Tensile Stress-strain Curves Research Articles

PHC 파일용 PC 강봉의 열처리에 따른 미세구조 및 기계적 특성

For prestressing concrete (PC) steel bar, high-strength steel bar with spiral groove is used by deform drawing and heat treatment of medium carbon steel, 30MnSi. Since the ø8.8 ㎜ PC steel bar has to be subjected to a different tempering temperature from the existing ø9.2 ㎜ PC bar, the microstructure after tempering through the induction heat treatment method was comparatively analyzed and the tensile stress-strain curves for each heat treatment condition were investigated. The experiment was conducted by controlling the heat treatment temperature by adjusting the current input value. The change of the linear speed compared to the current value has a great influence on the mechanical properties of the product, and the tempered martensite structure is observed in the specimen to which the current value of 98 A and the line speed of 48 m/min is applied, and the tensile strength is 1,455 N/㎟ satisfied.

Modeling of the tension-compression asymmetry reduction of ECAPed Mg-3Al-1Zn through grain fragmentation

In this work, a physically based model accounting for grain-to-grain interaction and grain refinement mechanisms is proposed to predict the anisotropic mechanical response and the texture evolution in ECAPed Mg-3Al-1Zn. The proposed model couples two approaches: crystal plasticity (CP), including twinning, and continuum dislocation dynamics (CDD). A grain refinement mechanism is also integrated into the model in order to predict the formation of refined grains during severe plastic deformation. A robust parameter identification method is proposed, in which experimentally reported process parameters are calibrated to fit the simulated mechanical behavior, texture evolution, and deformation systems-related activities. The anisotropic behavior evolution of the Mg-3Al-1Zn hot-rolled plate is examined by predicting the mechanical behavior, dislocation evolution, and slip/twin systems activities of the ECAPed material. The coupled CP-CDD model predicts grain size reduction with an average grain size which is in agreement with the experimentally measured values. Furthermore, the model generated textures are in accordance with those reported in the literature. Finally, a good agreement between the experimental and predicted true tensile stress–strain curves up to the ultimate tensile strength for both routes 4A and 4 K along extrusion and flow directions was found.

Static and fatigue tensile properties of carbon/glass hybrid fiber-reinforced epoxy composites

The static and fatigue tensile properties of high-strength polyacrylonitrile (PAN)-based carbon (IMS60) and electronic (E)-class glass (E-glass) hybrid fiber-reinforced epoxy matrix composites (HFRPs) were investigated. The fiber orientations of the HFRP specimens were set to unidirectional with [(0(IMS60))/(0(E-glass))]S (subscript S means symmetry and [(0(IMS60))/(0(E-glass))/(0(E-glass))/(0(IMS60))]), [(0(E-glass))/(0(IMS60))]S, [(0(E-glass))/(0(IMS60))2]S, [(0(E-glass))/(0(IMS60))3]S, [(0(E-glass))/(0(IMS60))5]S, [(0(E-glass))2/(0(IMS60))]S, [(0(E-glass))3/(0(IMS60))]S, and [(0(E-glass))5/(0(IMS60))]S. Under static loading for the [(0(IMS60))/(0(E-glass))]S, [(0(E-glass))/(0(IMS60))]S, [(0(E-glass))/(0(IMS60))2]S, [(0(E-glass))/(0(IMS60))3]S, and [(0(E-glass))/(0(IMS60))5]S HFRP specimens, the stress applied to the specimen was almost linearly proportional to the strain until failure. However, the tensile stress–strain curves of the [(0(E-glass))2/(0(IMS60))]S, [(0(E-glass))3/(0(IMS60))]S, and [(0(E-glass))5/(0(IMS60))]S HFRP specimens had a complicated shape (jagged trace). The Weibull statistical distributions of the tensile strength values were also examined. The Weibull moduli for the [(0(E-glass))/(0(IMS60))]S, [(0(E-glass))/(0(IMS60))2]S, [(0(E-glass))/(0(IMS60))3]S, [(0(E-glass))/(0(IMS60))5]S, [(0(E-glass))2/(0(IMS60))]S, [(0(E-glass))3/(0(IMS60))]S, and [(0(E-glass))5/(0(IMS60))]S HFRP specimens were higher than those for the mono carbon fiber-reinforced epoxy (CFRP) and glass fiber-reinforced epoxy (GFRP) specimens. Under fatigue loading, the fatigue properties of the HFRP specimens showed CFRP-dominant behaviour at high stress levels and GFRP-dominant behaviour at low stress levels. The fatigue properties of the HFRP specimens increased with increasing volume fraction of CFRP in the following order: ([(0(E-glass))/(0(IMS60))5]S > [(0(E-glass))/(0(IMS60))3]S > [(0(E-glass))/(0(IMS60))2]S > [(0(IMS60))/(0(E-glass))]S > [(0(E-glass))/(0(IMS60))]S > [(0(E-glass))2/(0(IMS60))]S > [(0(E-glass))3/(0(IMS60))]S > [(0(E-glass))5/(0(IMS60))]S).

