Increasing Standoff Distance Research Articles

Influence of printing parameters on the thermal properties of 3D-printed construction structures

3D printing in the construction sector is a promising, sustainable approach with the potential to build energy-efficient buildings. However, there is a lack of studies on the thermal properties of 3D-printed structures, which are fundamental to their energy efficiency. This study investigates the impact of printing parameters on thermal conductivity and defect development in 3D-printed concrete structures. Heat flow meter, scanning electron microscope and infrared imaging techniques were employed to assess the thermal properties and microstructure of 3D-printed samples. The results demonstrate that printing parameters significantly influence the porosity, void formation, and microstructural characteristics of 3D-printed concrete, ultimately affecting thermal properties. An increase in extrusion rate leads to higher thermal conductivity, whereas an increase in speed and standoff distance reduces thermal conductivity. Excessive spacing between printed lines can induce voids and gaps, contributing to lower thermal conductivity, while minimal spacing can promote higher porosity and larger pores. Infrared imaging revealed nonuniform thermal distribution in 3D-printed structures caused by the layered structure and voids in interlayer gaps. This study provides valuable insights for designing and constructing energy-efficient 3D-printed buildings, contributing to the development of sustainable building practices and the advancement of additive manufacturing in construction.

AN IN-DEPTH INVESTIGATION ON KERF ANGLE IN PIERCED HOLE ON INCONEL-625 SUPERALLOY USING ABRASIVE WATERJET CUTTING PROCESS

This work investigates the piercing of microholes in turbine shroud rings (Inconel-625) using the Abrasive Waterjet Cutting process. The concern with the hole piercing is the kerf angle caused by the attenuation of the jet energy and stand-off distance, which seriously impacts the processing precision of abrasive water jet piercing. The effects of piercing parameters like machining time (40, 60 and 80[Formula: see text]s), abrasive mesh size (80 mesh and 120 mesh), stand-off distance (1, 2, 3 and 4[Formula: see text]mm), abrasive jet pressure (100, 125, 150 and 175[Formula: see text]MPa) are studied to reduce the kerf angle. The kerf angle increased linearly with a stand-off distance increase at different machining times. By piercing for 60[Formula: see text]s and 80[Formula: see text]s, the lowest values of kerf angle are obtained (0.03∘ and 0.02∘). The optimum conditions for making a pierced hole with a minimum kerf angle of 0.02∘ were achieved with a machining time- of 60[Formula: see text]s, abrasive mesh size- of 20 mesh, and abrasive jet pressure- of Scanning electron microscope (SEM) images and visual measuring system (VMS) images are used to identify the surface characteristics in kerf zone. The features, including ploughing, particle embedment, lip impression and wear path due to the ductile mode of erosion caused by high energy impact, is also discussed.

Influence of magnetohydrodynamics configuration on aerothermodynamics during Martian reentry

This paper investigates the role of magnetohydrodynamics (MHD) on the aerothermodynamics (ATD) of a representative entry vehicle while flying into the Martian atmosphere. By strategically placing a flight-ready superconducting magnet at varied positions in the Schiaparelli reentry capsule of the ExoMars mission, we discern its impact on essential flow properties. The primary consequence of MHD during atmospheric entry is the generation of the Lorentz force, which increases the shock standoff distance resulting in a reduction of the heat flux on the spacecraft by pushing high-energy plasma particles away. Through different magnet configurations, three distinct cases are formed to comprehensively understand the effects and implications of each setup. The study is performed using the COOLFluiD MHD for EnTries, an in-house ATD solver. For case 1, the magnet's placement behind the ExoMars forebody at the stagnation point reduces the heat flux. In case 2, the magnet's relocation to the shoulder region explores its potential to mitigate communication blackouts by influencing the wake region's flow. However, this positioning also induces shock bending, leading to variations in post-shock species mass fractions and heat flux spikes in the post-shock region. Case 3, involving an additional magnet where the shock bends in case 1, showcases a consistent increase in shock standoff distance across the forebody, providing a longer relaxation zone for species equilibration. Our findings highlight that while the strength of the applied magnetic field is crucial, the magnet's size is equally pivotal in determining ATD behavior. Case 3 emerges as the most promising configuration, consistently reducing heat flux across the forebody and maintaining it in the afterbody. This study underscores the potential of multi-magnet configurations as next-generation MHD heat shields for Martian atmospheric entry, emphasizing the criticality of magnet placement and configuration in enabling future MHD-enhanced deep space exploration missions.

