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In this paper, an extension of the Timoshenko model for plane beams is outlined, with the aim of describing, under the assumption of small displacements and strains, a class of dissipative mechanisms observed in cementitious materials. In the spirit of micromorphic continua, the modified beam model includes a novel kinematic descriptor, conceived as an average sliding relevant to a density of micro-cracks not varying along time. For the pairs of rough surfaces, in which such a distribution of micro-cracks is articulated, both an elastic deformation and a frictional dissipation are considered, similarly to what occurs for the fingers of the joints having a tooth saw profile. The system of governing differential equations, of the second order, is provided by a variational approach, endowed by standard boundary conditions. To this purpose, a generalized version of the principle of virtual work is used, in the spirit of Hamilton–Rayleigh approach, including as contributions: (i) the variation of the inner elastic energy, generated by the linear elasticity of the sound material and, in a nonlinear way, by the mutual, reversible deformation of the asperities inside the micro-cracks; (ii) the virtual work of the external actions consistent with the beam model, i.e., the distributed transversal forces and the moments per unit lengths; besides these two contributions, constituting the conservative part of the system, (iii) the dissipation due to friction specified through a smooth Rayleigh potential, entering a nonlinear dependence of viscous and Coulomb type on the sliding rate. Through a COMSOL Multiphysics implementation, 1D finite element analyses are carried out to simulate structural elements subjected to three- and four-point bending tests with alternating loading cycles. The dissipation of energy is investigated at varying the model parameters, and the predictions turn out to be in agreement with preliminary data from an experimental campaign. The present approach is expected to provide a valuable tool for the quantitative and comparative assessment of the hysteresis cycles, favoring the robust design of cementitious materials. [ABSTRACT FROM AUTHOR]

Acidic contaminants are one of the major pollutants that penetrate the soil through various pathways, such as breaking pipes, factory effluents, and chemical leakages. In this study, systematic static and cyclic simple shear tests were performed to explore the behavior of marine sands subjected to acidic conditions, considering the influences of the different cyclic stress ratios and acid erosion durations. The peak shear strength, pore pressure, deformation, stiffness degradation, damping ratio, and liquefaction resistance were investigated. Test results show that increasing the acid erosion duration causes an increase in the monotonic peak shear strength, a decrease in the rate of pore pressure build-up, and enhances the liquefaction resistance of marine sands. The liquefaction resistance of tested marine sands subjected to acid erosion is about 1-1.2 times greater than that of sands without acid erosion. On this basis, a modified model was established to predict the pore pressure generation of marine sands, and an assessment method of the liquefaction resistance suitable for marine sands that is independent of the acid erosion duration was obtained, providing an effective means for early evaluation of soil liquefaction in engineering practice. Furthermore, by carrying out an energy-based assessment of liquefaction behavior, a unique correlation between various cyclic behaviors and dissipated energy was revealed, indicating the potential applicability of the energy-based method for evaluating the characteristics of marine sands even under acidic conditions. [ABSTRACT FROM AUTHOR]

Upon dynamic loading, saturated soils lose their strengths and undergo deformations resulting in volumetric-induced settlements that vary according to the excess pore pressure generation and dissipation variations. Traditionally, these settlements have been evaluated using standard charts based on one soil type and its relative density (RD). To assess these settlements, this study established a unique experimental methodology based on two laboratory testings: triaxial simple shear and piezoelectric ring actuator technique. Fifty-seven tests were performed on Ottawa F65 sand under strain-controlled cyclic and post-cyclic conditions. A chart was generated, revealing a relationship between the dissipated energy from cyclic loading and volumetric strain (εv), based on the shear wave velocity as a controlling factor. This study was compared with previous studies to verify the compatibility of the proposed approach. Another novelty was revealed by studying εv variation with the dissipated pressure. This variation is presented in a post-seismic chart in which deformations are tracked based on the initial soil state and maximum excess pore pressure generation ratio (Rumax) at the end of the loading phase. For each RD, the soil is divided between liquefied and non-liquefied states according to a specific Rumax (Rumax-trigger point). The calculation of the volume compressibility coefficient is proven to serve as a liquefaction-triggering criterion identifying the liquefied state. [ABSTRACT FROM AUTHOR]

The fracture surface regarded as the three-dimensional morphological characteristics of crack propagation is formed under the impetus of energy, and its characteristics can be described by the fracture surface roughness. Investigating the fracture surface roughness is of high importance for prediction and assessment of earthquakes, calculating shear strength at the fracture zone, and comprehending fluid flow. However, an excess of available energy flowing to the crack tip would cause crack branching, and the influence of the energy on fracture surface roughness of branching is rarely considered. This paper aims to evaluate the effect of the dissipated energy on fracture surface roughness based on rock dynamic fracture experimental study of crack branching. A set of split Hopkinson pressure bar measuring systems (SHPB-PS50) for rock dynamic fracture tests was established. The morphological characteristics of crack branching on the specimen surface, the three-dimensional surface topography of the fracture surface, and the changes in the dissipated energy characteristics with the fracture surface roughness were analyzed. It is concluded that the attenuation function is suitable for expressing the relationship between the roughness parameters and the dissipated energy, and an energy model with non-symmetrical branching of different roughness is established. Additionally, a numerical simulation analytical approach is developed for building the fracture surfaces through the coordinates of the discrete fracture network to measure roughness. The numerical simulation results support the experimental conclusions. The energy-based model with non-symmetrical branch fractures of different roughness is correct. [ABSTRACT FROM AUTHOR]

This study investigates the effect of non-plastic fines content of sand–silt mixtures on excess pore water pressure generation using an energy-based approach. For this purpose, an experimental program was designed and conducted on mixtures of Firoozkuh sand No. 161 and Firoozkuh silt. A total of 35 undrained strain-controlled cyclic triaxial tests were performed on the reconstituted specimens of sand–silt mixtures, with a wide range of effective parameters such as relative density, effective confining stress, and fines content. Also, to present a more generalized and precise model, 37 undrained cyclic tests were collected from previous studies. Then, using nonlinear regression analysis and the results of these 72 tests, a model, relating residual excess pore water pressure ratio ( r u ) to the ratio of dissipated energy to capacity energy ( W / W liq ), is proposed. The results indicated that initial effective confining stress has a negligible effect on the r u - W / W liq trend and so, the calibration parameter of the model only depends on the relative density and fines content. Convincingly, the accuracy of the proposed model was verified using the results of a series of centrifuge tests, reported by others, and the recorded data of wildlife downhole array site during the Superstition Hills 1987 earthquake. The proposed model is practical, applicable to various sands and sand–silt mixtures with nonplastic fines contents, and able to be calibrated using convenient parameters (i.e., relative density and fines content). Finally, the model can be easily implemented in site response analysis for energy-based liquefaction potential evaluation. [ABSTRACT FROM AUTHOR]

