Deformation Behavior Of Materials Research Articles

In situ SEM fatigue testing technology for metallic materials: a review.

Fatigue failure is one of the most common fracture modes of structural materials in the industrial field. The study of material fatigue mechanisms and methods for predicting fatigue life has always been of significant interest to researchers due to the abrupt and catastrophic failure mode. In recent decades, the performance and functionality of scanning electron microscopy (SEM) have been continuously improved and expanded. Based on this, the development of in situ fatigue testing in SEM has been rapidly developed. This technology plays a crucial role in providing insights into the deformation behavior of materials under fatigue. Keeping this in view, a comprehensive review of the development and application methods of in situ SEM fatigue testing technology is provided here. The development of in situ SEM fatigue testing devices is provided in brief overview, and the application and research progress of this technology in some representative metal structural materials (nickel-based single-crystal superalloys, steel, aluminum alloys and additive manufacturing materials) are analyzed in detail. Moreover, the perspectives on evaluating fatigue damage, particularly about small cracks and the plastic accumulations fatigue behavior, are presented in this study, utilizing the latest advancements in in situ SEM fatigue testing. Remarks about the present and outlook for future work to be done are then provided.

Auxetic hybrid metamaterial with tunable elastic wave bandgap

Auxetic metamaterials have shown good stability and uniform deformation capabilities against influences (vibration, temperature change, load change), making them significant in maintaining and adjusting the bandgap of phonon crystals. The low-frequency and broadband are the important goals of phonon crystals. For most traditional re-entrant honeycomb structures (T-RHS), the bandgap range is narrow and tunability is poor. Here, an auxetic hybrid structure with tunable acoustic bandgap (AHS-T) consisting of periodic mass inclusions integrated with traditional re-entrant honeycomb and chiral hybrid is proposed. Aiming at investigating the tunability of the bandgap in the low-frequency range. Compared with T-RHS, the bandgap real-time adjustment and wider bandwidth of the AHS-T be realized during compression and tension. The numerical results show that the bandgap of the AHS-T can be flexibly tailored by reasonably adjusting the strain and geometrical configurations of AHS-T. The bandwidth of AHS-T can be increased to 87.1% when the bottom diameter Db and column height H of the scatterer are changed reasonably. Moreover, the deformation behavior of auxetic material has an auxiliary effect on expanding the bandwidth. Compared with the structure which is not subjected to load, the adjustable amplitude of the bandgap is 41%. The findings of this work provide a design idea for manipulating elastic waves in dynamic environment.

Strength and deformation behaviour of zinc tailing waste material for embankment construction

Strength and deformation behaviour of zinc tailing waste material for embankment construction

A model for physical dislocation transmission through grain boundaries and its implementation in a discrete dislocation dynamics tool

The mechanical behavior of most metals in engineering applications is dominated by the grain size. Physics-based models of the interaction between dislocations and the grain boundary are important to correctly predict the plastic deformation behavior of polycrystalline materials. Dislocation-grain boundary interaction is complex and a challenge to model. We present a model for simulating the physical transmission of dislocations through grain boundaries within Discrete Dislocation Dynamics tools. The properties (glide plane, Burgers vector, initial length) of the transmitted dislocation are chosen based on geometric criteria as well as a maximization of the resolved shear stress of the transmitted dislocation. Additionally, stress and displacement transparency as well as the discontinuity are ensured via a grain boundary dislocation – a butterfly-like geometry in the general case – whose properties are selected to minimize the residual Burgers vector at the interface. This additional ‘grain boundary dislocation’ allows a direct comparison as well as a calibration of the model with experiments on the macroscale particularly for neighboring grains with a high dislocation density contrast. Two basic examples illustrate the model and an application to a 40-grain polycrystal demonstrates the scalability of the approach.

