Jin San Ju

The Analytical Trial Function Method (ATFM) for Finite Element Analysis of Plane Crack/Notch Problems

A new technique, Analytical Trial Function Method (ATFM), is proposed to formulate new finite element models for analysis of plane crack/notch problems. A new analytical finite element, named ATFM-CN, is successfully constructed. Furthermore, in order to determine the eigenvalues of the crack/notch problems, which utilized in above analytical trial functions, a modified sub-region accelerated Müller method is also suggested. Numerical examples show the present approach exhibits excellent performance in the analysis of stress-singularity problems.

Fracture Analysis for Damaged Aircraft Fuselage Subjected to Blast

This paper primarily presents the development and application of automation computational analysis techniques to determine the dynamic stress intensity factor for the damaged aircraft fuselage subjected to triangle blast load. A program based on automated procedure to simulate cracked fuselage is developed. It may create 3-dimention panel model using parameterization. The stress around the crack tips will be captured and the dynamic stress intensity factor can be obtained at every moment of the blast automatically. A typical curved panel model which consists of 7 frames and 8 stringers is calculated. The calculation results shown that the form of the dynamic SIF curve is similar to that of the triangle load curve while the peak point of dynamic SIF curve occurs a little later than that of the load curve due to the inertia effect. The longer the crack is, the more obvious the effect is. The peak SIF value of the crack under blast load is bigger than that under the static load for certain crack length. The longer the crack is, the bigger the difference between the dynamic peak SIF value and static SIF is. At the same time, the load time has effect on the dynamic SIF curve and its peak value. These results show good agreements with theoretical principles.

Global-Local Hierarchical Analysis Techniques for Damaged Aircraft Fuselage Considering Bulging Deformation of Crack

In order to calculate the fracture parameters (Stress intensity factor) in a complicated 3- dimention aircraft model with damage in the aircraft panel, a new two steps global-local hierarchical analysis strategy is used. This paper primarily describes the development and application of advanced computational analysis techniques to determine stress intensity factors for the damaged panels based on the two steps hierarchical analysis strategy from global to 3-D local model, the bulging deformation of crack can be considered in the local model. A fracture parameter calculation programme based on automated global-local procedure to simulate cracked aircraft panel tests is developed for the hierarchical strategy. This programme may create models of two stages, transfer boundary conditions, calculate and obtain fracture parameter automatically. Finally, this paper presents some of the experimental data and the calculated fracture parameters are compared with the experimental results.

Finite-Element Analysis of Ultrahigh Leaf-Shaped Steel Sculpture

In this paper, a three-dimensional model of a steel sculpture was analyzed by using the finite element software ANSYS. The structural static response were achieved respectively under gravity load, ice load and wind load based on wind tunnel tests with the dynamic response under earthquake action. Besides, the structural parameters such as strength and stiffness under different conditions were also got. It is hoped that the analysis of ultrahigh steel sculpture will offer some technical support for practical engineering.

Analysis of Sliding Cable Element

The sliding cable structures have found its application in many practical structures, such as ski lifts, electrical transmission lines, and cable systems in the erection procedures of long-span bridges. This paper presents a method for modeling the cable sliding on a pulley or sheaves. “Sliding cable element” is developed to solve the general problem. Based on the foundational principles of finite element analysis, the relation of the forces in the element on equilibrium state is used. The computation is simplified by automatically adjusting the cable length on each side of a pulley or sheave in order to maintain equilibrium. The element models are implemented in a geometrically nonlinear, transient implicit finite element program. Several numerical examples are developed to validate the effective of the sliding cable element.

Effect of Beam Height on Elastic Impact Load Subjected to Transverse Impact of Bar

The procedure of beam subjected to transverse impact by bar is simulated using numerical method. The method considers the propagation of the expansion wave and shear wave in beam. The effect of beam height on elastic impact loads with different bar lengths and beam heights are investigated. With condition that the length of beam is longer than or equal to that of bar, the numerical solution shows that: when the bar length is constant, if the length of bar is shorter than the height of beam, the longer the bar, the bigger the peak value of impact force; the impact load curve consists of ascending and descending part basically; When the bar length is longer than or equal to beam height, the peak value of impact force is not related to the bar length and equal to that of bar with the same length as the beam height; the impact load curve is trapezium. The contact time is proportional to bar length and equal to the duration time of stress wave propagation in the bar for once return. If the bar length is constant, when bar length is shorter than beam height, the impact load is not related to beam height; when bar length longer than or equal to beam height, the peak value of impact force increases along with the beam height and approach to that of bar with the same length as the beam height.

