2136) Bond Resistance under Repeated Loading : Part II. Repeated Loading with Constant Load Amplitude

For structural concrete members that may expose to serious earthquake, overload or accident impact, the design of ductility must be given the same importance as the flexural strength. The aim of this investigation is to study the change in ductility of structural concrete flexural members during their exposure to limited cycles of repeated loading. Twenty full-scale beam specimens have been fabricated in to two identical groups; each group consisted of ten specimens. The first group was tested under monotonic static loading to failure and regarded as control beams, while the specimens of the second group were subjected to ten cycles of repeated loading with constant load interval, which ranged between 40% and 60% of ultimate load. Specimens in each group were categorized as follows: two traditional reinforced concrete specimens with different intensity of tension reinforcement; three partially prestressed specimens with bonded strands; three partially prestressed specimens with unbonded strands; and two fully prestressed concrete specimens. The main variable, which was considered for all specimens was the partial prestressing ratio (PPR). It was observed that, the ductility of reinforced concrete beams was insignificantly increased during subjecting to limited repeated loading. For fully prestressed and partially prestressed concrete beams with high level of PPR, the ductility was significantly enhanced, while, it was decreased for specimens with small level of PPR.

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Static and Flexural Fatigue Behavior of GFRP Pultruded Rebars

Materials ◽

10.3390/ma14020297 ◽

2021 ◽

Vol 14 (2) ◽

pp. 297

Author(s):

Michał Barcikowski ◽

Grzegorz Lesiuk ◽

Karol Czechowski ◽

Szymon Duda

Keyword(s):

Composite Materials ◽

Composite Structures ◽

Fatigue Behavior ◽

Constant Load ◽

Fatigue Tests ◽

Bending Test ◽

Radial Compression ◽

Sinusoidal Waveform ◽

Constant Load Amplitude ◽

Steel Rebars

This paper presents the experimental results of composite rebars based on GFRP manufactured by a pultrusion system. The bending and radial compression strength of rods was determined. The elastic modulus of GFRP rebars is significantly lower than for steel rebars, while the static flexural properties are higher. The microstructure of the selected rebars was studied and discussed in light of the obtained results—failure processes such as the delamination and fibers fracture can be observed. The bending fatigue test was performed under a constant load amplitude sinusoidal waveform. All rebars were subjected to fatigue tests under the R = 0.1 condition. As a result, the S-N curve was obtained, and basic fatigue characteristics were determined. The fatigue mechanism of bar failure under bending was further analyzed using SEM microscopy. It is worth noting that the failure and fracture mechanism plays a crucial role as a material quality indicator in the manufacturing process. The main mechanism of failure under static and cyclic loading during the bending test is widely discussed in this paper. The results obtained from fatigue tests encourage further analysis. The diametral compression test reflects the weakest nature of the composite materials based on the interlaminar compressive strength. The proposed methodology allows us to invariantly describe the experimental transversal strength of the composite materials. Considering the expected durability of the structure, the failure mechanism is likely to significantly improve their fatigue behavior under the influence of cyclic bending. The reasonable direction of searching for reinforcements of composite structures should be the improvement of the bearing capacity of the outer layers. In comparison with steel rebars (fatigue tensile test), the obtained results for GFRP are comparable in the HCF regime. It is worth noting that in the near fatigue endurance regime (2–5 × 106 cycles) both rebars exhibit similar behavior.

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Fatigue Crack Growth of Duplex Stainless Steel Castings at 4 K

Journal of Engineering Materials and Technology ◽

10.1115/1.3225793 ◽

1985 ◽

Vol 107 (2) ◽

pp. 161-165 ◽

Cited By ~ 1

Author(s):

P. T. Purtscher ◽

Y. W. Cheng ◽

P. N. Li

Keyword(s):

Stainless Steel ◽

Fatigue Crack ◽

Fatigue Crack Growth ◽

Duplex Stainless Steel ◽

Crack Growth ◽

Growth Rates ◽

Constant Load ◽

Steel Castings ◽

Constant Load Amplitude ◽

Crack Growth Rates

Constant-load-amplitude stage II fatigue crack growth rates at 4 K were measured for duplex stainless steel castings. The results show that at a ΔK of 60 MPa•m1/2, da/dN = 7.6 × 10−4 mm/cycle for an alloy with 1 percent ferrite. For an alloy with 8 percent ferrite, da/dN is 35 percent, and for an alloy with 29 percent ferrite, da/dN is 260 percent greater than for the 1 percent ferrite alloy. However, the exponent in the Paris equation does not change appreciably (less than 18 percent) as the ferrite content changes from 1 to 29 percent.

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Fatigue Life for Type 316L Stainless Steel under Cyclic Loading

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.701.77 ◽

2013 ◽

Vol 701 ◽

pp. 77-81

Author(s):

Khairul Azhar Mohammad ◽

Edi Syam Zainudin ◽

S.M. Sapuan ◽

Nur Ismarrubie Zahari ◽

Ali Aidy

Keyword(s):

Stainless Steel ◽

Fatigue Life ◽

316L Stainless Steel ◽

Load Ratio ◽

Constant Load ◽

Fatigue Tests ◽

Constant Frequency ◽

Technology Market ◽

Constant Load Amplitude

The paper presents the determination of fatigue life of 316L stainless steel at room temperature. Plenty of steel in the world has been investigated for a lot of application in the science and technology market. The mechanisms of fatigue of 316L stainless steels were studied and investigated. Fatigue tests of specimens were performed in accordance with ASTM E466-96. The fatigue tests were performed in constant load amplitude, constant frequency of 5 Hz with load ratio R=0.1. Fracture surface of specimens were examined by using Scanning Electron Microscope (SEM). The results showed that the endurance fatigue limit of 316L stainless steel was 146.45 MPa.

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Study on temperature rise distribution of contact surface under cyclic load

Proceedings of the Institution of Mechanical Engineers Part J Journal of Engineering Tribology ◽

10.1177/1350650120919877 ◽

2020 ◽

Vol 235 (1) ◽

pp. 138-148

Author(s):

Ling Li ◽

Haifei Tian ◽

Qiangqiang Yun ◽

Wei Chu

Keyword(s):

Contact Surface ◽

Temperature Rise ◽

Cyclic Load ◽

Thermal Structure ◽

Constant Load ◽

Contact Center ◽

Tangential Load ◽

Cycle Number ◽

Load Amplitude ◽

Depth Direction

A large amount of heat is generated during the friction of joint surfaces, which has a significant influence on the contact characteristics of surfaces, causing deformation or failure of key components. A two-dimensional friction-thermal structure coupling contact model of cylinder/plane was established in ABAQUS. The effects of roughness under different fractal parameters, tangential load amplitude and cycle number on the temperature rise distribution of a contact surface under normal cyclic loading were studied. The results show that with the increase of roughness and tangential load amplitude, the area of thermal effect becomes more obvious and the temperature rise of the contact surface increases. It is also found that the heat affected zone is mainly distributed near the surface of the contact area with a high-temperature field generated, while the temperature rise amplitude decreases gradually along the depth direction. In addition, the contact surface nodes have a similar temperature rise distribution process and the farther away from the contact center ( x = 0.3 mm), the smaller the temperature rise, which is consistent with the simulation results of the published literature. For the same tangential load amplitude, the surface temperature rise amplitude under the normal cyclic load is lower than that of the normal constant load. The temperature rise of the surface increases with the increase of the number of fretting cycles.

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