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In this paper, formability of dissimilar friction stir welded AA 6061 and AA 5083 blanks during single point incremental forming (SPIF) is investigated numerically and experimentally. Sheets from AA6061, AA5083 and FSWed AA6061 to AA5083 are formed by SPIF with different cone angles, and the limiting wall angles are determined. Additionally, the effects of SPIF and FSW processes on the microstructure, mechanical properties and fracture mode are investigated. The empirical results demonstrate that the formability of dissimilar FSWed sheets are not so much different from that of the base metal sheets. Dissimilar FSWed specimen is fractured from the AA 6061 base metal and far from the FSWed region. Although investigation of the fracture surfaces of the tensile tests shows a ductile fracture for AA 5083, AA 6061 and dissimilar FSWed sheets, it is a combination of ductile and brittle fracture after the SPIF. Furthermore, the SPIF of FSWed sheets is simulated numerically using the ABAQUS/Explicit. The results show that the thickness and the major strain have uniform distributions for both FSWed and base metal sheets. On the other hand, minor strain has a non-uniform distribution in the wall of the formed conical part of the FSWed sheet, despite the base metal sheets. [ABSTRACT FROM AUTHOR]

The present investigation systematically analyzes and compares the influence of microstructure and crystallographic texture of AA1050 sheet to that of the most critical process parameters, namely tool dimension, and incremental step depth, in single-point incremental forming (SPIF) process. The sheet samples were preheated at different temperatures to reform the original, i.e., distorted and misoriented grain distribution. The results from experimental and statistical analyses report higher sensitivity of global spring back, surface topography and forming limits strains to variations in microstructure and texture than tool diameter and incremental step depth. The preheating of the sheets resulted in the formation of preferential texture by grain reformation, which leads to the increase in the fraction of homogeneous orientated grains. Such grains increase the maximum forming limit strains and reduce the global spring back in SPIF. Fractography analysis of the failed components revealed that improvement in formability due to grain homogenization (developed texture) may be attributed to larger average void diameter. Empirical models were also developed, and optimized levels of parameters were identified to maximize the efficiency of the SPIF process. Further, qualitative and quantitative characterization of orange peel roughness was carried out by segregating the external formed surface into surfaces subjected to orange peel roughness and tool-induced texture. [ABSTRACT FROM AUTHOR]

In the present work, deformation mechanism in single-point incremental forming (SPIF) of drawing quality steel with a fully ferritic microstructure was studied. The effect of tool diameter and vertical step size on the micromechanisms of plastic deformation in SPIF was investigated by observing changes in microstructure and lattice rotation. It was observed that the fraction of grains with {111} ‖ normal direction (ND), which constitutes the gamma fiber in BCC materials, decreased with decrease in tool diameter and vertical step size. It is known that the state of deformation in SPIF is near to plane strain with the direction of major strain being always perpendicular to tool travel direction and negligible strain parallel to tool movement direction. Microstructural evidence for this observation and also for the presence of through thickness shear (TTS) components at smaller step size and tool diameter was observed. Viscoplastic self-consistent (VPSC) simulations revealed that the activity of 112 < 11 1 ¯ > slip system decreased in comparison to 110 < 1 1 ¯ 1 > slip system in the presence of TTS which manifested as the deviation from {111} ‖ ND position at smaller step size and tool diameter. [ABSTRACT FROM AUTHOR]

