Viscoelastic mechanical performance of dense polyurethane mixtures based on dynamic and static modulus testing and creep testing

2022 ◽  
Vol 320 ◽  
pp. 126207
Author(s):  
Qian Zhang ◽  
Shankun Wang ◽  
Rongpei Lv ◽  
Jiaqi Wu ◽  
Hongxing Qi
2020 ◽  
Vol 71 (3) ◽  
pp. 243-252
Author(s):  
Davor Kržišnik ◽  
Miha Humar ◽  
Aleš Straže ◽  
Milan Šernek ◽  
Bogdan Šega ◽  
...  

The performance of the composites is influenced by the service life of input raw wood material and used adhesives. The aim of the study was to assess the durability and mechanical performance of glulam beams treated in a different way (thermally modified and/or treated with copper-based wood preservative) and exposed in an outdoor application. Glulam beams (83 mm × 68 mm × 1100 mm), made of three layers of Norway spruce (Picea abies) with PUR adhesives used have been exposed in use class 3.2 in a horizontal position since 4th November 2016. Part of the specimens was equipped with MC sensors. Every year, the degradation was evaluated visually. The dynamic modulus of elasticity was determined by longitudinal vibration, and the static modulus of elasticity using a 4-point bending test. On the smaller specimens, cut from glulams, compressive strength, delamination, and shear strength of adhesive bonds were determined. After two years of exposure, the results indicate that the performance of glulams is determined by the wood modification and applied wood preservative.


2019 ◽  
Vol 81 (4) ◽  
Author(s):  
M. R. M. Asyraf ◽  
M. R. Ishak ◽  
M. R. Razman ◽  
M. Chandrasekar

Most of transmission line (TL) towers are designed and fabricated in the form of lattice using galvanized steel. The crossarm of the TL is made of Neobalanocarpus or Chengal wood. Recently, it has been reported by an electrical corporation situated in Malaysia that mechanical performance of the wooden crossarm declined below their service life of 40 years due to the extreme tropical weather in Malaysia. At present, composite crossarm made of glass fibre reinforced polymer composite were introduced as substitute in the 132 kV TL tower. However, the research findings lack of information on creep life estimation for the full-scale crossarm. Hence, a new test rig has to be developed to cater the testing operation using the uniaxial tension creep test. The primary objective of this review is to provide an overview of the creep theory and the existing creep testing methodology.


2019 ◽  
Author(s):  
Peter Peter ◽  
Claudia Creighton ◽  
David Fox ◽  
Pablo Mota Santiago ◽  
Adrian Hawley ◽  
...  

Author(s):  
Kulwant Singh ◽  
Gurbhinder Singh ◽  
Harmeet Singh

The weight reduction concept is most effective to reduce the emissions of greenhouse gases from vehicles, which also improves fuel efficiency. Amongst lightweight materials, magnesium alloys are attractive to the automotive sector as a structural material. Welding feasibility of magnesium alloys acts as an influential role in its usage for lightweight prospects. Friction stir welding (FSW) is an appropriate technique as compared to other welding techniques to join magnesium alloys. Field of friction stir welding is emerging in the current scenario. The friction stir welding technique has been selected to weld AZ91 magnesium alloys in the current research work. The microstructure and mechanical characteristics of the produced FSW butt joints have been investigated. Further, the influence of post welding heat treatment (at 260 °C for 1 h) on these properties has also been examined. Post welding heat treatment (PWHT) resulted in the improvement of the grain structure of weld zones which affected the mechanical performance of the joints. After heat treatment, the tensile strength and elongation of the joint increased by 12.6 % and 31.9 % respectively. It is proven that after PWHT, the microhardness of the stir zone reduced and a comparatively smoothened microhardness profile of the FSW joint obtained. No considerable variation in the location of the tensile fracture was witnessed after PWHT. The results show that the impact toughness of the weld joints further decreases after post welding heat treatment.


Author(s):  
Byung-Jae Kim ◽  
Hyeon-Seok Seo ◽  
Won-Ho Lee ◽  
Jong-Hyun Ahn ◽  
Youn-Jea Kim

Diabetes ◽  
1984 ◽  
Vol 33 (12) ◽  
pp. 1138-1143 ◽  
Author(s):  
B. H. Tan ◽  
G. L. Wilson ◽  
S. W. Schaffer

Author(s):  
I. A. Shibaev ◽  
V. A. Vinnikov ◽  
G. D. Stepanov

Geological engineering often uses geomechanical modeling aimed to enhance efficiency of mining or performance of structures. One of the input parameters for such models are the static elastic moduli of rocks. This article presents the studies into the physical and mechanical properties of rocks-limestone of non-metamorphic diagenesis. The precision measurements of Pand S-waves are carried out to an accuracy of 0.2% by laser ultrasonics. The static moduli of elasticity and the deformation characteristics of rocks are determined in the uniaxial compression tests by the standards of GOST 21153.2-84 and GOST 28985-91, respectively. The correlation dependence is found between the static and dynamic elasticity moduli in limestone samples. The found correlation allows drawing the conclusion that the static modulus of elasticity can be estimated in non-destructive tests, which largely simplifies preliminary diagnostics of samples in case of limited number of test core.


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