Modeling Creep Analysis of Thermally Graded Anisotropic Rotating Composite Disc

Mathematical modeling for steady-state creep has been done for an anisotropic disc of aluminium-silicon carbide particulate composite rotating at elevated temperatures under a thermal gradient. Creep modeling and analysis has been done using Hill’s yield criterion for a disc operating under a parabolic distributed temperature and its comparison is made with the disc operating under uniform temperature throughout the radius. The results are expressed graphically in designer friendly manner for the stress and strain rate distributions under a graded temperature field. It can be seen that the parabolic temperature field has a significant effect on the creep behavior of the anisotropic disc. Thus, the temperature gradient effect should be considered while designing the anisotropic rotating disc.

Creep Analysis in Anisotropic Composite Rotating Disc with Hyperbolically Varying Thickness

Steady state creep in a anisotropic rotating disc made of Al-SiCp composite having hyperbolically varying thickness has been investigated using Hill’s yield criterion. The creep behavior is supposed to follow the Sherby’s law in present study. The stress and strain distributions are calculated for different combinations of anisotropic constants. The change in the radial stress is not significant while the tangential stress is changed with the change in the material constants. The tangential strain rates are highest at the inner radius of the disc and then decreases towards the outer radius of the disc. The radial strain rate which is compressive in nature becomes tensile in middle of the disc for some specific values of anisotropic constants. The study reveals that the anisotropy has a significant effect on the creep behavior of rotating disc. Thus for the safe design of the rotating disc the effect of anisotropy should be taken care of.

Numerical Modelling of the Compression Behaviour of Single-Crystalline MAX-Phase Materials

In this article a numerical model to describe the mechanical behaviour of nanophased singlecrystalline Ti3SiC2 is proposed. The approach is a two dimensional finite element periodic unit cell consisting of an elastic matrix interlayered with shear deformable slip planes which obey the Hill’s yield criterion. The periodic unit cell is used to predict compression material behaviour of Ti3SiC2 crystals with arbitrary slip plane orientations. Stress strain relationships are derived for Ti3SiC2, and the effect of slip plane volume fraction as well as orientation of the slip planes are investigated. The two main deformation mechanisms of the material namely; ordinary slip and so called kinking are considered in the study.

Limit Load of Anisotropic Components Using the M-Beta Multiplier Method

The mβ-multiplier method is based on Mura’s extended variational theorems in plasticity, and has been applied previously to isotropic components containing notches and cracks. Lower bound limit loads rapidly converge to inelastic analysis results when the method is used in conjunction with elastic modulus adjustment procedures. In this paper, the mβ-multiplier method is applied to pressure components exhibiting anisotropy. Specifically, the method is applied to the limit load determination of a heat exchanger tubesheet, wherein the tubesheet is modeled as an equivalent solid plate with anisotropic properties. Results are presented for a finite element model where plasticity is represented with Hill’s yield criterion, and a model using a fourth order yield criterion that accounts for compressibility of the tubesheet.

Design Sensitivity Analysis and Optimization of Nonlinear Anisotropic Structures

Nonlinear analysis of anisotropic structures is described by using Hill's yield criterion that anisotropic yield contour is assumed to be retained its shape during the hardening process. Nonlinear constitutive equation of anisotropic material is derived using plastic potential concept. Linear strain hardening model is utilized and forward Euler method is employed as a stress integration method. Newton-Raphson method is implemented for numerical nonlinear analysis. Direct differentiation method differentiating directly the equilibrium equation with respect to design variables is applied to design sensitivity analysis of nonlinear anisotropic plate. The results of design sensitivity analysis are compared with those of finite difference method to verify the accuracy. Optimization is accomplished for a rectangular plate using evaluated sensitivity coefficients.

Limit Load of Anisotropic Components Using the M-Beta Multiplier Method

The mβ multiplier method is based on Mura’s extended variational theorems in plasticity, and has been applied previously to isotropic components containing notches and cracks. Lower bound limit loads rapidly converge to inelastic analysis results when the method is used in conjunction with linear matching techniques. In this paper, the mβ-multiplier method is applied to pressure components exhibiting anisotropy. Specifically, the method is applied to the limit load determination of a steam generator tubesheet, wherein the tubesheet is modeled as an equivalent solid plate with anisotropic properties. Results are presented for a finite element model where plasticity is represented with Hill’s yield criterion, and a model using a fourth order yield criterion that accounts for compressibility of the tubesheet.

Analysis of a Tubesheet Undergoing Rapid Transient Thermal Loading

Some Class I CANDU heat exchanger tubesheets experience very high in-plane thermal gradients under Level A/B transients. If the thermal stresses exceed the ratcheting limit of the ASME Boiler and Pressure Vessel Code, shakedown has to be demonstrated by an elastic-plastic analysis. The choice of the plasticity model and its parameters must ensure that shakedown is predicted only if it occurs in reality. Differences to uniaxial modeling are discussed, and a conservative way of predicting shakedown is presented. The perforated region of the tubesheet is replaced by an equivalent solid plate with anisotropic yield properties (Hill’s yield criterion). A lower-bound shakedown limit for this material is derived. An example analysis is presented that has been performed using a commercial finite element code. [S0094-9930(00)00303-6]