Stress Curves Research Articles

Optimizing process parameters for hot forging of Ti-6242 alloy: A machine learning and FEM simulation approach

In this study, we investigated the hot deformation behavior of Ti–6Al–2Sn–4Zr–2Mo (Ti-6242) alloy and propose a method to derive optimal hot process parameters for grain refinement and avoidance of flow instability. Microstructural Risk Index (MRI) was introduced as a microstructural evaluation index consisting of grain size, standard deviation of grain size, and flow instability. The initial temperature of the material and the stroke speed of the die were selected as design variables. Finite element analysis (FEA) was used to calculate grain size and flow instability and determine MRI of the forgings. The grain size model coefficient and flow instability were calculated based on the flow stress curve and verified with optical microscope (OM) and electron backscatter diffraction (EBSD) analysis results. The Deep Neural Network (DNN) model was used to determine the optimal process parameters for the forging process. The MRI prediction accuracy of the trained DNN models showed excellent performance at 97.01 %. The MRI of the optimized process variables was improved by 7.95 % compared to the minimum MRI of the training data set. Optimized process parameters can improve the quality of forgings through grain refinement and avoidance of flow instability regions.

Microstructure evolution and constitutive analysis of nuclear grade AISI-316H austenitic stainless steel during thermal deformation

Compression experiments were performed on AISI-316H austenitic stainless steel using Gleeble-3800 at temperatures ranging from 900 °C and 1200 °C and strain rates ranging from 0.01 and 10 s−1, up to the actual strain of 0.69. The tests aimed to examine the material’s microstructure evolution and flow stress behavior. Based on OM and EBSD studies, it was found that thermal deformation mostly induces discontinuous dynamic recrystallization (DDRX). The proportion of recrystallization nucleation increases steadily with increasing deformation temperature, while the impact of strain rate on recrystallization is complex. At the same deformation temperature, the recrystallization volume fraction initially declines and rises as the strain rate rises. In low strain rate regime, the longer (deformation) time available for grain boundary migration, the higher recrystallization volume fraction. In high strain rate regime, the higher stored energy (and thus the increased boundary velocity) raises the probability of nucleation events, stimulating twin formation. As a result, the twin promotes a dynamic recrystallization (DRX) process. An abundance of Σ3 twins was notably observed in uniformly refined recrystallized grains at a true strain of 0.69, at a temperature of 1200 °C, and a strain rate of 10 s−1. As a result, it was discovered that DRX occurs at higher strain rates and deformation temperatures. In addition, the flow stress curves were modified to account for adiabatic heating at strain rates exceeding 1 s−1. The findings demonstrated that adiabatic heating increased when strain level and strain rate increased and deformation temperature decreased. The strain compensation Arrhenius model is developed following the given stress–strain curve while considering strain. The model exhibits high accuracy, with a correlation value of 0.986. According to a kinetic study, the average activation energy for hot deformation of the tested steel was 444.994 kJ/mol. These findings provide fundamental insights into the microstructure control technology and the outstanding mechanical properties of the austenitic stainless steel AISI-316H.

Dynamic recrystallization behavior and microstructure evolution of high-Mn austenitic steel for application in a liquefied natural gas carrier

The hot-working behavior of high-Mn austenitic steel for liquefied natural gas carriers at the deformation temperature in the range of 1073–1273 K and the strain rate in the range of 0.01–10 s−1 was studied on a Gleeble-3800 thermomechanical simulator using a compression test. Electron backscatter diffraction was used to study the microstructure after deformation. Under each deformation condition, a peak stress appears in the stress-strain curve, which conforms to traditional dynamic recrystallization hot-working flow stress curves. A hyperbolic sine-law-type constitutive equation was established to predict the peak stress. The thermal deformation activation energy was 414.19 kJ/mol, and the stress index n was 4.94. The texture of the deformed grains consisted of strong <110> and weak <100> fibers along the compression direction. The main recrystallization mechanism was discontinuous dynamic recrystallization. The grain size of the discontinuous dynamic recrystallization grains tended to increase with increasing deformation temperature or decreasing strain rate. Processing maps were drawn based on the dynamic material model. At high deformation temperatures, the power consumption factor of dynamic recovery was greater than that of dynamic recrystallization, whereas at low deformation temperatures, the power consumption factor of discontinuous dynamic recrystallization was greater than that of dynamic recovery. There are two flow instability regions in the processing maps, 1243–1273 K/1-10 s−1 and 1073–1203 K/0.05–10 s−1. The formation of a ‘necklace microstructure’ was the main cause of deformation instability. The optimized process parameters for industrial production were 1243–1273 K/1-10 s−1.

