Creep small-punch testing and its numerical simulations

A study on the evolution of the contact angle of small punch creep test of ductile materials

“…simply supported constrains, are adopted instead of modelling the holder and the support [26][27][28]. In particular Dymáček et al show that if the punch load is less than 400 N and the upper and lower dies are not allowed to deform during the test, the time to rupture obtained by the FE analyses is closer to the experimental time to failure [26].…”

“…Figure 2 shows the mesh used for the FE analyses, where four regions can be identified. A coarse mesh has been generated in Region IV, because that location is not critical for the numerical results (as it is away from the area of the specimen where necking occurs) and the corresponding deformation is expected to be small [9,25]. The necking area, Region II in Figure 2, where the most severe deformations are expected, is characterised by the smallest element size.…”

“…A mesh sensitive study was carried out in order for this region to be centred on the location where necking is expected, which agrees with the findings reported in refs. [9,25]. Regions I and III are also characterised by a relatively fine discretisation because they are adjacent to the necking area and the contact interaction with the punch has been defined on them as well.…”

“…Indeed, the interaction of several non-linearities, such as large deformations, large strains, non-linear material behaviour and non-linear contact interactions between the specimen and the punch, induces a very complex multi-axial stress field in the specimen which also evolves in time. This affects the SPCT fracture mechanism [2,7] and introduces several challenges into the identification of a robust correlation to convert SPCT data into respective standard uniaxial creep test data [7,[9][10][11]. Another major concern is the non-repeatability of the testing method, since the experimental results depend on the set up geometry [1, 4,12,13].…”

Damage modeling in Small Punch Test specimens

“…The aforementioned testing methodology, commonly known as Small Punch Test (SPT), employs very small specimens (generally, 8 mm diameter and 0.5 mm thickness) and may be considered as a non-destructive experiment. The SPT has consistently proven to be a reliable tool for estimating the mechanical [2,3] and creep [4,5] properties of metallic materials and its promising capabilities in fracture and damage characterization have attracted great interest in recent years (see, e.g., [6][7][8][9][10][11][12][14][15][16][17][18]). …”