Effect Of Shear Loading Research Articles

Sand-sand and sand-steel interface grain-scale behavior under shearing

The behavior of a sand-steel interface can be different than the shearing behavior of a sand. This study focuses on the effect of shear loading on a sand-to-sand and a sand-steel interface as well as on particle breakage. A series of ring shear and simple shear tests were conducted to measure the effects of particle shape and surface roughness characteristics before and after shearing at the shear zones within a sand-to-sand and at a sand-steel plate interface. It was found that sand density had a large effect on the interface shearing behavior. While interface sliding began at a shear displacement of 0.9 mm (corresponding to 22% of the total shear displacement) in dense specimens, this occurred at a much higher displacement of 5.6 mm (62% of total displacement) in loose sand at rough steel interface. Sliding displacement prevailed at the sand-steel plate interface in simple shear tests as the sand sample became denser. Critical states were observed in the sand-to-sand ring shear tests after shear displacements of 65–79 mm and 87–98 mm in medium-dense and loose samples, respectively. Comparing sand-to-sand and sand-steel interface results indicated that sand-steel interface behaves less dilative with the critical state occurring at much smaller shear displacements of about 12–14 mm at the interface compared to that occurring within the sand at 65–79 mm. Both loose and dense sands reached a residual strength of 98 kPa at a shear displacement of 7 mm in simple shear tests. The inter-particle shear resistance and particle crushing, combined with particle rearrangement/rotation were the mechanisms which developed shear resistance. An interface friction angle of 27° was subsequently mobilized at the critical states of the simple shear tests, while particle crushing and abrasion resulted in a slightly elevated (by 2°) interface friction angle in the ring shear tests. The difference between sand-steel interface and sand-to-sand interaction mechanism highly influenced particle damage induced by particle fracturing and abrasion. As a result of particle crushing, roughness and aspect ratio of sand particles sheared at the interface with a steel plate reduced by respectively 39.7% and 12–14% sheared at normal stresses of 50 to 200 kPa. In particular, particles' circularity increased from 0.685 to 0.817, indicating symmetrically rounded particles. The maximum size of particles in all tests reduced to about 16.9–18.1% of the original maximum particle size (Dmax = 0.85 mm). While the skewness of particles sheared within the sand increased from −0.231 to 0.656 (indicating increased surface roughness), those of particles collected from the sand-steel interface decreased to −1.31 reflecting smoother particle surfaces.

Reaction mechanism of blood coagulation factors in shear flow field.

Thrombus formation in blood pumps is a major problem. It has been reported that the shear rate is closely related to thrombus formation in blood pumps; however, the mechanism of blood coagulation in a shear flow field is not yet fully understood. The purpose of this study is to evaluate the effect of shear loading on the reaction of blood coagulation factors quantitatively. Human blood and porcine blood were used as test blood and sheared at 2,880 s-1 for 3 h using a rheometer. After shear loading to the test blood, the activated partial thromboplastin time (APTT) and prothrombin time (PT) of sample plasma were measured using an automated coagulation analyzer. The APTT and PT of mixed plasma containing human blood coagulation factor-deficient plasma and sample plasma were also measured. The APTT and PT of mixed plasma reflected the reaction of the particular blood coagulation factor. Results show that shear loading prolonged the APTT and PT of human sample plasma. Accordingly, the APTT and PT of mixed plasma containing human blood coagulation factor V-deficient plasma and human sample plasma were prolonged after shear loading. Thus, the reaction of human blood coagulation factors was inhibited by specific inhibition of the reaction of human blood coagulation factor V in the shear flow field. The reaction time of porcine blood coagulation factors after shear loading differed from that of human blood coagulation factors. The result suggest the evaluation difficulty of animal blood coagulation reaction, that is, porcine blood coagulation reaction did not fully proceed with clinical reagents due to species specificity.

Experimental and numerical analysis of micromechanical damage for DP600 steel in fine-blanking process

In fine-blanking process, metallographic inspection shows that highly elongated and densely packed grains extend along the shear direction within a narrow large deformation region, meanwhile micro-cracks initiate and grow up. By taking the effect of shear loading into account, the recent modified GTN model proposed in 2014 is implemented and validated. The shear damage model combines the damage mechanics concept with the porous plasticity model and is applied to simulate fine-blanking process to verify its accuracy in predicting material damage and tearing fracture. The formation and propagation of shear band in fine-blanking process are studied. Both numerical results and experimental observations reveals that the effect of shear damage plays a significant role in inducing tearing, which eventually leads to fracture failure in the fine-blanking process.