A method for determining the rheological properties of viscoplastic fluids using a rectangular die

This study introduces a method for determining the rheological parameters of viscoplastic fluids with the use of rectangular dies. The relationship between the wall shear rate and the wall shear stress is investigated for the Casson, Herschel-Bulkley, and Robertson-Stiff rheological models, using two geometric constants for non-circular dies with a regular cross-section. Then, the rheological behavior and parameters of a collagen material were examined by an analytical method and by the proposed approximate method, using experimental data obtained by a slit viscometer and a rectangular die. The yield stress value of the collagen was determined employing the pressure relaxation method. The values were 2940 (±209) Pa from the slit viscometer and 3100 Pa (± 200) Pa from the rectangular die. The rheological parameters of collagen were then obtained using the analytical method and the proposed approximate methods for Casson, Herschel-Bulkley, and Robertson-Stiff rheological models. It was shown that the wall shear rate and the wall shear stress values of the analytical method and the proposed method are in good agreement. It was found that the Herschel-Bulkley and Robertson-Stiff models successfully fitted the wall shear rate-wall shear stress curves with a coefficient of determination equal to or greater than 0.97, and the evaluated consistency values were 165 (±71) Pa.sn for the Herschel-Bulkley model and 947 (±225) Pa.sn for the Robertson-Stiff model, and the flow index values were found to be 0.50 (±0.06) for the Herschel-Bulkley model and 0.32 (±0.03) for the Robertson-Stiff model. However, it was shown that the Casson model is not suitable for describing the rheological characteristic of collagen material. Experimentally obtained parameters for the Herschel-Bulkley model were validated with the use of simulations, and it was found that the numerically and experimentally evaluated results showed good agreement. The maximum deviation was found to be less than 12%.

Fast atomic crack kinking and branching in WS2

Abstract Dynamic nanocrack propagation in 1T- and 2H-WS2 strips is studied by molecular dynamics, and the T-stress and circumferential stress in linear elastic fracture mechanics are considered. As the crack propagates, the crack-tip speed (v) experiences a rapid acceleration, and then oscillates at ∼55% (1T) and ∼65% (2H) of the Rayleigh-wave speed followed by crack kinking/branching. The critical energy release rates of crack instability are estimated to be ∼1.5 J/m2 (1T) and ∼4.0 J/m2 (2H). The crack path in 1T-WS2 exhibits higher sensitivity of strain rates for atomic asymmetry around the crack tip. Examination of the dynamic crack-tip field shows that the T-stress obtained by the over-deterministic method always fluctuates in negative, and the theoretical circumferential stress curve does not accurately capture the v-dependent atomic stress distribution. Consequently, both T-stress and circumferential stress are limited in predicting the crack kinking/branching directions, which can be attributed to the discrete crystal lattice and local anisotropy of WS2, where a preferred crack path along the zigzag surface is observed. The fracture properties of WS2 might provide useful physics for its applications in nano-devices.

Bond properties between lapped steel rebars and UHPC under direct tension

Ultra-High Performance Concrete (UHPC) is a highly advanced cement-based composite that offers higher mechanical properties and exceptional durability over Normal-Strength Concrete (NSC). Bond properties between steel rebars and UHPC are the key to designing reinforced UHPC structures. The goal of this study was to characterize the bond properties between lapped steel rebars (uncoated) and UHPC. A total of 20 modified pullout tests having two-row lap splices were performed to examine the variation of diameters of 10, 14, 20, 25 and 32 mm. It was shown that the splitting of UHPC covers was a dominant failure mode, and samples with smaller bar diameters exhibited good ductility. Higher bond strengths were found in samples with smaller bar diameters. Specifically, bond strengths in samples having diameters of 20 mm, 25 mm, and 32 mm showed reductions of 14.8 %, 27.6 %, and 35.2 % in comparison to those featuring a diameter of 10 mm. The distributed curves of bond stress with two peaks were identified when maintaining a lapped length of four times the bar diameter. Furthermore, the mechanical model for lapped steel rebars in UHPC and the theoretical equation for calculating the bond-splitting strength and minimum lapped length were presented and validated by the available studies.

