Uniaxial Tensile Stress Strain Research Articles

Tensile characteristics of ultra-high-performance fibre-reinforced concrete with and without longitudinal steel rebars

Ultra-high-performance fibre-reinforced concrete (UHPFRC) specimens with and without longitudinal reinforcement were experimentally tested under direct tensile loading. The variables considered were the volume fraction of fibres (1.0% and 2.0%), the type of steel fibres (straight and hooked end) and the longitudinal steel reinforcement ratio (none and 1.2%). All of the specimens were tested using a servo-controlled fatigue testing machine in displacement control mode. The changes in displacement were monitored using linear variable displacement transducers and the digital image correlation technique. The strain profiles at different loading stages were used to identify the crack evolution process. The average localised strain was found to be 0.2–0.36%, with corresponding crack widths of 0.3–0.6 mm. A uniaxial tensile stress–strain model was developed based on the test results and data from the literature. Longitudinally steel-reinforced specimens showed both stiffening and strengthening effects. Tension-stiffened specimens with 1.0% fibres failed at a higher strain due to the formation of multiple macrocracks. In the specimens with 2.0% fibres, the rebar fractured in a brittle manner due to crack localisation. It is concluded that a higher longitudinal reinforcement ratio is needed to utilise UHPFRC effectively under tension-dominant loads.

A Continuously Derivable Uniaxial Tensile Stress-Strain Model of Cold-Formed Circular Steels

Promoting prefabricated steel structures is considered one of the crucial approaches to meeting the objectives of “carbon peak” and “carbon neutrality” in the construction industry. Due to insufficient practical experience and incomplete fine engineering techniques in civil construction, the sustainable development of prefabricated building systems in China faces many challenges. Taking steel components as an example, the design process of tubular columns does not pay enough attention to the influence of the cold-working effect on material mechanical properties, and the constitutive relationship of cold-formed steels is not clear, which will cause an engineering economic burden and may affect the judgment of catastrophic problems. To serve the refined design and meet the intelligent construction technology using the computer platform, a modified Menegotto-Pinto model using a continuously derivable function is proposed in the paper. The proposed model can successfully describe the complete stress-strain curve of cold-formed circular mild steels as long as the basic mechanical parameters of the parent material are determined. Taking into account the influence of the strength and thickness of the parent steel sheets, as well as the internal bending radius r, on the cold-rolling effect, the model can also flexibly track the elastic-plastic nonlinearity of the cold-formed materials. In addition, the research shows that the cold-rolling effect will weaken with the increase of the yield strength fsy,0 of the parent steels and r/t ratio, and may disappear when fsy,0 reaches 1748 MPa or the r/t ratio is approximately 60, which can be used as economic indicators during the design process.

Multi-scale numerical simulation of fracture behavior for the gadolinia-doped ceria (GDC) under mechano-electrochemical coupling fields at high temperature

The fracture toughness of gadolinia-doped ceria (GDC) solid oxide fuel cells (SOFCs) electrolyte with a central crack is significantly reduced under the mechano-electrochemical coupling fields at high temperature. In this work, an atom-to-continuum (AtC) multi-scale method combining the finite element method (FEM) and the molecular dynamics (MD) simulation is developed. Firstly, the AtC multi-scale method is validated by investigating the uniaxial tensile stress–strain curves of GDC with a central crack at different temperatures. Then, based on the theory of fracture mechanics, the macrostructure of GDC is transformed into a microscopic intermediate transition model, and a detailed computational procedure for analyzing the fracture toughness of the macrostructure of the GDC is given by the AtC multi-scale method. Finally, the fracture toughness of GDC macrostructure under the mechano-electrochemical coupling fields is studied by the proposed approach. The simulation results show that the fracture toughness of 10GDC and 20GDC under the mechano-electrochemical coupling fields is clearly reduced compared to the uniaxial tensile loading. Among them, the fracture toughness of 10GDC under the mechano-electrochemical coupling fields is decreased by 12.28% and 30.67% at 800℃ and 900℃, and the fracture toughness of 20GDC under the mechano-electrochemical coupling fields is decreased by 17.25% and 29.52% at 800℃ and 900℃. These findings are critical in predicting the fracture behavior of GDC electrolyte under real working conditions.

