Severe Operating Conditions Research Articles

Designing polyoxometalate based hybrid catalysts for efficient removal of hazardous sulfur from fuel via heterogeneous oxidative desulfurization

Hydrodesulfurization is a common but less effective technique to remove sulfur content of oils due to severe operating conditions of temperature, pressure and cost. Oxidative desulfurization(ODS) is preferable due to low cost and mild operating conditions. Coupling of the extractive catalytic desulfurization with the ODS give rise to extractive catalytic oxidative desulfurization(ECODS), a more promising for the elimination of sulfur contents of fuel oil. Herein we present by polyoxometalate based hybrids, [H2TPP][K5BVW11O40]•2CH3CN•2H2O (1), [H2TPP]2[K3BVW11O40]•CH3CN•3H2O (2), and [H2TPP]3[KBVW11O40]•2CH3CN (3) for efficient ECODS of hazardous model fuel. These were synthesized by facile method and characterized by elemental analysis, inductive couple plasma, powder X-ray diffraction analysis, thermo-gravimetric/differential thermal analysis, fourier transform infrared, and UV–visible analysis. These polyoxometalate based hybrids contain cations [H2TPP]2+(organic) and [BVW11O40]7−(inorganic) with stoichiometric ratios(i.e., 1:1, 2:1, 3:1). The stoichiometry of these hybrids was also established by Job’s analysis which agreed well with the results of TG-DTA and elemental analyses. Interestingly, an increase in catalytic efficiency is observed with increase of organic cations. The maximum ∼99.5 % conversion of dibenzothiophene at 60 °C after 2 h has been achieved with hybrid 3 which could be employed up to ten cycles without a significant decrease in efficiency.

A REVIEW: FERRITIC-MARTENSITIC STEELS – TREATMENT, STRUCTURE AND MECHANICAL PROPERTIES

The constantly growing consumption of electricity requires the development and implementation of more powerful and energy-intensive systems of the new generation. Fusion and fission reactors of the 4th generation (Gen-IV) will make it possible to cover the growing demand for electricity. Since Gen-IV reactors will operate at higher temperatures and radiation doses, the problem of selecting scientifically based structural materials arises, since conventional reactor materials are not suitable for use in such severe operating conditions. Among the structural materials under consideration for future generations of reactors, special attention is paid to 9…12% Cr ferritic-martensitic steels due to their higher radiation tolerance and excellent mechanical properties compared to traditionally used austenitic steels. This review presents the main ferritic-martensitic steels that will be used as structural materials, their structure, mechanical properties and various thermal and thermomechanical treatments applied to them.

Overcharge‐Induced Phase Heterogeneity and Resultant Twin‐Like Layer Deformation in Lithium Cobalt Oxide Cathode for Lithium‐Ion Batteries

Overcharging is expected to be one of the solutions to overcome the current energy density limitation of lithium-ion battery cathodes, which will support the rapid growth of the battery market. However, high-voltage charging often poses a major safety threat including fatal incendiary incidents, limiting further application. Numerous researches are dedicated to the disadvantages of the overcharging process; nonetheless, the urgent demand for addressing failure mechanisms is still unfulfilled. Herein, it is revealed that overcharging induces phase heterogeneity into layered and cobalt oxide phases, and consequent "twin-like deformation" in lithium cobalt oxide. The interplay between the uncommon cobalt(III) oxide and the deformation is investigated by revealing the atomistic formation mechanism. Most importantly, abnormal cracking is discovered in the vicinity of the cobalt oxide where structural instability induces substantial contraction. In addition, surface degradation is widely observed in the crack boundary inside the particle. As unintentional overcharging can occur due to local imbalance in state-of-charge in severe operating conditions such as fast charging, the issues on overcharging should be emphasized to large extent and this study provides fundamental knowledge of overcharge by elucidating the crack development mechanism of layered cathodes, which is expected to broaden the horizon into high voltage operation.

