Dynamic Strain Research Articles

Research on dynamic response and deformation evolution of a rectangular recycled aggregate concrete-filled steel tubular column under small-equivalent loads and weak disturbances

To study the dynamic response and deformation evolution of the rectangular recycled aggregate concrete-filled steel tubular (RRACFST) column under small-equivalent loads and weak disturbances, the measuring methods of blasting and the arrangement of measuring points were precisely handled. Three contact explosion tests were conducted on the RRACFST column to obtain their failure modes, dynamic strains, and accelerations. The research results indicate that the range of 20-30g TNT equivalent represents the starting point and critical point of plastic deformation for the RRACFST column. When the explosive quantity increases incrementally under small-equivalent loads and weak disturbances, the radius and size of the explosion crater do not exhibit a linear relationship. The methods of explosive treatment under small-equivalent loads and weak disturbances adhere to the core principles of precision and quantification, meeting engineering requirements. This study provided a theoretical basis and experimental basis for the safety study of RRACFST columns structure under explosion load.

Flow behaviour and microstructural stability in an Al–3Mg-0.2Sc alloy processed by high-pressure torsion at different temperatures

Experiments were performed to examine the flow behaviour at room temperature (RT ≈ 300 K) and the microstructural stability of a solution-treated Al–3Mg-0.2Sc alloy processed through 10 turns of high-pressure torsion (HPT) at either RT or 450 K and further annealed for 1 h at temperatures (T) up to 773 K. The results revealed that the Al–3Mg-0.2Sc alloy achieved yield strengths of ∼590 and 540 MPa after HPT at RT and 450 K, respectively. This followed from the higher dislocation densities achieved after processing at RT since both microstructures had average grain diameters of ∼320 nm. After annealing at T ≥ 523 K, there was evidence for the onset of dynamic strain ageing (DSA) during tensile testing at RT and this occurred concurrently with increases in the elongations to failure. The grain structures developed during HPT at 450 K exhibited superior microstructural stability than after HPT at RT for comparable heating conditions. A model derived for materials having second-phase particles was applied to understand the microstructural evolution observed during heating. It is shown that the values calculated for the driving and restraining pressures for boundary migration and the boundary stability factors are consistent with the experimental results.

A crystal plasticity model of Dynamic Strain Aging for a near-[formula omitted] Ti-alloy

Timetal-834, a near-α Ti-alloy, finds use in aeroengines due to its favorable properties. However, the alloy exhibits Dynamic Strain Aging (DSA) in the temperature range of 375-475 °C, that can cause it to fail early during service. As DSA is due to the micro-scale interaction between the diffusing solutes and mobile dislocations, a crystal plasticity model is developed in this work to capture this phenomenon. Additionally, the influence of the α (HCP) and β (BCC) laths of the transformed-β colony of this alloy on the DSA behavior is captured by using an equivalent model based on Taylor’s assumption. The effect of slip system dependent lath and colony size effect due to Burger’s Orientation Relation is also incorporated. Crystal plasticity finite element method simulations of polycrystalline domains, representative of Timetal-834, are performed for calibration and validation of the model using the available temperature dependent experimental data, and successfully capture the flow stress and DSA behavior. The strain rate dependency of DSA predicted by the model also shows an excellent agreement when compared with experimental data. Microstructural analysis of the simulations show that the orientation of grains/colonies have a strong influence on the aging time and hence the DSA response. Also, the initiation of DSA and frequency of serrated slip on the aligned systems of laths show differences due to dissimilar resistances and constraints on plastic flow. Overall, the model developed in this work can capture the microstructure dependent DSA and can be utilized for engineering of Timetal-834.

Dynamic strain aging in Inconel718 additively manufactured lattices

The aim of this work is to investigate the manifestations of dynamic strain aging (DSA) on the mechanical behavior of Inconel718 body centered cubic (BCC) and face centered cubic (FCC) strut-based lattices manufactured via laser powder bed fusion. With that goal, both lattices were tested uniaxially in compression at temperatures ranging from 25 to 600 °C at 1x10-3 s−1 and strain rate jump tests were carried out at the same temperatures between 1x10-5 and 5x10-2 s−1 in order to detect the occurrence of serrated flow and to analyze the strain rate sensitivity. It was found that DSA manifests at the metamaterial level within a range of testing conditions that is highly dependent on the lattice topology. In particular, DSA is comparatively more pronounced in the FCC architecture. This study emphasizes the importance of analyzing the incidence of DSA in additively manufactured lattice structures targeted for structural applications.

