Plate Shear Test Research Articles

Study on Proportioning Scheme of Coal System Rocky Similar Material Based on Orthogonal Test.

Similar materials play an important role in model testing. In order to meet the demand for similar materials in modeling tests, such as those on coal mining, coal system rocky similar materials were formulated using yellow sand as a coarse aggregate, heavy calcium carbonate as a fine aggregate, and cement and gypsum as binders. Based on the orthogonal experimental design method, four influencing factors, namely the aggregate-binder ratio, heavy calcium carbonate content, cement-gypsum ratio, and moisture content, were selected. Each factor was designed at five levels. Through weighing, uniaxial compression, Brazilian splitting, and variable-angle plate shear tests on 225 specimens under 25 different ratios, five physico-mechanical property indicators of the material, including density, compressive strength, tensile strength, cohesion, and internal friction angle, were obtained under different ratios. The test results indicate that the similar materials formulated with the above raw materials had a wide range of mechanical properties, which met the simulation needs of different types of coal rocks, such as main coking coal, anthracite, shale, etc., in the similar model test. Range analysis was adopted to analyze the sensitivities to each factor, which showed that the density and internal friction angle of similar materials are mainly controlled by the aggregate-binder ratio; the cement-gypsum ratio mainly controls the compressive strength, tensile strength, and cohesion of the material. Analysis of variance (ANOVA) was adopted to analyze the sensitivities to each factor, which showed that the aggregate-binder ratio had a highly significant effect on the density of the material, the cement-gypsum ratio had a highly significant effect on the compressive and tensile strength of the material, the cement-gypsum ratio had a significant effect on the cohesion and density of the material, and the moisture content had a significant effect on the compressive strength of the material. The remaining factors did not significantly affect the material parameters. The results of this study can provide some reference for the selection of coal system rocky similar materials in subsequent physical modeling tests.

Experimental investigation on mechanical behaviors of composite sandwich panels with a hybrid facesheet

AbstractA multi‐functional composite sandwich panel was developed with a hybrid facesheet, which was composed of a quartz fiber reinforced plastic (QFRP) laminate and two copper layers. The other facesheet was made of QFRP laminate. The Nomex® honeycomb was used as the core material. The aim of this paper is to investigate the effects of the hybrid facesheet on the mechanical characterizations of the sandwich panel. Four mechanical performances of both composite sandwich panel with and without copper layers were considered, including the flatwise tensile strength test, the edgewise compressive strength test, the three‐point bending test and the tensile plate shear test. The experimental results show that all the four mechanical performances of the sandwich panel with copper layers were lower than the sandwich panel without copper layers. The flatwise tensile strength decreased by 26.1%. The edgewise compressive strength decreased by 9.5%. The shear strength obtained from the three‐point bending test decreased by 14.9%. The shear strength obtained from tensile plate shear test decreased by 13.7%.

Tensile and Shear Mechanical Characteristics of Longmaxi Shale Laminae Dependent on the Mineral Composition and Morphology

Laminae are well developed in shale and generally influence fracture propagation during hydraulic fracturing. Hence, comprehensively understanding the tension and shear behaviors of shale laminae is crucial. There have been limited systematic studies thus far on the tensile and shear strength as well as fracture morphology of shale laminae. In this study, the Lower Silurian Longmaxi Shale (China) was investigated via Brazilian tensile and angle-varied plate shear tests. Five lamina types were tested, i.e., calcite (Cal), pyrite (Py), organic-enriched (Oc), the interface between Cal and Oc (Cal-Oc), and the interface between Py and Oc (Py-Oc) laminae. Results showed that the tensile strength was in the range 0.43–8.22 MPa, mainly in the order of Cal > Py > Cal-Oc > Py-Oc > Oc. The modes of fracture morphology were highly related to the occurrence, continuity, and mineralogy fillings of laminae. Shear strength parameters were within the range 22.50–29.64 MPa for cohesion and 37.29–43.60° for internal friction angle. Fracture surface roughness was strongly related to its cohesion. Calcite laminae considerably influenced the tensile fracturing of shale, suggesting that the geometry and properties of calcite lamina should receive more attention during the design of shale gas exploration.

