Electrospray Drop Test Method for Green Hypergolic Propellants

2021 ◽  
pp. 1-4
Author(s):  
Hongjae Kang ◽  
Seonghyeon Park ◽  
Kyounghwan Lee ◽  
Dae Hoon Lee ◽  
Jongkwang Lee
Keyword(s):  
Test Method ◽  
Drop Test ◽  
Hypergolic Propellants

Head Impact Modeling to Support a Rotational Combat Helmet Drop Test

2021 ◽  
Author(s):  
Ryan Terpsma ◽  
Rika Wright Carlsen ◽  
Ron Szalkowski ◽  
Sushant Malave ◽  
Alice Lux Fawzi ◽  
...  
Keyword(s):  
Human Head ◽  
Mechanical Stimulus ◽  
Scientific Basis ◽  
Test Method ◽  
Drop Test ◽  
Head Impacts ◽  
Digital Twin ◽  
Brain Deformation ◽  
Acceleration Time Histories ◽  
Hybrid Iii

ABSTRACT Introduction The Advanced Combat Helmet (ACH) military specification (mil-spec) provides blunt impact acceleration criteria that must be met before use by the U.S. warfighter. The specification, which requires a helmeted magnesium Department of Transportation (DOT) headform to be dropped onto a steel hemispherical target, results in a translational headform impact response. Relative to translations, rotations of the head generate higher brain tissue strains. Excessive strain has been implicated as a mechanical stimulus leading to traumatic brain injury (TBI). We hypothesized that the linear constrained drop test method of the ACH specification underreports the potential for TBI. Materials and Methods To establish a baseline of translational acceleration time histories, we conducted linear constrained drop tests based on the ACH specification and then performed simulations of the same to verify agreement between experiment and simulation. We then produced a high-fidelity human head digital twin and verified that biological tissue responses matched experimental results. Next, we altered the ACH experimental configuration to use a helmeted Hybrid III headform, a freefall cradle, and an inclined anvil target. This new, modified configuration allowed both a translational and a rotational headform response. We applied this experimental rotation response to the skull of our human digital twin and compared brain deformation relative to the translational baseline. Results The modified configuration produced brain strains that were 4.3 times the brain strains from the linear constrained configuration. Conclusions We provide a scientific basis to motivate revision of the ACH mil-spec to include a rotational component, which would enhance the test’s relevance to TBI arising from severe head impacts.

Failure Analysis of the Solder Joints in Flip-Chip BGA Packages under Free-Drop Test

2014 ◽  
Vol 936 ◽  
pp. 628-632 ◽  
Author(s):  
Guo Zheng Yuan ◽  
Xia Chen ◽  
Xue Feng Shu
Keyword(s):  
Flip Chip ◽  
Solder Joints ◽  
Ball Grid Array ◽  
Test Method ◽  
Drop Test ◽  
Test Reliability ◽  
Internal Crack ◽  
The Real ◽  
Plastic Ball ◽  
Free Drop

The failure of plastic ball grid array under intense dynamic loading was studied in the project. This paper presents the drop test reliability results of SnPb flip-chip on a standard JEDEC drop reliability test board. The failure mode and mechanism of planar array package in the drop test was comprehensively analyzed. High acceleration dropping test method was used to research the reliability of BGA (ball grid array) packages during the free-drop impact process. The model RS-DP-03A drop device was used to simulate the falling behavior of BGA chip packages under the real conditions, The drop condition meets the JEDEC22-B111 standards (pulse peak 1500g, pulse duration 0.5 ms) when dropping from the 650mm height . In the testing, according to the real-time changes of dynamic voltage, the relationship between drop times and different phases of package failure was analyzed. With the dye-penetrated method and optical microscopy, it was easy to observe the internal crack and failure locations. The growth mechanism of the cracks in solder joints under the condition of drop-free was analyzed and discussed.

An Investigation of the NOCSAE Linear Impactor Test Method Based on In Vivo Measures of Head Impact Acceleration in American Football

2009 ◽  
Vol 132 (1) ◽  
Author(s):  
Joseph T. Gwin ◽  
Jeffery J. Chu ◽  
Solomon G. Diamond ◽  
P. David Halstead ◽  
Joseph J. Crisco ◽  
...  
Keyword(s):  
Laboratory Test ◽  
Impulse Response ◽  
Test Method ◽  
Drop Test ◽  
Process Models ◽  
American Football ◽  
Head Impacts ◽  
Response Characteristics ◽  
Direct Head