Damage-coupled unified constitutive modeling of 316LN stainless steel including dynamic strain aging under various tension dwell time: A macroscopic phenomenological study

A damage-coupled unified constitutive model is developed for 316LN stainless steel based on the framework of the Abdel-Karim and Ohno model. In the modified model, a kinematic hardening coefficient related to accumulated plastic strain is introduced in the linear hardening term, and a damage coefficient is incorporated in the static recovery term. Meanwhile, the parameters of isotropic hardening and kinematic hardening are associated with the maximum plastic strain rate and plastic strain memory to describe the effects of dynamic strain aging and plastic strain memory. Additionally, the kinematic hardening coefficients and static recovery coefficients correlate with dwell time to simulate stress relaxation throughout the whole-life time. The comparison between the simulation and experimental results indicates the validity of the modified model under the conditions of low-cycle fatigue and creep-fatigue interaction. After identifying the material parameters using a combination of classic parameter determination methods and optimization algorithms, the cyclic stress response and hysteresis loops can be accurately simulated throughout the whole-life time.

Spin-acoustic control of silicon vacancies in 4H silicon carbide

Bulk acoustic resonators can be fabricated on the same substrate as other components and can operate at various frequencies with high quality factors. Mechanical dynamic metrology of these devices is challenging as the surface information available through laser Doppler vibrometry lacks information about the acoustic energy stored in the bulk of the resonator. Here we report the spin-acoustic control of naturally occurring negatively charged silicon monovacancies in a lateral overtone bulk acoustic resonator that is based on 4H silicon carbide. We show that acoustic driving can be used at room temperature to induce coherent population oscillations. Spin-acoustic resonance is shown to be useful as a frequency-tunable probe of bulk acoustic wave resonances, highlighting the dynamical strain distribution inside a bulk acoustic wave resonator at ambient operating conditions. Our approach could be applied to the characterization of other high-quality-factor microelectromechanical systems and has the potential to be used in mechanically addressable quantum memory.

Modal strain monitoring of the old Nieuwebrugstraat Bridge: Local damage versus temperature effects

Vibration-Based Monitoring (VBM) from modal strains is a promising alternative to traditional VBM methods, which are primarily based on exclusively monitoring natural frequencies. The advantages of modal strains are that they offer a lower sensitivity to temperature and a higher sensitivity to small-scale damage, when compared to natural frequencies, rendering them ideal for detecting damage at an early stage. Furthermore, modal strains can be obtained in a dense grid with a relatively low cost, when fiber-optic sensors, such as fiber-Bragg gratings (FBG) are employed, which enables the monitoring of several critical locations and increases the possibility of early damage detection and localization. Modal strains can be obtained with high accuracy and precision thanks to a recently developed methodology that makes use of FBG sensors and of a high resolution acquisition system. The temperature sensitivity of modal strains has been investigated in the field but their damage sensitivity has previously only been investigated through laboratory experiments and numerical simulations. In this study, a 110-years-old steel railway bridge is monitored with 80 FBGs. Its modal strains and natural frequencies are automatically identified with the use of hierarchical clustering from ambient and operational dynamic strains. Before the scheduled replacement of the bridge, artificial damage is introduced by means of local cuts, simulating fatigue cracks, in order to investigate the damage detection and localization capabilities of modal strains on a full-size civil structure for the first time. The influence of temperature and operational factors is also investigated and compared with that of damage.

Study on dynamic mechanical properties and meso-damage mechanism of carbon fibers recycled aggregate concrete under freeze-thaw environment

