Tensile Stress Research Articles

Optimization of Flywheel Design for the Engine CT-195 to Reduce Weight & Minimized Cost

Abstract: A flywheel stores energy in the form of kinetic (rotational) energy. Whereas each energy storage system has its inherent advantages and disadvantages compared to the others, it is the overall system performance and simplicity of flywheels that make them especially attractive for a variety of applications. Flywheel is mechanical device which is used to store the kinetic energy. There are many causes of flywheel failure. But maximum tensile and bending stresses induced in the web and rim under the action of centrifugal forces are the main causes of flywheel Failure. By changing the dimensions and shape and the materials and use such materials which increases stored energy and maintain minimum stresses with reduce mass of flywheel. It shows that smart design of flywheel geometry could both have a significant effect on the Specific Energy performance and reduce the operational loads exerted on the shaft/bearings due to reduced mass at high rotational speeds. we will compare the theoretical values of moment of Inertia with the Creo-Mechanic values so that the clear objective of the project can be seen. Our Main object is to optimise the flywheel weight without changing other important parameter like moment of inertia and its kinetic energy storage capacity.

Effect of crack on morphology evolution of the precipitates in Nickel-based superalloys under applied stress

Nickel-based superalloys are widely used in turbine blades and aviation engine due to their outstanding mechanical property at elevated temperatures. The superior mechanical property of nickel-based superalloys is highly relevant to the morphology evolution of γ′ precipitates in the γ matrix phase. At high temperature, the directional coarsening of γ′ precipitates may result in rafting behavior under applied stress. In addition, defects such as the cavities, inclusions and micro-cracks introduced during the manufacturing process in superalloys have significant influence on the evolution of the γ′ precipitates. In this work, a phase field model with crack and precipitate as order parameters has been proposed to investigate the effect of crack on the morphology evolution of the γ′ precipitates. The morphology evolution and volume fraction evolution of the γ′ precipitates in the Nickel-based superalloys with different cracks have been investigated under the tensile and shear stresses. It is found that the local high equivalent stress and high elastic strain energy near the crack lead to the migration of solute atoms from the high stress region to the low stress region. The migration of solute atoms results in the disappearance of the γ' phases in the vicinity of cracks, which is consistent with the experimental observation. The disappearance of the γ' phases around the crack reduces the volume fraction of the γ′ precipitates, which will affect the mechanical property of the superalloys.

Evaluating the Impact of Environmental and Operational Conditions on the Characteristics of CFRP Epoxy Composites

The purpose of this study is to determine the material properties of CFRP composites in the form of a fabric for the construction of racing car bodywork. This work focused on the determination of the strength and tribological properties as well as investigating the effects of the operating environment on the developed material. Three material variants, differing in the number of layers used to produce the reinforcement, were used in this study. The tests were carried out on two-/three-/four-layer sheets produced by infusion. Due to the later use of the tested composites for the sheathing of a racing car, the results obtained were analysed in terms of the most favourable strength properties while keeping the weight as low as possible. In this study, the hardness, impact strength, and tensile and bending stresses of the developed composites were examined. In addition to the strength properties, the density, the effects of immersion in water, and the composite’s resistance to staining and friction in the presence of aggressive media were also checked. The structure and the breakthroughs resulting from the strength tests were observed using a stereoscopic microscope. The material’s resistance to sunlight and UVB was also tested.

Self-healing property of a gel-elastomer two-phase composite material

While self-healing silicones are required for many practical applications, conventional methods of incorporating self-healability in silicones involve generation of bond-forming moieties within the backbone of the oligomer itself. Such processes involve multiple synthesis steps that turn the silicone expensive and less amenable for scale-up. In contrast, hydrogels can be made self-healing by different simple yet robust chemical routes. Hydrogels however lack mechanical strength, necessary for most engineering applications. To meet the above need, we have introduced here a novel two-phase material, consisting of self-healing hydrogel droplets embedded as microscopic healers inside the continuous matrix of silicone. The hydrogel phase, consisting of starch and polyvinyl alcohol (PVA) as the oligomers and multivariate borate ion as the crosslinker is dispersed in silicone oligomer mixed with the curing agent and both phases are allowed to crosslink. Controlled fracture tests on the resultant crosslinked material show that two cut surfaces of it get joined instantaneously with the tensile failure stress reaching as high as 35 kPa; this material remains healable also over ten cycles of incision and reattachment. The hydrogel can act also as an external glue to heal two incised surfaces of the two-phase composite to achieve durable fracture strength and thereby help forming different polygonal structures with angled joints. We have demonstrated also bio-compatibility of the two-phase material thereby opening up its possible use in large variety of biomedical applications.