Enhancing the physical and structural properties of poly(glycolide-co-trimethylene carbonate-co-ε-caprolactone) copolymer fibers.

Nowadays, due to the methodological needs in the application of internal surgery new methods evolving novel design for surgical suture are recommended. In this work, the effect of cold drawing process and the thermal annealing process on the different optical and structural properties of surgical suture fibers were studied. For the thermal annealing process, samples of Monosyn monofilaments suture fibers were thermally annealed at temperatures ranging from 50 to 100 for annealing time=120 min. The thermal treatment was carried out under free end condition. For the cold drawing process, an Instron was used to mechanically draw and measures the tensile stress strain curve of Monosyn samples. Using differential scanning calorimetry, X-ray diffraction techniques, and optical polarizing microscope the different properties of the tested sutures, such as the crystallinity, sample radius, birefringence, molecular orientation, and tensile properties were measured. From the resulting data, there was a marked increase in the physical and structural properties during the thermal annealing and cold drawing processes. This means that a new reorientation of Monosyn suture molecular chains were performed and approved by calculating the different orientations f(θ) and fc . This is an important improvement for these biodegradable materials to widen their medical use and improve their clinical results. RESEARCH HIGHLIGHTS: The stress-strain curve for Monosyn surgical fiber is J shape and identical to the human tissue stress-stain curve. The different orientation calculated improve that the drawing process affect directly on the fiber chain orientations. The fiber chains orientation due to the cold drawing process causes strain induced crystallinity.

A viscoelastic constitutive model for shape memory polymer composites: Micromechanical modeling, numerical implementation and application in 4D printing

In this work, a novel micromechanics-based thermo-viscoelastic constitutive model for shape memory polymer composites (SMPCs) is proposed and applied to four-dimensional (4D) printed SMPCs. The multi-branch constitutive model is used to simulate the time- and temperature-dependent mechanical behavior of the shape memory polymer matrix. According to the elastic–viscoelastic correspondence principle, the equivalent viscoelastic stiffness tensor of the composite is obtained in the micromechanics framework of energy-based effective strain theory and the Mori-Tanaka homogenization scheme, in which a two-parameter interfacial damage model is adopted to consider the displacement discontinuity and traction continuity conditions at the interface between the inclusion and the matrix. The numerical integration scheme for the three-dimensional (3D) viscoelastic constitutive model of SMPCs is presented, and the finite element application is implemented by the user material subroutine UMAT of ABAQUS. After identifying the model parameters with experimental data, the tensile stress-strain curves and stress relaxation phenomena of 4D printed unidirectional SMPCs are successfully described by theoretical simulations. Besides, theoretical simulations also adequately predict the shape memory behavior of 4D printed composites and complex members.

Effect of loading frequency on the strain of MI-SiC/SiC composites

In this work, we tried to answer the question: what is the role loading frequency plays in strain accumulation during time-dependent tests of Melt-infiltrated SiC/SiC CMCs? Time-dependent tests were conducted at room temperature, 815°C as a possible temperature for the phenomenon of pesting, and 1204°C as an oxidizing temperature. Stress levels were selected from tensile stress–strain curves to range from 110.4 MPa where no major cracks could be detected to 220.8 MPa at the end of the knee region at a point of possible matrix crack saturation. Loading frequencies of 30 Hz and 1 Hz fatigue, and 2-h dwell-fatigue were investigated. Residual tensile strength tests of samples that did not fail during time-dependent experiments were carried out. Initial observations lead us to divide the question above to two parts, one addressing the value of the strain to failure and the other addressing the steady-state strain rates. Strain to failure during residual tests added to strain accumulated during time-dependent tests for 22 samples tested at different stresses, load frequencies, and temperatures had a consistent average of 0.005 with a small standard deviation. This could mean that there is a reasonable possibility that this material has a finite “strain capacity.” Strain versus time curves of all time-dependent tests were successfully fitted using a single 3-parameter equation while accounting for the effect of temperature and stress-level, to a reasonable extent. Such observation, despite of some of the variability in the data, could mean that loading frequency have a small, or negligible, effect on the strain-rate.

