An Experimental Surface-Wave Method for Recording Force-Time Curves in Elastic Impacts

1959 ◽  
Vol 26 (1) ◽  
pp. 3-7
Author(s):  
J. N. Goodier ◽  
W. E. Jahsman ◽  
E. A. Ripperger
Keyword(s):  
Surface Wave ◽  
Plane Surface ◽  
Hopkinson Pressure Bar ◽  
Time Curve ◽  
Experimental Surface ◽  
Force Time ◽  
Steel Balls ◽  
Pressure Bar ◽  
Surface Wave Method ◽  
The Impact

Abstract The recording of impacts by means of the longitudinal strain wave generated in a Hopkinson pressure bar is no longer possible when the impact is very brief, on account of dispersive effects. The Rayleigh surface wave generated on the plane surface of a block is nondispersive. A method is given for deducing the force-time curve of the impact from the oscilloscope record of the surface wave, and applied to impacts of small steel balls on a block.

Analysis of the Impact of the Frequency Range of the Tensometer Bridge and Projectile Geometry on the Results of Measurements by the Split Hopkinson Pressure Bar Method

2013 ◽  
Vol 20 (4) ◽  
pp. 555-564 ◽  
Author(s):  
Wojciech Moćko
Keyword(s):  
Test Bench ◽  
Split Hopkinson Pressure Bar ◽  
Dynamic Deformation ◽  
Spectral Width ◽  
Hopkinson Pressure Bar ◽  
Computing Environment ◽  
Split Hopkinson ◽  
Pressure Bar ◽  
The Impact ◽  
Bench Model

Abstract The paper presents the results of the analysis of the striker shape impact on the shape of the mechanical elastic wave generated in the Hopkinson bar. The influence of the tensometer amplifier bandwidth on the stress-strain characteristics obtained in this method was analyzed too. For the purposes of analyzing under the computing environment ABAQUS / Explicit the test bench model was created, and then the analysis of the process of dynamic deformation of the specimen with specific mechanical parameters was carried out. Based on those tests, it was found that the geometry of the end of the striker has an effect on the form of the loading wave and the spectral width of the signal of that wave. Reduction of the striker end diameter reduces unwanted oscillations, however, adversely affects the time of strain rate stabilization. It was determined for the assumed test bench configuration that a tensometric measurement system with a bandwidth equal to 50 kHz is sufficient

scholarly journals Biomechanical assessment of various punching techniques

2020 ◽  
Author(s):  
Jiri Adamec ◽  
Peter Hofer ◽  
Stefan Pittner ◽  
Fabio Monticelli ◽  
Matthias Graw ◽  
...  
Keyword(s):  
High Speed ◽  
Vertical Wall ◽  
Force Plate ◽  
Physical Parameters ◽  
Time Curve ◽  
Biomechanical Assessment ◽  
Sports Science ◽  
General Terms ◽  
Force Time ◽  
The Impact

Abstract Punches without the use of instruments/objects are a common type of body violence and as such a frequent subject of medicolegal analyses. The assessment of the injuries occurred as well as of the potential of the assault to produce severe body harm is based on objective traces (especially the documented injuries of both parties involved) as well as the—often divergent—descriptions of the event. Quantitative data regarding the punching characteristics that could be used for the assessment are rare and originate mostly in sports science. The aim of this study was to provide physical data enabling/facilitating the assessment of various punching techniques. A total of 50 volunteers took part in our study (29 males and 21 females) and performed severe punches with the fist, with the small finger edge of the hand (karate chop), and with the open hand with both the dominant and the non-dominant hands in randomized order. The strikes were performed on a boxing pad attached to a KISTLER force plate (sampling frequency 10,000 Hz) mounted on a vertical wall. The punching velocity was defined as the hand velocity over the last 10 cm prior to the contact to the pad and ascertained by using a high-speed camera (2000 Hz). Apart from the strike velocity, the maximum force, the impulse (the integral of the force-time curve), the impact duration, and the effective mass of the punch (the ratio between the impulse and the strike velocity) were measured/calculated. The results show a various degree of dependence of the physical parameters of the strikes on the punching technique, gender, hand used, body weight, and other factors. On the other hand, a high degree of variability was observed that is likely attributable to individual punching capabilities. In a follow-up study, we plan to compare the “ordinary” persons with highly trained (boxers etc.) individuals. Even though the results must be interpreted with great caution and a direct transfer of the quantitative parameters to real-world situations is in general terms not possible, the study offers valuable insights and a solid basis for a qualified forensic medical/biomechanical assessment.

