Application of a split-Hopkinson tension bar in a mutual assessment of experimental tests and numerical predictions

2011 ◽  
Vol 38 (10) ◽  
pp. 824-836 ◽  
Author(s):  
Y. Chen ◽  
A.H. Clausen ◽  
O.S. Hopperstad ◽  
M. Langseth
Keyword(s):  
Experimental Tests ◽  
Numerical Predictions ◽  
Split Hopkinson ◽  
Split Hopkinson Tension Bar

Dynamic Constitutive Relation and Fracture Model of Q235A Steel

2013 ◽  
Vol 274 ◽  
pp. 463-466 ◽  
Author(s):  
Li Lin ◽  
Feng Fan ◽  
Xu Dong Zhi
Keyword(s):  
Fracture Strain ◽  
Stress Triaxiality ◽  
Rate Sensitivity ◽  
Experimental Tests ◽  
Model Parameters ◽  
Element Calculation ◽  
Tension Tests ◽  
Split Hopkinson ◽  
Strength And Ductility ◽  
Split Hopkinson Tension Bar

Strength and ductility data for Q235A steel from 20 oC to 950 oC was obtained from a series of experimental tests. The stress rate sensitivity was studied by conducting Split-Hopkinson Tension Bar (SHTB) test and uniaxial tension test on smooth cylindrical specimens while the influence of stress triaxiality on ductility was revealed by conducting upsetting tests, tension tests on pre-notched cylinder specimens and torsion tests on SASs. Slightly modified versions of the two Johnson–Cook (J–C) models describing flow stress and fracture strain are presented to characterize the properties of Q235A steel as function of strain rate, temperature and stress triaxiality. Corresponding model parameters were calibrated based on the test data and with the help of finite element calculation. It was found that the modified Johnson–Cook (MJC) models give more close predictive results compared with the original J–C models.

scholarly journals Numerical Evaluation of a Light-Gas Gun Facility for Impact Test

2014 ◽  
Vol 2014 ◽  
pp. 1-6 ◽  
Author(s):  
C. Rahner ◽  
H. A. Al-Qureshi ◽  
D. Stainer ◽  
D. Hotza ◽  
M. C. Fredel
Keyword(s):  
High Velocity ◽  
Numerical Evaluation ◽  
Impact Test ◽  
Experimental Tests ◽  
Reservoir Pressure ◽  
One Stage ◽  
Gas Gun ◽  
Numerical Predictions ◽  
High Velocity Impacts ◽  
Different Types

Experimental tests which match the application conditions might be used to properly evaluate materials for specific applications. High velocity impacts can be simulated using light-gas gun facilities, which come in different types and complexities. In this work different setups for a one-stage light-gas gun facility have been numerically analyzed in order to evaluate their suitability for testing materials and composites used as armor protection. A maximal barrel length of 6 m and a maximal reservoir pressure of a standard industrial gas bottle (20 MPa) were chosen as limitations. The numerical predictions show that it is not possible to accelerate the projectile directly to the desired velocity with nitrogen, helium, or hydrogen as propellant gas. When using a sabot corresponding to a higher bore diameter, the necessary velocity is achievable with helium and hydrogen gases.

scholarly journals Modelling of Tsunami Due to Submarine Landslide by Smoothed Particle Hydrodynamics Method

2018 ◽  
Vol 203 ◽  
pp. 01001 ◽  
Author(s):  
Vo Nguyen Phu Huan ◽  
Indra Sati H. Harahap ◽  
Wesam Salah Alaloul
Keyword(s):  
Smoothed Particle Hydrodynamics ◽  
Experimental Tests ◽  
Offshore Structures ◽  
Submarine Landslide ◽  
Tsunami Waves ◽  
Numerical Predictions ◽  
Particle Hydrodynamics ◽  
Smoothed Particle ◽  
Smoothed Particle Hydrodynamics Method ◽  
Run Up

