Plastic Deformation Research Articles

Competitive Fracture Mechanism and Microstructure‐Related Life Assessment of GH4169 Superalloy in High and Very High Cycle Fatigue Regimes

ABSTRACTHigh and very high cycle fatigue tests were performed to examine the microstructure and fracture mechanism of GH4169 superalloy in combination with techniques including electron‐backscatter diffraction (EBSD). Fractographic analysis revealed that surface failures are induced by surface flaws, whereas internal failures are caused by pores, facets, and inclusions. The three‐dimensional observation shows that fracture surfaces exhibit an irregular texture due to crystallographic mismatch of grains and plastic deformation at the crack tip. Based on EBSD analysis, Euler angles exhibited a complex geometry of grain orientation at the crack tip area, hindering crack propagation as evidenced by lower values of the Schmid factor and misorientation at the crack tip. Furthermore, the threshold values of small and long cracks decrease, whereas the transformation sizes from small to long crack growth increase from surface to internal failure. Finally, a novel microstructure defect‐based life prediction model is established, and the predicted results demonstrate a close resemblance to experimental outcomes.

Modelling of a Cylindrical Battery Mechanical Behavior under Compression Load

The extensive utilization of lithium-ion (Li-ion) batteries within the automotive industry necessitates rigorous measures to ensure their mechanical robustness, crucial for averting thermal runaway incidents and ensuring vehicle safety. This paper introduces an innovative methodology aimed at homogenizing the mechanical response of Li-ion batteries under compression load, using Finite Element Method (FEM) techniques to improve computational efficiency. A novel approach is proposed, involving the selective application of compression loads solely to the Jelly Roll and its casing, achieved by cutting the battery heads. Through this method, distinct mechanical behaviors are identified within the battery force displacement curve: an elastic region, a zone characterized by plastic deformation, and a segment exhibiting densification. By delineating these regions, our study facilitates a comprehensive understanding of the battery’s mechanical response under compression. Two battery models were employed in this study: one representing the battery as a solid volume, and another featuring the jelly roll as a solid volume enclosed by a shell representing the casing. The material utilized was LS Dyna MAT24, chosen for its piecewise characteristics’ definition, and its validation was primarily conducted through the curve fitting method applied to the force–displacement curve, taking in account the three regions of the compression force behavior. This approach not only optimizes computational resources but also offers insights crucial for enhancing the mechanical stability of Li-ion batteries in automotive applications.

Structural origin of relaxation in dense colloidal suspensions

Amorphous solids relax via slow molecular rearrangement induced by thermal fluctuations or applied stress. Microscopic structural signatures predicting these structural relaxations have been long searched for but have so far only been found in dynamic quantities such as vibrational quasi-localized soft modes or with structurally trained neural networks. A physically meaningful structural quantity remains elusive. Here, we introduce a structural order parameter derived from the mean-field caging potential experienced by the particles due to their neighbors, which reliably predicts the occurrence of structural relaxations. The structural parameter, derived from density functional theory, provides a measure of susceptibility to particle rearrangements that can effectively identify weak or defect-like regions in disordered systems. Using experiments on dense colloidal suspensions, we demonstrate a strong correlation between this order parameter and the structural relaxations of the amorphous solid. In quiescent suspensions, this correlation increases with density, when particle rearrangements become rarer and more localized. In sheared suspensions, the order parameter reliably pinpoints shear transformations; the applied shear weakens the caging potential due to shear-induced structural distortions, causing the proliferation of plastic deformation at structurally weak regions. Our work paves the way to a structural understanding of the relaxation of a wide range of amorphous solids, from suspensions to metallic glasses.

