Search Results (43)

The accurate modelling of material removal mechanisms in grinding processes requires precise constitutive equations describing dynamic material behaviour under extreme strain rates and large deformations. This study presents a novel methodology for optimising the Johnson–Cook (J–C) constitutive model parameters for micro-grinding applications, addressing the limitations of conventional mechanical testing at strain rates exceeding 10⁵ s⁻¹. The research employed single abrasive grain micro-cutting experiments using a diamond Vickers indenter on aluminium alloy 7075-T6 specimens. High-resolution topographic measurements (130 nm lateral resolution) were used to analyse the scratch geometry and lateral material displacement patterns. Ten modified J–C model variants (A1–A10) were systematically evaluated through finite element simulations, focusing on parameters governing plastic strengthening (B, n) and strain rate sensitivity (C). Quantitative non-conformity criteria assessed agreement between experimental and simulated results for cross-sectional areas and geometric shapes of material pile-ups and grooves. These criteria enable an objective evaluation by comparing the pile-up height (h), width (l), and horizontal distance to the peak (d). The results demonstrate that conventional J–C parameters from Hopkinson bar testing exhibit significant discrepancies in grinding conditions, with unrealistic stress values (17,000 MPa). The optimised model A3 (A = 473 MPa, B = 80 MPa, n = 0.5, C = 0.001) achieved superior convergence, reducing the non-conformity criteria to Σk_A = 0.46 and Σk_K = 1.16, compared to 0.88 and 1.67 for the baseline model. Strain mapping revealed deformation values from ε = 0.8 to ε = 11 in lateral pile-up regions, confirming the necessity of constitutive models describing material behaviour across wide strain ranges. The methodology successfully identified optimal parameter combinations, with convergence errors of 1–14% and 7–60% on the left and right scratch sides, respectively. The approach provides a cost-effective alternative to expensive dynamic testing methods, with applicability extending to other ductile materials in precision manufacturing. Full article

The paper presents the results of numerical simulation of the dynamic behaviour of the post-tensioned beams subjected to a constant force impulse load over time and a short-term force impulse load varying over time. Abaqus programme was used for numerical analysis, introducing necessary and detailed modifications to the modelling and calibration parameters. The numerical dynamics models were calibrated using results previously obtained from our own experimental and numerical static analysis. To estimate the dynamic strength of structural materials, the dynamic strength coefficient was applied in the concrete damage plasticity model, and the Johnson–Cook model was used to describe the evolution of the dynamic yield strength of steel elements. An explicit procedure was used to solve the dynamic equilibrium equations. The selection of the Rayleigh damping parameter and the methodology for determining the external load in a dynamic problem are discussed. The study presents new results on the influence of the type of force impulse loading and variable prestressing eccentricity in numerical simulations of post-tensioned beams. The results of the simulation show that the post-tensioned beams achieved a lower dynamic load capacity under a constant force impulse load of approximately 5% compared to the static load capacity achieved in the experimental static tests, regardless of the assumed prestressing eccentricity. A dynamic load capacity significantly exceeded the static load capacity under short-term time-varying force impulse loading. The beam with the larger prestressing eccentricity achieved a dynamic load capacity of 211% of the static load capacity, while the beam with the smaller prestressing eccentricity achieved a dynamic load capacity of 198% of the static load capacity. Full article

To accurately assess the effect of different plate thicknesses on the residual stress field of laser shock peened GH3039 superalloy, residual stress measurements were performed on GH3039 alloy plates with thicknesses of 2 mm and 5 mm after laser shock peening (LSP) treatment. Both quasi-static and high strain rate mechanical tests of GH3039 were conducted, and the Johnson-Cook (J-C) constitutive equation for GH3039 alloy at specific strain rates was fitted based on the experimental results. To obtain the parameter C in the J-C constitutive equation of GH3039 alloy under ultra-high strain rates, a modified method was proposed based on LSP experiment and finite element simulation results. Using the modified GH3039 alloy J-C constitutive equation, numerical simulations and comparative analyses of the residual stress field of GH3039 alloy plates of different thicknesses under LSP were carried out using ABAQUS software. The simulated residual stress fields of laser-shocked GH3039 alloy plates of different thicknesses were in good agreement with the experimental measurements, indicating that the modified GH3039 alloy J-C constitutive equation can accurately predict the mechanical behavior of GH3039 alloy under ultra-high strain rates. Based on the modified GH3039 alloy J-C constitutive equation, the effect of different plate thicknesses on the residual stress distribution of laser-shocked GH3039 alloy was studied, along with the underlying mechanisms. The unique distribution characteristics of residual stresses in laser-shocked GH3039 plates with varying thicknesses are primarily attributed to differences in plate bending stiffness and the detrimental coupling effects of reflected tensile waves. Full article

