Hysteretic and Elastic Properties of Rubberlike Materials Under Dynamic Shear Stresses

1944 ◽  
Vol 15 (4) ◽  
pp. 309-323 ◽  
Author(s):  
J. H. Dillon ◽  
I. B. Prettyman ◽  
G. L. Hall
Keyword(s):  
Elastic Properties ◽  
Shear Stresses ◽  
Dynamic Shear ◽  
Rubberlike Materials

Hysteretic and Elastic Properties of Rubberlike Materials under Dynamic Shear Stresses

1944 ◽  
Vol 17 (3) ◽  
pp. 597-616 ◽  
Author(s):  
J. H. Dillon ◽  
I. B. Prettyman ◽  
G. L. Hall
Keyword(s):  
Natural Rubber ◽  
Elastic Properties ◽  
Shear Stresses ◽  
Dynamic Shear ◽  
Small Problem ◽  
Principal Problem ◽  
Synthetic Rubber ◽  
Truck Tire ◽  
Hysteretic Properties ◽  
Rubberlike Materials

Abstract The principal problem of the rubber technologist and engineer today is that of applying the various types of synthetic rubber to products which undergo rapid repeated flexure. All commercially available synthetic rubbers possess a greater hysteresis defect than does natural rubber. Hence, the task of designing a product such as a large truck tire, where heat development has been no small problem even with natural rubber, is much more difficult. Consequently, the accompanying problem of evaluating the hysteretic properties of rubberlike materials has assumed new importance.

Effect of Dynamic Shear Force on Fastener Loosening in Assemblies

1997 ◽  
Author(s):  
Yubo Dong ◽  
Daniel P. Hess
Keyword(s):  
Cantilever Beam ◽  
Static Load ◽  
Nodal Line ◽  
Shear Stresses ◽  
Dynamic Shear ◽  
Bernoulli Beam ◽  
Cyclic Shear ◽  
Nodal Lines ◽  
Inertial Loading ◽  
Euler Bernoulli Beam

Abstract Placement and orientation of fasteners in assemblies is generally based on convenience or static load and strength considerations. Vibration and other dynamic loads can result in loosening of threaded product, particularly when cyclic shear stresses are present. This paper investigates the placement of a bolt and nut on a compound cantilever beam subjected to dynamic inertial loading. Calculations for an inertial loaded, cantilever, Euler-Bernoulli beam show that the dynamic shear stress is maximum near the dynamic nodal lines, and essentially vanishes near the anti-nodes. Experiments with a compound cantilever beam assembly with one fastener reveal that loosening occurs more readily when the bolt and nut are placed near a nodal line. Data presented include time to loosen, break-away torque, and acceleration level. The data shows that fastener integrity is maintained for longer periods of time and with lower tightening torques, when the bolt and nut are positioned away from nodal lines where shear stresses are lower, even though acceleration levels are higher.

On the Development of a 3D Printer for Combinatorial Structural Composite Research

2015 ◽  
Author(s):  
Seyed Allameh
Keyword(s):  
Mechanical Properties ◽  
3D Printing ◽  
Partial Slip ◽  
Shear Stresses ◽  
3D Printer ◽  
Dynamic Shear ◽  
Structural Composites ◽  
Structural Composite ◽  
The Right ◽  
Selection Of

Bioinspired materials have enabled the fabrication of tough lightweight structures for load- and impact-bearing applications of which an example is fiber-reinforced plastics use in aerospace. If applied to the field of construction, biomimicked composites can save lives, otherwise lost to earthquakes and other disasters that cause collapse of buildings. The main culprit is the low resistance of structures exposed to dynamic shear stresses, typical of earthquakes. Recent work on the application of biomimicry to structural composites has clearly shown the advantage of these materials in resisting dynamic shear. Adding natural or synthetic reinforcement fibers may alleviate the need for conventional steel rebars and make it possible to print buildings by conventional 3D printing technology. The main hurdles are to find the right type of composite that is compatible with 3D printing and the right process for deposition of such material. In the past, combination of carbon fiber, glue and concrete has been demonstrated to enhance the toughness of resulting structural composites. Inspired by the microstructure of oyster and mother of pearl, layering of these materials mitigates the localization of deformation by distributing the imposed displacement over a large area. The intricate structure of these layers, and the minute details of the interfaces are important for affecting good dynamic shear resistance. In nacre, a partial slip of sandwiched layers occurs before it stops and deformation is transferred to the adjacent area. This energy-absorption capability underlies the high-toughness behavior of nacre and similar structures. By mimicking nacre, bone and tooth, it is possible to benefit from their good properties, however, it is important to determine the type of material, layering scheme, geometry, and other factors that affect mechanical properties. A recently-developed medium-sized 3D printer was developed to deposit structural materials. These include cement, plaster, polymer and clay. Combinatorial structural composite research (CSCR) comprising the simultaneous fabrication and characterization of multiple specimens with different microstructures allows fair comparison of mechanical properties of various structural composites. Novel application of deposition techniques to the extrusion of plaster, cement and clay paves the way to layer these materials along with glue and fibers in desired schemes. Use of ANOVA tables in the selection of various types of ceramics, polymers and reinforcement materials for the fabrication of different composites will be discussed. In addition to selection of the type of the materials, deposition schemes such as those of solid and hollow structures, different layer thickness applications, and the effect of timing will be elucidated. Microscopy conducted on the fractured surfaces enables the investigation of the mechanisms of fracture and failure for these CSCR composites. The details of experiments conducted, microscopy performed and the results of mechanical tests will be presented.

