Exam experience and Swipe Cards - SoSe 24

  • Hi there,

    I took the exam in Lightweight engineering I this summer term and want to share my experience regarding the exam. All the questions asked in the exam could be found in the "Leichtbau 1 Fragen und Antworten" Document. There is also a translated variant of the document. Notable Questions were the following:

    • Know about the unkowns in a 3D static problem
    • Know the 15 required equations and be able to write them down and explain them
    • Characteristics of Plates and Discs
    • 3D Material law
    • Know the following symmetries (Name, Behaviour -> coupling, Symmetry planes, example): Anisotropy, Monotropy, Orthotropy, Transverse Orthotropy, Isotropy.

    • Know Euler-Bernoulli and Timoshenko beam theory, and be able to point out the differences
    • Know Integrals for Static Moments and Area moments of ineratia --> What happens in the 1st and 2nd cross-sectional normalization? --> Be able to draw the circle of Moments of Inertia (Deviation moment = 0 in principal axis system, Iyy and Izz are min and max)
    • Know normal stresses in Euler - Bernoulli beam based on load and geometry and be able to integrate bending line from constitutive law in Euler-Bernoulli beam
    • Know DOF in Timoshenko
    • Know why we need a shear correction factor (constant shear) and how it is determined (comparison shear deformation energy) --> Be able to give internal shear deformation energy integral and K for a rectangular cross section (5/6)!

    • Know the formula for shear flow in a open cross section. Be able to argue why it is zero at the free edge (argue via Static Moment = 0 at free edge)
    • Be able to draw static moment and shear flow for presented cross sections
    • Know how to calculate shear flow in a closed cross section (displacement discontinuity...)
      From the last exams, people reported that they had to draw the opened cross section, and know about the displacement discontinuity calculation and compatibility requirement. I didn´t had to do so.
    • Know what the shear center is (resultant Moment equates to zero), know the technical relevance (Apply load in shear center to avoid unwanted torsion) --> Be able to locate shear center for presented profiles.

    • Know assumptions in torsion and why torsional stresses in open cross sections is much higher (also know factor 3Rm/t!)
    • Know constitutive law for St. Venant torsion and Bredts 1st formula for shear flow
    • How can It be calculated (Know integral)? And how can it be done for a multicellular cross section (same theta' --> Sum of It over cells) --> Be prepared to do this for an I beam, therefore you need to know It for a rectangular cross section and then add them up.
    • Be prepared to explain warping torsion and issues caused.
    • Be able to explain omegaD and what it is used for, Be further able to give integral formulation of omegaD
    • Be able to draw warping torsion in an I beam and explain why the web doesnßt experience warping torsion (no lever arm)

    • Know what Flexural torsional buckling is (DOF, Behaviour with and without symmetries, driving cause - excentricities, guiding differential equations)
    • Be able to give boundary conditions for a fork support and Ansatzes used for flexural torsional buckling
    • Bonus if you can give buckling condition for flexural torsional buckling (But at least know it´s 3rd order and describe behaviour under symmetries)
    • Be able to draw buckling modes for C-cross sections
    • No lateral buckling in my exam

    The communication and atmosphere were really good as described by the previous protocolls. Be prepared, Mr. Mittelstedt knows his stuff, so he will notice if you are not firm!

    Swipecards I used to learn for the exam: https://app.buffl.co/join/course/c4…2d-4525c7399432

    Best regards and best of luck!