Crack Propagation of CCT Foam Specimen under Impact Fatigue

2010 ◽  
Vol 118-120 ◽  
pp. 32-36 ◽  
Author(s):  
Jae Ung Cho ◽  
Li Yang Xie ◽  
Chong Du Cho ◽  
Sang Kyo Lee
Keyword(s):  
High Strain Rate ◽  
Impact Loading ◽  
High Strain ◽  
Nickel Foam ◽  
Fatigue Properties ◽  
Foam Material ◽  
Impact Fatigue ◽  
Repeated Impact ◽  
Repeated Impacts ◽  
The Impact

The objective of this study is to investigate the effect of the low or high strain rate on the impact fatigue properties of the nickel foam material and to understand the lifetime of this material which is subjected to the repeated impacts at different energy levels. Failures of foam materials under single and repeated impacts analogous to fatigue are essential to designers and users in military and aerospace structures. The material failure induced by repeated impact loading becomes a critical issue because of significant loss of stiffness and compressive strength in the foam material. Testing methods to study impact(that is, high strain rate) fatigue are quite numerous; no single standard testing procedure is defined for studying the impact fatigue property of a material. The increasing application of foam material in aerospace structures, owing to high specific stiffness and strength has attracted a great concern about the high sensitivity to impact damage introduced during manufacture or in service, and the effects of such damage on structural degradation. To investigate this issue, this study sets up an experimental procedure to determine the impact fatigue properties of nickel foam material. This study performs both experimental and numerical investigations to catch the impact fatigue behavior of nickel foam with open type. Design life and probability of failure or survival at specified life can be calculated so that the fatigue life of nickel core material subjected to repeated impact loading is predicted.

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 High-strain-rate mechanical response of HTPE propellant under SHPB impact loading

AIP Advances ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 035145
Author(s):  
Heng-ning Zhang ◽  
Hai Chang ◽  
Jun-qiang Li ◽  
Xiao-jiang Li ◽  
Han Wang
Keyword(s):  
High Strain Rate ◽  
Strain Rate ◽  
Impact Loading ◽  
Mechanical Response ◽  
High Strain

Rupture by impact-induced fatigue of a copper foil strip embedded in a multifunctional composite material

2021 ◽  
pp. 002199832199432
Author(s):  
Yacine Ouroua ◽  
Said Abdi ◽  
Imene Bachirbey
Keyword(s):  
Composite Material ◽  
Mechanical Characteristics ◽  
Glass Fibers ◽  
Energy Levels ◽  
Fatigue Tests ◽  
Repeated Impact ◽  
Aeronautical Industry ◽  
Repeated Impacts ◽  
Cracking Mode ◽  
The Impact

Multifunctional composite materials are highly sought-after by the aerospace and aeronautical industry but their performance depends on their ability to sustain various forms of damages, in particular damages due to repeated impacts. In this work we studied the mechanical behavior of a layered glass-epoxy composite with copper inserts subjected to fatigue under repeated impacts with different energy levels. Damage evolution as a function of impact energy was carefully monitored in order to determine the effect of the copper inserts on mechanical characteristics of the multifunctional composite, such as endurance and life. Results of repeated impact tests show that electric current interruption in the copper inserts occurs prior to the total perforation of the composite material, and after about 75% of the total number of impacts to failure. This is the case for the three energy levels considered in this study, [Formula: see text] = 2, 3 and 4 Joules. The epoxy resin was dissolved chemically in order to preserve the mechanical structure of the damaged copper inserts and the composite fibers for further inspection and analysis. Scanning electron microscopy (SEM) of the fractured copper inserts revealed interesting information on the nature of the damage, including information on plastic deformation, strain hardening, cracking mode, temperature increase during the impacts, and most importantly the glass fibers and their roles during the impact-fatigue tests.

scholarly journals Carbon Nanotube Peapods Under High-Strain Rate Conditions: A Molecular Dynamics Investigation

MRS Advances ◽  
2020 ◽  
Vol 5 (33-34) ◽  
pp. 1723-1730
Author(s):  
J. M. De Sousa ◽  
C. F. Woellner ◽  
L. D. Machado ◽  
P. A. S. Autreto ◽  
D. S. Galvao
Keyword(s):  
Molecular Dynamics ◽  
Carbon Nanotube ◽  
High Strain Rate ◽  
Strain Rate ◽  
High Strain ◽  
Optical Modulation ◽  
Carbon Structures ◽  
Dynamics Simulations ◽  
Forms Of Carbon ◽  
The Impact

ABSTRACTNew forms of carbon-based materials have received great attention, and the developed materials have found many applications in nanotechnology. Interesting novel carbon structures include the carbon peapods, which are comprised of fullerenes encapsulated within carbon nanotubes. Peapod-like nanostructures have been successfully synthesized, and have been used in optical modulation devices, transistors, solar cells, and in other devices. However, the mechanical properties of these structures are not completely elucidated. In this work, we investigated, using fully atomistic molecular dynamics simulations, the deformation of carbon peapods under high-strain rate conditions, which are achieved by shooting the peapods at ultrasonic velocities against a rigid substrate. Our results show that carbon peapods experience large deformation at impact, and undergo multiple fracture pathways, depending primarily on the relative orientation between the peapod and the substrate, and the impact velocity. Observed outcomes include fullerene ejection, carbon nanotube fracture, fullerene, and nanotube coalescence, as well as the formation of amorphous carbon structures.

