High Thermal Cycling Research Articles

High Cycle Thermal Fatigue Crack Initiation Behavior of Austenitic Type 304 Stainless Steel in Pure Water.

Temperature fluctuations in power plants may cause thermal fatigue in structures, In order to maintain integrity of structures, the thermal fatigue life has to be evaluated including high cycle fatigue conditions on which few investigation has been performed so far. In the last study, a facility for high cycle thermal fatigue testing in pure water was developed. To clarify the high cycle thermal fatigue crack initiation behavior of type 304 stainless steel in pure water environment, high cycle thermal fatigue tests were conducted using the developed facility for various water temperature fluctuation frequency and water temperature fluctuation range in this study. The thermal stresses induced on the labyrinth corner of the cylindrical specimen were analyzed by FEM. The heat transfer coefficient experimentally evaluated using the thermal fatigue testing facility was applied to the analysis. Thermal fatigue cracks were initiated at the corner of the labyrinth for the stress amplitude and over 294 MPa. On the other hand, the mechanical fatigue crack initiation lives were derived from the mechanical fatigue of type 304 stainless steel. It was demonstrated that the number of cycles to thermal fatigue crack initiation agreed with that of the mechanical fatigue crack initiation when the fictitious stress amplitudes were identical.

Crack propagation in first wall of fusion reactor by cyclic thermal stress

To clarify the crack propagation behavior of first wall materials under high thermal load cycles, cyclic high heat flux loading tests were carried out on SUS316. A specimen with a thickness of 5 mm was used, and the tests were performed under three types of external load conditions in order to investigate the effect of stationary tensile stress, simulating gravitational load on the first wall. To get rid of the effect of creep, the duration time of the beam was limited to 0.5 s in every 30 s high heat flux loading cycle. Two-dimensional thermal and elasto-plastic stress analyses and non-linear fracture mechanics analysis were carried out, and the fatigue crack propagation lengths were evaluated using Ĵ-integral amplitude Δ Ĵ eff. Through this study, it was concluded that crack propagation lengths were decreased by applying stationary moderate tensile load, and that the evaluated crack lengths roughly agreed with experimental ones.

Characteristics of Ferroelectric Transistors with BaMgF4 Dielectric

The structure and electrical characteristics of metal-ferroelectric-semiconductor FET(MFSFET) for a single transistor memory are presented. The MFSFET was comprised of polysilicon islands as source/drain electrodes and film as a gate dielectric. The polysilicon source and drain were built-up prior to the formation of the ferroelectric film to suppress a degradation of the film due to high thermal cycles. From the MFS capacitor, the remnant polarization and coercive field were measured to be about and 100 kV/cm, respectively. The fabricated MFSFETs also showed good hysteretic I-V curves, while the current levels disperse probably due to film cracking or bad adhesion between the film and the Al electrode.

The effect of thermal cycling on the mechanical properties of sic whisker reinforced magnesium alloy-based composites

The effect of thermal cyclings on mechanical properties at room and some elevated temperatures of SiC whisker-reinforced magnesium-matrix composites produced by squeeze casting and hot extrusion are clarified. Subsequent thermal cycling produces internal stress at the matrix/SiC whisker interfaces causing fatigue. The mechanical properties of composites are more influenced by the low thermal cycling of 298 K— 77 K than the high thermal cycling 673 K—298 K. The high thermal cycling of 673 K—298 K has only a slight affect on such mechanical properties as tensile strength and proof stress at temperatures lower than 473 K. However, at 473 K and 573 K, the thermal cyclings there almost no influence on the mechanical properties of SiC whisker reinforced AE42 alloy-matrix composites.

Development of a Facility for High Cycle Thermal Fatigue Testing in Pure Water and Measurement of Heat Transfer Coefficient in an Annular Gap between Rotating Inner and Stationary Outer Cylinders.

Temperature fluctuations in power plants may cause thermal fatigue in structures. In order to maintain integrity of structures, the thermal fatigue life has to be evaluated. Although a Coffin type thermal fatigue testing apparatus induces a homogeneous thermal strain in a specimen, high cycle thermal fatigue with strain distribution under the specimen surface can not be performed by it. In this study, a facility for high cycle thermal fatigue testing in pure water was developed. High and low temperature water are continuously supplied into an autoclave with a rotating cylindrical fatigue specimen, so that the specimen surface is simultaneously surrounded by high and low temperature water. Since the specimen is driven by a motor outside of the autoclave, the specimen suffers from the rotation synchronized thermal fatigue. Using the developed facility, heat transfer coefficients on the specimen surface of type 304 stainless steel were measured at various revolution frequency. The heat transfer coefficients were found to increase with the revolution frequency and were greater than 50 kW/m2K at the frequency higher than 5 Hz. High cycle thermal fatigue cracks are expected to be initiated since higher stress than the fatigue limit of mechanical fatigue can be initiated with this facility.

