Development of a torsional theory for radially functionally graded porous shape memory alloy circular bars

This work develops a novel torsional theory for a radially functionally graded (FG) porous shape memory alloy (SMA) circular bar. Prior to the theoretical development, the effective three-dimensional (3D) phenomenological constitutive model for SMAs with high porosity is proposed. To help derive successfully the theory, the pure shear-driven material parameters in the effective model are expressed in the cubic polynomial. Subsequently, the torsional theory for radially FG porous SMA circular bar is derived considering the evolution of effective phase evolution in the bar. This phase evolution consideration guarantees the accuracy of the developed theory. Indeed, the soundness of effective constitutive model is confirmed by 3D finite element method (FEM) simulation of porous SMA structure in Abaqus using the well-established ZM’s model for dense SMAs. Specifically, the simulating results in terms of the shear stress-shear strain response obtained from two prediction methods considering a variation of SMA volume fraction and temperature are in good agreement. Furthermore, accuracy of torsional theory is validated by 3D FEM simulation using the 3D effective constitutive model with a good agreement observed. It is found that the superelasticity of the bar can be enhanced by increasing the gradient index and decreasing the temperature and wall thickness.

Investigation of Bearing Capacity of the Drill-Impact Micropiles with Enlarged Toe in the Soils of Different Type

The reinforced concrete micropiles with enlarged toe is the effective construction for the arranging of new and reinforcing of existing foundations which a drill-impact method are made as a circular bar with a diameter to 250 mm from the flow consistency concrete with prefabricated reinforcement cage and enlarged to two diameters toe cone-shaped form. For research of them real work by the authors of the article and engineers of PP BKF “Osnova” were conducted them field tests on the objects of building in the different soil conditions and the analysis of them calculation and experimental bearing capacity is given. The analysis of quantitative correlation of experimental and theoretical bearing capacity for the different types of soils is the task of researches.

Tensile strength and thermal cycle analysis of AA6061 friction weld joints with different diameters and various friction times

The paper reports measurement of tensile strength and the thermal cycle of AA6061 aluminum alloy circular bar friction weld with different diameters and various friction times. A continuous drive friction welding (CDFW) of AA6061 was conducted to weld the AA6061 circular bar with different diameters of 30 mm for the rotating part and 15 mm for the stationary part. The CDFW process was carried out with the revolution speed of 1,600 rpm, the initial compressive force of 2.8 kN during the friction stage for various friction times of 10, 12, and 14 seconds, and an upset force of 28 kN for 60 seconds. The flash temperature was measured using a digital infrared thermometer gun. Computer simulation using the finite element method was also done by coupling transient thermal and static structural methods. The flash temperature becomes higher along with increasing friction time based on the digital infrared thermometer gun measurement and finite element analysis. The results of tensile strength testing show that the specimen with a friction time of 12 seconds has the highest tensile strength. Based on the hardness testing result, it is found that the specimen with a friction time of 10 seconds has higher hardness, but it has an incomplete joint flash so that the tensile strength is lower than that of the specimen with a friction time of 12 seconds. Besides, the hardness of the specimen with a friction time of 12 seconds is higher than that of the specimen with a friction time of 14 seconds. The flash size becomes bigger along with the increase of the friction time based on the macrostructure observation on the longitudinal section of the CDFW specimen. It is confirmed by the temperature measurement and finite element analysis that the specimen with a friction time of 12 seconds has heat input to form the CDFW joint that has a maximum tensile strength in the range of this study

Columns with Different Cross Section using ANSYS Work Bench

In this paper we are going to analyze the strength of material and deflection due to applying load on the column. The column of different materials will be cross sectioned and will present the difference of strength of materials by ANSYS workbench. The strength of material will depend upon the young’s modulus and moment of inertia of the metal plate. We use different size of metal plates such as I-section, circular bar, rectangular bar and square bar for a specific material to know the strength of material when a load applied on the cross sections. In this paper we taken a condition that one side of column is fixed and another side is free when load is applying on the column.

Thermomechanical response of a viscoelastic Ni-Ti – Shape Memory Alloy composite beam

This investigation is concerned with the mechanical behavior of Shape Memory Alloy Hybrid Composite Beams (SMAHC), that consist of a circular bar of NiTi alloy incorporated in a 500 mm long cylindrical pipe of polypropylene (PP), with external diameter 50 mm and nominal wall thickness 7 mm, wound with a nylon/epoxy layer. The Ni-Ti alloy was characterized using: scanning electron microscopy (SEM); X-ray diffraction (XRD) and Differential thermal analysis (DSC). The nominal chemical composition of the alloy is 50.05 %Ni / 49.95%Ti, and the softer martensite is the predominant phase at room temperature. The approximate martensite (M) to Austenitic (A) phase transformation temperatures were Mstart = 32°C, Mfinal = 46°C, Astart = 38 °C and Afinal = 60°C. For temperature T<Mfinal, Ni-Ti bar presents 100% martensitic phase, whereas for T>Afinal it is fully converted in the Austenitic phase; and its elasticity modulus increases by a factor up to three times. This significant change in stiffness of Ni-Ti, without changing its mass, has motivated the application of such alloy in machine vibration control. The SMAHC beams were subjected to static three-point bending tests, in the elastic regime. Experimental results showed that, in average, at 21°C, the PP pipes effective flexural elastic modulus increased 112%, from 757 MPa to 1609 MPa, when the Ni-Ti bar and the external layer of nylon/epoxy were incorporated to the PP pipe, creating a smart beam. These last results indicate that the SMAHC beam can work as an adaptative structure.

Optimization of Functionally Graded Structural Members by Means of New Effective Properties Estimation Method

An innovative method of effective composite mechanical properties estimation is applied to optimize the distribution of reinforcement in a functionally graded structural element. The concept is based on the assumption of the mechanical equivalence between two configurations: The real heterogeneous composite configuration and the fictitious quasi-homogeneous one. It allows to obtain the analytical formulae describing the dependence of the effective elastic composite properties on the volume fraction of reinforcing inclusions. As an example of application, a circular bar subjected to torsion is considered.