Tensile Test Data Research Articles

Mechanical performance of dissimilar Al6082 aluminum and AZ91 magnesium alloy joints produced by friction stir welding

Abstract The current research work aims to produce a defect free joint of Al6082 aluminum and AZ91 magnesium alloy sheets by friction stir welding (FSW) at various tool rotational and travel speeds with an objective to obtain the best combination of welding parameters to produce quality joint. The weld joint that was produced at the combination of 1400 rpm tool rotational speed and 30 mm min−1 feed exhibited defect free stir zone. Microstructural studies carried out in the weld joint demonstrated mechanical mixing of base materials from both the alloys in the stir zone. The mixing of Al6082 and AZ91 alloys was clearly appeared in the weld zone. It can be observed that the x-ray diffraction studies clearly demonstrated the development of intermetallics in the weld region. Higher hardness was observed for the joints that can be ascertained to the presence of more mixed regions in the stir zone that contains hard and brittle intermetallics. From the tensile test data, lower strength (175.71 ± 4.24 MPa) was observed for the weld joint compared with Al6082 (242. 6 ± 11.4 MPa) and AZ91 (205.27 ± 6.39 MPa) base materials. Furthermore, the ductility of the weld joint was measured as marginally higher than the AZ91 Mg alloy and lower than the Al6082 alloy. It can be concluded that the defect free weld joints of Al6082-AZ91 alloys can be successfully produced by FSW for structural applications targeted for dry environment.

Mechanical properties of aramid and UHMWPE thermoplastic composites: numerical and experimental trials

The out-of-plane behaviour of 8 different composites exposed to very high deformation rates and non-standard conditions was investigated in our previous studies. The mechanical properties of these composites have been evaluated through tests conducted at deformation rates comparable to those experienced during explosions. Based on the relevant test results, this study conducted a numerical analysis of 3 best-performing Aramid UD GS3000, Artec Aramid/Woven Aramid CT736, and H62 UD-UHMWPE-reinforced composites. In this regard, LS-DYNA's MAT54 model was compared with other failure mechanics-based models and preferred because it requires less experimental data and can simulate damage progression in dynamic failures. Since the samples used in the study were non-standard, quasi-static tensile and shear tests were performed based on the loads to which the composites would be exposed to create an accurate numerical analysis. Both tensile and shear strength values of the Artec Aramid/Woven Aramid CT736 composite are higher than those of the Aramid UD GS3000 and H62 UD-UHMWPE composites. When the numerical analysis results were compared with the tensile test data, compliance rates of 99.84% for Aramid UD GS3000 reinforced composite, 99.34% for Artec Aramid/Woven Aramid CT736 reinforced composite, and 96.42% for H62 UD-UHMWPE reinforced composite were determined. The analysis showed that the shear stress-strain curves provided 100% agreement at the maximum stress value.

Failure evaluation of outdoor polymeric insulators based on statistical condition-assessment methods

Field aging of outdoor polymeric insulators results in unscheduled outages in power systems particularly in harsh climate conditions. In this paper, a strategic maintenance framework is proposed in order to prevent overhead line outages. The presented scheme is based on condition assessment of the real aged polymeric insulators. Data of tensile test, hardness test, thermogravimetric analysis (TGA), and Fourier transform infrared spectroscopy (FTIR) are used to extract critical features of the aged samples based on classification of fuzzy c-means clustering. Then, a lifetime prediction analysis is done based on Cox hazards analysis to develop further maintenance strategy. The proposed model is validated through numerical analyses on polymeric insulators for various validation evaluations including pollution severity analysis and hydrophobicity class (HC) measurement. Obtained results verify accuracy of the intelligent model to predict lifetime of the aged polymeric insulators. The presented strategic framework can be effectively applied to online monitoring, condition assessment and preventive maintenance programs of the power system utilities.