Stresses at the Interface between the Functionally Graded Coating and the Elastic Half-Space Caused by Spherical Indentation

2007 ◽  
Vol 345-346 ◽  
pp. 833-836 ◽  
Author(s):  
S.M. Aizikovich ◽  
L.I. Krenev ◽  
I.S. Trubchik
Keyword(s):  
Half Space ◽  
Elastic Properties ◽  
Layered Structures ◽  
Elastic Half Space ◽  
Functionally Graded ◽  
Shear Stresses ◽  
Functionally Graded Coating ◽  
Graded Coatings ◽  
Graded Coating ◽  
Functionally Graded Coatings

Recent advances in nanotechnology have revealed numerous new methods of manufacturing functionally graded coatings and materials, but progress in this field is limited by the lack of knowledge about the mechanical behavior of such structures. Existing models of the mechanics of layered structures are not generally adequate for this purpose, since functionally graded structures can exhibit both qualitative and quantitative behavioral differences in comparison with homogeneous or layered structures, particularly if there is a significant gradient of elastic properties in the coating. In applications, interest is focused mainly on the deformation fields and stresses inside the inhomogeneous material caused by the contact tractions. Stresses at the interface between the functionally graded coating and the elastic half-space are of particular interest because of their influence on the propagation of cracks and other defects on this interface. Shear stresses at this interface associated with rapid variation in elastic properties with depth are particularly dangerous because of potential delaminations. In their work the authors: • develop a precise mathematical model and of the computational methods which makes it possible to achieve stable numerical results while analyzing the mechanical properties of functionally graded coatings; • study the variation effect in elastic properties on the maximum stresses in the surface layers of materials with functionally graded coatings caused by indentation.

scholarly journals Effects of dynamic shear and transmural pressure on wall shear stress sensitivity in collecting lymphatic vessels

2015 ◽  
Vol 309 (9) ◽  
pp. R1122-R1134 ◽  
Author(s):  
Jeffrey A. Kornuta ◽  
Zhanna Nepiyushchikh ◽  
Olga Y. Gasheva ◽  
Anish Mukherjee ◽  
David C. Zawieja ◽  
...  
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Contractile Response ◽  
Lymphatic Vessels ◽  
Stress Sensitivity ◽  
Transmural Pressure ◽  
Shear Stresses ◽  
Dynamic Shear ◽  
Contraction Frequency ◽  
Wall Shear

Given the known mechanosensitivity of the lymphatic vasculature, we sought to investigate the effects of dynamic wall shear stress (WSS) on collecting lymphatic vessels while controlling for transmural pressure. Using a previously developed ex vivo lymphatic perfusion system (ELPS) capable of independently controlling both transaxial pressure gradient and average transmural pressure on an isolated lymphatic vessel, we imposed a multitude of flow conditions on rat thoracic ducts, while controlling for transmural pressure and measuring diameter changes. By gradually increasing the imposed flow through a vessel, we determined the WSS at which the vessel first shows sign of contraction inhibition, defining this point as the shear stress sensitivity of the vessel. The shear stress threshold that triggered a contractile response was significantly greater at a transmural pressure of 5 cmH2O (0.97 dyne/cm2) than at 3 cmH2O (0.64 dyne/cm2). While contraction frequency was reduced when a steady WSS was applied, this inhibition was reversed when the applied WSS oscillated, even though the mean wall shear stresses between the conditions were not significantly different. When the applied oscillatory WSS was large enough, flow itself synchronized the lymphatic contractions to the exact frequency of the applied waveform. Both transmural pressure and the rate of change of WSS have significant impacts on the contractile response of lymphatic vessels to flow. Specifically, time-varying shear stress can alter the inhibition of phasic contraction frequency and even coordinate contractions, providing evidence that dynamic shear could play an important role in the contractile function of collecting lymphatic vessels.

