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To investigate the microstructural changes that occur in stainless steel (SS) 304 during single point incremental forming (SPIF), experiments and finite element (FE) simulations were conducted for a truncated square pyramid geometry. Results from material characterization experiments for four stress states, i.e., uniaxial tension, equibiaxial tension, shear, and uniaxial compression, were combined to construct a material model based on the constituent phases and transformation kinetics. The material model was implemented into numerical analyses, where a two-step FE approach was utilized to predict martensite transformation in SPIF with increased computational efficiency. Validation experiments showed good agreement with the martensite transformation predictions from the FE simulations. The four locations along the pyramid wall revealed varying martensite volume fractions because of the differing stress states of bending, stretching, and shear that the blank is subjected to during SPIF, which can affect the microstructure. The stress state can be defined in terms of the stress triaxiality and Lode angle parameter. The FE results indicate that stress triaxiality impacted the martensitic transformation kinetics in SS304 more than the Lode angle parameter for SPIF for this particular material and geometry. Thus, distinct stress states in incremental forming can affect the martensitic transformation locally and, when used strategically, achieve functionally graded materials. This is pertinent to industrial applications requiring custom components, e.g., trauma fixation hardware for medical applications. [Display omitted] • SPIF pyramids exhibit heterogeneous microstructures affected by stress states. • A two-step FEA efficiently predicts the phase transformation of SS304 during SPIF. • SS304 models for constituent phases and transformation kinetics are identified. • Stress triaxiality impacted transformation kinetics more than Lode angle parameter. • Controlling microstructure can create functionally graded materials through SPIF. [ABSTRACT FROM AUTHOR]

The single-point incremental forming process is useful for manufacturing prototypes and customised sheet metal parts. The application of single-point incremental forming to perform hole-flanging operations has been explored by many researchers. The flange can be formed by a single-stage or a multi-stage strategy of single-point incremental forming. A comparative study of both strategies is essential to understand their applicability. In this work, the formability of AA5052-H32 sheet metal has been analysed by finding the Limit Forming Ratio and thickness of the flanges formed with the single-stage and multi-stage strategies. The single-stage strategy reduced the operation time by 105%, whereas the multi-stage strategy increased the formability by 11%. Further, an experimental study has been carried out to understand the effect of process parameters on the flange quality in single-stage single-point incremental hole-flanging. The results show that the step depth is the most effective process parameter and there is a high interaction between the spindle speed and the feed rate. [ABSTRACT FROM AUTHOR]

The hybrid method, known as Incremental Sheet Hydro Forming (ISHF), is a combination of the techniques of Incremental Sheet Forming and Sheet Hydro-Forming. The primary concern identified in the incremental sheet forming formation strategy relates to the potential failure of the product due to the thinning of the sheet and subsequent springback. In response to the issue of sheet failure resulting from thinning, a revised iteration of the integrated sheet hydroforming (ISHF) method was proposed. The revised version of the ISHF process has demonstrated notable improvements in the malleability of the material. The ISHF technique entails the movement of a single ball tool along one side of the sheet's surface, while hydraulic support is applied on the opposite side through the use of pressurized hydraulic fluid. The present study sought to investigate the impact of hydraulic support on metal formability and thickness distribution. In addition, a modified variant was also considered. The experimental results are in close agreement with the predictions made by the analytical models. The strain distribution throughout the length of deformation for the sheet has been calculated. The surface quality of the products was found to be satisfactory and a preliminary simulation has been performed. This study examines the influence of process factors, specifically spindle speed (1000/1500/2000 RPM), feed rate (400/600/800 mm/min), tool diameter (8/10/12 mm), and step-down (0.2/0.4/0.6 mm), on the cone-shaped feature at the specimen of aluminum alloy A 5010. The results demonstrated that, through analysis of variance, the most influential factor in the distribution of thickness was speed. Regarding formability, the rate of change was found to be the highest at 50%. [ABSTRACT FROM AUTHOR]

This article presents experimental research conducted on polycarbonate sheets deformed via single-point incremental forming (SPIF). Building upon established frameworks from previous studies, the analysis focuses on evaluating the formability and failure modes, particularly necking and fracture, of polymeric sheets in both conventional and incremental forming processes. The experimental design encompasses an investigation of spindle speed and step down process parameters, utilizing both oil and water as lubricants, to comprehensively assess their effects. The findings provide insights into how these parameters influence formability and affect the failure mode. When using oil as a lubricant, three distinct failure modes were observed during deformation: fracture, twisting, and crazing. An increased twisting was associated with higher step down values, whereas elevated spindle speeds contributed to increase crazing. Additionally, these tests revealed a “post-crazing” failure mode following deformation. Conversely, when water was used as a lubricant, only fracture and twisting were observed in the SPIF specimens. This work introduces, for the first time ever, a complete investigation of these failure modes through scanning electron microscopy analysis of the failure surface. This analysis scrutinizes surface features and interprets them, thus providing a valuable tool for failure analysis.

