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This study aims to establish an effective method for predicting the fatigue life of an automotive wheel in the accelerated dynamic cornering fatigue test. The test was simulated by linear transient dynamic finite element analysis, in which a rotating force of constant magnitude was applied to the moment arm tip to simulate the rotational bending effect on the wheel, with the wheel being fixed. Furthermore, transient strain histories of the elements were obtained and the critical elements with the largest amplitudes in their respective steady radial strain histories were found. The steady radial strain histories of all the critical elements were processed based on the local stress-strain approach, and the shortest simulated fatigue lives were taken as the predicted wheel fatigue lives. The predicted fatigue life was in good agreement with the average real-world test life of the investigated wheel.

Reactive powder concrete (RPC) shows a great application potential owing to its superior strength and excellent durability. However, creep behavior at high temperature is a major concern, as scanty information is available in the past literature. Therefore, the aim of this paper is to investigate the creep behavior of RPC at high temperature. Creep behavior is further segregated into free thermal strain, short-term creep and transient strain based on different thermo-mechanical regimes. Steady-state thermal and loading conditions and transient thermal and loading conditions were considered. Tests were carried out from 10 to 60% stress level of ambient and high-temperature compressive strength ratios and up to target temperature of 900 °C. The result shows that short-term creep of RPC increases considerably above 500 °C and the increase under the same loading ratios at 700 and 900 °C is approximately 13 and 23 times as that of short-term creep at 120 °C, respectively. Furthermore, increased stress level also triggered the short-term creep within the same target temperature. The evolution of free thermal strain and transient strain were slow below 250 °C. However, at higher temperature, the increase in strain rate becomes noticeable. It was found that heating rate has a direct influence on the expansion of RPC. On the other hand, transient strain was not affected by increasing heating rate from 3 to 5 °C/min. Finally, fitting equations were proposed which will be useful in fire safety design of RPC structures in computer programmes.

A leading hypothesis for the mechanism of fast supraglacial lake drainages is that transient extensional stresses briefly allow crevassing in otherwise compressional ice flow regimes. Lake water can then hydrofracture a crevasse to the base of the ice sheet, and river inputs can maintain this connection as a moulin. If future ice sheet models are to accurately represent moulins, we must understand their formation processes, timescales, and locations. Here, we use remote-sensing velocity products to constrain the relationship between strain rates and lake drainages across ∼ 1600 km2 in Pâkitsoq, western Greenland, between 2002–2019. We find significantly more extensional background strain rates at moulins associated with fast-draining lakes than at slow-draining or non-draining lake moulins. We test whether moulins in more extensional background settings drain their lakes earlier, but we find insignificant correlation. To investigate the frequency at which strain-rate transients are associated with fast lake drainage, we examined Landsat-derived strain rates over 16 and 32 d periods at moulins associated with 240 fast-lake-drainage events over 18 years. A low signal-to-noise ratio, the presence of water, and the multi-week repeat cycle obscured any resolution of the hypothesized transient strain rates. Our results support the hypothesis that transient strain rates drive fast lake drainages. However, the current generation of ice sheet velocity products, even when stacked across hundreds of fast lake drainages, cannot resolve these transients. Thus, observational progress in understanding lake drainage initiation will rely on field-based tools such as GPS networks and photogrammetry.

Considering the harm that residual stress causes to the mechanical properties of a weld joint, the evolution mechanisms of transient strain and residual stress distribution are investigated in laser welding of Al 6061, considering that these originate from non-uniform temperature distribution and are intensified further by the unbalanced procedure of melting and solidification. Thermal-elastic-plastic finite element method is developed and analyzed, while the actual weld profile is novel fitted by a B-spline curve. Transient strain is extracted by strain gauges. Longitudinal strain starts from a fluctuating compressive state and progresses to an ultimate residual tension state at the starting and ending welding positions, respectively. The maximum fitting deviation of the weld profile is 0.13 mm. Experimental and simulation results of residual strain are 842.0 μ and 826.8 μ, with a relative error of 1.805% at the starting position and −17.986% at the ending position. Near the weld center, mechanical behavior is complexly influenced by thermal expansion and contraction in the weld zone and the reaction binding force of the solid metal. Within a distance between −10 mm and 10 mm, and longitudinal stress is in a tension state, transverse stress fluctuates with a high gradient (~100 MPa).

