Rate Dependent Material Model for Helmet Pads

2020 ◽  
Author(s):  
Timothy G. Zhang ◽  
A. H. Fulton ◽  
K. Ravi-Chandar ◽  
Sikhanda S. Satapathy
Keyword(s):  
Mechanical Properties ◽  
Material Properties ◽  
High Speed ◽  
Material Model ◽  
High Speed Camera ◽  
Low Velocity ◽  
Rate Dependent ◽  
Military Helmet ◽  
The Impact ◽  
Impact Experiments

Abstract Foam pads are commonly used in sports and military helmet for energy absorption, form-fitting and comfort. Both for low velocity and high velocity applications, their rate-dependent mechanical properties need to be characterized to understand their ability to effectively modulate the transmitted stress pulse. Impact experiments were conducted on bilayer helmet pads at a range of velocities covering low to medium rates up to ∼7000/s. Images from high-speed camera were used to construct x-T diagrams to measure the shock speeds from the impact experiments. Numerical simulations were carried out to validate a foam pad model and to understand experimental uncertainties. The scatter in the measured shock speeds was found to be related to the scatter in the material properties.

Modeling of Tread Block Contact Mechanics Using Linear Viscoelastic Theory3

2008 ◽  
Vol 36 (3) ◽  
pp. 211-226 ◽  
Author(s):  
F. Liu ◽  
M. P. F. Sutcliffe ◽  
W. R. Graham
Keyword(s):  
High Speed ◽  
Slip Rate ◽  
Material Model ◽  
Contact Forces ◽  
Block Modeling ◽  
Rate Dependent ◽  
Linear Viscoelastic Material ◽  
Linear Viscoelastic ◽  
The Impact ◽  
Good Agreement

Abstract In an effort to understand the dynamic hub forces on road vehicles, an advanced free-rolling tire-model is being developed in which the tread blocks and tire belt are modeled separately. This paper presents the interim results for the tread block modeling. The finite element code ABAQUS/Explicit is used to predict the contact forces on the tread blocks based on a linear viscoelastic material model. Special attention is paid to investigating the forces on the tread blocks during the impact and release motions. A pressure and slip-rate-dependent frictional law is applied in the analysis. A simplified numerical model is also proposed where the tread blocks are discretized into linear viscoelastic spring elements. The results from both models are validated via experiments in a high-speed rolling test rig and found to be in good agreement.

scholarly journals Analyzing the Effect of Temperature on Squash Ball Impacts Using High-Speed Camera Recordings

2021 ◽  
Author(s):  
Bence Ferenc Berencsi ◽  
Attila Kossa
Keyword(s):  
High Speed ◽  
Elevated Temperatures ◽  
Primary Objective ◽  
Effect Of Temperature ◽  
High Speed Camera ◽  
Compression Tests ◽  
Low Velocity ◽  
Different Types ◽  
Dynamical Parameters ◽  
The Impact

Description of the impact characteristics of different types of balls has a great importance in sport science and in engineering. The primary objective of the present paper is to investigate the effect of the temperature on the impacts of different types of squash balls from a given company. The shots were performed using a self-built air-cannon. The impacts were recorded by a high-speed camera and the recorded videos were analyzed by an image-processing method based on a background subtraction technique. Summarizing the main dynamical parameters, we can conclude that increasing the initial speed will decrease the contact time, the coefficient of restitution (COR) and the rebound resilience, whereas these parameters increase at elevated temperatures. The compression tests revealed that within the low velocity range the deformation of the ball’s material and not the compression of the inner gas is the main contribution in the force needed to compress the ball. However, when the ball suffers large deformations, the internal air pressure has a huge effect on the rebound behavior. The measurements revealed that there is an optimal initial velocity distinct from the maximum one where the rebound velocity of the ball is higher than in all other cases. From the results we can state that the ball's overall stiffness grows as the temperature increases.

