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Environmental pollution by plastic waste has become a serious problem, and there is increasing demand to reduce the weight of PET bottles. To fabricate reduced weight PET bottles, research on the PET blow molding process is essential. In this study, experiments and computer simulations were performed on the stretch blow molding process used to fabricate carbonated soft drink PET bottles. The computer simulations were performed under the same conditions as the experiment using isothermal and non-isothermal models to analyze the blowing phenomena, thickness and temperature distributions, stretch ratio, and the stretching path of PET bottles. Experimental and simulation results were compared, confirming that the stretch blow molding simulation was useful for designing and fabricating improved PET bottles through the stretch blow molding process. [ABSTRACT FROM AUTHOR]

Predicting the results of multi-stage deep drawing in determining the thickness distribution and thinning of the workpiece are measures that will help reduce production costs by saving materials and production time. Machine Learning (ML) technique is a promising method for predicting the thickness distribution (TD) of drawn copper metal. Macro and micro products are currently used in sensitive electronic and structural applications. In this study, ML defines the relationship between the scaled thickness and the respective number of stages governed by the scaling law. It includes the development of Artificial Neural Network (ANN) tools based on machine learning to model the relationship between thickness by scaling law and stages based on multi-stage deep-drawn cups. TD is a measure of consistency. The TD is measured from the initial blank of 1500 mm long, 750 mm wide, and 6 mm thick Cu strip, reduced by 50% in nine successive steps until a final thickness of 0.1875 mm. Two ANN models used for TD prediction are Bayesian regularization (BR) and Levenberg-Marquardt (LM) algorithms. A trained machine learning model can successfully predict and verify the unseen data of 1.5 and 0.38 mm TD. ANN is used to predict the Finite Element Analysis (FEA) results and confirm them through the experimental results. The developed model can predict the TD of the multi-stage cup with the die design parameters. The difference between the TD predicted value and the measured value is based on the simulation results of multi-stage cups using the finite element method. When the predicted and measured TD, the difference in cup drawing depth is 0.5%–2.0%. The results show that the LM model is suitable for predicting the TD of formed copper cups following the scaling law. [ABSTRACT FROM AUTHOR]

Thermoplastic composite sheets have great potential for use in industrial applications owing to their fast-forming properties in the mold. One of the important matters of forming is the tendency of the part to recover elastically after it comes out of the mold. This behavior affects the dimensional accuracy of the final part. In this study, V-bending experiments were carried out to understand the spring-back phenomenon of continuous glass fiber-reinforced polyamide- 6 composite sheets. Unidirectional and cross-ply composite sheets were used in the experiments and bending angle, die radius, pressure, and dwell-time were investigated systematically. After bending, the spring-back angles of the parts were measured and the effects of the inspected parameters were compared. Also, variations in part thickness caused by springback were evaluated. Finally, the deformations in the specimens resulting from the residual stress were visualized with a scanning electron microscope. When the results were compared, it was determined that the bending conditions where the spring-back defect could be minimized were 6 mm radius, 90° angle, 120 s dwell-time, and 3 MPa pressure. Under these situations and in sheets bent 90°, the amount of spring-back was determined as 22° for unidirectional composites and 15° for cross-ply composites. [ABSTRACT FROM AUTHOR]

Thermoplastic composite sheets have great potential for use in industrial applications owing to their fast-forming properties in the mold. One of the important matters of forming is the tendency of the part to recover elastically after it comes out of the mold. This behavior affects the dimensional accuracy of the final part. In this study, V-bending experiments were carried out to understand the spring-back phenomenon of continuous glass fiber-reinforced polyamide-6 composite sheets. Unidirectional and cross-ply composite sheets were used in the experiments and bending angle, die radius, pressure, and dwell-time were investigated systematically. After bending, the spring-back angles of the parts were measured and the effects of the inspected parameters were compared. Also, variations in part thickness caused by spring-back were evaluated. Finally, the deformations in the specimens resulting from the residual stress were visualized with a scanning electron microscope. When the results were compared, it was determined that the bending conditions where the spring-back defect could be minimized were 6 mm radius, 90° angle, 120 s dwell-time, and 3 MPa pressure. Under these situations and in sheets bent 90°, the amount of spring-back was determined as 22° for unidirectional composites and 15° for cross-ply composites. [ABSTRACT FROM AUTHOR]

In the present work, novel serpentine-shaped micro-channels were successfully fabricated in ultra-thin sheets of AA1050, C101, and SS304 materials using the sheet hydroforming (SHF) process. In-house fabrication methods, namely punch-less SHF and die-less SHF processes were designed and developed on a 20-t press to manufacture these channels. The finite element (FE) modeling of both processes was developed for the prediction of the deformation behavior of these sheets. The elasto-plastic FE models incorporated the elastic properties, Barlat 89 anisotropic yield model, and Hollomon hardening law for all the three sheets, and their corresponding forming limit diagrams (FLDs) were implemented as damage criteria. It was observed that the maximum pressure was 28 MPa and 32 MPa for the punch-less and die-less SHF process, respectively. The manufacturability of the hydroformed channels was examined through channel depth, aspect ratio, and thickness distribution. The average channel depth and aspect ratio were found to be higher in the case of the die-less SHF compared to punch-less SHF. The failure occurred in the AA1050 channel under plane strain deformation mode near the die corner region and punch corner region for punch-less and die-less SHF processes, respectively, indicated by a sudden dip in the thickness distribution profile. Moreover, the surface quality of the formed channels was investigated through surface roughness value, and this was further correlated with effective plastic strain incurred in the deformation process. It was observed that the surface roughness of the deformed channels fabricated by the punch-less SHF process was lower than those formed through the die-less SHF process in the present study. [ABSTRACT FROM AUTHOR]