A Battery Thermal Management System Coupling High-Stable Phase Change Material Module with Internal Liquid Cooling

In this work, we develop a hybrid battery thermal management (BTM) system for a 7 × 7 large battery module by coupling an epoxy resin (ER)-enhanced phase change material (PCM) module with internal liquid cooling (LC) tubes. The supporting material of ER greatly enhances the thermal stability and prevents PCM leakage under high-temperature environments. In addition, the other two components of paraffin and expanded graphite contribute a large latent heat of 189 J g−1 and a high thermal conductivity of 2.2 W m−1 K−1 to the PCM module, respectively. The LC tubes can dissipate extra heat under severe operating conditions, demonstrating effective secondary heat dissipation and avoiding heat storage saturation of the module. Consequently, during the charge-discharge tests under a 40 °C ambient temperature, the temperature of the PCM-LC battery module could be maintained below 40.48, 43.56, 45.38 and 47.61 °C with the inlet water temperature of 20, 25, 30 and 35 °C, respectively. During the continuous charge-discharge cycles, the temperature could be maintained below ~48 °C. We believe that this work contributes a guidance for designing PCM-LC-based BTM systems with high stability and reliability towards large-scale battery modules.

CFD Investigation of Reynolds Flow around a Solid Obstacle

The Reynolds equation defines the lubrication flow between the smooth contacting parts. However, it is questionable that the equation can accurately anticipate pressure behavior involving undeformed solid asperity interactions that can occur under severe operating conditions. Perhaps, the mathematical model is inaccurate and incomplete, or some HL (hydrodynamic lubrication) and EHL (elastohydrodynamic lubrication) assumptions are invalid in the mixed lubrication region. In addition, the asperity contact boundary conditions may not have been properly defined to address the issue. Such a situation motivated the recent study of a 3D CFD investigation of Reynolds flow around the solid obstacle modelled in between the converging wedge. The produced results have been compared to analytical and numerical results obtained by employing the Reynolds equation. The validated CFD simulation is compared with the identical wedge, with cylindrical asperity at the center. A significant increase in pressure has been predicted because of asperity contact. The current study shows that the mathematical formulation of the ML problem has shortcomings. This necessitates the development of a new model that can also include fluid flow around asperity contacts for the accurate prediction of generated pressure. Consequently, sustainable tribological solutions for extreme loading conditions can be devised to improve efficiency and component performance.

ОСОБЕННОСТИ СХЕМОТЕХНИКИ ОПЕРАЦИОННЫХ УСИЛИТЕЛЕЙ НА КОМПЛЕМЕНТАРНЫХ ПОЛЕВЫХ ТРАНЗИСТОРАХ С УПРАВЛЯЮЩИМ PN-ПЕРЕХОДОМ

The systematic component of the offset voltage (Voff) of two-stage BJT and CMOS operationalamplifiers (Op-Amps) with classical architecture significantly depends on the numericalvalues (difference from unity) of the current transfer coefficient (Ki≈1) of the current mirrors (CM)used. This parameter of CM is also influenced by the Earley stress of their dominant active components.Current JFET mirrors are today a weak link in modern JFET analog circuitry and theyare impractical to use in the structure of JFET Op-Amps. The article posed and solved the problemof the conditions for the elimination of CM in an Op-Amps based on field-effect transistorswith a control pn-junction for the case when it is necessary to obtain a small Voff. Variants of practicalcircuits of input (InS) and intermediate (IntS) stages of microelectronic operational amplifiersbased on complementary field-effect transistors with a control pn-junction (CJFET) are proposed.Their main feature is the absence of a current mirror, which, when implemented on aCJFET, negatively affects the main parameters of the Op-Amps in terms of the systematic componentof the offset voltage, the attenuation coefficients of the input common-mode signal, and thesuppression of noise on the power buses. In this regard, InSs and IntSs circuits are promising,which do not use this CJFET functional unit. The circuits of Op-Amps based on the developed InSswith an open gain of more than 80 dB and a systematic component of the offset voltage within 300μV with low current consumption in a static mode are presented. The relevance of the performedstudies lies in the need to develop the theory of designing high-precision JFET and CJFET IPmodulesfor use in structures of low-noise analog interfaces of sensors of various physical quantities,including those operating in severe operating conditions (exposure to low temperatures andradiation) The proposed circuits can be implemented on wide-gap semiconductors (SiC JFET,GaN JFET or GaAs JFET).