The single point incremental forming process (SPIF) is materialized to form the desired shapes in low-cost sheet metal processing and well suited for low batch components and customized designs. Many modifications have been attempted in recent years to maximize the formability, geometric accuracy and quality of the SPIF formed parts. In this work, an attempt has been made to analyse the influence of process parameters namely ball tool diameter, step size, spindle speed and sheet thickness on final wall thickness, forming force and surface roughness. The optimized results exhibit the desirable formability when the roller ball tool diameter of the tool is 12 mm. The results also project that formability of the sheet metal is minimized when the spindle speed is increased and the ball diameter maximizes the accuracy and surface roughness. Also minimizing the step size increases the product quality features. Upon conducting this multi-response optimization by grey based response surface methodology (RSM) technique It is identified that 12 mm ball diameter of the tool, 0.25 mm step size, 2445 rpm spindle speed, and 2 mm sheet thickness are the obtained optimized SPIF process parameters as confirmed through confirmation experiments. [ABSTRACT FROM AUTHOR]

Knowledge of the deformation behaviour of Ti-6Al-4V using single-point micro incremental forming (SPMIF) is very important to understand the physics behind the microstructural changes, and forming limit. In SPIF, shape changes in sheet metals up to ultra-thin sizes can be performed without using a die and punch (does not require any specific tooling as in the conventional forming process) and hence, this process is recommended for the fabrication of parts in the aerospace, automobile, and bio-medical industries. Furthermore, in SPIF, the components are manufactured using a hemispherical end tool moving along a predefined path with an enhanced forming limit. The present research work has focused on studying the formability, microstructure, mechanical properties and fracture mechanics of Ti–6Al–4V alloy foils during SPMIF. The importance of spindle speed on the forming limits of the Ti–6Al–4V alloy foil was studied and it was found that the maximum forming limits were achieved at higher spindle speeds (200 rpm) due to strengthening of basal texture and weakening of prismatic texture components. A forming limit strain (FLS) was drawn at different spindle speeds (100, 150, and 200 rpm). XRD, EBSD and TEM analyses were performed for the phase analysis, orientation and dislocation density respectively. The fracture behaviour was investigated and the void coalescence parameters were compared with respect to spindle speed. [ABSTRACT FROM AUTHOR]

A bumper beam prototype was fabricated in the present work by deforming laser welded tailored blank (LWTB) of extra deep drawing (EDD) steels of thicknesses 1.6 mm and 1 mm through a single point incremental forming (SPIF) process. Initially, a finite element (FE) model of SPIF was developed incorporating weld zone properties, material anisotropy and experimental fracture forming limit diagram as a damage model to understand the geometrical profile and strain evolution in the prototype. Subsequently, crushing performance was evaluated numerically at three different locations along the length of the LWTB prototype using a hemispherical indenter and compared with that of the prototype of EDD 1.6 mm (BM). Results showed that the presence of thinner sections in the LWTB prototype altered the deformation mode, and the load was distributed more uniformly compared to the BM prototype during crushing. The numerically predicted deformation modes and crushing load–displacement response were validated at mid-section with experimental findings. It was concluded that the application of non-associated flow rule-based Stoughton model improved the FE-predicted results in comparison to Hill48 and YLD89 models. Approximately 9.33% and 11.28% increase in the crushing force efficiency and specific energy absorption was achieved in the LWTB prototype compared to the BM prototype. These findings revealed that the SPIF process could be applied in developing lightweight bumper beams with improved crushing performance using LWTB. [ABSTRACT FROM AUTHOR]

Estimation of the loading conditions during incremental sheet forming is important for designing dedicated equipment, safely utilizing adapted machinery, and developing online process control strategies or trajectory compensation for robot compliance. In this study, we investigate the forming force of pyramidal components of uniform wall angles through analytical, experimental, and numerical approaches. After reviewing the existing research, the accuracy of the estimations from two analytical models and finite element simulations was assessed. Experimental results revealed that the maximum force occurs at 45° and 60° for AA1050-H24 and AISI-SAE 304 materials, respectively. FEA simulations leveraging tensile test data and refined isotropic hardening laws provided conservative estimations for the two materials. In the case of the AA1050-H24, numerical models accurately reproduce the experimental trend of components formed with Single Point Incremental Forming (SPIF) at different wall angles. On the other hand, alternative hardening models may be required to improve the force predictions for the AISI-SAE 304 material. [ABSTRACT FROM AUTHOR]

A device combining ultrasonic vibration plastic processing technology and single point incremental forming was developed in this work, with maximum power output of 2 kW at frequency of 20 kHz. On this basis, together with theoretical study, experiments and finite element simulation on forming force with aluminum alloy sheet 1060, the results showed that the forming force reduced evidently by appropriate selection of amplitude and frequency, meanwhile, the change of them had a remarkable influence on plastic behavior which can be summarized into two opposite aspects: the softening and the hardening effect. When a lower amplitude and frequency was applied to the forming process, the softening effect dominated, leading to a decrease of forming force, however, under the application of a high-vibrating amplitude and frequency, the harden effect dominated resulting in the decline of plasticity and the increase of flow resistance. The theoretical analytical results and the finite element simulation results are in good agreement with the experimental results, which verified the accuracy of the theoretical model and simulation model. The research results provide theoretical and technical basis for selecting vibration parameters of ultrasonic vibration single point incremental forming. [ABSTRACT FROM AUTHOR]

