Internal Residual Stresses

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Questions and Answers

Given the equation $\sqrt{3} \tan(2\theta) + \sqrt{3} \tan(3\theta) + \tan(2\theta)\tan(3\theta) = 1$, what is the general value of $\theta$?

  • $(n + \frac{1}{3})\frac{\pi}{5}$ (correct)
  • $n\pi + \frac{\pi}{5}$
  • $(n + \frac{1}{6})\frac{\pi}{5}$
  • $(2n \pm \frac{1}{6})\frac{\pi}{5}$

Determine $\theta$ if $\tan(\theta) + \tan(2\theta) + \tan(\theta)\tan(2\theta) = 1$.

  • $\frac{n\pi}{2} + \frac{\pi}{6}$ (correct)
  • $\frac{n\pi}{2} + \frac{\pi}{12}$
  • $\frac{n\pi}{2} + 6$
  • $\frac{n\pi}{3} + \frac{\pi}{12}$

If $2\tan^2(\theta) = \sec^2(\theta)$, find the general value of $\theta$.

  • $n\pi - \frac{\pi}{4}$
  • $n\pi \pm \frac{\pi}{4}$ (correct)
  • $2n\pi \pm \frac{\pi}{4}$
  • $n\pi + \frac{\pi}{4}$

What is the general solution of the equation $\tan(\theta)\tan(2\theta) = 1$?

<p>$n\pi \pm \frac{\pi}{6}, n \in I$ (C)</p> Signup and view all the answers

Given $\cos(\theta) + \cos(7\theta) + \cos(3\theta) + \cos(5\theta) = 0$, find the value of $\theta$.

<p>$\frac{n\pi}{4}$ (B)</p> Signup and view all the answers

If $\tan(30) + 1 = \sqrt{3}$, what is the general form of the solution?

<p>$n\pi + \frac{\pi}{12}$ (B)</p> Signup and view all the answers

What is the value of $x$ in the equation $\sin(3\alpha) = 4\sin(\alpha)\sin(x + \alpha)\sin(x - \alpha)$?

<p>$n\pi \pm \frac{\pi}{3}$ (C)</p> Signup and view all the answers

Determine the value of $\theta$ that satisfies the equation $\tan(\theta) + \tan(20) + \tan(\theta)\tan(20) = 1$.

<p>$\frac{n\pi}{2} + \frac{\pi}{6}$ (D)</p> Signup and view all the answers

Find the general solution for $\theta$ in the equation $2\tan^2(\theta) = \sec^2(\theta)$.

<p>$n\pi \pm \frac{\pi}{4}$ (C)</p> Signup and view all the answers

What is the general solution to the equation $\tan(\theta)\tan(2\theta) = 1$, where $n \in I$?

<p>$n\pi \pm \frac{\pi}{6}$ (C)</p> Signup and view all the answers

Determine the value of $x$ if $\sin(3\alpha) = 4\sin(\alpha)\sin(x + \alpha)\sin(x - \alpha)$.

<p>$n\pi \pm \frac{\pi}{3}$ (D)</p> Signup and view all the answers

If $\cos(\theta) + \cos(7\theta) + \cos(3\theta) + \cos(5\theta) = 0$, then what is $\theta$?

<p>$\frac{n\pi}{4}$ (A)</p> Signup and view all the answers

If $\sqrt{3} \tan{20} + \sqrt{3} \tan{30} + \tan{20} \tan{30} = 1$, find the general value of $\theta$.

<p>$(n + \frac{1}{3})\frac{\pi}{5}$ (B)</p> Signup and view all the answers

Determine the value of $\theta$ satisfying $\tan(\theta) + \tan(20) + \tan(\theta)\tan(20) = 1$.

<p>$\frac{n\pi}{2} + \frac{\pi}{6}$ (B)</p> Signup and view all the answers

Solve for the general value of $\theta$ given $2\tan^2(\theta) = \sec^2(\theta)$.

<p>$n\pi \pm \frac{\pi}{4}$ (D)</p> Signup and view all the answers

Given $\tan(\theta)\tan(2\theta) = 1$, identify the general solution.

<p>$n\pi \pm \frac{\pi}{6}, n \in I$ (C)</p> Signup and view all the answers

If $\sin(3\alpha) = 4\sin(\alpha)\sin(x + \alpha)\sin(x - \alpha)$, find $x$.

<p>$n\pi \pm \frac{\pi}{3}$ (B)</p> Signup and view all the answers

Given that $\tan(30) + 1 = \sqrt{3}$, what is the general solution?

<p>$n\pi + \frac{\pi}{12}$ (A)</p> Signup and view all the answers

Flashcards

General solution of ( \tan \theta \tan 2\theta = 1 )

The general solution is ( n\pi \pm \frac{\pi}{6} ), where ( n ) is an integer.

General value of ( \theta ) if ( 2\tan^2 \theta = \sec^2 \theta )

The general value of ( \theta ) is ( n\pi \pm \frac{\pi}{4} ), where ( n ) is an integer.

Value of ( x ) if ( \sin 3\alpha = 4 \sin \alpha \sin (x + \alpha) \sin (x - \alpha) )

After solving, ( x = n\pi \pm \frac{\pi}{3} ) where ( n ) is an integer.

Study Notes

  • Internal residual stresses exist within a material or object without external loads or forces.
  • These stresses can be either beneficial or detrimental.
  • The impact depends on their magnitude, distribution, and whether they are compressive or tensile.

Origin of Internal Residual Stresses

  • Non-uniform plastic deformation: Uneven plastic deformation leads to internal stresses to maintain material compatibility.
  • Heat treatments: Processes like quenching and tempering create internal stresses due to temperature differences and phase transformations.
  • Phase transformations: Volume changes during transformations (e.g., martensitic in steels) can generate internal stresses.
  • Welding: Generates residual stresses from the weld metal's contraction and temperature variations.
  • Machining: Induces surface stresses due to plastic deformation from the cutting tool.
  • Other processes such as rolling, extrusion, forging and shot peening.

Effects of Internal Residual Stresses

  • Fatigue resistance: Compressive surface stresses enhance fatigue resistance, while tensile stresses reduce it.
  • Corrosion resistance: Stresses can influence corrosion rates, accelerating it in areas with tensile stress.
  • Dimensional stability: Internal stresses may cause instability, leading to deformation over time.
  • Fracture resistance: Affects fracture resistance by altering crack initiation probabilities.
  • Behavior under load: Stresses impact how a material behaves under load by changing the stress and strain distribution.

Measuring Internal Residual Stresses

  • Destructive methods: These methods involve partly or completely destroying the material to measure the internal stresses, like the hole drilling, layer removal, and dissection methods.
  • Non-destructive methods: These methods measure the internal stresses non-invasively without destroying the material Some examples are X-ray diffraction, ultrasonic method, and magnetoelastic method.

Methods for Reducing or Redistributing Internal Residual Stresses

  • Heat treatments: Annealing and tempering reduce stress by allowing the material to relax.
  • Vibration: Reduces stress by facilitating dislocation movement.
  • Shot peening: Compressive surface stresses are introduced, which increases resistance to fatigue and corrosion.
  • Stretching: Controlled plastic deformation is used to reduce existing stresses.

Examples of Internal Residual Stress Applications

  • Surface hardening of steels: Compressive stresses are created on the surface, thus increasing resistance to fatigue and wear.
  • Shot peening aircraft components: Increases fatigue resistance and reduces failure.
  • Pre-stressed concrete: Introduces compressive stresses, which enhances tensile strength and allows lighter structures to be built.

Summary

  • Understanding the source, effects, measurement, and control allows them to be used beneficially which minimizes failures.

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