Leading edge stabilisation of vertical boundary layer diffusion flames

The leading edge stability of vertical boundary layer diffusion flames established over a 3D-printed porous gas burner is revealed through Planar Laser-Induced Fluorescence imaging of the OH radical (OH-PLIF). Flame stability is studied by premixing methane and ethylene with increasing volume fractions of bromotrifluoromethane (CF3Br/Halon-1301) to increase the characteristic chemical timescale. Blow-off occurs at 15.7% and 37.3% CF3Br addition for methane and ethylene respectively, which are remarkably large limits compared to other flame configurations. As CF3Br is added, the flame stand-off distance increases and the reaction zone broadens, thereby increasing the flame length. This accelerates the buoyancy-induced flow ahead of the leading edge, promoting O2 entrainment into the flame anchor. Consequently, the radical scavenging effects on the flame anchor reactivity are dampened, resulting in the flame re-anchoring slightly downstream along the plate. Towards extinction, the flame shortens dramatically due to efficient catalytic cycling and radiative quenching at the flame tip resulting from the brominated species and excessive soot formation. This reduces the O2 mass flux into the kinetically dampened flame anchor resulting in blow-off extinction. Therefore, blow-off is controlled by both the leading edge reactivity and trailing edge length. Methane is shown to be considerably more sensitive compared to ethylene to CF3Br owing to its larger flame speed. These results demonstrate that fire-induced buoyancy greatly increases blow-off limits when using chemically active or inert agents in vertical wall fire configurations.

Influence of Stand-off Distance on the Blast-Resistance of Steel Plate Supported Concrete Walls

The influence of stand-off distance for the protective performance and capability of the steelplate supported concrete barriers is modelled, within the current work. Steel and concrete have been used for centuries to build protective structures. Due to the military's concern with mitigating the effects of explosions and bullets, they have both collectively seen major improvements as a material for protective constructions. The significance of stand-off distance on the durability of steel plate supported concrete wall is investigated through simulations. Johnson-Cook hardening and damage molds have been used to define the mechanical behavior of steel, while concrete damage plasticity has been used to define the behavior of concrete. The growth of detonation products is modeled using the JWL equation of state, in which Comp B is selected as explosive. Coupled-Eulerian-Lagrangian methodology is employed in the constructed finite element model. The outcomes demonstrated that the stand-off distance has a substantial impact on a structure's durability. The explosives' ability to cause damage is less effective as stand-off distance increases. For the case that the stand-off distance is 50 mm, the explosion completely destroyed both the 10 mm thick steel plate and the concrete. However, according to the simulation's findings at the stand-off distance of 300 mm, the structure has sustained relatively minor damage. Also, the steel plate functioned as a protective barrier in most cases, as designed.

Experimental and theoretical evaluation of tubing cutting with rotating particle jet in oil and gas borehole operation

The rotating particle jet cutting technology is an efficient way to deal with downhole stuck tubing efficiently in oil and gas borehole operation. To make full use of the rotating particle jet energy, a thorough understanding of the cutting process is needed. In this work, the Euler-Lagrange theory was utilized to establish the Computational Fluid Dynamics (CFD) model of tubing cutting with a rotary particle jet. A field-scale testing apparatus was developed to investigate the cutting effect achieved by rotating particle jet impact. The flow field characteristics of tubing cutting with a rotary particle jet were studied. The effects of operating parameters on the cutting efficiency were analyzed and the key cutting parameters were optimized. Validation of the theoretical model was carried out. The results show that the highest pressure is achieved when the rotating particle jet impacts the tubing wall. The average erosion rate increases with increasing standoff distance when the standoff distance is less than 7 mm. When the particle concentration is greater than 6%, the average erosion rate of tubing begins to increase slowly. The recommended particle diameter is 0.6–0.8 mm. This work can provide a theoretical foundation for field application of the rotating particle jet cutting technology.

Exclusion and Verification of Remote Nuclear Reactors with a 1-kiloton Gd -Doped Water Detector

To date, antineutrino experiments built for the purpose of demonstrating a nonproliferation capability have typically employed organic scintillators situated as close to the core as possible (typically at a distance of a few meters to tens of meters) and have not exceeded a few tons in size. One problem with this approach is that proximity to the reactor core requires accommodation by the host facility. Water Cherenkov detectors located offsite, at distances of a few kilometers or greater, may facilitate nonintrusive monitoring and verification of reactor activities over a large area. As the standoff distance increases, the detector target mass must scale accordingly. This paper quantifies the degree to which a kiloton-scale gadolinium-doped water Cherenkov detector can exclude the existence of undeclared reactors within a specified distance, and remotely detect the presence of a hidden reactor in the presence of declared reactors, by verifying the operational power and standoff distance using a Feldman-Cousins-based likelihood analysis. A 1-kton scale (fiducial) water Cherenkov detector can exclude gigawatt-scale nuclear reactors up to tens of kilometers within a year. When attempting to identify the specific range and power of a reactor, the detector energy resolution is not sufficient to delineate between the two.

