Papers by Keyword: Shear

Abstract: Studying of the strength characteristics of polymer composite materials, which are used in the structures for various applications, is an important subject for research. Here one of the major issues is the development of fastening techniques to maximize the strength characteristics of composite fibers. Based on the modification of the available test methods, a set of specimens and devices has been developed to determine the shearing (cut) strength from the fastener hole to the edge of the composite part. For this purpose, we used the modified specimen sequentially shearing along the contour after each test cycle in order to find the required parameter depending on the distance from the fastener to the part edge. According to the result of experimental studies, possible types of shearing test and shear test failures were identified. It is demonstrated that shearing strength and shear strength in the specimen plane are different characteristics with no correlation between them. It is found that a shearing in the classic sense is observed only for high-anisotropy structures when they are loaded in the more rigid direction, whereas the complex modes of failure occur for the heavily reinforced composites used. For example, during testing a pure shearing was observed in 0° planes in the specimens with the package structure of [0^°_0.7; ±45^°_0.2; 90^°_0.1], while it was observed both for the holes drilled in 0° and 22.5° directions in the specimen with the structure of [0^°_0.8; ±45^°_0.2]. We obtained the quadratic engineering dependence to predict shearing strength of the heavily reinforced basic composite. Based on processing of the experimental results, a recommendation has been made on the need for constant experimental support of the design process, which can be implemented by the proposed specimen and testing device.

Abstract: Copper (Cu) foam is a promising material that owns a high surface area that can be utilized in a thermal application. In this research, the brazing of Cu substrate to Cu foam in the sandwich configuration using Cu alloy filler foil was carried out. The foam at different pore per inch (PPI) of 15, 25 and 50 are brazed at different brazing temperatures. Mechanical and microstructure analysis were conducted to investigate a suitable brazing temperature and the best pore density of foam. The compressive strength of brazed 50 PPI foam has yielded the highest due to the highly dense interconnected branches. While the highest shear strength of brazed interface using 15 PPI foam has been recorded. The large branch size of 15 PPI foam has contributed to the sound joint between the brazed joint interface of Cu substrate and foam. Both mechanicals analysis above exhibits a highest strength at 660 °C as a brazing temperature The shear stress-strain curve of Cu substrate and foam brazed joint interface shows a brittle behaviour which accordance with the discoverable brittle phases of Cu₃P and Ni₃P using X-ray diffraction (XRD). Scanning electron microscopy (SEM) and Energy dispersive X-ray spectroscopy (EDX) have presented the formation of Cu₃P and Ni₃P at the brazed joint interface of Cu substrate and foam.

Abstract: In this research, a main matrix has been derived from the stress components in the inclined plane with an angle θ that calculates the normal stresses and shear stress in the inclined plane to be used in calculating the main stresses and the maximum shear stress in one step, this is done using the principal stress angle which is calculated from known stress compounds. As well as calculating the maximum shear stress after using the correction factor. The inverse of this derived matrix can be used to calculate the stress compounds through the known principal stresses and this applies to the components of the principal strain and strain, and the maximum shear strain. All this is done through MATLAB simulation Keywords: Normal Stresses and Strains, Shear, Principal Stresses, max. Shear Stress

Abstract: Since the material properties of paperboard depend on the processing strain rate and the temperature elevation of the paperboard, the mechanical conditions of the scoring tool (creasing knife) are important for precisely and stably folding the scored zone of the paperboard. When the temperature and the indentation velocity of the creasing knife are changed irregularly during the scoring process, the permanent-indented (residually scored) depth of the paperboard seems to be affected by the temperature and the indentation time of the creasing knife. Although the temperature-dependent and time-dependent behavior of several thin paperboards have been known in the past, their combined behavior was not sufficiently discussed regarding the crease bending characteristics of the paperboard. In this work, the time-dependent and temperature-dependent scoring, and the corresponded bending characteristics of liquid-container-purpose paperboard of basis weight 313g/m² (thickness of t = 0.47mm) were experimentally investigated using a bending (folding) tester, when varying the holding time and the temperature of a flat-edge creasing knife at two levels of the normalized indentation depth d/t = 0.68 and 1.02. As the results, the first peak bending moment M_p1, the first stiffness C₁ (the gradient of bending moment resistance by the folding angle at an angle of 0—4 degrees), and the rating bending moment resistance at the right-angle M_90,1(0) were characterized with the holding time and the temperature elevation of the creasing knife at the pre-stage (scoring) process. Also, some explicit expressions of C₁, M_p1, M_90,1(0) with the permanent scored depth were revealed as a static relationship. It is concluded that the temperature variation and the holding time of the creasing knife are important parameters which must be controlled in the manufacturing process of liquid package.

