Variational principles employing independent rotation fields are investigated. In the two-dimensional case these lead to membrane elements with “drilling degrees of freedom”, of practical use in shell analysis. We argue that convenient interpolatory patterns require modifications of the classical variational framework. Several formulations are proposed and shown to be convergent for displacement/rotation interpolations of all orders.

On drilling degrees of freedom

Modeling dressed characters is known as a very tedious process. It u sually requires specifying 2D fabric patterns, positioning and assembling them in 3D, and then performing a physically-bas ed simulation. The latter accounts for gravity and collisions to compute the rest shape of the garment, with the ad equate folds and wrinkles. This paper presents a more intuitive way to design virtual clothing. We start w ith a 2D sketching system in which the user draws the contours and seam-lines of the garment directly on a v irtual mannequin. Our system then converts the sketch into an initial 3D surface using an existing method based on a p recomputed distance field around the mannequin. The system then splits the created surface into different pan els delimited by the seam-lines. The generated panels are typically not developable. However, the panels of a realistic garment must be developable, since each panel must unfold into a 2D sewing pattern. Therefore our sys tem automatically approximates each panel with a developable surface, while keeping them assembled along the s eams. This process allows us to output the corresponding sewing patterns. The last step of our method computes a natural rest shape for the 3D gar ment, including the folds due to the collisions with the body and gravity. The folds are generated using procedu ral modeling of the buckling phenomena observed in real fabric. The result of our algorithm consists of a realisticlooking 3D mannequin dressed in the designed garment and the 2D patterns which can be used for distortion free texture mapping. The patterns we create also allow us to sew real replicas of the virtual garments.

/pdf/virtual-garments-a-fully-geometric-approach-for-clothing-22pcg7a7uy.pdf

Virtual Garments: A Fully Geometric Approach for Clothing Design

Progress update on failure mechanisms of advanced thermal barrier coatings: A review

Thermal protection systems (TPS) are designed to protect re-entry space vehicles from the severe heating encountered during hypersonic flight through a planet’s or the earth’s atmosphere. A carbon–phenolic ablative TPS was developed, manufactured and tested with the aim of fulfilling the thermal and mechanical requirements corresponding to the actual loads experienced by a vehicle during a moon-earth re-entry. Experimental activities were carried out on two different composite systems (a resole resin coupled with a graphitic felt and a graphitic foam), and were aimed to the optimization of the manufacturing procedure and to the characterization of the mechanical behaviour and of the insulation performance of the fabricated composites.

Carbon-phenolic ablative materials for re-entry space vehicles: Manufacturing and properties

Topic Collections Related Content Customize your page view by dragging and repositioning the boxes below. Related Journal Articles Filter by Topic > Homogenization of Reticulated Structures Appl. Mech. Rev (July, 2001) Research Advances in the Dynamic Stability Behavior of Plates and Shells: 1987â€“2005â€”Part I: Conservative Systems Appl. Mech. Rev (March, 2007) Historical review of Zig-Zag theories for multilayered plates and shells Appl. Mech. Rev (May, 2003) [+] View More Related Proceedings Articles Filter by Topic > A Combined Experimental-Numerical Method to Evaluate Powder Thermal Properties in Laser Powder Bed Fusion MSEC2018 (2018) A Simplified and Efficient Analysis of Morton Effect GT2018 (2018) Thermal Transport in Thorium Dioxide IMECE2017 (2017) [+] View More Related eBook Content Various Structures Design of Plate and Shell Structures> Chapter 12 Axially Loaded Members Design & Analysis of ASME Boiler and Pressure Vessel Components in the Creep Range> Chapter 2 Members in Bending Design & Analysis of ASME Boiler and Pressure Vessel Components in the Creep Range> Chapter 3 [+] View More Sections PDF Email Share Get Citation Get Alerts Some tools below are only available to our subscribers or users with an online account. SEARCH ADVANCED SEARCH Search Applied Mechanics Applied Mechanics Heat Transfer About ASME Digital Collection Email Alerts Library Service Center ASME Membership Contact Us Publications Permissions /Reprints Privacy Policy Terms of Use © 2019 ASME The American Society of Mechanical Engineers Journals Submit a Paper Announcements Call for Papers Title History Conference Proceedings About ASME Conference Publications Conference Proceedings Author Guidelines Conference Publications Toolbox eBooks About ASME eBooks Press Advisory & Oversight Committee Book Proposal Guidelines This site uses cookies. By continuing to use our website, you are agreeing to our privacy policy. | Accept Loading [Contrib]/a11y/accessibility-menu.js

