Effect Of Thermal Loading Research Articles

Nonlinear Vibration and Stability Analysis of Functionally Graded Nanobeam Subjected to External Parametric Excitation and Thermal Load

Analysis of vibration stability of simply supported Euler-Bernoulli functionally graded (FG) nanobeam embedded in viscous elastic medium with thermal effect under external parametric excitation is presented in this work. An attempt has been made for the first time is investigating the effect of thermal load on dynamic behavior, amplitude response, instability region and bifurcation points of functionally graded nanobeam. Thermal loads are supposed to be uniform, linear or nonlinear distribution along the thickness direction. Nonlocal continuum theory and the principle of the minimum total potential energy are applied to derive the governing equations. The partial differential equations (PDE) are transported to the ordinary differential equations (ODE) by using the Petrov-Galerkin method and the multiple time scales method are manipulated to solve the motion equation. To study the effect of external parametric excitation and thermal effect, different temperature distributions along the thickness such as uniform, linear, and nonlinear distribution are considered. Moreover, stable and unstable regions and bifurcation points are determined. It is obtained that the thermal load can affect the amplitude response of FG nanobeam. Also, it is observed that the instability of the system is affected by the detuning parameter and the parametric excitation amplitude plays great role in the instability of system. Nanobeams are used in many devices like nanoresonators, nanosensors and nanoswitches. This paper is helpful for designing and manufacturing nanoscale structures specially nanoresonators under different thermal loads.

Finite Element Analysis of the Effect of Dental Implants on Jaw Bone under Mechanical and Thermal Loading Conditions

Dental implants have been studied over the years to replace missing teeth. One of the conditions for the success of implants is their stability and resistance under the applied forces and minimal tension in the surrounding bone. The purpose of this dissertation is numerical and three-dimensional analysis of jaws with implants under mechanical and thermal loading by the finite element method. For this purpose, implant simulations (including ceramic crown, titanium root, and jaw bone) under dynamic and thermal load have been performed in Abacus software. In this simulation, it is considered that the jawbone is composed of two areas, one area is the superficial bone tissue (cortical) and the other part is the spongy tissue. Implants are usually made of different metals or ceramics with a bone-like structure that are compatible with body tissues. Implants are currently made of titanium metal. Therefore, titanium metal has been used for modeling implants in this dissertation. The implant crown is also considered as a ceramic material. In the simulation, the effect of stresses imposed by the implant on the jawbone is performed. In this simulation, mechanical force is applied to the upper part of the implant and force enters the jawbone through the implant, which causes tension at the junction of the implant to the jawbone. To investigate the effect of thermal loads, different temperature conditions are considered by considering the decrease in temperature and increase in temperature on the tooth surface and its effect on the implant and the jaw bone. After validation and ensuring the accuracy of the modeling, it has been observed that, with increasing mechanical load, the stresses created in all parts of the ceramic coating, titanium implants, and jawbone have increased. It is also observed that the stress created in the titanium implant due to the application of negative heat flux was about twice as much as the stress created due to the application of positive heat flux.

TU15. GENETIC VARIABILITY IN IMMUNE TRAITS AND ITS RELATIONSHIP WITH AUTISM SPECTRUM DISORDERS

In thermo-mechanical processes, the effect of mechanical and thermal loads on resulting material modifications are not independent of each other. In order to analyze and understand their interaction, they should be varied independently from each other. Combined laser and deep rolling processing is a suitable model process for this, since the rolling pressure and laser power can be set independently. A FE model of the process has been developed and validated with measurements of surface temperatures and residual stresses. It is found that the temperature development can be accurately simulated but substantial differences between experimental and simulated residual stresses occur.

Tool-Work Contact Ratio and Parametric Influence in Ultrasonic Vibration–Assisted Turning of Ti6Al4V Alloy

Abstract The performance of the machining process depends on the time of contact of the cutting tool with the workpiece. In this work, the effect of vibrating and cutting parameters on tool-work contact ratio (TWCR) in ultrasonic vibration–assisted turning (UVAT) is evaluated. Machining performance is measured in terms of average cutting force, cutting temperature, and average surface roughness. Full factorial experiments are conducted on a Ti6Al4V alloy to evaluate the performance of the UVAT process in terms of TWCR. The performance of the UVAT process is analyzed and compared with the conventional turning process at various conditions, such as intensity of ultrasonic power (80, 90, and 100 %), cutting speed (10, 30, and 50 m/min), feed rate (0.055, 0.103, and 0.161 mm/rev), and depth of cut (0.1, 0.3, and 0.5 mm). The cutting force, cutting temperature, and surface roughness are decreased with the increase in percentage intensity of ultrasonic power. The effectiveness of UVAT process is greater at higher levels of vibrating parameters and lower levels of cutting parameters in the selected range. Finally, it is concluded that the maximum benefit from the UVAT process is obtained at TWCR of 0.136 and its effect is dominant at lower levels of cutting conditions. However, the effect of thermal loading is dominant at higher levels of cutting conditions in the selected range.

