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The issues of import substitution of the working tool of foreign press brakes were considered using reverse engineering. The main cause of failure is the deformation of the tool's working edges, which cannot be restored, so the only solution is to replace it. The complexity of manufacturing the working tool lies in the absence of design documentation for punches and dies, which requires creating it independently through reverse engineering, including the technology of creating a product model through direct measurements. Laser 3D scanning was used to create digital models, based on which drawings of the punch and die were developed, as well as the technology for their manufacture. Experimental-industrial tests of the manufactured bending tool showed that its operational durability practically does not differ from imported counterparts. [ABSTRACT FROM AUTHOR]

Sheet metal stamping is widely used for high-volume production. Despite the wide adoption, it can lead to defects in the manufactured components, making their quality unacceptable. Because of the variety of defects that can occur on the final product, human inspectors are frequently employed to detect them. However, they can be unreliable and costly, particularly at speeds that match the stamping rate. In this paper, we propose an automatic inspection framework for the stamping process that is based on computer vision and deep learning techniques. The low cost, remote sensing capability and simple implementation mean that it can be easily deployed in an industrial setting. A particular focus of this research is to account for the harsh lighting conditions and the highly reflective nature of products found in manufacturing environments that affect optical sensing techniques by making it difficult to capture the details of a scene. High dynamic range images can capture details of an environment in harsh lighting conditions, and in the context of this work, can capture highly reflective metals found in sheet metal stamping manufacturing. Building on this imaging technique, we propose a framework including a deep learning model to detect defects in sheet metal stamping parts. To test the framework, sheet metal 'Nakajima' samples were pressed with an industrial stamping press. Then optimally exposed, sequence of exposures, tone-mapped and high dynamic range images of the samples were used to train convolutional neural network-based detectors. Analysis of the resulting models showed that high dynamic range image-based models achieved substantially higher accuracy and minimal false-positive predictions. [ABSTRACT FROM AUTHOR]

Galling wear in sheet metal stamping processes can degrade the product quality and adversely affect mass production. Studies have shown that acoustic emission (AE) sensors can be used to measure galling. In the literature, attempts have been made to correlate the AE features and galling wear in the sheet metal stamping process. However, there is very little attempt made to implement machine learning (ML) techniques to detect AE features that can classify non-galling and galling wear as well as provide additional wear-state information in the form of strong visualisations. In the first part of the paper, time domain and frequency domain analysis is used to determine the AE features that can be used for unsupervised classification. Due to galling wear progression on the stamping tools, the behaviour of AE waveform changes from stationary to a non-stationary state. The initial change in AE waveform behaviour due to galling wear initiation is very difficult to observe due to the ratio of change against the large data size of the waveform. Therefore, a time-frequency technique "Hilbert Huang transform" is applied to the AE waveform as that is sensitive to change of wear state and is used for the classification of "non-galling" and the "transition of galling." Also, the unsupervised learning algorithm fuzzy clustering is used as comparison against the supervised learning techniques. Despite not knowing a priori the wear-state labels, fuzzy clustering is able to define three relatively accurate distinct classes: "unworn", "transition to galling" and "severe galling". In the second part of the paper, the AE features are used as an input to the supervised ML algorithms to classify AE features related to non-galling and galling wear. An accuracy of 96% was observed for the prediction of non-galling and galling wear using classification, regression tree (CART) and neural network techniques. In the last part, a reduced short time Fourier transform of top 10 absolute maximum component AE feature sets that correlates to wear measurement data "profile depth" is used to train and test supervised neural network and CART algorithms. The algorithms predicted the profile depth of 530 unseen parts (530 unseen cases), which did not have any associated labelled depth data. This shows the power of using ML techniques that can use a small data training set to provide additional predicted wear state on a much larger data set. Furthermore, the ML techniques presented in this paper can be used further to develop a real-time measurement system to detect the transition of galling wear from measured AE features. [ABSTRACT FROM AUTHOR]