Abstract In case of Single Point Incremental Forming (SPIF) process, the deformation mechanism, absence of material localization prior to fracture and enhanced formability are still not satisfactorily explained. The objective of this work is to understand the sheet deformation characteristics, forming behavior, and dominant deformation mechanism of SPIF process. Process deformation characteristics such as dimensional accuracy, thickness distribution, true surface strain, von Mises stress and equivalent plastic strain, evolved at different forming stages, were evaluated through experimental investigation and Finite Element Analysis (FEA) of the formed parts. The evolved microstructural features for different stages and modes of strains have been analyzed by Electron Back Scatter Diffraction (EBSD) and X-Ray Diffraction (XRD) techniques. Analysis has also been carried out to identify the reason of typical failure under biaxial strain mode. An abundance of {001} <100> Cube texture component in the early forming stage indicates the occurrence of dominant shearing in this stage. The intermediate forming stage develops dominant {011} <111 > P texture component, which remains intact up to the final forming stage. This shows that Particle Stimulated Nucleation (PSN) has taken place due to excessive strains occurring in the sheet material during SPIF, causing grain refinement and shear band formation, and simulating kind of recovery or recrystallization process. Enhanced formability in SPIF can be attributed to the depletion of {001} <100> Cube texture, and development of {011} <111 > P texture and {011} <211> Brass texture component with the progression of SPIF. [ABSTRACT FROM AUTHOR]

The mechanical properties of a component are significantly influenced by the prevailing residual stress state. A deliberate induction of compressive residual stresses or a reduction of tensile residual stresses can improve the component properties, such as fatigue strength. Single point incremental forming is a flexible manufacturing process to produce complex shaped parts by the computerized numerically controlled movement of a hemispherical forming tool. Because the process parameters can be locally adjusted it is possible to influence the residual stress state of the component. The influence of the forming mechanisms bending, shearing and membrane stretching, as well as the role of the hydrostatic compression on the residual stress state is widely unknown. This work aims to fill this gap. Therefore, linear grooves are formed into AA5083 sheets in a single-stage incremental forming process. The residual stress state of the unclamped sheet is measured on both sides of the groove center by means of X-ray diffraction. The relative intensity of the dominant forming mechanism is adjusted by adapting the relevant process parameters step-down increment Δz and tool radius RTool. The forming mechanisms are analyzed numerically by splitting the total plastic energy into the three forming mechanisms bending, shearing and membrane stretching. The numerical results for bending and membrane stretching could be validated by crystallographic analysis. A shift in the energy ratio of the forming mechanism from bending to shearing with increasing relative step-down increment Δz/RTool could be observed numerically. The maximum residual stress amplitudes are found for Δz/RTool < 1. The results indicate that a deliberate residual stress state can be induced by adjusting the dominant forming mechanism of the process. [ABSTRACT FROM AUTHOR]

Abstract Compared with monolithic metal sheet, Single Point Incremental Forming (SPIF) of bimetal composite sheet has attracted increasing attention, as it takes advantages of materials with different superior properties, such as high strength, low density, and good corrosion resistance. However, deformation behaviors of bimetal composite sheet in SPIF may differ from the single-layer sheet, which depends on the layer arrangements and mechanical properties of each layer. In this regard, a comprehensive study was conducted to investigate the deformation behaviors of roll-bonded Cu-Al composite sheets in SPIF through predictive modeling, including analytical, empirical as well as numerical approaches, and extensive experimental work taking into consideration effects of key process parameters. It was demonstrated that overall, the formability, surface roughness, thickness variation and forming force in different layer arrangements, in terms of various process parameters, follow the similar trends to single-layer sheets. However, it was further revealed that deformation mode of layer-up sheet tends to a compression state and that of layer-down sheet tends to a stretching state. This leads to higher formability and larger forming force in Al/Cu layer arrangement compared to Cu/Al layer arrangement, as the exterior thinner but stronger Cu layer could endure more stretching deformation. [ABSTRACT FROM AUTHOR]

Deficiencies in formability and forming quality are the key factors to restrict the wide industrial application of single point incremental forming (SPIF) technology. Ultrasonic vibration is introduced into the single point incremental forming process to increase the forming limit of a material by changing its de¬formation mechanism. For 1060 aluminum sheet, the effects of vibration amplitude and frequency on the constitutive relation of material are analyzed. And the sidewall forming angle of a cone frustum part is taken as a measure standard. The influences of ultrasonic vibration parameters on the forming accuracy are studied through numerical simulation and experiment. The results show that the formability of 1060 a¬luminum sheet can be significantly changed by applying ultrasonic vibration, and the single point incre¬mental forming limit and the forming quality can be improved under the conditions of 120 W and 25 kHz. [ABSTRACT FROM AUTHOR]

