Tensile Bending Stress Research Articles

Experimental Investigations on the Application of Natural Plant Fibers in Ultra-High-Performance Concrete.

Due to its high strength, the use of ultra-high-performance concrete (UHPC) is particularly suitable for components subjected to compressive loads. Combined with its excellent durability, UHPC can be used to produce highly resource-efficient components that represent a sustainable alternative to conventional load-bearing structures. Since UHPC fails in a brittle manner without the addition of fibers, it is typically used in conjunction with micro steel fibers. The production of these steel fibers is both expensive and energy-intensive. Natural plant fibers, due to their good mechanical properties, cost-effective availability, and inherent CO2 neutrality, can provide a sustainable alternative to conventional steel fibers. Thanks to the low alkaline environment and dense matrix of UHPC, the use of natural plant fibers in terms of durability and bond is possible in principle. For the application of natural plant fibers in UHPC, however, knowledge of the load-bearing and post-cracking behavior or the performance of UHPC reinforced with natural plant fibers is essential. Currently, there are no tests available on the influence of different types of natural plant fibers on the load-bearing behavior of UHPC. Therefore, five series of compression and bending tensile tests were conducted. Three series were reinforced with natural plant fibers (bamboo, coir, and flax), one series without fibers, and one series with steel fibers as a reference. Under compression loads, the test specimens reinforced with natural plant fibers did not fail abruptly and exhibited a comparable post-failure behavior and damage pattern to the reference specimens reinforced with steel fibers. In contrast, the natural plant fibers did not perform as well as the steel fibers under bending tensile stress but did show a certain post-cracking bending tensile strength. A final life cycle assessment demonstrates the superiority of natural plant fibers and shows their positive impact on the environment.

Investigation on fatigue crack propagation failure mechanism of hydraulic lifting pipe in deep‐ocean natural gas hydrate exploitation

AbstractIn deep‐ocean natural gas hydrate exploitation operation, the fatigue failure mechanism has attracted more and more attention from scholars, but it has not been effectively disclosed. Therefore, in this work, a multifield coupling and multiple‐nonlinear vibration model of lifting pipe is established, which can accurately determine the alternating stress of deep‐ocean lifting pipe. Second, according to Forman theory, the calculation method of crack propagation length and depth on the surface of a deep‐water riser is established, which is verified by the comparison between the experimental and theoretical model calculation results. The results demonstrate that, first, the effect of residual stress in the welded joint of deep‐ocean lifting pipe should be considered in the later parameter influence analysis. Second, the fatigue growth life of deep‐water pipe with small outflow velocity is mainly determined by tensile stress, and that is determined by both tensile stress and bending stress with large outflow velocity. Third, more attention should be paid to the vibration of the lower pipe on‐site to reduce its vibration frequency and vibration stress amplitude, which can effectively reduce the surface crack propagation state of the deep‐ocean pipe and improve the service life of the pipe. Fourth, properly adjusting the tension coefficient of the tensioner during field operation can effectively improve the safety of the pipe, and the optimal tension coefficient is related to the configuration of the deep‐ocean pipe system, which can be analyzed and determined by the model.

Reproduction of fissure corrosion and mechanism for fissure formation on ductile cast iron

On some cast iron pipes corroded under tensile stress, corrosion with a characteristic surface appearance, known as “fissure corrosion,” was occasionally observed. Because fissure corrosion on ductile cast iron pipes has been rarely studied, the detailed conditions and mechanism for fissure formation are still elusive. In this study, the levels of tensile stress and anodic current density causing fissure corrosion on ductile cast iron were investigated through laboratory experiments to reproduce fissure corrosion and elucidate its mechanism. Fissure corrosion was reproduced at bending tensile stresses ≥200 MPa. The depth difference between the peak and valley of fissures increased with increasing anodic current density, and the fissure corrosion was attributed to the difference between the anodic current densities of the peak and valley due to plastic deformation by stress concentration. Fissure corrosion was likely to be suppressed by reducing the anodic current flowing out of ductile cast iron surface.

