Materials Science Forum Vol. 969

Abstract: Energy absorbers in the form of hollow profiles are used in automobiles to mitigate energy transfer to passenger cabin during a crash event. A similar event is carried out in this research work to study the progressive compression behaviour of aluminium tubes with triggering mechanisms in the form of cut-outs. Various hollow profiles are used as energy absorbing elements. In this work, square aluminium tubes of 50x50 mm side and 150 mm length with wall thickness of 1.5 mm with cut-outs are tested under axial compression loading and the results are compared with tubes without any cutouts. Crash parameters like minimum compressive force required to fail the aluminium tube, energy absorption, peak load and progressive collapse behaviour are studied. Results reveal that tubes with slots exhibited better crash parameters than plain tubes and tubes with circular cutouts.

Abstract: Commonly used analysis and design methods are applicable only to Bernoulli’s region or B-region where strain distribution is linear. Due to the peculiarity of the geometry for certain structural members like deep beams, corbels, etc, their entire strain distribution is nonlinear. Hence, they will act as discontinuous regions or D-regions where strain distribution is nonlinear. The designers are forced to depend on empirical relations and their past experience for designing such elements. Since, deep beams form an important structural element in bridges and high-rise buildings as pier caps and transfer girders, their design deserves much more importance. Strut-and-Tie method (STM) is a unified approach that can be used for both regions. The main parameter that influence the accuracy of results produced by STM is the strength reduction factor (β_s). In this paper, new relations are developed for predicting strength reduction factor for concrete struts with and without steel fibres. The effect of steel fibres content and percentage of vertical and horizontal reinforcement were considered for developing this relation.

Abstract: The objective of this review article is to review literature on fatigue analysis and biomaterials studies in Endodontics. The nitinol and gutta-percha are widely used biomaterials in the Endodontic fields. The nitinol is used to manufacture the Endodontic files which are used for preparation of the root canal. The preparation of the root canal consist of removal of dead tissue, substrates and debris from the decayed root canal. During the preparation of root canal shaping of the root canal is done to develop the perfectly prepared cavity. The gutta-percha is used to fill the prepared cavity. The nitinol and gutta-percha are important contributing biomaterial for success of root canal treatment. This review article has been reviewed contemporary studies on nitinol and gutta-percha biomaterials. For the success of root canal treatment the fatigue of Endodontic file and three dimensional filling of root canal are two important aspect. The Endodontic files during the cleaning and shaping of the canal gets subjected to torsion fatigue failure or cyclic fatigue failure. The past studies lacks the exact knowledge about these failures as well as analysis approaches to be followed for correct diagnosis. This review article helps to overcome this difficulties. Moreover, the fatigue factors are discussed so that researcher can get little idea about failure point of the nitinol rotary files. The review consist of A contemporary review of nitinol alloy studies, A review of fatigue failure diagnosis, A contemporary review of gutta-percha quality assessment techniques studies, A novel approach for fatigue analysis of nitinol file and A novel approach for quality assessment of gutta-percha etc.

Abstract: Now a days R134a can be used in domestic refrigerators and in air conditioning of automobiles. As per Kyoto protocol the usage of R134a is restricted due to their higher GWP value. The GWP value of this refrigerant is around 1430. So in this article, thermodynamic analysis of HFC-152a, HFO refrigerants-1234ze(E) and 1234yf was done in a household refrigeration system as direct substitute to HFC-134a.The performance of the household refrigerator was compared in terms of outlet temperature of the compressor, volumetric cooling capacity (VCC), refrigeration effect, work done by the compressor and coefficient of performance (COP). The entire analysis is carried out at various operating conditions of condenser and evaporator temperatures i.e. condensation temperature of 25°C,35°C & 45°C and evaporating temperatures ranging between −20°C to 10°C.From the theoretical results, it can be concluded that R1234yf can be used as a direct substitute to R134a.

