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The resistance of a typical shear connection with headed shear studs in a composite beam is analysed for the normal case in accordance with EN 1994-1-1. The reducing effect of a trapezoidal metal decking to the ultimate loadbearing capacity is considered with empirically derived reduction factors and equations that were developed between the late 1970s and early 1980s. The RFCS research project ”DISCCO“ [1] investigated the shear stud resistance with novel types of steel decking. In many cases, the shear resistance predicted by EN 1994-1-1 [2] was not reached in tests. In the respective experiments with composite beams and deep decking, a concrete cone failure mode was identified and not a pure shear failure of the stud. This failure mode acted in combination with the loadbearing capacity of the shear stud, which formed one or two plastic hinges in the shaft depending on the actual geometry. Based on these observations, new equations have been developed to predict the shear connection's resistance with more accuracy. The yield hinge mechanism of the shear stud, which was developed by Lungershausen [3], was extended by the aforementioned loadbearing component ”concrete cone“. The formulae consider the geometry of the stud and the steel decking and the material strength of the stud and the concrete. The statistical evaluation of the equations developed demonstrates good agreement with test results.

Summary In precast technology, the effective design and construction are related to the behaviour of the connections between the structural members in order to cater for all service, environmental and earthquake load conditions. Therefore, the design and detailing of the connections should be undertaken consistently and with awareness of the desired structural response. In the research presented herein, an analytical expression is proposed for the prediction of the resistance of precast pinned connections under shear monotonic and cyclic loading. The proposed formula addresses the case where the failure of the connection occurs with simultaneous flexural failure of the dowel and compression failure of the concrete around the dowel, expected to occur either when (i) adequate concrete cover of the dowels is provided (d > 6 D) or (ii) adequate confining reinforcement (as defined in the article) is foreseen around the dowels in the case of small concrete covers (d

Microstructure, rheological properties and their relationships of PA6/NBR/nano-clay nanocomposite have been investigated. Scanning electron microscopy (SEM) and transmission electron microscopy imaging techniques were used to study micro-structure. The nano-clay dispersion was measured by small angle X-ray diffraction. Frequency sweep, steady shear, startup shear transient, and startup shear free transient experiments were carried out to study rheological characteristics of nanocomposite. SEM micrograph revealed that nano-clay decreased the size of rubber droplets to a half in comparison with samples without nano-clay. Storage modulus of nanocomposite containing 7%wt nano-clay exhibited frequency independent behavior because of physical network which formed in matrix, in contrast to pure PA6 which showed terminal storage modulus at low frequencies. Shear thinning at high shear rates was observed by addition of rubber to PA6 matrix caused by deformation of rubber droplets. Nano-clay orientation in shear flow field accelerated non-Newtonian behavior in steady shear experiment. Transient shear viscosity studies were used for measurement the strength of nano-clay physical network. It was found that network breakdown is more stress consuming factor in comparison with nano-particle orientation and hydrodynamic forces. Elongation transient viscosity studies showed that critical Hencky strain for linear–nonlinear viscoelastic transition shifted to higher strains by increasing nano-clay concentration. POLYM. COMPOS., 2016. © 2016 Society of Plastics Engineers

Fascia is a highly organized collagenous tissue that is intimately connected with muscles. The mechanical properties of fascia strongly affect muscular actions and development of pathologies. The objective of this paper is to determine the mechanical properties of the deep and superficial fascia by uniaxial and pure shear tests and to propose and address the feasibility of a material hyperelastic constitutive model using combined Digital Image Correlation strain measurements and Finite Element (FE) computations. Experiments on deep and superficial fascia samples from the hindlimbs of six adult sheep along or perpendicular to collagen fibres and FE simulations of each experiment were compared. An anisotropic strain energy function was proposed to reproduce the mechanical behaviour of deep and superficial fascia and the material parameters were fitted using an optimization method and included in the FE simulations. The mechanical response of the deep and superficial fascia shows typical behaviour of soft connective tissues. It is shown that the samples in longitudinal direction are stiffer than the samples in transversal direction for both kinds of tissues. When considering the deep and superficial samples, it is evident a greater stiffness of deep samples for both longitudinal and transversal directions with respect to superficial samples. Overall good predictions were obtained with the model proposed which present relatively low e values, e = 0.1189 and e = 0.0722 for deep and superficial fascia respectively. The experimental and FE results were compared. The simulated curves slightly underestimated or overestimated the load for uniaxial and pure shear tests, respectively, but very accurately captured the stiffness and the overall response. These results demonstrate that the proposed model and the fitted material properties applied have a good capability of reproducing the experimental conditions.

The application of the digital image correlation technique to the determination of the J-integral at fracture initiation for carbon black-filled natural rubber compounds is discussed. Three different compounds with varying carbon black content were tested, using two different test configurations: pure shear and biaxial tensile test. Digital image correlation was used to measure the displacement field around the crack tip in the tested specimens. From the displacement field, which was interpolated using a finite element scheme, the stresses were evaluated by using Ogden's hyperelastic model, and the J-integral could be calculated. The results compare well with both theoretical and finite element results.

