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Chapter 8: Problem 13

Following is tabulated data that were gathered from a series of Charpy impact tests on a tempered 4140 steel alloy. $$ \begin{array}{rc} \hline \text { Temperature }\left({ }^{\circ} \boldsymbol{C}\right) & \text { Impact Energy }(\boldsymbol{J}) \\ \hline 100 & 89.3 \\ 75 & 88.6 \\ 50 & 87.6 \\ 25 & 85.4 \\ 0 & 82.9 \\ -25 & 78.9 \\ -50 & 73.1 \\ -65 & 66.0 \\ -75 & 59.3 \\ -85 & 47.9 \\ -100 & 34.3 \\ -125 & 29.3 \\ -150 & 27.1 \\ -175 & 25.0 \\ \hline \end{array} $$ (a) Plot the data as impact energy versus temperature. (b) Determine a ductile-to-brittle transition temperature as that temperature corresponding to the average of the maximum and minimum impact energies. (c) Determine a ductile-to-brittle transition temperature as that temperature at which the impact energy is \(70 \mathrm{~J}\).

Short Answer

Expert verified
Answer: The estimated ductile-to-brittle transition temperature can be obtained from a graph plotted with the given data. Using the method of average impact energy (57.15 J), the estimated transition temperature can be found. Similarly, the temperature at which the impact energy is 70 J can also be determined from the graph.

Step by step solution

01

Plot the data

Create a graph with Temperature on the x-axis and Impact Energy on the y-axis. Plot all the given data points (Temperature, Impact Energy) from the table into the graph.
02

Calculate the average of maximum and minimum impact energies

From the table, find the maximum and minimum impact energies, then calculate their average Maximum Impact Energy: 89.3 J (at 100°C) Minimum Impact Energy: 25.0 J (at -175°C) Average Impact Energy: \(\frac{89.3 + 25.0}{2} = 57.15 J\)
03

Estimate the ductile-to-brittle transition temperature from the average impact energy

Now that we have calculated the average impact energy, we need to find the temperature value corresponding to this impact energy from our graph. Estimate the value of the temperature at an impact energy of 57.15 J. This temperature will be our ductile-to-brittle transition temperature for the method of average impact energy.
04

Determine the temperature at which impact energy is 70 J

From our graph, locate the data point where the impact energy is 70 J, and estimate the temperature at that point. This temperature value will be our ductile-to-brittle transition temperature at 70 J of impact energy.

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Most popular questions from this chapter

Give the approximate temperature at which creep deformation becomes an important consideration for each of the following metals: nickel, copper, iron, tungsten, lead, and aluminum,

An aircraft component is fabricated from an aluminum alloy that has a plane strain fracture toughness of \(35 \mathrm{MPa} \sqrt{\mathrm{m}}(31.9 \mathrm{ksi} \sqrt{\text { in. }})\). It has been determined that fracture results at a stress of \(250 \mathrm{MPa}\) (36,250 psi) when the maximum (or critical) internal crack length is \(2.0 \mathrm{~mm}\) (0.08 in.). For this same component and alloy, will fracture occur at a stress level of \(325 \mathrm{MPa}\) (47,125 psi) when the maximum internal crack length is \(1.0 \mathrm{~mm}(0.04\) in.)? Why or why not?

Cite five factors that may lead to scatter in fatigue life data.

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