Characteristics of bending strength and residual stress distribution on high thermal cycle of ceramic and metal joint

Characteristics of bending strength and residual stress distribution on high thermal cycle of ceramic and metal joint

Effects of moisture and thermal cycling on in-plane shear properties of graphite fibre-reinforced cyanate ester resin composites

The weight change and retention of in-plane shear (±45°) strength of graphite fibre-reinforced cyanate ester resin matrix composites have been estimated on exposure to high humidity and thermal cycling, respectively. Cyanate ester resin matrix composites absorbed a remarkably small amount of moisture on exposure to high humidity. However, the degree of moisture absorption underwent a rather sudden increase to a new equilibrium level after prolonged exposure. A morphology study showed the occurrence of extensive cracking in the matrix/interface region in the form of delamination between plies as well as translaminar cracking within plies. The phenomenon is believed to be caused by weakening of the fibre-matrix interface, which was confirmed by microscopic analysis of fracture surfaces. A sudden moisture gain associated with extensive matrix/interface cracking was found to reduce the in-plane shear strength and fatigue lifetime at a given stress amplitude. The slope of the S-N curve was lower for wet specimens, implying a higher growth rate of local cracks as well as delamination. The rate of in-plane shear strength degradation was also measured on static exposure to dry heat as well as after thermal cycling to a peak temperature of 150 or 204°C. At a frequency of 10 min/cycle and for a relatively short duration, the effect of thermal cycling seems to be represented by the cumulative sum of thermal oxidation effects at the peak temperature.

Rapid Isothermal Processing of Strained GeSi Layers

AbstractThe effects of high temperature-time thermal cycles on the structural stability of GexSi1−x/Si and Si/GexSi1−x/Si layers are studied, using double-crystal x-ray diffraction. The temperature-time cycles chosen in this study are useful for the fabrication of submicron Si MOSFETs. The electrical characteristics of GeSi/Si p-n heterojunctions as a function of annealing temperature and time are also presented.

A microstructural study of the thermal fatigue failures of 60sn-40Pb solder joints

When an electronic package encounters thermal fluctuations, cyclical shear strain is imposed on the solder joint interconnections. The thermal cycling leads to a condition of thermal fatigue and eventual solder joint failure. This study was performed in order to understand the microstructural mechanisms that lead to solder joint failures in thermal fatigue. Thermal cycling tests were performed on 60Sn-40Pb joints using a -55° C to 125° C cycle and 19% imposed shear strain. A heterogeneously coarsened region of both Pb and Sn-rich phases develops within the 60Sn-40Pb solder joints. Cracks initiate in the heterogeneously coarsened Sn-rich phase at the Sn-Sn grain boundaries. Heterogeneous coarsening and failure occurs in both high (35 to 125° C) and low (-55 to 35° C) thermal cycles. The elevated temperature portion of the thermal cycle was found to be the most significant factor in the heterogeneous coarsening and failure of the solder joints.

Organic coolants and their applications to fusion reactors

Organic coolants offer a unique set of characteristics for fusion applications. Their main advantages include high temperature (670 K) but low pressure (2 MPa) operation, limited reactivity with lithium and lithium—lead, reduced corrosion and activation, good heat transfer capabilities, no MHD effects, and an operating temperature range that extends to room temperature. The major disadvantages are decomposition and flammability. The organic fluid characteristics are described in sufficient detail to allow fusion system designers to evaluate organic coolants for specific applications. Analyses are presented for organic-cooled blankets, first walls, high heat flux components and thermal power cycles. Designs are identified that take advantage of organic coolant features, yet have fluid decomposition related costs that are a small fraction of the overall cost of electricity. Particularly interesting applications include organic-cooled high heat flux components (up to about 8 MW/m 2) for use with liquid metal cooled blankets.

ACI TYPE HU

Abstract Type HU is an iron-chromium-nickel alloy containing about 60% alloying elements in the iron base. Its high chromium and nickel contents give this grade excellent resistance to corrosion by either oxidizing or reducing hot gases, particularly those containing appreciable amounts of sulfur. This excellent corrosion resistance and its excellent combination of high-temperature strength, resistance to thermal fatigue and resistance to carburization make this alloy especially suited for severe service conditions involving high stress and rapid thermal cycling. This datasheet provides information on composition, physical properties, hardness, and tensile properties as well as fracture toughness and creep. It also includes information on high temperature performance and corrosion resistance as well as casting, heat treating, machining, and joining. Filing Code: SS-374. Producer or source: Various stainless steel casting companies.