A theoretical and experimental study of deformation mechanism dictated by disclination-dislocation coupling in Mg alloys at different temperatures

Dislocations and disclinations are fundamental topological defects within crystals, which determine the mechanical properties of metals and alloys. Despite their important roles in multiple physical mechanisms, e.g., dynamic recovery and grain boundary mediated plasticity, the intrinsic coupling and correlation between disclinations and dislocations, and their impacts on the deformation behavior of metallic materials still remain obscure, partially due to the lack of a theoretical tool to capture the rotational nature of disclinations. By using a Lie-algebra-based theoretical framework, we obtain a general equation to quantify the intrinsic coupling of disclinations and dislocations. Through quasi in-situ electron backscatter diffraction characterizations and disclination/dislocation density analyses in Mg alloys, the generation, coevolution and reactions of disclinations and dislocations during dynamic recovery and superplastic deformation have been quantitatively analyzed. It has been demonstrated that the obtained governing equation can capture multiple physical processes associated with mechanical deformation of metals, e.g., grain rotation and grain boundary migration, at both room temperature and high temperature. By establishing the disclination-dislocation coupling equation within a Lie algebra description, our work provides new insights for exploring the coevolution and reaction of disclinations/dislocations, with profound implications for elucidating the microstructure-property relationship and underlying deformation mechanisms in metallic materials.

Model for predicting temperature-dependent indentation yield strength and hardness considering size effects

The development of theoretical models to facilitate access to the mechanical properties of materials has been a long-standing pursuit of scholars. In this study, temperature-dependent yield strength models and temperature-dependent hardness models considering indentation size effects were developed under different loading modes (loading to the same displacement or the same load at different temperatures), respectively. Based on the Force-Heat Equivalence Energy Density Principle, the proposed models are free of any adjustable fitting parameters, and the quantitative relationships among temperature, yield strength/hardness, Young's modulus, and indentation load/displacement were successfully captured. All the available 36 groups of experimental data validate the accuracy of the proposed models over a wide temperature range. The yield strength and hardness of metallic materials over a wide temperature range can be easily predicted by using the developed models. Based on the parametric analysis of the models, it has been theoretically clarified for the first time that the two loading modes have opposite indentation size effects for the same material. Although the indentation size effect all decreases gradually with increasing temperature for different loading modes. The influence of loading modes should be noted in future studies where temperature-dependent indentation size effects need to be considered. This work systematically considers the effects of temperature, loading mode, indentation load/displacement, and Young's modulus on the indentation yield strength and hardness, which is important to facilitate the study of the deformation behavior of materials at different temperatures by indentation methods.

A granular micromechanic-based model for Ultra High Performance Fiber-Reinforced Concrete (UHP FRC)

There is a growing interest in the application of UHP FRC (Ultra-High Performance Fiber-Reinforced Concrete) which has been under vigorous development since its inception over two decades ago. The advantages of these advanced materials is that they overcome the problems that plague conventional concrete, these include among others low residual strength and low tensile strength, poor crack control and resistance to crack propagation, which leads corrosion of the rebars and spalling. The aim of this paper is to provide a granular micromechanics-based model to describe the deformation behavior of UHP FRC material as it gives a robust method to link the micro-scale mechanisms with the macro-scale performance of materials with granular textures. In this model, the micro-scale is described by damage-elasto-plastic spring elements that represent the effective grain pair interactions decomposed into the so-called normal and tangential directions. Since the grain-pairs are variously oriented, the macro-scale response is obtained by integrating these interactions over the orientational space. Here we specialize the granular micromechanic model for UHP FRC by introducing a novel expression for the parameterized dissipation energy at the micro or the grain-pair scale. The newly introduced constitutive parameters are identified using experimental results for uniaxial extension and compression tests. The model is then applied to simulate the case of homogeneous compression, extension and shear to show the directional evolution of damage and plasticity and the consequent emergent anisotropy.

Constitutive modeling and tensile behavior of a fully austenitic gradient nanostructured stainless steel

The constitutive relationship can effectively describe and predict the deformation behavior of materials, and it is critical to establish appropriate constitutive relationships to obtain the mechanical response of gradient nanostructured (GNS) metallic materials during deformation. In this work, a general method for establishing the multi-layer constitutive relationship of the GNS metallic materials was proposed. A fully austenitic 310S stainless steel specimen with a thickness of 1.4 mm was fabricated by surface mechanical rolling treatment (SMRT) technology, and its depth-dependent microstructures and macroscopic mechanical properties were experimentally investigated. Based on the experimental results of uniaxial tensile and microhardness, using the quantitative relationship between microhardness and flow stress, the reverse analysis was conducted using a separation parameter method to establish the constitutive relationship of the 28 thin shells of the GNS310S specimen. Finite element analysis (FEA) confirmed that GNS310S was in a multiaxial stress state at low strains, and the evolution of stress and strain gradients during non-uniform deformation was analyzed. The method for establishing the constitutive relationship is independent of the microstructure and synergistic strengthening factors, and the experiment performs conveniently and has great generalizability, which can provide a useful guide for the mechanical modeling of the GNS metallic materials to obtain the intrinsic mechanical response.

