Tool wear analysis is essential in high speed machining, especially in the intermittent cutting and milling processes. Analyses of tool wear mechanisms will be beneficial for proposing the suggestions in the tool design process how to enhance the tool material properties to improve the cutting performance and eventually tool life. Wear mechanisms of coated carbide tools in high-speed dry milling of Ti-6A1-4V were assessed by characterization of the cross-section of worn tool cutting edge utilizing scanning electron microscopy, and the element distribution of the worn tool surface was detected by using energy dispersive spectroscopy. Results show that flank wear, chipping and flaking of tool material on the rake face and/or at the nose of tools were the dominant failure modes. And synergistic interaction among coating delamination, erosion wear, adhesion, dissolution-diffusion wear, and thermal-mechanical fatigue wear were the main wear mechanisms analyzed from cross-sectional worn cutting edge. Erosion wear was identified in high speed milling of Titanium alloy and introduced into the wear mechanisms of metal cutting tools. The hydromechanics characteristic of the chips produced in high-speed machining should be responsible for erosion wear of cuttings tools.
The fatigue failure of the piston pin hole is considered as a key factor affecting the service life of engines. In this work, the piston pin hole profile was designed as tapered shape following a power law. By combining finite element analysis and hydraulic pulsating fatigue tests, the pin hole profile was optimized. It has been found that the maximum contact pressure on the pin hole surface was reduced by 16,7% with appropriate increasing the radius enlarging rate of the piston pin hole, the maximum tensile stress of the piston pin seat was reduced by 13,1%, and the piston pin seat fatigue safety factor was increased by 41,4%, the piston pin hole fatigue safety factor was increased by 15,9%. The piston pin hole's hydraulic pulsating fatigue test results were found to be consistent with the FEA results. It could be concluded that appropriate increasing the radius enlarging rate of the pin hole could significantly weaken the fatigue wear of the pin hole, further improving its fatigue resistance.
The indoor air pollution produced by the ventilating system of the central air-conditioning draws many people's attention. In this paper, a new style of the central airconditioning pipe aseptic sampling inspection robotic system is developed. The entire system comprises three parts: the caterpillar robot, computer and control box. Through realtime video transferred from cameras on robot, operators can remote control the robot in pipe to move flexibly, sample and high-pressure dust absorption effectively. The integral separation PID improved algorithm applied in the control system makes the robot in pipe travel straight accurately, ensuring the actual speed fluctuation deviation ratio range is in 5% ± .
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