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Cracks caused by environmental temperature and humidity variation are generally considered one of the most important factors causing durability deterioration of concrete structures. The seasonal or daily variation of ambient temperature and humidity can be considered periodic. The dynamic modulus of elasticity is an important parameter used to evaluate the performance of structural concrete under periodic loads. Hence, in this paper, the dynamic elastic modulus test of concrete under simulating periodic temperature-humidity variation is carried out according to monthly meteorological data of representative areas (Nanjing, China). The dynamic elastic modulus attenuation pattern and a dynamic elastic modulus degradation model of concrete under periodic temperature-humidity are investigated. The test results show that the dynamic elastic modulus of concrete decreases and tends to be stable under the action of periodic temperature-humidity. Comparative analysis shows that the two-parameter dynamic elastic modulus degradation model is more suitable for describing the dynamic elastic modulus attenuation pattern of concrete under periodic temperature-humidity action than the single-parameter one.

The mechanics of rock masses in cold regions have attracted the attention of researchers from all over the world, and the concern here is that the mechanical properties of rock masses are inevitably weakened under freeze–thaw cycles. In this paper, first, granite samples were subjected to different freeze–thaw cycles, and then treated in four different states, such as saturated and frozen states, saturated and normal temperature states, dry and frozen states, as well as dry and normal temperature states. The impact compression test was carried out using the Split Hopkinson Pressure Bar (SHPB) device. Results show that the impact strength of granite samples deteriorates with the increase of freeze–thaw cycles in the same state; for samples in different states, although the number of freeze–thaw cycles is equal, the degree of deterioration of the impact strength is different. For freeze–thawed granite samples in the same state, the dynamic elastic modulus decreases with the increase of freeze–thaw cycles, and its degree of decrease is different for different states. Under the same freeze–thaw cycles, the deterioration of mechanical properties of granite samples is different in four different weather states; for example, the dynamic elastic modulus from large to small is generally as follows: saturated and frozen states, saturated and normal temperature states, dry and frozen states, as well as dry and normal temperature states. Finally, the freeze–thaw influence factor is proposed to describe the damage of granite samples. All in all, it can be concluded that water and low temperature strengthen the influence of freeze–thaw cycles on the dynamic mechanical properties of granite.

The simultaneous influence of hydrogen H and ultrasound deformation on internal friction Q − 1 and dynamic elastic modulus E of intermetallic Ti 3 Al alloy after cutting and polishing were studied. The relaxation maximum of internal friction Q − 1 M1 at temperature Т М1 ≈ 398 К, conditioned by the mechanism caused by reorientation interstitial atoms in dumbbell configurations H-H was discovered. Internal friction maximum Q − 1 M2 in intermetallic Ti 3 Al at temperature T M2 ≈ 439 K was discovered with an activation energy H 2 = 0.86±0.1 eV. 2D and 3D atomic force microscopy microstructure images of Ti (VT8) alloy after mechanical and thermal treatment are presented. Strengthening of Ti alloys is related to the cooperation of dislocations with point defects.

The bedrock of hydropower stations is susceptible to irreversible failure due to dynamic unloading and loading related to earthquakes, rock bursts or blasting. To ensure operational safety, the damage evolution process of bedrock under cyclic loading must be investigated. Hence, this study investigates the mechanical properties and acoustic emission (AE) characteristics of the bedrock from different positions of the Badantoru hydropower station under different confining pressures. First, the relationship between the dynamic elastic modulus and residual strain is analyzed, and then the brittleness and damage of the rocks are quantitatively characterized. Subsequently, the failure process and crack development of the rocks are revealed from the obtained AE characteristics. The results show that as the applied confining pressure increases, the peak differential stress and fatigue life of the rock specimens increase; whereas, the shear failure angle decreases. Under the same confining pressure, the rocks with a greater number of internal joints and pores (Dam Site I) have a lower bearing capacity under cyclic loading, a greater brittleness after strain softening, and a smaller shear failure angle. With increasing plastic strain, all of the specimens exhibit cyclic softening, and an obvious four-stage fatigue damage evolution can be observed.

