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ATI 718plus is a novel nickel-based high-temperature alloy that delivers superior mechanical properties and higher working temperatures compared to the In718 superalloy. In order to study the machinability of ATI 718plus, a combination of experiments and finite element simulation is used to explore the mechanism of serrated chip formation and the evolution of microstructure under high-speed cutting conditions. Firstly, the Johnson-Cook constitutive model parameters of the ATI 718plus alloy were obtained through a split Hopkinson pressure bar experiment. Secondly, we established a 2D orthogonal cutting model on the AdvantEdge FEM platform by implementing the Johnson-Cook constitutive model and damage model via a custom subroutine. Through the comparison of orthogonal cutting experimental data and finite element simulation results, we verified the accuracy of the finite element model and analyzed the mechanism of serrated chip formation. Finally, combining the multi-physics field distribution of different parameters from the finite element simulation and EBSD test results, it is revealed that the microstructural evolution mechanism during the high-speed cutting of ATI 718plus involves grain lamellar refinement induced by CDRX and grain growth induced by DDRX. The interaction of these two processes results in different forms of microstructures. Under specific cutting parameters, a superfine grain layer with a thickness of 10 µm was formed on the machined surface, which holds great referential significance for our control and improvement of the surface properties in cutting machining. [ABSTRACT FROM AUTHOR]

This work presents an optimum methodology for producing friction stir spot welding (FSSW) joints using a detachable consumable pin. The study is carried out by welding two AA6061-T6 sheets using a consumable pin of the same material attached to the H13 steel tool. Three methods for attaching the consumable pin to the tool are explored: (1) push-fitting the pin in an indentation on the tool, (2) adhesively bonding the pin to the tool with a cyanoacrylate adhesive, and (3) adhesively bonding the pin to the tool with a thermosetting glue. After welding, the pin gets detached and assimilated into the workpiece. Cyanoacrylate adhesive–bonded consumable pin was the most effective in producing exit-hole–free FSSW joints with good joint strength. The use of lubricants along with adhesive-bonded consumable pins resulted in a reduction of energy requirement by 35 − 42% without compromising joint strength. Optimization was carried out using data from experiments as well as finite element method simulations. For simulating the lap shear test, the Cockcroft-Latham damage model was used. The optimum process parameters for obtaining the maximum joint strength were a rotational speed of 900 revolutions per minute and a plunge rate of 15 mm/min. Based on the study, a strategy for batch production is also proposed for enhancing productivity. [ABSTRACT FROM AUTHOR]

The clearance flow in dry-running vacuum pumps is the main loss mechanism. To reduce the clearance mass flow rate in rarefied gas flows, sawtooth structures transversing to the direction of flow can be utilized. However, due to the sawtooth's structure size, micro-machining is necessary, whereby burr formation is a central challenge. First, the effectiveness of non-idealized sawtooth structures is investigated, demonstrating a high sensibility of the performance regarding the geometry of the tip. Therefore, burr formation in the cutting process must be minimized. For this reason, a 3D finite element (FE) chip formation model capable of predicting the burr formation is developed. An analysis of the burr formation zone showed positive triaxialities; thus, the triaxiality-dependent Johnson–Cook damage model is utilized. To minimize the mesh-induced error, a convergence analysis is conducted, showing no convergence of the maximum burr height. This is caused by the pathological mesh size dependence of local continuum damage models. A comparison of the cutting experiments and simulations revealed a reasonable prediction of cutting forces. In contrast, the passive force is predicted poorly, which is attributed to the underestimation of the ploughing force for non-elastic simulations. The prediction quality regarding the maximum burr height differs for the investigated cutting speeds, which can be explained by a built-up edge and a change in the machine tool compliance. Thereby, an analysis of the burr formation revealed that the burr height is captured by a non-physical remeshing algorithm and that the burr volume might be a more appropriate characteristic. [ABSTRACT FROM AUTHOR]

There has not been any damage prediction using Johnson-Cook's (JC) hardening and damage model in the hydraulic bulging (HB) and hydroforming (HF), which are the advanced manufacturing processes, of the Ti-6Al-4V (Ti64) alloy. In the presented study, the damage behavior of the Ti64 alloy sheet in the HB and HF processes was investigated both experimentally and numerically for the first time to address the existing research gap. In this context, firstly, tensile tests (TT) were carried out on samples with different stress triaxiality values at three different tensile speeds, and the fracture morphologies of the samples were examined to evaluate whether it was appropriate to use the JC hardening and damage model. Since the fracture surfaces generally exhibit a ductile fracture morphology and are affected by stress triaxiality and strain rate, it was determined that it would be appropriate to use the JC hardening model and damage criterion to predict the damage of the Ti64 alloy in finite element analysis (FEA). Then, JC model parameters were determined by fitting the stress-strain curve obtained from the FEA and experimental tensile tests. In the HB experiments, bulging height and thickness thinning were predicted by FEA with an accuracy of 97% and 96.85%, respectively. In the HF experiments, the experimental burst pressure, die inlet radius, and base radius were predicted correctly at a rate of 92.5%, 95.5%, and 97.8%, respectively. Also, the thickness of the sample showed good agreement with the FEA results. The fracture zones in each process exhibited good agreement with the experimental results. Thus, it has been demonstrated that the JC damage criterion can be successfully applied in FEA if the Ti64 titanium alloy is damaged in various processes. [ABSTRACT FROM AUTHOR]

Additively manufactured lattice structures are extensively utilized because of their unique characteristics, including lightweight design, high energy absorption capabilities, and exceptional specific strength. This study focuses on accurately simulating the dynamic mechanical behavior of AlSi10Mg lattice structures produced using selective laser melting (SLM). A series of experimental studies has been conducted to establish the parameters of the J–C hardening and damage model for additively manufactured AlSi10Mg alloys. The lattice structures, featuring face-centered cubic (FCC) and diamond topologies with a 25% designed relative density, underwent scanning electron microscopy (SEM) for geometrical precision assessment. Dynamic compressive behavior was investigated via split Hopkinson pressure bar (SHPB) tests. Numerical simulations in Ls-Dyna, utilizing the identified J–C parameters, were employed to replicate SHPB tests. Findings indicate that the specific strength and the specific energy absorption values of FCC lattice samples have higher than those of diamond samples at strain rates of 750 and 1100 s−1. While the overall strains and deformation modes were well predicted by numerical analyzes, a deeper insight into local stress concentrations under dynamic loads was achieved. Consequently, the obtained J–C model parameters offer valuable insight into characterizing the dynamic behavior of AlSi10Mg lattice structures produced by SLM. [ABSTRACT FROM AUTHOR]