In this article, the design process of a novel vibrating tool is presented to improve some key aspects of Single Point Incremental Sheet Forming (SPISF). The overall effect of a vibration assistance is an improvement of the process by decreasing certain constraints occurring during manufacturing (e.g., high forming forces, poor roughness and elastic springback). For developing such assistance, the objective of this study is to present the design methodology and characterization of an innovative tool. The horn-shape design of the tool is optimized to resonate at its natural frequencies in the 4–16 kHz frequency bandwidth. A frequency decoupling of the tool modes is obtained by a successful desymmetrization of the tool design to precisely control the vibration direction, focusing on axial, radial or coupled vibrating motion of the tool tip. Then, the unidirectional vibrating force generated by a piezoelectric actuator is transformed into a controlled multidirectional vibrating motion of the tool tip depending on the frequency and the amplitude of the actuator input signal. The core contribution of the paper is the design methodology itself of the forming tool, which encompasses a novel approach focused on the tool/sheet contact coupling analysis and its effect on the vibrating behavior of the tool during SPIF process conditions. All steps of the design methodology are described: from the design specifications to the prototype validation, including a finite element analysis and an experimental characterization of its modal behavior in free-end tool conditions as well as in different tool/sheet contact conditions through a simple indentation forming test inside an AA5086 metal sheet. Experimental results highlight the importance of considering process boundary conditions for modal identification and the influence of the vibration direction on the force reduction in forming conditions. A forming force reduction up to 26% is obtained exciting the 2 nd bending mode of vibration of the presented forming tool identified in tool/sheet contact configuration, while reduction is less significant for the 1 st and 3 rd bending modes. [ABSTRACT FROM AUTHOR]

This research presents a comprehensive investigation into the pioneering domain of single point incremental forming (SPIF), focusing on elucidating the nuanced interplay between tool radius and formability. By employing a combination of rigorous simulation and experimental methodologies, the study sheds light on the pivotal influence of tool radius on forming performance. Various tool radius values spanning from 2 to 7 are systematically tested in conjunction with corresponding forming angles, revealing crucial insights into their synergistic effects. A critical threshold radius (Rt) is discerned, representing the point at which optimal formability is attained. Below this threshold, a decline in formability is observed, attributed to excessive surface cutting and metal pressing phenomena evident in tests utilizing pointed tools. Finite element (FE) analysis corroborates these findings, demonstrating that compression beneath the tool center induces unstable strain, consequently diminishing forming height as tool radius decreases. Conversely, beyond the Rt, an increase in tearing is noted due to reduced compression. This underscores the delicate balance required in selecting an appropriate tool radius to maximize shaping capacity in SPIF processes. Importantly, the research highlights the significance of achieving high compression capacity alongside an optimal tool radius, emphasizing the intricate yet essential factors influencing SPIF’s formability and shaping capabilities. Furthermore, this study contributes to the advancement of SPIF technology by uncovering novel insights into the dynamic relationship between tool geometry and formability, thereby paving the way for enhanced process optimization and design in various manufacturing applications. This research delves into the innovative realm of SPIF by exploring the intricate relationship between tool radius and formability. Through meticulous simulation and experimentation, the study unveils the pivotal role of tool radius in forming performance. The different values of tool radius, ranging from 2 to 7, are coupled with appropriate forming angles. A critical Rt is identified, where optimal formability is achieved. Conversely, below this threshold, formability declines due to excessive surface cutting and metal pressing, observed in tests employing pointed tools. FE analysis substantiates that compression below the tool center triggers unstable strain, diminishing forming height with decreasing tool radius. Notably, above the Rt, an increase in tearing is observed due to decreased compression. In this context, attaining high compression capacity alongside an appropriate tool radius emerges as the key to maximizing shaping capacity in SPIF. [ABSTRACT FROM AUTHOR]

The single point incremental forming process has a wide range of applications, and the process can be carried out without any specialized tooling and punches. However, if the process parameters are not carefully chosen, the components being manufactured are limited. This paper presents the single point incremental forming of 316L stainless steel sheets of 0.8 mm in thickness by varying input process parameters, such as tool diameter, wall angle, step depth, spindle speed, and feed rate, to study their effect on output parameters, strain and surface roughness. The Taguchi method was coupled with principal component analysis to identify the optimum process parameter combination to improve strain and reduce surface roughness. The wall angle has been determined to be the most influential process parameter, and the analysis of variance showed that the wall angle had the highest contribution (52.44 %), followed by step depth (18.55 %), tool diameter (9.72 %), spindle speed (1.64 %), and feed rate (0.83 %). The suggested design of experiments determined the best process parameter combination and executed the confirmation run. The grey relational analysis combined with principal component analysis improved the single point incremental forming of316L stainless steel sheets. [ABSTRACT FROM AUTHOR]

