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Yield surface characterization for lightweight alloy sheets via an improved combined shear–tension experimental method

Zheng L. H., Wang Z. J., Wan M., Meng Bao

Archives of Civil and Mechanical Engineering

2022

Vol. 22, no. 2

art. no. e96, 1--17

Combined shear and tension (CST) tests are important experimental methods for characterizing yield surfaces for metal sheets, which is vital to ensure the effectiveness of the constitutive models employed in finite element simulation. However, the existing CST experimental method with a reduced thickness specimen, designed for advanced high strength steel sheets, is not suitable for accurately characterizing yield surfaces for lightweight alloy sheets, such as aluminum alloy sheets. In this paper, an improved experimental method employing CST loading along with an appropriate full-thickness specimen is proposed to address the problem. To establish the proposed experimental method, an appropriate full-thickness specimen is presented through finite element method and combined with a newly developed biaxial testing machine. To verify the effectiveness and feasibility of the improved experimental method, virtual simulations and real experiments on the proposed full-thickness specimen obtained from 6K21-T4 aluminum sheets under different CST loading cases are conducted. Research results show that the yield surfaces of the aluminum alloy sheets between simple shear and plane strain (SSPS) can be described accurately by employing the improved experimental method. In addition, according to the experimental results, the prediction capability of the Yld2000 and Hill48 yield criteria is studied. It is found that the commonly used Yld2000 yield criterion cannot accurately predict the yield behavior of the aluminum alloy sheets under shear-dominant loading.

Engineering properties of normal concrete grade 40 containing rice husk ash at different grinding time

Bakar B., Jaya R., Johari M., Wan M.

Advances in Materials Science

2011

Vol. 11, nr 1(27)

81-92

The effect of rice husk ash with different grinding time on the engineering properties of concrete was studied. Eight rice husk ashes with different grinding were used in this investigation. Rice husk ash was used to partially replace Portland cement Type I at 15% by weight of cementitious material. The 100-mm concrete cube specimens were cast and cured in water for 7 and 28 days. The compressive strength of concrete was designed to achieve of grade 40 N/mm2 at 28 days. A superplasticizer was added to all mixes to provide workability in the range of 110 – 120 mm. However, the water to cement ratio (w/c) of the concrete was maintained at 0.49. Based on the results, the morphology of the rice husk ashes were changed by grinding. These appear to be an optimum grinding time of approximate 90 minutes which the compressive strength increased significantly. Generally, incorporation of RHA at varies grinding time can be decrease or increased the engineering properties of concrete extremely.

Numerical and experimental studies of the strength of riveted joints

Chen N., Chenot J. -L., Wan M., Malrieu J., Thonnerieux M., Ducloux R.

Computer Methods in Materials Science

2010

Vol. 10, No. 4

259-270

In general, there are two main types of failure observed in solid riveted joints: tensile failure and shear failure. To study these phenomena, four sizes of riveted joints are utilized to do the riveting, tension and shear process. Meanwhile, corresponding FEM models are built in Forge 2009 to simulate each process for these joints. In the simulations, Bauschinger Effect of the rivet material is taken into account to obtain more accurate simulation results. Based on Oyane and Cockcroft & Latham damage criteria, a new damage model in which the first principal stress and hydrostatic pressure are both considered is proposed to predict the fracture initiation and growth in the tension and shear process of riveted joints. The results from the simulations are in quite good agreement as compared with those from the experiments.

Ogólnie obserwuje się dwa rodzaje zniszczenia połączeń nitowanych: przez zerwanie w wyniku rozciągania i przez ścinanie. W celu zbadania tych mechanizmów cztery połączenia o różnych rozmiarach poddano procesom rozciągania i ścinania. Równocześnie opracowano model w programie Forge registered trademark 2009, który wykorzystano do symulacji tych połączeń. W symulacjach uwzględniono efekt Bauschingera w materiale co poprawiło dokładność obliczeń. Bazując na kryteriach pękania Oyane i Cockcrofta-Lathama opracowano nowy model pękania, w którym inicjacja i propagacja pęknięcia w połączeniu nitowa nym jest przewidywana na podstawie pierwszego naprężenia głównego i średniego naprężenia. Wyniki symulacji są zgodne z wynikami doświadczeń.