Metal additive manufacturing (AM) is the process of creating a metal part by selectively melting powdered metal in layers from a digital file. Metal AM revolutionizes part production, yet challenges like residual stress and distortion persist. In this study, we conduct a comprehensive quantitative analysis of the selective laser melting (SLM) process' impact on Inconel 718 parts. The use of thermo-mechanical finite element analyses (FEA), coupled with the Johnson–Cook failure model, represents a novel approach, providing a deeper understanding of the additive manufacturing process; it captures the complex dynamics of rapid heating and solidification, exposing potential defects. The significance of this research lies in its ability to address the longstanding challenges associated with metal 3D printing. By integrating the Johnson–Cook constitutive model into a validated User Material (UMAT) subroutine in Abaqus, the study ensures robust and accurate modeling. The round tensile specimen analysis showcases a stress–strain response that aligns closely with the built-in Johnson–Cook model, demonstrating the model's fidelity and predictive capability. The thin-walled cylinder model validates the simulation's accuracy in predicting real-world distortions, emphasizing the practical application of the findings. Performance metrics are central to this research, with the ultimate stress at failure quantified at 0.2040 mm/mm in the tensile specimen analysis. The thin-walled cylinder model quantifies radial distortions, reaching a maximum of 0.11 mm, providing tangible performance benchmarks. Furthermore, the simulation of a bridge geometry for the SLM process predicts significant process-induced damage, offering engineers a quantitative measure of susceptibility to failure. [ABSTRACT FROM AUTHOR]

In this work, experimental and numerical investigations are conducted to investigate the precision cutting cutting of Ti42Nb titanium alloy produced by laser-based powder bed fusion. Experimental precision cutting tests are carried out using precision turning lathe. Trials are performed with two cutting velocities of 60 m/min and 90 m/min and different feed rates, varying from 5 to 40 μ m/rev. For the numerical study, a porous crystal plasticity-based model is proposed to address the impact of anisotropy and microstructure heterogeneities of the polycrystalline material. The crystal plasticity-based model is identified using strain–stress curves obtained from compression tests performed under two strain rates and a wide range of temperatures. Numerical precision cutting simulations are performed in order to gain insight into the impact of crystallographic orientation and grain size on the machinability of the alloy. According to the results, the effect of the strain rates and the temperature on the thermomechanical behavior of the Ti42Nb alloy produced by laser-based powder bed fusion is correctly depicted. The model captured the strain localization on adiabatic shear band. According to the precision cutting simulations, the local variables such as temperature, damage and plastic deformation are strongly impacted by the crystallographic orientation and the grain size. Depending on the crystallographic orientations, the chip morphology changes form continues, slightly segmented to largely segmented. [ABSTRACT FROM AUTHOR]

The constitutive model and its material parameters largely determine the effectiveness and accuracy of the finite element (FE) simulation for metal cutting processes. However, even for the same workpiece material, there are multiple constitutive models with different predictive abilities that are applicable to the cutting simulation. Therefore, a method for evaluating the constitutive models based on the coupled Eulerian-Lagrangian (CEL) orthogonal cutting model incorporating the experimentally determined Coulomb friction coefficient is proposed. The evaluation method can effectively avoid the influences of chip separation criteria, damage models, and adaptive remeshing on the evaluation results with the ability to simulate material side flow. This paper evaluates Johnson-Cook (JC) and Zerilli-Armstrong (ZA) constitutive models, which are often applied in cutting simulations. Material parameters for these constitutive models are identified from the constitutive data of the primary or secondary shear zone in cutting tests. A series of FE simulations for orthogonal cutting of 42CrMo4 steel is carried out under various cutting conditions using different constitutive models. The simulated cutting forces, chip thickness, and average temperature over the tool-chip interface are compared with experimental results under the same cutting conditions. The conclusion is that no constitutive model is the most accurate for all predictions. Nevertheless, for 42CrMo4 steel, the ZA model with material parameters identified from constitutive data of the secondary shear zone has the best comprehensive predictive performance. The evaluation method contributes to selecting the most suitable constitutive model and conducting efficient cutting simulations. Furthermore, several feasible approaches for improving the constitutive models are presented through error analysis. [ABSTRACT FROM AUTHOR]

Single-point incremental forming (SPIF) is a technology that allows obtaining complex parts using a hemispherical end tool by applying a local deformation process in sheet metal. This dieless process presents the advantage of high formability limits and low cost. The increasing need for micro-components, namely, in the medical industry (implants and medical tools and accessories), has contributed to the development of the micro-single-point incremental forming (µ-SPIF) technique. However, this technique requires meeting certain challenges related to tool wear, resistance and precision of the manufactured parts, and increased formability. So, understanding the deformation and failure mechanisms in µ-SPIF is important to achieve improved formability. This paper is aimed at improving the predictions of the shear-modified GTN damage model by proposing an identification procedure for its numerous material parameters based on an inverse method coupling the numerical predictions with experimental results. The extended GTN model is first implemented into the finite element code Abaqus. The numerical approach is assessed through numerical simulations under shear and uniaxial tension loading. Then, a complete methodology is proposed to identify the set of material parameters using tensile and micro-single-point incremental forming (µ-SPIF) experimental results. The identification approach is based on the comparison of the numerical and experimental forces used to carry out the micro-incremental forming test with a pyramidal shape tool. To show the pertinence of the identification procedure, the numerical predictions of the modified GTN model with these material parameters are compared to the experimental results of µ-SPIF tests with different tool paths and geometrical forms. Finally, it is shown that the shear modification of the GTN model can predict the failure of sheets during metal forming. [ABSTRACT FROM AUTHOR]

Punching is an important process of the production for ultra-high-strength steel automobile components. By selecting the appropriate punching parameters, the punching quality can be effectively improved and the punching force can be reduced. In this study, several typical fracture damage models applicable to the punching process of high strength steel were compared, where the critical damage values were calculated through an iterative predictor–corrector approach. Meanwhile, the effects of punching parameters on maximum punching force (MPF) and punched face quality for hot stamped ultra-high strength steel Usibor1500P were investigated experimentally. The results show that the Oyane damage model is the most suitable one in simulating the punching process of Usibor1500P, which can better predict the punched profile features and the variation of punching force within one stroke. The increase in die clearance decreases the MPF, while the plate thickness, punch diameter and punch corner radius increase the MPF. The change of the punch corner radius has the most significant effect on the improvement of the punched face quality. [ABSTRACT FROM AUTHOR]