Investigation of fracture behavior and mechanical properties of epoxy composites supported with MWCNTs microscopically

Adding of a multi-walled carbon nanotubes (MWCNTs) to epoxy resin has shown promising results in improving fracture toughness in bulk epoxy and carbon fiber-reinforced epoxy composites (CFRP). using a hand layup proceeding followed by the so called vacuum bagging process method, carbon fiber-reinforced polymer multi-wall carbon nanotubes (MWCNTs) was added to an epoxy resin with a weight percentage mixing of 1% wt., 1.25% wt., and 1.5 % wt. MWCNTs. Furthermore, the specimen underwent analysis via Fourier-Transform Infrared (FTIR) spectroscopy, and X-ray Diffraction (XRD) spectroscopy, the composites were subjected to a microscopic examination using a Scanning Electron Microscope (SEM). FTIR and XRD verified the folding and unfolding of the polymer, in addition, the mechanical properties including tensile strength, bending stress, and impact behavior were investigated as well as the hardness test. The obtained results showed a significant improvement of about (40 %) in tensile strength, (53 %) in bending stress at 1 % wt. MWCNTs, and (70 %) percentage increment in the strength of Impact at 1.25 % wt. MWCNTs. And the gained hardness was about 40.5 HV which were compared with a reference substance named Carbon Fiber (CF) without any addition of nano materials. Carbon nanotubes have demonstrated their potential to enhance the mechanical properties of fiber-reinforced polymers, so this investigative study employs comprehensive characterization techniques, and demonstrates significant improvements in mechanical properties for the modified polymeric composite materials supported with nano materials.

Influence on Physical and Mechanical Properties of Concrete Using Crushed Hazelnut Shell

Concrete production requires a significant amount of natural resources, with aggregates comprising between 55% and 80% of the total volume. However, the over-exploitation of natural aggregates has led to the exploration of alternative materials for use in concrete production. In this study, crushed hazelnut shells were investigated as a partial replacement for fine aggregate, addressing the problem of natural resource depletion and offering a second use for this important agricultural waste product available in Chile. Hazelnut shells were incorporated in percentages of 2.5%, 5%, and 10% by weight of sand for water/cement ratios of 0.4 and 0.5. The compressive strength at 7 and 28 days and bending strength at 28 days were determined, alongside physical properties such as the workability, temperature, air content, fresh density, and hardened density of the concrete. Our findings showed that replacing 2.5% of the fine aggregate with hazelnut shells led to a higher compressive strength at 28 days, exceeding the strength of the standard specimens by 9.5%, whereas replacing 5% of the fine aggregate led to the highest bending strength, exceeding the strength of the standard specimens by 3.5%. Moreover, the 0.4 w/c ratio consistently led to better results for both compressive and bending strength, with fewer and lower reductions in mechanical strength compared to the standard mixture. Our results suggest that concrete mixes with hazelnut shells as a replacement for fine aggregate at a percentage of up to 2.5% can be used in construction systems with a compression strength lower than 17 MPa, and mixtures with up to 10% hazelnut shell replacement can be used in structures with tensile bending stress requirements lower than 6 MPa. Overall, the use of hazelnut shells as a partial replacement for fine aggregate in concrete production presents an environmentally friendly and cost-effective solution for the construction industry.

Effect of Chemical and Physical Treatments on Mechanical Properties of Diss Fibers-Based Biocomposites Materials

ABSTRACT This work highlights the exploitation of fibers from a promising plant, commonly called Diss, in polymer matrix reinforcement. In this context, various untreated and treated (with acetic acid, silane, NaOH, thermal) Diss fibers were used to reinforce a thermoplastic matrix, polypropylene (PP). The effect of fiber treatments was evaluated at a ratio of 10% (by mass) of fiber, using mechanical, microstructural and physical characterization. A fiber content optimization study was carried out after choosing the fiber treatment by varying the fiber content from 10% to 40%. The microstructure observations showed a multi-layer structure for the biocomposites studied. The particular morphology of Diss fibers, with the presence of thorns, seems to improve the mechanical adhesion between the two phases. For 10% fiber content composites, the incorporation of the different fibers in the PP matrix led to improvements in most mechanical properties. The biocomposite reinforced with NaOH treated fibers (NPP-10%) showed the best mechanical performance with an improvement of 30%, 22% and 9% in tensile modulus, bending modulus and bending stress, respectively. For the fiber content variation, the NPP was retained, and an enhancement in the tensile modulus was found when the fiber content was below 20%.

