A Cobalt Diffusion Based Model for Predicting Crater Wear of Carbide Tools in Machining Titanium Alloys

2005 ◽  
Vol 127 (1) ◽  
pp. 136-144 ◽  
Author(s):  
Jiang Hua ◽  
Rajiv Shivpuri

In machining titanium alloys with cemented carbide cutting tools, crater wear is the predominant wear mechanism influencing tool life and productivity. An analytical wear model that relates crater wear rate to thermally driven cobalt diffusion from cutting tool into the titanium chip is proposed in this paper. This cobalt diffusion is a function of cobalt mole fraction, diffusion coeficient, interface temperature and chip velocity. The wear analysis includes theoretical modeling of the transport-diffusion process, and obtaining tool–chip interface conditions by a nonisothermal visco-plastic finite element method (FEM) model of the cutting process. Comparison of predicted crater wear rate with experimental results from published literature and from high speed turning with WC/Co inserts shows good agreement for different cutting speeds and feed rate. It is seen that wear rates are independent of cutting time.

The machinability of a material can be defined in terms of the wear rate of the cutting tool used to machine the material. The lower the tool wear rate or the greater the tool life the better the machinability. The wear processes of cutting tools are complicated, but recent work has shown that cutting tool wear rates during machining can be directly related to tool material wear rates when rubbing in a modified crossed cylinder wear experiment (Mills & Akhtar 1975). The wear of cutting tools can be simulated by simple experiments. Here I present results on the effect of total residual levels in leaded low carbon free machining steels on the tool life of M2 high speed steel. The results will be discussed in terms of a simple wear model.


2019 ◽  
Vol 141 (5) ◽  
Author(s):  
Linkai Niu

The effects of the race surface waviness on the cage dynamics, including cage slip ratios, cage instabilities, and time-averaged cage wear rates, in high-speed ball bearings are investigated. A dynamic model of high-speed ball bearings considering the cage effect and the race surface waviness is proposed. Based on the proposed dynamic model, the effects of the maximum wave amplitude (MWA) and the wave order (WO) of race surface waviness on cage slip ratio, cage instability, and time-averaged cage wear rate are investigated. The results show that the race surface waviness has a great effect on the cage dynamics. The waviness would increase the random impacts between balls and cage pockets and thus cause more instable motion of the cage. Although the ball skidding and the cage slip ratio decrease with the increase of MWA, the cage instability and the cage wear rate become severe when MWA increases. In addition, the effect of WO on cage dynamics is nonlinear. The current investigation could provide a theoretical tool for an in-depth understanding of the dynamics in a high-speed ball bearing.


Author(s):  
Jingmang Xu ◽  
Ping Wang ◽  
Jian Wang ◽  
Boyang An ◽  
Rong Chen

In this study, a numerical procedure is developed to predict the wear of turnout rails, and the effect of track parameters is investigated. The procedure includes simulation of the dynamic interaction between the train and the turnout, the rolling contact analysis, and the wear model. The dynamic interaction is simulated with the validated commercial software Simpack that uses a space-dependent model of a railway turnout. To reproduce the actual operating conditions of a railway turnout, stochastic variations in the input parameters are considered in the simulation of the dynamic interaction. The rolling contact is analyzed with the semi-Hertzian method and improved FASTSIM algorithm, which enable the contact model to deal with situations of multipoint contact and nonelliptic contact. Based on the Archard’s wear law, the wear model requires the calculation of normal/tangential stresses and a relative slide on the contact patches. The numerical procedure is performed for the selected sections of the vehicle, which runs through the railway turnout in the diverging route. By using the numerical procedure, the effect of track parameters (track gage, rail inclination, and friction coefficient) on the wear of turnout rails is analyzed. The results show that the wear of the front wheelset is more serious than the wear of the rear wheelset for a single vehicle. The degree of wear of switch rails is more severe than that of the stock rails and the difference is more obvious for the front wheelset of the switch rails. The wear of switch rails is mainly concentrated on the rail gage corner, while the wear of stock rails is mainly concentrated on the rail crown. For the analysed CN60-1100-1:18 turnout and the high-speed vehicle CRH2 in China, the rail wear rate could be slowed down by increasing the track gage and decreasing the rail inclination. Alternatively, the rail wear rate could be slowed by decreasing the friction coefficient; however, the variation of wear depth is quite small for friction coefficients that are larger than 0.3.


1969 ◽  
Vol 91 (3) ◽  
pp. 652-658 ◽  
Author(s):  
T. C. Hsu¨

A technique is developed for measuring accurately the flank wear by using polished tungsten carbide tool tips. The technique is applied to the study of the variation of machinability in mild steel bars and of the possible effect of surface finish of tool face on the wear rate. The specific wear rate, which is the volume of material worn away per unit contact area per unit distance of rubbing, is used to analyze the results on flank wear in this investigation and Trent’s results on crater wear. The constants in an equation representing Trent’s results and in Taylor’s equation for tool life are shown to have physical meanings and to be related to the specific wear rate. The reciprocal of the specific wear rate may be used as a machinability index.