Effect of strain rate on glass fiber reinforced polymer composite using split hopkinson pressure bar

The aim of this study is to examine the stress–strain behavior of Glass Fibre Reinforced Polymer (GFRP) composite with three different orientations, namely [0°/90°]s, [±45]s, [0°/+45°/−45°/90°]T. To achieve this, the GFRP was simulated using the Split Hopkinson Bar (SHPB) setup in ABAQUS/CAE. The striker bar was used at three different velocities (9.7 m s−1, 12.7 m s−1, and 14.3 m s−1) to produce strain rates ranging from 1000 s−1 to 2000 s−1. The dynamic response of the GFRP composite was studied by considering its stress–strain behavior. The effect of strain rate on the elastic modulus and energy absorption capacity of GFRP laminates was analyzed through complete stress versus strain curves. The results showed that the elastic modulus and energy absorption capacity of GFRP laminates were sensitive to strain rates, with an increase in strain rate leading to an increase in the elastic modulus and energy absorption capacity.

Fatigue and Fracture Behaviors of Short Carbon Fiber Reinforced Squeeze Cast AZ91 at 20 °C and 250 °C

AZ91 is one of the most broadly used Mg alloys because of its good castability and reasonable mechanical properties. Strengthening AZ91 with carbon short fibers aims to increase tensile and fatigue strength, creep, and wear resistance. One of the proposed applications of reinforced AZ91 is the production of pistons for trucks. Such reciprocating parts are subjected to alternating fatigue loads which can lead to fatigue failure. In this respect, studying the tensile and fatigue behavior of materials subjected to such loading conditions is of great interest. The alternating low-cycle fatigue (LCF) and high-cycle fatigue (HCF) of unreinforced AZ91 and carbon fiber-reinforced AZ91 (AZ91-C) were investigated at 20 °C and 250 °C. Tensile tests were carried out at the same testing temperature to find the appropriate fatigue testing stress and strain for stress-controlled and strain-controlled tests, respectively. The fatigue curves of stress against the number of cycles (S–N) revealed that the composite AZ91-C’s fatigue strength was 55 MPa under HCF, while that of the matrix alloy AZ91 was only 37 MPa at 250 °C. Fracture investigations were conducted on the broken test samples. The fracture approach in the matrix material (AZ91) is mixed ductile/brittle containing fatigue serration, fiber fracture, and separation in the reinforced material (AZ91-C).

Biaxial Tensile Mechanical Properties of HTPB Solid Propellant

The purpose of this work is to study the effects of different loading rate ratios and loading speeds on the biaxial tension of hydroxyl-terminated polybutadiene (HTPB) solid propellant. A proper kind of biaxial tensile specimen with which the stresses in its central part can be obtained with the loads acted on each loading direction is designed and used in the study, and the strains in its central parts are obtained with the digital image correlation (DIC) method. The stress and strain relationship at each direction can be obtained by experiments. The uniaxial stress vs. strain curves and the biaxial stress vs. strain curves were obtained, and it was found that the loading speed remarkably influenced the biaxial tensile behaviors of HTPB propellant. The Mises equivalent stress and strain could be used to describe the biaxial tension stress and strain state, and the exponential constitutive model obtained in the study could be used to predict the stress vs. strain curve under different test conditions.

Progressive damage process and destabilization precursor recognition of sulfate tailing-cemented paste backfill based on acoustic emission

Sulfate-rich tailings are commonly used as aggregate materials for mine filling, and the sulfate retained within them significantly affects the structural characteristics of cemented paste backfill (CPB). A series of microstructure tests, uniaxial compressive strength (UCS) tests, and acoustic emission (AE) monitoring were carried out on CPB and sulfate tailing-cemented paste backfill (ST-CPB) to investigate the progressive damage pattern and identify the destabilization precursor information of the backfill. The results showed that the UCS of the backfill increased and then decreased with the increase in sulfate content, and 1.5% was the optimal content. The AE counts, energy, amplitude, and peak frequency time series corresponded to each other, exhibited the stage characteristics of a stress curve and were significantly affected by sulfate content. CPB and 0.5% ST-CPB displayed more active AE counts and energy during the initial loading stage, with high amplitude and low-frequency signals. However, the 1.5% ST-CPB exhibited active AE events and medium-high amplitude and medium-low frequency signals only during the plastic yielding and damage stages. 2.5% ST-CPB exhibited more active AE signals during the entire loading process. RA-AF values indicate that CPB and 2.5% ST-CPB reached 93.12 and 96.62% of tensile cracks at final failure, respectively. Meanwhile, the percentages of tensile cracks at the final failure of 0.5 and 1.5% ST-CPB were 76.65 and 76.86%, respectively. The sudden increase in the variance curve and the rapid decrease in the b value of AE in the critical slowdown theory were identified as the precursor characteristics of the backfill instability. This investigation can provide technical and theoretical support for the progressive damage characteristic and stability assessment of ST-CPB.

