Development of finite element analysis program and simplified formulas of bellows and shape optimization

A bellows is frequently applied in piping systems for absorbing mechanical movement. Its geometry is an axial symmetric shell, which is composed of two toroidal shells and one annular plate. The mechanical behavior of U-shaped bellows under axial force and internal pressure is estimated by changing the dimensions of the geometric parameters. The changing ranges of the geometric dimensions is so selected as to invest the results with practical environments in many fields. The minimization of strength and spring rate is considered simultaneously as a multiple objective function. The weighting objective method is implemented, in which a vector function is transformed to a scalar function. The structure is analyzed by the energy method for toroidal sections. Optimization is carried out by the Recursive Quadratic Programming algorithm.

A unified Fourier series solution for vibration analysis of FG-CNTRC cylindrical, conical shells and annular plates with arbitrary boundary conditions

The present study deals with the free torsional vibration of a composite conical shell made of a polymeric matrix reinforced with carbon nanotubes (CNTs). Distribution of CNTs across the thickness of the conical shell may be uniform or functionally graded. Five different cases of functionally graded reinforcements are considered. First-order shear deformable shell theory compatible with the Donnell kinematic assumptions is used to establish the motion equations of the shell. These equations are two coupled equations which should be treated as an eigenvalue problem. The generalized differential quadrature method is used to obtain a numerical solution for the torsional frequency parameters and the associated mode shapes of the shell. After validating the results of this study for the cases of isotropic homogeneous cone and annular plates, parametric studies are carried out to analyze the influences of geometrical characteristics of the shell, volume fraction of CNTs, and grading profile of the CNTs. It is shown that volume fraction of CNTs is an important factor with regard to torsional frequencies of the shell; however, grading profile does not change the torsional frequencies significantly.

Vibration analysis of laminated composite conical shells by the method of discrete singular convolution based on the shear deformation theory

In view of safety design against fatigue failure in cylindrical storage tank of low temperature use, low cycle and low temperature fatigue bebaviour of shell to annular tee-fillet welded joint in tank was investigated experimentally and analytically, in case of liquefied propane gas tank, using a displacement-controlled bend test of model specimens.The experiments and analyses were done either by strain and displacement measurements around weld toe in annular plate under cyclic deformation or by finite element analysis mainly to clarify quantitatively the effects of type of weld joint as well as dimensions of weld joint, including the effects of annular plate thickness, on the fatigue crack initiation life of tank.Principal results obtained are as follows.(1) In bend test of model specimen, a distribution of strain range in front of weld toe indicates that its maximum value is found at weld toe as far as the deformation range examined, although maximum value of strain distribution is found at 510mm distant from weld toe under large extent of deformation.(2) Experiments and analyses show that there is no difference practically between fillet weld joint and full penetration joint in cyclic deformation as well as in fatigue strength.(3) The expression of evaluating the fatigue crack initiation life in the displacement controlled bend test of model specimen was derived in terms of weld joint parameters, which isNc=2.3×1015·ρ0.35/Δδp3.78t3.86 (SL) 0.19 (unit in mm) where Nc, ρ, Δδp, t, SL denotes fatigue crack initiation life, weld toe radius, displacement range at the loading point, annular plate thickness, and leg length of shell plate respectively.(4) By introducing a parameter θS-A, an angle which defines an extent of deformation around weld toe, the fatigue crack initiation life in tank is predicted from the results on model specimen.(5) The finite element analysis shows that as to the bend test on model specimen, the increase of annular plate thickness decreases the initiation life in displacement controlled test, and increases it in load controlled test. However, the incorporation of the results on model specimen to the behaviour in deformation of the tank indicates that these two expressions are essentially the same as far as the fatigue crack initiation in tank concerned. As of now, it seems that the thicker the annular plate becomes the longer the fatigue crack initiation life in this type of tank.

