The primary plant cell wall is a dynamically regulated composite material of multiple biopolymers that forms a scaffold enclosing the plant cells. The mechanochemical make-up of this polymer network ...regulates growth, morphogenesis, and stability at the cell and tissue scales. To understand the dynamics of cell wall mechanics, and how it correlates with cellular activities, several experimental frameworks have been deployed in recent years to quantify the mechanical properties of plant cells and tissues. Here we critically review the application of biomechanical tool sets pertinent to plant cell mechanics and outline some of their findings, relevance, and limitations. We also discuss methods that are less explored but hold great potential for the field, including multiscale in silico mechanical modeling that will enable a unified understanding of the mechanical behavior across the scales. Our overview reveals significant differences between the results of different mechanical testing techniques on plant material. Specifically, indentation techniques seem to consistently report lower values compared with tensile tests. Such differences may in part be due to inherent differences among the technical approaches and consequently the wall properties that they measure, and partly due to differences between experimental conditions.
This paper reports on the microstructural evolution of resistance spot welded 1000MPa dual phase steel under two different welding conditions, and their relation to the mechanical performance and ...failure mechanisms. It is shown that a double pulse weld scheme leads to an enhancement in cross-tension strength compared to single pulse welding. The second pulse subdivides the initial fusion zone of the first pulse into two zones. The inner part is solidified with a columnar structure after the second pulse, whereas with the second pulse the outer layer becomes recrystallized (named as Rex-zone) leading to the formation of an equiaxed structure of prior austenite grains. Characteristics of martensite formed in the Rex-zone and coarse-grained heat affected zone, where the crack initiated and propagated, were investigated using orientation imaging microscopy. It was found that a change in welding scheme from single to double pulse effectively alters the characteristics of martensitic microstructure of weld zones. The results obtained demonstrate that the Rex-zone has a lower fraction of high-angle grain boundaries and coarser structure of Bain groups as opposed to the coarse-grained heat affected zone with large fraction of high-angle grain boundaries and finer Bain groups. Besides, double pulse welding creates softer sub-critical heat affected zone which reduces stress concentration at the nugget edge during cross-tension test. The better mechanical performance of double pulse weld is attributed to the significant softening at sub-critical heat affected zone, formation of thick Rex-zone with lower residual strain and high fraction of high-angle grain boundaries and finer Bain groups in the coarse grained heat affected zone.
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•Double pulse welding enhances mechanical properties of the weld compared to the sample welded with single pulse process.•Softer sub-critical heat affected zone is achieved using double pulse welding scheme.•Coarser structure of Bain groups are formed in the recrystallized zone of double pulse welds.•Finer structure of Bain groups are formed in the Coarse-grained heat affected zone of double pulse weld.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Enhancing tensile strength is crucial to increasing the applicability of nanoporous materials including nanoporous gold (np-Au) that show mechanical weakness because of their nanoporous structure ...despite other superior characteristics. We fabricated twinned and textured np-Au foils with an average twin spacing of 7.9 nm. The foils exhibit an ultimate tensile strength (UTS) of 87.5 MPa when the loading axis is normal to the twin boundaries. This UTS value is approximately three times greater than that for np-Au with rare twins of 27.4 MPa. The high UTS can be ascribed to the twin boundaries acting as effective barriers to dislocation slip, resulting in the strain-hardening of the load-bearing ligaments.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
•Crack failure analysis has been done on exhaust manifold of a diesel engine.•Crack propagation at maximum work temperature has been discussed.•Crack failure toughness has been determined during ...finite element analysis.•Critical fracture force of D5S has been determined at 800 ˚Cby tension test.Critical fracture toughness has been determined by using of finite element analysis.Critical crack length has been calculated.It was concluded that assumed crack does not propagates during worst work condition.
