Development of a Curved Hopkinson Bar for Long Wavelength Impact Events

2011 ◽  
Author(s):  
Glenn E. Vallee ◽  
Micah C. Bowen
Keyword(s):  
Wave Propagation ◽  
Impact Energy ◽  
Hopkinson Bar ◽  
Experimental Results ◽  
Bend Radius ◽  
Impact Pulse ◽  
Long Wavelength ◽  
Bend Angles ◽  
The Impact ◽  
Impact Events

A study of the feasibility of using a curved Hopkinson bar for the measurement of impact load and energy transmission is presented. The length requirements of straight prismatic bars commonly used to measure long wavelength impact events are often prohibitive, and the use of curved bars can result in a significant increase in wavelength capabilities while reducing the overall size of the measurement apparatus. The ABAQUS/Explicit finite element analysis (FEA) program is used to model steel bars of circular cross section bent with various bend radii and at various bend angles ranging from 15 to 180 degrees. A uniform compressive pressure pulse of known amplitude and wavelength is applied to the FEA models and the wave propagation behavior predicted by ABAQUS/Explicit is then compared to the response predicted by the theory of wave propagation in curved bars and experiments performed using curved bars. The numerical results show good agreement with the theoretical and experimental results. Significant distortion of the incident wave as it travels around the bend results in a transmitted pulse that is not characteristic of the input pulse, particularly at larger bend angles and long wavelengths. The energy transmitted around the bend radius contains only a fraction of the initial impact energy due to large reflections that develop at the bend radius, and this loss increases significantly at larger bend angles and smaller bend radii. However, the transmitted energy can be used to predict the incident energy at a variety of bend angles and bend radii. A curved carbon steel Hopkinson bar is fabricated with a bend angle of 180 degrees and instrumented with strain gauges to monitor the wave propagation within the bar at several locations resulting from a compressive impact pulse. The experimental results agree well with the results predicted using explicit dynamic FEA. The results of this study indicate that a curved Hopkinson bar can be used to predict the impact energy applied to the incident end of the bar using the measurement of the energy transmitted around the bend in the bar. The overall length of the curved Hopkinson bar apparatus can be significantly less than a comparable straight bar apparatus.

Study on a Novel MEMS High G Acceleration Sensor

2012 ◽  
Vol 490-495 ◽  
pp. 499-503
Author(s):  
Ping Li ◽  
Yun Bo Shi ◽  
Jun Liu ◽  
Shi Qiao Gao
Keyword(s):  
Resonant Frequency ◽  
Natural Frequency ◽  
Impact Load ◽  
Hopkinson Bar ◽  
Experimental Results ◽  
Structure Parameters ◽  
Acceleration Sensor ◽  
Piezoresistive Effect ◽  
Sensor Structure ◽  
The Impact

This paper presents a novel MEMS high g acceleration sensor based on piezoresistive effect. For the designed sensor structure, the formula of stress, natural frequency and damping was derived in theory, and the resonant frequency can up to 500kHz. After the structure parameters were designed, the sensor was fabricated by the standard processing technology, and the sensitivity was tested by Hopkinson bar. According to the experimental results, the sensitivity of the high g acceleration sensor is 0.125μV/g at the impact load of 164,002g.

scholarly journals A Control Method of High Impact Energy and Cosimulation in Powder High-Velocity Compaction

2018 ◽  
Vol 2018 ◽  
pp. 1-11 ◽  
Author(s):  
Dongdong You ◽  
Dehui Liu ◽  
Hangjian Guan ◽  
Qingyun Huang ◽  
Zhiyu Xiao ◽  
...  
Keyword(s):  
Impact Energy ◽  
High Velocity ◽  
Mechanical Energy ◽  
High Impact ◽  
Experimental Results ◽  
Hydraulic Control ◽  
Green Density ◽  
High Impact Energy ◽  
High Velocity Compaction ◽  
The Impact