(1) Background: Romanian earthquakes caused severe damage over time to a significant number of constructions, and that is why efforts are being made to make structural systems safer. (2) Methods: For structural systems with protection against seismic actions or vibrational actions that have linear viscous dissipation devices, the requirement to assess the equivalent modal damping rate for the entire functional assembly related to the other dynamic parameters arises. (3) Results: This article presents the analytical development of formulas for the compound damping and circular frequency when anti-seismic devices have different dynamic characteristics and their application in order to solve some real engineering cases of bridges and viaducts in Romania with distinct viscoelastic supports. In support of this idea, some experimental tests on a beam system resting on two different anti-seismic elastic supports highlighted the fact that the compound damping of the system can be calculated with the relations established in this paper, provided that the displacements in the horizontal direction of excitation are in the linear domain. Also, we determined the seismic response considering the Vrancea 1977 accelerogram for critical damping ratios of 5% and 18.5%, and then we obtained the variation in the factor of transmissibility depending on the frequency, in order to highlight the optimized value of the equivalent amortization/damping. (4) Conclusions: In the specific context of Romanian seismicity, seismic isolation through the use of isolators with different characteristics represents an optimal technical solution, and it is also optimal from an economic point of view, with an appropriate level of dynamic isolation obtained. [ABSTRACT FROM AUTHOR]

Purpose: Prior studies have indicated an impact of cardiac muscle viscoelasticity on systolic and diastolic functions. However, the studies of ventricular free wall viscoelasticity, particularly for that of right ventricles (RV), are limited. Moreover, investigations on ventricular passive viscoelasticity have been restricted to large animals and there is a lack of data on rodent species. To fill this knowledge gap, this study aims to develop a biaxial tester that induces high-speed physiological deformations to characterize the passive viscoelasticity of rat RVs. Methods: The biaxial testing system was fabricated so that planar deformation of rat ventricle tissues at physiological strain rates was possible. The testing system was validated using isotropic polydimethylsiloxane (PDMS) sheets. Next, viscoelastic measurements were performed in healthy rat RV free walls by equibiaxial cyclic sinusoidal loadings and stress relaxation. Results: The biaxial tester's consistency, accuracy, and stability was confirmed from the PDMS samples measurements. Moreover, significant viscoelastic alterations of the RV were found between sub-physiological (0.1 Hz) and physiological frequencies (1–8 Hz). From hysteresis loop analysis, we found as the frequency increased, the elasticity and viscosity were increased in both directions. Interestingly, the ratio of storage energy to dissipated energy (Wd/Ws) remained constant at 0.1–5 Hz. We did not observe marked differences in healthy RV viscoelasticity between longitudinal and circumferential directions. Conclusion: This work provides a new experimental tool to quantify the passive, biaxial viscoelasticity of ventricle free walls in both small and large animals. The dynamic mechanical tests showed frequency-dependent elastic and viscous behaviors of healthy rat RVs. But the ratio of dissipated energy to stored energy was maintained between frequencies. These findings offer novel baseline information on the passive viscoelasticity of healthy RVs in adult rats. [ABSTRACT FROM AUTHOR]

The mechanical properties of concrete structures change under repeated sulfate salt erosion, a transformation observable through the evolving energy characteristics during compression. This study conducts uniaxial compression tests on ordinary concrete under repeated sulfate solution and pure water erosion, referencing uniaxial compression tests on concrete with admixtures under sulfate solution erosion, comparing and analyzing their mechanical properties and energy conversion characteristics. Findings indicate: (1) Repeated sulfate erosion increases the nonlinearity of the concrete’s stress-strain curve, especially during the initial compaction phase. Regardless of peak strength, both the energy dissipation curve and damage variables defined by dissipated energy show consistent trends. This suggests that sulfate salts react within the concrete, generating new substances that fill pores, temporarily increasing the elastic modulus while degrading the original structure, ultimately leading to brittle failure. (2) Considering repair effectiveness, protection of repair products, and the evolution of dissipated energy, peak strength variations, and SEM images of internal microcracks, the optimal timing for self-healing in ordinary concrete is suggested to be after 14 wet-dry cycles. (3) Under repeated sulfate salt erosion, the stress-strain relationship of ordinary concrete significantly deviates from traditional damage constitutive models, especially during initial compaction phase. Constitutive models based on damage variable evolution and dissipated energy show better agreement with experimental results in this phase.

Test results of beam-column moment connections of storage racks are presented. Quasi-static tests were performed using a displacement-controlled electromechanical actuator on connections with two different bolting torques. The experimental setup contemplates a 1.48 m long column, labeled at both ends, and a 1.72 m long beam. The actuator has a 900 kg capacity load cell at its connection end with the beam and registers the applied deformation through a 300 mm travel displacement sensor. The beam was instrumented with rotation sensors, having one just before the support, and two in the L profile that connects it with the column. The loading corresponds to sawlike cyclic displacement sequences with increasing amplitudes, adapted from the AISC341 (2022) section K. The results showed that, by increasing the torque from 54.2 Nm to 108.5 Nm, the elastic stiffness increased by 45%. A higher tightening torque generated a reduction in pinching and an increase in the energy dissipated from the connection, compared to the case with lower torque. In general, the connections were capable of resisting rotations of up to 0.07 rad. [ABSTRACT FROM AUTHOR]

The biaxial tension–tension cyclic loading experiments were conducted on the cruciform specimens prepared using a silane‐modified polyurethane sealant to investigate their mechanical behavior. The finite element method was employed to validate the mechanical behavior of cruciform specimens under the biaxial cyclic loading conditions. It is shown that the highest stress concentration is in the central region of the cruciform specimens, indicating that the shape design of the specimen is suitable for the biaxial tension–tension cyclic tests. Additionally, the effects of loading path, mean stress, and stress amplitude on ratcheting strain and dissipated energy were analyzed through the experimental data. The experimental results demonstrated that the loading path had an influence on the mechanical behavior of the cruciform specimen. The additional ratcheting strain caused by the non‐proportional loading path was found to be loading path dependent of the adhesive. Moreover, the mean stress and stress amplitude greatly affected the strain response curves of the specimen under biaxial cyclic loading. The ratcheting strain and dissipated energy increased with increasing mean stress and stress amplitude; nevertheless, stress amplitude had more influence on the mechanical behavior than the mean stress. Highlights: The biaxial cyclic loading tests were conducted on the cruciform specimens.The effects on ratcheting strain and dissipated energy were analyzed.The loading path has influences on the mechanical response of the specimen.The mean stress and stress amplitude have effects on the strain response [ABSTRACT FROM AUTHOR]

In coal mining, the rock mass is often in the process of repeated cyclic loading due to the influence of excavation and unloading factors. In order to study the damage and failure characteristics and energy evolution law of coal and rock under cyclic gradient loading, a uniaxial cyclic gradient loading experiment was carried out on coal samples, and deformation failure characteristics, input energy density, dissipated energy density and damage variables of the coal samples under different cyclic gradient loading were compared and analyzed. The results show that with the increase of the cyclic gradient stress, the number of cycles and the peak strength of the coal samples decrease, which are 17.97, 14.86, 11.23, and 10.53 MPa; in cyclic gradient loading, most of the input energy density is stored inside the rock sample in the form of elastic strain energy, and the dissipation energy increases between 0.2% and 40% of the total input energy in a single cycle. Cumulative dissipation is selected as the quantitative index of the whole process of coal and rock damage, and the Logistic equation is used to fit the coal and rock damage, and the evolution model of coal and rock damage is obtained.

