Fatigue resistance design of rubberized asphalt mixture pavement under three-dimensional stress state

Flexible printed circuitry (FPC) is a patterned array of conductors supported by a flexible dielectric film made of high strength polymer material such as polyimide. The flexibility of FPC provides an opportunity for three dimensional packaging, easy interconnections and dynamic applications. The polymeric core layer is the primary load bearing structure when the substrate is not supported by a rigid plate. In its composite structure, the conductive layers are more vulnerable to failure due to their lower flexibility compared to the core layer. Fatigue data on FPCs are not commonly available in published literature. Presented in this paper is the fatigue resistance and reliability assessment of polyimide based FPCs. Fatigue resistance of a specific material system was analyzed as a function of temperature and frequency through experiments that utilized a specially designed experimental setup consisting of sine servo controller, electrodynamic shaker, continuity monitor and temperature chamber. The fatigue characteristics of the selected material system are summarized in the form of S-N diagrams. Significant decrease in fatigue lifetime has been observed due to higher displacements in high cycle fatigue. Observed temperature effect was however counter-intuitive. Failure mechanisms are discussed and complete fracture analysis is presented. In various FPC systems, it has been found that the changes take place in FPC failure mechanisms from well-developed and aligned single cracks through the width at low temperature to an array of multiple cracks with random sizes and locations at high temperature.

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A Finite Element for the Analysis of Shell Intersections

Journal of Pressure Vessel Technology ◽

10.1115/1.2842205 ◽

1996 ◽

Vol 118 (4) ◽

pp. 399-406 ◽

Cited By ~ 4

Author(s):

W. J. Koves ◽

S. Nair

Keyword(s):

Finite Element ◽

Stress State ◽

Three Dimensional ◽

Shell Element ◽

Theory Of Elasticity ◽

Shell Elements ◽

Asme Code ◽

Form Theory ◽

Computation Scheme ◽

Shell Intersections

A specialized shell-intersection finite element, which is compatible with adjoining shell elements, has been developed and has the capability of physically representing the complex three-dimensional geometry and stress state at shell intersections (Koves, 1993). The element geometry is a contoured shape that matches a wide variety of practical nozzle configurations used in ASME Code pressure vessel construction, and allows computational rigor. A closed-form theory of elasticity solution was used to compute the stress state and strain energy in the element. The concept of an energy-equivalent nodal displacement and force vector set was then developed to allow complete compatibility with adjoining shell elements and retain the analytical rigor within the element. This methodology provides a powerful and robust computation scheme that maintains the computational efficiency of shell element solutions. The shell-intersection element was then applied to the cylinder-sphere and cylinder-cylinder intersection problems.

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Fatigue Resistance and Cracking Mechanism of Semi-Flexible Pavement Mixture

Materials ◽

10.3390/ma14185277 ◽

2021 ◽

Vol 14 (18) ◽

pp. 5277

Author(s):

Shiqi Wang ◽

Huanyun Zhou ◽

Xianhua Chen ◽

Minghui Gong ◽

Jinxiang Hong ◽

...

Keyword(s):

Low Temperature ◽

Fatigue Resistance ◽

Stress Ratio ◽

Asphalt Binder ◽

Asphalt Mixture ◽

Fatigue Cracking ◽

Flexible Pavement ◽

The Poor ◽

Grouting Material ◽

Cracking Mechanism

Semi-flexible pavement (SFP) is widely used in recent years because of its good rutting resistance, but it is easy to crack under traffic loads. A large number of studies are aimed at improving its crack resistance. However, the understanding of its fatigue resistance and fatigue-cracking mechanism is limited. Therefore, the semi-circular bending (SCB) fatigue test is used to evaluate the fatigue resistance of the SFP mixture. SCB fatigue tests under different temperature values and stress ratio were used to characterize the fatigue life of the SFP mixture, and its laboratory fatigue prediction model was established. The distribution of various phases of the SFP mixture in the fracture surface was analyzed by digital image processing technology, and its fatigue cracking mechanism was analyzed. The results show that the SFP mixture has better fatigue resistance under low temperature and low stress ratio, while its fatigue resistance under other environmental and load conditions is worse than that of asphalt mixture. The main reason for the poor fatigue resistance of the SFP mixture is the poor deformation capacity and low strength of grouting materials. Furthermore, the performance difference between grouting material and the asphalt binder is large, which leads to the difference of fatigue cracking mechanism of the SFP mixture under different conditions. Under the fatigue load, the weak position of the SFP mixture at a low temperature is asphalt binder and its interface with other materials, while at medium and high temperatures, the weak position of the SFP mixture is inside the grouting material. The research provides a basis for the calculation of the service life of the SFP structure, provides a reference for the improvement direction of the SFP mixture composition and internal structure.

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