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The purposes of this review are to summarize the historical progress in the last 60 years of lightweight metal forming, to analyze the state-of-the-art, and to identify future directions in the context of Cyber-physically enabled circular economy. In honoring the 100th anniversary of the establishment of the Manufacturing Engineering Division of ASME, this review paper first provides the impact of the metal forming sector on the economy and historical perspectives of metal forming research work published by the ASME Journal of Manufacturing Science and Engineering, followed by the motivations and trends in lightweighting. To achieve lightweighting, one needs to systematically consider: (1) materials and material characterization; (2) innovative forming processes; and (3) simulation tools for integrated part design and process design. A new approach for process innovation, i.e., the Performance-Constraints-Mechanism-Innovation (PCMI) framework, is proposed to systematically seek new processes. Finally, trends and challenges for the further development in circular economy are presented for future exploration. [ABSTRACT FROM AUTHOR]

The cyclic and compressive mechanical behavior of ultrathin sheet metals was experimentally investigated. A novel transparent wedge device was designed and fabricated to prevent the buckling of thin sheets under compressive loads, while also allowing full field strain measurements of the specimen using digital imaging methods. Thin brass and stainless steel sheet metal specimens with thicknesses on the order of 10-100 µm were tested using the microwedge device. Experimental results show that the device can be used to delay the onset of early buckling modes of a thin sheet under compression, which is critical in examining the compressive and cyclic mechanical behavior of sheet metals. [ABSTRACT FROM AUTHOR]

Single point incremental forming (SPIF) is plagued by an unavoidable and unintended bending in the region of the sheet between the current tool position and the fixture. The effect is a deformation of the region of the sheet in between the formed area and the fixture as well as deformation of the already formed portion of the wall, leading to significant geometric inaccuracy in SPIF. Double sided incremental forming (DSIF) uses two tools, one on each side of the sheet to form the sheet into the desired shape. This work explores the capabilities of DSIF in terms of improving the geometric accuracy as compared to SPIF by using a novel toolpath strategy in which the sheet is locally squeezed between the two tools. Experiments and simulations are performed to show that this strategy can improve the geometric accuracy of the component significantly by causing the deformation to be stabilized into a local region around the contact point of the forming tool. At the same time an examination of the forming forces indicates that after a certain amount of deformation by using this strategy a loss of contact occurs between the bottom tool and the sheet. The effects of this loss of contact of the bottom tool on the geometric accuracy and potential strategies, in order to avoid this loss of contact, are also discussed. [ABSTRACT FROM AUTHOR]

Surface textures have various applications, such as friction/wear reduction and light absorbing enhancement. Deformation-based surface texturing has the potential of economically creating micro-scale surface textures over a large surface area. A novel desktop surface texturing system is proposed for efficiently and economically fabricating microchannels on the surface of thin sheet material for microfluid and friction/wear reduction applications. Both the experimental and numerical studies were employed to analyze the problems of the flatness of the textured sheet, the uniform of the channel depth and pile-ups built up during the surface texturing process. The results demonstrated a char relationship betwekn relative velocity of the upper and lower rolls and the flatness of the textured sheet and the final profile of the microchannels. [ABSTRACT FROM AUTHOR]

A grand vision of an algal biofuel energy manufacturing system is presented here. The proposed system, from manufacturing engineering and system points of view, aims to provide technical solutions to two major challenges that the algal biofuel industry faces, i.e., low productivity and energy intensive harvesting and drying, which result in prohibitively high costs. The proposed idea is to have an integrated "conveyor belt" system floating on the water surface powered by windmills or a hybrid energy source. The conveyor belt is made of corrosion-resistant steel sheets that have microdimple surface features to significantly enhance the attachment of algae cells to the "belt" compared with a surface without microdimple features. The grown algae on the belt will then be mechanically scraped off collected, dried, and squeezed for oil extraction. This paper addresses one of many fundamental problems in this vision, i.e., whether algae can grow effectively on textured stainless steel surfaces. Through both static and dynamic tests, it was found that the growth of algae on textured surfaces was several times more active than that on a flat sample. [ABSTRACT FROM AUTHOR]