The uniaxial compression mechanical properties tests of carbon fibers recycled aggregate concrete (CFRAC) were carried out in order to investigate the effect law of coupling freeze-thaw cycles (FTCs) and dynamic strain rates on the mechanical properties of CFRAC. Two cases of carbon fibers (CFs) doping of 0% and 0.3% were considered. The full CFRAC uniaxial compressive stress-strain curves at different strain rates (10−5/s, 10−4/s, 10−3/s, 10−2/s) after different FTCs (0, 50, 100) were obtained. The microscopic characteristics and microcrack propagation process of the specimens were analyzed by means of nuclear magnetic resonance (NMR), scanning electron microscope (SEM) and acoustic emission (AE). The results showed that the specimens still had significant strain rate sensitivity after FTCs. With the same amount of CFs doping and strain rate, the strength and elastic mode (E) of the specimens kept decreasing as the number of freeze-thaw cycles (N) increased. With the same N, the strength and E of the specimens increased and the deformation capacity decreased as strain rate increased. With the addition of 0.3% CFs, the frost resistance and crack resistance of the specimens were significantly enhanced. Combined with the statistical damage constitutive model, the influence of FTCs and dynamic strain rates coupling on the meso-damage mechanism of CFRAC was analyzed. The meso damage evolution process was characterized by five characteristic parameters E0, εa, εh, εb and H. The results showed that there was an obvious regularity between the change of characteristic parameters and CFs content, dynamic strain rate and the N. An effective link between the fine-scale damage mechanism and the macroscopic nonlinear intrinsic behavior was established. The phenomenon of AE signal lag in uniaxial compression was explained from the perspective of effective stress.

Piezotronic Antimony Sulphoiodide/Polyvinylidene Composite for Strain-Sensing and Energy-Harvesting Applications.

This study investigates the piezoelectric and piezotronic properties of a novel composite material comprising polyvinylidene fluoride (PVDF) and antimony sulphoiodide (SbSI) nanowires. The material preparation method is detailed, showcasing its simplicity and reproducibility. The material's electrical resistivity, piezoelectric response, and energy-harvesting capabilities are systematically analyzed under various deflection conditions and excitation frequencies. The piezoelectric response is characterized by the generation of charge carriers in the material due to mechanical strain, resulting in voltage output. The fundamental phenomena of charge generation, along with their influence on the material's resistivity, are proposed. Dynamic strain testing reveals the composite's potential as a piezoelectric nanogenerator (PENG), converting mechanical energy into electrical energy. Comparative analyses highlight the composite's power density advantages, thereby demonstrating its potential for energy-harvesting applications. This research provides insights into the interplay between piezoelectric and piezotronic phenomena in nanocomposites and their applicability in energy-harvesting devices.

Nonlinear dynamic responses of ballasted railway tracks using concrete sleepers incorporated with reinforced fibres and pre-treated crumb rubber

Abstract Damages on railway sleepers due to heavy impact loads induced by the movement of trains can be reduced by improving their impact resistance. Fibre-reinforced/pre-treated crumb rubber concrete sleepers (RCSs) have the potential to display significant impact resistance to withstand a high-magnitude impact load. The ideal proportions of pre-treated crumb rubber, steel fibres, and polypropylene fibres (PFs) can be identified based on the minimum cost-to-impact energy ratio after conducting a drop weight impact test on prisms. The numerical model developed to assess the behaviour of ballasted tracks has been validated using both simulation results and field measurements. Numerical studies have been conducted on ballasted rail tracks with steel and PF-reinforced/pre-treated RCSs using LS-DYNA software. Dynamic strain rate-dependent material parameters are introduced in the numerical simulations. The nonlinear effect of higher train speeds on dynamic track responses has been highlighted in this article. Although the static load-carrying capacity and modulus of elasticity of rubber concrete are low, their dynamic performance controls the track displacements from exceeding permissible limits. The outcome of this study will provide new insights into the effects of railway concrete sleepers incorporated with reinforced fibres and pre-treated crumb rubber on railway track performance in order to ensure safety and reliability before it is put into services.

Solute strengthening of prism edge dislocations in Mg alloys

The poor ductility of hcp Mg is attributed to the low activity of non-basal slip systems and so activation of prismatic slip can aid ductility in rolled sheets by providing three additional <a> Burgers vector slip systems. Experimental studies show that dilute additions of alloying elements such as Zn and Al leads to softening of prismatic slip at low temperatures but strengthening at higher temperatures. Here, the role of solute strengthening of prismatic edge dislocations is investigated as a possible explanation for the higher-T strengthening. Mg–Zn is studied using first-principles inputs in a parameter-free solute strengthening theory. First-principles DFT is necessary to accurately assess the strong solute chemical interaction energies in the core of the compact edge dislocation. Such calculations are subtle due to motion of the dislocation in the presence of the solute, and methods to obtain reliable results with acceptable computational cost are discussed. While interaction energies of Zn in the prism edge core can be quite large ( ± 0.34 eV), the edge solute strengthening of prismatic slip in dilute Mg–Zn remains well below experiments at high temperatures. However, the large difference (0.68 eV) in Zn/dislocation interaction energies across the core of the edge dislocation suggests strengthening by dynamic strain aging as an explanation for the higher-T strengthening.

