Djordjević Milan T, Aleksandrović Srbislav, Arsić Dušan, Nikolić Ružica R, Szmidla Janusz, Todić Aleksandar, Čukanović Dragan, Ulewicz Robert
Faculty of Technical Sciences, University of Pristina, 38220 Kosovska Mitrovica, Serbia.
Faculty of Engineering, University of Kragujevac, 34000 Kragujevac, Serbia.
Materials (Basel). 2023 May 25;16(11):3968. doi: 10.3390/ma16113968.
The influence of various process parameters on the deep drawing process is a current research topic in sheet metal forming technology. Starting from the application of the previously constructed original testing device, an original tribological model was developed based on the process of sheet metal strip sliding between flat contact surfaces under variable pressures. A complex experiment was executed using an Al alloy sheet, tool contact surfaces of different roughness, two types of lubricants and variable contact pressures. The procedure included analytically pre-defined contact pressure functions based on which, for each of the mentioned conditions, the dependencies of the drawing forces and friction coefficients were obtained. The pressure in function P1 constantly decreased from a high initial value until the minimum, while in function P3 the pressure increased until the minimum value at the halfway point of the stroke, after which it increased up to the initial value. On the other hand, the pressure in function P2 constantly increased from the initial minimum value until the maximum value, while in function P4 the pressure increased until reaching the maximum value at the halfway point of the stroke, after which it decreased to the minimum value. This enabled the determination of the influence of tribological factors on the process parameters of intensity of traction (deformation force) and coefficient of friction. The pressure functions starting with decreasing trends produced higher values for the traction forces and the friction coefficient. In addition, it was established that the roughness of the contact surfaces of the tool, especially those with titanium nitride coating, has a significant influence on the process parameters. For surfaces of lower roughness (polished), a tendency of the Al thin sheet to form a glued-on layer was noticed. This was especially prominent for lubrication with MoS-based grease under conditions of high contact pressure (functions P1 and P4 at the beginning of the contact).
各种工艺参数对拉深工艺的影响是金属板成型技术当前的一个研究课题。从先前构建的原始测试装置的应用出发，基于金属板带在可变压力下在平面接触表面之间滑动的过程，开发了一个原始摩擦学模型。使用铝合金板、不同粗糙度的工具接触面、两种润滑剂和可变接触压力进行了一项复杂实验。该程序包括分析预定义的接触压力函数，基于此，针对上述每种条件，获得了拉拔力和摩擦系数的相关性。函数P1中的压力从高初始值持续下降直至最小值，而在函数P3中，压力增加直至行程中点的最小值，之后又增加到初始值。另一方面，函数P2中的压力从初始最小值持续增加直至最大值，而在函数P4中，压力增加直至行程中点达到最大值，之后又降至最小值。这使得能够确定摩擦学因素对牵引强度（变形力）和摩擦系数等工艺参数的影响。以下降趋势开始的压力函数产生了更高的牵引力值和摩擦系数。此外，还确定了工具接触面的粗糙度，特别是那些有氮化钛涂层的接触面，对工艺参数有重大影响。对于较低粗糙度（抛光）的表面，注意到铝薄板有形成胶合层的趋势。在高接触压力条件下（接触开始时的函数P1和P4），用基于MoS的润滑脂润滑时，这种情况尤为突出。
