ISSN: 1945-7553
CODEN: JTEVAB
Page Count: 6

Prediction of Specimen Strain from Extensometer Deflection Measurements in a Direct Stress Fatigue Test Specimen under Static Tensile Loading

Arora, PR
Senior Scientific Officer and Professor, Indian Institute of Science, Bangalore,

Raghavan, MR
Senior Scientific Officer and Professor, Indian Institute of Science, Bangalore,

(Received 29 December 1986; accepted 8 January 1988)

Abstract

The displacement between the ridges situated outside the filleted test section of an axially loaded unnotched specimen is computed from the axial load and shape of the specimen and compared with extensometer deflection data obtained from experiments. The effect of prestrain on the extensometer deflection versus specimen strain curve has been studied experimentally and analytically. An analytical study shows that an increase in the slope of the stress-strain curve in the inelastic region increases the slope of the corresponding computed extensometer deflection versus specimen strain curve. A mathematical model has been developed which uses a modified length ¯ℓ_ef in place of the actual length of the uniform diameter test section of the specimen. This model predicts the extensometer deflection within 5% of the corresponding experimental value. This method has been successfully used by the authors to evolve an iterative procedure for predicting the cyclic specimen strain in axial fatigue tests on unnotched specimens.

Keywords:
specimen strain, ridges, test section, extensometer deflection, tensile prestrain, calibration

Paper ID: JTE11082J
DOI: 10.1520/JTE11082J
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