Shock Experiments Research Articles

Contrasting responses of Thermocyclops crassus and T. oithonoides (Crustacea, Copepoda) to thermal stress.

Thermal tolerance is a critical factor influencing the survival of living organisms. This study focuses on the thermal resistance of copepod species, Thermocyclops crassus (Fischer, 1853) and T. oithonoides (Sars G.O., 1863), with overlapping distribution ranges in Europe. Short-term heat shock experiments were conducted to assess the thermal resistance of these copepods, considering various temperature increments and exposure durations. Additionally, the study explored the influence of heat shock on egg sac shedding, a vital indicator of population dynamics. Results indicate that widely distributed T. crassus exhibits higher thermal tolerance compared to narrowly distributed T. oithonoides, with survival rates varying under different heat shock conditions. Furthermore, T. crassus demonstrated a quicker response in dropping egg sacs in response to thermal stress, suggesting a potential adaptive mechanism for the survival of adults. However, rapid egg sac droppings pose high risks for eggs facing unfavorable conditions. T. crassus, inhabiting environments with greater temperature fluctuations such as the littoral and pelagial zones, exhibited better survival mechanisms compared to T. oithonoides, which predominantly resides in the pelagic zone. The findings have implications for understanding copepod responses to global warming and thermal pollution. This research contributes insights into the adaptive strategies of thermophilic copepod species and their ecological consequences.

Finite element simulation and experiment of residual stress evolution in MEMS structures

The MEMS device structure is usually formed by the combination of thick film and thin film deposition of many different materials, and the residual stress generated in the process of integration/superposition of different materials has a significant impact on the performance and reliability of the device.In this study, a test structure of a multilayer thin film was designed and processed. Based on this, finite element modeling analysis and reliability experiment, analyze the evolution of residual stress and construct the corresponding theoretical analysis model. The finite element modeling analysis can characterize the evolution and distribution laws of residual stress. The reliability experiment is mainly by carrying out the temperature shock experiment, and measuring the resistance value, resonance frequency and the surface morphology of the device, so as to better reflect the change of residual stress. Through this study, the resonant frequency and surface morphology of the device can reflect the residual stress of the device, which provides help for the test and analysis of the residual stress. To a certain extent, it can help reduce the harm caused by the residual stress in the design and manufacturing process, and improve the performance and reliability of MEMS devices.

On the Thermal Shock Resistance and Failure Mechanism of the Pt-Modified Aluminide Bond Coating

The failure mechanism of the Pt-modified aluminide (Pt-Al) bond coating (β-(Ni, Pt)Al coating) in a simulated service environment has seldom been investigated. Based on a self-developed thermal barrier coating service environment simulator, a thermal shock experiment of single-phase Pt-Al bond coating on DD419 substrate at a temperature of 1170 °C was conducted combined with a real-time monitoring infrared thermal imager. The lifespan and failure mechanism of the coating are analyzed in detail. The results reveal that specimens of the Pt-Al bond coating, subjected to three repeated tests, exhibit failure after 650, 528, and 793 thermal shock cycles at 1170 °C, respectively. After failure, the contents of Pt and Al elements in the peeled region are lower than those in the unpeeled area, and a diffusion zone emerges in the bond coating. The failure mechanism of the Pt-Al bond coating during the thermal shock test can be attributed to three main aspects: (1) the diffusion and consumption of the Pt element reduced the oxidation resistance of the Pt-Al bond coating; (2) the diffusion and depletion of elemental Al causes a phase change in the coating, leading to the failure of the coating; (3) thermal stresses are generated in the Pt-Al bonded coating during the thermal shock test, which ultimately leads to wrinkling.

Amorphous alloys surpass E/10 strength limit at extreme strain rates

Theoretical predictions of the ideal strength of materials range from E/30 to E/10 (E is Young’s modulus). However, despite intense interest over the last decade, the value of the ideal strength achievable through experiments for metals remains a mystery. This study showcases the remarkable spall strength of Cu50Zr50 amorphous alloy that exceeds the E/10 limit at strain rates greater than 107 s−1 through laser-induced shock experiments. The material exhibits a spall strength of 11.5 GPa, approximately E/6 or 1/13 of its P-wave modulus, which sets a record for the elastic limit of metals. Electron microscopy and large-scale molecular dynamics simulations reveal that the primary failure mechanism at extreme strain rates is void nucleation and growth, rather than shear-banding. The rate dependence of material strength is explained by a void kinetic model controlled by surface energy. These findings help advance our understanding on the mechanical behavior of amorphous alloys under extreme strain rates.

