Strain softening of siltstones in consolidation process using a constant strain-rate loading system

2020 ◽  
Author(s):  
Nana Kamiya ◽  
Feng Zhang ◽  
Weiren Lin
Keyword(s):  
Strain Rate ◽  
Mechanical Behavior ◽  
Strain Softening ◽  
Constant Strain Rate ◽  
Soft Rock ◽  
Consolidation Process ◽  
X Ray ◽  
Soft Rocks ◽  
Loading System ◽  
Strain Rate Loading

<p><span>The mechanical behavior of soft rocks is dominated by the mechanical properties of the rock itself. Because soft rocks have different physical properties to hard rocks, it is essential to understand the mechanical behavior of soft rocks when tunnels and huge structures are constructed in these. Strain softening is the mechanical behavior of soil and rock materials and is important in understanding soft rock foundation. To investigate the mechanical behavior of siltstone, a sedimentary soft rock, we performed the one-dimensional consolidation tests (hereafter called K0-consolidation test) using a constant strain-rate loading system. We also took high-resolution X-ray CT images of the test specimens before and after the consolidation tests to observe the consolidation deformation. Using Quaternary siltstones distributed in the Boso Peninsula, central Japan as specimens, strain softening in the consolidation process was confirmed in some formations using two test machines at Kyoto University and Nagoya Institute of Technology. </span></p><p><span>All specimens yielded and the consolidation curves showed over- and normal-consolidation areas. Some specimens’ stress decreased suddenly at increasing strain just before yielding, which can be regarded as a real strain softening because no strain localization could be confirmed within specimens. The stress at the time of the softening differed even for specimens taken from the same formation. Furthermore, the micro-focus X-ray CT images indicated that the specimens had no macro cracks inside. This suggests that strain softening is not due to brittle failure in local areas but due to the softening of the framework structure of the siltstone itself. The samples used in this study are siltstone taken from the Quaternary forearc basin, whose development is related not only to consolidation but also tectonic effects such as horizontal compaction accompanied by plate subduction. Therefore, it is possible that the strain softening confirmed in this study reflects the micro cracks and internal structure that developed during siltstone formation.</span></p>

Strain Rate and Loading Waveform Effects on an Energy-Based Fatigue Life Prediction for AL6061-T6

2012 ◽  
Author(s):  
Todd Letcher ◽  
M.-H. Herman Shen ◽  
Onome Scott-Emuakpor ◽  
Tommy George ◽  
Charles Cross
Keyword(s):  
Fatigue Life ◽  
Strain Rate ◽  
Constant Strain Rate ◽  
Hysteresis Loops ◽  
Sine Wave ◽  
Wave Loading ◽  
Cumulative Energy ◽  
Loading Pattern ◽  
Loading Waveform ◽  
Strain Rate Loading

The energy-based lifing method is based on the theory that the cumulative energy in all hysteresis loops of a specimens’ lifetime is equal to the energy in a monotonic tension test. Based on this theory, fatigue life can be calculated by dividing monotonic strain energy by a hysteresis energy model, which is a function of stress amplitude. Recent studies have focused on developing this method for a sine wave loading pattern — a variable strain rate. In order to remove the effects of a variable strain rate throughout the fatigue cycle, a constant strain rate triangle wave loading pattern was tested. The testing was conducted at various frequencies to evaluate the effects of multiple constant strain rates. Hysteresis loops created with sine wave loading and triangle loading were compared. The effects of variable and constant strain rate loading patterns on hysteresis loops throughout a specimens’ fatigue life are examined.

scholarly journals Transient x-ray diffraction with simultaneous imaging under high strain-rate loading

2014 ◽  
Vol 85 (11) ◽  
pp. 113902 ◽  
Author(s):  
D. Fan ◽  
L. Lu ◽  
B. Li ◽  
M. L. Qi ◽  
J. C. E ◽  
...  
Keyword(s):  
High Strain Rate ◽  
Strain Rate ◽  
High Strain ◽  
X Ray Diffraction ◽  
X Ray ◽  
Simultaneous Imaging ◽  
Strain Rate Loading

Rate Dependent Deformation of Semi-Crystalline Polypropylene Near Room Temperature

1997 ◽  
Vol 119 (3) ◽  
pp. 216-222 ◽  
Author(s):  
E. M. Arruda ◽  
S. Ahzi ◽  
Y. Li ◽  
A. Ganesan
Keyword(s):  
Plastic Deformation ◽  
Strain Rate ◽  
Room Temperature ◽  
Strain Softening ◽  
High Strain ◽  
Constant Strain Rate ◽  
Strain Rates ◽  
High Strain Rates ◽  
Rate Dependent ◽  
Static Conditions

We examine the strain rate dependent, large plastic deformation in isotropic semi-crystalline polypropylene at room temperature. Constant strain rate uniaxial compression tests on cylindrical polypropylene specimens show very little true strain softening under quasi-static conditions. At high strain rates very large amounts (38 percent) of apparent strain softening accompanied by temperature rises are recorded. We examine the capability of a recently proposed constitutive model of plastic deformation in semi-crystalline polymers to predict this behavior. We neglect the contribution of the amorphous phase to the plastic deformation response and include the effects of adiabatic heating at high strain rates. Attention is focused on the ability to predict rate dependent yielding, strain softening, strain hardening, and adiabatic temperature rises with this approach. Comparison of simulations and experimental results show good agreement and provide insight into the merits of using a polycrystalline modeling assumption versus incorporating the amorphous contribution. Discrepancies between experiments and model predictions are explained in terms of expectations associated with neglecting the amorphous deformation.

The mechanical response of Hysol 4183 under constant strain rate loading and creep

2019 ◽  
Vol 24 (3) ◽  
pp. 301-315
Author(s):  
Nofar Stivi ◽  
Arieh Sidess ◽  
Daniel Rittel
Keyword(s):  
Strain Rate ◽  
Mechanical Response ◽  
Constant Strain Rate ◽  
Strain Rate Loading

Strain Rate and Loading Waveform Effects on an Energy-Based Fatigue Life Prediction for AL6061-T6

2013 ◽  
Vol 136 (2) ◽  
Author(s):  
Todd Letcher ◽  
M.-H. H. Shen ◽  
Onome Scott-Emuakpor ◽  
Tommy George ◽  
Charles Cross
Keyword(s):  
Fatigue Life ◽  
Strain Rate ◽  
Constant Strain Rate ◽  
Hysteresis Loops ◽  
Sine Wave ◽  
Wave Loading ◽  
Cumulative Energy ◽  
Loading Pattern ◽  
Loading Waveform ◽  
Strain Rate Loading

The energy-based lifing method is based on the theory that the cumulative energy in all hysteresis loops of a specimens' lifetime is equal to the energy in a monotonic tension test. Based on this theory, fatigue life can be calculated by dividing monotonic strain energy by a hysteresis energy model, which is a function of stress amplitude. Recent studies have focused on developing this method for a sine wave loading pattern—a variable strain rate. In order to remove the effects of a variable strain rate throughout the fatigue cycle, a constant strain rate triangle wave loading pattern was tested. The testing was conducted at various frequencies to evaluate the effects of multiple constant strain rates. Hysteresis loops created with sine wave loading and triangle loading were compared. The effects of variable and constant strain rate loading patterns on hysteresis loops throughout a specimens' fatigue life are examined.

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