Elastic Limit Research Articles

ВЛИЯНИЕ СУБМИКРОСКОПИЧЕСКОЙ СТРУКТУРЫ СПЛАВА «МЕДЬ — БЕРИЛЛИЙ» НА СЛУЖЕБНЫЕ ХАРАКТЕРИСТИКИ УПРУГИХ ЧУВСТВИТЕЛЬНЫХ ЭЛЕМЕНТОВ

The dependence of the properties of elastic sensitive elements made of beryllium bronze on the modes of their heat treatment is studied. It is shown that the duration of aging significantly affects the value of nonlinearity of elastic characteristic, hysteresis, shrinkage of elements and mechanical properties of membrane material (hardness, elastic limit). The relations between submicroscopic structure and properties of elastic elements are established. The greatest nonlinearity of the elastic characteristic, hysteresis and shrinkage belong to elements subjected to short-term aging at 310–350 °С. With increasing duration of aging, the corresponding values of the above parameters decrease. For aging temperatures 310–320 °С, the nonlinearity of elasticity characteristics reaches the minimum values after 4–5 h of aging, and for 340 °С — after 3 h. At 350 °С minimum values of nonlinearity are reached after aging duration of 45–60 min. From the obtained data it follows that from the point of view of obtaining the minimum hysteresis and nonlinearity characteristics of aneroid sensing elements made of bronze of БрБНТ-1,9Мг (BrBNT-1.9Mg) grade, heat treatment of membranes should be carried out according to the regimes of 1 h at 350 °С or 3 h at 340 °С.

Damage State of Non-Engineered Residential Buildings Owing to Earthquakes: A Case Study in Pacitan Regency, Indonesia

Abstract The Pacitan Regency of Indonesia is located in an area of high seismic activities. Regrettably, field surveys held in Pacitan Regency, Indonesia have revealed the prevalence of low-income housing structures that do not meet the engineering standards and are vulnerable to damage during earthquakes. The seismic evaluation of these buildings is urgently required. This study proposes realistic damage state limit values for the seismic damage evaluation of non-engineered buildings. For this purpose, an incremental dynamic analysis was conducted on a sample of non-engineered buildings in Pacitan to evaluate their probable seismic damage. As a result, curves showing the dynamic pushover responses of buildings to various input earthquakes were plotted. These curves were then summarized as three-linear curves, providing a single value for the average response of the structure. Based on this simplified curve, a more realistic damage-state limit for non-engineered structures are proposed. The damage levels of slight (DS1), moderate (DS2), extensive (DS3), and complete (DS4) were determined using the drift ratio at the linear elastic limit, midway point between the linear elastic and yield limits, yield state, and 80% rupture limit, respectively.

Effects of heat, moisture/water, and compressive force on frequency response spectrum of super sensitive carbon nanofiber aggregates (SSCNFA)

Cement-based sensors should exhibit accurate measurements of strain with high sensitivity and reliability under various environmental conditions. The ability of such sensors to perform in adverse situations needs to be well developed and critically examined. Cement-based sensors are generally embedded in structural/non-structural concrete components for health monitoring. This paper provides an in-depth study of the performance and response of Super Sensitive Carbon Nanofiber Aggregates (SSCNFA) under challenging and adverse environmental conditions, including different temperature, moisture/water exposure, and compressive forces. The SSCNFA detects changes in temperatures, moist environments, and compressive forces through changes in the electrical impedance. In this study, the change in the total impedance of SSCNFAs are experimentally examined by alternating current (AC) measurements (20 Hz–300 kHz) under various environmental conditions. The thermal tests (21 °C–120 °C) and the impedance recovery tests examine and elaborate the phenomenon of resistance and total impedance reduction. The waterproofing test identifies the suitable polymer to prevent moisture percolating through the SSNCFA. Also, compression tests examine the stress/strain sensing through piezoresistivity in the linear elastic limit of the SSCNFA. The effects of these external conditions in the selective frequency range are measured to monitor the stability, reliability, recovery, and performance of the SSCNFA.The research reveals that the SSCNFA exhibited a linear electrical response against the temperature at higher frequencies (higher or equal to 10 kHz) with a standard deviation of less than 5 %. The SSCNFA's porous structure absorbs moisture during concrete casting. This absorbed moisture will be influenced by the environmental temperature variations and mechanical stresses during the service period of the structure. Additionally, the impedance recovery test results of uncoated SSCNFAs provide insight into the frequency response against the moisture/water and the stability of electrical response at the higher frequencies (higher or equal to 100 kHz). The waterproofing of the SSCNFA using M-coat A and M-coat B (polymers) proves to be effective, with the waterproofed SSCNFA sensor embedded in concrete exhibiting stress-sensing ability due to piezoresistivity. The electrical response of the SSCNFAs is more sensitive to temperature, moisture/water, and compressive stresses at low frequencies with higher standard deviations than at higher frequencies. Therefore, the experiments performed on SSCNFAs show that the SSCNFA embedded in a concrete structure is suitable for structural health monitoring. Furthermore, this research offers various avenues for the application of the SSCNFA as a multifunctional tool for temperature sensing and moisture detection of concrete structures due to cracks at critical locations.

