Mechanical Properties of Piping Materials

Introduction

          The primary objective of study properties of piping materials is to provide an piping engineer with tools of analyzing and designing piping components. To determine the suitability of a material under the given loading conditions requires the knowledge of various types of stresses incurring on the components as well as the mechanical properties of the materials. No material can possess all the  desired properties in one material. Depending upon the requirements, sometimes a compromise may have to be made while choosing a particular material for a part of a machine and Piping. This blog describes some of the properties most commonly to determine these properties.

        The main properties of materials are as follows:  

Ductility

        It is the property of a material by virtue of which it can be drawn into wires under the action of tensile force. A ductile material must have a high degree of plasticity and strength so that large deformations can take place without failure or rupture of the material. In ductile exhibits a certain amount of elasticity along with a high degree of plasticity.

Brittleness

       It is opposite to ductility, i.e., when a material. Cannot be drawn out by tension to smaller sections. A brittle fails instantly under the load with out exhibiting any significant deformation. Examples of brittle materials are cast iron, concrete, glass, stone, etc. 

Malleability

       This property of a material allows it to expand in all directions without rupture. A malleable material has to be highly plastic, though it may not possess high strength. This property is of great use in processes such as forging, hot rolling, etc.

Hardness

       The resistance of a material to indentation including scratching or surface abrasion is termed as hardness.

Strength

       It may be defined as the capability of a material to withstand load. It is obtained by divided the load by area. The ultimate strength of material is the load. Required to cause fracture divided by the area of the test specimen.

Toughness

       It is the capacity of a structure to withstand an impact load, i.e.., the capacity to absorb without fracture. It depends upon the ductility of a material and its ultimate strength. toughness is represented by the area under the stress- strain diagram and is the energy per unit volume required to cause the material to rupture. This property is highly desirable in components subject to shock or cyclic loading. A general test for toughness is the bend test in which the capability of a material is tested for angular bending.

Fatigue

       When loading are repeated thousands or millions of times, rupture occurs at a stress much below the static breaking strength. This phenomenon is known as fatigue. Consideration of fatigue is an integral part of design if the structural or machine components are subjected to fluctuating or repeated loads.

Creep

       If the stress in a material exceeds the yield point, the strain caused in the material by the application of load does not disappear totally on the removal of load. The plastic deformation caused to the material is known as creep. At high temperatures, the strain due to creep is quite appreciable.

       More detail about the creep is already covered in article; Time Dependent Stresses: Creep