assignment

1. HW 7
1. If I see log N in the graph, it is a “S N diagram”. Dotted line is the
endurance limit
2. Factors that affect the fatigue properties of a material are surface
stress concentration, treatment, roughness, chemical
environment( surface imperfection).
3. Kic=Y(sigma)sqrt(pi*a); Kic=plane strain fracture toughness;
Y=parameter that is given; sigma= max stress;a=largest surface
crack; convert everything to meters. If sigma<given stress, then it will
fracture. Oppositeit will not fracture.
4. B and c, use interpolation for both. d=d1+((g-g1)/(g2-g1))(d2-d1); g is
given value, d is what you want to find.
5. Min creep rate= E2-E1/(t2-t1); you pick two points on the graph that
are close to each other.
6. (10^3)T(20+logt) is the formula given on the chart; t is the time in
hours, has to be in hours; T is the temp, keep in kelvin. Once I
calculate it, I match the point on the graph and that is my stress for
that amount of hours.
HW 8
1. From a complete P-T phase diagram of iron, one can find the melting
temp at 1atm pressure
2. The equilibrium line (phase boundary) in a P-T phase diagram of a
metal indicates the Maximum allowance of two phases
3. Pure iron is processed to the conditions at the α-γ-ε triple point. How many degree
of freedom in this system? 0
4. The figure below shows the cooling curve of Copper(Cu); on the
“liquid and solid” phase, if it is a straight line, it is a pure substance
If its on the top it’s a liquid, if it is inside the lines, it’s a mixture of liquid
and solid, and if it is on the bottom, it is a solid.
Composition is the percentages.
Weight fraction: Xl=1, Xs=0. For solid and liquid: Xl=(Ws-Wo)/(Ws-
Wl), Xs=1-Xl. For Solid: Xs1=Xl, Xs2=Xs
5. 4. You memerized the pictures.
6. 5. Gotthat from point (a) 80% Cu, 20% Ni
7. 6. Higher temp=higher melting point
8. 7. The alloy has the higher yield strength

2. 3. Phases are easy. Compositions are the %s. Liquid is given, Solid+liquid
is the alpha line, given 7.9% on the opposite side. Make sure you have two
sets of percentages for both solid and liquid for both samples. EX alpha is
7.9%Ag 92.1% Cu, lambda is 50%Ag 50%Cu. The 3rd Phase has an alpha
alpha beta. Good Luck.
HW 9
A TTU diagram is a time-temperature-transformation diagram
Heat to above 700, salt bath to 600, keep at 600 to whatever time you choose,
quench. The result is on the chart.
HW10
A galvanized cell consists of an electrode of Zn in a .01 ZnSl solution
and….. There is chart that is given on a separate paper.
The formula: E=E^o+((.0592)/n)*logC; n is the # of solutions, E^o is on the
paper, and C is given in the problem. After getting both values, you should
see which one is bigger, switch the sign and add bothvalues together for
Etotal.