Even though high-strength steel is a favourable material because of its high strength and good formability, this material poses new challenges on the structure of stamping dies owing to potential damages of the die during production. Stamping dies are conventionally produced according to design manuals and standard manufacturing guidelines, where a high safety factor is specified to ensure that the stamping die is heavy and thick. A structural topology optimization method for a stamping die is presented in this study based on finite element simulations of the sheet metal stamping process. The finite element model of the stamping die is first established. Next, the boundary forces acting on the sheet metal are obtained from simulations and these forces are applied to the punch surface by means of load mapping during topology optimization. These forces are equivalent to the interaction between the blank and die. The objective function is to maximize the static stiffness under multi-conditions, which is defined by using the compromise programming approach. The analytic hierarchy process method is used to determine the weight ratio of the body stiffness in various load conditions and conduct topology optimization of the comprehensive objective function. The results show that the weight of the optimal punch is reduced while its performance is improved. More importantly, the reconstructed punch can be manufactured practically. [ABSTRACT FROM AUTHOR]

Electromagnetically assisted stamping (EMAS) process is an innovative hybrid sheet metal forming technique that combines electromagnetic forming (EMF) into quasi-static conventional stamping. This paper presents a numerical modelling based on a novel triangular prism solid and shell interactive mapping element for EMAS process. In the present work, the triangular prism solid and shell interactive mapping element builds a bridge between conventional stamping and electromagnetic forming (EMF) process, in which shell element is employed in conventional stamping process. A linear six-node prism element is developed for transient eddy current analysis in electromagnetic field of EMF process. An interactive mapping rule is established to transfer information between different type elements, accordingly. That is to say, one can take full advantages of shell element solving stamping problems with contact condition in EMAS process. Electromagnetically assisted stamping example is used for validation of the present modelling. The proposed numerical modelling can successfully simulate the combined quasi-static-dynamic process, and the numerical results predict the experimental ones. The present modelling produces potential for further study in EMAS process. [ABSTRACT FROM AUTHOR]

With the increased usage of Advanced High Strength Steels, galling wear has become a significant challenge for sheet metal stamping industries. Galling, in particular, can have a large economic impact due to the high costs and lost productivity associated with manual monitoring, refinishing/resurfacing damaged tooling and formed parts, and the need to apply expensive treatments or coatings to tool surfaces. This has led to a push for automated galling wear detection systems. However, developing such systems requires an accurate measurement of galling wear severity that can be easily implemented in industrial situations. Parameters used for measuring galling wear are often difficult to collect in large industrial style trials, and can be inaccurate as they are not targeted towards characterising the localised features associated with galling wear damage. In this study, a new galling wear characterisation and measurement methodology is introduced that accurately measures galling wear severity by targeting the localised features on sheet metal parts. This methodology involves calculating Discrete Wavelet Transform detail coefficients of 2D surface profiles. A case study on a series of deep drawn channel parts demonstrates the accuracy of the Discrete Wavelet Transform methodology when compared to visual assessment of galling wear severity. Based on comparison to visual assessment the presented Discrete Wavelet Transform galling wear measurement methodology outperforms other commonly used wear measures. The methodology provides a targeted, repeatable and non-subjective measure of galling wear severity. The specific outcome of this work provides an important tool for research into galling wear monitoring and detection systems in sheet metal forming, and the study of galling wear and its prevention in general. [ABSTRACT FROM AUTHOR]

For the potential defect produced in drawing progress, the response curved surface test was designed based on Box-Benhnken method by choosing the three important process parameters like the gap between punch and die, the equivalent force factor of drawbead and the blank-holder force as the key influencing factors. And the response surface model between the process parameters and the max thinning rate and the max thickening rate of seat support plate was established. Then the optimal parameters were obtained, which are 1mm for the gap between the punch and the die, 0.36 for the equivalent force factor of the drawbead, and 305 kN for the blank holder force. These optimal stamping parameters prove to be less than 3% in error in comparison with the simulation results, indicating a good agreement between physical and numerical data. The results show that it is feasible to optimize the process parameters by using the response surface method, which provides an effective method for the optimization of drawing formability for sheet metal. [ABSTRACT FROM AUTHOR]

As a promising solution to lighter vehicles, warm stamping of magnesium alloy sheet has gained intense attention in automotive industry. Firstly, boron nitride (BN), graphitic (C), molybdenum disulfide (MoS), and polytetrafluoroethylene (PTFE) were evaluated as high-temperature lubricants for magnesium sheet forming. BN demonstrated the best comprehensive performances for good lubrication effect, load-carrying capacity, and excellent low-cost water washing convenience. Limit drawing ratio (LDR) was then determined for 1.5-mm-thick AZ31B magnesium sheet with and without BN as lubricant, and LDRs of 2.5 and 2.1 were achieved for lubricated and unlubricated situations. It was demonstrated that lubricated LDR of AZ31B magnesium sheet under warm stamping is comparable to most known mild steel sheets. The discussion through lubrication status and sheet thinning investigated the effect of lubricant on the increase of LDR compared with unlubricated case. [ABSTRACT FROM AUTHOR]

