Stress in piping system must be analyzed to know the strength of overall pipe and its components. Stress analysis is required to determine material strength against all of load which occurs in piping system. Stress will be most important parameter to know the strength of material. These parameters can be known by testing material strength and show it into graphic diagram stress and strain. Generally there are two types of stress-strain diagram; stress-strain diagram for mild steel and brittle steel. Both figures can be seen below.
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| Figure 1: Stress-Strain Diagram |
On both figures above, there is straight line profile at the beginning of loading which indicate the existence of elastic deformation phenomenon in steel material. The end point of this straight line is called the yield point. Phenomenon of plastic deformation is initiated by curvature of the curve which can be known as ludders band. The highest point on the stress-strain diagram shows the ultimate strength of material. The ultimate point is a stress value of steel material at begin experience phenomenon of necking. The end boundary point in diagram show the failure point of material and show stress value when material begins to crack.
There are differences of curve characteristic in mild steel and brittle steel. It is influenced by properties of both materials. Mild steel tend to has relatively long strain in the elastic region and plastic region, while brittle steel tend to has relatively short strain. In the piping system, it is used as the basic consideration to select pipe material with optimum performance.