Abstract: The following paper deals with the comparison of characteristic initial shear strength of masonry specimens made of innovative Heluz bricks and selected adhesives. The characteristic initial shear strength of masonry was determined according to ČSN EN 1052-3. Five different adhesives were tested in total. The characteristic initial shear strength of masonry was also researched depending on the amount of applied adhesive – this was determined for two adhesives. The specimens were made of three shaped bricks and a defined adhesive. Twenty-one large specimens were produced in total and they were put to the shear test in the age of one day. Adhesives available on the Czech market and foreign adhesives were tested. Selected adhesives were applied to the bed joints of bricks according to the usual standards. The produced specimens were stayed overnight in the production hall of the Heluz brick plant in Dolní Bukovsko and tested in the age of one day in the laboratory according to stated methods in appropriate norm. This paper deals with procedure of preparation of specimens, the course of the test and comparison of gained results.

Abstract: The paper presents the results of laboratory studies of the influence of the physical properties of landfill soils on the stability of slopes, namely, the determination of mechanical properties – the angle of internal friction, specific adhesion, and the shear angle of experimental landslide blocks under conditions of different humidity, density and temperature; determination of physical properties – humidity, temperature and density on the fact of shear of the experimental blocks, taking into account the gradual increase in humidity. The results of laboratory tests are processed using the classical statistical method. This made it possible to confirm the reliability of the mathematical model, which includes the solution of individual tasks for assessing the physical properties of landfill soils, and the corresponding methodology developed on its basis for preventing emergencies associated with shear of landfill soils at potentially hazardous burial sites for solid domestic waste.

Abstract: Geometrically non-linear problem of orthotropic thin rectangular panel post-buckling behavior with shear is solved. Deflection function takes all-boundary rigid support conditions into account. Based on derived solution method of smooth panels design which can be used for aircraft structures rib and spar webs optimal parameters is suggested.

Abstract: Deck slabs of box girder bridges designed according to the theory of allowable stresses are mostly without shear reinforcement. In the case of new bridges, designed according to Eurocodes, significantly increases an application of shear reinforcement. This raises a question: are bridges built before implementation of the Eurocodes safe? The paper deals with safety analysis of the models for prediction of the shear capacity using results of more than 40 tests carried out on clamped slabs subjected to concentrated load. The analyses have shown that methods based on an effective shear width provide unsafe results for shear span to effective depth ratio larger than 3. A significant improvement of the model's safety has been attained by limiting the distance of critical section from the inner edge of the loaded area.

Abstract: . A primary current focus in concrete shear design is how to ensure the shear resistance of the concrete structures to withstand the possible adverse creep effects during the service life. All shear-carrying actions are supposed to depreciate due to the enhanced critical shear cracks under sustained loads. However, only a few studies that evaluated the performance of concrete structures failing in shear due to long-term loading. As the longitudinal tensile reinforcement strain influences the shear strength of RC beam, the shear resistance of the beam under sustained load may also be affected by the amount of longitudinal reinforcement. The present study aims at investigating the influence of flexural reinforcement ratio on the shear creep failures of reinforced concrete (RC) beams without stirrups by non-linear finite element analysis. In this study, the numerical model of RC beams with reinforcement ratios varying from 0.4% to 3.2% was evaluated under different loading rates. A loading rate of 1000 and 10000 times slower than the static loading rate were adopted to reveal the creep effects of RC beams.

Abstract: The article considers the local stability of hinged supported beams with a flexible wall, supported by paired stiffeners on the supports and loaded with a concentrated force in the middle of the span. To prevent the loss of stability of the wall from compression, another edge was installed in the area of ​​application of force. The materials considered as beams were steel, aluminum, and stainless steel. In this work, the beam material is steel C345. The study was conducted by analyzing the requirements of the Code of Practice for beams with a flexible wall in terms of the stability loss caused by the two types of deformations - shear and bending. By means of small simplifications, the requirements of the Code of Practice have been transformed into empirical dependencies convenient for practical calculations for estimating the critical loads on the beam. The finite element method with ANSYS software was used as an effective analysis tool. It has been established that in some cases the cause of loss of stability is a shift, and in others - a bend. A criterion for changing the forms of buckling was also obtained. The calculation results for the obtained dependences are in satisfactory agreement with the FEM and experimental data.