Advances in Structures, Systems and Materials

Aluminum matrix material is considered as advanced material because of its very good mechanical, tribological properties which have been used in automobile, aerospace industries at the larger end, and now aluminum matrix materials have been used in medical and electronics industries because of its good and high strength to weight ratio and low coefficient of thermal expansion. The present work is focused about the improvement in mechanical properties and fracture graphic studies of aluminum matrix reinforced with ceramic particulate silicon carbide and cerium oxide of laboratory grade size, respectively. Here, the reinforcement is varied in terms of weight percent ranging from 0 to 8% in the steps of 2%, and the composites were fabricated using a stir casting route. Prepared specimens were tested as per ASTM standard and performed tensile, compressive, impact and hardness test and fracture surfaces studies done under the scanning electron microscope (SEM) and X-ray diffraction (XRD). The results reveal that with increase in percentage of reinforcement, the mechanical properties of the composite system have increased, SEM images clearly reveal the modes of fracture, and XRD shows the presence of reinforcement.

Pulse detonation engines, due to its simplistic design, have gone through critical acclaim in recent years as a viable solution of high-speed propulsion in the aerospace industry. Through various experimental and theoretical methods, researchers are trying for the most explicit method for initiating a controlled detonation in a plain tube. Studies are being conducted on various types of cross sections and multiple forms of blockages to evolve detonation using several chemical and mechanical procedures. Previous study shows a rectangular blockage which blocks about 60% of the flow at 2/3rd distance from the origin produces best detonation wave initiating a sustained exit velocity and increment in pressure. The current paper studies the variation effect of placing multiple blockages in different permutations along the length of the plain tube and their effect on the onset of detonation. It has been observed that multiple blockages placed throughout the length inhibit the possibility of formation of the detonation wave. Further, it has been summarized that an ascending rectangular cascade produces the best onset of detonation wave with a proximal maximum velocity of 10,858 m/s at the outlet when a mixture of kerosene and air at a maximum pressure of 100 MPa is given at the inlet of the tube.

Turbulence due to wind around conventional square shape bluff body creates the pressure difference of different planes of the body. Nevertheless, the unconventional bluff body creates a large amount of turbulence around its face and on the roof region. This paper highlights the pressure variation of top roof and setback roof of square and setback tall building with respect to different time domains. The frequency of the roof due to wind also affects the pressure fluctuation on neighbor faces. Most of the pressure fluctuation develops at 0.06 s which forms the initial time and maximum pressure difference occurred at the setback roof for along wind condition. The present study concentrated on the fluctuation of time-dependent pressure between top and setback roof to take special care during the design.

Wind effect is the most interesting and important parameter for different structural elements like sidewall, roof and around the building also. A number of researchers were presented their thoughtful inspections on different, unconventional tall buildings due to wind issue. The present study focuses on the pressure distribution around the square and setback tall buildings due to wind load. The models have single and double type setback at different elevations. The pressure calculation was conducted by analytical study of plane and highlights the pressure fluctuation. Some amount of pressure bulb was observed on the leeward side of setback model, which mean the increase of suction on that particular region. The excessive amount of suction envelop recognized at the top roof of setback model compared to square model.

Cellular polymer foams find extensive applications as energy absorbers under static, impact and blast loads due to their capacity to absorb energy under constant stress up to full densification strain (Ashby et al. Metal foams: a design guide. Butterworth-Heinemann, Oxford, 2000 [1]; Gibson and Ashby, Cellular solids: structure and properties. Cambridge University Press, Cambridge, 1999 [2]). In the present paper, the material characterization of natural latex cellular polymer foam used in the field air blast experiments (Venkataramana et al. Proc Eng 173:547–554, 2017 [3]; Venkataramana et al. Numerical simulation of blast wave mitigation using foam impregnated with water. DAE BRNS Symposium on Multiscale Modeling of Materials and Devices (MMMD-2014), 2014 [4]) performed to assess the blast mitigation effect of fluid-filled open-cell pin-core polymer foam is presented. Static compression tests were performed to study the quasi-static behavior of the pin-core latex polymer foam. The Ogden hyper-elastic material parameters are determined from the analysis of static compression test data using ADINA (automatic dynamic incremental nonlinear analysis) v 9.2, ADINA R&D, Inc., Watertown [5]). Further, results of the static compression tests on dry foam and water-saturated foam are compared and discussed. In addition, the dynamic behavior of the pin-core latex cellular foam is investigated by conducting drop tower impact experiment and numerical simulation of the drop tower experiment using LS-DYNA (LS-DYNA v971, Livermore Software Technology Corporation, Livermore [6]). The stress–time history from the drop tower experiment is compared with that of simulation, and good correlation is found between the two sets of results.

