Technology of Plasticity

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Authors: Un Chin Chai, Gow Yi Tzou, Ing Kiat Tiong
Abstract: An optimization research based on the drawing force is done on several forming parameters of metal rod drawing through a rotating die under Coulomb friction. The metal rod and the rotating die are constructed in SolidWorks and imported into FEM simulation software named DEFORM 3D. In this study, the FEM simulation is carried out by using DEFORM 3D combining with Taguchi method to explore the effective stress, the effective strain, and the velocity field. The influence rank of parameters to the drawing force is obtained, and the optimal parameters’ combination is determined by using Taguchi method. Results show that the optimization of drawing force is achieved and the minimum drawing force is successfully obtained.
Authors: Kuang-Jau Fann, Che Yi Lin, Ying Ju Chen
Abstract: Because of relative low investment cost on the installation of equipment and extensive product quality with other advantages, roll forming process has been broadly applied to produce profiles from steel strip bands and has gradually replaced aluminum profiles made by hot extrusion. Moreover, a lightweight design is the trend for reducing carbon emissions and waste. Therefore, a lightweight design of structures with local thinning used the roll forming production will make metal profiles more market competitiveness. In this study, the commercial Finite Element software DEFORM is used to investigate the rolling process preparing the metal strips with local thinning feature for the subsequent roll forming process to form a lightweight metal profile. Two kinds of roll configuration are used in this study, namely symmetrical and non-symmetrical. The symmetrical rolling process has the same diameter for the upper and the lower roll, while the non-symmetrical rolling process has different diameter in both rolls. As the process parameters, the roll speed ratio between the upper and the lower roll is used for the symmetrical rolling process, while the distance between the axis of the upper and lower roll is used for the non-symmetrical rolling process. As a result, the rolled thinning feature has its sidewalls flaring outwards, so that it has a narrow bottom and a wide opening. Furthermore, it can be regarded as defect that the thickness of the rolled thinning feature is not thinned enough as required and a raising at the opening is observed. In general, increasing the roll diameter or keeping the speed of the two rolls as the same can have a better thinning result for the symmetric rolling. In the non-symmetric rolling, increasing the roll diameter can improve the thickness, but no significant effect can be found by changing the roll diameter ratio.
Authors: Chien Yi Chen, Tsung Chia Chen
Abstract: This study is mainly based on five sets of mold cone angle and friction coefficient of micro-tube tube end necking forming analysis, and the tool cone angle of 60° experimental verification is carried out to analyze the titanium alloy (Grade 1) micro-tube for different mold cone angle and the different friction coefficient caused by the difference between the shrinkage forming. In this paper, Prandtl-Reuss's plastic flow rule, combined with finite element deformation theory and updated Lagrangian formulation (ULF) concept, establish an incremental elasto-plastic finite element analysis program for simulating the miniature tube end necking. The forming process also uses the generalized rmin algorithm to deal with elasto-plastic state and contact problems. From the simulation data of necking process, deformation history, punch load and punch stroke, stress and strain distribution is obtained. The analysis results show that by increasing the mold cone angle and friction coefficient, the thickness tends to be thicker in the certain area.
Authors: Yeong Maw Hwang, K.S. Jhuang, Hao Cheng Yu
Abstract: In this study, finite element analyses of Rotating Compression Forming (RCF) of magnesium alloy AZ31 with 20mm in diameter are carried out. A commercial software DEFORM-3D is used to simulate the plastic deformation behavior of magnesium alloy during rotating compression forming processes. Various forming parameters, such as the compression pressures (55, 60, 62 MPa), rotation speeds (10, 20, 30 rpm), rotation numbers (10, 20, 30 revolutions) and forming temperatures (280°C, 320°C, 360°C), are used in the FE simulation to obtain different effective strain distributions. Observation of the gradient microstructure and hardness measurement in the specimens of Magnesium alloy are carried out. From the comparisons of effective strain distributions and the obtained grain size distributions. It is known that a larger effective strain corresponds to a smaller grain size and the maximum effective strain is occurred at the middle of the contact plane of the specimen. Larger effective strain gradients generated with compression pressure of 62 MPa and rotation number of 30 revolutions at the radius of 4 mm.
