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# Materias

### Strength of Materials 1

Question | Answer |
---|---|

Elasticity & Hooke's Law | Solid Materials deform when they are stressed. as stress increases deformation increases. |

Define Elastic? | When a material returns to its original size and shape on removal of load. |

What is Elastic Limit? | This is a point which is reached when, after the removal of load, not all the induced strain is removed. Usually the end of the linear part of a force strain graph. |

What is Hooke's Law? | Hooke's Law states that providing the limit of proportionality of a material is not exceeded, when a force is applied, the extension is proportional to the applied force. F = k × Dx F is applied force, x is the extension and k is a constant. |

What is Direct Stress? | Direct Stress = Applied Force (F) divided by Cross Sectional Area (A). Units - N/m2, N/mm2, Direct Stress may be Tensile ot Compressive. |

What is Normal Strain? | When loads are applied to a body, some deformation will occur resulting in a change in dimension. Normal Strain = Change in Length Divided by Original Length |

Analysis of a Tensile Stress - Strain graph? | Point A - Proportional Limit - shows the end of the region in which the material exhibits linear stress - strain behaviour. Point B - Elastic limit - permanently deformed even after load is removed. |

Analysis of a Tensile Stress - Strain graph 2 ? | Yield Point (C)- ductile polymer continues to deform without a corresponding increase in stress. Break Point (D)- strain value at which the test bar breaks Ultimate Strength-Point (E). |

Note!! | Stress and Strain relate to the material, while Load and Deformation relate to the Structure. |

What is Young's Modulus? | This is defined as Stress over Strain. Young's Modulus: (F/A)/(CHANGE IN LENGTH/ORIGINAL LENGTH). |

What Happens in Bending of Beams? | When a beam experiences a bending moment it will change its shape and internal stresses will be developed. The material is in Compression on the inside of the Curve of bend and in tension on the outside of the curve. |

How Does Shear Stress work? | Shear stresses are produced by opposite and parallel forces not in line. the forces tend to make one part of the material slide over the other part. shear stress is tangenital to the area over which it acts. |