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Limited geometric accuracy in incremental sheet forming is a major obstacle for its wide adoption in industry. This paper develops a generic methodology, suitable for arbitrary part geometries and various ISF processes, for addressing one of the main causes of geometric inaccuracy, i.e., in-process springback. The methodology consists of three main elements: determination of key control points to treat geometric complexity, simplified simulation models to predict springback offline, and in-situ toolpath modification during forming. It is shown experimentally that the method provides an efficient and robust solution for various geometries with negligible setup cost.

In a new era of mass entrepreneurship and innovation, Yanjiang Street in Jiangbei new district of Nanjing city actively introduces private capital and jointly builds Dingmeng E-commerce Pioneer Park with enterprises. The two sides respectively input government services and supporting resources, enterprise innovation and driving resources, to establish the first e-commerce pioneer park in the whole region, and gather social innovation forces and innovative talents, fully stimulate the entrepreneurship and innovation vitality of enterprises in the incubation base. In this process, both the government and enterprises gather strength and focus on the cultivation and reconstruction of excellent Internet brands. At present, this model has achieved good stage results and has been widely recognized by all sectors of society.

A novel method using special featured tools is proposed for double-sided incremental hole-flanging (DSIHF), which can perform successful hole-flanging in one-step due to the globally cumulated deformation mode. Tools with complementary-shape section curves are used to constrain the material flow for better part geometry. The proposed method has been verified by two cases: an axisymmetric circular flanging and an asymmetric clover flanging. Experimental results demonstrate that the new method is feasible for flanging of complex shapes with simplified tools, reduces processing time and improves geometric accuracy. Moreover, numerical simulations were conducted to show that the proposed method has a different deformation mode compared with the conventional incremental forming. Specifically, the circumferential strain becomes the dominant strain, and its value depends on the in-plane curvature and the distance from the part edge.

Incremental sheet metal flanging is efficient and cost-effective in prototyping and low-volume production. However, how the sheet metal fails and how the overall formability is enhanced during incremental sheet flanging are still not well understood. This study attempts to provide an updated level of understanding for the deformation mechanics in fabricating a clover hole-flange with complex in-plane curvatures by double-sided incremental forming. Compared with traditional flanging methods, higher formability has been achieved for both stretch flanging and shrink flanging on a single part. Additionally, numerical simulation is conducted complementarily to reveal the strain evolution, based on which failure modes and reasons are analyzed. Moreover, DMV (Donell–Mushtari–Vlasov) equations are employed to analytically study the shrink flanging process. The investigations lead to the conclusions that meridional tension has positive effect in improving the formability during shrink flanging, while an adverse effect is found in the formability during stretch flanging.

The utilization of a supporting tool in Double-Sided Incremental Forming (DSIF) imposes a stabilizing compressive stress through the sheet’s thickness, increasing, thereby, the material’s formability and fatigue life. However, these favorable effects strongly depend on a steady tool-metal contact condition. This work presents a general DSIF control scheme, which augments the conventional position servo-loop with explicit force feedback control. The algorithm is examined for its robustness and effectiveness using complex geometries with varying curvatures and wall angles. The resulting parts have demonstrated enhanced material formability and geometric accuracy.

Woven composites are considered as a promising material choice for lightweight applications. An improved non-orthogonal material model that can decouple the strong tension and weak shear behavior of the woven composite under large shear deformation is proposed for simulating the preforming of woven composites. The tension, shear and compression moduli in the model are calibrated using the tension, bias-extension and bending experiments, respectively. The interaction between the composite layers is characterized by a sliding test. The newly developed material model is implemented in the commercial finite element software LS-DYNA® and validated by a double dome study.

Cyber-physical systems (CPS) enable unprecedented communication between product designers and manufacturers. Effective use of these technologies both enables and requires a new paradigm of methods and models to identify the most profitable and environmentally friendly production plans for a manufacturing network. The operating system for cyber-physical manufacturing (OSCM) and the paired network operations administration and monitoring (NOAM) software are introduced. These technologies guide our development of a mixed integer bilevel programming (BP) model that models the hierarchy between designers and manufacturers as a Stackelberg game while considering multiple objectives for each of them. Designers select and pay manufacturers, while manufacturers decide how to execute the order with the payment provided by the designer. To solve the model, a tailored solution method combining a decomposition-based approach with approximation of the lower level Pareto-optimal solution set is proposed. The model is applied to a case study based on a network of manufacturers in Wisconsin and Illinois. With the proposed model, designers and manufacturers alike can take full advantage of CPS to increase profits and decrease environmental impacts.

The success of a toolpath in double-sided incremental forming (DSIF) is strongly related to the specified tool gap. It is hypothesized in this work that maintained contact between tools and the sheet can improve the distribution of sheet thickness and hence, improve material formability and prevent premature fracture. Simulation and experimental studies reveal that thickness prediction models solely dependent on the local wall angle are inadequate for general part geometries. A ‘Shamrock’ geometry is proposed leading to the development of a novel improved thickness correction model that incorporates wall angle, in-plane curvature, and tool direction.