Authors: Tatsuhiko Aizawa, Hiroshi Morita
Abstract: The dry progressive stamping was strongly required to make mass production of clothing parts and beverage cans. The duplex coating was one of the most reliable means to protect the dies and punches from wear and friction and to prolong their life time. In this coating, the die and punch was first surface-treated to have sufficient hardness in compatible to the hard ceramic coatings. In the present study, the low temperature plasma nitriding at 673 K was employed to harden the six kinds of punches and dies for progressive stamping of copper alloyed fucks. The micro-structure and nitrogen mapping were investigated by SEM with EDS to demonstrate that the hardening took place by nitrogen super saturation into SKD11 matrix without nitride precipitations. These nitrogen super-saturated punches and dies were fix into the progressive die set for dry stamping. No significant wear of tools as well as reduction of stamping loads even after a million shots proved that the low temperature plasma nitriding should be suitable to make hardening of dry stamping die substrates even without use of hard ceramic coatings.
Authors: Zhe Wang, Rong Gao Cui, Xin Ke Wang, Ji He, Shu Hui Li
Abstract: Non-oriented electrical steel, as the core magnetic material, is firstly blanked into lamination in motor manufacturing. As for the newly developed steel, there is a general tendency toward thinner and coarser-grained. Due to blanking clearance and thickness are both down to the sub-millimeter scale, grain size becomes an important role in formation of blanked edge quality, which mainly determines the deterioration level of magnetic properties. This paper aims to systemically investigate the influence of blanking clearance and grain size on blanked edge quality. In this research, non-oriented electrical steel sheets of the same chemical composition, 3 thicknesses and 3 grain sizes are prepared for blanking tests over the conventional relative blanking clearance range. The blanking edges are quantitatively examined by means of optical microscopy to visualize the distribution of plastic deformation. The results show that there exists an optimum clearance that leads to a fine blanked edge. In further study, an approximate linear equation of the ratio of clearance/grain size (c/D) vs. D is found for optimizing the blanked edge quality. This research thus provides an in-depth understanding and guidance for optimum blanking clearance determination influenced by size effect.
Authors: Il Yeong Oh, Sang Wook Han, Young Yun Woo, Jae Hyeon Ra, Young Hoon Moon
Abstract: The process of tube bending involves using mechanical force to push stock material pipe or tubing against a die, forcing the pipe or tube to conform to the shape of the die. For some tube bending processing, a mandrel is placed inside the tube to prevent collapsing. In this study, the elbow bending process using mandrel has been investigated to fabricate precise elbow-shaped tubes. To fabricate tube having target shape within the dimensional tolerance, the process analysis has been performed at various processing parameters such as tube dimensions, tilting angles, curved cutting surface and the radius of curvature. To estimate the dimensional accuracies of formed tubes, the standard deviations of dimensional errors between target and formed tubes have been used as a quantitative index. Results show that the elbow tube having larger radius of curvature shows higher dimensional accuracy due to the relatively uniform strain distribution. And the convex cutting surface is desirable to increase contacts between the punch and the tube ends during the bending process.
Authors: Young Yun Woo, Pil Gyu Kang, Il Yeong Oh, Young Hoon Moon
Abstract: Flexible roll forming is an advanced sheet metal forming process which allows the production of variable cross-section profiles. In flexible roll forming process, nonuniform transversal distribution of the longitudinal strain can cause the longitudinal bow, which is deviation in height of the web over the length of the profile. To investigate the effect of flange length on the transversal distribution of the longitudinal strain, FEM simulations are conducted with different flange length for three blank shapes; trapezoid, convex and concave. The result shows that the longitudinal strain and longitudinal bow decrease with increasing flange length for a trapezoid and a concave blank. For a convex blank, the longitudinal strain and longitudinal bow increase with increasing flange length. To validate FEM simulation result, numerically obtained longitudinal strain has been compared with experimental results.
Authors: Sang Wook Han, Hee Seok Jung, Young Yun Woo, Young Hoon Moon
Abstract: Tailored blanks with different blank thicknesses are semi-finished parts that can be used to produce stamping parts having a real tailor-made solution. This study investigates a manufacturing process that can produce a tailored rolled blanks(TRB) having variable thickness variations both in longitudinal and width directions. The process was experimentally and numerically investigated using three types of the conventional blank and blanks having circular and square holes. To characterize the process, the deformation behaviors of blanks were intensively analyzed. In order to understand the effect of the blank shape on the manufacturing TRB, the strain behaviors was compared by numerical simulation. The results show that the hollow blanks have good formability in the manufacturing of TRB having variable thickness variations both in longitudinal and width directions compared with the conventional blank.

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