A specimen of copper having a rectangular cross section \(15.2 \mathrm{~mm} \times 19.1 \mathrm{~mm}(0.60 \mathrm{in} . \times 0.75 \mathrm{in} .)\) is pulled in tension with \(44,500 \mathrm{~N}\left(10,000 \mathrm{lb}_{\mathrm{f}}\right)\) force, producing only elastic deformation. Calculate the resulting strain.

Short Answer

Expert verified
Answer: The resulting strain of the copper specimen is 1.39 × 10^-3.

Step by step solution

01

Recall the stress-strain relationship for an elastic material

In an elastic material, the stress and the strain are linearly related by the Young's modulus (Y). The relationship can be expressed as: $$ \sigma = Y \cdot \epsilon $$ Where \(\sigma\) is the stress, \(\epsilon\) is the strain, and \(Y\) is the Young's modulus.
02

Calculate the stress

To calculate the stress experienced by the specimen, we first need to find the cross-sectional area it. After that, we can use the formula: $$ \sigma = \frac{F}{A} $$ Where \(F\) is the force applied on the specimen and \(A\) is its cross-sectional area. Given the dimensions of the copper specimen in meters: \(15.2 \mathrm{~mm} \times 19.1 \mathrm{~mm} = 0.0152 \mathrm{~m} \times 0.0191 \mathrm{~m}\) The cross-sectional area is: $$ A = 0.0152 \mathrm{~m} \times 0.0191 \mathrm{~m} = 2.9 \times 10^{-4} \mathrm{m^2} $$ Now, given that the tensile force is \(F = 44,500 \mathrm{~N}\), we can calculate the stress: $$ \sigma = \frac{44,500 \mathrm{~N}}{2.9 \times 10^{-4} \mathrm{m^2}} = 1.53 \times 10^8 \mathrm{~Pa} $$
03

Calculate the strain

Now that we have the stress, we can find the strain using the stress-strain relationship. The Young's modulus for copper is \(Y = 11 \times 10^{10} \mathrm{~Pa}\). We can rearrange the formula to solve for the strain: $$ \epsilon = \frac{\sigma}{Y} $$ Calculating the strain using the given values: $$ \epsilon = \frac{1.53 \times 10^8 \mathrm{~Pa}}{11 \times 10^{10} \mathrm{~Pa}} = 1.39 \times 10^{-3} $$ The resulting strain of the copper specimen is \(1.39 \times 10^{-3}\).

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Most popular questions from this chapter

As noted in Section \(3.15\), for single crystals of some substances, the physical properties are anisotropic that is, they depend on crystallographic direction. One such property is the modulus of elasticity. For cubic single crystals, the modulus of elasticity in a general \([u v w]\) direction, \(E_{\text {uww }}\) is described by the relationship $$ \begin{aligned} \frac{1}{E_{u v w}}=& \frac{1}{E_{(100)}}-3\left(\frac{1}{E_{(100)}}-\frac{1}{E_{\\{111)}}\right) \\\ &\left(\alpha^{2} \beta^{2}+\beta^{2} \gamma^{2}+\gamma^{2} \alpha^{2}\right) \end{aligned} $$ where \(E_{\\{100)}\) and \(E_{\langle 111\rangle}\) are the moduli of elasticity in the \([100]\) and \([111]\) directions, respectively; \(\alpha, \beta\), and \(\gamma\) are the cosines of the angles between \([u v w]\) and the respective [100], [010], and [001] directions. Verify that the \(E_{\\{110\rangle}\) values for aluminum, copper, and iron in Table \(3.4\) are correct.

A cylindrical specimen of steel having a diameter of \(15.2 \mathrm{~mm}(0.60\) in.) and length of 250 \(\mathrm{mm}(10.0 \mathrm{in} .)\) is deformed elastically in tension with a force of \(48,900 \mathrm{~N}\left(11,000 \mathrm{lb}_{e}\right)\). Using the data contained in Table \(6.1\), determine the following: (a) The amount by which this specimen will elongate in the direction of the applied stress. (b) The change in diameter of the specimen. Will the diameter increase or decrease?

In Section \(2.6\), it was noted that the net bonding energy \(E_{N}\) between two isolated positive and negative ions is a function of interionic distance \(r\) as follows: $$ E_{N}=-\frac{A}{r}+\frac{B}{r^{n}} $$ where \(A, B\), and \(n\) are constants for the particular ion pair. Equation \(6.31\) is also valid for the bonding energy between adjacent ions in solid materials. The modulus of elasticity \(E\) is proportional to the slope of the interionic force-separation curve at the equilibrium interionic separation; that is,Derive an expression for the dependence of the modulus of elasticity on these \(A, B\), and \(n\) parameters (for the two-ion system), using the following procedure: 1\. Establish a relationship for the force \(F\) as a function of \(r\), realizing that $$ F=\frac{d E_{N}}{d r} $$ 2\. Now take the derivative \(d F / d r\). 3\. Develop an expression for \(r_{0}\), the equilibrium separation. Because \(r_{0}\) corresponds to the value of \(r\) at the minimum of the \(E_{N}\)-versus- \(r\) curve (Figure 2.10b), take the derivative \(d E_{N} / d r\), set it equal to zero, and solve for \(r\), which corresponds to \(r_{0}\) - 4\. Finally, substitute this expression for \(r_{0}\) into the relationship obtained by taking \(d F / d r\).

Consider a metal single crystal oriented such that the normal to the slip plane and the slip direction are at angles of \(60^{\circ}\) and \(35^{\circ}\), respectively, with the tensile axis. If the critical resolved shear stress is \(6.2 \mathrm{MPa}\) (900 psi), will an applied stress of 12 MPa (1750 psi) cause the single crystal to yield? If not, what stress will be necessary?

A brass alloy is known to have a yield strength of \(240 \mathrm{MPa}(35,000\) psi), a tensile strength of \(310 \mathrm{MPa}(45,000 \mathrm{psi})\), and an elastic modulus of 110 GPa \(\left(16.0 \times 10^{6}\right.\) psi). A cylindrical specimen of this alloy \(15.2 \mathrm{~mm}(0.60 \mathrm{in}\).) in diameter and \(380 \mathrm{~mm}(15.0\) in.) long is stressed in tension and found to elongate \(1.9 \mathrm{~mm}(0.075\) in.). On the basis of the information given, is it possible to compute the magnitude of the load necessary to produce this change in length? If so, calculate the load; if not, explain why.

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