A study on the neck-in process by flow-forming

Abstract

The neck-in process is developed to produce very small and thin cylindrical elements by flow forming machine. In this study, neck-in process is applied to the production of thin-walled combustion tube. The purpose of this study is to search for the relations among the processing parameters and find a optimal processing condition to produce precise product. For these purposes, we investigated some of the critical factors in neck-in process and processing parameters by experiment and numerical analysis. FEM analysis is carried out based on elastic-plastic work hardening model using commercially available code ABAQUS/ Standard. The results obtained from the numerical analysis and experimental data can be used to design the optimal production in neck-in process.Key word : neck-in, flow-forming, combustion tube, elastic-plastic FEM I N T R O D U C T I O NThe flow forming technique is unmached in its efficiency for the chipless production of dynamically balanced hollow precision bodies. Neck-in process by flow-forming [1] is developed to produce very small and thin cylindrical elements. In neck-in process, cylindrical workpiece which attached to rotating mandrel deformed by rollers. The deformation of workpiece can be described as reductions in outer diameter, inner diameter, and wall thickness of cylindrical workpiece. In recent days, flow forming is variously applied to the many industrial areas, such as aerospace, medical., printer, automotive and missile industry, etc.[2]The purpose of this study is to search for the critical processing parameters such as filling of tapered part, ~lection of flow forming method (backward or forward method), spring back and wrinkling or fracture possibility. Numerical analysis is carried out based on elastic-plastic work hardening model using commercially available code ABAQUS/Standard and for experiment we used CNC flow forming machine in Samsung Aerospace Industry Inc. D E S C R I P T I O N S F O R N E C K -I N PRO-CESSIn neck-in process of combustion tube, three milers are move to axial direction with a radial preset. By this axial movement cylindrical workpiece contacted with rollers and undergoes a plastic deformation. The l~lastic deformation means decrease in diameter and wall thickness and increase in axial length of workpiece.The dimensions of the workpiece are given 88 mm outer diameter, 78 mm inner diameter and 5 mm wall thickness for the actual combustion tube. After neck-in process, final shape with changed dimensions (outer dia.: 80.7 mm, inner dia.: 73 mm, wall thickness: 4.75 ram). The reduction ratio of wall thickness is 5% and calculated as following equation.reduction ration (%)t o --t -x 1 0 0 = 5 l0 Fig. 1 shows a schematic drawing for neck-in process. Fig. 1. Schematic drawing for Necking-In process.

Comparative Study on Description Schemes to Perform Finite Element Analysis in Incremental Forming Process

“…점진성형 공정을 이차원(2-Dimensional) 유한요 소해석으로 접근하기 위한 노력이 있었다 (8) . 라그랑지언 묘사기법은 소재절점이 변형할 때요 소절점이 소재절점과 같이 이동하면서 해석하는 방법이다( Fig.…”