Experimental and Numerical Analysis of Repeated Impacts between Two Spheres

2014 ◽  
Vol 566 ◽  
pp. 250-255
Author(s):  
Hirofumi Minamoto ◽  
Robert Seifried ◽  
Peter Eberhard ◽  
Shozo Kawamura
Keyword(s):  
Full Detail ◽  
Repeated Impact ◽  
Velocity Change ◽  
Spherical Surfaces ◽  
Plastic Materials ◽  
Dynamic Material Properties ◽  
Repeated Impacts ◽  
The Impact ◽  
Method Analysis ◽  
Material Tests

The impact of spheres and bodies with spherical surfaces is frequently occurring in engineering applications. Only little research on repeated impacts of spheres is available and the variation of the COR (Coefficient of Restitution) due to repeated impacts is not fully understood yet. Further, the variation of the COR for impact repetition of visco-plastic materials, such as steel, has not been investigated in full detail yet. Therefore, the aim of this study is to investigate the behavior of steel spheres during repeated impact in detail in both, experiments and numerical simulations. In the experiments, two steel spheres are suspended like pendula, and the two spheres collide at the same position with the same initial velocity for every repeated impact. The COR is obtained from the velocity change of the spheres which is measured by LDVs (Laser Doppler Vibrometers) set at both sides of the spheres. The static and dynamic material properties are obtained from material tests and are incorporated into an FEM (Finite Element Method) analysis. The experimental results and the FEM results agree fairly well. It is observed that the COR increases toward to 1 by the repetition of impacts, indicating decreasing amount of plastic deformation in the successive impacts.

Performance of 3-D Printed Thermoplastic Polyurethane Under Quasi-Static and High-Strain Rate Loading

2016 ◽  
Author(s):  
S. Chaudhry ◽  
M. Al-Dojayli ◽  
A. Czekanski
Keyword(s):  
High Strain Rate ◽  
Strain Rate ◽  
High Strain ◽  
Split Hopkinson Pressure Bar ◽  
Kolsky Bar ◽  
Pulse Shaper ◽  
Input And Output ◽  
The Impact ◽  
Printing Direction ◽  
Printing Parameters

As 3-D printed materials are being embraced by the manufacturing industries, understanding the response mechanism to high strain rate events becomes a concern to meet requirements for a specific application. In order to improve the mechanical performance of a 3-D printed part, it is necessary to quantify the impact of various printing parameters on the mechanical properties. Initial studies have shown that a difference in 3-D printed material is expected due to the effect of manufacturing parameters such as anisotropy relating to printing direction, infill pattern, infill percentage, layer height and orientation of the part being printed. The main focus of the study is to characterize the effect of the previously mentioned printing parameters under quasi-static and high strain rate (100–1000 /s). In this strain rate regime, the most common apparatus used is the Split Hopkinson pressure bar (also known as Kolsky bar). It consists of a cylindrical metallic bar that has a striker, input and output bar. While the specimen is fixated between the input and output bar, the striker bar is accelerated and triggers the incident bar. As a result, an elastic wave is generated which travels towards the specimen/input bar interface, where some part of it is reflected and the rest is transmitted. The Kolsky bar is adjusted by using a hollow transmitter tube and pulse shaper. Due to an impedance mismatch between the samples and bar material, the amplitude of the transmitted pulse is low. Using a hollow transmitter bar increases this amplitude due to area mismatch between the specimen and tube. Using a pulse shaper between the striker and input bar, the rise time of the elastic compressive wave increases and assists in achieving a constant rate of loading. The compressive stress strain curves were obtained under high strain rates to determine the strain rate effect. To measure the response under static testing conditions, a commercial load frame was used. A comprehensive comparison of dynamic compressive response of samples was performed to characterize the effect of printing parameters.

scholarly journals 2-Step Drop Impact Analysis of a Miniature Mobile Haptic Actuator Considering High Strain Rate and Damping Effects

Micromachines ◽  
2019 ◽  
Vol 10 (4) ◽  
pp. 272 ◽  
Author(s):  
Choi ◽  
Choi ◽  
Kang ◽  
Jeon ◽  
Lee
Keyword(s):  
High Strain Rate ◽  
Strain Rate ◽  
Impact Analysis ◽  
High Strain ◽  
Drop Impact ◽  
Tactile Feedback ◽  
Smart Device ◽  
Damping Effects ◽  
Impact Characteristics ◽  
The Impact

In recent times, the haptic actuators have been providing users with tactile feedback via vibration for a realistic experience. The vibration spring must be designed thin and small to use a haptic actuator in a smart device. Therefore, considerable interests have been exhibited with respect to the impact characteristics of these springs. However, these springs have been difficult to analyze due to their small size. In this study, drop impact experiments and analyses were performed to examine the damages of the mechanical spring in a miniature haptic actuator. Finally, an analytical model with high strain rate and damping effects was constructed to analyze the impact characteristics.

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