This paper focuses on numerical simulation of single point incremental forming (SPIF) process. Via a user-defined material (VUMAT) subroutine is employed to implement a non-associated mixed isotropic-kinematic hardening material model. The accuracy of the proposed non-associated flow rule model to predict the material behavior and the anisotropy in sheet metal forming simulations is examined by comparing numerical results with experimental measurements. The suggested model shows good agreement with experimental results compared to the associated Hill_R and Hill_S models. The proposed non-associated flow rule demonstrates a good efficiency to simulate the springback after sheet metal forming and to predict the thickness variation during incremental sheet metal forming process. The present non-associated model can improve the prediction of both anisotropic and hardening behaviors of material used in numerically controlled sheet metal forming technology. [ABSTRACT FROM AUTHOR]

The paper presents a novel solution for improving the accuracy of the wall area of parts manufactured by single point incremental forming. Thus, a forming tool with a special design that works according to the principle of circumferential hammering is deployed, with a direct improving effect of the forming conditions and consequently of the dimensional accuracy of the part. The research is focused on an experimental study of frustum-of-cone shapes manufactured from sheet metal blanks of DC05 deep drawing steel of 1 mm thickness. A typical customary technological setup is used for the single point incremental forming process, without any additional elements, and two forming tools, a hemispherical and a special one, which use the circumferential hammering effect. Several preliminary tests using both tools were performed in order to prove that part accuracy can be significantly improved by using the circumferential hammering tool. The research was further expanded to investigate the influence on part wall dimensional accuracy of three factors: tool spindle speed, tool feed rate and part dimensional configuration. Using a full factorial plan of experiments the results of 32 test runs were processed. All parts were machined adequately, free of any material fracturing. Based on the achieved machining accuracy of the part walls, precision mathematical models were developed for the prediction of part dimensional accuracy in those areas. The mathematical models were validated by practice, as the predicted accuracies were matched by the experimental results.

The present paper aims to study the behaviour of Metal Active Gas (MAG) tailor welded blanks during the single point incremental forming process (SPIF) from an experimental point of view. The single point incremental forming process was chosen for manufacturing truncated cone and truncated pyramid shaped parts. The same material (S355) and the same thickness (0.9 mm) were selected for the joining of blank sheets because the main goal of the paper was to study the influence of the MAG welding process throughout the SPIF process. A Kuka robot, equipped with a force transducer and an optical measurement system were used for manufacturing and evaluating the parts by SPIF. The selected output data were major and minor strain, thickness reduction, forces and springback at the SPIF process. Another line test was performed to evaluate the formability in SPIF. The main conclusion of the paper is that during the SPIF process, fractures occur in one side welded blanks even at moderate wall angles, while in the case of double side welded blanks there is a decrease of formability but parts can still be produced at moderate angles (55 degrees) without any problems.

The residual stress state of a sheet metal component manufactured by metal forming has a significant influence on the mechanical properties, and thus determines the time until the component fails, especially for dynamic loads. The origin of the resulting residual stress state of incrementally formed parts with regard to the forming mechanisms of shearing, bending, and the normal stress component is still under investigation. The relationship between the process parameters, the forming mechanisms, and the resulting residual stress state for a complex part geometry manufactured by single point incremental forming (SPIF) is presented in this publication. For this purpose, a validated numerical process model is used to analyze the influence of the step-down increment Δz for truncated cones on the characteristics of the forming mechanisms and the resulting residual stress state. For the first time the forming mechanisms are evaluated numerically on both sides of the formed component. A relationship between the process parameters, forming mechanisms, residual stresses, and the mechanical properties of an incrementally formed component is shown. Shearing-induced hardening is identified as a relevant influence on the residual stress state of cones.