This paper presents a comprehensive experimental study and detailed mechanistic interpretations of the shear deformation of three-dimensional (3D) reinforcements. Six types of 3D angle interlock glass fiber preforms (3DAP) were fabricated using a range of weave parameters including the fabric density, fabric layer, and yarn linear density. A modified picture frame was developed to ensure a pure shear load during the test. Through a series of comprehensive tests, our results demonstrated that the fabric density played a key role in the mechanical properties of 3DAP and that the reinforcements with low fabric density and yarn linear density were easy to shear. The shear deformation mechanism was analyzed based on the meso-structure. It is expected that this research will provide preliminary work for building a theoretical model of 3D woven preform. POLYM. COMPOS., 2015. © 2015 Society of Plastics Engineers

New microstructural data on the mylonites from the well-exposed Palmi shear zone (southern Calabria) are presented with the aim to shed light on both the kinematics and the geometry of the southwestern branch of the Alpine belt during Eocene. In the study area, located between the Sardinia–Corsica block and the Calabria–Peloritani terrane, previous large-scale geodynamic reconstructions suggest the presence of strike–slip or transform fault zones dissecting the southwestern branch of the Alpine belt. However, there are no field data supporting the occurrence of these structures. This paper uses vorticity analysis technique based on the aspect ratio and the long axis orientation of rigid porphyroclasts in mylonitic marbles and mylonitic granitoids, to estimate the contribution of pure and simple shear of deformation during the movement of the Palmi shear zone. Porphyroclasts aspect ratio and orientation were measured on thin sections using image analysis. Estimates of the vorticity number, Wm, indicate that the Palmi shear zone recorded general shear with a contribution of pure shear of c. 65%. Then, the Palmi shear zone can be interpreted as a segment of a left-lateral transpressive bend along the southern termination of the Eocene Alpine front. Copyright © 2015 John Wiley & Sons, Ltd.

The tectonic evolution of South Qinling, which is a main part of the Qinling orogenic belt, is still in dispute and deformation history of South Qinling is poorly studied. In this paper, detailed structural, microstructural, quartz c-axis fabric analysis, and geochronology results for the Madao gneiss in South Qinling are presented to characterize the deformation history. Results show that rocks in the northern part (Tiefodian-Laozhanggou) experience general shearing and deform at relative low temperature. The shear sense generally is south to north. In contrast, rocks in the southern part (Laozhanggou-Panjiahe) are weakly sheared with pure shear features and evidence of high-temperature deformation. Based on the analyses, we conclude that there exist two distinct deformation geometries in the Madao gneiss and accordingly we can divide the deformation into two stages. The early stage is represented by regional shortening, while the late stage features northward thrust shearing and evidence shows that it was a progressive process between them. LA-ICP MS U-Pb dating of zircons from pre-deformational migmatite veins yields age of 198.5 ± 2.0 Ma. This result, in combination with the age of post-deformational granite, indicates that the northward thrust shearing of the Madao gneiss occurred in the Late Triassic. In view of these results and other reported data in South Qinling, we propose that deformation in Madao gneiss may result from the initial collision and subsequent northward accretion in Late Triassic.

In this article, influence of strain rate on nonlinear response of unidirectional fiber-reinforced composites is studied. The fibers are assumed to be periodic arrays in composite structures. By studying a representative volume element, a microscopic constitutive model for characterizing macro-mechanical response of polymer matrix composites is developed. Viscoplastic material parameters of polymer matrix are acquired by axial tension and pure shear experiment, and the proposed method is validated by experimental data. The results showed that mechanical behavior of composites, which is affected by strain rate, can be ignored in the linear stage of loading. Furthermore, with the increase in strain rate, stiffness behavior of composites tends to be stiffer at the stage of nonlinear deformation. POLYM. COMPOS., 36:800–810, 2015. © 2014 Society of Plastics Engineers

In this work, a novel multi-hinged test fixture, which can apply a pure shear load to thin panels, is presented. The new device has been used to perform several experimental tests on the shear behaviour of aluminium alloy panels. Four different test configurations have been considered: stiffened and not stiffened panels, with and without a central rectangular cut-out. The specimens, made of Al 6082 T6, are tested under shear load boundary conditions up to buckling and post-buckling occurrence. Furthermore, finite element analyses have been performed in order to simulate the four panel configurations tests. The new test fixture has shown the capability to buckle a panel attaining very large out-of-plane displacements, if compared to the outcomes of a traditional picture frame test fixture, under the same external load. Numerical and experimental results are finally compared, showing a satisfactory agreement.

Silicon carbide (SiC) samples have been joined by a pressureless slurry based method. The CaO–Al2O3 (CA) glass-ceramic joining material has been characterized in term of crystalline phases and thermal and mechanical properties. A torsion test based on miniaturized hourglass shaped specimens has been used as pure shear strength test method for joined ceramic samples. Torsion results are compared to those obtained by a single lap offset (SLO) test in compression on the same joined materials. Pure shear strength of 104 ± 25 MPa has been measured by torsion test, whereas single lap offset gave 36 ± 8 MPa.

We report on the influence of a uniaxial applied stress on flash-sintering and field assisted superplastic behavior of cylindrical powder preforms of 3 mol% tetragonal-stabilized zirconia. The experiments use the sinterforging method, where, in addition to pressure, a dc electrical field is applied by metal electrodes sandwiched between the push-rods and the specimen. The axial and radial strains in the experiment provide simultaneous measurement of the time-dependent densification and shear strains. Large effects of the electric field on sintering and superplasticity are observed. We see flash-sintering which is characterized by a threshold level of temperature and electric field. With higher applied fields, the sample sinters at a lower furnace temperature. Surprisingly, the applied stress further lowers this critical temperature: a sample, which sinters at 915°C under a stress of 1.5 MPa, densifies at only 850°C when the stress is raised to 12 MPa. This stress induced reduction in sintering temperature maybe related to the additional electrical fields generated within the specimen by the electro-chemo-mechanical mechanism described by Pannikkat and Raj [Acta Mater., 47 (1999) 3423]. Remarkably, we also show that the sample deforms in pure shear to 30% strain in just a few seconds at anomalously low temperatures. The specimen temperature was measured with a pyrometer, during the flash sintering, as a check on Joule heating. A reading of 1000°C–1100°C was obtained, up to 200° above the furnace temperature. This temperature is still too low to explain the sintering in just a few seconds. It is suggested that the electric field can nucleate a defect avalanche that enhances diffusion kinetics not by changing the activation energy but by increasing the pre-exponential factor for the diffusion coefficient, noting that the pre-exponential factor depends on concentration of defects, and not upon their mobility.

