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.

Mechanical Properties of the Human Heel Pad: A Comparison between Populations

2008 ◽  
Vol 24 (4) ◽  
pp. 377-381 ◽  
Author(s):  
John H. Challis ◽  
Chloe Murdoch ◽  
Samantha L. Winter
Keyword(s):  
Mechanical Properties ◽  
Energy Loss ◽  
Analysis Of Variance ◽  
Distance Runners ◽  
Long Distance ◽  
Heel Pad ◽  
Significant Difference ◽  
Competitive Cyclists ◽  
Different Populations ◽  
Loading And Unloading

The purpose of this study was to compare the heel pad mechanical properties of runners, who repetitively load the heel pad during training, with cyclists who do not load their heel pads during training. Ten competitive long distance runners and 10 competitive cyclists volunteered for this study. The thickness of the unloaded heel pad was measured using realtime B-mode ultrasonography. A heel pad indentation device was used to measure the mechanical properties of the heel pads. To evaluate the differences between the two groups, in heel pad properties, a repeat measures analysis of variance was used (p< .05). Heel pad thickness was not different between groups when normalized with respect to subject height. There was no significant difference between the groups in percentage energy loss during loading and unloading (runners: 61.4% ± 8.6; cyclists: 62.5% ± 4.6). Heel pad stiffness for the runners was statistically significantly less than that of the cyclists (p= .0018; runners: 17.1 N·mm−1± 3.0; cyclists: 20.4 N·mm−1± 4.0). These results indicate that the nature of the activity undertaken by individuals may influence their heel pad properties. This finding may be important when considering differences in heel pad properties between different populations.

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.

Damage Growth in Porous Ceramics

2005 ◽  
Vol 290 ◽  
pp. 86-93 ◽  
Author(s):  
Tomasz Sadowski ◽  
Sylwester Samborski ◽  
Zdzislaw Librant
Keyword(s):  
Mechanical Properties ◽  
Experimental Method ◽  
Deformation Process ◽  
Porous Ceramics ◽  
Elastic Behaviour ◽  
Damage Growth ◽  
Deformation Stages ◽  
Loading And Unloading

The paper deals with the experimental method of the mechanical properties estimation at the beginning of deformation process (elastic behaviour) of the material as well as during the whole deformation stages. The idea of the method results from the observation of the loading and unloading process of the material and analysis of the strain stage.

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.

scholarly journals Mechanical properties of hollow polyester monofilament: Compression and tension behaviors

2019 ◽  
Vol 14 ◽  
pp. 155892501983753
Author(s):  
Xiaohui Zhang ◽  
Chao Zhang ◽  
Pibo Ma
Keyword(s):  
Mechanical Properties ◽  
Compressive Strain ◽  
Compressive Loading ◽  
Tensile Fracture ◽  
External Diameter ◽  
Hollow Core ◽  
Compressive Properties ◽  
Manufacturing Method ◽  
Study Results ◽  
Polyester Monofilament

Comparative analysis has been performed on the mechanical properties of hollow and solid polyester monofilament with identical external diameter. Tensile test of hollow polyester monofilament was conducted to study the influence of hollow core and the manufacturing method on the tensile fracture mechanism of hollow monofilament. The compressive properties of hollow monofilament were determined to provide a bundle-compression method to study the behavior of hollow polyester monofilament under axial compressive loading and compare with solid one. The results show that the tensile property of the hollow monofilament has smaller breaking force and higher breaking elongation than solid monofilament in case of identical external diameter. Under compression loading, the solid monofilament show better compressive properties than hollow one with identical diameter. The hollow core only affects the values of compressive strain and stress, but it has no effect on the compression and deformation mechanism. The study results also show that the polyester monofilament can show better mechanical properties than the solid polyester monofilament for the same weight. This study can help to design the lighter textile materials with the hollow polyester monofilament.

scholarly journals Enhancing Properties of Aerospace Alloy Elektron 21 Using Boron Carbide Nanoparticles as Reinforcement

2019 ◽  
Vol 9 (24) ◽  
pp. 5470
Author(s):  
Sravya Tekumalla ◽  
Ng Joo Yuan ◽  
Meysam Haghshenas ◽  
Manoj Gupta
Keyword(s):  
Mechanical Properties ◽  
Boron Carbide ◽  
Compressive Loading ◽  
Hot Extrusion ◽  
Microstructural Characterization ◽  
Thermal Insulating ◽  
Damping Characteristics ◽  
B4c Particles ◽  
Superior Mechanical Properties ◽  
Melt Deposition