Composite laminates are widely used in various engineering applications due to their excellent mechanical properties and lightweight nature. However, predicting their behaviour and damage evolution remains a challenge due to the complexity of the inter/intralaminar failure modes. In this paper, we propose a new progressive damage model that takes into account both inter and intralaminar failure modes to accurately predict the flexural behaviour and damage evolution of composite laminates under three-point bending. The proposed model incorporates a progressive failure algorithm and gradual stiffness degradation rules through a user defined subroutine UMAT to predict further damage evolution following damage initiation, estimated by the combination of the three-dimensional Puck failure criteria and the cohesive zone model. One of the objectives of this research is to develop a finite element model (FEM) capable of simulating the behaviour of different composite laminates under three-point bending, to reduce effectively processing time and testing costs. As part of the investigations carried out in this study of two types of composite laminates IMS194/CYCOM977-2 and AS4/PEEK, we considered the prediction of ultimate load and stiffness. The results showed significant agreement with the experiments, as well as degradation trends in the load vs. deflection curves. In addition, the interaction between matrix cracking and delamination has been addressed, alongside the impact of cohesive zone elements on the strength of the material. Corrodingly, we found that the interface strength should be considered, to fully exploit the laminate features, and to reduce the effect of delamination which causes intra-laminar longitudinal cracks to appear under the effect of higher inter-laminar stresses. Furthermore, a mesh dependency of the model used has been conducted, to determine the optimal mesh size and shape required to accurately capture the behaviour of the composite laminates. The significance of our study lies in the development of a more accurate and reliable progressive damage model that can improve the design and engineering of composite laminate. [ABSTRACT FROM AUTHOR]

The effects of structural parameters on the forming quality and mechanical properties of CFRP (carbon fiber reinforced polymer)/Al (aluminum) self-piercing riveting (SPR) were investigated and optimized by combining experiment and numerical simulation. Firstly, the SPR 3D finite element model (FEM) was established, in which a continuous damage model (CDM) based on the strain-determined Hashin failure criterion was established to simulate the intra-layer damage of CFRP, and the inter-layer damage was simulated by using cohesive behavior. Subsequently, the effects of rivet length, die diameter, die depth, sheet thickness and width, rivet end distance, and CFRP layup sequence on the SPR cross-sectional dimensions (interlock, bottom remaining thickness) and shear results (peak shear load, energy absorption) were systematically investigated based on the established FEM. Finally, a multi-objective optimization of the structural parameter combinations was performed using Grey relational analysis (GRA) combined with entropy weight method. The results showed that the interlock increased with the increase of rivet length and die diameter, and decreased with the increase of die depth and sheet thickness. The peak shear load increased with the increase of sheet width and rivet end distance. The peak shear load of the joint with [0°/90°]3 s was the largest and the energy absorption of the joint with complex layups was the largest. Normally, the peak shear load and energy absorption were proportional to the interlock. The final optimized combination of joint parameters achieved significant improvement in each indicator compared with the original FEM. [ABSTRACT FROM AUTHOR]

This research numerically investigates the effect of the energy transfer medium on the deformation behavior of the 2024-T351 Al alloy tube during the explosive forming process. Simulations were carried out in air, water, and plasticine mediums by using the finite element method to study the effect of the medium on the formability of the tube. Explosive forming experiments were performed in air with C-4 as a high explosive and the results were used to verify the developed finite element model (FEM). In computational modeling, to simulate hydrodynamic interaction Coupled-Eulerian–Lagrangian (CEL) method was selected. To simulate the expansion of the explosive Jones-Wilkins-Lee (JWL) model was chosen. Also, Johnson–Cook (J-C) strength and damage models were employed to define the mechanical response of the 2024-T351 Al alloy tube. Hillerborg's fracture energy was calculated with the Charpy impact tests and given as input to the FEM to delete the elements that lost their stress-carrying capacity. The results of the constructed finite element model were then analyzed for verification purposes. The simulations conceded that the energy transfer medium has an influence on both the strain rate and the final shape of the Al tube The highest strain rate was obtained in air explosions and thus the highest flow stress. Also, higher stress triaxiality in the air medium led to an earlier fracture. A linear dependence was obtained with the normalized maximum principal stress and normalized dilatation stress for all mediums. By carrying out manufacture in water, the mass of explosives used in the air can be diminished. [ABSTRACT FROM AUTHOR]

During the metal forming process, the avoidance of ductile fracture has been of great interest to the scientific and engineering communities over the past decades. Hence, ductile damage prediction remains a key issue for achieving defect-free products. In this paper, the elastoplastic damage behaviour of DC04 steel has been studied and simulated to predict the fracture during the deep drawing process and reduce the industrial trial cost. In this context, a fully coupled elastoplastic damage model has been developed and implemented in the Abaqus explicit code using the VUMAT subroutine, knowing that the used elastoplastic and the damage parameters were identified by experimental tests. Numerical simulations have been performed to validate this model, followed by comparisons with the experimental results. These comparisons show a good correlation between the experimental and simulation results and good agreement with the empirical observations. Thus, the initiation of damage and its evolution leading to ductile fracture can be predicted using this model. [ABSTRACT FROM AUTHOR]

In longitudinal vibration-assisted milling (LVAM), the tool flute is retracted from the bottom of the machined surface along the axial/longitudinal direction. Nevertheless, there is still a limitation in the knowledge of LVAM during Ti-6Al-4 V cutting regarding the cutting forces pattern in analysis using finite element (FE) simulations and analytical prediction comparatively. This study developed an FE model of the cutting force using ABAQUS and a mathematical model of the cutting force using MATLAB. The FE model was developed based on the Johnson–Cook plastic deformation and the Johnson–Cook damage model. The analytical prediction was developed based on the fluctuated undeformed axial chip thickness and the influence of the longitudinal vibration on the undeformed chip thickness. According to this comparative study, the analytical prediction of the cutting force coded in MATLAB has remarkable similarity with the FE simulation model cutting force. The experimental cutting forces were also carried out to validate both the FE simulation model and the mathematical model. According to the comparison results in the LVAM, the FE simulation model has higher quantitative error than that in the mathematical model, with the highest error in the mathematical model being about 7.146% and the highest error in the numerical model being about 9.913%. In addition, a comparative study between LVAM and CM in terms of the experimental cutting temperature, machined surface morphology, and chip morphology was also carried out. In evidence, LVAM provides better machining performance than CM. [ABSTRACT FROM AUTHOR]

