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The study investigated the creep-fatigue interaction behavior, fracture mechanism, and microstructure evolution of C630R ferritic/martensitic heat-resistant steel at 630 °C and 1% strain amplitude. The results indicate that C630R ferritic/martensitic heat-resistant steel exhibits noticeable cyclic softening behavior, with a decrease in the softening ratio from 0.46 to 0.40 as loading time increases. Microstructure evolution was examined using optical and scanning electron microscopes, revealing the appearance of secondary cracks on the longitudinal section of the sample. These cracks exhibited a curved expansion trend with multiple deformations and highly bifurcated micro-cracks at a low loading time of 30s. However, when the load holding time was increased to 300s, the fatigue cracks tended to expand in a straight line with fewer branches. Furthermore, the observed crack growth path under different loading times showed enrichment in Fe and Cr, with the crack tip containing Cr oxide, which helped prevent fatigue crack propagation. As the loading time increases, the rise in crack closure resulting from oxidation leads to a decrease in crack propagation. Electron backscatter diffraction observation revealed the formation of numerous substructures and recrystallized grains after varying holding times, enhancing the material's resistance to crack propagation. Moreover, the study found that with increasing load dwell time, the deformed grains decreased, and substructural grains became dominant (57.68% and 62.77% under 30s and 300s, respectively). This increased crack resistance resulted in shorter secondary cracks under prolonged load retention, with the secondary crack length decreasing from 146.36 μm at 30s loading time to 109.09 μm at 300s loading time. Additionally, the kernel misorientation angle value decreased significantly after different loading times, leading to a higher likelihood of cracks or holes forming in regions with high KAM values, where low-angle grain boundaries were formed.

Liquid hydrogen (LH 2) is a future energy carrier compared to most conventional fuels. One of the practical bottlenecks in non-venting LH 2 tanks is to accurately predict the pressure evolution. Accordingly, many thermal models and correlations were developed; however significant deviations arose due to inherent complex thermal phenomena which have not been addressed yet. A general artificial neural network (ANN) model has been first developed based on 448 datasets amassed from different literature sources to predict the pressure evolution under different heat fluxes, initial filling ratios, as well as tank volumes and shapes. The model has been configured with a typical multi-layer feed-forward structure using a back-propagation learning algorithm and Levenberg-Marquardt training algorithm. For the ANN model, a preliminary optimization process has been conducted for reaching the optimal values for training-to-testing datasets ratio, learning parameters and optimum network structure. Besides, some criteria were set to evaluate the ANN model performance. The ANN model with the configuration of 5-11-11-1 was found to be adopted for such a prediction task. Compared to experimental results and literature models and correlations, the ANN model has been proven to predict the pressure evolution in non-venting self-pressurized LH 2 tanks with a mean square error of 1.1779 × 10−5 s2, root mean square error of 0.0034 s, mean absolute error of 6%, mean relative error of 0.2% as well as a satisfactory correlation coefficient of 0.99934 between the network outputs and corresponding targets. This research work provides an effective modeling approach based on artificial neural network to solve one complex problem related with LH 2 tanks with fast, accurate and consistent results. Also, the results of the present work can offer some practical guidance for the design of LH 2 tanks. Further, the present work gives some insights into new application areas of ANN which will be the emphasis of future research work. • Artificial neural network is applied for predicting pressure evolution in LH 2 tanks. • ANN model with a configuration of 5-11-11-1 is proposed for LH 2 tanks. • ANN prediction error of 1.95% was achieved lower than other thermal models. • Studied results reveal the ANN model can map the implicit relationship accurately. [ABSTRACT FROM AUTHOR]

In this work, cast steel G17CrMoV5-10 was investigated. The material subject to investigation as part of this study is commonly used to manufacture steam turbine casings. Modern steam turbines operate under elevated temperature and complex oscillated loads. Thus, the focus of this study was to investigate material under behavior during low cycle fatigue (LCF) test performance at 500°C with and without hold time in tension. During all types of test, cyclic softening of cast steel was noticed. Increasing of total strain rate and applying hold time significantly reduce fatigue life. During hold time, due to temperature and tension the material creep what is confirmed by increasing inelastic stain accommodation.