Millimeter-Wave Near-Field Evaluations of Polylactic Acid (PLA) Filament Used in Polymer-Based Additive Manufacturing (AM)

ABSTRACT Additive manufacturing (AM) remains to be a rapidly growing industry with applications that are extended beyond metals and to other materials, such as polymers, ceramics, and concrete, to name a few. However, advancement in the development of inspection techniques, particularly in-line nondestructive testing (NDT) methods, lags significantly. Most of the research in developing such methods has focused on metal-based AM. This paper investigates the efficacy of three high-resolution near-field millimeter-wave probes for detecting small voids in the feedstock polymeric filaments used for AM. The electromagnetic (EM) design and optimization of these probes are discussed in this paper. The design of the probes is based on concentrating the interrogating electric field of an open-ended waveguide in a small region corresponding to the area of a thin dielectric slab insert. This results in achieving a higher spatial resolution than when using only the open-ended waveguide. Extending the dielectric slab to an optimum value out of the waveguide makes the electric field more concentrated and potentially further improves the spatial resolution. These modifications also reduce the detection sensitivity as a function of increasing standoff distance. However, the spatial resolution of these probes varies more rapidly as the standoff distance increases. Subsequently, the efficacy of these three probes was studied and compared using a comprehensive set of numerical EM simulations at V-band (50–75 GHz). Afterward, three such probes were fabricated, at V-band (50–75 GHz), and were used to measure the reflection responses of the stock Polylactic Acid (PLA) filaments with a very small hemispherical surface void. Root-Mean-Squared-Error (RMSE), between reference and defective filaments and over the simulated and measured frequency range, was calculated as a criterion to compare the detection capability of the three probes in the entire frequency band. The results showed that at V-band (50–75 GHz) the spatial resolution of the standard open-ended rectangular waveguide is deemed sufficient detecting small surface voids of the stock PLA filaments.

Investigating the effect of electromagnetic impact welding parameters on the microstructure evolution and mechanical properties of SS-Cu joint

In the present research, the desirable values of electromagnetic impact welding parameters such as spacer distance, standoff distance and voltage were estimated to improve the mechanical properties of the dissimilar joint between stainless steel and copper. The numerical and experimental techniques were applied to perform the electromagnetic impact welding process using the response surface methodology. The microstructure and quality of the joints were assessed by tensile test, hardness test, scanning electron microscopy, X-Ray diffraction analysis and energy dispersive X-ray spectroscopy. The results indicated that an increase in voltage from 11.5 to 12.5 kV led to an enhancement in the hardness and tensile strength by about 6.7% and 7% respectively, while the weld length and elongation reduced by about 45.5% and 39.6% respectively. Moreover, the values of hardness and tensile strength improved by 3.4% and 4.3% respectively when the standoff distance increased from 1 to 2 mm. However, the increase of standoff distance from 1 to 2 mm indicated a reduction in the weld length and elongation by 6.6% and 12.5% respectively. The mechanical properties of the weld joint were improved simultaneously at a spacer distance of 1.8 cm, standoff distance of 2 mm and a voltage of 12 kV. The microstructure analysis showed that the initiation of crack in the intermetallic phases and the entrapment of oxides in the weld joint were responsible for reduction of the weld quality.

ON MICROSTRUCTURE AND CAVITATION EROSION BEHAVIOR OF MICROWAVE-SYNTHESIZED Ni-Al2O3-BASED COMPOSITE CLADDINGS

In this study, Ni-Al2O3-based composite clads on SS-316 substrates using a microwave irradiation method have been developed. Microwave-processed clads were characterized using various nondestructive techniques to investigate microstructure, phase analysis, porosity assessment and measurement of microhardness. The findings of the microstructural analysis demonstrated the formation of solid, metallurgically bonded and defect-free clads with a thickness of approximately 970[Formula: see text][Formula: see text]m. X-ray diffraction (XRD) phase analysis study confirmed the existence of hard and intermetallic phases in the clad region. Composite clad region exhibited a low porosity value of [Formula: see text]1.3%. The average microhardness of the clad region was 3.63 times that of the substrate region. Further, cavitation erosion (CE) behavior of the developed clads was investigated using vibration CE test rig under various stand-off distances and immersion depths. CE results showed that the composite clads exhibited 6.9 times better erosion resistance than SS-316 substrate. CE resistance increased with an increase in stand-off distance and the depth of immersion.