To enhance the impact energy of powder high-velocity compaction (HVC) and thus improve the green density and mechanical properties of the resulting compacts, a mechanical energy storage method using combination disc springs is proposed. The high impact energy is achieved by modifying existing equipment, and the hydraulic control system is developed to implement the automatic control of the energy produced from the disc springs. An interdisciplinary cosimulation platform is established using the ADAMS, AMESim, and LabVIEW software packages to perform the interactive control of the simulation process and the real-time feedback of the simulation results. A mechanical-hydraulic cosimulation of the energy control virtual prototype of the testing machine is conducted using this platform. The influence of the impact energy on the green density is studied according to the HVC experimental results of the iron-based powders, and then, the green compact with the higher relative density is produced. The experimental results indicate that the energy enhancement method using the combination disc springs is reasonable and that the hydraulic control scheme is reliable.

scholarly journals Experimental Investigation of a Novel Blast Wave Mitigation Device

2006 ◽  
Author(s):  
Zhenbi Su ◽  
Zhaoyan Zhang ◽  
George Gogos ◽  
Reed Skaggs ◽  
Bryan Cheeseman ◽  
...  
Keyword(s):  
Shock Wave ◽  
Experimental Investigation ◽  
Wave Propagation ◽  
Blast Wave ◽  
Hopkinson Bar ◽  
Honeycomb Structure ◽  
Experimental Results ◽  
Maximum Pressure ◽  
Propagation Process ◽  
Piston Cylinder

A novel blast wave mitigation device was investigated experimentally in this paper. The device consists of a piston-cylinder assembly. A shock wave is induced within the cylinder when a blast wave impacts on the piston. The shock wave propagates inside the device and is reflected repeatedly. The shock wave propagation process inside the device lengthens the duration of the force on the base of the device to several orders of magnitude of the duration of the blast wave, while it decreases the maximum pressure by several orders of magnitude. Two types of experiments were carried out to study the blast wave mitigation device. The first type of experiments was done with honeycomb structures protected by the blast wave mitigation device. Experimental results show that the device can adequately protect the honeycomb structure. A second type of experiments was done using a Hopkinson bar to measure the pressure transmitted through the blast wave mitigation device. The experimental results agree well with results from a theoretical model.

scholarly journals Wall Properties and Slip Consequences on Peristaltic Transport of a Casson Liquid in a Flexible Channel with Heat Transfer

2018 ◽  
Vol 3 (1) ◽  
pp. 277-290 ◽  
Author(s):  
P. Devaki ◽  
S. Sreenadh ◽  
K. Vajravelu ◽  
K. V. Prasad ◽  
Hanumesh Vaidya
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Wave Propagation ◽  
Peristaltic Flow ◽  
Physical Parameters ◽  
Viscous Damping ◽  
Damping Force ◽  
Long Wavelength ◽  
Wall Properties ◽  
The Impact

AbstractIn this paper, the peristaltic wave propagation of a Non-Newtonian Casson liquid in a non-uniform (flexible)channel with wall properties and heat transfer is analyzed. Long wavelength and low Reynolds number approximations are considered. Analytical solution for velocity, stream function and temperature in terms of various physical parameters is obtained. The impact of yield stress, elasticity, slip and non-uniformity parameters on the peristaltic flow of Casson liquidare observed through graphs and discussed. The important outcome is that an increase in rigidity, stiffness and viscous damping force of the wall results in the enhancement of the size and number of bolus formed in the flow pattern.

Monitoring of Impact Damage in Composites Using Wave Propagation Methods

2007 ◽  
Author(s):  
G. P. Tandon ◽  
J. Kang ◽  
R. Y. Kim ◽  
T. J. Whitney
Keyword(s):  
Wave Propagation ◽  
Impact Energy ◽  
Composite Structures ◽  
Impact Force ◽  
Source Location ◽  
Low Velocity Impact ◽  
Critical Threshold ◽  
Flexural Wave ◽  
Low Velocity ◽  
The Impact