Strong piezoelectricity of the nm-thick flexible Hf0.5Zr0.5O2 ferroelectric film

Integrated nanoelectromechanical systems (NEMS) exhibit enormous potential for replacing current microelectromechanical systems in various fields, such as 5G/6G wireless communication, in the future. However, their advancement is impeded by the challenge of achieving nanometer-thick ferroelectric oxide films with a high piezoelectric coefficient of d33. Herein, the nm-thick flexible Hf0.5Zr0.5O2 (HZO) films were deposited on mica substrates, and they exhibited a remnant polarization of ≥ 8.1 μC/cm2 at 25–320 °C and a high d33 value of 37.8 pC/N at 25 °C. After the HZO films with inter-digitated electrodes were fully polarized, the flexible HZO film with a dynamic bending strain of 0.102 % at 4 Hz produced an open-circuit voltage of 1.1 V. This HZO film with strong piezoelectricity can promote the development of novel NEMS and flexible piezoelectric sensors.

3D hot laser shock peening without coating based on Leidenfrost effect enables self-armored hydrophobic surface with enhanced fatigue properties

Hydrophobic metal surfaces have widespread applications in self-cleaning, ice removal, corrosion resistance, and drag reduction. The fine structure of these surfaces is crucial for their hydrophobic properties. Currently, pulse laser direct surface texturing is commonly employed to create hydrophobic surfaces, but this method primarily operates at room temperature. However, the rapid cooling rate and significant temperature gradient of the thin melted layer generated at room temperature often result in high stress concentration and cracks within the fine structure, compromising the overall integrity of the hydrophobic surface when subjected to complex external loads. To assess structural robustness by evaluating crack propagation, fatigue performance serves as a vital indicator. The thermal effect helps mitigate thermal cracking caused by direct laser irradiation and introduces an additional strengthening mechanism through dynamic strain aging. By utilizing the Leidenfrost effect, water can act as a confinement layer to achieve high temperature laser shock, which is expected to enhance the fatigue performance of hydrophobic structures. In this study, we propose a technique called 3D hot laser shock peening without coating (3HLSPwoC) as a cost-effective and efficient method to fabricate multi-scale self-armored hydrophobic surfaces with enhanced fatigue properties. We systematically discuss and analyze the wettability and mechanical properties of samples manufactured using different approaches. Furthermore, we reveal the underlying mechanism responsible for the fatigue performance improvement achieved through the 3HLSPwoC process, supported by molecular dynamics calculations and finite element simulations. Compared with the samples manufactured at room temperature, the surface of 3HLSPwoC samples exhibit greater plastic deformation, with no visible cracks on the surface. Additionally, these samples possess higher compressive residual stress and hardness. Notably, 3HLSPwoC samples demonstrate superior fatigue performance and enhanced durability of the hydrophobic properties. 3HLSPwoC has proved to be a novel process for manufacturing advanced hydrophobic surfaces with comprehensive mechanical properties.

Dynamic impact tests and temperature rise induced damage constitutive model of ice-rich frozen sandy soil

In this study, a soil-ice particle mixing method was used to prepare ice-rich frozen sandy soil specimens. Subsequently, the mechanical behaviors of ice-rich frozen sandy soil with a wide range of total moisture contents (15%–150%) were studied at three negative temperatures (−5, −10, and −15 °C) under the impact pressures from 0.2 MPa to 0.4 MPa. The melting of ice particles caused by the rise in temperature of frozen soil specimens was identified as temperature damage. Moreover, damage mechanism of ice-rich sandy frozen soil specimen during failure process was considered as the combined action of crack propagation and temperature rise. The analysis of the relationship between temperature rise value and dynamic strain was then calculated based on the heat conduction theory. Additionally, the phase transition equilibrium between unfrozen water and effective ice was used to determine the variation in ice volume content as the temperature rises, and the temperature damage variable was defined according to the reduction of dynamic elasticity modulus of ice-rich frozen sandy soil. Lastly, the compound damage variable was deduced and considered in the damage constitutive model. Accordingly, the theoretical and test data were compared to determine the model parameters. The results of the curve comparison indicate that the proposed model is feasible and suitable to be applied to predict the dynamic mechanics of ice-rich frozen sandy soil.

