IHI Corporation (Czechia)

Abstract Creep tests were conducted on weld joints under welding conditions that have high creep performance. The creep performance of weld joints is governed by the stress distribution in the fine-grained heat affected zone (HAZ) during welding, which is governed by the HAZ shape. In this study, we demonstrated that creep performance can be controlled by welding conditions. The welding condition is obtained by the tandem Bayesian model that combines welding conditions and creep life via HAZ shape factors. This framework is a probabilistic combination of two surrogate models: Gaussian process which predicts the HAZ shape from welding parameters, and Bayesian linear regression which estimates the rupture life. The search targets are the number of layers, layer thickness, and heat input. Long-life conditions that were 1.8 times longer than the maximum life of the initial train data were searched. Two other conditions were selected: standard welding conditions, short-life welding conditions. Welding and creep tests were performed, and the results of the creep tests were long > standard > short. The HAZ shapes reflected the differences in life, as expected from the welding conditions. In conclusion, it is possible to control the creep life by adjusting the welding conditions was proved.

Abstract This paper reports on the fatigue life of objects manufactured by additive manufacturing (AM) using Type 316L Stainless Steel (Type 316L SS), an austenitic stainless steel commonly used in the nuclear power industry. Fatigue tests were performed with axial strain control from low cycles to high cycles of about 1 million times, and the strain amplitude εta for the target fracture life was set using a prediction equation for conventional materials. Powder Bed Fusion (PBF) and Directed Energy Deposition (DED) were used as AM methods to manufacture the test objects. In addition, the effects of heat treatment conditions (with or without Heat Isostatic Pressing (HIP)), test direction (horizontal/vertical), and surface condition (polished/as-built) were evaluated as factors that are thought to affect fatigue life. As a result of conducting fatigue tests on specimens manufactured using PBF or DED, the surface condition of the as -built surface showed a shorter life than the polished surface, but no clear significant differences were observed for other factors. In this paper, a prediction equation for conventional materials was used, but the predicted values for specimens manufactured using AM were equivalent to those for the conventional material, indicating that this prediction equation may also be applicable to AM specimens. In addition, both the PBF and DED specimens had fatigue lives that satisfied the rules on design and construction of the Japan Society of Mechanical Engineers (JSME).

Abstract This study presents the replication analysis of the shaking test for floating seismic isolation system (FSIS) conducted using the world largest shaking table “E-Defense” in Japan. The FSIS technology can provide prominent seismic isolation effects not only for the horizontal direction but also for the vertical direction. One of the unique features in FSIS is the air cavity rooms equipped with the bottom side of the floating structure. These air cavity rooms play a role of suspensions reducing resonant frequency of the floating structures in the vertical motions so that the seismic isolation effect can be obtained for the vertical direction. Although the seismic isolation effects were substantiated by the shaking tests, there were some limitations in the shaking test. In this study, the dynamic analyses have been performed to comprehend the dynamic behaviors of the floating structures in the shaking test by replicating the same situation as the shaking test, and to evaluate the actual seismic isolation performance by eliminating factors disturbing the seismic isolation effects in the shaking test. Through the replication analyses, main dynamic modes of the FSIS test facilities could be represented. Also, the simulation results revealed that the bulging effect of the pool vessel augments the response of the floating structure so that the seismic isolation effects were reduced. This effect was underpinned by conducting the sensitivity analyses on the condition that the pool vessel was changed to be stiffer. This fact will contribute to the development of the seismic analysis methodology applicable to the actual design of FSIS paired nuclear power plants.

To reduce carbon dioxide emissions from mobility, electrified vehicles and mobility have been rapidly increasing in recent years. In this regard, this paper presents the latest trend of technologies supporting mobility electrification, such as electric motors, inverters, and related technologies including vehicle-to-everything, as social systems.

During the development of high by-pass aircraft engine fans, stall flutter often becomes a major issue because it restricts their part-speed operability at near-stall conditions. Stall flutter is usually experienced on the first flexure mode, where a few nodal diameters are dominant. However, our recent tests showed strong non-synchronous excitation for the second flexure (2F) mode containing multiple nodal diameters, which is a distinguishing characteristic from well-known stall flutter. This paper aims to understand the mechanism of the observed 2F excitation. Aerodynamic damping is evaluated by nonlinear transient CFD simulations across a range of fan massflow near stall. The aerodynamic damping turns negative when vortex shedding near the blade tip spills upstream and interacts with the leading edge of the neighbouring blade. Also, the vortex shedding behaviour and resulting aerodynamic damping clearly depend on the blade amplitude. The vortex shedding has broadband spectra for both frequency and circumferential modes under low amplitude, and they lock on the blades’ motion under large amplitude. From these observations, it is concluded that the observed 2F excitation can be categorized into non-synchronous vibrations found in recent literature. The coincidence of blade vibration and vortex shedding is also discussed from unsteady signal processing.