Large column-free areas are a need of today’s industrial units. This need can be fulfilled by thin laminated shell structures made of composite material. Conoidal shell, being a doubly curved shell structure with a ruled surface, is comparatively easy to construct and is ideal for roofing purposes of such large areas. High specific strength of composite materials and curved form of shells provide greater stability to these shell roofs. The behaviour of these shell structures under loading largely depends on support conditions. Now, separation of layers, known as delamination, is considered to be a major critical defect of composite laminates, which occurs due to repeated cyclic stresses, impact and manufacturing defects. Delamination causes remarkable loss in mechanical toughness and ultimate failure. The most notable thing regarding delamination is that, in most cases, it is not visible from outside. Hence, this type of damage needs a wider attention from researchers. In this paper, the composite conoidal shells with delamination under static loading have been studied. A finite element formulation has been developed with Fortran code to observe the change in deflection in a conoidal shell with varying number of support conditions. An in-depth analysis is done based on number of supports, laminations, stacking sequences and percentage of damage; thereafter, some helpful observations have been highlighted so as to narrate the characteristics of this shell structure as a roofing unit.

The modern buildings are becoming taller due to lack of land space and this makes the tall buildings more sensitive to lateral loads such as wind. The outer shape of the building is one of the main parameters which affects the design wind loads. Various types of minor corner modifications on tall buildings result a huge change in force and pressure. The present study is carried out to find the effect of corner modification on square plan-shaped tall building. The corners are modified as corner recessed, corner chamfered, and corner rounded, and a series of simulation is done in ANSYS CFX (k − ε model) to find out the effects on force coefficients, pressure coefficients, wind flow pattern around the buildings, etc. The numerical analyses are done considering the model scale as 1:300 and for 0° angle of wind attack.

The excessive use of natural aggregates is having an adverse effect on the environment and raises major environmental issues; hence, an attempt has been made to develop artificial aggregates. These artificial aggregates are made from using GGBS, sodium hydroxide and sodium silicate. This paper focuses on the fresh, hardened and durability properties of self-compacting concrete with artificial geopolymer aggregates (GPAs) as partial to full replacement of natural aggregates. Mix design was carried out with varying content of GPA (0–100%) and cements contents (300, 350 and 400 kg/m³). Flow, passing ability and segregation resistance were found to increase when 400 kg of cement and 100% replacement of 10 mm GPA is used as compared to crushed gravel. However, the compressive strength was found to be marginally less with the increase in aggregate size. After examining, the properties of SCC with geopolymer aggregate of size varying from 10 to 20 mm are used in casting of the sleepers. The sleepers were precast in Malu sleeper yard, Birur, Karnataka, and subjected to bending, electrical resistivity and durability tests. The results from static bending test showed that the resistance load of a sleeper with 50% of 6 M aggregate is 238 and 230 kN for conventional concrete. Electrical resistivity and durability of a sleeper with 6 M was found better than conventional concrete sleeper. The prediction of self-compacting concrete properties with artificial geopolymer aggregate and natural aggregate was investigated by using MATLAB.

Impact of wind force is more critical on tall buildings with an increase in height. Horizontal irregularity on plan shape and randomness of wind makes the structure more vulnerable. A detail analytical study has been done considering various wind incidence angle ranging from 0° to 90° at an interval of 30° using computational fluid dynamics (CFD) on U-plan shaped tall building with corner modifications. The present study has shown that the introduction of minor aerodynamic modifications has major a role in minimizing the wind-induced responses. Drag coefficient and the lift coefficient are reduced due to the application of corner chamfered and corner roundness on the basic model. Most of the cases both maximum pressure and suction occur on the different faces of corner chamfered models. It is also noted that the modified corner exerts more pressure than the basic model.

