Microstructural level response of HMX–Estane polymer-bonded explosive under effects of transient stress waves

2012 ◽  
Vol 468 (2147) ◽  
pp. 3725-3744 ◽  
Author(s):  
A. Barua ◽  
Y. Horie ◽  
M. Zhou
Keyword(s):  
Impact Velocity ◽  
Bonding Strength ◽  
Scaling Laws ◽  
Volume Fraction ◽  
Stress Waves ◽  
Transient Wave ◽  
Transient Stress ◽  
Impact Surface ◽  
The Impact ◽  
Interface Bonding Strength

The effect of transient stress waves on the microstructure of HMX–Estane, a polymer-bonded explosive (PBX), is studied. Calculations carried out concern microstructures with HMX grain sizes on the order of 200 μm and grain volume fractions in the range of 0.50–0.82. The microstructural samples analysed have an aspect ratio of 5:1 (15×3 mm), allowing the transient wave propagation process resulting from normal impact to be resolved. Boundary loading is effected by the imposition of impact face velocities of 50–200 m s −1 . Different levels of grain–binder interface strength are considered. The analysis uses a recently developed cohesive finite element framework that accounts for coupled thermal–mechanical processes involving deformation, heat generation and conduction, failure in the forms of microcracks in both bulk constituents and along grain/matrix interfaces, and frictional heating along crack faces. Results show that the overall wave speed through the microstructures depends on both the grain volume fraction and interface bonding strength between the constituents and that the distance traversed by the stress wave before the initiation of frictional dissipation is independent of the grain volume fraction but increases with impact velocity. Energy dissipated per unit volume owing to fracture is highest near the impact surface and deceases to zero at the stress wavefront. On the other hand, the peak temperature rises are noted to occur approximately 2–3 mm from the impact surface. Scaling laws are developed for the maximum dissipation rate and the highest temperature rise as functions of impact velocity, grain volume fraction and grain–binder interfacial bonding strength.

Relation between Interfacial Strength and Impact Properties of UHMWPE/LLDPE Laminates

2010 ◽  
Vol 150-151 ◽  
pp. 926-929
Author(s):  
Lei Chen ◽  
Jia Lu Li ◽  
Zhi Wei Xu ◽  
Liang Sen Liu
Keyword(s):  
Bonding Strength ◽  
Volume Fraction ◽  
Interfacial Strength ◽  
Woven Fabric ◽  
Interface Bonding ◽  
Impact Properties ◽  
Polyethylene Fiber ◽  
Matrix Volume ◽  
The Impact ◽  
Interface Bonding Strength

Ultra-high molecular weight polyethylene fiber plain woven fabric reinforced line-low-density polyethylene composites with different matrix volume fraction were prepared. The interfacial bonding strength and the impact property of the laminates were investigated. The experiment results revealed that the sample with a matrix volume fraction 14% showed better impact properties than other ones, while the interface bonding strength continued to drop when the matrix volume fraction was decreased. It is also indicated that in high fiber interface bonding strength, the impact resistance of the laminate would grow by decreasing the interface bonding strength. However, when the interface bonding strength was lower than the threshold, there would be an opposite effect.

scholarly journals Fluctuation Characteristic Test of Oblique Stress Waves in Infilled Jointed Rock and Study of the Analytic Method

2020 ◽  
Vol 2020 ◽  
pp. 1-12 ◽  
Author(s):  
Jin Yu ◽  
Zehan Liu ◽  
Ze He ◽  
Xianqi Zhou ◽  
Jinbi Ye
Keyword(s):  
Transmission Coefficient ◽  
Impact Velocity ◽  
Joint Angle ◽  
Split Hopkinson Pressure Bar ◽  
Strain Curve ◽  
Stress Waves ◽  
Transmitted Wave ◽  
Impact Rate ◽  
Dip Angle ◽  
The Impact

