Shear Fatigue Performance Research Articles

Study on Shear Fatigue Performance of Scarf Repaired Honeycomb Sandwich Structure

The shear static and shear fatigue tests of the honeycomb sandwich composite were carried out to study the effects of three different repair methods on shear fatigue performance: the unilateral panel scarf repair, the unilateral panel and core scarf repair, and the bilateral panel and core scarf repair. The stress ratio R=0.1 was selected. The results show that the failure mode of the honeycomb sandwich structure is the destruction of the honeycomb core. The structure is torn into two halves from the core, and the core tends to squeeze to one side. There is no debonding between the panel and the core, and no delamination in the panel. The static strength, fatigue limit, fatigue life and residual strength of the specimens are significantly decreased by the scarf repair. The rank of reduction from most to least is: the unilateral panel scarf repair, the bilateral panel and core scarf repair, and the unilateral panel and core scarf repair.And the latter two are remarkably similar.

Investigation of interlayer bonding performance between asphalt concrete overlay and Portland cement concrete using inclined shear fatigue test

The interlayer bonding between the asphalt concrete (AC) overlay and the Portland cement concrete (PCC) layer has an essential influence on the composite asphalt pavement performance. However, there is still little work on the interlayer bonding performance of composite pavement by inclined shear fatigue test. The purpose of this study is to investigate the interlayer bonding performance with four tack coat types and three PCC surfaces under the effect of repeated loading and water erosion. The optimal tack coat application rates were first determined by shear strength and applied in the following study. The shear fatigue performance of interlayer bonding with different tack coats and PCC surfaces was analyzed based on the conventional S-N fatigue model. Then, the effect of freeze–thaw cycles on the interlayer bonding was investigated according to fatigue lives and fatigue life ratios. Furthermore, the axle load conversion factor was calculated based on the shear fatigue life used for the composite pavement design. The analysis results indicate that the interlayer applied modified asphalt as the tack coat realizes higher strength and more extended shear fatigue life, which means better loading and moisture resistance. The calculated conversion factor shows a higher value compared to the specification stipulation. This research contributes to the interlayer design and construction of composite pavement, including tack coat selection, PCC surface treatment, interlayer fatigue life prediction, and axle load conversion.

The fatigue mechanism of asphalt mixture with an interlayer under the combined effect of multiple factors

As a common method of asphalt pavement maintenance, thin overlays performance is easily affected by interlayer bonding performance because of their thinness. To study the effects of immersion, freeze–thaw, stress ratio and loading frequency on the interlayer bonding performance and reveal the interlayer failure mechanism, an asphalt mixture with interlay (AMI) was prepared for direct shear strength test, direct shear fatigue test (DSFT) and CT scanning test. The results verify that the interlay shear fatigue performance of AMI was sensitive to immersion, freeze–thaw, stress ratio and loading frequency. With the increased of immersion days and freeze–thaw cycles the interlay shear fatigue life (ISFL) was decreased. The interlayer shear strength was affected by the tack coat oil and the aggregate inlay and extrusion, and the shear strength provided by the two was basically the same. The interlayer bonding performance was affected significantly more by water than freeze–thaw action, and the main reason for increased void numbers was immersion days, and the main reason for void size expansion was freeze–thaw action. ISFL decreased with the increase of stress ratio, but increased with enhancing of loading frequency; and the fatigue life at high frequency was more susceptible to the alter of stress ratio. Based on Grey Relational Analysis, the influence of the four factors on ISFL was loading frequency > stress ratio > freeze–thaw cycles > immersion days; based on the prediction model of stress ratio obtained by the phenomenological method, the ISFL prediction model under the influence of the four factors was obtained by coefficient correction of loading frequency, freeze–thaw cycles and immersion days.

Shear Fatigue Performance of Epoxy Resin Waterproof Adhesive Layer on Steel Bridge Deck Pavement