The factors that influence dissipated energy and pore pressure generation patterns with respect to the cycle ratio and dissipated energy ratio were analyzed using the results of cyclic triaxial and cyclic direct simple shear tests. These analyses revealed several interesting differences in pore pressure generation patterns when related to cycle ratio than to dissipated energy ratio. Soils with different pore pressure generation patterns when plotted against the cycle ratio were found to have nearly identical pore pressure generation patterns when plotted against the dissipated energy ratio. The differences exist as the result of the fundamental differences between cycle ratio and dissipated energy ratio. The fundamental difference is that pore pressure generation is directly linked to the process of energy dissipation; it is not inherently linked to cycles of loading. Therefore, to achieve an understanding of the pore pressure response of a soil that is independent of the specifics of the applied loading, one needs to evaluate it in terms of energy dissipation, not in terms of cycles of loading, especially irregular loadings.

Incorporating masks into building materials offers a potential solution to the environmental threat of disposable masks with promising material performance. However, research on their dynamic properties is lacking to further determine the application range of the new composite. This study addresses this gap by shredding face masks into strips and incorporating them into mortars at varying volume ratios. The integrity and compactness of the mortar was measured and characterized by P-wave velocity, while dynamic compression properties were explored using a split Hopkinson pressure bar (SHPB) system. Subsequently, sieve analysis was conducted on the fractured specimens. The results indicate that incorporating masks generally improves the mortar integrity and the fragmentation after impacting. The dynamic uniaxial compression strength (DUCS) decreased for all mixing designs compared to plain ones under a constant loading rate. Meanwhile, the dissipated energy density showed a similar trend to the P-wave velocity, exhibiting less pronounced enhancement at higher loading rates. According to the dynamic characteristics, a dynamic constitutive model based on the Lemaitre principle and Weibull distribution of damage is developed and validated. The test results are further understood through the perspective of the mechanism of mask inclusion. [ABSTRACT FROM AUTHOR]

A novel Timoshenko beam model enriched to account for dissipation in cement-based materials was presented in this paper. The model introduced a new variable representing the relative sliding inside microcracks within the material. In the paper, the microcrack density was not supposed to increase, assuming a small deformation regime that implied no damage growth. The model utilized an expanded version of the principle of virtual work whose contributions came from external forces, internal elastic forces, and dissipation due to the microcrack's microstructure. The elastic energy included terms related to microcrack sliding and micro-macro interactions, accounting for nonlinearity in the material behavior. Numerical simulations, conducted using the finite element method, evaluated the mechanical properties of cement-based materials under three-point flexural tests and compression tests. These tests enabled the assessment of the material dissipative behavior under cyclic loading. Results showed dissipated energy cycles and mechanical responses influenced by the microcrack mechanics. Additionally, a parametric study, varying the friction force amplitude, revealed its impact on dissipated energy. The study highlighted a non-monotonic relationship between friction force amplitude and dissipated energy, with an optimal value maximizing dissipation. Overall, the model provided insights into the mechanics of cement-based materials, particularly regarding dissipation, which was essential for understanding their behavior in structural applications. [ABSTRACT FROM AUTHOR]

The liquefaction of saturated marine coral sand is of a great issue for the safety of ocean engineering. A series of undrained cyclic torsional shear tests on saturated coral sand are carried out to further explore the liquefaction characteristics of coral sand. Based on the energy method, the effects of relative density (Dr), effective mean principal stress ( p ′ 0 ), and cyclic stress ratio (CSR) on undrained responses of saturated coral sand are investigated. Two failure criteria are discussed to evaluate the dissipated energy required to cause initial liquefaction (Wl). The test results show that the Wl is significantly affected by Dr and p ′ 0. The generation patterns of excess pore water pressure (EPWP) and single amplitude torsional strain amplitude (γSA) along with cumulative dissipated energy (Wc) are described, and the unified generation model of both ue and γSA along with Wc are established. The liquefaction resistance curves for various Dr and p ′ 0 are strongly related to Wl. Analyzing the cumulative dissipated energy required to trigger liquefaction, a modified stress level index termed CSRe is proposed to normalize the liquefaction resistance curves of saturated coral sand under different Dr and p ′ 0. The test data in literature also verify the applicability of CSRe. [ABSTRACT FROM AUTHOR]

Pond ash is a byproduct obtained from the combustion of coal in thermal power plants. It can be used as an alternative to conventional granular materials in compacted subgrade or subbase layers in pavements. The properties can be further enhanced by the addition of small doses of cement. Typically, the modulus parameters required for the design of pavements are based on resilient modulus models. Such models presume that the material attains a shakedown response in every loading sequence and the resilient modulus (MR) can be defined. However, it is not very clear whether a nonconventional material such as pond ash or cemented pond ash attains shakedown within 100 cycles of each sequence as stipulated in the resilient modulus test protocol. The number of loading cycles required to reach the shakedown limit is explored in this study. There are two sets of experiments conducted: the conventional resilient modulus tests with 100 cycles in each sequence and repeated load triaxial tests with 10,000 cycles for three confining pressures (41.4, 27.6, and 13.8 kPa) at a deviator stress of 69 kPa. The effect of cement dosage (2% and 3%), compaction condition (standard and modified Proctor compaction), and water content (optimum moisture content (OMC), OMC−2%, and OMC+2%) were studied. The shakedown theory is explained in terms of permanent deformation increment per cycle, dissipated energy, and tangent modulus. The resilient modulus is defined as the tangent modulus of the material which has attained shakedown. The cemented pond ash did not strongly correlate to confining pressure and hence, a constant value of the resilient modulus may be used. [ABSTRACT FROM AUTHOR]