Biomechanical characteristics of the meniscocapsular junction of the posterior segment of the medial meniscus.

Despite extensive literature available on the mechanical properties of knee ligaments and menisci, research on the mechanical properties of the meniscus-capsular junction (MCJ) is lacking. This study aims to investigate the biomechanical behavior of the MCJ of the medial meniscus using a tensile failure test. Seven dissected cadaveric knees were used for biomechanical analysis. Tensile failure tests were performed using an INSTRON ElectroPuls E1000 stress system to measure stress/strain curves, maximum load at failure, elastic limit load, elongation at break, elongation at the elastic limit, and linear stiffness, were collected and analyzed. All ruptures occurred at the MCJ. The MCJ displayed similar mechanical properties to knee ligaments. Average values were: maximum load at failure (63.9 ± 3.2N), yield load (52.9N ± 2.6N), elongation at break (2.5mm ± 0.3mm), elongation at the elastic limit (1.25mm ± 0.15mm), strain at break (47.0% ± 3.5%), strain at yield (23.2% ± 2.3%), and stiffness (56.6 ± 9.N/mm-1). The meniscus-capsular junction's mechanical properties are similar to other knee ligaments and may play a role in knee stability. The findings provide insights into the the behavior of the meniscus-capsular junction could have clinical implications for diagnosing and surgical treatment of meniscocapsular lesions.

Impact of NaOH based perfusion-decellularization protocol on mechanical resistance of structural bone allografts

ABSTRACT Introduction To mitigate the post-operative complication rates associated with massive bone allografts, tissue engineering techniques have been employed to decellularize entire bones through perfusion with a sequence of solvents. Mechanical assessment was performed in order to compare conventional massive bone allografts and perfusion/decellularized massive bone allografts. Material and methods Ten porcine femurs were included. Five were decellularized by perfusion. The remaining 5 were left untreated as the “control” group. Biomechanical testing was conducted on each bone, encompassing five different assessments: screw pull-out, 3-points bending, torsion, compression and Vickers indentation. Results Under the experimental conditions of this study, all five destructive tested variables (maximum force until screw pull-out, maximum elongation until screw pull-out, energy to pull out the screw, fracture resistance in flexion and maximum constrain of compression) were statistically significantly superior in the control group. All seven nondestructive variables (Young’s modulus in flexion, Young’s modulus in shear stress, Young’s modulus in compression, Elastic conventional limit in compression, lengthening to rupture in compression, resilience in compression and Vickers Hardness) showed no significant difference. Discussion Descriptive statistical results suggest a tendency for the biomechanical characteristics of decellularized bone to decrease compared with the control group. However, statistical inferences demonstrated a slight significant superiority of the control group with destructive mechanical stresses. Nondestructive mechanical tests (within the elastic phase of Young’s modulus) were not significantly different.

On how pseudo-ductility modifies the translaminar fracture toughness of composites and the nominal strength of centre-cracked specimens

Among the efforts to revert the traditionally brittle characteristic of laminated composites, pseudo-ductility relies on utilising hybridisation to stimulate sub-critical damage mechanisms. However, how such pseudo-ductility would translate into an increase in material toughness or an improvement in the strength of the sub-components remains unclear. To elucidate this, we perform a numerical study departing from a parameterised pseudo-ductile model implemented in a finite element model. We use non-dimensional analysis to investigate the effect of the two most relevant parameters: pseudo-ductile strain (ɛd) and the ratio of ultimate strength to pseudo-ductile yield strength (σf/σy). We infer material toughness from the simulation of Compact Tension specimens, and it is shown to increase linearly with ɛd, and non-linearly with σf/σy but tends to a plateau. Then, the simulation of Centre Cracked scaled specimens reveal that the nominal strength increases on the elastic limit extreme (large specimens) but decreases below a given size.

