شبیه‌سازی شکست مخازن CNGفولادی در پدیده ضربه با رهیافت مکانیک آسیب

نوع مقاله: مقاله پژوهشی

نویسندگان

1 دانشکده مهندسی مکانیک، دانشگاه صنعتی اصفهان

2 دانشکده مهندسی مکانیک، دانشگاه صنعتی شریف

چکیده

هزینه بالا و پرخطربودن آزمایش‌های تجربی استفاده از روش‌های عددی را روی مخازن گاز طبیعی فشرده اجتناب‌ناپذیر ساخته است. در مقاله حاضر با رهیافت مکانیک آسیب به بررسی اثر تصادم و آسیب ناشی از برخورد مخازن CNG فولادی تحت فشار پرداخته شده است. معیار شناسایی آسیب و قابلیت به کارگیری مجدد مخزن پس از برخورد، مطابق استاندارد سازمان توسعه استاندارد کانادا و ایالات متحده در مخازن CNG می‌باشد. شبیه‌سازی صدمات وارد بر مخزن در تصادف و سقوط خودرو با به کارگیری مدل آسیب جانسون و کوک صورت گرفته است. محاسبات در جهت‌های مختلف برخورد و با در نظر گرفتن تأثیر فشار داخل مخزن، سرعت تصادم و ارتفاع سقوط انجام شده است. انباشتگی آسیب ناشی از برخورد برای حالت‌های مختلف به‌دست آمده است. تحلیل‌های عددی انجام گرفته در مقاله برای حالت‌های مختلف برخورد شامل سقوط و تصادف نشان می‌دهد بیشترین آسیب در حالت برخورد عمودی ایجاد می‌شود و با تغییر زاویه برخورد از امتداد عمودی به افقی، آسیب وارده به مخزن کمتر خواهد بود.
 

کلیدواژه‌ها


عنوان مقاله [English]

Simulation of All-steel CNG Cylinders Fracture in an Impact by Damage Mechanic Approach

نویسندگان [English]

  • Mohammad Yazdani Ariatapeh 1
  • Mohsen Azadi 2
  • Mohammad Mashayekhi 1
  • Saeid Ziaei Rad 1
1 School of Mechanical Engineering, Isfahan University of Technology, Isfahan
2 School of Mechanical Engineering, Sharif University of Technology
چکیده [English]

The high cost and risk of empirical tests on CNG cylinders make the use of numerical methods inevitable. In this paper, damage mechanics approach is used to investigate the effect of crash and damage caused by impact in CNG all-steel cylinders. The CSA standard in CNG cylinders is used as a damage detection criterion and cylinder ability to reuse. The simulation of cylinder failures caused by collision and drop is done by using Johnson-Cook damage model which is one of the efficient models in impact problems. Accomplished simulations are carried out in different impact directions, and the effects of cylinder internal pressure, collision velocity, and fall height are analyzed. Also, failures due to collision for various situations are discussed. These investigations for different cases, including crash and drop tests show that the maximum damage created in case of vertical impact and the resultant damage by changing direction from vertical to horizontal will be decreased. Furthermore, by eliminating failed elements and comparing damage depth caused by collision with CSA standard, it is observed that, in most cases of vertical accident and drop tests, the cylinders have been damaged and lost their ability to be used, while in horizontal impact cases the cylinders are intact or can be reused after repairing. The results show that, in collision process, the cylinder rear wall and the front hemisphere of the cylinder have further damaged and are the critical areas in the horizontal and vertical collisions respectively. For a specific impact direction in lower cylinder internal pressure, the damage caused by higher collision velocity and a higher altitude of falling will be more serious. The resulted diagrams indicate that the damaged area of the cylinders predominately are under compression and endure large plastic deformation. The low difference between the results by various meshes shows that this solution does not depend on the mesh size. Therefore, this damage model is insensitive to meshing in the various impact cases.

کلیدواژه‌ها [English]

  • All-steel CNG cylinder
  • Damage Mechanics
  • Fracture
  • Impact
  • Finite Element Method
[1]. Trudgeon M., An overview of NGV cylinder safety standards, Production and In-Service Requirements, 2005.

[2]. Chamberlain S. S., Development of a physics of failure model and quantitative assessment of the fire fatality

risk of compressed natural gas bus cylinders, PhD Thesis, Mechanical Engineering Department, University of

Maryland, 2004.

[3]. Becker D. L., Burgess D. M. and Lindquist M. R., “Drop testing conducted to benchmark the shipping port

reactor pressure vessel package safety analysis”, Nuclear Engineering and Design, Vol. 130, pp. 133-145, 1991.

[4]. Rosenberg Z., Mironi J., Cohen A. and Levy P., “On the catastrophic failure of high-pressure vessels by projectile

impact”, Int. J. Impact Engineering, Vol. 15, pp. 827-831, 1994.

[5]. Teng X. and Wierzbicki T., “Evaluation of six fracture models in high velocity perforation”, Engineering Fracture

Mechanics, Vol. 73, pp. 1653–1678, 2006.

[6]. Teng X. High velocity impact fracture, PhD thesis, Massachusetts Institute of Technology, 2004.

[7]. Johnson G. R. and Cook W. H. “A constitutive model and data for metals subjected to large strains, high strain

rates and high temperatures”, in: Proceedings of the seventh international symposium on ballistics. Hague, Netherlands,

pp. 541–47, 1983.

[8]. Johnson G. R. and Cook W. H., “Fracture characteristics of three metals subjected to various strains, strain

rates, temperatures and pressures”, Engineering Fracture Mechanics, Vol. 21, No. 1, pp. 31–48, 1985.

[9]. CSA America Inc., “CNG fuel system inspector study guide”, National Energy Technology Laboratory, U. S.

Department of Energy, DE-FC26-05NT42608, pp. 27-32, 2008.