An experimentally validated multiscale machine learning fatigue damage model for fiber reinforced composites

In this paper, a fatigue model is formulated and implemented to predict fatigue life of fiber reinforced composite laminates. The developed model is based on experimental data collected at different spatial and temporal scales, and reported in [1] and [2]. The model is first validated against quasistatic tensile test data and is shown to accurately capture damage modes and the sequences in which the modes occur. Next the fatigue damage model is formulated and for computational efficiency the cycle jumping approach is used to implement the model for predicting fatigue life. The computational efficiency is further enhanced through the use of a neural network that allows for very fast computation. Details of the model are presented and shown to be an efficient way to predict fatigue life of composite laminates.

Recrystallization kinetics and mechanical properties of cold-rolled and annealed CoCrFeNi multi-principal element alloy

The microstructure and mechanical properties have been investigated in a CoCrFeNi alloy cold-rolled to 80 % thickness reduction and subsequently annealed at 600 °C. It is observed that the as-rolled microstructure comprises extended regions of different dominant crystallographic orientations along with layers of mixed orientations. Shear bands are also present in this microstructure, with the susceptibility to shear banding varying significantly from region to region. Shear bands are most pronounced in extended regions containing narrow deformation twins, and are a crucial source of recrystallization nuclei. Analysis of the recrystallization kinetics indicates that the Avrami exponent is 1.6 for the first 30 min at 600 °C and that it decreases during further annealing. Tensile test data provide evidence that the sample annealed for 8 min, with a recrystallized fraction (fRX) of 13 % and an average recrystallized grain size of 0.8 μm, does not show any significant improvement in ductility compared to that in the as-rolled condition. However, the ductility is considerably improved in the sample annealed for 15 min, where fRX is 43 % and the average recrystallized grain size is 1.1 μm. This sample demonstrates a yield strength of 850 MPa and a total elongation to failure of 25 %. The data obtained in this work and in previous publications on partially recrystallized CoCrFeNi indicate that for samples annealed after 80–85 % deformation optimized combinations of strength and ductility are obtained when the recrystallized fraction is in the range 30 % < fRX ≤ 50 %.

Investigation of hot deformation behavior and three-roll skew rolling process for hollow stepped shaft of Al–Zn–Mg–Cu alloy

The increasing demand for high-strength lightweight hollow shafts in transportation highlights the need for advanced fabrication techniques. Al–Zn–Mg–Cu alloys, noted for their superior properties, are selected for three-roll skew rolling (TRSR). In TRSR, the material undergoes combined axial tensile and radial compressive stresses. This study evaluates the feasibility of TRSR for producing high-strength lightweight hollow stepped shafts from Al–Zn–Mg–Cu alloy. An integrated approach, including constitutive modeling, hot processing map development, and TRSR numerical simulations/experiments, is employed to optimize the TRSR forming process. The constitutive model was established based on 300°C–450 °C & 0.01–10 s−1 hot compression and 350°C–430 °C & 0.1–5 s−1 high-temperature tensile test data. The established Johnson-Cook optimization by genetic algorithms (GA-JC) model and unified viscoplastic constitutive model, accurately capture the alloy's hot deformation behavior, exhibiting minimal average absolute relative errors (AARE) of 5.431% and 5.808%, respectively. Microstructure evolution analyses shed light on the predominant softening mechanisms, emphasizing dynamic recovery (DRV) at elevated strain rates and diminishing texture intensity with escalating deformation temperatures. The composite hot processing map delineates optimal process parameters (400°C–450 °C & 0.1s−1-1s−1), facilitating informed decision-making in manufacturing practices. The validation of numerical simulations through TRSR forming experiments with initial temperature of 450 °C for the billet and axial moving speed of 10 mm/s for the chuck in affirms the feasibility of producing hollow stepped shafts from high-strength Al–Zn–Mg–Cu alloy. Close agreement was found between simulated and experimental wall thickness variations. This study enhances understanding and optimization of TRSR forming for high-strength lightweight alloys, advancing industrial manufacturing methodologies.