Towards better understanding of the strain–stress curve of cork: A structure–mechanical properties approach

If the compressive strain–stress curve of cork has already been largely described, its relationship with the cork structure still requires a better understanding. In this study, quasi-static and Progressive Repeated Loading (PRL) tests in compression have been performed on natural cork with a tensile machine. The elastic modulus was measured by a quasi-static compression test on cube or parallelepiped specimens considering different strain measurements methods: crosshead displacement, extensometer, and full field measurements method (Digital Image Correlation or DIC method). Regardless of the considered strain measurement method, the elastic modulus of cork remains in the same order of magnitude. The PRL test carried out at different nominal strains (3 %, 20 %, 46 %, 66 %, 80 %) highlighted the time dependant behaviour of cork (viscous properties). Moreover, a stiffening of the material was observed when increasing the strain at each loading/unloading cycle. Finally, the full field measurement following compression revealed the heterogeneity of the strain distribution on the cork external surface, resulting in localised regions of deformation. From the perspective of compression behaviour, these results lead to a new interpretation of cork which can be considered as a composite material.

MPM vs. CEL: Numerical modelling of penetration processes

MPM vs. CEL: Numerical modelling of penetration processes

Research on acoustic emission multi-parameter characteristics in the failure process of imitation steel fiber reinforced concrete

Studies of the damage process of fiber-reinforced concrete through acoustic emission are very significant for concrete structural health monitoring. In this study, three specifications of fiber concrete and one group of plain concrete were prepared to carry out the uniaxial compression test and acoustic emission monitoring test; then, b value, entropy H, and variance D, were calculated and compared their characterization effect. The main results showed that fibers increased the degree of internal inhomogeneity of the specimens, making the acoustic emission response more active. For every 2% increase in fiber content, the total acoustic emission count and energy increased by about 20%, the acoustic emission precursor parameters changed more significantly, the b-value decreased by 2%–10%, the entropy and variance increased by 3%–5% and 2%–22%, respectively. The variation of b value, entropy, and variance can be divided into three phases: initial rising/falling, unstable transition, and fluctuating slow-rising/falling, which had good consistency with the stress curve. According to the linear fitting results, the b value that dropped below the envelope in the post-peak phase can be taken as the damage precursor point, and its accuracy and generalizability were better. The entropy at the failure moment was around 0.6, but the value close to or above 0.6 occurred several times during the damage process, and taking the entropy value beyond the envelope range as the failure precursor point may lead to the error early warning. The variance was slightly worse to distinguish small-scale fracture, but was not susceptible to high-energy events. Therefore, variances close to 5 or beyond the envelope interval can be regarded as the precursor of final failure. As for studying concrete damage processes with acoustic emission, it is suggested to combine multiple parameters for comprehensive discrimination.

Reinforcing Cold-Sprayed Al Coatings With Boron Nitride Nanotubes and Micro-Boron Carbide and Their Effect on Surface Mechanical and Dry Sliding Behavior

Abstract This investigation explores the reinforcement effects of both boron nitride nanotubes (BNNTs) and micro-boron carbide (μB4C) on the tribological and mechanical properties of aluminum matrix composite (MMC) cold-sprayed coatings. The synthesis process involved high-energy ball milling (HEBM) and cold spraying with helium to create four distinct Al-MMC coatings on a magnesium (AZ31) substrate. These coatings consisted of pure aluminum, a composition containing 4 vol% B4C, a composition with 4 vol% BNNTs, and a composition with 2 vol% B4C and 2 vol% BNNTs. Successful dispersion of nanoparticles within the aluminum matrix was achieved. The hardness of the coatings exhibited significant improvements compared to the pure aluminum coating. Specifically, the Al-BNNT coating showed a hardness increase of 14.1%, the Al-B4C-BNNT coating displayed a hardness increase of 20.8%, and the Al-B4C coating demonstrated the highest increase of 33.3% over the pure aluminum coating. Furthermore, the Al-B4C coating exhibited remarkable reductions in wear volume loss and wear track depth, amounting to eight and two orders of magnitude, respectively. Adhesion testing revealed that the Al-B4C-BNNT coating failed cohesively, while the pure aluminum coating failed adhesively at approximately the same force. The Al-B4C coating experienced a combination of the two failure modes at a 31.2% increase in force compared to the pure aluminum coating. Tensile testing stress versus strain curves indicated that the load was partially supported by the cold spray coating until the coating ruptured.