A Coupled Nonlinear Viscoelastic–Viscoplastic Thermomechanical Model for Polymeric Lithium-Ion Battery Separators

One of the major concerns in ensuring lithium-ion battery (LIB) safety in abuse scenarios is the structural integrity of the battery separator. This paper presents a coupled viscoelastic–viscoplastic model for predicting the thermomechanical response of polymeric battery separators in abuse scenarios under combined mechanical and thermal loadings. The viscoplastic model is developed based on a rheological framework that considers the mechanisms involved in the initial yielding, change in viscosity, strain softening and strain hardening of polymeric separators. The viscoplastic model is then coupled with a previously developed orthotropic nonlinear thermoviscoelastic model to predict the thermomechanical response of polymeric separators before the onset of failure. The model parameters are determined for Celgard®2400, a polypropylene (PP) separator, and the model is implemented in the LS-DYNA® finite element (FE) package as a user-defined subroutine. Punch test simulations are employed to verify the model predictions under biaxial stress states. Simulations of uniaxial tensile stress–strain responses at different strain rates and temperatures are compared with experimental data to validate the model predictions. The model predictions of the material anisotropy, rate and temperature dependence agree well with experimental observations.

Uncertainty quantification and propagation in the microstructure-sensitive prediction of the stress-strain response of woven ceramic matrix composites

Hierarchical multiscale modeling of heterogeneous materials has traditionally relied upon a deterministic estimation of constitutive properties when making microstructure-sensitive predictions of effective response at each subsequent length-scale. Such an approach is wholly unsuitable for a variety of material classes, such as ceramic matrix composites, which exhibit large variability at multiple length-scales. This work demonstrates a framework for approaching two open problems towards improved microstructure-sensitive predictions, namely, (i) probabilistically calibrating complex constitutive models at the mesoscale to sparsely observed macroscale experimental data, and (ii) propagating this stochastic constituent behavior at the mesoscale towards low-cost homogenized predictions for unseen microstructures. The proposed stochastic scale-bridging framework displays a continuity of information flow where no portion of the experimental data is neglected out of convenience, facilitating the greatest information gain from oftentimes costly experiments. In this paper, suitable protocols were developed to address the challenges described above. The protocols were subsequently demonstrated on ceramic matrix composite’s uniaxial tensile stress–strain response, where constituent behavior at the mesoscale was described using continuum damage mechanics, and predictions encapsulating constitutive model parameter uncertainty were made for novel microstructures. The methodology presented in this work is broadly applicable to various material classes and constitutive models with high-dimensional parameter sets.

Uniaxial tensile properties of pre-stretched ethylene-tetrafluoroethylene (ETFE) foil

The ETFE foil is a type of good cladding material in the field of architecture and its uniaxial tensile properties are important considerations in the design analysis. In engineering application, the stress of ETFE foil may exceed the first and second yield stress under external load and the large plastic deformation is usually observed. Previous studies mainly focus on its uniaxial tensile properties along the uniaxial pre-stretching direction after the uniaxial pre-stretching stress is over the yield stress. Uniaxial pre-stretch will cause the ETFE film to compress in the other direction due to Poisson’s ratio, while the uniaxial tensile properties perpendicular to the uniaxial pre-stretching direction is still unknown. Besides, the study on its uniaxial tensile properties along the biaxial pre-stretching direction after the biaxial pre-stretching stress is over the yield stress is also quite limited. In order to investigate this issue, the uniaxial pre-stretching tests, the asynchronous biaxial pre-stretching tests and the synchronous biaxial pre-stretching tests were performed to make the uniaxial stress and the biaxial stress reach over the first and second yield stress respectively. Square specimens for subsequent uniaxial tensile tests were prepared from these pre-stretching tests and the uniaxial tensile stress–strain curves of specimens of different pre-stretching tests were obtained. The uniaxial tensile test results demonstrate that in some cases the bearing capacity of ETFE foil was strengthened after pre-stretching tests while in many cases both the uniaxial pre-stretching and the biaxial pre-stretching lowered the bearing capacity of ETFE foil. Additionally, the pre-stretching strain correlates strongly with the bearing capacity of pre-stretched ETFE foil and the relationship between them is discussed.