In many geological conditions, obtaining the static elastic moduli of crustal rocks is an essential subject for accurate mechanical analyses of crust. The elastic wave method may be the best choice if rock specimens cannot be taken since elastic wave propagation can be applied to in-situ environments. Although many signs of progress have been made in the elastic wave method, some issues still restrict the accurate extraction of static moduli and its applications. A review of this method and its further research prospect is urgently needed. With this purpose, this paper summarized and analyzed the published experimental data about the relationship between the static and dynamic Young’s moduli of rock, and the frequency dependence of wave velocities and dynamic elastic moduli. P- and S-wave velocities, Young’s, and bulk moduli of rock, especially the saturated rock, have strong frequency dependence in a wide frequency range of 10 –6 –10 6  Hz. Different rocks or conditions (such as water content, amplitude, and pressure), have different frequency-dependent characteristics. The current elastic wave method can be classified into two methods: the empirical correlation method and the multifrequency ultrasonic method. The basic principle, advantages, and disadvantages of both methods are analyzed. Especially, the reasonability of the multifrequency ultrasonic method was elaborated given the nonlinear elasticity, strain level/rate, and pores/cracks in rock materials. Existing problems and prospects on the two methods are also pointed out, such as the choice of a proper empirical correlation, accurate determination of the critical P- and S-wave velocities, the prediction of Young’s modulus at each strain level, and the reasonability of the method under various water contents and fracture structures.

In this paper, the relationship between the static and dynamic elastic modulus of concrete and the relationship between the static elastic modulus and compressive strength of concrete have been formulated. These relationships are based on investigations of different types of concrete and take into account the type and amount of aggregate and binder used. The dynamic elastic modulus of concrete was tested using impulse excitation of vibration and the modal analysis method. This method could be used as a non-destructive way of estimating the compressive strength of concrete.

The propagation and attenuation characteristics of blast stress waves in geotechnical media directly influence the fracture behavior of the medium and serve as a crucial basis for optimizing blasting parameter design. To examine the attenuation characteristics of cylindrical blast waves in rocks, the indoor blasting experiments were conducted using sandstone with cylindrical charges. Digital image correlation technology was employed to successfully capture the full-field strain evolution around the borehole during blasting, and the strain–time curves of the rock surrounding the borehole were obtained. To account for the influence of blasting stress wave loading rates on dynamic elastic modulus, Split Hopkinson Pressure Bar tests were performed to establish a precise relationship between dynamic elastic modulus and strain rate. By analyzing the attenuation of the peak strain, a stress wave attenuation equation within the fractured zone was developed, and the stress wave attenuation index was examined. The results indicated that the experimental method effectively simulated the blasting process of cylindrical charges. The strain wave propagation was accompanied by energy transformation, where the descending phase of the strain–time curve represented the rapid energy input to the rock near the borehole due to blast loading, whereas the ascending phase reflected the radial release of elastic energy, further promoting the development of circumferential cracks, albeit at a lower energy release rate than the descending phase. As the distance from the blast center increased, both the dynamic elastic modulus and strain rate of the rock under blast loading decreased, leading to differences between the attenuation characteristics of stress waves and strain waves, with the former following a power function decay. The complex nature of stress wave attenuation in rocks was primarily governed by physical attenuation properties, with the physical attenuation index exceeding the geometric attenuation index in crushed and cracked zones. Finally, the accuracy of the stress wave attenuation equation and the reliability of the experimental method were validated by analyzing the fracture morphology of the blasted specimens and the extent of the cracked zone.