Experimental investigation on the effect of process variables for the quality characteristics of AA 2024 processed in cold extrusion

Extrusion process has many applications in manufacturing industries due to its ability to produce products of high quality. Extrusion process can be classified into hot extrusion and cold extrusion. The cold forward extrusion is carried out at ambient temperature and has the additional benefit of improved mechanical characteristics. The metarial is compressed under intense pressure through a die orifice with a specific shape during the extrusion process. This process is effected by a few process variables, including die angle, punch speed, and lubrication are in greater extent towards the extrusion force requirement, microstructure and the product quality. Hence, the present experimental work focuses on extrusion of circular billet to produce cylindrical rod. Studying the behaviour of the material and the importance of the input process parameters during the cold extrusion process is the primary goal of this work. The experiments are carried out with AA 2024 alloy because of its wide applications in navy and aircraft structures. The varying die angles (10°, 20° &amp; 30°) as well as punch speed (1.6 mm/min, 3.2 mm/min and 4.8 mm/min) and lubricants (molybdium sulphide (MoS2), zinc stearate and grease) chosen as input parameters. The out put responses of this extrusion process are extrusion force, displacement, time and surface roughness. Extrusion forces are calculated based on flow stress curves at the locations of greatest elastic deformation. The results shows that increasing the punch speed and die angle increases the extrusion force. The microstructure evolutions and grain refinement at different die angles are examined using electron back scatter diffraction analysis. At 30° die angle, the microstructure showed grain refinement. It is also noted that the damage is significant at 30° die angle with a punch speed above 4.8 mm/min.

Effect of silica fume on rheology of slag-fly ash-silica fume-based geopolymer pastes with different activators

This study examined the effect of silica fume contents on the rheological behavior of slag-fly ash-silica fume-based geopolymer pastes by packing density measurement, low-field NMR, zeta potential, dynamic light scattering and FTIR analyses. Incorporating silica fume into sodium hydroxide (SH)-activated geopolymer pastes resulted in the decrease of packing density and the increases of yield stress, plastic viscosity and hysteresis loop curve area. The contrary results were found in the pastes activated by sodium silicate (SS). The water states of geopolymer pastes were influenced by SiO2/Na2O ratio of activator and silica fume dosage. The mobile water content in the sample increased as the silica fume dosage increased, regardless of the SiO2/Na2O ratio of activator. The particle size of the silica species in the activator and interstitial fluids is close to that of silica fume. The incorporation of silica fume resulted in the variation in the silicate structural characteristics of the interstitial fluids. The influence of silica fume on the rheological behaviors of geopolymer systems is strongly governed by the interparticle repulsion or attractiveness and activator nature, opposed to the filler effect and dissolution of silica fume. In SS-activated systems, the repulsion between the silanol groups on the silica fume surface and silicate species adsorbed on the surface of precursors particles contributed to the particle separations, thereby enhancing rheological behaviors. In SH-activated system, the attractiveness between divalent metal cations and silanol groups on the surfaces of precursor and silica fume particles was increased and the particle space was restrained. This study would provide new insights into the role of silica fume in the particle interaction of fresh ultra-high performance geopolymer concrete.