In the near future, to operate reusable spacecraft safely and efficiently, it is necessary to have failure prediction technology for reusable rocket engines. Among the components that constitute a rocket engine, the failure of the turbo pump inducer has a significant impact on missions. Therefore, we have been researching to monitor the remaining life of the inducer. This method estimates the fluctuating stress field excited in the inducer section based on the time-series signals from pressure sensors installed upstream. It predicts the remaining life using a Rain flow model to account for high- cycle fatigue (HCF) phenomena. To validate the effectiveness of the proposed method, we attempted to acquire experimental data, particularly for the challenging pressure-stress transfer section where concrete specifications are difficult to define. Through experiments using an elemental model, we demonstrated that a certain degree of remaining life can be predicted based on measurement from the upstream sensor. This indicates that the proposed method is a promising option for solving the remaining life prediction problem of reusable spacecraft.

<div class="section abstract"><div class="htmlview paragraph">Aircraft electrification is one of technological innovations to achieve the goal of CO<sub>2</sub> emission reduction in civil aviation. In present research, we focus ourselves on an Electric Fuel Metering System (EFMS). Aircraft systems are commonly expected to make not only simplified configuration and improvement of controllability, but also safety and reliability. The electrification of fuel system also requires the similar approach. Therefore, a simple and reliable redundancy concept is a crucial challenge. In addition, stable and responsive controllability that does not affect engine operation is required, especially in fuel system, it is desired to achieve both accurate metering and short settling time without overshoot or undershoot. However, in such a system, the response is nonlinear due to the fuel flow circuit and the motor drive during current limiting. Systemizing a control design that takes these constraints into considerations and that satisfies the requirements over a large dynamic range, has not been discussed. This paper discusses a design methodology to achieve optimal fuel flow control in the EFMS with redundant electric fuel pumps, considering motor current limitation by current limiters. The flow control model is created by adding the flow command increment limiter estimated as equivalent to the current limiter. Using this model, the gain characteristic map is derived analytically. The control system is extended to an active-active control redundant system. The compensating action of that system ensures that if one of the fuel pumps suddenly shut down, the remaining fuel pumps will autonomously increase their flows to maintain the required flow for the engine fuel burn.</div></div>

Piping systems in nuclear power plants exhibit significant elastic-plastic behavior before failure due to displacement responses under severe seismic loads. The current Code Case (JSME NC-CC-008) that was published in 2019 considers the elastic-plastic behavior of the piping system itself but assumes elastic behavior for the support structure. Hence, future Code Case upgrades should incorporate the inelastic behavior of piping support structures. The JSME task group conducted benchmark analyses of piping support structures to establish an evaluation method for their inelastic behavior. The objective of the benchmark analysis was to evaluate the influence of analysis parameters in the elastic-plastic analysis of piping support structures and gain knowledge on analysis result variability. This paper presents an outline of the benchmark analyses and their progress.

地球温暖化抑制のために，CO2排出量の削減が世界で強く求められている。日本においても，2050年カーボンニュートラルの実現を目指すことを，政府が宣言した。IHIでは政府方針である2050年カーボンニュートラルに向けて，脱CO2循環型社会と快適で安心な自律分散コミュニティの実現を目指している。火力発電で使用される燃料の多くは石炭，石油，天然ガスなどの化石燃料であり，燃焼にはCO2の排出を伴う。今後はCO2ゼロエミッションに向けてCO2を排出しないカーボンフリー燃料への転換を進める必要がある。その一つとして有望なものがアンモニアである。石炭焚設備へのアンモニア導入については，石炭に対して発熱量ベースで20%混焼する技術開発を行なってきており，実証段階に来ている。開発段階では窒素酸化物（NOx）と灰中未燃分の抑制が重要課題であったが，これらを所定の値に抑制することが確認できた。実証に向けては実機の実運用に即した運用特性の把握が必要であり，これについても検証を行ない実証試験バーナの設計条件を見出すことができた。アンモニアのガスタービンでの利用については，従来の気化したアンモニアガスを燃焼させる方式から変更し，液体アンモニアをガスタービン燃焼器に直接噴霧して利用する技術の開発に取り組んでいる。この手法のメリットとしては，アンモニアを気化する装置や熱源が不要となるため，アンモニア供給装置全体の構造が簡略化できる点などが挙げられる。液体アンモニアの安定燃焼やエミッション低減に着目した燃焼器の開発を進めた結果，GHGが99%以上削減可能である燃焼技術を開発した。