Preprocessing of Hopkinson Bar Experiment Data: Filter Analysis

Abstract

This work presents a data preprocessing procedure for signal acquired during high strain-rate loading using a custom Split Hopkinson Pressure Bar (SHPB). Before the evaluation of the experimental data, preprocessing of the measured signals including application of suitable digital or analog filter needs to be performed. Our department mainly focuses on measurements performed on advanced materials (e.g. materials with predefined structures or hybrid foams). For such measurements, it is essential to perform data preprocessing and apply suitable filter, to be able to appropriately determine deformation pulses on the measuring bars. This paper focuses foremost on spectral analysis of the measured signals, and design of optimal method of data filtering. Data from several different SHPB experiments were processed and results of different filtering methods are shown in this paper. Parameters of the best performing filter were optimized and shown to be universal for wide range of SHPB measurements.

Numerical and Experimental Studies on the Deformation of Missing‐Rib and Mixed Structures under Compression

“…Different theoretical analysis and single cell approach works have been conducted on estimating Poisson's ratios in tension or compressions. [49][50][51][52] The upper bound based on the rigid-rod rotational spring model showed that the upper Poisson's ratio bound of a 90 MR is around À0.45, [52] indicting a clear auxeticity, which supports the stable auxetic behavior observed. However, this work was focused on the overall deformation of samples with different-sized structures, and Poisson's ratio is calculated based on the averaged displacement of the center point of the outer column.…”

“…The contact, sample size/cell number effects, and Poisson's ratio stability are particularly important for compression loads, as for some applications, a relatively smaller number of the cells is required, whereas for other applications, a large lattice system might be involved. Different theoretical analysis and single cell approach works have been conducted on estimating Poisson's ratios in tension or compressions . The upper bound based on the rigid‐rod rotational spring model showed that the upper Poisson's ratio bound of a 90° MR is around −0.45, indicting a clear auxeticity, which supports the stable auxetic behavior observed.…”

“…Furthermore, if the auxeticity effects are induced by instability in porous materials or lattice structures, the instability or contact at cell level may influence symmetric structures at a macroscale, thus directly affect the deformation process of the cell and shape of the deformed samples as well as the properties and their stability, including Poisson's ratio and auxeticity. MR auxetic structures have attracted many research attentions recently . Many of the applications are intended for application under in‐plane compression loads, and it is important to establish a detailed understanding on the deformation process, in particular, the contact between the edges and cell walls at high strains for normal MR and MSs, which are directly relevant to the mechanical behaviors and the stability of the cell and overall sample deformation.…”

“…MR auxetic structures have attracted many research attentions recently. [34,[48][49][50][51][52][53][54][55] Many of the applications are intended for application under in-plane compression loads, and it is important to establish a detailed understanding on the deformation process, in particular, the contact between the edges and cell walls at high strains for normal MR and MSs, which are directly relevant to the mechanical behaviors and the stability of the cell and overall sample deformation. MSs could offer opportunities to further enhance the freedom in structures design.…”