A novel mathematical-based approach to predict the high-speed deformation behavior of cryodeformed materials with varying stacking fault energies

Cryodeformed (CR) materials have complex microstructures containing nano-twins, dislocation clusters, tangles, and others, depending on the stacking fault energy (SFE). Such unique microstructure makes them suitable for several engineering applications under a high strain rate environment. The high-speed deformation (HSD) behavior of CR materials is difficult to understand due to their complex microstructure. The present work is focused on developing a novel mathematical modeling method to understand the high strain rate deformation of CR materials with varying SFE. The model equation correlates the microstructure-based variables to deformation-based variables like stress, strain, and strain rate. High-speed deformation was conducted using a crossbow test. Transmission electron microscopy (TEM) was conducted on these materials to validate the model output.

Influence of Interface Type on Dynamic Deformation Behavior of 3D-Printed Heterogeneous Titanium Alloy Materials.

Using the Split Hopkinson Pressure Bar technique, strain-limited dynamic compressive loading experiments were performed on TA1/TA15 heterostructure (HS) materials. The plastic deformation mechanisms, fracture forms, and energy absorption properties of an HS material with a metallurgical bonding interface (MB) and an HS material without a metallurgical bonding interface (NMB) are compared and analyzed. The results show that there is no significant difference between the two deformation mechanisms. The fracture forms are all "V-shaped" fractures within the TA1 part. The NMB was carried for 57 μs before failure and absorbed 441 J/cm3 of energy. The MB was carried for 72 μs before failure and absorbed 495 J/cm3 of energy. Microstructure observations show that there is a coordinated deformation effect near the MB interface compared to the NMB, with both TA1 and TA15 near the interface carrying stresses. This causes an enhancement of the MB load-bearing time and a 12% increase in energy absorption.

Effects of interface friction states on plastic deformation in metal surface and bulk

Interface friction at the tool/die-material interface plays a pivotal role in metal plastic processes, significantly impacting material deformation behavior near the contact surface. This study focuses on understanding friction-induced deformation, particularly the plastic boundary layer and surface expansion behavior, at the tool/die-material interface by employing direct in-situ observations, coupled with high-speed imaging and particle image velocimetry techniques. It proves that interface friction determines the wall-slip behaviors and subsequently results in the non-uniform surface expansion distribution. Moreover, our results indicate that the application of lubricant alters the wall-slip velocity and localized surface expansion by 60% and 76%, respectively, at the contact interface. Based on these observations, a quantitative method for assessing the effectiveness of lubrication is proposed.

Study on Plastic Constitutive Relation and Ductile Fracture Criterion of AM60B Magnesium Alloy.

It is currently a challenge to accurately predict the deformation and fracture behavior of metal parts in automobile crashes. Many studies have shown that the deformation and fracture behavior of materials are significantly affected by the stress state during automobile crashes with complex stress state characteristics. In order to further promote the application of die-cast magnesium alloys in automobiles, it is particularly important to study the material deformation and fracture behavior of die-cast magnesium alloys. In this paper, the mechanical properties of the AM60B die-cast magnesium alloy sheet under four stress states (shear, tension, R10 notch tension, and cupping) were designed and tested. Based on the von Mises isotropic constitutive model and Swift weighted Hockett-Sherby hardening model, the plastic constitutive model of die-cast magnesium alloy was established. Based on the plastic model and the fracture model (JC, MMC, and DIEM) considering the influence of three stress states, the deformation and fracture behavior of the AM60B die-cast magnesium alloy front-end members in three-point bending were predicted by experiments and finite element simulation. The experimental results show that the deformation mode and loading-displacement curve trend of the AM60B die-cast magnesium alloy front members are the same, the crack initiation point and crack initiation time are the same, and the crack shape is similar. The results show that the complex stress state constitutive model parameters and the DIEM fracture model obtained in this paper can accurately predict the deformation and fracture failure behavior of the AM60B die-cast magnesium alloy sheet.