2016 ◽  
Vol 836-837 ◽  
pp. 402-407
Author(s):  
Rui Tao Peng ◽  
Jing Li ◽  
Xin Zi Tang ◽  
Zhuan Zhou

In high speed machining superalloys processes, tool wear is strongly influenced by the cutting temperature and contact stresses. Finite element analysis of machining can be used as a supplementary to the physical experiment, this paper provides investigations in 2D and 3D finite element modeling and simulation of prestressed cutting for GH4169 superalloy, a tool wear model for the specified tool and workpiece pair is developed based on the Usui's wear model, furthermore, tool temperature, wear rate and nodal displacement on the face of tool in prestressed cutting of superalloy is analyzed under various prestress condition and cutting parameters, and Python language is adopted to modify the Abaqus code used to allow tool wear calculation and tool geometry updating. The results of the simulation indicate that the tool wear rate increases with the increase of cutting time, and the influence of the prestress to tool wear in prestressed cutting process of shaft part is unremarkable.


1999 ◽  
Vol 122 (1) ◽  
pp. 340-347 ◽  
Author(s):  
Patrick Kwon

The purpose of this paper is to develop predictive models for flank wear that explicitly incorporate cutting temperature and the physical properties of coatings and work materials. The development of such models can minimize time-consuming machining experiments in predicting tool life by establishing flank wear models that can be applied to wide classes of coated inserts and work materials. To develop such models, a set of experiments was performed to understand the effect on flank wear due to the morphology and amount of the second phase in work materials. The plain carbon steels of AISI designation 1018, 1045, 1065, 1070, and 1095 in hot-rolled (pearlitic) and/or spherodized conditions were turned. The inserts with a single coating of TiN, TiCN, or Al2O3 were used in the cutting experiments. The temperature history at a remote location on the rake face was measured during cutting by using an infrared pyrometer with a fiber optic attachment. This temperature information was used to estimate the steady-state tool-chip interface temperatures using the inverse estimation scheme by Yen and Wright, 1986, ASME J. Eng. Ind., 108, pp. 252–263. The results were then used to predict the work-tool interface temperature using the scheme suggested by Oxley, 1989, The Mechanics of Machining: An Analytical Approach to Assessing Machinability, Wiley, New York, NY, p. 168. The results of this experiment showed that, for the spherodized steels, flank wear per sliding distance (the flank wear rate) increased with the cementite content. For the hot-rolled (pearlitic) steels, no conclusive evidence was found that correlates the flank wear rate with the cementite content. However, for pearlitic steels the wear rates, in general, were shown to increase with the flank temperature while for spherodized steels the rates decrease with the flank temperature. The reason for these trends can be explained by the microstructural difference between pearlitic and spherodized steels; therefore, the semi-empirical models of two-body and three-body wear developed by Rabinowicz (1967) and Rabinowicz et al. (1972) can be applied to describe the flank wear process. [S0742-4787(00)04501-X]


2017 ◽  
Vol 140 (2) ◽  
Author(s):  
Kishor Kumar Gajrani ◽  
Mamilla Ravi Sankar ◽  
Uday Shanker Dixit

Strict environmental laws enforced on manufacturing industries resulted in the development of alternative techniques to reduce or eliminate the use of lubricants during sliding contact as well as machining. Tribology plays a very important role for tool life in machining. To improve the life of cutting tool, cutting fluids are used. However, cutting fluids only penetrate into the region of sliding contact. In this study, the effect of surface texturing on plasma nitrided high-speed steel (HSS) pins during dry sliding test is investigated for understanding the performance of textured HSS tools in machining. Microtextures were fabricated using Vickers hardness tester on the surface of HSS pins. Tribological tests of molybdenum disulphide (MoS2) filled as well as unfilled microtextured HSS with area density of textures varying from 2% to 14% were performed with the aid of pin-on-disk tribometer against an abrasive sheet. Friction and wear performance were assessed in terms of the pin surface temperature, coefficient of friction (COF), wear, weight loss of the pin and wear rate. Worn-out test surfaces were observed under scanning electron microscope to understand the wear mechanism. The best results were obtained with MoS2-filled microtextures having 10% texture area density. Tool–chip interface temperature, cutting force, feed force, and centerline average (CLA) surface roughness were also assessed during machining test with 10% area density of textured cutting tools.


Alloy Digest ◽  
1988 ◽  
Vol 37 (5) ◽  

Abstract UNS No. T11310 is the high vanadium type of molybdenum high-speed steel. It is a deep-hardening steel and offers high cutting ability and excellent finishing properties. It is a general-purpose steel for cutting tools and is used in such applications as taps, lathe tools and reamers. This datasheet provides information on composition, physical properties, hardness, elasticity, and tensile properties. It also includes information on heat treating and machining. Filing Code: TS-490. Producer or source: Tool steel mills.


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