Direction Of Tensile Stress Research Articles

High temperature tensile creep behavior and microstructure evolution of Ti60 alloy rolled sheet

In this work, the high temperature tensile creep test of 2 mm Ti60 alloy rolled sheet was carried out, and the creep behavior and microstructure evolution were studied. The initial microstructure of the 2 mm Ti60 alloy rolled sheet is mainly composed of primary α phase and secondary α phase, and there are many dislocations and dynamic recrystallization (DRX) inside the rolled sheet. According to Norton-Bailey law, the creep stress exponent at 600 °C is calculated to be 3.6, and creep activation energy at 200 MPa is calculated to be 286.4 kJ/mol. It implies that the creep mechanism of the rolled sheet includes dislocation slip and dislocation climb. The initial Ti60 alloy rolled sheet has the {0001}<10–10>α texture. Stretching along the RD makes the texture direction gradually change from B-type (<0001>//ND) to T-type (<0001>//TD). Whether it is the B-type texture or T-type texture, the (0001) plane of the α phase always exhibits a basal texture state parallel to the tensile stress direction, contributing a good tensile creep property of this alloy sheet.

A transient radial cortical microtubule array primes cell division in Arabidopsis

Although the formation of new walls during plant cell division tends to follow maximal tensile stress direction, analyses of individual cells over time reveal a much more variable behavior. The origin of such variability as well as the exact role of interphasic microtubule behavior before cell division have remained mysterious so far. To approach this question, we took advantage of the Arabidopsis stem, where the tensile stress pattern is both highly anisotropic and stable. Although cortical microtubules (CMTs) generally align with maximal tensile stress, we detected a specific time window, ca. 3 h before cell division, where cells form a radial pattern of CMTs. This microtubule array organization preceded preprophase band (PPB) formation, a transient CMT array predicting the position of the future division plane. It was observed under different growth conditions and was not related to cell geometry or polar auxin transport. Interestingly, this cortical radial pattern correlated with the well-documented increase of cytoplasmic microtubule accumulation before cell division. This radial organization was prolonged in cells of the trm678 mutant, where CMTs are unable to form a PPB. Whereas division plane orientation in trm678 is noisier, we found that cell division symmetry was in contrast less variable between daughter cells. We propose that this "radial step" reflects a trade-off in robustness for two essential cell division attributes: symmetry and orientation. This involves a "reset" stage in G2, where an increased cytoplasmic microtubule accumulation transiently disrupts CMT alignment with tissue stress.

Fretting fatigue behavior of helical-torsional contact steel wire in wire rope

Fretting wear and torsional deformation of steel wire can reduce the performance of wire rope and threaten the safety of mine hoisting system. In this study, to explore the influence of different torsional deformation on the fretting fatigue wear behavior under multi-wire spiral contact, an experimental study was conducted on a self-made test apparatus. The results show that the increase of torsional deformation can reduce the breaking force of steel wire by about 2.6%, and reduce the bending fatigue performance by about 36.4%. In addition, the maximum wear depth, wear amount and coefficient of wear increase with the increase of torsional deformation. The torsion and deformation of the pearlite lamellae parallel to the tensile stress direction are the main reasons for the decrease of the wear resistance of the main steel wires. More torsional deformation makes the steel wire produce less furrow morphology in fretting fatigue wear. The main wear mechanism of steel wire with small torsional deformation is abrasive and tribochemical reactions, and the main wear mechanism of steel wire with large torsional deformation is surface fatigue and tribochemical reactions.