In this study, the effects of temperature, shear stress, and coating quantity of waterproof adhesive layer on the shear fatigue performance of a steel bridge deck pavement were investigated. Direct shear fatigue tests of a pavement comprising an epoxy resin waterproof adhesive layer with stone matrix asphalt were conducted at different temperatures, stress levels, and coating quantities. The results show that temperature and stress have significant effects on the shear fatigue life. With increasing temperature and stress, the shear fatigue life of the waterproof adhesive layer decreased gradually. Therefore, for steel bridge deck pavements under high temperatures and heavy loads, the use of asphalt waterproof adhesive layers or pavement layers should be evaluated carefully while limiting the traffic of heavily loaded vehicles. Shear failure occurs at the waterproof adhesive layer–pavement interface and not at the steel–waterproof adhesive layer interface. The shear strength of the epoxy resin waterproof adhesive layer is mainly provided by the bond strength between the waterproof adhesive and pavement mixture as well as the interlocking force between the cured epoxy resin and the bottom interface of uneven pavement mixture. The shear strength increases with the coating quantity of the waterproof adhesive layer; however, after reaching the maximum value, the shear strength becomes stable. In contrast, the interlaminar shear fatigue life increases continuously with the coating quantity of the waterproof adhesive layer. Appropriately increasing the coating quantity is beneficial for improving the resistance of the waterproof adhesive layer to interlaminar shear fatigue failure.

Interface shear strength and shear fatigue resistance of fibreglass grid-reinforced asphalt concrete test specimens

ABSTRACT This research was undertaken to study the effects of grid opening size and tack coat type on both the shear strength and shear fatigue resistance at the interface of fibreglass grid-reinforced asphalt concrete specimens and, more importantly, to correlate these effects with the interfacial fatigue performance under four-point bending beam fatigue loading. The specimens were fabricated using a 12.5-mm nominal maximum aggregate size surface mixture. Two types of fibreglass grid, differing only in the grid opening size, and two tack coats, a PG 64-22 asphalt binder and a slow-setting anionic asphalt emulsion with low viscosity, were used to reinforce the specimen interfaces. The digital image correlation technique was utilised to measure displacements, strains, and crack lengths. The test results indicate that a strong tack coat and a grid with large openings can potentially improve the shear resistance of a grid-reinforced interface but the effects of these two parameters might differ under monotonic and cyclic loading conditions. The cyclic shear, beam fatigue, and monotonic displacement-controlled shear test results suggest that the grid opening size plays a key role in the interface shear fatigue performance, however tack coat quality plays a more important role on the interface shear strength of the specimens.

Influence of Multiple Factors on the Shear Fatigue Resistance of Asphalt Pavement Interlayer Adhesive Materials

AbstractAsphalt pavements on steep slope sections in regions with seasonal freezing are affected by loads and the environment, and the shear resistance and shear fatigue performance attenuation of ...

Shear-Torque Fatigue Performance of Geogrid-Reinforced Asphalt Interlayers

Interlayer reinforcement systems represent a valid solution to improve performance and extend the service life of asphalt pavements, reducing maintenance costs. The main issue is that the presence of reinforcement may hinder the full transmission of stresses between asphalt layers, reducing the overall pavement bearing capacity. This study aimed at evaluating the mechanical behavior of geogrid-reinforced asphalt interlayers under cyclic shear loading. To this purpose, a trial section, characterized by three types of interface (reinforced with carbon fiber grid, reinforced with glass fiber grid and unreinforced), was built. Cores were taken from the trial section to carry out shear-torque fatigue tests. Static Leutner shear tests were also performed on cored specimens having the same interface configuration. From data gathered in the present study, shear-torque fatigue tests have proved to be a powerful tool for investigating reinforced specimens. Results clearly ranked the investigated materials, showing that the glass fiber grid has the lowest shear fatigue performance in comparison with the other two interfaces at 20 °C. However, the shear fatigue resistance of glass fiber grid increases significantly at 10 °C. Finally, an interesting correlation was found between cyclic and static shear test results that should be better investigated in future studies.

Micromechanical Discrete Element Modeling of Asphalt Mixture Shear Fatigue Performance

AbstractThis study aims to investigate the shear fatigue performance of asphalt mixture and factors influencing performance using a three-dimensional (3D) discrete element method (DEM) incorporated...

Analysis of shear-torque fatigue test for bituminous pavement interlayers

The laboratory characterisation of bituminous interlayers is a challenging issue because of the difficulty of establishing loading conditions that can simulate field behaviour. This paper describes a shear-torque fatigue test procedure aimed at investigating the fatigue behaviour of bituminous pavement interlayers. A preliminary experimental investigation, able to evaluate the damage process occurring in both single- and double-layered specimens, showed that the presence of the interface constitutes a weakness zone, noticeably influencing the shear fatigue performance of the pavement structure. Thus, a model for the description of the evolution of the interlayer damage by using the variation of the interlayer complex shear modulus was proposed and preliminarily validated. Moreover, a new fatigue failure criterion has been proposed to be used in the result analysis of the shear-torque fatigue tests.

