Failure analysis of tower axle in the wet drawing machine

Investigation methods 
The samples were cut in which tower axle fractured. Surface morphology of macro fracture was 
observed. Fracture was analyzed by scanning electron microscope of Zeiss EVO 18. The 
microstructure and nonmetallic inclusions were analyzed. The hardness of the subcenter of 
specimen was measured by using Brinell hardness tester. Micro-elements were analyzed by EDS. In 
addition, organizational performance and inclusions axle of 40Cr were compared and analyzed 
before and after heat treatment. 
 
Applied Mechanics and Materials
Online: 2013-09-03
ISSN: 1662-7482, Vols. 395-396, pp 782-786
doi:10.4028/www.scientific.net/AMM.395-396.782
© 2013 Trans Tech Publications, Switzerland
All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of Trans
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Observation results and analysis 
The location and macroscopic morphology of the fracture
The location of fracture in the tower axle is shown in Fig.1. It is in the variable cross-section 
between 65 mm and 70 mm in diameter. The macro-topography of fracture is shown in Fig.2. We 
can clearly distinguish the source of crack, crack spreading area and transient breaking area from 
the figure. As shown in Fig. 2, fracture in the axle began form surface according to radioactive line 
direction on surface crack of the fracture. We can see the steps fracture in the source parts of crack. 
The surface of fracture is dim, and there are many pollutants. It turns out that the crack has been 
formed for a long time, and crack radiations gather here.
It turns out that this part is starting point of 
crack and the location of crack source. The edge of fracture source area has obvious squeeze traces. 
Crack growth areas are relatively flat, pale, and have no apparent edge. Transient fault areas have 
obvious tearing ridge [2]. 
Combined with the actual working condition, it easily occurs alternating torsional stress when 
the wire drawing machine starts, stops, and occurs torque fluctuation. It has the condition of fatigue 
stress. Fracture surface is smooth, and there is unobvious plastic deformation. In general, tower axle 
fracture can be initially determined for brittle fracture. 
Fig. 1 Schematic of tower axle and situation of fracture Fig. 2 Macro-morphology of the fracture
axle 
Scanning electron microscopy (SEM) analysis of fracture 
The microstructure observation by scanning electron microscopy (SEM) is shown in Fig.3. Edge 
smooth surface of fracture source area and visible extrusion morphology are shown in Fig.3 (a). It 
suggests that they are the original defects. Crack extension since the fracture edge smooth area is 
shown in Fig.3 (b). The microstructure observation on extension area is shown in Fig.3 (c). In 
addition, the characteristic of brittle fracture is obvious [3]. It is conformed that the tower axle 
fracture belongs to brittle fracture.