Bridging the gap between rate-dependent plasticity and stress wave dynamics: Calibrating a constitutive model for high-strength steel by inverse optimization

We present an approach for quantifying the flow stress of metals under dynamic loads, based on experiments that involve distinct but related physical phenomena. In modified Taylor tests, a stress-wave generated velocity–time signal is measured, which indirectly provides information on the plastic deformation behavior of the tested material at high strain rate. The Johnson–Cook plasticity model is calibrated for a high-strength steel on the basis of such measurements in combination with quasi-static and dynamic tensile test data. The plasticity model parameters are found with differential evolution through the inverse optimization of material test simulations. A consistent set of model parameters is identified that reproduces measurements from all types of tests. The obtained plasticity model features a small initial yield stress, which is compensated by large strain hardening so as to produce a realistic engineering yield stress. An independent calibration method is employed, by regression of the model on quasi-static and dynamic tensile test results, that confirms the validity of the plasticity model parameter values.

Finite Element Ductile Fracture Simulation of Charpy and Drop Weight Tear Tests for API X52

This paper presents a systematic procedure for performing finite element (FE) impact ductile fracture simulation of Charpy (CVN) and Drop Weight Tear Tests (DWTT) with validation using test data of API X52. For deformation and fracture models, the Johnson-Cook (J-C) model is used, of which seven parameters are determined by analyzing (1) round bar tensile test data at three different temperatures (two parameters), (2) tensile test and fracture toughness test at room temperature (three parameters) and (3) instrumented Charpy test (load–displacement) data at room temperature (two parameters). FE impact fracture simulation results with the determined parameters show good agreement with instrumented CVN test data at three different temperatures (0 °C, −30 °C and −60 °C) and DWTT data at temperatures of RT and −30 °C. For DWTT simulation, an analysis of the pre-strain due to flattening is included. Additionally, sensitivity analyses for the effect of adiabatic heating and strain rate on simulation results show that, although both phenomena should be considered in simulation, the strain rate effect is more significant than the adiabatic heating effect.

A unified model of tensile and creep deformation for use in niobium alloy materials selection and design for high-temperature applications

There is renewed interest in refractory alloys that possess higher service temperatures than incumbent Ni-based superalloys (e.g., ⪆1100 °C). This study provides a review of the high-temperature constitutive responses of Nb-alloys measured over a wide range of temperatures (≈860 °C < T < ≈1760 °C) and strain rates (≈10–9 s-1< ε˙ < ≈10–1 s-1). Nevertheless, the extant data is sparse and informed materials selection decisions require constitutive expressions to interpolate and reliably extrapolate. The Larson-Miller parameter approach to describe creep-life provides a conservative estimate of material response at the highest temperatures and lowest strain rates, whereas the Sellars-Tegart model describes both steady-state creep and high-temperature tensile test data with a single, universal equation. A minimum flow stress based on the combination of these two models is proposed for design considerations to address the overprediction of strength that can arise from applying one or the other independently. This effort highlights the fact that refractory alloys exhibit strain rate sensitive flow strengths in the temperature range of interest for applications. The roles of alloying, thermomechanical processing, and impurity levels are discussed, and highlight the fact that these advanced Nb-alloys evidence Class 1 (Class A) solute drag controlled creep behavior, except the carbide precipitation strengthened alloy, D-43. In addition, the high-temperature strengths are confirmed to be strongly correlated with alloy melting point.

Fatigue life prediction of rubber suspension bushings based on virtual road load spectrum pulses

Rubber suspension bushings have mainly been studied under single- or multi-axis load cycling, while research on rubber suspension bushings under random load cycling is not deep enough. This study conducted uniaxial tensile and fatigue tests on N60 rubber dumbbell-shaped plate samples to obtain stress–strain curves and S–N curves. Using the uniaxial tensile test data, a Mooney–Rivlin hyperelastic constitutive model was fitted using Abaqus software, and a finite element model of the rubber suspension bushing was established. A 3D virtual road surface was constructed using Adams software, and characteristic features of typical road surfaces were extracted for statistical analysis, resulting in the generation of a load spectrum showing variations in force over time. Based on the Miner linear damage accumulation theory, finite element fatigue life prediction of the rubber suspension bushing was conducted using pulses from the 232 s region of the load spectrum. The predicted fatigue life was compared to the results from benchtop fatigue testing, resulting in a relative error of less than 6.443 %. The findings suggest that the method is effective in predicting the fatigue life of rubber suspension bushings under random loads.