Guided wave propagation of porous functionally graded plates: The effect of thermal loadings

Because there is no literature on the effect of thermal loadings on guided wave propagation in FG plates, the present paper is to fill the gap. In the present paper, the wave propagation analysis of porous FG plates with clamped ends in thermal environments based on first order shear deformation theory are presented. The plates are exposed to various types of thermal loading including uniform and non-uniform temperature changes, the material properties of FG plates are temperature- and porosity-dependent. Using the Galerkin method, we obtain the dispersion relation of thermoelastic waves in porous functionally graded plates. Compared with the previous results, the correctness of the present work is verified. In the end, the effects of the temperature changes, porosity as well as power law index on the phase velocity and group velocity of the guided wave are investigated.

Thermal stress analysis in a hemispherical shell made of transversely isotropic materials under pressure and thermo‐mechanical loads

AbstractThis article deals with the study of thermal stress in a hemispherical shell made of transversely isotropic material under the effect of thermal, pressure and mechanical load. Seth's transition theory and generalized strain measure are used for finding the governing equation. Mathematical modelling is based on stress–strain relation and equilibrium equation. Analytical solutions are presented for the hemispherical shell made of transversely isotropic material and isotropic material. The effects of different pertinent parameters (i.e., temperature, pressure and load) are considered for the spherical shell made of transversely isotropic material. The behaviour of stress distribution, mechanical load, pressure rise, and temperature distribution are investigated. From the obtained results, it is noticed that carbon fiber material hemispherical shell requires higher pressure at the internal surface in comparison to magnesium/polypropylene material. With the introduction of mechanical load, the value of pressure decreases at the internal surface, but reverse results are obtained in the case of thermal condition for the hemispherical shell made of carbon fiber/magnesium/polypropylene material. By applying thermal condition, the hemispherical shell made of carbon fiber material requires maximum hoop stress at the external surface as compared to the magnesium/polypropylene material. The transversely isotropic material hemispherical shell more convenient than that of isotropic material hemispherical shell. Results have been discussed numerically and graphically.

Mechanism study and power transmission feature of acoustically stimulated and thermally loaded composite shell structures with double curvature

Because of the modification in environmental conditions, thermal stresses may induce dynamic instability in a composite shell model. Therefore, according to the double Fourier series solution, an analytical strategy is proposed in this study for the first time to acoustically determine the vibration response of a doubly curved composite shell in a thermal environment. The main aim is to show the effect of thermal loads on sound transmission loss (STL). The motion equations of the structure integrated with thermal stresses are derived considering shear deformation shallow shell theory (SDSST) through Hamilton’s principle. Before verifying the outcomes, the convergence of the STL curve is also checked to prove that the obtained results are reliable. Parametric studies are performed to either show the temperature effect on acoustic characteristics or propose a 3D configuration of thermo-acoustic pressures through the system. Based on the temperature variations, it is found that there is an opposite trend between the increase of this term and the STL of structure. This issue also causes to move the dip point of the STL spectrum to lower frequencies. To manifest the fact of these behaviors, the natural frequency ratio against temperature rise is also plotted.

Thermal-magneto-mechanical stability analysis of nanofluid conveying carbon nanotubes based on nonlocal couple stress theory

Carbon nanotubes (CNTs) have extensive biomedical applications in which a heat pulse is applied to the CNTs. The present study encompasses the novelty by focusing on the complicated effect of thermal loads and heat generation on the CNT stability with the aim of preserving and improving the stability. There is also a lack of research that evaluates the size-dependence using appropriate robust non-classic theory, which is incorporated by employing a hybrid method of nonlocal couple stress theory and nonlocal elasticity theory. Additionally, Euler–Bernoulli beam theory is employed for coupling the Navier–Stokes equation of magnetic-fluid flow with the CNT deformation. The CNT stability is evaluated by considering nonlocal and couple-stress sizing effect parameters, Knudsen number, magnetic field intensity, thermal effect, heat generation, and fluid flow velocity. Results indicate that, by rising the temperature gradient and the couple stress sizing effect parameter, the system stability is improved up to 19.07% and 16.58%. Whereas, by increasing the heat generation, the dimensionless critical velocity shows 6.91% decrease, which deteriorates the CNT stability. Results of the present study demonstrates that in CNT applications with the presence of thermal loads, neglect of thermal effects leads to misinterpretation of the system stability.

