Name: blast quantification using hopkinson pressure bars
Uploaded: 2016-07-05T14:00:00
Description: Watch this Scientific Journal Video about Blast Quantification Using Hopkinson Pressure Bars at JoVE.com

The authors wish to thank the Defence Science and Technology Laboratory for funding the published work.

1. 엄밀한 반응 프레임 <ol><li> 테스트 R은 폭발성의 중심으로부터의 거리를 수학 식 1을 이용하여 열린다되는 스케일링 된 거리를 결정하고, W는 질량 TNT의 등가 질량 표현 전하이다. Z = R / W 1/3 (1) </li><li> 이 배열은 수치 모델링을 통해 생성됩니다 대략적인 최대 충격을 계산합니다 (부록 A 참조) 또는 ConWep 3과 같은 특정 도구를 제공합니다. 참고 : 매...

<ol>
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저자 위에 설명 된 프로토콜을 사용하는 것이 홉 킨슨 압력 바의 배열을 사용하여 폭약에서 매우 다양한 로딩의 높은 정확도 측정치를 얻을 수 있음을 보여 주었다. 이산 감압 시간 이력을 보간 루틴을 사용하는 것이 가능 약술 수치 모델링 또는 모델의 출력을위한 검증 데이터로서로드 함수로서 직접 사용할 수있다 연속 충격 앞쪽으로 변형 될 수있다. 매립 된 전하를 사용?...

폭발물의 출력을 특성화하는 것은 두 (현재 분쟁 지역에서 폭발 장치를 즉석에서 매립형 방어) 군사 및 민간 (구조 구성 요소를 설계), 많은 혜택이 있습니다. 최근에이 주제에 상당한 관심을 받고있다. 수집 된 지식의 대부분은보다 효과적인 보호 구조의 설계를 가능하게 전하의 출력 정량 대상으로하고있다. 여기에 주요 문제는 만든 측정이 높은 충실도의하지 않은 경우 다음이 폭발 사건의 하중 전달의 메커니즘 불분명 남아 있습니다. 이것은 차례로 검증을위한 이러한 측정에 의존하는 수치 모델을 검증하는 문제로 이어집니다. 근접장 용어는 스케일링 거리, Z, 이하 1 ~ M / Z = R / W 1/3, R은 폭발성의 중심으로부터의 거리이다 1/3 kg 미만, W와 폭발을 설명하는 데 사용되는 전하 대량 발현TNT의 등가 질량있다. 이 정권에서로드는 일반적으로 높은 공간 및 시간적으로 비 균일 부하 매우 높은 크기, 특징입니다. 강력한 기기는 이에 근접장 로딩과 관련된 극도의 압력을 측정 할 필요가있다. 스케일 거리 Z에서 &lt;0.4 m는 / 1/3 kg의 폭발 매개 변수를 직접 측정 존재 또는 거의 1이 범위에 대한 반 경험적 예측 데이터가 파라 메트릭 연구에 거의 전적으로 기반 중 하나입니다. 이것은 저자의 의도 된 범위를 벗어나 Kingery 및 Bulmash 2에 의해 주어진 반 경험적 예측을 사용하는 것입니다. 이러한 예측 3,4에 기반 도구가로드의 우수한 일차 추정을 허용하는 동안 그들은 완전히 현재의 연구의 초점이다 근접장 이벤트의 역학을 캡처하지 않습니다. 근거리 폭발 측정이 최근에이은 OUTP을 정량화에 초점을 맞춘매몰 비용에서 유타. 사용 된 방법은 글로벌 임펄스 측정 8-13을 직접 구조 대상 5-7로 인한 변형을 평가 다릅니다. 이러한 방법은 보호 시스템 설계의 검증을위한 유용한 정보를 제공 할 수 있지만 완전히 하중 전달의 메커니즘을 조사 할 수 없습니다. 시험은에 의해 생성되는 등의 매장 깊이를 제어하거나 충격 전면에는 고유의 모양을 보장하지 않습니다 같은 실제적인 이유와 함께, 또는 주변의 풀 스케일 (&gt; 1/4)에 양쪽 실험실 저울 (1/10 풀 스케일)에서 할 수 있습니다 뇌관보다는 베어 요금 (14)의 사용. 매립 전하 토양 조건은 높은 테스트 (15)의 재현성을 보장하기 위해 제어 될 필요가있다. 전하가없는 공기에 배치 또는 매설 여부 독립적 얻어진 폭발 측정에서 가장 근본적인 문제는 계측 deplo 의한 측정의 유효성을 보장하는 것이다YED. 설계된 시험 장치 (16)에 고정 된 &#39;강성&#39;타겟 플레이트는 바의 단부에만 완전히 반영 압력을 기록 할 수 있음을 보장하는 동시에 하다니 홉 킨슨 압력 바 (17) (HPBs)를 보호하기 위해 사용된다. 단단한 목표는 &#39;자유 필드&#39;측정 18-20보다 정확하고 사건보다 반복, 또는이다에서 저자는 이전에 반사 된 압력의 측정을 보여 주었다. 이 판의 형상은 타겟 에지 (21) 주위에 삭제 또는 유동에 의해 생성 된 압력 릴리프 무시할 것이라고 예이다. 이 새로운 시험 장치는 1/4 규모로 건설되고있다. 매장 조건과 폭발물을 통해이 규모 엄격한 제어에서 25mm의 매장 깊이에서 78g으로 축소 5kg의 풀 스케일 충전 크기, 확보 할 수있다.