Failure analysis based on microvoids damage model for DP600 steel on in-situ tensile tests

Considering the effect of shear loading, an original GTN damage model is extended by combining the damage mechanics concept and the porous plasticity model. The extended model in terms of various stress triaxiality was deduced in detail. The model is extended by coupling two damage parameters into the yield function. The implementation is achieved by the development of the user material subroutine. Internal damage evolution was observed by scanning electron microscopy (SEM). Parameters were determined from experimental data and previous studies. The damage model was applied to in-situ tensile tests to compare its predictability in various specimens. The obtained numerical results were in good agreement with experimental results, showing better ductile fracture predictions.

血流によるせん断負荷が血液凝固因子の反応に及ぼす影響

血流によるせん断負荷が血液凝固因子の反応に及ぼす影響

Mixed mode fracture of a piezoelectric–piezomagnetic bi-layer structure with two un-coaxial cracks parallel to the interface and each in a layer

The purpose of the present work is to study the mixed mode fracture of a piezoelectric–piezomagnetic composite with two un-coaxial cracks parallel to the interface and each in a layer. Methods of generalized dislocation simulation, Green’s function, Cauchy singular integral equation and Lobatto–Chebyshev collocation are combined together to get the numerical results of mechanical strain energy release rate (MSERR). Three kinds of effects are revealed by parametric studies, i.e., the free-surface effect, the shielding effect and the interference effect, and they are used to interpret the characteristics of COD and MSERR curves. In addition, the effects of shear loading, magnetic loading and electric loading on MSERR are also disclosed, respectively, by varying the corresponding loading factor.

圧縮－せん断複合負荷成形による鉄系粉末の高密度成形に及ぼす試料サイズの影響

To improve the strength of sintered parts, it is important that the density of green compacts should be as high as possible. In the present work, the possibility of achieving a higher density of green compacts by applying compression and shear combined loadings simultaneously than by uniaxial compaction is investigated. The effect of shear loading on powder compact density and the effect of cylindrical specimen size are investigated by compressive and rotational loadings. The internal density distributions are also examined. The improvement in density by applying shear loading was clearly observed. The effects of shear loading on specimen diameter and height were observed, and the gradient of density was decreased by applying shear load.

Mixed-mode crack propagation of stiffened curved panels repaired by composite patch under combined tension and shear cyclic loading

In this study, finite element method is used to investigate the fracture analyses, crack growth trajectory and fatigue life of curved stiffened panels repaired with composite patches subjected to combined tension and shear cyclic loadings. For this purpose, finite element modeling is performed for consideration of real 3-D crack-front in general mixed-mode conditions. Contact elements are used between the crack surfaces on two crack sides to prevent interferences of crack surfaces and a complementary program was developed to handle the automatic fatigue crack growth modeling. The effects of various patch layups and shear–tension loading ratios on fracture parameters of repaired aluminum panels are investigated. It is shown that as the shear to tension ratio increases, the patch layups with orientations of almost perpendicular to the crack trajectory become more efficient in term of fatigue crack growth life when compared with the patch layups parallel to the tension orientation like [90]4. It will be shown that as the effect of shear loading is decreased around the crack-front due to the increasing of stiffener spacing ratio the values of KII are decreased and consequently shear loading effects on tilting the crack trajectories are decreased.

Conservative Failure Criteria for Optimal Design of Composite Structures Including Effect of Shear Loading

A minimum weight design of laminated composite structures is carried out for different loading conditions and failure criteria using genetic algorithm. The phenomenological maximum stress (MS) and Tsai-Wu (TW) criteria and the micro-mechanism-based failure mechanism based (FMB) failure criteria are considered. A new failure envelope called the Most Conservative Failure Envelope (MCFE) is proposed by combining the three failure envelopes based on the lowest absolute values of the strengths predicted. The effect of shear loading on the MCFE is investigated. The interaction between the loading conditions, failure criteria, and strength-based optimal design is brought out.

