Thermo-mechanical large deformation responses of Hydrogenated Nitrile Butadiene Rubber (HNBR): Experimental results

AbstractA comprehensive study on the large uniaxial deformation responses of two elastomers, Hydrogenated Nitrile Butadiene Rubbers (HNBR A and HNBR B), over wide ranges of strain rates (10-4⩽ε˙⩽5×103s-1) and temperatures (348⩽T⩽450K) are presented. The material is found to be non-linearly dependent on strain-rate and temperature. The large deformation responses of HNBR are determined to be almost purely viscoelastic. It is observed that, the instantaneous stress drop during the stress relaxation is dependent on the strain-rate. The relaxation and creep responses during the equilibrium state (a state where there is no drop in stress during relaxation and no increase in strain during creep) are dependent on strain/stress level at which the phenomenon is started

A critical review of supersonic flow control for high-speed applications

In high-speed fluid dynamics, base pressure controls find many engineering applications, such as in the automobile and defense industries. Several studies have been reported on flow control with sudden expansion ducts. Passive control was found to be more beneficial in the last four decades and is used in devices such as cavities, ribs, aerospikes, etc., but these need additional control mechanics and objects to control the flow. Therefore, in the last two decades, the active control method has been used via a microjet controller at the base region of the suddenly expanded duct of the convergent-divergent (CD) nozzle to control the flow, which was found to be a cost-efficient and energy-saving method. Hence, in this paper, a systemic literature review is conducted to investigate the research gap by reviewing the exhaustive work on the active control of high-speed aerodynamic flows from the nozzle as the major focus. Additionally, a basic idea about the nozzle and its configuration is discussed, and the passive control method for the control of flow, jet, and noise are represented in order to investigate the existing contributions in supersonic speed applications. A critical review of the last two decades considering the challenges and limitations in this field is expressed. As a contribution, some major and minor gaps are introduced, and we plot the research trends in this field. As a result, this review can serve as guidance and an opportunity for scholars who want to use an active control approach via microjets for supersonic flow problems

Advancements and limitations in 3D printing materials and technologies: a critical review

3D printing has revolutionized various industries by enabling the production of complex designs and shapes. Recently, the potential of new materials in 3D printing has led to an exponential increase in the technology’s applications. However, despite these advancements, the technology still faces significant challenges, including high costs, low printing speeds, limited part sizes, and strength. This paper critically reviews the recent trends in 3D printing technology, with a particular focus on the materials and their applications in the manufacturing industry. The paper highlights the need for further development of 3D printing technology to overcome its limitations. It also summarizes the research conducted by experts in this field, including their focuses, techniques, and limitations. By providing a comprehensive overview of the recent trends in 3D printing, this review aims to provide valuable insights into the technology’s prospects

Effect of fiber orientation-based composite lamina on mitigation of stress intensity factor for a repaired plate: a finite element study

The bonded composite repair has proven to be an effective method for addressing crack damage propagation. Numerous studies have employed experimental and simulation techniques to demonstrate the repair performance through the composites. These studies have explored various parameters related to bonded composites, such as size and properties, to enhance repair effectiveness. However, one aspect that has not been thoroughly investigated is the impact of fiber orientation within the composites. Therefore, the current work investigates the effect of the fiber direction of the composite patch bonded on a thin plate under plane stress conditions. Three types of fiber orientation of composite patch have been considered. In this investigation, the finite element method was used to determine the stress intensity factor using the ANSYS commercial code. The research findings showed that the fiber direction influenced the mitigation of stress intensity factor. This study is particularly important for designing the composite patch based on the fiber direction.  

Response surface analysis of nozzle parameters at supersonic flow through microjets

Base pressure is a crucial component in the measurement of flow parameters in a high-speed aerodynamic flow. In this paper, the microjets impact as a control mechanism is experimentally tested for the nozzles with abrupt expansion at supersonic Mach in an axisymmetric conduit. The flow regulation mechanism is placed at a 90-degree interval in the shape of an orifice of 0.5 mm in radius along the nozzle’s exit diameter, which generates jets at sonic Mach numbers. The flow constraints studied are inertia level (Mach number), expansion level (NPR), and the geometric parameters considered are the pipe’s length (L/D). These three relevant parameters were selected for the design of experiments (DOE). In the management of base pressure, this analysis’s primary objective is to evaluate the parameters influencing the flow. The experiments were carried out in two ways: without and with microjets. For the DOE, an L27 orthogonal series, polynomial expression, analysis of variance, and predicted plots were carried out to test the experimental findings. The established prototypes are statistically appropriate and achieved when making precise projections for all the cases. According to the present results, the L/D ratio for a given parameter is the most critical parameter influencing the maximum increase or decrease in the base pressure

Investigation on rheological properties of water-based novel ternary hybrid nanofluids using experimental and Taguchi method

This study presents the rheological behavior of water-based GO-TiO2 -Ag and rGO-TiO2 -Ag ternary-hybrid nanofluids. The impact of nanoparticles’ volumetric concentration and temperature on the rheological properties were studied. All experiments were performed under temperatures ranging from 25 to 50 ◦C in the solid volume concentration range of 0.5–0.00005%. The data optimization technique was adopted using the Taguchi method. The types of nanomaterials, concentration, temperature, and shear rate were chosen to optimize the viscosity and shear stress. The effect of shear stress, angular sweep, frequency sweep, and damping factor ratio is plotted. The experimental results demonstrated that the rheological properties of the ternary hybrid nanofluid depend on the ternary hybrid nanofluid’s temperature. The viscosity of ternary hybrid nanofluids (THNf) change by 40% for GO-TiO2 -Ag and 33% for rGO-TiO2 -Ag when temperature and shear rates are increased. All the ternary hybrid nanofluids demonstrated non-Newtonian behavior at lower concentrations and higher shear stress, suggesting a potential influence of nanoparticle aggregation on the viscosity. The dynamic viscosity of ternary hybrid nanofluid increased with enhancing solid particles’ volume concentration and temperature

Responses of Engineering Materials, Anisotropy and Forming Limit Diagrams at different strain-rates and temperatures.