Frictional properties of sliding surfaces have practical importance in a variety of applications. Therefore, the present study investigates the ageing or holding time-dependent static friction of a wet granular layer using a slide-free-slide (SFS) friction test. It is observed that the static friction varies as a logarithm of hold time. Further, the Mohr–Coulombs' law of friction is used to determine adhesive friction and normal stress-dependent friction. The scaling law analysis has shown that the exponent of adhesive friction is more prominent in magnitude than the corresponding coefficient of friction. A static friction model, based on the formation and rupture of capillary bridges, has also been proposed for predicting the peaks of static friction at different hold times. At the end, the power laws, which correlate the number of attached capillary bridges and adhesion constant with hold time, are proposed to justify the present results. [ABSTRACT FROM AUTHOR]

Ensuring correct functionality is the basic objective of any digital design and this can be done only if the circuit obeys all the timing constraints. Static Timing Analysis is the procedure performed to calculate the setup and hold time of any digital circuit and to check for any setup and hold time violations. This paper presents the methodology to perform setup and hold time analysis for different designs of Master Slave D Flip-Flop using 18 nm FinFET technology. FinFET technology was chosen since it is the prevalent technology in the industry. Implementation of D Flip-Flop design, suitable test circuit and timing analysis is performed on the Cadence virtuoso analog design environment tool. Using appropriate excitations, parametric analysis is carried out to obtain the setup and hold time values for various designs of D Flip-Flop including the proposed design. From the results, it was observed that the setup time and hold time varied with different clock edge rates. For the edge rates of 0.01, 0.05, and 0.1 ns, it was observed that the proposed design gave setup times of 54.9, 61.2, and 69.8 ps and hold times of −30.7, −43.6 and, −48.8 ps, respectively. On comparing all the results, it was observed that the GDI MUX and pass transistor-based designs gave a good trade-off between transistor count, setup time and hold time. For the proposed design, although the setup times were slightly on the higher side, the hold time values were more negative which is always preferred. [ABSTRACT FROM AUTHOR]

The effect of hold time with 0, 20, and 40 s on in-phase thermomechanical fatigue (TMF) behavior and life of P92 steel is investigated in this study. TMF tests are carried out under mechanical strain control with strain amplitudes of 0.40.4, 0.60.6, and 0.8%0.8\text{\%}, and temperature range of 550–650°C which is closely relevant to the operating condition in power plant. TMF tests are performed in a mechanical strain ratio of R=−1R=-1 and cycle time of 120 s. The fatigue life variation follows the sequence of Nf0s

The operation of a capacitorless (1T) dynamic random access memory (DRAM) can be compromised if the storage region is located near metal–semiconductor junction in a reconfigurable field-effect transistor (RFET). Through subtle modifications, without affecting current drive, capacitance, and reconfigurable features, the present work showcases feasible 1T-DRAM operation in a RFET with an intentionally misaligned polarity gate. Analysis based on device physics and operation, highlights 1T-DRAM for standalone and embedded applications with impressive performance indicators: sense margin $\ge 6~\mu \text{A}/\mu \text{m}$ , retention time ≥16 ms (for embedded), and ≥64 ms (for standalone) at 85 °C, current ratio of ~104 along with a low write (~ 1 ns) and read (~ 2 ns) time. Guidelines in terms of scalability of total length and biases for implementing 1T-DRAM cell are presented. [ABSTRACT FROM AUTHOR]

Featured Application: The approach proposed in this paper can be applied to the fire safety field using total flooding Clean Extinguishing Agents. Accurate prediction of the hold time of a CEA can achieve reliable fire control and extinguishment, as well as prevent overdesign of the CEA system. When estimating the theoretical hold time of a Clean Extinguishing Agent (CEA), the hold time is predicted using a leakage exponent and leakage characteristics that are measured through an Enclosure Integrity Test (EIT). In particular, the leakage exponent n is conventionally applied as 0.5, but recently, a variable exponent has been applied through measurement (approximately 0.48 to 0.85). When variable n is applied, the hold time varies greatly depending on the size of n. Therefore, in this study, a modified theoretical model for the hold time of a CEA is proposed to improve the accuracy of the hold time depending on the leakage exponent n. The modified theoretical model applies a different analysis of the inflow and outflow volumetric flow, and the results enable a more accurate hold time prediction. The modified theoretical equation shows an improvement of up to 8.6% for outflow volumetric flow V ˙ o and a maximum improvement of approximately 10.7% for hold time t h . [ABSTRACT FROM AUTHOR]

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Sterile generic dosage development requires that specific critical quality attributes be considered and evaluated, regardless of the route of delivery or the type of registration application. The review briefed with an overview of Pharmaceutical Development study requirements. Each of the various stages of studies like Compatibility with the packaging materials, manufacturing vessels, processing aids, MOCs, Filters, Tubing's and Gaskets also with special studies to be conducted as part of Regulatory Submission, process considerations. Thus, the chapter offers the formulator an overview of the foundational principles associated with formulation development/Pre-formulation studies of sterile products. [ABSTRACT FROM AUTHOR]

