Effects of press-forming parameters on the dimensional stability of paperboard trays

The dimensional stability of press-formed paperboard trays was investigated during heating and cooling of trays packed with oatmeal. Female mold tool temperature, dwell time, pressing force, and blank holding force were altered in the press-forming of the trays to observe their impacts on the dimensional stability. Dimensional measurements of the trays showed reduced tray width, and the trays exhibited distortions on the tray flange and outer wall. The results showed smaller effects on the tray length, parallel to the machine direction of the material. Improved dimensional stability of the trays was found with a 180 °C female mold tool temperature, a 600-ms dwell time, a 150-kN pressing force, and a 1.44-kN blank holding force. The optimal press-forming parameters were concluded to enhance bonding of the paperboard fibers during the press-forming. The optimization of the press-forming parameters was found necessary to reduce the observed negative response of the material to the challenging environmental conditions in the production of prepared food.

Earing Reduction by Varying Blank Holding Force in Deep Drawing with Deep Neural Network

In the present study, we propose a novel method of varying blank holding force (BHF) with the segmental blank holder and investigated its influence on the earing reduction in the circular deep drawing process of an aluminum alloy sheet. Based on the analysis of cup height profile, the principle of varying BHF using segmental blank holder was presented and analyzed by analytical theory and numerical simulation. The optimal varying BHF was reasonably determined and compared by using the analytical model and deep neural network (DNN) model integrated with genetic algorithm (GA). The integrated DNN-GA model revealed an accurate prediction and optimization of varying BHF for the minimum earing height variation, which showed a superior result to the analytical model. The optimal varying BHF exhibited a significant influence on the earing formation, resulting in the noticeable decrease of earing height variation. For volume consistency, it was found that an increase in thickness at the cup wall region predicted with the optimal varying BHF was achieved in the transverse direction, which implies an improvement of deep-drawability. Such results indicate that the varying BHF is more reasonable and effective than the uniform BHF. Furthermore, the material properties of the blank sheet also affected the reduction of earing in the deep drawing with varying BHF. The present study revealed that the lower the material strength, the more significant the earing reduction in the deep drawing with varying BHF will be.

Hot Stamping of a B-Pillar Reinforced Panel With 7075 Aluminum Alloy and the Feasibility Study of Short-Time Aging

The hot stamping of a B-pillar reinforced panel with 7075 aluminum alloy was carried out in an industrial production line. The effect of blank holding force (BHF) on the formability of the B-pillar reinforced panel and the effect of solution heat treatment (SHT) time on the mechanical properties were studied. Additionally, the forming precisions of a formed part before and after standard aging were detected further. Finally, both standard aging and short-time aging processes were carried out to investigate the feasibility of short-time aging for real parts. The stamping results demonstrated that lower BHF or no blank holding should be used during hot stamping to avoid cracking and wrinkling. The detection of forming precisions indicated that the great majority of measured points on the part were within ±1 mm of nominal. The mechanical property testing showed that the strength of the formed parts after a short-time aging was up to more than 90% of the as-received T6 state and more than 93% of the time can be reduced if the 90% of strength can be accepted.

GLARE Hydro-Mechanical Deep Drawing Analysis Based on the Forming Depth

The Fiber metal laminates (FMLs) combine the advantages of fiber-reinforced polymer properties, like stiffness and strength, with metallic alloys, like toughness and durability. These hybrid materials can unravel some problems in the industrial sector, particularly in aerospace, and advanced automotive industry. Still, there are significant challenges in the GLARE sheets forming process even for small drawing ratios, notably smaller and complex-shaped fiber metal laminate with low thickness. As a case study, a cylindrical GLARE cup was chosen. This shape with sharp bends and vertical geometrical features, still face many challenges and difficulties in the forming process. Numerical simulations have been used utilizing ABAQUS and compared with the experimental results in the Hydro-mechanical deep drawing to achieve good forming quality with higher depth. An extensive investigation of the effect of process variables has been done such as cavity pressure, blank holding force, and blank diameter. Also, their roles in wrinkles formation, tearing and thinning, and formability has been performed. Furthermore, the friction in two cases; cured, and semi-cured condition, has been considered. The results show that the application of cavity pressure within specified limits has a positive effect on the quality of the formed cup and leads to higher depths. The same conclusion for the blank holder, which has a positive impact on wrinkling elimination and friction reducing between the aluminum layers and the fiberglass. The result shows that the semi-cured condition of the GLARE has a good effect on wrinkling reduction, due to the uniform movement of the fiberglass inside the aluminum layers. Understanding these parameters and the GLARE forming behavior and have a good selection of these parameters can give the advantage to achieve smaller and more complex shapes with higher depth, particularly for mass production. Finally, this study can extend the industrial application areas of FMLs and GLARE parts.