The paper reports the deformation behavior of single point incremental formed part with sheet oscillation. Single point incremental forming is an emerging manufacturing technology. This technology provides the competition to the other innovative technologies such as electric-assisted manufacturing, hydroforming, high-speed forming, etc., to produce the lightweight and highly deformed components. Single point incremental forming is the die-less sheet metal forming process in which the single point tool incrementally forces any single point of sheet metal at any processing time to undergo plastic deformation. In single point incremental forming, the part stays fixed and the tool pin makes the planar and downward motion to shape the part. It has several advantages over the conventional process such as high process flexibility, elimination of die, complex shape, and better formability. Previous literature provides enormous research on the formability of metal during this process, process with various metals and hybrid metals, the influence of various process parameters, but research on the deformation behavior of the part through the oscillation of the tool was limited. In this paper, the single point incremental forming was simulated on ABAQUS finite-element software. The spiral tool path was studied. First, the part was formed without oscillation. Then the oscillation of the sheet with the help of a die and blank holder was set with a frequency to deform the part. The variation of frequency and amplitude was also studied. The formability of the part was analyzed and compared. The deformation, profile shape, strain path, thickness, and force requirement were analyzed and presented. It was found that with lower cycles the maximum stress increases with an increase in amplitude. Also, with an increase in the number of cycles the achieved strain values were lower as compared to the no oscillation case for the same cup height and thus higher deformation is possible with oscillation. [ABSTRACT FROM AUTHOR]

Low formability, low productivity and forming quality are the main factors restricting the industrial application of single point incremental forming technology. Ultrasonic vibration was introduced into the single point incremental forming process to improve the forming limit of sheet metal by changing the deformation mechanism of material. A device combining ultrasonic vibration with plastic deformation processing technology and single point incremental forming was developed in this work. Taking cone parts of 1060 aluminum as the research object, the effects of ultrasonic vibration amplitude and frequency on equivalent stress and equivalent plastic strain in forming process were analyzed by combining numerical simulation and experimental research. Then, the forming angle of cone parts was used as the standard to study the influence of ultrasonic vibration parameters on formability. The results show that the equivalent stress decreased and equivalent plastic strain increased by superimposing ultrasonic vibrations, ultrasonic vibration can significantly change the formability and improve the forming limit of 1060 aluminum, the forming limit of 1060 aluminum can be maximized by selecting ultrasonic vibration parameters: amplitude 0.03 mm and frequency 30 kHz. [ABSTRACT FROM AUTHOR]

We investigated the parametric optimization on incremental sheet forming of stainless steel using Grey Relational Analysis (GRA) coupled with Principal Component Analysis (PCA). AISI 316L stainless steel sheets were used to develop double wall angle pyramid with aid of tungsten carbide tool. GRA coupled with PCA was used to plan the experiment conditions. Control factors such as Tool Diameter (TD), Step Depth (SD), Bottom Wall Angle (BWA), Feed Rate (FR) and Spindle Speed (SS) on Top Wall Angle (TWA) and Top Wall Angle Surface Roughness (TWASR) have been studied. Wall angle increases with increasing tool diameter due to large contact area between tool and workpiece. As the step depth, feed rate and spindle speed increase, TWASR decreases with increasing tool diameter. As the step depth increasing, the hydrostatic stress is raised causing severe cracks in the deformed surface. Hence it was concluded that the proposed hybrid method was suitable for optimizing the factors and response. [ABSTRACT FROM AUTHOR]

This paper investigates the applicability of single point incremental forming to fabricate stiffening grooves in thin metallic panels. The work combines experimentation, finite element and analytical modelling to determine the required forces and the maximum allowable groove depths that can be produced without tearing. The analytical modelling is based on a framework that was previously developed by the authors and combines in-plane membrane stretching and fracture forming limits. Comparison of the results obtained by the analytical framework against experimental and finite element data proves its effectiveness to replicate the deformation mechanics of groove stiffening by single point incremental forming. Results also prove that groove stiffening by single point incremental forming is an easy and effective alternative to conventional reinforcement of thin metallic panels by welding or fastening of stringers. [ABSTRACT FROM AUTHOR]

The multifunctional structure, i.e., multilayer sandwich panel (MLSP), exhibits properties like high rigidity, good specific strength, and lightweight and thermal resistance. Structural performance is attributed to these properties, making MLSP very favourable for producing highly reliable structures and increasing fuel efficiency due to its lightweight structure. Forming MLSP through conventional forming techniques such as deep drawing and punching is very challenging because it not only limits the formability but also requires special tooling and produces other undesirable effects. This work researched the feasibility of MLSP's formation through the single-point incremental sheet forming (SPIF) process. The SPIF process was modelled in the LS-DYNA to form MLSP into a benchmark shape. A tensile test was performed to evaluate the mechanical properties of the AL-1050. In the simulation, six more cases were also evaluated to see the effects of tool diameter, feed rate, and step size on the forming forces, formability, maximum percent thinning, etc. CATIA software generated the numerical code (NC) for the constant Z-level tool path and fed it to the CNC machine to perform the SPIF experiment on the MLSP. The larger tool diameter contributed to smaller forming forces, good formability, and less fracture area. The crack area and wrinkling tendency increase with the increase in feed rate first and then decrease with a further increase in feed rate. There was good agreement between the simulated and experimental formed geometrical shapes, proving that SPIF is feasible for forming multilayer sandwich structures.

