Testing of Lubricants for DIC Tests to Measure the Forming Limit Diagrams of Aluminum Thin Sheet Materials

Abstract

We investigated lubricants and thin teflon foils that can be applied in the formability testing of the thin aluminum sheets used in the electronics and automotive industries. For the tests, thirteen different industrial lubricants (oils and greases) (i.e., L1–L13) and two Teflon films (i.e., 0.08 and 0.22 mm thick) were applied. The authors conducted an Erichsen test, and the thickness reduction of the discs was measured first. In forming-limit curve (FLC) tests, it is crucial that the stresses are localized in the central area of the specimen during forming and that biaxial deformation is maintained throughout, if possible. We aimed to achieve and fulfill this task. To perform this measurement, the GOM ARAMIS measuring system was utilized. It is an optical measuring system based on the digital image correlation (DIC) principle, capable of measuring both stresses and displacements in real time. A specific validation method was also developed to qualify the DIC system. We concluded that there was a 5% difference in Erichsen indentation (IE) number diagrams between the best (L12) and worst (L4) cases for the lubricants and oils tested, which is a significant difference for thin plates. We found that this value could be increased and improved by using Teflon discs. Furthermore, the localization of stress maxima, i.e., the centering of cracks in the specimen, could be achieved by combining Teflon discs and L12 lubricant (with appropriate layer order), which significantly aids in the recording of standard FLC diagrams. Using foils is also advantageous because they are readily available, have no expiry date, and are of less environmental concern.

Numerical Investigation of Pre-Stressed Reinforced Concrete Railway Sleeper for High-Speed Application

“…• considering real laboratory tests and validating the results from FE modeling with them; • considering material models that allow for the calculation of crackings and their effect in the concrete, in addition to being based on measurements of real cubes and cylindrical specimens in the laboratory (compressive and splitting tensile tests); • considering more sophisticated models with regard to ballast behavior [66] and/or dynamic stress analysis [67]; • the real pattern of the crackings can be measured by GOM DIC technology [11,[68][69][70][71][72][73][74][75]; • taking into consideration the prestressing loss more exactly instead of the approximate calculation; • the ABAQUS model and the traditional (hand-made) calculation can be compared.…”

Evaluation of cracking risk of 80MnSi8-6 nanobainitic steel during hot forging in the range of lower temperature limits

“…Therefore, the DIC method is widely applied to evaluate the behavior of metals and alloys during deformation under various conditions. An interesting approach to this issue was presented by Szalai et al [23], who used a DIC system to assess the effectiveness of lubricants and polytetrafluoroethylene (PTFE) films applied during the deformation of thin aluminum sheets manufactured for the electronic and automotive industries. In another study [24], this measurement technique was applied to accurately determine the thermo-mechanical properties of the agehardenable Inconel 718 alloy.…”

Investigation of “Open” Superstructure Tramway Tracks in Budapest

“…The following disciplines are considered to be closely related to transport sciences: (i) transport engineering with logistics-transport-packaging sub-disciplines [1][2][3][4][5], (ii) civil engineering [6][7][8][9][10][11][12][13], (iii) mining and metallurgical engineering [11,12,14], (iv) urban, municipal and architectural engineering [15,16], (v) mechanical engineering [17][18][19][20][21], (vi) electrical engineering [7,[22][23][24][25][26], and (vii) vehicle engineering However, in reality, these fields often entirely overlap, or overlap to a lesser or greater extent.…”