Metallographic Investigation of Plastic Deformation for Aluminum Alloys Under Different Loading Conditions

Metallographic Investigation of Plastic Deformation for Aluminum Alloys Under Different Loading Conditions

Study of plastic deformation and quality of flexible medium forming of bionic egg-shaped shell

Study of plastic deformation and quality of flexible medium forming of bionic egg-shaped shell

Molecular dynamics simulations of nanoparticle sintering in additive nanomanufacturing: insights from sintering mechanisms

The sintering behavior of nanoparticles (NPs), which determines the quality of additively nanomanufactured products, differs from conventional understanding established for microparticles. As NPs have a high surface-to-volume ratio, they are subjected to a higher influence from surface tension and a lower melting point than microparticles, resulting in variations in both crystallographic defect-mediated and surface diffusion mechanisms. Meanwhile, the interplay between these controlling mechanisms in NPs has not been well understood, primarily because sintering occurs on the nanosecond timescale, making it an exceptionally transient process. In this work, sintering of both equal and unequal sized Ag and Cu NP doublets with and without misorientation (both tilt and twist) is modeled through molecular dynamics (MD) simulations. The formation and evolution of crystallographic defects, such as vacancies, dislocations, stacking faults, twin boundaries, and grain boundaries, during sintering are investigated. The influence of these defects on plastic deformation and diffusion mechanisms, such as volume diffusion and grain boundary (GB) diffusion, is discussed to elucidate the responsible sintering mechanisms. The surface diffusion mechanism is visualized by using detailed atomic trajectories generated during the sintering process. Finally, the overall effectiveness of all diffusion sintering mechanisms is quantified. This study provides first insights into the complexity and dynamics of NP sintering mechanisms which can aid in the development of accurate predictive models.

Technology and application of through layer borehole ultra-high pressure hydraulic slotting in soft coal seam to pressure relief and permeability enhancement

ABSTRACT It is a vital method that controls outburst disasters through gas drainage to reduce gas pressure. But the permeability of coal seam in China is low. Therefore, technologies that can decrease pressure and increase permeability such as ultra-high pressure hydraulic slotting (UPHS) are widely applied. Based on the technology of UPHS, the principle of coal breaking and mechanism of pressure relief and permeability enhancement (PRPE) were first analyzed. The effects of PRPE between contrast borehole and UPHS were compared through numerical simulation. Finally, combined with the field test, the parameters of UPHS were determined, and difference in gas drainage effect between contrast borehole and UPHS was investigated. It is found that the exposed area of coal increased due to macroscopic slotting formed by hydraulic slotting, which provide space for coal deformation. The stress of coal relieved the permeability enhanced, resulting in the gas drainage efficiency increasing. The simulated results showed the pressure relief area and plastic deformation caused by UPHS are significantly increased compared with contrast borehole. The average concentration and total of gas drainage in UPHS are 1.49 and 3.13 times than that of contrast borehole. And radius of gas drainage of UPHS 1.77 times than that of contrast borehole under reduce the 46% engineering quantities.

Study on Dynamic Mechanical Properties and Failure Pattern of Thin-Layered Schist

This paper studies the effect of schistosity on the dynamic mechanical properties and failure pattern of thin-layered schist. Wudang Group schist with thin layers is selected as the research object, and the influence of the dynamic mechanical properties and failure pattern of schist under different angles and spacing is studied by combining an SHPB test and numerical simulation. The results indicate that under dynamic loading, the stress–strain curve demonstrates elastic compression, plastic deformation, and strain softening stages. Moreover, it is observed that the dynamic critical failure strength of schist exhibits typical “U”-type strength anisotropy. Specimens with a schistosity angle of 0° or 90° exhibit higher dynamic compressive strength under dynamic loading, with axial splitting and schistosity splitting as predominant failure modes. Conversely, when the schistosity angles are 30°, 45° or 60°, there is a noticeable decrease in compressive strength accompanied predominantly by shear failure along with local compressive shear failure. We additionally noted that as the spacing between schists decreases from 22 mm to 7 mm, there is a gradual reduction in dynamic compressive strength by approximately 20.3%.