Ceramic detachment is a serious problem that persists in modern building constructions despite technological advances and updated regulatory documents. Most of these detachments occur at the interface between the adhesive mortar and the ceramic tile, due to the action of simultaneous tensile and shearing efforts. However, despite this understanding, experimental studies that evaluate the integrity of the adhesion of façades covering materials subjected to simultaneous stress are scarce. In this sense, this study proposes to evaluate the integrity of adhesive mortar joints using the mixed-mode flexure (MMF) crack propagation test. Force and elastic and dissipated energy data were used in this analysis. Prismatic specimens, with a size of 160 × 40 mm2 and a thickness of 6 mm, were produced consisting of two ceramic plates joined by a layer of adhesive mortar at 5 ± 0.5 mm. An acetate film was inserted into one of the mortar–ceramic interfaces in order to simulate the presence of a previous crack, and different crack sizes were used. The results showed the high stress-concentrating effect that the existence of flaws in the interface region has on fracture resistance, as well as the importance of effective contact between the materials. The energy parameters confirmed the analyses carried out based on the load values. The elastic energy of the system fell in the cracked samples, showing that there is a close relationship between the interface energy and the adhesive strength of the material. An energy release of the order of 0.053 ± 0.031 J was required for a 15 mm crack to propagate, creating a fracture surface. [ABSTRACT FROM AUTHOR]

The factors that influence dissipated energy and pore pressure generation patterns with respect to the cycle ratio and dissipated energy ratio were analyzed using the results of cyclic triaxial and cyclic direct simple shear tests. These analyses revealed several interesting differences in pore pressure generation patterns when related to cycle ratio than to dissipated energy ratio. Soils with different pore pressure generation patterns when plotted against the cycle ratio were found to have nearly identical pore pressure generation patterns when plotted against the dissipated energy ratio. The differences exist as the result of the fundamental differences between cycle ratio and dissipated energy ratio. The fundamental difference is that pore pressure generation is directly linked to the process of energy dissipation; it is not inherently linked to cycles of loading. Therefore, to achieve an understanding of the pore pressure response of a soil that is independent of the specifics of the applied loading, one needs to evaluate it in terms of energy dissipation, not in terms of cycles of loading, especially irregular loadings. [ABSTRACT FROM AUTHOR]

Dynamic mechanical characteristics of coral sand is of vital importance for foundation compaction. In the present study, a series of tests were conducted to estimate the dynamic behaviors of coral sand under drop weight impact. The coral sands with original and uniform gradations were impacted with different energies and different repeating times. The test results show that the dynamic force–displacement or the stress–strain response roughly undergoes the initial intense fluctuation, quasi-free fall, subsequent descending fluctuation and the inverse rebound periods. The reduction in the void ratio of coral sand increases with single impact energy increasing, while it decreases with the repetition of impact. The breakage of coral sand under impacting is progressive along the height of the sample, revealing by the multiple yield points in the e-logp curve. It is found that the predominant size fraction of fragmented particles corresponds well to the inflection interval of its initial PSD curve. The ratio of the dissipated energy to the absorbed energy generally reduces as the repetition of impact loading. The breakage index can be closely correlated to the dissipated energy. As compared to the original coral sand, the uniform coral sand exhibits more sensitive behaviors in terms of compressibility, particle crushing and energy dissipation. Furthermore, the scenario of few impacts at high energy level is proved to be more efficient than that of multiple impacts at low energy level in the reinforcement of coral sand. [ABSTRACT FROM AUTHOR]

Waste-tire textile fibers (WTTF) represent a challenge for the recycling industry since there are currently very few alternatives for their use. In this study, an evaluation of the effect of a new additive developed in two granular formats from WTTF on the fatigue behavior of asphalt mixtures was performed. For the first format of the WTTF-based additive, its effect was evaluated on hot-mix asphalt (HMA), while for the second format of the additive, the effects were evaluated on stone mastic asphalt (SMA). This second format represents an alternative that allows for the total replacement of the cellulose stabilizing additive used in the reference mix. The evaluation of fatigue damage in the mixes was performed using the four-point bending beam (4PB) test specified in European standard EN 12697-24. The test results show that the asphalt mixtures manufactured with WTTF-based additives exhibited a higher capacity to resist load cycles before failure compared to the reference mixtures. Likewise, once the asphalt mixtures were evaluated in a pavement structure by means of an empirical mechanistic analysis, the pavement structures composed of asphalt mixtures with WTTF-based additives showed significant improvements in their durability for the different load axes evaluated. For an average thickness of 15 cm of asphalt mix of a pavement-type structure, the use of the WTTF additive increases the durability of the structures by up to 129% and 112% compared to the HMA and SMA reference mixtures, respectively. These results show that both formats of the WTTF-based admixture improve the fatigue damage resistance of the HMA and SMA asphalt mixtures. [ABSTRACT FROM AUTHOR]

The undrained cyclic behavior of rubber-sand mixture (RSM) is usually investigated under the cyclic loads with unidirectional shear stress. However, bidirectional shear stress exists in many engineering practices subjected to complex loads, under which the liquefaction resistance of soil may be overestimated. Furthermore, the soil behavior under bidirectional shear stress exhibits quite differently from that under unidirectional shear stress. Therefore, undrained cyclic behavior of RSM under bidirectional shear stress should be further investigated. In this study, several specimens made by RSM with different rubber contents (from 10 % to 30 % by volume) are consolidated under two conditions, K0 consolidation and the combination of K0 consolidation with consolidation shear stress (CSS). Subsequently, numerous tests are conducted under the unidirectional and bidirectional cyclic loading paths to investigate the cyclic undrained behavior of RSM. The results show that the bidirectional shear loads incur a larger normalized pore water pressure (PWP) than unidirectional shear loads. In addition, an energy-based method is employed to understand the relationship between cumulative energy and normalized PWP. During the stage of rapidly accumulating PWP, the dissipated energy required to generate the same normalized PWP is identical, and it is independent of the shapes of loading paths.

(1) Background: Romanian earthquakes caused severe damage over time to a significant number of constructions, and that is why efforts are being made to make structural systems safer. (2) Methods: For structural systems with protection against seismic actions or vibrational actions that have linear viscous dissipation devices, the requirement to assess the equivalent modal damping rate for the entire functional assembly related to the other dynamic parameters arises. (3) Results: This article presents the analytical development of formulas for the compound damping and circular frequency when anti-seismic devices have different dynamic characteristics and their application in order to solve some real engineering cases of bridges and viaducts in Romania with distinct viscoelastic supports. In support of this idea, some experimental tests on a beam system resting on two different anti-seismic elastic supports highlighted the fact that the compound damping of the system can be calculated with the relations established in this paper, provided that the displacements in the horizontal direction of excitation are in the linear domain. Also, we determined the seismic response considering the Vrancea 1977 accelerogram for critical damping ratios of 5% and 18.5%, and then we obtained the variation in the factor of transmissibility depending on the frequency, in order to highlight the optimized value of the equivalent amortization/damping. (4) Conclusions: In the specific context of Romanian seismicity, seismic isolation through the use of isolators with different characteristics represents an optimal technical solution, and it is also optimal from an economic point of view, with an appropriate level of dynamic isolation obtained.

