Traditional Stamping Research Articles

Manufacturing a high-transmittance quantum-dot pixel frame using magnetic field and vibration field composite stamping

A simple way to complement full-color micro-light-emitting diode (micro-LED) displays is to employ ultraviolet or blue micro-LEDs with quantum dot (QD) converters. A pixel frame is essential for precisely locating the QD converter on a micro-LED chip and to limit the optical cross-talk effect. The limitations of pixel frames prepared by the commonly-used lithography technique, such as shallow depth and high dependence on high-transmittance substrates, have not been resolved in previous studies. In this study, we propose a magnetic-vibration composite stamping (MVCS) process to prepare a high-aspect-ratio and high-transmittance QD pixel frame. Magnetic extinction particles were employed, regulated, and converged into the wall of the pixel frame under the combined function of magnetic and vibration fields. Compared with the pixel frame prepared by the traditional stamping process, the pixelated QD converter achieved a 4.5-fold increase in the maximum photoluminescence intensity. Combining the micro-LED and pixelated QD converters in the pixel frame prepared by MVCS provides an alternative and practical approach for full-color micro-LED displays.

A Non-Thinning Forming Method with Improvement of Material Properties

Thickness thinning is one of the processing defects that tend to occur in traditional stamping or mechanical bending of the plate and tube. In the field of high mechanical performance requirements (such as pressure vessels), the thinning phenomenon cannot be ignored. Thermal stress forming has excellent characteristics of forming without thinning, but the forming angle of this method is small, thus limiting the promotion and application of the process in the field of the form. To solve the problem, thermal stress forming with the baffle pressure method (BPM) is proposed. The coupled thermodynamic model of BPM is established, and the bending angle and deformation mechanism of the BPM are investigated. Lastly, the grain size and microhardness are measured and discussed. Results of the bending angle show that the proposed method can increase the bending angle by 57.71 times compared with the traditional method. The bending angle of BPM is determined by both the thermal buckling and the baffle, and the baffle plays a major role. The results of grain size and microhardness analysis show that the method refines the grain size, increases the material microhardness by 1.31 times and thickens the deformation zone by about 2.75%. In addition, the analytical equation of beam bending with laser as the heat source is given in this paper; this has some significance for further enrichment and development of the basic theory of beam thermoplastic bending.

A highly efficient method of thermal stress bending with non-thinning and grain refinement

Thickness thinning is one of the processing defects that tend to occur in traditional stamping or mechanical bending of plate (tube). In the field of high mechanical performance requirements (such as pressure vessel), the thinning phenomenon can not be ignored. Thermal stress forming has excellent characteristics of forming without thinning, but the forming angle of the method is small, thus limiting the promotion and application of the process in the field of forming. To solve the problem, an applying baffles method (ABM) to both ends of workpiece based on thermal stress forming is proposed. A coupled thermodynamic model about ABM is developed, and the bending angle and deformation mechanism are investigated. Finally, the grain size and thickness of the deformed region are observed. The results show that ABM can increase the bending angle by 14.26 times compared with the traditional method. The bending angle of ABM is determined by both the temperature difference and the baffle, and the baffle plays a major role. Compared with the traditional method, ABM can obtain smaller grain size and increase the microhardness by 1.39 times. ABM can increase the thickness of the upper surface by 121 μm and the thickness of the lower surface by 47 μm. For upper surface thickening, ABM is 9.31 times greater than the traditional method. This thickening will effectively avoid thinning problems in stamping (mechanical bending). This method can make thermal stress forming a high-quality process in the forming field.

Study on the key process parameters of hydrodynamic deep drawing on the stainless steel single sink with countertop

Stainless steel single sink with countertop (SC) has the characteristics of large depth and asymmetric countertop. Its traditional stamping process is mainly realized by the combination of multi-stage deep drawing and annealing process, which leads to the complex manufacturing process, long production chain and poor consistency of products. Based on finite element analysis software (Dynaform) with nonlinear dynamic display algorithm, numerical simulation analysis and research are carried out on the parameters of hydrodynamic deep drawing. First, the sink and the part of countertop are preformed into a cylinder shell, and then the excess of the cylinder shell is drawn back to the countertop. The research results show that the hydrodynamic deep drawing process can effectively improve the flow uniformity of stainless steel sheet, increase the forming of stainless steel tank, drawing a more uniform wall thickness, thus effectively improve the quality of single tank with countertop by setting up reasonable preform structure, controlling the liquid pressure and its loading paths and blank-holder force.