Machine-Learning Metacomputing for Materials Science Data

Abstract Materials science requires the collection and analysis of great quantities of data. These data almost invariably require various post-acquisition computation to remove noise, classify observations, fit parametric models, or perform other operations. Recently developed machine-learning (ML) algorithms have demonstrated great capability for performing many of these operations, and often produce higher quality output than traditional methods. However, it has been widely observed that such algorithms often suffer from issues such as limited generalizability and the tendency to “over fit” to the input data. In order to address such issues, this work introduces a metacomputing framework capable of systematically selecting, tuning, and training the best available machine-learning model in order to process an input dataset. In addition, a unique “cross-training” methodology is used to incorporate underlying physics or multiphysics relationships into the structure of the resultant ML model. This metacomputing approach is demonstrated on four example problems: repairing “gaps” in a multiphysics dataset, improving the output of electron back-scatter detection crystallographic measurements, removing spurious artifacts from X-ray microtomography data, and identifying material constitutive relationships from tensile test data. The performance of the metacomputing framework on these disparate problems is discussed, as are future plans for further deploying metacomputing technologies in the context of materials science and mechanical engineering.

Crack Initiation in Compacted Graphite Iron with Random Microstructure: Effect of Volume Fraction and Distribution of Particles.

Thanks to the distinctive morphology of graphite particles in its microstructure, compacted graphite iron (CGI) exhibits excellent thermal conductivity together with high strength and durability. CGI is extensively used in many applications, e.g., engine cylinder heads and brakes. The structural integrity of such metal-matrix materials is controlled by the generation and growth of microcracks. Although the effects of the volume fraction and morphology of graphite inclusions on the tensile response of CGI were investigated in recent years, their influence on crack initiation is still unknown. Experimental studies of crack initiation require a considerable amount of time and resources due to the highly complicated geometries of graphite inclusions scattered throughout the metallic matrix. Therefore, developing a 2D computational framework for CGI with a random microstructure capable of predicting the crack initiation and path is desirable. In this work, an integrated numerical model is developed for the analysis of the effects of volume fraction and nodularity on the mechanical properties of CGI as well as its damage and failure behaviours. Finite-element models of random microstructure are generated using an in-house Python script. The determination of spacings between a graphite inclusion and its four adjacent particles is performed with a plugin, written in Java and implemented in ImageJ. To analyse the orientation effect of inclusions, a statistical analysis is implemented for representative elements in this research. Further, Johnson-Cook damage criteria are used to predict crack initiation in the developed models. The numerical simulations are validated with conventional tensile-test data. The created models can support the understanding of the fracture behaviour of CGI under mechanical load, and the proposed approach can be utilised to design metal-matrix composites with optimised mechanical properties and performance.

Dynamic response analysis of ship reef hard grounding

Abstract With the rapid growth of the world economy, the shipping industry has developed rapidly on a global scale, and the water traffic has become increasingly busy. Therefore, the risk of ship transportation has become bigger and bigger, and ship grounding and collision occupy about 50% of the total number of all accidents, among which the consequences of oil tanker grounding accidents are more serious, which not only jeopardize the safety of the personnel but also cause a large area of pollution to the sea. Therefore, it is particularly important to study the ship grounding and collision of oil tankers. Based on the nonlinear finite element software ABAQUS, a calculation model for oil tanker grounding is established, and simplified boundary conditions that can be used for grounding simulation analysis are determined. At the same time, material strain rate sensitivity and material hardening properties are considered. Based on the quasi-static tensile test data of Q235 steel used in ships, material parameters that meet the requirements of collision simulation calculation are calibrated and calculated. The dynamic response of hard grounding is analyzed from both external and internal mechanisms. The research results can provide a reference for improving the grounding collision performance of oil tankers.

Modeling Analysis of Complex Deformation of Woven Coating Film during the Cyclic Tensile Process.