Characterization of ejecta in shock experiments with multiple light scattering

Upon impact, the free surface of a solid metal may eject a cloud of fast and fine particles. Photon Doppler Velocimetry (PDV) is one of the optical diagnostics used to characterize these ejecta. Although the technique provides a direct way to estimate the particle velocities in the single scattering regime, it has been shown that multiple scattering cannot be neglected in real ejecta. Here, we derive a model for PDV measurements starting from the first principles of wave scattering. We establish rigorously the relationship between the specific intensity and the measured signal, as well as the Radiative Transport Equation (RTE) that describes the evolution of the specific intensity upon scattering and absorption in dynamic ejecta, including the effects of inelastic scattering and inhomogeneities in the optical properties. We also establish rigorously the connection between the Monte Carlo scheme used for numerical simulations and the solution to the RTE. Using numerical simulations, we demonstrate the crucial contribution of multiple scattering to PDV spectrograms as well as the effect of statistical inhomogeneities in particle size distribution. These results could substantially impact the analysis of ejecta by PDV.

Restoration and Transformation: The Response of Shocked and Oxidized Magnetite to Temperature

AbstractLarge impact craters on Earth are associated with prominent magnetic anomalies, residing in magnetite of the shocked target rocks and impactites. Shock experiments on magnetite suggest that up to 90% of magnetic susceptibility is lost at pressures >5 GPa, but can be partially restored by post‐shock thermal annealing. The magnetic property changes are caused by shock induced grain size reduction and fragmentation, as well as domain wall‐pinning at crystal lattice defects. A recent study of granitoids from the peak‐ring of the Chicxulub crater found that annealing may occur naturally, but can also be overprinted by high‐temperature hematite‐to‐magnetite transformation in non‐oxidizing environments. In this study, we isolate the effect of defect annealing and hematite‐to‐magnetite transformation using the evolution of hysteresis, isothermal remanent magnetization components and first order reversal curve (FORC) diagrams at different high‐temperature steps. We used a laboratory‐shocked magnetite‐quartz ore, a non‐shocked naturally oxidized granite, and a naturally shocked and oxidized granite. Our findings suggest that annealing of shock‐induced lattice defects partially restores some pre‐shock magnetic behavior and causes an apparent average bulk‐sample domain state increase. Hematite‐to‐magnetite transformation creates new fine‐grained magnetite that strongly overprints the original signal, and decreases the average bulk‐sample domain state. Where annealing and hematite‐to‐magnetite transformation both occur, the new magnetite masks the annealing‐induced property restoration and apparent domain state modification in the shocked magnetite. As magnetite oxidation is a ubiquitous process in surface rocks, these findings are fundamental to understand hematite‐to‐magnetite transformation as a potential overprint mechanism, and could have broad implications for paleomagnetic interpretations.

Dynamic response of additively manufactured Ti–5Al–5V–5Mo–3Cr as a function of heat treatment

Both shock and shockless compression experiments were performed on laser powder bed fusion (LPBF) Ti–5Al–5V–5Mo–3Cr (Ti-5553) to peak compressive stresses near 15 GPa. Experiments were performed on the as-built material, containing a purely β (body centered cubic) microstructure, and two differing heat treatments resulting in a dual phase α (hexagonal close packed) and β microstructure. The Hugoniot, Hugoniot elastic limit (HEL), and spallation strength were measured and compared to wrought Ti-6Al-4V (Ti-64). The results indicate the LPBF Ti-5553 Hugoniot response is similar between heat treatments and to Ti-64. The HEL stress observed in the LPBF Ti-5553 was considerably higher than Ti-64, with the as-built, fully β alloy exhibiting the largest values. The spallation strength of the LPBF Ti-5553 was also similar to Ti-64. Clear evidence of initial porosity serving as initiation sites for spallation damage was observed when comparing computed tomography measurements before and after loading. Post-mortem scanning electron microscopy images of the recovered spallation samples showed no evidence of retained phase changes near the spall plane. The spall plane was found to have kinks aligned with the loading direction near areas with large concentrations of twin-like, crystallographic defects in the as-built condition. For the heat-treated samples, the concentrations of twin-like, crystallographic defects were absent, and no preference for failure at the interface between the α and β phases was observed.

Temperature shock to manipulate the optical properties of Al-doped ZnO films

We constructed the 2 × 2 × 2 Aluminum-doped Zinc Oxide (AZO) supercrystal cell structure and developed the temperature shock experiment at −40 °C–85 °C. The results showed that the temperature shock can increase the absorption rate of AZO, decrease the transmittance and the band gap of AZO, and change the density of electronic states near the Fermi level. The AZO films were also subjected to temperature shock of −40°C–85 °C, it shows that the transmittance and band gap of AZO films both decreased after temperature shock. The experimental results show that the temperature shock reduce the transmittance and the band gap width of the AZO films. The results are hoped to be helpful to understand the degeneration and improvement of the optical properties of AZO films under temperature shock loading and predict the performance of AZO films.