The constitutive model is widely employed to characterize the rheological properties of metallic materials under high-temperature conditions. It is typically derived from a series of high-temperature tests conducted at varying deformation temperatures, strain rates, and strains, including hot stretching, hot compression, separated Hopkinson pressure bar testing, and hot torsion. The original experimental data used for establishing the constitutive model serves as the foundation for developing phenomenological models such as Arrhenius and Johnson–Cook models, as well as physical-based models like Zerilli–Armstrong or machine learning-based constitutive models. The resulting constitutive equations are integrated into finite element analysis software such as Abaqus, Ansys, and Deform to create custom programs that predict the distributions of stress, strain rate, and temperature in materials during processes such as cutting, stamping, forging, and others. By adhering to these methodologies, we can optimize parameters related to metal processing technology; this helps to prevent forming defects while minimizing the waste of consumables and reducing costs. This study provides a comprehensive overview of commonly utilized experimental equipment and methods for developing constitutive models. It discusses various types of constitutive models along with their modifications and applications. Additionally, it reviews recent research advancements in this field while anticipating future trends concerning the development of constitutive models for high-temperature deformation processes involving metallic materials. Full article

Owing to potential inaccuracies in the current stress–strain curve used for constructing the Johnson–Cook (JC) constitutive model of amorphous alloys, the parameters of the JC constitutive equation were derived using Oxley’s cutting theory, negative chamfer theoretical mechanics modelling, and the particle swarm optimisation algorithm. A two-dimensional finite element cutting model was subsequently established using AdvantEdge software. The optimised constitutive model was used to simulate the main cutting force (Fz) and the backward force (Fy), which resulted in average errors of 12.461% and 9.161%, respectively. Based on the optimised constitutive model in which the JC constitutive equation parameters were derived using Oxley’s method, the variations in temperature, strain rate, and stress in the deformation zone during the cutting process were analysed. The chip microstructures revealed the transformation of lamellar chips into serrated chips resulting from a combination of plastic deformation, adiabatic shear, and shear slip. Full article

In this paper, GH4079 alloy was thermally compressed under processing conditions of 1025 °C–1200 °C and 0.001 s⁻¹–1 s⁻¹. This article established the strain compensation Arrhenius constitutive equation, the improved Johnson–Cook constitutive equation, and the strain compensation Arrhenius constitutive model based on phase transition temperature segmentation and calculated the correlation coefficient (R) and local relative error (AARE) to verify the accuracy of the model, respectively. Finally, a certain microstructural analysis was combined. It can be concluded that the rheological stress of alloy GH4079 gradually decreases with the increase in temperature and strain rate. The AARE values of these three models are 21.09%, 20.47%, and 10.62%, respectively. The strain compensation Arrhenius model based on phase transition temperature segments can better describe the thermal deformation behavior of GH4079. By integrating this model, appropriate processing conditions can be selected to regulate the microstructural organization and achieve optimization during the practical application of the alloy. Full article

The coupling effects of electrical pulse, temperature, strain rate, and strain on the flow behavior and plasticity of 7075-T6 aluminum alloy were investigated and characterized. The isothermal tensile test and electrically assisted isothermal tensile test were performed at the same temperature, and the typical models were further embedded in ABAQUS for numerical simulation to illustrate the electroplastic effect. The results showed that electrical pulses reduced deformation resistance but greatly increased elongation. Compared with the traditional Johnson–Cook model, the proposed modified electroplasticity constitutive equations have a certain improvement in calibration accuracy for a highly nonlinear and thermoelectric coupling dynamic behavior. Moreover, combined with the electrically assisted three-point bending experiment, it was found that the springback angle decreases with the increase in current density. This is very close to the experimental result, further verifying the effectiveness of the thermoelectric coupling constitutive equation. Full article

The chip compression ratio is the most important characteristic of various machining processes with chip generation. This characteristic enables the determination of kinetic and other energy loads on the tool and the machined material. This provides an overall evaluation of the machining process and the possibility of its subsequent optimization. This paper presents the results of determining this cutting characteristic by experimental method, analytical calculation, and numerical modeling. For the analytical calculation of the chip compression ratio, an analytical cutting model developed based on the variational principle of the minimum potential energy was used. A finite element model of orthogonal cutting was used for the numerical simulation of the above process characteristic. Experimentally, the chip compression ratio was determined by the ratio of the chip thickness to the cutting depth (undeformed cutting thickness). The chip thickness was determined by direct measurement using chip slices obtained during the cutting process. The Johnson–Cook constitutive equation was used as the machined material model and the Coulomb model was used as the friction model. The generalized parameters’ determination of the constitutive equation was performed through a DOE (Design of Experiment) sensitivity analysis. The variation range of these parameters was chosen based on the analysis of the effect of individual parameters of the constitutive equation on the chip compression ratio value. The largest deviations between the experimental and analytically calculated values of the chip compression ratio did not exceed 21%. At the same time, the largest deviations of simulated values of the indicated cutting characteristic and its experimental values did not exceed 20%. When comparing the experimental values of the chip compression ratio with the corresponding calculated and simulated values, the deviations were within 22%. Full article