Ultrasonic Vibration assisted Single Point Incremental Forming (UVaSPIF) process is an attractive and adaptive method in which a sheet metal is gradually and locally formed by a vibrating hemispherical-head tool. The ultrasonic excitation of forming tool reduces the average of vertical component of forming force and spring-back rate of the formed sample. The spring-back phenomenon is one of the most important geometrical errors in SPIF process, which appear in the formed sample after the process execution. In the present article, a statistical analysis and optimization of effective factors on this phenomenon is performed in the UVaSPIF process based on DOE (Design of Experiments) principles. For this purpose, RSM (Response Surface Methodology) is selected as the experiment design technique. The controllable factors such as vertical step size, sheet thickness, tool diameter, wall inclination angle, and feed rate is specified as input variables of the process. The obtained results from ANOVA (Analysis of Variance) and regression analysis of experimental data, confirm the accuracy of mathematical model. Furthermore, it is shown that the linear, quadratic, and interactional terms of the variables are effective on the spring-back phenomenon. To optimize the spring-back phenomenon, the finest conditions of the experiment are determined using desirability method, and statistical optimization is subsequently verified by conducting the confirmation test.

Single point incremental forming（ SPIF） is a new metal forming method without Die ＆cutting. Using this method,the product cycle shorten,the production costs reduced. The main process parameters of the single point incremental forming : tool diameter d、the incremental depth ΔZ、sheet thickness sthimpacting on the simulation results are analyzed using Abaqus. Law of sine on incremental forming reaction sheet thickness variation is verified through simulation,the law of sine draw sheet thickness greater than the numerical simulation of the distribution is analyzed. thickness distribution of the sheet metal forming is presented,it’s application is analyzed.

Incremental sheet metal forming in general and Single Point Incremental Forming (SPIF) specifically have gone through a period of intensive development with growing attention from research institutes worldwide. The result of these efforts is significant progress in the understanding of the underlying forming mechanisms and opportunities as well as limitations associated with this category of flexible forming processes. Furthermore, creative process design efforts have enhanced the process capabilities and process planning methods. Also, simulation capabilities have evolved substantially. This review paper aims to provide an overview of the body of knowledge with respect to Single Point Incremental Forming. Without claiming to be exhaustive, each section aims for an up-to-date state-of-the-art review with corresponding conclusions on scientific progress and outlook on expected further developments. [ABSTRACT FROM AUTHOR]

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Abstract Lubrication improves surface finish in Single Point Incremental Forming (SPIF). However the reason behind this improvement needs to be investigated. In this study a polycrystalline Copper sheet was incrementally formed to a truncated conical geometry using different lubrications till fracture. The selection of the tool material for optimal surface finish is also discussed. The effect of lubrication on the surface roughness was studied. To understand the effect of the lubrication from a microstructural point of view, Scanning Electron Microscopy (SEM) analysis of the components was carried out. The SEM images from different lubrication states were compared and found that there is some influence of lubrication on the surface. The surface roughness varied along the depth of the formed truncated conical geometry. It was observed that the marks left by the forming tool and the development of valley like structures along the grain boundaries were the cause for increased surface roughness. Other important observation regarding the microstructure study was that due to high strain deformation the grain shape has elongated in its direction. The lubrication conditions had no significant effect on the formed grain size or shape. [ABSTRACT FROM AUTHOR]

Abstract Single point incremental forming (SPIF) has several advantages over traditional forming, such as the high formability attainable by the material. Different hypotheses have been proposed to explain this behavior, but there is still no straightforward relation between the particular stress and strain state induced by SPIF and the material degradation leading to localization and fracture. A systematic review of the state of the art about formability and damage in SPIF is presented and an extended Gurson–Tvergaard–Needleman (GTN) model was applied to predict damage in SPIF through finite element (FE) simulations. The line test was used to validate the simulations by comparing force and shape predictions with experimental results. To analyze the failure prediction, several simulations of SPIF cones at different wall angles were performed. It is concluded that the GTN model underestimates the failure angle on SPIF due to wrong coalescence modeling. A physically-based Thomason coalescence criterion was then used leading to an improvement on the results by delaying the onset of coalescence. [ABSTRACT FROM AUTHOR]