The propagation of stress waves in filled jointed rocks involves two important influencing factors: transmission-reflection phenomena and energy attenuation. In this paper, the split Hopkinson pressure bar (SHPB) test is used to shock the filled rock with joint angles of 0, 30, and 45° and the thickness of 4 mm and 10 mm, respectively, in three different velocities. The wave curves of the incident wave, reflected wave, and transmission are obtained. The effects of the filling angle and joint thickness on wave propagation are analyzed. Based on the propagation characteristics of stress waves in joints, the stress expression of oblique incident stress waves propagating in filling joints is derived, and the energy coefficient of transmission and reflection is calculated. The results show that the propagation of stress wave in filling joints is related to the impact rate. The larger the impact rate is, the larger the maximum voltage amplitude of the three waves is. And the increasing amplitude of the incident and reflected waves is larger than the transmitted wave; the greater the impact velocity is, the smaller the stress-strain curve gap of the three dip joints is, and the fracture strength of the specimen decreases with the increase of the joint dip angle. The larger the joint dip angle is, the smaller the deformation of the rock-like specimen is. The change of the transmission coefficient is related to the joint angle, and the larger joint angle weakens the influence of the joint width on the transmission of the transmitted wave; under each impact velocity, the theoretical and experimental stress peaks are approximately the same, and the transmission coefficient maintains a good consistency with the oblique incident angle.

Effect of Random Defects on Dynamic Response of Honeycomb Structures

2012 ◽  
Vol 706-709 ◽  
pp. 805-810 ◽  
Author(s):  
Zhi Jun Zheng ◽  
Ji Lin Yu
Keyword(s):  
Impact Velocity ◽  
Cell Walls ◽  
Plateau Stress ◽  
Impact Surface ◽  
Critical Impact Velocity ◽  
Crushing Behavior ◽  
The Impact ◽  
Stress Uniformity ◽  
Random Defects ◽  
Deformation Modes

The dynamic crushing behavior of cellular metals is closely related to their microstructure. Two types of random defects by randomly thickening/removing cell walls are investigated in this paper. Their influences on the deformation modes and plateau stresses of honeycombs are studied by finite element simulation using ABAQUS/Explicit code. Three deformation modes, i.e. the Homogeneous Mode, the Transitional Mode and the Shock Mode, are used to distinguish the deformation patterns of honeycombs under different impact velocities. The critical impact velocity for mode transition between the Homogeneous and Transitional modes is quantitatively determined by evaluating a stress uniformity index, defined as the ratio between the plateau stresses on the support and impact surfaces. It is found that the critical impact velocity decreases with increasing thickening ratio but increases with increasing removing ratio. The plateau stress on the impact surface heavily depends on the impact velocity due to the inertia effect. The random defects lead to a weakening effect on the plateau stress. For the honeycombs with randomly removing cell walls, the weakening effect is especially obvious at a moderate impact velocity. For the honeycombs with randomly thickening cell walls, the weakening effect is particularly severe at a low impact velocity, but this effect almost disappears when the impact velocity is high enough.

Characterization of deformation behaviour and fracture mode of recycled aluminium alloys (AA6061) subjected to high-velocity impact

2020 ◽  
Vol 14 (3) ◽  
pp. 7222-7234
Author(s):  
Choon Sin Ho ◽  
Mohd Khir Mohd Nor
Keyword(s):  
Impact Velocity ◽  
Aluminium Alloys ◽  
Deformation Behaviour ◽  
Economic Benefits ◽  
Fracture Modes ◽  
Impact Surface ◽  
Impact Area ◽  
Footprint Analysis ◽  
Dynamic Loading Conditions ◽  
The Impact

