scholarly journals Suggestion of a Framework of Similarity Laws for Geometric Distorted Structures Subjected to Impact Loading

2020 ◽  
Author(s):  
Shuai Wang ◽  
Fei Xu ◽  
Xiaoyu Zhang ◽  
Zhen Dai
Keyword(s):  
Strain Rate ◽  
Impact Loading ◽  
Dynamic Pressure ◽  
Equivalent Stress ◽  
Analytical Models ◽  
Dimensionless Number ◽  
Dimensionless Numbers ◽  
Strain And Strain Rate ◽  
The Impact ◽  
Similarity Laws

A framework of similarity laws, termed oriented-density-length-velocity (ODLV) framework, is suggested for the geometric distorted structures subjected to impact loading. The distinct feature of this framework is that the newly proposed oriented dimensions, dimensionless numbers and scaling factors for physical quantity are explicitly expressed by the characteristic lengths of three spatial directions, which overcome the inherent defects that traditional scalar dimensional analysis could not express the effects of structural geometric characteristics and spatial directions for similarity. The non-scalabilities of geometrical distortion as well as other distortions such as different materials and gravity could be compensated by the reasonable correction for the impact velocity, the geometrical thickness and the density, when the proposed dimensionless number of equivalent stress is used between scaled model and prototype. Three analytical models of beam, plate and shell subjected to impact mass or impulsive velocity are verified by equation analysis. And a numerical model of circular plate subjected to dynamic pressure pulse is verified in more detail, form the view of point of space deformation, deformation history and the components of displacement, strain and stress. The results show that the proposed dimensionless numbers have attractively perfect ability to express the dimensionless response equations of displacement, angle, time, strain and strain rate. When the proposed dimensionless numbers are used to regularize impact models, the structural responses of the geometrically distorted scaled models can behave the completely identical behaviors with those of the prototype on space and time —not only for the direction-independent equivalent stress, strain and strain rate but also for the direction-dependent displacement, stress and strain components.

High Strain Rate Behavior of Epoxy Graphene Oxide Nanocomposites

2018 ◽  
Vol 10 (07) ◽  
pp. 1850072 ◽  
Author(s):  
Suneev Anil Bansal ◽  
Amrinder Pal Singh ◽  
Suresh Kumar
Keyword(s):  
Graphene Oxide ◽  
High Strain Rate ◽  
Strain Rate ◽  
Impact Loading ◽  
High Strain ◽  
Chemical Oxidation ◽  
Uniform Dispersion ◽  
Mixing Method ◽  
Strain Rate Loading ◽  
The Impact

The present work investigates the novel impact loading response of two-dimensional graphene oxide (GO) reinforced epoxy nanocomposites at high strain rate. The testing was performed up to 1000[Formula: see text]s[Formula: see text] of high strain rate, where maximum damage occurs during the impact loading conditions. The Split Hopkinson Pressure Bar (SHPB) was used for the impact loading of the composite specimen. The nanofiller material GO was synthesized by chemical oxidation of graphite flakes used as the precurser. Synthesized GO was characterized using FTIR, UV-visible, XRD, Raman Spectroscopy and FE-SEM. Solution mixing method was used to fabricate the nanocomposite samples having uniform dispersion of GO as confirmed from the SEM images. Strain gauges mounted on the SHPB showed regular signal of transmitted wave during high strain rate testing on SHPB, confirming the regular dispersion of both the phases. Results of the transmission signal showed that the solution mixing method was effective in the synthesis of almost defect-free nanocomposite samples. The strength of the nanocomposite improved significantly using 0.5[Formula: see text]wt.% reinforcement of GO in the epoxy matrix at high strain rate loading. The epoxy GO nanocomposite showed a 41% improvement in maximum stress at 815[Formula: see text]s[Formula: see text] strain rate loading.

scholarly journals Measurement of Strain and Strain Rate during the Impact of Tennis Ball Cores

2018 ◽  
Vol 8 (3) ◽  
pp. 371 ◽  
Author(s):  
Ben Lane ◽  
Paul Sherratt ◽  
Xiao Hu ◽  
Andy Harland
Keyword(s):  
Strain Rate ◽  
Tennis Ball ◽  
Strain And Strain Rate ◽  
The Impact

