scholarly journals Numerical Investigation of Pyrotechnical Initiators and Their Impact in Airbag Inflator Applications: Ballistic Modeling and Functional Analysis

2021 ◽  
Vol 03 (02) ◽  
pp. 1-1
Author(s):  
Peng Li ◽  
◽  
Chi-Yao Chang ◽  
Amsini Sadiki ◽  
◽  
...  
Keyword(s):  
Shock Wave ◽  
Grain Size ◽  
Quantitative Agreement ◽  
Product Development Process ◽  
Parameter Study ◽  
Main Function ◽  
Surface Area Ratio ◽  
Electric Line ◽  
Coupling Strategy ◽  
Temperature Levels

A numerical model describing the ballistic behavior of a commercially used initiator is presented in this article. This model was built on the principle of conservation of mass and energy in the multi-phase framework incorporated with multi-loaded conditions. After obtaining the information about the grain size distribution in each composite, a fixing factor was proposed based on the surface area ratio of the composites. Thus, the solid propellant burning process based on distributed grain size was described, and the burn rate parameters of the applied pyrotechnic compositions were re-evaluated for different preconditioned temperature levels according to Vieille’s law. The influence of bridge wire and initiator metal cap was further modeled concerning their characteristic properties according to the observed measurements. The validation of the entire initiator model in the closed bomb test showed quantitative agreement with the measured pressure evolution, while the parameter study for evaluating the ballistic sensitivity of each component delivered some insights into the product development process. Furthermore, the configuration of a cold gas inflator was utilized to evaluate the initiator impact for a realistic application, where the shock wave intensity during deployment serves the main function in the inflator design. Incorporated with CFD simulations to capture the shock wave propagation, 0D-3D coupling strategy for initiator ballistics to inflator configuration was realized. Besides, the simulation results reflected the physical conditions in a proper manner. In particular, the parameter study led to a better understanding of interactions between inflator components, which were barely possible to be quantified through the measurements. The proposed initiator model could also be used in combination with other mechanical principles as a component of pyrotechnic devices such as pin-puller, electric line cutters, or airbag inflators. The detailed information gained in describing the physical properties enabled us to assess the existing design quantitatively and to have better control of the product quality.

Controlled experiments and finite element simulations with the Swiss plate geophone bedload monitoring system: particle size identification and transport mode

2021 ◽  
Author(s):  
Zheng Chen ◽  
Siming He ◽  
Tobias Nicollier ◽  
Lorenz Ammann ◽  
Alexandre Badoux ◽  
...  
Keyword(s):  
Particle Size ◽  
Grain Size ◽  
Finite Element ◽  
Quantitative Agreement ◽  
Bedload Transport ◽  
Material Structure ◽  
Flume Experiments ◽  
Fem Simulations ◽  
Transport Mode ◽  
Signal Response

<p>The Swiss plate geophone (SPG) system is an indirect bedload transport monitoring device that records the acoustic signals generated by bedload particle impacts, with the goal to derive the bedload flux and grain size distribution. Particle drop experiments with quartz spheres in quiescent water in a flume setting were performed to investigate the dynamic signal response of the SPG system impacted by particle-like objects varying in size and impact location. Systematic flume experiments with natural bedload particles in flowing water were conducted to study the effects of impact angle and transport mode (saltating, rolling and sliding) on the SPG signals. For each impact caused by a single particle, the number of signal impulses, the amplitude, the positive area surrounded by the signal envelope, and the centroid frequency were extracted from the raw geophone monitoring data. The finite element method (FEM) was used to construct a virtual model of the SPG system and to determine the propagation characteristics of the numerical stress wave in the material structure. The experimental and numerical results showed a qualitative and partially quantitative agreement in the changes of the signal impulses, the amplitude, and the envelope area with increasing colliding sphere size. The centroid frequencies of the SPG vibrations showed qualitatively similar dependencies with increasing particle size as some field measurements for the coarser part of the investigated range of impact sizes. The effects of variable particle impact velocities and impact locations on the geophone plate were also investigated by drop experiments and compared to FEM simulations. In addition, the signal response for different bedload transport modes and varying impact angles were explored. In summary, the FEM simulations contribute to the understanding of the signal response of the SPG system and the findings in this study may eventually result in improving the bedload grain size classification and transport mode recognition.</p>

Numerical Modeling of Continuous Dynamic Recrystallization in Sn-Based Solder Connection Under Cyclic Loading

2021 ◽  
Author(s):  
Marta Kuczynska ◽  
Ulrich Becker ◽  
Youssef Maniar ◽  
Steffen Weihe
Keyword(s):  
Grain Size ◽  
Dynamic Recrystallization ◽  
Cyclic Load ◽  
Fe Simulation ◽  
Operation Time ◽  
Inelastic Strain ◽  
Parameter Study ◽  
Continuous Dynamic Recrystallization ◽  
Gradual Evolution ◽  
Continuous Dynamic

