Papers by Author: F. Xu

Abstract: For properly choosing grinding parameters, predicting probable faults and processing quality, simulation of grinding based on virtual reality technology was study. Physiognomy forming mechanism of grinding wheel was analyzed and a 3D virtual grinding wheel models was built. Effects to grinding wheel physiognomy by grain size and organization number were analyzed and grain distribution was visually represented. Effect to processing quality by grinding wheel granularity, dressing parameters, grinding wheel speed, feed speed and grinding depth was simulated. And experiments were carried out for comparative analyzing. Experiments result proved the reliability and practicality of the virtual grinding wheel model.

Abstract: A grinding wheel spindle with squeeze film damper—SFD is designed based on squeeze film damping theory and relevant grinding experiments have been performed. Experimental results indicate that the rationality of design for SFD can make the vibration of the grinding wheel spindle is reduced by 25%. The precision of hole machining is improved by 20%. At the same time, work efficiency of the grinder can be raised about 15%. So it has very important research value and wide application prospect in the field of machining.

Abstract: Based on the shortcoming and deficiency of deep hole machining, a grinding wheel spindle with squeeze film damper—SFD is design based on squeeze film damped theory. The motion differential equation of SFD grinding wheel spindle is constituted according to D’ Ale mbert principle，and a lot of simulated research has been carried out about the locus of grinding wheel spindle affect by SFD. Founded on the simulated result, the SFD grinding wheel spindle of internal grinder have designed, and the grinding experiments have been performed. Experimental result indicate that the rationality of design for SFD can make the vibration of the grinding wheel spindle reduce 25% , and make machining precision of hole improve 20% , make work efficiency of the grinder raise 15%.

Abstract: In this paper the modeling method of object entity in the environment of virtual is introduced and the three-dimensional simulation model of grinding wheel is established in Visual C++ programming language and OpenGL tool. The simulated experiment is made, which can indicate the effect of different parameters to grinding process. It proved the reliability and practicability of virtual wheel through comparing the simulation results and experimental data.

Abstract: Objective: To compare biocompatibility, degradation, and mechanical properties of polyglycolic acid (PGA) unwoven and woven fibers as scaffolding materials for tendon engineering in vitro. Methods: Three kinds of PGA fibers were included in this study. PGA raw material (Purac Co, Holland) was spun into single PGA filaments that were further twisted into woven fibers (PGA- 1). PGA filaments (Nantong Holycon, China) were twisted into woven fibers (PGA-2) as well. PGA-1 and PGA-2 served as experimental groups 1 and 2, while unwoven PGA fibers (Albany Co, USA) served as control group. Three types of PGA fibers were made into cord-like scaffolds that mimic tendon shape and compared with each other for biocompatibility, degradation and biomechanical properties. Avian tenocytes were isolated from digital flexor tendon and expanded in vitro. Cells of the second passage were seeded onto the PGA scaffolds. In the first 2 weeks, the cell- PGA constructs were in vitro cultured without tension and observed for cell adhesion and matrix production. The constructs were then cultured under dynamic loading in a bioreactor for another 2 weeks followed by gross and histological examinations. Results: PGA unwoven fibers have the median diameter of 10µm, while PGA-1 and PGA-2 fibers have the median diameters of 200µm and 60µm, respectively. Microscopy showed that tenocytes adhered well to all three types of PGA fibers in the first 10 days and produced abundant matrices. However, cells showed poor viability on PGA-2 fibers after 10 days, yet good viability on the other two PGA fibers over 2 weeks of observation period. H&E staining showed that there were viable cells and abundant matrices in the control and PGA-1 groups, but not in PGA-2 group after 4 weeks of in vitro culture. Additionally, PGA unwoven fibers degraded faster than woven fibers (PGA-1 and -2). Interestingly, the PGAtenocyte constructs formed tendon-like tissue after 4 weeks of in vitro culture grossly and histologically. Furthermore, mechanical test demonstrated that both PGA woven fibers had much higher tensile strength than unwoven fibers. Conclusion: Different PGA fibers have different biocompatibility with seeded tenocytes. PGA woven fibers could bear more intense mechanical loading and degrade slower than unwoven fibers, which is essential for in vitro generation of tendon tissue. Thus PGA woven fibers might serve as a proper form of scaffolding material for in vitro tendon engineering in a bioreactor.