Xiangyu Zhang

Bio: Xiangyu Zhang is an academic researcher from Beihang University. The author has contributed to research in topics: Machining & Surface roughness. The author has an hindex of 9, co-authored 26 publications receiving 263 citations.

Study of Phase Shift Control in High-Speed Ultrasonic Vibration Cutting

Abstract: High-speed ultrasonic vibration cutting (HUVC) applies an ultrasonic vibration to a cutting tool transverse to the cutting direction. The advantage of this method is that the high-speed cutting exceeds the critical cutting speed restrictions of ultrasonic vibration cutting. However, irregular dimple arrays are machined on the work-piece surface, increasing the surface roughness. In this paper, a phase shift control method is proposed, which aims to overlap dimples in a regular pattern to decrease the surface roughness for HUVC. First, this paper investigates the theory of phase shift control to guarantee the surface quality of HUVC. Then, a closed-loop direct digital synthesis (DDS) system is designed to keep the phase shift of the machined dimples stable and controllable. A contrast experiment is conducted to compare the performance of the closed-loop DDS and the open-loop DDS methods in HUVC process. The results show that the closed-loop DDS method can render the dimple phase stable and controllable during the HUVC process. The phase shift value influences the surface roughness. Setting the phase shift to 0.94π with an appropriate feed-rate, the surface roughness is reduced to 0.303, compared to a surface roughness of 0.785 when using the open-loop DDS method.

Review of ultrasonic vibration-assisted machining in advanced materials

Abstract: Compared to conventional machining (CM), ultrasonic vibration-assisted machining (UVAM) with high-frequency and small-amplitude has exhibited good cutting performances for advanced materials. In recent years, advances in ultrasonic generator, ultrasonic transducer, and horn structures have led to the rapid progress in the development of UVAM. Following this trend, numerous new design requirements and theoretical concepts have been proposed and studied successively, however, very few studies have been conducted from a comprehensive perspective. To address this gap in the literature and understanding the development trend of UVAM, a critical overview of UVAM is presented in this study, covering different vibration-assisted machining styles, device architectures, and theoretical analysis. This overview covers the evolution of typical hardware systems used to achieve vibratory motions from the one-dimensional UVAM to three-dimensional UVAM, the discussion of cutting characteristics with periodic separation between the tools and workpiece and the analysis of processing properties. Challenges for UVAM include ultrasonic vibration systems with high power, large amplitude, and high efficiency, as well as theoretical research on the dynamics and cutting characteristics of UVAM. Consequently, based on the current limitations and challenges, device improvement and theoretical breakthrough play a significant role in future research on UVAM.

Improvement of machinability of Ti and its alloys using cooling-lubrication techniques: a review and future prospect

Abstract: Products made of titanium and its alloys are widely used in modern areas like the mechanical engineering, instrument making, aerospace and medical sector. High strength and low thermal conductivity are the causes of difficulties with the machinability of these alloys. It is important to find ways to increase machinability by cutting titanium alloys. One way to implement this is to apply various methods of cooling on workpieces of titanium alloys and on cutting tools during machining. In this review article, an extensive analysis of the literature on such cooling techniques as dry, conventional cooling system, minimum quantity of lubricant (MQL), minimum quantity cooling lubrication (MQCL), cryogenic lubrication, and high-pressure cooling (HPC) is performed. The following groups of Ti alloys are considered: high-strength structural and high-temperature Ti alloys, intermetallic compounds, pure titanium, as well as composites CFRPs/Ti alloys. For the processes of turning, milling, drilling, and grinding, etc. it is shown how the type of cooling affects the surface integrity include surface roughness, tool wear, tool life, temperature, cutting forces, environmental aspects, etc. The main advantages, disadvantages and prospects of different cooling methods are also shown. The problems and future trends of these methods for the machining of Ti and its alloys are indicated.

International standards

Abstract: On a computer you can delete directories with reckless abandon. Whole tree structures of folders can be obliterated with just one multiple selection and a control key combination. It's great fun but maybe a bit too powerful at times. Anyway, I have just been doing the real world equivalent; burning real world direc-tories/folders on a real world bonfire, also great fun even if it lacks an undo function. This may seem rather wasteful but there is a reason. I'll start, though, with the filing cabinets I bought 15 years ago from an Ameri-can town planner. They were 50's styled, rounded corners, Cole Steel, just the right height for a desk-top placed on top of them; absolutely perfect. There was only one slight, minor, tiny drawback; they were for paper of the American 'letter' size and here in the UK we use 'A4' which is a slight, minor, tiny bit bigger. I tried A4 paper in the drawers and they fit... but only just. So I bought the cabinets. It was like when you find a great pair of secondhand shoes that are just that incy-wincy bit too small; you kid yourself they fit and then spend the next month walking around with curled up toes and blisters. Well, I kidded myself about the Cole Steel cabinets and spent the next month with A4 paper that was always slightly crumpled at the edges. Eventually I could stand it no more and while living in Holland I switched to European sizes. Faced with a choice of A4 or the larger Folio I chose Folio having had more than enough of curled edges. I built up a large collection of information (partly through a policy of never throwing anything out!) and when I returned to the UK I took all the files with me. On purchasing a filing cabinet to hold all the files I discovered that the UK, like Holland, has two sizes. Unfortunately, they are not the same two sizes; we have the choice between A4 or something called Foolscap. (I'm still unsure what a cap for a fool has got to do with paper, but there you go!). So I paid my money, got my cabinets, re-filed everything in foolscap-sized files and burned the Dutch folders on the bonfire. Such international compatibility horror stories are not new. It's not just a paper thing, it covers many other facets of life …