The objectives of this work are 1) to predict the yield locus, 2) normal anisotropic ratio (R-value), 3) stress response and 4) Forming Limit Diagram (FLD) of an aluminum alloy sheet, at different strain-rates using an appropriate anisotropic yield criterion and constitutive model. In order to achieve these objectives, a comprehensive study of quasi-static and dynamic responses of two FCC metals is performed to understand the material behaviors at large deformations and over wide ranges of strain-rate (103-10-5s-1) and temperature (223-755K). The two FCC metals include Oxygen Free High Conductivity (OFHC) copper and an aluminum alloy (AA5182), which have applications in the defense and automotive industries, respectively. In the case of AA5182, the material includes the base alloy and welded materials called Tailor Welded Blanks (TWBs). Quasi-static tensile strain-rate jump experiments at room temperature are performed on aluminum alloy (AA5182) sheet. Tensile split-Hopkinson pressure bar (SHPB) experimental setup is developed to perform tensile experiments at high strain rates and at different temperatures. Further, to determine the anisotropy in the material, several experiments are performed in different directions of the sheet metal. It was observed that AA5182-O exhibited negative and positive strain-rate sensitivities at room and 473K, respectively. The r-value increased with increase in temperature. The comprehensive study of OFHC copper includes results from quasi-static compression experiments performed at different strain-rates and temperatures. Dynamic compression experiments performed using the conventional SHPB technique are also presented. The material responses under quasi-static and dynamic torsion loading conditions, using the MTS and torsional Kolsky bar respectively, are also presented. The compressive responses of the material under non-proportional paths are also studied at different strain rates. Constitutive modeling of this comprehensive response is performed using a modified phenomenological model earlier developed by Khan et al. (1999 & 2004). This constitutive model captures the experimental response reasonably well (within 2%) given the few material constants involved and the ease with which they can be obtained. To remove any doubts of bias, this model is also used to correlate and predict the experimental observations on the same material by McDowell et al. (1999), and Nemat-Nasser et al. (1998). The correlations and predictions are again in good agreement with the experimental results. In conclusion, this model shows excellent capability to correlate and predict the experimental response of FCC and BCC metals and can be used in predicting the FLD for the aluminum alloy

Advanced composite materials for structural maintenance, repair, and control

A newly added Special Issue (SI) of the Materials journal, titled "Advanced Composite Materials for Structural Maintenance, Repair, and Control" focuses on the foundations, characterizations, and applications of several advanced composites. This SI aims to publish reviews and research papers on the most recent scientific and practical studies, including those on product development and the lifecycle analysis of improved advanced composites for engineering applications, particularly aeronautical, mechanical, automotive, material, and structural engineering. In several engineering applications, defects including delamination, notch, and fracture are unavoidable. These damages are mostly brought on by fatigue and accidents. Structural repair, rather than replacing the entire component, is sometimes the only viable option when the damage to the material is not extensive. Since passive repairs utilize composite materials, they offer enhanced stress transfer mechanisms and joint efficiency. Over the last four decades, bonded composite repair methods by means of various composite material patches, such as carbon-fiber-reinforced polymers, boron-epoxy, carbon-epoxy, and glass-epoxy, have been developed to repair damaged structures. Because they can withstand the imposed stresses at a fraction of the weight of metallic alloys, these materials were appealing to those who dealt with the maintenance, repair, and control of damaged structures. Since then, the usage of composite materials has spread throughout the world, from secondary to primary structures of the aerospace industry, automotive industry, and other fields. New advanced composite materials, repair methods, simulation approaches, and optimization techniques are still being continuously developed with the objective to control structural damage, minimize fracture parameters, enhance cost efficiency, decrease energy consumption, and offer advanced solutions for repair methods and the maintenance of damaged structures

Advanced Composite Materials for Structural Maintenance, Repair, and Control

A newly added Special Issue (SI) of the Materials journal, titled "Advanced Composite Materials for Structural Maintenance, Repair, and Control" focuses on the foundations, characterizations, and applications of several advanced composites [...

Numerical analysis of a microjet-based method for active flow control in convergent-divergent nozzles with a sudden expansion duct

A method based on microjets is implemented to control the flow properties in a convergent-divergent nozzle undergoing a sudden expansion. Three different variants of this active control technique are explored numerically by means of a finite-volume method for compressible fluid flow: with the first one, the control is implemented at the base, with the second at the wall, while the third one may be regarded as a combination of the other two variants. When the jets are over-expanded, the control is not very effective. However, when a favorable pressure gradient is established at the nozzle, the control becomes effective, leading to an increase in the base pressure