Residual Strain Behavior Research Articles

Experimental and numerical study on the mechanical properties of NiTi-SMA bars

This paper presents an experimental investigation that aims to study the mechanical properties of NiTi shape memory alloy (SMA) bars, with a particular emphasis on comprehensively evaluating their superelastic properties and energy dissipation capabilities. The study examines the influence of thermal treatment processes, loading rates, pre-training, and loading amplitudes on crucial parameters such as residual strain, energy dissipation capacity, initial stiffness, and equivalent viscous damping ratio of SMA bars. Additionally, the microstructure of the SMA bars' cross-sections, both prior to and following thermal treatment, is examined using scanning electron microscopy. The existing Graesser constitutive model is improved, and its validity is verified through numerical fitting. The findings demonstrate that SMA bars with a direct working section of 10 mm exhibit favorable superelastic properties after undergoing heat treatment at 350 °C for 35 min. It is recommended that the loading rate of SMA should not exceed 0.15 % per second, and appropriate pre-training measures should be implemented in practical engineering applications. Microstructural analysis reveals distinct dimples and intergranular fracture marks in the cross-sections of heat-treated SMA bars, indicating a high level of material toughness. Moreover, the improved Graesser constitutive model accurately calculates the mechanical characteristics of SMA bars and effectively describes their residual strain behavior. The research outcomes of this study provide valuable theoretical and technical insights for the practical application of shape memory alloy bars in engineering contexts.

Residual strain investigation of a polycrystalline quartzite rock sample using time-of-flight neutron diffraction

In this work, we studied the residual micro lattice strain of an onyx sample, which is a micro- to the cryptocrystalline variety of the mineral quartz SiO2. That the investigation has been carried out using in-situ stress experiments with the time-of-flight neutron diffraction method. The aim of the study is to investigate residual lattice strains and pressure directions in the sample using time-of-flight neutron diffraction, which is a powerful tool for the study of the residual strain behavior in bulk materials, like geological rock samples containing large grains. The residual strain was detected in different sample directions turning the sample in steps of 30° by 180° around the cylindrical z-axis. These experiments have been performed at the time-of-flight neutron strain diffractometer EPSILON, situated on the pulsed neutron source IBR-2M of the Joint Institute for Nuclear Research in Dubna, Russia. The results of this study will provide insights into the compressional and tensional residual strain of the crystallographic lattice planes, and will have implications for our understanding of the tectonic history of this region. These different strains are arranged in the sample by a sinusoidal distribution in radial directions.

The regional-dependent biaxial behavior of young and aged mouse skin: A detailed histomechanical characterization, residual strain analysis, and constitutive model

Skin fulfills several vital functions, many of which are dependent on its mechanical properties. Therefore, as mice have become an invaluable model for skin research, determining murine skin's mechanical properties is important. Specifically, skin's mechanical properties are important for functional tests as well as for prognostic and diagnostic purposes. Additionally, computational simulations of skin behavior are becoming commonplace, rendering accurate models of murine skin's constitutive behavior necessary. To date, our knowledge of mouse skin mechanics shows significant gaps. For example, there are no comprehensive reports correlating skin's mechanical properties with region, age, and direction. Moreover, mouse skin's residual strain behavior has not been reported on. In our current work, we set out to fill these gaps. Based on histology, 2-photon microscopy, and planar biaxial testing, while accurately tracking various reference configurations, we report on differences in gross structure, microstructural organization, and constitutive response of skin, and cast those properties into a versatile Fung-type hyperelastic constitutive law for three reference configurations. Our data is the most comprehensive report contrasting the mechanical properties of young (12 weeks) and aged (52 weeks) mouse skin and will, thus, be valuable to basic science as control data, and provide accurate constitutive laws for mouse skin modeling. Statement of significanceOur findings are significant as they fill several gaps in our understanding of mouse skin mechanics. This is particularly important as mouse skin is becoming a frequent and critical model of human skin for cosmetic and medical science. Specifically, we quantified how mechanical properties of mice skin vary with age, with location, and with direction. Additionally, we cast our findings into constitutive models that can be used by others for predictive computer simulations of skin behavior.

The Regional-Dependent Biaxial Behavior of Aging Mouse Skin: A Detailed Histomechanical Characterization, Residual Strain Analysis, and Constitutive Model

Skin fulfills a number of vital functions, many of which are dependent on its mechanical properties. Therefore, as mice have become an invaluable model for skin research, determining murine skin's mechanical properties is important. Specifically, skin's mechanical properties are important for functional tests as well as for prognostic and diagnostic purposes. Additionally, computational simulations of skin behavior are becoming commonplace, rendering accurate models of murine skin's constitutive behavior necessary. To date, our knowledge of mouse skin mechanics shows significant gaps. For example, there are no comprehensive reports correlating skin's mechanical properties with region, age, and direction. Moreover, mouse skin's residual strain behavior has not been reported on. In our current work, we set out to fill these gaps. Based on histology, 2-photon microscopy, and planar biaxial testing, while accurately tracking various reference configurations, we report on differences in gross structure, microstructural organization, and constitutive response of skin, and cast those properties into a versatile Fung-type hyperelastic constitutive law for three reference configurations. Our data is the most comprehensive report on the mechanical properties of mouse skin and will, thus, be valuable to basic science, as control data, and provide accurate constitutive laws for mouse skin modeling.