P‐29: Influence of the Static Bending Stress on LTPS TFT

We investigated the degradation behavior of p‐channel LTPS TFTs on PI substrate under the static bending stress. In order to evaluate the bending durability of flexible LTPS TFTs, device‐bending tests under different bending strains and directions have been performed. The performance of TFT under tensile bending stress degraded (ΔVth≈ 0.38V) worse than compressive bending stress (ΔVth ≈0.07V), which might be originated from both the generation of interface trap states (ΔNit) and channel boundary trap density (ΔNtrap) under tensile bending stress much higher than compression‐bent. In the meanwhile, the stress distribution has also been simulated. According to the results of test and simulation, we speculated the mechanical stress near the source and drain electrodes caused the traps in gate insulator, which in turn cause electron trapping.

Bio-Physical Properties of Acetylated Chitosan/Poly(ɛ-Caprolactone) Composites for Three-Dimensional Printing Material Applications.

For three-dimensional (3D) printing material applications in tissue engineering, acetylated chitosan (AC)/poly(ɛ-caprolactone) (PCL) composites were prepared by the melt mixing method using the acetylation of chitosan with PCL. The physiochemical properties of the AC/PCL composites were examined by measuring the water contact angles, dispersity of AC on the cross-section using scanning electron microscopy, and temperature stability. In addition, mechanical properties such as tensile strength and bending stress recovery were measured to determine the elasticity of the composite films. The fibroblast cell line NIH-3T3 was used to test the relative cell affinities based on the AC content and cell viability on AC/PCL at various temperatures. There was no difference between the melting points and tensile strengths of the AC/PCL composites and pure PCL. Overall, the AC/PCL composites showed high initial cell adhesion after 4 h of cell culture and increased cell proliferation compared to those of PCL composites used as a control. Based on these tests, an AC of 10.7 wt% was determined to be the optimal composition for the AC/PCL composite. Thus, these composites can be used in various 3D printing material applications in tissue engineering.

Enhancing Reliability and 2 mm-Axial Mechanical Bending Endurance by Gate Insulator Improvements in Flexible Polycrystalline Silicon TFTs

In this study, the electrical performance and bending stress endurance of flexible low-temperature polycrystalline silicon thin film transistors (LTPS TFTs) are enhanced by increasing the helium concentration (1500 sccm) during gate insulator (GI) manufacture to create a high-quality GI device. Experimental results confirm that the subthreshold swing (S.S.) and mobility of these new &#x201C;high-flow&#x201D; devices are better than those with a lower helium concentration, which we term &#x201C;low-flow&#x201D; devices. The flow of helium gas is increased to achieve a better-quality oxide layer. The energy-dispersive X-ray spectroscopy (EDS) line data show a clear enhancement in oxygen content in the devices under this helium gas process. After mechanical compression and tensile bending stresses of 100000 iterations in the channel width-axis direction, perpendicular to the channel, with bending at <inline-formula> <tex-math notation="LaTeX">${R} = {2}$ </tex-math></inline-formula> mm, the modified GI devices with their more Si-O bond content exhibit less stress damage in the GI layer than do low-flow devices. As a result, this new manufacturing condition can effectively reduce the electrical degradation after negative-bias temperature stress (NBTS), and improve the overall electrical performance.

EXPERIMENTAL STUDY OF THE INTERACTION OF CORROSION DAMAGE AND OUT-OF-CIRCULARITY IN THE COLLAPSE OF SUBMARINE PRESSURE HULLS

