Understanding Torque-End Forming Signatures of Brake Lines Brake lines are used in hydraulic brake systems that are connected to many different components. These components need to work properly with each other in order to provide a safe braking. Brake lines are provided the transmission of the brake fluid between several components of the brake system such as hydraulic unit, master cylinder and other brake fitting connections. As a way to change the shape of tube ends; end forming is an extremely important part of brake line assemblies. End forming are used to connect the end of brake lines to mating parts on various components of the brake system. Usually one or both tube end can be formed to mate to another part. The mating part might be another tube, a small component such as drum (wheel cylinder), or a large component such as a master cylinder. The geometry of end formings and mating parts depends on the assemblies between various brake components according to engineering specifications. While end formings have been using for several years in automotive industry, the leakage that can be observed in the connection points continue to be a problem for OEMs and suppliers. OEMs are consumed time, money and energy to detect and correct the leakage problems before releasing vehicles from the production plant. Thus, tightening the brake tube joint properly is significant point in the first time vehicle assembly. The most popular method of tightening a threaded fastener is by applying a specific tightening torque. The relationship between the tightening torque and end forming of the brake tube provided by the fastener, is a function of it is geometry that contains end forming and mating part face dimensions. The use of female end forming-female nut to male end forming-male nut is common joint method in conventional brake lines. However, the risk of casued leakage problem might be higher in this type of connection method after assembling by OEMs. In order to eliminate leakage problem, OEMs tend to use for female end forming-male nut and union connector instead of tube to tube connection. This study researches observed features in leaking and non-leaking parts, current specifications for brake tube joints and obvious relationships both of them. Also, differences and effects between conventional method that consists of female end forming-female nut and new trend that uses female end forming-male nut are analyzed. In addition, parts of the relationship between brake tube joint components and how this relationship change as different combinations of brake tube end forming dimensions is examined.

Mr. Kerim Önder, R&D Engineer, Bantboru; Mrs. Kezban Duran Özer, R&D Engineer, Bantboru