Friction factor evaluation by FEM and experiment for TA15 titanium alloy in isothermal forming process

Abstract

The friction at die-workpiece interface is an important parameter in metal forming processes, which affects the metal flow, cavity fill, surface quality, etc. The friction in the forming process is influenced by material properties and forming conditions. The friction in forming process of TA15 (Ti-6Al-2Zr-1Mo-1V) titanium alloy under high temperatures (isothermal forming) and low strain rates is studied here by ring compression test. The friction calibration curves are elaborated by means of finite element method. The research on the calibration curves and friction factor at the loading speed v=0.1-1.0 mm/s and the conventional forging temperature (950°C) and near-beta forging temperature (970°C) is carried out. The influence of loading speed on friction calibration curves is similar to the influence on friction factor m: at the low (m <about 0.1) or high (m >about 0.7) friction condition, the influence of loading speed can be ignored, however the influence is notable in the midst magnitude (about 0.2-0.5). The temperature variation from 950°C to 970°C has little influence on friction calibration curves, but has notable influence on m under lubricated condition.

Variation of the friction conditions in cold ring compression tests of medium carbon steel

“…Later, Sofuoglu and Rasty [23] used FEM to elaborate friction calibration curves for ring compression tests on black and white plasticines to enable these variables to be analyzed. Since this time, FEM has been widely used to elaborate friction calibration curves for ring compression tests [24]. It has also been used to elaborate curves for double cup extrusion [9], T-shape compression [10], and barrel compression tests [25,26].…”

Analytical and numerical analyses of local loading forming process of T-shape component by using Coulomb, shear and hybrid friction models

“…(48) and the friction parameters determined by friction calibration curves will be performed in Section 5.3. For shear friction model, the friction factor m is about 0.2 to 0.3 in lubricated hot forming process recommended by DEFORM manual [21], and is about 0.35 for Ti-6Al-4V alloy in nonisothermal forming process with glass lubricant [25], and is about 0.12-0.40 at 950 1C and 0.16-0.50 at 970 1C under different glass lubricants for Ti-6Al-2Zr-1Mo-1V alloy in isothermal forming process [26]. Thus, m ¼0.3 was chosen in this section, and consequently friction coefficient μ is about 0.1731.…”

“…Using the ring compression test, many of the researches of the friction in the bulk forming have been published [22][23][24][25][26]. However, extrusion friction test such as double cup extrusion may be more suitable for determining the magnitude of friction in the bulk forming under high contact pressures such as extrusion [27].…”

Modeling of Hot Forging

“…Thus, the sparse solver should be used before the billet contact with dies steadily although the conjugate-gradient solver can converge (78). The magnitude of friction factor, m ¼ 0.5, was determined via the ring compression test (82). The glass lubricant is adopted in the isothermal local loading process of large-scale complex components, and it is used not only used to lubricate but also to prevent oxidizing.…”