Stamping tool wear can significantly degrade product quality, and hence, online tool condition monitoring is a timely need in many manufacturing industries. Even though a large amount of research has been conducted employing different sensor signals, there is still an unmet demand for a low-cost easy to set up condition monitoring system. Audio signal analysis is a simple method that has the potential to meet this demand, but has not been previously used for stamping process monitoring. Hence, this paper studies the existence and the significance of the correlation between emitted sound signals and the wear state of sheet metal stamping tools. The corrupting sources generated by the tooling of the stamping press and surrounding machinery have higher amplitudes compared to that of the sound emitted by the stamping operation itself. Therefore, a newly developed semi-blind signal extraction technique was employed as a pre-processing technique to mitigate the contribution of these corrupting sources. The spectral analysis results of the raw and extracted signals demonstrate a significant qualitative relationship between wear progression and the emitted sound signature. This study lays the basis for employing low-cost audio signal analysis in the development of a real-time industrial tool condition monitoring system. [ABSTRACT FROM AUTHOR]

Formability is an important property requirement in sheet metal forming and mostly useful to automobile and aerospace industries. Every product design starts with finite element simulation before the die design and material selection stage. The forming limit curve along with finite element results acts as tool to investigate whether the design is feasible. Hence, it is of utmost importance that the forming limit curve is accurate over a wide range of strain path. Generally, a forming limit curve is derived from discrete failure strain points corresponding to different strain ratios by fitting a smooth curve. It has been observed from many studies that the generated forming limit curves are devoid of any failure points corresponding to equibiaxial strain path. This is found to be true even when the test conditions are supposed to produce biaxial state of strain. To understand the reason behind this observation, a set of forming limit diagram experiments and finite element analyses were carried out for high-strength interstitial free steel and interstitial free galvannealed steel with three different friction conditions. It was observed that friction plays an important role in right-hand side of the forming limit curve. Finite element results and experimental validation suggest that failure strain points for biaxial strain paths can be obtained only if the tests are conducted with proper lubrication system. [ABSTRACT FROM PUBLISHER]

A method of using the ultrasonic waves for measuring the contact states between the workpieces and the die during stamping has been developed. Ultrasonic waves are reflected by air, so the contact states between the workpieces and the die can be examined by measuring the height of ultrasonic waves. However, it is not clear how the ultrasonic waves propagate around the workpieces and the dies. Therefore, the authors analyzed the propagation behavior of ultrasonic waves on the boundary surfaces of the workpiece and the die using numerical analysis. To examine the acoustic field in the die and the workpiece, the elastic wave equations were solved by finite-difference time-domain method. The results shows that reflected/transmitted waveforms are affected by workpiece properties. The reflected waves are most affected by the properties of the workpiece. [ABSTRACT FROM AUTHOR]

Highlights: [•] Suggested 2-step model aims at a lower susceptibility to cracking. [•] Strain at weak point could be reduced by 16% compared to 1-step model. [•] A more uniform thickness distribution is achieved by the 2-step model. [•] The maximum stress in the FLSD and the GTN damage variable reduced at the weak point. [•] The 2-step model provides an enhanced formability compared to the 1-step model. [Copyright &y& Elsevier]

Abstract: This paper investigates the influence of the die corner radius shape on wear behavior during sheet metal stamping. In particular, small and localized changes from an ideal circular die profile shape were examined and the effect on tool life determined. A novel technique to test and characterize the die profile shape and wear behavior, based on a semi-industrial channel forming process, is presented. It will be shown experimentally that small changes in die radius profile shape (of less than 15μm) can result in significantly reduced tool life. In all cases examined, the small variations in shape were the result of inherent variations associated with the machining, grinding and polishing processes typically used to manufacture stamping dies and die corner inserts. Numerical simulation shows that these small shape ‘defects’ at the die corner radius can result in a significant increase in local contact pressures, explaining the large adverse changes in tool life. These results are of direct importance to stamping engineers and tool designers and indicate that careful control over die manufacture and maintenance procedures may result in significant improvements in tool life. [Copyright &y& Elsevier]