Electrochemical study and structural comparison of Ni electrodepositions on W/Si and Cr/C multilayered structure films

Abstract The Ni electrodeposition combined with multilayered structure film is a promising strategy in modern optical manufacturing, while less effort has been devoted to comprehending the electrochemical reaction process, which is essential for their practical applications. In view of this, the initial reduction dynamics and nucleation mechanisms of Ni electrodepositions on multilayer W/Si and Cr/C films were analyzed in this work, and the morphological, crystal, and mechanical characteristics of produced Ni electrodeposits were further determined and compared. The results show that the considerably irregular crystals accompanied by high tensile stress of 119.5 MPa were formed for the Ni electrodeposit on W/Si film, which were mainly attributed to the progressive nucleation process with more severe side reaction of hydrogen evolution. By contrast, the instantaneous nucleation mode with lower reduction resistance were revealed for the Ni electrodeposition on Cr/C film, which presented a comparatively fine–grained texture, less roughness, and smaller stress structure. To summarize, the more stable electrochemical reaction process and improved structure uniformity are obtained for the Ni electrodeposition on metal/C–based film, which offers a theoretical guidance for optimized fabrication of multilayer optical devices in extreme ultraviolet, X–ray, and neutron focusing fields.

Directed biomechanical compressive forces enhance fusion efficiency in model placental trophoblast cultures.

The syncytiotrophoblast is a multinucleated structure that arises from fusion of mononucleated cytotrophoblasts, to sheath the placental villi and regulate transport across the maternal-fetal interface. Here, we ask whether the dynamic mechanical forces that must arise during villous development might influence fusion, and explore this question using in vitro choriocarcinoma trophoblast models. We demonstrate that mechanical stress patterns arise around sites of localized fusion in cell monolayers, in patterns that match computational predictions of villous morphogenesis. We then externally apply these mechanical stress patterns to cell monolayers and demonstrate that equibiaxial compressive stresses (but not uniaxial or equibiaxial tensile stresses) enhance expression of the syndecan-1 and loss of E-cadherin as markers of fusion. These findings suggest that the mechanical stresses that contribute towards sculpting the placental villi may also impact fusion in the developing tissue. We then extend this concept towards 3D cultures and demonstrate that fusion can be enhanced by applying low isometric compressive stresses to spheroid models, even in the absence of an inducing agent. These results indicate that mechanical stimulation is a potent activator of cellular fusion, suggesting novel avenues to improve experimental reproductive modelling, placental tissue engineering, and understanding disorders of pregnancy development.

Mixed mode I/II and I/III fracture toughness investigation for preplaced aggregate concrete mixtures: Experimental study and theoretical prediction

AbstractIn this paper, mixed mode I/II and I/III fracture toughness of preplaced aggregate concrete was studied using an edge‐notched disc bend specimen. The results showed the dependency of the fracture toughness value on the mode mixity. The values of modes I, II, and III fracture toughness were obtained to be equal to , , and , respectively. Several theoretical fracture criteria were examined for predicting the trends of experimental data in the tested preplaced aggregate concrete material. The 3D averaged strain energy density criteria provided the best predictions for the KIIIc/KIc ratio. Mixed mode I/III fracture toughness data were between the predicted envelopes of the maximum tensile stress and 3D maximum tangential strain theories. The generalized maximum tangential stress criterion provided accurate predictions for pure mode II and mixed mode I/II fracture data among the investigated mixed mode fracture criteria. By comparing the preplaced aggregate concrete fracture results with those of other types of concrete, it is observed that preplaced aggregate concrete has acceptable and in‐the‐range fracture resistance.

Assessing the Stress Induced by Novel Packaging in GaN HEMT Devices via Raman Spectroscopy

Micro-Raman spectroscopy was carried out to evaluate the localized residual stresses in commercial Gallium-Nitride-based devices, specifically, AlGaN/GaN high-electron-mobility Transistors (HEMTs) with a novel packaging design provided by STMicroelectronics S.r.l. (Catania, Italy). The packaging plays a key role in protecting the device core against the external environment, thus minimizing damages caused by mechanical shocks, exposure to light, and contact with chemicals, conjointly achieving an efficient heat dissipation rate. Even though the packaging is a required step for the proper functioning of ready-to-use electronic devices, its application typically may introduce mechanical stress to AlGaN/GaN HEMTs, which can result in various reliability issues. In this paper, we investigate the impact of packaging on residual stress by analyzing the frequency shift of the E2 Raman peak along GaN layers and at the GaN/Si interface. An extensive evaluation was conducted using both a packaged device and a wafer-level device. The correlation between Raman frequency shifts of the E2 mode was accurately quantified, revealing a stress mitigation of approximately 0.1 GPa. This reduction is ascribed to the compressive stress introduced by the packaging, which partially offsets the intrinsic tensile stress of the wafer-level device. The proposed methodology could, in principle, be implemented to improve the development of packaging.