This paper addresses the critical issue of turbine blade containment in aircraft engines, crucial for ensuring flight safety. Through a comprehensive approach integrating numerical simulations and experimental validations, the containment capabilities of gas turbine engine casings are thoroughly analyzed. The study investigates the impact dynamics, deformation characteristics, and energy absorption mechanisms during blade detachment events, shedding light on the containment process. Based on the multi-stage nature of gas turbines, two different blade structures were designed for turbine blades. Utilizing finite element simulation and the Johnson–Cook constitutive equation, this study accurately simulated single-blade and dual-blade containment scenarios. The simulation results of the single blade indicate that the process of a gas turbine blade impacting the casing primarily consists of three stages. The second stage, where the tenon root strikes the casing, is identified as the main cause of casing damage. Meanwhile, in the dual-blade simulation, the second blade, influenced by the first blade, directly impacts the casing after fracturing, resulting in greater damage. Then, eight corresponding containment tests were conducted based on the simulation results, validating the accuracy of the simulation parameters. Experimental verification of simulation results further confirms the validity of the proposed containment curves, providing essential insights for optimizing casing design and enhancing the safety and reliability of aircraft engines. Full article

Composite materials, such as aluminum alloy FGMs, provide advantageous weight reduction properties compared to homogenous pure structures while still preserving sufficient stiffness for diverse applications. Despite various research on drilling simulation concepts and ideas for these materials, there still needs to be an agreement on the process modeling. Researchers have looked into a lot of different numerical methods, including Lagrangian, Eulerian, arbitrary Lagrangian–Eulerian (ALE), and coupled Eulerian–Lagrangian (CEL), to find solutions to problems like divergence issues and too much mesh distribution, which become more of a problem at higher speeds. This research provides a global analysis of bottom-up meshing for eleven 1 mm layers using ABAQUS^® software. It combines the internal surface contact approach with the Lagrangian domain’s kinematic framework. The model uses the Johnson–Cook constitutive equation to precisely predict cutting forces, stress, and strain distributions, optimizing cutting parameters to improve drilling performance. According to Taguchi analysis, the most favorable parameters for reducing cutting force and improving performance are a rotational speed of 700 rpm, a feed rate of 1 mm/s, and a depth of cut of 3 mm. The findings suggest that increasing the feed rate and depth of cut substantially affects the cutting force, while the rotational speed has a comparatively little effect. These ideal settings serve as a foundation for improving FGM drilling efficiency. Full article

An understanding of the dynamic behavior of materials plays a crucial role in machining improvement. According to the literature on this issue, one of the alloys whose dynamic behavior has been investigated less is AA 5052-H34, despite its numerous industrial applications. Using finite element (FE) modeling greatly reduces machining research costs. This research delved into the dynamic behavior modeling of AA 5052-H34 during dry-turning FE simulation. The dynamic behavior of AA 5052-H34 was achieved using the Johnson–Cook (J-C) constitutive equation, which was calculated using the uniaxial tensile and Split-Hopkinson pressure bar (SHPB) tests. To confirm the accuracy of the material model, these SHPB tests were then simulated in Abaqus. The J-C constitutive equation, paired with a J-C damage criterion, was employed in a chip formation and cutting temperature simulation. It was found that the feed rate significantly influences the dynamic behavior of AA 5052-H34. The thickness and morphology of the chip were investigated. The experimental and numerical chip thicknesses showed a direct relationship with the feed rate. The simulation temperature was also analyzed, and, as expected, it showed an upward trend with increasing cutting speed and feed rate. Then, the accuracy of the proposed FE simulation was confirmed by the agreement of the experimental and simulation results. Full article

