PSI - Issue 60

Behrooz Tafazzolimoghaddam et al. / Procedia Structural Integrity 60 (2024) 575–581 Author name / Structural Integrity Procedia 00 (2019) 000–000

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calculated [10] [11] by measuring the displacement field and applying Bueckner’s principle of elastic superposition [12]. The following steps are done to carry out a contour measurement: 1- A planar cut is performed on the desired cross section of the specimen using an electric discharge machine (EDM). To create a uniform thickness for the EDM cut a sacrificial layer was glued on top of the weld on the cutting path and the specimen was fixed on the machine using bespoke fixtures. Two pilot holes were drilled where each cutting stages started. 2- The out-of-plane displacements are measured on the two cut surfaces. 3- The measured data from the two sides are averaged (to remove the effect of shear stress) and the cutting induced artefacts and noise is removed. 4- A surface function such as polynomials or spline is fitted onto the data. 5- An FE model of one of the halves of the specimen is created and meshed. The smoothed displacement data is mapped onto the nodes on the cut surface (with a negative sign) as the boundary conditions. The elastic FE analysis calculates the residual stresses on the surface which was present in the part before the cut. 2.2. Contour Method An AISI 316 SS plate with 150 × 150 × 20 mm dimensions was cut from the large size plate for the experiment. The hardfacing alloy 75Ni13.5Cr2.7B-3.5Si was deposited on the plate using PTA process on an 80 × 80 mm square with 11 passes and 10 mm weave, oscillating at 750 mm / min. The weld parameters and the dimensions are presented in Table 1.

Table 1 PTA process parameters for Hardfacing with 75Ni13.5Cr2.7B-3.5Si on AISI 316 SS plate

Parameter Voltage Current Weld Speed

Value

27v

110A

100mm/min

Pre-heat

450 ° C 25g/min 10mm

Powder Feed Rate Oscillation Width Oscillation speed

750mm/min

Oscillation shift distance Weave bead patch size

5mm

80mm 2

Figure 1 AISI 316 SS plate with 11 weld beads on 80 × 80 mm square at the centre of the plate. 1. The specimen before the cut and the weld direction 2. Cut specimen and the cutting steps / directions

Figure 1 AISI 316 SS plate with 11 weld beads on 80 × 80 mm square at the centre of the plate. 1. The specimen before the cut and the weld direction 2. Cut specimen and the cutting steps / directions

The specimen was cut perpendicular to the weld beads at the centre of the sample as shown in Figure 1. Two pilot holes were drilled 5 mm from each side between which the first cut is done. This allows self-constraining of the part