The stress-strain relationships of concrete at elevated temperatures given in EN1992-1-2 is found to result in partial recovery of the transient strain of concrete upon unloading. Consequently, numerical models that adopt these stress-strain relationships to predict the response of concrete structures under fire conditions will underestimate their deformations and might result in unsafe predictions. Therefore, this paper proposes a modified-elastic modulus (Modified-E) method to correctly model the compressive behaviour of C120 concrete at elevated temperatures. The proposed method is implemented in a three-dimensional (3-D) finite element model to predict the fire performance of a high-strength concrete encased steel (CES) column under ISO834 fire condition. Results from the numerical analysis show that compared to the conventional method in the current EN1992-1-2, the Modified-E method reduces the error in the modelled transient strain of concrete by 55%. It also enables the 3-D finite element model to better capture the axial displacement of the CES column specimen under fire conditions.

In this citizen science project, we ask citizens to listen to relevant sections of seismograms that are accelerated to audible frequencies. The events we are asking citizens to help identify are local seismic events that generate much smaller signals than those associated with the seismic surface waves that might have triggered these local events. The local events include small earthquakes as well as tectonic tremor (series of deep low-frequency earthquakes). While progress has been made in understanding how these events might be triggered by the surface waves from large teleseismic earthquakes around the world, there is no consensus on its physical mechanism. The aim of our project is to receive the help of citizens to increase general knowledge of when and which triggered seismic events occur or not occur during transient strain events, such as from propagating surface waves. A better understanding of such triggered seismic events is expected to provide important clues towards a fundamental understanding of how earthquakes nucleate and how large earthquakes might interact with small ones. From the citizens’ classifications we determined that citizen scientists achieve a higher reliability in detecting earthquakes and noise than in detecting tremor or other signals and that citizen scientists more accurately identified earthquake signals than a trained machine-learning algorithm. For tremor classifications we depend entirely on the citizens as no machine has yet learned to detect tremor.

There is currently no established method for the non-invasive characterization of arrhythmia and differentiation between endocardial and epicardial triggers at the point of care. Electromechanical wave imaging (EWI) is a novel ultrasound-based imaging technique based on time-domain transient strain estimation that can map and characterize electromechanical activation in the heart in vivo. The objectives of this initial feasibility study were to determine that EWI is capable of differentiating between endocardial and epicardial sources of focal rhythm and, as a proof-of-concept, that EWI could characterize focal arrhythmia in one patient with premature ventricular contractions (PVCs) before radiofrequency (RF) ablation treatment. First, validation of EWI for differentiation of surface of origin was performed in seven (n = 7) adult dogs using four epicardial and four endocardial pacing protocols. Second, one (n = 1) adult patient diagnosed with PVC was imaged with EWI before the scheduled RF ablation procedure, and EWI results were compared with mapping procedure results. In dogs, EWI was capable of detecting whether pacing was of endocardial or epicardial origin in six of seven cases (86% success rate). In the PVC patient, EWI correctly identified both regions and surface of origin, as confirmed by results from the electrical mapping obtained from the RF ablation procedure. These results reveal that EWI can map the electromechanical activation across the myocardium and indicate that EWI could serve as a valuable pre-treatment planning tool in the clinic.

This paper introduces a numerical analysis method to evaluate the residual fire-resistance of reinforced-concrete (RC) structures and proposes considerations in designing RC structures on the basis of a comparison between numerical results and design codes. The proposed analysis method consists of two procedures, a transient heat transfer analysis and a non-linear structural analysis. To precisely simulate the structural response with temperature, the material properties of concrete and steel according to two representative temperature conditions, “under-fire” and “after-cooling”, have been taken into account. Furthermore, non-mechanical strains of concrete and steel such as thermal strain, transient strain, and creep strain, which change with temperature variation induced by fire, are implemented into the formulation. Upon validation of the introduced numerical method through a comparison between experimental data and numerical results, the importance of an exact consideration of the non-mechanical strains as well as material properties of concrete and steel corresponding to the changing temperature has been emphasized. Moreover, the importance of the after-cooling analysis to ensure the safety of fire-damaged RC structures has been shown. Finally, through a comparison of the numerical results with the design code EN1992-1-2, it has been concluded that the design code should consider the influence of temperature decrease after experiencing high temperature to ensure the safety of fire-damaged structural members.

