Shock Processing Research Articles

A general shock model for modelling coupled lives and its application to life insurance

In this paper, we develop a general common shock model for coupled lives by employing a new point process of shocks which generalizes the nonhomogeneous Poisson process (NHPP) and also by considering more plausible practical setting. We study the dependence structure and the dependence orderings of the proposed shock model. Based on it, we investigate the influence of dependence on the pricings of insurance policies involving multiple lives which are subject to common shocks. Furthermore, we discuss relevant stochastic bounds.

Feasibility study of microscale laser shock processing without absorbing coating to improve high-cycle fatigue performance of DZ17G directionally solidified superalloy

A kind of turbine blade in an aero-engine, made of DZ17G directionally solidified superalloys, often fractured at the tenon tooth root. Microscale laser shock processing (LSP) without absorbing coating (microscale LSPwC) under water was suggested to improve its high-cycle fatigue performance. In this paper, a DZ17G superalloy simulated-blade was designed and treated by microscale LSPwC with different impacts. Surface microhardness was improved from 410 to 502 HV with a 70 μm thick hardened layer post one LSP impact, and increasing LSP impact could improve the depth of hardened layer effectively. There was no new phase formed and grain refinement, only with high-density dislocations generated. The density of dislocations on section decreased sharply with depth. The fatigue limit of DZ17G superalloy simulated-blade was improved from 253.14 to 301.14 MPa, and there was still a fatigue strength improvement of 9.0% after insulation treatment under 800 °C for 2 h.

DC SHOCK SIMULATOR

Defibrillators are electronic devices that carry shock electrical signals (pulses) to the heart muscle to maintain myocardial depolarization that is undergoing cardiac fibrillation (ventricular fibrillation or atrial fibrillation) (Bronzino, 2000). There are several conditions that must be met for the occurrence of shock processes including shock time, energy to be provided, patient and operator safety. In this defibrillator the use of selectors / energy selection is linear in the range 1-30 Joules with the use of tools at 10, 15, 20, 25, 30 Joules. The energy will then be discarded or given to the patient via a paddle when pressed the Discharge / shock button. The result of the signal given to the patient is monophasic. This study used a pre-experimental type with a One Group post test design research design. Measurements were made 5 times the volt meter at the test points determined by the compiler.

RuO2-Doped TiO2 Nanotube Membranes Prepared via a Single-Step/Potential Shock Sequence

Anodic TiO2 nanotubes were simultaneously grown and doped with RuO2 by single-step anodization in a negatively-charged RuO4<sup>−</sup> precursor. Subsequently, a high positive voltage was imposed on the nanotubes in an F<sup>−</sup>-based electrolyte (a process referred to as potential shock), which led to the formation of a through-hole RuO2-doped TiO2 nanotube membrane without significant loss of the RuO2 catalyst. XPS results confirmed that the doped Ru metal was converted into RuO2 as the potential shock voltage increased. Further increases in the potential shock voltage led to the formation of RuOx/Ru in the TiO2 nanotubes. All of our results clearly showed that a through-hole catalyst-doped TiO2 nanotube membrane can be produced by a sequence consisting of single-step anodization and the potential shock process.

Optimal mission abort policies for multistate systems

All previous research on optimal mission abort policies was devoted to binary systems that can be only in two states, i.e., operable or failed. This paper considers mission abort and rescue strategies for multistate systems that, apart from a completely operable state and the state of a total failure, can operate in intermediate states with different levels of performance. A system operates in a random environment modeled by a renewal process of shocks. With each shock, the state of a system can deteriorate with certain probabilities that can eventually result in the total failure. Therefore, in order to increase system's survival probability, a mission can be aborted and a rescue procedure can be activated. The trade-off between the mission success probability and the system's survival probability is studied and an optimal number of shocks for initiating the abort procedure is defined by solving the corresponding optimization problem. The detailed numerical example illustrates our findings.