Cellular lattice structures have applications in crash resistant and protective equipment. This study involves designing rectangular beams of lattice structures with different unit cell configurations, fabricating them on fused deposition modelling (FDM) 3D printing machine and subsequently finding out the structural design for the best flexural performance in engineering applications. All the test specimens were fabricated on Stratasys Dimension 1200 ES FDM machine in acrylonitrile butadiene styrene (ABS) material. Five types of 2D unit cells for building lattice structures were investigated which included honeycomb, diamond, square, circle, and triangle shapes. Three-point bending tests were carried out to study flexural properties like flexural strength and modulus of these cellular lattice structures. After mechanical testing, the obtained data for the five different lattice structures were mutually compared for their flexural behaviour and also with the beams built in solid and sparse shapes. Results of flexural tests indicate that the cellular lattice structures based on triangular and honeycomb shapes exhibit maximum flexural strength. The triangular structure also proved to be the highest in the value of flexural modulus among all the five cellular lattice structures. This study also includes investigating the effects of varying porosity of a particular cellular structure (honeycomb) on its flexural behaviour. Results show that for honeycomb structures, the higher porosity led to higher flexural strength and flexural modulus and shorter build time up to a porosity of 61%.

The problem of getting living and working spaces is increasing with the rise in human population. To minimize the effects of this problem, modern technology introduces tall buildings. Wind-based structural analysis of tall buildings helps us to build tall structures keeping them safe. Interference effect is one such important wind phenomenon, which affects the structure greatly. That is why the need of the study on interference effect is so significant these days. In this study, two virtual building models are used. The principal one is a square-plan tall building, and the interfering one is a setback tall building, which is placed in front of the principal building obstructing a time bound wind flow of a gust lasting for 3 s. This particular study offers power spectral density (PSD) variation with respect to Strouhal number for top near corner target points at a level of 0.975h on each surface of the principal model as well as the streamline variation in the altitude level of 0.475h. All the variations are obtained due to the positional changes of the interfering building, as it is rotated about its own axis with an interval of 15° from 0° to 90°. The maximum PSD value is obtained for 15° orientation of the interfering building from the windward face of the principal building. For the 90° orientation of the interfering building, the PSD values obtained from leeward and side faces of the principal building are nearly same.

World has been suffering from energy crisis since 1970. This is because of the increased population and industrialization. Buildings have a significant contribution to total energy consumption across the globe. The increased urbanization leads to boom in construction of buildings. The materials used for the construction of buildings affect the climate of the city up to a great extent and affect the energy consumption as well. So, construction materials should be chosen wisely. The surface temperature of the building envelope is affected by the coatings used. Cool coatings help in reducing the surface temperature of the building envelope. Time lag and decrement factor are the indicators of energy saving in building. In this paper, the effect of cool coating on time lag and decrement factor was studied. Values of time lag and decrement factor were evaluated in different climatic zones of India. It has been found that as the absorptivity of the building envelope increases, the decrement factor increases. By changing the absorptivity from 0.2 to 0.73, a minimum change of 16% (New Delhi) in decrement factor and 11.75% (Jodhpur) in surface temperature was observed. The maximum change in decrement factor was 56.44% (Jodhpur). The maximum change in surface temperature was 39.02% (Bangalore). So, it should always be practised to keep the absorptivity of the building envelope as low as possible.

Spindle stiffness is the ability of spindle to resist deformations under the influence of cutting forces. The magnitude of deflections at the spindle nose, where cutting forces from the tool are transmitted, decides the machining accuracy of the machine tool. In this paper, a method to evaluate the static stiffness of the spindle with a bearing system subjected to cutting force is presented. The static stiffness of the spindle is calculated analytically by evaluating the radial stiffness of the bearings and the deflection at the front end of the spindle. Finite Element Analysis is carried out on the spindle bearing system, and results are compared with analytical results. Further, experiments are carried out to validate the analytical and numerical results.