Lattice destabilization in electron-beam-irradiated antimony in TEM

This study investigates the effect of electron-beam heating in transmission electron microscopy (TEM) on the structure of antimony (Sb) thin films. TEM of Sb irradiated with 300 keV electrons reveals a significant deviation (2–3°) from the theoretical interplanar angle between certain planes within the irradiated region. We relate this anomaly to electron-beam heating under electron-beam irradiation. Our FEA simulations reveal localized heating within the irradiated region caused by Auger electron excitation. These simulations predict temperatures as high as 949 K, accompanied by ultrafast heating and quenching rates. This extreme thermal cycling likely induces significant thermal stress in localized regions, possibly exceeding their elastic limits. This stress is likely related to the observed structural anomalies. This work highlights the importance of considering beam heating, particularly when interpreting TEM data from nanoscale materials with reduced thermal conductivity due to surface scattering effects.

Shock compression of single-crystal stainless steel

We studied the orientation-dependent dynamic properties and plastic deformation mechanisms in single-crystal austenitic FeCr18Ni12.5 stainless steel shocked to peak stresses ranging 3.8-12.0 GPa. The 〈110〉 and 〈111〉 principal Hugoniots generally match that of polycrystalline 304L stainless steel, but the 〈100〉 Hugoniot exhibits lower shock velocities and comprises two distinct regions. The Hugoniot elastic limits (HELs) and spallation strengths range 0.5-1.2 GPa and 2.2-3.8 GPa, respectively, and exhibit trends previously observed in polycrystalline steels. We generally observed the largest HELs along 〈100〉 and the largest spallation strengths along 〈111〉. Microscopy revealed larger twin and martensite fractions in the 〈100〉 samples, correlations in twinning and martensite prevalence with dynamic response, and orientation-dependent differences in dislocation behavior near the spallation plane.

Highly Mechanical Strength, Flexible and Stretchable Wood-Based Elastomers without Chemical Cross-Linking

Wood exhibits a limited elastic deformation capacity under external forces due to its small range of elastic limit, which restricts its widespread use as an elastic material. This study presents the development of a stretchable wood-based elastomer (SWE) that is highly mechanical and flexible, achieved without the use of chemical cross-linking. Balsa wood was utilized as a raw material, which was chemically pretreated to remove the majority of the lignin and create a more abundant pore structure, while exposing the active hydroxyl groups on the cellulose surface. The polyvinyl alcohol (PVA) solution was impregnated into delignified wood, resulting in the formation of a cross-linked structure through multiple freeze–thaw cycles. After eight cycles, the tensile strength in the longitudinal direction reached up to 25.68 MPa with a strain of ~463%. This excellent mechanical strength is superior to that of most wood-based elastomers reported to date. The SWE can also perform complex deformations such as winding and knotting, and SWE soaked in salt solution exhibits excellent sensing characteristics and can be used to detect human finger bending. Stretchable wood-based elastomers with high mechanical strength and toughness have potential future applications in biomedicine, flexible electronics, and other fields.

The Effect of Temperature on the Hugoniot Elastic Limit and the Spall Strength of a Lead–Bismuth Alloy at the Pressure of Shock Compression up to 2.4 GPa

The Effect of Temperature on the Hugoniot Elastic Limit and the Spall Strength of a Lead–Bismuth Alloy at the Pressure of Shock Compression up to 2.4 GPa

Bioanthropological and Biomechanical Perspectives on Skeletal Senescence Variation: A Literature Review