In the fatigue design and analysis of concrete structures, an understanding of the dissipated energy characteristics of the material under cyclic loading is important. However, due to the heterogeneity of concrete, the quantitative analysis of dissipated energy is extremely challenging. To investigate the evolution characteristics and influencing factors of dissipated energy, a series of fatigue tests were conducted. Four variable-amplitude cyclic loading schemes were designed to study the relationship between dissipated energy and stress levels, loading frequency, and loading history. The results show a three-phase characteristic of falling-stable-rising in the evolution of single-cycle dissipated energy. The steady value in the second phase is related to the fatigue damage accumulation rate and presents an exponential function with the maximum and minimum stress level. A stress level of 0.75 is considered as the threshold for evaluating the effect of loading history on fatigue damage. The total energy dissipated in the fatigue test has a lower limit close to the energy absorbed in the static test. The relationship between the total dissipated energy and the fatigue life can be described by a linear function in logarithmic coordinates. Based on the evolution characteristics of dissipated energy, a nonlinear fatigue life prediction formula was proposed from the linear damage accumulation model. This study is of great significance for the development and application of the energy-based concrete fatigue damage models. [ABSTRACT FROM AUTHOR]

Fatigue failure in asphalt pavements, caused by continuous loading, primarily occurs at the interface between the asphalt binder and the aggregate (adhesive failure) or within the asphalt binder itself (cohesive failure). This study conducted variable stress fatigue tests on asphalt binders to investigate the fatigue damage evolution mechanism that aligns most closely with actual road conditions. By altering test conditions such as stress amplitude and loading frequency, the study summarized the patterns of change in the fatigue performance parameters of binder samples and analyzed their fatigue life. The research methods employed are of significant value for refining the existing asphalt fatigue evaluation systems. Indicators such as dissipated energy ratio, cumulative dissipated energy ratio, rate of change in dissipated energy, and the G-R constant n × Gn* were used as criteria for fatigue failure. The fatigue life of samples under different stress levels was calculated, and the applicability of each dissipated energy fatigue indicator was evaluated. The evaluation indicators, like dissipated energy ratio and cumulative dissipated energy ratio, failed under large stress outside the non-linear viscoelastic range, whereas the rate of change in dissipated energy and the G-R constant n × Gn* accurately determined the fatigue life of samples in fatigue tests at all stress levels, covering a broader range of applicable stresses. In variable stress fatigue tests, the rate of change in dissipated energy and the G-R constant were used as indicators for determining fatigue failure. Under a small-to-large loading mode, the second stage of the sample's fatigue life was too short, causing the G-R constant curve to not reach its peak, and hence it could not accurately determine the sample's fatigue life. Under a large-to-small loading mode, there are sufficient loading cycles before fatigue failure occurs, allowing the G-R constant curve to reach its peak, demonstrating that the G-R constant remains applicable in this loading mode. Under both small-to-large and large-to-small loading modes, the fatigue failure point of the samples could be determined based on the rate of change in dissipated energy curve. It is recommended to use the rate of change in dissipated energy as the failure criterion for samples in variable stress fatigue tests on asphalt binders. [ABSTRACT FROM AUTHOR]

This research analyzes the fatigue behaviours of asphalt mixture under haversine wave and two more realistic loading waveforms induced by the single axle and tandem axles, based on the pseudo-strain-based approaches. It is found that the fatigue lives of asphalt mixture under the single-axle wave are higher than those under the haversine wave, while the tandem–axle wave generates the lowest fatigue life. This fact suggests testing asphalt mixture using the actual loading waves occurring in the field to improve fatigue life prediction of the asphalt layer. Three PSE-related indicators, namely initial dissipated PSE, cumulative dissipated PSE and the average changing rate of PSE per cycle, all generate a unique linear relationship with the mixture's fatigue life on the log–log scale. The linear relationship is independent of strain level and loading waveform. The damage characteristic curves of asphalt mixture obtained from the VECD approach are independent of strain level but affected by loading waveform. One of VECD-related indicators named DR stays stable as the loading wave or strain level changes, while another indicator named Sapp changes considerably at different waves and strain levels. The latter indicator shows the high potential to predict the asphalt mixture's fatigue life. [ABSTRACT FROM AUTHOR]

In this paper, the mechanical damage characteristics and energy dissipation patterns of fibre-reinforced cemented tailings backfill (FRCTB) under different strain rates are investigated based on the Hopkinson pressure bar apparatus equipped with confining pressure facilities, and this investigation is conducted by combining the theories of box fractal dimension and energy dissipation. The findings reveal notable observations: under lower confining pressures, the strain rate strengthening effect exhibits pronounced influences on both failure patterns and energy dissipation. However, as the confining pressure escalates, the strengthening effect gradually diminishes. The dissipation energy density displays an increasing trend with the rise in confining pressure, while the energy dissipation rate exhibits a quadratic decline as the strain rate increases. The stress-strain curves of FRCTB, under both unconfined and confined conditions, can be subdivided into four and five distinct segments, respectively. Under the lower confining pressure conditions, the fractal dimension exhibits linear growth with the increasing dissipation energy. As the confining pressure increases, this trend gradually transforms into a cubic function. Remarkably, a strong resemblance emerges between the fractal dimension, energy dissipation rate, strain rate, and confining pressure, reflecting the intricate interplay among these crucial mechanical parameters. [ABSTRACT FROM AUTHOR]

The fracture features of shape memory alloy samples (nitinol) under low-cycle fatigue with different load frequencies (0.1; 1 and 10 Hz) were investigated. The frequency dependences on the number of cycles before the samples fracture, the maximum, and the residual deformation before and after their fracture, respectively, were analyzed. The maximum value of the dissipated energy in the load cycle decreases with an increase in frequency from 0.1 to 10 Hz. Fractography showed that the mechanism of samples fatigue failure depends on the loading frequency. At high frequency classical fatigue striations decorated with secondary cracks dominated at the nitinol fracture surface. While at low frequency, a special type of striated relief with alternate changes in the striation spacing and the orientation of shear planes, in which a local crack growth occurred in the loading cycle, were found. The appearance of fatigue striations was explained by phase transformations inherent in nitinol, due to the rearrangement of its crystal lattice at the crack tip with multiple direct and reverse phase transformations (austenite→martensite→austenite), respectively which occur in half-cycles of loading and unloading of samples. [ABSTRACT FROM AUTHOR]