Creep-recovery deformation of 304 stainless-steel springs under low forces

The deformation behavior of materials at high temperatures determines the structural stability of mechanical structures under high-temperature service conditions. In this work, we prepare helical springs from 304 stainless-steel wires and study creep-recovery deformation of the helical springs under small forces at temperatures of 475–575 °C. In contrast to most methods reported in the literature, we use Kelvin representation of the Burgers model with a nonlinear dashpot in series connection to analyze the creep-recovery deformation of the helical springs and suggest the deformation mechanisms of the diffusion of interstitial atoms and dislocation generation/annihilation in transient creep and recovery of the helical springs under small forces. For the creep deformation, the stress exponent and activation energy for the plastic flow of the nonlinear dashpot are 2 and 57.8 kJ/mol, respectively, and the activation energy for the deformation flow of the linear dashpot is 41.8 kJ/mol. The nonlinear dashpot does not play any role in the recovery deformation, and the formation energy of defects for the recovery deformation of the helical springs is 51.4 kJ/mol. The approach used in this work provides a simple method to use a phenomenological model with a nonlinear dashpot to capture the power-law creep deformation of metallic materials.

A neural network peridynamic method for modeling rubber-like materials

Peridynamic (PD) is a powerful tool for simulating the large deformation and failure process of many types of materials. However, its use in modeling rubber-like materials is limited due to the complex constitutive nature of the material, and low efficiency and numerical oscillation caused by PD. To address this issue, a neural network (NN) non-ordinary state-based peridynamics (NOSB PD) method is developed to model the large deformation and failure behavior of rubber-like materials. This method is free of the zero-energy modes, and can significantly improve the computational efficiency. Unlike the traditional NOSB PD method that formulates the force density vector based on the deformation gradient, this method uses a deep NN to map the bond related quantities to the force density vector. The accuracy and efficiency of the proposed method are demonstrated through a series of numerical examples. Additionally, this method can be applied to various hyperelastic materials for which analytical constitutive models exist.

Influence of mechanical properties on material deformation behavior of different ceramics in scratching

To understand the differences in material removal behavior during grinding for different ceramics, scratching of Al2O3, AlN, Si3N4 and ZrO2 (3Y-TZP) ceramics by a cube-corner diamond indenter was investigated in this paper. Scratching characteristics, including material deformation, scratching force, coefficient of friction (COF) and scratching damage of different ceramics were compared and analyzed. Elastic recovery rate model and stress field model were built to analyze the mechanism of material deformation and scratching damage during scratching on different ceramics. The results demonstrated that material deformation behaviors vary significantly, and depend on mechanical properties of the ceramics. Ceramics with higher hardness exhibit shallower penetration depth of scratching, while higher fracture toughness results in shorter maximum surface damage distance. Elastic recovery rate model can predict the extent of material deformation. The ceramic with the highest elastic recovery rate is Al2O3, followed by Si3N4, ZrO2, and finally AlN. Elastic recovery rate decreases with increase in force. In stress field model, AlN exhibits the highest maximum principal stress, followed by Al2O3 and Si3N4, with ZrO2 displaying the lowest stress. These distribution patterns are consistent with the results of scratching damage pattern.

Assessment of cyclic deformation behaviour of wire arc additively manufactured carbon steel

Wire Arc Additive Manufacturing (WAAM) has gained popularity due to its speed and cost-effectiveness. However, the current knowledge on the cyclic deformation behaviour of WAAM materials is limited. To address this issue, this study investigates the cyclic deformation behaviour of WAAM ER70S-6 carbon steel. Coupons were extracted from printed walls with horizontal and vertical orientations and from surface and interior locations. Low-cycle fatigue tests were performed under fully reversed strain-controlled conditions, spanning strain amplitudes from 0.20 % to 1.50 %. Regardless of the group, the material exhibited cyclic hardening for strain amplitudes above 0.60 % and cyclic softening for smaller strain amplitudes. Significant non-Masing hysteretic behaviour was also observed. Cyclic stress–strain curves and fatigue-life relationships written in terms of stress, strain and energy-based parameters were derived for all groups. Fatigue life was not significantly influenced by printing orientation or location across thickness. However, horizontal orientation resulted in a slightly superior fatigue response. A statistical analysis revealed no significant difference in the accuracy of fatigue-life relationships between the groups. Finally, a comparative study between WAAM materials and conventional steels showed promising results. Yet, conventional steels outperform WAAM carbon steel, at least doubling the fatigue life for the same value of the damage parameter.