Since its advent in the 1970s, digital image correlation (DIC) applications have been rapidly growing in different engineering fields including composite material testing and analysis. DIC combined with a stereo camera system offers full-field measurements of three-dimensional shapes, deformations (i.e., in-plane and out-of-plane deformations), and surface strains, which are of most interest in many structural testing applications. DIC systems have been used in many conventional structural testing applications in composite structures. However, DIC applications in automated composite manufacturing and inspection are scarce. There are challenges in inspection of a composite ply during automated manufacturing of composites and in measuring transient strain during in-situ manufacturing of thermoplastic composites. This article presents methodologies using DIC techniques to address these challenges. First, a few case studies where DIC was used in composite structural testing are presented, followed by development of new applications for DIC in composite manufacturing and inspection.

To obtain a complete understanding of the stability of deep caverns after excavation disturbance, a laboratory simulation method for testing surrounding rock under excavation disturbance was systematically proposed. The rock creep mechanical behavior considering excavation disturbance was compared with that of rock without excavation disturbance, and the results show that the long-term rock strength considering excavation disturbance is significantly lower than that without excavation disturbance at a 2400 m depth. Based on this method, a step-loading triaxial creep and associated acoustic emission (AE) test was carried out with a single-stage loading time of 5 days and a total loading time of approximately 50 days. The results show that with an increase in stress level, the transient strain of the deep rock increases nearly linearly, while the axial creep strain rate increases exponentially. The AE monitoring results demonstrate that when the rock creep transforms from the initial creep stage to the steady-state creep stage, and from the steady-state creep stage to the accelerating stage, the AE amplitude will clearly exhibit a band-shaped distribution, and the AE count rate and AE energy rate will show a single peak or multiple peaks. Multistage AE data can be used to determine the long-term strength of rock. In addition, with an increase in the stress level, the microcracks of the deep rock under excavation disturbance transform from closed primary microcracks to initiating, propagating and coalescence secondary microcracks, which ultimately leads to macroscopic shear failure. The above research results can provide a reference for deep resource exploitation and deep cavern stability evaluation.

This paper introduces a numerical evaluation of the fire-resistant capacity of reinforced concrete structures. On the basis of a time-dependent temperature distribution across a section determined from a transient heat transfer analysis considering heat conduction, convection and radiation, a layered fibre section method is adopted to take into account the non-linear material properties depending on the temperature. Furthermore, non-mechanical strains of concrete and steel such as thermal strain, transient strain and creep strain, which increase with elevated temperature variation induced by fire, are implemented into the formulation. Numerical results for structural members are compared with experimental data obtained from standard fire tests to investigate the influence of non-mechanical strains at elevated temperature. Beyond the member level, frame structures exposed to fire are also analysed to evaluate the influence of fire on statically indeterminate structures exposed to practical fire conditions. Finally, consideration of the change in material properties induced by elevated temperature in design practice is emphasised through correlation studies between the resisting capacities evaluated by the introduced numerical algorithm and those determined by the design code EN 1992-1-2.

Effect of tungsten on transient creep deformation and minimum creep rate of reduced activation ferritic-martensitic (RAFM) steel has been assessed. Tungsten content in the 9Cr-RAFM steel has been varied between 1 and 2 wt pct, and creep tests were carried out over the stress range of 180 and 260 MPa at 823 K (550 °C). The tempered martensitic steel exhibited primary creep followed by tertiary stage of creep deformation with a minimum in creep deformation rate. The primary creep behavior has been assessed based on the Garofalo relationship, $$ \varepsilon = \varepsilon_{\text{o}} + \varepsilon_{\text{T}} [1-\exp (-r^{\prime} \cdot t)] + \dot{\varepsilon }_{\text{m}} \cdot t $$ , considering minimum creep rate $$ \dot{\varepsilon }_{\text{m}} $$ instead of steady-state creep rate $$ \dot{\varepsilon }_{\text{s}} $$ . The relationships between (i) rate of exhaustion of transient creep r′ with minimum creep rate, (ii) rate of exhaustion of transient creep r′ with time to reach minimum creep rate, and (iii) initial creep rate $$ \dot{\varepsilon }_{\text{i}} $$ with minimum creep rate revealed that the first-order reaction-rate theory has prevailed throughout the transient region of the RAFM steel having different tungsten contents. The rate of exhaustion of transient creep r′ and minimum creep rate $$ \dot{\varepsilon }_{\text{m}} $$ decreased, whereas the transient strain ɛ T increased with increase in tungsten content. A master transient creep curve of the steels has been developed considering the variation of $$ \frac{{\left( {\varepsilon - \varepsilon_{\text{o}} } \right)}}{{\varepsilon_{\text{T}} }} $$ with $$ \frac{{\dot{\varepsilon }_{\text{m}} \cdot t}}{{\varepsilon_{\text{T}} }} $$ . The effect of tungsten on the variation of minimum creep rate with applied stress has been rationalized by invoking the back-stress concept.

