“…( 10), for industrial application of t-HPS, there exists a limit on the aspect ratio h/R of the tube processed by t-HPS, and this limit is based on the ratio of allowable shear stress of the t-HPS mandrel and the deformation resistance to the processing tube. 16,23) Alternatively, according to the above described principle of t-HPS, geometrical and mechanical similarity 24) could be easily maintained in scaling up for industrial applications, and the complex barriers retarding the scale up of HPT, such as the increased strain heterogeneity, 25,26) seems not as obvious because of the different principle between t-HPS and HPT. This will need to be examined by further experimental investigations.…”