Accurate characterization of machine compliance for simple compression testing

Abstract

ABSTRACT--Correction for machine compliance is an important step in analyzing the data obtained in many mechanical testing procedures. The difficulties associated with compliance correction, as they apply to the simple compression mode of testing, are explored in this paper. The commonly employed approach is to extend the procedure suggested in the ASTM standards for testing high modulus, single-filament materials, which implicitly assumes that the machine behaves as a linear spring with a constant compliance factor. It is shown in this paper that this approach results in different values for the machine compliance factor for different materials. The nonuniqueness of the machine compliance factor is attributed to the inherent nonlinearity of the machine compliance, i.e., the nonlinear dependence of the nonsample displacement on the applied load. Through a set of mechanical tests on a range of materials, it has been demonstrated that it is necessary to characterize this nonlinear compliance relationship for the machine to obtain accurate and consistent measurements.

On the use of cryomilling and spark plasma sintering to achieve high strength in a magnesium alloy

“…Compression tests were conducted using a Zwick/Roell universal testing machine at a crosshead speed of 0.06 mm/min until failure. All experimental data has been corrected for machine compliance [35]. shows a deformed particle where evidence of cold welding and fracture can be clearly seen, in agreement with other published observations [32].…”

Splitting fracture in bovine bone using a porosity-based spring network model

“…The compliance in the experimental set-up was 2 + 0.2 Â 10 25 mm N 21 , which is of similar order as reported in [53]. Additionally, the predictions of compressive strength from simulations, as described later in §4, were found to be largely insensitive to the minor variations observed in machine compliance.…”

Effect of silica nanoparticles on compressive properties of an epoxy polymer

“…The compliance of the testing machine for compression, based on a technique proposed in [26], was performed to calculate the actual displacement of the specimen. In the 'direct technique' demonstrated by Kalidindi et al [26], the load-displacement relationship for the machine was measured without any specimen between the compression bars. The actual deformation of the sample can then be calculated by subtracting the non-sample displacement of the testing fixture from the total displacement recorded by the actuator.…”