MT-1620 Fall 2002 Unit 15 Shearing and Torsion (and Bending of shell beams Readings Rivello Ch. 9, section 8.7(again), section 7.6 T&g 126,127 Paul A Lagace, Ph. D Professor of aeronautics Astronautics and Engineering Systems Paul A Lagace @2001
MIT - 16.20 Fall, 2002 Unit 15 Shearing and Torsion (and Bending) of Shell Beams Readings: Rivello Ch. 9, section 8.7 (again), section 7.6 T & G 126, 127 Paul A. Lagace, Ph.D. Professor of Aeronautics & Astronautics and Engineering Systems Paul A. Lagace © 2001
MT-1620 al.2002 Thus far, we have concentrated on the bending of shell beams. However, in the general case a beam is subjected to axial load. F · bending moments,M · shear forces,S torque(torsional moments), T Figure 15.1 Examples of general aerospace shell beam structures Air T T connecting nodes Paul A Lagace @2001 Unit 15-2
MIT - 16.20 Fall, 2002 Thus far, we have concentrated on the bending of shell beams. However, in the general case a beam is subjected to: • axial load, F • bending moments, M • shear forces, S • torque (torsional moments), T Figure 15.1 Examples of general aerospace shell beam structures Aircraft Wing Space Habitat Shell connecting nodes Paul A. Lagace © 2001 Unit 15 - 2
MT-1620 al.2002 Idealize the cross-section of the shell beam into two parts Parts that carry extensional stress, O(and thus the bending and axial loads Parts that carry shear stress Oxs(and thus the shear loads and torques TWo examples again igh aspect ratio wing with semi-monocoque construction Notes monocoque construction all in one piece without internal framing from French "coque" meaning" eggshell “mono”= one plece seml-monocoque stressed skin construction with internal framework still have "eggshell to carry shear stresses, o internal framework to carry axial stress,O Paul A Lagace @2001 Unit 15-3
MIT - 16.20 Fall, 2002 Idealize the cross-section of the shell beam into two parts: • Parts that carry extensional stress, σxx (and thus the bending and axial loads) • Parts that carry shear stress σxs (and thus the shear loads and torques) Two examples again… • high aspect ratio wing with semi-monocoque construction Notes: • monocoque construction • – all in one piece without internal framing • – from French “coque” meaning “eggshell” • – “mono” = one piece • semi-monocoque – stressed skin construction with internal framework – still have “eggshell” to carry shear stresses, σxs – internal framework to carry axial stress, σxx Paul A. Lagace © 2001 Unit 15 - 3
MT-1620 al.2002 Figure 15.2 Representation of wing semi-monocoque construction web flanges spal skin web flanges Stiffeners realize this section as: Figure 15. Idealization of wing semi-monocoque construction Paul A Lagace @2001 Unit 15-4
MIT - 16.20 Fall, 2002 Figure 15.2 Representation of wing semi-monocoque construction web + rib skin stiffeners flanges web flanges = spar Idealize this section as: Figure 15.3 Idealization of wing semi-monocoque construction Paul A. Lagace © 2001 Unit 15 - 4
MT-1620 Fall 2002 Skins and webs are assumed to carry only shear stress o Flanges and stringers are assumed to carry only axial stress Space habitat Figure 15.4 Representation of space habitat semi-monocoque construction flanges wall spar wall stiffeners Idealize as for wing Paul A Lagace @2001 Unit 15-5
MIT - 16.20 Fall, 2002 → Skins and webs are assumed to carry only shear stress σxs → Flanges and stringers are assumed to carry only axial stress σxx • Space habitat Figure 15.4 Representation of space habitat semi-monocoque construction wall wall stiffeners spar flanges Idealize as for wing: Paul A. Lagace © 2001 Unit 15 - 5