The energy dissipation during fatigue crack growth

Fatigue failures are a major concern in aeronautics. The growth of fatigue cracks in metallic structures and adhesively bonded joints has been studied for decades. Nowadays, most researchers evaluate and predict the fatigue damage growth rate (da/dN) with empirical and phenomenon based approaches, using Linear Elastic Fracture Mechanics with...

Application of data reconciliation to a dynamically operated wastewater treatment process with off-gas measurements

This study deals with the application of data reconciliation to wastewater treatment processes which are subject to dynamic conditions and therefore do not reach a steady-state behaviour sensu stricto. The SHARON partial nitritation process, which is operated cyclically with alternating aerated and anoxic periods, is studied as an example....

The energy dissipation during fatigue crack growth in metallic materials

An energy equation for fatigue crack growth was proposed. It equates the total external work per cycle (dW/dN) to the sum of plastic dissipation (dU_pl/dN), change in strain energy stored (dU_e/dN) and the energy dissipated in new crack surface formation (dU_a/dN). Fatigue crack growth experiment of 7075-T6 was...

The energy dissipation during fatigue crack growth in adhesive joints under Mode-I loading

An energy equation for fatigue crack growth in adhesive joints is proposed. Fatigue experiment on DCB adhesive joint specimens was used to derive the relation between fatigue crack growth rate (da/dN) and energy variables in this equation. The result shows plastic dissipation and change in stored strain energy, whose relation with da/dN both...

On the effect of plastic model on simulation of adhesive bonded joints with FM94

The stress-strain relationship of adhesive material is important as an input for numerical simulation. In this paper, a series of quasi-static experiments to measure the stress-strain relationship of FM94 adhesive material is reported. The experiments include the bulk tension test to obtain the tensile property and the V-notched beam shear...

The relation between fatigue crack growth rate and plastic energy dissipation in 7075-T6

Plastic dissipation accompanies fatigue crack growth in ductile materials. Previous studies presented a relation between plastic dissipation (dW/dN) and the fatigue crack growth rate (da/dN), where some researchers assumed a linear relation between both to enable crack growth predictions. To study the validity of this assumption, this paper...

Experimental design for evaluating WWTP data by linear mass balances

A stepwise experimental design procedure to obtain reliable data from wastewater treatment plants (WWTPs) was developed. The proposed procedure aims at determining sets of additional measurements (besides available ones) that guarantee the identifiability of key process variables, which means that their value can be calculated from other,...

The stress ratio effect on plastic dissipation during fatigue crack growth

Plastic energy dissipation is inevitable during fatigue crack growth. There have been previous attempts reported in literature to correlate the plastic dissipated energy (dW/dN) to fatigue crack growth rate (da/dN). However, at a given dW/dN, the da/dN changes with the ratio of minimum and maximum loads, known as the stress ratio. This paper...