Thermal Simulations of a New SiC Detector Design for Neutron Measurements in JSI Nuclear Research Reactor

Today, to respond to the increase of development of accurate, precise and relevant experiments in nuclear research reactors and tokamaks with their severe and intense operating conditions, there is a major need of innovative sensors that can accurately measure key parameters such as neutron and photon fluxes or nuclear heating rates. Thus, innovation in the field of nuclear instrumentation and measurements is a privileged research topic. It is crucial to develop optimized devices for accurate on-line in-core measurements, and scientific/technological requirements for various applications such as ageing of materials, safety applications, beam monitoring or nuclear physics. Nowadays, more and more semiconductors are used as sensor materials in nuclear instrumentation to measure various kinds of nuclear radiations. Silicon Carbide (SiC) is among them. In fact, SiC detectors could be used for the on-line measurement of key quantities such as neutron (thermal and fast) and photon fluxes. One main challenge is to enlarge the measurement range of this detector type. The work presented in this paper deals with this aim. Firstly, an introduction dedicated to the use of SiC versus other wide bandgap semiconductors and the characteristics of the studied sensor is shown. Secondly, this paper presents 3D numerical results obtained with a parametrical thermal study of the SiC detector using COMSOL Multiphysics code for a nuclear heating range corresponding to TRIGA nuclear research reactor conditions (integral neutron flux ~2.0 x1013 n·cm‑2·s-1 leading to a nuclear heating rate of 0.25 W·g-1 in Tungsten). The main objective is to adapt and optimize the design and the housing of the detector by determining its temperature field for different configurations. The influence of various parameters is presented such as that of the housing material nature, the gas nature around the diode, the gas-gap height and the housing thickness.

Influence of porosity and blistering on the thermal fatigue behavior of tungsten

Tungsten is the leading plasma-facing material (PFM) for nuclear fusion applications. It faces severe operating conditions, including intense hydrogen plasma exposure and high-cycle transient heat loading, which create various defects in tungsten. Additionally, defects have often already been introduced during manufacturing. Little is understood regarding the synergistic effect of such defects on the lifetime of tungsten so far. Here, we investigate the influence of porosity and blistering on the thermal fatigue behavior of tungsten. The pores resulted from powder metallurgy whereas the blistering was induced by hydrogen plasma exposure. Both conditions were subjected to transient heat loading by a high-power pulsed laser. The exposure was performed in the linear plasma generator Magnum-PSI, which closely mimics the expected particle and heat flux in the world’s largest fusion experiment, ITER. Both porosity and blistering degraded the fatigue resistance of tungsten. Pores tended to aggregate at high-angle grain boundaries (HAGBs) and assisted crack initiation therein, as revealed by focused ion beam cross-sectioning and electron backscatter diffraction (EBSD) analysis. The blisters were characteristic of subsurface cavities, which were located at a depth close to the surface roughness induced by transient heat loading. The stress concentration at the tip of the cavities is considered to promote crack initiation. The results highlight the necessity of a ‘life cycle assessment’ of the tungsten PFM for nuclear fusion reactors.