The Effect of Cross-Linking Type on EPDM Elastomer Dynamics and Mechanical Properties: A Molecular Dynamics Simulation Study.

The cross-linking structure of the Ethylene-propylene-diene monomer (EPDM) is made up of a number of cross-linking types, including carbon atoms from the main chain or monomer and ether crosslinks formed during degradation. Through molecular dynamic simulations, the contribution of each type of cross-linked structure to the dynamics and mechanical properties of EPDM, the study’s focus, were investigated. Cross-linking between the tertiary carbons of two main chains, cross-linking at the monomer’s unsaturated position, ether cross-linking after oxidation, and other combinations of target cross-linked carbon atoms from different positions, totaling eight types of cross-linked types, were mixed with EPDM free chains in a 1:1 ratio to form eight types of cross-linked EPDMs. These varieties of cross-linked EPDMs were then compared to an uncross-linked EPDM in terms of density, radius of gyration, free volume, mean square displacement, and uniaxial tensile stress-strain curves. It was found that the cross-linking was always proven to have a favorable influence on mechanical characteristics; however, the relaxation inhibition effect varied. The cross-linking between the diene monomer at the C9 position resulted in a more flexible molecular shape and was more than double the free volume of the uncross-linked EPDM, resulting in an improved diffusion ability. The ether cross-linking produced by the oxidation of the side chain cross-linking improved the positive contribution to stiffness and enhanced the inhibitory impact on diffusion properties, whereas the main chain cross-linking had the opposite effect. The research presented in this study leads to a better knowledge of the microscopic aspects underlying EPDM performance.

Tensile Examination and Strength Evaluation of Latewood in Japanese Cedar.

With the crisis awareness of global warming and natural disasters, utilization of local wood has drawn increasing attention in achieving the Sustainable Development Goals (SDGs). It is necessary to investigate the deformation and fracture of the structural tissue in wood in order to improve the safety and reliability of wood application. However, deformation and fracture mechanisms of the structural tissue in each annual ring are unknown. The mechanical characteristics of wood are reflected in the properties of earlywood and latewood. In the present study, microstructural observation and tensile tests were conducted to examine the relationship between the mechanical properties and fracture behavior of latewood in the growth direction in Japanese cedar. Brittle fracture behavior of the latewood specimen was confirmed based on the tensile stress–strain curve and features of the fracture surface. Moreover, two fracture modes, tensile fracture and shear fracture, were recognized. Weibull analysis of tensile strength in each fracture mode was performed to evaluate the reliability and utility of brittle latewood. Lastly, two fracture mechanisms were discussed based on the failure observation findings by a scanning electron microscope.

Predicting mechanical properties of engineering cementitious composite reinforced with PVA using artificial neural network

This paper developed an artificial neural network (ANN) models to predict engineered cementitious composites (ECC) mechanical properties such as compressive strength, flexural strength, and direct tensile stress-strain curve. ANN models were created, trained, validated, and tested based on a large data set with variable mix designs. The used data set was 151,76, and 44 test results for compressive strength, flexural strength, and direct tensile stress-strain curve collected from recently published research. Models data analysis showed outstanding predictive performance with accepted accuracy near to 100%. Additional evaluation using an extra experimental data set confirmed the accuracy of the proposed ANN models with minimum relative errors around (0.15:9.40) % for compressive strength, (0.05:4.71) % for flexural strength, and (1.40:5.00) % for the tensile strength. Based on the model’s data analysis, additional data sets evaluation, and the statistical tools for the external data set including the absolute fraction of variance (R2), and the degree of agreement (d) the models were capable of predicting the mechanical strengths of ECC mixtures. Finally, stress-strain relations can be predicted precisely using ANN models with a maximum variance of 7.10%.

