J.L. Mo
Southwest Jiaotong University
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Featured researches published by J.L. Mo.
Tribology Transactions | 2015
J. Luo; Z.B. Cai; J.L. Mo; Jinfang Peng; M.H. Zhu
The effects of applying a bonded MoS2 solid lubricant to a 1050 steel substrate were investigated using a torsional fretting wear apparatus. Tests were conducted under a normal load of 50 N with angular displacement amplitudes ranging from 0.1 to 5°. Wear scars were examined using scanning electron microscopy, energy-dispersive X-ray spectrometry, optical microscopy, and surface profilometry. The MoS2 coating exhibited different torsional fretting regimes than those of the substrate. Fretting regimes of the coating were primarily in the partial slip regime (PSR) and the slip regime (SR) with no mixed fretting regime. The width of the PSR narrowed. Due to the lubricating effects of the coating, the friction torque was consistently lower than that of the substrate. The damage to the coating in the PSR was very slight, and its granular structure remained even after 1,000 cycles. The damage mechanism to the SR coating was a combination of abrasive wear, oxidative wear, and delamination. The MoS2 coating had potential to alleviate torsional fretting wear.
Tribology Letters | 2017
Meng Zhang; J.L. Mo; Jing Ye Xu; Xin Zhang; Dong Wei Wang; Zhong Rong Zhou
The contact characteristic between finger and objects changes due to the different deformation of a fingerprint when the finger slides in different directions. To understand this mechanism better, a new type of experimental setup was designed, and specific tests were conducted. We analyzed the regularity of the friction coefficient in two sliding directions. When the finger was sliding on surfaces with different roughness values, normal forces, and contact angles, the fingerprint deformation was captured by the Asana microscope. The following were inferred from the conducted experiments. Firstly, the friction coefficient decreases with increasing sample roughness and normal force. Secondly, the friction coefficient first decreases and then increases with increasing contact angle. Thirdly, the distance between the fingerprints increases when the finger is dragged, leading to an increase in contact area, thereby improving the friction coefficient. Finally, the result will be opposite to the previous inference when the finger is squeezed hard for fingerprinting.
Chinese Journal of Mechanical Engineering | 2016
Jun Luo; Z.B. Cai; J.L. Mo; Jinfang Peng; Minhao Zhu
Rotational fretting which exist in many engineering applications has incurred enormous economic loss. Thus, accessible methods are urgently needed to alleviate or eliminate damage by rotational fretting. Surface engineering is an effective approach that is successfully adopted to enhance the ability of components to resist the fretting damage. In this paper, using a high-velocity oxygen fuel sprayed (HVOF) technique WC-17Co coating is deposited on an LZ50 steel surface to study its properties through Vickers hardness testing, scanning electric microscope (SEM), energy dispersive X-ray spectroscopy (EDX), and X-ray diffractrometry (XRD). Rotational fretting wear tests are conducted under normal load varied from 10 N to 50 N, and angular displacement amplitudes vary from 0.125° to 1°. Wear scars are examined using SEM, EDX, optical microscopy (OM), and surface topography. The experimental results reveal that the WC-17Co coating adjusted the boundary between the partial slip regime (PSR) and the slip regime (SR) to the direction of smaller amplitude displacement. As a result, the coefficients of friction are consistently lower than the substrate’s coefficients of friction both in the PSR and SR. The damage to the coating in the PSR is very slight. In the SR, the coating exhibits higher debris removal efficiency and load-carrying capacity. The bulge is not found for the coating due to the coating’s higher hardness to restrain plastic flow. This research could provide experimental bases for promoting industrial application of WC-17Co coating in prevention of rotational fretting wear.
Key Engineering Materials | 2008
J.L. Mo; Min Hao Zhu; J. An; H. Sun; Y.X. Leng; Nan Huang
CrN coatings were deposited on cemented carbide substrates by filtered cathodic vacuum arc technique (FCVA). The effect of different deposition parameters: nitrogen partial pressure, substrate-bias voltage and preheating of the substrate, on the structural and mechanical properties of the coating was investigated. X-ray diffraction analysis was used to determine the structure and composition of the coatings. The tribological behaviour and wear properties of the coatings against Si3N4 ball at different normal loads were studied under reciprocating sliding condition. The results showed that a smooth and dense CrN coating with good properties can be obtained provided a pure Cr interlayer was pre-deposited. The optimal deposition parameters were the nitrogen partial pressure of 0.1 Pa, substrate-bias voltage of -100 V. Preheating of the substrate was no good for improving the properties of the coating. The FCVA CrN coating showed high hardness and good wear resistance, which was probably attributed to its smooth surface and dense microstructure. The wear mechanism of the CrN coating was a combination of abrasion and oxidation. However, the coating flaked off at high normal load due to the deficient adhesion strength of the coating to the substrate.