Thermal Buckling of Plates and Shells

Curved beam element stiffness matrix formulation

Free vibration of skew laminates

The linear buckling analysis of laminated composite cylindrical and conical shells under thermal load using the finite element method is reported here. Critical temperatures are presented for various cases of cross-ply and angle-ply laminated shells. The effects of radius/thickness ratio, number of layers, ratio of coefficients of thermal expansion, and the angle of fiber orientation have been studied. The results indicate that the buckling behavior of laminated shell under thermal load is different from that of mechanically loaded shell with respect to the angle of fiber orientation. Content H IGH-speed aerospace vehicles consisting of thin-shell elements are subjected to aerodynamic heating. This induces a temperature distribution over the surface and thermal gradient through the thickness of the shell. The compressive stresses, which in these circumstances develop, may cause buckling. Recently fiber-reinforced, laminated composites have begun to be used extensively in aerospace vehicle construction due to the high specific properties of the composites. In view of the above, the thermal buckling analysis of laminated composite shell assumes importance. Thermal buckling of isotropic cylindrical and conical shells have been reviewed by Bushnell. 1 Chang and Card2 investigated thermal buckling of stiffened, orthotropic, multilayered cylindrical shells. The governing equations obtained through the minimization of the total potential energy were solved by the finite difference technique with a few cases of practical problems. Nevertheless, this technique cannot be extended to other complex geometries and loading conditions. In this paper the Semiloof shell element formulated by Irons,3 which was adapted by the authors for thermal stress analyses of laminated plates and shells,4 is being extended to thermal buckling problems. The derivation of governing equation is a standard procedure, which uses the principle of minimum total potential energy. The characteristic finite element equilibrium equation thus obtained is [Ks] [q] = [F] where [Ks] is the structural stiffness matrix, [q} is the nodal displacement vector and [F] is the consistent nodal load vector. In order to establish the critical buckling state corresponding to the neutral equilibrium condition, the second variation of the total potential must be equated to zero, which gives rise to the condition, | [Ks] + \[Kg] j = 0, where [Kg] is the geometric stiffness matrix and X is the eigenvalue. The computer program (COMSAP) developed based on this formulation can handle general temperature variations, lamination parameters, and various boundary conditions. The material properties considered in the analysis of laminated shells are En/En = 10, Glt/Ett = 0.5,

Thermal buckling of laminated composite shells

Finite element analysis of laminated shells with exact through-thickness integration

An integrated thermomechanical modeling of response of low-temperature ablative thermal protection system under thermal loading encountered by reentry vehicles is presented. Of the three thermal protection mechanisms, thermal, chemical, and mechanical ablations, only the latter is assumed to influence the recession in the presence of aerodynamic surface shear for materials with low shear strength at higher temperatures. A model for the mechanical ablation (erosion) is presented that is based on the matching point scheme. The degenerated doubly curved shell element is employed in the modeling. This enables consideration of the general type of aerodynamic loads, distributed and varying with surface and time coordinates, which differs from the earlier studies reported in the open literature. The finite element method uses polynomial approximation to represent the nonlinear through-thickness temperature profile and explicit-through-thickness integration in the computation of element matrices. This brings in computational efficiency without loss of numerical accuracy, particularly in the context of multilayered construction. No attempt is made to compute the incident heat flux and other aerodynamic loads. Numerical examples are presented for specified loads to bring out the influences of material properties and heating rates on surface recession and are based mostly on assumed material properties.

R. Palaninathan

Papers

Curved beam element stiffness matrix formulation

Free vibration of skew laminates

Thermal buckling of laminated composite shells

Finite element analysis of laminated shells with exact through-thickness integration

Modeling of Mechanical Ablation in Thermal Protection Systems