Role of Cu addition in enhancing strength-ductility synergy in transforming high entropy alloy

The mechanical properties of transformation induced plasticity high entropy alloys (TRIP HEAs) are affected by tailoring the metastability via alloying and processing. The current work focuses on as-cast and friction stir processed alloy where the initial microstructure is altered by Cu addition (a γ-fcc phase stabilizer) to the ε-hcp dominated HEA. With the Cu addition, the tensile stress-strain curves exhibited improved ductility and a delay in TRIP effect, suggesting an increased stacking fault energy, along with improved strength and work hardening. Improved properties with Cu addition are credited to almost 100% stabilized γ-fcc phase, increased type and number of interfaces: Cu-rich precipitates, shorter faults, phase separation, and increased grain boundary fraction. The new alloy was then friction stir processed (FSPed) to further improve the properties. An advanced TRIP effect is observed with FSP as compared to as-cast alloy, attributed to increased ε-hcp fraction and finer grain size. Based on microscopic observations, the improved strength is due to finer grain size, increased dislocation density, low density of faults, whereas reduced ductility is reasoned to be due to dissolution of Cu-rich precipitates and increased width of modulations from phase separation.

Microstructure and Tensile Behavior of a Novel Monocrystalline Co‐Based Superalloy at Different Temperatures

Microstructures and tensile properties of a novel monocrystalline Co‐based superalloy are investigated by experiments and finite element simulation. Microstructures of heat‐treated alloys are composed of γ and cubical γ' precipitates without the presence of the secondary phase, and the fraction of γ' phase is about 86%. The experimental results show that tensile properties of the novel monocrystalline Co‐based superalloy have abnormal yield behavior. In low and medium temperature ranges (R.T. 850 °C), the yield stress increases gradually with temperature increase and the tensile fracture surface is characterized by cleavage rupture. At 850 °C, fracture mechanism is composite of cleavage and microporous. While above 850 °C, the yield stress decreases rapidly, and fracture surface is constituted of mixed fracture surface of dimples and micropores. The simulation results show that the tensile stress‐–strain curves are well fitted to the experimental data at different temperatures.

Temperature effect on the tensile properties of unplasticized polyvinyl chloride

AbstractThe present paper investigates the effect of temperature of unplasticized polyvinyl chloride (UPVC) under tension. UPVC specimens were tensile tested across a range of temperatures (from −20°C to 60°C). The UPVC, like other polymers, was strongly affected by temperature. Those below room temperature were more fragile but had greater tensile strength and stiffness. When room temperature is exceeded, the UPVC test specimens became softer, with lower strength and stiffness. Considering the results, an analytical expression to predict the mechanical behavior of UPVC in tensile tests at different temperatures—more specifically a description of the experimental tensile stress–strain curves by an algebraic equation is proposed. A reasonable approximation of the stress–strain curve was possible to obtain with a minimum of three tests performed at different temperatures. The analytical results were in good agreement with experimental ones.

Analysis of High Strength Concrete processed from Recycled Concrete Aggregates

Abstract: As everyone is aware of the fact that Natural Coarse Aggregate (NCA) is the main constituent of traditional concrete mixes. Whenever an existing concrete structure is demolished, it produces smashed concrete waste in the large amount. Concrete waste give rise to negative effects on the environment. To evade the environmental pollution and mark effective reuse of the concrete waste as Recycled Aggregates in the place of NCA. This operative initiative provides an opportunity to reduce air pollution and soil exploitation to some extent. Such concrete is sustainable in nature and also eco-friendly to the environment. Also, such waste material will lower the usage of naturally occurring stone to produce NCA and thus various natural energy resources will be safeguarded. This study covers the suitability norms for a material to be used for Recycled Aggregate. In this study the natural aggregate is replaced with recycled aggregate in the different percentages (0%, 25%, 50%). When percentage of recycled aggregate mixed in the fixed proportion as percentage replacement to natural aggregates, it imparts improvement in the property of fresh as well as hardened concrete like, compressive strength & split tensile strength. Laboratory results of this research indicates that the value of compressive strength, tensile strength stress-strain curve & NDT of these mixes drives on decreasing, but at the 25% replacement level, it achieves target mean strength. Hence, for the fundamental concrete mix Natural Coarse Aggregate can be efficiently replaced by the Recycled Aggregate to the range of 25%. Keywords: Concrete, Recycled aggregate, Natural Coarse Aggregate (NCA), Compressive Strength, Tensile strength, , NDT, Stress-Strain Curve