A Finite Element Study of Thermal Shock Load Effects on Dental Material before on the Two-body Wear Mechanisms

Abstract Background: The thermal changes environment is a parameter that affects the dental mechanical and esthetic behavior of materials. Dental materials placed in the human oral environment are inevitably exposed to thermal changes environments during chewing movement and hot or cold fluids. Aim: Therefore, this study aims to analyze the surface behavior of a dental material placed in the human mouth in thermal changes according to the finite element method. Materials and Methods: Cylindrical titanium alloy samples with a diameter of 12 mm were prepared for thermal shock load simulation. Withinthe scope of this study, the samples were divided into two equal groups. While the first group test samples were subjected to thermal shock experiments, the others were determined as the control group. The surface temperature distributions of the samples in the test procedures were analyzed and evaluations were made on the wear behavior of the materials. Results: The temperature distributions showed density on the material surface and it was analyzed that a temperature transfer took place toward the inside of the material. Conclusion: This result is evaluated as behavior that reduces the wear resistance since it directly affects the contact surface in the two-body (direct-contact) wear mechanism.

Planar shock compression of spark plasma sintered B4C and B4C–TiB2 ceramic composites

Blending of ceramic constituent phases enhances sinterability and performance in high strength ceramics. Here, a near fully dense blended boron carbide (B4C)–titanium diboride (TiB2) composite produced through spark plasma sintering (SPS) is probed to understand the mechanical performance under dynamic uniaxial strain, or shock compression. This study on the shock performance of blended B4C–TiB2 measures the effect of initial TiB2 powder size on the dynamic response of the composite and compares results to those of monolithic SPS B4C. These shock experiments reveal a strengthening of the Hugoniot elastic limit (HEL) with an addition of TiB2 and mitigation of the adverse post-HEL response observed in many brittle ceramics, such as monolithic B4C. The TiB2 particle size in the composite does not noticeably influence these results. The tough nature of TiB2 along with compressive residual stresses in the B4C matrix resulting from high temperature processing and a mismatch of the thermal expansion coefficients of the constituent phases are postulated to strengthen the B4C.

Validating methods for modeling composition gradients in planar shock experiments

An interface is Rayleigh–Taylor (RT) unstable when acceleration pushes a less dense material into a more dense one, and the growth of the instability is governed partly by the Atwood number gradient. Double-shell inertial confinement fusion capsules have a foam spacer layer pushing on an inner capsule composed of a beryllium tamper and high-Z inner shell, and so have RT unstable interfaces that require benchmarking. To this end, the results of a planar shock experiment with beryllium/tungsten targets are presented. One target had the normal bilayer construction of beryllium and tungsten in two distinct layers; the second target had the beryllium grading into tungsten with a quasi-exponential profile, motivated by the potential for reduced RT growth with the gradient profile. Simulations mimic the shock profiles for both targets and match the shock velocity to within 5%. These results validate the ability of our simulations to model double-shell capsules with bilayer or graded layer Be/W inner shells, which are needed to design future experiments at the National Ignition Facility.

Ground shock attenuation performances of wire-rope-based meta-isolators

In this research, two types of novel meta-isolators were designed based on traditional wire-rope isolators and made by embedding mass-spring resonators into the wire-rope isolator. Measurement methods to reveal attenuation abilities of these meta-isolators were suggested through quasi-static cyclic loading tests, shaking table tests, and in-field explosion experiments. In the quasi-static tests, meta-isolators have greater hysteresis area under the same excitation displacement, which represents much greater energy consumption. Using shaking table tests and measurement, the vibration attenuation ability of the meta-isolators is improved in the designed resonant frequency, and the response amplitudes are significantly reduced compared with the conventional wire-rope isolators. Blast-induced ground shock experiments reveal that the meta-isolators indeed have an advantage over the conventional isolators in the aspect of shock resistance and the attenuation efficiency exceeds 98 %, providing a new idea and reference for protective engineering.

AbInitio Phase Diagram of Gold in Extreme Conditions.