<table border="0" cellpadding="0" cellspacing="0" width="573">
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Load Cell</td>
			<td style="width:71px;">RDP</td>
			<td style="width:119px;">RSL0960</td>
			<td style="width:167px;">This is only indicative, the exact load cell should be able to resolve the required loading</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Steel target plate / HPBs</td>
			<td style="width:71px;">Garratts&#160;</td>
			<td style="width:119px;">N/A</td>
			<td>Fabricated to order</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Strain gauge</td>
			<td style="width:71px;">Kyowa</td>
			<td>KSP-2-120-E4</td>
			<td>To use with steel HPBs</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Cyanoacrylate</td>
			<td style="width:71px;">Kyowa</td>
			<td>CC-33-A</td>
			<td>Check with manufacturer depending on mar material to be used</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Digital Oscilloscope</td>
			<td style="width:71px;">TiePie</td>
			<td>HS4 16-bit Handyscopes&#160;</td>
			<td>6 used in parallel in current testing</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Leighton Buzzard sand</td>
			<td style="width:71px;">Garside sands</td>
			<td style="width:119px;">Garside 14/25</td>
			<td>Uniform silica sand&#160;</td>
		</tr>
	</tbody>
</table>

blast quantification using hopkinson pressure bars

그들은 매우 공격적인 환경을 견딜과 메가 파스칼의 수백까지 압력을 측정 할 수 있어야로 근거리 폭발 하중 측정은 여러 센서 유형에 대한 문제를 제시한다. 이 점에서, 홉 킨슨 압력 바의 단순성은 홉 킨슨 바의 측정 끝이 견딜 수 및 가혹한 조건에 노출되는 동안, 스트레인 게이지가 약간의 거리에 부착 할 수있는 막대에 장착한다는 점에서 큰 장점이있다. 이 보호 틀은 스트레인 게이지를 보호하지만, 측정 수집을 방해하지 않은 이용 될 수있다. 압박 막대의 어레이의 사용은 공지 된 이산 지점에서 압력의 시간 이력을 측정 할 수있다. 이 문서는 또한 관심의 평면에 미 계측 위치에서 압력 - 시간 이력을 유도하는 데 사용되는 보간 루틴을 설명합니다. 현재이 기술은 자유 공기 내의 높은 폭발물의 로딩을 측정하기 위해 사용 된 다양한 토양에 얕게 매장.

실효 적 반응 강성 프레임을 제공 할 필요가있다. 현재는 수백 뉴턴 초 총 부과 된 충격 테스트에서 최소 편향에 저항해야합니다. 사용되는 경질 반응 프레임의 그림은 그림 1에 제시되어있다. 각 프레임에서 50mm 스틸 &#39;수용체&#39;판은 크로스 빔의 바닥에 던져되었습니다. 명시 적으로 요구되지 동안,이로드 셀 / 표적 판 쉽게 고정 가능 콘크리트 빔의면에 ?...

Watch this Scientific Journal Video about Blast Quantification Using Hopkinson Pressure Bars at JoVE.com

Blast Quantification Using Hopkinson Pressure Bars

This protocol details the use of Hopkinson pressure bars to measure reflected blast loading from near-field explosive events. It is capable of interpolating a pressure-time history at any point on a reflective boundary and as such can be used to fully characterize the spatial and temporal variations in loading produced.

폭발 정량화는 홉 킨슨 압력 막대를 사용하여

Near-field blast load measurement presents an issue to many sensor types as they must endure very aggressive environments and be able to measure pressures ...

