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Chattering in Rolling of Advanced High Strength Steels
Published in Jingwei Zhao, Zhengyi Jiang, Rolling of Advanced High Strength Steels, 2017
Maria Cristina Valigi, Mirko Rinchi
The origin of the vibrations can be self-excited or forced (for instance, due to the inlet transients of the steel in the rolling stands). The chatter occurs more frequently in the early stands, for high values of the rolling speed and high values of the reduction ratio and especially in the cold-rolling of special steels. One of the classical consequences of chatter is the manifestation of regular parallel marking across the width of the metal sheet, called “chatter marks” or “skid marks”. The presence of these signs compromise the quality of the steel and must be absolutely avoided in the production of the AHSSs. Figure 13.1 shows an example of marks on the steel sheet.
Strategy development for chatter-free milling of Ti-6Al-4V thin-walled surfaces using stability region diagram (SRD)
Published in Machining Science and Technology, 2021
Gaurav Bhakar, Pratik Khandagale, Harshad Sonawane, Suhas S. Joshi
The cutting tool exhibits periodic excitation forces onto the workpiece during a typical machining operation. The workpiece and machine tool system experience vibrations, as a response to the dynamic forces which further result in waviness onto the machined surface, also called as chatter. A chatter mark is an irregular surface flaw left by a wheel that is out of true in grinding or regular mark left when turning or milling at an insufficient stiff machine tool system due to machining vibrations. Among the machine tool system components, the lower rigidity associated to the cutting tool and the workpiece is one of the major concerns as it limits the possibilities of stable machining (Wiercigroch, 2001). The rigidity of cutting tool can be controlled by reducing tool overhang (Mendes de Aguiar et al., 2013; Mishra et al., 2014); however, flexibility associated to thin-wall workpieces remains an issue (Sol et al., 2019). The industrial applicability of thin-walled low rigidity structures is wider and includes applications such as, thin-walled cylinders, axi-symmetric thin-walled components, engine casings, impeller blades, blisks, tombstone fixtures, etc. It is commonly observed that the chatter may get intensified during machining of thin-walled impeller blade like structures. The low stiffness of thin-walled workpieces further gets lowered as the cutting tool progresses onto the workpiece surface with a definite radial and axial depth of cut. This instantaneously varies the dynamic characteristics of tool-workpiece interaction system further affecting the predictability of stability lobe diagrams (SLDs). Significant recent attempts were observed so far addressing the machining issues resulted due to instantaneous reduction of stiffness of thin-walled workpieces along the cut and its subsequent effect on the machining quality.