Experiment and numerical simulation of micro dent fabricated by laser shocking 2024 aluminum alloy

PurposeThe purpose of this paper is to investigate the dynamic forming process of the micro dent fabricated by laser shock processing on 2024-T3 aluminum alloy. The effect of laser pluse energy on the deformation of micro dent was also discussed in detail.Design/methodology/approachIt uses finite element analysis method and the corresponding laser shocking experiment.FindingsThe results demonstrate that the dynamic formation process of micro dent lasts longer in comparison with the shock wave loading time, and the depths of micro dents increase with the increasing laser energy. In addition, laser shocking with higher energy can result in more obvious pileup occurred at the outer edge of micro dent.Originality/valueSurface micro dents can serve as fluid reservoirs and traps of the wear debris, which can decrease the effects of the wear and friction in rolling and sliding interfaces. The investigations can not only be propitious to comprehensively understand the forming mechanism of laser-shocked dent, but also be beneficial to get sight into the residual stress field induced by laser shocking.

The euro exchange rate and Germany's trade surplus

AbstractIn the context of debates about the euro exchange rate's (EXR) impact on Germany's (DE) trade surplus, we estimate a multiregion macroeconomic model (1999–2018) and provide a counterfactual in which we simulate the shocks of the estimated model in an alternative setting with freely floating nominal EXRs. The results suggest a reduction of the DE trade surplus by up to 1.3% of gross domestic product (GDP; around 1/4 of the surplus) during 2010–2015 compared to the data, together with a stronger real effective EXR (REER). The rest of the euro area (REA) net exports are more negative (by up to −0.6% of GDP) in the counterfactual before the EA crisis, but more positive (by up to 0.4% of GDP) in recent years. Overall, the counterfactual DE and REA trade balance and REER trajectories are very similar to the actual paths. Modifying shock processes in the counterfactual would give rise to larger differences.

Scaled boundary finite element modelling of thermally induced crack propagation

AbstractNumerical modelling of thermal shock processes is a very challenging task due to the rapid development of complex crack networks. In the context of linear elastic fracture mechanics, the scaled boundary finite element method (SBFEM) has gained popularity due to its semi‐analytical nature. Here, modelling of stress singularities can be achieved efficiently and accurately. It also facilitates the derivation of generalized polygon elements and thus provides great flexibility in meshing of complex geometries. In crack propagation modelling, such polygon meshes require minimal re‐meshing in the vicinity of the crack.

Stochastic modeling of quality of systems operating in a heterogeneous environment

AbstractWe consider systems that are subject to an external mixed Poisson shock process. Each shock can result in a failure of a system with a given probability and is survived with the complementary probability. Each shock additionally decreases the quality function that describes the performance of a system, thus forming the corresponding stochastic process. Expectations (unconditional and conditional on survival) and relevant variability characteristics for the stochastic quality function are derived. Some monotonicity properties of the conditional quality function are investigated and the future values of this function are derived.

Raman spectroscopy of high-pressure phases in shocked L6 chondrite NWA 5011

In the paper we present results of studies of thick shock melt veins in NWA 5011 L6 chondrite. The veins contain a wide variety of high-pressure phases that correspond to contrast values of pressure-temperature parameters on equilibrium phase diagrams. Olivine was transformed to ringwoodite and wadsleyte, orthopyroxene to majorite, akimotoite, and bridgmanite glass, maskelenite is converted to jadeite (+SiO2) and lingunite, apatite to tuite, and chromite to the phase with the calcium ferrite (mCF-FeCr2O4) structure. ) The peak PT shock parameters for NWA 5011 seem highest among the ones for other shocked chondrites according to wide occurrence of lingunite and bridgmanite glass and are considerable higher than 25 GPa and 2500 K. Akimotoite crystals in a quenched matrix of shock melt veins were found for the first time. Probably, they initially crystallized as bridgmanite, since akimotoite is not a liquidus phase in related systems. Plagioclase-chromite aggregates have been established, which characterize the late stages of the shock process and are formed during successive crystallization from isolated pockets of the impact melt.

Thermal Relaxation Features of Residual Stresses Arising upon Laser Shock Processing of Heat-Resistant Materials

In this paper, we study the thermal relaxation features of compressive residual stresses generated during laser-shock wave processing in high-alloyed heat-resistant Iron GH2036 alloy. A finite element modeling of thermal relaxation of the generated compressive residual stresses was performed. The features of the thermal effects on the redistribution of the compressive residual stresses in the temperature range from 200 to 650°C are studied. Based on comparative analysis, the results of the finite element modeling correlated well with the experimental data known in the literature.

