(i) To make an S-N plot, we need to plot stress amplitude (MPa) on the y-axis and logarithmic cycles to failure on the x-axis. Using the given data, we can plot the points as follows:

Stress Amplitude (MPa) Cycles to Failure
310 2 x 10^10
223 1 x 10^19
168 3 x 10^16
153 1 x 10^15
143 3 x 10^14
134 1 x 10^13
127 3 x 10^12

(ii) To determine the fatigue lifetime at a stress amplitude of 200 MPa, we can estimate the cycles to failure at this stress level from the S-N plot. By interpolating between the data points, we can estimate the cycles to failure to be around 5 x 10^14.

(iii) To estimate the fatigue strength at 5 x 10^5 cycles, we can again use the S-N plot. By interpolating between the data points, we can estimate the stress amplitude to be around 150 MPa.

The Coffin-Manson's law determines low cycle fatigue, which states that the plastic strain amplitude is proportional to the logarithm of the number of cycles to failure. The Basquin's law determines high cycle fatigue, which states that the stress amplitude is inversely proportional to the fatigue life.

Crevice corrosion is a localized form of corrosion that occurs in confined spaces or crevices, such as gaps between metal surfaces. It is caused by the restricted access of oxygen and the accumulation of corrosive substances. To control crevice corrosion, measures such as proper design to minimize crevices, regular inspection, and maintenance are necessary.

Passivity is a phenomenon where a metal surface becomes resistant to corrosion due to the formation of a protective oxide layer. This oxide layer acts as a barrier between the metal and the corrosive environment. Two common types of alloys that passivate are stainless steel and aluminum.

Cold-worked metals are more susceptible to corrosion than non-cold-worked metals due to the introduction of dislocations and strain during the cold-working process. These dislocations and strain create sites for corrosion initiation and propagation, leading to increased susceptibility to corrosion.

Question

(i) To make an S-N plot, we need to plot stress amplitude (MPa) on the y-axis and logarithmic cycles to failure on the x-axis. Using the given data, we can plot the points as follows:

Stress Amplitude (MPa)    Cycles to Failure
310                               2 x 10^10
223                               1 x 10^19
168                               3 x 10^16
153                               1 x 10^15
143                               3 x 10^14
134                               1 x 10^13
127                               3 x 10^12

(ii) To determine the fatigue lifetime at a stress amplitude of 200 MPa, we can estimate the cycles to failure at this stress level from the S-N plot. By interpolating between the data points, we can estimate the cycles to failure to be around 5 x 10^14.

(iii) To estimate the fatigue strength at 5 x 10^5 cycles, we can again use the S-N plot. By interpolating between the data points, we can estimate the stress amplitude to be around 150 MPa.

The Coffin-Manson's law determines low cycle fatigue, which states that the plastic strain amplitude is proportional to the logarithm of the number of cycles to failure. The Basquin's law determines high cycle fatigue, which states that the stress amplitude is inversely proportional to the fatigue life.

Crevice corrosion is a localized form of corrosion that occurs in confined spaces or crevices, such as gaps between metal surfaces. It is caused by the restricted access of oxygen and the accumulation of corrosive substances. To control crevice corrosion, measures such as proper design to minimize crevices, regular inspection, and maintenance are necessary.

Passivity is a phenomenon where a metal surface becomes resistant to corrosion due to the formation of a protective oxide layer. This oxide layer acts as a barrier between the metal and the corrosive environment. Two common types of alloys that passivate are stainless steel and aluminum.

Cold-worked metals are more susceptible to corrosion than non-cold-worked metals due to the introduction of dislocations and strain during the cold-working process. These dislocations and strain create sites for corrosion initiation and propagation, leading to increased susceptibility to corrosion.

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