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Failures in hydraulic systems in offshore wind turbines represent an enormous challenge for manufacturers and operators, as the pitch system statistically is one of the subsystems contributing the most to the downtime of the turbines, which is the case for both electrical and hydraulic pitch systems. However, the complex failure mechanisms of the various different hydraulic components mean that, typically, the critical components of hydraulic systems must be tested to better understand the failure mechanisms. Nonetheless, conventional testing procedures are lengthy and costly. Accelerated testing plays a critical role as it can mimic hydraulic system failure mechanisms in a shorter period. However, the lack of standardized test methods and detailed knowledge about the failure-accelerating effects complicates the process. Therefore, this paper offers a comprehensive examination of approaches applicable to conducting accelerated tests on hydraulic systems. It identifies and discusses five primary component types or sub-components related to the acceleration of testing in hydraulic systems: pumps, cylinders, seals, valves, and hoses. Each section references studies that delve into accelerated testing methodologies for these individual components. Furthermore, within each component, a concise overview of the current techniques is provided, followed by a discussion and summary based on the state of the art. [ABSTRACT FROM AUTHOR]

Failures in hydraulic systems in offshore wind turbines represent an enormous challenge for manufacturers and operators, as the pitch system statistically is one of the subsystems contributing the most to the downtime of the turbines, which is the case for both electrical and hydraulic pitch systems. However, the complex failure mechanisms of the various different hydraulic components mean that, typically, the critical components of hydraulic systems must be tested to better understand the failure mechanisms. Nonetheless, conventional testing procedures are lengthy and costly. Accelerated testing plays a critical role as it can mimic hydraulic system failure mechanisms in a shorter period. However, the lack of standardized test methods and detailed knowledge about the failure-accelerating effects complicates the process. Therefore, this paper offers a comprehensive examination of approaches applicable to conducting accelerated tests on hydraulic systems. It identifies and discusses five primary component types or sub-components related to the acceleration of testing in hydraulic systems: pumps, cylinders, seals, valves, and hoses. Each section references studies that delve into accelerated testing methodologies for these individual components. Furthermore, within each component, a concise overview of the current techniques is provided, followed by a discussion and summary based on the state of the art.

This article presents accelerated failure time models with and without frailty for modeling multiple systems subject to minimal repair. The study considers the conventional accelerated failure time model, the accelerated failure time model with Gamma frailty, and proposes the accelerated failure time model with weighted Lindley frailty, which has attractive properties such as a closed‐form Laplace transform. The proposed model extends the accelerated failure time model with the intensity function of a power law process. It retains the direct physical interpretation of the original accelerated failure time model, in which the role of covariates is to accelerate or decelerate the time to each repair. This framework includes parametric approaches to model fitting, which we consider for estimating the vector of regression parameters under this model and the parameter in the baseline intensity functions. The methodology is illustrated with a simulation study and a toy example to demonstrate the applicability of these models in the industrial context. [ABSTRACT FROM AUTHOR]

This paper presents the results of an in-depth investigation of 3D-printed plastic gears made of ABS, PLA, and annealed PLA. Wear tests performed on a specialized rig underscore the superior wear resistance of ABS gears, while the annealing process shows a modest improvement in PLA gear durability. The novelty of this study is a comprehensive evaluation of the wear behavior of different 3D printed materials under different loading conditions. This study introduces an innovative accelerated testing method, emphasizing efficiency in product development through reduced testing durations and adaptability to various scenarios. [ABSTRACT FROM AUTHOR]

In order to investigate the quality changes during the storage period and predict the shelf life of Xinjiang pepper chicken legs, this study focused on pH value, color, thiobarbituric acid reactive substances (TBARS), total volatile basic nitrogen (TVB-N), total viable count, coliform bacteria, and sensory attributes as evaluation criteria. Accelerated degradation tests were conducted to examine the quality changes of the chicken legs at different storage temperatures (35 ℃ and 45 ℃). The shelf life endpoint was based on a sensory score of 70 points or a total bacterial count close to national standards and to predict the shelf life at room temperature (25 ℃). The results showed that with the continuous extension of storage time, the pH value of pepper chicken legs at different storage temperatures first decreased and then increased, and the overall L* value showed a downward trend. The a* value, b* value, TBARS value, TVB-N content, and total bacterial count all showed an upward trend, while the sensory score continued to decline. During the storage period, the change rate at 45 ℃ was higher than 35 ℃. At 35 ℃ storage temperature, the theoretical shelf life was 24 days, and at 45 ℃ storage temperature, the theoretical shelf life was 9 days, and there was an unacceptable loss of sample quality at the end of the shelf life. According to the Q10 model, Q10=2.6 was calculated, and the theoretical shelf life was predicted to be 62 days under room temperature (25 ℃) conditions.