The plastic deformation ability of aluminum alloys is poor and cracking can easily occur during traditional stamping. Electromagnetic forming is a high-speed forming method that can increase the forming limits of aluminum alloys. However, shape deformation of the part is difficult to control owing to fast deformation speeds and uneven electromagnetic force distribution. In this paper, electromagnetic driven stamping (EMDS) is used that combines electromagnetic forming with traditional stamping is proposed. The deformation process of 5052 aluminum alloy sheets during static and dynamic stamping was analyzed through experimental investigations and numerical simulations. Under dynamic conditions, the forming height of 5052-O aluminum alloy increased by 11.4% compared with quasi-static stamping. The Gurson–Tvergaard–Needleman damage model was adopted to predict deformation and fracture behavior during the stamping process. During dynamic stamping, the strain rate reached 405 s−1, which is much higher than that in quasi-static stamping. With EMDS, the void volume fraction in the cracked region decreased by 17.6% compared with quasi-static stamping. Under a high strain rate, the sheet forming height improved as void formation was inhibited and dimples were more evenly distributed. [ABSTRACT FROM AUTHOR]

Central cracking refers to the formation of internal cavities in cross wedge rolling (CWR) products. It occurs in various materials such as aluminium/titanium alloys, steels and plasticine at room or elevated temperatures, driven by different central cracking mechanisms. However, these mechanisms are still elusive, and a unified central cracking predictive model is absent due to the complex stress states within the workpiece, including triaxial stress states, cyclic loading and severe shear effects. In this study, the underlying fracture mechanisms were revealed, and a robust unified damage model with sound physical meanings was developed using a lab-scale CWR physical model and finite element models. The physical model with the plasticine billets was built, allowing the CWR dies with different geometries rapidly 3D printed and the billets with various ductility efficiently manufactured. The central cracking transiting from brittle to ductile fracture was experimentally observed for the first time using specifically designed plasticine/flour composite samples at varying ductility. The corresponding physics-based central cracking predictive model was proposed and validated quantitatively with 60 groups of CWR tests and compared with ten existing damage models/fracture criteria. This study effectively solves the long-lasting central cracking problem in the CWR industry and enhances the scientific understanding of fracture mechanics in complex engineering applications. [ABSTRACT FROM AUTHOR]

Hot stamping patchwork blanks technology can flexibly adjust the mechanical properties by designing different thicknesses and profiles of the main blank and the patched blank. Due to the spot welding connection between the main blank and the patched blank, the material flow between them is uneven and crack defects easily occur. To investigate the influence of the forming parameters, especially welding spot arrangement, on the formability, a high-temperature welding spot failure damage model was established through high-temperature tensile shear and cross-tension experiments. Subsequently, the thermal–mechanical coupling finite element model (FEM) of A-pillar patchwork blanks in hot stamping process was established. The results indicated that the strength of the welding spots satisfied the forming requirements, and the forming defects were mainly caused by the excessive thinning of the base material around the local welding spots. By analyzing the causes of the cracking and then optimizing the welding spot arrangement, the thinning rate of the base material around the welding spot decreased from 33% to less than 12%. The thickness distribution of different sections was compared with the simulated and the experimental results and the error was less than 10%. [ABSTRACT FROM AUTHOR]

During the development of an automobile part obtained by stamping process, time and money are required aiming process planning and setup of a new tooling. One of the difficulties in stamping is to know if the chosen material will have sufficient formability to reach the final form required by the project. Because of this difficulty, it is very interesting to propose a method that can accurately simulate the forming process. The failure criteria can be mathematical or empirical models capable of determining the onset of necking for each stress/strain states. It is interesting to find a failure criterion that can be easily determined and provides a good ability to detect the failure accurately. In this study, six different failure criteria were studied. Five of them are classified as ductile damage models and they depend on the stress triaxiality and plastic strain. The last criterion depends only on the deformations in the main directions and it is called the forming limit curve (FLC). Computational models through finite element analysis (FEA) were used. The formability was evaluated by monitoring the displacement of the punch until the failure of the material. Lou and Huh criterion and Johson-Cook criterion have been able to provide approximation errors in the range of 0.7–5% which makes them interesting for practical implementation in the industry. [ABSTRACT FROM AUTHOR]

Micro-scaled progressive sheet metal forming is a promising process for producing bulk microparts, given its advantages of high efficiency and low cost. To enhance forming quality and efficiency, it is important to have an in-depth understanding of the forming mechanism and model the forming process and fracture behavior accurately. However, the prediction of fracture formation in sheet materials at the micro-scale has not yet been well explored, and thus current knowledge is not sufficient to support the continued development and application of microforming technology. This study investigated progressive sheet forming of magnesium-lithium alloy sheets of different grain sizes to produce bulk microparts directly from sheet metal via shearing, extruding, piercing, and blanking. Using the Gurson–Tvergaard–Needleman (GTN) damage model, the effects of the size factor on the formation and evolution of voids were considered, and the shear-modified GTN model was established by combining Thomason's and Lemaitre's damage mechanics models. The modified model could predict not only the ductile fracture behavior dominated by tension under high-stress triaxiality at the micro-scale, but also the damage behavior controlled by shear deformation under low-stress triaxiality. The progressive forming process was simulated using the modified model, which was verified by experimentation and simulation. Comparisons of the experiments and simulations revealed the size effects on the forming defects and fracture behaviors of microparts during progressive sheet forming. The results show that the stress during deformation is mainly concentrated at the edge of microparts, and irregular geometric defects including burr, rollover, incline, and bulge become deteriorated with the increase of the initial grain size. This study enhances the understanding and prediction of ductile fracture in the micro-scaled progressive forming of sheet metals. [ABSTRACT FROM AUTHOR]

A large number of thick-walled tubes of nickel-based superalloy (TWNS) are required in aviation industry and nuclear industry. The rotary tube piercing (RTP) process has great advantages in preparing the seamless tubes. However, the external separation layer defect (ESLD) hinders the application of RTP process in nickel-based superalloy. In the study, the combinations of experiment analysis and numerical simulation were adopted to explore the formation mechanism of ESLD. The experiment results reveal that the ESLD is closely related to the roll speed and diameter reduction rate, and the radial position of ESLD is determined as r/R = 0.8–0.9. The average grain size and micro-hardness on both sides of ESLD vary greatly, which reveals that the formation of ESLD is closely related to the radial strain gradient. The simulation results reveal that the positions of maximum radial strain gradient, maximum shear strain, and maximum temperature rise are all closed to the position of ESLD. Further, a novel damage model considering the effects of maximum shear strain and maximum shear stress on ESLD was proposed. By comparing the experiment results and simulation results, it is found that the proposed damage model is reliable to predict the ESLD. The formation mechanism of ESLD includes crack initiation and crack propagation. The crack initiation is related to the damage of proposed model, and the crack propagation is controlled by radial strain gradient, which provides a path for the crack propagation. The severe temperature rise intensifies the metal flow and further promotes the evolution of crack. [ABSTRACT FROM AUTHOR]