Background: Senescence is the deterioration of the body’s biological and physiological function throughout later life. Senescent populations are more prone to diseases, though other than osteoporosis, skeletal senescence is a less discussed topic in Indonesia. Furthermore, a global and national increase in the aging population showed that they will be a major group in society, thus raising the urgency to review this matter. This study aims to comprehend the physiological and biomechanical mechanisms of skeletal senescence, as well as senescent variations in a certain sex or population affinity. Literature Review: Age-related skeletal cellular death and imbalance contribute to bone damage in elders. Senescence also affects skeletal biomechanics, expressed in increased bone porosity and brittleness. Stresses in aged bone risk straining above its elastic limit and causing fractures due to its inability to tolerate stresses. The loss of sex hormones is related to skeletal senescence, especially in females, though the effects of testosterone on skeletal senescence are underresearched. Dietary change, estrogen replacement therapy, and calcitonin consumption are effective measures in reducing the effects of osteoporosis. Variations were found in the bone aging process in different populations, especially regarding bone mineral density loss in white, African-American, Asian, and Hispanic populations. Summary: Specific population-based healthcare services in geriatrics and gerontology are highly suggested to ensure inclusive healthcare for every aged individual. Due to the minimum data about bone aging in Indonesia (other than osteoporosis), the authors encourage data procurement on local populations to create more suitable medical guidelines for elders in Indonesia.

Mechanical properties of hydrated electrospun polycaprolactone (PCL) nanofibers

Polycaprolactone (PCL) nanofibers are a promising material for biomedical applications due to their biocompatibility, slow degradation rate, and thermal stability. We electrospun PCL fibers onto a striated substrate with 12 μm wide ridges and grooves and determined their mechanical properties in an aqueous solution with a combined atomic force/inverted optical microscopy technique. Fiber diameters, D, ranged from 27 to 280 nm. The hydrated PCL fibers had an extensibility (breaking strain), εmax, of 137%. The Young's modulus, E, and tensile strength, σT, showed a strong dependence on fiber diameter, D; decreasing steeply with increasing diameter, following empirical equations E(D)=(4.3∙103∙e−D51nm+1.1∙102) MPa and σT(D)=(2.6∙103∙e−D55nm+0.6∙102) MPa. Incremental stress-strain measurements were employed to investigate the viscoelastic behavior of these fibers. The fibers exhibited stress relaxation with a fast and slow relaxation time of 3.7 ± 1.2 s and 23 ± 8 s and these experiments also allowed the determination of the elastic and viscous moduli. Cyclic stress-strain curves were used to determine that the elastic limit of the fibers, εelastic, is between 19% and 36%. These curves were also used to determine that these fibers showed small energy losses (<20%) at small strains (ε < 10%), and over 50% energy loss at large strains (ε > 50%), asymptotically approaching 61%, as Eloss=61%·(1−e−0.04*ε). Our work is the first mechanical characterization of hydrated electrospun PCL nanofibers; all previous experiments were performed on dry PCL fibers, to which we will compare our data.

Вплив кверцетину на органічний матрикс і біомеханічні властивості нижньої щелепи щурів після її неповного перелому за умов хронічної алкогольної інтоксикації

This article investigates the impact of water-soluble form of quercetin (corvitin) on the depolymerization of the organic matrix biopolymers and biomechanical properties of the rat mandible following its incomplete fracture during chronic alcohol intoxication. The study was conducted on the 14th day after inducing chronic alcohol intoxication by daily intragastric administration of a 40% ethanol solution in a daily dose of 12 ml/kg body weight; on that day the incomplete fracture of the mandible was modelled by drilling the bone to a depth of 1 mm using a carbide drill with a diameter of 1.5 mm at a speed of up to 1000 rpm. The administration of a water-soluble form of quercetin for 14 days during the posttraumatic period in a daily dose of 10 mg/kg (in recalculation for quercetin), following an incomplete mandibular fracture during chronic alcohol intoxication, significantly reduced the activity of acid phosphatase and its tartrate-resistant isoform by 35.3% and 23.1%, respectively, as well as led to a decrease in the concentration of free hydroxyproline, hexuronic and N-acetylneuraminic acids by 17.0%, 30.6%, and 43.3%, respectively, compared to the findings revealed in animals, which did not receive the drug. The Young’s modulus exceeded the values of this group by 72.3%, the elastic limit by 53.2% the tensile strength by 59.6%, and the relative elongation to failure by 30.0%. We concluded that the administration of a water-soluble form of quercetin for 14 days following an incomplete mandibular fracture during chronic alcohol intoxication improves reparative processes in the injured area; it also restricts bone resorption and the depolymerization of connective (bone) tissue biopolymers such as collagen, proteoglycans, and sialoglycoproteins. Under these conditions, the biomechanical properties of the mandibular bone in the fracture area, particularly its elasticity and strength, are significantly enhanced.