Effect of Reaction Layers on Internal Stresses in Co‐Fired Multilayers of Calcium Manganate and Calcium Cobaltite

A widespread recovery of waste heat requires a cost‐effective production of thermoelectric generators. Thermoelectric oxides are predestined for use at high temperatures. For manufacturing reasons, a multilayer generator design will be easily scalable and cost‐effective. To evaluate the potential of ceramic multilayer technology for that purpose, a multilayer of the promising thermoelectric oxides calcium cobaltite (Ca3Co4O9), calcium manganate (CMO, CaMnO3), and glass–ceramic insulation layers is fabricated. Cracks and reaction layers at the interfaces are observed in the microstructure. The compositions of these reaction layers are identified by energy‐dispersive X‐ray spectroscopy and X‐ray diffraction. Mechanical and thermal properties of all layers are compiled from literature or determined by purposeful sample preparation and testing. Based on this data set, the internal stresses in the multilayer after co‐firing are calculated numerically. It is shown that tensile stresses in the range of 50 MPa occur in the CMO layers. The reaction layers have only a minor influence on the level of these residual stresses. Herein, it is proven that the material system is basically suitable for multilayer generator production, but that the co‐firing process and the layer structure must be adapted to improve densification and reduce the tensile stresses in the CMO.

Long-Term Drying Shrinkage Strain of Engineered Cementitious Composite Concrete Contains Polymeric Fibers

The lack of concrete tensile stress endurance led to the invention of engineered cementitious composite. However, the absence of gravel from the mixture in addition to the high binder content may lead to high shrinkage strain. Therefore, a radical solution to this problem is worth to be anticipated. The importance of this research lies in investigating the long-term drying shrinkage strain of the engineered cementitious composite since there is a lack of information regarding this behavior. Mixes of 30 and 60 MPa strengths were produced with polyvinyl alcohol fibers PVA-ECC and polypropylene fibers PP-ECC. The drying shrinkage strain of PVA-ECC mixes has been compared to PP-ECC mixes for both short term (0–28 days) and long term (0–360 days). Results indicated that all PVA-ECC mixes exhibited lower drying shrinkage strains than PP-ECC mixes. The ultimate drying shrinkage strain was recorded to be 1200 microstrain at 28 days. The increment in drying shrinkage strain after 28 days was 5.6% in PVA-ECC mixes when compared to that in PP-ECC mixes which was 6.77%. For high strength levels, the drying shrinkage strain at the age of 360 days declared a reduction of 3.5% for PVA-ECC compared to PP-ECC mixes. Also, it was lower for mixes with 60 MPa (6.3%) than for mixes with 30 MPa (7.6%). Therefore, despite the higher cement content for mixes with 60 MPa strength, the higher fiber volume fraction and the higher PVA solution percentage restricted the drying shrinkage strain increment. The research also addresses some mechanical tests of engineered cementitious composite concrete such as compressive strength, flexural strength, and strain capacity that may provide a strong relation to the drying shrinkage behavior of the different mixes. The scanning electron microscope images were involved in this research to declare the impact of fiber types on the microstructure of the ECC mixes.

Mechanical behavior of full-thickness burn human skin is rate-independent

Skin tissue is recognized to exhibit rate-dependent mechanical behavior under various loading conditions. Here, we report that the full-thickness burn human skin exhibits rate-independent behavior under uniaxial tensile loading conditions. Mechanical properties, namely, ultimate tensile stress, ultimate tensile strain, and toughness, and parameters of Veronda–Westmann hyperelastic material law were assessed via uniaxial tensile tests. Univariate hypothesis testing yielded no significant difference (p > 0.01) in the distributions of these properties for skin samples loaded at three different rates of 0.3 mm/s, 2 mm/s, and 8 mm/s. Multivariate multiclass classification, employing a logistic regression model, failed to effectively discriminate samples loaded at the aforementioned rates, with a classification accuracy of only 40%. The median values for ultimate tensile stress, ultimate tensile strain, and toughness are computed as 1.73 MPa, 1.69, and 1.38 MPa, respectively. The findings of this study hold considerable significance for the refinement of burn care training protocols and treatment planning, shedding new light on the unique, rate-independent behavior of burn skin.