This study compared module power loss for 36 modules that endured various accelerated aging test sequences before installation outdoors on a 10-kWp array in Birmingham, AL, USA for 1.72 to 2.72 years. Twelve modules endured standard IEC 61215 aging tests and 24 endured Qualification Plus (Qual Plus). Modules in each group were further split into two test sequences with different exposures. Electrical parameter variations were analyzed as a function of aging test and field exposure history. Fill factor loss was determined to be the cause of observed decreases in power output during accelerated aging tests, while decreases in both open circuit voltage and fill factor dominated the power loss during subsequent on-sun testing. Quantified cell crack features were extracted via computer vision tools from electroluminescence images and correlated with power loss. Results illustrate that standard aging tests led to negligible cracks, while Qual Plus test sequences yielded more severe cracks. While correlating results from qualification tests with in-field performance degradation parameters remains a challenge, this study provides new insights on specific environmental stressors and crack features that may play a role in power loss. Insights on accelerated aging protocols are discussed.

The library of redox-active organics that are potential candidates for electrochemical energy storage in flow batteries is exceedingly vast, necessitating high-throughput characterization of molecular lifetimes. Demonstrated extremely stable chemistries require accurate yet rapid cell cycling tests, a demand often frustrated by time-denominated capacity fade mechanisms. We have developed a high-throughput setup for elevated temperature cycling of redox flow batteries, providing a new dimension in characterization parameter space to explore. We utilize it to evaluate capacity fade rates of aqueous redox-active organic molecules, as functions of temperature. We demonstrate Arrhenius-like behavior in the temporal capacity fade rates of multiple flow battery electrolytes, permitting extrapolation to lower operating temperatures. Collectively, these results highlight the importance of accelerated decomposition protocols to expedite the screening process of candidate molecules for long lifetime flow batteries. [ABSTRACT FROM AUTHOR]

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This research investigates the durability of large-format 3D-printed thermoplastic composite material systems under environmental exposure conditions of moisture and freeze–thaw. Durability was evaluated for two bio-based composite material systems, namely wood-fiber-reinforced semi-crystalline polylactic acid (WF/PLA) and wood-fiber-reinforced amorphous polylactic acid (WF/aPLA), and one conventionally used synthetic material system, namely short-carbon-fiber-reinforced acrylonitrile butadiene styrene (CF/ABS). The moisture absorption, coefficient of moisture expansion, and reduction of relevant mechanical properties—flexural strength and flexural modulus—after accelerated exposure were experimentally characterized. The results showed that the large-format 3D-printed parts made from bio-based thermoplastic polymer composites, compared to conventional polymer composites, were more susceptible to moisture and freeze–thaw exposure, with higher moisture absorption and greater reductions in mechanical properties. [ABSTRACT FROM AUTHOR]

The accelerated testing methodology (ATM) for the statistical life prediction of carbon fiber reinforced plastics (CFRP) under creep and fatigue loads based on the viscoelasticity of matrix resin has been proposed by authors. This method has been successfully applied to the life predictions of unidirectional CFRP with thermosetting epoxy resin as the matrix under tensile and flexural loads. In this paper, this method was applied to the fatigue life prediction of unidirectional CFRP (CF/PP laminates) with thermoplastic polypropylene (PP) as the matrix under tensile and flexural loads, and the effect of matrix viscoelasticity and load cycles on the fatigue behavior of CF/PP laminates were discussed under tensile and flexural loads. First, the viscoelasticity of matrix PP was measured. Second, the static and fatigue strengths of CF/PP laminates were statistically measured at various temperatures and frequencies under tensile and flexural loads. Third, all of material parameters in the fatigue strength formulation in ATM were determined using measured data, and the statistical long-term fatigue strengths of CF/PP laminates were predicted under tensile and flexural loads. As results, comparison with tension and bending test results clarified that the long-term tensile fatigue strength of CF/PP laminates decreases at an accelerated rate as the number of cycles increases, and that the flexural fatigue strength is affected by temperature and frequency rather than by the number of cycles to failure. [ABSTRACT FROM AUTHOR]