Effect of Decoking Pretreatment on Catalyst Rejuvenation Using Glycerol and Mono Ethylene Glycol (MEG)

Hydrotreating process is one of the crucial processes in petroleum refinery to remove sulfur with the aid of catalyst. By the end of hydrotreating life cycle, the catalyst contaminated by silicon cannot be reused or regenerated and have to be sent to final disposal. The previous study reported that glycerol was able to selectively remove silic on from industrial spent catalysts using severe operating conditions. However, the treatment used did not consider carbon/ coke removal steps. The present work focuses on investigating the effect of decoking pretreatment on silicon removal process using glycerol, mono ethylene glycol, and a combination of glycerol + mono ethylene glycol. It was found that the decoking pretreatment will worsen solvent selectivity. In addition, XRD analysis also revealed that decoking pretreatment caused formation of MoO3 particles agglomerate as indicated by the presence of high crystalline. Compared with glycols, glycerol showed the best selectivity and could preserve catalyst phase from transformation that was occurred during decoking.

Structure Formation in Antifriction Composites with a Nickel Matrix and Its Effect on Properties.

The paper is devoted to studying the chemical elements distribution in the material’s structure depending on the manufacturing technological parameters and their effect on properties of a new self-lubricating antifriction composite based on powder nickel alloy EP975 with CaF2 solid lubricant for operation at temperature 800 °C and loads up to 5.0 MPa, in air. The study is focused on the features of alloying elements distribution in the composite matrix, which depends on the manufacturing technology. A uniform distribution of all alloying elements in the studied composite was shown. The chemical elements’ uniform distribution in the material is associated with one of the most important preparatory technological operations in the general manufacturing technology used. This is a technological operation of mixing powders with subsequent analysis of the finished mixture. The uniform distribution of chemical elements determines the uniform arrangement of carbides and intermetallics in the composite. General manufacturing technology, which includes the main operations, such as hot isostatic pressing technology and hardening heat treatment, contributed to the obtainment of a practically isotropic composite with almost the same properties in the longitudinal and transverse directions. Because of the composite’s structural homogeneity, without texturing, characteristics are isotropic. Improving the material’s structural homogeneity helps to keep its mechanical and anti-friction qualities stable at high temperatures and stresses in the air. The performed studies demonstrated the correctness of the developed manufacturing technology that was confirmed by the electron microscopy method, micro-X-ray spectral analysis, mechanical and tribological tests. The developed high-temperature antifriction composite can be recommended for severe operating conditions, such as friction units of turbines, gas pumping stations, and high-temperature units of foundry metallurgical equipment.

Aromatic free Fenton process for rapid removal of phenol from refinery wastewater in an oscillatory baffled reactor

The need for clean, safe, and unpolluted water has recently become an important issue. Industrial processes such as petrochemical, pharmaceutical, pulp, and paper industries emit organic products in water, such as phenols, which are extremely toxic to aquatic life. The severe operating conditions, such as high pressure and temperature, of the conventional chemical oxidation processes of phenols cost a lot and limited the extensive application of the process. The present work depicts the development of a highly efficient and rapid oxidation process in an oscillating baffled reactor (OBR) to allow continuous and safe phenol removal under moderate operating conditions. Phenol conversion was studied as a function of initial concentration (300–500 ppm), pH (3–5), residence time (1–5 min), at constant amplitude (A = 4 mm), and frequency (f = 4 Hz) of oscillation and room temperature to achieve up to 94.6%. At 70 °C, 300 ppm starting concentration, pH = 3, 4 Hz frequency, and 4 mm amplitude, an exceptional removal of 99.858% phenol was achieved without additional extraction in just 3 min by optimizing the working parameters. This is a significant improvement over comparable processes at this temperature, and it was done in a reactor that scales up reliably, so this performance can likely be replicated on a large scale. Also, the present process was safe as it produced a nil concentration of the hazardous Fenton intermediate compounds.