Fracture prediction using ductile damage models in incremental sheet metal forming has recently become an indispensable approach. Prediction accuracy of damage models depends upon the approach followed to model the anisotropic nature of the sheet metal to a large extent. In this regard, this study is performed to understand the degree of influence of anisotropy in fracture prediction compared to the isotropic model. The Bao and Wierzbicki (2004) damage model was used for predicting fracture in the case of single-point incremental forming (SPIF) of the AA6061-T6 sheet. von Mises and Hill48 yield functions were used to develop the isotropic and anisotropic material behavior in finite element (FE) simulations. A “D” shape geometry with a wall angle of 70° was formed till the fracture. The damage model was calibrated with fracture strains obtained using digital image correlation (DIC) in uniaxial and shear tests. The accuracy of the developed finite element model was validated by comparing the forming height, thickness, and surface strains with experiments. A non-linear damage accumulation rule was utilized to capture the non-linear loading scenarios, and it was calibrated using SPIF of a cylindrical geometry. Finite element simulation using the Hill48 yield function predicted forming height more accurately when compared to the isotropic von Mises yield function. [ABSTRACT FROM AUTHOR]

In the present study, both the experimental and numerical investigations are carried out to understand the dynamic forming behavior of friction stir spot-welded (FSSW) sheet made of AA 5052-H32 sheets of 1 mm thickness using a shock tube. A hemispherical end nylon striker is propelled at high velocity to deform the FSSW sheet in biaxial mode of deformation. Furthermore, the effect of tool rotational speed and plunge speed on the FSSW joint is studied. During this analysis, a new strategy is followed to evaluate the rate-dependent flow stress–strain properties, which are incorporated during FE simulation using FE code, DEFORM-3D. Tensile test data obtained from the unwelded section of the deformed FSSW sheet is fit to Modified Johnson–Cook (MJC) model, and the rate-dependent properties are identified. In the case of the spot-welded region, a hardness-based multiplying factor is generated to evaluate the stress–strain data by fitting to MJC model. The effect of tool rotational speed and plunge speed on the welding and forming outputs are presented. Temperature evolution during FSSW is validated with the experimental data, and good correlation is obtained. The predicted material flow visualization during FSSW gives insight into the mixing of the material during the joint formation. The results agree with available findings. Various forming outputs such as effective strain distribution, necking height, and the failure pattern are predicted using MJC model in combination with Freudenthal damage model, and the results have good agreement with the experimental data. [ABSTRACT FROM AUTHOR]

To prevent the occurrence of localized necking, the concept of forming limit diagram is often used, thus playing an important role in sheet metal forming processes. The aim of the present study is to develop a numerical tool for the theoretical prediction of forming limit diagrams, which would be a cost-effective procedure as compared to experimental measurements. The proposed numerical tool is based on the Marciniak and Kuczyński imperfection approach combined with the Gurson–Tvergaard–Needleman damage model, which is implemented into the MATLAB program within the framework of plane-stress conditions. Forming limit diagrams have been predicted by assuming both geometric (thickness) as well as material initial imperfections in the Marciniak and Kuczyński imperfection approach. These forming limit diagrams, for different sizes of geometric or material imperfections, are also compared with the forming limit diagram obtained by using the bifurcation theory. It is shown that the bifurcation-based forming limit diagram provides an upper bound as compared to the Marciniak and Kuczyński imperfection approach predictions. The results also reveal that irrespective of the imperfection type considered in the Marciniak and Kuczyński imperfection approach, the corresponding forming limit diagram tends to that predicted by bifurcation theory when the size of initial imperfection tends to zero. Additionally, the predicted ductility limits are lowered as the magnitude of initial imperfection increases; however, the decrease in the ductility limits at balanced biaxial tension is more significant than for the other strain-path ratios. The results for the forming limit diagrams indicate that the predicted ductility limits are more sensitive to the initial imperfection in the thickness and the isotropic hardening coefficient as compared to the other types of material imperfections. Moreover, the initial imperfection in the critical porosity is the most influential one among the Gurson–Tvergaard–Needleman damage parameters. [ABSTRACT FROM AUTHOR]

Electromagnetic forming is a high-speed forming process, and it can generate high contact force between the sheet metal and die. Therefore, the effects of die counter-impact on aluminum alloy sheet during electromagnetic forming were numerically and experimentally investigated. Firstly, the numerical simulations of electromagnetic free forming and electromagnetic die forming were performed with the Gurson-Tvergaard-Needleman damage model. When the aluminum alloy sheet impacted the die, an unignorable normal stress occurred along the thickness direction. The void volume fraction was reduced due to the negative stress triaxiality, and the residual stress became smaller. Secondly, the effect of die counter-impact on the pre-deformed aluminum alloy sheet was numerically inspected for quasi-static and dynamic hybrid electromagnetic forming. Compared with the electromagnetic die forming of aluminum alloy sheet without pre-deformation, the void volume fraction and residual stress reductions were more significant for the pre-deformed aluminum alloy sheet. Finally, the aluminum alloy sheets after different electromagnetic forming experiments were compared by optical microscope and Vickers hardness. The results show that the damage suppression and hardness enhancement are attributed to the effect of die counter-impact, especially for the hybrid quasi-static and dynamic forming processes. [ABSTRACT FROM AUTHOR]

Aluminum alloys are characterized by low formability limits under cold forming conditions. The accurate prediction of deformation and failure in sheet metal forming allows for the optimization of forming process parameters and reduces tooling modifications and materials costs. Several models for ductile damage have been developed in the past decades to quantify and predict forming and damage response of sheet metal under complex-forming conditions. However, there is a need to identify a robust model which can provide realistic predictions for the behavior of aluminum sheet metal under the cold forming condition and different loading conditions. This work aims to investigate the prediction capabilities of different damage models for AA-5754 during the cold forming process. The experimental tensile and forming limit diagram (FLD) data of AA-5754 sheet metal used for the damage models' calibration were obtained from literature. In this article, four damage models available in two broadly used the FE software; namely, LS-DYNA and PAM-STAMP were investigated. The models utilized from LS-DYNA material library were MAT_JOHNSON_COOK, MAT_GURSON, and MAT_GISSMO; while from the PAM-STAMP software, the novel CDM model was used. The cross-die formability tests for AA-5754 sheets were performed to validate these damage models. The predictions of the novel CDM model were found to give a good agreement with the experimental results obtained from the formability tests. [ABSTRACT FROM AUTHOR]

