Load Cell Ringing in High Rate Compression Tests

Flow stress is the most important information for hot strip rolling as it affects the rolling force and the thickness of the rolled product. A high-speed compression test up to a strain rate of 300 s − 1 , which is the compression speed of 3 600 mm•s − 1 for a 12-mm-high cylindrical specimen, is necessary as a strain rate of 100-300 s − 1 is the normal rate in the production of hot-strip-rolled steel sheets. An experiment is conducted using a servo-hydraulic compression test machine, which enables a high compression speed and a high temperature, but the oscillation is observed in stress-strain curve at high strain rate over 50 s − 1. To determine the natural frequency of the compression test machine, the Savitzky-Golay filtering method is used for regression and the fast Fourier transformation (FFT) is adopted. To explain the mechanism of this phenomenon, a spring-mass-damper model is used and the results are compared with the FFT analysis result. After eliminating oscillation on the time versus load curve, a flow curve is obtained by inverse analysis, which compensates for the nonuniform strain rate, the inhomogeneous distribution of deformation, and the temperature increase during deformation.

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“…Accordingly, the ram is programmed to be accelerated in the run-up. Solving the above equation, we obtain the following formulation: 11,19)…”

Section: Stress Oscillation Modelmentioning

confidence: 99%

Flow Stress Measurement and Dynamic Response Analysis of Hot Compression Test Machine at High Strain Rates

et al. 2020

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“…The experimental forces along the two perpendicular directions are measured by deformation gauge load sensors. (11) where p and q are the numbers of points to be averaged in each direction and t is the time. Here, the average strains are calculated for p = q = 3, corresponding to a square area defined by .…”

Section: Testing Specimen and Experimentsmentioning

confidence: 99%

“…Various dynamic tests have been performed to identify strain rate dependent hardening law in the intermediate strain rate range. For dynamic tests, depending on the initial impact velocity at the beginning of the test, an oscillation phenomenon of the force signal measured by the load cell, called as loading ringing [11], can be observed. Those variations of the experimental force can be induced by the propagation of an elastic stress or strain wave or by the vibratory response of mechanical parts of the experimental device [12].…”

Section: Introductionmentioning

confidence: 99%

Identification of strain rate-dependent mechanical behaviour of DP600 under in-plane biaxial loadings

Liu

Guines

Leotoing

et al. 2016

Materials Science and Engineering: A

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International audienceThe rate-dependent hardening behaviour of dual phase DP600 steel sheet is investigated by means of in-plane biaxial tensile tests, in an intermediate strain rate range (up to 20 s−1) and for large strains (up to 30% of equivalent plastic strain) at room temperature. The dynamic biaxial in-plane tensile tests are performed on a dedicated cruciform specimen shape previously developed and validated for large strains at quasi-static conditions. To perform dynamic biaxial tensile tests, a specific device is used to reduce oscillations on measure of forces. Based on these experiments, parameters of two phenomenological strain-rate hardening models (saturated and power law), are identified. Material parameters are obtained from an optimisation process, based on the finite element modelling of the biaxial test, by minimising differences between experimental and simulated principal strains at the specimen centre. A comparison of the strain hardening functions calibrated from both biaxial and uniaxial tensile tests under static and dynamic conditions are then proposed. Results show that the biaxial procedure developed in this work, associated with a specific shape of the cross specimen, are more efficient to determine the rate-dependent hardening behaviour for large strains than the conventional uniaxial tensile test. © 2016 Elsevier B.V

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“…In the present work axisymmetric compression tests using Gleeble 3800 simulator were carried out to extend the experimental strain rate to 100 s -1 . With the advent of high speed compression tests, load cell ringing [2], vibrational load response, and sharp temperature rise were encountered. In addition, multi-pass compressions using a long sample could be successfully made when the strain rate was relatively low, but buckling occurred at low temperatures when the strain rate was high.…”

Section: Introductionmentioning

confidence: 99%

Hot Deformation Resistance of an AA5083 Alloy under High Strain Rate

Chen¹,

Wu²,

Ou³

et al. 2014

KEM

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Axisymmetric compression tests using Gleeble 3800 simulator were carried out to investigate hot deformation behaviors of an AA5083 alloy under high strain rate conditions. Sharp temperature rise and load cell ringing characterized by severely vibrational load responses were encountered at strain rates higher than 20 s-1 and sample buckling occurred at low temperatures. The load cell ringing was corrected using a moving average method with a two-way filtering operation to correct phase distortion. Isothermal flow curves were obtained by fitting the instantaneous temperatures into a binomial function, while buckling was correlated with sample height and Young’s modulus. After the corrections, hyperbolic sine equation was successfully used to extend from the hot tensile data having strain rates lower than 3 s-1 to 100 s-1. Quantitative analyses were accordingly made over the effects of temperature, strain rate and work hardening behavior on the flow curves. The previous constitutive equation in form of temperature, strain and strain rate was modified to predict the hot deformation resistance of the AA5083 alloy at temperatures of 250-450oC under the high strain rate operations.

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Load Cell Ringing in High Rate Compression Tests

Cited by 6 publications

References 4 publications

Flow Stress Measurement and Dynamic Response Analysis of Hot Compression Test Machine at High Strain Rates

Flow Stress Measurement and Dynamic Response Analysis of Hot Compression Test Machine at High Strain Rates

Identification of strain rate-dependent mechanical behaviour of DP600 under in-plane biaxial loadings

Hot Deformation Resistance of an AA5083 Alloy under High Strain Rate

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