants. In additin, the vehicle structure is designed t maintain its integrity and prvide adequate prtectin in survivable crashes. The autmbile structure has evlved ver the last ten decades t satisfy cnsumer needs and demands subject t many cnstraints. Amng these cnstraints are materials and energy availability, safety regulatins, ecnmics, cmpetitin, engineering technlgy and manufacturing capabilities. Current car bdy structures and light trucks include tw Crash Simulatin Evlutin categries: bdy-ver-frame structure r unit-bdy structure. The latter designatin includes space-frame structures. In the present thesis an attempt has been made t (i) T investigate the deflectin and stresses in a chassis using static analysis (ii) (ii) T see the transient respnse f a car frame under crash simulatin Frame structure Safety engineers design and manufacture vehicle bdy structures t Unibdy Cnstructin: Mst vehicles tday are manufactured with a Unitized Bdy/Frame (Unibdy) cnstructin. This is a manufacturing prcess where sheet metal is bent and frmed then spt welded tgether t create a bx which makes up the structural frame and functinal bdy f the car. These vehicles have "crumple Znes" t prtect the passengers in case f a cllisin. Bdy-n-Frame Cnstructin: Mst heavy duty trucks and a few premium full-size cars are still manufactured with a bdy-n-frame cnstructin. This is a manufacturing prcess which a weight-bearing 2

3 frame is welded tgether and then the, engine, driveline, suspensin, and bdy is blted t the frame. In an accident, the Unibdy frame is designed t "crumple" and absrb the energy f an impact better than a Bdy-n-Frame cnstructin. The chassis frame supprts the engine, transmissin, pwer train, suspensin and accessries. In frntal impact, the frame and frnt sheet metal absrb mst f the crash energy by plastic defrmatin. The three structural mdules are blted tgether t frm the vehicle structure. The vehicle bdy is attached t the frame by shck absrbing bdy munts, designed t islate frm high frequency vibratins. Unibdy vehicles cmbine the bdy, frame, and frnt sheet metal int a single unit cnstructed frm stamped sheet metal and assembled by spt welding r ther fastening methds. The cnstructin f the unit bdy structure, als knwn as unit-frame-and-bdy r frame-less bdy, is claimed t enhance whle vehicle rigidity and prvide fr weight reductin. Materials used Mst aut bdies tday use stamped sheet as structural members that are spt welded tgether t frm a unitized bdy. This unitized structure is called the bdy-in white (BIW). BIW structural members supprt mst f the lads designed fr strength, fatigue resistance, stiffness, as well crush lads fr crashwrthiness. Material prperties f steel Yung's mdulus Prperty Nmenclature Value CRASHWORTHINESS TESTS CRITERIA AND MODEL REQUIREMENTS In the autmtive industry, crashwrthiness cnntes a measure f the vehicle's structural ability t plastically defrm and yet maintain a sufficient survival space fr its ccupants in crashes invlving reasnable deceleratin lads. Restraint systems and ccupant packaging can prvide additinal prtectin t reduce severe injuries and fatalities. Crashwrthiness evaluatin is ascertained by a cmbinatin f tests and analytical methds. Currently vehicle crashwrthiness is evaluated in fur distinct mdes: Frntal Side Rear Rllver crashes Types f crash tests: All cars underg frnt- and sideimpact testing, which includes 64kph (40mph) Frnt impact test: t assess car's perfrmance in severe accident 50kph (30mph) Side impact test 29kph (18 mph) ptinal Ple impact test: t driver's head 40kph (25mph) child and adult pedestrian impact tests Rules EX N/mm 2 Density DENS 7800 kg/mm 3 Pissn s rati NUXY 0.3 Ultimate strength UT MPa Crash Tests - Regulatry The fllwing are the requirements fr the cnsumer 3

4 rash tests cnducted by Federal Mtr Vehicle Safety Standard (FMVSS) Insurance Institute fr Highway Safety (IIHS) FMVSS Frntal impact requirements: 30 mph (48kph) int a fixed barrier Hybrid III in frnt driver and passenger seats Uses dummy injury measures fr regulatin chest G's <= 60 HIC <=1000 Femur lads <= 10KN Prtectin must be autmatic Purpse f this test is t examine the perfrmance f the ccupant restraint systems (seatbelts, airbags, etc.) IIHS Frntal impact requirements: 40% ffset, 40 mph (64kph) int a defrmable barrier Male Hybrid III dummy in frnt driver seat Gd, Acceptable, Marginal and pr ratings t assess vehicle's verall crashwrthiness Rating based n: dummy injury measures structural perfrmance restraint/dummy kinematics Evaluates the structural perfrmance f the vehicle FMVSS Side impact requirements: 33.5 mph (54kph) crabbed impact Impact r mass kg (3015lb) uses SID dummy in frnt and rear seats uses dummy injury measures fr regulatin TTI(d) <= 85g fr 4 dr passenger cars TTI(d) <= 90g fr 2 dr passenger cars pelvic acceleratin <= 130g Where TTI(d) = 0.5 x (Gr + Gs) IIHS Side impact requirements: Gr = Max. Rib acceleratin Gs = Lwer spine acceleratin impactr mass = 1500 Kg impactr shape derived frm Frd F150 frnt prfile 30 mph perpendicular impact driver and rear passenger dummies purpse is t represent crash type that pses greatest risk t ccupants (pickups/suv as striking vehicle)prmte head prtectin Mdelling and meshing f chassis CATIA mdel f car frnt part Element Descriptin Slid45 is used fr the 3-D mdeling f slid structures. The element is defined by eight ndes having three degrees f freedm at each nde: translatin in the ndal x, y, and z directins.the element has plasticity, creep, swelling, stress stiffening, large deflectin, and large strain capabilities. A reduced integratin ptin with hurglass cntrl is available Shell63 has bth bending and membrane capabilities. Bth in-plane and nrmal lads are permitted. The element has six degrees f freedm at each nde: translatins in the ndal x, y, and z directins and rtatins abut the ndal x, y, and z-axes. 4

