FIGURE 13. (A) Experimental signals on different radius of curvature with a crack depth of 2 mm; (B) Experimental signals on different radius of curvature with a crack depth of .4 mm (C) Experimental signals on different radius of curvature with a crack depth of .6 mm (D) Peak and valley values of the experimental signal of different models bearing rings at different curvature.
Citation: Yang Y, Peng G, Qiu S, Chen C and Liang Z (2023) Influence of curvature radius on the axial crack signal of the magnetic flux leakage detection for tapered roller bearing rings. Front. Phys. 10:1075549. doi: 10.3389/fphy.2022.1075549
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Stretch flanging is the important sheet metal-forming process which is widely used in automobile and aerospace sectors. The formability of sheet metal depends on various parameters such as material properties, geometry of the tool setup and process parameters. In the present work, effects of different die radius and sheet width on deformation behavior of sheet are studied by FEM simulation and experiments. The predicted FEM results are presented in the form of edge crack location and its propagation, crack length, forming load and strain distribution in sheet along the die profile radius. This study indicates that crack length increases with increase in the sheet width, while the crack length decreases with increase in the die radius. It is found that the crack propagation in stretch flanging process is affected by the strain distribution in sheet and this distribution of strain depends on many parameters. The crack initiates during deformation of the sheet at the die corner edge and propagates toward the center of the sheet along the die profile radius. Simulation results are compared with the experimental one in terms of crack length and variation in sheet thickness. FE simulation results are found in very good agreement with experimental results. Fractography study is also presented in terms of size, shape of the dimples along with their distribution on the fractured surface.
In the past, various researchers have been attempted to predict the failure phenomenon in the sheet metal-forming operation by using FEM simulation. Wang and Wenner [6] used numerical procedure for the study of strain and stress distribution in stretch flanging process. This theory is based on the total membrane strain of rigid-plasticity and approximate theory. Li et al. [7] analyzed the stretch flanging of V-shaped sheet metal forming and study the effect of material parameters and geometrical parameters on flanging. An analytical model was developed for axisymmetric case on total strain theory and membrane assumption. Hu et al. [8] found that the smaller die radius than the punch radius is detrimental for the deformation. Further, this study also presented the effect of geometrical parameters and anisotropic characteristics on stretch-curved flanging by using different sheet metal-forming processes. Hu et al. [9] developed two analytical model for analysis of introflexion/stretch and outcurve/shrink flanges and used them to predict the trim-line of the blank and the shape of the rolling-stock and it is based on the total plasticity theory and the membrane strain assumption. Asnafi [10] studied the fracture limit in vertical stretch and shrink flanging by fluid-forming process and compared the results, experimental results with theoretical predictions. Yoshida et al. [11] prevented the crack initiation in high-strength steel sheets by using burring process and developed the suitable die shape and piercing method. The method of stretch flangeability was improved by using the side bending test method and limit diagram. Paul et al. [12] analyzed the forming limit diagrams (FLD) on the basis of strain and stress. Voswinckel et al. [13] used the method for improving the geometrical accuracy in flanging process by incremental sheet metal-forming method and new adaptive blank-holder technique. Lu et al. [14] developed two models, forward and inverse model by using adaptive network-based fuzzy inference system (ANFIS) for the prediction of initial circle hole diameter and deformed circle hole diameter in the sheet bore-expanding process. Zhang et al. [15] proposed the analytical model for the prediction of circumferential strain. This model is based on uniaxial stress in shrink flanging assumption. Chen et al. [16] studied the failure due to wrinkling in shrink flanging process by using the rubber forming process. It is based on the effect of four points such as-die radius, flange length, die fillet radius and forming pressure in aluminum alloy AA2024-O, AA7075-O and 2024-T3 sheet metal. Cao et al. [17] analyzed the onset of the wrinkling condition based on the energy method in shrink flanging process. Kasaei et al. [18] developed the mathematical model and studied the flange wrinkling on the basis of FEM simulation in flexible roll forming process. Wang et al. [19] proposed the analytical approach (model) for the prediction of wrinkling in sheet metal flange-forming operation under a constant binding force and pressure. Centeno et al. [20] studied the formability of aluminum alloy AA 2024-T3 sheet in different sheet metal-forming processes such as stretching, stretch bending and single-point incremental forming. Dewang et al. [21] studied the effect of punch-die