In single point incremental forming (SPIF) process, parts suffer from dimensional inaccuracy and limited formability, mainly, due to occurrence of springback and abrupt fracture, respectively. Orientation imaging microscopy of the original AA1050 sheet revealed dislocated and distorted microstructure and texture in comparison to the same sheet preheated at different temperatures. The objective of this work is to investigate formability and geometrical accuracy due to variations in microstructure and texture of the sheet and to propose a methodology, which can predict the geometric profiles and springback effect at different preheating temperatures. The work reports enhanced formability and geometrical accuracy of parts formed by SPIF, owing to the reformation of grain structure due to preheating. However, preheating at higher temperatures, i.e., 330 and 500 °C deteriorated the surface quality, as homogenization of grain orientation led to orange peel effect. The proposed methodology, based on reverse engineering and numerical formulation, is capable of predicting two-dimensional cone and pyramid profiles as well as global spring back values associated with different preheating temperatures. The results predicted by proposed method were validated by experiments and could be implemented to enhance the accuracy of SPIF process. [ABSTRACT FROM AUTHOR]

Abstract Single point incremental forming (SPIF) is a promising forming process, yet not entirely accepted and implemented on industrial scale, due to several reasons, presented in the paper. The approach presented here develops an evaluation method for the degree of its industrial implementation. Several factors which will favor the industrial implementation of ASPIF are identified and their weights are hierarchized by means of AHP. To assess the robustness of the AHP, a sensitivity analysis was also presented. Furthermore, a fuzzy inference system was built, having as output the degree of industrial implementation of SPIF. [ABSTRACT FROM AUTHOR]

This article investigates, experimentally, the failure loci in transition region between failure by crack-opening by mode I and by mode II of fracture mechanics. This investigation determines the fracture forming limit (FFL) and the shear fracture forming limit (SFFL) for copper with 0.8 mm and brass with 1 mm of thickness, by means of conventional sheet metal tests. Special focus is given to the use of staggered C-slit shear tests in order to obtain fracture strain pairs in the transition zone between FFL and SFFL, and the obtained results are presented. The procedure makes use of circle-grid analysis, thickness measurements and digital image correlation system (DIC). The fracture loci for the copper sheet were validated by simple and complex geometries deformed by single point incremental forming (SPIF). These different geometries allowed to obtain different strain paths (plane strain, shear and bi-axial deformation) with and without fracture, and revealed a good agreement between the results. [ABSTRACT FROM AUTHOR]

In this article, the temperatures at sheet-tool interface are observed with non-contact temperature sensors in single point incremental forming at high relative tool velocities. A flat-ended tool was used to form AA5754-H32 sheets, and the results were recorded to study the heat generation from relative tool motion over the sheet metal surface. This paper proposes a new geometry to study the effects of temperature on formability and resulting geometrical errors. The regions of large geometrical errors are presented in cross-sectional and isometric views in colour contrasts. As the tool moves along a prescribed path, a moving comet type temperature structure is observed with two heat generation zones for the first few step downs. The resulting microstructures are observed for each of the following cases and the disparities are reported. Generally, the blankholder is assumed to be at a constant temperature. Results show this is not true; the actual temperature rises with a heat loss to the blankholder via backing plate. High rotation speeds are used, with an upper limit being observed, before forming of sheet metal becomes untenable. At this limit, high wear followed by lubricant fuming is observed. The result at higher rotational speeds is similar to friction stir welding, which are explained in detail by the microstructures. Surface roughness of the formed components as a response to the high tool linear speeds with flat tools is also presented. [ABSTRACT FROM AUTHOR]

The sheet with 1060 Al often is used to fabricate aluminum parts at room temperature in the incremental sheet forming process due to the fact that the metal has a high ductility in the normal temperature. However, the material can cause a large quantity of springback for parts formed to influence dimensional accuracy. In this paper, the use of the electric hot incremental forming process (EHIF) can effectively improve the dimensional accuracy of parts compared to single-stage forming and double-stage forming at room temperature. The effect of main process parameters, such as tool diameter, feed rate, step size, and current, on temperature is studied in detail using the EHIF. Some target values, namely, the maximum temperature, the average temperature, and the maximum temperature difference, are measured with a cone using 1060 Al. Moreover, the response surface methodology and Box-Behnken design have been employed to analyze results in detail and to establish respectively corresponding models to predict target values. Finally, the evaluating model of temperature uniformity is proposed and verified according to the previous models. [ABSTRACT FROM AUTHOR]

