# Analysis of Sheet Metal Tapping Screw Fabrication Using a Finite Element Method
## 3 Research Methodology  
Thread rolling was simulated with the following objectives in this study.  
1. To predict the required forming load to support the design or selection of proper dies and thread rolling machines.
2. To model material flow (stress, strain, and velocity field) to evaluate thread plate design and material selection.
3. To determine simulation parameters to further thread plate design.  
The mechanical properties of materials must be analyzed, such as by analyzing cylindrical test results for flow stress, before a flat-die thread rolling simulation can be performed. In the experiment herein, the material AISI (American Iron and Steel Institute) 1022 is firstly cut as is a hex nut to form the test cylindrical sample; the external diameter to length ratio is 1:1.5; the external diameter of the completed cylindrical sample is 3.7 mm, and its height is 5.55 mm. A universal testing machine with 20 tons of pressure is used to perform the compression test; the cylindrical sample is coated with lubricant (MoS2) before compression so the material is tested under conditions close to those of an actual production line.  
After 30%, 60%, 75%, and 90% compression of the cylindrical sample, as shown in Figure 5, the computer automatically records the cold forging load, compressing step, and the deformation time. These data are further calculated and organized with Excel and curve fitting, and the true stress-strain equation is found to be \(\sigma=625.16\varepsilon^{016}\) (Figure 6), where the constant 625.16 is the strength coefficient and 0.16 is the hardening index. The higher R-squared 0.9723, in this study, means the better the model fits the experiments data.  
Figure 7 displays the research process. The computer-aided design software SolidWorks was utilized to depict the produced thread rolling plate and to transform it into an STL file for simulation using DEFORM finite element forming analysis software. Table 1 presents the relevant analytic settings. The sheet metal forming process is not easily analyzed and simulated because the fixed thread plate and the sliding thread plate are more complicated than mechanical threads. In the simulation process, the fixed flat die is fixed in all the directions. The moving flat undergoes reciprocation with the workpiece (blank) between them, and shifts towards a fixed direction shown in Figure 3.  
Figure 5: Compression experiment and compressed cylindrical samples at 30%, 60%, 75%, and 90%.  
Figure 6: True Stress versus true strain for AISI 1022 (\(h_{i}\) is initial height of compressed cylindrical sample, and \(d_{i}\) is diameter).  
Figure 7: Research flow chart.  
In the above analytical process, thread rolling, but not the thermal conduction mode, is taken into account in the preprocessing simulation environment of DEFORM. The blank is a plastic body; the rest of the die is a rigid body, and the planned conditions conform as much as possible to those of real thread rolling in the forming process. In this study, the forming temperature is assumed to be room temperature; temperature variations that arise from plastic deformation of formed pieces during cold forming is small, and the local effects of temperature are therefore ignored. Field observations revealed that four major factors affect the quality of thread rolling and the service life of the thread plates; they are constant shear friction, thread rolling compression (screw thread plate gap), material flow stress (true stress-strain relation), and geometry of the screw thread plate.