Experimental method and failure mechanisms investigation for out-of-plane shear fatigue behavior of 3D woven composites

A set of experimental method is proposed for the out-of-plane shear fatigue performance and damage mechanisms of a type of three-dimensional (3D) woven composites. The S-N curves based on the ultimate failure cycles and the shear fatigue stiffness degradation curve of specimens are obtained. Simultaneously, the relation between the system stiffness degradation and the specimen temperature increase is discussed. Moreover, the damage evolution is captured and analyzed. Microscopic observation of the damage zone on the specimen surface is carried out. Based on the images of infrared thermography and the corresponding crack distribution, the mechanism of heat generation are discussed. It can be found that the temperature distribution of the specimen is positively correlated with the shear strain distribution and crack distribution. The stiffnesses and temperature changes of the specimen show certain consistency. The out-of-plane failure mechanisms under shear fatigue loading for 3D woven composites are revealed on the basis of observation and analysis.

Research of Test of Shear Resistance of Modified Emulsified Asphalt by Waterborne Epoxy Resin

In view of diseases like slippage and surge of pavement structure that result from being lack of interlayer cohesive force performance of asphalt pavement, interlayer shear stress of five kinds of typical pavement structure was calculated by means of finite element software Ansys; the shear fatigue performance and shear strength performance of epoxy emulsified asphalt were tested on the basis of calculation of interlayer maximum shear stress and shear strength. Results indicate that the shear strength increases with the increase of normal stress by approximate linearly trend; the optimum epoxy emulsified asphalt distributing amount is 0.8kg/m2 under the high temperature of 60℃; the shear strength decreases with the increase of temperature, while the distributing amount and normal stress are the same, in fact, it is mainly caused by the decrease of cohesive force; the maximum interlayer shear stress under the loads of 100kN and 200kN are less than allowable shear stress and shear strength, shear fatigue damage and ultimate shear failure under the condition of high temperature and heavy load will not be generated on the asphalt surface course.

Fatigue investigation on asphalt mixture layers’ interface

In this paper, the interface shear fatigue performance is investigated based on a new fatigue test protocol, which includes both cyclic shear and normal static compressive load. Several asphalt structure types are tested at five temperatures (from −10°C to 50°C) and three normal stress levels (from 0 to 0.50 MPa). Based on fatigue tests at three different shear amplitude levels unique fatigue functions of the layers’ interface were identified. It was found that the interface shear fatigue performance is highly dependent on normal stress state and increases with increasing normal stress. This is a direct consequence of the enhanced friction, adhesion and interlock at the shear interface. Observing the fatigue lives at different test temperatures, the best resistance was observed at lowest temperature. From a practical viewpoint, it is highly recommended to perform the test without normal stress application, since this can better reflect the research and practice experience, while keeping the testing protocol to a reasonable level of complexity.

해상 운송 플랜트 구조물의 고장력 볼트 피로성능 평가

해양플랜트 구조물은 현장에서의 제작이 어려워 작업장에서 중 소단위의 모듈로 제작한 뒤 바지선을 이용해 현장으로 운송 후 설치 제작하는 방식이 사용되고 있다. 이 때 운송 시 발생하는 반복적인 환경하중으로 인해 구조물의 접합부에 피로하중이 작용하게 된다. 따라서 본 연구에서는 플랜트구조물의 운송과정에서 발생하는 피로하중을 적용한 고장력 볼트 접합부의 피로강도에 대한 구조적 신뢰성을 확인하고자 도입축력, 마찰계수, 볼트종류를 변수로 한 실험연구를 수행하였다. 다양한 변수를 고려한 고장력 볼트의 축력변화에 따른 볼트 풀림 현상 규명 연구결과, 고장력 볼트의 축력변화가 1% 내외에서 나타나 구조적 안전성에는 영향을 미치지 않는 것으로 판단된다. The offshore plant structure has been transported to the site by barge because it is hard to manufacture in site. When the structure was transported on the sea, offshore plant structures and connection were experienced repetitive submarine load. For this reason, it was known for that the axial force of high-strength bolted connection was declined. Therefore, in this study, high-strength bolted connection was evaluated the shear fatigue performance under longtime fatigue load during marine transport. The experimental variables were selected intial axial force, surface type, and bolt type because they ar important factors in the change of axial force of bolts. As a experimental results of considering various variables, the variation of axial force showed within 1%. Therefore, the high-strength bolted connection was verified structural safety under longtime fatigue load.