D5S is an alloy used in the manufacture of exhaust manifold of the internal combustion (IC) engines. Considering that exhaust manifold is one of the engine components that are under intense thermal and mechanical loads, fracture failure analysis should be regarded for this engine part. Fracture toughness determination is the main criterion for structural fracture analysis. In this research, crack failure was analyzed based on the finite element method (FEM), upon which critical fracture toughness was determined. Using the FEM analysis, a crack was assigned on the exhaust manifold model in order to obtain its fracture toughness at the first mode (KI) under thermo-mechanical loads. According to the ASTM standard, four compact tension (CT) specimens with different notch lengths of 4 mm, 5 mm, 9 mm, and 12 mm were prepared. Then, using the tension test at a high temperature, critical fracture force was determined. CT specimens were simulated by the finite element ABAQUS software. Fracture force obtained from the tension test was exerted on the CT specimen in the simulation software. Then, critical fracture toughness (KIC) was gained by using the fracture analysis in FE simulation. Finally, KI was compared with KIC and crack propagation was discussed.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
This study proposes an inverse methodology for determining the strain hardening behaviors at large deformation of titanium alloys using uniaxial tensile and notched tests with finite element ...analysis. Various hardening laws and data fitting range are considered to characterize the stress-strain relationships of commercially pure titanium (CP-Ti) and Ti6Al4V alloys which can increase the flexibility of identifying the proper models. A new hybrid HHSL hardening model is presented for CP-Ti and its parameters are obtained by iteratively minimizing the difference between the finite element simulation and experimental data. The hardening behavior of Ti6Al4V alloy is predicted by the weighted HSV model. The results show that mechanical response and loading curves from the identified numerical models are consistent with the experimental results of titanium alloys, demonstrating the validity and effectiveness of the proposed inverse approach in practical use.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
The indirect tension test is an important laboratory test for rock characterization. The presence of rock fabric, such as schistosity, complicates the assessment of test results. One hundred and ...forty-five indirect tension tests were conducted on mica schist specimens to investigate the effect of schistosity orientation on failure mode and tensile strength. Tensile strength results did not provide a clear relationship between schistosity orientation and tensile strength, so the failure patterns were investigated. A new naming scheme for failure modes was developed, incorporating fracture patterns observed in the specimen faces and edges. The Single Mode failure group specimens had only one failure pattern that appeared on both specimen faces, either axial failure (seventy-three specimens), schistosity failure (six specimens), or out-of-plane failure (seven specimens). The Mixed Mode failure group had thirty-two specimens that exhibited one failure pattern on one face and another on the other. The Hybrid Mode failure group had twenty-seven specimens with multiple failure patterns on both specimen faces. It was noted that Mixed Mode and Hybrid Mode specimens with components of axial failure had higher indirect tensile strengths than specimens without elements of axial failures. Statistical analyses of the tensile strength data using Levene’s Test for equal variances and two-sample t-tests showed no statistical difference between the Mixed Mode and Hybrid Mode failure groups. However, there was a statistical difference between the tensile strengths of the Single Mode axial failure specimens and the combined Mixed Mode and Hybrid Mode failure groups. These results clearly emphasize that indirect tensile strength should be assessed using schistosity orientation and failure mode.
Hydrogen embrittlement of a precipitation-hardened Fe–26Mn–11Al-1.2C (wt.%) austenitic steel was examined by tensile testing under hydrogen charging and thermal desorption analysis. While the high ...strength of the alloy (>1 GPa) was not affected, hydrogen charging reduced the engineering tensile elongation from 44 to only 5%. Hydrogen-assisted cracking mechanisms were studied via the joint use of electron backscatter diffraction analysis and orientation-optimized electron channeling contrast imaging. The observed embrittlement was mainly due to two mechanisms, namely, grain boundary triple junction cracking and slip-localization-induced intergranular cracking along micro-voids formed on grain boundaries. Grain boundary triple junction cracking occurs preferentially, while the microscopically ductile slip-localization-induced intergranular cracking assists crack growth during plastic deformation resulting in macroscopic brittle fracture appearance.
•Hydrogen embrittlement was observed in an austenitic steel with κ-carbide.•The hydrogen embrittlement was caused by grain boundary cracking.•An important crack initiation site is grain boundary triple junction.•Strain localization was observed particularly along grain boundaries.•The strain localization promotes the hydrogen embrittlement.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
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