Traditional optimization algorithms often have the problems of slow convergence and poor accuracy when facing complex situations. Therefore, a parameter optimization method based on multi-modal butterfly optimization algorithm is proposed for parameter adjustment of support vector machine and infinite impulse response digital filter. By introducing storage mechanism strategy, the accelerated detection mechanism and purification program strategy, the global searching ability and solving efficiency of the algorithm are improved. The results showed that the improved multi-modal butterfly optimization algorithm reached its optimal solution in the fifth iteration, and the objective function value reached its minimum without changing. The precision and recall of this algorithm were above 0.9, and the variance was close to 0. This algorithm successfully solved 942 epochs with a success rate of 93.314%. The total solution time was 14.338 seconds, and the average solution time was 0.014 seconds. The improved multi-modal butterfly optimization algorithm showed excellent performance in optimizing parameters, effectively improving parameter optimization performance, and showed high efficiency, stability, and reliability. This study is helpful to promote optimization algorithms and provide more efficient and reliable methods for solving practical problems.

The corrosion of steel in post-tensioned tendons has been associated with deficient grout materials containing high free sulfate ion concentrations. In a Florida bridge in 2011, tendon corrosion failures occurred for a prepackaged thixotropic grout that had developed material segregation. However, the available grout and corrosion testing prescribed in material specifications, such as grout bleed water testing, was not able to identify the propensity or modality for the grout deficiencies and the associated steel corrosion that was observed in the field. It was of interest to identify corrosion testing methods that could prescribe grout resistance to segregation-related deficiencies that can form by aberrations in construction. The objectives of the work presented here included (1) characterizing the development of physical and chemical grout deficiencies due to excess mix water and water volume displacement, (2) developing small scale test methodologies that identify deficient grout, and (3) developing test methodologies to identify steel corrosion in deficient grout. The inverted-tee test (INT) and a modified incline-tube (MIT) test were assessed and both were shown to be useful to identify the robustness of grout materials to adverse mixing conditions (such as overwatering and pre-hydration) by parameters such as sulfate content, moisture content, electrical resistance, and steel corrosion behavior. It was shown that the different grout products have widely different propensities for segregation and accumulation of sulfate ions but adverse grout mixing practices promoted the development of grout deficiencies, including the accumulation of sulfate ions. Corrosion potentials of steel < −300 mVCSE developed in the deficient grout with higher sulfate concentrations. Likewise, the corrosion current density showed generally high values of >0.1 μA/cm2 in the deficient grouts. The values produced from the test program here were consistent with historical data from earlier research that indicated corrosion conditions of steel in deficient grout with >0.7 mg/g sulfate, further verifying the adverse effects of elevated sulfate ion concentrations in the segregated grout.

The corrosion of steel in post-tensioned tendons has been associated with deficient grout materials containing high free sulfate ion concentrations. In a Florida bridge in 2011, tendon corrosion failures occurred for a prepackaged thixotropic grout that had developed material segregation. However, the available grout and corrosion testing prescribed in material specifications, such as grout bleed water testing, was not able to identify the propensity or modality for the grout deficiencies and the associated steel corrosion that was observed in the field. It was of interest to identify corrosion testing methods that could prescribe grout resistance to segregation-related deficiencies that can form by aberrations in construction. The objectives of the work presented here included (1) characterizing the development of physical and chemical grout deficiencies due to excess mix water and water volume displacement, (2) developing small scale test methodologies that identify deficient grout, and (3) developing test methodologies to identify steel corrosion in deficient grout. The inverted-tee test (INT) and a modified incline-tube (MIT) test were assessed and both were shown to be useful to identify the robustness of grout materials to adverse mixing conditions (such as overwatering and pre-hydration) by parameters such as sulfate content, moisture content, electrical resistance, and steel corrosion behavior. It was shown that the different grout products have widely different propensities for segregation and accumulation of sulfate ions but adverse grout mixing practices promoted the development of grout deficiencies, including the accumulation of sulfate ions. Corrosion potentials of steel < −300 mVCSE developed in the deficient grout with higher sulfate concentrations. Likewise, the corrosion current density showed generally high values of >0.1 μA/cm2 in the deficient grouts. The values produced from the test program here were consistent with historical data from earlier research that indicated corrosion conditions of steel in deficient grout with >0.7 mg/g sulfate, further verifying the adverse effects of elevated sulfate ion concentrations in the segregated grout. [ABSTRACT FROM AUTHOR]