This article presents an experimental research performed on a polycarbonate sheet deformed by single point incremental forming (SPIF). The analysis is implemented within the framework developed in previous research work for assessing formability and failure by necking and fracture of polymeric sheets in conventional and incremental sheet forming (ISF) processes. The experimental plan is taking into account a series of process parameters, including tool diameter, feed rate, spindle speed and step down. The results allow an evaluation of the influence of these parameters on the formability and their effect on the failure modes. In this regard, three modes of failure were observed: fracture, twisting and crazing. It was shown that most of the typical forming conditions in SPIF lead to failure by fracture in the absence of necking (crack opening in mode I), and all the test conditions presented a combination of twisting and fracture. Higher values of the step down increased the intensity of twisting whereas high values of spindle speed resulted in crazing. A scanning electron microscopy (SEM) evaluation was performed as well as an integral temperature analysis to provide a complete window for understanding the conditions upon which the different failure modes of this thermoplastic material are developed in SPIF.

The demand for small-batch manufacturing processes has increased considerably in recent years due to the need for personalized and customized products. Single point incremental forming (SPIF) has emerged as a time-efficient approach that offers increased material formability when compared to conventional sheet metal forming techniques. However, the complexity of SPIF requires a complete understanding of the material deformation mechanism. In this study, a non-conventional contactless tool in the form of hot compressed air is employed to form a polycarbonate sheet. The influence of the contactless tool on the shaping process is modeled and analyzed with a finite element modelling (FEM). Two different models were developed and coupled to estimate the resulting shape of the sheet. A CFD model was created to obtain pressure and temperature values of the air impacting the sheet, while a transient structural model was employed to study the deformation of the sheet. The research provides a working model that is able to predict the performance of this contactless incremental forming process of polymers with high accuracy. The comprehensive FE model developed in this work is able to forecast the final part geometries and dimensions in addition to the normal strain progression. It also revealed that the primary modes of deformation in SPIF were stretching, thinning, and bending. The model was validated by experimental results, and the predicted sheet deformation was compared to the one generated experimentally, and the results obtained were in good agreement. [ABSTRACT FROM AUTHOR]

The present paper aims to study the behavior of tailor welded blanks subjected to a single point incremental forming (SPIF) process from an experimental point of view. This process was chosen to deform truncated cone shapes of AA1050 aluminum alloy with different thicknesses. A uniaxial tensile test was performed to determine the mechanical characteristics of the alloy. Initial experimental tests implicated the use of variable wall angle parts which were processed on unwelded sheet blanks for determination of the behavior of the material and the forming forces. Afterwards, the wolfram inert gas (WIG) welding technique was used for joining two sheet blanks with different thicknesses either through one pass on one side, or by one pass on both sides. The conclusion of this paper indicates that one-sided welded blanks cannot be deformed successfully without fracture. In case of two-sided welded blanks, the results showed that the desired depth of 25 mm can be reached successfully. In case of the SPIF process, if welded blanks must be deformed, then the suitable method is to weld the blanks on both sides. [ABSTRACT FROM AUTHOR]

Single Point Incremental Forming process is subjected to the complex state of stresses that lead to plastic deformation instabilities during the process. Apart from formability and deformation analyses, the characterization and prediction of damage and or fracture in SPIF is of utmost importance. Prediction of fracture in SPIF by continuum-based models is satisfactory for low triaxiality conditions. However, fracture prediction under high stress triaxiality conditions i.e., under biaxial stresses in SPIF still needs attention. For this purpose, an accurate identification and characterization of damage model parameters is of utmost importance as the prediction accuracy of damage model majorly depends on it. In this work, a modified microhardness-based approach to damage parameter characterization is presented for predicting ductile fracture under biaxial stresses in SPIF. Strategy has been proposed to evaluate damage parameter (D) for Lemaitre continuum damage models by evaluating micro-hardness in the through-thickness direction of the fractured SPIF samples. Additionally, a methodology is proposed to evaluate hypothetical hardness by precisely obtaining the plastic stress–strain characteristics of the AA1050 H14 material subjected to biaxial straining. Prior to indentation test, in SPIF, Digital Image Correlation (DIC) technique is utilized to evaluate true plastic strain and thickness strain values. The values of damage parameter obtained from conventional as well as revised approaches are used to simulate fracture in SPIF by incorporating Lemaitre damage model as a user subroutine (VUMAT) in Abaqus software. Experimentally obtained maximum plastic strain and wall thickness are compared to simulated maximum plastic strains subjected to conventional and revised methodology. [ABSTRACT FROM AUTHOR]

Estimation of the loading conditions during incremental sheet forming is important for designing dedicated equipment, safely utilizing adapted machinery, and developing online process control strategies or trajectory compensation for robot compliance. In this study, we investigate the forming force of pyramidal components of uniform wall angles through analytical, experimental, and numerical approaches. After reviewing the existing research, the accuracy of the estimations from two analytical models and finite element simulations was assessed. Experimental results revealed that the maximum force occurs at 45° and 60° for AA1050-H24 and AISI-SAE 304 materials, respectively. FEA simulations leveraging tensile test data and refined isotropic hardening laws provided conservative estimations for the two materials. In the case of the AA1050-H24, numerical models accurately reproduce the experimental trend of components formed with Single Point Incremental Forming (SPIF) at different wall angles. On the other hand, alternative hardening models may be required to improve the force predictions for the AISI-SAE 304 material.