Thermal expansion on volcanic tuff rocks used as building stones: examples from Mexico

Three cities in the center of Mexico, declared as cultural heritage, were erected mainly of volcanic tuffs as main construction element. Many of the historic buildings of these cities show significant damage and deterioration. One of the causes of these damages can be attributed to a phenomenon poorly studied in volcanic tuffs, the thermal expansion. To understand the response of volcanic tuffs to thermal expansion, as well as to know their thermal expansion coefficient, thermal expansion test was performed on 12 representative tuffs of these localities. In the same way and to know which of their petrographic, petrophysical, mineralogical, and geochemical properties influence this phenomenon, several laboratory studies were carried out to determine which of these plays an important role in the expansion. The results of our tests showed that volcanic tuffs rocks have very varied thermal expansion values, ranging from 0.7 mm/m at their maximum expansion to even contraction in the order of − 0.5 mm/m. Equally varied were the thermal expansion coefficient values ranging from 10.1 to − 7.2 10−6/K. The most dominant behavior type is the “anisotropic no residual strain behavior”. In general, the behavior of the tuffs in practically all the tests carried out showed a very important heterogeneity in the rocks; however, in spite of the non-homogeneous behavior of the tuffs, three main factors could be identified that play an important role in the thermal expansion of the studied rocks, the chemical composition, e.g., acid volcanic tuff rocks (rhyolitic composition) had greater expansions, while the more basic rocks (basaltic composition) expanded less, the textural and fabrics homogeneity, e.g., the most homogeneous rocks texturally have higher expansion values and the degree of crystallinity, and, e.g., the tuff rocks with the largest amount of glass showed smaller thermal expansions than the tuffs composed of microcrystals.

Experimental validation of vibration-excited subsidence model of seasonally frozen soil under cyclic loads

Validation of the vibration-excited subsidence model is limited for seasonally frozen soil. Based on constant-amplitude load tests by a new low-temperature triaxial device under realistic confining pressure, amplitudes of dynamic stress, consolidation and freezing methods, we determined the residual strain behavior and validated the vibration-excited subsidence model of frozen soil during frozen period considering the influence caused by temperatures, loading amplitudes and loading cycles. Results show that the residual strain during the frozen period increased with increasing cycles of loading, but decreased with decreasing temperatures. The residual strain development model indicates that residual strain increased dramatically in the initial loading cycles followed by a gradual increase over time. In most cases, the frozen soils tested are not failing that the developing curves of residual strains under different temperatures develop nearly parallel after certain cycles of loading. Residual strain was fairly sensitive to the negative temperatures at large amplitudes of dynamic stress, and the influence of low temperature was limited after a critical temperature in −5°C to −10°C. The two-parameter exponential model is able to express exactly the change rule of vibration-excited subsidence under different temperature. With the increase of dynamic stress amplitude, parameters A and B increase rapidly, especially when the soil approaches the failure state. In contrast, parameters A and B decrease as temperature decreases, but decrease little as the temperature decreases below the critical temperature. Our test layout overcomes previous testing limitations such as excessively large consolidating pressure and dynamic loading so that the test results are more consistent with the real conditions of seasonally frozen soil. The vibration-excited subsidence of subgrade in seasonally frozen soil regions could be predicted through this model.

Experimental Investigations on the Residual Strain Behavior of a Rockfill Material Subjected to Dynamic Loading

AbstractA large-scale triaxial testing apparatus was upgraded by incorporating two pressure stabilization techniques so as to suppress the confining pressure fluctuation in dynamic experiments. The...

Residual strain analysis of non-prestressed reinforcement in PPC beams under fatigue loading

This paper presents the results of an experimental and analytical study on the residual strain behavior of non-prestressed reinforcement in partially prestressed concrete (PPC) beams under fatigue loading. For the strain measurements, fiber Bragg grating sensors were used. Two beams were initially tested under monotonic loading in order to determine their ultimate load-bearing capacity. Six were tested under fatigue loading conditions. The experimental results show that fatigue failure mode of PPC beams is fracture of the non-prestressed reinforcement. Moreover, residual strain in the non-prestressed reinforcement gradually increases during the fatigue life and the corresponding residual strain evolution can be divided into three stages. Finally, an analytical model for estimating the residual strain of non-prestressed reinforcement in beams is developed. Comparisons of the predicted curves with the experimental data indicate a good agreement. The results of investigation in this paper furnish the experimental basis for the fatigue design and analysis of PPC beams.

Time-dependent damage accumulation under stress relaxation testing of bovine trabecular bone

Time-dependent loading of trabecular bone consists of both cyclic and sustained static loads. Numerous studies have investigated the effects of fatigue and creep loading on the apparent and damage behavior of bone; however, microdamage formation in trabecular bone under stress relaxation tests has not been characterized. Bovine trabecular bone specimens (1.5–3 years old) were loaded in uniaxial compression to 0.9% strain and held for six different time points: 0 s, 250 s, 2000 s, 5000 s, 10,800 s, and 36,000 s. Total microdamage increased with hold time and leveled off after 10,800 s. The qualitative patterns of microdamage progressed from surface damage for short hold times to microcracks extending through the trabecular thickness as hold time increased. Residual strain behavior corresponded well with microdamage formation over time. These results indicate that under static compressive deformation, microdamage accumulation leads to the development of residual strains with time. This mechanism has important implications on reloading of specimens where degradations in bone strength may contribute to age-related skeletal fragility and traumatic fractures.