It is difficult for the existing Burgers model to accurately depict the off-axis cyclic drawing process of woven coatings. In this paper, the mechanical deformation of woven PVC (polyvinyl chloride)-coated film at different temperatures is investigated. One-dimensional (1D) and two-dimensional (2D) constitutive models were established to characterize cyclic deformation processes. The 1D model is an improved Burgers model. The effects of the time dependence of the viscosity coefficient and the ratio of elastic to viscous deformation are considered simultaneously. The accuracy of the 1D model for predicting the cyclic nonlinear deformation at different temperatures and loading rates is improved. The 2D model is a nonlinear orthotropic model using polynomials. On the basis of the single-objective genetic algorithm, the inverse algorithm is used to obtain the shear polynomial coefficients in the tension phase and the shear modulus in the unloading phase, which circumvents performing the difficult shear test. UMAT subroutines of off-axis stretching and off-axis cyclic stretching are written separately. The intelligent inverse algorithm program consists of a single-objective genetic algorithm program, a finite element parametric modelling program, and a UMAT subroutine. The simulation results are compared with the off-axis cyclic tensile test data to validate the effectiveness and accuracy of the proposed 2D model for the analysis of the woven PVC-coated films in the tension-shear coupling state.

Tensile testing data of additive manufactured ASTM D638 standard specimens with embedded internal geometrical features

Additive manufacturing (AM) is now widely used for research and industrial production. The benchmark data for mechanical properties of additively manufactured specimens is very useful for many communities. This data article presents a tensile testing dataset of ASTM D638 size specimens without and with embedded internal geometrical features printed using polylactic acid (PLA) in a Fused Filament Fabrication (FFF) additive manufacturing process. The added features can mimic defects of various shapes and sizes. This work is a supplement to the published research article Assisted defect detection by in-process monitoring of additive manufacturing using optical imaging and infrared thermography (Additive Manufacturing, 2023, 103483). The printed specimens were tensile tested. Stress-strain graphs were developed and used to calculate the mechanical properties such as ultimate tensile strength (UTS) and strain at UTS. The mechanical properties, the correlations between mechanical properties and size, shape and location of geometrical features (defects), and the trends in mechanical properties can be useful in benchmarking the results of other researchers.

A numerical model simulating cyclic behavior of high-strength steel

High-strength steel (HSS) can effectively and economically design structural members that withstand large forces induced by extreme events such as earthquakes. To evaluate the seismic performance of HSS members and structures using nonlinear finite element (FE) analyses, using an accurate material model is important, which can simulate the inelastic cyclic behavior of the HSS. The peculiar material behavior of HSS needs to be considered in the model. This study used a combined hardening model to construct the material model. The configuration of the model and the constituent model parameter values are determined to precisely simulate the low-cycle fatigue (LCF) behavior of HSS. An efficient particle swarm optimization (PSO) algorithm is used to determine parameter values with LCF test data of 54 individual HSS coupons. In additions, to conveniently determine the model parameter values with only monotonic tensile test data instead of conducting expensive LCT tests, empirical equations are proposed. It is shown that the LCF curves of HSS can be accurately simulated using the constructed material model with the proposed equations.

Fracture analysis of hydrogen-embrittled API X52 pipes at low temperature

This paper quantifies the effect of temperature (ranging from room temperature (RT) to -90 °C) on fracture toughness for hydrogen-embrittled API X52 by combining small punch (SP) test data and finite element (FE) damage analysis. For the FE damage analysis, a multi-axial fracture strain damage model was used, and the parameters were determined by analyzing the tensile and SEN(T) test data in air at RT. The hydrogen-enhanced ductile fracture was considered using the hydrogen-embrittlement constant, which was determined by analyzing the SP test results in hydrogen. Due to the effect of the interaction between strength and hydrogen-induced ductility loss on fracture toughness, the predicted fracture toughness in terms of temperature does not show a monotonic decrease up to -90 °C; rather, it decreases up to -30 °C, then increases slightly before decreasing again. Fracture mechanics analysis of a hydrogen-embrittled pipe with an axial surface crack using the determined fracture toughness values showed that the maximum pressure decreased slightly (less than 9 %) with decreasing temperature up to -90 °C, suggesting that the effect of temperature on the maximum pressure would not be so significant for API X52.