Alkali‐silica reaction continues to be a challenging durability issue for portland cement‐based concrete. While myriad of preventive options is known to reduce the risk of ASR, changes in availability and consistency of materials make either prescriptive or performance‐based approaches difficult to develop and then quickly adapt. In general, the research community has supported industry with practical solutions based on empirically derived relationships, mostly from accelerated test methods and to a lesser extent realistic exposure/field structures. It is time to increase the level of science behind our approach. The research team represented in this talk is investigating a new methodology that combines the alkali availability needed to initiate ASR (aggregate specific) with the available alkali from the total cementitious blend. The relationship between reactivity of a supplementary cementitious material and the ASR expansion is also explored. This keynote lecture will: 1) Explore performance‐based testing versus prescriptive approaches and why a hybrid approach should be considered ASR prevention; 2) Evaluate the relationship between accelerated laboratory tests, outdoor exposure blocks and field structures; 3) Examine the use of "non‐traditional" supplementary cementitious materials and/or chemical admixtures to prevent alkali‐silica reaction; 4) Propose future research needs and; 5) Make recommendations for how best to prevent alkali‐silica reactivity following the proposed approach. [ABSTRACT FROM AUTHOR]

In the on-board environment of new energy passenger vehicles, IGBT modules are prone to the risk of vibration fatigue failure due to the influence of road roughness and engine rotation. In order to ensure the reliability of IGBT modules in service, it is of great significance to evaluate their vibration fatigue lifetime. The internal structure of IGBT module is complicated, so it is impossible to directly evaluate the vibration fatigue lifetime based on a physical model alone. To this end, an evaluation method is proposed in this paper to determine the vibration fatigue lifetime of IGBT modules. Firstly, the failure lifetime data of IGBT modules under high vibration magnitudes are obtained by an acceleration test. Secondly, the reliability lifetime distribution under the actual working conditions is obtained from the lifetime distribution statistical model based on the Weibull distribution, and then the reliability lifetime data in the practical application is obtained. The experimental results show that this method can effectively predict the failure rate of IGBT modules used in batches, which provides guarantee for reasonable management and control of application risks.

As power densification demands are placing electronic packages under greater reliability risk, the consequences of complementary or interacting stresses in producing failure are becoming increasingly significant. As such, it is important that reliability methods and package designs consider how multiplestress interactions may impact product life. Here, the coordination between a novel accelerated testing method and electronic design automation efforts has demonstrated a successful optimization approach for a wire-bonded 2D module layout combining failure mechanisms of electromigration and mechanical stressing. Utilizing custom, physics-of-failure approaches in accelerated testing, interactions can be observed in failure acceleration, which then can be incorporated into design for reliability (DfR) optimization tools. The PowerSynth 2 platform has been utilized as a DfR tool to perform a rapid reliability evaluation incorporating multistress scenarios. This work demonstrates the value added to reliability evaluation techniques when accounting for interacting failure mechanisms and suggests that next-generation power devices consider these effects in lifetime estimation. [ABSTRACT FROM AUTHOR]

Due to the complex aviation operation environment, the test method that only considers the separate action of multi-stress ignores the interaction between stresses, and it is difficult to accurately obtain the life index of domestic avionics components, which makes the life deviation of the theoretical results large. Thus, a multi-stress accelerated life evaluation method considering generalized coupling is proposed. Firstly, a multi-stress generalized coupling acceleration model considering the fuzzy mapping relationship of failure mechanism under actual engineering conditions is established, and fuzzy correlation is introduced to select the best coupling term. Then, the multi-stress generalized coupling maximum likelihood estimation method of different experimental types is constructed, and the adaptive sine cosine algorithm is used to solve the problem of difficult multi-parameter solution. Finally, a three-stress acceleration test is carried out on a low-noise amplification module of an airborne electronic device to achieve life evaluation. The results show that considering the generalized coupling is closer to the actual working environment, compared with the traditional numerical calculation method, the error is controlled within 5%, which proves the fast convergence and accuracy of the proposed method. [ABSTRACT FROM AUTHOR]

Controller Area Network (CAN-bus) is a default solution for digital control in machinery. The CAN-bus structure uses connector components to extend cabling and join subsystems. The connectors are IP-classified, so they tolerate humidity and particle ingress. Ingress protection also provides durability against other stress factors. Usually, connectors are exposed to multiple stress factors, but the stress levels are durable. In mining applications, however, stress levels can be high, and other factors become significant, so IP classification does not necessarily indicate sufficient durability. Tailored testing can be used to identify suitable components for a specific purpose. In this study, the actual stress factors of an underground mine drill were used in tailored tests. The results showed significant differences in reliability between connector models with the same IP code. The ranking of the components varied depending on the stress factors used. This highlights the importance of using actual operating conditions when evaluating reliability. [ABSTRACT FROM AUTHOR]