The Ti-6Al-4V with significant anisotropy was taken as the research object to analyze the influence of sampling direction and cutting speed on the chip morphology. Based on the fracture damage model of Ti-6Al-4V which was constructed in the previous stage, high-speed orthogonal cutting simulation was carried out in finite element software. The accuracy of the model was verified by cutting experiments. The chip morphology was quantitatively characterized by the chip segmentation degree and chip segmentation frequency. The results showed that the accuracy of the model was high, and it could accurately reproduce the chip formation process of the material in the high-speed cutting process. It was found that material direction and cutting speed had significant effects on chip morphology. When the cutting speed was constant, the chip morphology under different directions was different. The critical cutting speed of chip changing from serrated chips to fragmented chips was different when the direction ranged from 0° to 90°. [ABSTRACT FROM AUTHOR]

Two-point incremental forming (TPIF) shows higher forming limits than single-point incremental forming (SPIF) especially for producing complex industrial functional components. However, unexpected failure still occurs occasionally under certain forming conditions in TPIF. In this paper, the applicability of six damage models for failure prediction in TPIF is evaluated. The procedure of damage parameter calibration and finite element modelling are presented. The predicted failure depth and location with these damage models are evaluated under different loading conditions. Furthermore, the stress and strain and damage evolution in TPIF are provided and discussed in detail. It is concluded that the failure location and depth can be predicted more accurately by the Ayada model than others in this work. It is noted that once double-sided contact occurs in TPIF, it reduces the variation of triaxiality through the thickness, altering the accumulation of damage. [ABSTRACT FROM AUTHOR]

In order to solve the problem of forming parts with complex shape and small local feature size, solid granules medium forming (SGMF) was adopted. A part of magnesium alloy AZ31B with double-cone shape was taken as an example to analyze the forming process. The parameters of Gurson–Tvergaard–Needleman (GTN) were identified by an inverse method, comparing the experimental results with the numerical results. Based on the GTN model, the coupled finite element and discrete element (FE-DE) method was applied to simulate the forming process of the double-cone part with SGMF technology, and the relevant forming experiments were carried out. The results show that the quality of the workpiece can be improved with different friction coefficient of different area of the part. The fracture behavior and final wall thickness distribution obtained by experiment consist with those by simulation. So, it demonstrates the applicability of the FE-DE method with GTN damage model in analyzing formability of magnesium alloy, and the FE-DE method could embody the medium discrete characteristics fully during SGMF technology. [ABSTRACT FROM AUTHOR]

Single-point diamond turning (SPDT), which cuts the workpiece with a single crystal diamond tool, is considered as a promising manufacturing technology in modern industry. In SPDT, it is found that the surface roughness near the center of the workpiece is poor when the cutting depth is small or the feed rate is large. In order to obtain better surface quality, the spindle speed must be increased, which thus reduces the productivity and causes the unnecessary abrasion of the cutting tool. Meanwhile, the influence of feature size effect to the fracture formation in SPDT has not yet been mentioned. In tandem with this, this paper has provided a hybrid damage model to predict appropriate feed rate, cutting depth, and cutting speed of SPDT. Based on the Johnson Cook model, a revised function to quantify the influence of size effect is introduced, and the pre-strained method using the split Hopkinson pressure bar (SHPB) is conducted to calculate the unknown coefficients of the model. The experimental result shows that feature size effect will cause surface rough patterns when feed rate and cutting speed are lower than the predicted critical speed. By implementing the critical energy, which is calculated by the hybrid damage model with different strain rates and heat treatment conditions, the multi–strain-rate fracture diagram (MFD) is carried out and the fracture caused by size effect in SPDT is revealed and predicted. This paper has thus provided an in-depth understanding of the influence of size effect in SPDT. [ABSTRACT FROM AUTHOR]

To manufacture semi-finished hybrid workpieces with tailored properties, a finite element simulation assisted process chain design was investigated. This includes the process steps of cross wedge rolling, hot geometry inspection, induction hardening, and fatigue testing. The process chain allows the utilisation of material combinations such as high-strength steels with low-cost and easy to process steels. Here, plasma transferred arc welding is applied to supply the process chain with hybrid specimen featuring different steel grades. An overview of the numerical approaches to consider the various physical phenomena in each of the process steps is presented. The properties of the component behaviour were investigated via the finite element method (FEM) and theoretical approaches. At first, the manufacturing of a hybrid workpiece featuring a near net shape geometry with improved mechanical properties due to recrystallising the weld was computed, using the example of a cross wedge rolling process. The rolling process was designed by means of FEM to determine suitable process parameters and to reduce experimental testing. An optical multi-scale geometry inspection of the hot workpiece is meant to be carried out after each manufacturing step to detect potential undesired forming or cooling-induced deformations. Due to the heat transfer from the hot component to the ambient medium, an optical measurement is affected by the developing inhomogeneous refractive index field in air. To gain a basic understanding of the refractive index field and induced light deflection effects, computations were conducted using heat transfer and ray tracing simulations. According to the proposed process route, a subsequent local heat treatment of the hybrid component is required to adapt the mechanical properties by a spray cooling assisted induction hardening. The heat treatment step was computed via a 2D FEM calculation. After finishing by machining, the hybrid material shafts are examined in fatigue tests under load conditions. To predict the component's lifetime under rolling contact fatigue, a damage accumulation model was combined with an FE simulation. The resulting residual stress state after quenching and the geometry after the finishing process were used as input data for the fatigue life calculations. [ABSTRACT FROM AUTHOR]

The finite element method (FEM) has considerably contributed to the development of advanced manufacturing methods for metal structures. The prediction of the final shape of a component is of great interest to the manufacturing industry. The level of demand may increase due to multistage processes. Therefore, including all steps of the manufacturing chain in the simulations is a key to being successful. This has been done for a long time in the stamping industry, which involves sequences of forming, trimming, and springback. However, more complex manufacturing procedures that include assembling of formed parts with forgings and castings via welding have been modelled with simplifications, resulting in a reduced prediction accuracy. In the present study, a double-curved part manufactured from alloy 718 is formed at 20 °C and laser-welded using the bead-on-plate procedure. The coupling of different manufacturing analyses, including cold forming, trimming, result mapping, welding, cooling, and springback, is achieved using LS-DYNA. Additionally, the effect of adding a damage and failure model in the forming simulation is studied. The results of the forming analysis are used as inputs for the material model *MAT_CWM in the welding simulation. The anisotropic thermomechanical properties of alloy 718 are determined at temperatures up to 1000 °C. Encouraging agreement is found between the model predictions and the results of forming and welding tests. The findings underscore the importance of including the material history and accurate process conditions along the manufacturing chain to both the prediction accuracy of shape distortions, and to the potential of the industry. [ABSTRACT FROM AUTHOR]