In this study, the effect of nano-B4C addition on the property profile of Elektron 21 (E21) alloys is investigated. E21 reinforced with different amounts of nano-size B4C particulates was synthesized using the disintegrated melt deposition technique followed by hot extrusion. Microstructural characterization of the developed E21-B4C composites revealed refined grains with the progressive addition of boron carbide nanoparticles. The evaluation of mechanical properties indicated a significant improvement in the yield strength of the nanocomposites under compressive loading. Further, the E21-2.5B4C nanocomposites exhibited the best damping characteristics, highest young’s modulus, and highest resistance to ignition, thus featuring all the characteristics of a material suitable for several aircraft applications besides the currently allowed seat frames. The superior mechanical properties of the E21-B4C nanocomposites are attributed to the refined grain sizes, uniform distribution of the nanoparticles, and the thermal insulating effects of nano-B4C particles.

scholarly journals Dynamic Fracture Experiment of Fractured Rock under Dynamic Loading

2020 ◽  
Vol 2020 ◽  
pp. 1-22
Author(s):  
Yanbing Wang ◽  
Xingyuan Zhou ◽  
Ji Kong ◽  
Bingbing Yu
Keyword(s):  
Mechanical Properties ◽  
Energy Loss ◽  
Dynamic Loading ◽  
Split Hopkinson Pressure Bar ◽  
Fractured Rock ◽  
Dynamic Mechanical Properties ◽  
Dynamic Crack ◽  
Loading Test ◽  
Dynamic Mechanical ◽  
The Impact

In order to examine the dynamic mechanical properties, dynamic crack proposition process, and energy loss of fractured rock under dynamic loading, the specimens with different fracture dig angles were processed with Φ50 mm × 50 mm cylindrical sandstone, the impact loading test was conducted on 50 mm stem diameter split Hopkinson pressure bar (SHPB) experiment platform, and the whole process of crack propagation and dynamic failure was recorded using a high-speed camera. As a result, the dynamic mechanical properties such as stress wave fluctuation characteristics, peak strength and stress-strain relationship, crack initiation angle, stress and other dependencies with prefabricated fracture angle of the prefabricated fracture specimens under high strain rate were obtained, and the incident energy, absorbed energy, and energy absorption rates were compared to investigate the energy loss law in the dynamic loading; on the contrary, the effects of different loading rates on the dynamic mechanical properties of the sandstone specimens were identified, and finally a set of findings were presented.

scholarly journals A Novel Method of Light Weighting Aluminium Using Magnesium Syntactic Composite Core

Crystals ◽  
2020 ◽  
Vol 10 (10) ◽  
pp. 917
Author(s):  
Penchal Reddy Matli ◽  
Joshua Goh Yong Sheng ◽  
Gururaj Parande ◽  
Vyasaraj Manakari ◽  
Beng Wah Chua ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
Hybrid Composite ◽  
Compressive Loading ◽  
Core Region ◽  
Core Material ◽  
Novel Method ◽  
Light Weighting ◽  
Melt Deposition ◽  
Shell Region

In this study, hybrid composite consisting of aluminium (Al) shell and magnesium/glass microballoon (Mg-20 wt.% GMB) syntactic composite core was fabricated in a shell-core pattern by combining powder metallurgy and disintegrated melt deposition (DMD) techniques. Physical, microstructural and mechanical properties of as-cast Al and Al/Mg-20GMB hybrid composite were examined. Approximately 13% reduction in density (with respect to aluminium) was realized through the use of a syntactic composite core. Microstructural investigations revealed reasonable interfacial integrity between aluminium shell and Mg-GMB core material and the presence of Al, Mg and GMB phases. The interface region showed a hardness of 109 ± 2 Hv in comparison to the hardness of Al shell region (68 ± 4 Hv) and Mg-20GMB core region (174 ± 5 Hv). In comparison to as-cast Al, the yield strength and ultimate compressive strength of the as-cast Al/Mg-20GMB hybrid composite increased by ~65.4% and ~60%, respectively. Further, the energy absorption under compressive loading for the Al/Mg-20GMB hybrid composite was ~26% higher compared to pure Al. This study validated that Al/Mg-20GMB hybrid composite with superior absolute and specific mechanical properties can be fabricated and used for weight critical applications.

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