A non-linear viscoelastic model is described that can predict the time-dependent deformation of a polymer under a multiaxial stress. The main material property requirements are tensile creep compliances over a suitable time range and at different stress levels. Some creep data under uniaxial compression are also required. Relationships are derived between stress and strain components for arbitrary stress or strain histories. An assumption is required that either the Poisson?s ratio or the bulk modulus does not change significantly with time over the time scale of the predictions. The model has been coded into a finite element system to enable stress analyses to be carried out on objects of complex geometry. The validity of the model is explored through comparisons of predicted and measured results from a test that is designed to produce a predominantly pure shear stress state in the gauge region of the specimen. Results are presented for loading under constant stress and constant deformation rate.

Steady state shear flow of wood/high density polyethylene composites is investigated through capillary rheometry to gain better insight into rheology, extrudate distortions, and wall slip phenomena of wood/polymer composite melts. Effects of filler content and temperature on onset and end of stick-slip transition, in terms of shear rate and shear stress, are also studied. Results show that shear rates at stick-slip transition decrease while corresponding shear stresses increase with the addition of filler. Furthermore, temperature raises the shear rate and the shear stress at which the transition occurs. It is observed a log-linear relationship in the plots of wall slip versus the shear stress, in particular, increasing the filler content and decreasing the temperature, these plots are shifted to higher shear stress, as a consequence of viscosity increment. Wall slip and filler content play a fundamental role in surface morphology; specifically, extrudates become smoother with increasing filler content and shear rate, whose increment always results in a rise of the wall slip. POLYM. COMPOS., 32:796–809, 2011. a 2011 Society of Plastics Engineers

We study the development of microstructure inside the shear band in granular media consisting of elliptical-shaped particles. Plane strain biaxial compression test was simulated using two-dimensional distinct element method. The generation of large voids and concentration of excessive particle rotation inside a shear band are found in a quite similar manner to those observed in natural soils. Evolution of the microstructure inside and outside the shear band is studied. The magnitude and direction of particle rotation inside the shear band is influenced by orientation of long axes of elliptical particles. Because of such particle rotations inside the shear band, the preferred alignment of particles becomes horizontal in the residual state, which results in a more anisotropic contact normal distribution oriented along the major principal stress axis. Copyright © 2010 John Wiley & Sons, Ltd.

In seismic exploration, effective medium theories based on the Hertz-Mindlin contact model are often used to predict seismic elastic properties of unconsolidated sands. But these theories usually give relatively larger shear modulus comparing to measured data. By using 3D discrete element simulation, a series of uniaxial compression and pure shear test were carried out on granular material with the aim to study the insufficiencies of these effective medium theories on a micro-scale of particle size and a meso-scale of force chain. The simulation result indicates that stress relaxation resulting from the rotation and rearrangements of particles has negligible influences on the calculation of bulk modulus. But the stress relaxation has significant influence on the calculation of shear modulus under the shear stress perturbation. The shear stiffness calibration factor (C) and combined parameter are utilized to calibrate these effective medium theories based on the Hertz-Mindlin contact model, so that to the influence of relaxation between grains and grain irregularity on the model calculation. This method has been applied to real data and proved to be correct.

Mode I and II fracture studies were performed from quasistatic to low velocity impact rates on polymethyl methacrylate (PMMA) and polycarbonate (PC). Mode II tests used an angled double-edge notched specimen loaded in compression. The shear banding response of PMMA is shown to be highly sensitive to rate, with diffuse shear bands forming at low rates and sharp distinct shear bands forming at high rates. As the rate increases, shear deformation becomes more localized to the point where Mode II fracture occurs. PC is much less rate dependent and stable shear band propagation is observed over the range of rates studied with lesser amounts of localization. A new theory is formulated relating orientation in a shear band to intrinsic material properties obtained from true-stress true-strain tests. In a qualitative sense the theory predicts the high rate sensitivity of PMMA. A kinematic limit for orientation within a shear band is also derived based on entanglement network parameters. Mode II fracture in PMMA is shown to occur at this kinematic limit. For the case of PC, the maximum impact rates were not high enough to reach the kinematic limit.

The kinematic vorticity number and strain of the mylonitic zone related to the detachment fault increase from ESE to WNW along the moving direction of the upper plate of the Xiaoqinling metamorphic core complex (XMCC) and the geometry of quartz c-axis fabrics changes progressively from crossed girdles to single girdles in the same direction. Therefore, pure shear is dominant in the ESE part of the XMCC while simple shear becomes increasingly important towards WNW. However, the shear type does not change with the strain across the shear zone, thus the variation of shear type is of significance in indicating the formation mechanism. The granitic plutons within the XMCC came from the deep source and their emplacement was an active and forceful upwelling prior to the detachment faulting. The PTt path demonstrates that magmatism is an important cause for the formation of the XMCC. The formation mechanism of the XMCC is supposed to be active plutonism and passive detachment. Crustal thickening and magmatic doming caused necking extension with pure shear, and magmatic heating and doming resulted in detachment extension with simple shear and formed the XMCC.

