Effect of Deformation Condition on Axial Compressive Precision Forming Process of Tube with Curling Die

The effect of the deformation condition on the axial compressive precision forming process of tube with curling die was investigated by using a rigid-plastic FEM. The results show that the forming accuracy depends mainly on geometric condition rp/d0, little on tube material properties and friction condition; the relative gap △/2rp of double-walled tubes obtained decreases with Increasing rp/d0, and there is a parameter k for a given to/do or rp/t0, when rp/d0 >k, △/2rp< 1, otherwise △/2rp>1.

Dynamic Recrystallization Behavior in Mn-Cr Gear Steel

Using a Gleeble 1500 hot simulator, the dynamic recrystallization （DRX） behavior of Mn-Cr type gear steel was investigated. The experimental results show that the Mn-Cr gear steel exhibits a typical DRX behavior at higher deformation temperature, lower strain rate and smaller initial austenite grain size. The DRX takes place under the conditions that Zener-Hollomon parameter （Z） is less than a critical value Zc. The DXR grains are formed by the bulging mechanism. Activation energy and stress exponent were calculated to be 378.6 kJ · mol^-1 and 5.8 respectively by regression analysis.

Effect of Cold Deformation on the Friction–Wear Property of a Biomedical Nickel-Free High-Nitrogen Stainless Steel

The microstructural,mechanical and corrosion properties of different cold-rolled biomedical nickel-free highnitrogen stainless steels（NFHNSSs） were investigated to study the effect of cold deformation on its dry wear resistance as well as corrosion–wear behaviors in distilled water and Hank＇s solution. The results indicated that NFHNSS was characterized by stable austenite and possessed excellent work-hardening capacity; due to increasing cold deformation,the corrosion resistance just decreased very slightly and the dry wear rate decreased initially but subsequently increased,while the corrosion–wear resistance was improved monotonically in both distilled water and Hank＇s solution in spite of the presence of corrosive ions. The friction coefficients for different cold-rolled NFHNSSs were very close under the same lubricating condition,but they were the largest in distilled water compared to that in dry wear tests and Hank＇s solution.

Research on Voids Deformation Welding Condition for Manufacturing of Heavy Forgings

Crushing and diffusion welding are two critical healing stages of interior void defects in heavy forgings.The healing result depends on many factors during the forging process,such as stress,temperature,deformation and type of material,while the void diffusion welding condition is still not well known at the present.This paper is concerned with the deformation welding condition of the closed void interface in heavy ingot during the hot forging process.A void crushing experiment is carried out to recognize the microstructure of the closed void interface.According to the healing mechanism at high temperature,a new physical simulation model is setup to study the deformation welding process of the closed void interface based on the theory of atom diffusion and the interface contact mechanics prototype.Compared with the experimental results,the influence of deformation degree,forming temperature and holding time on the welding quality is discussed,and then the deformation welding condition of closed void interface is presented.The proposed condition helps to improve forging technology and product quality.

Computational fluid dynamics simulation of friction stir welding:A comparative study on different frictional boundary conditions

Numerical simulation based on computational fluid dynamics （CFD） is a useful approach for quantitatively investigating the underlying thermal-mechanical conditions during FSW, such as temperature field and material deformation field. One of the critical issues in CFD simulation of FSW is the use of the frictional boundary condition, which represents the friction between the welding tool and the workpiece in the numerical models. In this study, three-dimensional numerical simulation is conducted to analyze the heat transfer and plastic deformation behaviors during the FSW of AA2024. For comparison purposes, both the boundary velocity （BV） models and the boundary shear stress （BSS） models are employed in order to assess their performances in predicting the temperature and material deformation in FSW. It is interesting to note that different boundary conditions yield similar predictions on temperature, but quite different predictions on material deformation. The numerical predictions are compared with the experimental results. The predicted deformation zone geometry by the BSS model is consistent with the experimental results while there is large difference between the predictions by the BV models and the experimental measurements. The fact that the BSS model yields more reasonable predictions on the deformation zone geometry is attributed to its capacity to automatically adjust the contact state at the tool/workpiece interface. Based on the favorable predictions on both the temperature field and the material deformation field, the BSS model is suggested to have a better performance in numerical simulation of FSW than the BV model.

Folded Radiolarite Unit as a Kinematic Indicator of the Zagros Collision Processes, Southwestern Iran

Radiolarites have an important role in the reconstruction of the paleogeography, bathymetry and their coexistence with ophiolites gives an opportunity to determine the tectonic his- tory of collisional zones. The radiolarite units of the southwestern Neyriz are part of the Zagros ac- cretionary prism and positioned beneath the thick bedded carbonate sediments of Tarbur Forma- tion. The existing various structural elements within this unit give a unique fortunate for investiga- tion on the deformation history and studying of the kinematics of the Zagros collision zone. The nu- merous evidence show that this unit has experienced different deformation conditions during ongo- ing evolution, including ductile, brittle-ductile and brittle deformation conditions. The main strike of E-W for axial planes of folds, eastward trend and plunge of fold axes, boudins＇ neck axes and Type III of the fold interference patterns are indicators of formation and evolution of folds during tran- spressional deformation. Structural evolution of the study area has been affected by an NE-dipping subduction zone of Neo-Tethyan oceanic lithosphere below the Iranian microcontinents. These structural elements suggest that high mechanical anisotropy and two successive generations of fold- ing simultaneously with thrusting and extrusion of this unit had led to formation and evolution of this highly asymmetrical folded unit on top of the subducted oceanic crust.