Sharif Digital Repository

Using a mechanical model and dislocation density based model, the evolutions of dislocation density and flow stress of pure copper during constrained groove pressing (CGP) process are investigated. In this regard, the strain and strain rate are achieved from the mechanical model and then input into the dislocation model. To verify the predicted flow stress, the process of constrained groove pressing is performed on the sheets of pure copper from one to three passes. The predicted flow stresses are compared with the experimental data and a good agreement is observed. Also, it is found that during the straining of the copper sheet in CGP process, the dislocation density and strength dropping... 

In this study a severe plastic deformation method called constrained groove pressing (CGP) is used for imposing a high magnitude of strain into the low carbon steel sheets. Microstructural changes during process are examined by X-ray diffraction and optical observations. The grain size evolution during severe plastic deformation is studied using Williamson-Hall analysis on XRD pattern of the deformed samples. In effective strain of 4.64, ferrite grains with a submicron size of 200-300nm are achieved. The results show that constrained groove pressing can effectively refine the coarse-grained structure to an ultra fine grain range. Mechanical properties changes due to microstructure evolution... 

A new modification of constrained groove pressing (CGP) process named as constrained groove pressing-cross route (CGP-CR) was suggested for severe plastic deformation (SPD) of sheet form metals with great potential for fabricating high strength nanostructured sheets. This process is based on the conventional CGP process including some modifications. One pass of this process includes eight stages (four corrugation and four flattening) and involves 90° cross-rotation between each two stages. As a result of each CGP-CR pass, a strain magnitude of ∼2.32 is imparted to the sample. To simulate the process, finite element modeling (FEM) was carried out using three-dimensional finite element... 

A modified method of severe plastic defomation (SPD) entitled constrained groove pressing-cross route (CGP-CR) was introduced for imposing a high magnitude of equivalent strain of about 2.32 per pass on the sheet form samples. The major benefit of this improved route compared to previous common route was the more homogeneity of strain in the rolling (RD) and transverse (TD) directions of sheets. In this study, low carbon steel samples were used for examination of evolutions in microstructure and mechanical properties during SPD via CGP-CR process. Mechanical properties improvement were measured by tensile and macro hardness tests. The results indicate that CGP-CR process can effectively... 

The grain size of constrained groove pressed aluminum has been predicted through the genetic programming approach. “Sheet thickness,” “elongation,” “yield strength,” “ultimate tensile strength,” “total strain,” and “hardness,” along with “primary grain size” of the ultrafine-grained sheets were utilized as input parameters to obtain the ultimate grain size. A total number of 73 available data in the literature were gathered and randomly divided into 60 and 13 sets for algorithm training and testing, respectively. Among the presented models, the one with best performance utilized parameters of total strain, ultimate tensile strength, and primary grain size with 40 chromosomes, 10 head sizes,... 

Commercial purity aluminum sheets are subjected to a severe plastic deformation technique called constrained groove pressing. In this study for the first time by using some technical optimizations, a strain magnitude of 6.9 is imposed to the sheets. The grain size evolution during severe plastic deformation is studied using Williamson-Hall analysis on X-ray diffraction pattern of the deformed samples. These results and transmission electron microscopy observations show that constrained groove pressing process can effectively refine the coarse-grained structure to an ultrafine grain range. The results of mechanical tests show that imposing strain in range of 0-5.75 causes to strengthening of...