Trilinear tensile stress–strain constitutive model for high ductility cementitious composite with totally recycle fine aggregate

In this paper, the crushed waste concrete particles with original particle grade were adopted as recycled fine aggregate (RFA) to completely substitute the natural fine aggregate in preparing high ductility cementitious composite (HDCC) for fully utilizing waste concrete, simplifying the sieving steps, reducing the environmental pollution and obtaining better tensile performance. The tensile stress–strain behavior of HDCC with 100% RFA (termed as R-HDCC) was explored by the uniaxial tensile test and compared with that of HDCC with totally natural fine aggregate. Then the effects of RFA-binder ratio, water-binder ratio, fly ash content and fiber volume fraction on the properties of R-HDCC were investigated in detail. The test results showed that the increase of both water-binder ratio and fly ash content reduced the tensile strength of R-HDCC but improved the strain capacity significantly. The increase of fiber volume fraction was beneficial to both tensile strength and strain capacity. As RFA-binder ratio increased, the strain capacity of R-HDCC decreased continuously while the tensile strength increased first and then decreased. Most notably, there was apparently three stages on the tensile stress–strain curve of R-HDCC, which was very different from the bilinear tensile response of ordinary HDCC. Therefore, a new trilinear tensile stress-train constitutive model was proposed for R-HDCC and validated in comparation with test results in this study and relevant literatures. It demonstrated that the trilinear model could well match with the measured curves of HDCC with PVA fibers and recycled fines crushed from concrete or clay brick.

High temperature mechanical properties and strain hardening mechanism of directionally solidified Mg-Gd-Y alloy

The Mg-6.0Gd-0.5Y alloy, with straight grain boundaries and preferred growth orientation [224(_)3], was prepared by directional solidification. The microstructure evolution during tensile tests at 150–350 °C was investigated using Electron Back-Scattered Diffraction (EBSD) and High-Resolution Transmission Electron Microscopy (HRTEM). Subsequently, the relationship between the deformation mechanism and mechanical properties was discussed. The results show that there are obvious uniform plastic deformation stage and work hardening stage after yield for the tensile stress-strain curves of the Mg-6.0Gd-0.5Y samples tested at 150°C–250 °C, while evident dynamic recrystallization characteristic can be observed for the curve of the sample tested at 350 °C. It is found that the stable high-temperature strength of the Mg-6.0Gd-0.5Y alloy can be attributed to the delayed dynamic recrystallization, the formation of compression twins and I1-type stacking faults. In addition, the superior plasticity of the alloy is related to the high concentration of crystal orientation, the activation of tensile twins, and non-basal slip which can provide more than 5 independent systems.

Tensile Behavior of Hybrid Fiber-Reinforced Ultra-High-Performance Concrete

Thirty dog bone-shaped specimens were tested to study the effects of steel fiber mixed with seven kinds of non-metallic fibers on the tensile properties of ultra-high-performance concrete (UHPC). Through experiments and micromorphological analysis, the effects of hybrid fibers on the compressive strength, tensile strength, peak strain, fracture energy, and characteristic length of UHPC were analyzed. The results showed that the hybrid fiber-reinforced UHPC showed good ductile failure characteristics, which reflected the good crack resistance and toughening effect of different fibers. The tensile stress–strain curves of UHPC with different hybrid fibers can be divided into two parts: ascending section and softening section, and the softening section was greatly affected by the type and content of fibers. Basalt fiber with a diameter of 0.02 mm had the most obvious strengthening effect on UHPC, and polyvinyl alcohol fiber with a diameter of 0.2 mm and length of 8 mm had the best toughening effect. The mixing of steel fiber and non-metallic fiber cannot only reduce the preparation cost but also improve the fracture energy and toughness of UHPC.