Optimization of pulmonary artery mechanical testing

Pulmonary arterial hypertension (PAH) is an incurable disease with mortality within 3 years in 28-55% of high-risk patients. The progression of PAH has been known to be associated with increased vascular stiffness and vascular remodeling. Recent studies have suggested that increased stiffness may in fact be a driver for some of the metabolic abnormalities observed during PAH. To gain more insights into this relationship, we need to quantify the differences in mechanical properties of healthy and hypertensive pulmonary arteries. The stress-strain relationship is the gold standard for the ex-vivo stiffness measurement of arteries. This is obtained by obtaining force vs. distension data by tensile testing and using sample dimensions, i.e. length, lumen diameter, and wall thickness, to calculate engineering stress and strain. While this approach is well-optimized for large muscular arteries, it has not been used to test pulmonary arteries as their thin walls and low basal tone make it challenging to make precise measurements of sample wall thickness and lumen diameter. Thus, the goals of this study were to: 1) establish a reliable protocol for rat pulmonary artery tensile testing and 2) quantify the differences in stiffness between hypertensive and healthy pulmonary arteries. First, a methodology to improve the fidelity of determining the lumen diameter and wall thickness was developed. Using this approach, we observed that the modulus was negatively correlated with the length of the vessel segment tested. This suggests that vessel length should be standardized to perform reliable comparisons between groups. Next, we performed tensile tensing on both control and hypertensive pulmonary arteries, after standardizing vessel segment lengths. We initially modeled this tensile testing data using a one-term exponential equation and we observed that intact hypertensive arteries were ~2.7 times stiffer than control arteries at low strain (strain = 0.8). Whereas at high strain (strain = 2.8) intact and decellularized hypertensive arteries were 20 and 29 times stiffer than control arteries respectively. To better capture the viscoelastic properties of both, the cellular and ECM components of the vessels we also fit the tensile testing data using a two-term exponential equation. Using this two-term exponential model, we observed that hypertensive vessels were 2.2 times stiffer than the controls at normal hoop stress (20 kPa), and at the hypertensive hoop stress (66 kPa) the diseased vessels showed less variability in stiffness as compared to the controls. These findings and the methods developed in this study will be helpful in conducting and analyzing experiments to investigate the relationship between changes in biomechanical signals and the progression of PAH. R01HL151530 (KS), R01HL126514 (LS). This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Strain-Based damage model for ductile tearing simulation under combined tensile and shear modes

This paper proposes a strain-based damage model to simulate ductile tearing under combined tensile and shear modes. For tensile mode, the multiaxial fracture strain model depending only on the stress triaxiality is used, determined by analysing smooth bar tensile test and fracture toughness test data. For shear mode, a simple constant fracture strain model is used, determined by analysing smooth bar torsion test and torsion fracture test using a deep surface cracked cylinder specimen. The proposed damage model is applied to simulate circumferential surface cracked pipe made of SUS 304 under combined bending and torsion. Comparison with full-scale surface cracked pipe test data suggests that the use of the combined tensile and shear damage model with the linear interaction rule gives good and conservative prediction results.

Structure and properties of starch - BaSO4 composite obtained using mechanical activation techniques

The aim of this study is to obtain and characterize starch films structurally modified by in situ precipitation of BaSO4 combined with mechanical activation of casting dispersion in a rotor-stator device. By the rheological method, it was found that the modification causes a decrease in the ability of casting dispersions to structure over time. Composite films with a filler content of 0 %–15 % (w/w) were characterized using optical and SEM microscopy, FT-IR spectroscopy, and tensile and moisture resistance testing data. The maximum increase in strength (by 70 %) and elongation at break (by 870 %) is achieved with a filler content of 5 % and 15 %, respectively. An increase in the filler content to 5 % causes an increase in starch recrystallization rate, but at concentrations above 5 % of BaSO4, it inhibits retrogradation. The films obtained by mechanical activation with optimized parameters were uniformly translucent, had lower water vapor permeability than films made from starch alone, had high flexibility, and did not warp or shrink. The developed high-performance, environmentally friendly method can be recommended for the large-scale production of starch-based composite materials.