Acoustic emission sensing in fiber Bragg grating based on phase demodulation for material health detection

Acoustic emission detection is widely employed in the field of material health monitoring as an important non-destructive testing method. An acoustic emission sensing system based on phase demodulation in fiber Bragg grating is demonstrated in experiment to solve the problems existing in acoustic emission sensor, such as low sensor sensitivity and poor anti-interference capabilities. According to experimental results, the system can effectively detect both continuous and burst acoustic emission signals from 100 kHz to 700 kHz. The signal-to-noise ratio can reach 77 dB and the sensor phase sensitivity is 0.012 rad/με. The dynamic strain resolution of the system is 3.77 nε/√Hz. The system is also able to detect weak burst acoustic emission signals emitted during concrete damage, and the signal-to-noise ratio is 21.5 dB in the acoustic emission sensing in corrosion of reinforcement.

Dynamic characteristics and deterioration mechanism of coal under distinct initial gas pressure

Additional to dynamic and static superimposed loads, gas effects frequently affect coal seams throughout the coal mining process. It is crucial to comprehend coal samples’ mechanical properties and deterioration mechanisms under distinct initial gas pressure conditions. Consequently, the dynamic compression experiment of coal samples was conducted utilizing a self-developed observable combined dynamic and static loading test system of gas-bearing coal (GAS). The mechanical characteristics including failure mode in coal samples under distinct initial gas pressures were studied. Furthermore, the mechanism of gas deteriorated mechanical parameters and aggravated the propagation of cracks when combined with dynamic and static loads was revealed. The conclusions are drawn as follows: The GAS can go through four stages of deformation: elastic stage, elastoplastic stage, plastic stage, and failure stage. Furthermore, the dynamic strength and failure strain deteriorated with increasing gas pressure. Based on computed tomography (CT) technology, it is found that the splitting-spallation composite cracks of impacted samples become more noticeable with rising initial gas pressure, and finally, the two kinds of cracks create a complex reticular crack system. Meanwhile, the crack volume and fractal dimension increase with rising gas pressure, indicating that gas can aggravate the coal’s failure degree. Under combined dynamic and static loads, the deterioration model of mechanical parameters of GAS is obtained, that is, with rising initial gas pressure, the dynamic strength of coal samples reduces and the failure strain rises synchronously. The main reason for the aggravation of compound failure in impacted samples is that the stress intensity factor rises with the rise of gas pressure. These conclusions enrich the basic theories such as the inducing mechanism of dynamic disasters caused by coal-rock-gas compounds and can offer a theoretical foundation for the technology employed in monitoring, early warning, and prevention of dynamic disasters in compounds.

Research on the Accumulated Plastic Strain of Expansive Soil under Subway Loading

Expansive soil near Hefei Xinqiao International Airport was selected as the research focus. The effects of different loading modes on the dynamic strain of the saturated remodeled expansive soil was investigated by indoor dynamic triaxial tests and the effect of three factors, intermittent loading ratio, static deviatoric stress, and cyclic stress ratio, on the accumulated plastic strain of saturated remodeled expansive soil under intermittent subway cyclic loading was analyzed. Finally, the corresponding accumulated plastic strain calculation model was established based on the test results. The research results show that the loading modes do not affect the overall development mode of the strain and, under intermittent loading, the strain tends to be more stable. Under intermittent loading, when the number of cycles is the same, the larger the intermittent loading ratio, the smaller the accumulated plastic strain. The effect of static deviatoric stress and cyclic stress ratio on strain accumulation is significant. Based on the hyperbolic model, an accumulated plastic strain calculation model related to the number of cycles of remolded expansive soil under the load of the Hefei subway was proposed, which has a certain reference significance for the design, safety assessment, and safe operation of the Hefei subway.

