FEM-based comparative study of SQUARE & RHOMBIC INSERT machining performance during turning of AISI-D3 steel

Nowadays, employment of the Finite Element Method (FEM) in machining simulation is a common practice to decrease development times and costs, as well as to investigate numerous parameters that affect machining processes. In the present work, the 3D modelling of AISI-D3 hard turning with both square and rhombic inserts is being presented by utilizing a commercially available Finite Element Analysis (FEA) software. Eighteen tests were carried out based on cutting conditions that are recommended for the used tools. Specifically, three levels of cutting speed (75m/min, 110m/min and 140m/min), three levels of feed (0.12mm/rev, 0.16mm/rev and 0.20mm/rev) and depth of cut equal to 0.40mm for all tests, were applied. In order to describe the complex factors that define the model, such as the friction forces, the heat transfer and the pressure due to contact between the tool and the workpiece, a number of acknowledged models were utilized. A comparison of the performance between the two types of tools was made with respect to the developed machining forces and temperature distribution on the workpiece. The findings of the investigation indicate that the specific square tools produce higher values of forces compared to the rhombic ones and approximately the same temperature patterns on the workpiece. The average increase on the produced cutting forces is about 26.4%.

Finite element modelling for orthogonal machining of AA2024-T351 alloy with an advanced fracture criterion

Numerical modelling of the plastic deformation and fracture during the high speed machining is highly challengeable. Consequently, there is a need for an advanced constitutive model and fracture criterion to make the numerical models more reliable. The aim of the present study is to extend the recent advanced static Lou-Yoon-Huh (LYH) ductile fracture creation to high strain rate and temperature applications such as machining. In the present work, the LYH static fracture creation was extended to machining conditions by introducing strain rate and temperature dependency terms. This extended LYH fracture criterion was calibrated over the wide range of stress triaxialities and different temperatures. Modified Khan- Huang-Liang (KHL) constitutive model along with the variable friction model was employed to predict the flow behaviour of work material during the machining simulation. Damage evolution method was coupled to identify the element deletion point during the machining simulation. Orthogonal machining experiments were carried out for an aerospace grade AA2024-T351 at cutting speeds varying between 100 and 400m/min with the feed rates varying between 0.1 and 0.3mm/rev. To assess the prediction capabilities of extended LYH fracture criterion numerical simulations were also carried out using Johnson-Cook (JC) fracture criterion under all experimental conditions. Specific cutting energy, chip morphology and compression ratio predictions were compared with the experimental data. Numerical predictions with coupled extended LYH criterion showed good agreement with experimental results compared to coupled JC fracture criterion.

Digital Twin–oriented real-time cutting simulation for intelligent computer numerical control machining

Digital Twin has become a frontier research topic in recent years and the important development direction of intelligent manufacturing. For numerical control machining, a Digital Twin system can be used as an intelligent monitoring and analysis center by reflecting the real machining process in a virtual environment. The machining simulation is the key technology to realize this kind of application. However, existing machining simulation systems are designed for off-line situation that cannot be used directly in Digital Twin environment. The challenges for machining simulation are analyzed and explained in this article: (1) complete process data representation in simulation system; (2) executing in cooperating with computer numerical control system; (3) more efficient simulation algorithm. In order to meet these challenges, a new machining simulation system is proposed. STEP-NC standard is used to save complete process data exported from the computer-aided manufacturing system and synchronization algorithm is developed based on the communication data of computer numerical control system. Most importantly, an optimized tri-dexel-based machining simulation algorithm is developed to perform high efficiency that can follow the real machining process. Finally, a Digital Twin system for NC machining is presented that has been tested and verified in a workshop located in COMAC (Commercial Aircraft Corporation of China Ltd).

A novel specific four-axis linkage method for processing the hourglass worm

To improve the flexibility of hourglass worm processing equipment, a specific four-axis linkage method for processing hourglass worm, which is called CZXB method, is presented in the paper. Based on the forming principle of the hourglass worm, machining principle and the traditional processing method were elaborated in detail. And then, the CZXB method that aims to apply four feed-movements linkage to simulate the conjugated rotary motions between the worm and its worm gear was proposed. According to the basic theory of rigid body kinematics, the scientific and feasibility of the CZXB method were demonstrated. Based on the computer numerical control machining simulation system, VERICUT, a virtual model of the machine tool with CZXB function, was established. A multi-thread hourglass worm was taken as an example to simulation processing by the CZXB method. Trial manufacturing was performed: tooth grooves of the hourglass worm were cut out by the traditional method, and tooth surfaces of the hourglass worm were finishing machined by the CZXB method. The result shows that machining center distance of the CZXB method is less than center distance of the worm gear pairs. Implementing the CZXB method can significantly enhance the flexibility of machining equipment of the hourglass worm.