---
# System prepended metadata

title: Compressive stress & Tensile stress
tags: [Materials Mechanics, Mechanical Mechanics]

---

# Compressive stress & Tensile stress
## Stress and strain
**Type of Stress**
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* Tensile stress
* Compressive stress
* Shear stress
* Bending
* Torsion
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$$\text{Stress} = \frac FA$$

$$\sigma = \frac PA$$

unit :
* $1 MPa = 10^6Pa = 10^6N/m^2 = 1N/mm^2$
* $1 GPa = 10^9Pa = 10^3N/mm^2 = 1kN/mm^2$
* $1Pa = 1.02\times 10^{-5}kg/cm^2$
* $1MPa = 10.2kg/cm^2$
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$$\text{strain} = \frac{dL}{L}$$

$$\varepsilon = \frac\delta L$$
## Elastic modulus
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$$E = \frac{P/A}{\delta/L} = \tan(\theta)$$

$$\sigma = E\varepsilon$$

$$\delta = \frac{PL}{AE}$$
## Internal Force
$$\sum F_{int} = F_{int_1}+F_{int_2}+...+F_{int_n} = 0$$
## Safety Factor
$$SF > 1$$
* Ductile Materials
$$SF_{DM} = \frac{\text{Yield stress}}{\text{Allowable stress}}$$
* Brittle materials
$$SF_{BM} = \frac{\text{Ultimate stress}}{\text{Allowable stress}}$$