This paper reviews the phenomena of concrete behavior which is captured in the material data of the Eurocode and reviews additional phenomena which may be included to improve results in certain cases. As a case study, a series of tests which were conducted by Anderberg and Thelandersson in the 1970’s in Sweden on concrete samples are studied using first of all the temperature dependent material model which is used in the Eurocodes. The impact of load induced thermal strain is discussed through comparison of the implicit model which is used in the Eurocode and a simple explicit model based on the test results.

A total of six specimens were tested to failure to investigate the effects of uniaxial bending, axial restraint, and initial load level on the structural responses of reinforced concrete columns at elevated temperatures. The full-scale column specimens (nominal height of 3.3 m and square cross-section of 300 mm) were cast with concrete of 55 MPa compressive strength and reinforcing steel of 550 MPa yield strength, and were tested with different levels of initial load and uniaxial eccentricity. Temperature-dependent axial deformations, lateral deflections, thermal-induced restraint forces, failure modes, and failure times of the test specimens are compared with those obtained from numerical analyses using SAFIR program. It is experimentally shown that the lateral deflection at elevated temperatures is adversely affected by uniaxial eccentricity and initial load level. Besides, the development of thermal-induced restraint forces increases with eccentricity but decreases with initial load level, and can be overpredicted by the numerical analysis that ignores concrete spalling and implicitly accounts for concrete transient strain at elevated temperatures.

This paper presents elevated-temperature analysis on a Shanley-like column model, as part of a study on the effect of transient strain on the strength of concrete and concrete-filled tubular columns in fire. Three high-temperature concrete material models are applied and the structural behaviours of the Shanley-like model using these three material models are compared. The effects of transient strain of concrete have been investigated by comparing the results of the analyses with and without considering this property, under the assumption that the temperature distribution within the model is uniform. The model has been evaluated against the tangent-modulus and reduced-modulus critical buckling loads at elevated temperatures. Numerical analyses have been carried out under both steady-state and transient heating scenarios, in order to investigate the influence of each on high-temperature structural analysis of the type described in this paper. It is seen that considering transient strain causes a considerable reduction of the buckling resistance, irrespective of the concrete material models and loading–heating schemes used.

In this paper, a complete strain model is derived that describes the strains developed during fire (up to 400 °C) and is based on the model of Anderberg et al., published in 1976. This model describes the total measured deformation as a superposition of four strain types: free thermal strain, instantaneous stress-related strain, creep strain and transient strain. The strains are derived from loading tests on cylinders with dimensions O106 × 320 mm, submitted to load ratios of 0%, 20% and 30% of the initial strength before heating. For damage to the oven to be avoided, the instantaneous stress-related strain is found from Young's modulus tests immediately after cooling. All tests occurred at a heating rate of 5 °C/min, and the specimens were pre-dried to avoid explosive spalling. The investigated concretes are a traditional and a self-compacting concrete with a testing age of about 30 months. Only small differences between both concrete types are found for the transient strain despite the different fracture of cement matrix. For the studied test conditions, the modern siliceous concretes such as self-compacting concrete yielded similar results as the traditional siliceous concretes tested in the 1970s. Copyright © 2012 John Wiley & Sons, Ltd.

This study aims to evaluate theoretically the fire resistance capacities of concrete filled tubular columns subjected to fire and axial compression. A strength analysis has been made in which all strains found in heated concrete including stress strain, thermal expansion and transient strain are taken into account. Since, among others, transient strain plays a key role on the behavior of heated columns, a new theoretical procedure to treat this strain is postulated and an explicit closed form solution is derived for the ultimate column strength. With comparison between the solutions and test data, it is found that the strength of a heated column is decreased significantly below its full plastic strength due to transient strain, if the column is made of higher strength concrete, is subjected to larger axial force or if it is of a larger cross section. For all the cases, the solutions are found in good agreement with the test results.

