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Fretting Wear Behaviors of Hoisting Rope Wires in Acid Medium

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Fretting Wear Behaviors of Hoisting Rope Wires in Acid Medium Materials and Design 55 (2014) 50–57 Contents lists available at ScienceDirect Materials and Design journal homepage: www.elsevier.com/locate/matdes Technical Report Fretting wear behaviors of hoisting rope wires in acid medium ⇑ Linmin Xu a,b, Dekun Zhang b, , Yan Yin b, Songquan Wang a, Dagang Wang a a School of Mechatronic Engineering, China University of Mining & Technology, Xuzhou 221116, China b School of Materials Science and Engineering, China University of Mining & Technology, Xuzhou 221116, China article info abstract Article history: The fretting wear behaviors of hoisting rope wires in acid medium were investigated in this paper. Fret- Received 11 July 2013 ting wear tests of steel wires were conducted on a self-made fretting wear rig, and their fretting running Accepted 18 September 2013 characteristics, coefficient of friction, dissipated energy and wear morphology were analyzed. The results Available online 27 September 2013 show that the relative sliding between steel wires can be promoted in the acid medium. As the contact load increases, the fretting of steel wires changes from a slip regime to a mixed one, and the coefficient of friction decreases significantly. Moreover, the coefficient of friction changes from about 1.2 in the dry friction environment to about 0.5 in the acid medium. Energy loss presents the same variation trend. Wear scar depth is larger in the acid medium than in the dry friction environment. The primary wear mechanism in the dry friction environment is peeling as compared to peeling, particle attrition and cor- rosion in the acid medium. Ó 2013 Elsevier Ltd. All rights reserved. 1. Introduction tic deformation, wear and cracking due to fretting. Perier et al. [16] studied fretting wear behavior of wire rope in sodium chloride Wire rope is an important bearing component in mine hoisting solutions and pointed out that the lubrication and galvanized layer systems. Fretting wear and fretting corrosion usually occur be- can effectively reduce corrosion and fretting fatigue caused by the tween the contacting wires of the steel wire rope. It is subjected sodium chloride solution. Ding and Dai [17] studied fretting wear to repeated stretching and bending, which results in fretting wear characteristics of a titanium alloy in seawater and analyzed the im- of the steel wires under different displacements amplitude and pact of sea water on the coefficient of friction and wear. As men- loads [1,2]. Moreover, the humid and oxygen-rich working envi- tioned above, most studies are concentrated on the fretting wear ronment of the wires can cause corrosion. Therefore, the fretting of materials under dry friction and marine environments, few of wear behavior of steel wires will change somewhat in corrosive them have been focused on fretting wear behaviors of wire rope environments [3,4]. According to the published statistics [5,6], in acid medium. According to the literature [18], acid rain is a prob- the failure proportion among scrapped wires caused by corrosion lem in South China and this may be a problem for steel wires in is about 70–80%. Therefore, to prolong the service life of the wire this area. The wire damage caused by the interaction between rope, it is necessary to study the fretting wear behavior of steel the acid medium and fretting wear is far greater than that caused wires under corrosive conditions. by simple corrosion and fretting wear. Therefore, the objective of Zhang [7–10] and others mainly studied the fretting wear this paper is to explore the fretting properties and damage mech- mechanism of hoisting rope between steel wires and fatigue failure anisms of steel wires in acid medium. behavior under dry friction and alkaline corrosive environments. Li [11] studied the fretting corrosion characteristics of the Zr-4 alloy 2. Experimental details in Na2SO4 solution. Han et al. [12] studied the fretting behavior of self-piercing riveted aluminum alloy joints under different interfa- Fig. 1 is a self-made fretting corrosion test rig. This rig consists cial conditions. Ramesh and Gnanamoorthy [13] found that the of a driving device, movement device, load-measuring device and fretting wear damage was frequently reported in the races of roll- lifting platform. The upper wire specimen was installed in the ing element bearings and leaded to the increased noise and vibra- force-measuring device and the lower one was fixed on the speci- tion in the total machinery. Zhou et al. [14,15] studied fretting men slider. The slide moves left/right due to the screw rotation wear and fretting fatigue performance of a single aluminum wire that is driven by the step motor, and this achieves the relative hor- and found