Design and flexural behavior of steel fiber-reinforced concrete beams with regular oriented fibers and GFRP bars

In this study, steel fiber-reinforced concrete (SFRC) beam structures with regular oriented steel fibers are designed and prepared by using an assembled solenoid device. Fiber orientation is not arranged in a single direction but is similar to the direction of tensile stress of the beam in bending load conditions. With application of inductive test method and image processing technology, fiber orientation coefficient of SFRC was evaluated and increased from 0.5 to 0.7–0.8 after fiber alignment. To describe and analyze the flexural behavior of SFRC beams with regular oriented fibers and glass fiber-reinforced polymer (GFRP) rebars, 14 concrete beams with different parameters were fabricated and subjected to a four-point bending test. Specifically, the parameters included fiber content, fiber orientation, GFRP reinforcement ratio and different layer sections. The results showed that optimizing fiber orientations to the tension zone of the section led to a higher flexural strength and can well restrain the development of crack widths with comparison to randomly distributed fibers. The peak load and energy absorption increased by 7 % and 12.4 % after fiber alignment with a fiber volume fraction of 1.5 %. The combination of randomly and regularly distributed steel fibers in the form of two-layer composite members can be an efficient solution to improve the flexural performance for purpose of the optimum distribution and direction of steel fibers, and reduce the engineering cost.

Effect of steel fiber orientation on punching shear resistance of steel fiber reinforced cementitious composites round slabs

The slab-column structure is commonly used in civil engineering. At the slab-column joints, the load from the slab is transmitted to the column. In the extreme state, punching shear failure may occur at the joints, and the failure is brittle without warning. When the punching shear failure occurs at the joint of round slab and column, usually the cracking is a conical shape because the direction of tensile stress caused by punching shear is generally radial. By incorporating steel fibers into cementitious composites round slabs, the steel fibers can bridge the conical surface, and therefore enhance the punching shear resistance of round slabs. If the steel fibers in the round slab are dispersed in the direction conducive to the punching shear resistance, the steel fibers can take full effect of strengthening and toughening, thus improving the punching shear resistance of the slab. So, the purpose of this investigation is to improve the punching shear resistance of steel fiber reinforced cementitious composite slabs by maximizing the reinforcement of steel fibers on the composites. Firstly, a model of punching shear resistance of steel fiber reinforced cementitious composite round slabs was derived based on the Modified Compression Field Theory with consideration of the orientation of steel fibers. According to the model, the slab with radial distribution of steel fibers around the punching shear area shows the highest punching shear resistance. Secondly, the approach of radially aligning steel fibers in the slab around the punching area by magnetic driving is proposed using a self-developed magnetic device. And, radially dispersed steel fiber reinforced cementitious composites (JD-SFRC) round slabs were prepared. Thirdly, the punching shear resistance of JD-SFRC round slabs, as well as unidirectionally aligned (1D), two-dimensionally aligned (2D), and randomly distributed (RD) steel fiber reinforced cementitious composites round slabs were tested. At last, the effect of the orientation of steel fibers on the punching shear resistance and failure characteristics of the round slabs were analyzed by comparing the results from tests and the model. Meanwhile, the effect of the volume fraction of steel fibers on the punching shear resistance of the slab was examined. The results show that, When the volume fraction of steel fiber is 1.0 %, compared with RD-SFRC round slabs, the ultimate shear resistance of 1D-SFRC, 2D-SFRC and JD-SFRC round slabs is increased by 14 %, 15 %, and 24 %, respectively.

Towards development of cement-based composites reinforced with architected 3D-printed polymers

In the present work, mortar beams reinforced with polymeric reinforcing elements are manufactured using Polylactic acid (PLA), inspired by crack propagation deflecting architectures found in nature such as Sinusoidal and Bouligand architectures. Mechanical flexural properties of mortar beams are studied and compared with that of reinforcing elements with an architecture parallel to the direction of tensile stress as well as non-reinforced mortar beams. Furthermore, the reinforcement configuration and ratio are designed using principles from mechanics of materials. A Digital Image Correlation (DIC) technique is used to obtain the load-deflection curves during flexural evaluation. Results show that changing the microarchitecture of the reinforcement can enhance the flexural performance of the beam. Additionally, interface properties between the mortar and the reinforcing element are studied using pull-out tests. Interface properties were enhanced by introducing architectural patterns on the surface of the reinforcement. Finally, using material properties of the mortar, reinforcement and the interface obtained from experiments, a numerical model is developed and calibrated. The outcome of this study helps explore the opportunities of using novel nature-inspired reinforcement to enhance the mechanical properties of cementitious composites.

