Adam Zaborski Tensile test Politechnika （亚当Zaborski Politechnika拉伸试验）.pdf

Adam Zaborski – handouts for Afghans Tensile test Outline Tensile test purpose Universal testing machines and test specimens Stress-strain diagram Mild steel :  proportional stage,  elastic limit,  yielding plateau, strain hardening,  unloading and reloading,  ultimate strength,  necking stage, fracture Hard steel: conventional proportional limit, conventional yield limit Other structural materials Schematizations of tensile test diagram Adam Zaborski – handouts for Afghans Tensile test purpose The primary use of the testing machine is to create the stress-strain diagram. Tensile test determines the strength of the material subjected to a simple stretching operation. Typically, standard dimension test samples are pulled slowly (static loading) and at uniform rate in a testing machine while the strain ( the elongation of the sample) is defined as: Engineering Strain = = (change in length)/(original length) = /L0 and the stress ( the applied force divided by the original cross-sectional area) is defined as: Engineering Stress = = (applied force)/(original area) =P/A0 The aim of the test is to assess some mechanical characteristics of testing material: its elasticity, ductility, resilience and toughness. There are two kinds of typical diagrams: with distinct yielding limit without distinct yielding limit Adam Zaborski – handouts for Afghans The diagram with distinct yielding limit. In red marked engineering stresses, in blue – true stresses. Adam Zaborski – handouts for Afghans The diagram without distinct yielding limit. Some conventions should be used instead. Adam Zaborski – handouts for Afghans Univ