We report on shear-induced nanotube agglomerate formation in low viscous multiwalled carbon nanotube/epoxy suspensions during steady shear rate step tests. A combined setup allows monitoring of the electrical, rheological, and optical properties of the system. High initial shearing was found to be necessary to achieve the insulator-to-conductor transition as well as low shear rate viscosity enhancement. Depending on the applied pre-shear, conductivity improvement of about four orders of magnitude was observed. Different morphologies for shear-induced agglomerates were detected before and after high shear. The critical minimal shear rate for the system was determined and a simple model using phase separation due to high shear forces is proposed.

Shear properties of epoxy LY 556 under high strain rate loading are presented. Torsional Split Hopkinson Bar apparatus was used for the studies in the shear strain rate range of 385-880 per sec. Experimental details, specimen configuration and development, data acquisition, and processing are presented. Shear strength, shear modulus, and ultimate shear strain are presented as a function of shear strain rate. For comparison, studies are presented at quasi-static loading. It is observed that the shear strength at high strain rate is enhanced up to 45% compared with that at quasi-static loading in the range of parameters considered. Further, it is observed that, in the range of parameters considered, the change in shear properties with the change in shear strain rate is not significant. Comparison of torque versus time behavior derived from signals obtained from strain gauges mounted on incident bar and transmitter bar is also presented. POLYM. ENG. SCI., 50:780-788, 2010. (C) 2010 Society of Plastics Engineers

This investigation focuses on the axial-torsional loading interaction of an epoxy polymer, Epon 826/Epi-Cure Curing Agent 9551. Thin-walled tubular specimens were subjected to combined constant tensile (or shear) stress and cyclic shear (or tension) loading schemes. Pure tensile creep and shear creep tests were also performed to compare the creep deformation to that with superimposed cyclic shear or cyclic tension. Test data clearly showed that cyclic shear (or cyclic tension) have a readily discernible effect on the tensile (or shear) creep deformation. Similarly, a superimposed constant tensile (or shear) load affects the hysteresis responses in cyclic shear (or cyclic tension). A nonlinear constitutive model developed by the authors was used to simulate the observed normal-shear stress interaction. Due to the inclusion of an effective stress parameter in its nonlinear function, this model was able to account for the normal-shear coupling effect. However, the incorporation of a general loading/unloading rule led to inaccurate simulation of the observed oscillatory creep response. A modification of the general rule was proposed and better predictions on both the cyclic and the creep responses could be obtained. POLYM. ENG. SCI., 2010. © 2009 Society of Plastics Engineers

An experimental study was conducted to evaluate the tear energy of unfilled and 25 phr carbon black-filled natural rubber with varying loading rates. The variation of the tear energy with far-field sample strain rate between 0.01 to 10 s−1 was found to be different from tensile strip and pure shear specimens. Above a sample strain rate of 10 s−1, the tear energy calculated from either specimen was comparable. The differences in the tear energy derived from the tensile strip and pure shear specimens were attributed to differences in the local crack tip stress state and strengthening of the material due to strain-induced crystallisation. Both of these factors resulted in crack speeds 3–4 times higher in the pure shear specimen as compared to the tensile strip specimen. Finite element analysis (FEA) indicated that fracture would initiate at the crack tip either when the strain energy density approached the material toughness or when the maximum principal stress and strain approached the material tensile strength and fracture strain, respectively. It was concluded that these parameters would be better than the tear energy in predicting fracture of natural rubber under dynamic loading.

A summary of the development of a new coupled shear-bending model for analysis of stacked wood shear walls and multi-story wood-frame buildings is presented in this paper. The model focuses on dynamic response of light-frame wood structures under seismic excitation. The formulation is intended to provide a more versatile option than present pure shear models in that the new model is capable of accurately capturing the overall lateral response of each story diaphragm and separates the inter-story shear deformation and the deformation associated with rotation of the diaphragm due to rod elongation, which is an analogue to the bending deformation in an Euler–Bernoulli beam model. Modeling the coupling of bending and shear deformation is shown to provide more accurate representation of stacked shear wall system behavior than a pure shear model, particularly for the upper stories in the assembly. The formulation is coupled with the newly developed evolutionary parameter hysteretic model for wood shear walls. Existing data from a shake table test of an isolated three-story wood shear wall were used to verify the accuracy of the model prediction. The numerical results agreed very well with shake table test measurements. The influence of a continuous rod hold-down system on the dynamic behavior of the three-story stacked wood shear wall was also successfully simulated. Copyright © 2009 John Wiley & Sons, Ltd.