Research on rheological properties and phenomenological theory-based constitutive model of magnetorheological shear thickening fluids

This paper investigates the rheological properties of magnetorheological shear thickening fluid (MRSTF) and proposes a phenomenological theory-based constitutive model. Multiple samples with varying mass fractions and particle sizes were prepared. Then, the rheological properties were experimentally studied, including the effects of silicon particle size and concentration, carbonyl iron powder concentration and magnetic field on rheological properties. Next, the sedimentation stability experiment was also carried out by the static observation method. Finally, based on phenomenological theory, a constitutive model called the M-S model was derived through geometric transformation of shear stress curves. The results show that there is an inhibitory relationship between magnetorheological and shear thickening effect, and the correlation between composition and rheological properties was established, which can provide guidance for preparation of MRSTF with required properties. It also shows that the MRSTF under specific preparation scheme could effectively avoid sedimentation, and its performance is clearly superior to traditional materials in terms of sedimentation resistance and damping adjustment. The accuracy and universality of the proposed model are fully verified by fitting shear stress curves and calculating the goodness of fit values. All these investigations can offer an effective guidance for further study of MRSTF in controllable damping equipment development.

Effect of strain inhomogeneity on flow behavior, dynamic recrystallization and substructure evolution of a 904 L super austenitic stainless steel

In this work, two typical deformation processes were conducted on a 904 L super austenitic stainless steel to investigate its hot deformation behavior. Two regions with distinct effective strains were selected on identical cross section to examine the microstructural features, including substructures in the deformed matrix and dynamically recrystallized grains. The flow stress curves generally reflect the physical events that occurred at low strain range. When inhomogeneous microstructure and external factors such as friction become more remarkable at high strain level, some metallurgical events (e.g., partial dynamic recrystallization) are hard to be deduced from the flow curves. Meanwhile, strain dependent friction correction on the flow curves does not completely eliminate an obvious abnormal increase in flow stress, especially for the process with the deformation condition of 900 ℃ - 1 s−1. Based on the crystallographic analysis on the barreling zone of the deformed samples, it can be concluded that the strain-induced sub-boundaries that formed in the deformed matrix play a vital role in restricting the material flow behavior because these dense boundaries have a Hall-Petch strengthening effect. This is an intrinsic microstructure mechanism to explain the reason that the flow stress increases abnormally at large strains in the absence of dynamic recrystallization. In addition, the formation of twin boundaries at different deformation conditions are also discussed.

Predictive Modeling of Spring-Back Behavior in V-Bending of SS400 Steel Sheets under Elevated Temperatures Using Combined Hardening Laws

This research presents an innovative methodology for accurately predicting spring-back tendencies in V-bending of SS400 steel sheets under elevated temperatures. The study leverages extensive tensile test data to determine parameters for pure isotropic and kinematic hardening laws at varying temperatures, crucial inputs for Finite Element Method (FEM) simulations. While using pure isotropic or kinematic hardening laws alone has limitations, especially at elevated temperatures, a hybrid approach is recommended for robust predictive models in ABAQUS 6.13 software. To address this challenge, a novel method is introduced, utilizing flow stress curve ratios between elevated and room temperatures as a function of equivalent strain to derive combined hardening law parameters. Rigorous comparison of simulation and experimental results confirms the model’s effectiveness in predicting spring-back in the V-bending of SS400 steel sheets, particularly under elevated temperatures. This innovative approach enhances understanding of material behavior at high temperatures and improves predictive capabilities for designing and optimizing complex V-bending processes.

Monotonic and cyclic axial compressive responses of concrete specimens externally confined with different types of FRP composites: experimental and analytical investigations

The main objective of this study was to investigate the monotonic and cyclic axial stress versus strain response of the concrete confined with different types of fiber reinforced polymer (FRP) composites such as cotton fiber rope reinforced polymer (CFRRP), glass fiber reinforced polymer (GFRP) composites and carbon fiber reinforced polymer (CFRP) composites. Another objective was to investigate the applicability of existing ultimate strength models to predict the ultimate strength of concrete confined with CFRRP, GFRP and CFRP composites. For this, a total number of 28 concrete cylinders were cast, strengthened and tested under pure axial compression. The concrete cylinders were strengthened with two and four layers of FRPs. The experimental results indicate that all kinds of FRPs are very useful to alter the ultimate strength and strain of the confined concrete. The highest increase in ultimate strength was recorded for CFRP composite confined specimens and the highest increase in ultimate strain was observed for CFRRP composite confined specimens. Further, both ultimate strength and ultimate strains are found higher in the case of cyclic loads compared with the monotonic load. In general, the stress versus strain curves of cotton fiber rope and glass FRPs are found trilinear. Whereas, stress versus strain curves of CFRP confined specimens are observed to be bilinear. Existing ultimate strength models developed for CFRRP and CFRP composites are found well accurate to predict the ultimate strengths of CFRRP and CFRP confined concrete specimens tested in this study.