Arrhenius Accelerated Growth Test (AAGT) models is the next generation accelerated testing models used for design validation and reliability assurance of electronics systems. These models are used in design and manufacturing phases towards reliability enhancement of the system respectively. AAGT Models uses Highly Accelerated Stresses for screening of the components towards uncovering product defects as compared to traditional qualification test methods, these models are used to quickly identify design flaws, latent defects, component selection problems, and manufacturing flaws. The procedure includes thermal dwells and rapid temperature changes while subjecting the test unit to increasing degrees of stress. Dynamic stresses (Pseudo-Random Vibration covering all 6DOF systems) and a combination of thermal and dynamic PSD stresses are used towards quickly precipitating inherent/hidden defects. These Accelerated models are used in the research to qualify active array radar modules like Transmit Receive Modules (TRMs) which will be in used in large numbers for modern radar systems, as compared to a traditional approach that will be difficult and time-consuming to filter these modules individually. To increase the quality and dependability of electronic devices, these accelerated life tests models have been extensively adopted. However, extremely accelerated life tests may only be used as a qualitative approach to assess a product’s dependability; they cannot be used to quantify a product’s reliability, such as MTBF/MTTF. Consequently, in order to efficiently assess the level of product reliability while improving product reliability in a timely manner. HALT/HASS uses Arrhenius Accelerated Growth Model that is an effective technique used for screening of the module with in short period. This paper discuss in detail with a case study on active array modules deliberating about the test methodology, challenges faced during Using Arrhenius accelerated test models, rapid testing and assessment of these Four channel TRMs used for airborne Fire Control Radar for combat operations. [ABSTRACT FROM AUTHOR]

This research investigates the durability of large-format 3D-printed thermoplastic composite material systems under environmental exposure conditions of moisture and freeze–thaw. Durability was evaluated for two bio-based composite material systems, namely wood-fiber-reinforced semi-crystalline polylactic acid (WF/PLA) and wood-fiber-reinforced amorphous polylactic acid (WF/aPLA), and one conventionally used synthetic material system, namely short-carbon-fiber-reinforced acrylonitrile butadiene styrene (CF/ABS). The moisture absorption, coefficient of moisture expansion, and reduction of relevant mechanical properties—flexural strength and flexural modulus—after accelerated exposure were experimentally characterized. The results showed that the large-format 3D-printed parts made from bio-based thermoplastic polymer composites, compared to conventional polymer composites, were more susceptible to moisture and freeze–thaw exposure, with higher moisture absorption and greater reductions in mechanical properties.

Polymeric materials have multiple potential applications in nuclear power reactors including advanced and small modulus reactors, in addition to their extensive usage in safety electronic cables in the existing light water reactors. Through the qualification programs, knowledge accumulates about the polymer degradation kinetics under gamma-irradiation environment to facilitate the development of service-life predictive models. This paper aims to promote mechanistic-based predictability as a new approach to the qualification of polymeric components. Reviewed in this article are the current qualification standards and procedures, the current understandings of the degradation mechanisms, and kinetic models applicable to accelerated experiments for qualification.

Herein, electroluminescence (EL) and thermal imaging are used to examine p–i–n metal halide perovskite (MHP) photovoltaic (PV) mini‐modules (MA0.6FA0.4PbI3, 20 cells, 78 cm2) before and after indoor‐accelerated stress testing or outdoor deployment. Distinct spatial patterns in the EL images emerge, which depend on the external stress conditions experienced by the mini‐module. Imaging results highlight a distribution of dark speckle features that dominate after UV stress, attributed to widespread interfacial contact degradation. Lateral intensity gradients across cells dominate after thermal cycling (TC) stress, attributed to current crowding near scribe defects. While current–voltage analysis alone does not give full insight on the degradation process, this study shows that distinct degradation modes can be further defined by multimodal electro‐optical imaging (i.e., EL combined with photoluminescence and dark lock‐in thermography). Neither UV exposure nor TC‐accelerated stress testing alone replicates the same degradation signatures observed after outdoor deployment, suggesting that multiple degradation modes occur under concurrent stressors outdoors. Spatial characterization of degradation modes in MHP PV mini‐modules before and after accelerated stress testing lays the groundwork for developing targeted accelerated stress testing procedures through comparison with outdoor aging. [ABSTRACT FROM AUTHOR]