clearance, coefficient of friction, punch and die profile radius on strain distribution for the prediction of crack location and propagation of aluminum alloy AA-5052 sheet metal blank. Feng et al. [22] studied the effect of geometrical parameters on the formability of stretch curved flanging by using large-step static implicit FE code and proposed that punch curvature radius should be larger than the die radius for the better results. Yohei Abe et al. [23] used the gradually contacting punch approach for improving the stretch flangeability of ultra-high strength steel (UHSS) sheet. Inclined bottom punch was used to reduce the tensile stress around the corner edge of the sheet. Sartkulvanich et al. [24] developed the FEM model for the characterization of blank edge quality for different punch/die clearance of advanced high-strength steel (AHSS) in stretch flanging process. Vafaeesefat Abbas and Khanahmadlu Morteza [25] compared the FEM simulation with experimental results in terms of shell-element in stretch z-flange-forming process. Golovashchenko [26] improved the quality of trimming process in stretch flanging of aluminum alloys AA6111-T4 sheet. Wen et al. [27] used tapered shoulder tool like a two-step procedure in flanging process of aluminum alloys AA 6061 and it is based on single-point incremental sheet-forming (ISF) technique. McDougall et al. [28] studied on the fracture in the deep drawing of steel sheet. It was revealed from metallographic evaluation that a severe variation with respect to grain size through the thickness of the steel sheet, as well as a slight segregation of pearlite. Gupta et al. [29] carried out a detailed microstructural analysis, mechanical properties evaluation on the samples drawn from the failed deep drawing component. Pantazopoulos and Sampani [30] carried out the Failure Analysis of Fractured Deep-Drawn Aluminum Circles and revealed that the tensile strength was leading to fracture during the process. Wu and Zou [31] studied on deep drawing of a coated metal sheet by finite element simulation and dimensional analysis. A failure map was established based on a few dimensionless process parameters, which can be divided into three regions, i.e., fracture, wrinkling and success. Yoganjaneyulu and Narayanan [32] carried out investigation to study and compare the forming limit diagrams (FLDs) and fracture limit curves (FLCs) of titanium grade 2 and titanium grade 4 sheets. Kumbhar [33] discussed on different failures like wrinkling, fracture, tearing and earring of the sheet metal in deep drawing process that are generally experienced in industries.
In the past few years, a lot of research had been done in the field of different sheet metal forming processes but less focus is given on the curved flanging process which is widely used in automobile industries, aerospace industries and in the manufacturing of household components. FE simulation tool like ABAQUS/Explicit software is capable in designing the tool setup and various process parameters before the experimental setup for such manufacturing process, which helps in reducing the manufacturing cost. Failure likes crack at the edge corner of the flange occurs in stretch flange-forming process depends on the strain distribution in sheet during deformation, and this distribution of strain depends on many geometrical and process parameters like die radius, flange length, friction, punch profile, width of sheet and sheet profile. In this study, effect of the sheet width and the die radius are investigated on the aluminum alloy AA-5052 sheet metal blank. Effect of others parameters are also studied and has been published in the other manuscript [34]. The work was carried out by ABAQUS/Explicit software to predict the edge crack location and propagation, thickness distribution in the flange, forming load and strain distribution. Experiments are conducted on double acting hydraulic press to validate the results of simulation for the same parameters and results show a very good relationship. In the passed a very less attention had been paid by the researchers in the area of fractography, i.e., the study of fractured surface. Second part of this investigation is fractography that is the study of fractured surface of sheet through field emission scanning electron microscopy (FESEM) and results are discussed in terms of size, shape and distribution of dimples on the cracked surface.
Finite element simulation of stretch flanging process was carried out by using commercially available ABAQUS/Explicit software. CAD model of a stretch flange is shown in Fig. 2. FE model, as shown in Fig. 3, was developed to perform the stretch flanging simulation and to predict the crack initiation and propagation in the flange, strain distribution in the sheet along the die profile radius and to obtain the maximum forming load. In this, die was modeled with radius of 20, 25, 30 and 35 mm with the height of 60 mm. The shape of the blank-holder was considered similar to the top surface of the die for better distribution of load and contact among the blank-holder, die and blank. In the simulation, die, blank-holder and punch were considered as rigid bodies and modeled with R3D4 element. R3D4 are rigid 3D four-nodded elements and formed the master surfaces during the contact definition conditions. 2ff7e9595c
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