Local flanging process on a curved wind deflector using electromagnetic forming

Electromagnetic forming (EMF) is a high-speed forming method which utilizes non-contact electromagnetic force to achieve forming compared with the traditional stamping process. Server spring-back and poor surface quality during the traditional forming process, which would lead to low geometrical accuracy and unacceptable painting quality, are two major problems challenging the manufacture of the curved products. In this study, the EMF process and deformation behavior of curved plate were analyzed by experimental and numerical methods. The experimental result showed that the initial profile from blank unfold-bend approach was unable to achieve reasonable flanging accuracy. Based on the simulation model, the deformation process from multiple aspects, such as electromagnetic force, velocity, impact process, strain state and distribution, was investigated and inconsistent deformation behavior of the work-piece was revealed. A design process of initial profile was carried out with the aid of simulation method and the deviations between the front edge of flanged part to the die profile were quantified. Although the average deviation was reduced to 0.384 mm in geometrical deviation-based compensation method, compared to other regions, the deviations reduced significantly were found from the area corresponding to region with the large radial strain. A geometric compensation method was proposed which took the radial strain into consideration as a factor. The simulation results demonstrated that the excessive deviations of forming profile decreased to a very low level and the feasibility of the approach was verified by experiments. The final average deviation was 0.229 mm.

Fracture behavior of 7075-T6 aluminum alloy under electromagnetic forming and traditional stamping

Fracture behavior of 7075-T6 aluminum alloy under electromagnetic forming and traditional stamping

Large ellipsoid parts manufacture using electromagnetic incremental forming with variable blankholder structure

Large ellipsoid parts are prone to wrinkle when forming by using traditional stamping. Aiming to solve the wrinkling problem in large parts, the EMIF method with a variable blank holder is proposed in this paper. The numerical simulation has shown that the sheet material near the blank holder is, as a consequence of stamping, subjected to circumferential compressive stress. When the drawing height was 100 mm, the sheet metal was notably wrinkled. In the electromagnetic forming (EMF) process, the sheet region facing the coil becomes thinner. However, the sheet metal thickness corresponding to the coil edge increases with the increase in forming height. If the EMF forming height is 150 mm, the sheet, which is in contact with the smooth mold, is deformed without a wrinkle. Compared to traditional stamping, the EMF can significantly reduce the sheet metal wrinkling, improving the deformation height of the sheet metal smooth area.

Discussion on Several Problems of Metallogenic Geological Condition and Genesis of Shoushan Stone

Shoushan stone is one of the four traditional stamp stones in China. The study for Shoushan stone has a long history, but mostly focuses on the classification and mineralogical and gemmological research for major varieties. And the study for metallogenic geological condition and genesis of Shoushan stone is relatively weak. The main problems of geological conditions and genesis of Shoushan stone are discussed in this paper. It considers that the acidic pyroclastic rocks of the second member of Xiaoxi formation in Shoushan Early Cretaceous volcanic eruption basin are the material basis of ore-forming. And it is proposed that the ore-forming and ore-controlling model is the NE-trending structure controling basin (Shoushan basin), NW-trending fault controling rock (volcanic rocks and volcanism), volcanic mechanism controling ore (deposit) and volcanic fault controling body. Secondary quartzite type altered mineral facies and mineral assemblage zoning in Shoushan orefield are discussed and established, which can be divided into five altered mineral facies and six mineral assemblage zoning. The discussions will promote the exploration, potential evaluation and prospecting prediction of Shoushan stone deposit, and even the interpretation of difficult problems in mineralogy.