Damage of a large-scale reinforced concrete wall caused by an explosively formed projectile (EFP)

To quickly break through a reinforced concrete wall and meet the damage range requirements of rescuers entering the building, the combined damage characteristics of the reinforced concrete wall caused by EFP penetration and explosion shock wave were studied. Based on LS-DYNA finite element software and RHT model with modified parameters, a 3D large-scale numerical model was established for simulation analysis, and the rationality of the material model parameters and numerical simulation algorithm were verified. On this basis, the combined damage effect of EFP penetration and explosion shock wave on reinforced concrete wall was studied, the effect of steel bars on the penetration of EFP was highlighted, and the effect of impact positions on the damage of the reinforced concrete wall was also examined. The results reveal that the designed shaped charge can form a crater with a large diameter and high depth on the reinforced concrete wall. The average crater diameter is greater than 67 cm (5.58 times of charge diameter), and crater depth is greater than 22 cm (1.83 times of charge diameter). The failure of the reinforced concrete wall is mainly caused by EFP penetration. When only EFP penetration is considered, the average diameter and depth of the crater are 54.0 cm (4.50 times of charge diameter) and 23.7 cm (1.98 times of charge diameter), respectively. The effect of explosion shock wave on crater depth is not significant, resulting in a slight increase in crater depth. The average crater depth is 24.5 cm (2.04 times of charge diameter) when the explosion shock wave is considered. The effect of explosion shock wave on the crater diameter is obvious, which can aggravate the damage range of the crater, and the effect gradually decreases with the increase of standoff distance. Compared with the results for a plain concrete wall, the crater diameter and crater depth of the reinforced concrete wall are reduced by 5.94% and 9.96%, respectively. Compared to the case in which the steel bar is not hit, when the EFP hit one steel bar and the intersection of two steel bars, the crater diameter decreases by 1.36% and 5.45% respectively, the crater depth decreases by 4.92% and 14.02% respectively. The EFP will be split by steel bar during the penetration process, resulting in an irregular trajectory.

Experimental investigation into the synergetic damage of foam-filled and unfilled corrugated core hybrid sandwich panels under combined blast and fragment loading

Foam filling strategy has been demonstrated to owing the ability to improve the blast resistance of sandwich panels under bare blast loading. But it is unclear that the effect of foam filling for performance improvement of sandwich panels in response to combined blast and fragments loading. In this paper, the corrugated core sandwich panels with and without aluminum foam fillers were designed, fabricated and finally tested under combined blast loading. Main attention focused on the influence of stand-off distance, foam filler density and core configuration on the dynamic responses in terms of deformation modes and failure mechanisms. The perforation failure of target panels could be alleviated with the increase of stand-off distance. The increase of foam filler density hardly affected the deformation/failure modes of panels, but it could reduce the permanent deformation of core webs and front face sheet. Relative to unfilled sandwich panels, foam filling behavior is an effective way to relieve the debonding failure between face sheet and core webs. Overall, the performance of foam-filled sandwich panels under combined blast loading is mediocre. The failure mode of foam-filled sandwich panels would transform from localized plastic deformation mode under bare blast loading to catastrophic failure under combined blast loading.

Near-surface gas discharge effect on a steady bow shock wave position in a supersonic flow past a cylindrically blunted body in the air

The problem of the bow shock wave control using a near-surface gas discharge in a supersonic flow past a semi-cylindrical body at Mach number M = 4 in the air is investigated experimentally and numerically. The possibility of controlling the position of a steady bow shock wave and the characteristics of a streamlined body by creating a volumetric plasma region using a surface gas discharge organized on the entire front surface of the body is shown. An increase in the stand-off distance of a steady bow shock is experimentally and numerically obtained, which is the greater, the higher the discharge power and the greater the adiabatic index in the plasma region created by the discharge. A comparison of the numerical and experimental data showed good agreement. It is established that the relative value of the steady bow shock stand-off distance increases linearly in the power range from 1.5 × 105 to 2.4 × 105 W at the discharge current from 430 to 670 A, and the adiabatic index in the plasma region can be estimated as 1.3. It is also found that at higher values of the discharge power, the adiabatic index in the plasma region decreases. The average plasma parameters were expressed as functions of the discharge specific power and the adiabatic index. The mechanism of the gas discharge effect on the bow shock wave is established, and it is shown that the plasma parameters in the region created by the discharge, including the degree of ionization and the degree of nonequilibrium, affect the position of the steady bow shock wave.