Identification of probabilistic distribution parameters for the mesoscopic stochastic fracture model

As a kind of multiphase composite material, the basic mechanical behaviors of concrete are randomness and nonlinearity. The mesoscopic stochastic fracture model (MSFM) which can reflect the coupling effect of randomness and nonlinearity, has been widely used for the nonlinear analysis of concrete structures. In this paper, we proposed a new stochastic modeling principle to identify the probabilistic distribution parameters of MSFM. In order to reduce the modeling works, a dimension-reduced algorithm is proposed as well. In this paper, an overview of MSFM is firstly presented to introduce the background of the research. Then the stochastic harmonic function (SHF) representation is introduced to express the random field mentioned in the MSFM, and the probability density evolution method (PDEM) is applied to obtain the theoretical probability density function (PDF) of the stress–strain relationships. Furthermore, a stochastic modeling principle is proposed, in which minimizing the Kullback–Leibler divergence (KLD) is taken as the optimization object. Based on the framework of genetic algorithm, a dimension-reduced algorithm is proposed to identify the parameters with reference to the data from tested complete curves of uniaxial compressive and uniaxial tensile stress–strain relationship of concrete. The results indicate that the proposed principle and algorithm can be used to identify the parameters of MSFM accurately and efficiently.

Tensile Mechanical Properties and Dynamic Constitutive Model of Polyurea Elastomer under Different Strain Rates.

In order to clearly explain the large deformation mechanical characteristics of polyurea under impact and to construct a dynamic model that can be used for finite element analysis, two kinds of polyurea materials were prepared by formula design, and their uniaxial tensile properties were tested with strain rates ranging from 10−3~103 s−1 using an electronic universal testing machine and a split Hopkinson tensile bar (SHTB). The tensile stress–strain curves of polyurea were obtained under different strain rates. The difference in tensile mechanical properties of the materials was analyzed under dynamic loading and quasi-static loading. Based on the nonlinear viscoelastic theory and the energy dissipation rate inequality, a dynamic visco-hyperelastic constitutive model of polyurea elastomer was established. The research results showed that the uniaxial tensile stress–strain curves of two kinds of polyurea at different strain rates had obvious nonlinear characteristics and strain rate sensitivity and that their tensile strength increased with increased strain rate. The polyurea gradually changed from exhibiting rubbery mechanical behavior under quasi-static loading to glassy mechanical behavior under dynamic loading. The fitting analysis of experimental data and the results of finite element simulation showed that the dynamic constitutive model can predict the nonlinear mechanical behavior of polyurea elastomers over a wide range of strain rates. The research results could contribute to a deepening of the understanding of the damage and failure behavior of polyurea under impact load and provide a theoretical basis for numerical studies on impact safety design of polyurea-coated protective structures.

Effects of sodium aluminate on the performance of seawater sea-sand engineered cementitious composites

In this study, a quick setting seawater sea-sand engineered cementitious composite (SS-ECC) was prepared using sodium aluminate (NaAlO2, NA). The effects of the amount of NA and different types of water (seawater and freshwater) on the setting time, compressive strength, flexural strength, and tensile properties of the SS-ECC were studied. The influence of NA on the hydration reaction and microstructure of the SS-ECC was examined through X-ray diffraction (XRD), thermogravimetric analysis (TGA), and field emission scanning electron microscopy (FE-SEM). Experimental results revealed that NA and seawater reduced the setting time of the SS-ECC, particularly at 4% NA, and slightly improved the early strength of the SS-ECC. However, too much NA would decrease the late strength of the SS-ECC. The incorporation of NA enhanced the ultimate tensile strain of the SS-ECC. And the SS-ECC with 4% NA exhibited evident strain-hardening characteristics under tension, with the ultimate tensile strain reaching a maximum of 4.61%. The calculated toughness and residual strength indexes indicated that the SS-ECC could be defined as an ideal elastoplastic material. Based on this, a bilinear uniaxial tensile stress–strain constitutive model of the SS-ECC was established. In addition, the XRD and TGA results demonstrated that NA promoted the hydration of cement, generation of AFt and AFm, and polycondensation reaction to generate C-A-S-N and N-A-S-H gels. This decreased the setting time of the SS-ECC and improved the early strength. However, the product obtained by the early rapid reaction might have encapsulated the cement raw materials, thereby preventing further hydration in the later stage. This was not conducive to the long-term strength development of the SS-ECC.