Incremental forming (IF) is one of the sheet metals forming technique where is a sheet formed into a final workpiece using a series of small incremental sheet deformations. In Incremental sheet metal forming process, one of the important steps is to produce the forming part with acceptable performance such as product accurate and uniform thickness distribution with a homogenous grain distribution that consider as the main challenge of incremental sheet metal forming process. This work is carried out to find the best method to control the product performance of the final parts using a new method of applying a primary stretching forming process with a hemispherical forming tool followed by single point forming SPIF. Different primary forming depth (10, 20, 30 and 40 mm) were applied to find their effect on the forming behavior of the final product and compare them to the single point forming product without using a primary forming process. The experimental results showed the improvement in microstructure by applying SPIF process after primary stretching, with grain size of 36 μm at 40 mm forming depth as compared to 52 μm when using pure SPIF, a twining effects presence in both cases. A high improvement with a minimum dimension deviation of (6%) with respect to the forming process in single point incremental forming process without a primary forming process that result forming deviation equal to (11.6%) with respect to the desired design. The thickness distribution of the final product also improved by applying the primary stretching forming process before the SPIF process reaches to (6.9%, 9.1%, 14.9% and 21.5%) at forming depth (10, 20, 30 and 40) mm, respectively. [ABSTRACT FROM AUTHOR]

Multi-layer sheets with combined properties such as a high strength-to-weight ratio, good corrosion resistance, and desirable electrical and thermal conductivity are employed in various application fields. In this research, the deformation behavior and fracture of a bimetal sheet during the single point incremental forming process (SPIF) are investigated. The AA1050 aluminum and 10100 copper sheets are utilized to fabricate the laminated sheet through the explosive welding process. Various geometries are designed to induce different stress and strain states through the SPIF of the two-layer sheets. To describe fracture phenomena, the Xue-Wierzbicki damage criterion incorporating the Hill48 anisotropic yield model is implemented in the Abaqus/Explicit finite element (FE) code via user subroutine VUMAT. The SPIF experiments are also carried out to validate predictions from the FE model considering fracture depths of different geometries and sheet thinning. The effect of layer arrangement is also studied, and the comparison between the fracture depths of SPIF experiments with predicted ones shows an average discrepancy of 6.5% for both layer arrangements of bimetal. Using the element deletion technique, the fracture location of SPIF parts was obtained through the FE simulations, which was in line with the real observations. The stress states of the localized deformation field in SPIF of the two-layer sheets are analyzed in the space of the stress triaxiality and Lode angle parameter. The strain states are also investigated in the forming limit diagram space, which indicated highly nonlinear loading conditions in this process. Using the damage criterion, the participation of influential factors at the fracture initiation of SPIF parts is discussed. It is found that regardless of the layers arrangement of the laminated sheets, initiation and propagation of the cracks take place from the outer layer. Experimental results in agreement with FE predictions revealed that various geometries of the bimetal sheets would have higher fracture depths when the aluminum layer is the outer layer and the forming tool contacts the inner copper layer. In addition to showing excellent predictions, the fracture forming limit curve (FFLC) of the bimetal sheet in SPIF is compared to that in the hemispherical punch stretching process. The comparison demonstrates the higher level of the calculated fracture strains in the SPIF process than in the stretching tests. It highlights the positive role of nonlinear loading versus a proportional loading condition in improving formability. • The deformation of bimetallic sheets is analyzed incorporating the sheets' anisotropy into the Xue-Wierzbicki damage model. • Stress states are explored through SPIF of various geometries with the aid of lode angle and stress triaxiality. • The fracture initiation mechanism is discovered in different arrangements and thickness ratios of laminated sheets layers. • The effect of non-linear loading path on increasing the fracture limiting strains is demonstrated. [ABSTRACT FROM AUTHOR]

Single point incremental forming has no support on the back of the sheet, which leads to the defects such as sheet instability and poor forming accuracy. In this paper, isostatic pressing technology is introduced into single point incremental forming process to provide effective support for the back of sheet metal. Taking cone parts with 1060 aluminum as the research object, the forming force under different static pressure parameters was analyzed by finite element analysis and experimental study. The results show that the horizontal forces Fx and Fy increase slightly under static pressure. The axial force Fz has a relatively large change, and with the static pressure increasing, the axial force increases significantly. The experimental equipment of isostatic pressing single point incremental forming was designed to obtain the forming force variation under different static pressing conditions. Compared with the simulation results, the accuracy of the finite element model was verified. [ABSTRACT FROM AUTHOR]