Combined‐accelerated stress testing (C‐AST) is developed to establish the durability of photovoltaic (PV) products, including for degradation modes that are not a priori known or examined in standardized tests. C‐AST aims to comprehensively represent the sample, stress factors, and their combinations using levels at the statistical tails of the natural environment. Acceleration factors for relevant climate sequences within the C‐AST cycle with respect to the Florida USA climate are estimated for selected degradation mechanisms. It is found that for degradation of the outer backsheet polymer layer, the acceleration factor of the tropical climate sequence (the longest of the climate sequences) is f (T, G) = 17.3 with ultraviolet photodegradation; for polyethylene terephthalate hydrolysis (backsheets), f (T, RH) = 426; for electrochemical corrosion (PV cell), f (I) = 14.1; and for PbSn solder fatigue f (ΔT, r (T)) = 17.3. Here, T is the module temperature, G is the broadband spectrum irradiance on the plane of array of the module, RH is the relative humidity on the module surface, I is the leakage current through the module packaging, and r(T), the number of temperature reversals. The methods discussed herein are generally applicable for evaluating acceleration factors in other accelerated test methods. [ABSTRACT FROM AUTHOR]

• Degradation analysis of PV module after 20 years of exposure in the field. • A methodology designed for the accelerated UV stress test for different climatic conditions. • A procedure proposed to estimate the UV radiation for different climatic conditions. • Accelerated UV stress testing condition design for Indian climatic condition. One of the significant environmental stress factors for degradation in the PV module is UV irradiation exposure in the field during its operational lifespan. In this work, degradation analysis of 20-years field-operated PV modules have been performed. The defects that occurred in those modules are due to the combined effect of environmental conditions like temperature, humidity, soiling, etc., along with UV irradiation. Based on the literature resources, efforts have been made to analyze the role of UV irradiation on the degradations that happened during 20 years of field operation of the PV modules. Average P max , I sc and V oc degradation are found to be 1.49 %/ year, 0.59 %/year and 0.29 %/year after 20 years of exposure, respectively. The effect of UV irradiation and temperature in indoor conditions has been analyzed for the 20 years of field-exposed PV modules. The effect of browning in the module is also studied in this research work at the cell level. Since the UV irradiation doses mentioned in IEC 61215 are not sufficient as compared to the amount of UV irradiation faced by the PV modules throughout their lifetime, therefore, a procedure is proposed to estimate the UV irradiation doses for different climatic conditions. The UV radiation data for India's climatic zones have been estimated and analyzed, to design accelerated UV stress test conditions using the procedure reported in this paper. The accelerated testing time equivalent for five years of UV irradiations on PV modules in the field is proposed to be around 40 days. [ABSTRACT FROM AUTHOR]

A one-day Nordic Concrete Research workshop on “Accelerated freeze-thaw testing of concrete” attracted approx. 30 participants. The workshop included presentations on various aspects, such as observed frost damage in the field and the importance of the temperature curve during testing as well as other interactions with the surroundings of the concrete. The workshop also included examples of recent research, which can improve our knowledge about the frost damage mechanism and therefore provide input to improving the standardised test methods. The present paper is a summary of the nine presentations and the discussion arising from the presentations.

When evaluating the individual reliability of semiconductor devices by gradual failures for a given operating time, the value of the electrical parameter of a particular instance for this operating time is predicted using the simulation method. To obtain a prediction of an electrical parameter, it is necessary to have a simulation model in the form of a function of the relationship between a given operating time and the level of simulation impact. The simulation model is obtained with the help of preliminary studies (training experiment) of a training sample of semiconductor devices of the type of interest with the volume of approximately 50 ... 100 copies. The application of the model is reduced to the calculation of the level of simulation impact corresponding to a given operating time. The result of measuring the electrical parameter at the calculated level of the imitation impact in a new specimen of the same type that did not take part in the training experiment should be considered as a prediction of this parameter for a given operating time. An integral part of the preliminary research to obtain a simulation model is the testing of semiconductor devices of the training set for a long operating time, which can be tens of thousands of hours, which necessitates planning and conducting accelerated tests. The article substantiates the conditions for conducting accelerated forced tests in relation to high-power bipolar transistors of the KT872A type. The increased temperature and the reverse voltage applied to the collector junction of the transistors are chosen as factors accelerating the tests. The test acceleration coefficient is calculated relative to the operating mode of the transistors. Based on the results of the accelerated tests for the electrical parameter (collector-emitter saturation voltage), a mathematical model was obtained in the form of a dependence of its average value on the operating time. The presence of this model is necessary to determine the function of recalculating the given operating time of transistors to the value of the simulation impact.