Abstract: The need to reduce the use of lubricants and the increased use of high strength steels has resulted in increased wear of die materials employed in the sheet metal stamping industry. In this study, unlubricated sliding wear tests of mild carbon steel sliding on D2 tool steel were performed using a pin-on-disc tribometer to investigate the wear mechanisms relevant to stamping tools. Constant force and speed were applied while the sliding distance and temperature were varied to investigate the effect of temperature on the two paired steel materials. It was found that the wear mechanisms of D2 tool steel were temperature dependent, showing a significant transition in dominant mechanisms in the ambient to 150°C temperature range. Such wear behavior has not been reported in literature. An interesting aspect of this study is that material transfer between the tool and sheet can be minimized at a certain temperature range. Hence, the results of this study may be of economic importance to the automotive industry and influence the wear models employed for future tool wear analysis in sheet metal stamping. [Copyright &y& Elsevier]

Abstract: In sheet metal stamping, it is known that wear is unevenly distributed over the die radius and that multiple wear mechanisms may occur simultaneously. However, there has been little or no work that details the types of wear mechanisms, and quantifies the locations at which they occur. Furthermore, the link between recently identified time-dependent contact conditions and the wear response is currently unknown. An experimental study is presented in this paper to examine the location, type and severity of wear that occurs over the die radius during a typical sheet metal stamping process. It is found that the wear over the die radius consists of a combination of ploughing and galling mechanisms. The relative severity of the ploughing mechanism is divided into two distinct zones on the die radius, which correlate well with the contact pressure and sliding distance behavior predicted in our recently published numerical study. The galling mechanism results in failure of the stamping process and is, therefore, critical to the overall tool wear response. Our analysis indicates that the severe contact pressure/small sliding distance conditions, which occur during the initial stage of the process, cause the galling behavior observed over the radius. Therefore, it is concluded that the overall tool wear response and tool life is primarily dependent on the initial transient stage of the stamping process. [Copyright &y& Elsevier]

To gain a better understanding about the influence of initial texture on deformation behaviour of sheet metals, an incremental-update formulation is adopted for implementing rate-dependent crystal plasticity model into the explicit finite element package, ABAQUS/Explicit. In this formulation, the configuration in the last increment serves as a reference frame, and the stress, grain orientation and hardening behaviour of crystal are updated at the end of each increment. Two user subroutines VUMAT are developed, respectively, for face-centred cubic and hexagonal close packed alloys due to different deformation mechanisms. Earing behaviours of aluminium sheet and AZ31 alloy sheet are simulated for model validation. [ABSTRACT FROM AUTHOR]

This paper presents an analysis of the dynamic contact pressure distribution at the sheet metal-tooling interface in normal and defective panel stamping operations. Specifically, the stamping of a 1.27 × 20 × 15 cm rectangular aluminum alloy panel has been simulated using finite-element modeling methods. The modeling results are leveraged to determine the forces acting on sensors embedded in the die structure. Based on these results, a customized stamping test bed has been designed, which incorporates an array of force sensors embedded into the stamping die to enable online measurement of the forces in the die. The force measurements are processed by the thin plate spline numeric surface interpolation method to evaluate a continuous contact pressure distribution map of the die cavity. The pressure distribution in the die cavity in normal and defective scenarios has been presented along with a suggested volume thresholding method for automated defect detection. By leveraging the numeric surface generation method to analyze experimental data, the present study establishes the basis for intelligent tooling and in-process monitoring for improved observability in sheet metal stamping. [ABSTRACT FROM AUTHOR]

Abstract: This paper directly examines the contact sliding distance experienced during a typical sheet metal stamping process—an area that has largely been neglected in the literature. A method to numerically quantify the sliding distance is proposed. The sliding distance predicted from this method, and the contact pressure obtained from numerical simulation, allow the recently identified time-dependent contact conditions on the die and blank surfaces to be completely characterized. Consequently, a new insight into the wear/galling that occurs at the die radius in sheet metal stamping is gained. The results show that the region close to zero degrees on the die radius is likely to experience the most wear, with the identified transient stage contributing to a large proportion of the total wear. Additionally, the region on the blank surface often observed to be heavily burnished – the die impact line – is estimated to experience the highest wear severity due to the transient contact conditions. The proposed method to numerically quantify the sliding contact conditions can be applied as a general approach to study any other two-body sliding contact situations. [Copyright &y& Elsevier]