The effects of thermal loadings on wave propagation analysis of multi-scale hybrid composite beams

This research is concerned with the analysis of wave propagation of multi-scale hybrid composite beams subjected to various types of thermal loading. Carbon fiber (CF) and carbon nanotube (CNT) are assumed as reinforcements that are distributed in the matrix. The homogenization process is performed exerting the Halpin–Tsai model and the rule of mixture. Different types of temperature rise, namely, uniform, linear and sinusoidal temperature rise are presumed to present a more trustworthy thermal analysis. The beam is rested on Winkler–Pasternak foundation. A refined trigonometric shear deformable beam theory is used to compute the kinetic relations without any external shear correction coefficient. Governing equations are derived implementing Hamilton’s principle and then solved analytically. Eventually, the effects of different parameters, such as CNT’s weight fraction, the volume fraction of CF, elastic foundation, different types of temperature rise, etc., on wave frequency and phase velocity. are provided numerically in the framework of a set of illustrations.

Comparative thermal fatigue behavior of AlSi7Mg alloy produced by L-PBF and sand casting

By increasing the demand for additively manufactured Al parts for industrial applications, the knowledge about their thermal and mechanical behavior in service environments becomes highly required. Since Al alloys are widely used for the production of lightweight structures in transportation industry including several engine components, their thermo-mechanical behavior deserves special attention, considering the thermal and mechanical load fluctuations experienced in parts like cylinder heads, pistons, brake disks and calipers. In the present study, a comparative research has been carried out on the thermal fatigue (ThF) behavior of an AlSi7Mg (A357) alloy processed either by sand casting or laser powder bed fusion (L-PBF). Both alloy conditions were cycled within three temperature intervals with a lower temperature of 100 °C and upper limits of 200, 240 and 280 °C, in presence of a constant uniaxial tensile load. Three tensile loads of 110, 120 and 150 MPa were applied for each temperature range in order to explore the effect of both thermal cycling and concurrent tensile load on thermal fatigue resistance. Both alloys showed a similar ThF lifetime when exposed to temperature cycles from 100 to 200 °C under all the three tensile loads investigated, while the L-PBF A357 alloy tested to the highest temperature limits of 240 °C and 280 °C comparatively revealed an improved ThF resistance than the cast counterpart. Microstructural analyses on the cross-sections of both samples revealed that a large amount of strain was accumulated close to the fracture regions and several micropores and microcracks were developed in these areas. Microcracks preferentially nucleated at eutectic Si and Fe-bearing coarse intermetallics in the ThF tested cast alloy, while micropores nucleated from the fragmented silicon network in L-PBF samples on exposure to thermal cycling.

Finite element thermo-mechanical analysis of concrete box-girders

A full-scale 3D thermo-mechanical Finite Element (FE) model was conducted in this research to investigate the effect of open-field thermal loads on the structural response of box-girder bridges. A box-girder bridge with a span of 50 m was analyzed for temperature, radiation and displacement fields using COMSOL Multiphysics. To verify the FE model, a full-scale experimental box-girder segment was constructed and instrumented with temperature, radiation and other sensors. From the experimental records, three days with extreme temperature and radiation measurements were selected. The stresses and displacements are discussed at specific points along the 24 h of the selected days and at specific times along critical sections. The FE analysis showed that the vertical and lateral stress distributions exhibited approximately similar behaviors to their corresponding temperature distributions with minor differences but with reversed sign. The results also showed that the maximum stress was compressive, which was −3.35 MPa in summer −3.83 MPa in winter. On the other hand, the maximum vertical and lateral displacements were 12.5 and 1.2 mm, respectively in summer and 2.7 and 1.9 mm in winter.

Numerical Simulation of Cracks in Automotive Coatings Under Mechanical and Thermal Loading Using Element Free Galerkin Method

ABSTRACT The work presented in this paper aims to delve into the applications of Element Free Galerkin Method (EFGM) which is a type of Meshless Method (MM) to the area of Automobile Engineering. EFGM is implemented to detect a change in the material property at the interface of the coating along with the identification of crack. Simulation of centre crack in coatings has been reported for the first time using EFGM. Simulations with change in crack inclination angle, change in crack length are reported. Multiple cracks are reported in the form of collinear cracks, coplanar cracks and the effect of their presence on primary crack has been discussed. This work involves the study which leads to understanding the effect of temperature on the stress fields of the cracks present in coatings. Variations of the temperature field parallel to crack and perpendicular crack shows enticing results. The effect of variation in materials properties of coating and substrate is discussed. The work reveals the nature of crack severity in automobile coatings. Various conditions depicted in this work enhance the understanding of researches in comprehending the effect of thermal load in coated materials.