Microforming is a relatively new realm of manufacturing technology that addresses the issues involved in the fabrication of metallic microparts, i.e., metallic parts that have at least two characteristic dimensions in the submillimeter range. The recent trend towards miniaturization of products and technology has produced a strong demand for such metallic microparts with extremely small geometric features and high tolerances. Conventional forming technologies, such as extrusion, have encountered new challenges at the microscale due to the influence of ‘size effects’ that tend to be predominant at this length scale. One of the factors that of interest is friction. The two companion papers investigate the frictional behavior and size effects observed during microextrusion in Part l and in a stored-energy Kolsky bar test in Part II. In this first paper, a novel experimental setup consisting of forming assembly and a loading stage has been developed to obtain the force-displacement response for the extrusion of pins made of brass (Cu/Zn: 70/30). This experimental setup is used to extrude pins with a circular cross section that have a final extruded diameter ranging from 1.33 mm down to 570 μm. The experimental results are then compared to finite-element simulations and analytical models to quantify the frictional behavior It was found that the friction condition was nonuniform and showed a dependence on the dimensions (or size) of the micropin under the assumption of a homogeneous material deformation. Such assumption will be eliminated in Part II where the friction coefficient is more directly measured. Part I also investigates the validity of using high-strength/low-friction die coatings to improve the tribological characteristics observed in micro-extrusion. Three different extrusion dies coated with diamondlike carbon with silicon (DLC-Si), chromium nitride (CrN), and titanium nitride (TiN) were used in the microextrusion experiments. All the coatings worked satisfactorily in reducing the friction and, correspondingly, the extrusion force with the DLC-Si coating producing the best results. [ABSTRACT FROM AUTHOR]

Model validation has become an increasingly important issue in the decision-making process for model development, as numerical simulations have widely demonstrated their benefits in reducing development time and cost. Frequently, the trustworthiness of models is inevitably questioned in this competitive and demanding world. By definition, model validation is a means to systematically establish a level of confidence of models. To demonstrate the processes of model validation for simulation-based models, a sheet metal flanging process is used as an example with the objective that is to predict the final geometry, or springback. This forming process involves large deformation of sheet metals, contact between tooling and blanks, and process uncertainties. The corresponding uncertainties in material properties and process conditions are investigated and taken as inputs to the uncertainly propagation, where metamodels, known as a model of the model, are developed to efficiently and effectively compute the total uncertainly/variation of the final configuration. Three model validation techniques (graphical comparison, confidence interval technique, and r² technique) are applied and examined; furthermore, strength and weakness of each technique are examined. The latter two techniques offer a broader perspective due to the involvement of statistical and uncertainty analyses. The proposed model validation approaches reduce the number of experiments to one for each design point by shifting the evaluation effort to the uncertainty propagation of the simulation model rather than using costly physical experiments. [ABSTRACT FROM AUTHOR]

Microforming using a small machine (or so-called desktop machine) is an alternative new approach to those using full-size heavy equipment for manufacturing microparts. Microparts are commonly defined as parts or structures with at least two dimensions in the submillimeter range, which are used extensively in electronics and micromechanical products. However; when scaling down a conventional forming process to microscale, the influence of the so-called size effect needs to be considered. The individual micro structure (size, shape, and orientation of grains) and the interfacial conditions show a significant effect on the process characteristics. In this paper; the process of extrusion is investigated to establish it as a viable process for microforming. A forming assembly is fabricated and used in conjunction with a loading substage to extrude micropins with a final diameter of 1 mm. The effect of grain size is investigated by using workpieces heat treated to produce grain sizes varying from 32 µm up to 211 µm. Two extrusion dies with different roughness are used to study the effect of surface finish. While experiments lead to interesting questions and new discoveries, theoretical or numerical solutions are necessary tools for process optimization. Here, knowing the limits of the current widely used numerical simulation tools [i.e., the Finite Element Method (FEM)], a new method, the Reproducing Kernel Element Method (RKEM), has recently been developed to address the limitations of the FEM (for example, remeshing issue), while maintaining FEM's advantages, e.g., the polynomial reproducing property and function interpolation property. The new RKEM method is used to simulate the microextrusion problem. Its results are compared with that obtained from the FEM and the experiment result Satisfactory results were obtained. Future directions on the experimental and simulation work are addressed. [ABSTRACT FROM AUTHOR]

Excessive coil deformation can complicate normal handling of a wound or rolled coil, cause difficulties in mass production, and introduce undesirable variations in the subsequent manufacturing processes. Four critical factors for coil deformation have been identified, i.e., radial stiffness of the coil material, winding tension, stiffness of the core which supports the coil, and lubrication. In this paper, we advance the understanding of coil deformation by developing an equivalent material model based on the internal stress distribution obtained from a two-dimensional winding-analysis model. The proposed material model is then implemented in a multi-layer finite element model to study the coil deformation under gravitational loading. This proposed framework can quantify the contribution of each factor in the coil deformation and thereby provide more scientific base in the engineering design process. The approach is used to analyze the deformation of laminate sheet coils. [ABSTRACT FROM AUTHOR]