Strain-hardening fiber reinforced polymer concrete with a low carbon footprint

Epoxy resin, fly ash, and silica sand were used to produce polymer concrete reinforced with glass, carbon, polyvinyl alcohol (PVA), and high strength steel micro-fibers. The effects of two resin contents: 15% and 18%, and two curing regimes: ambient and heat were assessed. Their compressive strength, permeable porosity, and uniaxial tensile stress–strain behavior were studied. The compressive strength of 15% and 18% polymer concrete were 48–62 MPa and 61–74 MPa respectively. The porosity of all types of polymer concretes was less than 1%, except 15%-PVA and 15%-glass fiber reinforced polymer concrete. Under uniaxial tensile loading, glass and carbon fiber reinforced polymer concrete portrayed a sudden brittle failure resulting from complete fiber rupture, whereas PVA and steel fiber reinforced polymer concrete demonstrated a ductile strain-hardening response. A significantly higher tensile strength was observed when the resin content was increased from 15% to 18%, particularly for glass and carbon fiber reinforced polymer concrete, whereas for PVA and steel fiber reinforced polymer concrete this improvement was small. The brittle carbon fiber reinforced polymer concrete demonstrated the highest tensile strength, whereas the ductile steel fiber reinforced polymer concrete had the highest post-crack residual strength at large strains, irrespective of the resin content. Overall, heat curing had no impact on compressive or tensile properties of any type of polymer concrete investigated.

Effect of solid waste ceramic on uniaxial tensile properties and thin plate bending properties of polyvinyl alcohol engineered cementitious composite

As a kind of non degradable waste, solid waste ceramics has caused serious negative impact on land resources and ecological environment. Therefore, the reasonable recycling of solid waste ceramics is of great significance to the sustainable development of society. In this study, solid waste ceramic powder (CP) was taken as a supplementary cementing material to replace cement (Cement) partly in polyvinyl alcohol-engineered cementitious composites (PVA-ECC) materials. Twelve groups of PVA-ECC materials were designed, with a CP substitution rate of 10%, 15%, 20% (proportion in the mass of cementing materials) respectively. The uniaxial tensile properties and thin plate bending properties of PVA-ECC with different substitution rate solid waste CP were compared and analyzed. The theoretical calculation model of uniaxial tensile stress-strain is established. The results show that recycling of solid waste CP is helpful to clean production of PVA-ECC materials. PVA-ECC with solid waste CP shows good tensile strain and bending toughness. Therefore, CP was taken as a supplementary cement material is feasible. When the content of fly ash (FA) is 70%, the content of Cement is 10%, and the content of solid waste CP is 20%, the uniaxial tensile strain of the material is the largest, which is 4.94%; at the same time, the ultimate bending toughness index of the material is the largest, which is 352.21. Therefore, the mix proportion of this group of specimen is the optimal mix proportion. Compared with the uniaxial tensile test results, the accuracy of the model established in this study is verified. It can effectively predict the uniaxial tensile constitutive model of PVA-ECC material with any substitution rate when the substitution rate of solid waste CP is 10%–20%. This study can play a certain role in promoting the resource utilization of solid waste CP.

Mechanical Properties of Cu-B/Diamond Composites Prepared by Gas Pressure Infiltration

Diamond particles reinforced boron-alloyed Cu matrix (Cu-xB/diamond, x = 0.1, 0.2, 0.3, 0.4, 0.5, and 1.0 wt.%) composites were prepared by gas pressure infiltration. The size of the diamond particles was ~ 230 μm and the diamond volume fraction in the composites was ~ 66%. The interfacial carbide evolution plays an important role in improving the interfacial bonding and enhancing the mechanical properties of the Cu-B/diamond composites. The tensile, compressive and bending strengths firstly increase and then decrease with increasing boron content, giving a maximum tensile strength of 204 MPa, a maximum compressive strength of 608 MPa, and a maximum bending strength of 513 MPa at 0.5 wt.% B addition. The monotonic uniaxial tensile stress–strain curves of the Cu-B/diamond composites were predicted by using the Mori–Tanaka, generalized self-consistent, and Torquato identical hard spheres approximation models. The results suggest that alloying B to Cu matrix is an effective route to strengthening Cu/diamond composites.

Modeling the thermomechanical behaviors of particle reinforced shape memory polymer composites

Shape memory polymer composites (SMPCs) possess superior thermomechanical properties while keep good shape memory capabilities, so SMPCs attract great research interest from academia and industry. In the paper, a modified thermoviscoelastic finite deformation constitutive model is developed to investigate the thermomechanical properties and shape recovery behaviors of particle reinforced SMPCs. The model is incorporated with the modified Adam–Gibbs model and the Eyring model to describe the structural relaxation and yielding behaviors. Also, a non-Gaussian chain molecular network model is used to capture the hyperelastic properties in the large deformation situation. Then, the constitutive model is employed to estimate the free recovery behaviors of SMPCs with different particle fractions, and the comparison between the simulation results and the test data shows good agreement. Furthermore, the model is applied to predict the constrained recovery properties and uniaxial tensile stress–strain response of the composites. The thermomechanical model provides an efficient method for designing and optimizing particle reinforced SMPCs.