Innovations in Engineering and Technology of Worm-Type Gears

Relatively small changes in engineering and technology of traditional established products turn over time into a series of milestones that determine both technical characteristics and production methods, and as a consequence - the competitiveness of the final product. Accordingly, it is relevant to periodically look at the evolution of the accumulated solutions and make some conclusions on it. For this purpose, the paper reviews innovations in design and production of worm-type gears obtained in Izhevsk scientific school in the field of gears for the last two decades: spiroid gears operating at low rotational speeds and transmitting high loads, leading to plastic deformations due to compactness of gears; spiroid gears with small gear ratios (3...8) competing with more expensive in production bevel and hypoid ones; worm gears with steel hardened gearwheels with increased strength and manufacturability; planetary spiroid gears providing extremely high gear ratio, improved methods and techniques of design and preproduction of gear cutting. The paper presents the review of innovations in design of worm-type gears made in Izhevsk scientific school in the field of gears for the last two decades: spiroid gears for cases of low speeds and small gear ratios, worm gears with steel hardened gearwheels, planetary and spiroid gears, improved methods and techniques of design and preparation of gear cutting.

Three-Dimensional Site Response Analysis of Clay Soil Considering the Effects of Soil Behavior and Type

To understand changes in bedrock motion at the ground surface, frequency effects, and spatial distribution within the soil, it is important to look at how a site responds to earthquakes. This is important for soil–structure interaction in structural and geotechnical earthquake engineering. This study deals with the effect of classifying clays according to shear wave velocity (stiff/medium/soft) and nonlinearity in behavior (linear/nonlinear) on the analysis of the site response. A 3D soil model with a combination of free fields and quiet boundaries and advanced constitutive models for soil to obtain accurate results was used to conduct this study. A strong TABAS earthquake was used to excite the compliant base of the model after converting the velocity record of TABAS to an equivalent surface traction force using a horizontal force–time history proportional to the velocity–time history. This study reveals that the site response analysis is affected by the type of clay soil and the soil material behavior, with soft clay soil causing higher PGV and PGV values in the linear case and lower values in the nonlinear case due to soil yielding, which causes soil response attenuation. This results in extremely conservative and expensive building designs when linear soil behavior is adopted. On the other hand, the applied earthquake exhibits greater attenuation at longer frequencies and greater amplification at mid and short frequencies. However, at frequencies near the applied earthquake frequency, neither attenuation nor amplification occurs. Furthermore, nonlinear soil behavior is crucial for soil evaluation and foundation design due to higher octahedral shear strain and settlement values, especially in softer soils, resulting from extensive plastic deformation.

Thermodynamically consistent model of dislocation-mediated plasticity

ABSTRACT We present a thermodynamically consistent damage theory of deformation where the damage mechanism is determined by the presence of dislocations and their motion is the origin of plasticity. The damage parameter is proportional to the square root of the dislocation density of a network. For the evolution of damage, a gradient-flow equation, which describes the relaxation process of plastic deformation, is derived. Analysis shows that the dislocation-mediated plasticity is an activated process with upper and lower yield points, as opposed to a barrierless plasticity with a single yield point, which may be realised by other mechanisms of deformation. Dislocation nucleation is not a limiting factor of the dislocation-mediated plasticity because the free energy barrier for the nucleation is rather low. Application of the theory to the description of uniaxial deformation revealed many features of the experimentally observed deformation processes of metals, e.g. three stages of strain hardening with various characteristics dependent on the material and rate of loading. Applications of the theory to processes of dynamic loading of materials, which simultaneously undergo phase transformations, can bring deeper understanding of the material behaviour.