Sheet metal forming is one of the most important and frequently used manufacturing processes in industry today. One of the key parameters affecting the forming process is the blank holder force (BHF). In the past, researchers have demonstrated the advantages of varying the blank holder force during the forming process, that is, the two primary modes of failure in sheet metal forming (wrinkling and tearing) are avoided. This gives rise to improved formability, higher accuracy and better part consistency. In recent years, researchers have also shown increasing interest in forming processes where the blank holder force is varied spatially with the help of segmented binders or flexible binders. In this paper, we have combined the above two aspects and used a robust method to determine the blank holder force trajectories for a non-circular part using segmented binders. The proposed strategy is verified by implementing it into a finite element simulation. Binder force is treated as a system input. The displacement of the binder is used as a measure of the tendency to wrinkle, and is therefore treated as a system output. The parameters of the system are continuously identified and updated using a deterministic Auto-Regressive Moving-Average model (ARMA). The model is then used to control the binder displacement to a prescribed value by adjusting the system input, i.e., the binder force. In this manner, individual binder force profiles for each of the segmented binders are obtained. Due to the generic nature of the ARMA model, the strategy proposed in this paper can be applied to a variety of forming problems, making it a robust approach. [ABSTRACT FROM AUTHOR]

Tailor Welded Blanks (TWBs) offer several notable benefits including decreased part weight, reduced manufacturing costs, increased environmental friendliness, and improved dimensional consistency. In order to take advantage of these benefits, however, designers need to overcome the reduced formability of TWBs and be able to accurately predict unique characteristics related to TWB forming early in the design process. In this paper, an analytical model to predict the weld line movement and forming height for a uniform binder force, TWB forming application is presented. Comparison to numerical simulation results demonstrates the accuracy of this methodology. The analytical model provides designers a valuable tool to determine the location of steps on the die surface to accommodate the weld line movement and the potential forming height for a TWB forming with a uniform binder force. The methodology presented here has the potential to be extended to analyze a non-uniform binder force forming of TWBs. [ABSTRACT FROM AUTHOR]

Examines the onset and post-buckling behavior of a sheet under various boundary constraints. Use of a wedge strip test; Incorporation of the device into a conventional tensile test machine; Measurement of material resistance to buckling; Outcome of the design; Verification of a hybrid approach to buckling prediction.

Presents an energy approach to provide a stress-based criterion for the general double-curvature sheet under compression. Effective dimensions over the region undergoing compressive hoop stress; Effects of tube thickness, tube radius and material properties on the minimum bending radius without the occurrence of wrinkling; Use of the criterion to predict the onset of wrinkling in tube bending.

Presents an energy approach to predict the onset of wrinkling during a shrink flanging operation. Establishment of curved sheet model to obtain critical buckling stress in terms of stress state, geometry properties and material properties; Increased sensitivity of wave number on plan view radius (PVR) with increased PVR; Influence of PVR, sheet thickness and material work-hardening on critical flange length.

Discusses an analytical model in calculating the offsets of the simplified two-dimensional (2D) axisymmetric models for predicting the corner failure height of three-dimensional parts during deep sheet metal drawing process. Relationship between process parameters and required center offset of 2D model; Comparison of probability of errors in failure height prediction.

Demonstrates the ability of a neural network and a stepped binder force trajectory to control springback angle and maximum principal strain in a simulated channel forming process of sheet metal parts. Determination of the high binder force and total punch displacement of the stepped binder force trajectory; Presentation of the flowchart of the proposed control system.

The forming of sheet metal into a desired and functional shape is a process, which requires an understanding of materials, mechanics, and manufacturing principles. Furthermore, producing consistent sheet metal components is challenging due to the nonlinear interactions of various material and process parameters. One of the major causes for the fabrication of inconsistent sheet metal parts is springback, the elastic strain recovery in the material after the tooling is removed. In this paper, springback of a steel channel forming process is controlled using an artificial neural network and a stepped binder force trajectory. Punch trajectory, which reflects variations in material properties, thickness and friction condition, was used as the key control parameter in the neural network. Consistent springback angles were obtained in experiments using this control scheme. [ABSTRACT FROM AUTHOR]

Studies the prediction of springback angle in the straight flanging operation of sheet metal. Use of an analytical model, finite element method and reproducing kernel particle method (RKPM); Development of contact algorithm and computation of springback angle; Material property parameters used in flanging simulation; Evidence that kinematic hardening law has a better prediction than the isotropic hardening law.

Accumulative plastic deformation due to repeated loading is crucial to the lives of many mechanical components, such as gears, stamping dies, and rails in rail-wheel contacts. This paper presents a three-dimensional numerical model for simulating the repeated rolling or sliding contact of a rigid sphere over an elasto-plastic half-space. This model is a semi-analytical model based on the discrete convolution and fast Fourier transform algorithm. The half-space behaves either elastic-perfectly plastically or kinematic plastically. The analyses using this model result in histories of stress, strain, residual displacement, and plastic strain volume integral (PV) in the half-space. The model is examined through comparisons of the current results with those from the finite element method for a simple indentation test. The results of rolling contact obtained from four different hardening laws are presented when the load exceeds the theoretical shakedown limit. Shakedown and ratchetting behaviors are discussed in terms of the PV variation. The effect of friction coefficient on material responses to repeated sliding contacts is also investigated. [ABSTRACT FROM AUTHOR]