A phase diagram of gold is proposed in the [0; 1000]GPa and [0; 10 000]K ranges of pressure and temperature, respectively, topologically modified with respect to previous predictions. Using finite-temperature abinitio simulations and nonequilibirum thermodynamic integration, both accelerated by machine learning, we evaluate the Gibbs free energies of three solid phases previously proposed. At room temperature, the face-centered cubic (fcc) phase is stable up to ∼500 GPa whereas the body-centered cubic (bcc) phase only appears above 1TPa. At higher temperature, we do not highlight any fcc-bcc transition line between 200 and 400GPa, in agreement with ramp-compressed experiments. The present results only disclose a bcc domain around 140-235GPa and 6000-8000K, consistent with the triple point recently found in shock experiments. We demonstrate that this re-stabilization of the bcc phase at high temperature is due to anharmonic effects.

Effects of Rapid Thermal Cycling (Cold Shock) on Fish Health: Evidence from Controlled Laboratory Experiments, Behavior, and Telemetry

Powerplants frequently use river water for cooling, subsequently discharging warm effluent. Some of these plants can cycle on and off rapidly based on electricity demand, resulting in dramatic temperature fluctuations in the receiving waters. To understand the impacts on resident fish populations in the Upper Mississippi River, we (i) assessed the effects of rapid water cooling on three native fish species; (ii) investigated whether smallmouth bass (Micropterus dolomieu) behavior favored movement into thermal plumes when given a choice of cooler or ambient water; and (iii) tracked native M. dolomieu with acoustic tags and recorded core body temperature during the thermal cycling process of a steam electric powerplant. In cold shock experiments, mortality was associated with rapid temperature declines and dependent on the final (cold) holding temperature. The species or developmental stage of the tested organism did not affect survival. When given a choice between warm and ambient waters, M. dolomieu exhibited little inclination to acclimate to the warmer water and instead “self-regulated” by moving in and out of the warm water plume. This finding was supported by telemetry data on M. dolomieu. The core temperature of the fish never increased more than 2 °C above the ambient (upstream) Mississippi River temperature, even during warm effluent discharge.

Abnormal variation of P-wave velocity of red sandstone after cyclical thermal shock in water

Hot dry rock (HDR) has great development potential because of its advantages of clean, environmental protection and renewable. The study of physical and mechanical properties of HDR is one of the important links in the process of geothermal energy development. Previous studies have mainly focused on the granite thermal reservoir but research on the sandstone thermal reservoir, especially the physical properties of sandstone after multiple thermal shocks, is scarce. Therefore, in this study, cyclic thermal shock experiments of sandstone at different temperatures are carried out, and the variation law of P-wave velocity of sandstone after heat treatment is revealed. It is found that the P-wave velocity of red sandstone decreases with the increase of temperature and cycle times, especially when the temperature is higher than 400 °C, the maximum change rate of wave velocity reaches 52.6%. It is particularly noteworthy that the P- wave velocity of sandstone increases abnormally at about 600 °C. And this article puts forward three hypotheses to explain the wave velocity anomaly. In addition, the nonlinear relationship model among P-wave velocity, temperature and number of cycles is established for the first time, and the correlation coefficient R2 is more than 0.9. This study serves as a reference for the development and utilization of the sandstone geothermal reservoir.

Blast wave attenuation of nonlinear meta-isolation system: Theoretical analysis and experimental validation

In the field of protective engineering, wire rope isolators are usually applied in the isolation floor to mitigate the impact and vibration induced by explosive blast. In this paper, two kinds of meta-isolation systems were proposed and designed based on the local resonance, and investigated by means of theoretical analysis, numerical calculation and experimental research. First, the force-displacement hysteresis loops of the selected wire rope isolators are obtained by the cyclic loading tests, and identified by a mathematical model to make preparations for numerical calculation. Then, in order to discuss the influence of mass ratio, stiffness ratio and damping ratio on the shock isolation, the two-degree-of-freedom (TDOF) linear and nonlinear models are studied based on the mode superposition method and fourth-order Rugga-Kutta method respectively. Finally, the blast-induced ground shock experiments were conducted to evaluate the isolation efficiencies of conventional isolation systems and meta-isolation systems. The experiment results reveal that the isolation efficiency of meta-isolation system can increase by 10% points vertically and 16% points horizontally compared to conventional systems, which indicates that the meta-isolation system has great potential to be adopted in the engineering structures and provides a new idea and reference for protective engineering.