We examine the effect of sample geometry and analysis procedures on the fatigue life results of asphalt mastics obtained using the linear amplitude sweep (LAS) test. Asphalt mastic samples are prepared using two fillers (Red mud and Limestone), one base binder (VG-30) and three filler binder (F-B) ratios (0.5, 1, and 1.5 by weight (w/w)). The LAS test is conducted on mastic samples using cylindrical and hyperbolic geometry at three different temperatures (+10 ∘C, +20 ∘C, and +30 ∘C). We use the dissipated energy (DE) based approach, pseudo-strain energy (PSE) based approach, and R-based approach to calculate the fatigue life of asphalt mastic samples. The fatigue ranking of asphalt mastics at varying temperatures for each test geometry is found to be independent of the analysis procedure. PSE-based approach gives the highest fatigue life followed by DE- and R-based approaches, respectively. The effect of geometry is quantified using the variation of dissipated energy versus strain level. This study suggests that the LAS test can only characterize the accurate fatigue performance of the asphalt mastic if the amplitude of the complex modulus is less than 20 MPa. Hyperbolic geometry is found to be more effective in the quantification of fatigue damage of asphalt mastics. [ABSTRACT FROM AUTHOR]

This study established a rapid estimation method for the fatigue limit of laser welds of aluminum alloys in order to optimize welding conditions, an important factor in ensuring the safety and reliability of laser welding. This study focused on an estimation method of fatigue limit based on the dissipated energy. Dissipated energy is the temperature change caused by local plastic deformation. The stress amplitude at which the temperature change due to dissipated energy rapidly increased in the laser welds was defined as the estimated fatigue limit, and it was almost consistent with the fatigue limit of the joint. [ABSTRACT FROM AUTHOR]

This study explores the hysteresis phenomenon in DPPC (1,2-dipalmitoyl-sn-glycero-3-phosphocholine) monolayers, considering several variables, including temperature, compression and expansion rates, residence time, and subphase content. The investigation focuses on analyzing the influence of these variables on key indicators such as the π-A isotherm curve, loop area, and compression modulus. By employing the Langmuir–Blodgett technique, the findings reveal that all the examined factors significantly affect the aforementioned parameters. Notably, the hysteresis loop, representing dissipated energy, provides valuable insights into the monolayer's viscoelasticity, molecular packing, phase transition changes, and resistance during the isocycle process. These findings contribute to a comprehensive understanding of the structural and dynamic properties of DPPC monolayers, offering insights into their behavior under varying conditions. Moreover, the knowledge gained from this study can aid in the development of precise models and strategies for controlling and manipulating monolayer properties, with potential applications in drug delivery systems, surface coatings, as well as further investigation into air penetration into alveoli and the blinking mechanism. [ABSTRACT FROM AUTHOR]

Colloidal silica (CS) grouting is a soil improvement technique for seismic liquefaction risk mitigation consisting of the injection of a time-hardening, colloidal silica–based grout into potentially liquefiable sandy soils. A published laboratory test database—consisting of cyclic undrained triaxial tests on liquefiable clean untreated sand and on sand stabilized by 5% CS under different levels of initial stress anisotropy—is here discussed following an energy-based approach. The test results are presented and analyzed in terms of dissipated energy during cyclic loading. The obtained results show that (1) the development of dissipated energy is clearly related to the buildup of residual extra pore water pressure only for untreated sand samples; (2) under the same testing conditions, the dissipated energy at failure is significantly higher in stabilized sand than in untreated sand; and (3) the dissipated energy at failure is found to be independent of the cyclic stress amplitude and dependent on the degree of initial stress anisotropy for the untreated sand, while opposite trends are observed for stabilized sand. Therefore, contrary to the untreated sand, there is no evident advantage for using the dissipated energy at failure to assess the capacity of the stabilized sand. [ABSTRACT FROM AUTHOR]

Extended service life of components is playing an increasingly important role in society and economy. Accordingly, this also applies to elastomeric materials, which are used for example for tires, seals, and hoses. These are often exposed to cyclic loading, with crack initiation and growth playing a decisive role. Corresponding phenomena have been investigated for many years and are still not fully understood. For the fatigue behavior, the crosslinking state of the material is of particular importance. This is accompanied by various production parameters, such as processing temperature and curing time, which have been of little importance in research to date. For this reason, plain strain test specimens out of nitrile butadiene rubber (NBR) were produced by injection molding at different mold temperatures and crosslinking times in the present work. With the aid of these, the crack growth rate at different crosslinking states under cyclic loading was investigated. It has been shown that a longer crosslinking time toward fully cured specimens results in a 20% reduction in dissipated energy, with a corresponding increase of the crack growth rate by the factor of 100. Furthermore, a 20 K increase in mold temperature during manufacturing of fully cured specimens leads to a four times slower crack growth.

While usually we don't know complete geometrical and physical information on the occurred inhomogeneity, but in order to study the related phenomena, continuum mechanics theory as well as exiting energy-based models need direct information from the desired system in order to A General Approach to the Mechanical Analysis of Continuous Local Inhomogeneity Using Continuum Mechanics Theory and A New General Energy-Based- Modelapply the field equations. Of course, theories and ideas based on the unification of mechanics and thermodynamics can offer other solutions. This paper establishes a general energy based model to study effects of local inhomogeneity on the mechanical behavior of materials using thermodynamic laws with a new deviation as well as new approach to the total energy. In fact, the main goal is that the established model can be used with a wide range of applications and appropriate accuracy, both theoretically and experimentally, while not getting involved with excessive computational complexity. It can be noted that the extracted formulations develop possibility to study inhomogeneity effects on the mechanical behavior without any more limiting conditions. In addition, due to that study of the stored and dissipated energy, usually, has the main role in the investigating of the inhomogeneity effects on the mechanical behavior, also the point of view in the presented model is in complete agreement to provide the conditions for this study directly. Therefore, the prediction possibility of the inhomogeneity effects on the mechanical behavior will be provided with the smallest volume of needed calculations. Also, due to that the structure and properties of the inhomogeneity are unknown usually, the formulations aren't dependent to these knowledge directly, and can be analyzed theoretically and experimentally to study the homogeneity part, as a known material. In the following, feasible processes are studied using extracted formulations. To validate the equations, a rectangular material shape with local inhomogeneity is considered, and extracted equations are developed for that. To consider our mean on the stored and dissipated energies, it is assumed that the homogeneity part of material has viscoelastic behavior, and the equations are developed to Maxwell and Kelvin viscoelastic models in different homogeneity parts of the body. In the following, classical continuum mechanic theory due to elasticity theory is used, and the field equations are developed to the considered body. Finally, results are discussed, compared as well as their differences, and corresponding capabilities for functional completion are discussed. Finally, the fundamental equivalence of the results is studied, and matching of the results between continuum mechanics theory and extracted formulations is shown.