Commercially pure titanium (CP-Ti) Grade-2 has many applications due to its good weldability, strength, ductility, formability, and superior corrosion resistance. Although, CP-Ti Grade-2 can be formed at room temperature, however, it has lower ductility at room temperature. Therefore, heat treatment or thermal activation is required to increase its ductility and formability. In this paper, the process capabilities of CP-Ti Grade-2 to form the components through warm incremental sheet forming (ISF) has been investigated. To identify the optimal temperature at which CP-Ti Grade-2 sheets can be incrementally formed, straight groove tests were performed experimentally at various temperatures. Two geometries, namely, varying wall angle truncated cone, and constant wall angle truncated cone were used as test cases to evaluate the formability of CP-Ti Grade-2, in terms of limiting wall angle. The formability was also assessed through forming limit diagram obtained by Finite Element (FE) simulation. With forming limit damage criterion, fracture in the formed component was predicted with FE simulation using Abaqus Explicit software. To assess the process capabilities of CP-Ti Grade-2 sheet formed through warm ISF, thickness distribution, forming forces, geometrical accuracy, and surface roughness were analyzed through both FE simulation and experimental work. [ABSTRACT FROM AUTHOR]

Incremental sheet forming is a cost-effective process for rapid manufacturing of sheet metal products. However, incremental sheet forming also has some limitations such as severe sheet thinning and long processing time. These limitations hamper the forming part quality and production efficiency, thus restricting the incremental sheet forming application in industrial practice. To overcome the problem of sheet thinning, a variety of processes, such as multi-step incremental sheet forming, have been proposed to improve the material flow and thickness distribution. In this work, a new process has been developed by introducing multi-point forming as preforming step before conducting incremental sheet forming processing. Employing an established hybrid sheet forming system and the corresponding thickness prediction model, the preform shape can be optimized by employing a two-step optimization approach to improve the sheet thickness distribution. In total, two case study examples, including a hemisphere part and an aerospace cowling part, are fabricated using the developed hybrid flexible process in this study. The experimental results show that the hybrid flexible forming process with the optimal preform design could achieve sheet parts with more uniform thickness distribution and reduced forming time. [ABSTRACT FROM AUTHOR]

In this article, tube hydroforming along with stamping, a compound forming technology of thin-walled tube using stamping and hydroforming processes, was presented to cut forming costs, reduce number of forming and assembly operations, and improve forming efficiency. A simple experimental tooling was designed and manufactured. Forming experiments of stamping and tube hydroforming along with stamping processes in two square cross-section dies were performed for SS304 tubes at different upper die velocities. The experimental results indicated that the better formability and the more uniform thickness distribution are obtained by the tube hydroforming along with stamping processes than by the stamping. [ABSTRACT FROM AUTHOR]

The objective of this research is to examine the influence of low frequency pulsed electroforming process parameters, such as current, pulse-on time, pulse-off time, and electrolyte temperature, to obtain good thickness uniformity. For this purpose, a pulsed electroforming system was designed and made. Three level, four-parameter experiments were designed using Taguchi method. The effect of parameters and optimal parameters combination were obtained through signal-to-noise ratio (S/N), analysis of variance (ANOVA) and Pareto ANOVA method. Also the regression analysis was performed to obtain a predictive model. The results demonstrated that current has a dominant effect on thickness distribution and pulse-on time, temperature and pulse-off time affect thickness distribution, respectively. Optimum electroforming process parameters were determined and experimental tests were conducted to verify the optimized parameters. The results showed the effectiveness of the proposed optimization method. [ABSTRACT FROM PUBLISHER]

Conventional sheet metal forming operations require component-specific and costly tooling, and their design and fabrication add to the lead time. Incremental forming is one of the technologies that has emerged as an alternative to the conventional sheet-metal forming processes for mass customization, where the necessary part is obtained by gradually tracing its contours on a sheet of required thickness using stepwise tool indents. In this investigation, stainless steel AISI 304 sheets were incrementally formed using a hemispherical tool under varying step depths, spindle speeds and horizontal feeds. The limit of formability and thickness distribution of the formed sheet were characterized. The microstructure of the formed specimens was studied using an optical microscope. [ABSTRACT FROM PUBLISHER]

Single-point incremental forming (SPIF) presents a great competitive advantage with respect to the conventional stamping processes, in particular when small batches have to be produced. The competitiveness of such a process cannot be evaluated only by comparison with other traditional manufacturing processes. It is clear that the process allows metal forming in the critical ‘necking-to-tearing’ zone and this results in a strong thinning before failure if the process is well designed. What is more, the process is complex because of the number of variables involved. Thus, it is not possible to consider that the process has been well assessed; several aspects remain that must be clarified. In this paper a wide-ranging investigation of tool trajectory selection versus material formability is presented. In particular, although the same shape has to be manufactured, it is possible to select a particular trajectory among the many possible ones; this choice will affect the final thickness distribution and formability, accordingly. In conclusion, it is possible to state that tool trajectory can be regarded as an optimization variable in the process design. [ABSTRACT FROM AUTHOR]