Improvement of a topological level-set approach to find optimal topology by considering body forces

PurposeBody forces are always applied to structures in the form of the weight of materials. In some cases, they can be neglected in comparison with other applied forces. Nevertheless, there is a wide range of structures in civil and mechanical engineering in which weight or other types of body forces are the main portions of the applied loads. The optimal topology of these structures is investigated in this study.Design/methodology/approachTopology optimization plays an increasingly important role in structural design. In this study, the topological derivative under body forces is used in a level-set-based topology optimization method. Instability during the optimization process is addressed, and a heuristic solution is proposed to overcome the challenge. Moreover, body forces in combination with thermal loading are investigated in this study.FindingsBody forces are design-dependent loads that usually add complexity to the optimization process. Some problems have already been addressed in density-based topology optimization methods. In the present study, the body forces in a topological level-set approach are investigated. This paper finds that the used topological derivative is a flat field that causes some instabilities in the optimization process. The main novelty of this study is a technique used to overcome this challenge by using a weighted combination.Originality/valueThere is a lack of studies on level-set approaches that account for design-dependent body forces and the proposed method helps to understand the challenges posed in such methods. A powerful level-set-based approach is used for this purpose. Several examples are provided to illustrate the efficiency of this method. Moreover, the results show the effect of body forces and thermal loading on the optimal layout of the structures.

Effect of thermal axial load on vibration of cracked single-walled carbon nanotubes modelled as Timoshenko nanobeams using nonlocal theory

ABSTRACT This paper investigates free vibration of cracked single-walled carbon nanotubes modelled as Timoshenko nanobeams under axial thermal load. The main objective of this work is a deep, true, and precise formulation to analyse truly the thermal effects on the Timoshenko nanobeam model. Nonlocal elasticity theory is applied to Timoshenko beam model. It is assumed that a crack divides the beam into two segments. The crack is modelled by a torsional spring connecting the beam segments to each other. The thermal load acts as an axial force on the nanobeam. Galerkin’s method is used to solve the partial differential equation of motion. The effect of the crack location, crack severity, thermal load, and nonlocal parameter on the frequencies are examined. As the crack severity increases, the frequencies decrease except the modes in which the crack locates at one of their nodes. All mode frequencies decrease at the high temperatures and increase at the low temperatures. Increasing the nonlocal parameter causes a reduction in the frequencies at any temperature. The nonlocal parameter effect on the frequencies increases at high or elevated temperatures.

Tests to estimate the heat rate effect on the flexural durability of transport vehicle gear wheels

The article presents the test results concerning the effect of thermal loads on the flexural durability of gear wheels of transport vehicle high-loaded transmissions. The tests were performed using a universal hydraulic pulsation machine and a thermal loader at five fixed temperature levels from twenty to two hundred degrees Celsius. As a result of the performed tests, a significant dependence of the flexural durability of gear wheels on their thermal state was established. In the expected maximum temperature area, corresponding to the temperature of the low tempering of the gear wheel material, it decreased sharply more than ten times.

In-situ monitoring of deformation in rapid prototyped injection molds

The ever growing demand for reducing costs and decreasing the time to market in today’s plastics industry makes rapid tooling and rapid prototyping a highly researched area. 3D printed injection mold inserts make it possible to produce prototype parts in small series fast and cost-effectively. The mechanical strength and therefore the life expectancy of 3D printed polymeric injection mold inserts are low compared to their traditional steel counterparts. In order to increase the reliability and life expectancy of polymeric mold inserts, in-situ state monitoring during injection molding is essential. In this paper, we analyse the effect of thermal and mechanical loads on the resulting strains of the mold inserts. Three series of rectangular plate products were injection molded with a different type of insert in each series. The pressure inside the cavity and the strain of the 3D printed inserts were measured during injection molding. We correlated maximal cavity pressures and changes in strain with each other in order to set up the deformation characteristic of the inserts. The results indicate a satisfactory correlation between the maximal cavity pressures and the strain change of the inserts. The second important result was that strain gauges can be applied to in-situ monitor the state of the inserts during injection molding.