Wireless body sensor networks may be defined as an aggregate of smart sensor nodes that are deployed in the human body primarily for remote health monitoring purposes. These characterize systems that monitor the daily routine activities of the host without having any adverse effect on the health of or hinder the activities of the individual. Such networks are quite efficient in the detection of health complications that may arise due to sustained comorbidities such as diabetes, asthma, heart attacks, etc. This makes them a highly desirable field of research: optimum models may serve well to bridge the demand gap in the medical healthcare field and ensure that patients can get quality healthcare in critical time frames. One of the medical subdomains that has the highest discrepancy of doctor to patient ratio is the psychotherapy discipline. The present work aims to suggest a packet transmission protocol that can be employed specifically in this field. Wireless body area networks, in the field of psychology, can be used in the discipline of cognitive-behavioral therapy. These sensor networks can manifest themselves as multimedia tools that can be used in elevated gameplay. This in turn can help with the emotional regulation of afflicted individuals. Since gamification of cognitive-behavioral therapy would produce optimum results when the model is fed appropriate real-time data, the establishment of a highly efficient, low-latency sensor network is required to make this multimedia application a success. The present article thus focuses on the enhancement of energy characteristics of the transmission protocol employed. To enhance system performance, a new packet transmission model has been proposed and presented. This is a keystone disadvantage in many of the existing methodologies for WBAN data transfer as well. A systematic comparison of the output characteristics of the multiple forwarding functions proposed therein has also been performed. The results produced as a consequence of these exercises indicate superior model performance in terms of both energy consumption and packet volume when compared to baselines such as the SIMPLE, ATTEMPT, iM-SIMPLE, etc. [ABSTRACT FROM AUTHOR]

An approach to determine the specific energy dissipated during cyclic loading of metal alloys with load ratios between 0 and 1 is developed. The dissipated energy per cycle is determined by using a limiting procedure to obtain the area enclosed between successive loading and unloading curves and can be used for low‐, medium‐, and high‐cycle fatigue. Comparisons with published data from two aluminum, one titanium, and one steel alloy show that the predictions capture the test results very well. A universal curve relating cycles to failure to two nondimensional parameters is derived. It is shown, in some limiting cases, that the method leads to power law equations with the parameters in these equations determined directly from the complete stress–strain curve of the material with no need to fit experimental data. Furthermore, if certain conditions are satisfied, the method is consistent with the existence of an endurance limit and Miner's rule. Highlights: Model describing the shape of loading and unloading curves during fatigue is developed.A closed‐form expression for the fatigue cycles to failure initiation is obtained.A single master curve for fatigue is created in terms of two variables.Comparisons with test results for four alloys show good to excellent agreement. [ABSTRACT FROM AUTHOR]

The surface and interior of natural frozen soil often feature numerous holes, cracks, and other initial defects of different sizes. In this study, three types of circular holes with different diameters were prefabricated on the surface of frozen soil samples, and a dynamic compression test was conducted using a split Hopkinson pressure bar (SHPB) device. The hole and temperature effects of frozen soil with prefabricated holes were explored. Meanwhile, fractal theory was used to show the self-similarity of the sample fragment after impact crushing, and its fractal characteristics were determined using the fractal dimension. Combined with the one-dimensional stress wave theory applied from the SHPB, the influence of temperature and diameters on the energy dissipation characteristics of defect samples was analyzed. Finally, to determine the coupling effect of temperature and diameter, an energy-based dynamic constitutive model was established to describe the dynamic stress–strain behavior of the frozen soil samples with prefabricated holes. The results indicated that the model could better describe the diameter sensitivity and temperature dependence of the defect samples, and the calculation results were in good agreement with the experimental results. [ABSTRACT FROM AUTHOR]

The present paper analyses some possibilities to improve the provisions concerning the seismic design of diagonal braced frames according to the in charge European and Romanian seismic design code (EN 1998‐1:2004 [1], respectively P100‐1/2013 [2]). Three design variants were used for the dimensioning under seismic actions of two ten story concentrically braced frames, taking into consideration different contributions of the tensioned and compressed braces in carrying horizontal seismic forces. The considered braced frames had two spans of 6.0m and ten storey of 3.5m. One of the frames had ascendant diagonal braces (from the lateral columns to the central column) and the other had descendant diagonal bracings (from the lateral columns to the central column). Static nonlinear analyses were performed with all the designed variants of the frames. The loading and deformation states at different steps during the analyses were compared. The distribution of plastic hinges in the structure was analysed. A more favourable behaviour of the frame during static nonlinear analysis was ensured by providing reduced cross‐sections along all frame girders ends (resembling the dog‐bone detail). [ABSTRACT FROM AUTHOR]

T-shaped fractured rocks in the engineering rock mass with different inclination angles, quantities, and cross patterns will cause slope landslides, cavern collapse, roof fall, and other disasters under the action of external forces. Deformation evolution of the T-shaped fractured rock is also significant for monitoring the stability of rock engineering structures. In this paper, the compression test of T-shaped fracture specimens was carried out under different loading rates. By modulating both the fracture inclination angle and the loading rate, the attributes pertaining to energy dissipation in the T-shaped fractured specimen were scrupulously scrutinized and subsequently expounded upon. The difference in the energy characteristics between fractured rock and intact rock was investigated to understand the deformation evolution of T-shaped fractured rock samples. The results show that when the fracture angle is 45° and 90°, the elastic strain energy and dissipated energy decrease as the secondary fracture angle increases. At the peak point, as the secondary fracture angle increases from 0°, the total absorbed energy, elastic strain energy, and dissipated energy of the T-shaped fractured rock increase, the ratio Ue/U of elastic strain energy to total energy increases, and the ratio Ud/U of dissipated energy to total energy decreases. The increase in loading rate leads to an increase in Ue/U and a decrease in Ud/U at the peak point of the T-shaped fractured rock specimen. The increase in loading rate leads to an increase in the total absorbed energy and elastic energy at the peak point of the T-shaped fractured rock, while the dissipated energy decreases. Investigative endeavors into the mechanics and energetic attributes of T-shaped fractured rocks bestow pragmatic and directive significance upon the safety assessment and stability prognostication of sundry geological undertakings. [ABSTRACT FROM AUTHOR]

Surrounding rock deformation and consequent support failure are the most prominent issues in red-bed rock tunnel engineering and are mainly caused by the effects of unloading, rheology, and swelling. This study investigated the mechanical responses of two kinds of red-bed mudstone and sandstone under unloading conditions via laboratory observation. Volume dilation was observed on the rocks during unloading, and the dilatancy stress was linear with the initial confining pressure. However, the ratios of dilatancy stress to peak stress of the two rocks kept at a range from 0.8 to 0.9, regardless of confining pressures. Both the elastic strain energy and the dissipated energy evolved synchronously with the stress–strain curve and exhibited conspicuous confining pressure dependence. Special attention was paid to the evolution behavior of the dilatancy angle. The dilatancy angle changed linearly during unloading. When the confining pressure was 10 MPa, the dilatancy angle of mudstone decreased from 26.8° to 12.5° whereas the dilatancy angle of sandstone increased from 34.6° to 51.1°; when the confining pressure rose to 25 MPa, the dilatancy angle of mudstone and sandstone decreased from 45.8° to 17.4° and increased from 21.7° to 39.5°, respectively. To further understand the evolution of the dilatancy angle, we discussed the links between the variable dilatancy angle and the processes of rock deformation and energy dissipation. [ABSTRACT FROM AUTHOR]