Quasi-static and dynamic splitting of high-strength concretes – tensile stress–strain response and effects of strain rate

Quasi-static and dynamic splitting tensile tests were performed on three high-strength concretes with different compressive strengths – 60 MPa, 80 MPa and 110 MPa, denoted by C60, C80 and C110 respectively – to examine their tensile properties. Quasi-static tests were conducted at a strain rate of ∼2 × 10−6 s−1, using a Shimadzu Universal Testing Machine; and dynamic tests were performed at strain rates of ∼1–10 s−1, using an 80 mm-diameter split Hopkinson pressure bar (SHPB) device. Strain gauging and digital image correlation (DIC) techniques were employed to determine the deformation in specimens. From the force applied and the average tensile strain at the specimen centre, obtained from strain gauge measurements, the uniaxial tensile stress–strain response at that location was derived, by adopting an elastic-plastic analysis, whereby tensile plastic hardening is assumed to be piecewise linear. The effects of strain rate on the tensile response were also examined and analysed. For all three high-strength concretes, significant rate dependence was observed; the yield stress, tensile strength and failure strain all increase with strain rate, and their dynamic values are much higher than their static values. The Dynamic increase factor (DIF), i.e. the ratio between the dynamic and static tensile strengths, was calculated to quantify the rate sensitivity. Similar DIFs were obtained for C60, C80 and C110, and the DIFs determined were compared with predictions based on two empirical formulae, i.e. the CEB-FIP model (2010), and that proposed by Malvar and Ross, which are frequently used for normal-strength concrete. These two formulae appear inadequate in defining the rate dependence of high-strength concrete. Consequently, a bilinear description of the DIF as a function of log10(ɛ˙), with a transition at a strain rate at 1 s−1, was proposed for high-strength concrete, based on the experimental data.

Postcracking tensile behavior of blended steel fiber‐reinforced concrete

Fiber blends have the potential to improve the mechanical and sustainability credentials of steel fiber‐reinforced concrete (SFRC), but at which ratios these can work is not known a priori. This paper investigates the uniaxial tensile stress–strain ( σ − ε) relationship of blended SFRC using manufactured steel fibers on their own, or blended with sorted steel fibers recycled from end‐of‐life tires (recycled tire steel fiber [RTSF]), at total fiber dosages of 30, 35, and 45 kg/m3. The accuracy of two σ − ε relations proposed by RILEM TC 162‐TDF and Model Code 2010 is assessed using the experimental results from concrete prisms. By using nonlinear finite element (FE) analysis, it is found that the RILEM approach can lead to significant overestimation (up to 72%) of peak flexural load and energy absorption capacity (up to 39%), while the Model Code 2010 can provide a rather accurate prediction of the energy absorption capacity and some overestimation (less than 34%) of the peak flexural load. Inverse FE analysis is used to determine indirectly the uniaxial tensile σ − ε relations of the examined SFRC mixes, and a simplified trilinear relation for SFRC is proposed. It is concluded that the tensile strength of SFRC with RTSF at a low total fiber dosage is only marginally improved by fiber addition, and the postcracking tensile strengths at different strains can be determined directly from residual flexural tensile strengths (f Ri) of prisms.

Uniaxial Tensile Stress–Strain Behavior of Carbon-Fiber Grid–Reinforced Engineered Cementitious Composites

AbstractCarbon fiber–reinforced polymer (CFRP) grid–reinforced engineered cementitious composites (ECC) have been developed as an alternative to epoxy resin–based FRP plates for the strengthening o...

Uniaxial Tensile Simulation of 3D Orthogonal Woven Fabric

Mesoscale modelling approach has shown close simulation approximations of woven fabric tensile performance. The main purpose of the work is to develop understanding of geometrical model development, finite element analysis procedure and to compare the differences of 2D and 3D woven fabric uniaxial tensile stress-strain. 3D woven fabric structures selected for the work is three-layer orthogonal woven fabrics. The woven structure will have 2 through-thickness warps, 4 non-crimps warp and 6 wefts. Through-thickness warp yarn will apply plain 1/1 weave structure for stitching all weft layers and non-crimps weft yarn together. Woven geometric models were developed with pre-processor program at detail yarn configurations. Simulation results showed that 3D orthogonal woven fabric had a better tensile response than its 2D woven fabric structures.