Effect of elastic tensile stress on the pitting corrosion mechanism and passive film of 2205 duplex stainless steel

The effects of elastic tensile stress on the pitting corrosion mechanism and passive film of 2205 duplex stainless steel (DSS) in an NaCl solution containing sulfide ions are investigated. The results reveal that as the elastic tensile stress increases, the pitting corrosion sensitivity of 2205 DSS first decreases and then gradually increases, which is attributed to the changes in the chemical state, thickness, and micro-defects of passive film. Furthermore, the initial pits occur at the austenite phase under low elastic stress but at the ferrite phase under higher elastic stress. The corrosion pits grow rapidly along the pit bottom direction and the perpendicular direction of tensile stress.

Fibre alignment in fresh concrete with coarse aggregates and its visualization in transparent model concrete

Steel fibres distributed in concrete can greatly improve the mechanical performance of concrete, especially flexural and tensile behavior, if their orientations align to the direction of principal tensile stress. The study attempts to find diversified characters of fibre alignment in fresh concrete with consideration of adding coarse aggregates. A transparent concrete model, consisting of Carbopol gel, glass beads and crystals, is designed for the observation of fibre orientation. It shows good transparency and visibility, and can consider the effect of coarse aggregates since the volume fraction and particle size distribution of crystals are the same as coarse aggregates in real concrete mixture. The rheological properties of the model can be adjusted by the dosage of Carbopol and glass beads. Using this concrete model, the distribution and orientation of fibres can be directly observed and analyzed, considering the effect of aggregate sizes, concrete rheology and vibration time. The results show that coarse aggregates could limit the distribution space of fibres and lead to the decrease of fibre orientation coefficient. Fibre dispersion coefficient also decreases with the increase of aggregate sizes.

The trabecular architecture of the popliteal sesamoid bone (cyamella) from a New Zealand white rabbit (Oryctolagus cuniculus).

Sesamoid bones are ossified structures that are embedded in tendons near articulation. They consist of an inner trabecular bone architecture surrounded by a thin cortical shell. While the formation of sesamoid bones is probably mainly controlled by genetic factors, the proper development and mineralization of a sesamoid bone depends also on mechanical stimulation. While most sesamoid bones are not loaded directly by other bones during locomotion, they still experience forces directed from the tendon in which they are embedded. In cases when the sesamoid bone is experiencing forces only from a single tendon, such as the cyamella in the rabbit, this may give us a tool to study bone functional adaptation in a relatively simple loading setting. This study investigates the internal trabecular architecture of the popliteal sesamoid bone (cyamellae) in New Zealand white (NZW) rabbits (Oryctolagus cuniculus). Five hind limbs of NZW rabbits were micro-computed tomography scanned and the cortical and trabecular architectures of the cyamellae were evaluated. The results revealed that similar to the patella, the cyamella has a thin cortex and a high trabecular bone volume fraction (BV/TV), which is derived mostly from the high trabecular thickness (Tb.Th). Trabecular BV/TV and Tb.Th were not distributed homogeneously, but they were lower at the periphery and higher closer to the proximal and middle of the cyamella, near the musculotendinous junction. The results also demonstrated that trabeculae tend to align along two recognizable orientations, one with the direction of tensile stresses, in line with the popliteal tendon, and the second bridging the narrow space between the cranial and caudal cortical faces of the bone.

Orientation dependence of the nanocrystallization and magnetic behavior during annealing of the FINEMET alloy

The microscopic strain evolution and microstructural of FeCuNbSiB amorphous alloy samples were studied under both free and tensile stress annealing conditions using in-situ synchrotron X-ray diffraction (XRD) and transmission electron microscopy (TEM). An amorphous-nanocrystalline structure was developed in both samples after annealing at 813 K, as the microstrains increased and decreased along the parallel and perpendicular stress directions respectively. The applied stress during annealing imposed limitations on the size of nanocrystals along the tensile and perpendicular stress directions, resulting in smaller sizes compared to those obtained under free annealing conditions, due to the reduction in Gibbs free energy by the applied stress and the subsequent enhancement of nucleation rates. The nanocrystalline size perpendicular to the stress direction was slightly larger than that along the parallel stress direction because the suppression of atomic diffusion perpendicular to the stress direction during crystallization could be favorable for local atomic rearrangement.