AA-6061 aluminum alloy is extensively used in automobile and aerospace industries due to its high strengthto- weight ratio. However, this material shows limited formability in age-hardened condition at room temperature. Therefore, a new forming method known as single point incremental forming (SPIF) to deform the sheet was adopted. The SPIF experiments and finite element method (FEM) simulation were performed to form the sheet into the desired conical shape. Digital image correlation (DIC) method was used to measure the major and minor strains post deformation experimentally, and results were compared with FEM results. Detailed microstructural study was performed to understand the deformation behavior of AA-6061 aluminum alloy sheets during SPIF. It is observed that plastic anisotropy has strong effect on microstructure and texture development in different directions of AA-6061 alloy sheet during SPIF. It is also observed that volume fraction of goss and S texture components remains stable, whereas volume fraction of cube and brass texture changes significantly. [ABSTRACT FROM AUTHOR]

In this research, a new hybrid forming strategy is proposed and investigated numerically and experimentally to improve the formability in single point incremental forming (SPIF). At the first stage, the hydraulic bulging of the sheet metal is performed under a specified fluid pressure to obtain an intermediate shape, then the fluid pressure is removed and the bulged sheet is inverted upside down. Finally, the SPIF of the truncated cone with a certain wall angle is carried out on the pre-bulged sheet. To this end, a die set was designed and manufactured. To study the deformation mechanics and the thickness distribution, finite element modeling using Abaqus/Explicit was employed. The maximum achievable forming depth and the thinning in the hybrid forming strategy were compared with those in the single-stage and the equivalent two-stage SPIF. Results of the 70° wall angle cone show that by implementing the two-stage hybrid forming, the forming depth and the thinning can be improved by 26 and 45% compared to the single-stage SPIF, respectively. On the other hand, the equivalent two-stage SPIF can lead to an improvement of about 10% in the forming depth compared to the single-stage SPIF. [ABSTRACT FROM AUTHOR]

Incremental forming is one of the most well-known forming processes for complex and asymmetric parts. This method uses a CNC machine, simple forming tool, and a die. This study focused on effects of some parameters such as the material, feed rate, pitch, rotational speed and movement strategy of tool on the dimensional precision, forming force, thickness distribution and fracture in the welding area. The results showed that single point incremental forming (SPIF) led to a better thickness distribution with lower tool force, whereas two-point incremental forming led to better dimensional accuracy. Rotational speed does not have any significant impact on the forming process while decreasing the feed rate partially reduced the forming force. According to the results, although dimensional precision in double point incremental forming is better than SPIF, when it comes to the thickness distribution, forming force, and economic issues, SPIF is in favor. The results also showed that by connecting two materials, different parameters for the two materials could be investigated simultaneously in one simulation process. [ABSTRACT FROM AUTHOR]

Multistage forming is usually adopted to fabricate the part of steep angles during single point incremental forming (SPIF). However, the central sinking of specimens is usually a major defect during the multistage negative incremental forming process. In this study, three materials (1060 aluminum, Q235, and DC04 steel) were used separately to fabricate specimens with different heights and to study the effect of materials on dimensional accuracy of parts formed. Meanwhile, the effect of stepping rates on the largest error was investigated. In addition to this, a mathematic model was proposed to predict the central sinking value of specimens based on the law of energy conservation. The experimental result demonstrates that the stepping rate and the strain strength coefficient ( K) are mainly influential factors on the dimensional accuracy and that the mathematic model is feasible. [ABSTRACT FROM AUTHOR]