Strain rate and temperature dependence of the mechanical properties of polymers: A universal time-temperature superposition principle.

Establishing the Time-Temperature and Frequency-Temperature Superposition Principles (TTSP and FTSP) to describe the mechanical behavior of polymeric materials is always of paramount significance. In this work, by adopting the classic coarse-grained model, we investigate the validity of these superposition principles for a series of networks, such as the pure polymer network, interpenetrating polymer networks composed of stiff and flexible networks (IPNs-SF), interpenetrating polymer networks composed of different cross-linking networks (IPNs-DC), polymer nanocomposites (PNCs), and surface grafted modified PNCs. The study focuses on the three critical mechanical properties such as the stress relaxation, the storage modulus versus the frequency obtained from the dynamic periodic shear deformation, and the uniaxial tensile stress-strain. The glass transition temperature (Tg) is about 0.47 for the simulated polymer network (CL400), and a smooth master curve is obtained for the stress relaxation process by setting the reference temperature Tref = 0.6 via the horizontal shifting process, indicating the validity of TTSP. Furthermore, similar smooth master curves are also achieved for both dynamic periodic shear and uniaxial tensile deformation, which exhibit similar trends and share the identical linear viscoelastic regime in the temperature interval above Tg: 0.55<T<1.0. Importantly, the Williams-Landel-Ferry and Vogel-Fulcher-Tammann equations are both adopted to quantitatively analyze non-linear TTSP behavior when the temperature approaches Tg. For the three mechanical properties, we emphasize that the master curve from TTSP or FTSP is independent of the reference temperature if it is higher than Tg, and based on the linear relation of the shift factor versus the inverse of the temperature higher than Tg, we propose a universal framework for the description of the TTSP or FTSP on the various mechanical properties. Then, we verify that the TTSP seems to be valid for the IPNs-DC system, while it does not hold for both PNCs and IPNs-SF systems because of their structural and dynamic heterogeneity. Furthermore, for PNCs filled with NPs grafted with polymer chains, the TTSP recovers back to be valid because of the enhanced compatibility between polymer and NPs attributed to the grafted polymer chains.

An improved method of determining Gotoh’s nine material constants for a sheet metal with only seven or less experimental inputs

A method is described for estimating the material constants in Gotoh’s fourth-order yield stress function for modeling anisotropic yielding and plastic flow of a sheet metal with only up to seven available experimental inputs. The yield function is assumed to have a reduced degree of planar anisotropy so its nine material constants can be computed directly via simple algebraic relations using seven or less experimental inputs available for the sheet metal. The key idea behind the proposed method is to first transform a polynomial yield function such as Gotoh’s in terms of two principal stresses and one loading directional angle and to set coefficients of some high order Fourier cosine terms in the transformed yield function to be zero as needed. Not only the method is much simpler to use in comparison with many other existing methods appeared in the literature, the results obtained for many representative sheet metals also give consistent and even superior description of directional dependence of uniaxial tensile yield stress and plastic strain ratio without any undesired spurious and large oscillations. As Gotoh’s yield function is one of the simplest complete non-quadric polynomials with the enhanced modeling capability, the simple analytical calculations of all of its material constants should facilitate its wider application as the new default choice of orthotropic plasticity modeling in industrial sheet metal forming analyses.

Tensile properties of 6061-T6 friction stir welds and constitutive modelling in transverse and longitudinal orientations

Tensile stress–strain properties of Al alloy 6061-T6 (AA6061-T6) and its butt welds produced by the friction stir welding (FSW) process were characterized in two different loading orientations. AA6061-T6 FS welds were made under three sets of welding conditions. Micro-hardness tests were performed to investigate microstructural evolution during the FSW process. Flat tensile specimens were machined normal and parallel to the weld line. Transvers and longitudinal tensile tests were run on the base material (AA6061-T6) and its FS welds in an Instron testing machine. The strength and ductility (or fracture strain) of the FS welds observed in the transverse orientation were substantially less than those in the longitudinal orientation. Constitutive modelling of uniaxial tensile stress–strain behaviour in both orientations was presented using a rate-independent Ludwik equation. In addition, microstructures of the base material and its FS welds were examined with optical and transmission electron microscopy to discuss the decrease in the flow stress level and the increase in the strain hardening rate of the FS welds.