Plastic Work Research Articles

Predicting tensile and fracture parameters in polypropylene-based nanocomposites using machine learning with sensitivity analysis and feature impact evaluation

This study examines the efficacy of decision tree and AdaBoost algorithms in predicting mechanical and fracture parameters of polypropylene nanocomposites toughened with ethylene-based and propylene-based thermoplastic elastomers and reinforced with fumed silica and halloysite nanotube nanoparticles. The essential work of the fracture approach was utilized to study the fracture parameters, including elastic and plastic works of the blended polymer nanocomposites. The data were divided into 80 % for training and 20 % for testing. AdaBoost consistently achieved superior performance compared to the decision tree model in all variables throughout both the training and testing stages. During the testing phase, the AdaBoost model obtained R2 values of 0.90 for Young's modulus, 0.93 for elongation at break, 0.87 for tensile strength, 0.86 for plastic work, and 0.60 for elastic work. Also, the mean absolute percentage error for the AdaBoost model during the test phase was 3.10 % for Young's modulus, 3.25 % for tensile strength, 10.34 % for elastic work, 13.55 % for plastic work, and 24.78 % for elongation at break. Furthermore, a sensitivity analysis examining the effects of various features such as TPO type, nanoparticles, and nanoparticle type on mechanical properties reveals that TPO has the most significant overall influence. The results also include an analysis of the impact of the key features on each mechanical property based on the sensitivity analysis.

Fundamental cracking performance of asphalt-filler mastics with hydrated lime

This study evaluates the impact of hydrated lime (HL) on the cracking performance at intermediate temperature of asphalt-filler mastics, specifically as a partial replacement for limestone filler (LF). HL, is an active filler known for its multiple benefits in asphalt applications. The Double Edge Notched Tension (DENT) test was used to assess fracture properties, including specific total work of fracture, plastic work of failure, essential work of fracture, and average critical tip opening displacement. The results revealed several key findings: a notable loss of ductility and toughness with increasing HL dosages, a stiffening effect evidenced by increased peak loads and reduced failure deformation, and a decrease in the specific total work of fracture, indicating a loss of fracture energy. However, an enhancement in fracture resistance to plastic deformation is observed with HL addition, although identifying trends at high dosages remains challenging due to complex interactions between HL and LF. Furthermore, using low volumetric concentrations of HL minimizes the adverse impact on fracture performance while leveraging its other beneficial active filler properties. These findings suggest that while HL can improve certain fracture properties, optimal dosages are crucial to avoid adverse effects. Overall, this paper provides an updated and comprehensive study of the fracture of mastics at intermediate temperatures, which adds up to the understanding of asphalt-filler interactions, which can potentially lead to further investigations, such as how the partial replacement of LF with HL affects asphalt mixtures’ performance-related characteristics, particularly the fatigue cracking resistance.

Simulation of thermal-mechanical coupling in Al alloy/steel inertia friction welding

Inertia friction welding (IFW) is a complicated thermal-mechanical coupling process. In-depth understanding of the thermal-mechanical process can improve the joint quality. In this study, a three-dimensional (3D) thermal-mechanical coupling model was successfully established to simulate the evolution of temperature, energy density, stress, strain, and flow behavior of the IFW process between 2219-O Al alloy and 304 stainless steel. The developed model was validated by comparing it with the measured temperature and deformation. Results show a transforming distribution of interface temperature from a M-shape to a squished V-shape during the IFW process. The characterization is attributed to the transformation of the accumulated friction energy density at the interface from a M-shape to an approximate V-shape due to the combined effect of varying sliding velocity and contact pressure. The Mises stress at the region near the interface is high and low at the steel and Al alloy sides, respectively. A significant portion of the kinetic energy stored in the flywheel is dissipated in the form of plastic deformation energy and cannot be neglected. The tracer particles show that most Al alloy at the initial interface is extruded to form flash, while a small amount of Al alloy is sticky and remains at the interface center. Increasing friction pressure and initial rotation speed result in higher interface temperature, axial shortening distance, and proportion of plastic work in total energy input.

