Modular correction method of bending elastic modulus based on sliding behavior of contact point

Abstract

During the three-point bending test, the sliding behavior of the contact point between the specimen and supports was observed, the sliding behavior was verified to affect the measurements of both deflection and span length, which directly affect the calculation of the bending elastic modulus. Based on the Hertz formula to calculate the elastic contact deformation and the theoretical calculation of the sliding behavior of the contact point, a theoretical model to precisely describe the deflection and span length as a function of bending load was established. Moreover, a modular correction method of bending elastic modulus was proposed, via the comparison between the corrected elastic modulus of three materials (H63 copper–zinc alloy, AZ31B magnesium alloy and 2026 aluminum alloy) and the standard modulus obtained from standard uniaxial tensile tests, the universal feasibility of the proposed correction method was verified. Also, the ratio of corrected to raw elastic modulus presented a monotonically decreasing tendency as the raw elastic modulus of materials increased.

Measurement error of Young’s modulus considering the gravity and thermal expansion of thin specimens forin situtensile testing

“…The ideal gage length of the C11000 Cu specimen l o is 72 mm, and after mechanical polishing using a Bni62 ultraprecision polishing machine, a thin specimen is obtained with a thickness of 10.6 μm. As shown in figure 7(a), the absolute value of the tested deflection of the midpoint | f omax | is 5.67 ± 0.63 mm, which is close to the theoretical | f omax | of 6.05 mm on the basis of the calculation method shown in equation (5). The tested deflec tions of the specimen with an axial interval distance of 6 mm are also close to the respective theoretical values.…”

“…As is well known, Young's modulus is an important mechani cal parameter and of great value in materials development and engineering design [1][2][3][4][5]. Young's modulus measured by uniax ial tensile testing is affected by many inevitable factors, such as misalignment of the tensile axis [6][7][8][9], initial residual stress [10] and clamping position [4].…”

Correction method for mechanical performance testing instrument with tension–torsion coupling loading

“…The strain of the miniaturized specimen cannot be measured using the extensometer in accordance with the common standards, such as ASTM E8/E8M [13], because of space limitation. According to [14,21,22,24], the mechanical properties calculated from small specimens present a significant deviation.…”

“…To obtain credible properties by such device, the measured curves must be corrected. However, correction methods that have been reported on previously [21][22][23][24] mainly focus on the uniaxial tension testing while ignoring torsion testing and tensiontorsion coupling testing. The measuring error is also related to the shape of the specimen.…”