Investigation on the performance of annularly aligned steel fiber reinforced cementitious composites pipe under internal water pressure

Steel fiber reinforced concrete pipes are commonly used in the municipal, agricultural, and industrial fields because of their superior internal water pressure performance. However, the randomly distributed steel fibers hinder the further improvement of internal water pressure performance. To maximise the reinforcement effect of steel fibers and improve the internal water pressure performance, an external circular magnetic field was first utilised to prepare annularly aligned steel fiber reinforced cementitious composite (AASFRC) pipes in which the steel fibers were aligned in the direction of tensile stress. Subsequently, the internal water pressure performance of AASFRC and steel fiber reinforced cementitious composite (SFRC) pipes was experimentally and numerically investigated. Finally, the reinforcement mechanism of the annularly aligned steel fibers was revealed from the aspects of fiber distribution and fiber resultant force. The results showed that the deformation and bearing capacity were enhanced by annularly aligned steel fibers. The ultimate internal water pressure of the AASFRC pipes was greater than that of the SFRC pipes by 22–32% with fiber volume fractions (Vf) of 0.8%, 1.2%, and 1.6%, implying that using less fiber in AASFRC pipes can ensure an internal water pressure performance equivalent to that of SFRC pipes. Both the fiber orientation efficiency factor and number of fibers bridging the principal cracking section of the AASFRC pipes were greater than those of the SFRC pipes. The fiber resultant force of AASFRC specimens was 2.04–2.64 times greater than that of SFRC, contributing to the enhancement in the bearing capacity of AASFRC pipes.

Correlation between stress relaxation induced anisotropy, magnetic domain, and permeability of Co-doped FeCuSiBNbMn alloys

The effect of Co contents on the permeability, magnetic anisotropy, and structure has been investigated for FeSiBNbCuMn amorphous alloys during annealing with and without tensile stress. Large stress relaxation-induced anisotropy (Ku) of 482.0–1485.4 J/m3 is observed with an easy axis perpendicular to the direction of tensile stress (i.e., ribbon axis), which results in constant permeability of 1–2.8 × 103 at 1 kHz − 1 MHz. Different from the irregular domain structure in the samples annealed without tensile stress, stress annealing generates regular domains and 180° straight walls, and domain width increases with the increases of Co contents. Besides, the correlation between permeability, induced anisotropy, and domain width is established. These results could provide a good guide for improving the frequency stability of permeability by adjusting anisotropy and domain structure.

Effect of the orientation of steel fiber on the strength of ultra-high-performance concrete (UHPC)

Copper-plated microwire steel fiber is generally added to ultra-high-performance concrete (UHPC) to reduce its brittleness. In the UHPC, the steel fibers are randomly dispersed. When subjected to a specific load, the steel fibers that have an orientation consistent with or close to the direction of tensile stress can take full effect of reinforcement on the matrix, while the reinforcing effect of those steel fibers perpendicular to the tensile is relatively weak. From this point of view, the influence of steel fiber orientation on the strength of UHPC was modeled and analyzed in this investigation. During modeling, the tensile, flexural, and compressive strength of the UHPC were correlated with the orientation efficiency factor of steel fiber. In the tests, aligned steel fiber reinforced ultra-high-performance concrete (ASF-UHPC) specimens were prepared by using electromagnetic field treatment to align the steel fibers in the specimens, and the tensile, flexural, and compressive properties of ASF-UHPC specimens were tested and compared with the modeling results. The reinforcement mechanism of aligned steel fiber on the properties of UHPC was analyzed. The results showed that the mechanical properties of ASF-UHPC specimens are significantly higher than those of UHPC with randomly distributed steel fibers (RSF-UHPC) specimens, and the model can well predict the mechanical properties of UHPC.