The effects of high temperature on the mechanical properties of 100N/mm2 high strength concrete have been studied experimentally at various temperatures ranging from room temperature to 700°C. Test results indicated that transient strain accounts for a big rate to total strain, and the effect of transient strain of high strength concrete is bigger than that of moderate strength concrete. We tried to formulate transient strain on the basis of Anderberg's model and obtained transient strain coefficient k2=5.56. Displacement constraint condition tests at elevated temperature were carried out and the constitutive model of high strength concrete was verified by thermal stress analysis. The results indicated that taking into account transient strain improved the analytical estimation of the variation in thermal stress of high strength concrete exposed to fire.

The effects of nitrogen content on deformation-induced martensitic transformation (DIMT) in Fe–18Cr–10Mn–N alloys were investigated. During tensile deformation, the stress–strain response was changed at different transient strains (e ≅ 0.19–0.22) depending on the nitrogen content. At the beginning of the deformation, a γ → e martensitic transformation occurred, whereas the formation of α′-martensite was predominant after transient strain. Increasing the nitrogen content caused the transient strain for DIMT to shift to higher strain and, finally, DIMT did not occur when nitrogen content was above 0.5 wt.%.

Performance of steel reinforced concrete (SRC) columns under fire is investigated in this paper. A three-dimensional finite-element analysis (FEA) modeling is developed for sequentially coupled heat transfer and structural analysis, in which the classical creep strain and the transient strain of concrete together with thermal strain are included explicitly by subroutines. Four SRC columns with H-shaped steel and cross-shaped steel are experimentally investigated, and the test results are adopted to verify the FEA modeling. The FEA modeling is then used to construct the model of a typical full-scale SRC column and perform analysis to the behavior of the column in fire. Extensive parametric studies are performed to investigate the fire resistance of the SRC column, and the key influencing parameters are identified. Finally, a simplified calculation method is proposed to predict the fire resistance of the SRC column.

Concrete behaviour at high temperature was investigated in depth since the 1970s, in order to highlight the main issues linked to its mechanical performance in hot conditions, such as chemical processes, kinematic behaviour (transient and creep strains) and evolution of the physico-mechanical properties. Thanks to these studies, a few constitutive models have been proposed in the literature for concrete at high temperature, with the aim of modelling reinforced concrete structural behaviour during heating. Within this context, a Beam Finite Element code for thermo-mechanical analyses has been developed by using a Fortran solver and GID as pre- and post-processor. A number of well-documented full-scale tests on reinforced concrete columns exposed to Standard Fire (without cooling) was simulated numerically, by implementing four different constitutive models proposed in the literature for concrete at high temperature. The main goals are: to highlight the role of some critical aspects regarding reinforced concrete members in hot conditions, in particular second-order effects, transient and creep strains (a), and to make a systematic comparison between numerical and experimental results in order to assess the reliability of both 1D numerical modelling (b) and the adopted constitutive models for concrete (c). The results confirm that 1D numerical modelling is generally consistent with the experimental evidence if transient and creep strains, as well as second-order effects are carefully taken into account. Moreover, the differences among the four investigated models for concrete behaviour in compression are quite limited.

An inverse artificial neural network (ANN) assessment for locating defects in bars with or without notches is presented in the paper. Postulated void defects of 1mm x 1mm were introduced into bars that were impacted with an impulse step load; the resultant elastic waves propagate impinging on the defects. The resultant transient strain field was analyzed using the finite element method. Transient strain data was collected at nodal points or sensors locations on the boundary of the bars and used to train and assess ANNs. The paper demonstrates quantitatively, the effects of features such as the design of ANN, sensing parameters such as number of data collection points, and the effect of geometric features such as notches in the bars.

The paper presents a critical review of the currently available models for the mechanical behaviour of concrete at elevated temperatures. Based on these models and experimental data a stress-strain-temperature model is proposed which incorporates the effect of transient strain implicitly. This model can be easily incorporated into existing commercial finite element analysis software. A numerical example on a wall element heated on two opposite faces indicates that at very early stages of heating transient strain does not play an important part, but that as the exposure time increases the effect of ignoring transient strain progressively increases and produces unconservative estimates of load carrying capacity.