| 1. |
- Hu, Cheng, et al.
(författare)
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On the steady-state workpiece flow mechanism and force prediction considering piled-up effect and dead metal zone formation
- 2021
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Ingår i: Journal of Manufacturing Science and Engineering. - : ASME International. - 1087-1357 .- 1528-8935. ; 143:4
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Tidskriftsartikel (refereegranskat)abstract
- The manufacturing of miniaturized components is indispensable in modern industries, where the uncut chip thickness (UCT) inevitably falls into a comparable magnitude with the tool edge radius. Under such circumstances, the ploughing phenomenon between workpiece and tool becomes predominant, followed by the notable formation of dead metal zone (DMZ) and piled-up chip. Although extensive models have been developed, the critical material flow status in such microscale is still confusing and controversial. In this study, a novel material separation model is proposed for the demonstration of workpiece flow mechanism around the tool edge radius. First, four critical positions of workpiece material separation are determined, including three points characterizing the DMZ pattern and one inside considered as stagnation point. The normal and shear stresses as well as friction factors along the entire contact region are clarified based on slip-line theory. It is found that the friction coefficient varies symmetrically about the stagnation point inside DMZ and remains constant for the rest. Then, an analytical force prediction model is developed with Johnson-Cook constitutive model, involving calibrated functions of chip-tool contact length and cutting temperature. The assumed tribology condition and morphologies of material separation including DMZ are clearly observed and verified through various finite element (FE) simulations. Finally, comparisons of cutting forces from cutting experiments and predicted results are adopted for the validation of the predictive model.
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| 2. |
- Weng, Jian, et al.
(författare)
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A comprehensive study on cutting mechanisms and surface integrity of AISI 304 when turning a curved surface
- 2021
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Ingår i: Materials and Manufacturing Processes. - : Informa UK Limited. - 1042-6914 .- 1532-2475. ; 36:11, s. 1285-1298
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Tidskriftsartikel (refereegranskat)abstract
- Most of the studies on cutting mechanisms and surface integrity in turning are investigated with a straight tool path (longitudinal/end face turning) while few contributions have been done in curved surface turning. This work explores the evolutions of cutting force, chip morphology and surface integrity when turning a curved surface, using fillet surface machining of AISI 304 stainless steel. The varying cutting conditions caused by the presented turning are revealed by detailed geometric analysis and employed as indicators for further discussions on cutting force, chip morphology, and machined surface integrity (including surface roughness, microhardness, microstructure, and residual stress). Apart from the difference of cutting force components in tangential, radial, and cutting speed directions along the fillet surface, wider and thinner chips are obtained from end face turning. The measured microhardness, microstructural alternation, and stress condition results comprehensively illustrate a reduction of severe plastic deformation from the outer face to the end face.
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| 3. |
- Weng, Jian, et al.
(författare)
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A hybrid model for force prediction in orthogonal cutting with chamfered tools considering size and edge effect
- 2020
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Ingår i: International Journal of Advanced Manufacturing Technology. - : Springer Science and Business Media LLC. - 0268-3768 .- 1433-3015. ; 110:5-6, s. 1367-1384
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Tidskriftsartikel (refereegranskat)abstract
- Researches on the modeling of machining difficult-to-cut metals are important for optimization of the processing parameters, in which the force modeling is essential due to its significant influence on the performance of tools and the quality of parts. A semi-analytical method for force prediction in orthogonal cutting with chamfered tools considering both edge and size effect is proposed in this paper. The plastic deformation in the shear band was investigated using a parallel shear zone model and unequal division shear zone model. The influence of size effect on cutting force was discussed and a simplified expression of improvement factor is introduced to describe the sharp increase of shear stress under the condition of low feed rate. Simulations of orthogonal cutting with different chamfer lengths are conducted to analyze the variation of cutting force with respect to chamfer length, which reveals that the influence of chamfer length on cutting force is determined by the ratio of chamfer length to uncut chip thickness. A modified function considering the trend of material flow condition is proposed, which treats the total cutting force as a combination of cutting forces caused by chamfered edge and rake face. The calibration of constants in the proposed method is achieved using particle swarm optimization (PSO), a meta-heuristic algorithm for complicated non-linear models. The experiments show that the method works well on both fitting and predicting modules in orthogonal cutting of AISI 304 using cemented carbide tools with 15° chamfer angle or 25° chamfer angle.
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| 4. |
- Weng, Jian, et al.
(författare)
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A machine learning based approach for determining the stress-strain relation of grey cast iron from nanoindentation
- 2020
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Ingår i: Mechanics of Materials. - : Elsevier BV. - 0167-6636. ; 148
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Tidskriftsartikel (refereegranskat)abstract
- Apart from microhardness and elastic modulus, the stress-strain relation is another important characteristic that more and more scholars have been trying to extract from nanoindentation. With the development of artificial intelligence and computer technology, a machine learning based method is proposed in this paper to extract stress-strain curve of grey cast iron using sharp nanoindentation. Firstly, the average curve is achieved by the grid-design nanoindentation to avoid the influence of different phases on indentation results. The plastic behavior is considered as a power law function in this paper. Then, finite element method supports to generate a simulation data set, with full-factor and full-level design of constants of stress-strain relation. With the simulation data set, the support vector regression machine establishes a surrogate model to correlate the input (constants of stress-strain function) and output (the mean error between predicted and measured results). The best parameters of support vector machine are determined through grid search and cross-validation. PSO serves as the optimization algorithm to find the optimum of input related to the measured results, with an inertia factor to improve the local search ability. Finally, the simulation loading curve with the optimal constants provided by PSO perfectly fits the measured loading curve, which shows the effectiveness of the inverse method proposed in this paper.