The growing interest in sheet metal stamping processes, particularly in automotive industry, led to three main issues in this field: request of very complex shapes; growing interest in springback control; solution of multi-objective problems. This makes the design of the sheet metal stamping processes very difficult, since the number of both design variables and design objectives are progressively increased; therefore, proper design methodologies to reduce times and costs are highly required. In this paper, an innovative design approach able to manage and optimize complex stamping operations is proposed. In particular, a progressive design approach based on the integration between numerical simulations, Response Surface Methodology (RSM) and Pareto optimal solutions search techniques was applied in order to design a complex automotive sheet stamping operation. [ABSTRACT FROM AUTHOR]

One of the most relevant research issues in automotive field is focused on the reduction of stamped parts weight also increasing their strength. In this way, a strong research effort is developed on high strength steels which are widely utilized and they require a proper springback control. Springback reduction in sheet metal forming is a typical goal to be pursued which is conflicting with thinning reduction for instance. Thus, such problems can be considered as multi-objective ones characterized by conflicting objectives. What is more, nowadays, a great interest would be focused on the availability of a cluster of possible optimal solutions instead of a single one, particularly in an industrial environment. In this paper, integration between numerical simulations, response surface methodology and Pareto optimal solutions search techniques was applied in order to design a DP 600 U-channel shape stamping operation. In particular the friction conditions and blank holder force were optimized as design variables in order to accomplish two different objectives: reduce excessive thinning and avoid excessive geometrical distortions due to springback occurrence. [ABSTRACT FROM AUTHOR]

Abstract: The contact conditions at the die radius are of primary importance to the wear response for many sheet metal forming processes. In particular, a detailed understanding of the contact pressure at the wearing interface is essential for the application of representative wear tests, the use of wear resistant materials and coatings, the development of suitable wear models, and for the ultimate goal of predicting tool life. However, there is a lack of information concerning the time-dependant nature of the contact pressure response in sheet metal stamping. This work provides a qualitative description of the evolution and distribution of contact pressure at the die radius for a typical channel forming process. Through an analysis of the deformation conditions, contact phenomena and underlying mechanics, it was identified that three distinct phases exist. Significantly, the initial and intermediate stages resulted in severe and localised contact conditions, with contact pressures significantly greater than the blank material yield strength. The final phase corresponds to a larger contact area, with steady and smaller contact pressures. The proposed contact pressure behaviour was compared to other results available in the literature and also discussed with respect to tool wear. [Copyright &y& Elsevier]

Strain path transition is a common phenomenon during continuous stamping operations of sheet metal and can potentially alter the forming limit of the material. Enabling strain path change in a single experiment is a key challenge faced by several researchers. To understand the effect of continuous strain path change on material forming limits, detailed material characterisation is needed where the material is deformed while the strain path of the material is changed continuously. In this work, a test method was developed, which consisted of a novel mechanical rig and specimen design. The mechanism allowed DP600 steel and AA5182-O aluminium samples to change strain paths continuously without unloading the specimen. Digital image correlation measurements of the strain evolution of the samples during tests showed that the technique was able to alter the strain path of the sample from uniaxial to biaxial strain path. In particular, the measurements showed that the transition from uniaxial to biaxial strain paths was sharper in DP600 than AA5182-O. The test was repeated in a scanning electron microscope (SEM) chamber to observe the behaviour of the microstructure during the strain path transition. The microstructural strain evolution showed rotation of strain bands while the evolution of electron back scattered diffraction (EBSD) maps conveyed grain rotation during continuous strain path change in both the materials. The strain path transition controlled the rotation of grains with preferred crystallographic orientations. [Display omitted] • An experimental technique was developed to perform continuous strain path change. • The continuous strain path change was gradual in aluminium but it was sharp in steel. • Developed technique was capable to study micro-strain and texture evolution in-situ. • Micro-strain study revealed heterogeneous strain banding and rotation of the bands. • Texture analysis unveiled grain rotation with preferred crystallographic orientation. [ABSTRACT FROM AUTHOR]

