Effect of aging on hardness in the upsetting tests using experimental and finite element investigations

This paper investigates the hardness distribution in cold upsetting operation of the aged billets. Three sets of cylindrical billets were solutionized at 504 ℃ and then each set of billets were aged at 150 ℃ for a period of 9 h, 13 h, and 18 h, respectively. The billets were upset to different levels of strain and flow stress equation was evaluated for all the aging conditions. The flow stress equation was given as input to the finite element software and simulated to the same level of strain as in the case of experiments. An attempt to predict metal hardness was made by correlating the equivalent strain with the hardness. The hardness measurements predicted were in good agreement with the experimental results. The demand for producing billets with more hardness on the surface and softness inside encourages this investigation to measure hardness experimentally and theoretically.

Hot Deformation Behavior of Nano-Precipitation Strengthening Steel

The hot deformation behavior of nanoprecipitation strengthening steel was studied using a Gleeble-3500 thermo-mechanical simulator. The results show that the peak stress reduces as the temperature increases, and increases as the strain rate increases. The dynamic recrystallization will more likely occur at higher deformation temperature and lower strain rate. The deformation activation energy of the tested steel at 950-1150οC is calculated to be 333.844kJ/mol by regression analysis. Flow stress equation of the tested steel is also established.

Fabrication Improvement of Cold Forging Hexagonal Nuts by Computational Analysis and Experiment Verification

Cold forging has played a critical role in fasteners and has been applied to the automobile industry, construction industry, aerospace industry, and living products so that cold forging presents the opportunities for manufacturing more products. By using computer simulation, this study attempts to analyze the process of creating machine parts, such as hexagonal nuts. The DEFORM-3D forming software is applied to analyze the process at various stages in the computer simulation, and the compression test is also used for the flow stress equation in order to compare the differences between the experimental results and the equation that is built into the computer simulation software. At the same time, the metallography and hardness of experiments are utilized to understand the cold forging characteristics of hexagonal nuts. The research results would benefit machinery businesses to realize the forging load and forming conditions at various stages before the fastener formation. In addition to planning proper die design and production, the quality of the produced hexagonal nuts would be more stable to promote industrial competitiveness.

Finite Element Analysis for the Tube Sinking Process of the Micro Ti-0.2Pd Tube

In this study, the tube sinking process for manufacturing the micro Ti-0.2Pd tube (2.4 mm external diameter, 0.4 mm thickness) was simulated by finite element analysis. The external diameter of the initial tube was 5.0 mm. In order to simulate the tube sinking process, the flow stress equation was deducted from the result of the tensile test and friction coefficient was indirectly obtained through the parameter studies. The simulation results showed the simulation error according to the change of diameter predicted to be less than 2%. The defect of the internal surface by stress was found through the experiment result.

Thermal Deformation Behavior of 1Cr12Ni3Mo2VNbN Alloy and Its Application in the Blade Forging

Thermal deformation flow stress equation of 1Cr12Ni3Mo2VNbN in the temperature range of 980 °C~1180 °C is established by means of hot simulation test and the regression analysis. The results show that the data obtained accords with hyperbolic sine function and the equation will also enrich the material performance database. The established equation is used in the blade forging production based on numerical simulation technology, and the numerical simulation results show that utilizing flat head billet can solve the problem of filling dissatisfaction at the root of the blade. Adopting water-based graphite lubricant provides better lubrication condition for blade forging. The equipment wear and energy consumption can be reduced by applying initial forging temperature of 1130°C in the blade forging process. The application of thermal deformation flow stress equation and numerical simulation technology can reduce the number of trial production, shorten the process design cycle and improve production efficiency in a large extent.

Finite Element Simulation on Superplastic Forming of Outer Jacket of Combustion Chamber

In this paper, mould configurations are studied by finite element simulation for superplastic blow forming of combustion chamber outer jacket. One concave and two convex mould configurations are basically considered to determine which type would be advantageous in terms of forming time and thickness distribution. For the simulation, the flow stress equation of duplex stainless steel was determined from free bulging test. The simulation results showed that the concave type was quit a bit different from the other two cases. The concave mould configuration produced shorter forming time and thicker thickness distribution than the others, and it seems to be more effective for superplastic forming of outer jacket. The obtained pressure profile for the concave mould configuration was employed in actual forming and the thickness distribution was compared for the verification.