Abstract The reoccurring cyclic load imposed onto soldered electronic components during their operation time leads to accumulation of inelastic strains in the structure. On a microscale level, the degree of plastic deformation is determined by the formation and annihilation of dislocations, leading to continuous refinement by creation of new grain boundaries, precipitates relocation and growth. This microstructure rearrangement, triggered by an increasing amount of inelastic deformation, is defined as dynamic recrystallization. This work presents a macroscale modelling approach for the description of continuous dynamic recrystallization observed in Sn-based solder connections. The model used in this work describes kinetics of macroscopic gradual evolution of equivalent grain size, where the initial grain size is continuously refined with increasing accumulated inelastic strain until a saturation grain size is reached. The rate and distribution of dynamic recrystallization is further numerically modelled dependent on the effective accumulated inelastic strain and governing stress multiaxiality. A parameter study of the presented model and its employment in finite element (FE) simulation is further described. Finally, FE simulation of the grain size evolution is demonstrated on an example of a bulky sample under isothermal cyclic mechanical loading, as well as a BGA-like structure under tensile, shear and mixed mode cyclic load.

Parameter Study of a Thermal Analysis of a Bead-on-Plate Weld

2018 ◽  
Author(s):  
Spyridon A. Alexandratos ◽  
Lei Shi ◽  
Noel P. O’Dowd
Keyword(s):  
Grain Size ◽  
Steel Plate ◽  
Martensitic Steel ◽  
Sensitivity Study ◽  
Parameter Study ◽  
Stainless Steel 316L ◽  
Material Microstructure ◽  
Simulation Techniques ◽  
Subsequent Effect ◽  
Thermal Histories

Failures in engineering components operating at high temperature often initiate in welded joints, particularly in the heat-affected zone (HAZ) adjacent to a weld. This is due to the inhomogenous microstructure of the weld and adjacent material due to the different thermal histories experienced during the weld cycle. It is therefore important to accurately predict the temperature distributions arising during welding and the subsequent effect on material microstructure. The NET TG1 bead-on-plate weld geometry is examined in this work. This geometry is a single weld bead laid on the surface of an AISI 316L austenite steel plate. Experimental data from the TG1 study are available to validate different weld simulation techniques. Here, a sensitivity study to the thermal properties is carried out and the influence on the HAZ temperatures and grain size is examined. The study shows that the conductivity and the specific heat capacity significantly affect the temperature prediction in the HAZ with a similar influence on predicted grain size following welding. Results are presented for a stainless steel (316L) and a martensitic steel (P91) plate.

Boundary Layer Suction via a Slot in a Transonic Compressor: Numerical Parameter Study and First Experiments

2004 ◽  
Author(s):  
K. Hubrich ◽  
A. Bo¨lcs ◽  
P. Ott
Keyword(s):  
Boundary Layer ◽  
Shock Wave ◽  
Mach Number ◽  
Numerical Study ◽  
Pressure Ratio ◽  
Parameter Study ◽  
Flow Angle ◽  
Boundary Layer Suction ◽  
Transonic Compressor ◽  
Shock Mach Number

In the present paper a numerical and experimental study aiming at the enhancement of the working range of a transonic compressor via boundary layer suction (BLS) is presented. The main objective of the investigation is to study the influence of BLS on the interference between shock wave and boundary layer and to identify the possible benefit of BLS on the compressor working characteristics. An extensive numerical study has been carried out for the DATUM blade and for 2 different suction location configurations for one speed line and varying back-pressure levels, ranging from choked conditions to stall. It was found that the working range of the transonic compressor with a nominal inlet Mach number of 1.2 and a nominal pre-shock Mach number of 1.35 could be increased by sucking 2% of flow on the SS away, in such a way that the maximum pressure ratio and maximum diffusion could both be increased by 10%, when compared to the DATUM case. For smaller pressure ratios with respect to the design pressure ratio, the BLS is located in a supersonic flow region and thus creates additional losses due to a more divergent flow channel, which additionally accelerates the flow and results in a higher pre-shock Mach number creating higher losses. First measurements carried out in LTTs annular cascade, do show reasonable agreement with the computations in terms of inlet Mach number, flow angle, main shock location and stall limit. The most pronounced difference between measurements and computations is the occurrence of a terminal normal channel shock behind a bowed detached shock wave and a separation on the SS of the blade, which were both not predicted by the CFD.

scholarly journals On the self-regulating effect of grain size evolution in mantle convection models: Application to thermo-chemical piles

2019 ◽  
Author(s):  
Jana Schierjott ◽  
Antoine Rozel ◽  
Paul Tackley
Keyword(s):  
Grain Size ◽  
Recovery Time ◽  
Subduction Zones ◽  
Shear Velocity ◽  
Large Temperature ◽  
Diffusion Creep ◽  
Parameter Study ◽  
Mantle Viscosity ◽  
Size Evolution ◽  
Dynamic Recrystallisation

