Steel Compression Test at room temperature, ASTM E9/E9M

Steel Compression Test at room temperature, ASTM E9/E9M

Introduction

The compression test is one of the vital tests used in the analysis of the mechanical properties of steel. Excellent mechanical properties of materials such as steel are necessary for the sustainability and safety of engineering structures. The compression test of steel helps in the determination of properties such as yield point, the Young’s Modulus of elasticity, compressive strength, and the stress-strain curve. This information is vital in understanding the structural properties of materials, especially for steel subject to bending or compressive loads. This test is also essential for processes involving extreme compressive deformation, for instance, rolling and forging.

Objectives

1. To determine the Modulus of elasticity of steel
2. To determine the proportional limit stress
3. To assess yield strength based on 0.2% yield strain

Theory – the origin of the test.

The compression test for steel is vital in engineering practice. It is mostly based on Hooke’s law, and it was developed by engineers to provide for the testing of the mechanical properties of steel under compression loading. The test has been standardized, and with improved technology, carrying out the test is much efficient today. To conduct the test, one must have a hydraulic universal testing machine or an electromechanical machine with the necessary deflectometer, platens, and software.

Materials

Steel- steel grade 60 ( Yield strength of K0 Psi), AISI 1012 steel.

Apparatus

A micrometer, a compressometer, a hammer, a punch gage, and the compression testing machine.

Calculations

The Modulus of  Elasticity is given by stress/ strain, that is, E = σ / ε

This value can also be calculated as the gradient of the stress-strain graph.

The yield strength is another parameter that is necessary for the compression test of steel. It is defined as the stress at which a predetermined deformation will occur. It is normally determined at the elastic portion of the deformation graph. For steel, the yield strength is often approximated as 0. 2% of the Young’s Modulus of elasticity, that is,

Yield stress = 0.002* E

The stress-strain graph is also key in the compression test. Typical stress-strain graph has the following format:

It explains the relationship between stress and strain I, and it is the basis of understanding the behavior of steel under loading.  From the graph, it is evident that steel undergoes several stages when loaded. These include the proportional limit, the elastic limit, the yield point, the ultimate stress point, and the breaking point. The proportional limit is a key aspect in engineering and overall the ability of steel to withstand certain loads. From the graph, it is the point up to which the relationship between stress and strain remains proportional. This point is sometimes referred to as the proportionality limit.

Discussion

The compression test is vital in engineering in several aspects. The mechanical properties of steel can help in deciding on the various uses of steel. It is worth noting that not all steel is structural, and the use of steel for any purpose is dependent on its mechanical properties. This is the whole essence of the classification of steel into grades. For instance, the steel used in concrete reinforcement is not the steel used in fabrication. The modulus of elasticity and yield strength are two parameters that are always used in steel design calculations, and hence the compression test is a fundamental test om engineering.

Standard values for properties of steel