Failure Analysis of Torsion Bar of Projectile Weaving Machine
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CASE HISTORY—PEER-REVIEWED
Failure Analysis of Torsion Bar of Projectile Weaving Machine Tezcan Sekercioglu
Submitted: 24 January 2010 / in revised form: 28 May 2010 / Published online: 15 June 2010 The Author(s) 2010. This article is published with open access at Springerlink.com
Abstract Torsion bars are some of the most important elements used in projectile weaving machines. In this study, the fracture of a torsion bar for weaving machine produced from spring steel is investigated. Specimens prepared from the damaged torsion bars were subjected to visual inspection, hardness testing, chemical analysis, and metallurgical evaluations. The failed torsion bars had been fabricated from spring steel, and the calculated stress on the bars suggested that the steel did not have sufficient torsional strength. Examination of fractured parts showed that all fractures started at a shoulder radius due to high stress concentrations. Keywords Fatigue
Failure analysis Torsional fracture
Introduction Projectile weaving machines use a projectile equipped with a gripper to insert the filling yarn across the machine. The unique principle of projectile filling insertion allows the insertion of practically any yarn such as cotton, wool, and polypropylene ribbon into the cloth being produced. The torsion bar is one of the most important elements of the projectile weaving machines. A torsion bar system is used for picking and transfers strain energy to the projectile before it separates from the picker shoe. The torsion bar can be adjusted to deliver the energy required to propel the projectile through the guide teeth to the shuttle brake [1, 2]. T. Sekercioglu (&) Mechanical Engineering Department, Engineering Faculty, Pamukkale University, Kinikli 20070, Denizli, Turkey e-mail: [email protected]
The torsion bar mechanism is shown in Fig. 1. Before picking, the torsion bar (9) is twisted via the cam (8), roller lever (6), and picking shaft (10) until the knee joint (5) tilts slightly beyond dead point. The front end of the torsion bar fits in the picking shaft, which is clamped on the picking lever (11) so that it performs the rotary movement of the picking shaft and torsion bar. When the projectile (2) is ready for picking, the rollers (12) to the left and right of the cam run up on to the ribs of the roller lever and cause the knee joint to yield. After picking, the picking lever jerks forward quickly, accelerating the projectile through the picking shoe (1). The unloading movement of the torsion bar is cushioned by an oil brake (7) [2]. The investigated failed bars are made of spring steel. The spring steel (50CrV4, EN10132-4) is a heat-treatable alloy material. Two bars are damaged virtually every month in textile factory and the damage and resulting machine downtime resulted in significant loss of production. Therefore, the damaged torsion bars were evaluated and the cause of fracture of a bar manufactured was determined. The main dimensions of the torsion bars are shown in Fig. 2. A number of mechanical and microstruc
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