&#x0D; &#x0D; &#x0D; The effect of corrosion damage on overall collapse strength of submarine pressure hulls was studied experimentally. Ring-stiffened cylinders were machined from aluminium tubing and loaded to collapse under external pressure. In selected specimens, some of the outer shell material was machined away in large single patches, representing general corrosion. Other specimens had many smaller patches, representing corrosion pitting from the outside of the hull, followed by grinding. Large-amplitude out-of-circularity (OOC) was introduced by mechanically deforming selected cylinders. Clusters of artificial corrosion pits were found to have approximately the same effect on collapse pressure as equal-depth general corrosion covering the same region of plating. General corrosion was found to be most severe when it was “in-phase” with OOC, since, during pressure loading, high compressive stresses resulting from corrosion were compounded by compressive bending stresses associated with OOC, and furthermore, the corrosion tended to increase the geometric imperfection itself. On the other hand, out-of-phase corrosion reduced the effect of OOC, while at the same time the thinning-associated compressive stresses were counteracted by local tensile bending stresses associated with OOC, so that strength reductions were correspondingly smaller. Overall collapse pressures for corroded specimens were reduced by, on average, 0.85% for each 1% of shell thinning. That result is based on a linear approximation of the nonlinear relationship between thinning and collapse pressure. The linear trend-line, which was used to account for the experimental scatter, is based on specimens with 13 to 27% shell thinning, and with a variety of corrosion areas and OOC amplitudes.&#x0D; &#x0D; &#x0D;

Tensile Bending Stresses in Mortar-Grouted Riprap Revetments Due to Wave Loading

One of the most common revetment types in Germany is the mortar-grouted riprap revetment (MGRR), which is constructed by placing riprap on a filter or separation layer and subsequent grouting with mortar. Existing technical standards and guidelines for MGRRs do not consider the interaction between dynamic wave loading and structural response. To date, scientifically sound design approaches verified by model tests are missing. Therefore, the aim of this work is to establish a process-based model for the calculation of the acting bending tensile stresses during wave attack for MGRRs to asses crack formation. To this end, MGRRs were modelled as plates on an elastic foundation (PEF). Hydraulic boundary conditions were determined with full-scale hydraulic model tests. Model parameters of the PEF model were established by investigations into the mechanical parameters of the constituents of MGRRs. The results show that tensile bending stresses are particularly dependent on the pressure difference between the top and bottom edge of the top layer, which varies significantly for MGRRs as their porosity and permeability varies significantly depending on the amount of mortar used for grouting. Enveloping functions for maximum relative tensile bending stress σx,max/(ρwgHm0) are given for four configurations of MGRRs that are of great practical relevance.

Study on Control Standard of Frost Heave Deformation and Freeze-thaw Strength of Cohesive Soil of Expressway Widening Subgrade in Seasonal Frozen Region

This paper is aiming at control standard of frost heave deformation and freeze-thaw strength of cohesive soil of expressway widening subgrade in seasonal frozen region. Research was proposed to study the deformation law of high water content clay subgrade in freeze-thaw condition through laboratory test, field monitoring and theoretical analysis. According to the results, frost heave deformation control standard of cohesive soil subgrade has been proposed. Considering the overload load, the subgrade’s differential deformation rate should be less than 3.07‰ and the differential deformation rate must be less than 2.27‰. Considering the allowable bending tensile stress and the pavement structure service life, the differential deformation rate of the top surface of the subgrade under the effect of frost heaving of the high water content cohesive soil subgrade in the seasonal frost zone should be controlled within 2‰. After that, control standard for freeze-thaw strength of cohesive soil subgrade is put forward that, the subgrade-soil strength ratio of the high water content cohesive soil subgrade in the seasonal frost zone should be controlled within 0.75 under the standard load and within 1 under the overload load considering the allowable flexural stress and service life of the pavement structure.

Stability analysis of block-flexural toppling of rock blocks with round edges

One of the most conventional toppling instabilities is the block-flexural toppling failure that occurs in civil and mining engineering projects. In this kind of failure, some rock columns are broken due to tensile bending stresses, and the others are overturned due to their weights, and finally, all of the blocks topple together. A specific feature of spheroidal weathering is the rounding of the rock column edges. In the mode of flexural toppling failure, rounding of edges happens only at the upper corners of the block but in the block toppling failure mode, due to the presence of cross-joints at the base of the block, rounding of edges also occurs at the base of the block. In this work, a theoretical model is offered to block-flexural toppling failure regarding the erosion phenomenon. The suggested methodology is evaluated through a typical example and a case study. The results of this research work illustrate that in the stable slopes with rectangular prismatic blocks, where the safety factor value is close to one, the slope is subjected to failure due to erosion. Also the results obtained show that the recommended approach is conservative in analyzing the block-flexural toppling failure, and this approach can be applied to evaluate this failure.