Numerical Simulation Analysis of Collision between Ship and Steel Sheet Pile Quay-Wall

2015 ◽  
Vol 744-746 ◽  
pp. 1175-1179 ◽  
Author(s):  
Peng Liu ◽  
Hong Wang ◽  
Chao Zhu
Keyword(s):  
Numerical Simulation ◽  
Steel Sheet ◽  
Impact Force ◽  
Simulation Analysis ◽  
Sheet Pile ◽  
Time Curve ◽  
Finite Element Software ◽  
Quay Wall ◽  
Force Time ◽  
The Impact

The impact process of 50000t ship and steel sheet pile bulkhead is simulated by finite element software ANSYS/LS-DYNA. This article acquires the impact force-time curve, equivalent force-time curve of steel sheet pile and the pressure-time curve of breast wall. Comparing the impact force of numerical simulation with the result of ship-bridge collision specifications, and general rules and characteristics are obtained. At the same time, put forward some measures to prevent the damage of wharf structure under the ship of large velocity impact, which provide theoretical references during the design, maintenance, and transformation of similar wharf.

scholarly journals On backward dispersion correction of Hopkinson pressure bar signals

2014 ◽  
Vol 372 (2023) ◽  
pp. 20130291 ◽  
Author(s):  
A. Tyas ◽  
Z. Ozdemir
Keyword(s):  
Impact Load ◽  
Wide Spectrum ◽  
Accurate Determination ◽  
Experimental Studies ◽  
Dispersion Correction ◽  
Impact Event ◽  
Hopkinson Pressure Bar ◽  
Phase Velocity Dispersion ◽  
Pressure Bar ◽  
The Impact

Elastic theory shows that wide spectrum signals in the Hopkinson pressure bar suffer two forms of distortion as they propagate from the loaded bar face. These must be accounted for if accurate determination of the impact load is to be possible. The first form of distortion is the well-known phase velocity dispersion effect. The second form, which can be equally deleterious, is the prediction that at high frequencies, the stress and strain generated in the bar varies with radial position on the cross section, even for a uniformly applied loading. We consider the consequences of these effects on our ability to conduct accurate backward dispersion correction of bar signals, that is, to derive the impact face load from the dispersed signal recorded at some other point on the bar. We conclude that there is an upper limit on the frequency for which the distortion effects can be accurately compensated, and that this can significantly affect the accuracy of experimental results. We propose a combination of experimental studies and detailed numerical modelling of the impact event and wave propagation along the bar to gain better understanding of the frequency content of the impact event, and help assess the accuracy of experimental predictions of impact face load.

Experimental Study of Impact Strength of Al-6063 Alloy Processed by Equal Channel Angular Extrusion

2014 ◽  
Vol 911 ◽  
pp. 158-162 ◽  
Author(s):  
Shamsuddin Sulaiman ◽  
J. Nemati ◽  
Hani Mizhir Magid ◽  
B.T.H.T. Baharudin ◽  
G.H. Majzoobi ◽  
...  
Keyword(s):  
Impact Strength ◽  
Equal Channel Angular Extrusion ◽  
Split Hopkinson Pressure Bar ◽  
Hopkinson Pressure Bar ◽  
Angular Extrusion ◽  
Split Hopkinson ◽  
Ram Speed ◽  
Pressure Bar ◽  
The Impact ◽  
Strength Improvement