Q-switched Nd:YAG laser shock processing effects on mechanical properties of C86400 Cu-Zn alloy

The aim of this paper is to investigate the effects of Nd:YAG laser shock processing (LSP) on micro-hardness and surface roughness of 86400Cu-Zn alloy. X-ray fluorescence technique was used to analyze the chemical composition of this alloy. LSP treatment was performed with a Q-switched Nd: YAG laser with a wavelength of 1064 nm. The results show that laser shock processing can significantly increase. The micro-hardness and surface roughness of the LSP-treated sample. Vickers diamond indenter was used to measure the micro-hardness of all samples with different laser pulse energy and the different number of laser pulses. It is found that the metal hardness can be significantly increased to more than 80% by increasing the laser energy and the number of laser pulse irradiated per unit area. The relationship between laser pulse energy and the value of surface roughness is a proportionality due to the increase in ablation processes which are associated with LSP at sample surface caused by the increasing of laser pulse energy.

Uniform, Scalable, High-Temperature Microwave Shock for Nanoparticle Synthesis through Defect Engineering

Summary Here we demonstrate a thermal shock synthesis method triggered by microwave irradiation for the rapid synthesis of nanoparticles on reduced graphene oxide (RGO) substrate. With properly controlled reduction, RGO has high electrical conductivity while maintaining functional groups, leading to an extremely efficient microwave absorption of ∼70%. The high utilization of microwaves results in the ability to raise the temperature to 1,600 K in just 100 ms, which is followed by rapid quenching to room temperature. The defects on the RGO are crucial for achieving this record-high microwave-induced temperature as these defects play a fundamental role in absorbing the radiation as well as the self-quenching mechanism. By loading precursors onto RGO, we can utilize rapid temperature change to synthesize nanoparticles. The nanoparticles are ∼10 nm with uniform distribution. This facile, rapid, and universal synthesis technique has the potential to be employed in large-scale production of nanomaterials and suggests a new direction for nanosynthesis.

Investigation on Residual Stress Loss during Laser Peen Texturing of 316L Stainless Steel

Laser peen texturing (LPT) is a novelty way of surface texturing based on laser shock processing. One of the most important benefits of LPT is that it can not only fabricate surface textures but also induce residual compressive stress for the target material. However, the residual stress loss leads to partial loss of residual compressive stress and even causes residual tensile stress at the laser spot center. This phenomenon is not conducive to improving the mechanical properties of materials. In this study, a numerical simulation model of LPT was developed and validated by comparison of surface deformation with experiments. In order to investigate the phenomenon of residual stress loss quantitatively, an evaluation method of residual stress field was proposed. The effects of laser power density and laser spot radius on the residual stress, especially the residual stress loss, were systematically investigated. It is found that with the increase of laser power density or laser spot radius, the thickness of residual compressive layer in depth direction becomes larger. However, both the magnitude and the affecting zone size of residual stress loss will be increased, which implies a more severe residual stress loss phenomenon.

Reliability modeling for a two-phase degradation system with a change point based on a Wiener process

A two-phase degradation system with a change point is commonly seen in many real-world degradation systems due to influence of internal mechanisms and external environments, such as lithium-ion batteries, light-emitting diodes (LEDs), plasma display panels (PDPs), and vacuum fluorescent displays (VFDs). Random jumps exist at the change points of the degradation processes. Motivated by this phenomenon, this paper attempts to model such kinds of systems based on the Wiener process. Specifically, In Model 1, a constant change point model is first considered. The analytical results of the system reliability, lifetime distribution, and the remaining useful lifetime (RUL) are obtained. Then, based on Model 1, a random change point model, i.e., Model 2, is proposed to explain the change point phenomenon which is influenced by the accumulative effect of a shock process. Two phase-change patterns (PCPs) are considered in Model 2. For PCP I, the change point is triggered when the number of shocks reaches a predetermined threshold. For PCP II, the change point is triggered when the accumulative shock damage exceeds the corresponding threshold. The system reliability indexes are studied by using analytical and simulation methods. Finally, several numerical examples are given to illustrate the approaches and results.