Corrosion is the degradation of a metal by an electrochemical reaction with its surrounding environment. The corrosion of embedded steel reinforcement in concrete causes durability issue in reinforced concrete structures and cement concrete pavements. The impact of corrosion of embedded steel rebars on the performance of reinforced concrete structures and pavements is a subject of concern for the engineers and scientists working in the construction industry. One of the effective ways of studying such influence is to understand the effect of corrosion on the mechanical and durability properties of concrete. The bond strength between steel rebar and concrete is also an important parameter of study. This study focuses on probing the effect of corrosion on bond strength and other mechanical properties of reinforced concrete. A pull-out test was conducted on 18 concrete cube specimens having steel bars of 12 and 16 mm diameter Fe500 grade. These bars were corroded with the help of commercial grade hydrochloric acid solution 10% v/v. Each group of bar specimens included three levels of corrosion: 0, 3 and 5%. Tension test on steel bars and compression test for concrete cubes were conducted.

Stress distribution in an infinite plate with circular hole subjected to uniform tension is determined by employing a modified body force method. In this method, the problem of a plate with a hole under uniform tension is considered as a plate with an imaginary hole. The boundary of the imaginary hole is divided into a number of divisions. At the mid-point of each division, concentrated forces known as body forces are applied. The magnitudes of these body forces are computed from complex potential functions, and stress at an arbitrary point is obtained by the summation of stresses due to these body forces applied at the mid-point of each division and stresses due to applied load. Results obtained from the modified body force method show trends in line with theoretical results. However, more accurate results can be obtained by using better estimate of body forces which satisfy boundary conditions at the circular hole. Setting Poisson’s ratio ν = 0 has little effect on the computed stress distribution.

The massive wind load is always harmful to tall building structure, especially the structure which has sharp edges. The separation of wind near the sharp edge creates local effects around the neighbor faces of the building and also creates enormous damage on that region. The present study illuminated the pressure variation around the sharp edge setback and corner cut setback tall building models. The models are inducted inside the computational domain and simulated with different wind angles. One model has a sharp edge corners and other models has a corner cut at the bottom part of setback zone and rounder corner at top part of setback zone. The considerable amount of pressure, drag and lift variation has been detected for across- and along-wind consideration. The tremendous amount of pressure fluctuation observed at corner cut region. The local pressure recognized on the wall due to sharp edges for the sharp edge model. However, the local pressure is minimized by the use of rounded edges at the top portion of the setback. The drag and lift coefficient decrease with the decrease of sharpness of edges. The study tries to catch the minimum local pressure due to corner cut edges of the tall building model.

Carbon fiber-reinforced polymer (CFRP) is used in the aeronautical industry in the manufacture of different aircraft components. This paper is about studying the mechanical (tensile, flexural, interlaminar shear strength), thermal and moisture characterizations of the laminate. A carbon-reinforced polymer laminate of G939 material and 913 resin systems are selected to study the effect of moisture and thermal on the properties of the laminate. The composite lamina is made of different layer orientations like 0°/90°, 0°/45°, 0°/45°/90°, 0°/0° and 90°/90°. The laminate is fabricated by vacuum bagging and cured using autoclave. Interlaminar shear strength (ILSS) was carried out for the specimens. Thermal degradation of CFRP is molecular deterioration as a result of overheating, and as the temperature increases the bonding between the molecules gets weaker and starts reacting with each other which results in the change of properties of composites. Laminates of 0–90 orientation are fabricated, and interlaminar shear strength (ILSS) at 50, 100 and 150 °C was carried out according to Dutch Institute for Norms (DIN) for the specimens. Micro cracks in the matrix are observed due to moisture diffusion. Five different test liquids are chosen: water, diesel, petrol, lubricating oil and acid in which specimens are immersed for 2 days, 5 days and 7 days. This work will help composite materials’ designers and manufacturers in designing high strength composite parts for aerospace.