Aggressive ability improvement of self-resonating cavitating jets with double-hole nozzle

The aggressive ability of cavitating jets generated by a double-hole nozzle was investigated under an ambient pressure condition to improve the erosion efficiency for potential applications such as underground drilling. The erosion damage was experimentally investigated for a series of pitch–hole ratios to understand the erosion mechanism of the double-hole cavitating jets. The flow characteristics of various erosion patterns were numerically investigated using two-phase computational fluid dynamics (CFD) calculations. The stages of erosion suppression in the pitch–hole ratio range wp∈ [1.25, 3] and erosion enhancement in wp∈ [3.5, 6] were observed based on the mass loss Δm across the entire range of standoff distance ratio ls. Two erosion patterns were identified according to the erosion features, designated as A and B, with increasing standoff distance ratio ls. Erosion occurs in multiple scattered regions in pattern A and which appears as two symmetric D-shaped regions in pattern B. In contrast to the single-hole jet, the aggressive ability was significantly improved a wp = 4.5 with higher Δm peaks. Double-hole cavitating jets at the optimum pitch–hole ratio achieve the highest streamwise velocity and the weakest interaction between the two jets. The cavitation clouds in the impinging jets generated by the optimum pitch–hole nozzle primarily collapse in the D-shaped main erosion region, which enhances the erosion damage of the double-hole cavitating jets at the optimum standoff distance ratios.

Columnar-structured thermal barrier coatings deposited via the water-based suspension plasma spray process

Suspension plasma spray (SPS) has been developed as a rapid, facile and cost-effective process to deposit columnar-structured thermal barrier coatings (TBCs). In contrast to the most commonly used ethanol-based suspensions, water-based suspensions have not been used in the SPS process to deposit columnar-structured TBCs due to their high surface tension, although they are much cheaper and safer. In this work, a new water-based SPS process was prepared by adding surfactant to lower the surface tension. The optimum content of dispersant and surfactant added to the suspension was determined via measurements of viscosity, particle size, surface tension, contact angles, and atomized droplet size. Coatings deposited using suspensions with and without surfactant showed typical columnar-structured microstructures and vertically cracked microstructures, respectively. The coatings deposited using suspensions with surfactant also showed evolution from columnar-structured microstructures to mixed microstructures of columns and cracks, and to homogeneous microstructures with the increase in standoff distance. The formation of different coating microstructures was correlated to the size of droplets after aerodynamic breakup and the Stokes number of in-flight particles. The new water-based suspension together with the water-based SPS process show great potential to be a cheap and effective alternative to the ethanol-based SPS process.

Heat-fluid-solid coupling mechanism of supercritical carbon dioxide jet in rock-breaking

Aiming at the synergistic rock-breaking mechanism of supercritical carbon dioxide (SC-CO2) jet pressure and temperature difference, a heat-fluid-solid calculation model of rock-breaking stress was established and verified to be effective, and the variations of jet flow field and rock stress with jet standoff distance of SC-CO2, water and nitrogen were studied. With the increase of jet standoff distance, the jet pressure of SC-CO2 decreases and the jet temperature difference increases. The SC-CO2 jet is higher in pressure than the nitrogen jet and differs little from the water jet. Temperature difference of SC-CO2 jet is 5 times that of water jet and more than 2.5 times that of nitrogen jet when the jet standoff distance is larger than 10. The temperature stress is the main reason why SC-CO2 jet is superior to water and nitrogen jets in rock-breaking. The rock under the SC-CO2 jet has greater rock stress, effective rock-breaking jet standoff distance and rock-breaking area. The jet pressure plays a major role in rock-breaking when the jet standoff distance is small, while the jet temperature difference plays a major role in rock-breaking when the jet standoff distance is large. The SC-CO2 jet is an efficient volume rock-breaking method, which results in tensile and shear failure on the rock surface under short time jet and large area tensile failure inside the rock simultaneously under long time jet.

