外文翻譯--仿形線圈造成的發(fā)動(dòng)機(jī)連桿螺栓疲勞（英文）

1、Fatigue in engine connecting rod bolt due to forming lapsS. Griza *, F. Bertoni, G. Zanon, A. Reguly, T.R. StrohaeckerDepartamento de Metalurgia, Universidade Federal do Rio Grande do Sul, Av. Osvaldo Aranha, 99/610, Por

2、to Alegre 90035 190, Brazila r t i c l e i n f oArticle history:Received 30 September 2008Accepted 18 October 2008Available online 25 October 2008Keywords:Connecting rod boltFatigueFailure analysisDesignForming lapsa b s

3、 t r a c tAn analysis was performed to asses the failure root cause of an automotive diesel enginewhich experienced collapse only 6 month after revision. The connecting rod bolts torquedisassembly was monitored and fract

4、ured parts were selected to laboratory fracture anal-ysis. It was verified with fatigue rupture of one of the fourth connecting rod bolt. Tensiletests were performed in four of the remaining connecting rod bolts. During

5、this procedure,it was verified another bolt with fatigue crack propagation an indication that the first fati-gued bolt did not have suffer torque relaxation. A finite element analysis was performed inconnection with an a

6、nalytical fracture mechanics approach aiming to evaluate the relationbetween tightening force and fatigue crack propagation in connecting rod bolts. The enginecollapse occurred due to forming laps in the grooves of the b

7、olt shank. Finally, some designimprovements were suggested for avoid future failures: a gap in the groove length at theconnecting rod cap interface, enough to avoid combination of forming laps and higherstress amplitude;

8、 increase of the bolt torque assembly to reduce stress amplitude.? 2008 Elsevier Ltd. All rights reserved.1. IntroductionFailure of bolts can result in catastrophic events in an overall complex system [1]. Despite the wi

9、de understanding regard- ing bolt mechanics, cases of failure are still reported. The most common factors which contribute to failure are low tighten- ing force, design defects specially concerning thread root radius, ma

10、terial or fabrication defects which can be achieved in material selection, heat or mechanical treatment [2–6]. In this paper, a failure analysis was performed in a 6.6 automotive diesel engine which experienced collapse

11、in service only 6 months after revision. It was reported that at the time of revision, the engine was opened and some parts such as seals, bushings and connecting rod bolts were replaced. The failure analysis methodology

12、 was evaluated, based on the experimental sequence suggested by the ASM [7]. For this analysis the engine dis- assembly was performed and preliminary visual analysis of damaged parts was conducted to select the fractured

13、 parts that could be the failure root cause. Laboratory fracture analysis, mechanical tests, metallographic analysis and numerical mod- eling with an analytical fracture mechanics approach were performed.2. Materials and

14、 methods2.1. Disassembly of the engineThe first observation showed fracture of the engine block, due to impact of the fourth connecting rod, whose cap was dis- assembled as a result of bolts failure. The engine head was

15、then disassembled showing camshaft fracture in three parts and some other resulting damages such as: piston marks due to valve contact, secondary cracks in the fourth piston, as well as1350-6307/$ - see front matter ? 20

16、08 Elsevier Ltd. All rights reserved.doi:10.1016/j.engfailanal.2008.10.002* Corresponding author. Tel.: +55 51 3308 4251; fax: +55 51 3308 3565.E-mail address: sandro@demet.ufrgs.br (S. Griza).Engineering Failure Analysi

17、s 16 (2009) 1542–1548Contents lists available at ScienceDirectEngineering Failure Analysisjournal homepage: www.elsevier.com/locate/engfailanaltightening. As a second step, external loads of 15, 30 and 60 kN were applied

18、 in the axis of symmetry, normal to the shell, in order to separate the cap of the connecting rod. This procedure increases the stress level at the bolt. The difference between stresses due to second and first steps resu

19、lts in the stress amplitude imposed to the bolt.2.4. Fracture mechanics analysisFor the connecting rod bolt stress intensity factor calculation, it was adopted the procedure described in the standard BS 7910:2000 [10]. T

20、he section M.6.2 of the standard is dedicated to geometric factor for cylindrical bars with semi-elliptic cracks and direction of propagation perpendicular to the axis. The stress intensity factor (KI) is related to crac

21、k length (a), stress amplitude (r) and geometrical factor (Y) according to Eq. (2). The geometrical factor (Y), was obtained from Eq. (3), the stress intensity magnification factor (Mn) was calculated from Eq. (4), while

22、 the geometrical factor (g) was taken from Eq. (5). These equations are valid for (a/2r) < 0.6, where (r) is the radius of the cylindrical bar.Fig. 2. Connecting rod–bolt assembly, boundary conditions and net generate

23、d.Table 1Net characteristics of four parts of the model.Part No of elements No of nodes Element typeBolt 3672 5044 Linear hexaedricConnecting rod cap 50,698 10,217 Linear tetraedricConnecting rod body 25,305 5239 Linear

24、tetraedricRigid shell 713 768 Linear quadractic rigidTable 2Tightening force simulated and the respective interferences.Model Thightening force (kN) Interference (mm)1 30 0.092 50 0.153 100 0.301544 S. Griza et al. / Eng