Page 91 - eBook_Proceedings of the International Conference on Digital Manufacturing V2

Fabrication and Characterization of a Low-Cost Piezoelectric using Rochelle
Salt for Energy Harvesting and Sensor Applications

Shear-thinning and time-dependent viscosity are closely
related. Figure illustrates the thixotropic behaviour of semi-solid
emulsions, showing how viscosity changes with time and shear
rate. Thixotropy is a time-dependent property where a material's
viscosity decreases under constant shear stress and recovers when
the stress is removed. The thixotropic effect accounts for
differences in instantaneous viscosity from steady values at the
onset, during, or after cutting, when the shear rate changes
suddenly. Instead of returning instantly, viscosity slowly stabilises
over time. The reverse effect, where viscosity rises with time, is
known as rheopexy (Megalingam, Ahmad, Maarof & Sudhakar,
2022; Modigell, Pola & Tocci, 2018; Atkinson & Rassili, 2010).

Figure 31: A schematic of thixotropic behaviour of semi-solid
emulsions (Megalingam, Ahmad, Maarof & Sudhakar, 2022;
(Megalingam, Ahmad, Alang, Muhammad & Muduli, 2024).

Thixotropic Behaviour of Ferrous vs Non-Ferrous

Thixotropic behaviour allows materials to flow when
experiencing stress, but remain stable when at rest. This property
is essential for SSMP, which requires a globular microstructure.
Mechanical shear and controlled cooling help form a
microstructure with rounded grains and a broad melting range,
improving flow and shaping.

75