## 2 Materials Processing and Design Procedures  
The standard samples and the applicable parts were prepared by the rheocasting semi-solid process using A357 aluminum alloy billets (Al-7%Si-0.65%Mg-0.1%Fe) as applied in [14; 15]. The semi solid casting process is coupled with a high pressure die casting (HPDC) press to produce the materials used for mechanical and micro-structural characterizations. Figure 1 shows the accelerating thermal aging treatments using multiple and interrupted cycles of T4/T6/T7. These thermal aging treatments were applied to the bending fatigue standard samples and to the applicable suspension mechanical components. Specific aging cycles, mainly T6, WA0, WA1, WB0, WC1, and WC3, were applied in this study according to their positive effects on both tensile and quality index characteristics by previous studies applied for A357 aluminum semi solid alloys [14; 15]. The bending fatigue samples were subjected to two step solution heat treatments, followed by water quenching maintained at 60 \({}^{\circ}\)C and then naturally aged at room temperature for 24 h before proceeding to the thermal aging cycles. Fatigue cycles and performance were applied for both standard bending fatigue samples and applicable suspension control parts of A357 semi solid materials using bending high cyclic fatigue tests and tension-compression low cyclic fatigue, respectively. The constant deflection cantilever bending fatigue testing was applied in this study. Specimens were subjected to constant deflection for a high number of cycles until fracture. The bending fatigue samples were mounted, to be completely restrained from one end, while the other end was attached to the machine rocker arm. The rocker arm was adjusted so that it maintained a constant stroke throughout the whole experiment regardless of the load on each specimen. The machine used was a crank-slider mechanism in which the specimen was attached to the slider part. Figure 2a shows a crank-slider mechanism representing the operating mechanism of the testing machine. The specimen was mounted in the slider position 'S' while the motor rotated the crank 'R' with a constant angular velocity '\(\omega\)'. The stroke length is of importance in this machine as it represents the deflection to be applied on the specimen. The stroke length can be altered by changing the length of the crank 'R'. The fatigue test machine used in this experiment uses an eccentric crank in which the eccentricity works as the crank length. Thus, changing the eccentricity of the device would change the stroke length and the deflection applied to the test specimen. Figure 2b shows the eccentric crank in which the stroke can be adjusted from 0 to 2.0 inches (50.8 mm). The machine used operates using an electric motor of 0.5 HP (373 Watt) power and a maximum force transmitted to specimens of 40 Ib (178 N). Operating frequency was set to 12 Hz for all test samples with a deflection of 6.35 mm (0.25 in). The samples were machined as shown in Figure 2c, and were then grinded to remove any scratches resulting from machining. Scratches and macro cracks act as stress raisers initiating fatigue cracks and causing much lower fatigue life. A MATLAB code was used in the calculation of the stress developed in the fatigue specimen using [PERSON]'s modulus of 70 GPa for aluminum, and [PERSON]'s ratio of 0.33 for isotropic material. Solid mechanic equations were used in the stress calculation as follows:  
\[\text{I}=\text{(bh^{*}3)/12~{}\&~{}\sigma=\text{m}\text{y}/\text{I}} \tag{1}\]  
where 'I' is the 2 nd moment of area, 'b' is the specimen width, 'h' is the specimen thickness, '\(\sigma\)' is the stress,'m' is the maximum bending moment, and 'y' is half the thickness. Figure 2d shows the resulting plot of the code, showing a maximum stress of 50 MPa at the center of the reduced width area; stress then decays, reaching zero near both the restrained and the free ends.