The rheology of a range of polymer melts has been measured at strain rates above those attained during conventional rheometry using an instrumented injection molding machine. Deviations from shear thinning behavior were observed at high rates, and previously unreported shear thickening behavior occurred for some of the polymers examined. Measured pressure and volumetric throughputs were used to calculate shear and extensional viscosity at wall shear strain rates up to 107 s−1. Parallel plate rheometry and twin bore capillary rheometry were used to provide comparative rheological data at low and medium shear strain rates, respectively. Commercial grades of polyethylene, polypropylene, polystyrene, and PMMA were studied. Measured shear viscosity was found to follow Newtonian behavior at low rates and shear thinning power law behavior at intermediate strain rates. At shear strain rates approaching or above 106 s−1, shear viscosity reached a rate-independent plateau, and in some cases shear thickened with further increase in strain rate. A relationship between the measured high strain rate rheological behavior and molecular structure was noted, with polymers containing larger side groups reaching the rate-independent plateau at lower strain rates than those with simpler structures. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

The Eastern Himalayan Syntaxis (EHS) is a singular point of continental collision between the Indian and Eurasian plates, and has been a focus of geoscientific researches. We added the ISC data of 1964~2006 to a previous Chinese data set used by Pei et al., and 349475 Pn arrivals were selected in all. We have obtained seismic velocities and anisotropy in the uppermost mantle around EHS and surrounding regions by performing tomographic inversion of Pn travel times. Comparing Pn velocity variation with geological results, we find that they have distinct correlation: particularly high velocities always exist in old stable regions such as Sichuan Basin and Indian Plate. Low Pn velocities lie in active tectonic regions, volcanic areas and magmatic rock regions, for example, eastern Tibetan Plateau and North-South Seismic Zone, southern Yunnan province and northern Indochina. The Pn anisotropy shows that the fast directions of Pn turn around the EHS from NE in southeastern Tibet Plateau, then SE to NS in North-South Seismic Zone. But the direction changes sharply to EW in the northern Indochina. The rotation of Pn fast direction may be a result of mass extrusion from Tibet under simple shear, which is caused by mass flow in southeastern Tibetan Plateau and North-South Seismic Zone relative to stable EHS and Sichuan Basin. The EW Pn direction probably results from pure shear, which is caused by compression in NS and extension in EW in Burma back-arc extensional area. The polarization directions of SKS have similar rotation to Pn, but in northern Indochina the area of EW-oriented fast direction of Pn has a southward offset of about 3° than SKS, which may result from the faster movement of upper lithosphere in this area.

The hybrid composite joint structures considered in this work, for application in a tilting railroad car body, are subjected to shear and bending loads. Two types of the joint specimens were fabricated and tested under both static and fatigue conditions: a hybrid bolted-joint specimen subjected to a shear loads, and a hybrid beam-joint specimen for the bending tests. The fracture behaviours of these specimens under static loads were different from those under cyclic loads. For the hybrid bolted-joint specimens, static shear loads caused a pure shear fracture in the bolt pin body itself. However, cyclic fatigue shear loads brought about an opening-mode fracture at the local site of the bolt which was the valley of the screwed region of the bolt pin and/or the perpendicularly angled region between the bolt head and the pin body. On the other hand, for the hybrid beam-joint specimens, static bending loads caused shear deformation and fracture in the honeycomb core region, while fatigue cyclic bend loading caused delamination along the interface between the composite skin and the honeycomb core, and/or caused a fracture in the welded part jointed with the steel under-frame. These fracture behaviours could arise in other industrial hybrid joints with similar sub-structures, and were used in developing a design parameter to improve a hybrid joint structure.

The (three)-rail shear test is rarely considered for testing of fibre-reinforced composites under pure shear fatigue loading conditions because of all experimental difficulties. How- ever, in this article, a carbon fabric-reinforced PPS is tested using a modified three-rail shear test setup. The results are compared with ((+45 ◦ ,−45 ◦ ))4s tensile tests with good correspondence. All fatigue experiments were done with R = 0 and the influence of max- imum shear stress and frequency is investigated. It can be concluded that an increase in maximum shear stress decreases fatigue lifetime, whereas an increase in frequency in- creases the lifetime. Before failure, a sudden increase in both temperature and permanent deformation could be detected. Creep tests yielded that the occurring deformation is mainly due to the fatigue loading, rather than due to creep phenomena.

To follow palm oil crystallization under shear, a new rheological method was developed. This method can be split up into two parts: In the first part, continuous shear is applied for a pre-defined period and crystallization is monitored by measuring the apparent viscosity as a function of isothermal time under shear. In the second part, shear is halted and oscillation is applied during 30 s, thus recording moduli and phase angle. These moduli and phase angle are then characteristic of a sample crystallized under shear during this pre-defined period. After repeating this procedure for increasing shearing periods in the first part, complex modulus and phase angle were plotted as a function of isothermal time under shear. The thus obtained results were compared with crystallization data obtained via time-resolved X-ray diffraction and polarized light microscopy.

An electro-rheological (ER) fluid showing trembling shear behavior was fabricated with chitosan particles that had benzene, amine and azo-pendent side groups. This modified-chitosan dispersed suspension showed four regions in a plot of shear stress against shear rate at high electric field. We analyzed this specific behavior with our suggested model. The model was developed with the spring-damper model. Our suggested model equation treated the wide range of shear rate and specific behaviors of shear stress in ER fluids. In this study, we successfully obtained various ER fluids showing different behaviors just by changing the side functional groups of the particles in the ER fluids. All of the curves of the shear stress plotted against shear rate were fitted well by our spring-damper model.