Abstract: Formability analysis is an important step in design of successful sheet metal forming processes before a physical tryout can be carried out. This paper presents a design process in an industrial practice for a forming process of a new body jack case. The design needs to conform to the functionalities and reduce production steps, especially the welding step, which is required in the previous design. The part is then produced by stamping a flat steel sheet and needs no further welding. The stamping process is consistently analyzed by using a nonlinear finite element method (FEM). The formability is verified by using a forming limit diagram (FLD) as the main key performance index (KPI). In addition to the formability, other manufacturing aspects (i.e., trim line, and cost) are also taken into account. In order to determine an optimal process condition, major parameters (i.e., part configuration, blank configuration, and blank material) are explored. A blank configuration from inverse analysis (IA) results in an acceptable stamped part according to FLD. However, it requires extra trimming cost and causes the stamped part''s perimeter to be too close to the trim line. A simpler blank configuration has shown in this study that it can meet the design requirement. It is also seen that a material selection plays an important role in the formability of the part. In this study, JIS SPCE is chosen over JIS SPCC and JIS SPCEN due to its formability and cost merit, respectively. [Copyright &y& Elsevier]

Currently, more and more tailor-welded blanks (TWBs) are used in the automobile industry. It is very important to locate the weld line and predict its movement during the forming process. The initial weld line can be predicted by one-step finite-element analysis according to the desired weld line in the final workpiece. Meanwhile, weld line movement during the deformation process can be evaluated in advance. In this paper, the procedures of finite-element analysis of one-step FEM with TWBs are established. The contact between tool and blank and the effect of restraining forces under the blankholder due to drawbead and blankholder pressure are considered as well. Forming limit diagram (FLD) is used to show not only the tendency of reduction in thickness and fracture but also of increase in thickness and wrinkle. Hydraulic controlled pads used to clamp the weld line during the deep drawing process are simplified as static external force to eliminate the movement of the weld line. In order to speed up and ensure the convergence of Newton-Raphson iterations, energy-based 3D mesh mapping algorithm is introduced to obtain the initial solution. The above-mentioned methods have been implemented in the authors’ in-house one-step FEM code InverStamp. A rectangular cup drawing case demonstrates that this approach can be easily implemented to evaluate weld line movement and develop initial blank in sheet metal stamping with tailor-welded blanks. [ABSTRACT FROM AUTHOR]

Abstract: FASTAMP is a fast FE analysis system for sheet metal stamping, which is based on an improved inverse approach and dynamic explicit method. The improved algorithm successfully avoids the strain localization problem existing in plastic deformation theory to lay foundation for the inverse approach. Quadrilateral membrane elements together with DKQ bend element are used in the algorithm to considering bending effect. More accurate model is built in the system so that the process parameters, such as blank-holding force, friction and drawbead restriction, can be taken into account. Press types, eject plate and other influence factors on sheet metal forming are also considered. As a result, the system can be applied to potential defects detection, formability analysis, material selection and process verification. Product design, process planning and die design can be integrated by FASTAMP, so that product formability can be ensured, optimization of stamping process and die structure achieved. [Copyright &y& Elsevier]

Pulsed electromagnetic forming is based on high-voltage discharge of capacitors through a coil. An intense transient magnetic field is generated in the coil and through interaction with the metal work-piece; pressure in the form of a magnetic pulse is built up to do the work. Data on formability of two aluminum alloys employed for exterior (6111-T4) and interior (5754) automotive body panels will be shown. Comparison of traditional Forming Limit Diagrams obtained by stretching of aluminum sheet with hemispherical punch to the results on formability, where hemispherical punch is replaced by a coil will be provided. It will be shown that material formability in high-rate forming conditions can significantly depend upon interaction with the forming die: electromagnetic forming into an open round window provides only slight improvement in formability, while forming in a V-shape die or into a conical die indicates a significant improvement. An important part of the electromagnetic forming technology is the design of the coil. The coil failure modes and measures preventing them are discussed. [ABSTRACT FROM AUTHOR]

In most cases, manufacturers follow a net build strategy for process development. Functional build represents an integrated approach to product and process development developed by automotive body manufacturers due to the non-rigid nature of sheet metal stampings. This paper proposes a hybrid approach that combines both net build and functional build approaches which results in lower costs than using either method individually. The decision criteria are developed using a Bayesian decision model in the context of purchasing a sheet metal stamping die. The decision rule maps the tool bias to the three actions available to the decision-maker: buy the die, rework the die, and perform a functional evaluation of the panels stamped with the die. [ABSTRACT FROM AUTHOR]

