NOPR Collection:

Effects of process parameters of GMAW on bead geometry, tensile strength, hardness, microstructure and thermo-mechanical simulation of AISI 202 steel

Fri, 01 Dec 2017 00:00:00 GMT

Title: Effects of process parameters of GMAW on bead geometry, tensile strength, hardness, microstructure and thermo-mechanical simulation of AISI 202 steel Authors: Kamble, A G; Rao, R Venkata Abstract: This paper presents a study on welding of AISI 202 steel using AISI 308L filler wire using gas metal arc welding process. The experiments are conducted using central composite design matrix by varying four input process parameters, viz., welding speed, welding voltage, wire feed rate and gas flow rate. The output parameters like bead height, bead width, bead penetrations and mechanical properties like hardness and tensile strength are measured. Also, microstructure at base metal zone, heat affected zone and weld zone of the weldments are observed. The mathematical models for output parameters are developed using response surface methodology and effects of process parameters on response parameters and microstructure are found out. Furthermore, thermo-mechanical simulation using ANSYS software is carried out to predict the thermally induced residual stresses distribution in the weldment. This work helps the manufacturer in selecting the process parameters to achieve desirable results and improve the weld quality. Page(s): 413-428

Multi-objective optimization of material removal rate and surface roughness in electrical discharge turning of titanium alloy (Ti-6Al-4V)

Fri, 01 Dec 2017 00:00:00 GMT

Title: Multi-objective optimization of material removal rate and surface roughness in electrical discharge turning of titanium alloy (Ti-6Al-4V) Authors: Gohil, Vikas; Puri, Y M Abstract: Electrical discharge turning (EDT) is a unique form of electrical discharge machining (EDM) process, which is being especially developed to generate cylindrical forms and helical profiles on difficult to machine materials at both macro and micro levels. This study presents an experimental investigation of electrical discharge turning of titanium Ti-6Al-4V alloy. The objective is to investigate the influence of machining parameters including polarity, pulse-on time, peak current, gap voltage and spindle speed on performance characteristics. Taguchi-grey relational approach based on multi objective optimization has been used to maximize material removal and to minimize surface roughness. It has been found that polarity followed by peak current has most influent nature in EDT process. The confirmation experiment shows an improvement in material removal rate of 12.70% and surface roughness of 5.57% through this approach. Page(s): 429-436

Optimization of gas protected stir casting process using GRA and TOPSIS

Fri, 01 Dec 2017 00:00:00 GMT

Title: Optimization of gas protected stir casting process using GRA and TOPSIS Authors: Sharma, Amit; Belokar, R M; Kumar, Sanjeev Abstract: In this paper, multi-response optimization of gas protected stir casting process parameters is carried out for the development of Al2024/red mud composite in order to maximize the responses such as tensile strength and microhardness. Process parameters considered are reinforcement, grain size and blade angle which are varied at three levels and Taguchi’s L₂₇ orthogonal array is used for designing the experiments. Optimum condition of the process parameters are established for the multi-response optimization problem using TOPSIS and grey relational analysis (GRA). Response surface methodology (RSM) is used to derive the regression equations for the responses which are found to be effective within the design space. ANOVA analysis is carried out to study the effect of process parameters on the responses and it is observed that reinforcement is having a dominating effect on both the responses followed by grain size and blade angle. Results of GRA and TOPSIS are found to be in good agreement with each other. Page(s): 437-446

Hot compression deformation behavior and microstructure evolution rule of a high-speed railway axle steel

Fri, 01 Dec 2017 00:00:00 GMT

Title: Hot compression deformation behavior and microstructure evolution rule of a high-speed railway axle steel Authors: Huo, Yuanming; Wang, Baoyu; Lin, Jianguo; Bai, Qian; Ji, Hongchao; Tang, Xuefeng Abstract: The high performance of high-speed railway axle (HSRA) depends on the stress-strain state and microstructure formed in the hot processes, it is necessary to investigate the deformation behavior and microstructure evolution during hot uniaxial compression. Hot compression test was performed on specimen of a HSRA steel 25CrMo4 at a deformation temperature of 1040-1160^oC at a strain rate of 1.0-10.0 /s using a Gleeble thermal mechanical simulator. During hot compression test, samples were compressed to different true strain: 0, 0.2, 0.4, 0.6 and 0.8. Hot compressive deformation behaviors and effects of processing parameters, including forming temperature, strain rate and deformation degree, on microstructure evolution of HSRA steel 25CrMo4 are investigated and studied by metallurgical analysis. Experiments results show that the peak value of flow stress increases about 30 MPa at a certain deformation temperature when the strain rate increases from 1.0 /s to 10.0 /s. At a certain strain rate, the peak value of flow stress increases about 20-30 MPa when the forming temperature decreases about 60^oC. The average grain sizes increases with the increasing of forming temperature at a certain strain rate and a given strain. For a given forming temperature, grain size decreased before the critical strain of 0.4 and increased after strain of 0.4 due to grain growth, especially at lower strain rate. Therefore, grain size at lower strain rate is larger than that at higher strain rate when true strain reached 0.8. Page(s): 447-454