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| 5. |
- Weng, Jian, et al.
(författare)
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An analytical method for continuously predicting mechanics and residual stress in fillet surface turning
- 2021
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Ingår i: Journal of Manufacturing Processes. - : Elsevier BV. - 1526-6125. ; 68, s. 1860-1879
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Tidskriftsartikel (refereegranskat)abstract
- A novel and effective approach for determining mechanics and residual stress when turning a component with curved surfaces is presented in this paper. This predictive approach is based on a three-dimensional analytical model to study the distributed mechanics and residual stress caused by vary cutting condition during the machining process. The variation of uncut chip area in this process can be divided into several stages based on different tool-workpiece contact and the discretization of cutting edge is conducted at an arbitrary tool position. The chip flow direction is calculated through the equilibrium of the incremental interaction forces. The cutting force can be determined by integrating the force components along the cutting edge, with each incremental force component obtained based on a fully analytical model. Distributed heat source intensity is considered to model the temperature rise at an arbitrary point in workpiece. The residual stress in curved surface machining is obtained considering the loading-unloading-relaxation procedure at the engagement of cutting edge and machined surface. Finally, Finite Element (FE) modeling and experiments are performed to validate the correctness and robustness of the analytical model proposed in this paper. The results of predicted chip flow direction, cutting force, temperature, and residual stress show good agreement with the simulated and measured results.
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| 6. |
- Zhuang, Kejia, et al.
(författare)
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Investigation on work hardening phenomenon in turning Inconel 718 with chamfered inserts considering thermal-mechanical loads
- 2020
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Ingår i: 5th CIRP Conference on Surface Integrity (CSI 2020). - : Elsevier BV. - 2212-8271. ; 87, s. 47-52
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Konferensbidrag (refereegranskat)abstract
- Work hardening layer on and beneath the machined surface is one of the key factors that affects the performance and service time of the final component. However, the mechanism of the work hardening generation and its behavior are still great challenges and open issues to the academic and industry. In this paper, an investigation of the work hardening layer generated by chamfered tools is conducted based on the simulation and experimental study with the consideration of cutting force and temperature. Series of cutting tests and simulations using various edge preparation and feedrate are conducted to obtain the cutting forces, temperature and micro hardness profiles. Then, models for cutting force prediction and temperature simulation are used to reveal the generation of thermal-mechanical loads during the cutting operation. The effect of cutting edge preparation and feedrate on the generation of cutting force, temperature and work hardening was studied. The results indicate that the depth of work hardening layer can achieve to more than 60 μm under the given cutting conditions with chamfered tools. The role of feedrate and chamfer length playing in the generation of work hardening behavior in machining Inconel 718 was also discussed in the paper.
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| 7. |
- Zhuang, Kejia, et al.
(författare)
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Numerical investigation of sequential cuts residual stress considering tool edge radius in machining of AISI 304 stainless steel
- 2022
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Ingår i: Simulation Modelling Practice and Theory. - : Elsevier BV. - 1569-190X. ; 118
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Tidskriftsartikel (refereegranskat)abstract
- Residual stress affects component performance, and the existence of pre-stress changes the residual stress of machined surfaces as well, emphasizing the importance of studying the evolution of residual stress in sequential cutting. This paper reports a numerical investigation of the machining-induced residual stress profile of sequential cuts for orthogonal cutting of AISI 304, considering the effects of edge radius and cutting depth. A Coupled Eulerian-Lagrangian (CEL) model is employed for the first time to stably simulate the evolution of residual stress of multiple sequential cuts. The effectiveness of the proposed method is verified by comparing the chip formation and surface residual stress between simulated and experimental results. The cutting force and cutting temperature, as well as mechanical and thermal loads, are extracted to explain the generation and evolution of residual stress in sequential cutting. It is found that the residual stress on the machined surfaces will decrease during sequential cutting, and a stable value can be reached after approximately six sequential cuts. With the progress of sequential cutting, a larger honed tool edge radius and cutting depth will lead to a slower reduction of residual stress.
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| 8. |
- Zhuang, Kejia, et al.
(författare)
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Numerical investigations on residual stresses in orthogonal cutting of Ti-6A1-4V
- 2022. - C
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Ingår i: Procedia CIRP. - : Elsevier BV. - 2212-8271. ; 108, s. 199-204
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Konferensbidrag (refereegranskat)abstract
- Titanium is widely employed in aerospace space, where the surface integrity plays an important role in part quality. This paper presents the numerical and experimental results of residual stress when machining Titanium based on a CEL (Coupled Eulerian-Lagrangian) method. The performance of proposed model is compared with LAG (Lagrangian) and ALE (Arbitrary Lagrangian-Eulerian) methods regarding segment chip formation and residual stress. The correctness of simulation results is validated by orthogonal cutting experiments of Ti-6Al-4V as well as the experimental data given in recent published literature. The effects of uncut chip thickness, cutting velocity and edge radius on residual stress are discussed through simulation results.
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