Recent studies have proven the possibility of polymer sheet forming by incremental sheet forming (ISF) process, while there are limited studies on ISF of polymer matrix composites. Fiber-reinforced polymers (FRP) are significantly useful in industries due to their unique properties. In the current study, owing to the merits of ISF and the wide applicability of FRP, single point incremental forming (SPIF) of polyamide 6 (PA6) sheets reinforced by glass fibers (GF) is taken into account at various forming temperatures. In this regard, a fixture equipped with a ceramic infrared heating element was designed. The effect of some important parameters such as the volume fraction and orientation of fibers and the forming temperature on the formability, the thickness distribution, and the dimensional accuracy of PA6 and PA6/GF sheets is investigated. According to the results, an improvement in the formability of the composite sheet can be obtained using SPIF by increasing the forming temperature and decreasing the volume fraction of fibers. The formability of the composite sheet with the fiber orientation of [0/90] is far less than the one with unidirectional fibers. In the most of the successfully formed samples, the transverse compaction and the fracture of fibers at the part bottom, the buckling of fibers at the edge of the backing plate, and the draw-in of the sheet along the main direction of fibers can be detected. The thinning of the composite sheet is most affected by the volume fraction and orientation of fibers, while the forming temperature has the least effect. Moreover, the feasibility of SPIF of a circular flange with a wall angle of 90° from the composite sheet is assessed at elevated temperature. [ABSTRACT FROM AUTHOR]

Friction characteristics have great influence on forming quality and formability during single point incremental forming. At the same time, the friction coefficient has a significant influence on the finite element model of forming process. In this paper, the friction coefficient of forming process was studied deeply through the combination of theoretical research and experimental research. Firstly, a single point incremental forming mechanical model considering friction was established, and a method to solve the friction coefficient of forming process was obtained. On this basis, the direct relationship between forming parameters and friction coefficient was established by response surface method, and the influence law of forming parameters on friction coefficient was analyzed. The results provided theoretical and technical support for the improvement of friction mechanism and forming quality in single point incremental forming. [ABSTRACT FROM AUTHOR]

In light of the analysis on the single point incremental forming (SPIF) principle of perforated titanium sheet and the corresponding peculiarities during the forming process, it is found that the wall angle constitutes the pivotal parameter influencing the SPIF quality of the perforated titanium sheet, and this is also the key evaluation index to test the application of SPIF technology on a complex surface. This method for integrating the experiment and the finite element modelling was utilized in this paper to study the wall angle range and fracture mechanism of Grade 1 commercially-pure α titanium (TA1) perforated plate, plus the effect of different wall angles on the quality of perforated titanium sheet components. The forming limiting angle, fracture, and deformation mechanism of the perforated TA1 sheet in the incremental forming were obtained. In accordance with the results, the forming limit is related to the forming wall angle. When the limiting angle of the perforated TA1 sheet in the incremental forming is around 60 degrees, the fracture mode is the ductile fracture. Parts with a changing wall angle have a larger wall angle than parts with a constant angle. The thickness of the perforated plate formed part does not fully satisfy the sine law, and the thickness of the thinnest point of the perforated titanium mesh with different wall angles is lower than that predicted by the sine law; therefore, the actual forming limit angle of the perforated titanium sheet should be less than that predicted by a theoretical calculation. With the increase in the forming wall angle, the effective strain, the thinning rate, and the forming force of the perforated TA1 titanium sheet all increase, while the geometric error decreases. When the wall angle of the perforated TA1 titanium sheet is 45 degrees, the parts with a uniform thickness distribution and good geometric accuracy can be obtained. [ABSTRACT FROM AUTHOR]

Single point incremental forming (SPIF) is an advanced, flexible, and cost-effective approach for producing complicated sheet metal objects quickly. Because of its low equipment cost, the process is best suited toward low or medium quantity batch production as the conventional stamping method remains cost-effective only for mass manufacture. During SPIF formation of titanium grade 5 materials, a response surface methodology and artificial neural network (ANN) model was created to optimize and estimate wall angle (Ømax) and average surface roughness (R a). The ANN model is developed using feed forward back propagation networks. Various combinations of transfer functions and number of neurons were used to create the ANNs (3- n -1, 3- n -2). The confirmation runs have been used to ensure that the ANN anticipated and practical findings have been in agreement. The generated ANN model (3- n -1) was capable of accurately forecasting the results of the experiment, with an overall R -value and Mean Square Error (MSE) of 0.99987 and 0.010905 for R a, and 0.99999 and 0.00700 for wall angle. The best 3- n -2 models has an average R -value of 0.99992 and MSE of 0.05532, respectively. As a consequence of rapid ANN modeling technique, it became discovered that technical effort inside the SPIF process could be decreased. [ABSTRACT FROM AUTHOR]