Composite structures in an aircraft are susceptible to impact damage, which can occur during manufacture, service or maintenance. Recent studies show that impacts with ground support equipment are the major cause of in-service damage to composite structures in an aircraft. Other sources of impact include collision with birds, runway stones or ballistic impacts. These impacts can produce various types of damage, including fiber breakage, matrix cracking, delamination, and interfacial debonding. The results of such damage can have detrimental effects on the overall structural performance and safety. A comprehensive structural health monitoring (SHM) system provides a means to significantly reduce life-cycle costs of aerospace vehicles by providing accurate diagnostics and prognostics of structural damage to reduce unnecessary inspections and support vehicle life extension. The main objective of this paper is to develop a methodology to detect and identify the damage sources and their severity in composite laminates subjected to low velocity impact using wave propagation methods. When damage occurs in a material due to mechanical load or impact, an acoustic wave emits and propagates through the material. The material chosen for this work is a 12″ long and 12″ wide, +/− 60 degree braided composite. Two edges of the plate were fixed by clamping the plate between two steel bars and secured by bolts spaced 1″ apart, while the other two edges were free, as shown in Figure 1. In order to characterize the wave propagation and damage process, two resonant type AE sensors and four accelerometers were mounted on the specimen. The specimen was then tapped lightly with a hand-held acoustic impact hammer at several different chosen locations, and stress wave signals were monitored using a commercial dynamic signal process system which contains software capable of detecting impact source location. The impact force was kept to a minimum initially such that no damage occurred in the specimen. After this initial test, the specimens were subjected to low velocity impact using drop weight impact machine with 0.5 inch spherical indenter. The impact force was increased by a number of times until substantial damage observed while monitoring signals generated from the specimen. After each incremental impact, both acoustic hammer tapping test and nondestructive inspection such as ultrasonic C-scan and/or X-ray radiography were carried out to delineate the damage source and severity. Figure 2 is an example of C-Scan of the composite plate after a series of impacts with various drop heights. Recorded signals were analyzed to determine the origin of the source and its severity. The impact hammer produced both an extensional wave and a flexural wave in these composite plate specimens. Because of dispersive characteristics of the flexural wave, the first arrival time of the extensional wave was used for source location algorithm. Besides the source location, discussion will be given on parameters such as amplitude, energy, frequency, number of events related with impact force, and damage size in detail. As an example, Figure 3 is a plot of the measured damage size as a function of the dead-weight drop height for tests conducted on various panels. As expected, the size of the damage increases with amount of drop height (or impact energy). Thus, based on C-scan measurements, critical threshold impact height of approximately 5″ is identified for “any measurable” damage to occur. The corresponding magnitude of the impact energy is ∼ 108 in-lb. On the other hand, the critical threshold for any visual damage to be detected is approximately 502 in-lb for the laminate material investigated. In summary, a methodology has been developed for estimating the damage severity from the amplitude of the signal received. The approach entails constructing design curves relating the size of the damage to impact energy, and establishing relationships between impact energy and the magnitude of the signal. These relationships can then be used to predict the estimated size of the damage based on the amplitude of the arriving signal. A critical threshold impact energy has been identified below which “no measurable” damage occurs. Three regions of damage growth, namely, a decreasing rate with magnitude of impact energy. A constant damage growth rate characterizes the steady-state region, while damage size increases almost exponentially with impact energy in the tertiary region potentially leading to catastrophic failure.

The Impact of Cash Mobs in the Vote with the Wallet Game: Experimental Results

2016 ◽  
Author(s):  
Leonardo Becchetti ◽  
Maurizio Fiaschetti ◽  
Francesco Salustri
Keyword(s):  
Experimental Results ◽  
The Impact

scholarly journals Experimental study of the supercritical CO 2 diffusion coefficient in porous media under reservoir conditions

2019 ◽  
Vol 6 (6) ◽  
pp. 181902 ◽  
Author(s):  
Junchen Lv ◽  
Yuan Chi ◽  
Changzhong Zhao ◽  
Yi Zhang ◽  
Hailin Mu
Keyword(s):  
Porous Media ◽  
Diffusion Coefficient ◽  
Oil Recovery ◽  
Carbon Capture ◽  
Carbon Capture And Storage ◽  
Elevated Pressure ◽  
Experimental Results ◽  
Saturated Porous Media ◽  
Reservoir Conditions ◽  
The Impact