Dynamic Strength Estimates for a High Strength, Experimental Steel

2005 ◽  
Author(s):  
Karen L. Torres ◽  
Hollie A. Clements ◽  
Stanley E. Jones ◽  
Morris Dilmore ◽  
Bradley Martin
Keyword(s):  
Strain Rate ◽  
Dynamic Testing ◽  
Dynamic Strength ◽  
High Strength ◽  
High Mass ◽  
Performance Requirements ◽  
Cylinder Test ◽  
Strain And Strain Rate ◽  
Initial Shock ◽  
The Impact

For several years, the Air Force has been engaged in the development of high velocity air to surface missiles. The objective is to replace larger, high mass weapons with smaller, more versatile projectiles that can achieve the same goals. The reduction of mass requires that the impact velocity be increased to meet the performance requirements. This has presented researchers with several challenges. First, the steel must be such that it survives the initial shock at impact. Second, because the tunnel is long, the material must resist friction and wear, which could erode the projectile nose, thereby degrading performance. The purpose of this paper is to present the results of dynamic testing of an experimental, high-strength steel. Using a one-dimensional model for the Taylor cylinder test, the constitutive behavior of the steel as a function of strain and strain-rate can be assessed through a strain-rate of roughly 105/second. This behavior is consistent with that required for successful modeling of the response of a penetrator casing in the ultra-ordinance velocity range.

Dynamic Strength Estimates for a High-Strength Experimental Steel

2008 ◽  
Vol 131 (2) ◽  
Author(s):  
K. L. Torres ◽  
H. A. Clements ◽  
S. E. Jones ◽  
M. Dilmore ◽  
B. Martin
Keyword(s):  
Strain Rate ◽  
Dynamic Testing ◽  
Dynamic Strength ◽  
High Strength ◽  
High Mass ◽  
Performance Requirements ◽  
Cylinder Test ◽  
Strain And Strain Rate ◽  
Initial Shock ◽  
The Impact

For several years, the Air Force has been engaged in the development of high velocity air to surface missiles to defeat hard targets, such as concrete, sand, and soil. The objective is to replace larger, high mass weapons with smaller, more versatile projectiles that can achieve the same goals. The reduction of mass requires that the impact velocity be increased to meet the performance requirements. This has presented researchers with several challenges. First, the steel must be such that it survives the initial shock at impact. Second, because the travel distance in the target is long, the material must resist friction and wear, which could erode the projectile nose, thereby degrading performance. The purpose of this paper is to present the results of dynamic testing of an experimental high-strength steel, also called Eglin steel. Using a one-dimensional model for the Taylor cylinder test, the constitutive behavior of the steel as a function of strain and strain rate can be assessed through a strain rate of roughly 105∕s. This behavior is consistent with that required for successful modeling of the response of a penetrator casing in the ultra-ordinance velocity range.

Variability of the interplanetary magnetic field as a driver of electromagnetic induction in Mercury’s interior

2021 ◽  
Author(s):  
Sophia Zomerdijk-Russell ◽  
Adam Masters
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Interplanetary Magnetic Field ◽  
Current Sheet ◽  
Electromagnetic Induction ◽  
Dynamic Pressure ◽  
Analytical Models ◽  
Appreciable Effect ◽  
The Impact ◽  
The Imf

