Warm Incremental Forming Research Articles

Influence of heating mode on orange peel patterns in warm incremental forming of magnesium alloy

Orange peel patterns on the surface of the magnesium alloy generated in warm incremental sheet forming significantly affect the appearance of the products. In this work, the influence of the heating modes on this phenomenon is investigated. Two heating methods, i.e., hot air heating and carbon fiber electric pipe heating, were developed for the warm incremental forming respectively. An octagonal pyramid is taken as example and four different forming temperatures are set for the two heating systems. The results indicate that the occurrence of orange peel patterns is strongly affected by the temperature distribution. The surface quality of the parts formed with the hot air heating system is generally better than that with the electric pipe heating system. The influence of the forming temperatures is also discussed based on the microstructural observation.

Process Parameter Enhancement for Incremental Forming of Titanium Ti–6Al–4V Truncated Cone with Varying Wall Angle at Elevated Temperatures

In the present investigation, the effects of the initial temperature of the sheet, tool diameter and vertical pitch on the final temperature, drawing depth, forming limit diagrams and thickness reduction, resulted from warm incremental forming of titanium sheets are investigated using the Taguchi method. The geometry of a truncated cone with varying wall angle was used for further reduction in the necessary experiments, materials and time. It was shown that any growth in the initial temperature of the sheet or vertical pitch would enhance the formability of the sheet due to the metal softening. The vertical pitch was also the main factor in increasing the final temperature, whereas the tool diameter was the most effective parameter for improving the drawing depth, the average of the major strains and thickness reduction. Moreover, the Sine law was applicable for estimation of final thickness of the incrementally deformed sheets.

Microstructure and mechanical properties of 2060-T8 Al-Li alloy after warm incremental forming

This study was aimed in the mechanical properties exploration of warm incremental forming of a newly developed 2060 aluminumlithium (Al-Li) alloy. One method of oil heating was utilized in this article. Following the tensile and hardness tests of the components, it could be obtained that the tensile strength and hardness of the incremental forming component decreased with increasing the temperature and increased with increasing the feed rate. Meanwhile, the tensile strength and hardness of the component manufactured at 120 °C and 160 °C were higher than the base material, due to strain hardening. Dynamic recovery existed in the component manufactured at 200 °C and dynamic recrystallization existed in the component manufactured at 240 °C. Also, the results were in a good agreement with the optical micrograph microstructure and the tensile fracture morphology. The tensile fracture mechanism of the component manufactured at 120 °C was mainly brittle fracture. In contrast, the tensile fracture mechanism of the component manufactured at 200 °C and 240 °C was ductile fracture. In addition, the accurate prediction models of the component mechanical properties with different forming temperatures and feed rate were obtained through response surface analysis.

Application of the Taguchi method for efficient studying of elevated-temperature incremental forming of a titanium alloy

The incremental forming technique is a relatively new sheet forming process, normally used for prototype or low-quantity manufacturing of components with complicated geometries. This article is concerned with the warm incremental forming of Ti-6Al-4V titanium alloy. To reduce the time and costs involved for the investigation, on one hand, the groove test which is simple and requires small specimens is employed and, on the other hand, the experiments are designed based on the Taguchi method, which considerably reduces the number of necessary tests. With regard to this, the influence of some important process variables, namely the initial sheet temperature, tool diameter and vertical pitch, on several objective parameters such as forming limit, thickness reduction, drawing depth and the final sample temperature are studied. Based on the Taguchi and variance analyses, the rank and contribution percentage of each process variable are, respectively, determined. In all the cases, there is a good agreement between the results of these analyses. Moreover, the vertical pitch is shown to be the most effective parameter for different objective variables, excepting the final temperature where the tool diameter is the most influencing variable. The optimum test conditions based on various criteria are then specified using the Taguchi method. After conducting the practical experiments with these optimum test conditions, a very good correlation between the relevant findings and the Taguchi predictions are found.

An Inclusive Experimental Investigation on Influences of Different Process Parameters in Warm Incremental Forming of AZ31 Magnesium Sheets

The incremental forming (IF) is a flexible sheet metal forming process, which is extensively used for low-quantity and/or prototype productions. Light alloys, such as magnesium alloys, are also interesting candidates for reducing the weights of different vehicles to reduce their fuel consumption. The present investigation is concerned with the warm incremental forming of AZ31 magnesium sheets. In this regard, the effects of different operational variables, namely the initial temperature, vertical pitch and tool diameter, on various outcome parameters such as actual in-process temperature, drawing depth, major and minor strains (forming limit diagrams), thickness reduction, spring-back, microstructure and hardness of the deformed sample are experimentally studied using the groove test. Among various parameters, it was found that the initial temperature and, consequently, the actual final temperature significantly affected the outputs of the IF process. Regarding this, a transition temperature of about 160 °C was obtained for AZ31 sheets, above which considerable changes were observed in the material behavior and the influences of several operational variables. Based on the experimental findings, a couple of predictive equations are also proposed in this article for estimation of the actual final temperature and the drawing depth of AZ31 samples incrementally deformed via the groove tests.