Reliable measurement of the CO 2 diffusion coefficient in consolidated oil-saturated porous media is critical for the design and performance of CO 2 -enhanced oil recovery (EOR) and carbon capture and storage (CCS) projects. A thorough experimental investigation of the supercritical CO 2 diffusion in n -decane-saturated Berea cores with permeabilities of 50 and 100 mD was conducted in this study at elevated pressure (10–25 MPa) and temperature (333.15–373.15 K), which simulated actual reservoir conditions. The supercritical CO 2 diffusion coefficients in the Berea cores were calculated by a model appropriate for diffusion in porous media based on Fick's Law. The results show that the supercritical CO 2 diffusion coefficient increases as the pressure, temperature and permeability increase. The supercritical CO 2 diffusion coefficient first increases slowly at 10 MPa and then grows significantly with increasing pressure. The impact of the pressure decreases at elevated temperature. The effect of permeability remains steady despite the temperature change during the experiments. The effect of gas state and porous media on the supercritical CO 2 diffusion coefficient was further discussed by comparing the results of this study with previous study. Based on the experimental results, an empirical correlation for supercritical CO 2 diffusion coefficient in n -decane-saturated porous media was developed. The experimental results contribute to the study of supercritical CO 2 diffusion in compact porous media.

Response and failure modes of biaxial warp-knitted flexible composite subject to low-velocity impact

2021 ◽  
pp. 152808372110154
Author(s):  
Ziyu Zhao ◽  
Tianming Liu ◽  
Pibo Ma
Keyword(s):  
Impact Energy ◽  
Linear Density ◽  
Failure Modes ◽  
Impact Response ◽  
Low Velocity Impact ◽  
Minor Effect ◽  
Low Velocity ◽  
Velocity Impact ◽  
Flexible Composites ◽  
The Impact

In this paper, biaxial warp-knitted fabrics were produced with different high tenacity polyester linear density and inserted yarns density. The low-velocity impact property of flexible composites made of polyurethane as matrix and biaxial warp-knitted fabric as reinforcement has been investigated. The effect of impactor shape and initial impact energy on the impact response of flexible composite is tested. The results show that the initial impact energy have minor effect on the impact response of the biaxial warp-knitted flexible composites. The impact resistance of flexible composite specimen increases with the increase of high tenacity polyester linear density and inserted yarns density. The damage morphology of flexible composite materials is completely different under different impactor shapes. The findings have theoretical and practical significance for the applications of biaxial warp-knitted flexible composite.

scholarly journals Impact resistance of steel materials to ballistic ejecta and shelter development using steel deck plates

2021 ◽  
Vol 10 (1) ◽  
Author(s):  
Hiroyuki Yamada ◽  
Kohei Tateyama ◽  
Shino Naruke ◽  
Hisashi Sasaki ◽  
Shinichi Torigata ◽  
...  
Keyword(s):  
Impact Energy ◽  
Impact Test ◽  
Impact Resistance ◽  
Protective Layer ◽  
High Strength ◽  
Steel Plates ◽  
Corrugated Plates ◽  
Shelter Construction ◽  
The Impact ◽  
Ballistic Ejecta

AbstractThe destruction caused by ballistic ejecta from the phreatic eruptions of Mt. Ontake in 2014 and Mt. Kusatsu-Shirane (Mt. Moto-Shirane) in 2018 in Japan, which resulted in numerous casualties, highlighted the need for better evacuation facilities. In response, some mountain huts were reinforced with aramid fabric to convert them into shelters. However, a number of decisions must be made when working to increase the number of shelters, which depend on the location where they are to be built. In this study, we propose a method of using high-strength steel to reinforce wooden buildings for use as shelters. More specifically, assuming that ballistic ejecta has an impact energy of 9 kJ or more, as in previous studies, we developed a method that utilizes SUS304 and SS400 unprocessed steel plates based on existing impact test data. We found that SUS304 is particularly suitable for use as a reinforcing material because it has excellent impact energy absorption characteristics due to its high ductility as well as excellent corrosion resistance. With the aim of increasing the structural strength of steel shelters, we also conducted an impact test on a shelter fabricated from SS400 deck plates (i.e., steel with improved flexural strength provided by work-hardened trapezoidal corrugated plates). The results show that the shelter could withstand impact with an energy of 13.5 kJ (2.66 kg of simulated ballistic ejecta at 101 m/s on impact). In addition, from the result of the impact test using the roof-simulating structure, it was confirmed the impact absorption energy is further increased when artificial pumice as an additional protective layer is installed on this structure. Observations of the shelter after the impact test show that there is still some allowance for deformation caused by projectile impact, which means that the proposed steel shelter holds promise, not only structurally, but also from the aspects of transportation and assembly. Hence, the usefulness of shelters that use steel was shown experimentally. However, shelter construction should be suitable for the target environment.

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