Journal of Tribology-transactions of The Asme | 2015
X.C. Wang; J.L. Mo; Huajiang Ouyang; D.W. Wang; G.X. Chen; M.H. Zhu; Zhongrong Zhou
In this work, an experimental and numerical study is performed to understand squeal generation and suppression of a pad-on-disk friction system. Several friction material specimens having various orientation degrees of grooves cut on their surfaces are tested. Numerical studies using the methods of complex eigenvalue analysis and dynamic transient analysis are conducted to simulate the experimental process with the finite element (FE) software abaqus. Both experimental and numerical results show that surface modifications of friction material specimens have a significant influence on the squeal instability: cutting a 45 deg or 90 deg groove on the material surface can significantly reduce squeal noise, cutting a 135 deg groove just reduces squeal noise moderately and cutting a 0 deg groove cannot reduce squeal noise. Moreover, the contact pressure distributions for the original surface and modified surfaces are studied to provide a physical explanation of the noise phenomenon. The major finding that friction-induced noise can be reduced by means of suitable structural modifications of the contact interface is expected to have important and much wider applications.
Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology | 2010
V Clement; J.L. Mo; M.H. Zhu; Ming-xue Shen; Z.R. Zhou
The rotational fretting of Ti6Al4V titanium alloy flat against silicon nitride (Si3N4) ceramics ball has been investigated by using a special rotational fretting wear test rig. Under various parameters of normal load and angular displacement amplitude, three fretting regimes were observed (i.e. partial slip regime, mixed fretting regime, and slip regime), corresponding to the different evolutions of the running condition at the contact interface. The micro-examination of the wear scars revealed an accumulation of plastic deformation within the centre of the wear scars in the gross slip condition. The damage mechanisms in the different fretting regimes were analysed in detail. The results showed that the mechanisms were quite different in the different fretting regimes.
Tribology Letters | 2018
D.W. Wang; J.L. Mo; Huajiang Ouyang; Z.R. Zhou
In this work, the effect of the damping component with/without individual grooved surface features on the friction-induced vibration and noise (FIVN) and surface wear performance is studied experimentally and numerically. The experimental results show that introducing a grooved damping component in the system has a significantly improved capability in suppressing the generation of FIVN. In addition, it is observed that the friction system with a grooved damping component suffers slighter wear. Numerical results show good agreement with the FIVN events observed in the experimental test. Through analysing the deformation behaviour of damping component and the contact behaviour of the friction system during friction process, it is speculated that the deformation behaviour of damping component plays a significant role in affecting the contact pressure and FIVN behaviour. In addition, linking the vibration performance and wear evolution, the connection between damping, and vibration and wear behaviour is discovered, which can further explain why the friction system with a grooved damping component shows improved capability in suppressing the FIVN of friction system.
Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology | 2018
M.Q. Liu; J.L. Mo; D.W. Wang; Jx Li; M.H. Zhu; Z.R. Zhou
This study experimentally investigated the influence of angular distribution of a grooved surface on wear properties as well as friction-induced vibration and noise characteristics. The surfaces of brake disc material were modified by cutting grooved surfaces with different angular distributions. The differences between the grooved and smooth surfaces in friction and wear and friction-induced vibration and noise were evaluated. This was performed via a pad-on-disc test configuration where the brake pad material was used as a counterface. The test results indicated that all the grooved surfaces with different angular distributions had significant potential in improving friction and wear behaviors of the contact surfaces and also in reducing the amplitudes of high-frequency vibration accelerations and noise pressure levels. Additionally, the results indicated that the ability of the grooved surfaces to suppress the generation of noise is closely related to the angular distribution of the grooves and the interference length of the grooved surfaces on the contact interface. The grooved surface allowed for entrapping and exhausting wear debris from the contact interface, which improved the wear status, and this was one of the reasons for the noise reduction of the grooved surface to a certain extent. Meanwhile, another reason was that the grooved surface interrupted the concentrated contact pressure and changed the contact pressure distribution on the leading edge of the contact surface.
Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology | 2018
B Tang; J.L. Mo; Xin Zhang; Q. Zhang; M.H. Zhu; Z.R. Zhou
In this study, a bespoke small-scale brake dynamometer was developed to simulate the braking conditions of a railway disc brake system. Braking squeal experiments were performed with this brake dynamometer at different braking pressures and disc rotation speeds, and the influence of these braking parameters on the generation and characterization of the squeal noise was evaluated and discussed. The obtained results show that both the braking pressure and the disc rotation speed have a significant influence on the generation and evolution of the squeal noise. Higher rotation speeds are found to result in higher sound pressures and more complicated squeal noise spectra, except at a particular braking pressure, for which the highest sound pressure level is found at various disc rotation speeds. This phenomenon indicates that a combination of specific braking parameters may lead to a strong instability of the brake system and consequently to squeal noise. Additionally, a possible correlation of the squeal noise characteristics with the pressure distribution at the braking interface was found and discussed.
Journal of Materials Engineering and Performance | 2018
Zongtao Zhu; J.L. Mo; D.W. Wang; Junwen Zhao; M.H. Zhu; Z.R. Zhou
In this work, the interfacial friction and wear and vibration characteristics are studied by sliding a chromium bearing steel ball (AISI 52100) over both multi-grooved and single-grooved forged steel disks (20CrMnMo) at low and high rotating speeds in order to reveal the effect mechanism of groove-textured surface on tribological behaviors. The results show that the grooves modify the contact state of the ball and the disk at the contact interface. This consequently causes variations in the normal displacement, normal force, and friction force signals. The changes in these three signals become more pronounced with increasing groove width at a low speed. The collision behavior between the ball and the groove increase the amplitude of vibration acceleration at a high speed. The test results suggest that grooves with appropriate widths could trap wear debris on the ball surface while avoiding a strong collision between the disk and the ball, resulting in an improvement in the wear states.