Multi-factor coupled failure mechanism of W–Cu functionally graded material under thermal shock service

The stability of W–Cu functionally graded material (FGM) as a heat sink connecting material is of significant importance for long-term service under high-temperature thermal cycling conditions. In this study, W–Cu FGM was successfully fabricated by powder metallurgy method. Various thermal shock experiments were performed on the samples at different temperatures and cycles, and a comprehensive investigation was conducted into its service failure mechanisms. The findings demonstrate that as the temperature increases to 1000 °C, the layer with low copper content gradually developed microcracks, and the microstructure changed from the original uniform distribution to a copper granular exudation, ultimately forming a network-like copper layer. The layer with high copper content undergoes a transition from slight undulations and roughness to the emergence of numerous cracks and pores, accompanied by the formation of a larger area of copper pool structures. After 1000 °C thermal shock for 200 cycles, the thermal conductivity decreases from 215.33 W m−1 K−1 to 168.24 W m−1 K−1, the bending strength decreased from 686.75 MPa to 115.77 MPa at room temperature, with reductions of 22.4 % and 81.2 %, respectively. At this point, the sample severely failed. The study highlights that the thermal shock failure mechanism of the gradient W–Cu samples is a novel multifactor coupled failure mechanism. It is influenced by the combined effects of crack initiation and propagation induced by thermal stress and the evolution of microstructural changes.

Preparation of transparent anodic aluminum oxide films and their structural characteristics under thermal shock

Anodic aluminum oxide (AAO) films have a wide range of research and applications in the field of nanoscience and technology. Transparent AAO films require the oxide layer to be peeled off from the aluminum substrate to which it is attached, involving a complex preparation process and immersion in a variety of caustic solutions, resulting in the prepared AAO films that are very prone to fragmentation and unfavorable for applications. Here, we have prepared transparent AAO films by double-sided anodization method with secondary anodization, which consists of a double-sided porous structure spaced with a barrier layer. These transparent AAO films can be bent into bow shape and exhibit good toughness under the action of external forces applied at both ends. Then, the transparent AAO films were subjected to thermal shock experiments, and the changes in the microstructure of the AAO films before and after the thermal shock were analyzed. The relationship between the microstructure of the AAO films and the good toughness they exhibit was also investigated.

Improving the high-temperature oxidation resistance of CrN coating by gradient deposition considering internal stress effects

In this study, two different CrN coatings were deposited on the surface of Zr-4 via a multi-arc ion-plating method using gradient and non-gradient deposition processes. The effects of two deposition processes on the high-temperature oxidation resistance and internal stress of the coatings were investigated. The microstructure and phase structure of the coatings were characterized by scanning electron microscopy, X-ray diffraction (XRD), and energy dispersive spectrometry. The high-temperature oxidation resistance of the specimens was investigated by performing thermal shock experiments and simulated loss-of-coolant accident high-temperature steam oxidation experiments. The residual stresses of both coatings during deposition were determined by XRD analysis. In addition, the thermal stresses of both coatings during the high-temperature oxidation tests were modeled and calculated. Under long-term high-temperature oxidation conditions, the gradient-deposited CrN coating exhibited improved high-temperature oxidation resistance performance than that exhibited by non-gradient-deposited CrN coating. In addition, the residual stresses of gradient-deposited CrN coating during deposition and thermal stresses during high-temperature oxidation were significantly lower than those of the non-gradient-deposited CrN coating. The results obtained herein confirm the promising potential of gradient-deposited CrN coating as an accident-tolerant fuel cladding material.

Collective motion in hcp-Fe at Earth’s inner core conditions

Earth's inner core is predominantly composed of solid iron (Fe) and displays intriguing properties such as strong shear softening and an ultrahigh Poisson's ratio. Insofar, physical mechanisms to explain these features coherently remain highly debated. Here, we have studied longitudinal and shear wave velocities of hcp-Fe (hexagonal close-packed iron) at relevant pressure-temperature conditions of the inner core using in situ shock experiments and machine learning molecular dynamics (MLMD) simulations. Our results demonstrate that the shear wave velocity of hcp-Fe along the Hugoniot in the premelting condition, defined as T/Tm (Tm: melting temperature of iron) above 0.96, is significantly reduced by ~30%, while Poisson's ratio jumps to approximately 0.44. MLMD simulations at 230 to 330 GPa indicate that collective motion with fast diffusive atomic migration occurs in premelting hcp-Fe primarily along [100] or [010] crystallographic direction, contributing to its elastic softening and enhanced Poisson's ratio. Our study reveals that hcp-Fe atoms can diffusively migrate to neighboring positions, forming open-loop and close-loop clusters in the inner core conditions. Hcp-Fe with collective motion at the inner core conditions is thus not an ideal solid previously believed. The premelting hcp-Fe with collective motion behaves like an extremely soft solid with an ultralow shear modulus and an ultrahigh Poisson's ratio that are consistent with seismic observations of the region. Our findings indicate that premelting hcp-Fe with fast diffusive motion represents the underlying physical mechanism to help explain the unique seismic and geodynamic features of the inner core.