High Speed Fracture Phenomena in Dyneema Composite

2007 ◽  
Vol 353-358 ◽  
pp. 120-125 ◽  
Author(s):  
Beate D. Heru Utomo ◽  
B.J. van der Meer ◽  
L.J. Ernst ◽  
D.J. Rixen
Keyword(s):  
Material Properties ◽  
Cohesive Zone ◽  
High Speed ◽  
Material Model ◽  
Protection Level ◽  
Projectile Impact ◽  
New Material ◽  
Specific Material ◽  
Strength And Stiffness ◽  
Impact Experiments

Dyneema composite is used in lightweight armour applications, because of its high specific material properties such as strength and stiffness. In armour applications, Dyneema composite is used to protect people or vehicles from projectile impact. In order to be able to guarantee a certain protection level, an accurate prediction of fracture phenomena that are caused by projectile impact is required. Currently, fracture phenomena such as delamination and fibre fracture are not accurately described. This is because a good understanding of fracture phenomena in Dyneema composite lacks. Therefore, both Dyneema fibre and Dyneema composite are analysed by different (impact) experiments to gain more insight in both the fracture phenomena as well as in the material properties. Parallel to these experiments, a start is made with the development of a new material model in ABAQUS\Explicit using cohesive zone techniques that is able to predict the fracture phenomena due to projectile impact.

scholarly journals Numerical–Experimental Correlation of Impact-Induced Damages in CFRP Laminates

2019 ◽  
Vol 9 (11) ◽  
pp. 2372 ◽  
Author(s):  
Andrea Sellitto ◽  
Salvatore Saputo ◽  
Francesco Di Caprio ◽  
Aniello Riccio ◽  
Angela Russo ◽  
...  
Keyword(s):  
Numerical Model ◽  
Composite Laminates ◽  
Transverse Direction ◽  
Material Model ◽  
Low Velocity ◽  
Cfrp Laminates ◽  
Experimental Correlation ◽  
Out Of Plane ◽  
Impact Phenomena ◽  
The Impact

Composite laminates are characterized by high mechanical in-plane properties and poor out-of-plane characteristics. This issue becomes even more relevant when dealing with impact phenomena occurring in the transverse direction. In aeronautics, Low Velocity Impacts (LVIs) may occur during the service life of the aircraft. LVI may produce damage inside the laminate, which are not easily detectable and can seriously degrade the mechanical properties of the structure. In this paper, a numerical-experimental investigation is carried out, in order to study the mechanical behavior of rectangular laminated specimens subjected to low velocity impacts. The numerical model that best represents the impact phenomenon has been chosen by numerical–analytical investigations. A user defined material model (VUMAT) has been developed in Abaqus/Explicit environment to simulate the composite intra-laminar damage behavior in solid elements. The analyses results were compared to experimental test data on a laminated specimen, performed according to ASTM D7136 standard, in order to verify the robustness of the adopted numerical model and the influence of modeling parameters on the accuracy of numerical results.

scholarly journals Experimental investigation of the impact response of novel steelbiocomposite hybrid materials

2018 ◽  
Vol 183 ◽  
pp. 02040
Author(s):  
KarthikRam Ramakrishnan ◽  
Mikko Hokka ◽  
Essi Sarlin ◽  
Mikko Kanerva ◽  
Reijo Kouhia ◽  
...  
Keyword(s):  
High Speed ◽  
Structural Integrity ◽  
Metal Layer ◽  
Rear Surface ◽  
Impact Resistance ◽  
Natural Fibre ◽  
Image Correlation ◽  
Impact Response ◽  
High Speed Camera ◽  
The Impact

Recent developments in the production of technical flax fabrics allow the use of sustainable natural fibres to replace synthetic fibres in the manufacture of structural composite parts. Natural fibre reinforced biocomposites have been proven to satisfy design and structural integrity requirements but impact strength has been identified as one of their limitations. In this paper, hybridisation of the biocomposite with a metal layer has been investigated as a potential method to improve the impact resistance of natural fibre composites. The impact response of biocomposites made of flax-epoxy is investigated experimentally using a high velocity particle impactor. A high-speed camera setup was used to observe the rear surface of the plates during impact. Digital Image Correlation (DIC) of the high speed camera images was used for full-field strain measurement and to study the initiation and propagation of damage during the impact. The different modes of damage in the hybrid laminate were identified by postimpact analysis of the section of the damaged composite plate using optical microscopy. The study shows the difference in impact response for different material combinations and configurations. The hybrid construction was shown to improve the impact resistance of the flax composite.

