MULTIPLE COMPRESSIVE LOADING AND UNLOADING BEHAVIOR OF POLYMERIC FOAMS

2007 ◽  
Vol 27 (8) ◽  
Author(s):  
Umud E. Ozturk ◽  
Gunay Anlas
Keyword(s):  
Compressive Loading ◽  
Polymeric Foams ◽  
Loading And Unloading

scholarly journals Stress-Softening in Particle-Filled Polyurethanes under Cyclic Compressive Loading

Polymers ◽  
2020 ◽  
Vol 12 (7) ◽  
pp. 1588
Author(s):  
Wenshuai Xu ◽  
Mangong Zhang ◽  
Yu Liu ◽  
Hao Zhang ◽  
Meng Chen ◽  
...  
Keyword(s):  
Compressive Loading ◽  
Compressive Load ◽  
Soft Materials ◽  
Constitutive Parameter ◽  
Spherical Indentation ◽  
Mullins Effect ◽  
Stress Softening ◽  
Loading And Unloading ◽  
Load Displacement ◽  
Constitutive Parameters

Elastomer compositions containing various particulate fillers can be formulated according to the specific functions required of them. Stress softening—which is also known as the Mullins effect—occurs during high loading and unloading paths in certain supramolecular elastomer materials. Previous experiments have revealed that the load–displacement response differs according to the filler used, demonstrating an unusual model of correspondence between the constitutive materials. Using a spherical indentation method and numerical simulation, we investigated the Mullins effect on polyurethane (PU) compositions subjected to cyclic uniaxial compressive load. The PU compositions comprised rigid particulate fillers (i.e., nano-silica and carbon black). The neo-Hooke model and the Ogden–Roxburgh Mullins model were used to describe the nonlinear deformation behavior of the soft materials. Based on finite element methods and parameter optimization, the load–displacement curves of various filled PUs were analyzed and fitted, enabling constitutive parameter prediction and inverse modeling. Hence, correspondence relationships between material components and constitutive parameters were established. Such relationships are instructive for the preparation of materials with specific properties. The method described herein is a more quantitative approach to the formulation of elastomer compositions comprising particulate fillers.

A Phenomenological Energy-Based Model for PBX Simulants Considering the Mullins Effect

2013 ◽  
Vol 535-536 ◽  
pp. 113-116
Author(s):  
Kee Sun Yeom ◽  
Seh Wan Jeong ◽  
Hoon Huh ◽  
Jung Su Park
Keyword(s):  
Experimental Data ◽  
Mechanical Properties ◽  
Residual Strain ◽  
Compressive Loading ◽  
Mullins Effect ◽  
Good Correspondence ◽  
Highly Nonlinear ◽  
Loading And Unloading ◽  
Nonlinear Behaviors ◽  
Test Result

PBX is known to exhibit highly nonlinear behaviors of deformation such as the Mullins effect of stress softening, hysteresis, residual strain, and frequency dependant responses. This paper proposes a phenomenological energy-based model for PBX considering the Mullins effect for isotropic, incompressible, hyperelastic, particle-filled materials. Uniaxial compressive loading and unloading tests at quasi-static states were undertaken in order to obtain the mechanical properties of the PBX simulants. The phenomenological energy-based model by Ogden-Roxburgh is, then, modified to make it consistent with the test result of PBX simulants in the case that the Mullins effect is dominant. Prediction with the new model shows a good correspondence to the experimental data demonstrating that the model properly describes the Mullins effect and the loading-unloading behavior of deformation.

scholarly journals The time-dependent mechanical properties of the human heel pad in the context of locomotion.

1996 ◽  
Vol 199 (7) ◽  
pp. 1501-1508 ◽  
Author(s):  
R F Ker
Keyword(s):  
Mechanical Properties ◽  
Energy Loss ◽  
Compressive Loading ◽  
Fold Increase ◽  
Deformation Curves ◽  
Heel Pad ◽  
Rest Periods ◽  
Percentage Area ◽  
Rest Time ◽  
Loading And Unloading

Previous measurements of the mechanical properties of the heel pad, especially of the energy loss during a cycle of compressive loading and unloading, have given contrasting values according to whether the investigators used isolated single impacts (e.g. pendulum tests; energy loss approximately 48%) or continuous oscillations (energy loss approximately 30%). To investigate this discrepancy, rest periods were inserted between single compressive cycles, giving intermittent loading as in locomotion. The energy loss, measured as the percentage area of the hysteresis loop, was found to change linearly with the logarithm of the rest time. It was approximately 33% when the rest time was 1 s. Each 10-fold increase in the rest time added approximately 3.7% to the energy loss. Thus, with rest times appropriate to locomotion, the pad is far from fully relaxed. The springy heel pad may help to reposition the foot during the transfer of load from the heel to the forefoot. Information is also included on the load-deformation curves for the heel pad and the way in which these change with rest time. This is presented as equations which may be useful in future models relating the mechanical properties of the heel to either its structure or its function.

Stress-displacement relation of fiber for fiber-reinforced ceramic composites during (indentation) loading and unloading

1989 ◽  
Vol 4 (6) ◽  
pp. 1529-1537 ◽  
Author(s):  
Chun-Hway Hsueh ◽  
Mattison K. Ferber ◽  
Paul F. Becher
Keyword(s):  
Shear Stress ◽  
Coulomb Friction ◽  
Interfacial Shear Stress ◽  
Compressive Loading ◽  
Ceramic Composites ◽  
Interfacial Shear ◽  
Frictional Stress ◽  
Fiber Reinforced ◽  
The Coefficient Of Friction ◽  
Loading And Unloading

The stress-displacement relation of the fiber is analyzed for fiber-reinforced ceramic composites during axial compressive loading (indentation) and unloading on the exposed end of an embedded fiber. An unbonded fiber/matrix interface subject to Coulomb friction and residual radial clamping stresses is considered in the present study. The results show that the stress-displacement curves during loading and unloading can be used to evaluate the magnitude of the clamping stress, the coefficient of friction, and the frictional stress distribution at the interface. Specifically, in the absence of Poisson's effect (i.e., when Poisson's ratio of the fiber is zero), the interfacial shear stress is constant, the loading curve is parabolic, and, after complete unloading, the residual fiber displacement equals half of the maximum fiber displacement at the peak loading stress. In the presence of Poisson's effect, the interfacial shear stress is not constant, and, after complete unloading, the residual fiber displacement is less than half of the maximum fiber displacement at the peak loading stress.

Sign in / Sign up

Export Citation Format

Share Document