A comprehensive experimental investigation on the influences of the process variables on warm incremental forming of Ti-6Al-4V titanium alloy using a simple technique

The incremental forming has recently acquired a significant importance in various applications, such as automotive, aerospace, and medical industries. The present investigation is concerned with the warm incremental forming of Ti-6Al-4V titanium alloy. With this regard, the groove test was employed as a simple technique to study the effects of different variables, namely, the process temperature, the vertical pitch, and the tool diameter, on the forming limit diagram of the material, the springback, drawing depth, final temperature of the sheet, and the thickness variation of the product. The sheet temperature was the most important parameter affected by the interfacial friction and the other process variables. The experimental findings illustrated that the greater the vertical pitch and/or the tool diameter, the larger the formability and drawing depth of the sheet sample before its fracture. Moreover, decreasing the tool diameter and increasing the vertical pitch and the initial process temperature resulted in more thickness reduction. The actual process temperature simultaneously affected the elastic modulus and the flow stress of the component. However, the flow stress reduction due to the temperature rise overcame the elastic modulus decrease and, finally, the springback was lower at higher process temperatures.

Warm Incremental Forming of Magnesium Alloys Using Hot Fluid as Heating Media

Industrial application of magnesium alloys is increasing in the last decade due to the very high mechanical strength to weight ratio they present. Typical applications are aeronautic parts but their use in the automotive industry is also growing. The bigger the reduction of the vehicle weight is, which can be obtain using these alloys, the bigger the energy saving will be in the near future. However, the formability of these alloys is poor and they are very difficult to be formed at room temperature. Several works have been presented by different authors on the positive influence the temperature increase has to form magnesium alloys. Normal process temperature is about 200-250°C. In this paper warm incremental forming of magnesium alloys is investigated. The work focuses in the formability limits of the alloys and the identification of the optimal process parameters. Aiming to obtain a homogeneous temperature in the forming areas, hot fluid is used as heating media. Experimental results for different temperatures are presented and final microstructures are related to the possible deformation mechanism.

Warm negative incremental forming of magnesium alloy AZ31 Sheet: New lubricating method

The present study has been undertaken in order to investigate the suitable lubricants and lubricating methods, which can be employed to form a magnesium alloy AZ31 sheet by warm negative incremental forming (NIF). For the intended purpose, Nano-K 2Ti 4O 9 whisker and organic binder were employed to improve the bonding strength at lubrication coating/sheet interface and lubricating properties at elevated temperatures. The Nano-K 2Ti 4O 9 whisker enhanced solid lubrication film and the solid graphite or MoS 2 powder-coated porous ceramic coatings by pulsed anodic oxidation (PAO) almost have the same coefficient of the initial friction about 0.07–0.1 at room and elevated temperatures, which was satisfied with friction and lubrication condition of warm incremental forming (IF) of the metal sheet. Solid graphite or MoS 2 powder-coated ceramic coatings possessed the remarkable lubrication and self-lubrication effect. These suggested lubricating methods gave an excellent solid lubrication performance and good surface quality of the formed parts in warm IF process of the metal sheet.

Formability of AZ31 magnesium alloy in warm incremental forming process

A number of scientists are currently involved in Incremental Forming investigation, in order to better understand the process and to extend its applicability to industrial practice. If flexibility is probably the main advantage deriving from Incremental Forming use, today a new point of view is given by the possibility to use the process instead of a sequence of operations, allowing also a better sustainability. Formability enhancing is one of the keyfactors of this success and for this reason it is widely investigated, also on lightweight materials, for which the use of a preliminary heating is required. In the paper the formability of Magnesium AZ31 is investigated in warm Incremental Forming, focusing the attention on the tools currently utilised for describing material formability. It is shown that Forming Limit Curves fail in this goal while a study of fracture, exploiting results of conventional tensile tests, supplies more appreciable results.

AZ31 합금 판재의 온간 점진 성형에 관한 연구

A fundamental study on warm incremental forming of a magnesium alloy sheet has been carried out. In order to enhance the incremental formability of the magnesium alloy sheet, a local heating device was newly designed and manufactured. Through the incremental forming tests of AZ31 under various forming conditions, the effects of process parameters such as the temperature, feeding depth per cycle, and inclination angle on the incremental formability of AZ31 were investigated. In addition, conventional FLDs at elevated temperatures were constructed experimentally and applied to predict the forming failure.