Nonlinear thermoelastic fractional-order model of nonlocal plates: Application to postbuckling and bending response

This study presents a comprehensive frame-invariant fractional-order framework for the geometrically nonlinear bending and postbuckling analysis of nonlocal plates subject to combined thermal and mechanical loads. The fractional-order kinematic framework, unlike classical nonlocal formulations based on integer-order mechanics, is positive-definite and thermodynamically consistent. The positive-definite nature enables the application of variational principles to derive well-posed thermomechanical governing equations. A direct advantage of these theoretical advancements is reflected in the ability of the fractional-order approach to enable an energy-based asymptotic method obtained by extending the classical (local) Koiter’s approach. This method allows the analytical assessment of the impact of nonlocal interactions on the nature of the bifurcation and post-critical response of slender structures when subject to compressive loads. Further, the positive-definite nature of the fractional-order approach allows the development of an accurate fractional-order finite element method enabling the simulation of nonlocal structures subject to any combination of thermomechanical loads and boundary conditions. The above stated advantages are particularly important for a comprehensive and consistent analysis of nonlocal structures in the postbuckling regime. The theoretical framework is used to provide analytical and numerical insights on the effect of combined thermal and mechanical loads on the nonlinear response of nonlocal plates. Numerical results also demonstrate the high-level consistency of the framework when applied to the nonlinear thermoelastic analysis of nonlocal plates under different loading and boundary conditions.

Evaluation of Thermal Effects on Slag Cement Concrete’s Strength Properties

The physical, chemical, and mechanical characteristics of concrete change with heat-fire. The effect of thermal load on Slag cement concrete output must be measured because of the crucial role of thermal resistance in concrete structure performance and operation. This work examines the thermal resistance of Slag cement concrete. The concrete cubes were produced and cured for 28 days and then subjected to varying temperatures range of 100°C, 150°C, 200°C, 250°C, and 300°C. Hardness and compressive strength were measured at 30, 45, and 60 minutes; the sample results were compared to those of ordinary Portland cement used for the study. The findings of this experiment demonstrate that strength loss was 0.45% at 100 °C, 1.75% at 150 °C, 2.67% at 200°C, 5.98% at 250°C and 12.04 % at 300 °C, the hardness property increased from 100° to 150°C but decreased with higher temperatures. However, average concrete loss at 300 °C exceeds 20 percent of its compressive strength. This means that higher temperatures have adverse effects on concrete strength. From the test, however, it has been noted that there was an insignificant loss of strength of concrete at temperatures below 250°C and however, above 250 °C, a significant loss of concrete strength was observed. The results indicate that slag concrete has a significantly higher thermal resistance potential than traditional concrete and can be used even in industrial applications.

Effects of high thermal loads produced by interaction of accelerated plasma with steel surfaces (100Cr6, 16MnCr5, 42CrMo4)

Magnetoplasma compressor (MPC), a type of plasma accelerators , is used for treatment and alloying of steel samples: steel 100Cr6, steel 16MnCr5 and steel 42CrMo4. The high-speed plasma flow formed within the MPC, from helium with 5% of hydrogen as working gas, is directed to the surface of the samples. The energy flux density of the plasma flow in the plasma-sample interaction area is 9 J c m 2 . Plasma melts the near-surface layer and during the rapid cooling process, a thin layer with structure different from initial is created. Changes in the physical composition of the substrate are monitored depending on the number of plasma treatments. After treatment with a plasma produced within MPC, a significant improvement of hardness has been achieved. • Steel surfaces are treated with plasma formed within a special type of plasma accelerator: magnetoplasma compressor (MPC). • Every plasma shot deposit 9 J/cm 2 of energy to the surface of the treated material. • Hardness of steel 100Cr6, steel 16MnCr5 and steel 42CrMo4 is improved after treatment with plasma produced in MPC. • Smoothing of the peripheral region of the surface microrelief occurs after a sufficient number of the plasma treatments. • There is a phase change from a singly α-Fe to combination of α and γ-Fe after steel 100Cr6 has been treated with plasma pulses.

Monarch Butterfly Optimization-Based Computational Methodology for Unit Commitment Problem

—This paper provides a computational methodology based on monarch butterfly optimization (MBO) to find a solution to the problem of cost-based unit commitment (CBUC). The binary variables of unit commitment problems are handled by modifying the continuous-time nature of the monarch butterfly algorithm. Thermal unit generation, uptime, downtime, ramp rate limits as well as system reserve are considered in the test systems. The computational approach has many parts that not only minimize the cost function but also handle the mixed constraints of the commitment problem. The effect of thermal turbine valve-point loading is also taken into consideration. The computational technique has been used to solve a ten-unit original system and five scaled-up adaptations obtained from this base system. The results obtained are in agreement with the recent results available in the literature. Comparative analysis shows the effectiveness of the proposed MBO-based solution methodology in terms of operating costs and execution time in relation to other techniques.