Crack propagation, failure and ultimate load capacity of the grout layer in the prestressed anchor bolt foundation of wind turbine tower

The finite element (FE) analyses based on linear elastic fracture mechanics (LEFM) for the crack propagation and failure of the grout layer in the wind turbine foundation with pre-stressed anchor bolts are presented. Firstly, one half-symmetric planar numerical model is developed. According to the linear elastic analytical results, one initial crack is set to be the zone of the maximum tensile streess and its direction is perpendicular to the direction of the maximum principle tensile stress. The crack will propagate in the direction of the zero mode-II stress intensity factor during the failure of the grout layer. The numerical simulations with different prarmeters are performed. The histories of mode-I stress intensity factor are analyzed and design formulas predicting the failure and ultimate load capacity of the grout layer are proposed based on parametric studies. The increasing width or the decreasing depth of the grout layer can significantly mitigate the failure. One case study of the grout layer with the typical size and the corresponding fatigue analyses are carried out. The numerical results show that the proposed equation can agree well with the cracking status and failure of the grout layer in practical engineering and help predict the fatigue life of the grout layer under the certain intial crack length.

Study on explosion in different cross-sectional shape charge cavity in tensile stress field

Purpose. To study nature and patterns of main cracks development in a solid medium during an explosion of explosive charge in charge cavity with longitudinal symmetrical incision and various cross-sectional shapes Methodology. Experimental methods were used to study process dynamics, nature and direction of cracks development during the explosion of explosive charge of various shapes and their transformation into a clear optical image under the influence of a focused laser beam through an optical system – the method of caustics. Study on stress field changes under the combined effect of static and dynamic loading on fracture medium by polarisation-optical method. Based on correlation analysis methods, study results are analysed. Findings. It is experimentally proved that changing angle from 0 to 45° between longitudinal cut and plane jointly affected by tensile stresses and explosion action promotes opening of main cracks both parallel and perpendicular to cut direction. Dependences of propagation of main cracks caused by an explosion in model under different loading conditions are constructed. Calculations of stress intensity coefficients in medium under explosion and tensile stresses were performed. Originality. Improved research methodology for establishing the mechanism of explosive loading of solid media by explosion of explosive charge of different cross-sectional shapes is proposed. Physical mechanism of main cracks formation and propagation in blast cavity under action of explosive charge of different shapes under different conditions of dynamic loading is revealed. Dimensions of symmetrical longitudinal incision and spatial location of crack along direction of tensile stresses are substantiated. Also, an idea of using a directed explosion to form a protective strip in the rock mass was further developed. Practical value. The research results received can be necessary for developing new technical solutions to provide additional protective measures in the field of environmental and seismic safety of protected civil and industrial facilities during blasting operations in quarries and mines.

Mechanical properties of a 3D-printed SFRC beam with steel fiber distribution adaptive to tensile stress

To maximize the reinforcement of steel fiber in the steel fiber reinforced cementitious composite (SFRC) simply supported beam subjected to concentrated load at the midspan, the steel fiber is distributed according to the magnitude and direction of the tensile stress at the section of the midspan, which is defined as the adaptively distributed steel fiber reinforced cementitious composite (DD-SFRC) beam. In the DD-SFRC specimens, the dosage of steel fiber increases with the magnitude of the tensile stress and the orientation of steel fibers is parallel to the direction of tensile stress. In the preparation of the DD-SFRC beams, the distribution density and orientation of steel fibers were controlled by 3D printing and magnetic field, respectively. The mechanical properties of the beam were investigated by three-point bending tests and compared with the beams with aligned (AD-SFRC) or random (RD-SFRC) steel fiber distribution. The results showed that the mechanical properties of the beam are significantly improved by the adaptive distribution of steel fibers.

Enhancing two-way shape memory behavior of polycaprolactone nanofibers through aligned crystallization optimization

Stress-free two-way shape memory polymers capable of reversible shifting between two distinct shapes offer versatile platforms for the development of future smart devices. However, improving the recovery performance of bidirectional shape memory polymers with good biocompatibility and stimulus temperature remains challenging. Studies have shown that enhancing oriented crystallization can effectively improve shape recovery performance. Herein, we demonstrate a simple approach to enhance the number of nanofibers aligned in the tensile stress direction by controlling the alignment direction of polycaprolactone nanofibers, which promotes the generation of oriented crystallization in the tensile state, thereby achieving a 230.8% improvement in recoverable strain. The optimization of the nanofiber structure offers a generalized method for enhancing the two-way shape memory behavior of semicrystalline polymers.

