PSI - Issue 47

Ezio Cadoni et al. / Procedia Structural Integrity 47 (2023) 268–273

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Author name / Structural Integrity Procedia 00 (2023) 000–000

Fig. 3. Stress versus strain curves as a function of strain rate.

a) b) Fig. 4. Raw input pulse signals at di ff erent temperatures (a); Strain rate versus temperature for three preloading levels (b).

of tungsten alloys under these conditions. This is why a preliminary study has been conducted. In a previous work Cadoni et al. (2020) the strain rate sensitivity of this alloy was investigated. There was an increase in proof and ulti mate tensile strength as well as modulus of toughness and a decrease in area reduction as a result of high strain rates. The stress versus strain curves as a function of strain rate are depicted in Fig. 3. Tensile mechanical properties of the examined commercial tungsten alloy, including ultimate tensile strength, frac ture strength, and nominal total elongation, are strongly dependent on test temperature. With increasing temperature, they usually show a decreasing trend. It has been found in Cadoni et al. (2021) that the strength and of this commercial tungsten alloys decreased with increasing temperature under high strain rate loading conditions. Fig. 4a shows how the initial conditions were maintained. All testing temperatures use the same input signals. Input signals are not a ff ected by temperature, but reflection waves are. There has been no measurement of the elastic modulus at high temperatures. With increasing temperature, the value is expected to decrease linearly. In relation to temperature, strain rate evolution exhibits a linear trend (Cadoni and Forni (2019a, 2021)). Fig. 4b collects the values measured for three preloading levels. The strain rate can be evaluated as:

˙ T = ˙ 20 ◦ C + η · T

(4)

where: ˙ T is the strain rate at the temperature T ; ˙ 20 ◦ C is the strain rate at room temperature; η average = 0.424 for this alloy. At room temperature, 850 s − 1 of strain is obtained with a 26 kN preload, resulting in a stress-strain curve as shown in Fig. 5a in the temperature range 20-1100 ◦ C. An example of a high temperature test setup is shown in Fig. 5b.