During the operation of a compressed air energy storage (CAES) salt cavern, the surrounding rock experiences creep damage during the stages of constant internal pressure and undergoes fatigue damage due to the periodical injection-production. To describe the damage evolution of salt rock under creep-fatigue loading, a novel damage accumulation model based on the ductility exhaustion concept is proposed by applying a nonlinear summation method to represent the synergistic effect of creep and fatigue damage. Low-cycle fatigue (LCF) and creep-fatigue tests of rock salt were conducted under stress-control mode for various cycle stress amplitudes and hold times. Results show that the deformation of rock salt under creep-fatigue loading consists of initial, steady and accelerated phases. The proposed model matches well with the test data and can accurately describe the damage evolution as the applied stress amplitudes and dwell times change. The introduction of the hold times at the upper limit stress causes a strain increment and life reduction, which become more evident as the duration periods prolong and can be understood by the dislocation theory of crystals. [ABSTRACT FROM AUTHOR]

The application of gas-fire-suppression systems encounters a challenge that oxygen concentration tends to return to the original value in post-discharge time if open vents are present in a protected enclosure. Extending discharge becomes necessary to maintain oxygen concentration to prevent a fire resurgence in this enclosure. Until now the extended discharge rate must be evaluated individually by full-scale tests and no international standards specify the requirements in extended discharge. In this study, a formula was proposed to calculate the extended discharge rate as a function of opening size. A series of tests were conducted to investigate the oxygen concentration against the opening size in an apartment, followed by numerical simulations to recreate these tests. Then the discharge was extended in the simulations. Results show that the oxygen concentration was maintained between 10.5 % and 12.9 % in the apartment excepted the location next to the open door if the proposed discharge rate was adopted in the extended discharge time. Thus, this study proposal a universal method to quantify the extended discharge rate for a protected enclosure with openings. [ABSTRACT FROM AUTHOR]

The effect of the hold time of a tensile overload on crack propagation behaviours following the overload was investigated. In the study, the crack propagation behaviour after the overload was observed under constant amplitude load with stress ratio zero and negative, respectively. The result of the study shows that the fatigue life, the deceleration and acceleration of the crack propagation depends on the magnitude, the hold time of the overload and the shape of the crack tip as well as the stress ratio of the constant amplitude load following the overload. The deceleration occurs if the compressive residual stress develops in the zone affected by the overload in front of the crack tip. Whereas, if the tensile residual stress develops in that zone, the crack is accelerated, and the fatigue life is shortened. In addition, the shape and the displacement of the crack tip affect the residual stress condition in front of the crack tip, and the crack can be advanced by the hold time of the overload, thus, it also enhances the acceleration of the crack propagation following the overload.

Featured Application: The approach proposed in this paper can be applied in the field of fire safety in industrial facilities where water extinguishing agents are not available. In particular, it can be useful for the design and maintenance of gas fire extinguishing systems. Accurate analysis of the O2 diffusion in inert agents provides an accurate prediction time (retention time) to prevent recurrence of fire. Gaseous agents are widely used in fire extinguishing systems (FESs) when water extinguishing agents are unavailable. The extinguishing ability of the FES-gaseous agent is determined by the retention time (hold time) at which its concentration is maintained. In particular, the retention time of the inert agent is determined by the O2 inflow from the outside. However, current theoretical models for inert agents do not provide an accurate model for the diffusion of incoming O2. Specifically, because the theoretical equations do not include O2 diffusion or include too large a value, there is a large difference between the measured and theoretical retention times. Therefore, in this study, accurate O2 diffusion was verified through experimental and numerical analyses using three types of deactivators and reflected in the existing theoretical model. O2 diffusion was analyzed through the interface slope α and diffusion velocity v d . As a result, this proposed method can predict the retention time more accurately than existing theoretical models. [ABSTRACT FROM AUTHOR]

When estimating the theoretical hold time of a Clean Extinguishing Agent (CEA), the hold time is predicted using a leakage exponent and leakage characteristics that are measured through an Enclosure Integrity Test (EIT). In particular, the leakage exponent n is conventionally applied as 0.5, but recently, a variable exponent has been applied through measurement (approximately 0.48 to 0.85). When variable n is applied, the hold time varies greatly depending on the size of n. Therefore, in this study, a modified theoretical model for the hold time of a CEA is proposed to improve the accuracy of the hold time depending on the leakage exponent n. The modified theoretical model applies a different analysis of the inflow and outflow volumetric flow, and the results enable a more accurate hold time prediction. The modified theoretical equation shows an improvement of up to 8.6% for outflow volumetric flow V˙o and a maximum improvement of approximately 10.7% for hold time th.