Laboratory investigation of interlayer shear fatigue performance between open-graded friction course and underlying layer

The objective of the study was to evaluate the bonding fatigue performance between open-graded friction course (OGFC) and underlying layer through laboratory testing at different tack coat application rates. Direct shear fatigue test was performed to obtain the shear fatigue properties of the composite specimens composed of OGFC and its underlying layer. Two types of dense graded asphalt mixture (named BM and TLD in Tennessee) were selected as the underlying layer. In addition to the fatigue life determined according to the conventional 50% stiffness reduction method, energy approach was also employed to analyze the fatigue behavior of the composite specimens. Results showed that the OGFC-TLD structure gave a better shear fatigue performance than OGFC-BM. With the increase in tack coat application rate, the plateau value (PV) increased and the total cumulative dissipated energy decreased for both combined structures. The contact area between OGFC and the underlying layer was measured and correlated to the fatigue life. The contact area between OGFC and TLD was larger than that between OGFC and BM, leading to a better fatigue performance of OGFC-TLD.

State of the art: interface shear resistance of asphalt surface layers

Interface shear resistance is a measure of the bonding between two layers under shear loading. Adequate interface shear resistance and long-term bonding of the surface to the underlying pavement are critical to the performance of pavement structures. Interface shear strength is a function of adhesion, friction and aggregate embedment or interlock and is commonly modelled as a Mohr–Coulomb type envelope. Measurement of interface shear resistance can be performed in the field on full-scale pavements, in the laboratory on cores recovered from the surface or in the laboratory using samples prepared in the laboratory. However, laboratory testing of cores recovered from the field is likely to be more reliable and repeatable than field testing. There is a large range of test methods and procedures for the measurement of interface bond. These test methods are generally grouped into three main loading mechanisms; axial tension, torsional shear and direct shear. Direct shear tests offer a more comprehensive assessment of the full interface strength. The interface’s resistance to shear can be characterised by its strength, modulus/stiffness or work/energy. The results are affected by the test protocol, tack coat type and application rate, test temperature, applied normal stress and rate of loading, interface condition and post-construction trafficking. Of these, the test temperature is the most influential factor. A number of studies have reported contradictory and conflicting conclusions with regard to the importance of various factors and conditions on the different measures of interface shear resistance. Such inconsistent findings likely stem from the complicated interaction between the various interface conditions and testing protocols. The fundamental factors affecting monotonic interface strength are now reasonably well understood. The focus of future research is expected to be on shear fatigue performance of interfaces.

Interlaminar Shear and Electrical Resistance Responses of Woven-Carbon-Fiber-Reinforced-Polymer Composite Laminates at Cryogenic Temperatures From Cyclic Short Beam Shear Tests

Abstract This paper studies the interlaminar shear and electrical resistance responses of woven-carbon-fiber-reinforced-polymer (CFRP) composite laminates subjected to fatigue loading at cryogenic temperatures. Fatigue tests were conducted on the composite specimens at room temperature and liquid-hydrogen temperature (20 K) using the short beam shear method, and measurements of the specimen electrical resistance were made during the tests. Also, the tested specimens were examined by microscopy to observe the damage and the failure mode. In addition, a finite-element analysis was performed to examine the stress distributions in the short beam shear specimens. The dependence of the interlaminar shear fatigue performance of the woven-CFRP laminates on the temperature was discussed, and the applicability of the electrical resistance method for assessing the fatigue failure was demonstrated.

Fatigue Investigation of High-Strength Concrete Members Reinforced with CFRP

Fatigue damage becomes an emerging problem in lots of concrete structures which will subject to cyclic loadings during their working life. This paper presents a study on interfacial shear fatigue performance of a high-strength concrete structure strengthened by carbon fiber-reinforced plastic (CFRP) plate, which has been established as an effective method for rehabilitation and strengthening of concrete structures. Based on the static test, a new experimental investigation of the shear fatigue performance along the concrete-plate interface under the low cycle fatigue load in the condition of R=0.1 is presented. The main variable is the concrete strength. Compared with the static ultimate strength, fatigue strength decreases. Therefore, a safety factor of the fatigue strength at the interface of CFRP and concrete should be applied in design.

Shear fatigue strength of a prismatic diamond sandwich core

The shear fatigue performance of stainless steel diamond cores has been measured and S – N curves reported for two core relative densities. The fatigue mechanism for the low relative density core involves the successive bending fatigue of constituent struts near the ends of the specimen, while the high density core fails by fatigue failure of the joints between the core and the face-sheets. A significant knock-down in the fatigue shear strength of the core is observed compared to its monotonic strength.