Forces in mechanics最新文献

In this paper, authors have investigated the heat transference rate of stagnation point flow of a nanofluid over a stretching sheet in a porous medium. The authors have examined the magnetohydrodynamic viscous flow of nanofluid. The transport equations involve Brownian motion and thermophoresis effects. The properties of heat transfer of nanofluids are acknowledged via a numerical algorithm. Diffusivity and conductivity characteristics of fluid are relying on nanoparticles volume fraction and the model is based on energy, momentum, mass conservation, and concentration equations. For the physical significance of the flow model, authors have utilized the zero mass flux condition at the surface. Similarity transformations are used to convert the PDEs (Nonlinear Partial Differential Equations) into a set of coupled ODEs (Ordinary Differential Equations). A built-in bvp4c algorithm in MATLAB software produces convergent implications of nonlinear systems. An exhaustive analysis of pertinent parameters, magnetic, porosity, heat source/sink parameter, etc, is done for clarification of the physical significance. The higher far-field velocity causes the temperature to rise but the heat transfer rate to reduce at the surface. The zero mass flux condition relates to the higher concentration of nanoparticles at the far field in comparison to the surface.

The primary obstacles to utilizing additively manufactured metallic alloys in industry are their inadequate ductility and manufacturing imperfections. Defects in the alloys can result in stress concentration, which can further deteriorate their tensile ductility and fatigue performance. In this study, defect tolerant design methods based on physics are explored to forecast the fatigue performance of 17-4 PH stainless steel that has been additively manufactured. A cyclic plastic zone size-based finite element approach is proposed in this work to predict the fatigue performance of additively manufactured alloys. Initially, defects will be identified from the microstructure of the material, and a finite element model will be created from the microstructure; then, a kinematic hardening model will be used to determine the size of cyclic plastic zone around all defects. The largest size of cyclic plastic zone will cause failure and be identified as a killer defect, and the fatigue life will be calculated on the basis of that killer defect. The proposed method predicts the fatigue life of additively manufactured alloys well.

This numerical study is dedicated to investigating the ballistic performance of three-component integral body armor comprising ceramic façade, layers of ultra-high molecular weight polyethylene fiber-based composite (Dyneema) and closed-cell aluminum foam against NIJ-Type IV armor-piercing bullets. A numerical model of integral armor with a ceramic façade and a fiber-reinforced composite backing plate was developed in IMPETUS Afea Solver and verified against experimental data. The verified model was used to design a "baseline configuration" of two-component integral armor that can stop the NIJ-Type IV projectiles. Three-component armor configurations were obtained by introducing layer(s) of closed-cell aluminum foam into the laminate. Laminates with different stacking sequences of composite and porous layers and different foam relative densities were studied and compared with the baseline two-component configuration. The study presents new insights into the mechanics of perforation of integral armor with closed-cell foam and provides design recommendations for such armor systems.

The fracture criterion is a critical topic in fracture mechanics. However, the equality of J-Integral (J) and energy release rate (G) has not been numerically verified under large strain theory. This paper aims to numerically justify the condition for equality in brittle and small-scale plastic fracture. The computation of the J in this study was performed using the commercial finite element program LS-DYNA and postprocessor LS-PrePost. The G was measured by node release method in LS-DYNA. Our result numerically verified the equality of G = J in elasticity, but not in plasticity. This is also supported by the analytical derivation. The critical energy release values in this work are considered in a reasonable range compared with experiment data. Note: The entire paper, with the exception of equations, was rephrased using ChatGPT. This was achieved by requesting ChatGPT to rewrite the original manuscript written by humans, paragraph by paragraph.

A novel hybrid experimental-computational study is performed to predict the flow fields and pressure distributions on the measured three-dimensional shapes of flexible, three-tab asphalt roofing shingles undergoing increasing uplift when exposed to hurricane velocity winds for two hours. To quantify the evolution of shingle shapes, StereoDIC analysis is used to measure the transient, full-field deformed shapes of full-sized, three-tab asphalt shingles that did not show separation or failure when subjected to hurricane velocity winds for two hours. Based on physical observations during wind loading, the authors performed steady state computational fluid dynamics (CFD) simulations to predict the full-field pressure distributions on as-measured, uplifted three-dimensional shingle shapes at selected time instances during wind loading.

Simulation predictions clearly show flow recirculation regions on both the front and top of the shingles that remain attached throughout wind loading and control the full-field uplift pressure distribution. For low velocity flow with maximum uplift ≤ 8.4 mm, CFD-predicted pressures are in good agreement with prior measurements. For both low and high-speed flows, the model predictions indicate that high pressures are formed at the leading-edge, upstream of the sealant layer, with maximum pressure occurring near the tab cutouts along the leading-edge of the shingle, providing a physical basis for the observed higher uplift and increased potential for shingle failure in these regions. The combined experimental-computational studies provide a contemporary way to eliminate the difficulties associated with attachment of pressure sensors to flexible materials that can alter shingle response, providing the basis for future design improvements by delineating the physical processes controlling pressure loading and shingle uplift in hurricane velocity winds.