Abstract. Seismic studies show two antipodal regions of lower shear velocity at the core-mantle boundary (CMB) called Large Low Shear Velocity Provinces (LLSVPs). They are thought to be thermally and chemically distinct, and therefore might have a different density and viscosity than the ambient mantle. Employing a composite rheology, using both diffusion and dislocation creep, we investigate the influence of grain size evolution on the dynamics of thermo-chemical piles in evolutionary geodynamic models. We consider a primordial layer and a time-dependent basalt production at the surface to dynamically form the present-day chemical heterogeneities, similar to earlier studies, e.g., by Nakagawa and Tackley (2014). We perform a parameter study which includes different densities and viscosities of the imposed primordial layer. Further, we test the influence of yield stress and parameters of the grain size evolution equation on the dynamics of piles and their interaction with the ambient mantle. Our results show that, relative to the ambient mantle, grain size is higher inside the piles, but due to the large temperature at the CMB, the viscosity is not remarkably different from ambient mantle viscosity. We further find, that although the average viscosity of the detected piles is buffered by both grain size and temperature, grain size dominates the viscosity development. However, depending on the convection regime, in the ambient mantle, viscosity can be dominated by temperature. All pile properties, except for temperature, show a self-regulating behaviour: although grain size, density and viscosity decrease when downwellings or overturns occur, these properties quickly recover and return to values prior to the downwelling. We compute the necessary recovery time and find, that it takes approximately 400 Myr for the properties to recover after a resurfacing event. Extrapolating to Earth-values, we estimate a much smaller recovery time. We observe that dynamic recrystallisation counteracts grain growth in the piles when the lithosphere is weakened and forms downwellings. Venus-type resurfacing episodes reduce the grain size in piles and ambient mantle to few millimetres. More continuous mobile-lid type downwellings limit the grain size to a centimetre. Consequently, we find that grain size-dependent viscosity does not increase the resistance of thermo-chemical piles to downgoing slabs. Mostly, piles deform in grain size- sensitive diffusion creep but they are not stiff enough to counteract the force of downwellings. Hence, we conclude that the location of subduction zones could be responsible for the location and stability of the thermo-chemical piles of the Earth because of dynamic recrystallisation.

Formation of nickel aluminides under shock-wave loading

1986 ◽  
Vol 44 ◽  
pp. 432-433
Author(s):  
I. K. Simonsen ◽  
Y. Horie ◽  
R. A. Graham
Keyword(s):  
Shock Wave ◽  
Grain Size ◽  
Low Temperature ◽  
Temperature Region ◽  
Nickel Aluminides ◽  
Microstructural Feature ◽  
Shock Wave Loading ◽  
Wave Loading ◽  
Nickel Powders ◽  
High Shock

Recently we reported the synthesis of nickel aluminides in a mixture of elemental aluminum and nickel powders under explosive shock-wave loading. The alloy products were found to be readily synthesized and controlled by shockloading conditions. A notable microstructural feature was the presence of unusually small Ni3 Al crystallites having a grain size of about 5 nm. They were found in a region of high shock-induced temperature where there were extensive alloying reactions. In this report we present the observation of similar crystallites in a low temperature region where observed reactions were sparse and localized. The structures of these crystallites were tentatively identified as those of NiAl and Ni2Al3.

scholarly journals A numerical study of oblique shock-wave reflections with experimental comparisons

1985 ◽  
Vol 398 (1814) ◽  
pp. 117-140 ◽  
Keyword(s):  
Shock Wave ◽  
Numerical Study ◽  
Wedge Angle ◽  
Quantitative Agreement ◽  
Oblique Shock ◽  
Computational Method ◽  
Oblique Shock Wave ◽  
Wave Reflections ◽  
Inviscid Flows ◽  
Reflection Transition

A direct comparison is made for several occurrences of oblique shock-wave reflections between interferometric results obtained at the University of Toronto Institute for Aerospace Studies (UTIAS) 10 cm x 18 cm hyper­-velocity shock tube and numerical results obtained by using a current computational method for solving the Euler equations. Very good qualitative agreement is obtained for equilibrium and frozen flow fields except in small regions where the experiments were dominated by viscous flow. The quantitative agreement is very close in some cases but can be out by 10–15% in cases with non-equilibrium flow or viscous structures or both. Additional parametrized sequences of calculations are presented to assess the utility of the present numerical method in constructing the various reflection–transition lines for perfect inviscid flows in the shock-wave Mach number, wedge-angle ( M s , θ w )-plane, and the validity of the ‘boundary-layer defect’ theory.