A crystal plasticity phase-field model for microstructure sensitive fatigue crack growth in a superalloy

In this work, a dislocation density-based crystal plasticity phase-field model (CP-PFM) is developed to simulate fatigue crack growth in nickel-based superalloys. Through normalization validation, the plastic dissipation work and crystallographic work are shown to be consistent with the fatigue indicator factors (FIPs), cumulative equivalent plastic strain and cumulative shear strain, and the two energies are computed as the main driving forces of the phase field. Both driving force models are able to obtain fatigue crack growth in close approximation to the experimental rate. However, the model with crystallographic work as the main driving force obtains crack growth paths that are in better agreement with electron backscattering pattern (EBSD) observations, which is attributed to its greater ability to characterize the microstructural susceptibility of fatigue crack growth. Specifically, the model is able to capture the tendency of cracks to crack along the close-packed planes and the hindering effect of grains with large misorientation angles on fatigue crack growth, which together contribute to the curved morphology of fatigue cracks. The combination of large grains or grains with small misorientation angles favors persistent slip band (PSB) formation and leads to softening of the crack tip, which results in lower fatigue crack growth rates.

Application of inverse heat transfer to fatigue fracture

Cyclic actuation tends to cause self-heating in the material as the structure experiences fatigue, where the movement and coalescence of defects lead to crack formation, propagation, and eventual fracture. This study explores the modeling aspects of the self-heating phenomenon using a one-dimensional inverse heat problem to analyze heat generation and dissipation to quantify the plastic work rates needed for predicting fatigue life. The approach is based on analyzing the surface thermography obtained using an infrared camera and numerically solving an inverse Fourier heat conduction equation. Formulation of the inverse problem via constrained optimization and method of solution for analyzing the fatigue behavior of CS 1018 flat dog bone specimens subjected to fully reversed bending fatigue are presented. The proposed model demonstrates superior accuracy in predicting the location of maximum heat generation and identifying potential fracture zones compared to traditional methods.

Investigation of the particle crushing characteristics of stacked stone materials under different stress path conditions

Stone fill materials are widely used in engineering projects such as earth-rock dams, railways, and highway embankments. Nevertheless, they are susceptible to particle breakage, which can lead to a decline in engineering performance. A complete set of studies on crushed stone aggregates was carried out to investigate particle crushing characteristics under various stress path conditions. To quantify the amount of particle crushing, the relative particle crushing rate was utilized as an indicator. The plastic work performed during the trials was compared across different stress routes, and the relationships between particle crushing and average stress p and generalized shear stress q were investigated. In triaxial testing, the differences in particle crushing behavior under different stress routes were thoroughly examined. The results show that particle crushing is substantially lower in the modelling of a rockfill dam constructed with a core wall and subjected to reservoir water pressure pathways than in conventional triaxial tests. A clear relationship was discovered. Across several stress routes, a clear link between plastic work and the relative particle crushing rate was detected, which was successfully characterized by a power function. Notably, the contributions of different stress components to the overall plastic work varied significantly. The plastic work exerted by the generalized shear stress q accounted for a large percentage of traditional triaxial testing, although the proportion of plastic work given by p and q changed significantly in complex stress path tests. This research enhances the understanding of the particle breakage characteristics of stone fill materials under complex stress paths.

Detailed particle breakage of crushable granular materials under cyclic shearing conditions using dyed gypsum technique

Particle breakage of granular materials under cyclic shearing is related to a variety of engineering problems in geotechnical and transportation engineering. However, there is limited understanding regarding the detailed evolution law of breakage under cyclic shearing. To this end, a series of cyclic simple shear tests were conducted on artificially dyed gypsum particles. It was observed that, in contrast to the particle size distribution of the whole sample, the fractional particle size distributions of gap-graded samples followed a unified breakage evolution path as those of the uniformly graded ones and tended towards fractional fractal distributions. These results have inspired the introduction of the fractional breakage index. Moreover, the breakage-plastic work relationship was further extended to describe the breakage of fractional particles, incorporating the effect of the number of cycles on the plastic work distribution. Finally, based on the concept of breakage-packing, a predictive model for plastic work-breakage-deformation of crushable granular materials under cyclic shearing was proposed. These results have the potential in understanding the detailed particle breakage evolution and establishing a predictive framework for the breakage-induced deformation of crushable granular materials.