Abstract: In the present study, aluminum alloy 2219 of two different heat treatment states were selected and welded using the friction stir welding process to evaluate the effect substrate on the joint properties. The microstructural observations have exhibited the difference in their characteristics between two heat treatment conditions of 2219-O and T6 conditions. The tensile strength of the AA2219-T6 joints much higher than the AA2219-O joints. Consequently, the microhardness distribution across the different zones varying with two different heat treated conditions. The failure locations and fracture surface features are revealed the significant differences among these two heat treated conditions with the change in their failure location and the fracture morphologies. The optimal welding conditions were analyzed to determine the high strength of the welds with excellent metallurgical properties of the welds.

Abstract: In the present study, dissimilar friction welding between super alloy 718 and carbon steel friction welded to evaluate the formation of microstructure in the weld interface and in superalloy 718. The temperature during friction welding at weld interface was recorded to determine the temperature effect on the microstructural changes on alloy 718 side. The finite element modeling of weld interface temperature, deformation and stresses were evaluated and validated with the experimental results. The microstructural observation along with the weld interface and adjacent regions are studied. The effect of friction welding on superalloy weld interface and microstructural formation were investigated under electron backscattered diffraction analysis to evaluate the grain size measurements. The effect of thermomechanical action on the microstructure was evaluated by texture analysis.

Abstract: The strength of metals and their alloys are enhanced by adding secondary reinforcement particles like Conventional crystalline and non-crystalline particles such as SiC, glass and Al₂O_3. These particles provide weak interfacial bonding due to the crystallographic structure mismatch or undesirable interface reaction products. Quasicrystals provide strong interfaces with the matrix due to their low interfacial energy. Their low strength and stiffness make them useful in non-critical stress applications such as instrument panels, seat frames and gear box housings. Reinforcing quasicrystals to Mg alloys greatly enhances their strength or stiffness. The literature on quasicrystal (in-situ and ex-situ) reinforced Mg alloy composites are critically reviewed to show the importance of quasicrystal reinforcement in Mg alloys and the effect of different manufacturing process technologies such as casting process, powder metallurgy, hot extrusion on mechanical properties.

Abstract: The performance of flexible pavement depends mainly on the subgrade soil characteristics as it serves as a foundation for pavement. Roads constructed over poor subgrade soil fails frequently leading to heavy economic burden apart from high initial cost of construction. In order to overcome these problems soil reinforcement technique has to be adopted. The use of geosynthetic material is a new and emerging technique and is gaining importance due to cost and time saving apart from less environmental sensitive nature. In the present study an attempt has been made to make use of non-woven geotextile and biaxial geogrid in various combinations. The geogrid was placed above geotextile, both in layers from the top of mold and heavy compaction, soaked CBR and unconfined compressive strength (UCS) tests were performed. Scanning electron microscopy (SEM) images indicate significant bonding between soil particles and geogrid surface.

Abstract: A comparative study of three different aluminium alloys, Al2618, Al4032 and Al6061 made internal combustion engine pistons is done on their responses under mechanical and thermal loads using finite element methods. In this study, a 3D solid model of piston is created in CATIA and the simulations of the static structural analysis, steady-state thermal analysis and transient thermal analysis are carried out in ANSYS. Stress and temperature distributions on critical areas of piston are pointed out for appropriate modification in piston design. The temperature and heat flux variations with time are presented in transient thermal analysis. Taguchi method and topological optimization are applied to optimize the process parameters and to select the appropriate material for the piston.

Abstract: Cadmium sulphide nanocrystallites have been synthesized using precipitation method. The average sizes of the prepared samples is determined by XRD (x-ray diffraction) method. Morphological studies are carried out by SEM (scanning electron microscopy) measurement. Necesssary elements present in prepared samples, are confirmed by EDAX (energy dispersive analysis of x-ray spectroscopy) method. By Ultraviolet visible spectroscopy measurement, the value of absorption wavelength, band gap values are calculated in optical method. The electrical properties are analysed using impedance analyser measurement for the Nanocrystallites.