FE simulation study of deep drawing process of SUS304 cups having no delayed cracks under enhanced blank holding force

In the experiment, delayed cracks in deep drawing processes of metastable stainless steel SUS304 cylindrical cups were prevented using elevated blank holding force aided by nanolubrication. Besides tensile residual hoop stresses, the elimination of the cracks was also attributed to the change in wall thickening profile along the wavy cup edges. The wall thickening is a result of the high circumferential stress acting in the flange, leading to the high concentration of deformation-induced martensite and high risk of cracks. The amount of increase in wall thickness in the valleys along the edge during the deep drawing process was higher than the peaks at low blank holding force range due to shorter heights. Therefore, the portions of blank equivalent to the valleys were subject to higher holding force during the process, resulting in decrease in degree of wall thickening with increase in height for blank holding force up to 25 kN. However, the wall thickening and the height increased at blank holding force of 28 kN due to the same amount of increase in wall thickness in both valleys and peaks, resulting in a larger contacting area and lower holding force. Therefore, the wall thickness in the valleys sharply increased, and the formation of the cracks persists. Within the crack-free range, that is, from 29 to 31 kN, both the heights and wall thickening decreased. The decrease in frictional force by means of the nanolubrication has facilitated the flow of material into the die, resulting in lower cup height. It also facilitated the flow of materials away from the thick valley regions under the high pressure, resulting in significant decrease in degree of wall thickening. The cracks were prevented. The amount of compression at blank holding force of 32 kN was insufficient to suppress the increase in wall thickening in valleys, resulting in the formation of the cracks again.

Effect on Blank Holding Force on Blank Deformation at Direct and Indirect Hot Deep Drawings of Boron Steel Sheets

This study involves performing direct and indirect hot press forming on ultra-high-strength steel (UHSS) boron steel sheets to determine formability. The indirect hot press process is performed as a cold deep drawing process, while the direct hot press process is performed as a hot deep drawing process. The initial blank temperature and the blank holding force are set as parameters to evaluate the performance of the direct and indirect deep drawing processes. The values of punch load and forming depth curve were obtained in the experiment. In addition, the hardness and microstructure of the boron steel sheets are examined to evaluate the mechanical properties of the material. The forming depth, maximum punch load, thickness, and thinning rate according to blank holding force were examined. The result shows that a larger blank holding force has a more significant effect on the variation of the thickness and thinning rate of the samples during the drawing process. Furthermore, the thinning rate of the deep drawing part in with and without fracture boundary was respectively examined.

Ultrasonic Welding of Carbon Fiber Reinforced Composite With Variable Blank Holding Force

Energy directors (EDs) have been widely used in ultrasonic welding (UW) of polymers and polymer-based composites. They help concentrate the welding energy and localize the weld at the location where the EDs are present. However, the utilization of EDs increases manufacturing cost and time, especially for complex parts and structures. This paper presents a method for UW of carbon fiber reinforced composite without using EDs. A reusable annular clamp (called a blankholder) is used as part of the weld tool to apply a variable force (called blank holding force) on the composite sheets during the UW. The effect of the blank holding force (BHF) on the weld formation is investigated. The results show that the duration of the BHF had significant impact on the weld formation. There is a critical duration with which a localized weld can form. Suitable durations of BHF at different levels of welding energy are determined by experiments. The main function of the BHF is to create an initial melting area by improving the contact condition. The initial melting area will act as an ED to concentrate the welding energy, and therefore, promotes the formation of a localized weld.

Study on Simulation of Stamping Forming and Die Surface Optimization of Aluminum Alloy Plate

Along with the automobile lightweight development, aluminum has become the focus of its own material characteristics. The aluminum alloy products with high efficiency, high quality and low cost are the guarantee of competitive advantage. High quality die surface is directly related to the product quality, cost, production efficiency, die life and so on. In this paper, the stamping process of two kinds of aluminum alloy products was simulated by Auto Form. The method of setting blank holding force and spring back compensation was introduced. At the same time, the setting of parameters such as die fillet, friction coefficient and draw bead was described in this paper. Finally, the optimization of die surface design was achieved by simulation.