www.bewet.fora.pl

loczytzn

6106 Failure Analysis of Diesel Engine Exhaust Valve

ooveoninitiationzoneof0sample macro fracture morphology of samples Figure 122 Figure 141 samples Fig12Fracturemacrographof2sample macro fracture morphology of Fig. Failure Analysis 14Fracturemacrographof1sample3 exhaust valve exhaust valve according to the general stress field ..., at the bottom (Figure 8, D,) compressive stress in the ACB of the neck region to form tensile stress field,[link widoczny dla zalogowanych], usually the highest C,[link widoczny dla zalogowanych],, A second area , B District, the minimum, which depends on tensile stress on the valve seat of the seated valve size and valve and valve seat force the actual degree of eccentricity. D, is the first hot spot, maximum temperature, B is the second hot zone, followed by C,[link widoczny dla zalogowanych], and A, ¨ J. O-like and 2-like \by high-frequency 3-way pull the world a long, Desks, Zhengdong, etc.: 6106 Failure analysis of diesel engine exhaust valve 37, a zero effect of alternating stress, this stress condition and Figure 9, Figure 12, the fatigue striations on the fracture development is consistent. Source found in the fracture surface of a cylindrical groove, is the micro-cracks from the micro view, it. Fracture surface similarities (Figure 10, Figure 13), suggesting that the crack initiation fracture neck of the exhaust valve rod in the cylindrical surface of the trench, the trench was the result of machining and grinding marks towel during The wear scar formed. Also observed in the fracture to the source has been corrupted on the fracture surface (Figure 11,13), can be inferred exhaust valve operation at high temperatures, fatigue by the tensile stress, the stress concentration at the groove, the groove itself is a micro-crack , together with the superposition effect of corrosive gas, and an extension of the crack instability, later in the alternating stress and corrosion cracking under the combined effect of continued expansion of the internal, from the fracture extended to the area to see about 3 / 5 4 / 5 occurred tear (pull off), resulting in the rupture valve, the occurrence of \Hit the cylinder caused the accident. A kind of \Truck runs 82,000 km, press the 60km / h rate, the exhaust valve and valve seat contact number reached 1 × 10 times. With the high temperature bending fatigue strength decreased with the increasing number of cycles, therefore, run 40,000 km ~ 82,000 km when the strength of the material yield strength can not be used to assess,[link widoczny dla zalogowanych], according to fracture observed (Figure 14,15) concluded that the ditch slot by the stress concentration and corrosion fatigue stress,[link widoczny dla zalogowanych], the grooves (cracks) instability of the expansion, development speed, and fatigue striations was the latter part of the fracture, at about 4 / 5 after tearing an area that \block out \Valve disc surface parallel to the fracture of a basic number of cracks indicate that the strength of the material is low enough to resist stress and fatigue cracks in the valve disk surface corrosion pits, indicating the contribution of corrosion on crack. Comprehensive analysis of a BU, we believe that the valve plate fracture occurred mainly due to high temperature strength of steel 21_4N already in critical state, at high alternating stress with defects and corrosion under the common cause failure, need to switch to better performance high material instead. Recommended 21 ~ NWNb valve steel, the use of good results. 4 Conclusion (1) 0 2-like samples and the risk of neck fracture caused by exhaust valve \The instability of the expansion of micro-cracks. (2) 1 disc-like occurrence of the Ministry of Local exhaust valve rupture caused by \Groove in the interaction of stress and corrosion and expansion of the micro-crack instability, resulting in fracture, need to use high-temperature properties of materials substitution 21-4N [1] Mao Jingjie. 12180Z diesel engine valve of [A]. National Rail Diesel Engine Technology Symposium timber [C], Qingdao :1985:185-192. [2] Wang Rongsheng. Material of internal combustion engine valve diesel engine [J]. Communication ,1994,4:16-34 rolling stock. [3J Wencheng. High-power diesel engine exhaust valve and the valve surface Cracks propagation mechanism [J], physical and chemical testing (physical volumes), 1984,20 (1) :41-45. What the G has G8G8GG8G8G Yap Yap G0G G8G Tun Tun G0G G

相关的主题文章：

[link widoczny dla zalogowanych]

[link widoczny dla zalogowanych]

[link widoczny dla zalogowanych]