Nonlinear/linear resonance ultrasound spectroscopy (N/RUS) of additively manufactured 316L stainless steel samples using in-contact and non-contact excitation

Due to their sensitivities to defects and microstructural changes, the linear and nonlinear parameters measured with nonlinear resonance ultrasound spectroscopy (NRUS) have the potential to evaluate the quality of additively manufactured parts. Here, NRUS with in-contact and non-contact excitation configurations is used to test a set of 316L stainless steel samples manufactured by laser powder bed fusion. Subgroups of the samples are heat treated to three temperatures to alter the samples' microstructure and mechanical performance. Results show that the hysteretic nonlinearity parameter measured with in-contact NRUS demonstrates sensitivity to heat-treatment-induced microstructural changes. However, due to the unwanted nonlinearity introduced by the bonding, variations in the repeated in-contact measurements of a single sample are almost as large as the differences between the heat treatment subgroups. The non-contact configuration allows measurement of two linear parameters (resonance frequency and damping) with exceptional repeatability, and results show clear distinction between samples in different heat treatment groups. The non-contact NRUS configuration could not produce a sufficient dynamic strain amplitude to allow a reliable measurement of the samples’ nonlinear response. In-contact and non-contact NRUS results are analyzed in relation to independently measured mechanical properties and microstructural information to investigate the feasibility of NRUS for the nondestructive evaluation of additively manufactured metals.

Failure behavior and strength deterioration model of high-performance concrete under coupled elevated temperature, biaxial constraint and impact loading

This research investigates the effects of high temperatures, multiaxial stress constraints, and impact loads on the failure behavior and strength deterioration of high-performance concrete. Combined with scanning electron microscopy and ultrasonic testing, the microscopic deterioration characteristics of thermally damaged concrete were revealed. Dynamic compression tests were performed on concrete, after exposed to elevated temperatures (from 25 °C to 750 °C), using a true triaxial Hopkinson pressure bar test system. The study analyzes the effect of temperature and strain rate on dynamic failure behaviors of concrete under biaxial stress constraints. The study establishes models for predicting the evolution of dynamic strength deterioration and strain rate. Additionally, the research discusses the mechanisms of influence of stress constraint states on the dynamic increasing factor (DIF) and failure modes of concrete. Results indicate that concrete's strength under biaxial stress constraints increases with the load rate and is hardened or weakened by changes in temperatures (taking 300 °C as a demarcation point). The strain rate effect of concrete becomes more significant with increasing temperature. Stress constraint states significantly affect the dynamic strength of concrete, and the DIF of concrete grows quasi-linearly with the logarithm of strain rate at different temperatures. Under biaxial stress constraints, concrete is dominated by oblique shear failure, and damage is less severe with the increase in the intermediate principal stress σ2. Macro-fractures are unlikely to appear under true triaxial stress constraints.

STUDY OF LOW-TEMPERATURE THERMOMECHANICAL BEHAVIOR OF THE Ti-18Zr-15Nb SUPERELASTIC ALLOY UNDER DIFFERENT TEMPERATURE-RATE CONDITIONS

The biomedical alloy Ti-18Zr-15Nb (at.%) with shape memory was subjected to a true deformation e = 0.7 in three different modes: in the temperature range from 20°C to 600°C at deformation rate ξ = 0. 1 s-1; at temperatures 250°C and 300°C with strain rates ξ = 0.1, 1 and 10 s-1; deformation at 300°C and strain rate ξ = 0.1 s-1 after annealing at 300°C (τ = 10, 60, 300, 600 and 1200 s). It is established that with increasing temperature the conditional yield strength σ0.2 continuously decreases, at that in the temperature range of deformation temperatures 250°С-300°С the increase of maximum stress σmax is observed. In the temperature range from 200°С to 400°С fluctuations are observed on the flow curves, the amplitude of which increases with increasing temperature. The change σ0.2 and σmax, as well as the presence of oscillations on the strain diagrams are connected with the course of dynamic strain aging accompanied by the release of excess ω-phase particles at temperatures 200°С - 400°С. Increasing the strain rate at temperatures of 250°С - 300°С has a strong effect on the deformation behavior of the alloy due to a significant increase in temperature during the deformation process. Thus, increasing the strain rate up to ξ = 10 s-1 leads to a stepwise decrease in stress, starting from e ≈ 0.3, after which the plastic flow curve acquires a wave-like form with a low frequency of stress fluctuations. The main phase after all modes of thermomechanical tests is the BCC β-phase. At annealing of 300°С and an exposure of more than 300 s weak ω-phase lines are observed, and at deformation after aging significantly broadened ω-phase lines are observed only after prolonged exposure (1200 s).