It has been observed previously that cracks in elastomers under repeated strain initially grow rapidly from sharp cuts, but as the cracks proceed, the rate decreases to a steady value. This work examines these transitions from a sharp crack tip, introduced by a razor blade into a pure shear test piece, for a range of elastomers. The changes in the rate of crack growth are also reflected by changes in the fracture surface appearance, which roughens as the crack develops. This phenomenon is of practical significance in engineering applications, in which an initially fast crack growth rate from a sharp cut in a rubber product can result in significantly lower fatigue life than anticipated from the steady-state value, which is usually presented and quoted. The change in the rate with the number of cycles can be represented by an empirical relation whose parameters are functions of the strain energy release rate. The roughening of the crack can be envisioned as the splitting of a sharp tip into several tips with a consequent sharing of the strain energy release rate between them, leading to a reduction in the crack growth rates. This representation of the roughening process has been analyzed with a FEA approach. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

The shear stress and the first normal stress difference were simultaneously measured in shear flow start-up experiments and a subsequent stress relaxation. The measured polydimethylsiloxane show shear thinning flow behavior with a first Newtonian region up to the shear rate at the onset of shear thinning. We found that the shear stress and the first normal stress difference have an equal shear rate at the onset of shear thinning. The shear stress at the onset of shear thinning does not depend on the molecular weight of the polymer and on temperature. Similar to the viscosity master curve, it is possible to create a normal stress master curve, outgoing from the first normal stress coefficient. The shear rate at the onset of shear thinning is estimated from the viscosity master curve and the shear rate at the onset of normal stress thinning from the normal stress master curve. The shear stress and the first normal stress difference have similar transient behavior with start-up stress curves without maximum in stress growth experiments with shear rates from the first Newtonian region. The shear flow start-up experiment with the shear rate at the onset of shear thinning leads to the first indication of an overshoot of the start-up curve. The shear flow start-up experiments with shear rates from the shear thinning region show start-up curves with a maximum for the shear stress and for the first normal stress difference. It was found that the shear rate at the onset of shear thinning and the shear rate at the onset of normal stress thinning, determined by the shear flow start-up measurements, are equal to the values obtained from the master curves. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci 2008

The mechanical behavior of nanocrystalline metals has been a research topic of interest for the past two decades. The current understanding is summarized in several recent reviews. Researchers have been investigating the deformation mechanisms in nanocrystalline metals and alloys through experimental and modeling routes. Modeling results indicate that there is a transition from dislocation generation at sources within grains to grain-boundary mediated dislocation generation in the grain size range between about 100 to 10 nm. Below 10 nm, grain boundary deformation modes (sliding, rotation, etc.) become dominant and inverse Hall-Petch effects have been reported. Experimental evidence to confirm these predictions is an active area of research. Two important experimental parameters that are useful in characterizing the deformation kinetics of materials are the strain rate sensitivity m and the activation volume V*. 11, 12] These are related by m = kT/V*r where k is Boltzmann’s constant, T is temperature (K) and r is the stress. There is a limited amount of data available on m and V* measurements for nanocrystalline metals. 5, 11–14] One aspect of this is the fact that research-scale synthesizing techniques often produce small quantities of material and mechanical testing procedures suited to small sample sizes are required. 5, 7, 13–18] In addition to this fact there is a tremendous scarcity of testing methodologies for testing the materials at small scales such as Micro-Electro-Mechanical-Systems (MEMS) where micro tensile and nanoindentation tests are used for understanding the deformation behaviour. 20] The aim of the present work was to extend the shear punch test (SPT) technique to the measurement of activation volumes on small scale specimens of few millimeters (∼ 1 mm to 3 mm). The advantage of SPT over nanoindentation and micro tensile tests is the deformation zone where a large number of grains undergo deformation within the shear zone and overcomes the problem of strain gradient plasticity effects, gain size effects as well as the specimen size effects. The SPT has been used for evaluating the yield and ultimate stress by numerous researchers, including us. The SPT shear yield or ultimate strength value s can be correlated with its tensile test counterpart r using the relation r = as. The correlation factor a depends upon the testing setup and data analysis methods. The Von Mises (VM) yield criterion predicts a = 3 if the SPT approximates pure shear loading conditions. This was the case in where the details and standardization of the SPT technique used in the present research work are given. The stress relaxation method has been used to determine activation volumes and dislocation dynamics in coarse-grain metals and alloys and in nanocrystalline Ni. The tests are normally done using uniaxial loading conditions. In the present study, we use the stress relaxation method in conjunction with the SPT technique. As far as we are aware, this is the first time that the full implementation of this method has been reported.

Service conditions experienced by rubber components often involve cyclic loads which are more complex than a constant amplitude loading history. Consequently, a model is needed for relating the results of constant amplitude characterization of fatigue behaviour to the effects of variable amplitude loading signals. The issue is explored here via fatigue crack growth experiments on pure shear specimens conducted in order to evaluate the applicability of a linear crack growth model equivalent to Miner's linear damage rule. This model equates the crack growth rate for a variable amplitude signal to the sum of the constant amplitude crack growth rates associated with each individual cycle. The variable amplitude signals were selected to show the effects of R-ratio (ratio of minimum to maximum energy release rate), load level, load sequence, and dwell periods on crack growth rates. In order to distinguish the effects of strain crystallization on crack growth behaviour, two filled rubber compounds were included: one that strain crystallizes, natural rubber, and one that does not, styrene-butadiene rubber. The linear crack growth model was found to be applicable in most cases, but a dwell effect was observed that is not accounted for by the model.