Effect of static tensile stress on enzymatic degradation of poly(glycerol sebacate).

Poly(glycerol sebacate) (PGS) is an excellent scaffold material in tissue engineering due to good biocompatibility and tunable mechanical properties. The degradation properties of PGS have been primarily explored in static phosphate buffer solution or enzyme solution. It is vital to understand how the tensile stress affect the degradation rate. In this study, PGS was synthetized by melt polycondensation and its properties were characterized. Then an in vitro degradation device which could provide different constant tensile stresses was carefully designed and established, and the enzymatic degradation of PGS was tested under 0-150 kPa at 37°C. It was found that holes of PGS surface arranged almost parallel to each other and perpendicular to the direction of tensile stresses at 100 kPa and 150 kPa after 2-4 days degradation. After 8 days degradation, the ultimate tensile strength (UTS) of PGS at 150 kPa was 0.28 MPa and the elastic modulus was 1.11 MPa, while the UTS of PGS was 0.44 MPa and the elastic modulus was 1.63 MPa before degradation, both of them have significant differences. Hence, the tensile stress and degradation time were proportional to the appear time and size of holes, leading to the decrease of mass loss, UTS and elastic modulus. The relationship between stress and PGS degradation rates was quantitatively described through our degradation experiments, providing guidance for suitable PGS applications in the future.

Experiment study on seismic behavior of squat UHPC shear walls subjected to tension-shear combined cyclic load

Five squat UHPC shear walls with high axial tension ratio ranging from 0.5 to 0.6 were tested under tension-shear combined cyclic load to replicate seismic performance of bottom shear walls in high-rise buildings. All specimens exhibited shear-sliding failure mode characterized by multiple shear-related cracks distributed in a dense array and full-length localization of horizontal crack along the end of anchorage rebars. The seismic behaviors were comprehensively evaluated by hysteretic responses, energy dissipation capacity, strength and stiffness degradation. Additionally, detailed analysis on the strain development of vertical reinforcement and web horizontal rebars were carried out to study their shear resistance contribution. It was found that, with the assistance of steel fibers providing an efficient shear resistance consistent with the varying direction of principal tensile stress, the shear capacity of UHPC shear wall was slightly improved even when axial tension ratio increased to 0.6. The ultimate drift capacity of UHPC specimens reached 3.3% drift with an excellent strength retention ability of more than 500kN in this test. Besides, the accumulated energy consumption of UHPC specimen after crack localization improved by 38% compared with the normal concrete shear wall. Results of strain analysis demonstrated that vertical reinforcement provided an effective clamping force in the shear-sliding resistance. A modified design formula considering efficient tension resistance offered by UHPC was proposed with adequate safety concerns and accuracy.

Microstructure and Properties of High Frequency Pulse MAG Butt Welded Joints of S355 Steel with Different Diameters

In this paper, the diameter of 1.2mm and 1.6mm welding wires were used to carry out high-frequency pulse MAG butt welding process test on S355J2W+N weathering steel. The analysis of the microstructure characteristics of the welded joints under the two working conditions shows that there is little difference and both are ideal. There were more acculate ferrite (AF), less pearlite (P) and bainite (BG), and no larger Weisserite structure and less ferrite side-plate (FSP) structure. The weld is well formed, weld defects such as gas pores and cracks are not found. The impact test showed that the impact energy Akv (-40 °C) of the welded joint at -40 °C was higher than the specified minimum impact energy of 27 J. Compared with the 1.2mm welding wire, the impact energy of the 1.6mm welding wire is lower. Tensile test results show that the fracture occurs at the base metal position. and the fracture height is uneven, forming an angle of 45° with the tensile stress direction, which is a ductile fracture. When the bending angle of the butt joint samples reaches 180°, no cracks are both found on the tensile surface, and the plastic index of the welded joint samples is qualified and has good bending performance.