On the nature of nano twin-induced shear band formation in a dispersion strengthened copper alloy under micro-mechanical loading

A key challenge in metallic alloys with high ductility is understanding how microstructural inhomogeneities influence shear localization, leading to localized plastic deformation and material failure. In this study, we explore the phenomenon of shear localization in coarse-grained copper, a material traditionally regarded as having low susceptibility to such behavior. Contrary to conventional understanding, our findings reveal that microstructural inhomogeneities play a pivotal role in inducing extensive strain localization during low strain rate micro-mechanical loading. The presence of fine precipitate particles leads to strain localization at small strains and low strain rates by activating shear localization driven by void formation mechanisms. Furthermore, nanoscale precipitates act as sites for dislocation pile-up within deformed structures of shear bands, leading to the formation of nano twins within these bands. Consequently, precipitate particles serve a dual role: contributing to strain localization and potential cracking, while also enhancing the alloy’s strength and ductility through nano-twinning mechanisms. This investigation offers a novel perspective on the interplay between material microstructure and deformation behavior, challenging existing paradigms in materials science.

Effect of plasma nitriding on microstructure and wear behavior of electrodeposited FeCoNiCr coating

An (FeCoNiCr)N high-entropy alloy coating with a single FCC phase was fabricated on 304 stainless steel by electrodeposition and plasma nitriding. The results indicated that the FeCoNiCr coating exhibited typical granular morphologies and a nearly equiatomic ratio of four elemental compositions. After nitriding, the coating primarily consisted of a high-entropy solid solution phase and a CrN phase, with the microstructure of the (FeCoNiCr)N coating being significantly refined due to the effect of crystallization. The microhardness of the (FeCoNiCr)N coating was 781.30 ± 20.3 HV0.5, considerably higher than that of the FeCoNiCr coating, which was 496.48 ± 21.82 HV0.5. Additionally, the (FeCoNiCr)N coating demonstrated a low friction coefficient and a wear rate of 0.59 and 6.8 × 10−8 mm3/N mm, respectively. The fine microstructure and high resistance to plastic deformation, attributed to solid solution strengthening and dispersion strengthening, were the primary factors contributing to the excellent wear performance of the (FeCoNiCr)N coating.

Approach Based on Response-Surface Method to Optimize Lining of Dies Used in 3D Free-Bending Forming Technology

In three-dimensional free-bending forming (3D-FBF), the tube is not overly constrained, and the plastic deformation behavior and forming quality of the bent tube are significantly affected by the critical structure of the forming die lining. However, the effects of die-lining structural parameters on the tube quality, and a method to determine the combination of die-lining structural parameters is yet to be devised. This study aims to propose a new framework that allows one to understand the effects of various die-lining structural parameters on tube quality and to propose the best combination of die-lining structural parameters. First, finite-element modeling is performed to simulate 3D-FBF and examine the effects of individual die-lining structures on the quality of tube formation. The simulation results show that the deformation-zone length and die gap are positively correlated with the tube-section distortion and wall-thickness variation, whereas it shows an opposite trend with respect to the bending radius. Additionally, the lining chamfer radius of the bending die and the guide lining chamfer radius minimally affect the tube forming quality. Subsequently, the optimal die-lining structure is obtained using the response-surface method. The tube cross-sectional distortion rate reduced from 2.73 to 2.53% after the die lining is optimized. Additionally, the average inner-wall thickness reduced to 1.06 mm, whereas the average outer-wall thickness increased to 0.97 mm. This paper proposes a method for optimizing the forming-die-lining mechanism and for improving the tube forming quality in 3D-FBF.

A molecular dynamics investigation of nano-twins and nano-precipitates effects in CoCrFeNi-based high-entropy alloys

Abstract This study systematically investigates the effects of twin boundaries and precipitates on the performance of CoCrFeNi HEAs matrix using molecular dynamics simulation methods. By constructing corresponding HEAs models and conducting simulations of their structural evolution and mechanical behavior at the nanoscale, the influence mechanisms of nanotwins (NTs) and nano-precipitates (NPs) on the mechanical properties of the material were explored through in-depth analysis of simulation results. The findings suggest that twin boundaries effectively impede the movement and slip of dislocations and stacking faults in the material. As a result, this enhances its mechanical properties and inhibits plastic deformation, ultimately improving its ductility. Meanwhile, precipitates also impact the material's performance, and the shape of precipitates may exert different effects on the material, while the phase interface between precipitates and the matrix can hinder the expansion of defects. The presence of twin boundaries can enhance the strengthening effect of precipitates, further improving the material's performance. This study provides a new perspective for understanding the relationship between the microstructure and mechanical properties of HEAs materials, offering important references for the design and optimization of HEAs materials.