Two-stage heat dissipation in plastic deformation of metals under ultra-high strain rate deformation

Understanding plastic heating at high strain rates is essential for designing material behavior. We employ molecular dynamics to analyze plastic heating and introduce a refined Taylor-Quinney coefficient (TQC) calculating approach. Our results reveal a two-stage heating behavior in high-strength systems, a relaxation stage characterized by rapid heating, stress relaxation, and increasing TQC, followed by a steady-state stage marked by linear temperature increase, constant stress, and stable TQC. The dislocation movement may behave as a plastic heating converter. During the relaxation stage, defect/dislocation nucleation dominates, leading to an increase in TQC as defect density rises upon yielding. Despite an increasing portion of plastic work being stored in defects, the data suggest that dislocations primarily act as sources of heat. In the steady-state stage, an unusual scenario emerges where defect density decreases as plastic deformation proceeds, yet TQC continues to increase due to the release of stored energy. This phenomenon is potentially explained by the annihilation of dislocation dipoles moving towards each other on the same slip plane. Additionally, TQC remains relatively insensitive to variations in temperature and strain rate over a broad range, challenging prior assumptions and expanding the understanding of plastic heating mechanisms.

Dangers and Risks of Plastic Screen Printing Work in Bolon Village, Colomadu District, Karanganyar Regency, Central Java Province

Dangers and Risks of Plastic Screen Printing Work in Bolon Village, Colomadu District, Karanganyar Regency, Central Java Province

A “poor-man’s” deformation plasticity based approach to topology optimization of elastoplastic structures

This paper presents a topology optimization framework utilizing a deformation plasticity model to approximate the isotropic hardening von-Mises incremental elastoplasticity model under monotone proportional loading. One advantage of the model is that it is based on a yield surface allowing for precise matching to uniaxial elastoplastic isotropic hardening response. The deformation plasticity model and the incremental plasticity model coincides for proportional loading and since the deformation plasticity model is path-independent, the computational cost and implementation complexity reduce significantly compared to the conventional incremental elastoplasticity. To investigate the deformation plasticity model combined with topology optimization, we compare three common elastoplastic optimization objectives: stiffness, strain energy and plastic work. The possibility to limit the peak local plastic work while maximizing the strain energy is also investigated. The consistent analytical sensitivity analysis which only requires the terminal state is derived using adjoint method. Numerical examples demonstrate that the proportionality assumption is reasonable and the deformation plasticity model combined with topology optimization is a competitive alternative to cumbersome incremental elastoplasticity.

Rational Function-Based Approach for Integrating Tableting Reduced-Order Models with Upstream Unit Operations: Dry Granulation Case Study.

We present a systematic and automatic approach for integrating tableting reduced-order models with upstream unit operations. The approach not only identifies the upstream critical material attributes and process parameters that describe the coupling to the first order and, possibly, the second order, but it also selects the mathematical form of such coupling and estimates its parameters. Specifically, we propose that the coupling can be generally described by normalized bivariate rational functions. We demonstrate this approach for dry granulation, a unit operation commonly used to enhance the flowability of pharmaceutical powders by increasing granule size distribution, which, inevitably, negatively impacts tabletability by reducing the particle porosity and imparting plastic work. Granules of different densities and size distributions are made with a 10% w/w acetaminophen and 90% w/w microcrystalline cellulose formulation, and tablets with a wide range of relative densities are fabricated. This approach is based on product and process understanding, and, in turn, it is not only essential to enabling the end-to-end integration, control, and optimization of dry granulation and tableting processes, but it also offers insight into the granule properties that have a dominant effect on each of the four stages of powder compaction, namely die filling, compaction, unloading, and ejection.

Self-formation of dual-phase nanocomposite Zr–Cu–N coatings based on nanocrystalline ZrN and glassy ZrCu

A novel type of nanocomposite Zr–Cu–N material based on hard nanocrystalline ZrN and amorphous glassy ZrCu was prepared by atom-by-atom deposition using reactive magnetron co-sputtering. The elemental composition of the coatings was systematically controlled over a wide range, so that the stoichiometry of both phases was the same in all coatings and only phase fractions varied. Experimental results obtained using X-ray diffraction and electron microscopies were complemented by thirteen ab-initio simulations for the same coating compositions. We found that the structure of the as-deposited Zr–Cu–N coatings undergoes a gradual transition from an amorphous to nanograined and finally to nanocolumnar structure. When ZrN fraction exceeds 20 mol.%, both phases exhibit the tendency for spontaneous segregation even without heating, forming a heterogenous dual-phase nanocomposite structure. At approximately 50 mol.% ZrN, the ZrN nanocrystals enveloped by a relatively thin amorphous ZrCu phase reach an optimum size (3–5 nm), resulting in a maximum enhancement of hardness by 38 % compared to the rule of mixture. For ZrN fractions > 80 mol.%, hardness and plastic work fraction follow the trend proposed by the rule of mixture and the coatings with a lower hardness but a higher plasticity compared to the ZrN coating are prepared.