Oxidation behavior of Ni-based superalloy GH4738 under tensile stress

Oxidation behavior of Ni-based superalloy GH4738 under tensile stress

Pressure Changes Across a Membrane Formed by Coacervation of Oppositely Charged Polymer-Surfactant Systems.

We investigate the mass transfer and membrane growth processes during capsule formation by the interaction of the biopolymer xanthan gum with CnTAB surfactants. When a drop of xanthan gum polymer solution is added to the surfactant solution, a membrane is formed by coacervation. It encapsulates the polymer drop in the surfactant solution. The underlying mechanisms and dynamic processes during capsule formation are not yet understood in detail. Therefore, we characterized the polymer-surfactant complex formation during coacervation by measuring the surface tension and surface elasticity at the solution-air interface for different surfactant chain lengths and concentrations. The adsorption behavior of the mixed polymer-surfactant system at the solution-air interface supports the understanding of observed trends during the capsule formation. We further measured the change in capsule pressure over time and simultaneously imaged the membrane growth via confocal microscopy. The cross-linking and shrinkage during the membrane formation by coacervation leads to an increasing tensile stress in the elastic membrane, resulting in a rapid pressure rise. Afterward, the pressure gradually decreases and the capsule shrinks as water diffuses out. This is not only due to the initial capsule overpressure but also due to osmosis caused by the higher ionic strength of the surfactant solution outside the capsule compared to the polymer solution inside the capsule. The influence of polymer concentration and surfactant type and concentration on the pressure changes and the membrane structure are studied in this work, providing detailed insights into the dynamic membrane formation process by coacervation. This knowledge can be used to produce capsules with tailored membrane properties and to develop a suitable encapsulation protocol in technological applications. The obtained insights into the mass transfer of water across the capsule membrane are important for future usage in separation techniques and the food industry and allow us to better predict the capsule time stability.

Lightweight Designs and Improving the Load-Bearing Capacity of Structures by the Method of Aggregation

Lightweight Designs and Improving the Load-Bearing Capacity of Structures by the Method of Aggregation

Stable and wide temperature range superelasticity in an Mo-doped nanocrystalline Ni–Ti–Mo shape memory alloy

The phase transformation and superelastic behavior of nanocrystalline Ni48Ti50Mo2 alloy wires were investigated. Nanocrystalline (NC) alloys were obtained via severe plastic deformation of cold-drawing followed by annealing at low temperatures. The results indicate that the NC Ni48Ti50Mo2 undergoes a single-step B2→R phase transformation and a two-step B2→R→B19′ phase transformation in coarse crystals (CG). The NC alloy wire exhibits 8 % recoverable strain under a tensile stress of 1.1 Ga and superelasticity exists in a wide temperature range from −60 °C to 100 °C. After 50 cycles of tension fatigue testing, the superelastic upper plateau stress reduction rate is 7 % with almost no residual strain accumulation, which has excellent superelastic stability compared with fine crystals and coarse crystals. Transmission electron microscope (TEM) reveals an average grain size of 20 nm. The stable superelasticity is attributed to the nanocrystalline reinforced matrix, which hinders dislocation generation and slip.

Effects of Selective Laser Melting Process Parameters on Structural, Mechanical, Tribological and Corrosion Properties of CoCrFeMnNi High Entropy Alloy

AbstractThe structural, tribological, mechanical, corrosion, and other properties of materials produced by laser-based powder bed fusion additive manufacturing methods are significantly affected by production parameters and strategies. Therefore, understanding and controlling the effects of the parameters used in the manufacturing process on the material properties is extremely important for determining optimum production conditions and for saving time and materials. This study aimed to determine the optimal laser parameter values for CoCrFeMnNi high-entropy alloy powders using the selective laser melting (SLM) method. The layer thickness was kept constant during experimentation. 5 different laser powers and 10 varying laser scanning speeds were tested, with hatch spacing from 30 to 90%. After determining the optimal laser parameters for SLM, prismatic samples were fabricated in different build orientations (0°, 45°, and 90°), and subsequently, their structural, mechanical, tribological, and corrosion properties were compared. Melt pool morphology could not be obtained at 20—40 and 60W laser powers and at all laser scanning speeds used at these laser powers. At 100 W laser power, 600 mm/s laser scanning speed, and 70% hatch spacing parameters, an ultimate tensile stress of 550 MPa and elongation of 48% were obtained. Among the samples produced in different build orientations, the sample produced with a 0° build orientation exhibited the highest relative density (99.94%), the highest microhardness (201.2 HV0.1), the lowest friction coefficient (0.7025), and the lowest wear and corrosion rates (0.7875 mpy). Additionally, SLM parameters were evaluated to have a significant impact on the performance of all properties of the samples. Graphical Abstract