Electric hot-assisted incremental forming is an effective technique to improve the formability of Ti6Al4V titanium alloy sheets. However, the unstable electric heat can also lead to the unacceptable accuracy and inhomogeneous microstructure. In this study, a water-cooled tool was employed to stable electric-assisted forming temperature. The research results show that the stable forming temperature can significantly improve the forming properties and maintain the consistent microstructure of Ti6Al4V sheets, and the forming force and the degree of springback for the parts also decrease with the increasing temperature. The maximum forming depth is 7.0 mm at 400 °C (forming tool temperature) compared with the forming height of 4.6 mm at room temperature. The microstructure results show that the α phase is refined, and the β phase grains are elongated. The fracture morphologies of the parts at room temperature, 300 °C and 400 °C were compared and analyzed, and the dimples increased in the size and denser at high temperature. [ABSTRACT FROM AUTHOR]

Uniform wall thickness plays an essential role in avoiding forming failure in incremental sheet forming. However, it is challenging to promote the uniform distribution of wall thickness in single-pass forming of high wall angle and complex three-dimensional thin-walled parts using flexible dieless incremental sheet forming technology. In this article, based on the hydraulic support single-point incremental sheet forming technology, the finite element software is used to simulate and analyze the influence of different support pressure on the wall thickness distribution and the uniform critical angle of single-pass incremental sheet forming truncated pyramid parts. The results show that the hydraulic support can effectively improve the thickness uniformity and critical forming angle. In addition, a single-point increment experiment system of hydraulic support is designed, and the uniform critical angle of wall thickness corresponding to different support pressure is obtained. The experimental results are consistent with the finite element simulation results. Therefore, this article provides guidance for manufacturing high wall angles and complex parts with uniform wall thickness in single-pass incremental sheet forming. [ABSTRACT FROM AUTHOR]

Deformation machining (DM), a hybrid manufacturing process, involves subtractive manufacturing and the incremental forming process. This hybridisation of manufacturing technologies produces monolithic components having complex profiles and reduces raw material wastage. In this work, the influence of different toolpath methods, approaches, and design of the tool on the geometrical features and surface quality of the fin formed through the bending mode of the DM process was investigated for aluminium alloy Al-6061 T6. Different combinations of straight and curved fin toolpath techniques with top-to-bottom and bottom-to-top approaches were investigated to bend the machined fin in the desired shape. Thereafter, different tool profiles were explored with the bottom-to-top approach and curved toolpath strategy. The fabricated fin was 3D scanned to evaluate the geometrical features, and the surface roughness was also measured. The better quality of the formed components in terms of geometrical features and surface roughness was identified with the optimal combination of the tool profile and toolpath strategy, i.e. tool profile T3 has a circular sector and nose radius of 0.5 mm, curved toolpath method, and bottom-to-top approach. This optimal combination was further utilised to analyse the forming forces during the bending mode of the DM process. [ABSTRACT FROM AUTHOR]

Continuous efforts are being made to improve the technology and the process involved in part production to meet the demands of society. Advancements in machining, as well as incremental forming, resulted in the generation of a technology that is capable of manufacturing monolithic components in a single setup. Such hybrid technological development, called deformation machining (DM), has the milling process contributing to thin structure generation and single point incremental forming (SPIF) leading to the desired geometrical deformation. Machining a material block to produce thin structure results in unwanted residual stresses in the workpiece, which hinders the part's formability during SPIF. In the current research, stress-relieve annealing of aluminum alloy (Al 6061) is done to compensate for these residual stresses. While doing so, the optimum temperature of reheating is identified, at which the strength of the selected material is not significantly compromised. For this, preliminary microstructural investigations are carried out on the machined components at different temperatures, followed by experimental investigations. The force measurement of different samples was done during the experiments for determining the effects of heat treatment. Geometrical observations suggest that heat treatment results in better forming depth and improved forming angle, however, an increase in surface roughness is observed on the heat-treated parts. [ABSTRACT FROM AUTHOR]

In the recent past, ultrasonic vibration-assisted single-point incremental forming has gained the attention of the metal forming researchers' interest. Being a latest development, the process is not completely established from the point of view of the underlying mechanism and the effect of the process variables on the formability of the component. The amplitude of vibration and frequency of vibration are two ultrasonic process-specific variables which may affect the formability of the component. In this research work, the effect of amplitude of vibration along with forming feed and step-depth have been studied by performing a groove test on AA3003 aluminum sheet. The FFL for the SPIF process is proposed based on the thickness strain of the tensile testing component. The critical value of amplitude of ultrasonic vibration and ultrasonic intensity is identified demarking the ultrasonic softening and ultrasonic hardening zone. [ABSTRACT FROM AUTHOR]

Nowadays, there is a high demand for rapid prototyping parts and for products manufactured through plastic cold deformation. Incremental forming process is one of many which presents numerous advantages for fast production of complex shape parts. The purpose of this study is to develop a numerical model through finite element analysis to simulate the incremental forming process. For this analysis a variable wall angle part (VWA) which ranges from a 45° wall angle at the higher base of frustrum cone to a 70° wall angle at the base of the shape was proposed. The numerical model showed where the maximum strains are localized, how big the forces are during the process and how much the material thinned. Although the model does not indicate a possible failure of the material, the integrity of the structural stiffness was altered due to a minimum thickness reached of just 0.26mm. [ABSTRACT FROM AUTHOR]