Superconducting single-flux-quantum (SFQ) technology is a beyond-complementary metal–oxide–semiconductor (CMOS) technology, promising ultrahigh processing speed and low power consumption. A timing analysis tool for SFQ circuits should check circuit timing behavior, including working frequencies and hold time violations to determine the circuit performance. Unlike CMOS gates, generic SFQ gates are clocked gates, which produce their output pulses in response to a clock pulse and have a fan-out capability of one. An SFQ splitter, a special clockless gate that has a fan-out capability of two, is used to address the fan-out limitation. This gate is also utilized in the clock tree, which distributes clock pulses to various SFQ gates. The delay of a clock path in a clock tree is determined by the wire delays of connection nets and gate delays of splitters. However, the splitter delays in a clock path are significantly affected by process variations, resulting in a challenging skew problem. Furthermore, existing timing analysis tools of SFQ circuits are developed based on the timing definitions, rules, and constraints from CMOS technology with very few modifications. This article demonstrates the incompleteness of the existing SFQ technology timing definitions. Precisely, it presents a novel static timing analysis (STA) tool, qSTA, which checks the timing behavior of SFQ circuits based on revised definitions of the setup time and hold times. qSTA encompasses the common path pessimism removal technique, which removes the delays of the shared path segments between two clock paths to achieve a better approximation of real skew values. qSTA takes only 5.33 s to check the timing behavior of a 16-bit integer divider with 36 732 gates and 55 939 nets. [ABSTRACT FROM AUTHOR]

With the purpose of further researching the fire-resistant performance of reactive powder concrete (RPC), the significant influence of hold times on the compressive stress versus strain relationship for RPC with 2% steel fibers (in volume) at elevated temperatures was investigated in this paper. Pursuing this objective, the experiment was performed at temperatures of 20 °C, 200 °C, 400 °C, 600 °C, and 800 °C. In addition, axial compressive strength, elastic modulus, peak strain and energy absorption capacity (toughness) of RPC were evaluated at elevated temperatures. Furthermore, the compressive stress-strain constitutive equation was developed based on regression analysis. Results from the tests demonstrate that, with the increase of hold time, axial compressive strength of the RPC increases below 400 °C, approximately decreases ranging from 400 °C to 600 °C and increases again at 800 °C. At the temperature of 800 °C, the elastic modulus (initial elastic modulus and peak secant modulus) and peak strain present adverse variation trends as the hold time increases. Moreover, the formula related to the initial elastic modulus and peak secant modulus was proposed. [ABSTRACT FROM AUTHOR]

Influences of hold time and stress ratio on cyclic creep properties of Grade 91 steel were systemically investigated using a wide range of cyclic creep tests, which were performed with hold times (HTs) of 1 minute, 3 minutes, 5 minutes, 10 minutes, 20 minutes, and 30 minutes and stress ratios (R) of 0.5, 0.8, 0.85, 0.90, and 0.95 under tension loading cycles at 600°C. Under the influence of HT, the rupture time increased to HT = 5 minutes at R = 0.90 and R = 0.95, but there was no influence at R = 0.50, 0.80, and 0.85. The creep rate was constant regardless of an increase in the HT, except for the case of HT = 5 minutes at R = 0.90 and R = 0.95. Under the influence of stress ratio, the rupture time increased with an increase in the stress ratio, but the creep rate decreased. The cyclic creep led to a reduction in the rupture time and an acceleration in the creep rate compared with the case of monotonic creep. Cyclic creep was found to depend dominantly on the stress ratio rather than on the HT. Fracture surfaces displayed transgranular fractures resulting from microvoid coalescence, and the amount of microvoids increased with an increase in the stress ratio. Enhanced coarsening of the precipitates in the cyclic creep test specimens was found under all conditions.