Conversion of plastic work to heat in crystal Cu: A microscopic view by molecular simulations

Conversion of plastic work to heat in crystal Cu: A microscopic view by molecular simulations

Evidence of non-isentropic release from high residual temperatures in shocked metals measured with ultrafast x-ray diffraction

Shock experiments are widely used to understand the mechanical and electronic properties of matter under extreme conditions. However, after shock loading to a Hugoniot state, a clear description of the post-shock thermal state and its impacts on materials is still lacking. We used diffraction patterns from 100-fs x-ray pulses to investigate the temperature evolution of laser-shocked Al–Zr metal film composites at time delays ranging from 5 to 75 ns driven by a 120-ps short-pulse laser. We found significant heating of both Al and Zr after shock release, which can be attributed to heat generated by inelastic deformation. A conventional hydrodynamic model that employs (i) typical descriptions of Al and Zr mechanical strength and (ii) elevated strength responses (which might be attributed to an unknown strain rate dependence) did not fully account for the measured temperature increase, which suggests that other strength-related mechanisms (such as fine-scale void growth) could play an important role in thermal responses under shock wave loading/unloading cycles. Our results suggest that a significant portion of the total shock energy delivered by lasers becomes heat due to defect-facilitated plastic work, leaving less converted to kinetic energy. This heating effect may be common in laser-shocked experiments but has not been well acknowledged. High post-shock temperatures may induce phase transformation of materials during shock release. Another implication for the study is the preservability of magnetic records from planetary surfaces that have a shock history from frequent impact events.

Earing Prediction of AA5754-H111 (Al-Alloy) with Linear Transformation-Based Anisotropic Drucker Yield Function under Non-Associated Flow Rule (Non-AFR).

The yield behavior of aluminum alloy 5754-H111 under different stress conditions for three kinds of plastic work is studied using an anisotropic Drucker model. It is found that when the plastic work is 30 MPa, the anisotropic Drucker model has the most accurate prediction. Comparing the Hill48 and Yld91 models with the Drucker model, the results show that both the anisotropic Drucker and Yld91 models can accurately predict the yield behavior of the alloy. Cylinder drawing finite element analysis is performed under the AFR, but it is not possible to accurately predict the position and height of earing appearance. The anisotropic Drucker model is used to predict the earing behavior under the non-AFR, which can accurately predict the earing phenomenon. Numerical simulation is conducted using three different combinations of yield functions: the anisotropic yield function and the anisotropic plastic potential function (AYAPP), the anisotropic yield function and the isotropic plastic potential function (AYIPP), and the isotropic yield function and the anisotropic plastic potential function (IYAPP). It is concluded that the influence of the plastic potential function on predicting earing behavior is more critical than that of the yield function.

On the anisotropic fracture behaviour of AA2050-T84 thick plate

Anisotropy in the fracture behaviour of AA2050-T84 was investigated using 2D digital image correlation (DIC)-assisted 3-point bending fracture toughness test on specimens with crack propagation direction oriented along the normal direction (ND) and rolling direction (RD). The tensile properties along the RD indicated slightly higher yield strength (482 ± 8 MPa) than ND sample (469 ± 9 MPa), while the fracture toughness in terms of energy release rate was higher when the notch was oriented along the ND (35.3 ± 1 kJ/m2) compared to the RD (18.5 ± 0.9 kJ/m2). Fractography of the fractured surfaces and detailed electron backscatter diffraction (EBSD) analysis of the microstructure along crack paths unveiled higher crack tortuosity with extensive secondary cracking in the TD-ND specimen than in the TD-RD. DIC measurements clearly showed a larger deformation zone for the TD-ND specimen also as which corroborated the plastic zone size determined using linear elastic fracture mechanics (LEFM). Additionally, the crystallographic model of tilt and twist angle differences between the neighbouring grains was employed to explain the increase in crack path tortuosity and higher dissipation of plastic work contributing to superior fracture toughness for the TD-ND sample.

Thermomechanical conversion of CoCrNi medium entropy alloy subjected to transient reverse loading

Heat dissipation of CoCrNi alloy is investigated under fast reverse loading. The Taylor-Quinney coefficient (TQC) decreases during the initial strain hardening, while the subsequent kinematic hardening is associated with gradually constant TQC of about 50 %, indicating the cyclic plastic work equally divided into heat and cold work stored in CoCrNi.

