Incremental sheet metal forming can manufacture various sheet metal products without a dedicated punch and die set. In this study, we developed a two-stage incremental forming process to decrease shape errors in the conventional incremental forming process. The forming process was classified into the first single point incremental forming (1st SPIF) process for forming a product and the counter single point incremental forming (counter SPIF) process to decrease shape error. The counter SPIF gives bending deformation in the opposite direction. Furthermore, the counter SPIF compensates for shape errors, such as section deflection, skirt spring-back, final forming height, and round. The tool path of the counter SPIF has been optimized through a relatively simple optimization method by modifying the tool path of the previous step. The tool path of the 1st SPIF depends on the geometry of the product. An experiment was performed to form a circular cup shape to verify the proposed tool path of the 1st and counter SPIF. The result confirmed that the shape error decreased when compared to the conventional SPIF. For the application, the ship-hull geometry was adopted. Experimental results demonstrated the feasibility of the two-stage incremental forming process.
This research aims to characterize damage at the sheared edge caused by the blanking operation of magnesium alloy AZ31B sheets. Shearing tests were carried out on an in-house blanking die-set and mechanical press (universal testing machine) by varying punch–die clearance and temperature. Edge damage was distinguished by the geometrical features of the sheared edge and by the distribution of the edge strain hardening (ESH) index. In this account, optical microscopy and scanning electron microscopy were applied to examine the characteristic dimensions of the sheared edge, fracture profile, and sheared edge quality, while the Vickers hardness test was applied to observe the surface micro-hardness in the shear zone (SZ) and the shear affected zone (SAZ). It was concluded that the blanking of magnesium alloy sheets at room temperature results in sheared edge defects, due to premature fracture, referred to here as micro-cracks, loose particles, and a jagged-plus-curved fracture profile. However, such deformities were completely suppressed with the rise in temperature. In addition, based on optical morphology, micro-hardness tests, and microstructure evolution, the recommendation regarding blanking temperature for the magnesium alloy AZ31B has was proposed.
The hot metalworking process is a typical procedure in the metallurgy industries for manufacturing many daily-life products that can not be produced using the cold working process. [1,2] The crucial advantages of the hot forming process are the higher material formability. Besides, the produced parts have no oriented grain structure due to hot processing conditions, resulting in highly isotropic strength characteristics. [3,4] In the metal forming process, the material will experience various loading conditions through strain, stress, strain rate, and temperature. Therefore, the material can be tested at different temperatures to explain the deformation behavior and strain rates, and besides essential key parameters can also be obtained. [5,6] The constitutive model can be established and implemented into the finite element analysis (FEA) software using received stressstrain (SS) curves for performing forming simulations to save experimental time and cost. [7] Many researchers have been devising various constitutive models by establishing the relationship between the external loading conditions and the thermomechanical behavior of test materials. [8] Because precise flow stress models could be exploited to perform accurate forming simulations, and optimal forming conditions can eventually be received. Studies showed that Johnson-Cook (JC) and modified Johnson-Cook (MJC) models are widely used to predict material behavior under hot deformation conditions. Therefore, Song et al., [9] Wang et al., [10] Tan et al., [11] Liang et al., [12] and Li et al., [13] had investigated the selected material dynamical behavior at higher strain rates and elevated temperatures using JC and MJC models. They documented that the MJC model could accurately describe the studied material's flow behavior. For example, Liang et al. [12] examined Al-Si-Mg alloy material at strain rates of 10 À3 s À1 and deformation temperatures of to 500 °C. They reported that the prediction error from the MJC model was about 1.65% and held well-agreement with the actual data. Similarly, Li et al. [13] studied T24 steel material at hot deformations using the MJC model. They also confirmed that the proposed model wellcaptured the material's dynamic behavior and agreed with the experimental observations.Researchers have also adopted the strain compensated constitutive equation, repeatedly called, the Arrhenius-Type constitutive model, to describe the material hot deformation characteristics. For example, researchers Zhao et al., [14] Li et al., [15] Zhang et al., [16] Liu et al., [17] and Li et al. [18] had exploited the Zener-Hollomon exponent-type equation for the hard-toform materials such as 14Cr ODS steel, 2219 aluminum, TA15 titanium, titanium-aluminum, and magnesium alloys, respectively. Liu et al.
The surface finish is an important characteristic in the incremental sheet forming (ISF) process and is often influenced by numerous factors within the forming process. Therefore, this research was aimed at identifying the optimal forming parameters through the Taguchi method to produce high-quality formed products. The forming tool radius, spindle speed, vertical step increment, and feed rate were chosen as forming parameters in the experimental design, with surface roughness as the response variable. Taguchi L16 orthogonal array design and analysis of variance (ANOVA) test were used to identify the parameter’s optimal settings and examine the statistically significant parameters on the response, respectively. Results confirmed that a significant reduction in surface roughness occurred with a drop in vertical step size and an increase in feed rate. In detail, the vertical step size has the most significant influence on the surface roughness, followed by the feed rate and the forming tool radius. In conclusion, the optimum level settings were obtained: forming tool radius at level 3, spindle speed at level 1, vertical step size at level 1, and feed rate at level 4. Additionally, confirmation experiment results based on the optimal settings indicated a good agreement against the experimental observation. Further, the response surface methodology (RSM) was also exploited to devise a mathematical model for predicting the surface roughness. The results comparison confirmed that both techniques could effectively improvise the surface finish.
In this study, the time-dependent mechanical behavior of the magnesium alloy sheet (AZ31B) was investigated through the creep and stress relaxation tests with respect to the temperature and pre-strain. The microstructure changes during creep and stress relaxation were investigated. As the tensile deformation increased in the material, twinning and dynamic recrystallization occurred, especially after the plastic instability. As a result, AZ31B showed lower resistance to creep and stress relaxation due to dynamic recrystallization. Additionally, time-dependent springback characteristics in the V- and L-bending processes concerning the holding time and different forming conditions were investigated. We analyzed changes of microstructure at each forming temperature and process. The uniaxial tensile creep test was conducted to compare the microstructures in various pre-strain conditions with those at the secondary creep stage. For the bending process, the change of the microstructure after the forming was compared to that with punch holding maintained for 1000 s after forming. Due to recrystallization, with the holding time in the die set of 60 s, the springback angle decreased by nearly 70%. Increased holding time in the die set resulted in a reduced springback angle.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.