In this study, rapid screening of creep resistance for additively manufactured (AM) materials is enabled using an accelerated creep test (ACT) called the dynamic negative stepped test (DNST). Additively manufactured components are on the rise in aerospace systems, particularly turbine engine parts. It can be challenging to identify the AM process parameters that correspond to high-temperature strength and creep resistance. Tests are needed that rapidly screen and qualify creep resistance. In DNST, the temperature is held constant, and the specimen is taken through a series of load holds from high to low. The DNST contains two distinct characteristics: (1) the hold duration for each step is "dynamically" controlled to ensure the minimum-creep-strain-rate is achieved at every step, and (2) the "descending" profile maximizes damage accumulation while remaining on the edge of instability. The DNST assesses a material's ability to resist creep damage accumulated across multiple deformation mechanisms. In this study, electron beam melted Ti–6Al–4V, built at six (6) directions: 0°, 30°, 45°, 60°, 90°, and V, is tested using a four-step DNST at 650 °C. Analysis of the minimum-creep-strain-rate (at each step), creep ductility, and rupture were performed. A strain energy density (SED) benchmark metric was established to rapidly screen and classify creep resistance using an "Ashby-like" plot that balanced energy dissipated and energy dissipation rate. The creep resistance was found to be ranked from V, 60, 45, 30, 90, and 0 in descending order. Microstructural and crystallographic characterization revealed grain refinement progressing from the strain-free to the high-strain regions, indicative of dynamic recrystallization (DRX). Further observations revealed that the material's energy capacity increased with the alignment of the grains' long axis and tensile direction. [ABSTRACT FROM AUTHOR]

Light and elevated temperature induced degradation (LeTID) can induce high power losses in photovoltaic modules built from various types of silicon wafers. After the industry's rapid transition from Boron- to Gallium-doping, it is still unclear how the new dopant atom affects the degradation process and why it entails an apparently higher resistance to LeTID. We treat identically processed Gallium-doped Czochralski silicon wafers at 16 different conditions by screening temperature and minority charge carrier density (in the following "injection"). The illumination source is regulated to keep the injection constant at each condition. This method allows for an improved quantitative analysis of the LeTID kinetics based on effective lifetime measurements. Our results show that Gallium-doping shifts the equilibrium between the formation of LeTID defects and their temporary recovery (TR) to the latter, leading to a reduced degradation extent at temperatures up to 80 °C. The efficacy of this TR-induced LeTID suppression depends delicately on both temperature and injection which explains why Gallium-doped silicon appears to be LeTID-immune at high illumination intensities. By accounting for the influence of TR, we extract activation energies and injection exponents that relate to the dominant defect transitions separately, revealing a large discrepancy to effective values reported in literature. The increased accuracy of our kinetic parameters enhances the reliability of existing efficiency models. Finally, we find that a degradation as expected under field conditions can be probed at a 100-fold accelerated rate in the lab. By shining light on LeTID kinetics in Gallium-doped silicon, we explain the dopant atoms' influence on the degradation behavior, establish a basis for precise yield modelling and formulate guidelines for accelerated test protocols. [Display omitted] • Gallium doping promotes temporary recovery induced LeTID suppression. • Probing LeTID at constant minority charge carrier density. • Improved determination of kinetic parameters for yield modelling. • 100-fold accelerated LeTID testing method proposed. [ABSTRACT FROM AUTHOR]

Effective intelligent driving test and evaluation methods can improve the development and deployment process of autonomous vehicles (AVs). However, due to the extreme complexity and high dimensionality of driving behavior, how to objectively and efficiently evaluate the multi-dimensional performance of AVs in simulation and real-world environments is a long-standing problem. This paper proposes an objective multi-dimensional comprehensive evaluation (OMDCE) method that divides the intelligent driving test into four modules: test scenarios, scenario complexity model, simulation test platform, and automated evaluation system. The scenario complexity model is proposed to bridge the gap between the test scenarios and the automated evaluation system, thus enabling adaptive scaling of the evaluation scale for test scenarios with different difficulty levels. Besides, based on the existing four evaluation metrics for ego performance, altruism performance evaluation is first proposed to comprehensively portray AVs' intelligence degree. The OMDCE method was evaluated by testing two different intelligent driving algorithms and conducting real vehicle testing. The experimental results demonstrated that the OMDCE method can effectively evaluate AVs in various scenarios and quantitatively measure their multi-dimensional performance. The proposed method reduces the subjectivity of manual evaluation and speeds up the evaluation. Moreover, it improves the universality and scalability of the evaluation metrics system. • Scenario complexity model is built as a scaling metric to reduce scoring variance. • Altruism performance evaluation is first proposed to portray AVs' intelligence. • MEREC and MARCOS combining complexity model are proposed to quantify performance. • Simulation and field testing are conducted to validate the proposed method. • The method enables a fully automated evaluation of the performance of AVs. [ABSTRACT FROM AUTHOR]

