Modelling the cutting forces in micro-end-milling using a hybrid approach

This paper presents the development of a cutting force model for the micro-end-milling processes under various cutting conditions using a hybrid approach. Firstly, a finite element (FE) model of orthogonal micro-cutting with a round cutting edge is developed for medium-carbon steel. A number of finite element analyses (FEA) are performed at different uncut chip thicknesses and velocities. Based on the FEA results, the cutting force coefficients are extracted through a nonlinear algorithm to establish a relationship with the uncut chip thickness and cutting speed. Then, the cutting force coefficients are integrated into a mechanistic cutting force model, which can predict cutting forces under different cutting conditions. In order to account for the cutting edge effect, an effective rake angle is employed for the determination of the cutting force. A comparison of the prediction and experimental measured cutting forces has shown that the developed method provides accurate results

Modelling and analyses of helical milling process

A comparison between the geometry of the helical milling specialized tool and conventional end mill was firstly introduced. Furthermore, a mathematical model, in which the cutting area was divided into different cutting zones, was established to simulate the cutting depths and volume of the different cutting edges (three kinds) on specialized tool. Accordingly, a specific ratio between the volume removed by different edges and the total hole volume was derived mathematically and modeled using 3D modeling software SolidWorks. Based on the established models, the cutting depths and cutting volume ratio variation trends under different cutting parameters were analyzed. The results showed that the change rules of cutting depths were different in every cutting zone and influenced greatly by the cutting parameters. In addition, the cutting volume ratio changes with different cutting parameters, but it can only vary in certain range due to the structure of the helical milling specialized tool. The cutting volume ratio obtained from the established model shows a good agreement with the data modeled using SolidWorks, proving that the established model is appropriate. Moreover, the undeformed chip geometry was modeled and observed using SolidWorks. The undeformed chip showed a varying geometry with different cutting parameters and it can be optimized to obtain a good cutting condition during helical milling process

A Review on Ultrafast-Laser Power Bed Fusion Technology

Additive manufacturing of metals by employing continuous wave and short pulse lasers completely changes the way of modern industrial production. But the ultrafast laser has the superiority to short pulse laser and continuous wave laser in additive manufacturing. It has higher peak power, small thermal effect, high machining accuracy and low damage threshold. It can effectively perform additive manufacturing for special materials and improve the mechanical properties of parts. This article reviews the mechanism of the interaction between ultrafast laser and metal materials to rule the manufacturing processes. The current application of ultrafast laser on forming and manufacturing special materials, including refractory metals, transparent materials, composite materials and high thermal conductivity materials are also discussed. Among the review, the shortcomings and challenges of the current experimental methods are discussed as well. Finally, suggestions are provided for the industrial application of ultrashort pulse laser in the field of additive manufacturing in the future

A Review on Ultrafast-Laser Power Bed Fusion Technology

Additive manufacturing of metals by employing continuous wave and short pulse lasers completely changes the way of modern industrial production. But the ultrafast laser has the superiority to short pulse laser and continuous wave laser in additive manufacturing. It has higher peak power, small thermal effect, high machining accuracy and low damage threshold. It can effectively perform additive manufacturing for special materials and improve the mechanical properties of parts. This article reviews the mechanism of the interaction between ultrafast laser and metal materials to rule the manufacturing processes. The current application of ultrafast laser on forming and manufacturing special materials, including refractory metals, transparent materials, composite materials and high thermal conductivity materials are also discussed. Among the review, the shortcomings and challenges of the current experimental methods are discussed as well. Finally, suggestions are provided for the industrial application of ultrashort pulse laser in the field of additive manufacturing in the future

Effect of cerium on mechanical, metallurgical and biomedical properties of NiCrMoB dental alloy

NiCrMo alloys are popular as non-precious dental casting alloys and appreciated specially in developing nations. A number of elements may be alloyed to achieve enhanced characteristics suitable for dental restorations. In this study NiCrMo dental casting alloy was alloyed with cerium to improve mechanical, metallurgical and biomedical characteristics. Three alloys were produced by vacuum induction melting technique. These cast alloys were tested for melting range, phase analysis, microstructure, mechanical and wear characteristics, corrosion behavior, coefficient of thermal expansion and biocompatibility properties. Test results revealed that 0.4% cerium addition in NiCrMoB alloy substantially improved the mechanical, metallurgical and corrosion characteristics of the cast alloy without compromising the biocompatibility and melting characteristics of the alloy. Mechanical testing and tribological results pointed out that the NiCrMoB alloy with 0.4% addition of cerium possessed tensile strength up to 515 MPa with impact strength around 7 J, while average coefficient of friction was calculated to be 0.1715; that was least of the investigated alloys. Corrosion rate for the alloy was found to be 25.92 × 10−3 mils per year that was also the least among the investigated alloy samples

Processing and characterization of beryllium free Ni–Cr–Mo biomaterial doped with cerium, boron and titanium for dental applications

Dental restoration has been a major concern of healthcare since centuries. Several alloys are in use for dental prostheses including Ni–Cr–Mo alloy. The Ni–Cr–Mo alloy has advantage of economy and density over other alloys, while possessing equivalent corrosion and biocompatibility characteristics. However, beryllium in Ni–Cr–Mo dental casting alloys has associated health hazards, being carcinogenic. In this research Ni–Cr–Mo alloys with minor additions of boron (0.2 wt %), cerium (0.4 wt %) and titanium (2 wt %), to replace beryllium were developed through vacuum induction melting and investment casting technique. Manufacturing steps are detailed for the alloy development to have medically clean alloy, suitable for biomedical applications. The cast alloy samples were tested for microstructure, phases, melting temperatures, wear and corrosion characteristics. Corrosion and wear test results demonstrate that the composition with minor addition of cerium had a significant effect to have low corrosion rate (25.92 × 10−3 mills per year), low wear rate (0.04 × 10−4 mm3/N.m) and lowest coefficient of friction

Research progress in potential high-entropy ceramic thermal barrier coating materials

Thermal barrier coating (TBC) materials are an important method to provide thermal protection and prolong service life for aero-engines and gas turbines. In recent years, various kinds of high-entropy (HE) rare earth oxides have emerged in the exploration of novel thermal barrier coating materials, in order to obtain thermal, mechanical, high temperature phase stability, sintering corrosion resistance and other properties better than single principal rare earth oxides through HE effect on the thermodynamics and kinetics of hysteresis diffusion effect, the structure of the lattice distortion effect and "cocktail" effect on the performance. The thermal, mechanical and other performances of HE rare-earth zirconates, cerates, hafnates, phosphates, tantalates, niobates, etc. were summarized and analyzed in comparison with the performance of the corresponding single phases to investigate the various factors affecting the performance. Finally, it was pointed out that in the future, it may be possible to combine experiments with first-principles calculations to select high-entropy ceramic thermal barrier coating materials with superior comprehensive performance; at the same time, extending high-entropy to complex components or medium-entropy ceramic thermal barrier coating materials is also an important development direction