It is essential to accurately describe the large shear behavior of woven fabrics in the composite preforming process. An analytical model is proposed to describe the shear behavior of fabrics with different weave patterns, in which tension-shear coupling is considered. The coupling is involved in two parts, the friction between overlapped yarns and the in-plane transverse compression between two parallel yarns. By introducing the concept of inflection points of a yarn, the model is applicable for fabrics with different weave patterns. The analytical model is validated by biaxial tension-shear experiments. A parametric study is conducted to investigate the effects of external load, yarn geometry, and weave structure on the large shear behavior of fabrics. The developed model can reveal the physical mechanism of tension-shear coupling of woven fabrics. Moreover, the model has a high computational efficiency due to its explicit expressions, thus benefiting the material design process.

Core needle biopsies are widely adopted medical procedures that consist in the removal of biological tissue to better identify a lesion or an abnormality observed through a physical exam or a radiology scan. These procedures can provide significantly more information than most medical tests and they are usually performed on bone lesions, breast masses, lymph nodes and the prostate. The quality of the samples mainly depends on the forces exerted by the needle during the cutting process. The reduction of these forces is critical to extract high-quality tissue samples. The most critical factors that affect the cutting forces are the geometry of the needle tip and its motion while it is penetrating the tissue. However, optimal needle tip configurations and cutting parameters are not well established for rotating insertions. In this paper, the geometry and cutting forces of hollow needles are investigated. The fundamental goal of this study is to provide a series of guidelines for clinicians and surgeons to properly select the optimal tip geometries and speeds. Analytical models related to the cutting angles of several needle tip designs are presented and compared. Several needle tip geometries were manufactured from a 14-gauge cannula, commonly adopted during breast biopsies. The needles were then tested at different speeds and on different phantom tissues. According to these experimental measurements recommendations were formulated for rotating needle insertions. The findings of this study can be applied and extended to several biopsy procedures in which a cannula is used to extract tissue samples.

In this paper, dynamic spherical cavity expansion model is developed for rate-dependent concrete material described by modified Drucker-Prager Cap plasticity model incorporated with size effect. Penetration resistance components are computed accordingly with static resistance dependent on projectile diameter scale. Saturated region is introduced to investigate the response of concrete target under high impacting velocity. The validation of the proposed model is conducted by modelling a rigid projectile with full-scale and 1/10-scale diameter penetrating a semi-infinite concrete target. Depth of penetration numerically obtained is also compared with some widely recognized empirical penetration formulae, and better agreement is achieved by the proposed model for penetration tests with various striking velocities.

Double-Sided Incremental Forming (DSIF) uses two small, independently moving, hemispherical tools on either side of the sheet to form a desired shape by following a predefined tool path. This study was motivated by the observation that the relative tool position of the tools, specified in the tool path generation algorithm, affects the formed geometric accuracy. A methodology for defining the relative tool positioning in the tool path generation algorithm based on local part geometry is proposed using simplified Finite Element Analysis (FEA) and sample physical experiments combined with Gaussian Process modeling techniques. This approach can take into account the mechanics of deformation in DSIF explicitly and physical compliance of the DSIF machine implicitly. Physical experiments were performed to demonstrate the effectiveness of the proposed framework.

This paper investigates the application of bioinspired serrated cutting edges in tissue cutting by biopsy punches (BPs) to reduce the insertion force. BPs are frequently used as a diagnostic tool in many minimally invasive procedures, for both tissue extraction and the delivery of medical fluids. The proposed work is inspired by the mosquito's maxilla that features microserrations on its cutting edges with the purpose of painlessly puncturing the human skin. The objective of this paper is to study the application of maxillalike microserrations on commercial BPs. The fundamental goal is the minimization of the puncture force at the BP tip during insertion procedures. Microserrations were created on the cutting edge by using a picosecond laser while cutting tests were implemented on a customized testbed on phantom tissue. A reduction of 20–30% in the insertion forces has been achieved with microserrated punches with different texture depths encouraging, thereby, further studies and applications in biomedical devices. Three-dimensional (3D) and two-dimensional (2D) finite element simulations were also developed to investigate the impact of microserrated cutting edges on the stresses in the contact area during soft tissue cutting.