This work involves the design of a MEMS single-axis capacitive-type accelerometer for low acceleration applications. In this paper, the displacement amplification complaint mechanism (DaCM) is used to increase sensitivity of the device by amplifying displacement. The DaCM model was designed using graphical method, and ANSYS tool is used to compare the displacement results. The DaCM model with maximum displacement is integrated with capacitive-type accelerometer. This integration was done using Coventerware turbo tool. The results obtained were compared with the accelerometer without DaCM. The displacement values that were obtained with and without DaCM are 3.1e−1 and 4.2e−2 µm, respectively. The results prove that DaCM gives an improved sensitivity.

Current chapter focuses on the variation of injection of opening pressure at various engine loading conditions. The biodiesel chosen for experimentation was neem oil methyl ester, and it was blended with diesel at volumetric concentrations of 25, 50 and 75% to form B25, B50 and B75, respectively. The experimental results revealed that higher (280 bars) IOP leads to higher carbon dioxide emission and BTHE. The observations recorded were subjected to grey relation grade analysis for blend and injection pressure optimization. The GRG technique revealed that IOP of 280 bars and blend concentration of 25% is optimal.

The increased demand for plastic components and greater requirement in the market has created necessity for wider study and research in the area of plastic flow behavior for intricate profiles of core and cavity in mold. Polymers rapidly replaced other materials because of its chemical and physical characteristics. Best part of the polymer is being lighter in weight and functionally suitable to large amount of parts/components produced day to day. The influence of venting and the injection time on the mold impression filling were examined. It was observed that improper injection time and incorrect venting parameters lead to either short filling of the impression or flash on the component. Also, component profile has vital role in placing the venting region. The controlled injection time and optimum venting parameters found to have zero flash and 100% impression filling. The functionality/application of the produced part is also found to be satisfactory.

The single degree of freedom legged robots are functional in terms of its simplicity and performance on both even and uneven terrains. The performance stability of these legged robots is determined by the trajectory of their foot locus. In the present work, Theo Jansen mechanism is used as locomotive drive mechanism for legged robot. The mechanism is designed and optimized using the Synthesis and Analysis of Mechanism (SAM) software during the conceptual design phase. The embodiment design was completed using CATIA. Simplex and evolutionary algorithms were utilized for optimization of foot locus to improve its step height and stride length. The influence of the link length and the input crank angle on the foot locus trajectory has been illustrated and compared for three different trials. The obtained results are compared with standard foot locus. Further, the results derived in this work can be utilized in selecting the link length for Theo Jansen mechanisms for various applications.

Rotation capacity of a joint in a structural member under constant moment depends on the characteristics of the formation of plastic hinge. The rotation capacity and plastic hinge formation in RC member depends on many parameters and therefore makes it different over the formation of plastic hinge in steel structural members. It has been observed from the literature that the rotation capacity in RC structural member is influenced by several parameters such as mechanical properties of concrete and steel, geometry of the member, external load and boundary conditions, thus makes it to be an interesting structural behaviour which has to be explored very well. Parametric analysis on the rotation capacity and formation plastic hinge was carried out by collecting more than hundred data from the available literature. Relevant graphs were plotted to demonstrate the variation of plastic hinge length (lp) over the influencing parameters such as cross-sectional dimensions of the beams, grade of the concrete, tension reinforcement and span-to-depth ratio. The length of plastic hinge was calculated based on existing analytical models given by the researchers. Owing to the advancement in the analysis of nonlinear behaviour of structures using sophisticated software, the characterization of plastic hinges has to incorporated in the analysis. These analytical models are very useful and provided more knowledge on the behaviour of RC structures. In this study, existing analytical models are evaluated based on the different parameters. The plastic hinge length was determined by nonlinear regression analysis. It was found from the analysis that, large variation was found over the length of plastic hinge for the existing plastic hinge models and the proposed nonlinear regression analysis model yielded better results.