A contraction for sovereign debt models

Using a dual representation, we show that the Markov equilibria of the one-period-bond Eaton and Gersovitz (1981) incomplete markets sovereign debt model can be represented as a fixed point of a contraction mapping, providing a new proof of the uniqueness and existence of equilibrium in the benchmark sovereign debt model. The arguments can be extended to incorporate re-entry probabilities after default when the shock process is iid. Our representation of the equilibrium bears many similarities to an optimal contracting problem. We use this to argue that commitment to budget rules has no value to a benevolent government. We show how the introduction of long-term bonds breaks the link to the constrained planning problem.

Evaluating methods for quality of laser shock processing

Laser shock processing is an advanced surface modification technology that can effectively enhance the mechanical properties of alloy and metallic materials, such as micro-hardness, fatigue resistance and corrosion resistance, by using laser-induced plasma shock waves, and it has a wide applications in the field of aerospace industry. In this work, the development of laser shock processing is introduced briefly, the research of evaluating methods for quality of laser shock processing is summarized emphatically, and the study necessary of online measuring methods for quality of laser shock processing is indicated.

The real-time acquisition and analysis software system for laser-induced plasma acoustic wave signal

In order to realize the online detection of laser shock processing and aim at the phenomenon of laser-induced plasma acoustic wave, the SIA-AEDAC-01 acoustic emission acquisition card is used to collect acoustic wave signals. The real-time acquisition and analysis software system for laser-induced plasma acoustic wave signal is studied and designed. The test experiment for feasibility and accuracy of the system is designed. Firstly, the laser-induced plasma acoustic wave signal propagating in air is collected by the online detection laser shock processing system, and then the system gets the laser-induced plasma acoustic wave signal energy. The residual stress of the test pieces after the treatment of laser shock processing was measured by an X-ray stress analyzer to verify the reliability. The experimental results show that the laser-induced plasma acoustic wave signal can be collected and analyzed in real-time by the real-time acquisition and analysis software system, which is designed and developed in this work, and the software system can accurately get the acoustic signal energy. At the same time, both the acoustic wave signal energy and the surface residual stress of the test pieces are increased with the laser energy, and their change curve is consistent. In conclusion, the real-time acquisition and analysis software system for laser-induced plasma acoustic wave signal can satisfy the requirements of online detection of laser shock processing with accurate and reliable performance, and meet the online monitoring requirements of laser shock processing.

Trace nanoscale Al2O3 in Al2O3-MgAl2O4 castable for improved thermal shock performance

Al2O3–MgAl2O4 castables are prepared using tabular alumina, fused spinel, α-Al2O3 micro-powder, calcium aluminate cement and nano-Al2O3 particles as starting materials. The effects of trace nano-Al2O3 particles (0.2–0.8 wt%) on the thermal shock resistance (TSR) and microstructure of Al2O3–MgAl2O4 castable are investigated. The results show that trace addition of nano-Al2O3 particles contributes to CA6 crystal development and microstructure optimisation. The platelet CA6 crystals form an interlocking network structure creating a toughening effect, which leads to a significant improvement in TSR. In addition, CA6 formation accompanied by volumetric expansion generates many microcracks, which are beneficial for relieving thermal stress during the thermal shock process and enhancing the TSR of the Al2O3–MgAl2O4 castable.

Experimental Determination of Electronic Density and Temperature in Water-Confined Plasmas Generated by Laser Shock Processing

In this work, diagnoses of laser-induced plasmas were performed in several Laser Shock Processing (LSP) experiments using the Balmer Hα-line (656.27 nm) and several Mg II spectral lines. A Q-switched laser of Nd:YAG was focused on aluminum samples (Al2024-T351) in LSP experiments. Two methods were used to diagnose the plasma. The first method, which required two different experiments, was the standard for establishing the electronic temperature through the use of a Boltzmann Plot with spectral lines of Mg II and self-absorption correction. The Stark width of the Balmer Hα-line was used to determine the electron density in each of the cases studied. The second method had lower accuracy, but only required an experimental determination. Two parameters, the electronic temperature and the electron density, were obtained with the aid of the Hα-line in a single data acquisition process. The order of magnitude of the temperature obtained from this last method was sufficiently close to the value obtained by the standard method (within a factor lower than 2.0), which is considered to be important in order to allow for its possible use in industrial conditions.