that the cable fatigue failure was mainly caused by plas- izontal position adjustment of both the upper and lower wire spec- imens. The loading device moves under the action of the step ⇑ Corresponding author. Tel.: +86 13952207958. motor and which results in the movement of the horizontal posi- E-mail address: [email protected] (D. Zhang). tion adjustment device and force-measuring device. When the con- 0261-3069/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.matdes.2013.09.046 L. Xu et al. / Materials and Design 55 (2014) 50–57 51 tact load between the upper and lower wire specimens reach the when Fn = 10 N and 15 N, all Ft–D curves in the fretting process present value, the step motor rotates and the eccentric derive de- are irregular parallelograms, which apparently illustrates the rela- vice moves. The displacement amplitude was maintained at a va- tive slip between the friction pairs and the slip regime. As the con- lue proportional to the eccentricity of the driving wheel. tact load exceeds 15 N, the Ft–D curves become perfect A typical steel wire based on the request of GB/T8918-2006 [19] parallelograms during the early period (about 100 cycles), which was used in this paper. Fretting wear tests of perpendicular steel represents complete slipping of the contacting wires. With the in- wires in corrosive environments were performed on the self-made crease of the fretting cycles, the Ft–D curve shifts to an elliptical fretting wear rig. Hoisting rope is made of high-quality carbon shape, indicating that the contact interface experiences significant structural steel, of which the components (in wt.%) are 0.84% C, plastic deformation and a mixed regime. However, in the acid med- 94.62% Fe, 4.53% Zn and its allowances are S and P. The hardness ium, the Ft–D curves are parallelograms for the entire testing pro- and tensile strength are 365 HV0.1 and 1600 MPa, respectively. cess, regardless of the load. This illustrates the slip state and slip The main test parameters are as follows: Displacement amplitude regime between contacting wires. The friction force increases with of ±150 lm, contact force of 10–30 N, frequency of 1.2 Hz, fretting the increase of the number of fretting cycles according to all the cycles ranging from 1 to 1 Â 104 and room temperature. The coal figures. mine water in South China was tested and the pH value of the acid The fretting running regimes of steel wires under different con- medium was about 2.97. The friction forces were recorded during tact loads in dry friction and acid medium are shown in Table 1.As the experiment. According to the friction (Ft) – displacement (D)– the contact load increases, the running regime of wires changes cycle (N) curve, the fretting running regional characteristics of steel from a slip regime to a mixed one, which reveals that shear stress wire and the final average coefficient of friction could be obtained. of the friction pair surface increases with the increase of the load In addition, the effect of acid medium on the fretting wear of steel and that the plastic deformation occurs on the contact interface. wire was analyzed. The impact of the acidic medium on the fretting However, in the dry friction environment, the wire fretting regime wear behavior of the steel wire was analyzed. starts to shift into the mixed regime slip regime at Fn = 20 N, while After each test, the length and width of the wire abrasion gap the fretting operates in the slip regime in the acid medium. This were measured using an optical microscope with video imaging shows that the acid medium significantly alters the fretting regime device, and the maximum wear depth of the gap was calculated of steel wires and forces the fretting regime into a full slip state un- according to the following formula [20]: der smaller loads than in the dry friction environment; this illus- rffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi trates that the lubrication of the acidic medium allows the a 2 h ¼ R À R2 À max ð1Þ relative sliding of contact steel wires to occur more easily. max 2 3.2. Coefficient of friction where R is the radius of the wire and amax is the maximum width of the fretting wear scar. An optical microscope and scanning electron Variation of the coefficient of friction vs. fretting cycles in dry microscope were used to observe the sample morphology of the friction environment and acid medium under different loads is wear scar. shown in Fig. 3. Under dry friction conditions, the curve is very low and stable at the beginning of the friction test (a few to hun- 3. Results and discussion dreds of cycles), namely, the running-in period of friction test. This is due to the oxide film and membrane fouling of the steel surface. 3.1. Analysis of wire fretting running characteristics The surface film was destroyed with the relative movement be- tween the friction pair.
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