Transected F1 fold structures in eastern Ireland are associated with subhorizontal stretching in the S1, cleavage whereas axial planar cleavage contains a vertical elongation direction. This suggests that the non-axial planar cleavage was influenced by a distributed strike-slip ductile shear. A major NE-SW trending F1 syncline is described in which the minor F1 folds show systematic variations in cleavage transection parameters. On the steep limb of the major syncline the cleavage transects the minor F1 folds in a consistently clockwise sense, whereas on the normal limb anticlockwise transected folds are seen. Axial planar cleavage occurs at the core of the major syncline. Fold profile analysis indicates that the buckling of the layers began before the initiation of the cleavage. Open, parallel folds at the major synclinal hinge zone are progressively ‘flattened’ on the steep limb towards a major D1 sinistral transcurrent fault. The angular transection, A, attains a maximum of 15° clockwise which diminishes to

The mathematics of irrotational deformation are simplified by presentation in matrix form. Matrix equations are easily programmed and are easily interpreted in geometrical terms. Graphical operations commonly carried out on orientation nets such as rotation of data can be translated into simple matrix equations for use with a computer. If the shape and orientation of the deformation ellipsoid for a pure shear are known, a matrix can be constructed for use as a deformation matrix. This can be used to deform other deformation ellipsoids to obtain a resultant ellipsoid. It can also be used to deform geological structures such as lineations and planes. The matrix equations for these operations are very simple, but their numerical solution often requires a computer.

A fracture criterion is proposed, based on maximum energy release rates at the tips of short kinks when the main cracks are subjected to mixed mode loading. The criterion differs from existing energy based criteria in that the fracture toughness, g c , is not independent of the stress mode prevailing in the region of the tip of the kink but is a function of the ratio of the mode II to mode I stress intensity factors at the tip of the kink, i.e., g c is determined directionally by an elliptical region with major and minor axes equal to the fracture resistances of the material, K Ir and K IIr , for pure mode I and pure mode II, respectively. Points inside the elliptical region are considered safe. When K IIr is equal to K Ir the ellipse degenerates into a circle and the fracture criterion reverts to the existing familiar maximum energy release rate criterion based on a single value of the fracture toughness, irrespective of the active mode prevailing in the region at the tip of the kink. In this case, under pure shear (mode II) applied load, K II , the angle of inclination of the fracture crack extension to the main crack, α, is in the region of -76°, in general agreement with previous well established results. However, when the ratio r (= K IIr /K Ir ) is less than r' (=0.82, approximately) a different pattern emerges and, in particular, under pure mode II load, the crack advance is co-planar with the main crack, i.e., in mode II. A lower transition value r (=0.582, approximately) was also detected under pure mode I applied load. Thus for values of r≥r, the crack extension is in pure mode I and is co-planar with the main crack but when r

Moderately concentrated polymer solutions are described as a suspension of interacting harmonic dumbbells. The interaction is treated in a mean field approximation. In the framework of this model the exact conformational distribution function for transversal shear flow is obtained. The shear viscosity and the first normal stress coefficient show the typical non-Newtonian form with a distinct power law behavior after the onset of shear rate dependence.

Macroscopic fracture is preceded by localized deformation and rupture processes that depend on the state of combined stress (i.e., on the stress state) and other test conditions as well as on polymer structure and morphology. To illustrate the effect of stress state on the mode of fracture initiation and crack growth, data obtained on elastomers in triaxial tension are reviewed along with those for an unfilled styrenebutadiene rubber vulcanizate in simple tension, equal biaxial tension, and under the biaxial tensile conditions that give a pure shear deformation. The behavior of plastics, including the dependence of the strength of a notched specimen on its thickness, is briefly considered.

Spun soy fibers fractured by the tensile test, Warner-Bratzler shear, Kramer Shear Press and a modified Volodkevich wedge were examined with the scanning electron microscope. Fracture in the tensile test occurred almost always at a macrocavity, the weakest point in the fiber. Warner-Bratzler shear induced compression and flow at the zone of rupture, but not as markedly as in the case of the modified Volodkevich wedge. Fracture by the Kramer Shear Press was the closest to pure shear. Some of the exposed fracture surfaces revealed internal structures in the fibers such as macrocavities and distinct skin and core sections. The mechanism of rupture by these tests was more complex than expected.

We consider discontinuous bifurcations as the indicator of a localized failure for a class of composites that are characterized by elastic fibres reinforcing an elastic–plastic matrix. A macroscopic tangent stiffness tensor for the fibre-reinforced composite is developed by consistently homogenizing the contribution of fibres in a spherical representative volume element. Analytical solutions are derived for the critical hardening modulus and corresponding bifurcation directions for the case of plane strain loading. Properties of the solutions are further illustrated on the example of the non-associated Drucker–Prager model at onset of yielding. Results show that presence of fibres decreases the critical hardening modulus, thus inhibiting the onset of strain localization. The rate of decrease in the critical hardening modulus is the highest for pure shear, followed by uniaxial tension, uniaxial compression, biaxial tension and biaxial compression. The main fibre parameters that control the onset of strain localization are their volumetric content and their stiffness modulus whereby very stiff fibres can produce the most significant decrease in the critical hardening modulus, especially for the state of biaxial tension. The critical hardening modulus for the non-associated Drucker–Prager model exhibits a full range of localization modes including compaction bands, dilation bands, and transition in the form of shear bands regardless of the presence of fibres. Presence of fibres affects bifurcation directions, except in the case when Poisson's ratio of the matrix is equal to 0.25. The results demonstrate stabilizing effects of fibres by which they provide the control against the onset of strain localization. Copyright © 2006 John Wiley & Sons, Ltd.