Local grid refinement in multigrid method for point contact problems of polycrystalline anisotropic material under dry and lubricated conditions

Predicting rolling bearing fatigue life requires knowledge of the three-dimensional (3D) stress fields in the roller and raceway near the lubricated contact. Owing to the increasingly severe operating conditions, the effect of localized features such as surface roughness, subsurface inclusions, and even the crystallographic structure of the material becomes important. Achieving such detail requires (locally) extremely dense gridding in simulations, which in 3D is a major challenge. Multigrid techniques have been demonstrated to be capable of solving such problems. In this study, multigrid techniques are shown to further increase the efficiency of the solution by exploiting local grid refinement while maintaining the simplicity of a uniform discretization. This is achieved by employing increasingly finer grids only locally, where the highest resolution is required. Results are presented for dry contact and elastohydrodynamically lubricated contact cases, circular as well as elliptic, with varying crystallographic structure, and with surface roughness. The results show that the developed algorithm is very well suited for detailed analysis, with also excellent prospects for computational diagnostics involving actual material crystallographic structure from electron backscatter diffraction measurements.

Evaluation of High-Temperature Martensitic Steels for Heavy-Duty Diesel Piston Applications

<div class="section abstract"><div class="htmlview paragraph">Five different commercially available high-temperature martensitic steels were evaluated for use in a heavy-duty diesel engine piston application and compared to existing piston alloys 4140 and microalloyed steel 38MnSiVS5 (MAS). Finite element analyses (FEA) were performed to predict the temperature and stress distributions for severe engine operating conditions of interest, and thus aid in the selection of the candidate steels. Complementary material testing was conducted to evaluate the properties relevant to the material performance in a piston. The elevated temperature strength, strength evolution during thermal aging, and thermal property data were used as inputs into the FEA piston models. Additionally, the long-term oxidation performance was assessed relative to the predicted maximum operating temperature for each material using coupon samples in a controlled-atmosphere cyclic-oxidation test rig. A current commercial steel piston alloy, quenched and tempered martensitic steel 4140, was tested in a single-cylinder research engine for a baseline oxidation and mechanical performance assessment using an abbreviated (50h) durability test plan. The predicted suitability of a candidate piston material in an engine is primarily based on its elevated temperature strength, oxidation resistance, and the complex influence of thermal conductivity, the latter of which is substantially lower for the candidate materials considered in this research relative to the traditional alloys. Although the lower thermal conductivity causes the candidate alloys to operate in higher temperature ranges under identical engine operating conditions and piston geometries, increasing the likelihood of partially or completely negating their strength and oxidation resistance advantages relative to 4140 and MAS steels, this evaluation indicates that several of the candidate piston alloys are predicted to enable improved oxidation resistance under more severe engine operating conditions relative to the current piston materials. However, further evaluation is required to determine if the elevated temperature fatigue strength and durability of these alloys are suitable for more severe engine conditions.</div></div>

Challenges and Opportunities for Renewable Ammonia Production via Plasmon‐Assisted Photocatalysis

AbstractDespite its severe operating conditions, associated energy consumption, and environmental concerns, the manufacture of nitrogen‐rich fertilizers still relies heavily on producing ammonia in centralized chemical plants via the Haber–Bosch process. A distributed and more sustainable scheme considers the on‐site production of carbon‐neutral fertilizers at ambient conditions in photocatalytic reactors powered by sunlight. Among the different strategies proposed to boost the nitrogen reduction ability of conventional catalysts, the incorporation of plasmonic nanomaterials is gaining widespread interest owing to their unique optical tunability and their potential to improve the efficiency and selectivity of many chemical transformations. This Perspective examines the state‐of‐the‐art for the nitrogen reduction reaction via plasmon‐driven photocatalysis and discusses design principles for advancing it. The different physical mechanisms underlying the operation of plasmonic materials in a catalytic setting, and the dimensions along which the catalysts can be tuned to harness them are detailed. Paths to overcome current frontiers in the field, including design strategies of plasmonic photocatalysts, the development of complementary characterization techniques, the standardization of the reaction conditions and ammonia quantification methods, and the possibilities offered by theoretical methods to drive material discovery, identifying fundamental bottlenecks, and proposing directions for the advancement of this emerging field are outlined.

