Lightweight Electric/Hybrid Vehicle Design

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X 210 Lightweight Electric/Hybrid Vehicle Design (a) (b) (c) RxL RyL RpL a1 KI XI Xyg h′ ′ h′′ ′ XI B′ A′ RpL Xxg Xxd Xyd PZ 2 Rpp h1 Yg Yd b 1 K3 h′ ′ h′′ ′ 1 3 RpL 4 XI B A A′ B′ RpL 5 Rx 2 K1 XI h1 A′ RpL 6 B a 1 K4 K3 Ry Xzg 7 z X2 B G C A M K3 K1 N L1 XI h h 1 Xzd O A A B Z x X2 K L L2 PZ 2 K5 K2 F′ K5 PZ X2 A′ B′ K4 D F K5 B′ A′ B I E J N F L3 Rtp L 1 K4 L4 K2 RtL F X h2 D F z X A B K2 y A B D′ F′ E′ 10 X2 2 R (X) P (R,X) RtL y 9 8 X2 a2 D E F h 2 RtL h2 Fig. 8.6 Structural idealization of punt structure: (a) punt structure for ERA 378; (b) SSS simplification; (c) structural surfaces; (d) planar representation; (e) cantilever forces; (f) bulkhead surfaces.
Design for optimum body-structural and running-gear performance efficiency 211 the use of large uniform-section box tube for the sills, A/C-posts and their upper and lower crossmembers. The use of a sandwich floor panel, with such a punt structure, would also allow central positioning of propulsion-battery packs in a structurally efficient manner for a mid-size electric car. 8.3.1 IDEALIZATION OF THIN-WALL STRUCTURES Initial analysis of this type of optimized lightweight structure, simplified for analysis as at (b top right), is best carried out by a method such as Pawlowski’s5 Simple Structural Surface (SSS) technique which gives a better feel for structural efficiency than the full finite-element analysis, carried out at a later stage. Pawlowski’s contribution was to adopt aeronautical thin-walled structural analysis techniques for automotive structures and his SSS method (nowadays much more readily applied with the assistance of computer simulation) involves dividing the key elements of the structure into systems of plates, assumed to carry shear loads, surrounded at their edges by bars assumed only to carry end load. These systems are represented in (c) by structural surfaces, the edge forces in which are those that occur in bending of the structure during, say, symmetrical impact of the front wheels against a ramp in the road, causing an upward force on the front-end reacted by a downward inertia force applied by the combined mass of the occupants and battery pack, assumed to act through the centre-line. The following key elements are involved: (1) front bulkhead; (2) dash upper panel; (3) left-hand side wall; (4) right-hand side wall; (5) floor; (6) rear parcel shelf; (7) rear bulkhead; (8) LH boot side-panel; (9) boot floor; (10) RH boot side panel. 8.4 Optimizing substructures and individual elements The connection points between the major structural elements (Fig. 8.7) are worthy of detailed attention so that the strength and stiffness of the connected members is preserved at the joint. At a joint between box members such as the important rear quarter to sill junction of a car, (a), consideration should be given to load transfer at the corner. In figures taken from the design of small car body structure, using aircraft thin-walled structural techniques, by T.K. Garrett 6 , a bending moment of 51 000 lbf in (5.76 kNm) induced end loads of 33 000 lbf (146.7 kN) in the top and bottom flanges of the 5 in (127 mm) sill. The 18.5 MN/m 2 safe working stress steel used in this application dictated an area of 0.123 in 2 (0.795 cm 2 ) edge material – a 3.4 in (86.5 mm) wide flange of 20 gauge sheet. The webs of sill and quarter panels overlap as shown by the dotted lines to provide the necessary transfer of the 1900 lbf (8.45 kN) shear force applying in this example. It is also important to maintain the cross-section shape of thin-walled box beams, both along their length and, crucially, at the corner joint where a diagonal diaphragm (bulkhead) might be required. The importance of structural continuity, in order to transfer loads from one part of a structure to another, is clear from the example shown. Here it is necessary to transfer both shear and bending moment between the sill and the rear end of the vehicle. The sill outer panel is joggled under the rear quarter panel and there is a vertical joint line CD. At the rear end the sill is closed by flanging outwards of the outer panel and its connection to the heel board at EF. End loads to be transferred from the top and bottom of the section to the rear quarter panel are found by dividing the section depth into the bending moment. These loads will govern the number of spot-welds required at the connection. The direction of the loads will determine whether a ‘kink strut’ is required at the joint, its dimensions being found by resolving the forces along the line of the strut. In the case of a curved corner, or angular, joint between box beams, (b), the web is subject to direct stress M/hRt where R is the radius of curvature and t the web thickness. For the lightly angled joint shown in the same figure, a ‘kink strut’ may be required at the junction to maintain
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Lightweight Electric/Hybrid Vehicle
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iv Contents Butterworth-Heinemann L
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vi Contents 4.5 Process engineering
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viii Preface natural gas, which is
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x About Prefacethe authors working
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xii Lightweight Electric/Hybrid Veh
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100 Lightweight Electric/Hybrid Veh
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PART TWO Battery/fuel-cell EV desig
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5 Battery/fuel-cell EV design packa
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(a) cell voltage 2,5 V 2,0 1,5 1,0
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Varta Electric Power: Nickel-metal-
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700 600 500 400 CurrentmA 300 (a) 2
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Battery/fuel-cell EV design package
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Intake filter Intercooler High spee
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Fig. 5.22 Bradshaw Envirovan. Batte
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6.1 Introduction 6 Hybrid vehicle d
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6.2 Hybrid-drive prospects Hybrid v
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TRAVEL ELECTRIFIED, % 80 70 60 STRA
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Hybrid vehicle design 147 750 kg to
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M [Nm] 500 450 400 350 300 250 200
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6.3.6 TAXI HYBRID DRIVE Hybrid vehi
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Hybrid vehicle design 153 The Rover
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Hybrid vehicle design 155 as a star
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Hybrid vehicle design 157 injection
Page 187 and 188: Hybrid vehicle design 159 In ‘sta
Page 189 and 190: Hybrid vehicle design 161 power and
Page 191 and 192: Hybrid vehicle design 163 The batte
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Page 195 and 196: Hybrid vehicle design 167 drive ele
Page 197 and 198: Hybrid vehicle design 169 The view
Page 199 and 200: Hybrid vehicle design 171 6.5.4 ADV
Page 201 and 202: Lightweight construction materials
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