The effect of multiplex shear stress on the cell nucleation during microcellular foaming process was investigated using a dynamic foaming experimental apparatus. The multiplex oscillatory shear, which is different from previous one-dimensional screw shear in a “stable” extrusion foaming process, is applied to the polymer melt through an axially vibrated rotor. The experimental results show that, by superimposing an axial vibration on the rotating rotor, the cell density increases and cell size decreases significantly when the shear rate is low. Both the uniformity of cell size and cell distribution are improved under vibration when compared with that without vibration regardless of how the shear rate changes. In addition, a simplified nucleation model based on shear energy has been carried out to qualitatively investigate the effect of both the simple steady shear and the multiplex oscillatory shear on the cell nucleation. Experiments and theoretical predictions all show that cell nucleation could be greatly improved by superimposing the oscillatory shear when the nucleation driving force induced by the steady shear is insufficient. Finally, the shear heat generated by excessive shear and strong vibration should be considered carefully although the isothermal condition was supposed in the present model.

This paper evaluates the mechanical behaviour of yielding frictional geomaterials. The general Double Shearing model describes this behaviour. Non-coaxiality of stress and plastic strain increments for plane strain conditions forms an important part of this model. The model is based on a micro-mechanical and macro-mechanical formulation. The stress–dilatancy theory in the model combines the mechanical behaviour on both scales. It is shown that the general Double Shearing formulation comprises other Double Shearing models. These models differ in the relation between the mobilized friction and dilatancy and in non-coaxiality. In order to describe reversible and irreversible deformations the general Double Shearing model is extended with elasticity. The failure of soil masses is controlled by shear mechanisms. These shear mechanisms are determined by the conditions along the shear band. The shear stress ratio of a shear band depends on the orientation of the stress in the shear band. There is a difference between the peak strength and the residual strength in the shear band. While peak stress depends on strength properties only, the residual strength depends upon the yield conditions and the plastic deformation mechanisms and is generally considerably lower than the maximum strength. It is shown that non-coaxial models give non-unique solutions for the shear stress ratio on the shear band. The Double Shearing model is applied to various failure problems of soils such as the direct simple shear test, the biaxial test, infinite slopes, interfaces and for the calculation of the undrained shear strength. Copyright © 2006 John Wiley & Sons, Ltd.

The asymmetrical four-point bend (AFPB) method, which provides a pure shear stress state in the middle of the test specimen, was utilized to measure the shear strength of the joints between Nicalon-fiber-reinforced SiC composites. The small test specimens were prepared as butt-joints with uniform depth (no notch). It was shown experimentally that the position of loading points is critical to induce shear fracture at the joint without the failure of base material. The appropriate positions for the present test specimen were determined and, as a result, an articulated ceramic fixture was designed. This test method is economical and involves small test specimens with simple geometry, and can be used at high temperatures.

A structure consisting of two elastic plates bonded by a thin and soft adhesive layer is considered. Non-linear plate models are obtained by using the method of formal asymptotic expansions. A distinguishing feature of this problem is that the only quantitative property of the adhesive that has to be taken into account is the response of the material subjected to a pure shear load.

Shear viscosity and melt fracture of a metallocene poly(ethylene-octene) were studied using a capillary rheometer and dies with different lengths. The true wall shear stresses determined at zero die length showed a dip at high shear rates. The shear viscosity was derived from the true wall shear stress. With increasing shear rates, the extrudate staged from smooth to three types of melt fracture with regular patterns, and then turned into irregular shapes. Three types of regular melt fractures—sharkskin, helix, and spiral (in sequence)—were observed with an increase of the shear rates. The wavelength of the regular melt fracture was measured from extrudates, and the corresponding frequency was calculated. The frequency increased at elevated melt temperatures. Both shear viscosity and frequency at different temperatures correlated well by using the time–temperature Williams–Landel–Ferry (WLF) superposition. Additionally, it was found that the frequency decreased slightly for a longer die but it increased when the shear rate went up. Three frequency functions were associated with three melt fracture patterns, respectively. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 903–911, 2005

This paper discusses experimental test methods for the purpose of defining the nonlinear properties of rubbery materials used for finite element analysis. The typical tests are simple tension, simple compression and pure shear tests. It has been found in the simple tension test that a narrow strip specimen whose length is 10 times longer than the width can be used more appropriately than a dumbbell type specimen. In order to eliminate the effect of friction between the specimen and the platens in the compression test, a tapered platen is suggested. The effect of the tapered platens is verified by experimental and finite element analysis. In a shear test, it has been shown that the specimen width must be at least 10 times larger than the height of the specimen. The mechanical preconditioning has significant effects on the prediction of the behaviours of rubbery materials and components. The static stiffness of an automotive engine mount is calculated by nonlinear finite element analysis using the experimentally determined material properties and is compared with experimental results that take into account the mechanical preconditioning effect, resulting in a good correlation. Copyright © 2004 Society of Chemical Industry

Development of shear bands in saturated soils is a multi-stage process based on the theoretical and numerical investigations in this paper. The soil is initially in homogenous shear strain state, and the instability can be characterized by a dimensionless number D. The inhomogenous distribution of shear strains appears when D > 1, and the shear band will initiate and develop gradually. Numerical solutions show that only single shear band that is finally formed in the central region of the specimen even several disturbances (distributed along the specimen) appear in the beginning. Copyright (C) 2004 John Wiley Sons, Ltd.

A formula for the thickness of a shear band formed in saturated soils under a simple shear or a combined stress state has been proposed. It is shown that the shear band thickness is dependent on the pore pressure properties of the material and the dilatancy rate, but is independent of the details of the combined stress state. This is in accordance with some separate experimental observations. Copyright (C) 2004 John Wiley Sons, Ltd.