Profilometry‐Based Indentation Plastometry and Uniaxial Testing of Pipelines: Detection of In‐Plane Anisotropy and Potential for Simplification of Test Procedures

This article concerns anisotropy in stress–strain relationships exhibited by steel pipelines. Since the stress from internal pressurization is highest in the hoop direction, standard industrial practice to measure these properties has focussed on tensile testing in this direction, requiring a prior flattening operation. The associated plastic deformation may affect properties, typically causing a (poorly‐defined) degree of hardening and the creation of inhomogeneity. Field testing of such pipelines, requiring in situ measurement of tensile properties (yield stress (YS) and ultimate tensile stress (UTS)), is based on indentation testing of the outer surface. One such test (profilometry‐based indentation plastometry (PIP)), not only gives the stress–strain curve, but also allows detection of any (in‐plane) anisotropy, with a high sensitivity. Both PIP testing and compression testing (with and without prior flattening) have confirmed that none of the eight pipes examined in the current work exhibited any such anisotropy, although the effects of flattening did tend to generate apparent anisotropy in the tensile test outcomes. It may therefore be appropriate to switch the focus of tensile testing to the axial direction, such that no flattening would be required.

Non-Contact Evaluation of Deformation Characteristics on Automotive Steel Sheets

Non-Contact Evaluation of Deformation Characteristics on Automotive Steel Sheets

Residual stress variations in substrate (AISI D2) during directed energy deposition process of high-speed tool steel (AISI M4) powder

This study aims to observe the residual stress in a substrate and predict stress behavior during the laser deposition process (DED) using finite element analysis (FEA). The residual stress observed on the substrate surface indicated that stress variation during the deposition process increases with proximity to the deposition area, resulting in higher residual stress levels. Additionally, tensile residual stress tends to increase with the height of the deposition area. While variations in the deposition area size influenced the residual stress, consistent stress levels were observed at the same measurement points across different area sizes. The deposition process was simulated using FEA, which confirmed that stress behavior is influenced by melting and solidification cycles. The residual stress levels after cooling aligned well with those observed in actual experiments. Therefore, this study suggests that stress variations can be effectively predicted by simulating the deposition process prior to conducting actual experiments.

Influence of bismuth addition on the physical and mechanical properties of low silver/lead-free Sn-Ag-Cu solder

The Sn–Ag–Cu (SAC) solders with low Ag content have been identified as promising candidates to replace the traditional Sn–Pb solder for flip-chip interconnects. This study examines the impact of incorporating Bi element on the microstructure, thermal behavior, and mechanical performance of low-silver-content Sn-1.5Ag-0.7Cu (SAC157) solder alloy. Besides using the conventional cross-sectioned microstructure image, X-ray diffraction (XRD), differential scanning calorimetry (DSC) and tensile stress- strain techniques were used to investigate the microstructure, thermal and mechanical properties after the addition of Bi, respectively. The results demonstrate that adding of Bi could refine the microstructure, optimize the thermal properties, and improve the tensile strength. Meanwhile, the ductility of the solder alloys reduced evidently in comparison to the Sn-1.5Ag-0.7Cu solder. From the microstructural analysis, 0.5 wt % Bi addition to SAC157 significantly enhanced the solid solution effect of Bi and refined β-Sn dendrite, as well as extended the eutectic area. Moreover, as the Bi addition increases to 5 wt %, finely dispersed bismuth precipitates within the β-Sn matrix, along with an enlarged eutectic area, lead to a remarkable enhancement in both ultimate tensile strength and yield strength. The electrical resistivity was characterized by the four-point probe technique. The results show that the electrical resistivity of Bi-modified SAC157 solder alloy decrease from 13.9 to 9.8 μΩ cm with the addition of 5 wt % Bi. These improvements can be attributed to the solid-solution and precipitation strengthening effects induced by the presence of bismuth. The results confirmed that the developed material is applicable as a potential high strength solder material in the context of advanced interconnecting applications.