Wear Characteristics Caused by Ti3AlC2 Particles under Impact-Sliding Conditions in Marine Engine

With the marine industry’s demands for carbon reduction and increased reliability, the friction and wear performance of marine engines is becoming increasingly important. MAX phase materials show great potential in marine engine tribopair materials due to their unique microstructure and performance. The typical MAX phase material Ti3AlC2 was combined with MoDTC and added to the lubricant containing ZDDP additive for the tribopair composed of chromium-based ceramic composite coated steel (CKS) piston rings and cast iron cylinder liners under impact-sliding conditions. Compared to Ti3AlC2 alone, the friction coefficient and wear depth of the designed composite additive MoDTC/Ti3AlC2 were reduced by 36.9% and 41.4%, respectively. The worn surface lubricated with the Ti3AlC2/MoDTC composite additive showed fewer scratches with significantly less plastic deformation and clearer honing grooves. The multi-component tribofilm containing FeS, MoS2, MoO3, ZnO, TiO2, Al2O3, unoxidised particles, short-chain phosphates, and some ZnS was present on the worn cylinder liner surface. The synergistic effect of Ti3AlC2, MoDTC and ZDDP additives in the lubricant can isolate the mutual contact, generate a solid tribofilm and reduce the scratching. This can provide some guidance for the development of high-performance lubricant additives under impact-sliding conditions.

Crashworthiness study of polyamide bi-tubular thin-walled tubes using hybrid lattice filling

Thin-Walled Tubes (TWT) are widely used as crashworthiness elements to absorb and dissipate kinetic energy during collision through plastic deformation. Various design strategies, including nested tubes, triggers, and filling with lattices, are commonly used to enhance the crashworthiness of TWT. Additive Manufacturing (AM) offers unique opportunities to produce complex lattice-filled TWT with higher precision, but challenges persist in the design and fabrication of bi-tubular TWT to enhance crashworthiness. The aim of this study is to propose an approach for hybrid lattice filling in bi-tubular structures. In the preliminary phase, the parametric study was conducted to understand the influence of tube cross-section geometry, thickness, and trigger hole diameter on the crashworthiness of empty TWT using Taguchi’s L9 orthogonal array. Empty TWTs were fabricated using Selective Laser Sintering (SLS) with PA12 material and compressed uni-axially at 8 mm/min speed. In the second phase, bi-tubular TWT was filled with three different unit cells such as Cube, Kelvin, and Octet Truss (OT) having 30% relative density. In the lattice filling approach, two different strategies were followed such as uniform and hybrid lattice filling. Designed TWTs were fabricated and tested under uni-axial compression at two different speeds such as 8 mm/min and 8 mm/sec. Based on the results of the preliminary study, it has been observed that cross-section geometry and tube thickness significantly enhance SEA through an increase in the stiffness and number of folding. With the help of the Signal to Noise (S/N) ratio graph, appropriate levels were selected as input for the hybrid lattice-filling approach. The results of the second phase revealed that hybrid lattice filling significantly enhances the deformation modes, energy absorption, and crashworthiness properties of TWTs. Hybrid lattice-filled TWT offers better Specific Energy Absorption (SEA) as 18.32 kJ/kg at 8 mm/sec compression speed, which is 113.9% higher than empty and 42.8% higher than uniform lattice-filled TWT. This work demonstrated that adopting the hybrid lattice-filling approach is one of the potential ways to enhance the crashworthiness of protective equipment such as crash boxes and frames.