ИССЛЕДОВАНИЕ АЛГОРИТМА СНИЖЕНИЯ ВЗАИМОНАГРУЖЕНИЯ ДВУХ ПРИВОДОВ, ОДНОВРЕМЕННО УПРАВЛЯЮЩИХ АЭРОДИНАМИЧЕСКИМ РУЛЕМ МАГИСТРАЛЬНОГО САМОЛЕТА

Some civil aircraft assume two actuators simultaneously turning aside the flight control surface(rudder, in some cases aileron or elevator). Thus resulting in onset of the force fighting (mutualloading force). There are several ways to reduce the mutual loading force. One of them is to insertspecific force equalization algorithm in actuators steering. This article deals with effectiveness offorce equalization algorithm as well as its influence on system “2 active actuators - elevator”. Mathematic model of two actuators on elevator has been formed and tested by the developed testing methodthat reproduces the most severe operation conditions. There are several nonlinearities which iscontained in mathematic model: sleeve-travel physical limits, nonlinear effects of fluid foil, rod-travelphysical limits and attachment rigidity. Force equalization algorithm comprises a pressure differentialfeedback loop with PID regulator. The results show that force equalization algorithm is highlyefficient (mutual loading force has been reduced over than 90%) in mode test without external load.However, in test mode with external load it is necessary to introduce a limitation on the magnitude ofthe corrective signal so as decrease the rod drop to level specified in terms of reference. Algorithmhas no effect on stability margin of the system. In conclusion, results of this study could also be usefulto expand the test program for two actuators simultaneously turning aside the flight control surfacesto further simplify the implementation of the force equalization algorithm.

Thermal behaviour assessment and electrical characterisation of a cylindrical Lithium-ion battery using infrared thermography

This paper presents an experimental evaluation of the thermal and electrical performance of a commercial 26650 cylindrical LiFePO 4 battery cell. The thermal management of lithium-ion batteries is a key problem for electric mobility applications, where batteries are subjected to severe operating conditions. Accordingly, this study aims to demonstrate the reliability of infrared thermography in the quantitative analysis of heat generation in battery cells. In our opinion, infrared thermography can be very attractive owing to: (i) the non-contact nature of this technique and (ii) its capability to quickly scan measurement areas. Consequently, infrared thermography and thermocouple probe results were compared, providing evidence of similar behaviour. Moreover, we present an electrical characterisation of our lithium-ion battery. In particular, the cell potential, open circuit potential, and entropic heat coefficient vis-à-vis the state of charge were experimentally measured. The obtained experimental data were used to evaluate a simplified heat generation term that is widely employed in numerical approaches. The different contributions to heat generation were carefully analysed. The results show that the reversible term considerably influences the total thermal power. Moreover, infrared-based heat generation estimation can be considered reliable. • Thermal behaviour of Li-ion battery was experimentally analysed using IR thermography and thermocouples. • Experimental data were used to evaluate the battery heat generation using a simplified equation. • IR thermography can be used to quantitative evaluate battery heat generation.

Energy consumption and carbon footprint of perovskite solar cells

Recently, perovskite solar cells (PSCs) emerged and promise to break the prevailing solar energy paradigm by combining both low-cost and high-efficiency. PSC technology actually shivered the solar photovoltaic (PV) community as a strong candidate to rival the efficiency of traditional PV devices; in less than 12 years its efficiency was improved from 3.8% to almost 26%. Despite the tremendous and successful effort for obtaining PSC devices with high power conversion efficiencies, little efforts have been devoted to study fundamental engineering aspects essential for future industrial production. In particular, this work makes an analysis of the energy consumed and the carbon footprint of producing a 3-mesoscopic PSC 8 × 8 cm2 module with an 8.7% efficiency in a life cycle perspective. A “cradle-to-gate” study was performed, using as much as possible primary data. Considering the PSC module as the functional unit the results show that the mesoporous layer deposition is the dominant term concerning the energy consumption. Regarding the carbon footprint, the gold layer, in particular gold, is the main factor. Changing the electricity source to renewable photovoltaic energy reduces significantly the carbon footprint. The results stress the need to replace gold, and use less severe operational conditions in the module production.