This study investigates machining superalloy Inconel 718 with polycrystalline cubic boron nitride (pcBN) tooling both numerically and experimentally. Particular attention is given to mechanical and thermal stresses in the cutting tool arising from segmented chip formation and associated forces and temperatures. The temperature dependence of the mechanical properties of pcBN has been investigated and incorporated into a numerical model. In order to capture the dynamic loads due to a serrated chip formation, the Johnson–Cook damage model has been used. The extreme deformations during a machining process often results in a numerical difficulties due to a distorted elements. This paper uses the coupled Eulerian–Lagrangian (CEL) formulation in Abaqus/Explicit, where the workpiece is modelled with the Eulerian formulation and the cutting tool by the Lagrangian one. This CEL formulation enables to completely avoid mesh distortion. The finite element simulation results are validated via comparison of the modelled static and dynamic cutting forces and thermal loads induced into the cutting tool. The numerical model predicts a temperature of 1100–1200 ∘C at the cutting interface, which is in line with experimental determined data. The principal stresses at the rake up to 300 MPa are recorded, whereas higher level of stresses up to 450 MPa are found in the notch region of the tool, well correlated with experimental observation. [ABSTRACT FROM AUTHOR]

Ductile fracture is one of the most common failure modes in hot metal forming. It can be predicted by means of so-called damage functions that describe the relation between stress, deformation and fracture initiation. A practical use of these functions requires the knowledge of the critical damage value of the material that is determined by calibration tests based on compression, tension and torsion. For the prediction to be correct, one must ensure that the modelled and real stresses are in agreement. Previous studies did not offer any effective test for determining critical values of damage under changing load conditions that occur in cross and skew rolling processes, among others. To compensate for this knowledge gap, researchers at the Lublin University of Technology have developed a new test consisting in rotary compression of a test-piece in a cavity between the tools, which is described in this paper. In the proposed test, a cylindrical test-piece is rolled over a cavity (impression) created by grooves on two mating tools. The cavity height is smaller than the test-piece diameter. At the critical value of the forming length, the state of stress induced thereby in the test-piece axis causes fracture. Knowing the critical forming length, it is possible to determine the critical value of damage by numerical modelling. The practical application of the proposed test is illustrated through the case of C45 grade steel subjected to forming in the temperature range 950–1150 °C. The analysis makes use of the normalized Cockcroft-Latham (NCL) criterion of ductile fracture. [ABSTRACT FROM AUTHOR]

Three-dimensional Hashin failure criterion and material stiffness degradation model were compiled by VUMAT subroutine. The Abaqus/Explicit solver was performed to establish progressive damage model of cutting force for CFRP high-speed milling, and high-speed milling experiments with different cutting parameters were carried out. Further, the impact mechanism of fiber cutting angle and cutting parameters on cutting force, stress, and material failure during milling was explored, and the material removal mechanism in high-speed milling of CFRP was revealed. The results show that the error between the experimental and simulated of cutting forces is less than 5%, which indicates that the progressive damage model is feasible. The fiber cutting angle has significant influence on cutting force and stress in cutting process, and the cutting direction has a significant influence on cutting force. In addition, cutting parameters play a critical role in cutting force, and the feed per tooth is the most significant factor affecting the cutting force. Simultaneously, the progressive damage model predicts that the shear failure of materials mainly concentrates in the cutting area and extends along the feed direction. Finally, the material removal mechanism of CFRP in high-speed milling was revealed combining cutting force experiment. [ABSTRACT FROM AUTHOR]

Oil-on-water (OoW) techniques, including external OoW sprayed to both the rake face and flank face (EOoWrf), as well as cryogenic air mixed with OoW (CAOoW), improve the machinability of compacted graphite iron (CGI). This paper proposes a modified material model for RuT400 CGI cutting, based on flow softening and weak thermal softening effect, as observed during split-Hopkinson pressure bar tests. Employing a modified material model and Cock-Latham damage model, a thermo-mechanical coupled finite element (FE) model, for RuT400 cutting, is presented. The simulations, considering dry cutting, EOoWrf, and CAOoW, are conducted for the purpose of revealing the causes for the RuT400 difficult-to-cut property and for establishing how the mechanism of OoW can improve cutting performance. The results show that the effective stress, required to form chip segments in RuT400 machining, is much lower than in hardened steel, so RuT400 is more likely to form a serrated chip. In dry cutting, the chip bottom surface is subject to high strain and temperature, leading to the work-material phase transformation, followed by aggravating adhesive and abrasive wears. Although EOoWrf has little influence on chip morphology and effective stress, it reduces the temperature and strain on chip bottom surface by reducing friction, thus suppressing the occurrence of phase transformation. Due to low friction and high heat exchange, CAOoW produces the lowest tool-chip interface temperature and minimal adhesive wear. For high-speed cutting of RuT400, compared to dry cutting, EOoWrf and CAOoW can effectively reduce cutting forces and maintain the tool temperature in a lower range, where low friction on tool-chip interface plays a key role. The proposed FE model can be used in the future to improve CGI's machinability, by changing cooling parameters, tool geometry/material, and other machining variables. [ABSTRACT FROM AUTHOR]

In the present study, tailor-welded blanks (TWBs) of dissimilar material combination were fabricated by laser welding of interstitial-free (IF) and dual-phase (DP) steels using 2.4-kW power and 4 m/min scan speed. Subsequently, TWBs of as-received sheet materials and IF steels were pre-strained up to 20% major strain in the deformed specimens through an equi-biaxial pre-straining setup. It was found that highly non-uniform strain distribution with nearly plane strain deformation mode was induced in the pre-strained TWBs, whereas an equi-biaxial strain was recorded for IF monolithic blank. Microhardness profiles and the effect of weld zone on the microstructural and mechanical properties of the as-received and pre-strained TWBs were studied. Further, the forming limit diagrams (ε-FLDs) of as-received TWB and IF steel were experimentally evaluated. The ε-FLD of pre-strained TWBs was experimentally determined, and ε-FLD of the pre-strained IF material was estimated using the Yld89 anisotropy plasticity model with the Hollomon hardening law. Subsequently, all these respective ε-FLDs were implemented as damage models in the FE simulations for predicting the limiting dome height (LDH) of as-received and pre-strained TWBs. It was observed that the error in LDH prediction of pre-strained TWB domes was within 9.1% when the estimated ε-FLD of the pre-strained IF material was used as a damage model. The FE-predicted strain distributions and weld line movements of TWBs after the second stage of deformation were also successfully validated with the experimental data. [ABSTRACT FROM AUTHOR]