Submarine landslide is the most serious threat on both local and regional scales. By way of addition to destroying directly offshore structures, slope failures may also generate destructive tsunami waves. This study has developed a numerical model based on the Smoothed Particle Hydrodynamics (SPH) method to predict four stages of generation, propagation, run-up, and impact of tsunami phenomenon. The numerical predictions in the research were validated with results in the literature and experimental tests. The results of the physical and numerical results presented in this study effort to develop these rule of thumbs to clearly understand some of the mechanics that may play a role in the assessment of tsunami waves.

scholarly journals Stress Transfer Mechanism of Flange in Split Hopkinson Tension Bar

2020 ◽  
Vol 10 (21) ◽  
pp. 7601
Author(s):  
Hyunho Shin ◽  
Sanghoon Kim ◽  
Jong-Bong Kim
Keyword(s):  
Stress Transfer ◽  
Transfer Mechanism ◽  
Explicit Finite Element ◽  
Impact Theory ◽  
Quantitative Basis ◽  
Split Hopkinson ◽  
One Step ◽  
The One ◽  
The Impact ◽  
Split Hopkinson Tension Bar

To reveal the stress transfer mechanism of the flange in a split Hopkinson tension bar, explicit finite element analyses of the impact of the hollow striker on the flange were performed across a range of flange lengths. The tensile stress profiles monitored at the strain gauge position of the incident bar are interpreted on a qualitative basis using three types of stress waves: bar (B) waves, flange (F) waves, and a series of reverberation (Rn) waves. When the flange length (Lf) is long (i.e., Lf > Ls, where Ls is the striker length), the B wave and first reverberation wave (R1) are fully separated in the time axis. When the flange length is intermediate (~Db < Lf < Ls, where Db is the bar diameter), the B and F waves are partially superposed; the F wave is delayed, then followed by a series of Rn waves after the superposition period. When the flange length is short (Lf < ~Db), the B and F waves are practically fully superposed and form a pseudo-one-step pulse, indicating the necessity of a short flange length to achieve a neat tensile pulse. The magnitudes and periods of the monitored pulses are consistent with the analysis results using the one-dimensional impact theory, including a recently formulated equation for impact-induced stress when the areas of the striker and bar are different, equations for the reflection/transmission ratios of a stress wave, and an equation for pulse duration time. This observation verifies the flange length-dependent stress transfer mechanism on a quantitative basis.

Design and Testing of a Miniaturized Five-Hole Fast Response Pressure Probe With Large Frequency Bandwidth and High Angular Sensitivity

2019 ◽  
Vol 141 (10) ◽  
Author(s):  
Elissavet Boufidi ◽  
Marco Alati ◽  
Fabrizio Fontaneto ◽  
Sergio Lavagnoli
Keyword(s):  
Dynamic Response ◽  
Three Dimensional ◽  
Experimental Tests ◽  
Fast Response ◽  
Pressure Probe ◽  
Probe Design ◽  
Directional Sensitivity ◽  
Angular Sensitivity ◽  
Numerical Predictions ◽  
Response Pressure

Abstract A miniaturized five-hole fast response pressure probe is presented, and the methods for the aerodynamic design and performance characterization are explained in detail. The probe design is aimed for three-dimensional (3D) time-resolved measurements in turbomachinery flows, therefore requiring high frequency response and directional sensitivity. It features five encapsulated piezoresistive pressure transducers, recessed inside the probe hemispherical head. Theoretical and numerical analyses are carried out to estimate the dynamic response of the pressure tap line-cavity systems and to investigate unsteady effects that can influence the pressure readings. A prototype is manufactured and submitted to experimental tests that demonstrate performance in line with the theoretical and numerical predictions of the dynamic response: the natural frequency of the central and lateral taps extends to 200 and 25 kHz, respectively. An aerodynamic calibration is also performed at different Reynolds and Mach numbers. The probe geometry offers a good angular sensitivity in a ± 30 deg incidence range, while a frequency analysis reveals the presence of pressure oscillations related to vortex shedding at large angles of attack.

