# Yield strength

**the yield strength** RH indicates the border, up to that duktile materials for course with one axle and moment-free without lasting plastic deformation „stretched “and/or. to be stretched can.

With exceeding of the yield strength the material returns to discharge no more to the original form, butit remains a plastic sample extension.

The yield strength is usually determined by the traction test.

With steel with smaller or to no alloy the yield strength is to be specified because of the Cotrollschen effect not clearly, it therefore also pronounced yield strength is called. Therefore a lower and an upper become frequentYield strength (<math> Re_L< /math> and <math> Re_H< /math>) fixed. The upper yield strength is the load, with which the steel is for the first time plastic deformed. Instead of exhibiting a constriction immediately, the tension oscillates briefly in favor of a stronger stretch. The measured tension smallest thereby is the point of the lower yield strength.

For technical materials usually not the yield strength, but the 0.2% becomes - elongation limit <math> Rp_0, _2< /math> indicated, since she (contrary to the yield strength) can be determined always clearly from the stress-strain curve. The 0.2% - Elongation limit is that mechanical stress (with one axle), with that on the initial length thatSample referred lasting stretch after discharge exactly 0.2% amounts to.

## upper yield strength

**the upper yield strength (deer)** is the tension, with which a plastic deformation without rise of the load occurs for the first time. It designates thus the end of the flexible solidification. The upper yield strength becomesindicated in N/mm ².

## lower yield strength

**the lower yield strength (ReL)** is the smallest tension in the range of the plastic deformation of the inspection piece, thus following the upper yield strength **(deer)**. The lower yield strength is indicated in N/mm ².

## 0,2%-Dehngrenzen of common materials

Aluminum - alloys (approximate values)

Al99.5 | 40 N/mm ² |

AlMg1 | 100 N/mm ² |

AlMg3 | 120 N/mm ² |

AlMg4.5Mn | 150 N/mm ² |

AlMgSi0.5 | 190 N/mm ² |

AlZnMgCu1.5 | 450 N/mm ² |

S235JR | 235 N/mm ² |

S355 | 355 N/mm ² |

E360 | 360 N/mm ² |

BSt 450 | ,450 N/mm ² |

BSt 500 | 500 N/mm ² |

sp 1370/1570 | 1370 N/mm ² |

sp 1570/1770 | 1570 N/mm ² |

Heat treatable steels

C22 | 340 N/mm ² |

C45 | 490 N/mm ² |

C60 | 580 N/mm ² |

42CrMo4 | 900 N/mm ² |

34CrNiMo6 | 1000 N/mm ² |

Case-hardening steels

C10E | 430 N/mm ² |

16MnCr5 | 630 N/mm ² |

18CrNiMo7-6 | 830 N/mm ² |

with still higher load the breaking point is exceeded and the material tears orbreaks (see tensile strength).

See also: Traction test, stress-strain curve