It has been proven that micro-geometry of abrasive grits can influence the maximum cutting depth, thereby strongly affecting the material removal mechanism in grinding of brittle materials. The influence of grit micro-geometry on subsurface integrity, however, is not yet fully understood. In this paper, we aim to understand how grit micro-geometry affects subsurface damage and the material removal volume. An analytical model that takes into account grit micro-geometry and the intrinsic material removal mechanism is developed for predictions of material removal volume and subsurface damage. Results show that increasing the apex angle or grit tip radius tend to deteriorate subsurface integrity by extending the depth of subsurface damage. Moreover, it is found that the grit tip radius strongly affects the ductile-to-brittle transition in one grit pass along the contact trajectory. If ductile-to-brittle transition occurs in a grit pass with the brittle mode dominated, the predictive model indicates that the material removal volume decreases with an increasing apex angle or edge radius of abrasives. On the other hand, non-monotonic dependence of material removal volume on grit micro-geometry turns up for ductile-material removal in grinding of brittle materials. The predictive model is validated qualitatively and quantitatively, demonstrating good agreement with earlier reports. The proposed predictive model enables making proper choice of highly engineered abrasives in grinding of brittle materials. [ABSTRACT FROM AUTHOR]

This article presents a fatigue damage cumulative model under variable loading devoted for defective materials. The multiaxial stress amplitude is reported to the equivalent stress by combining it with the S-N curve and an algorithm to evaluate the damage model. The proposed model is connected cycle by cycle with the Wöhler curve and it takes into account the history of loading. An application has been carried out on a C35 low alloy steel containing defects. The results of the model are compared with the experimental results made on this context and those computed by the most frequently used damage model in fatigue (Miner's model). It has been demonstrated that the proposed model presents a good prediction of the experimental results, allows a better fatigue damage prediction than the widely used Miner rule, and can be used as an interesting and a powerful engineering prediction for industrial users. [ABSTRACT FROM AUTHOR]

In this paper, a deep study of constitutive parameters definition effect is done in order to guarantee sufficient reliability of the finite element machining modeling. The case of a particular biphasic titanium alloy Ti6Al4V known by its low machinability is investigated. The Johnson-Cook (JC) elasto-thermo-visco-plastic-damage model combined with the energy-based ductile fracture criteria is used. Segmentation frequency, chip curvature radius, shear band spacing, chip serration sensitivity and intensity, accumulated plastic strain in the formed chip segments, and cutting forces levels are determined where their dependency to every constitutive coefficient is examined and highlighted. It is demonstrated from the separate variation of every plastic and damage parameters that an interesting finite element modeling (FEM) relevance is reached with the adjustment of JC strain hardening coefficients term, thermal softening parameter, exponent fracture factor, and damage evolution energy. Moderate and high cutting speeds are applied to the cutting tool in the aim to test their impact on shear localization, chip segmentation, and numerical forces levels as well as to approve previous highlighted findings related to constitutive parameters definition. In general, this study focuses on a prominent decrease in identification process cost with the previous knowledge of the most affecting constitutive coefficients while keeping an interesting agreement between numerical and experimental results. [ABSTRACT FROM AUTHOR]

Drilling-countersinking (DC) machining is one of the most popular methods for making holes with countersink in modern industry. In DC machining process of carbon fiber reinforced plastics (CFRP)-aluminum (Al) stacks, the force caused by each cutting edge in different materials is changing all the time and will affect the quality of holes. This paper focused on the cutting force for DC machining of CFRP-Al stacks, developed a novel cutting force model, which can represent the dynamic cutting force at any time of the DC process. The whole DC process is divided into six different states which contain drilling, reaming, and countersinking in different materials. Forces on different cutting edges are modeled on the base of the microscopic oblique cutting theory. And the dynamic cutting forces of every moment in the six-state DC machining process are integrated on base of the integral limits analysis and equivalent fiber orientation. Experiments with different cutting parameters are developed to analyze the dynamic cutting force of CFRP-Al stacks. The trend of cutting forces according to different machining parameters is similar, and the influence of different cutting edge on the cutting force will change in different state according to the result of both experiment and proposed model. The values of cutting force getting from the experiments can match with the results of dynamic model well, despite the fact that gaps between different materials will affect the change of cutting force. [ABSTRACT FROM AUTHOR]

Grinding of brittle materials will inevitably cause grinding damages characterized by fracture microcracks, which will greatly affect the grinding integrity. Traditional damage models are just concerned about the material properties and interaction depth between grit and workpiece without considering the dynamic effect on material strength. This paper proposed new damage analysis models which consider the effect of both strain rate and grinding parameters on grinding damages. It is believed that the material strength and dynamic fracture toughness vary under different grinding parameters due to the variation of strain rate brought by the grinding speed and chip thickness. By introducing the grinding-induced strain rate, the new damage models were further updated as the function of the grinding speed and chip thickness. The grinding damage models were verified through different grinding tests. Combining with the surface roughness results, the grinding damages under different grinding speed and damages are fully discussed. Finally, the damage-free grinding was proposed based on the proposed model. It can be concluded that a combination of the grinding speed and reduction of the chip thickness can help achieve damage-free ground surface. [ABSTRACT FROM AUTHOR]

We study the dynamics of a milling process of carbon fiber reinforced plastic based on experimental time series of cutting force with help of recurrence plots and recurrence quantifications methods. The two cases of composite machining are analyzed in detail. The first case is a milling of undamaged material, while the second is a milling of damaged material. The detailed recurrence analysis shows interesting results, and additionally some of all quantifications can be used to damage detection. [ABSTRACT FROM AUTHOR]

The aim of our work is the modeling of damage in the welded metal using the finite element method and the concepts of fracture mechanics based on local approaches. The use of Gurson-Tvergaard-Needleman (GTN) model has enabled us to model the behavior of damage of welded steel, which is described as being due to the growth of cavities. [ABSTRACT FROM AUTHOR]