Effect of Temperature on Tensile Curve of Polyaspartic Ester Polyurea and Its Activation Energy Analysis

The influence of ambient temperature on the tensile stress-strain curve of polyaspartic ester polyurea (PAE-PU) was investigated to discuss the yield and breakage mechanism of tensile deformation. Temperature has a significant effect on the tensile stress-strain curve of PAE-PU. At low temperature (27, 40 °C), it shows obvious yield and forced high elasticity. After the temperature exceeds 80 °C, the yield phenomenon disappears and shows high elasticity of rubber: the strain energy and breakage energy are significantly reduced. The yield activation energy of PAE-PU was calculated by yield strain time at different temperatures. It was found that the yield activation energy decreased with the increase of tensile rate. When the tensile rate is 500mm/min, among the activation energies calculated by breakage strength, yield strength and Young’s modulus at different temperatures, the ordinary elastic deformation activation energy is higher, while the yield and breakage activation energy are close and lower. The latter two are close to the hydrogen bond energy and one order of magnitude lower than the chemical bond energy of molecular chain.

Exceptional high-strain-rate tensile mechanical properties in a CrCoNi medium-entropy alloy

Alloys with combined outstanding strength and excellent ductility are highly desirable for many structural applications. However, alloys subjected to deformation at very high strain rates and/or cryogenic temperatures usually suffer from very limited ductility. Here, we demonstrate that a bulk CrCoNi medium-entropy alloy presents exceptional combination of high strength and excellent ductility during deformation at high strain rates over a wide temperature range. Full tensile stress-strain curves at a high strain rate of 2000 s−1 and temperatures down to 77 K were successfully obtained using an electromagnetic Hopkinson tension bar system attached with a cooling device, revealing high true ultimate tensile strength (σUTS,T) of 1.8 GPa and true strain of ∼54% at σUTS,T. These outstanding mechanical properties were mainly attributed to profuse deformation twinning. Both high strain rate and cryogenic temperature promoted deformation twinning. Grain refinement caused by deformation twinning, dislocation slip and dynamic recrystallisation added to work hardening and the excellent tensile strain.

Experimental Study on Tensile Mechanical Properties and Reinforcement Ratio of Steel-Plastic Compound Geogrid-Reinforced Belt.

The steel–plastic compound geogrid has been widely used as a new reinforcement material in geotechnical engineering and other fields. Therefore, it is essential to fully understand the mechanical properties of steel–plastic compound geogrid-reinforced belts to utilize steel–plastic compound geogrids efficiently. In this study, tensile mechanical tests of steel wire, polyethylene geogrid belt, and steel–plastic compound geogrid-reinforced belt were conducted with respect to the tensile mechanical properties of steel–plastic compound geogrid-reinforced belts. In addition, the minimum reinforcement and optimal reinforcement ratios of steel–plastic compound geogrid-reinforced belts were summarized. The results showed that the steel–plastic compound geogrid-reinforced belts possessed an incongruent force of the internal steel wire during the tensile process. The tensile stress–strain curve of the steel–plastic compound geogrid-reinforced belt can be divided into the composite adjustment, steel wire breaking, and residual deformation stages. The tensile strength of the steel–plastic compound geogrid-reinforced belt is proportional to the diameter and number of steel wires in the reinforced belt. The minimum and optimum reinforcement ratios of steel wire in the steel–plastic compound geogrid-reinforced belt were 0.63% and 11.92%, respectively.

Evaluation and comparison of concrete constitutive models in numerical simulation of reinforced concrete slabs under blast load

Numerical models have been used recently to analyze concrete structures subjected to high-impulsive loads. A material model that can well capture the mechanical behaviors is crucial to obtain reliable results. Present study, focused on reinforced concrete slab as a major load carrying element of the RC structures under blast loading. By performing several simulations in popular and powerful concrete constitutive models, including concrete damage R3, HJC, CSCM, and Winfrith the accuracy of these models was investigated. Maximum deflections have been compared with each other and expanded further to compare with experiments. Result showed all models have an acceptable accuracy in estimating maximum slab deflection. Concrete Damage R3 presented the highest accuracy. HJC has the second rank and CSCM and Winfrith have the third and the fourth places, respectively. HJC needed the minimum computation time. CSCM had minimum input parameters but includes maximum calculation time. Winfrith had the lowest accuracy, however this model presented very conservative results. Uniaxial compressive and tensile stress-strain curves showed that the models which presented higher values of strength, evaluated lower maximum values of deflection.