Dissemination of IT for the Promotion of Materials Science (DoITPoMS)

DoITPoMS Teaching & Learning Packages Optimisation of Materials Properties in Living Systems Questions
Optimisation of Materials Properties in Living Systems AimsBefore you startIntroductionYoung´s Modulus - Density selection mapStrength - Density selection mapYoung´s Modulus - Strength selection mapToughness - Young´s Modulus selection mapComparison of engineering materials and biomaterialsSummaryQuestionsGoing further
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Questions

Quick questions

You should be able to answer these questions without too much difficulty after studying this TLP. If not, then you should go through it again!

  1. Looking at the specific modulus - specific strength map for biomaterials, which material gives the greatest maximum elastic strain energy per unit mass?

    a cellulose
    b viscid silk
    c muscle
    d elastin

  2. For which engineering application does the best steel perform better than the best aluminium alloy?

    a Minimum elastic extension on loading a tie of given mass and length in tension.
    b Minimum deflection on bending a beam of given mass, with the cross-sectional area of the beam as a free parameter.
    c Greatest maximum elastic strain energy per unit volume
    d Strongest on loading a beam of a given mass in tension, with the cross-section of the beam as a free parameter.

  3. Why is it favourable for viscid silk to have a high value of the merit index ?

    a so that the silk worm's cocoon will not be easily damaged during the silk worms transition to a moth.
    b to absorb elastically the kinetic energy of a fly hitting the web.
    c to enable silk worms to easily break out of their cocoon.
    d so that the fly gets entangled in the capture threads of the spider's web.

  4. Looking at the materials-selection chart toughness-Young's modulus for biomaterials, which of the listed biomaterials has the greatest fracture toughness, Kc?

    a Antler
    b Skin
    c Calcite
    d Cork

  5. Why would diamond not be used as a material that gives the minimum extension for loading a beam of given mass in tension?

    a It has low strength and so would break too easily.
    b It is too expensive.
    c It has a low value of the merit index .
    d It has too great a mass.

  6. Which of the listed commonly used engineering materials will show the minimum deflection on bending a beam of given mass with the cross-sectional area of the beam as the free parameter (i.e. which material has the maximum value)?

    a Aluminium alloys.
    b Steels.
    c Alumina.
    d Polyethylene (HDPE and LDPE).

Deeper questions

The following questions require some thought and reaching the answer may require you to think beyond the contents of this TLP.

  1. Derive the merit index for the maximum elastic strain energy per unit volume .

  2. (...continued from previous question) Now derive the merit index for the maximum elastic strain energy per unit mass .

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