In the present study, the impact strength of annealed Al-6063 alloy developed by equal channel angular extrusion (ECAE), up to 6 passes at a temperature of 200°C following route A with a constant ram speed of 30 mm/min through a die angle of 90° between the die channels was investigated. The impact strength of extruded specimens is evaluated for different passes at a strain rate of 1800 s-1 using Split-Hopkinson pressure bar techniques. The results indicate that the major strength improvement occurs in the 5th and 6th passes while in primary passes, the strength improved but at a considerably lower rate. A total increasing in ultimate strength (UTS) and yield strength (YS) are 127% and 65% respectively and observed for the extruded material after 6 passes. Optical microscopic examinations show a grain refinement from 45 μm to 2.8 μm.

scholarly journals Wave Attenuation and Dispersion in a 6 mm Diameter Viscoelastic Split Hopkinson Pressure Bar and Its Correction Method

2020 ◽  
Vol 2020 ◽  
pp. 1-10
Author(s):  
Haotian Zhang ◽  
Linjian Ma ◽  
Zongmu Luo ◽  
Ning Zhang
Keyword(s):  
Impact Velocity ◽  
Wave Attenuation ◽  
Split Hopkinson Pressure Bar ◽  
Small Diameter ◽  
Correction Method ◽  
Hopkinson Pressure Bar ◽  
Amplitude Attenuation ◽  
Split Hopkinson ◽  
Pressure Bar ◽  
The Impact

The propagation characteristics of viscoelastic waves have been investigated with a 6 mm diameter split Hopkinson pressure bar (SHPB) made of polymethyl methacrylate (PMMA). The strain signals in SHPB tests were improved by the pulse shaping technique. Based on the experimentally determined propagation coefficients, the amplitude attenuation and wave dispersion induced by viscoelastic effects at different impact velocities were quantitatively analyzed. The results indicate that the high-frequency harmonics attenuate faster in a higher phase velocity. With an increase in the impact velocity, the amplitude attenuation of the viscoelastic wave changes slightly during propagation, while the waveform dispersion gradually intensifies. A feasible method by waveform prediction was proposed to verify the validity and applicability of the propagation coefficient. The results indicate that the strain obtained from the small diameter viscoelastic SHPB can be effectively modified by utilizing the propagation coefficient. Furthermore, it is preferred to adopt the propagation coefficient obtained at low impact velocity for correction when the impact velocity varies. Moreover, the PMMA-steel bar impact test was performed to further illustrate the accuracy of the propagation coefficient and the effectiveness of the correction method.

Impact Compressive Properties of Foamed Film with Closed Cell

2014 ◽  
Vol 566 ◽  
pp. 134-139 ◽  
Author(s):  
Hiroyuki Yamada ◽  
Ryo Okui ◽  
Nagahisa Ogasawara ◽  
Hidetoshi Kobayashi ◽  
Kinya Ogawa
Keyword(s):  
Strain Rate ◽  
Impact Test ◽  
Split Hopkinson Pressure Bar ◽  
Rate Dependency ◽  
Hopkinson Pressure Bar ◽  
Compressive Properties ◽  
Static Test ◽  
Closed Cell ◽  
Pressure Bar ◽  
The Impact

The compressive properties of foamed polyethylene (PE) film with a closed cell for electronic devices have been investigated. A commercial closed cell foamed PE film with a density of 330 kg/m3 was used. Quasi-static testing was carried out at strain rates of 10−3 to 10−1 s−1. The strain rate of the impact test was approximately 105 s−1 by means of split Hopkinson pressure bar method. Within the set of experiments, the compressive stress increased with the strain rate in both the quasi-static and impact test. In particular, the flow stress increased substantially with the increasing strain rate in the impact deformation. At strains of less than 0.4, the trapped air was locally compressed within the cells, which led to the strain rate dependency of strength in the quasi-static test and the impact test.

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