Electrical Resistance Change of Unidirectional CFRP Due to Applied Load

Carbon Fiber Reinforced Plastic (CFRP) is composed of electric conductive carbon fibers and electric insulator resin. Self-monitoring system has been reported utilizing electric resistance change of unidirectional CFRP due to fiber breakages and to applied strain. Piezoresistivity is electric resistance change with applied strain. Many researchers have already reported the piezoresistivity of unidirectional CFRP. There is, however, large discrepancy in the measured piezoresistivity even in the fiber direction during tensile loading: both positive piezoresistivity (electric resistance increase) and negative piezoresistivity (electric resistance decrease) are reported during tensile tests. Electric resistance change at electrodes due to poor electric contacts are reported to be a main cause of this large discrepancy. In the present study, therefore, basic properties of piezoresistivity were measured with specimens made from single-ply and multi-ply laminates using a four-prove method. Many cases of electric resistance changes in the fiber direction transverse direction were measured during tensile loading. Effect of shear loading was also investigated using a shear test. To investigate the effect of poor electric contact at the electrodes, electrodes were made without polishing specimen surface and a tensile test was performed with measuring piezoresistivity. After the test, the specimen surface was polished, and a tensile test was performed again using the identical specimen. As a result, positive piezoresistivity was obtained for both single-ply and multi-ply specimens and negative piezoresistivity is confirmed that it was caused by the poor electric contact at electrodes.

The effect of shear load on frictional healing in simulated fault gouge

We report on frictional strengthening (healing) in granular quartz gouge as a function of time of true stationary contact. To distinguish between the slip‐dependent [Ruina, 1983] and time‐dependent [Dieterich, 1979] friction constitutive laws, we designed tests similar to conventional slide‐hold‐slide (SHS) tests except that shear load was completely removed prior to holds. We find large healing values (0.033–0.054 for holds of 10¹–10² s) compared with quasi‐static SHS experiments, and our data indicate time‐dependent weakening in contrast with strengthening observed from SHS tests. Gouge layer compaction increases with increasing hold time, comparable to observations from conventional SHS tests. Our data indicate that purely time dependent processes have a minor influence on healing under the conditions studied and/or that such effects are efficiently erased by particle rearrangement during removal/reapplication of shear load. The data are not adequately described by either the time (Dieterich) or slip (Ruina) dependent state evolution laws.

Comparison of contact sensor localization abilities during manipulation

This paper presents an experimental comparison of tactile array versus force-torque sensing for localizing contact during manipulation. The manipulation tasks involved rotating objects and translating objects using a planar two fingered manipulator. A pin and a box were selected as limiting cases of point and line contact against a cylindrical robot finger tip. Practical implementations of the two sensor types are compared theoretically and experimentally, and three different localization algorithms for the tactile array sensor are considered. Force-torque contact sensing results suffered from difficulties in calibration, transient forces, and low grasp force. Tactile array sensing was immune to these problems and the effect of shear loading was only noticeable for a simple centroid algorithm. The results show that with care, both of these sensing schemes can determine the contact location within a millimeter during real manipulation tasks.

Transient failure analysis of liquid-filled shells PART II: Applications

In this paper, applications of the theory developed in the companion paper by Liu and Uras [1] are presented. The effects of various types of ground motion on the dynamic stability of the fluid-structure system are analyzed. The stability criteria of liquid-filled shells subjected to horizontal and rocking excitation, shear loading, bending/shear combined loading, and vertically applied load are established. The resulting instability regions and stability charts are given in tables and in ω-ϵ plots. Under horizontal and rocking motion, modal coupling in the circumferential direction as well as in the axial direction is observed. The possible buckling modes for a tall tank can be identified as cos2θ, cos3θ and cos4θ under horizontal and rocking motion, and cos5θ and cos6θ, under vertically applied load. For a broad tank two sets of instability modes are found: cos6θ through cos9θ, and cos12θ through cos14θ under horizontal and rocking motion. When subjected to vertically applied load, the failure modes of a broad tank shift to cos10θ through cos12θ, and cos14θ through cos15θ. The effect of shear load on a broad tank appears to be important only if damping is relatively small. Under bending/shear combined loading, the bending forces dominate the stability of the fluid-filled shells.

Effects of shear loads on vibration and buckling of antisymmetric cross-ply cylindrical panels

This work deals with the effects of shear loads on the vibration and buckling of typical antisymmetric cross-ply thin cylindrical panels, subjected to combined loads. Changes in the buckling loads due to geometric and material parameter variations are investigated with particular emphasis on distinguishing the symmetric and antisymmetric modes. The paper presents the first known results on shear buckling of cross-ply cylindrical panels as well as vibrations of these structures under shear loads. The resulting interaction curves will allow one to formulate effectively a preliminary design of these panels which will withstand shear loads.