Threshold voltage shift-proof circular oxide thin film transistor with top and bottom gates for high bending stability

Negligible threshold-voltage shift is reported for oxide thin-film transistors (TFTs) under high current (3 μA) and tensile bending stress (2 mm radius). The good stability is attributed to a circular TFT structure with electrically shorted top and bottom gates, and a polyimide substrate embedded with carbon-nanotubes for mechanical support and damage-free detachment from carrier glass. The circular structure leads to uniform electric field distribution across the channel, hard saturation in output characteristics, independence from tensile bending direction-related degradation, as well as isolation of the channel from stress concentrated points, which arise from local electric-field crowding at sharp corners or channel edges. The double-gate topology increases gate-drivability and achieves volume-accumulation, which minimizes the influence of defects at the channel surface and slight variations in carrier concentration during stress. Furthermore, the presence of two gates slightly shifts the location of the neutral bending plane towards the oxide semiconductor, thereby significantly reducing strain.

Study on the optical quality and strength of glass edges after the grinding and polishing process

Glass edges result from cutting glass sheets and a further optional finishing. The mechanical interference into the brittle material glass causes flaws and cracks at the edge surface. Those defects have an influence on the strength of the whole glazing. Within the scope of a research project at the Institute of Building Construction from the Technische Universität Dresden, the grinding and polishing process is examined in terms of characteristic visible effects on the glass edge and the edge strength. Thereby a special focus of the research project is the impact of various polishing cup wheels for the chamfer surface of annealed glass. The article presents some basics about the processing steps of glass edges surfaces, introduces the considered grinding and polishing cup wheels and gives an overview of the performed experimental examinations. A microscopic analysis enables a characterisation of typical defects at the surfaces. Furthermore, four-point bending tests are performed to determine the bending tensile stresses at failure. The combination of both methods enables an analysis of the fracture-causing defect before destruction and a correlation between the optical surface quality and the bending tensile stresses. Additionally, the microscopy could be used to support the adjustment of a grinding machine and control reproducible edge qualities. The evaluation shows that a special development of polishing cup wheels for the chamfer can improve the surface quality and consequently increases the edge strength.

Hybrid Method Analysis of Variance (ANOVA) and Loss Function to Analyzed Optimizing Composition of Fiber Baggase and Fly Ash

Research on the utilization of baggase fiber as a composite material has been done, but still has shortcomings in the composite material brilliance. Therefore, the use of baggase fiber combined with coal ash can be an alternative to make a composite material. The purpose of this research is to know the effect of baggase fiber composition and fly ash composition to tensile stress and bending stress. This paper discusses the application of Analysis of Variance (ANOVA) on composite material data. There are two variables measured are variable of tensile stress and variable of bending stress. The result obtained that there is influence composition of baggase fiber and composition of fly ash at tensile stress and bending stress. Furthermore, further tests using Tukey method showed that the different composition pairs significantly were 10% -30%, 10% -40% and 20% -40% in both compositions of the two variables studied. In the determination of loss function with Signal-to-Noise (SN) Ratio with larger-is-the-better criteria, the composition of 40% baggase fiber, 10% fly ash composition and 50% matrix can produce optimal tensile and bending strength.