In the context of classic conical shell formulation, nonlinear forced vibration analysis of truncated conical shells and annular plates made of multi-scale epoxy/CNT/fiberglass composites has been presented. The composite material is reinforced by carbon nanotube (CNT) and also fiberglass for which the material properties are defined according to a 3D Mori-Tanaka micromechanical scheme. By utilizing the Jacobi elliptic functions, the frequency-deflection curves of truncated conical shells and annular plates related to their forced vibrations have been derived. The main focus is to study the influences of CNT amount, fiberglass volume, open angle, fiber angle, truncated distance and force magnitude on forced vibrational behaviors of multi-scale truncated conical shells and annular plates.

Vibro-acoustic analysis of double-walled cylindrical shells through a novel semi-analytic method

Discontinuity effects at cone-cone axisymmetric shell junctions

Background: Functionally graded material (FGM) is popularly recognized as promising material for modern engineering applications, which has gained attention of researchers due to its composition design and mechanical behaviour. FGM is the most suitable choice as a structural material for conical pressure vessel and requires detailed analysis for its mechanical behaviour. Objective: The design optimization of the rotating truncated conical shell made from FGM subjected to internal pressure (variable and constant) using Finite Element Method. Method: Using a commercially available finite element code, the effect of various parameters (such as cone angle, internal pressure, and angular velocity) on truncated conical shell was analyzed. The material properties and composition vary along the radial direction according to the exponential function. Results: Under the chosen circumstances 10¹ cone angle, 4-12MPa internal pressure, and 50 rad/sec rotational velocity were found most suitable. Conclusion: The results also demonstrated that chosen parameters (such as, cone angle, internal pressure, and rotational velocity) significantly affect the stresses working on conical shell. This requires careful selection while designing the conical pressure vessel. These optimization results are helpful for research community to design a conical shell pressure vessel using FGM.

The influence of weld-improving method on fatigue strength enhancement and thickness effect was studied through the experiments on fillet-welded Tee joints under bending stress. To clarify the thickness effect of improved joints, fatigue tests for three kinds of improving methods such as toe grinding, TIG dressing, shot peening were carried out on the joints with thicknesses of 10, 22, 40 and 80 mm. Furthermore, five kinds of weld treatments were applied on 40 mm thick joints to investigate enhancement in fatigue strength. These results were compared with that of as-welded joints. In addition to the experiment, finite element analyses (FEA) were conducted on both Tee and cruciform joints to study the effect of stress distribution.Main results of the study are summarized as follows ;(1) The thickness effect for toe grinding is smaller than that of the as-welded joints. TIG dressing and shot peening have almost the same thickness effect as that of the as-welded joints.(2) The thickness effect exponent of effective stress concentration factor by FEA well corresponds to that of experiments, and explains the difference between the as-welded and toe-ground joints. The thickness effect for fatigue crack propagation life by analysis is rather small.(3) Not only the main plate thickness but the rib plate thickness should be considered in the evaluation of thickness effect. This combined effect can be expressed by a multiplication form of thickness effects for main plate and rib plate.(4) The fatigue strength of the toe-ground joints is highest among all the test series. The enhancement in fatigue strength by weld improvement is mainly due to the increase of fatigue strength for crack initiation.

