Regarding to the uprising need for production of new components with high efficiency, application of methods that could facilitate the prototyping and minimize the financial and time costs are of high importance. Single Point Incremental Forming, which is a process with no need for die manufacturing, was successful in minimizing the costs and the prototyping period required for design validations. Accordingly, studying this process from different perspectives and obtaining an accurate method for determination of failure in this procedure is important. Some of the benefits of this process are an increase in formability, high flexibility in production of complex shapes and reduction of Forming forces. In all available processes that are used for Forming of metallic sheets there is a certain Limit for formality beyond which typical failures including wrinkle, necking or rupture will occur. Today different experimental and numerical methods are developed for determination of Forming Limit. In this study in order to obtain the Forming Limits and to anticipate the failure in Single-Point-Incremental-Forming process, generalized Forming Limit Diagrams are utilized. Initially the Single Point Incremental Forming process is simulated using ABAQUS Software and then resulting strain path of critical elements of the part are compared against the Forming Limits obtained by generalized Forming Limit Diagrams to study the existence of failure in both simulations and experimental tests.

Because of high strength to weight ratio, 6061 aluminum has many applications in different industries like automotive and aerospace industries and can help to reduction of fuel consumption. Forming Limit Diagram (FLD) is a useful method for sheet metal formability identification. Whereas calculation of Forming Limit Diagram by experimental tests is expensive and time consumption, in the present research two numerical criteria is presented for Forming Limit Diagram calculation of 6061 aluminum. Numerical simulation is done by Abaqus software. Numerical criteria of FLD prediction are imported to the Abaqus software to predict the Forming Limit Diagram of 6061 aluminum. Bragard method was used for calculation of experimental Forming Limit Diagram. This method is more accurate than other methods which read Forming Limit strains from the elements which are near the fracture zoon. Numerical criteria are ductile fracture and FLD criteria which their prediction was compared with experimental Forming Limit Diagram. Results show that ductile fracture criterion has more accuracy for Forming Limit Diagram prediction of 6061 aluminum. Moreover, numerical results of punch’s force-displacement were compared with experimental results. Results show that numerical results have a good agreement with experiment.

Incremental tube Forming process is capable of manufacturing tubes with different cross sections and dimensions using simple and inexpensive Forming tools. In the current study, seven different ductile failure criteria are used in finite element simulations in order to obtain the Forming Limit Diagram (FLD) of Al6063 aluminium tubes at high temperatures. The predicted FLD using these criteria are compared with experimental data to select the optimum criterion. Standard universal tensile tests in different temperatures and strain rates along with Zener-holloman parameter are performed to calibrate the failure criteria. The effects of process parameters including temperature, Forming depth and Forming feed are considered. The results showed that failure criteria can predict the time and location of rupture in incremental tube Forming process with a good accuracy. In high temperatures, Cockroft-Latham and normalized Cockroft-Latham criteria which consider the effect of the largest tensile stress had the best prediction. Investigation of temperature and strain rate showed that by increasing temperature, the Forming Limit goes higher but increasing strain rate causes to decrease it.

This paper deals with experimental and numerical studies of fracture behavior of Al. 5083-H321 alloy, under uniaxial and biaxial tensile loadings. In order to experimentally investigate biaxial fracture behavior, cruciform specimens were prepared using electrochemical method, based on Lionel proposed model. The specimens were gridded by electrochemical etching method. A dependent biaxial tension mechanism was also designed and fabricated with relatively high precision machining methods. Installing the mechanism on an INSTRON-1343uniaxial machine, the experimental biaxial tests were performed at ambient temperature and strain rate of 0. 0003 $sec^{-1}$. Different aspects of the facture behavior, which may be of more interest to study, include initiation and development of fracture pattern, fracture path on the specimen section, and the force Diagram for each of the arms. ABAQUS commercial software was utilized to simulate the biaxial tension test. Damage model was incorporated into the FE simulations to enable the FE model to capture the fracture occurrence in the cruciform specimen. Displacement loading with different ratios was applied to the specimen arms in the FE model to study the effect of loading ratio on the fracture of the material. Experimental and numerical results for location of crack initiation, path of crack growth and also the arms force Diagram were compared and a good correlation was observed between. The experimental results reveal that the fracture grows along the corner-to-corner diagonal line, in the test section zone of the specimen. Simulation results show that minimal strains occur in the test section zone, near the arms. Experimentally measuring the fracture stress is one of the great challenges, and hence, numerical simulation would be very useful in this regard. Maximum of stress gradient in the simulation results is observed along the corner-to-corner direction, in the test section zone. Based on the simulation results, some fracture biaxial points were obtained in the first quarter of the biaxial stress plane subspace. These fracture stress point can be used to determine the material fracture loci in the first quarter of the biaxial stress plane subspace.