Adiabatic Stretching as a Method of Investigation of the Elastic Properties of Rubberlike Materials

1956 ◽  
Vol 29 (4) ◽  
pp. 1209-1214
Author(s):  
M. P. Votinov ◽  
E. V. Kuvshinskiĭ
Keyword(s):  
Elastic Properties ◽  
Direct Method ◽  
Rubber Compounds ◽  
A Direct Method ◽  
Rubberlike Materials ◽  
Elastic Characteristics

Abstract 1. A direct method has been proposed for the study of the elastic characteristics of rubber stocks under nonequilibrium deformation conditions. 2. This method has been successfully applied in the study of the elastic characteristics of “crystallizing” and “noncrystallizing” unloaded rubber compounds.

scholarly journals Study of Asphalt Binder Fatigue with a New Dynamic Shear Rheometer Geometry

2018 ◽  
Vol 2672 (28) ◽  
pp. 290-300 ◽  
Author(s):  
Panos Apostolidis ◽  
Cor Kasbergen ◽  
Amit Bhasin ◽  
Athanassios Scarpas ◽  
Sandra Erkens
Keyword(s):  
Asphalt Binder ◽  
Numerical Analyses ◽  
Asphalt Binders ◽  
Single Type ◽  
Shear Stresses ◽  
Dynamic Shear ◽  
Dynamic Shear Rheometer ◽  
Significant Difference ◽  
Sample Testing ◽  
Time Sweep

With the effort to precisely predict the lifetime of asphalt binders and subsequently optimize their utilization in a more economical way, the objective of this study was to introduce a new methodology to improve the fatigue characterization of asphalt binders through a new dynamic shear rheometer (DSR) sample testing geometry. Initially, numerical analyses were performed to study the geometry-related issues of a standard DSR sample on time sweep tests, and to assist in the effort to increase understanding of the DSR damage phenomena of asphalt samples. On the basis of these numerical analyses, a new testing geometry, the parallel hollow plate, was developed and its test results compared with the standard sample testing geometry. A single type of asphalt binder was assessed using amplitude sweep tests. The obtained results demonstrated a significant difference between the fatigue of the two sets of DSR sample geometries. On the basis of these, time sweep tests were conducted for the same sample geometries and the results demonstrated that the new testing geometry yields material response consistency under different loading conditions. The lifetime prediction of the standard parallel plates showed a significant difference with the newly developed DSR sample testing geometry by overestimating the total number of cycles until asphalt binder failure. The new testing geometry allowed the isolation of the damaged area of asphalt binder by localizing the shear stresses in the samples’ periphery.

Electron Microscopy and image reconstruction reveal the structural basis for spectrin's elastic properties

1992 ◽  
Vol 50 (1) ◽  
pp. 510-511
Author(s):  
Amy M. McGough ◽  
Robert Josephs
Keyword(s):  
Electron Microscopy ◽  
Elastic Properties ◽  
Conformational Changes ◽  
Quaternary Structure ◽  
Three Dimensional ◽  
Membrane Skeleton ◽  
Projection Algorithm ◽  
Structural Basis ◽  
Iterative Approximation ◽  
Membrane Skeletons

The remarkable deformability of the erythrocyte derives in large part from the elastic properties of spectrin, the major component of the membrane skeleton. It is generally accepted that spectrin's elasticity arises from marked conformational changes which include variations in its overall length (1). In this work the structure of spectrin in partially expanded membrane skeletons was studied by electron microscopy to determine the molecular basis for spectrin's elastic properties. Spectrin molecules were analysed with respect to three features: length, conformation, and quaternary structure. The results of these studies lead to a model of how spectrin mediates the elastic deformation of the erythrocyte.Membrane skeletons were isolated from erythrocyte membrane ghosts, negatively stained, and examined by transmission electron microscopy (2). Particle lengths and end-to-end distances were measured from enlarged prints using the computer program MACMEASURE. Spectrin conformation (straightness) was assessed by calculating the particles’ correlation length by iterative approximation (3). Digitised spectrin images were correlation averaged or Fourier filtered to improve their signal-to-noise ratios. Three-dimensional reconstructions were performed using a suite of programs which were based on the filtered back-projection algorithm and executed on a cluster of Microvax 3200 workstations (4).

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