Experimental investigation on electro-hydraulic forming with flexible-die

Recently, driven by the demand to reduce fuel consumption, light alloy has become one of the main metals used in automotive, aerospace and other fields. However, light alloys have tendency to fracture during the traditional stamping process. Researches have shown that high strain rate can greatly improve the metals’ formability and thus the electro-hydraulic forming process, as one kind of high strain rate forming process, has received great attention. However, the corresponding experimental research is limited due to few dies with simple shapes adopted in the literatures. Here in this study, we presented one flexible electro-hydraulic forming process, which was based on the electro-hydraulic forming machine and one simple flexible die, to widen the application of electro-hydraulic technology. The shape of the die can be changed by adjusting the height of each screw. Several electrohydraulic forming experiments with dies of various shapes were carried out for AA6061 aluminum alloy sheets under various discharged voltages. The reliability of the flexible combined forming process was validated and corresponding disadvantages were analyzed.

Inverse bending and springback-control using magnetic pulse forming

In this study, electromagnetic-assisted stamping (EMAS) with magnetic-force reverse loading was introduced to control springback. Compared to conventional EMAS, this new method does not change the mold structure used in traditional stamping technology. Thus, this approach can greatly extend the operating lifetime of the mold and readily be adopted for commercial production. Results indicate that the equivalent plastic strain and the plastic dissipation energy increase, while the tangential stress and the elastic strain energy decrease considerably, with increasing in discharge-voltage. The simulation results accurately predict the sheet deformation for quasi-static stamping and dynamic magnetic pulse forming. Both simulations and experiments show that the angle after springback decreases with increasing in discharge-voltage.

Springback Prediction of a Hot Stamping Component Based on the Area Fractions of Phases

Different from traditional hot stamping components with full martensite, the new tailored hot stamping (THS) components have different quenched microstructures, which results in their lower shape accuracy. To investigate the influence of different quenched phases on the springback of a component, a THS experiment of a U-shaped component was performed with segmented heating and a cooling tool. The area fractions of phases at different tool temperatures were obtained by a two-stage color tint etching procedure. Results showed that the quenched phase of the cold zone was almost full martensite. The area fraction of martensite in the hot zone was reduced to the lowest 13% at the tool temperature of 600 °C, while the bainite content reached the highest at 70%. The springback angles at different tool temperatures for quenching were measured by 3D scanning technology and the reverse modeling method. It was revealed that the springback angle increased with the increase of martensite and yet decreased with the increase of bainite. The relationship between the springback angle and the area fractions of the quenched phases was established by means of multiple linear regression analyses. The error analysis results of the predictions and measurements showed that the springback analysis model, based on the area fractions of quenched phases, could be used to predict the springback of hot stamping components with tailored properties.

An electromagnetic incremental forming (EMIF) strategy for large-scale parts of aluminum alloy based on dual coil

For the manufacturing of large-scale sheet parts, traditional stamping, spinning, and single-point incremental forming are limited by the rupture prone and severe springback of the formed parts and the requirement of large-scale forming equipment. In this paper, the method of electromagnetic incremental forming (EMIF) based on dual coil was creatively proposed to solve the manufacturing problem of large-scale parts of aluminum alloy. The forming results of EMIF based on single coil and EMIF based on dual coil are compared by finite element simulation. The effect of the two moving strategies on uniformity in EMIF based on dual coil was researched. In addition, the effect of the shaping voltage on uniformity in EMIF based on dual coil with the interval moving strategy was studied. It was observed that the forming quality of EMIF with dual coil was better than that of EMIF with single coil. For EMIF based on dual coil, the interval moving strategy is better than the sequential moving strategy in achieving better forming quality. For the first layer of EMIF based on dual coil with the interval moving strategy, the optimized forming voltage and shaping voltage were 12 kV and 18 kV, respectively. For the second layer of EMIF based on dual coil with interval moving strategy, the optimized forming voltage and shaping voltage were 18 kV and 27 kV, respectively. The shaping voltage was 1.5 times of forming voltage for both layers so that better forming uniformity was achieved. Then, the method of EMIF based on dual coil with interval moving strategy by multilayers is proposed to fabricate large-scale sheet parts. Finally, experiments were performed to confirm the feasibility of EMIF with dual coil, and the experiment results show good agreement with the simulation results. The findings of this work could provide guidance on deform large-scale parts of aluminum alloy by the EMIF method.