Study of the properties of a composite material Fe78Si9B13 / GNP in an epoxy matrix

This study investigates the properties of a composite material obtained by mixing Fe78Si9B13 metallic powders (at %) with graphene nanoplates (GNP) in an epoxy matrix. Four composite types were created with GNP weight proportions of 0%, 0.5%, 1.0%, and 1.5%. The composites were embedded in transparent epoxy with weight proportions of 10%, 15%, and 20%, and then filled into 7 x 20 mm cylindrical probes. Twelve samples were prepared, and another 12 samples were subjected to a longitudinal magnetic field of 1 kG. All samples were tested with a Universal Testing Machine (Model WDW 10E) up to a maximum force of 20 kN. The experiment recorded deformation (ΔH) vs. charge force. Most samples showed a maximum compression resistance of 390 MPa, except for a few that did not exceed 100 MPa. The magnetically oriented samples showed a greater elastic limit in the range of 200 to 270 MPa. Optical microscopy was used to observe the ordering of the particles after the application of the magnetic field. Scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray diffraction were used to characterize the structure of the composite components. A vibrating sample magnetometer (VSM) was used to characterize the magnetic behavior of the metallic powders in the composite.

Experimental and computational study of the NiTi thin wires mechanical behavior

NiTi wires used for biological implants demonstrated ductile fracture. NiTi 40, 60, and 90 µm thick wires were tested in uniaxial tension to fracture and loading-unloading. Uniaxial stress-strain curves demonstrate superelastic behavior. The inelastic martensite transformation strain is completely recovered upon unloading, forming thermo-mechanical hysteresis. A mathematical model was developed to describe superelasticity effects in NiTi wires. Modeling results are qualitatively and quantitatively similar to experimental data, and capture elastic deformation of austenite, forward martensite phase transformation stress plateau before the onset of martensite elastic deformation and the entire unloading range. The elastic limit and strength increase with the wire thickness.

Modification of response reduction factors of overhead water tanks based on ductility factor

In the earthquake-resistant design of overhead tanks, this research dealt with the determination of the response reduction factor applicable to overhead water tanks performing beyond the elastic limit. Eight existing water tanks were selected for the investigation and 127 ground accelerations due to 10 Indian earthquakes were selected. The magnitude of the earthquakes selected ranges from 4.5 to 7.2. Initially, 10.16 million nonlinear dynamic data of response reduction factor had been produced using Newmark’s β method by varying parameters. From the results obtained, multi-linear regression analysis was made to arrive at the empirical formula relating the parameters and it was found that ductility factor was the most significant factor among others such as damping ratio, pre-post stiffness ratio, natural period, and soil types, in influencing response reduction factor. Eventually, It is concluded that the values of the response reduction factor to be adopted in the dynamic analysis of Overhead water tanks should be based on the desired value of the ductility factor.

Solidified water at room temperature hosting tailored fluidic channels by using highly anisotropic cellulose nanofibrils

Highly anisotropic cellulose nanofibrils can solidify liquid water, creating self-supporting structures by incorporating a tiny number of fibrils. These fibrillar hydrogels can contain as much as 99.99 wt% water. The structure and mechanical properties of fibrillar networks have so far not been completely understood, nor how they solidify the bulk water at such low particle concentrations. In this work, the mechanical properties of cellulose fibrillar hydrogels in the dilute regime from a wt% perspective have been studied, and an elastoplastic model describing the network structure and its mechanics is presented. A significant insight from this work is that the ability of the fibrils to solidify water is very dependent on particle stiffness and the number of contact points it can form in the network structure. The comparison between the experimental results and the theoretical model shows that the fibrillar networks in the dilute regime form via a non-stochastic process since the fibrils have the time and freedom to find contact points during network formation by translational and rotational diffusion. The formed, dilute fibrillar network deforms by sliding fibril contacts upon straining the network beyond its elastic limit. Our results also show that before macroscopic failure, the fibril contacts are restored once the load is released. The exceptional properties of this solidified water are exploited to host fluidic channels, allowing directed fluid transportation in water. Finally, the microfluidic channels formed in the hydrogels are tailored by the layer-by-layer technique to be interactive against external stimuli, a characteristic envisioned to be useful in biomedical applications.