Experimental research on mechanical, material, and metallurgical properties of Inconel 600: Application in elevated temperature environment

Experimental research on mechanical, material, and metallurgical properties of Inconel 600: Application in elevated temperature environment

Towards understanding the influence of structured indenters geometry on material deformation behavior of indentation process

Nanoindentation has emerged as a pioneering technique for fabricating array structures at the nanoscale. This research incorporates molecular dynamics simulations to investigate the deformation mechanisms of materials influenced by structured indenters exhibiting diverse geometries. The primary objective of this study is to mitigate interference during the continuous indentation applied by the indenters, diminish the material's elastic recovery, and minimize the occurrence of defects. The simulation results unveil that plastic deformation of the workpiece induced by structured indenters manifests through the nucleation and slip of dislocations. The cylindrical indenter engenders the most pronounced residual indentation morphology, accompanied by substantial pile-up interference and an extensive range of dislocation expansion, surpassing that of other indenters. Conversely, pyramidal indenters exhibit minimal residual indentation morphology, albeit displaying considerable elastic recovery. A comprehensive evaluation that considers factors such as recovery after indentation, ease of processing, system stability, and material transfer against the indentation force is imperative for the determination of the ideally structured indenter. The meticulous analysis supports the efficacy of paraboloidal indenters possessing smaller taper angles in attaining consistent processing results, rendering them highly suitable for continuous indentation processing. The research content bears significant implications for advancing the application of structured indenters.

Potential deformation assessment of Semantok Main Dam in North Nganjuk Region at East Java Indonesia

Semantok Dam was constructed using a zone l embankment type and required safety measures for deformation control. This study aims to understand material specifications, geological conditions, and deformation behavior. The results of the material specifications indicate that the core material and fine filter material meet the design criteria. The geological conditions comprise sand, sandstone, and claystone. The rock’s bearing capacity and settlement in the core zone are considered safe. The elastic vertical deformation of the foundation, analyzed using a flexible foundation approach by Lord, is estimated to be between 4.36 and 6.10 cm. Dynamic analysis is also performed using the Plaxis 8.6 version software to estimate deformation. The software input includes soil properties from the borrow and quarry areas surrounding the dam site. Earthquake design criteria are based on the Operating Basis Earthquake (OBE) with a 100-year return period and the Maximum Design Earthquake (MDE) with a 10,000-year return period. The dynamic analysis results indicate that the maximum deformation during a 100-year return period earthquake is 7.37 cm (horizontal deformation) and 12.68 cm (vertical deformation). In the case of a 10,000-year return period earthquake, the maximum deformation is 83.41 cm (horizontal deformation) and 175 cm (vertical deformation) during rapid drawdown.

Crystal plasticity modeling of deformation behavior of Al–Al2Cu eutectics based on high-fidelity representative microstructures

A comprehensive understanding of material deformation behavior holds importance in enhancing the properties of materials, which can be achieved through modeling the relationship between microstructure and deformation behavior by an appropriate crystal plasticity (CP) model. However, before simulations, obtaining a high-fidelity representative microstructure (RM) to simultaneously meet the efficiency and accuracy requirements of the CP model is still a challenge. Thus, taking the Al–Al2Cu eutectics as an example, we successfully obtained a high-fidelity RM with two-point statistics and some fashionable image processing techniques. Then a high-resolution RMCP model was developed and the deformation behavior of Al–Al2Cu eutectics at room temperatures was uncovered. Due to multiple activated slip systems on {111}<110> inducing obvious cross-slip behavior, severe and heterogenous plastic deformation occurs in α-Al. And dislocations originate from the microstructure defects. In θ-Al2Cu, all possible slip systems are not activated, resulting in no plastic deformation. The predictions of the RMCP model are verified to be reliable by comparing with the results of in-situ tensile tests. Our proposed RMCP method is not only applicable to the two-phase eutectic systems, but also suitable for various multiphase and polycrystalline systems.