Incremental forming is a flexible dieless forming process. In incremental forming, the metal sheet is clamped around its periphery. One or multiple generic stylus-type tools move along a predefined toolpath, incrementally deforming the sheet metal into a final, freeform shape. Compared with the traditional sheet metal forming process, the incremental forming process is more flexible, energy efficient and cost effective due to lower capital investment related to tooling. However, maintaining tight geometric tolerances in incremental formed parts can be a challenge. Specifically, undesired global bending is usually induced near the region between the tools and fixture resulting in a compromise in geometric accuracy. To address this issue, Accumulated Double-Sided Incremental Forming (ADSIF) is proposed, which utilizes two tools on both sides of the metal to better achieve localized deformation while simultaneously constraining global bending outside the forming area. Moreover, in ADSIF, the two tools are moving from inward to outward, and thus the tools are always forming virgin material and so as to limit forces on the already-formed part. Thus, ADSIF has a higher potential to achieve the desired geometry. Nevertheless, tool deflection due to machine compliance is still an issue that can have a considerable effect on geometric accuracy. In this work, the effect of tool deflection related to part geometry is studied for the ADSIF process. The nature of using two tools, rather than one, in ADSIF inherently implies that relative tool position is a critical process parameter. It is the region near these two tools where local squeezing and bending of the sheet occurs, the primary modes of deformation found in ADSIF. The change of relative tool positions (i.e., tool gap and relative position angle) are studied in detail by first developing an analytical model. It is concluded that the tool gap will be enlarged under the influence of tool compliance while the relative position angle is less affected. Additionally, a finite element simulation capable of modeling tool deflection is established. The comparison between the simulation results using rigid tools and deformable ones clearly demonstrated the significant influence of tool compliance on part geometry. Lastly, an axisymmetric part with varying wall angles was formed, and it was confirmed that ADSIF demonstrates improved geometry accuracy compared with conventional Double-Sided Incremental Forming.

Double-sided incremental forming (DSIF) is a subcategory of general incremental sheet forming (ISF), and uses tools above and below a sheet of metal to squeeze and bend the material into freeform geometries. Due to the relatively slow nature of the DSIF process and the necessity to capture through-thickness mechanics, typical finite element simulations require weeks or even months to finish. In this study, an explicit finite element simulation framework was developed in LS-DYNA using fully integrated shell elements in an effort to lower the typical simulation time while still capturing the mechanics of DSIF. The tool speed, mesh size, element type, and amount of mass scaling were each varied in order to achieve a fast simulation with minimal sacrifice regarding accuracy. Using 8 CPUs, the finalized DSIF model simulated a funnel toolpath in just one day. Experimental strains, forces, and overall geometry were used to verify the simulation. While the simulation forces tended to be high, the trends were still well captured by the simulation model. The thickness and in-plane strains were found to be in good agreement with the experiments.

Double-Sided Incremental Forming (DSIF) is a developing sheet metal manufacturing process that has gained a lot of attention in recent years due to its inherent flexibility, low-overhead cost, and die-less nature. However, it can be challenging to define the tool gap so as to achieve a desired pressure through the sheet thickness since one must first predict sheet thinning. In this investigation, a novel part design is proposed which varies in-plane curvature as a function of depth. A finite element model for DSIF is developed and the strain histories in various regions are extracted. It was concluded that if the supporting tool loses contact with the sheet, localized necking can occur prior to part failure. Additionally, part geometry can have significant effects on the tool contact area which, consequently, affects the evolution of strain.

In Accumulated Double-Sided Incremental Forming (ADSIF), two hemispherical tools impart the local deformation to the sheet via their programmed in-plane spiral motion and the depth of the part is achieved via rigid body motion of the already formed part. Unlike Single Point Incremental Forming (SPIF) and Double-Sided Incremental Forming (DSIF), ADSIF does not impose forces on the already-formed part and therefore, has the potential of achieving higher geometric accuracy. A systematic method is proposed in this work to study the influences of the relative tool positions on the local formed shape and the final geometry, which is essentially the accumulation of all previously formed local deformations. Meanwhile, the concepts of the stable angle and the peak angle are introduced to better describe the cross-sectional geometry of a formed part with a constant wall angle at that particular cross-section. It is recommended, while multiple combinations of the relative positions of two forming tools may achieve the same stable angle, that the positioning parameters should be chosen such that the resultant forming force or the wall angle variation between the stable and peak angles is minimized.Copyright © 2015 by ASME

Double-sided incremental forming (DSIF) is a relatively new dieless forming process which uses two hemispherical ended tools, one on each side of the sheet, moving along a predefined trajectory to locally deform a peripherally clamped sheet of metal. DSIF provides greater process flexibility, higher formability, and eliminates the tooling cost when compared to conventional sheet forming processes. While DSIF provides much improved geometric accuracy compared to other incremental forming processes, current toolpath planning strategies suffer from long forming times. A novel mixed double-sided incremental forming (MDSIF) toolpath strategy is proposed in the present study. It simultaneously reduces the total forming time by half while preserving the best currently achievable geometric accuracy. The effect of the forming parameters, i.e., of the incremental depth and of tool positioning on the geometric accuracy of the parts formed with MDSIF was investigated and compared to those formed by traditional DSIF strategies.

Incremental sheet forming has attracted considerable attention in the recent past due to advantages that include high process flexibility and higher formability as compared to conventional forming processes. However, attaining required geometric accuracy of the formed part is one of the major issues plaguing this process. The Double-Sided Incremental Forming process has emerged as a potential process variant which can preserve the process flexibility while maintaining required geometric accuracy. This paper investigates a mixed toolpath for Double-Sided Incremental Forming which is able to simultaneously achieve good geometric accuracy and higher throughput than is currently possible. The geometries of parts formed using the mixed toolpath strategy are compared to the desired geometry. Furthermore, an examination of the forming forces is used to uncover the reasons for experimentally observed trends. Future work in this area is also discussed.Copyright © 2014 by ASME