Recycling aluminium alloys have been shown to provide great environmental and economic benefits. The global demands placed upon recycled aluminium and its product has further increased the need for better understanding and prediction of the deformation behaviour of such materials subjected to various dynamic loading conditions. It is also a topic of high interest for both the designer and the user of metal structures, specifically in the automotive industry. Even though numerous efforts have been made to improve recycling processes of aluminium alloys, very little attention is given on the fracture behaviour related damage and anisotropy during impact. In this study, therefore, the anisotropic-damage behaviour of the recycled aluminium alloys (AA6061) is examined via Taylor Cylinder Impact test. A gas gun was used to fire the projectiles towards a target at impact velocity ranging from 170m/s to 370 m/s. The deformation behaviour, including the fracture modes, digitized footprint and side profile of the deformed specimens, are observed and analysed. Scanning Electron Microscope (SEM) is further used to observe the damage behaviour, including microstructural changes of the impact surface. The damage progression is also analysed by observing the microstructural behaviour of location 0.5 cm from the impact area. General speaking, there are three different types of ductile fracture modes (mushrooming, tensile splitting and petalling) can be observed in this study within the impact velocity range of 170m/s to 370m/s. The critical impact velocity is defined at 212 m/s. The digitized footprint analysis exhibited a non-symmetrical (ellipse-shaped) footprint where the footprints showed plastic anisotropic behaviour and localized plastic strain in such recycled material. The damage evolution of the material is increasing with the increase in impact velocity.

Specimen Thickness and Impactor Mass Effects on Drop-Weight Impact Studies of GLARE 5 Fiber-Metal Laminates

2011 ◽  
Author(s):  
A. Seyed Yaghoubi ◽  
B. Liaw
Keyword(s):  
Impact Velocity ◽  
Volume Fraction ◽  
Energy Condition ◽  
Specimen Thickness ◽  
Fiber Metal Laminates ◽  
Drop Weight ◽  
Metal Volume ◽  
Fiber Metal ◽  
The Impact ◽  
Metal Volume Fraction

Impact responses and damage induced by a drop-weight instrument on GLARE 5 fiber-metal laminates (FMLs) with different thicknesses were studied. The effect of impactor mass was also considered. The damage characteristics were evaluated using both nondestructive ultrasonic and mechanical sectioning techniques. The ultrasonic C-scan technique could only assess the contour of entire damage area whereas more details of damage were obtained using the mechanical cross-sectioning technique. As expected, thicker GLARE 5 FMLs offered higher impact resistance. When subjected to the same impact energy, the entire damage contour enlarged as the specimen became thicker. Under the same impact condition, by reducing the impactor mass, the contact force escalated while the contact stiffness increased. Experimental results showed that the threshold cracking energy varied parabolically with respect to the impact velocity, metal volume fraction (MVF) and the specimen thickness. By increasing the metal volume fraction of the panels, the threshold cracking energy decreased parabolically. On the other hand, for the same MVF value, the cracking energy increased as the impactor mass increased. By increasing the panel thickness, the threshold cracking energy condition increased parabolically; whereas under the same impact velocity, the threshold cracking energy increased by increasing the impactor mass.

Shear Wave Attenuation and its Micro-Mechanism of Polymers

2013 ◽  
Vol 446-447 ◽  
pp. 249-253
Author(s):  
Zhi Ping Tang ◽  
Ting Li
Keyword(s):  
Shear Wave ◽  
Impact Velocity ◽  
Shear Failure ◽  
Wave Attenuation ◽  
Optical Microscope ◽  
Shear Loading ◽  
Impact Surface ◽  
Gas Gun ◽  
Electro Magnetic ◽  
The Impact

The impact shear response of crystallized polypropylene under combined compression and shear loading was studied by using an inclined gas gun and electro-magnetic particle velocity gauges. The experimental results show that the transverse wave velocity increases nonlinearly with the impact velocity, indicating its shear behavior is strongly related to the hydrostatic pressure. Remarkable shear wave attenuation occurs near the impact surface when the impact velocity and inclination angle reach the critical value. The micro-observation of recovered samples with a polarized optical microscope reveals that there exists a melting layer of about 2-3μm thick, i.e. adiabatic shear failure layer, very near the impact surface (about 5μm) which causes the shear wave attenuation.

scholarly journals Nanofluid flow containing carbon nanotubes with quartic autocatalytic chemical reaction and Thompson and Troian slip at the boundary