Constitutive description of distortional hardening in a TWIP steel: Addressing differential hardening under nonlinear strain paths

The present study aims to describe the in-plane differential hardening behaviour of the twinning induced plasticity sheet metal TWIP980 under various stress states, including uniaxial tension, plane strain tension, and pure shear, particularly focusing on non-proportional loading conditions. The true stress–strain curves for each stress states were inversely obtained from their corresponding load–displacement curves and modeled using a differential hardening model that can accommodate all three stress states simultaneously on plastic work (density) contours. For non-proportional loading tests, oversize specimens were initially stretched under uniaxial tension up to a 10% pre-strain along the rolling, diagonal, and transverse directions, respectively. Subsequently, the three stress states were applied to subsize specimens cut from the deformed oversize specimens along the rolling direction. To describe the hardening behaviours during non-proportional loading, a homogeneous anisotropic hardening model was adopted and calibrated using two-step uniaxial tension tests. Subsequently, the differential hardening model was successfully incorporated into the homogeneous anisotropic hardening model to describe both the differential hardening and the strain path change-induced hardening behaviours under the two-step loadings, i.e., uniaxial tension to pure shear and uniaxial tension to plane strain tension. Both experimental and simulation results underscore the necessity to consider differential hardening under non-proportional loading conditions.

Isothermal β grain growth kinetics and mechanical properties of Ti-351 titanium alloy

The Ti-3.6Al-5.2Mo-4.6Cr-4.7 V-0.7Fe (Ti-351) alloy was developed based on the d-electron theory and the β grain growth behavior during isothermal heat treatment (IHT) was investigated. The nanoindentation analysis of β grain and the tensile properties with different IHT states were carried out. The results showed the grain coarsening temperature of Ti-351 alloy is 850 °C. The grain growth activation energy Q of 75.11–133.92 kJ/mol and the grain growth exponents n of 0.28–0.33 were calculated, indicating a competition between alloy atom diffusion and grain boundary migration. Due to the enhanced diffusion of solute atoms and lower substructure density at higher IHT temperature and longer holding time, the hardness and creep stiffness of β grain would decrease as indicated by nanoindentation test, while the total work W and the plastic deformation work Wp would increase, suggesting an improved toughness of the alloy. In order to achieve full recrystallization of β grains and a better balance between tensile strength and plasticity at room temperature, it is recommended to select a solution heat treatment regime at 850–900 ℃ for 2–4 h.

Microstructure evolution and surface strengthening behavior of 300 M ultrahigh strength steel under engineered surface treatments

In this work, the most efficient and common engineered surface treatments identified as shot peening (SP), laser shock peening (LSP) and ultrasonic surface rolling process (USRP) were utilized to impact the 300 M ultrahigh strength steel. The microstructure evolution and surface strengthening behavior were carefully characterized and compared for the 300 M steel with various treatments. Besides, the underlying mechanisms for difference in grain refinement and surface mechanical properties by the arranged surface modification are revealed. The results indicate that a gradient structure with nano-grains at the top surface appears on the SP, LSP and USRP treated samples. The process of repeated impacts of SP in different directions leads to activation of multiple slip systems, which thus causes severe refined grains and dense dislocation activities associated with dislocation tangles, dislocation walls and blocking. A great variety of strikes per unit area by USRP results in higher plastic deformation compared to SP where numerous dislocation cells and deformation bands were generated. In contrast to SP and USRP, fewer slip systems are activated in LSP due to the short duration time which thus leads to the thinnest refined grain layer and more planar dislocation structures. The combination of low plastic work and lack of refined grains leads to lowest full width at half maximum (FWHM) in case of LSP samples whereas high FWHM comes from both fine grain size and dislocations in SP. The grain refinement and plastic work contributes to an increase of microhardness and compressive residual stress for the SP, LSP and USRP samples. To be clear, SP leads to a higher magnitude of hardness and compressive residual stress on the topmost surface while LSP causes a larger depth due to that shock wave in LSP influences material to much greater depth. Besides, the decomposition and redistribution of carbides are also noticed on the surface layer after the surface treatments with very high strain rate where numerous dislocations accumulate at the border of the carbides and slip trace is also observed within the carbides.