Plenty of research papers are available on the static and free vibration analysis of single-layer FG shells, however, literature on the analysis of FGM sandwich shells of double curvature is limited. Especially, the authors have not found any paper on the analysis of hyperbolic and elliptical paraboloid FGM sandwich shells. Therefore, FGM sandwich shallow shells with double curvature are analyzed in this study for the static and free vibration conditions. Face sheets of sandwich shells are made up of functionally graded material whereas the core is made up of isotropic material. A functionally graded material considered herein is a combination of alumina and aluminum. Sandwich shallow shells on rectangular planform are modeled using various equivalent single-layer shell theories via unified formulation considering the effects of shear deformation and rotary inertia. Different shell theories recovered from the present unified formulation satisfy the transverse shear stress-free conditions on the lower and upper surfaces of the shell. Hamilton's principle is applied to the present unified formulation for establishing equations of motion. Solutions to free vibration and static problems of simply-supported sandwich shells are obtained using Navier's technique. The numerical results of frequencies, displacements, and stresses are obtained for various types of shells, different sandwich schemes, different values of the power-law factor, and radii of curvature. The results available in the literature are used for the comparison of the present results and found in good agreement with those. However, many new and useful results are also reported in this paper for the reference of readers.

This paper presents the bending analysis of functionally graded material (FGM) plates using sinusoidal shear and normal deformation theory. The in-plane displacements include sinusoidal functions in the thickness coordinate to consider the effect of transverse shear deformation, and transverse displacement includes the effect of transverse normal strain using the cosine function in thickness coordinate. The displacement field of the theory enforces to satisfy shear stress-free boundary conditions on the top and bottom surfaces of the plate with realistic variations across the thickness. Plate material properties vary across thickness directions according to a power law. The boundary value problem of the theory is derived using the principle of virtual work. Simply supported plate bending problems are solved using the Navier solution technique. Response of the plate is obtained with respect to the type of load, type of plate, aspect ratio, and power law index. The results of present theory are compared with those of quasi-3D discrete layer theory and semi-analytical solutions based on the theory of elasticity to ensure the accuracy of theory. The current theory showed excellent agreement with more exact theories in bending response.

DMR 249A is a micro-alloyed high strength low alloy (HSLA) steel particularly designed for shipbuilding structures due to its excellent strength-to-weight ratio. In this investigation, the rotating-beam fatigue test was performed on the flux-cored arc welded (FCAW) butt joints of DMR 249A steel. And the fatigue test results compared to mechanical properties and microstructural characteristics. The transverse tensile, microhardness, impact, and fatigue properties were evaluated from across the butt weld. The S-N curve was constructed from the experimental data for the stress ratio R = -1. The evaluated fatigue life of the FCAW joint and parent metal was 366 MPa and 394 MPa, respectively. The maximum achieved transverse tensile strength and impact energy absorption of the FCAW joint was 578 MPa &174 J. The weld region contains an acicular ferrite microstructure, which exhibited improved properties of strength, toughness, and fatigue crack resistance. From the results, the fatigue strength of FCAW is 92.8% that of the parent metal and 62.8% equal to the tensile strength of the FCAW joint.

Heat transfer in Carreau–Yasuda fluid with mixed convection, effect of Cattaneo–Christov model of heat flux past a vertical flat plate has been studied in this paper. Using appropriate transformations, governing PDEs are reduced to higher order non-linear non-dimensional ODEs and subsequently these are solved using “bvp4c” package of MATLAB. The Carreau–Yasuda fluid is used to explore the behaviour of fluids having shear-thinning and shear-thickening characters for several values of the parameter called power law exponent involved in the fluid model. The effects of different physical parameters, such as Weissenberg number(We), thermal relaxation parameter(α), Carreau–Yasuda fluid parameter(d), mixed convection parameter(λ) and Prandtl number(Pr) on velocity and temperature has been investigated and depicted through graphs. Results reveals that for lower value of Pr velocity of fluid enhances with higher value of λ and reverse effect is witnessed for larger Pr. Also, velocity rises for shear-thinning fluid(STNF) and decreases for shear-thickening fluid(STKF) with We and d. Temperature exhibits growing behaviour for Cattaneo–Christov model of heat flux near the plate in comparison with Fourier's model, whereas velocity exhibits growing behaviour with α. For larger We, temperature in Carreau–Yasuda model upsurges for STKF and falls for STNF. The surface drag-force displays higher values for both STNF and STKF with growth in $\lambda$. The cooling rate rises/declines with We for STNFs/STKFs.