In this work, ink‐jet 3D printing materials were developed and investigated. Additionally, a UV‐thermal dual‐curable prepolymer was synthesized and introduced into liquid crystal display (LCD) 3D printing material. Subsequently, a UV‐thermal dual‐cured 3D printing material was developed as well. The different light stabilizers, photoinitiator content and different thermal annealing time were studied to reveal these effects on the mechanical properties of the ink‐jet 3D printed samples. FTIR was used to analyze the deblocking effect of blocked isocyanate in the synthesized resin. The mechanical properties of the UV‐thermal dual‐cured materials at different thermal annealing time and different ratios of UV content to thermal content were discussed. Scanning electron microscopy (SEM) was utilized to reveal the microscopic morphology of UV‐thermal dual‐cured material before and after thermal annealing. Finally, the dissipated energies of different 3D printing materials were revealed to indicate the difference in internal structure between ink‐jet, LCD and UV‐thermal dual‐cured 3D printing materials. [ABSTRACT FROM AUTHOR]

There has been little research on the impact resistance of mortar–rock slope protection structures. To ensure that the mortar–rock interface has good adhesion properties under the action of impact loading, in this paper, based on fracture mechanics theory, a theoretical impact model was established for mortar–rock binary material. Dynamic fracture tests were carried out on mortar–rock interfaces using the split-Hopkinson pressure bar (SHPB) system. The Brazilian disc (CSTBD) specimen was prepared with one half in granite and the other half in mortar. The specimen used for the dynamic impact test was 48 mm in diameter and 25 mm thick. The effects caused by the change in interface inclination and interface shape on the dynamic fracture mode were discussed. The dynamic model parameters were obtained for different inclination angles and interfaces. The results show that both the interface inclination and interface shape have significant effects on the dynamic mechanical properties of the mortar–rock binary material. The fracture modes of the mortar–rock specimens can be classified into three types. When the interface inclination is 0°, the specimen shows shear damage with an interface fracture; when the interface inclination is in the range of 0–90°, the dynamic splitting strength of the mortar–rock material increases with increasing interface inclination, and the interface undergoes composite fracture; and when the interface inclination is 90°, the dynamic splitting strength of the specimen reaches its peak, and the interface undergoes tensile fracture. The mortar–rock interface damage follows the M-C criterion. The roughness of the interface shape has a large influence on the dynamic splitting strength of the specimens. The rougher the interface shape, the higher the interface cleavage strength and the higher the peak load that causes the material to damage. The results of this study can provide a reference for the design of mortar–rubble structures to meet the demand for impact resistance and have strong engineering application value. [ABSTRACT FROM AUTHOR]

Reclaimed asphalt pavement (RAP) has been widely used in asphalt pavement. However, the fatigue performance of hot-mix asphalt (HMA) with RAP is a critical factor to ensure durability. In this study, fatigue tests using an Overlay Tester (OT) were conducted using a novel load-controlled mode. RAP contents were 0, 25% and 50%, respectively. In the cyclic loading, fatigue life and energy parameters were measured. Results indicated that RAP decreased both the fracture energy and tensile strength. Fatigue life was determined using two methods. RAP was proved to be beneficial in prolonging the fatigue life using the two methods at 25 °C. However, opposite conclusions were made about the effect of RAP on fatigue life at −10 °C. At −10 °C, compared to HMA without RAP, the cumulative dissipated energies decreased by 49.1% and 77.3% when RAP contents were 25% and 50%, respectively. At 25 °C, compared to HMA without RAP, the inclusion of 25% RAP increased the cumulative energy by 31.1%, while 50% RAP decreased the cumulative energy by 41.2%. The developments of the dissipated energy and the cumulative energy were consistent with the fatigue life results determined by the first method. [ABSTRACT FROM AUTHOR]

Incorporating masks into building materials offers a potential solution to the environmental threat of disposable masks with promising material performance. However, research on their dynamic properties is lacking to further determine the application range of the new composite. This study addresses this gap by shredding face masks into strips and incorporating them into mortars at varying volume ratios. The integrity and compactness of the mortar was measured and characterized by P-wave velocity, while dynamic compression properties were explored using a split Hopkinson pressure bar (SHPB) system. Subsequently, sieve analysis was conducted on the fractured specimens. The results indicate that incorporating masks generally improves the mortar integrity and the fragmentation after impacting. The dynamic uniaxial compression strength (DUCS) decreased for all mixing designs compared to plain ones under a constant loading rate. Meanwhile, the dissipated energy density showed a similar trend to the P-wave velocity, exhibiting less pronounced enhancement at higher loading rates. According to the dynamic characteristics, a dynamic constitutive model based on the Lemaitre principle and Weibull distribution of damage is developed and validated. The test results are further understood through the perspective of the mechanism of mask inclusion.

Ceramic detachment is a serious problem that persists in modern building constructions despite technological advances and updated regulatory documents. Most of these detachments occur at the interface between the adhesive mortar and the ceramic tile, due to the action of simultaneous tensile and shearing efforts. However, despite this understanding, experimental studies that evaluate the integrity of the adhesion of façades covering materials subjected to simultaneous stress are scarce. In this sense, this study proposes to evaluate the integrity of adhesive mortar joints using the mixed-mode flexure (MMF) crack propagation test. Force and elastic and dissipated energy data were used in this analysis. Prismatic specimens, with a size of 160 × 40 mm2 and a thickness of 6 mm, were produced consisting of two ceramic plates joined by a layer of adhesive mortar at 5 ± 0.5 mm. An acetate film was inserted into one of the mortar–ceramic interfaces in order to simulate the presence of a previous crack, and different crack sizes were used. The results showed the high stress-concentrating effect that the existence of flaws in the interface region has on fracture resistance, as well as the importance of effective contact between the materials. The energy parameters confirmed the analyses carried out based on the load values. The elastic energy of the system fell in the cracked samples, showing that there is a close relationship between the interface energy and the adhesive strength of the material. An energy release of the order of 0.053 ± 0.031 J was required for a 15 mm crack to propagate, creating a fracture surface.

This study established a rapid estimation method for the fatigue limit of laser welds of aluminum alloys in order to optimize welding conditions, an important factor in ensuring the safety and reliability of laser welding. This study focused on an estimation method of fatigue limit based on the dissipated energy. Dissipated energy is the temperature change caused by local plastic deformation. The stress amplitude at which the temperature change due to dissipated energy rapidly increased in the laser welds was defined as the estimated fatigue limit, and it was almost consistent with the fatigue limit of the joint.