Transient pellet-cladding interaction of LWR fuel rod — Computer code ISUNE-4

The transient pellet-cladding interaction (PCI) of a typical fuel element in a light-water reactor (LWR) fuel rod (or subassembly) is analyzed, formulated and discussed by taking into consideration temperature distribution, fuel densification, fuel restructuring, pellet-cladding gap opening, closure and fuel-cladding “bambooing,” gap conductance, irradiation swelling, irradiation creep, thermal cycling, fuel cracking, and clad stress fatigue and stress corrosion cracking (SFC-SCC). Based on the postulated models or theories, analytical equations and experimental data, computer code ISUNE-4 (a series of ISUNE-1,-2 and -3) has been developed. The computer code analyzes typical transient PCI, verifies a large quantity of accepted experimental data, and predicts fuel performance and fuel rod safety (as well as reactor safety) of LWR power plants. To improve the fuel (sintered UO 2 pellets) performance and fuel rod safety at high burnup during transient PCI, it is very important 1. (a) to strive for increasing strength and ductility of cladding materials (Zircaloy), 2. (b) to provide relatively large gap thickness and plenum space for accommodating fission gas release, 3. (c) to keep power increase rate slow in order to avoid SFC-SCC at the inner cladding surface, and 4. (d) to reduce the intensity and frequency of transient PCI in the high temperature, irradiation swelling, irradiation creep, thermal cycling, and stress fatigue and stress corrosion cracking (SFC-SCC) environment.

Developments in solar cell generators

The European satellite projects of today and the near future, to be applied for measuring tasks demanding highest accuracy or used in missions of extended lifetime, have stimulated the development of new solar cell module concepts. Low outgassing rates, magnetic and electric cleanliness (as achieved by conductive coatings), high thermal cycling capability and extended lifetime (by improved solar cell interconnection techniques), high temperature capability for sun missions or healing radiation damage, integral cover slips for reducing weight, and high module flexibility for use on deployable large-area panels mark the trends in module development. Based on the work for the German AEROS satellite project and the work on roll-up structures, the module concepts are described and test results given. Power data on the solar cells are reported and compared with the results of JPL balloon flights and the measurements in the DIAL project. Advanced developments are discussed.

Fundamental phenomena in thermal fatigue test of aluminum alloys

Failures due to thermal fatigue often occur in aluminum alloy pistons and cylinder heads of engines, especially in those of Diesel-engines owing to their high operating temperatures.This paper reports a method for investigating the resistance of aluminum alloys to thermal fatigue and the phenomena in thermal fatigue tests of Al-Si base alloy castings.The results obtained were summarized as follows:(1) It was found that a high rate thermal cycling could be achieved with a thermal fatigue testing apparatus of high frequency induction heating type (not the Coffin type.) (2) The number of cycles to failure was decreased with the increase in temperature amplitude, thermal stress amplitude, and plastic strain amplitude.(3) Specimens were tested at an average temperature of 300°C; they were radially expanded in the section heated to the maximum temperature and necking appeared in the both ends of the expanded section. The deformation of specimens was related with the distribution and variation of hardness in the specimens. The hardness was decreased in the section heated to above 300°C; and was minium in the necked parts, wehre the fracture took place.

Silicon planar epitaxial transistors as fast and reliable low-level switches

This paper attempts to accentuate all the salient factors of high-quality switches, such as their static properties, stability under various conditions of high temperature or thermal cycling, and some aspects of their transient response. It is shown that the silicon planar epitaxial transistor possesses the most advantageous combination of properites for general application as a low-level switch, and that simple low-injection level formulas are sufficiently accurate for the calculation of voltage offset and resistance of an "on" switch, as well as the "off" resistance, if extrinsic parameters and current dependence of β <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</inf> and β <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">i</inf> are taken into account. A simplified procedure is proposed for the selection of temperature-compensated switch pairs. Hysteresis in a single parameter β <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</inf> is shown to be the main cause of instability in voltage offset in germanium alloy-type transistors, an effect which is hardly detectable in silicon planar epitaxial devices. Suitability of the latter for fast operation in chopper amplifiers is discussed, and their capabilities in a rapid-sampling commutator is illustrated.

The symmetry of time in physics

Rotating detonation engines are widely studied because of their compact configurations and high thermal cycle efficiency. For briefty, most of the numerical simulations of rotating detonation engines used premixed reactant mixtures. The rotating detonation waves under non-premixed condition are not studied enough. Here, a series of three-dimensional numerical simulations of a rotating detonation engine under both premixed and non-premixed conditions using H2/air mixture are performed. The explicit formulation of density-based solver in ANSYS Fluent is used to perform the simulations. Two total mass flow rates of 272.3 g/s and 500 g/s are selected. When the total mass flow rate is 272.3 g/s, the engine operates at single-wave mode under both premixed and non-premixed conditions. When the total mass flow rate is 500 g/s, the engine operates at single-wave mode under premixed condition. While under non-premixed condition, a spontaneous formation of dual-wave mode is observed. This case agrees well with the phenomenon observed in experiments that as the total mass flow rate increases, the number of rotating detonation waves tends to increase. Pressure waves caused by the high pressure behind the detonation waves can propagate upstream to the H2 and air plenums. The pressure feedback in the H2 plenum is much more obvious than that in the air plenum. Due to the imperfect mixing of H2/air and the more deflagration combustion caused by the hot detonation products, the thrust of the RDE under non-premixed condition is smaller than that under premixed condition.