Basic mechanical properties of balloon-type TEEK-L polyimide-foam and TEEK-L filled aramid-honeycomb core materials for sandwich structures

The objectives of this study are to investigate the basic mechanical properties of TEEK-L polyimide-foam of a balloon type and TEEK-L filled aramid-honeycomb core-materials for sandwich structures and to compare their mechanical properties with those of AIREX R82 and ROHACELL WF foam core-materials. Compression, tension, and plate-shear tests provided their stress–strain relationships, elastic modulus, and strength. The test results are compared and discussed. The major results obtained are: (1) Filling the aramid honeycomb cells with TEEK-L can improve the basic mechanical properties of an aramid-honeycomb core-material, in particular making them higher than the values expected from the principle of superposition for compression tests and equal to the values expected from superposition for plate-shear tests. (2) The basic mechanical properties of the TEEK-L filled aramid honeycomb are superior to those of AIREX R82 110 and equivalent to those of ROHACELL WF 110, where the three materials have equal densities. (3) The basic mechanical properties of TEEK-L are inferior to those of AIREX R82 60 and ROHACELL WF 51, when materials with equivalent densities are compared. (4) TEEK-L filled aramid honeycomb has high potential as a new core material for aerospace sandwich structures.

Experimental studies on the yield behavior of ductile and brittle aluminum foams

Specimen size effects are a major cause of the unreliability of foam models in finite element codes. Here, the modified Arcan apparatus is used to investigate the biaxial yielding of ductile and brittle Al foams. This apparatus subjects a central section of a “butterfly-shaped” specimen to a uniform state of plane stress. The stresses have local maxima at the central section, thus ensuring that yielding occurs there. A yield envelope, which directly relates to the crushing process, can then be determined. Size effects are introduced when using conventional methods such as tri-axial or plate-shear tests. In such tests, averages of stress and strain are measured. These measures do not represent the actual yield event, because foam's internal structure is inhomogeneous and so is the deformation field. Strain localization and failure can occur at any weak layer of cells in the bulk. In this study, we have performed a series of biaxial tests on isotropic Alporas and anisotropic Hydro closed-cell Al foams of approximately equal densities. Alporas failed locally by a ductile phenomenon of progressive crushing of cells. It also possessed uniaxial strength asymmetry. Hydro specimens parallel and perpendicular to ‘foam rise’ were investigated. The Hydro foam developed a local, characteristic brittle crack at loads in the vicinity of the yield point. Phenomenological yield surfaces, which incorporate these features are obtained for the foams, and show dependence on both the deviatoric and hydrostatic stresses. We also provide expressions for the shear and hydrostatic strengths in terms of the uniaxial strengths. Finally, the size-independence of the yield surface is verified using the uniaxial compression of tapered specimens.

Shear properties of human brain tissue.

The objective of this study was to determine a relationship between shear stress and strain for human brain tissue by performing transient, single-pulse, high-rate, shear displacement tests. A constant velocity, parallel plate shear test device was designed and fabricated. This equipment generated constant rate shear strains in cylindrical tissue samples mounted between the shear plates. The transverse reaction force at the upper end of the sample was measured during the event with a sensitive quartz piezoelectric force transducer, thus obtaining the force associated with the displacement versus time ramp. Shear tests were performed on 125 tissue samples taken from twelve fresh cadaver brain specimens. The average true shear stress and finite strain were calculated. A nonlinear, viscoelastic, standard solid model was fit to the constant rate test data and the material constants were determined.

Experimental characterization of dynamic soil-track interaction on dry sand

A set of soil-track interaction relations was made developed for the morbility simulation of tracked or crawler system vehicles on dry, loose sand. These interaction relations were developed specifically for multibody mobility codes in which the soil-vehicle interaction is represented solely by soil-track interaction forces. By employing plate penetration and shear tests, an average pressure-sinkage relation, a shear force-slippage relation, and a sinkage-slippage relation were measured. These plate test data were sufficient only to describe the soil-track interaction on hard ground. On soft ground, however, it was found that intermittent sinkages induced by each passage of the road wheels become important. This dynamic contribution is called “agitation sinkage.” Based on this observation, the sinkage rate (velocity) was decomposed into elastic and plastic rates; the plastic part consists of normal force-induced, slip-induced, and agitation-induced components. Whereas the elastic and the first two components of the plastic sinkage rate were characterized by the conventional plate penetration and plate shear tests, the last term, agitation sinkage, required a new dynamic test in which the sinkage of the track after successive passages of moving road wheels was measured. It is recommended that this new field measurement technique be adopted to characterize the agitation sinkage for various terrains.