The overall goal of this experiment is to accurately measure the spatial and temporal distribution of pressure in the extremely aggressive environment generated close to an explosive charge. This method can help answer the key questions in the field of blast protection engineering such as the exact form of the imparted load and how factors such as explosive type and shape influence the imparted load. The main advantage of this technique is that it allows us to record pressures that are beyond the limits of traditional measuring approaches.Though this method can provide insights into free air explosions, it can also be applied to other events, such as buried or underwater charges. We first trialed the idea for this method using a single Hopkinson pressure bar, and soon realized a large array is needed to accurately capture the data. To begin, calculate the approximate maximum impulse the test frame arrangement will generate using software analysis, such as with ConWep.For buried charges, this process is less straightforward, cause it requires more advanced numerical techniques to model the interaction between the soil, explosives, and the target plate. Details on the production of the test frame and the load cells are each provided in the text protocol. Choose the position on the Hopkinson pressure bars that the strain gauge will be positioned, being as close as possible to the loaded face to minimize dispersion.In this setup, the thickness of the target plate and the maneuverability required to fit the bars results in the gauges being installed 250 millimeters from the loaded face. The calculated bar radius required to capture the event is in this case five millimeters. Use the tightest spatial resolution for the bars that does not compromise structural integrity.In this case, the distance is 25 millimeters. Further details are provided in the text protocol. To begin, using cyanoacrylate, attach semiconductor strain gauge to the Hopkinson pressure bars, then to the load cells.Fit the target plate to the rigid reaction frame using the load cells if needed. Make certain that all of the cabling is well grounded for improved signal quality. The wiring must also be long enough to connect to an oscilloscope outside the blast area.Any shielded wire should carry enough signal. Now, hang Hopkinson pressure bars from the bar assembly receiver. Pass the loaded end through the correct hole in the target plate, and hang the Hopkinson pressure bars freely from the nut screwed onto their distal ends.Using a level, adjust the nuts to position the bars vertically and to make their faces level with the target plate. Now, use trial and error to set the trim on the variable resistor in the conditioning circuit to keep the voltage within the limits of the oscilloscope. Zero the out of balance reading on each channel as reported by the amplifier boxes.Next, connect the amplified gauge output to a suitable digital oscilloscope. Configure the oscilloscope to a 1.56 megahertz sampling frequency with a 28.7 millisecond recording duration and set the pre-trigger duration to 3.3 milliseconds. 22 total gauges should be connected, 17 from Hopkinson pressure bars, four from load cells, and the one break wire.Record the voltage and time from each gauge. Set the recording to trigger when the voltage in the break wire exceeds an out-window value, such as plus or minus 100 millivolts. In the case of a free air charge test, use a thin strip of wood to suspend the charge below the target plate at the correct stand-off, in this case 200 millimeters.Position the charge co-axially with the measurement array to ensure valid readings. The critical element in the buried charge test is in the preparation of the soil bed and the burial process. Precision is required to ensure repeatable results are attained.Next, close the range. Deploy sentries to ensure the range is clear during the firing. Now, just before firing a free air charge, attach the break wire to the detonator and insert an electrical detonator halfway into the charge from the base.Now, move to the firing point and confirm that the instrumentation is operative. Then, supply power to the break wire. Now, make certain to check with the sentries that it is safe to proceed with the firing.Then, initiate the explosives. After the detonation, make the test area safe and download and back up the data. Whilst a protocol is being written to describe the steps required in this stage, a developed Matlab script is also being made available to allow the data processing to be done quickly using the exact methodology.Import the data from the raw data files into Matlab by double clicking on the file name and then clicking Finish in the Import Wizard. Next, open the interpolation Matlab script. In the meshing section of the code, define a regular grid over which the interpolation will run by changing the mesh.Use the same resolution in any future numerical modeling. This crucial step transforms the discreet data into a 2D map. The script will time shift all Hopkinson pressure bar pressure traces.The time shift is required to allow the interpolation routine to successfully locate the shock front at any given time. Now, align the data from each radial array so all the maximum pressures are synced. Next, calculate the radius, r, and angle, beta, for a given point of interest on the grid.Apply the 1D interpolation to the two Hopkinson pressure bar arrays closest to the point of interest of the current radius. For example, at 45 degrees, the interpolation would use the X, X and Y, Y arrays. Now, interpolate the linearity between the two pressures based on the angle.For example, at 45 degrees, use 50%X, X and 50%Y, Y.Then, time shift the pressure time history for each location based on cubic interpolation of the shock arrival time. Ultimately, the result is a fully interpolated pressure time history. An effectively rigid reaction frame capable of resisting several hundred Newton-seconds with minimal deflection was conceived using a 100 millimeter mild steel target plate.This frame withstood tests up to 500 Newton-seconds. A single test was made with 17 Hopkinson pressure bars configured in a 2D array utilizing 3.25 meter long bars with five millimeter radii. Spacing was set to 25 millimeters.For this test, the strain gauge was attached 0.25 meters from the loaded face. A charge buried in saturated soil was detonated. Data from each of the four radial arrays with a central Hopkinson pressure bar common to all the plots shows the very clear shock front, with the pressure decaying slowly with radial distance.The recorded pressure time histories were then run through the 2D interpolation routine. The interpolated pressure acting on the target plate shows a 20 millisecond delay in the arrival of the shock front. The shock front is the time taken for the shock wave to cover the distance between the charge and the target plate.The asymmetric nature of the loading is especially clear at 0.22 milliseconds. By 0.3 milliseconds after detonation, the shock front was almost symmetric along all axes. Once the apparatus is commissioned, up to six free air tests per day can be conducted.This number is greatly reduced with a test using buried charges due to the added complexity of preparing the soil. This is the first time that such high resolution measurements have been possible. As a result, we're now able to measure the difference in the form of the loading caused by variations in test geometry.The numerical routine developed offers a very powerful way to visualize the loading and then to apply this loading directly in numerical models to act as a first step in modeling the response of structures to explosive detonations. The data produced from the current test has provided unique validation data to enhance the next generation of numerical models, improving our understanding of the problem and our ability to protect ourselves against explosive blasts.

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