Papers by Keyword: Critical Load

Abstract: Instability is one of the factors causing damage and injury that results in permanent disability. To increase the stable load-carrying capacity, a simplified and efficient computational method for determining the first critical load is necessary for the structure's structural design, application and safety. This study aims to determine the characteristics of the critical bending moment M_bcr and the critical torsion moment M_Tcr due to geometric size variations in the square, diamond, and circle cross-sectional hollow pipes so that consideration of the selection of hollow pipe size and cross-sectional shape is obtained under pure bending and pure torsion to minimize the occurrence of instability of the structure. The geometric size variation is carried out by changing the value of a/t in the quadrilateral pipe, the value of D/t in the circular pipe, and the length of the pipe L in each cross-sectional shape. This research was conducted using Finite Element Analysis-based software with linear and nonlinear buckling analyses. The moment load is given at the centre point of the model end, and the boundary conditions are set to see the deformation on the mid-span section of the pipe. The results showed that M_bcr and M_Tcr were inversely proportional to the values of a/t, D/t, and . The largest value of M_bcr belongs to the circular pipe. The value of M_bcr in the diamond pipe is greater than the square pipe but getting closer to the same as the value of L increases the M_Tcr value of both cross-sections is the same. The M_Tcr curve in the cross-section of the circle has a higher degree of steepness than the square and diamond cross-section. At the same value, the more the value of a/t and D/t increases thickness change has more compared to the circular pipe. At the same L, the greater the value of a/t and D/t, the difference in the M_bcr between the cross-section of the circle and the quadrilateral is smaller, but the difference in M_Tcr tends to be the same. At the same value of a/t and D/t, the oval deformation value and angle of twist will get bigger, but the M_bcr and M_Tcr values are getting smaller and will be constant at a given pipe length.

Abstract: This paper presents a design method to optimize the material distribution of zirconia/aluminum-functionally graded material with respect to some buckling and vibration properties. The distribution of volume fractions of the FGM constituents is defined through the beam or column length by a trigonometric law. The finite element method is used for the buckling and vibration analysis, and a genetic algorithm is utilized for optimization of the chosen objective function. The efficiency of the method is demonstrated by two design problems. In the first design problem, FGM is used to maximize the buckling crical load to weight ratio. In the second design problem, the kinetic energy of a vibrating FGM beam is minimized at a specific excitation frequency. These design problems show that material tailoring of beam/column structures using FGM can result in substantial improvements of their buckling and vibration characteristics.

Abstract: The rheological and triboengineering properties are presented of hydrated calcium plastic greases based on intermediate products of oil refining (hydrofined vacuum gas oil and vacuum distillate). It is shown that application of liquid crystalline cholesterol compounds as an additional component of the dispersion medium of plastic greases permits significant reduction of the wear and losses for friction and boosts the load – bearing capacity of tribocouples.

Abstract: As part of European cooperation here is presented collaboration among Universities on Structural Analysis of Historical Constructions, which gives the chance to international young students and professionals to take part on investigations of selected cultural heritage treasures. This report summarizes a structural investigation on two churches from the Broumov Group. The attention was focused on damages within the walls and the roof structure. Moreover laboratory and numerical analyses permitted to gather very important information on the current state of the two buildings and led to several remarks recommendations.

Abstract: Scratch test is one of widely used, fast, and effective methods to obtain the critical loads that are related to adhesion properties of coatings. The determination of adhesion and the scratch resistance is essential for the mechanical characterization of surface layers for research and industry. To evaluate the performance of coatings the scratch test with a Rockwell-C diamond stylus as indenter is a commonly used test for the characterization of hard coatings on predominant metallic substrates due to its comparatively robust experimental setup, the easy use and the representative results. This is the only technique capable of imaging such interface defects which are due to the stressin duced by the scratch experiment.This paper aims to characterize the adhesion and scratch resistance using Millennium200 - Technical Tribo equipment of Ti layer deposited on steel surfaces by means of TIG/WIG welding technique. Ensuring appropriate functional properties of WIG welding coatings (Ti) requires a good compatibility with the substrate material (S235). For this reason was used to deposit titanium WIG welding an intermediary layer of copper, obtained in the same experimental conditions. The optimal selection of the coating material takes into consideration the metallurgical, mechanical and process technology compatibility. The mechanical properties of coatings must match the substrate. From this point of view, maintaining a high corrosion resistance is mainly conditioned by achieving a good adhesion and a microstructure free of internal cracks or other defects.

Abstract: Thermo-steel panels compose from steel thin-walled profiles and polystyrene. They are used as wall construction elements. We must follow stability problems. Finite strip method (FSM) has been used. Special arrangement had to be done for investigation of stability of thermo-steel panels. In thermo-steel panels compression stresses are carried in thin-walled steel profiles only. It means that polystyrene enter into stiffness matrix but it does not have increment in geometric matrix. Numerical examples were oriented for investigation of thermo-steel panels with 145 and 250 mm thickness. Obtained results proved ability of thermo-steel panel to be used as wall panel for two storey building.

Abstract: In the paper stated method that is grounded on the following idea, firstly applied in the work [1]. The critical state equation of compression plate is obtained from according equations of lateral bending of same plate, if is made the substitution -P=T10Wx''+2S0T10Wxy''+T20Wy'' where T10, S°, T20-are the components of external compressive loading. Further the obtained differential equations are transferred into algebraic equations by approximation of deflection by system of preliminary selected functions and application of one of variation methods. From the obtained algebraic equations are defined the parameters of critical loading. The applied in the work method is that firstly is solved the static problem and are found deflection functions, subjected to concentrated loading in the point x=ξ, y=η, corresponding for al singularities, arising due the cuts influence. Actually at this are found the Green’s functions. This task is solved analytically and due the application of special discontinuous functions, the function of deflection is expressed as rapidly convergence series. Practically for the definition of deflection is sufficient the keeping of one term of series. Due the stated above [2] also is considered the solution in the refined formulation. The definition of critical loading on three-layered plate on grounded on the accordingly static problem.

Abstract: An important aspect of the theory of optimal design of shells is a question technology of determination of optimal forms of shells with numerical methods, based on the variation definitions. The distribution of effort in sloping shell of revolution optimal form, uniformly loaded with despens intensity is analyzed. The mathematical model of shell optimal form is based on the maximum principle of L.S. Pontryagin. The solution of the objective is numerically made in MathCad. The relations of the distribution of the longitudinal forces and moments along the radius of the shell is shown.

Abstract: By means of resistance strain gauge and multifunctional test bench of materials mechanics, the relation curve between the axial compressive forces of the two-ends hinged column with a rectangular cross-section and total bridge strain was obtained by the resistance strain measurement method, accordingly, by the horizontal asymptote of this relation curve the critical load of compression column was obtained. The study indicates that the critical load obtained respectively by the resistance strain measurement method and Euler formula theory fits very well, and the research results verified the reliability of the experimental method.

Abstract: The high-voltage transmission tower transmission lines is a major component and typically a high steel tower, is a tall, flexible structures. In this paper, the finite element method to establish a large-scale three-dimensional model of the transmission tower space, computational analysis of the transmission tower structure first six buckling modes and critical load, examined the order buckling mode characteristics. Research on the structural stability of large power transmission tower design has some theoretical significance and application value.