In fundamental physics, sensors operating below liquid helium temperatures are highly vulnerable to vibrations, which can affect the sensitivity, for example, of high-performance particle detectors. Pulse-tube refrigerators, while generating vibrations lower than those of conventional systems, may still introduce several disturbances. Hence, flexible thermal connections are a commonly used mechanical solution to mitigate these undesirable effects. Among the materials that can be used, ultra-high-purity aluminum (UHP-Al) has attracted the attention for low-amplitude-vibration cryogenic applications, including gravitational wave interferometry, quantum information systems, precision space instrumentation, and cryogenic resonators. Thus, the aim of the paper is the characterization of the mechanical and microstructure properties of three UHP-Als (i.e., 5N—99.999 wt%, 5N5—99.9995 wt% and 6N—99.9999 wt%) intended for the production of thermal flexible connections with low stiffness, specifically designed to reduce vibration transmission in cryogenic environments. Mechanical properties were evaluated through standard tensile tests from room (+25 °C) to low temperature (i.e., −150 °C), providing insights into yield strength, ultimate tensile strength, elongation and elastic modulus. In addition, the dynamic elastic modulus of material loads, at cryogenic conditions (i.e., about −180 °C), was determined by measuring the natural resonance frequency, thereby assessing the material’s response to vibrational. Moreover, an extensive microstructural analysis was conducted using electron backscatter diffraction and x-ray diffraction. The correlation between the observed microstructure and the elastic properties was systematically examined. The results underscore the pivotal role of microstructural characteristics in dictating the elastic behavior of UHP Als. Eventually, the analysis provides valuable guidelines for the materials employment inside cryogenic systems, where severe vibration control is critical to maintain high operational performance.

During the construction of tunnels in the central and western regions of China, diorite is frequently affected by vibration, blasting and water which will lead to the questions of the quality and operational safety of project. However, there are few studies on the dynamic characteristics of diorite under the action of dry–wet cycles. Therefore, this paper selected the gray–green altered diorite from Ning shan County, Shaanxi Province, China, mainly composed of plagioclase, and used the Slit Hopkinson pressure bar (SHPB) to study the effect of dry–wet cycle on the dynamic characteristics of Diorite. The test results show that the strength decay rate of the peak strength of diorite is the maximum under 1–3 dry–wet cycles, then decreases gradually. The dynamic elastic modulus of diorite dropped by 35.02% after three dry–wet cycles, accounting for 98.45% of the total attenuation. Compared the test result of three dry–wet cycles, the decrease volumes of the stress growth rate of diorite are the largest after six dry–wet cycles. Because of the actions of the dry–wet cycles, the growth rate of the rapid growth stage of the reflected energy–time history curve reduces and the growth rate of the rapid growth stage of the transmitted energy–time history curve improves. Under the action of the dry–wet cycles, the dissipation energy ratio gradually decreases, and the decrease of energy consumption density follows a negative exponential function relationship. Under the action of multiple dry–wet cycles, the tension and compression stress frequently change between the particles of rock, resulting in a significant increase of micro-cracks and an obvious degradation effect on the dynamical properties of diorite.

Freeze–thaw damage is one of the most important factors affecting the durability of concrete in cold regions, and how to quantitatively characterize the effect of freeze–thaw cycles on the degree of damage of concrete is a widely concerning issue among researchers. Based on the hydraulic pressure theory, a new concrete freeze–thaw damage model was proposed by assuming the defect development mode of concrete during freeze–thaw cycles. The model shows that the total amount of defects due to freeze–thaw damage is related to the initial defects and the defect development capacity within the concrete. Based on the new freeze–thaw damage model, an equation for the loss of relative dynamic elastic modulus of concrete during freeze–thaw cycles was established using the relative dynamic elastic modulus of concrete as the defect indicator. In order to validate the damage model using relative dynamic elastic modulus as the defect index, freeze–thaw cycle tests of four kinds of concrete with different air content were carried out, and the rationality of the model was verified by the relative dynamic elastic modulus of concrete measured under different freeze–thaw cycling periods. On this basis, a freeze–thaw damage model of concrete was established considering the effect of air content in concrete. In addition, the model proposed in this paper was supplemented and validated by experimental data from other researchers. The results show that the prediction model proposed in this study is not only easy to apply and has clear physical meaning but also has high accuracy and general applicability, which provides support for predicting the degree of freeze–thaw damage of concrete structures in cold regions.