Analytical modeling and experimental validation of the forming force in several typical incremental sheet forming processes

Abstract Incremental sheet forming (ISF) is recognized as an advanced forming process which is highly flexible in cost-effectively producing small batched sheet metal parts. The forming force is dramatically reduced due to the local deformation and successive forming characteristics compared with traditional stamping process, and has vital impact on forming quality. It may however, be noted, that the forming force prediction models widely used are empirical ones, which needs further improvement for wider applicability. Besides, the force fluctuation in ISF has impact on the geometric accuracy, which has been less studied so far. In the present work, the analytical models for predicting the forming force for single-pass single point incremental forming (SPIF), multi-pass incremental forming (MPIF) and incremental hole flanging (IHF) processes are developed based on the new analytical models used to calculate the contact area and the through-thickness stress. A series of experiments of typical sheet metal parts in different geometries for different materials with varied process parameters including wall angle, step depth, tool radius and sheet metal thickness are used to validate the proposed analytical models. The new prediction models are proved to calculate the forming force and force components along the axial, tangential and radial directions with high accuracy for SPIF, MPISF and IHF processes. Moreover, the mechanism of force fluctuation is also investigated, and it's proved that the force fluctuation is caused by varied elastic deflection of the deforming sheet metal.

Multi-step forming punch (MFP) for improving stretch-flangeability of advanced high-strength steel

Dissimilar materials, such as aluminum alloys, magnesium alloys, and advanced high-strength steel, are being increasingly used in vehicle structures while the flangeability of lightweight materials is of great challenges to the traditional process. In the presented study, the multi-step flanging in one press stroke accomplished by a novel punch with a notch was designed. The concept of incremental forming was implemented to improve the punch shape of stretch flanging and enhance the stretch-flangeability of advanced high-strength steel. Analytical solutions and numerical simulations were carried out to investigate the deformation mechanism and thickness distribution. Compared with the single-step forming punch (SFP), flanging process was divided into three steps in one press stroke by multi-step forming punch (MFP), which combined multi-stage characteristic of incremental sheet forming with high efficiency of traditional stamping. The results showed that the maximum tensile strain with MFP dropped from 0.406 to 0.28 at the edge of the deformed blank comparing with the single-step flanging by transferring large strain around the stretch corner edge to straight flanging region, which was in agreement with the theoretical analysis. In addition, excessive thinning was suppressed with MFP which decreased from 25.63 to 18.13% by sacrificing punch stroke that increased from 23 to 53 mm. Both the theoretical analysis and simulation results illustrated the validity of MFP for advanced high-strength steel.

A discussion of airworthiness in terms of safety and integrity

System safety and integrity are regarded as two main aspects in aircraft airworthiness. Both are widely used in airworthiness design, verifying, and certifying. Firstly, a depth of understanding about the concept of airworthiness is given, and the total process of airworthiness based on safety standards and integrity ones is proposed. Secondly, airworthiness’ main aspects are discussed with the traditional safety assessment, current standards, STAMP and STPA. Lastly, the relationship between reliability, maintenance, safety, integrity and airworthiness is analysed.

Reduction of corner radius of cylindrical parts by magnetic force under various loading methods

To prevent small corner radius of cylindrical parts from cracking near the sheet bottom corner during deep drawing, a new method combining multidirection magnetic force electromagnetic forming and traditional stamping is proposed in this paper. First, a punch with an 8-mm corner radius is used to obtain a cylindrical part. Then, a coil-generated multidirection magnetic force is used to further deform the sheet corner radius and obtain a smaller corner radius. ANSYS/emag and ABAQUS/explicit software are used to calculate the multiphysical field coupling process in electromagnetic forming (EMF), and obtain accurate simulation data based on the experimental results. We found the following that the maximum thickness thinning ratio was 20% in the sheet corner region with an applied multidirection magnetic force in comparison to 33% if only a bulging coil was used.

