Ju Dong Liu

The Analysis of Tool Wear in Milling CFRP with Different Diamond Coated Tool

Carbon fiber-reinforced plastics (CFRP) are typical difficult-to-machine materials, which is easy to produce many defects such as burrs, dilacerations, layering in milling process. And selecting the appropriate cutting tool has become the key to machining CFRP with high quality and efficiency. In the paper, the machining principle of milling CFRP with new type end mill was analyzed. The diamond coating of general right-hand end mill, cross-flute router and fine-cross-nick router were used to cutting CFRP under the same cutting condition. Through the comparative analysis of the workpiece’s surface quality and tool wear, it concluded that: compared with right-hand diamond coated end mill, cross-flute diamond coated router or fine-cross-nick diamond coated router could effectively suppress the appearance of burrs and dilacerations; abnormal coating peeling appeared in the flank face of right-hand diamond coated end mill, forming the boundary wear, which accelerated wear failure; the flank wear of diamond coated cross-flute router and fine-cross-nick router were both abrasive wear. Due to having more cutting edge than cross-flute router in cutting process, the flank wear of fine-cross-nick router was slower, and the tool life was longer. So it was more suitable for cutting CFRP.

Study on the Grind-Hardening of the Loader Clevis Pin

On the basis of the cylindrical plunge grinding and intermittent axial feed grinding experiment, the grind-hardened layer structure and its property of the loader clevis pin were studied. The result shows that there are some arc shape medium/high-temperature tempered zones and some annular unhardened zone in external circumference surface, which is result of temperature gradient, induced grinding heat when circumferential feed and axial grinding heat conduction. The microstructure of hardened zone is mixture martensite, and the microstructure of tempered zone is tempered martensite and troostite. Different structure zone has same microhardness distribution regulation, but the microhardness of hardened zone can reach 640HV0.5. The loader clevis pin processed by grind-hardening meets the property request for working.

Numerical Simulation of Grinding-Hardened Layer's Depth in the Reciprocating Grinding of 45 Steel

Based on the experiment of reciprocating grinding and in accordance with Jaeger moving heat source theory and the triangle model of the heat source, this paper established temperature filed of grinding-hardening machine and conducted numerical calculation with the temperature filed of grinding by the software ANSYS. Then it predicated the grinding-hardened layers depth in accordance with the results of numerical calculation, and compared with the experimental results to verify the rationality of the simulation results.

Influence of Chamfer Size on the Two-Side Direction Burr Formed in Grinding-Hardening Machine

Based on the orthogonal experiment, this paper studied the influences of chamfer size on the two-side direction burr in grinding-hardening machine. The results show that: chamfer height size affected the two-side direction burr’s size significantly and the influence of chamfer degree α is general. On this experimental condition, it should adopted grinding parameter ap＝0.2mm,vw＝0.2m/min, the chamfer height h=1.0mm and chamfer degree α=20 o to reduce the two-side direction burr’s size effectively and decrease the workload of removing burr.

Influence of Grinding Parameters and Chamfer Size on the Grinding-Hardened Layer'S Depth

Based on the orthogonal experiment, this paper studied the combined effect of grinding parameters and chamfer size on grinding-hardened layers depth formed in grinding-hardening machine. The results show that, while the workpiece was chamfered, the grinding-hardened layers depth would lessen owing to the decreasing of metal removal in per unit time. On this experimental condition, the effect orders of grinding parameters and chamfer size on the average value of grinding-hardened layers depth are as follow, grinding parameters avchamfer degree α and chamfer height h. In actual application, it should adopt suitable combinations of grinding parameters and chamfer size according to the requirements of the grinding-hardened layers depth to minimize the burrs size and maximize the productivity of grinding-hardening machine.

Orthogonal Experimental Study on the Grinding-Hardened Layer’s Depth and its Uniformity of 45 Steel

Based on the orthogonal experiment of grinding-hardening machine, this paper studied the influence of depth of cut ap, table speed vw and grinding method gm on the grinding-hardened layer’s depth and its uniformity of 45 steel. The results show that, depth of cut ap is the significant factor affected the average value of grinding-hardened layer’s depth, but the influence of grinding conditions on the uniformity are very limited. In actual application, it should adopt ap=0.6mm, vw=0.4m/min and up-down grinding method to enhance the quality of grinding-hardened layer.

Quality and Control of Grinding-Hardening in Workpieces

On the basis of the surface grinding-hardening test, studied on the quality of grinding-hardening in 65Mn steel. The results show that grinding method has insignificant effect on the microstructure and the high hardness value of the completely hardened region at different locations alone the direction of length. The completely hardened region is composed of fine acicular martensites, residual austenites and a little carbides, and the high hardness value is between 760-820HV. As the changing of grinding method, the uniformity and depth of the hardened layer changed accordingly. The quality of grinding-hardening could be improved with big depth of cut, small table speed and combined with the grinding method of up-down grinding or down-up-down grinding which could effectively control the depth and uniformity of the hardened workpieces.

Study on the Two-Side Direction Burr in Grinding-Hardening Machine Based on Orthogonal Experimental Method

Based on the orthogonal experiment, this paper studied the influences of depth of cut ap, table speed vw and grinding method gm on the two-side direction burr in grinding-hardening machine. The results show that, with thermal-force coupling effect induced in the grinding-hardening machine, the metal in the workpiece’s surface flowed to two-side direction of the workpiece that without any constraint and leaded to the burr’s formation. The depth of cut ap and grinding method gm are significant factors that affected the size of two-side direction burr, and the significant order are as follows: depth of cut ap> grinding method gm > table speed vw >interaction av. With the increasing of depth of cut ap or the grinding trip, the max size of the two-side direction burr increased gradually; and with the raising of table speed vw, the max size decreased firstly and then increased. In actual application, it should adopted the grinding parameters ap＝0.2mm，vw＝0.6m/min and up-down grinding to improve the quality of grinding-hardening and reduce the size of the burr.

Influence of Grinding Parameters on the Depth and Uniformity of Cylindrical Grinding-Hardened Layer

On the basis of the cylindrical grinding-hardening test, the influences of the grinding parameters on surface hardened layer were studied. The result shows that when ap≤0.2mm, there is an unhardened area exist in cylindrical grinding hardened workpiece. When ap＞0.2mm, there is a tempered area exist in cylindrical grinding hardened workpiece due to the action of grinding heat during cut-in and cut-out of grinding wheel. When depth of cut increases, or feed speed decreases, the hardened layer depth increases accordingly. In the practical application, the satisfactory quality of the cylindrical grinding hardened layer can be obtained through reasonable combination of ap and vw.

Experimental Study on the Tool Wear in Milling Carbon Fiber Reinforced Plastics

Basing on the milling experiment of carbon fiber reinforced plastics (CFRP), the wear performance of CVD diamond coated tool with different cutting edge is compared and studied. The result shows that lifetimes of interlaced edge and herringbone edge milling cutters are significantly higher than general edge milling cutter, under the same parameters. The lifetime of interlaced edge milling cutter is about 2 times than herringbone edge milling cutter, and 3.5 times than general edge milling cutter. The wear failure mechanisms of CVD diamond coated tools are abrasive wear and coating peeling, which are caused by micro-cutting of hard carbon fiber and the impact action of mechanical load and thermal stress.