5 Pressure, MPa Static Mdal Transient Final mesh f a car frame Frm the hyper sftware mesh we can bserve fllwing in ur mdel The ttal number f elements is The ttal number f ndes is Fr 3Delements The maximum aspect rati is 7.29 Minimum interir angle is 4.61 Maximum interir angle is Minimum jacbian is 1 Fr 2Delements Maximum aspect rati is 4.84 Minimum jacbian is 1 Minimum interir angle Maximum interir angle is Types f Analysis Used ut Time, msec The fllwing analysis has been carried Car Frame with Impsed Bundary Cnditins Car frame with lad and impsed bundary cnditins Variatin f Pressure against Time RESULTS AND DISCUSSION Results fr Static Analysis: Frm the static analysis the deflectins and stresses are btained in the bumper under a lad f 0.1MPa. 5

6 Vectr plt f defrmatin fr shell thickness 3mm under static lad Vectr plt f Vn-mises stress fr shell thickness 4mm under static lad Frm the abve figure it is bserved that that the maximum deflectin is mm fr the bumper made f thickness 3mm at the pint which is indicated as MX which is at nde The minimum deflectin is btained at the cnstrained pints which are are indicated as MN. Vectr plt f defrmatin fr shell thickness 5mm under static lad Vectr plt f Vn-mises stress fr shell thickness 3mm under static lad Vectr plt f Vn-mises stress fr shell thickness 5mm under static lad Results fr Mdal Analysis: The mdal analysis Vectr plt f defrmatin fr shell thickness 4mm under static lad f the car frame is carried ut t estimate the natural frequencies and crrespnding mde shapes fr the structure f car frame. The table gives the first ten natural frequencies f the mdel with different thickness f the shell f the bumper f an autmbile, which varied frm 3mm t 6mm. 6

7 Natural Frequencies f Car Frame by Varying Thickness f the Bumper 1. The deflectin f the bumper is varying frm mm t mm fr varius thickness f bumper under applied lad Results f transient dynamic analysis: Natural Frequencies, Hz Bumper Thickness, mm Mde N cnditin, which is rigid. Hence based n the rigidity the design is safe. 2. By increasing the bumper made f thickness the stress induced are reduced frm MPa t MPa. Hence the bumper design is safe based n strength criteria. 3. The natural frequencies estimated fr varius thicknesses are very lw as the structure is statinary. 4. When the impact takes place n the bumper, the maximum amplitude is mm under transient lading. This value is very less than 2.8mm as per the Frd Mtr Vehicle CONCLUSIONS AND FUTURE SCOPE Design Test (FMVDT). Hence the bumper OF WORK : The fllwing cnclusins design is safe based n dynamic cnditins. are drawn frm the present wrk Future Wrk: The bumper f a car can be 7

8 made as sandwich mdel r springs can be placed in the bumper in rder t reduce the impact that is transferred t the passenger cmpartment. Analysis f these designs can be dne which may yield t better safety. These designs may als reduce the weight f the bumper leading t increase fuel efficiency. REFERENCES [1] Lnny L.Thmpsn, et al, Cliffrd C. Chu, Bahig B. Fileta, Tawfik B. Khalil, Albert King, Hikmat F. Mahmd, Harld J. Mertz, Jack Wismans, Vehicle Crashwrthiness and Occupant Prtectin, Spnsred by: Autmtive Applicatins Cmmittee, American Irn and Steel Institute, Suthfield, Michigan [2] Oijier, F., "Develpment and Validatin f High Fidelity Vehicle Crash Simulatin Mdels," [3] Cicek karaglu et al., Stress analysis using riveted jints, Internatinal Sympsium n Heavy Vehicle Weights & Dimensins, Delft, NL [4] Ts-Chien Pan et al, "Dynamic Vehicle Element Methd - Present and Future Develpments," The Internatinal Cnference n Vehicle Structural Mechanics. [5] Arbri.N.,et al, Future trend f autmbile and the high strength sheet steel. Tetsu-t-Hagane. vl. 68, n. 9, Japan [6]Narender Bumper beam-lngitudinal system subjected t ffset impact lading 8