Objective To evaluate the biomechanical characteristics of 4 fixation methods (single reconstruction plate, dual reconstruction plates, single cannulated screw and dual cannulated screws) in the treatment of pubic symphysis disruption. Methods Miniature spiral CT scans were performed on the complete pelvis in 5 healthy volunteers. The primary two-dimensional CT scan data at DICOM format were imported into software Mimics 15.0 for three-dimensional reconstruction of bilateral hips and sacrums. The finite element model of skeletal pelvis was obtained by grid partitioning and assignment using software Abqus 6.13. Models of pubic symphysis disruption were simulated by cutting off the unilateral sacroiliac ligament, sacral spine ligament, sacral tuberosity ligament, pubic ligament and pubic arch. Four implants(single reconstruction plate, dual reconstruction plates, single cannulated screw and dual cannulated screws) were simulated and emplaced onto the models according to standard surgical procedures. Compressive and rotational loads were implemented in all models for finite element analysis. The biomechanical properties were recorded and analyzed, including construct stiffness, micromotion of the pubic symphysis and von Misses stress. Results Under vertical load, the space of pubic symphysis disruption >25 mm. The vertical stiffness and rotational construct stiffness of the pelvis decreased significantly from 442.738±29.946 N/mm and 10.118±1.432 N·m/Deg in the normal group to 14.754±0.876 N/mm and 0.328±0.119 N·m/Deg, respectively. Dual reconstruction plates and dual cannulated screws displayed the best vertical tensile strength; their construct stiffness achieved 117.647±9.193 N/mm and 131.443±4.348 N/mm, respectively. Under anti-rotation load, dual cannulated screws displayed the best performance because they rebuilt 68.6% of the whole structural stiffness. For the local stability of the pubic symphysis, dual reconstruction plates showed a strong local anti-rotation capability and dual cannulated screws a good local anti-tensile capability. The displacement in the dual cannulated screws group was only -0.240±0.119 mm under vertical load while the angular displacement in the dual reconstruction plates group only 0.218°±0.182°. Single reconstruction plate endured the maximum von Misses stress which was obviously concentrated. Conclusion Dual cannulated screws may have biome-chanical advantages for treatment of pubic symphysis disruption. Key words: Pelvis; Finite element analysis; Biomechanical characteristics; Fractures fixation, internal; Comparative study

Hot Mix Asphalt Recycling: Practices and Principles

<div class="htmlview paragraph">A set of methods is described to calculate boundary conditions for thermal and mechanical finite element (FE) analyses and to assess and present the results of those analyses in a clear and understandable way. The approach utilizes a combination of engine simulation programs and an empirical database of engine measurements developed over many years. The methodology relies on the use of specialized FE pre- and post-processors dedicated to the analyses of engine components.</div> <div class="htmlview paragraph">Gas-side thermal boundary conditions for combustion chamber components are calculated using an engine simulation code for standalone FE analyses or for FE analyses directly coupled to the engine simulation code itself. Coolant side boundary conditions are calculated using multidimensional flow analysis (computational fluid dynamics). Boundary conditions in intake and exhaust manifolds are calculated using a one-dimensional gas dynamics code.</div> <div class="htmlview paragraph">Thermo-mechanical analysis results are assessed and presented using dedicated post-processing tools to determine the effects of temperature on local material strength, and to calculate distributions of safety factor against ultimate strength, yield strength and fatigue strength. New methods of results presentation are described for the analysis of cylinder bore distortion, piston-liner interaction, cylinder liner cavitation and valve seat wear.</div>

The goal of optimal shape design problems is to find a shape of the structure, belonging to an apriori defined class U ad and minimizing a cost functional J on U ad . Shape optimization of systems, governed by equations is now more or less standard. On the other hand there exist a lot of problems where the mathematical model leads to the so called variational inequality. It is the aim of this contribution to extend optimal shape design problems to systems described by variational inequalities. It is well known that the optimal control of such systems has one specific feature, namely the problem is non-smooth. Here we deal with one of the most typical applications of variational inequalities in solid mechanics, namely with the so called contact problems for linearly elastic bodies. A detailed mathematical analysis can be found in [3].KeywordsVariational InequalityContact ForceContact ProblemElastic BodyOptimal ShapeThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

This paper is concerned with shape optimization problems by the boundary element method (BEM) emphasizing the use of a reduced basis reanalysis technique proposed recently by the author. Problems of this class are conventionally carried out iteratively through an optimizer; a sequential quadratic programming-based optimizer is used in this study. The iterative process produces a succession of intermediate designs. Repeated analyses for the systems associated with these intermediate designs using an exact approach such as the LU decomposition method are time consuming if the order of the systems is large. The newly developed reanalysis technique devised for boundary element systems is utilized to enhance the computational efficiency in the repeated system solvings. Presented numerical examples on optimal shape design problems in electric potential distribution and elasticity show that the new reanalysis technique is capable of speeding up the design process without sacrificing the accuracy of the optimal solutions.