Epoxies and epoxy-based fiber reinforced polymers (FRP) are significantly affected by environmental impacts during their service life. Exposures to water, humidity, temperature and UV radiation are known to substantially influence the (thermo-) mechanical properties and durability of the materials. Design-relevant characteristics like strength, stiffness, or the glass transition temperature change with time. Therefore, expensive test campaigns are often necessary in advance of a structural design. Prediction models based on physical relations or phenomenological observations are typically required to reduce costs and increase reliability. Consequently, a combined methodology for fast prediction of long-term properties and accelerated aging purposes is presented in this work for a common DGEBA-based epoxy. Therefore, master curves are obtained by creep and constant-strain-rate tests under temperature and moisture impact. A combined time–temperature–water superposition and the Larson–Miller parametrization demonstrate that time-saving CSR tests and modeling can replace long-lasting creep testing. Resulting, the presented methodology allows to determine a polymer’s entire (environmental) failure envelope in a relatively short time and with low testing effort.

The current understanding of the carbonation and the prediction of the carbonation rate of alkali-activated concretes is complicated inter alia by the wide range of binder chemistries used and testing conditions adopted. To overcome some of the limitations of individual studies and to identify general correlations between mix design parameters and carbonation resistance, the RILEM TC 281-CCC 'Carbonation of Concrete with Supplementary Cementitious Materials' Working Group 6 compiled and analysed carbonation data for alkali-activated concretes and mortars from the literature. For comparison purposes, data for blended Portland cement-based concretes with a high percentage of SCMs (≥ 66% of the binder) were also included in the database. The analysis indicates that water/CaO ratio and water/binder ratio exert an influence on the carbonation resistance of alkali-activated concretes; however, these parameters are not good indicators of the carbonation resistance when considered individually. A better indicator of the carbonation resistance of alkali-activated concretes under conditions approximating natural carbonation appears to be their water/(CaO + MgOeq + Na2Oeq + K2Oeq) ratio, where the subscript 'eq' indicates an equivalent amount based on molar masses. Nevertheless, this ratio can serve as approximate indicator at best, as other parameters also affect the carbonation resistance of alkali-activated concretes. In addition, the analysis of the database points to peculiarities of accelerated tests using elevated CO2 concentrations for low-Ca alkali-activated concretes, indicating that even at the relatively modest concentration of 1% CO2, accelerated testing may lead to inaccurate predictions of the carbonation resistance under natural exposure conditions. [ABSTRACT FROM AUTHOR]

The linear dependence of abrasive wear under negligible shock actions as a function of the testing time has been established. The change of the wear intensity over time corresponds to the effect of the self-organization of wear. [ABSTRACT FROM AUTHOR]

There are potential sources of uncertainty when using default or generic profiles for vibration testing, particularly for large and complex payloads (Warren and Joiner, 2019). Replacing these severities with custom profiles generated using measured data offers one alternative; however, care must be taken not to select an inappropriate or inaccurate method. This research details the methodology and results of a trial which involved the design and implementation of a series of vibration tests, each to simulate a mixed-terrain environment applied to a complex payload. A systematic approach was used to develop and execute a test plan via the design of experiments method. An estimate of the damage potential for each was formed using Miner's rule (linear damage accumulation) applied to direct strain gauge data. This approach was compared with damage measured during a time waveform replication style test to be used as a baseline. The results of this test can be used to guide test specifiers and programme-level acceptance test guidelines and may be useful in implementing or guiding standards in this space. In addition, the damage measured in a series of increasing amplitude vibration tests (with an identical power spectral density) was compared with predicted values to assess the gain linearity assumptions often used in accelerated vibration testing. The research is unique as the authors could not source a thorough trial comparing the damage produced using a range of different profile development methods with a complex, real-world payload. Test houses and test specifiers seeking to improve the accuracy of their tests should consider the key findings and guidance in this article. [ABSTRACT FROM AUTHOR]