Failure Behaviour of 3D Printed ABS Lattice Structure under Compression

Lattice structure is a lightweight material that can be produced using the cutting edge additive layer manufacturing process or also known as 3D printing. Lattice structure material is a periodic cellular structure material that can be utilized in various applications especially as core material in sandwich structure configuration, where the ultimate aim is to be a lightweight material with load bearing capability. Researches are yet to be done to fully understand the behavior of lattice structure materials under several loading conditions such as tensile, bending and compression. The objective of this paper is to discuss the behavior of acrylonitrile-butadiene-styrene (ABS) lattice structure material that was produced using the layer by layer manufacturing, subjected to compressive load. Lattice structure specimens with dimension 20x20x20 mm3 were designed with body centered cubic (BCC) unit cells for three sets of strut diameter size. The specimens were produced using fused deposition modelling (FDM) Cubepro 3D printer, with varying default parameters of layer thickness, print strength and print pattern. All specimens were subjected to compressive load until densification stage and the stress-strain curves of the material were plotted. The compressed specimens were observed under an optical digital microscope and a common failure behavior of 3D-printed ABS lattice structure material was highlighted. It was shown that the failure of compressed lattice structure was initiated at joint node areas due to bending tensile stress. It can be concluded that this polymer material showed hybrid between stretch and bending-dominated characteristics. This is a good indicator for lightweight material with load absorbing capability. An understanding in the failure behavior of ABS lattice structure material is enriching the knowledge on this material under stress-strain condition.

A study of spot weld pull-out failure (PF) mechanism under different loading conditions for stainless steel and mild steel joints

ABSTRACTSpot weld pull-out failures (PFs) on mild steel and stainless steel joints were investigated under different loading conditions using lap-shear test, cross-tension (KSII) test and coach-peel test. Regardless of the joint type, joints tested with lap-shear test showed the highest weld strength followed by KSII and coach-peel tests, respectively, for the same welding current. Analyses with experimental samples and finite element analysis showed that PFs due to different loading conditions were governed by either tensile stress, shear stress or bending stress. The tendency to fail via weld PF increased from welds tested with KSII test, coach-peel test and lap-shear test for similar steel joints within a range of welding currents. This study also showed that the weld diameters for PF depend on the joint type as well as loading conditions and did not conform to the recommended weld diameters by the automotive standards.

The role of bending stress on the initiation of reverse transverse defects

This paper investigated the role of longitudinal reverse bending stress on the initiation of reverse transverse defects. The longitudinal reverse bending stress occurs due to the reverse bending of the rail between two-wheel passage leading to the generation of tensile bending stress at the railhead and the lower head areas. The longitudinal bending stress was investigated as part of a parametric study on the rail cant angle, rail stiffness, lateral-to-vertical load ratio, and rail profile. A finite element model was created by using ABAQUS to analyze the extent of reverse bending in rails with respect to the chosen set of parameters. Under different lateral-to-vertical load ratios of 0, 0.3, 0.5, and 0.7, the maximum stress at the rail lower gauge corner was found to vary between 14.57MPa and 15.47MPa under the reverse bending condition. Similarly, low values of tensile stress under the reverse bending scenario were observed with changes in the rail cant angle and axle spacing with respect to different coal and iron ore wagons. The results revealed that the magnitude of the bending stress under different conditions of reverse bending was not significant enough to initiate a crack at the lower gauge corner.

Uniaxial Strain-Controlled Ground States in Manganite Films.

Strongly correlated perovskite oxides exhibit a plethera of intriguing phenomena and stimulate a great potential for multifunctional device applications. Utilizing tunable uniaxial strain, rather than biaxial or anisotropic strain, delivered from the crystallography of a single crystal substrate to modify the ground state of strongly correlated perovskite oxides has rarely been addressed for phase-space control. Here, we show that the physical properties of La2/3Ca1/3MnO3 (LCMO) films are remarkably different depending on the crystallographic orientations of the orthorhombic NdGaO3 (NGO) substrates. More importantly, the antiferromagnetic charge-ordered insulating (COI) phase induced in the (100) or (001)-oriented LCMO films can be dramatically promoted (or suppressed) by a uniaxial tensile (or compressive) bending stress along the in-plane [010] direction. By contrast, the COI phase is nearly unaffected along the other transverse in-plane directions. Results from scanning transmission electron microscopy reveal that the (100)- or (001)-oriented LCMO films are uniaxially tensile strained along the [010] direction, while the LCMO/NGO(010) and LCMO/NGO(110) films remaining as a bulklike ferromagnetic metallic state exhibit a different strain state. Density functional theory calculations further reveal that the cooperatively increased Jahn-Teller distortion and charge ordering may be indispensible for the inducing and promoting of the COI phase. These findings provide a path to understand the correlation between local and extended structural distortions imparted by coherent epitaxy and the electronic states for quantum phase engineering.