Micromechanics Analysis of the Tensile Behavior of Twaron Fiber Tows at Various Strain Rates

2011 ◽  
Vol 181-182 ◽  
pp. 749-753
Author(s):  
Lv Tao Zhu ◽  
Bao Zhong Sun
Keyword(s):  
Mechanical Properties ◽  
Fracture Surface ◽  
Strain Rate ◽  
Failure Strain ◽  
Tensile Behavior ◽  
Failure Stress ◽  
Strain Rates ◽  
Split Hopkinson ◽  
Electronic Microscope ◽  
Split Hopkinson Tension Bar

In this study, tensile experiments of Twaron fiber tows under different strain rates (quasi-static:0.001s-1, dynamic: 800s-1~2400s-1) were carried out with MTS 810.23 materials tester and split Hopkinson tension bar (SHTB) respectively. The results showed that the mechanical properties of the Twaron fiber tows were sensitive to strain rate: the stiffness and failure stress of the fiber tows increased distinctly as the strain rate increased, while the failure strain decreased. From scanning electronic microscope (SEM) photographs of the fracture surface, it is indicated that the Twaron fiber tows failed in a more tough mode and the axial split will become more severe as the strain rate increases.

scholarly journals Static and Fatigue Failures of Adhesively Bonded Laminate Joints in Moist Environments

2011 ◽  
Vol 20 (8) ◽  
pp. 1217-1242 ◽  
Author(s):  
K. B. Katnam ◽  
A. D. Crocombe ◽  
H. Sugiman ◽  
H. Khoramishad ◽  
I. A. Ashcroft
Keyword(s):  
Cohesive Zone ◽  
Experimental Tests ◽  
Static Fatigue ◽  
Test Results ◽  
Adhesively Bonded ◽  
Aerospace Applications ◽  
Numerical Predictions ◽  
Fatigue Failures ◽  
Good Agreement

Advanced structural adhesives are now an important joining technique in automobile and aerospace applications. The perceived uncertainty in the long-term structural performance of bonded members when subjected to static/fatigue loads in aggressive environments is probably restricting an even more widespread use of this joining technology. In this article, the effect of moisture on the static and fatigue resistances of adhesively bonded laminate joints was investigated. Experimental tests were performed on both aged and unaged adhesively bonded laminate joints for static and fatigue responses. Further, using a cohesive zone approach for the adhesive bondlines, a combined diffusion–stress analysis was developed to predict the progressive damage observed in the joints tested experimentally. The numerical predictions were found to be in good agreement with the experimental test results.

scholarly journals Dependency of Air Curtain Performance on Discharge Air Velocity (Grille and Back Panel) in Open Refrigerated Display Cabinets

2009 ◽  
Author(s):  
Pedro Dinis Gaspar ◽  
L. C. Carrilho Gonc¸alves ◽  
Andreas Vo¨geli
Keyword(s):  
Heat Transfer ◽  
Porous Medium ◽  
Unit Length ◽  
Experimental Tests ◽  
Cfd Modeling ◽  
Air Velocity ◽  
Conservation Area ◽  
Air Curtain ◽  
Numerical Predictions ◽  
Back Panel