Liquid phase segregation frequently occurs in the process of semi-solid die forging, which makes the parts appear “weak point” or “weak region”, and usually, the “weak point” or “weak area” is the reason of crack and service condition failure. In order to analyze the influencing factors for the liquid phase segregation of the semi-solid die forging, in this paper, the sample of semi-solid 7075 alloy is prepared by hand stirring method. The casting-forging forming of the sample is made by means of press machine and cup mould to research the influence of alloy temperature, head preheating temperature, hold time and other process parameters on the uniformity of the microstructure. The results show that the semi-solid casting-forging process is feasible within a set of mold. Under the conditions of head temperature of 400 ℃, hold time of 2 s and the forming pressure of 50 MPa, the liquid phase segregation degree of cup sample increases, the uniformity of the microstructure becomes worse with increasing of alloy temperature. The segregation degree is up to 14.02% when the alloy temperature is 628 ℃. The liquid phase segregation degree of cup sample decreases and uniformity of the microstructure becomes better along with increasing of head preheating temperature. Under the conditions of alloy temperature of 621 ℃, the forming pressure of 50 MPa, and head preheating temperature of 400 ℃, the liquid phase segregation degree of cup sample decreases, the uniformity of the microstructure becomes better along with increasing of the hold time. The segregation degree is up to 2.99% when the hold time is 4 s. The results could provide theoretical reference for the process formulation and experimental research of aluminum alloy semi-solid casting-forging forming.

Creep‐fatigue crack growth (C‐FCG) rates in a P91 steel at 625°C were correlated as the average time rate of crack growth during hold time, (da/dt)avg, with (Ct)avg. At 60‐second hold time, the rates were lower than for 600‐second hold time. At 600‐second hold time, the crack growth rates converged on to the creep crack growth rate (CCGR) trend. Thus, the CCGR trend represents the upper bound for time‐dependent crack growth rates in P91 materials. The analytical expressions based on considering just the elastic and secondary creep deformation rates overestimated the magnitudes of (Ct)avg by as much as a factor of 10 for the 600‐second hold time tests. After accounting for the effects of cyclic plasticity during unloading, and accounting for only partial reversal of creep strains accumulated during hold time, the estimates of (Ct)avg compared well with the measured values. CR represents the extent of crack tip creep strain reversal, and tpl is the time required for the crack tip creep zone during the hold time to become equivalent in size to the cyclic plastic zone in terms of stress carried by that region. Together, these parameters accurately account for the effects of crack tip cyclic plasticity on the magnitude of (Ct)avg. Both tpl and CR depend on material properties, and the latter also depends on the hold time. A parameter ϕ is introduced that is dependent only on material properties and from which CR can be estimated for a given hold time. tpl and ϕ can be reported as part of the test results from C‐FCG testing. [ABSTRACT FROM AUTHOR]

• Investigation of creep-fatigue behavior of X20CrMoV12-1 from 300 °C to 600 °C in dependence of atmosphere. • Validation of the K-concept for application of damage tolerance concepts in flexibly operated power plants with consideration of the microstructural peculiarities of ferritic-martensitic steels. • Investigation of steam oxidation impact on the transition from fatigue to creep-fatigue interaction. • Analysis of the impact of different evaluation concepts on results and subsequent interpretation. • Detailed microstructural investigation of the cracking mechanisms. In this study the impact of frequency or rather hold time and atmosphere on the transition from fatigue dominated crack growth to creep fatigue of the ferritic/martensitic steel X20CrMoV12-1 was investigated from 300 °C−600 °C. This temperature range is most important for power plants operated in a flexible manner. Due to the increased share of renewable sources of energy, modern thermal power plants must be operated in a flexible manner to compensate fluctuating power supply from renewables. More damaging loading scenarios, including frequent start-up and shut-down cycles as well as load fluctuations, occur much more frequently than in the past as a consequence. Fatigue damage becomes more and more important, while creep damage reduces due to shorter full power operation durations. Furthermore, loss of passivation by fatigue induced cracking and delamination of protective oxide layers may constitute strong interdependencies of increased cyclic operation and steam oxidation resistance. This results in the necessity for a innovative surveillance concepts including operation mode dependent inspection intervals of thermal power plants. Application of a damage tolerance concept, based on fracture mechanics, can help to improve remaining life assessment of existing and fatigue tolerant design of future power plants. In order to develop codes for flexibly operated components, based on damage tolerance analysis by linear elastic fracture mechanics, its validity range and especially its limitation have to be evaluated first. The study has shown that the transition from pure fatigue to creep fatigue interaction begins at 500 °C and 3.33 × 10−3 Hz (300 s hold time). Furthermore this transition was found to be independent from steam atmosphere. The corresponding fracture mechanisms were investigated in detail. [ABSTRACT FROM AUTHOR]