Industrial validation of strain in cold roll forming of UHSS

Cold roll forming is a highly productive sheet metal forming process capable of producing an exceptional range of profile geometries. Over the last few years customers have increased the demand for high value components, through the specification of complex profiles, tighter tolerances and/or use of high strength materials. In particular, there has been a high interest by the automotive industry in utilising ultra-high strength steels (UHSSs) within the roll forming process. These steels are ideal for the forming of lightweight products, which possess increased material performance when compared to traditional low strength steels. The industry’s attraction towards the roll forming process may be due to the increased deformation capabilities it can provide and due to the formability limitations of UHSS when using traditional stamping or press braking processes. This investigation aimed to determine an appropriate approach to simulating the cold roll forming process using UHSSs for future industrial applications. Currently a large volume of research can be found on the material characterisation and formability of UHSS using traditional processes. While the interest in roll forming is rapidly increasing over time, there remains a large research gap in this field. Hence, a dual phase steel (DP1000) and complex phase steel (CP1000) provided by TATA Steel were analysed using a five pass roll forming assembly to form the following two profiles: (a) V-section; and (b) flat strip with rib feature. The principal strains along the outer radius of each specimen were analysed using a GOM Argus photogrammetry system. A circle grid analysis was the method used to complete these measurements. The strain analyses were compared with corresponding strains along the surface of the finite element (FE) analysis model results. The non-linear FE simulations were carried out using COPRA® FEA RF 2017. Correlations in the results were achieved, setting a foundation for further investigations on the formability of UHSSs.

Rotary Cutting of Electrical Steel Laminations – A Contrast to Traditional Stamping

Rotary Cutting of Electrical Steel Laminations – A Contrast to Traditional Stamping

An innovative approach for detection of surface quality based on specific work environment using experiments, aerodynamic simulation, and theoretical analysis

The surface quality of part using hydroforming process is superior to the surface quality of part using traditional stamping process, which is due to the fluid friction holding effect in the hydroforming process. In order to verify the point, a method for detecting the surface quality of parts based on the specific work environment has been proposed, which used the combination of the aerodynamic numerical simulation and theoretical analysis. The parts with the same dimensions were obtained by use of hydraulic bulge technology and traditional stamping process, the surfaces of the parts were scanned using laser tracker, and the measurement points were fitted to curved surfaces. According to four kinds of error values of fitting results, experimental procedure is judged to be accurate; the hydraulic bulge test and numerical simulation were carried out for the parts with different height to diameter ratio, and the finite element model is correct according to the distribution tendency of the wall thickness of the two measurement paths. The profile curves are fitted by using the 5° polynomial, and the curves are more accurate and passed through all the measurement points. The contour points along the diameter direction were fitted using the 5° polynomial, and then, the fitted curves were imported into FLUENT for simulation of transonic aerodynamic flow. According to the pressure distribution, velocity distribution, and the Mach number of flow field on the surface of parts, it is indicated that the surface quality of the parts using hydraulic bulge is better. Finally, the expressions of the third variable of the stress partial tensor for the two kinds of forming process were derived. Based on the different characterization parameters, the viewpoint above is further verified by the theory.

Incremental electromagnetic-assisted stamping (IEMAS) with radial magnetic pressure: A novel deep drawing method for forming aluminum alloy sheets

A new forming method denoted as incremental electromagnetic-assisted stamping (IEMAS) with radial magnetic pressure is proposed in this paper, which was adopted for the deep drawing of a cylindrical cup. In comparison with the traditional stamping process, the forming depth could be increased by 31% after three consecutive coil discharges. A 3D finite element model was built to determine the reason for the increase in forming depth. We found that a radial magnetic force is generated at the sheet center when placing the coil at the end of the sheet, which will produce a material flow from the sheet flange to the region corresponding to the corner of the die after the coil discharge. This ensures that the sheet does not become too thin in a certain region. Therefore, deeper cylindrical cups can be manufactured by IEMAS with radial magnetic pressure.