This study performs a Computational Fluid Dynamics (CFD) modeling of air flow and heat transfer of an open refrigerated display cabinet in order to evaluate the influence of the discharge air velocity on the performance of its recirculated air curtain. The physical-mathematical model considers the flow through the internal ducts, across the fans and the evaporator, and also the thermal response of food products. The fan boundary condition is modeled in order to vary the air velocity at the discharge grille. The back panel perforation is modeled as a porous medium. The density and dimension of the back panel perforation variation is modeled by the Darcy’s law with the Forchheimer extension, varying the viscous and inertial resistance coefficients of the porous medium, based on its porosity, permeability, air velocity and pressure loss coefficient. Experimental tests were conducted to characterize the phenomena near the physical borders and to prescribe boundary conditions as well as to validate the numerical predictions on the temperature, relative humidity and velocity distributions. The numerical results show that the lowest average temperature in the conservation area of the display cabinet is achieved at a discharge air grille velocity of 1.15 ms−1. This value is lower than the experimental one, 1.51 ms−1, measured on the real equipment. The absence of a velocity component in the third dimension, which can destabilize the air curtain, is assumed to be the reason for this discrepancy. The profiles of the numerical predictions of the air curtain indicate that in the optimum case the air curtain is not so stable to bear big disturbances from outside. In order to increase the thermal performance and to reduce the energy consumption of these equipments, it’s not recommended to run the re-circulated air curtain velocity below 1.15 ms−1. For each CFD model, the values and directions of the air mass flow rate and heat transfer across the re-circulated air curtain by unit length are predicted and compared with the experimental ones in order to evaluate its thermal energy gains and losses.

Update on the Design of a 1:33 Scale Model of a Modified Edinburgh Duck WEC

2008 ◽  
Author(s):  
Jorge Lucas ◽  
Joa˜o Cruz ◽  
Stephen Salter ◽  
Jamie Taylor ◽  
Ian Bryden
Keyword(s):  
Wave Energy ◽  
Control Strategies ◽  
Experimental Tests ◽  
Point Of View ◽  
Electricity Production ◽  
Scale Model ◽  
Random Waves ◽  
Numerical Predictions ◽  
Key Innovation ◽  
The University

A modified version of the Edinburgh Duck wave energy converter has been studied recently at the University of Edinburgh. From the design point of view the key innovation was a modification of the wetted profile. Wave energy is converted into useful work by the same pitching motion as in the original Duck, but by means of a circular cylinder with an off centred axis of rotation. This recent study was focused on a Duck version designed for vapour compression desalination rather than electricity production. An hydrodynamic numerical model (WAMIT) was used to predict first-order hydrodynamics quantities and to select and optimize configurations. The results obtained showed that it was possible, following the appropriate control strategies, to obtain similar energy absorption capabilities as the in the cam shaped original Duck. A 1:33 scale model was built to validate the numerical predictions. This paper extends the already published numerical predictions and experimental results obtained with this model. Experimental tests in random waves and measurements of the mooring forces for different submerged volumes will be reported for the first time.

Design and Testing of a Miniaturized Five-Hole Fast Response Pressure Probe With Large Frequency Bandwidth and High Angular Sensitivity

2019 ◽  
Author(s):  
Elissavet Boufidi ◽  
Marco Alati ◽  
Fabrizio Fontaneto ◽  
Sergio Lavagnoli
Keyword(s):  
Dynamic Response ◽  
Three Dimensional ◽  
Experimental Tests ◽  
Fast Response ◽  
Pressure Probe ◽  
Probe Design ◽  
Directional Sensitivity ◽  
Angular Sensitivity ◽  
Numerical Predictions ◽  
Response Pressure

Abstract A miniaturized five-hole fast response pressure probe is presented and the methods for the aerodynamic design and characterization performance are explained in detail. The probe design is aimed for three-dimensional time-resolved measurements in turbomachinery flows, therefore requiring high frequency response and directional sensitivity. It features five encapsulated piezoresistive pressure transducers, recessed inside the probe hemispherical head. Theoretical and numerical analyses are carried out to estimate the dynamic response of the pressure tap line-cavity systems and to investigate unsteady effects that can influence the pressure readings. A prototype is manufactured and submitted to experimental tests that demonstrate performance in line with the theoretical and numerical predictions of the dynamic response: the natural frequency of the central and lateral taps extend to 25 kHz and 200 kHz respectively. An aerodynamic calibration is also performed at different Reynolds and Mach numbers. The probe geometry offers a good angular sensitivity in a ±30° incidence range, while a frequency analysis reveals the presence of pressure oscillations related to vortex shedding at large angles of attack.

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