Nickel chromium irons such as Ni-hard of different grades (high chromium iron) are being employed as wear-resistant materials in thermal power generation applications in view of their excellent inherent material characteristics. They are being deployed in bull ring segments, orifice, rolls, MPO, liners, etc., in thermal power plants and other engineering industries. But, these materials being brittle fail to withstand transient load. To overcome this problem, manganese is added to chromium iron to improve its impact characteristics apart from being wear resistant. In this context, the erosion and abrasion properties affected by metallurgical features are considered important from the point of enhancing its impact energy, without much sacrificing the wear resistance. Considering these aspects, high chromium manganese irons have been prepared in grey cast iron metal mould of section size of 24 mm, followed by heat treatment. The erosion, abrasion and impact energy have been studied using jet erosion, rubber wheel abrasion and drop weight impact test setup for varying manganese content in the range of 5, 10 and 15%. It is very much evident from the metallurgical investigations involving light microscopy that the least Mn content sample (5% manganese content) shows the highest wear resistance, whereas on the other hand, the highest manganese addition of 15% exhibits highest impact energy. The hardness and the metallurgical features support these findings as one could visualize the phases and carbide morphological features getting transformed during the heat treatment process, thus favouring the abrasion, erosion and impact properties. These results have been compared and analysed with the results obtained from high chromium iron samples.

The erosion characteristics of HVOF-sprayed NiCrBSiFe and WC-Co/NiCrBSiFe coatings made on SS347 grade steel have been investigated for high-temperature behaviour, especially in the boiler tubes used in thermal power generation. The computational fluid dynamic model has been adopted to study the influence of the impingement angle on the erosion properties of the coatings. The self-fluxing NiCrBSiFe alloys have shown the best erosion resistance of about two times at room temperature and about four times at 700 °C when compared with a composite powered coating of WC-Co/NiCrBSiFe. At 700 °C, The WC-Co/NiCrBSiFe undergoes thermal cracking between nickel rich and WC metallic phases due to low oxidation and thermal expansion mismatch between them leading to degradation of the coating; however, at this temperature, the self-fluxing alloy of NiCrBSiFe performed better when compared to WC-Co/NiCrBSiFe coating. The simulation is done with turbulence model, namely shear stress transport (SST) model with a base on user-defined function predicted from the experimental results. The computational fluid dynamic simulated data obtained from SST model and the experimental results were compared, and they are in good agreement with each other.

The current research work investigated the optimization of the input parameters for the friction stir welding of AA3103 and AA7075 aluminum alloys for its applications in aerospace components. Friction stir welding is rapidly growing welding process which is being widely used in aerospace industries due to the added advantage of strong strengths without any residual stresses and minimal weld defects, in addition to its flexibility with respect to the position and direction of welding. Thus, the demand for this type of welding is very high; however, the welding of aluminum alloys is a key aspect for its use in aircraft components, particularly with respect to bracket mounting frames, braces and wing components. Henceforth in the current work, research is focused on optimization of welding of aluminum alloys, viz. AA 3103 and AA 7075; AA 3103 is a non-heat treatable alloy which is having good weldability, while AA 7075 is having higher strength. Therefore, the welding of these aluminum alloys will produce superior mechanical properties. The optimization of input parameters was accomplished in this work based on L9 orthogonal array designed in accordance with Taguchi method—using which the friction stir welding experiment was conducted. There were nine experimental runs in total after formulating the L9 orthogonal array table in Minitab software. The input parameters which were selected for optimization were—tool rotation speed, feed rate, tool pin profile. The output parameters which were optimized were hardness, tensile strength and impact strength. In addition, the microstructure of the fractured surfaces of the friction stir welded joint was analyzed. It was found from the optimization of the process parameters that strong friction stir welded joints for aerospace applications can be produced at an optimized set of parameters of tool rotational speed of 1100 rpm, traverse speed of 15 mm/min with a FSW tool of triangular pin profile of H13 tool steel material.

Analytical approaches determine the shear strength of geopolymer concrete on experimentally evaluated parameters of strength such as compressive strength, tensile strength and flexural strength. The analytical approach has been introduced by using the equations of the correlated stress functions to evaluate the shear strength. The new approach has been introduced over traditional Mohr’s failure envelope to assess the shear strength. The shear stress evaluated under these approaches is compared with the solution by the equation suggested by ACI-318-95. The variation of results from these approaches varied a maximum of 40% with results by the equation (ACI-318-95). The validation of each approach would be subjected to further discussion with previous research significance under the same context.