Experimental investigation on the load-bearing capacity and deformation behaviour of the composite lining with polyurethane compressible layer

Lining structures for tunnels in rheological rocks are susceptible to large deformations and damage. Installation of a polyurethane (PU) compressible layer between the primary and secondary lining provides a potential solution to mitigate large deformation hazards. Although the capability of PU-enhanced composite lining in adapting and absorbing large deformation has been found, its underlying load-bearing mechanism and deformation behaviour remain less understood. To fill the gap, large-scale model tests were conducted using a self-designed loading test setup, primarily focusing on the mechanical response of PU-enhanced composite lining. Ten lining specimens with varying thicknesses (25, 37.5, and 50 mm) and densities (50, 100, and 150 kg/m3) of the PU compressible layer were investigated. The digital image correlation (DIC) analysis technique was used to detect real-time deformation and strain fields under loading conditions. Results demonstrated that the PU compressible layer enhanced the ultimate load, toughness, and deformation capacity of the composite lining by an average of 17.6 %, 164.6 %, and 157.4 %, respectively. The load-displacement response of the specimens with PU compressible layer could be categorized into four stages: pre-cracking, post-cracking, strain-hardening, and failure. The primary lining experienced the largest vertical displacements among the specimens with the PU compressible layer, followed by the compressible layer and the secondary lining. Although the specimens exhibited similar progressive failure modes, there were variations in crack distribution and propagation. The analysis of rock-support interaction indicated that increasing the thickness of the PU compressible layer mainly affects the deformation capacity when the secondary lining reaches its elastic limit.

In-situ failure behavior and interfacial bonding of an interpenetrating metal matrix composite reinforced with lattice-like metallic glass (Ni60Nb20Ta20) preform

Metallic glasses (MG) have an amorphous atomic structure and exhibit several exceptional properties such as high strength, hardness associated with high elastic strain limit and elastic energy storage. But MGs are also prone to brittle fracture, making them difficult to use as monolithic structural components and might better be used as a reinforcement phase in hybrid composites such as metal matrix composites (MMC). The failure behavior of composites depends on the structure of the reinforcement phase. In this work, the failure behavior of an interpenetrating MMC reinforced with a MG (Ni60Nb20Ta20) lattice-like preform and AlSi12-matrix was investigated by in-situ compression tests under scanning electron microscopy to get a better understanding of the influence of the lattice-like preform and mechanical interference between both phases. Additionally, microstructure analysis by scanning transmission electron microscopy and energy dispersive X-ray measurements were carried out to gain insight into the chemical composition of the interfaces. The failure behavior in manufacturing direction of the MMC is dominated by shear stress whereas transversely to manufacturing direction by normal stress and exhibits therefore an anisotropic failure behavior. Investigations of the interfaces show more of a mechanical than chemical bonding but in general a good interfacial bonding was confirmed.

Mechanism of Electropulsing Treatment Technology for Flow Stress of Metal Material: A Review

Residual stress is caused by non–uniform deformation caused by non–uniform force, heat and composition, which is of great significance in engineering applications. It is assumed that the residual stress is always the upper limit of the elastic limit, so the reduction of the flow stress will reduce the residual elastic stress. It is particularly important to control the flow stress in metal materials. Compared with traditional methods, the use of electropulsing treatment (EPT) technology stands out due to its energy–efficient, highly effective, straightforward and pollution–free characteristics. However, there are different opinions about the mechanism of reducing flow stress through EPT due to the conflation of the effects from pulsed currents. Herein, a clear correlation is identified between induced stress levels and the application of pulsed electrical current. It was found that the decrease in flow stress is positively correlated with the current density and the duration of electrical contact and current action time. We first systematically and comprehensively summarize the influence mechanisms of EPT on dislocations, phase, textures and recrystallization. An analysis of Joule heating, electron wind effect, and thermal–induced stress within metal frameworks under the influence of pulsed currents was conducted. And the distribution of electric, thermal and stress fields under EPT are discussed in detail based on a finite element simulation (FES). Finally, some new insights into the issues and challenges of flow stress drops caused by EPT are proposed, which is critically important for advancing related mechanism research and the revision of theories and models.