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Hui Li, Yingshe Luo, Donglan Hu
Long term creep assessment of room-temperature cured epoxy adhesive by time-stress superposition and fractional rheological model

Appl. Rheol. 28:6 (2018) 64796 (10 pages)

The creep behavior of a new type epoxy resin adhesive which is room-temperature cured and used for reinforcing engineering structures was studied. The tensile strength of the adhesive has reached the desired values for the structural adhesive used for bonding concrete as the base material with steel. The short-term creep tests were conducted under four different stress levels. The generalized curve for reference stress was obtained by utilizing the time-stress equivalent principle. Moreover, compared with traditional Burgers model, an improved fractional KBurgers model obtained by replacing the Newton derivative with the fractional derivative element (Abel component) in the traditional Burgers model can capture the creep behavior of this epoxy adhesive with high precision in the condition of the room-temperature and tensile stress of 36 MPa.

Cite this publication as follows:
Li H, Luo Y, Hu D: Long term creep assessment of room-temperature cured epoxy adhesive by time-stress superposition and fractional rheological model, Appl. Rheol. 28 (2018) 64796.

Hansong Zhang, Zhide Hu, Hua Yan, Jianjian Yang, Fanghao Niu
The influences on field-induced chains by nonmagnetic microstructures inside the magnetorheological fluids Based on PTFE-oil organogel

Appl. Rheol. 28:5 (2018) 53921 (12 pages)

Polytetrafluoroethylene (PTFE) micropowders were used to prepare PTFE-oil organogel. Carbonyl iron particles were dispersed in this organogel to fabricate magnetorheological fluids. The main aim of this paper is to investigate the influences on fieldinduced chains by non-magnetic microstructures inside these organogel-based MRFs. The field-induced anisotropy of MRFs between first normal stress differences to shear stresses and dynamic modulus reveal that organogel widen the non- Newtonian elastic range of MRFs as long as the non-magnetic particles content is appropriate. Both theoretical and experimental results of static and dynamic normal forces indicate that normal forces are influenced by magnetic and non-magnetic microstructures comprehensively. The dynamic normal forces are lower than static ones under low magnetic field strength while the phenomenon becomes opposite in the presence of high strength magnetic field. Moreover, a 3ITT test of normal forces exhibits a significant time-dependent behavior of the normal forces. The investigations of recovery ratio demonstrate that the non-magnetic microstructures help field-induced chains to recover at relatively low magnetic field strength but hinder this structural recovery at high magnetic field strength. Finally, a new investigation method on amplitude-dependent normal forces is introduced showing a four-region behavior as a function of strain amplitude, which reflects the internal microscopic evolution of MRFs and could be a proper way to study the influences on field-induced chains by non-magnetic particles.

Cite this publication as follows:
Zhang H, Hu Z, Yan H, Yang J, Niu F: The influences on field-induced chains by nonmagnetic microstructures inside the magnetorheological fluids Based on PTFE-oil organogel, Appl. Rheol. 28 (2018) 53921.

Jingsi Zhang, Simon J Haward, Zhigen Wu, XiaoHu.Dai, Wenquan Tao, Zhuo Li
Evolution of Rheological Characteristics of High-solid Municipal Sludge during Anaerobic Digestion

Appl. Rheol. 26:3 (2016) 32973 (10 pages)

Rheological characterization of high-solid sludge is a fundamental requirement for optimizing the mixing and transport of high-solid sludge during anaerobic digestion in waste water treatment systems. We investigate the time evolution of physicochemical properties and rheological characteristics of high-solid digested sludge with total solids (TS) 15−20 wt.% during anaerobic digestion. A series of experiments are carried out over a period of 26 days during the operation of an anaerobic sequencing batch reactor. In equilibrium flow curves, high-solid digested sludge exhibits shear thinning behavior with a yield stress. Strong viscoelastic behavior is exhibited in the linear and non-linear regimes in dynamic and creep tests. A critical shear stress is found in the equilibrium flow curve, which accounts for the viscoelastic property. To accurately model the flow curves, a piecewise Herschel-Bulkley function separated by the corresponding critical shear rate is proposed. The digestion time plays an important role in determining the rheological behavior. Longer digestion times lead to a decreased yield stress in creep tests, and a decreased viscosity and a reduced critical shear stress in the steady flow curve. In addition, the storage modulus G' and the loss modulus G'' are reduced as digestion proceeds, leading to a shorter linear viscoelastic regime. Moreover, we find that the storage modulus G' varies linearly with the concentration of total organic matter in the sludge, suggesting that G' could be used as a new control parameter for monitoring of the anaerobic digestion process.

Cite this publication as follows:
Zhang J, Haward SJ, Wu Z, Dai X, Tao W, Li Z: Evolution of Rheological Characteristics of High-solid Municipal Sludge during Anaerobic Digestion, Appl. Rheol. 26 (2016) 32973.


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