Nowadays, two-layer metallic sheets have become as a useful solution to produce multi-functional products. Generally, two-layer metallic sheets can have advantageous characteristics such as increasing formability of the low formable component, improving the corrosion and wear resistance and reducing weight and cost of manufactured products. Therefore, understanding the Forming Limit behavior of a two-layer metallic sheet has an essential role in the design of sheet metal Forming processes. Forming Limit Diagram (FLD) is a suitable method to predict the formability of metallic sheets in sheet metal Forming operations. The aim of this research was to determine the Forming Limit Diagram in Aluminum-Copper two-layer metallic sheets experimentally. The Forming Limit Diagram can be used as a criterion in order to predict necking initiation which may cause tearing in sheet metal Forming processes. In this paper, the Forming Limit Diagrams of Aluminum-Copper two-layer metallic sheets have been obtained through an experimental procedure for the first time.

The Forming Limit Diagram (FLD) is probably the most common representation of sheet metal formability and can be defined as the locus of the principal planar strains where failure is most likely to occur. Low carbon steel sheets have many applications in industries, especially in automotive parts, therefore it is necessary to study the formability of these steel sheets. In this paper, FLDs, were determined experimentally for two grades of low carbon steel sheets using out-of-plane (dome) formability test. The effect of different parameters such as work hardening exponent (n), anisotropy (r) and thickness on these Diagrams were studied. In addition, the out-of-plane stretching test with hemispherical punch was simulated by finite element software Abaqus. The Limit strains occurred with localized necking were specified by tracing the thickness strain and its first and second derivatives versus time at the thinnest element. Good agreement was achieved between the predicted data and the experimental data.

One of the simple criteria for estimating the formability of sheet metals is use of Forming Limit Diagram (FLD). Determining the amount of accuracy and the range of proper prediction of this criterion is one of the most important challenges of researchers and engineers. In the present research first, employing the Forming Limit Diagram of St14 steel, number of practical experiments such as tensile test of standard, notched, and opened specimens, tube hydroForming and deep drawing processes are simulated, and possibility of crack initiation and fracture in them are predicted. Then, to evaluate the Forming Limit Diagram damage criterion, the above experiments are also practically performed and the practical results are achieved. Finally, comparing the results of numerical simulations and empirical observations, the amount of accuracy and proper range for fracture prediction of sheet metals by the FLD damage criterion is revealed.

Electrohydraulic Forming is a pulsed metal Forming process that uses the discharge of electrical energy across a pair of electrodes submerged in fluid to form sheet metal. An experimental procedure was developed to quantify the formability in electrohydraulic Forming (EHF) that is consistent with the quasi-static formability assessment convention. Furthermore, we investigate the procedure to comparison of theoretical Forming Limit Diagram and experimental results. The experimental EHF Forming Limit Diagram (FLD) was determined for aluminum alloy sheet and circle grids used to determine the minor and major strain in the path of necking on the specimens. Not only good agreement was found between the experimental curve that derived by quasi-static tests and theoretical Forming Limit curve, but also EHF on aluminum alloy shows formability improvement on major strains including 26% in comparison to low strain rate process.