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To investigate the effects of conventional shot peening and micro-particle shot peening on the surface properties of 42CrMo steel，ABAQUS software was employed to identify the primary and secondary influencing factors of these two processes on material surface roughness and the depth of the residual stress layer through orthogonal experiments.Based on the analysis results of the orthogonal experiments，practical experiments were conducted for validation.Considering the characteristics of micro-particle shot peening and conventional shot peening，a single-factor study of the shot peening coverage rate was carried out to examine the impact of these two processes on the residual stress，surface roughness and equivalent plastic strain of 42CrMo steel.Results showed that under the same coverage rate condition，micro-particle shot peening yielded higher residual compressive stress，lower surface roughness and higher equivalent plastic strain compared to conventional shot peening，accompanied by a slightly shallower strengthening layer.The increase in residual compressive stress contributed to improving wear resistance and fatigue performance of the material，while the lower surface roughness contributed to restraining crack initiation.Higher equivalent plastic strain could further refine grains and promote the generation of residual compressive stress.These advantages suggested the broad prospects of micro-particle shot peening in the surface strengthening of mechanical components.

In order to avoid the blindness of the hydraulic fracturing of the directional long borehole in coal mine 2130 of Xinjiang Coking Coal Group, and to accurately grasp the extension and expansion of hydraulic fracturing under different hole layout methods, this paper uses the numerical simulation method to carry out hydraulic fracturing numerical simulation for comb directional long borehole in 4# coal seam of coal mine 2130 with a buried depth of 500 m. The simulation results show that the different hole layout methods have obvious effects on hydraulic fracturing initiation pressure, crack initiation position, fracture mode and crack extension and expansion law, combined with the actual situation of 4# coal seam in coal mine 2130, the optimal drilling hole layout method and fracturing parameters are optimized for engineering practice, and good fracturing results have been achieved. Compared with the previous hydraulic fracturing measures at this level, the drainage concentration is increased by 2.7 times, and the scalar amount of drainage increased by 11.8 times.

BackgroundThe SXFEL (Soft X-ray Free-Electron Laser facility) is the first X-ray coherent light source in China. To monitor the beam loss in its undulator beamline, a quartz fiber beam loss monitoring system based on the Cherenkov radiation principle was designed and installed. The quartz fiber is insensitive to high-energy gamma rays, making it suitable for a strong SXFEL radiation field environment.PurposeThis study aims to apply quartz fiber beam loss monitoring (BLM) system to the undulator beamline of SXFEL, and carry out position calibration experiment to measure the fiber attenuation coefficient, and performance of the system in the beam tuning period.MethodsFirst, two pure quartz composition fibers with 400 μm inner diameter of core and high concentration of hydroxide ions were employed. The beam loss signal was generated by falling YAG (Ce:Y3Al5O12, target film) of the beam profile monitor at a fixed position and adjusting the trigger time delay to make the position of the beam loss signal the same as that of the beam profile monitor for position calibration experiment. Second, to measure the fiber attenuation coefficient, the coefficient was fitted by bringing the peak value of the beam loss signal generated by the falling YAG at different positions of the SBP (Shanghai-XFEL Beamline Project) beamline and the corresponding fiber position into the signal attenuation formula.ResultsThe fiber BLM can accurately reflect the position of the beam loss with upstream position resolution of approximate 0.2 m in the experiment test, as well as in the period of beam tuning. The refractive index of quazrtz firber core is approximately 1.5, hence the relationship between the beam loss position and signal arrival to upstream PMT time interval is 0.12 m·ns-1. The measured fiber attenuation coefficient is around 74 dB·km-1, which is consistent with the calculation result and similar to the measurement result of SPring-8 Angstrom Compact Free Electron Laser (SACLA) using the same type of optical fiber.ConclusionsThe fiber beam loss monitoring system has a good position resolution and has the potential to meet the requirements of SXFEL beam tuning.

The chemical composition and fracture toughness of thermal barrier coatings (TBCs) before and after heat treatment were characterized, and the cracks around the interface between the coating and the substrate could be successfully eliminated and meanwhile the porosity of the coatings tended to reduce. The XRD analysis revealed the coatings were composed of non-transformable tetragonal t’ phase of ZrO2 and γ $\gamma $-(Ni, Cr) with minor Ni3Al (γ′ $\gamma ^' $) precipitates. Additionally, the relationship between the heat treatment and wear resistance was systematically studied. The results indicated that both the hardness and fracture toughness increased after quenching process. The oxidation wear became more prominent after heat treatment, which probably resulted from the better bonding strength of coatings. Dense and homogeneous microstructure introduced by vacuum oil-quenching improved stabilization of the weight gain during thermal cycle test.