Performance of the Casing-Plug Joints of Square Steel Tube Structures

The performance of the casing-plug joint, including load carrying capacity, stiffness, failure modes, and its influence factors of the casing tubes set inside and outside of the main tubes are analyzed by simulating square steel tube casing-plug joints structures with ANSYS software in this paper. The formulas of the optimum l/L for the joints with the size of the main tube cross-section 200mm× 200mm are given in this paper.

Out-of-Plane Secondary Bifurcation Buckling Behavior of Elastic Circle Pipe Arch

The out-of-plane secondary bifurcation buckling load-displacement equilibrium paths of the elastic circle pipe arch with and without out-of-plane brace at the top of the arch are traced using a new numerical tracing strategy. The out-of-plane secondary bifurcation buckling loads of the arch with the same sections and different rise-span ratios are obtained under the concentrated load at the top of the arch and the full span uniformly distributed load, which are compared with out-of-plane linear buckling load and in-plane primary buckling load. The calculation results show: for the same section circle pipe arches without the out-of-plane brace and under the concentrated load at the top the arch, the out-of-plane secondary buckling load is always less than the in-plane primary buckling load and the out-of-plane buckling will occur before the in-plane primary buckling. The out-of-plane secondary bifurcation buckling load of the arch with 0.2 rise-span ratio is the biggest. The bigger the rise-span ratio is, the bigger the difference between out-of-plane and in-plane buckling load. When the arch is subjected to full span uniformly distributed load, the out-of-plane buckling will also occur before the in-plane primary buckling and the out-of-plane secondary bifurcation buckling load of the arch with 0.4 rise-span ratio is the biggest. The difference between out-of-plane and in-plane buckling load of the arch with 0.2 rise-span ratio is the biggest. For the circle pipe arch with the out-of-plane brace at the top of the arch, the out-of-plane buckling load of the arch with 0.4 rise-span ratio is the biggest under the two load conditions. The brace can raise the out-of-plane buckling load significantly especially for the arch with big rise-span ratio and under full span load. The out-of-plane buckling will occur before the in-plane primary buckling when the arch is under full span uniformly distributed load. The out-of-plane buckling will occur before the in-plane primary buckling only when the arch is under concentrated load and the rise-span ratio of the arch is less than 0.3. No matter there is or not brace for the arch, the ultimate load carry capacity of the arches increase a little bit after the out-of-plane secondary buckling occurs.

Fracture Analysis for Stiffened Aircraft Fuselage Subjected to Blast

This paper primarily presents the automation computational analysis techniques to determine the dynamic stress intensity factor for the stiffened damaged aircraft fuselage subjected to triangle blast load. 3-dimention panel models can be created using parameterization and the dynamic stress intensity factor can be obtained in the procedure of the blast automatically. A typical stiffened curved panel model which consists of 7 frames and 8 stringers is calculated. The calculation results show that the peak SIF value of the crack in the panel with strips under blast load is always smaller than that without strips for all longitudinal crack lengths; the strips can slow down the crack growth markedly and the effect of the strips on SIF is most obvious when the crack tips are close to the edge of strips; the blast load time has effect on the SIF peak value, and the effect is most significant when the load time is about 25 milliseconds for the panel with strips.

Fracture Analysis for Stiffened Aircraft Fuselage Using Substructure Method

This paper primarily describes the development and application of substructure computational analysis techniques in two-step hirarchical strategy to determine stress intensity factors for the stiffened damaged panels subjected to fatigue internal pressure. A program based on substructure analysis technique and global-local hierarchical strategy has been developed for the fracture analysis of curved aircraft panels containing cracks. This program may create superelements in global and local models, and obtain fracture parameter of the crack in local model by expanding results in superelements automatically. The technique is applied to the analysis of a cracked panel with 7 frames and 10 stringers. SIFs of four cracks in it with different crack lengths are obtained efficiently.