<p>Mercury’s magnetosphere is considered to be a unique and dynamic system, primarily due to the proximity of the planet to the Sun. The interaction between solar wind and embedded Interplanetary Magnetic Field (IMF) and the dayside Hermean magnetosphere drive an electric current on the magnetopause boundary of the system. The influence of the time-dependent magnetic field generated by this magnetopause current on Mercury’s interior is key to understanding the subsurface structure of the planet, as electromagnetic induction is a valuable technique for delineating electrical properties of planetary interiors. Here we assess the impact a changing IMF direction has on the Hermean magnetopause currents, and the resulting inducing magnetic field. Analytical models of conditions at the magnetopause are combined with measurements made by MESSENGER’s magnetometer as the spacecraft crossed the subsolar magnetopause boundary during the first ‘hot season’.</p><p>These MESSENGER magnetopause boundary crossings show that the introduction of the external IMF changes the direction of the magnetopause current by ~50°, compared to the case where only the internal planetary field is considered. Analytical modelling suggests that for a heliospheric current sheet crossing without any change in solar wind dynamic pressure (an east-west reversal of the IMF polarity typical at Mercury), the inducing field at Mercury’s surface caused by the resulting magnetopause current sheet dynamics is of the order of 10% of the global planetary field. The results suggest that variability of the IMF alone can have an appreciable effect on Mercury’s magnetopause current direction and generate a significant inducing magnetic field around the planet. The arrival of the BepiColombo mission will allow this response to be further explored as a method of probing Mercury’s interior.</p>

Simulation of Flexural Behavior of Reinforced Concrete Beams under Impact Loading

2013 ◽  
Vol 351-352 ◽  
pp. 1018-1023
Author(s):  
Arnaud Rouchette ◽  
Wei Ping Zhang ◽  
Hui Chen
Keyword(s):  
Reinforced Concrete ◽  
Strain Rate ◽  
Impact Loading ◽  
Concrete Beams ◽  
Kinematic Model ◽  
Experimental Results ◽  
Reinforced Concrete Beams ◽  
Flexural Behavior ◽  
Bond Model ◽  
The Impact

This paper focuses on the numerical simulation of the flexural behavior of reinforced concrete beams under impact loading by the LS-DYNA finite element code. An enhanced version of the Concrete Damage Model Release 3 (K&C) was used for the concrete materials and a Plastic Kinematic Model was adopted for steel reinforcement, both material models used parameters to cope with the effects of strain rate. The simulation also took the bond between concrete and steel bar into consideration, and its behavior model was based on high strain rate experimental results. The simulation of the mid span drop tests, both with and without bond consideration, were compared to experimental results to investigate the influence of bond consideration and the reliability of the overall simulation model. Compared with experimental results, the calculated mid-span deflections with the bond model agreed much better than those without the bond model, and a simplified formulation was drawn from the trend on deformation depending on the impact velocity.

scholarly journals Material Similarity of Scaled Models

2020 ◽  
Author(s):  
Shuai Wang ◽  
Fei Xu ◽  
Xiaoyu Zhang ◽  
Leifeng Yang
Keyword(s):  
Strain Rate ◽  
Strain Hardening ◽  
Solid Mechanics ◽  
Similarity Theory ◽  
Prediction Errors ◽  
Correction Factors ◽  
Dimensionless Numbers ◽  
Scaled Model ◽  
Strain And Strain Rate ◽  
Structural Strain

When different strain hardening and strain rate sensitive materials are used for scaled model and prototype, the traditional pure geometrical similarity laws of solid mechanics will fail. Although correcting the basic scaling factors of velocity, density and geometry have been developed to compensate for the material distortion in recent non-geometric scaling works, it is difficult to be widely used because of its inherent indirect (depending on the structural strain and strain rate responses) and inexact (having significant prediction errors for prototype) defects. In this paper, a framework of material similarity, based on the new suggested material dimensionless numbers and the ‘Material number vs. strain/strain-rate’ function curves, are further developed, which represents the objective requirement of similarity theory for the basic mechanical properties of materials. It is demonstrated what is similitude materials of solid mechanics and how to use the best similitude materials to overcome the non-scalabilities of materials for identical or different materials. The direct and exact solution of the basic correction factors is further obtained and therefore overcomes the previous inherent indirect and inexact defects radically. Based on the similarity evaluation of different materials of the classical constitutive models, the impacted structures of circular plate and crooked plate with strain hardening and strain rate sensitive materials are verified numerically. The results show the completely different materials can be exact similitude for various structural behaviors (strain, strain rate, stress and displacement) of time and space fields after using the best similitude materials; and the basic correction factors do not depend on the structural strain and strain rate responses. As a contrast, when the non-similitude materials are used, the similarity results are very sensitive to the selection of strain/strain-rate and often leads to failed predictions. In addition, for the material elastic and temperature effects, the proposed method is also discussed to be valid.