Process Parameters Optimization of Wet Shot Peening for Paint Cleaning

Wet shot peening (WSP) cleaning technology has the advantages of being green, having a high efficiency, and producing almost no pollution to the environment. Under the development trend of green environmental protection, WSP is more and more desired by the public. However, in the study of WSP cleaning paint, there is little research on process parameter optimization. Accordingly, this article uses an orthogonal experiment, taking the cleaning efficiency and the substrate removal mass as objectives, to optimize the parameters of pressure, stand-off distance, traverse rate, and cleaning times. The experimental results show that the cleaning efficiency is improved by increasing the pressure, stand-off distance, and traverse rate or decreasing the cleaning times within the scope of this experiment. The pressure and cleaning times are positively correlated with the substrate removal mass, whereas the traverse rate is negatively correlated. As the stand-off distance increases, the substrate removal mass initially increases and then decreases. The traverse rate has a significant influence on the cleaning efficiency and the substrate removal mass. The optimal process parameters based on the cleaning efficiency are 0.45 MPa pressure, 140 mm stand-off distance, 5 mm/s traverse rate, and one-time cleaning. Besides, the cleaning efficiency at such conditions is 64.23 %/min. Additionally, the substrate removal mass is optimized under 0.25 MPa pressure, 60 mm (or 140 mm) stand-off distance, 5 mm/s traverse rate, and one-time cleaning to give a substrate removal mass of approximately zero. The analysis of parameters provides a reference for selecting the parameters in the actual application of WSP cleaning.

Air Plasma Mitigation of Shock Wave

Theory is presented to show that shock wave structure can be modified via interacting with an air plasma plume generated symmetrically in front of a shock wave generator. Electron jet in the plasma plume deflects the impinging airflow via momentum transfer collisions. Symmetrical deflection makes it easy to satisfy the conservation of transverse momentum between the airflow and plasma. The charge transfer between N2+ and N2 randomizes the impinging airflow to increase the deflection angle. The flow deflection increases the effective cone angle of the shock generator; as the effective cone angle exceeds a critical value, the shock becomes detached and faded.  Experiments were conducted in a Mach 2.5 wind tunnel to mitigate shock wave via air plasma deflection. A non-thermal air plasma was symmetrically generated, in front of a wind tunnel model by on-board 60 Hz periodic electric arc discharge, as a deflector for shock wave mitigation. The results show a transformation of the shock from a well-defined attached shock into a highly curved shock structure, which has increased shock angle and appears in diffused form. Shown in a sequence with increasing discharge intensity, the transformed curve shock in front of the model moves upstream to become detached with increasing standoff distance from the model and is eliminated when the discharge is near the peak. The steady of the incoming flow during the discharge cycle is manifested by the repetition of the baseline shock front. The experimental observations confirm the theory and efficacy of this air plasma mitigator.

Expansion Tube Experiments of Magnetohydrodynamic Aerobraking for Superorbital Earth Reentry

A set of magnetohydrodynamic (MHD) aerobraking experiments was conducted with the aim of simulating the Earth reentry environment for Mars return trajectories, and to study the effects of MHD flow control on the ionizing shock layer surrounding a planetary entry vehicle. The X2 expansion tube of the University of Queensland was used, which could provide realistic flowfield boundary conditions, where ionization is spontaneously generated within the shock layer as in true flight and the freestream is nonconducting. Suitable flow conditions providing strong MHD interaction at superorbital Earth reentry velocities were developed. Steel ball and neodymium permanent magnet models were tested, both uncoated and coated with electrically insulating high-temperature epoxy. Shock-layer high-speed imaging showed a significant increase in shock standoff distance for the magnetic models. The experimental shock standoff results generally agreed well with analytical and numerical shock standoff predictions. These experiments demonstrate that a strong MHD interaction can be generated for a Mars return trajectory with moderate magnetic field strengths. Furthermore, they provide a promising framework for future MHD aerobraking experiments to investigate MHD drag force and heat-flux mitigation.

Influence of standoff distance on the deformation of square steel plates subjected to internal blast loadings

This study presents a combining experimental and numerical efforts on elucidating the influence of the standoff distance on large inelastic deformation of square steel plates subjected to the fully-confined internal blast loading from TNT detonation. Experimental results reveal that increasing standoff distance could lead to a monotonic increase of permanent central displacement of the target plate, which contradicts the well-known free-air blast scenarios. Detailed three-dimensional finite element simulations using LS-Dyna are carried out to provide additional insights into the pressure evolution and transient response of the ductile plates. The numerical results are validated against experimental data where they were found to be in reasonable agreements. Numerical predictions reveal that complex pressure wave interactions within the blast chamber, and the saturated impulse effect attribute, in part, or combination, to the aforesaid phenomenon. The discussions on the limitation of the current findings are also provided, highlighting its dependency on the confinement’s geometry.