The influence of a metal rod inside a spherical Luneberg lens on its characteristics

The paper discusses the option of installing a load-bearing element inside a spherical Luneberg lens (LL). The presence of a metal element inside the LL will increase the structural rigidity of the spherical antenna and thereby expand the scope of use of the LL at various mobile communications and radar facilities with severe operating conditions. The influence of a metal rod inside the main spherical structure on the radiation pattern in two main planes in the linear polarization mode and on the diffraction pattern of the radiation field is estimated. The results of the analysis of the directional characteristics and the diffraction pattern of the LL radiation field were obtained using modeling in the Ansys Electronics Desktop (HFSS Design) working environment, as well as mathematical modeling using the Green tensor function method. At the same time, the obtained mathematical relations can be used in the future to solve the problem of finding the optimal size and position of a metal element in the sphere of LL.

Динаміка відносних крутильних коливань при формуванні регулярного мікрорельєфу на внутрішніх циліндричних поверхнях

An analysis of modern literature sources to search for mathematical models describing the dynamics of the process of forming a regular microrelief on the inner cylindrical surface of parts, gas transmission equipment operating in severe operating conditions, in order to increase their life. It is established that there are no mathematical models describing this process and the peculiarities of its implementation under the point action of the deforming element on the workpiece surface. The molding movements accompanying the process of forming a regular microrelief on the inner cylindrical surface of the workpiece are considered and the driving forces that accompany this process are analyzed. On the basis of the conducted analysis the mathematical model of dynamic process of formation of a regular microrelief on an internal cylindrical surface of a detail is developed. The peculiarity of this process is that the process of microrelief formation occurs by a concentrated force, the point of application of which in relation to the part is constantly changing in radial and axial directions, and then the mathematical model describing this process will be with a discrete right. It is proposed to model such an action using Dirac delta functions with linear and temporal variables, using the method of regularization of these features, in particular, existing methods of integrating the corresponding nonlinear mathematical models of torsional oscillations of a part. Analytical dependences are obtained, which describe these oscillations in the process of formation of a regular microrelief. Using Maple software, 3D changes in the torsion angle depending on different output values are constructed. The conducted researches will allow to consider torsional fluctuations that is especially actual for long cylindrical details, such as sleeves of hydraulic cylinders, details of drilling mechanisms and others.

小型可搬型レーザーピーニング装置による金属材料の残留応力および疲労特性の改善

The advantage of laser peening is the possibility of fine execution management and the capability to introduce deep compressive residual stresses on the material surfaces. It is well known to be highly effective in inhibiting stress corrosion cracking and fatigue cracking on material surfaces. In addition, laser peening has an excellent effect on improving the fatigue strength of welds, which compensates for the disadvantage of high strength steels when welded. Laser peening has a high potential for enhancing material surface, but the high-power laser used requires clean room facilities, large equipment and severe operating conditions. Therefore, the application of the laser peening has been limited to the mitigation of high cycle fatigue of jet engine fan blades and stress corrosion cracking of nuclear reactor structures. If microchip lasers, which are small and easy to handle, could be used as a light source for laser peening, it would be possible to apply them not only to production processes in factories but also to existing structures such as bridges, airplanes, etc. to which conventional lasers have been difficult to apply for the above reasons. In this presentation, we report the results of the laser peening treatment of A7075 (aluminum alloy) and HT780 (high strength steel) with the laser pulse energy of less than 10 mJ. Even at such a low pulse energy, compressive residual stress was imparted and fatigue properties were improved.