Simulation of High-Speed Cutting Process Based on ABAQUS

2011 ◽  
Vol 230-232 ◽  
pp. 1221-1225 ◽  
Author(s):  
Xia Yu ◽  
Xu Yao Sun ◽  
Dan Ke Wei
Keyword(s):  
High Speed ◽  
Chip Morphology ◽  
Material Model ◽  
Rake Angle ◽  
Cutting Process ◽  
Fe Model ◽  
High Speed Cutting ◽  
Line Technology ◽  
Chip Separation ◽  
The Impact

Using the separation line technology, established a FE model of two-dimensional cutting process for AISI4340 steel and discussed some basic theory and pivotal questions associated with the simulation of cutting process including the Johnson-Cook material model, the contact model between tool and chip, criteria of chip separation and so on. In order to study the impact of tool rake angle on the chip morphology and the cutting forces, the high-speed cutting process for AISI 4340 steel was simulated based on ABAQUS software. Also, analyzed the influence of mesh azimuth on the chip morphology and its temperature distribution.

Structure and Properties Enhancement in High-Speed Steels upon Primary Solidification of a Melt

2008 ◽  
Vol 144 ◽  
pp. 267-272
Author(s):  
Alexander S. Chaus
Keyword(s):  
Mechanical Properties ◽  
High Speed ◽  
Chemical Elements ◽  
Structural Parameters ◽  
Structure Refinement ◽  
Structure And Properties ◽  
Theoretical Evaluation ◽  
Surface Active ◽  
The Impact ◽  
Toughness Enhancement

In order to exhibit good all-round performance the impact toughness enhancement of cast high-speed steels (HSS) is obligatorily needed. In general, different methods are used commercially to achieve cast structure refinement and, as a consequence, their properties are improved. Introduction into the melt of inoculants particles or surface-active additions is among most beneficial. However, the effect of modifying additions in cast HSS has been studied insufficiently. For this reason the theoretical evaluation and experimental confirmation of the modifying and refining effects of 23 chemical elements in HSS have been carried out. The relationships between the structural parameters and mechanical properties in the M2 and T30 HSS have been established.

Experimental Study on the Response Characteristics of Oilcans under High-Velocity Fragment Impact

2012 ◽  
Vol 510 ◽  
pp. 500-506
Author(s):  
Chang Hai Chen ◽  
Xi Zhu ◽  
Hai Liang Hou ◽  
Li Jun Zhang ◽  
Ting Tang
Keyword(s):  
Experimental Study ◽  
High Velocity ◽  
High Speed ◽  
Room Temperature ◽  
Experimental Results ◽  
Fuel Oil ◽  
High Speed Camera ◽  
Response Characteristics ◽  
Fuel Oils ◽  
The Impact

To explore the deflagration possibility of the warship cabin filled with fuel oil under impact of high-speed fragments in the condition of room temperature, experiments were carried out employing the small aluminium oilcans filled with fuel oil. Response processes of the oilcans were observed with the help of a high-speed camera. The disintegration as well as flying scattering of the oilcans were analyzed. The reasons for atomization of the fuel oils were presented. Finally, the deflagration possibility of warship oil cabin was analyzed. Results show that the pressure inside the oilcan is quite great under the impact of the high-speed fragment, which makes the oilcan disintegration and flying scattering. Simultaneously, fuel oils inside the oilcans are atomized quickly followed by ejected in front and back directions. Under the same condition as in present tests, deflagration will not occur for fuel oils used by warships. Experimental results will provide valuable references for the deflagration analysis of warship fuel oil cabins subjected to the impact of high-velocity fragments.

scholarly journals Numerical and Experimental Results on Charpy Tests for Blends Polypropylene + Polyamide + Ethylene Propylene Diene Monomer (PP+PA+EDPM)

2020 ◽  
Author(s):  
Catalin Pirvu ◽  
Andreea Elena Musteata ◽  
George Ghiocel Ojoc ◽  
Lorena Deleanu
Keyword(s):  
Equivalent Plastic Strain ◽  
Material Model ◽  
Element Model ◽  
Tensile Tests ◽  
Experimental Results ◽  
Low Velocity ◽  
Sem Images ◽  
Charpy Test ◽  
Simulation Results ◽  
The Impact