Ultrasonic vibration assisted (UVA) plastic forming technology has proven to be a highly effective processing method, particularly for materials that are challenging to deform. In this research, UVA tensile tests were carried out on Mg_98.5Zn_0.5Y₁ alloy at different vibration frequencies and amplitudes. The experimental results indicate that, compared with conventional tensile tests, the yield strength and tensile strength of Mg_98.5Zn_0.5Y₁ alloy exhibit a decrease. Furthermore, the application of ultrasonic vibration demonstrates an ability to enhance the material’s elongation and plasticity. In order to further predict the stress-strain relationship in the metal tensile process, a hybrid constitutive model coupling the frequency and amplitude of ultrasonic vibration was developed based on the modified Johnson Cook model. The calculated results of the constitutive equation are in good agreement with the experimental results, indicating that the established constitutive equation can accurately predict the trend of alloy stress change at different amplitudes and frequencies. It establishes a theoretical foundation for scrutinizing the deformation mechanisms of the alloy under ultrasonic vibration. Furthermore, Abaqus finite element analysis software was employed to simulate and analyze the UVA tensile process, elucidating the impact of ultrasonic vibration on stress distribution, strain patterns, and material flow in the tensile behavior of Mg_98.5Zn_0.5Y₁ alloys. Full article

Analytical cutting models have recently become quite widespread due to the simplicity and rapidity of calculations as well as the stability of the solutions. This paper considers a procedure for determining the mechanical properties of machined material based on parameters for the analytical model of oblique cutting for a certain range of changes in cutting modes and inclination angles of the tool cutting edge. The model is based on the energy method of determining the main cutting process characteristics using the extreme assumptions of continuum mechanics. It is proposed to determine the parameters characterizing the mechanical properties of the processed material using the Johnson–Cook constitutive equation in two stages: preliminary determination of the constitutive equation parameters based on the results of mechanical compression specimen tests and experimental data of the oblique cutting process, and specifying the generalized values of the constitutive equation parameters using the inverse method through the finite element cutting model. The adequacy of the applied analytical cutting model is confirmed by comparing the kinetic characteristic values calculated using the analytical model of oblique cutting with the application of the specified parameters of the constitutive equation and the measured values of the kinetic characteristics. The deviation between the calculated and measured values of the cutting force components when changing the cutting depth (undeformed chip thickness) does not exceed 15%. The difference between the calculated and measured values of the cutting force components when the cutting speed is changed is about 20%. Full article

The slot milling cutter is primarily used for machining the tongue and groove of the steam turbine rotor, which is a critical operation in the manufacturing process of the steam turbine rotor. It is challenging to predict the milling force of a groove milling cutter due to variations in rake, rake angles and cutting speeds of the main cutting edge. Firstly, based on a limited amount of experimental data on turning, we have developed an equivalent turning force model that takes into account the impact of the rounded cutting edge radius, the tool’s tip radius and the feed rate on tool’s geometric angle. It provides a more accurate frontal angle for the identification method of the Johnson–Cook material constitutive equation. Secondly, the physical parameters, such as shear stress, shear strain and strain rate on the main shear plane, are calculated through the analysis of experimental data and application of the orthogonal cutting theory. Thirdly, the range of initial constitutive parameters of the material was determined through the split Hopkinson pressure bar (SHPB) test. The objective function was defined as the minimum error between the theoretical and experimental values. The optimal values of the Johnson–Cook constitutive equation parameters A, B, C, n and m are obtained through a global search using a genetic algorithm. Finally, the shear stress is determined by the governing equations of deformation, temperature and material. The axial force, torque and bending moment of each micro-segment are calculated and summed using the unit cutting force vector of each micro-segment. As a result, a milling force prediction model for slot milling cutters is established, and its validity is verified through experiments. Full article

The predictions of mechanical responses (stress–strain variations) in the machining of Ti-6Al-4V alloy are important to analyze the deformation conditions of machining to optimize the machining parameters and investigate the generation of a machined surface. The selection of a constitutive model is an essential factor that determines the deformation behavior in the machining simulation model. In this paper, two constitutive models of a modified Johnson–Cook (JC) equation and visco-plastic self-consistent (VPSC) model were used to investigate the stress–strain evolutions in the machining process of Ti-6Al-4V. A finite element (FE) machining model was established, considering the influences of grain refinement and deformation twins, based on a modified JC equation. The VPSC model was fitted based on the macro-strain rate sensitivity of the JC equation. The prediction results of the stress–strain curves of two models were compared, and their validities were further proved. The results show that flow stress hardening and inhomogeneities are caused by multi-scale grain refinement during the machining process of Ti-6Al-4V. Five slip deformation modes and one compressive twinning mode were activated in the VPSC model to be consistent with the macro-deformation behavior predicted with the FE model. The validations show the effectiveness of the modified JC equation, considering microstructural changes and the fitted VPSC model, in predicting dynamic behavior in the machining process of Ti-6Al-4V. The results provide two aspects of macro-deformation and polycrystal plasticity to elucidate the stress variations that occur during the machining of Ti-6Al-4V. Full article