**4. Casting and Mechanical Testing**

The preparation of a mold requires a pattern which is an exact replica of the part to be cast. A wooden pattern of the optimized casting layout is developed as shown in Figure 10a to compact sand around it thereby forming a mold. The resulting sand mold

is shown in Figure 10b. In order to avoid direct interaction of molten metal with the mold material, a dense layer of zirconium-based coating is applied to the mold surface. Mold properties evaluation revealed a compression strength of 18 kg/cm<sup>2</sup> and a scratch hardness of 28–29. The pouring temperature is set to 1590–1600 ◦C for which steel is melted in an induction furnace which offers ease of operation, high quality of products, better metallurgical functions, and lower oxidation losses. The steel is deoxidized using Aluminum in the ladle prior to pouring into the mold. It is ensured to perform casting at similar conditions which are used in the simulations. Figure 10c shows the entire casting just after the removal of mold. As mentioned earlier, the specimens are considered as simple cast parts which are obtained after removing pouring basin, sprue, runner bar, and risers. The specimens are then annealed at 920 ◦C, held for half an hour, and cooled in furnace. Specimens after heat treatment are machined to final dimensions as per the ASTM E-466 standard [14]. The quality and surface finish of the specimens is enhanced during machining.

**Figure 10.** (**a**) Pattern, (**b**) Sand mold and (**c**) Cast Specimens prior to cleaning and finishing.

The quality of cast specimens is evaluated using radiographic examination. The results of X-ray imaging are presented in Figure 11. Some porosity is revealed within the test section of specimens which is observed as difference in appearance of grips and the test section as shown in Figure 11. However, the distribution of porosity from one specimen to another is not much different.

**Figure 11.** X-ray imaging of steel fatigue specimens.

The fatigue testing is done as per the ASTM E-466 standard [14]. The experimental setup is presented in Figure 12. Fully revered conditions where R = −1 is used to test all specimens under cyclic loading. The frequency of testing is set to be 5 Hz for all specimens. Fatigue testing is done until fracture for all specimens except for runout condition which is 10<sup>6</sup> cycles in this study. A careful selection of stress amplitude has led to the testing of six specimens for finite life and one for the infinite life. Table 3 lists the stress amplitude selected and number of cycles to failure for each specimen. Figure 13 depicts the SN curve developed as a results of fatigue testing of steel specimens.

**Figure 12.** Experimental setup for fatigue testing.

**Table 3.** Experimental results for fatigue testing of specimens.


**Figure 13.** S-N curve for cast steel specimens.