This paper presents results from numerical and experimental investigation on Charpy tests in order to point out failure mechanisms and to evaluate new polymeric blends PP+PA6+EPDM. Charpy tests were done for initial velocity of the impactor of 0.96 m/s and its mass of 3.219 kg and these data were also introduced in the finite element model. The proposed model take into account the system of four balls, including support and the ring of fixing the three balls and it has a finer discretization of the impact area to highlight the mechanisms of failure and their development in time. The constitutive models for four materials (polypropylene with 1% Kritilen, two blends PP+PA6+EPDM and a blend PA6+EPDM) were derived from tensile tests. Running simulations for each constitutive model of material makes possible to differentiate the destruction mechanisms according to the material introduced in the simulation, including the initiation and the development of the crack(s), based on equivalent plastic strain at break (EPS) for each material. The validation of the model and the simulation results was done qualitatively, analysing the shape of broken surfaces and comparing them to SEM images and quantitatively by comparing the impact duration, energy absorbed by the sample, the value of maximum force during impact. The duration of the destruction of the specimen is longer than the actual one, explainable by the fact that the material model does not take into account the influence of the material deformation speed in Charpy test, the model being designed with the help of tests done at 0.016 m/s (1000 mm/min) (maximum strain rate for the tensile tests). Experimental results are encouraging for recommending the blends 20% PP+42% PA6+28% EPDM and 60% PA6+ 40%EPDM as materials for impact protection at low velocity (1m/s). Simulation results are closer to the experimental ones for the more brittle tested materials (with less content of PA6 and EPDM) and more distanced for the more ductile materials (with higher content of PA6 and EPDM).

scholarly journals Investigation of Er:YAG laser-activated irrigation for the removal of biofilm and observations of laser-induced cavitation behavior

2022 ◽  
Author(s):  
Taiji Nagahashi ◽  
Yoshio Yahata ◽  
Keisuke Handa ◽  
Masato Nakano ◽  
Shigeto Suzuki ◽  
...  
Keyword(s):  
Laser Irradiation ◽  
Root Canal ◽  
High Speed ◽  
Er:Yag Laser ◽  
Positive Control ◽  
High Speed Camera ◽  
Pulp Chamber ◽  
Root Canal Irrigation ◽  
Biofilm Removal ◽  
The Impact

Abstract Background We investigated the biofilm removal effects of LAI using a pig model, focusing on the impact of the fiber tip position, and used a high-speed camera to observe the occurrence and positioning of the cavitation associated with laser irradiation. Methods A total of 16 roots of deciduous mandibular second premolars from 4 pigs were used. After a pulpectomy, the canals were left open for two weeks and sealed for 4 weeks to induce intraradicular biofilm. Then, root canal irrigation was performed with Er:YAG laser activation. The fiber tip was inserted at two different positions, i.e., into the root canal in the intracanal LAI group and into the pulp chamber in the coronal LAI group. Intracanal needle irrigation with saline or 5% NaOCl was utilized in the positive control and CNI groups. SEM and qPCR were carried out to evaluate treatment efficacy. For qPCR, ANOVA and a Tukey-Kramer post hoc test were performed with α = 0.05. A high-speed camera was used to observe the generation of cavitation bubbles and the movement of the induced bubbles after laser irradiation. Results The intracanal and coronal LAI groups showed significantly lower amounts of bacteria than either the positive control or CNI groups. There was no significant difference found between the intracanal and coronal LAI groups. SEM images revealed opened dentinal tubules with the destruction of biofilm in both LAI groups. High-speed camera images demonstrated cavitation bubble production inside the root canal after a single pulse irradiation pulse. The generated bubbles moved throughout the entire internal multi-rooted tooth space. Conclusions Coronal LAI can generate cavitation in the root canal with a simply placed fiber inside the pulp chamber, leading to effective biofilm removal. This method could thus contribute to the future development of endodontic treatments for refractory apical periodontitis caused by intraradicular biofilm.

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