The constitutive model is still not available for theoretical and engineering analysis of HNi55-7-4-2 alloy, which is a new type of wear-resistant brass alloy widely applied to car synchronizer rings and ship condenser tubes etc. In the current investigation, a friction-corrected stress-strain curve was obtained through a hot-compression test to develop the high-temperature constitutive model of HNi55-7-4-2 alloy based on the Hansel–Spittel model. By comparing predicted flow stress and a simulated force-stroke curve with experimental results, the proposed constitutive model was verified. The developed constitutive model was applied to numerically simulate the hot precision forging of a synchronizer ring. The simulation results based on two process plans on material flow and forging defects were validated by process experiment. The Hansel–Spittel high-temperature constitutive model proposed in this work enables the theoretical and engineering analysis of HNi55-7-4-2 alloy.

An accurate constitutive model is essential for designing the process of hot precision forging and numerical simulation. Based on the isothermal compression tests of as-extruded HMn64–8–5–15 manganese brass alloy at the deformation temperature of 873–1073 K and strain rate of 001–10 s⁻¹, the effect of the friction and deformation temperature rise on the flow stress during the hot compression process was analyzed, and the flow stress curves were corrected. Three constitutive models based on the modified Zerilli-Armstrong, Arrhenius, and a back-propagation neural network (BPNN) optimized by the grey wolf optimization (GWO) algorithm (GWO-BPNN) models were established to describe the high-temperature flow stress of this alloy. Meanwhile, the prediction ability of the three models was evaluated by the calculated values of mean absolute percentage error (MAPE) and root mean square error (RMSE). The values of MAPE for the modified Zerilli-Armstrong, Arrhenius, and GWO-BPNN models were computed to be, 3139 %, 2448 % and 1265 %, and the values of RMSE were calculated to be 1804, 1482 and 0467 MPa, respectively. The GWO-BPNN model was with the greatest prediction ability for the flow stress among these models. The GWO algorithm was introduced to optimize the initial weights and thresholds of the BPNN model, and it has good prediction accuracy and better stability. It can better describe the high-temperature flow behavior of HMn64–8–5–15 alloy.

The flow behavior of a new kind of high-strength nickel brass used as automobile synchronizer rings was investigated by hot compression tests with a Gleeble-3500 isothermal simulator at strain rates ranging from 0.01 to 10 s⁻¹ and a wide deformation temperature range of 873–1073K at intervals of 50 K. The experimental results show that flow stress increases with increasing strain rate and decreasing deformation temperature, and discontinuous yielding appeared in the flow stress curves at higher strain rates. A modified Arrhenius constitutive model considering the compensation of strain was established to describe the flow behavior of this alloy. A processing map was also constructed with strain of 0.3, 0.6, and 0.9 based on the obtained experimental flow stress–strain data. In addition, the optical microstructure evolution and its connection with the processing map of compressed specimens are discussed. The predominant deformation mechanism of Cu-Ni-Al brass is dynamic recovery when the deformation temperature is lower than 973 K and dynamic recrystallization when the deformation temperature is higher than 973 K according to optical observation. The processing map provides the optimal hot working temperature and strain rate, which is beneficial in choosing technical parameters for this high-strength alloy.

A comprehensive analysis of the physical processes that occur in Electroslag Remelting (ESR) process under steady state conditions and axisymmetric was performed using the simulation software MeltFlow. The detailed plots of current distribution, volumetric heating, flow, temperature and turbulent mixing provide insight into the various physical phenomena that occur in ESR process. The effect of current frequency on various physical fields was analyzed. It is shown that, the current in the slag tends to become more uniform due to the low electrical conductivity of the slag; after the current enters the ingot, the skin effect increases with the increase of the current frequency; the Joule heating and the Lorentz force are highest near the tip of the electrode in the slag, and increase with the increase of the current frequency; the velocities in the slag are slightly higher than those in the molten metal pool; with the increase of the current frequency, the liquidus temperature moves down, and the molten metal pool is deepened. Simulation results agree well with experimental results. Therefore, the generation and extent of defects could be predicted in different process.

Mobile positive pressure ventilation controls smoke in compartment fires, yet the downstream flow field of mobile fans is still not well quantified. This paper combines FDS simulation with full-scale measurements to examine jet attenuation, effective range, and practical smoke-exhaust use. A detailed fan model is validated against open-space velocity data and then applied to a residential fire scenario with different exhaust-window layouts. The results show that fan setting, opening area, and outlet position strongly affect inlet velocity, visibility, temperature, and exhaust efficiency. A 2.5-4.0 m deployment distance maintains useful inlet speed, and concentrating exhaust openings near the fire room improves smoke removal.