Single point incremental forming (SPIF) is highly flexible sheet metal forming process used for small quantity production and new product development. The product with high strength, good surface finish, and higher formability has paramount importance in industrial and marine applications. SPIF has been carried out on AA5052-H32 aluminum alloy which has high strength and difficulty in the conventional forming process. The response characteristics such as surface roughness $$({R}_{\mathrm{a}})$$ and maximum forming angle $$(\varnothing _{\mathrm{max}})$$ were evaluated by considering the independent process parameters such as spindle speed, table feed rate, step depth, tool diameter and sheet thickness through the design of experiments. The step depth and sheet thickness are the most influencing parameters for average surface roughness and maximum forming angle, respectively. It is found that neither the surface roughness nor the forming angle of formed sheets feels the effects of spindle speed significantly. An empirical relation has been formulated, and experiments were carried out to verify the reliability of the developed regression model. [ABSTRACT FROM AUTHOR]

In the present work, an experimental study was made to identify formability characteristics of aluminum 6061 fiction stir welded blank in an incremental forming process. Forming limit diagram, bowl height, minimum thickness and thickness distribution were studied to find formability of tailored welded blank. Firstly, series of experiments were carried out to find which joining direction caused higher formability and desired forming limit curve. For this purpose, joints with three different directions (i.e. rolling direction, transverse direction and diagonal direction) were prepared and formability i.e. formed bowl height until failure along with forming limit curves were compared. After finding the best joining direction, effect of welding process parameters i.e. rotational speed, plunge depth and travel speed on formability of welded blanks were analyzed by using response surface methodology (RSM). The results were discussed according to microstructure and fractography analysis obtained by scanning electron microscopy. After finding the effects, welded blanks with optimal parameter combination were fabricated and effect of incremental forming parameters i.e. spindle speed, feeding rate and axial step on thickness distribution were analyzed. Here, RSM was also used to find parametric and optimum setting of parameters. From the results, it was obtained that joints with diagonal direction caused higher value of bowl height. Also, tool rotary speed of 1600 RPM, travel speed of 40 mm/min and plunge depth of 0.15 mm caused higher value of bowl height implying high formability. Furthermore, it was found that selection of 0 RPM spindle speed, 600 mm/min feeding rate and axial depth of 0.6 mm resulted in higher thickness distribution. [ABSTRACT FROM AUTHOR]

Multistage forming is usually adopted to form those parts with steep angle or straight wall during single point incremental forming. In order to study multistage single point incremental forming further, based on an experiment method and a mathematic analysis method, straight wall cylinders are fabricated with different materials and different heights to investigate dimensional accuracy of specimens obtained. Three kinds of materials including 1060 aluminum, Q235 steel and DC04 steel are selected to deform specimens with four-stage single point incremental forming. The mathematic model of dimensional error is proposed to predict the sinking defect according to the law of energy conservation. In addition to this, the strain strength coefficient ( K) and the axial feed rate ( v ) are studied in detail for the largest deviation of specimens. Experiment results demonstrate that the mathematic model is feasible and an optimal v obtained effectively improves the dimensional accuracy of specimens. [ABSTRACT FROM AUTHOR]

In this paper, a new type of sheet metal forming technology using ultrasonic vibration applied to SPIF (single point incremental forming) process is presented. Forming force during forming process can induce fracture and affect accuracy of the sheet metal. Design of ultrasonic sheet metal forming equipment can be based on this study, which takes into account magnitude and changing law of the forming force. ABAQUS finite element software was used to simulate and analyze influence of different frequencies and amplitudes of ultrasonic vibration on the forming force in single point incremental forming process. Results show that ultrasonic vibration can reduce forming force and improve surface quality of the forming process. In addition, an experimental system using ultrasonic single point incremental forming was designed. Effect of the amplitude on ultrasonic vibration was studied experimentally. Experimental results were consistent with the result from finite element simulation. [ABSTRACT FROM AUTHOR]