Highlights • Detailed crack propagation behavior of X20CrMoV12-1 from 300 °C to 600 °C in steam. • Impact of the steam atmosphere depending on frequency and temperature on crack growth behavior. • Separation of steam impact on the crack propagation behavior. • Assessment of residual life and damage mechanisms of components in flexibly operated power plants. • Analysis of crack closure mechanisms depending on temperature, frequency and atmosphere. Abstract This paper deals with the influence of steam atmosphere on the crack propagation behavior in the ferritic/martensitic steel X20CrMoV12-1 depending on frequency (or hold time) and temperature with a focus on the temperature range from 300 °C to 600 °C, which is most important for flexibly operated power plants. Modern conventional power plants must be able to compensate fluctuations in residual load, caused by renewable energy sources. This results in higher numbers of start-up and shut-down cycles and therefore in more damaging loading scenarios than in the past. Due to the ever shorter operating time at constant high temperature, the importance of creep damage decreases, while fatigue damage gains in importance. Furthermore probable interactions of fatigue damage and steam atmosphere have to be considered. For this reason the influence of steam on the crack propagation behavior in X20 was investigated in detail. Steam oxidation strongly depends on temperature and time, i.e. on fatigue testing frequency and temperature. The effect of steam on crack propagation behavior was found to be not generally detrimental (for R = 0.1). Experiments with 3.33 × 10−3 Hz (300 s hold time) in the temperature range from 400 °C to 550 °C yielded significantly higher ΔK values to start crack propagation in comparison to experiments performed in air. In the temperature range from 300 °C to 550 °C the crack growth rate under steam atmosphere in the worst case corresponds to that measured in air, while in the best case it was found to be lower. Generally crack propagation in steam atmosphere was found to be accelerated at increased testing frequency (5 Hz, 20 Hz) starting from 500 °C up to higher temperature. [ABSTRACT FROM AUTHOR]

Water safety and management programs (WSMP) utilize field measurements to evaluate control limits and monitor water quality parameters including Legionella presence. This monitoring is important to verify that the plan is being implemented properly. However, once it has been determined when and how to sample for Legionella, it is important to choose appropriate collection and processing methods. We sought to compare processing immediate and flushed samples, filtration of different volumes collected, and sample hold times. Hot water samples were collected immediately and after a 2-min flush. These samples were plated directly and after filtration of either 100 mL, 200 mL, or 1 L. Additionally, unflushed samples were collected and processed immediately and after 1, 24, and 48 h of hold time. We found that flushed samples had significant reductions in Legionella counts compared to immediate samples. Processing 100 mL of that immediate sample both directly and after filter concentration yielded the highest concentration and percent sample positivity, respectively. We also show that there was no difference in culture values from time 0 compared to hold times of 1 h and 24 h. At 48 h, there were slightly fewer Legionella recovered than at time 0. However, Legionella counts were so variable based on sampling location and date that this hold time effect was minimal. The interpretation of Legionella culture results depends on the sample collection and processing methods used, as these can have a huge impact on the success of sampling and the validation of control measures.

In the present study the crack propagation behavior under constant amplitude loads emerging from the notch root after being overloaded and held in a certain period of time was investigated. When the stress ratio of constant amplitude load is zero, the longer period of hold time of the overload increases the number of delay cycles and decelerates the crack propagation emerging from the notch root. However, the number of delay cycles is reduced by the increasing of the hold time period, and the acceleration of the crack propagation was observed immediately after emerging from the notch root when the stress ratio is -1.5. The magnitude and the period of the hold time of the overload as well as the stress ratio of the constant amplitude load condition following the overload are responsible for the residual stress state in front of the notch root affecting the crack propagation behavior.

Gaseous agents are widely used in fire extinguishing systems (FESs) when water extinguishing agents are unavailable. The extinguishing ability of the FES-gaseous agent is determined by the retention time (hold time) at which its concentration is maintained. In particular, the retention time of the inert agent is determined by the O2 inflow from the outside. However, current theoretical models for inert agents do not provide an accurate model for the diffusion of incoming O2. Specifically, because the theoretical equations do not include O2 diffusion or include too large a value, there is a large difference between the measured and theoretical retention times. Therefore, in this study, accurate O2 diffusion was verified through experimental and numerical analyses using three types of deactivators and reflected in the existing theoretical model. O2 diffusion was analyzed through the interface slope α and diffusion velocity vd. As a result, this proposed method can predict the retention time more accurately than existing theoretical models.