Problem: polymethyl methacrylate $($PMMA$)$ is used extensively in medicine as

intraocular lenses and as bone cement due to its transparency, excellent

mechanical strength, and toughness. The mechanical properties of PMMA is a

strong function of temperature. The following Figure shows engineering stress

versus engineering strain curves for PMMA in tensile mode at different

temperatures ranging from $4C$ to $60C.$ The numerical values of the stress$-$strain

curves at $4C,40C$ and $50C$ are provided in Table $1.$

From the data in Table $1,$ determine stress $($strength$)$ and strain for the PMMA

at proportional limit$,$ elastic limit$,0\mathrm{.}2\%$ offset yield point, rupture point, modulus of

elasticity and the ultimate strength at the following temperatures.

a$.4C$

b$.50C$

From the data in Table $1,$ graph on the same plot for the PMMA for each

temperature stress$-$strain curves in terms of engineering $($Eng$.)$ stress$-$Eng. strain

and true stress$-$true strain; compare$/$discuss differences between Eng. and true

stress$/$strains for the following temperatures. $($One plot for each temperature$)$

a$.4C$

b$.50C$

From the data in Table $1,$ determine modulus of resilience and modulus of

toughness of the PMMA for the following temperatures.

a$.4C$

b$.50C$