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Muhammad Ramzan ◽  
Jae Dong Chung ◽  
Seifedine Kadry ◽  
Yu-Ming Chu ◽  
Muhammad Akhtar
Keyword(s):  
Mathematical Model ◽  
Carbon Nanotubes ◽  
Drag Force ◽  
Chemical Reaction ◽  
Slip Velocity ◽  
Volume Fraction ◽  
Surface Drag ◽  
Nanofluid Flow ◽  
Velocity Parameter ◽  
The Impact

Abstract A mathematical model is envisioned to discourse the impact of Thompson and Troian slip boundary in the carbon nanotubes suspended nanofluid flow near a stagnation point along an expanding/contracting surface. The water is considered as a base fluid and both types of carbon nanotubes i.e., single-wall (SWCNTs) and multi-wall (MWCNTs) are considered. The flow is taken in a Dacry-Forchheimer porous media amalgamated with quartic autocatalysis chemical reaction. Additional impacts added to the novelty of the mathematical model are the heat generation/absorption and buoyancy effect. The dimensionless variables led the envisaged mathematical model to a physical problem. The numerical solution is then found by engaging MATLAB built-in bvp4c function for non-dimensional velocity, temperature, and homogeneous-heterogeneous reactions. The validation of the proposed mathematical model is ascertained by comparing it with a published article in limiting case. An excellent consensus is accomplished in this regard. The behavior of numerous dimensionless flow variables including solid volume fraction, inertia coefficient, velocity ratio parameter, porosity parameter, slip velocity parameter, magnetic parameter, Schmidt number, and strength of homogeneous/heterogeneous reaction parameters are portrayed via graphical illustrations. Computational iterations for surface drag force are tabulated to analyze the impacts at the stretched surface. It is witnessed that the slip velocity parameter enhances the fluid stream velocity and diminishes the surface drag force. Furthermore, the concentration of the nanofluid flow is augmented for higher estimates of quartic autocatalysis chemical.

scholarly journals Low-carbon cast microalloyed steel intercritically heat-treated at different temperatures: microstructure and mechanical properties

2021 ◽  
Vol 21 (2) ◽  
Author(s):  
Hadi Torkamani ◽  
Shahram Raygan ◽  
Carlos Garcia Mateo ◽  
Yahya Palizdar ◽  
Jafar Rassizadehghani ◽  
...  
Keyword(s):  
Carbon Content ◽  
Volume Fraction ◽  
Block Size ◽  
Tensile Tests ◽  
Total Elongation ◽  
Martensite Phase ◽  
Low Carbon ◽  
Steel Increase ◽  
Different Temperatures ◽  
The Impact

AbstractIn this study, dual-phase (DP, ferrite + martensite) microstructures were obtained by performing intercritical heat treatments (IHT) at 750 and 800 °C followed by quenching. Decreasing the IHT temperature from 800 to 750 °C leads to: (i) a decrease in the volume fraction of austenite (martensite after quenching) from 0.68 to 0.36; (ii) ~ 100 °C decrease in martensite start temperature (Ms), mainly due to the higher carbon content of austenite and its smaller grains at 750 °C; (iii) a reduction in the block size of martensite from 1.9 to 1.2 μm as measured by EBSD. Having a higher carbon content and a finer block size, the localized microhardness of martensite islands increases from 380 HV (800 °C) to 504 HV (750 °C). Moreover, despite the different volume fractions of martensite obtained in DP microstructures, the hardness of the steels remained unchanged by changing the IHT temperature (~ 234 to 238 HV). Applying lower IHT temperature (lower fraction of martensite), the impact energy even decreased from 12 to 9 J due to the brittleness of the martensite phase. The results of the tensile tests indicate that by increasing the IHT temperature, the yield and ultimate tensile strengths of the DP steel increase from 493 to 770 MPa, and from 908 to 1080 MPa, respectively, while the total elongation decreases from 9.8 to 4.5%. In contrast to the normalized sample, formation of martensite in the DP steels could eliminate the yield point phenomenon in the tensile curves, as it generates free dislocations in adjacent ferrite.

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