Deformation Heat in Tension of Steel Elements

The purpose of the work is an approximate computational and experimental assessment of the specific energy intensity and heat generation at various stages of the material’s operation when the sample is stretched. The paper discusses an approximate method for estimating the specific energy intensity and heat generation at four stages of tensile deformation of a steel sample. Finite element modeling of the work of the manufactured sample under elastic-plastic tension was performed in the ANSYS multifunctional software package. The load in the digital model of the sample was applied according to the full-scale test program. The experiment used flat samples in accordance with GOST 1497, a WAW-1000 testing machine with a 100T microcomputer, and a testo 875i thermal imager with a temperature sensitivity of 0.05 °C at 30 °C. We compared the obtained values on graphs of full-scale tests and a digital model of the samples, identifying critical points and deviation values. Phased loading revealed that the development of destruction occurs on the descending branches and is accompanied by the gradual development of local instability of plastic deformation in the form of a “neck”. It is shown that the heating temperature of the tensile metal can be calculated using the formulas proposed in the paper or by calculation using the ANSYS software package. The test results showed that the surface temperatures of the samples at each stage differ significantly. Four main areas were identified on the graph of changes in the sample surface temperature at a point. An analysis of the existing database of measuring instruments and the ability to obtain and process data was carried out. Experimental values of surface temperatures during continuous quasi-static deformation exceed their calculated values (up to 5 times). The kinetics of changes in the temperature field of the sample surface was carried out using thermographic instruments.

Interfacial energy conversion mechanism between 3003 aluminum alloy and 321 stainless steel in vaporizing foil actuator welding process

Conventional welding methods encounter significant challenges, including poor weldability, low joint strength, and the formation of brittle intermetallic compounds, primarily due to the substantial disparities in the physical and chemical properties of aluminum and iron. To mitigate these issues, the vaporizing foil actuator welding (VFAW) process has emerged as a highly promising solid-phase welding technology, particularly suitable for joining dissimilar metals with pronounced differences in properties, such as aluminum alloys and stainless steels. The present study provides an innovative quantitative analysis of the interfacial impact energy conversion mechanisms within the VFAW process. The analysis reveals that the energy responsible for accelerating the flyer workpiece comprises burst vaporization energy (Ed\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$E_d$$\\end{document}) and continuous vaporization energy (Ep\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$E_p$$\\end{document}), with Ed\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$E_d$$\\end{document} identified as the primary energy source, contributing approximately 65–80% of the total energy required for acceleration. Further examination elucidates the mechanisms underlying heat generation and transfer during the interface collision. The investigation identifies the formation of an overheating zone at the interface, attributed to the combined effects of plastic deformation energy and adiabatic shear energy within the flyer workpiece. Consequently, the interface temperature can rise significantly, reaching up to 1394 K, with impact velocities as high as 925 m/s. The analyses contribute to establishing a theoretical foundation for understanding the interface bonding mechanisms characteristic of the vaporizing foil actuator welding method.

Microstructure Evolution and Forming Characteristics of Post-Weld Composite Treatment of 6061 Aluminum Alloy Tailor Welded Blanks

The mechanical properties and cross-sectional geometric dimensions of the fusion zone (FZ), heat affected zone (HAZ), and base metal (BM) of 6xxx series aluminum alloys are inconsistent after filler wire welding, which reduces the formability of aluminum alloy tailor welded blanks (TWBs). This paper proposes a post-weld cold rolling-solution heat treatment (PWCR-SHT) composite process, and the effects of weld excess metal, plastic deformation, and SHT on the formability of aluminum alloy TWBs are studied. The results show that the PWCR-SHT composite process eliminates the weld excess metal and internal pores, reduces the stress concentration at the weld toe, eliminates the local strain hardening behavior, and causes recrystallization in the FZ region. The cupping value of aluminum alloy TWBs using SHT is 105% of BM, in comparison, the cupping value of aluminum alloy TWBs using the PWCR-SHT composite process is 119% of BM, which is the result of the combined effect of geometric dimensions consistency and mechanical properties consistency.