In the single point incremental sheet forming (SPIF) process, the part accuracy and maximum forming angle are limited in comparison with conventional stamping method. The blank sheet boundary is fixed to prevent it from drawing in during the forming process. In addition, the maximum forming angle is reached when the sheet is deformed into critical thickness as described by sine law in the SPIF. This study gives another view on the role of blank shoulder area by hole lancing before forming process. The experiments showed that the hole lancing not only improve the formability but also part accuracy. The springback prediction by artificial neural network (ANN) were performed to clarify the springback dependence on the forming parameters and hole lancing. The 0.8 mm-thick AL5052-O metal sheet was used for all experiments. [ABSTRACT FROM AUTHOR]

Titanium and its alloys are widely used in cranioplasty because they are biocompatible with excellent mechanical properties and favor the osseointegration with the bone. However, when Titanium alloys have to be worked several problems occurred from a manufacturing point of view: the standard procedure for obtaining Titanium prostheses is represented by the machining processes, which result time and cost consuming. The aim of this research consist to introduce alternative flexible sheet forming processes, i.e. Super Plastic Forming (SPF) and Single Point Incremental Forming (SPIF), for the manufacturing of patient-oriented titanium prostheses. The research activities have already highlighted the potentiality of the investigated forming processes that can be alternatively used taking into account both the damage morphology and the need of urgency operation. In the present work, the way of manufacturing the Ti prostheses by SPF and SPIF is described. A comparative analysis has been performed, thus highlighting the peculiarities of the investigated processes and the prostheses feasibility. [ABSTRACT FROM AUTHOR]

Shallow sloped single point incrementally formed (SPIF) parts typically show undesirable geometric deviations from the designed shape due to accumulated unwanted bulging. In this study, the effect of global heating by forced-air warming on the geometric accuracy of low-angled parts with a conical geometry is investigated. A finite element (FE) model was developed to simulate the SPIF process at elevated temperatures. The simulation results show that the sheet metal is subjected to significantly higher levels of stress in cold forming condition with respect to parts formed at elevated temperatures. Due to the increase in strength caused by strain hardening, a larger area of the sheet (both in the wall and bulge regions) is affected by the tool during forming at room temperature. Softening of the material by heat-assisted forming reduces the strain hardening and extended straining of the part which results in a reduction of the bulge height and of the under-forming of the cone base. [ABSTRACT FROM AUTHOR]

This paper studies the mechanical properties, formability and effect of hole bridge (hole lancing) in the single point incremental forming for Al5052-O with the thickness of 0.8 mm. The mechanical properties, including anisotropy property and stress-strain relation, were evaluated by uniaxial tensile tests in three directions of 0°, 45°, 90° with the rolling direction. Varying wall angle conical frustum test was used to study the formability. The forming parameters of tool diameter, step depth, spin speed, and feed rate were optimized using multi-objective optimization with grey relational grade. The results show that the tool diameter strongly influences formability, springback and thickness reduction. To verify the effect of hole bridge on the formability, a predesigned hole bridge was machined by a laser on the blank shoulder nearby the forming periphery before forming. The optimized forming parameters found in previous step were applied for this test. As the result, the maximum forming angle was significantly improved in comparison with the non-hole-bridge part. Finite element simulation by ABAQUS explicit software was used to explain the strain evolution in the blank with cut-off hole of the incremental forming process. The simulation results were compared with experiment and discussed. [ABSTRACT FROM AUTHOR]

Single point incremental forming (SPIF) has higher formability limits than other sheet metal forming processes including stamping, and is therefore a desirable method of forming sheet metal components. To take advantage of this high formability it is necessary to understand how to maximise the limits through manipulation of parameters, increasing the likelihood of component success. In this paper, a systematic quantitative literature review was undertaken analysing experiments and results from 35 papers that studied the effect of process parameters on formability in SPIF. Collective results are presented regarding material thickness, tool diameter, tool shape and type, step down, feed rate, spindle speed and rotation direction, and some parameter interactions. The analysis provides evidence to support the hypothesis of an ideal operating range for each parameter and interdependency of parameters. A lack of focus in the literature on parameter interactions was found. A framework for important experimental parameters is proposed based on the review. Statement of originality Quantitative analysis of research presented in the literature about parameter effects on formability in SPIF. [ABSTRACT FROM AUTHOR]