Effects of pre-strain and stress level on stress relaxation ageing behaviour of 2195 Al–Li alloy: Experimental and constitutive modelling

2021 ◽  
Vol 851 ◽  
pp. 156829 ◽  
Author(s):  
He Li ◽  
Lihua Zhan ◽  
Minghui Huang ◽  
Xing Zhao ◽  
Chang Zhou ◽  
...  
Keyword(s):  
Stress Relaxation ◽  
Stress Level ◽  
Constitutive Modelling ◽  
Ageing Behaviour

scholarly journals Constitutive Modelling of Polylactic Acid at Large Deformation Using Multiaxial Strains

Polymers ◽  
2021 ◽  
Vol 13 (17) ◽  
pp. 2967
Author(s):  
John Sweeney ◽  
Paul Spencer ◽  
Glen Thompson ◽  
David Barker ◽  
Phil Coates
Keyword(s):  
Steady State ◽  
Stress Relaxation ◽  
Strain Hardening ◽  
Small Strain ◽  
Limited Range ◽  
Constitutive Modelling ◽  
True Stress ◽  
Final Strain ◽  
Transverse Stresses

Sheet specimens of a PLLA-based polymer have been extended at a temperature near to the glass transition in both uniaxial and planar tension, with stress relaxation observed for some time after reaching the final strain. Both axial and transverse stresses were recorded in the planar experiments. In all cases during loading, yielding at small strain was followed by a drop in true stress and then strain hardening. This was followed by stress relaxation at constant strain, during which stress dropped to reach an effectively constant level. Stresses were modelled as steady state and transient components. Steady-state components were identified with the long-term stress in stress relaxation and associated with an elastic component of the model. Transient stresses were modelled using Eyring mechanisms. The greater part of the stress during strain hardening was associated with dissipative Eyring processes. The model was successful in predicting stresses in both uniaxial and planar extension over a limited range of strain rate.

scholarly journals Stress Relaxation Aging Behavior and Constitutive Modelling of AA7150-T7751 under Different Temperatures, Initial Stress Levels and Pre-Strains

Metals ◽  
2019 ◽  
Vol 9 (11) ◽  
pp. 1215 ◽  
Author(s):  
Yixian Cai ◽  
Lihua Zhan ◽  
Yongqian Xu ◽  
Chunhui Liu ◽  
Jianguang Wang ◽  
...  
Keyword(s):  
Activation Energy ◽  
Stress Relaxation ◽  
Initial Stress ◽  
Stress Level ◽  
Relaxation Behavior ◽  
Average Error ◽  
Aging Behavior ◽  
Stress Relaxation Behavior ◽  
Stress Levels ◽  
Different Temperatures

Age forming is an advanced manufacture technology for forming large aluminum panels. Temperature, initial stress level and pre-strains have a great effect on the formability and performance. The stress relaxation aging behavior of AA7150-T7751 under different temperatures, initial stress levels and pre-strains was studied through stress relaxation tests, tensile tests and TEM observations. The results show that the formability can be improved with the increase of temperature, initial stress levels and pre-strains. Deformation mechanisms during stress relaxation of the material were analyzed on the basis of creep stress exponent and apparent activation energy. The aging precipitates of the studied alloy were not sensitive to the age forming conditions, but drastically coarsened at over aging temperature, which decreased the mechanical properties. In addition, the relationship between stress relaxation behavior and aging strengthening is discussed. Based on the dislocation theory and the modified Arrhenius equation, a stress relaxation constitutive equation considering the initial mobile dislocation density and temperature dependent activation energy was established. This model can predict very well the stress relaxation behavior under various temperature, stress level and pre-strain conditions, with an average error of 2%.

Constitutive modelling of compression and stress relaxation in pine pellets

2019 ◽  
Vol 130 ◽  
pp. 105370 ◽  
Author(s):  
Simon Klinge Nielsen ◽  
Hamid Rezaei ◽  
Matthias Mandø ◽  
Shahab Sokhansanj
Keyword(s):  
Stress Relaxation ◽  
Constitutive Modelling

Monotonic Testing and Tension-Tension Fatigue Testing of Free-standing Al Microtensile Beams

2003 ◽  
Vol 795 ◽  
Author(s):  
Nicholas Barbosa ◽  
Paul El-Deiry ◽  
Richard P. Vinci
Keyword(s):  
Thin Films ◽  
Stress Relaxation ◽  
Strain Rate ◽  
Stress Level ◽  
Fatigue Testing ◽  
Monotonic Loading ◽  
Free Standing ◽  
Relaxation Dependence ◽  
Relaxation Experiments ◽  
Cycles To Failure

ABSTRACTFree-standing Al thin films were loaded statically and dynamically through the use of a custom-built microtensile system. The system is capable of performing monotonic loading/unloading up to 50 μm/s (10-1/s) and tension-tension fatigue experiments at 100 Hz on 600 μm long, 100 μm wide, and 1 μm thick free-standing Al microtensile beams. Monotonic loading/unloading and stress relaxation experiments have been performed. The microtensile beams show plasticity as well as a relaxation dependence on strain rate and stress level. Displacement controlled tension-tension fatigue experiments have also been performed. A trend of decreasing cycles to failure with increasing displacement amplitude and increasing mean displacement has been noted but requires further experimental exploration.

Void Growth as a Function of Residual Stress Level in Thin, Narrow Aluminum Lines

1991 ◽  
Vol 225 ◽  
Author(s):  
M. A. Korhonen ◽  
P. Børgesen ◽  
C. A. Paszkiet ◽  
J. K. Lee ◽  
Che-Yu Li
Keyword(s):  
Residual Stress ◽  
Plastic Deformation ◽  
Stress Relaxation ◽  
Grain Boundary ◽  
Stress Level ◽  
Void Growth ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Silicon Substrates ◽  
Tensile Stresses

ABSTRACTHigh tensile stresses develop in passivated aluminum line metallizations on silicon substrates after excursion to elevated temperatures. The principal mechanisms to relax these stresses at room temperature are plastic deformation and grain boundary void growth. It is shown that stress relaxation and void growth are intimately connected.

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