NOPR Collection:

Turning processes investigation of materials austenitic, martensitic and duplex stainless steels and prediction of cutting forces using artificial neural network (ANN) techniques

Mon, 01 Apr 2019 00:00:00 GMT

Title: Turning processes investigation of materials austenitic, martensitic and duplex stainless steels and prediction of cutting forces using artificial neural network (ANN) techniques Authors: Ulas, Hasan Basri; Ozkan, Murat Tolga Abstract: In this study focus on the performance of machining parameters that are cutting forces and surface roughness when the turning processes AISI 304 (Austenitic), AISI 420 (Martensitic) and AISI 2205 (Duplex) stainless steels have been explored the machinability performance and cutting forces. The machining tests have been conducted on a CNC turning center using coated cemented carbide tools. Machining parameters have been chosen cutting speeds (120, 150, 180 and 210 m/min), feed rate (0.1 mm/rev) and depth of cut (1 mm/rev) according to cutting tool manufacturer recommendation catalog. Machining forces and surface roughness variables have been measured when the turning processes. It has also been investigated the worn of cutting tools and explored under the scanning electron microscope (SEM). An ANN model has been developed using experimental results. Experimental results and ANN model results have been compared with each other. It seemed that cutting forces have been modeled using ANN techniques and ANN results have been very close to experimental results. Page(s): 93-104

Flow behavior modeling and processing maps for P91 steel during hot deformation

Mon, 01 Apr 2019 00:00:00 GMT

Title: Flow behavior modeling and processing maps for P91 steel during hot deformation Authors: Chen, Zhiying; Zhang, Ying; Ren, Yunlai; Wang, Ying Abstract: Constitutive analysis and processing maps have been performed from hot compression tests on P91 steel over a range of temperatures between 950 °C to 1200 °C and strain rates of 0.05 to 1 s^-1. Hyperbolic sine type of constitutive equation has been established. The activation energy Q is 441.864kJmol⁻¹, larger than the austenite lattice self-diffusion activation energy. The processing maps have been developed based on the dynamic materials model (DMM) and Prasad’s instability criterion. The optimum hot deformation regions at 0.7 strain have at the temperature of 1000-1175 °C and strain rate of 0.05-0.14 s⁻¹; at the temperature of 1100-1200 °C and strain rate of 0.14-1s⁻¹. Page(s): 105-111

Wear resistance evaluation of cryogenically treated AISI–H11 steel: An optimization approach

Mon, 01 Apr 2019 00:00:00 GMT

Title: Wear resistance evaluation of cryogenically treated AISI–H11 steel: An optimization approach Authors: Katoch, Sanjeev; Sehgal, Rakesh; Singh, Vishal Abstract: The consequences of key process parameters of cryogenic treatment (i.e. holding time and temperature) on the average coefficient of friction and wear rate in dry sliding condition at different level of load (60, 80, 100, 120 & 140 N) and sliding velocity (0.628, 0.942, 1.257, 1.571 & 1.885 m/s) have been explored through cubic regression mathematical modeling technique. An average error of 1% and 9.9% has been observed in the experimental and model given values for coefficient of friction and wear rate. Mathematical model equation capability is within the range of 95% confidence level. Moreover, desirability function approach has been employed to find out the process parameter to have lower wear resistance. Worn out samples have been examined with field emission scanning electron microscope (FESEM) and reveals that the operative mechanism for wear is delaminating and rupturing of matrix. Page(s): 112-125

Effect of ball-to-powder weight ratio on microstructure evolution of nanocrystalline Mg-Zn powders prepared by mechanical milling

Mon, 01 Apr 2019 00:00:00 GMT

Title: Effect of ball-to-powder weight ratio on microstructure evolution of nanocrystalline Mg-Zn powders prepared by mechanical milling Authors: Chen, Xinrong; Teng, Jie; Xu, Zili; Li, Yuan Abstract: Nanocrystalline Mg-Zn powders have been prepared by mechanical milling using a planetary ball-mill with three ball-to-powder weight ratios of 30:1, 40:1 and 50:1 under argon atmosphere. The influence of ball-to-powder weight ratio on morphological changes, microstructural evolution and thermal behaviour of the milled powders has been examined by a combination of X-ray diffraction, differential scanning calorimetry, scanning electron microscopy and transmission electron microscopy. The crystallite size and microstrain of the Mg matrix of the milled powders have been estimated using the Williamson–Hall method. The results show that in the first two hours of milling the crystallite size decreases rapidly and then slowly decrease with increasing milling time. After 18 h of milling, the crystallite size has been refined to 60-80 nm and remained unchanged. An excessively high BPR is not conducive to the deformation of the milled powders and the reduction of nanograin size. Additionally, the effectiveness of the milling process with different BPRs has also been discussed. Page(s): 126-134