The performance characteristics of football helmets are currently evaluated by simulating head impacts in the laboratory using a linear drop test method. To encourage development of helmets designed to protect against concussion, the National Operating Committee for Standards in Athletic Equipment recently proposed a new headgear testing methodology with the goal of more closely simulating in vivo head impacts. This proposed test methodology involves an impactor striking a helmeted headform, which is attached to a nonrigid neck. The purpose of the present study was to compare headform accelerations recorded according to the current (n=30) and proposed (n=54) laboratory test methodologies to head accelerations recorded in the field during play. In-helmet systems of six single-axis accelerometers were worn by the Dartmouth College men’s football team during the 2005 and 2006 seasons (n=20,733 impacts; 40 players). The impulse response characteristics of a subset of laboratory test impacts (n=27) were compared with the impulse response characteristics of a matched sample of in vivo head accelerations (n=24). Second- and third-order underdamped, conventional, continuous-time process models were developed for each impact. These models were used to characterize the linear head/headform accelerations for each impact based on frequency domain parameters. Headform linear accelerations generated according to the proposed test method were less similar to in vivo head accelerations than headform accelerations generated by the current linear drop test method. The nonrigid neck currently utilized was not developed to simulate sport-related direct head impacts and appears to be a source of the discrepancy between frequency characteristics of in vivo and laboratory head/headform accelerations. In vivo impacts occurred 37% more frequently on helmet regions, which are tested in the proposed standard than on helmet regions tested currently. This increase was largely due to the addition of the facemask test location. For the proposed standard, impactor velocities as high as 10.5 m/s were needed to simulate the highest energy impacts recorded in vivo. The knowledge gained from this study may provide the basis for improving sports headgear test apparatuses with regard to mimicking in vivo linear head accelerations. Specifically, increasing the stiffness of the neck is recommended. In addition, this study may provide a basis for selecting appropriate test impact energies for the standard performance specification to accompany the proposed standard linear impactor test method.

scholarly journals Pengaruh Waktu Perendaman terhadap Daya Serap Air dan Drop Test pada Paving Block Plastik-Pasir

2020 ◽  
Vol 5 ◽  
pp. 301-306
Author(s):  
Rizki Andika Putra ◽  
N P G Suardana ◽  
C I P K Kencanawati
Keyword(s):  
Test Method ◽  
Drop Test

Sampah merupakan permasalahan yang terdapat di setiap Provinsi di Indonesia termasuk juga Provinsi Bali. Sebagian besar berasal dari sampah plastik yang menyebabkan banyak permasalahan yang sampai sekarang masih belum terpecahkan solusi untuk penanganannya. Peneliti menggunakan suatu alternatif dengan cara proses pencacahan dan proses pencairan limbah plastik yang dimanfaatkan sebagai paving block. Bahan yang digunakan diantaranya yaitu pasir dengan ukuran butiran 2-3 mm sebagai penguat dan limbah plastik sebagai pengikat pengganti semen. Plastik dan pasir dicampur pada tungku yang dipanaskan dengan suhu 200  C. Proses pengujian paving block plastik-pasir menggunakan beberapa standar sebagai acuan, seperti SNI-03-0691-1996 untuk syarat mutu bata beton dan ASTM D440-86 untuk Standart Test Method of Drop Shatter Test for Coal. Penelitian ini dilakukan untuk mengetahui pengaruh waktu perendaman air terhadap karakteristik fisik dan mekanik paving block plastik-pasir. Perendaman dilakukan secara berturut-turut selama 15, 30, 45, dan 60 hari yang kemudian dilakukan pengujian drop dari ketinggian 3m pada setiap lama waktu perendaman. Hasil penelitian menunjukkan bahwa waktu perendaman berpengaruh terhadap nilai persentase penyerapan dan kerusakan pada paving block plastik-pasir. Nilai penyerapan dan kerusakan terbesar diperoleh pada paving block dengan perbandingan 1:4 dan lama waktu perendaman 60 hari.

Hybrid Simulation Method for PWB Level Drop Tests

2005 ◽  
Author(s):  
Jiansen Zhu ◽  
Esa Hussa ◽  
Juscelino Okura ◽  
Santosh Shetty
Keyword(s):  
Large Deformation ◽  
Simulation Method ◽  
Standard Test ◽  
Test Method ◽  
Drop Test ◽  
Nonlinear Material ◽  
Time Curve ◽  
Impulse Duration ◽  
Drop Tests ◽  
The Impact

PWB level drop tests are widely used as a standard test method to evaluate the reliability of PWB and packages under drop conditions (JEDEC Standard JESD22-B104-A). The drop height and test setup need be adjusted in order to achieve the requirements of a peak shock of 1500g and an impulse duration of 0.5 ms. Generally, the ground need be covered with a thin layer of rubber pad to absorb some of the impact energy. However, this rubber pad will bring challenges for modelling due to large deformation, nonlinear hyperelasticity, and contact. And sometimes, it may also cause the convergence problem. Therefore, a hybrid drop simulation method was developed. This hybrid method can not only circumvent the difficulties mentioned, but also increase the efficiency and reduce the CPU time of PWB drop simulation. When simulating a PWB board level drop test, generally, not only the PWB and the components assembled on it need be modelled, but also the drop vehicle, rubber pad, and ground should be included in the model. For the hybrid drop simulation, however, only part of drop vehicle need be modeled and there is no need to model the ground and the contact between the ground and the drop vehicle. Then an acceleration time curve measured from drop test is applied to the hybrid model so that the responses of the model will mimic the real drop situation. In this way, not only the simulation time is reduced due to smaller model sizes, but also can some difficulties related to large deformation, contact, and nonlinear material properties be avoided. Finally, a comparison of a bare PWB and a populated PWB drop cases was used to validate this hybrid drop simulation method. A reasonable correlation was achieved.

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