A computational parameter study for the three-dimensional shock–bubble interaction

2007 ◽  
Vol 594 ◽  
pp. 85-124 ◽  
Author(s):  
JOHN H. J. NIEDERHAUS ◽  
J. A. GREENOUGH ◽  
J. G. OAKLEY ◽  
D. RANJAN ◽  
M. H. ANDERSON ◽  
...  
Keyword(s):  
Shock Wave ◽  
Fluid Velocity ◽  
Three Dimensional ◽  
Time Dependent ◽  
Parameter Study ◽  
One Dimensional ◽  
Wave Refraction ◽  
Bubble Interaction ◽  
Velocity Circulation ◽  
Grid Points

The morphology and time-dependent integral properties of the multifluid compressible flow resulting from the shock–bubble interaction in a gas environment are investigated using a series of three-dimensional multifluid-Eulerian simulations. The bubble consists of a spherical gas volume of radius 2.54 cm (128 grid points), which is accelerated by a planar shock wave. Fourteen scenarios are considered: four gas pairings, including Atwood numbers −0.8 < A < 0.7, and shock strengths 1.1 < M ≤ 5.0. The data are queried at closely spaced time intervals to obtain the time-dependent volumetric compression, mean bubble fluid velocity, circulation and extent of mixing in the shocked-bubble flow. Scaling arguments based on various properties computed from one-dimensional gasdynamics are found to collapse the trends in these quantities successfully for fixed A. However, complex changes in the shock-wave refraction pattern introduce effects that do not scale across differing gas pairings, and for some scenarios with A > 0.2, three-dimensional (non-axisymmetric) effects become particularly significant in the total enstrophy at late times. A new model for the total velocity circulation is proposed, also based on properties derived from one-dimensional gasdynamics, which compares favourably with circulation data obtained from calculations, relative to existing models. The action of nonlinear-acoustic effects and primary and secondary vorticity production is depicted in sequenced visualizations of the density and vorticity fields, which indicate the significance of both secondary vorticity generation and turbulent effects, particularly for M > 2 and A > 0.2. Movies are available with the online version of the paper.

Effect of shock waves on structural and dielectric properties of ammonium dihydrogen phosphate crystal

2019 ◽  
Vol 234 (9) ◽  
pp. 557-567 ◽  
Author(s):  
Sivakumar Aswathappa ◽  
Sahaya Jude Dhas Sathiyadhas ◽  
Balachandar Settu ◽  
Martin Britto Dhas Sathiyadhas Amalapushpam
Keyword(s):  
Shock Wave ◽  
Grain Size ◽  
Dielectric Properties ◽  
Shock Waves ◽  
Dihydrogen Phosphate ◽  
Ammonium Dihydrogen Phosphate ◽  
X Ray Diffraction ◽  
Research Article ◽  
Adp Crystal ◽  
Post Shock

Abstract In this research article, the authors pay attention to investigate the effect of structural and dielectric properties of ammonium dihydrogen phosphate (ADP) crystal under pre and post shock loaded conditions. A shock wave of Mach number 1.9 was utilized for the present investigation which was generated by a table-top pressure driven shock tube. The crystalline nature and grain size variations were estimated by powder X-ray diffraction technique. The grain size of post shock wave loaded ADP crystal is found to be larger than that of the pre shock wave loaded ADP crystal. The dielectric properties of the pre and post shock loaded crystals were analyzed by impedance analyzer as a function of frequency (1 kHz–1 MHz) at ambient temperature. The dielectric constant is observed to be varying from 346 to 362 at the frequency of 400 kHz for pre and post shock wave loaded ADP crystals, respectively. The obtained results suggest that shock waves can be an alternate tool to tailor the physical properties of materials without creating any change in the original crystal system and surface morphology.

scholarly journals Numerical analysis of damage kinetics in aluminium under axisymmetric loading

2018 ◽  
Vol 183 ◽  
pp. 01066
Author(s):  
Olga Tyupanova ◽  
Sergey Nadezhin ◽  
Pavel Duday ◽  
Andrey Ivanovsky
Keyword(s):  
Shock Wave ◽  
Numerical Analysis ◽  
Internal Surface ◽  
Quantitative Agreement ◽  
Spall Fracture ◽  
Compression Waves ◽  
Spall Damage ◽  
Wave Compression ◽  
Shock Wave Compression ◽  
Wave Arrival

Based on the analysis of the results of two R-Damage experiments, this paper provides a variant of a relation to simulate the spall damage recollection under the effect of weak compression waves. This relation closes the kinetic fracture model, considering both growth and recollection of damage. Using this model makes it possible to simulate adequately (with good quantitative agreement) the sequence of the processes “shock-wave compression – spall fracture – convergence of spall layer – recollection of damaged medium”, including the dynamics of the compacting wave arrival to the internal surface of the hollow cylindrical targets since it passed through the damaged media.

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