One-step finite element method (also called inverse approach) is more and more widely used in the automobile industry because of its unique advantages. Initial solution is an essential issue to ensure the success of the non-linear resolution in the implicit static one-step finite element solver. In order to speed up the convergence of the Newton–Raphson iterations, different kinds of initial solution methods are known. These are studied and compared in this paper. Several examples are followed to show their performance and efficiency. However most of these methods are based on geometric considerations like the geometric mapping method or the radial length development method. This kind of geometry based mapping methods could not reflect all aspects of the actual forming process. Therefore, an energy based mapping algorithm was implemented and coupled with the reverse deformation method which is based on the assumption of linear elastic deformation. This novel algorithm is proposed to provide the initial solution of one-step finite element method. For a complicated sheet forming modeling initial solutions obtained by different energy based algorithms coupled with the reverse deformation method are then compared in this paper. The results show that the Desbrun quadratic energy method and the accordant parameterization method combined with the inverse deformation method respectively are universal, efficient and robust initial solution schemes for the one-step finite element method. [Copyright &y& Elsevier]

In this paper, a new approach is proposed using the 3-D thermal energy distribution of the workpiece. The new approach is based on the fact that during the stamping process, the workpiece absorbs energy to deform. This mechanical energy is converted into thermal energy. Therefore, it is possible to diagnose the stamping by analyzing the 3-D thermal energy distribution. In practice, the thermal energy distribution can be acquired using an infrared camera. However, it is often necessary to reconstruct the 3-D thermal energy distribution, which can be accomplished by using the Octree algorithm. On the other hand, one can compute the thermal energy distribution through finite-element modeling (FEM) as the baseline for diagnosis. Then, by comparison, the diagnosis can be carried out. A couple of examples are presented in detail together with the experiment validation. [ABSTRACT FROM AUTHOR]

Abstract: Computer aided design in sheet metal forming using hard dies, which has a significant role in the automotive industry, was investigated. More specifically, the springback problem in stamping die design was elaborated and a solution method in die design was developed and evaluated. This compensation method assumes the necessary geometry change due to springback same as the springback and modifies the draw die surface geometry same amount with the calculated springback of finite element nodes in the reverse direction. The developed method was implemented in a computer program that uses panel data after drawing and springback simulations and a commercial surfacing program. This method was tested on a case part; member floor side rear of a light commercial vehicle, and the improvement in panel geometry after simulating with the modified die geometry was shown and discussed. [Copyright &y& Elsevier]

Aluminum sheet is becoming increasingly common as an automotive body panel material. The heat-treatable aluminum alloys of the 6xxx series are widely used as an outer panel material, due to their ability to precipitation harden during the paint-bake cycle, resulting in improved dent resistance. Increasing the formability of these alloys would allow for multiple parts of less complex geometry to be combined into a single more complex part, thereby avoiding the costs associated with any subsequent joining operations. Incremental forming is a process that can improve material formability through the use of short, recovery heat treatments applied between increments of deformation. The objective of this study was to investigate the incremental forming behavior of 6111-T4 an alloy, which is often used for exterior body panel applications. Interrupted tensile testing was used to simulate the incremental forming process. The effect of different heat-treatment parameters on mechanical properties was analyzed. The heat treat regimen developed for uniaxial testing was then applied to a series of plane strain tests using a hemispherical punch, to simulate the more complex states of stress found in forming operations. [ABSTRACT FROM AUTHOR]

This paper presents a new method to represent the tonnage signatures from the sheet metal stamping operations. First, the new method, called the snake skeleton graph, is introduced. It uses Bézier surface to model the instantaneous stamping force distribution and hence, can capture the three-dimensional spatial features of the tonnage signatures, such as the imbalance of the transient forces. These features have clear physical meaning and can be used for diagnosing the stamping operations. Based on the study of two practical examples, a failure map is developed that can be used in shop floor applications. [Copyright &y& Elsevier]

Global manufacturing chains have become common in the 21st century. To perform remote monitoring and diagnosis in such chains, real-time data compression has become a core factor in the efficient and effective exchange of information via computer networks. This paper presents a new technique for compressing data using a kernel-based method. Overcoming the drawbacks of support vector techniques - that is, fast decompression but slow compression - the new method exhibits high speed in both phases. In addition, the new method can also be applied for pattern classification. Based on strain signal, example tests derived from sheet metal stamping operations, the new method is shown to be very effective. The proposed technology has enormous potential in the application of advanced manufacturing processes monitoring and control through Internet or Intranet. [ABSTRACT FROM AUTHOR]