Short communication Influence of surface roughness on leakage of new metal gasket Shigeyuki Haruyama a , Didik Nurhadiyanto b, c, * , Moch Agus Choiron d , Ken Kaminishi a a Graduate School of Innovation and Technology Management, Yamaguchi University, Ube, Japan b Department of Mechanical Engineering, Yamaguchi University, Japan c Mechanical Education Engineering Department, Yogyakarta State University, Indonesia d Mechanical Engineering Department, Brawijaya University, Indonesia article info Article history: Received 30 December 2012 Received in revised form 12 June 2013 Accepted 21 June 2013 Keywords: Surface roughness Flange Metal gasket Minimize Leakage abstract Previous studies of new metal gaskets have established that the contact width, contact stress, and simulation process are important design parameters for optimizing the metal gasket performance. Op- timum designs are thus realized based on the elastic and plastic contact stress. However, the influence of the flange surface roughness has not been investigated thoroughly. In this study, we developed a gasket model that includes the flange surface roughness effect. A flange can have different surface roughness levels. A finite element method was employed to develop the simulation solution. The contact width, contact stress, and force per unit length for gasket in contact with a flange having different surface roughness levels were obtained through the simulation. The leakage performance improved with an increase in the contact width and contact stress. The slope of the force per unit length increased with a decrease in the surface roughness level. Furthermore, the slope of the force per unit length for a gasket in 400-MPa mode was higher than that for one in 0-MPa mode. The higher slope suggests that the gasket and flange are pressed together strongly. Finally, the helium leakage quantity was determined to evaluate the leakage performance. The experimental result shows that the gasket in 400-MPa mode shows better sealing performance than the gasket in 0-MPa mode. For a low axial force, changes in the surface roughness caused significant changes in the leakage; the same was not observed for a high axial force. Ó 2013 Elsevier Ltd. All rights reserved. 1. Introduction A new 25A-size metal gasket made of an asbestos substitute was developed. The main advantage of this gasket was that it had a corrugated shape, with a small contact area, that was suitable for realizing low loading; furthermore, the metal spring effect pro- duced a high local contact stress that created a sealing line with the flange [1]. The contact stress and contact width were consider important design parameters for optimizing the gasket perfor- mance. However, the value of the contact width as design has not yet been defined. Haruyama et al. investigated the allowable limits of the contact width [2]. A contact width for which no leakage occurs in the newly developed gasket was determined by comparing the evaluation results of the relationship between the clamping load of the flange and the contact width as obtained using FEM analysis with the experimental results of the clamping load and the leakage. These results were used to obtain the optimum contact width. The contact width shows a relationship with helium leakage; increasing the contact width results in a decrease the leakage. Choiron et al. [3] studied a method for validating the contact width measurement by using a simulation-based analysis. They compared the simulation result with experimental one ob- tained using pressure-sensitive paper and found good agreement between the two. Persson et al. [4] studied the contact stress dis- tribution. They compared the contact stress distribution result obtained using an analytical model with the (exact) numerical result obtained for contact between a cylinder and a nominal flat substrate with surface roughness having many different length scales and found good agreement between the two. Specially, the theory predicted that the area of contact in most cases varies lin- early with the load and that it depends on the magnification; both predictions showed excellent agreement with the (exact) numeri- cal results. Nurhadiyanto et al. [5] studied the optimization of gasket design based on an elastic and plastic contact stress analysis by considering the forming effect using FEM. A helium leakage test showed that a gasket based on plastic contact stress design was superior to one based on elastic contact stress design. Nonetheless, * Corresponding author. Mechanical Education Engineering Department, Yogya- karta State University, Indonesia. E-mail addresses: haruyama@yamaguchi-u.ac.jp (S. Haruyama), r502wc@ yamaguchi-u.ac.jp (D. Nurhadiyanto), agus_choiron@ub.ac.id (M.A. Choiron), kaminisi@yamaguchi-u.ac.jp (K. Kaminishi). Contents lists available at SciVerse ScienceDirect International Journal of Pressure Vessels and Piping journal homepage: www.elsevier.com/locate/ijpvp 0308-0161/$ e see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.ijpvp.2013.06.004 International Journal of Pressure Vessels and Piping 111-112 (2013) 146e154