Abstract 16418: The Impact of MitraClip® Procedure on Left Atrial Strain and Strain Rate

Circulation ◽  
2014 ◽  
Vol 130 (suppl_2) ◽  
Author(s):  
Esra Gucuk Ipek ◽  
Atif Qasim ◽  
Esperanza Viloria ◽  
Ted Feldman ◽  
Paul A Grayburn ◽  
...  
Keyword(s):  
Strain Rate ◽  
Left Atrial ◽  
Atrial Remodeling ◽  
Left Atrial Strain ◽  
Strain And Strain Rate ◽  
One Year ◽  
Atrial Strain ◽  
The Impact ◽  
Strain Measures

Background: Left atrial (LA) remodeling due to mitral regurgitation (MR) is associated with abnormal LA strain parameters which may correlate with degree of fibrosis. Although reverse atrial remodeling has been shown after MitraClip placement, changes in LA strain and strain rate have not been evaluated in these patients or compared with mitral valve repair (MVr). Methods: We measured peak positive LA strain (ε) and strain rates [peak systolic (SRp), peak early diastolic (SRe) and peak late diastolic (SRa)] in 107 subjects (mean age 61±12 yrs) with degenerative MR enrolled in the randomized EVEREST II trial. Individuals with paced rhythm, atrial fibrillation, functional MR and poor image quality were excluded. LA strain measures were obtained from 4-chamber and 2-chamber views and averaged at baseline and at 1 year follow up. Results: At one year all 44 MVr subjects had ≤2+ MR, whereas 22 of the 63 MitraClip had >2+ MR. Baseline average ε, SRp, SRe and SRa values were similar in MitraClip and MVr groups (Table 1). At one year follow up there was a significant decrease in LA volumes in the surgical group and in those with MR ≤2+ after MitraClip. Overall average ε was significantly reduced after MVr. There was a small decrease or no change in average ε after MitraClip. SRe was significantly decreased 1 year after MVr and also in the MitraClip arm, regardless of whether there was significant MR reduction. There were no changes in SRp and SRa at 1 year in either group. Conclusion: Average peak positive LA strain either decreased modestly or did not change after treatment of MR in chronic degenerative MR subjects. There was a significant decrease in SRe in both treatment arms at 1 year. This occurred despite evidence of reverse LA remodeling. Further investigation and replication in additional cohorts is needed to explore these findings, which may suggest persistence of LA dysfunction after correction of chronic MR, or irreversible fibrosis. Disclosure: EVEREST II was funded by Abbott Vascular.

The effects of strain and strain rate on residual microstructures in copper

1986 ◽  
Vol 44 ◽  
pp. 420-421
Author(s):  
M. F. Stevens ◽  
P. S. Follansbee
Keyword(s):  
Strain Rate ◽  
Applied Stress ◽  
Threshold Stress ◽  
Rate Sensitivity ◽  
Viscous Drag ◽  
Strain Rates ◽  
Strain And Strain Rate ◽  
Threshold Strength ◽  
Mechanism Transition ◽  
Intrinsic Strength

The strain rate sensitivity of a variety of materials is known to increase rapidly at strain rates exceeding ∼103 sec-1. This transition has most often in the past been attributed to a transition from thermally activated guide to viscous drag control. An important condition for imposition of dislocation drag effects is that the applied stress, σ, must be on the order of or greater than the threshold stress, which is the flow stress at OK. From Fig. 1, it can be seen for OFE Cu that the ratio of the applied stress to threshold stress remains constant even at strain rates as high as 104 sec-1 suggesting that there is not a mechanism transition but that the intrinsic strength is increasing, since the threshold strength is a mechanical measure of intrinsic strength. These measurements were made at constant strain levels of 0.2, wnich is not a guarantee of constant microstructure. The increase in threshold stress at higher strain rates is a strong indication that the microstructural evolution is a function of strain rate and that the dependence becomes stronger at high strain rates.

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