Nader G. Zamani

A numerical study on the quasi-static axial crush characteristics of square aluminum tubes with chamfering and other triggering mechanisms

Abstract This paper presents a numerical study on the effect of triggering mechanism on the load-displacement characteristics and folding pattern of square aluminum tubes subjected to quasi-static axial crushing. Chamfering was the principal triggering mechanism investigated. The other triggering mechanisms included a triangular hole pattern, a geometric imperfection and combinations thereof. The study has shown that triggering mechanism can significantly control the folding initiation force, but its effect on mean crush force was relatively small. The effects of tube thickness and corner radius were also considered. Both folding initiation force and mean crush force increase with tube thickness. The load-displacement response does not depend appreciably on the corner radius.

NUMERICAL MODELLING OF QUASI-STATIC AXIAL CRUSH OF SQUARE ALUMINIUM-COMPOSITE HYBRID TUBES

Abstract In this paper, we have used finite element method to study the quasi-static axial crush behaviour of aluminium-composite hybrid tube containing filament wound E glass-fibre reinforced epoxy over-wrap around an aluminium tube. The fibre orientation angle in the overwrap was ±45° to the tube axis. A modified Chang-Chang failure model was used for the composite layers. The effects of adhesion and friction between the aluminium tube and the composite overwrap were examined. Excellent correlation was observed between the numerical and experimental results.

Dynamic stress concentrations for an axially loaded strut at discontinuities due to an elliptical hole or double circular notches

Abstract Numerical modeling, simulation, and analysis of axial struts with geometrical discontinuities subjected to dynamic loading conditions is the focus of this paper. Understanding how geometrical discontinuities influence the stress distribution within a structural member is critical for design applications. Furthermore, understanding how axial struts perform under dynamic loading conditions is critical in the design of automobiles, airplanes, and a large number of potentially dynamically loaded structures. A large amount of research investigating static loading conditions of struts with geometrical discontinuities has been conducted. With the development of finite element (FE) codes, numerical dynamic analyses can be completed much easier and at much lower costs than would occur for experimental methods. In this research, FE simulations were conducted on struts with centrally located elliptical discontinuities. A good correlation was found between the results from these simulations and experiments conducted using the photolaserelastic technique. Based on these correlations, models of struts with circular notches located at the sides of the strut were simulated under the same loading condition. The stress distributions of the models were studied to determine the maximum stress state for each geometric configuration. This information was used to determine the dynamic stress concentration factor for each configuration. Three-dimensional surface plots were constructed illustrating how the numerically determined dynamic stress concentration factor varies with strut and discontinuity geometry. Design equations are presented that relate the dynamic stress concentration factor to non-dimensional geometric parameters. These equations are a useful tool for engineers involved in automotive and aerospace component design.

A fast algorithm for solving the tensor product collocation equations

Abstract A fast algorithm is presented for solving the tensor product collocation equations (Ax ⊗ By + Bx ⊗ Ay)u =b, obtained from the discretization of the Poisson equation in a rectangular region by the collocation method. The Fast Fourier Transformation (FFT) algorithm is employed to achieve the above objective. The operation count is shown to be 0(N2log2N) which makes the overall calculations very economical.

An experimental and finite element investigation into the energy absorption characteristics of a steering wheel armature in an impact

Abstract Understanding the energy absorption characteristics of automotive components is necessary for the development of safe and crashworthy vehicles. This research experimentally and numerically studies the energy absorption performance of a steering wheel armature in contact with a deformable chestform (bodyform) during a collision. Variations in the location of impact on the armature, armature orientation, and chestform impact velocity are considered to investigate how these factors affect the energy absorption characteristics of the two contacting entities. By implementing standardized testing procedures (under experimental and numerical testing methods) steering wheel armature design can be evaluated and improved on in the design stage of steering wheels. Comparisons between experimental and finite element analysis testing methods were conducted and correlated using load versus displacement profiles over the duration of impact. A good relationship between the two methods was found which allows for investigation into the energy analysis of the armature and the chestform. Experimental methods do not provide a method of determining the energy absorbed by any single entity in this “deformable to deformable” contact. The energy absorbed by both structures can be experimentally determined, however, this does not provide engineers and steering wheel designers with specific information regarding the safe design of just the steering wheel armature. Numerical simulations do provide a means of quantifying the energy absorbed by specific structures in the analysis and do significantly help in isolating the energy absorption characteristics of the steering wheel armature. The results of this research show that the steering wheel armature is responsible for the majority of energy absorbed by the impact. In addition, the percentage of energy absorbed by the armature is not significantly dependent upon the location of impact and the impact velocity.

The distribution of energy absorbed by a three-spoke steering wheel armature in an impact with a deformable chestform

Abstract This research deals with experimental and finite element simulation of impacts occurring between a deformable chestform and an aluminium three-spoke steering wheel armature. Experimental testing was conducted to investigate the effect of impact location and armature orientation on the energy-absorbing capabilities of the automotive component. Numerical (finite element) models were developed to simulate the experimental process and to investigate further how the energy absorption abilities of the armature, and specific sections of the armature, vary with different impact situations. An excellent correlation between the experimental testing observations and numerical simulation results was observed for this highly non-linear problem. Most importantly, the finite element simulations have illustrated that the steering wheel armature hub and rim regions are the locations where most energy, because of plastic deformation in the structure, is absorbed. These observations provide an understanding of the characteristics of energy management in crash situations for the steering wheel armature.

A direct method for calculating the stress intensity factor in BEM

Abstract The proposed algorithm employs singular crack tip elements in which the stress intensity factor appears as a degree of freedom. The additional degrees of freedom are compensated by constraint conditions which originate from imposing continuity across elements and a contour integration formula. The two benchmark problems indicate the proposed algorithm can accurately predict the stress intensity factor and the distribution of the primary and secondary variables in fracture problems.

Collocation finite element solution of a compressible flow

In this paper, the subcritical compressible small disturbance equation is employed to simulate the nonlifting flow over a 6% thick circular arc. The governing nonlinear elliptic boundary value problem is solved numerically with the collocation finite element technique using the Hermite bicubic shape functions. The lack of quadrature calculations makes the overall simulation fast and accurate. The calculation results are compared with experimental measurements supporting their validity.

A finite element based collocation method for eigenvalue calculations

Abstract The Method of Weighted Residuals (MWR) is a powerful tool in solving boundary value problems. A particular MWR is the “collocation method”. The main theme of this paper is eigenvalue calculations with the collocation method. The bench mark problems considered are second and fourth order differential operators in one dimension and a Helmholtz eigenvalue problem in two dimensions.

Effect of Combined Cold Temperature and Fatigue Load on Performance of G40.21 Steel

Many structures such as bridge decks and ship hulls are required to withstand fatigue load cycles throughout their service life. These structures are also required to withstand zero and subzero temperatures if located in northern and Arctic regions, where winter temperatures can drop down to −40°C. The combined effects of cold temperature and cyclic loads can lead to potential damage to the material performance and subsequent failure. In this study, CSA G40.21 350WT steel, which is typically used in ship building, was tested in strain-controlled fatigue load cycles to determine the effect of zero and subzero temperatures on the mechanical properties and fatigue life. The experimental results show a significant effect of temperature on the fatigue life of this steel. The tensile strength was not affected by low temperatures. The yield strength and fracture strength increased and the ductility decreased at low temperatures. This paper discusses the test procedure, test parameters, and test data obtained from this study.