Average Tensile Stress Research Articles

Numerical analysis on the thermal mismatch stress of quasi-isotropic strand with square cross section during cool-down

The quasi-isotropic strands (Q-IS) with high current-carrying capacity can effectively improve the anisotropy of the critical current in the magnetic field. However, when a quasi-isotropic strand is cooled from room temperature (300 K) to the liquid helium temperature (4.2 K), it may cause the irreversible degradation of the critical current, the plastic deformation, and even mechanical damage. In order to achieve the safe and stable operation of quasi-isotropic strands, it is important to analyze the thermal mismatch stress during cool-down. In this study, two mechanical models (i.e. a bulk model and a contact model) were developed by considering different material elastoplastic characteristics to study the mechanical behaviors of quasi-isotropic strands with square cross section in the cooling process. Compared with the bulk model, the contact model can simulate the contact and separation between adjacent REBCO conductors in quasi-isotropic strands. Therefore, the contact model should be chosen to estimate the thermal mismatch stress of quasi-isotropic strands during cool-down. In addition, plastic deformation was clearly observed in the Cu and Ag layers with peak equivalent plastic strains of 0.016% and 0.171%, respectively. When the stainless steel sheath is replaced by the copper sheath to encase a quasi-isotropic strand, the interlaminar normal tensile stress between the superconducting layer and Hastelloy substrate was decreased from 101 MPa to 16.2 MPa. Therefore, a quasi-isotropic strand encased in a copper sheath could reduce the risk of delamination during cool-down.

Assessment of the Structural Integrity of a Laser Weld Joint of Inconel 718 and ASS 304L

For high-temperature industries operating at nearly 750 °C (advanced ultra-super critical boilers), dissimilar welding between Inconel alloys and austenitic stainless steel (ASS) are commonly adopted. The high-temperature resistive properties of Inconel and ASS alloys are highly qualified for high-temperature applications. In this experimental study, dissimilar autogenous laser beam welding (LBW) between Inconel 718 and ASS 304L is investigated. This paper explains the detailed study on the microstructural and mechanical behavior of the LBW dissimilar joint. The microstructural study indicates the presence of laves phases in the weld zone. Additionally, the weld zone shows heterogeneous microstructural formation, owing to the non-uniform welding heat in the different areas of the weld zone. The optical images show the presence of mixed dendrites, i.e., equiaxed, cellular, and columnar morphology, in the weld zone and in the fusion zones of either side. The energy-dispersive spectroscopy (EDS) results show the presence of segregated elements (Nb, Mo, Cr, and Ti) at the weld center. These segregated elements are the reason for the occurrence of the laves phases in the weld zone. The presence of Nb and Mo may form the laves phase (Fe, Ni, Cr)2 (Nb, Mo, Ti) along with Fe, Ni and Cr. The presence of an unmixed zone is observed in the HAZ of the Inconel 718, whereas the HAZ of the ASS 304L shows the presence of an unmixed zone (UZ) and a partially mixed zone (PMZ), as observed on the optical and SEM images. To obtain the mechanical properties of the laser weld, the tensile test, microhardness test, and impact test were measured at room temperature. The tensile specimens show a brittle failure at the ASS 304L side, which was initiated from the weld top, with average tensile stress of 658.225 MPa. The reason for the ASS 304L fracture is because of the presence of UZ and PMZ, and the lower hardness value of the ASS side. The UZ and PMZ lead to the fracture of the tensile specimen along the ASS 304L side’s HAZ. The measurement of microhardness carried out along the transverse length indicates an average microhardness of 214.4 HV, and the value is 202.9 HV along the weld depth. The mixed morphology of the microstructure promotes the variation in hardness in both directions. The hardness along the length shows a high hardness value in the weld zone and uniformly decreases along the base materials. The Charpy impact test of the weld zone shows the brittle fracture of the impact specimens. From the microstructural and mechanical results, the LBW dissimilar weld between Inconel 718 and ASS 304L is qualified for safe use in high-temperature end applications, such as AUSC power plants.

Investigation on the Mechanical Properties of Paper Water Hyacinth (Eichhornia Crassipes)

The widely use of papers and for the promotion of conservation of the forest ecosystem in making papers from the falling of trees. This work is focused on the realization of paper and its mechanical properties. Water hyacinth (Eichornia crassipes) is aquatic plant with a high growth rate that usually cover the river surface and has an impact to the environment and other living things. The work done was to produce a paper from water hyacinth through cutting, grinding, refining, molding, the bleaching process and drying process we obtained different papers. In the realization process of the papers, we have used Hydrogen peroxides for the bleaching process to obtain white paper (Bleached paper). In our case we have both the bleached and the unbleached paper. Papers were successfully produced under experimental condition. Mechanical properties of each paper were investigated. The various density of paper water hyacinth plant of the bleached and unbleached was 21.68 g/m3 and 26.37 g/m3 respectively, average tensile rupture stress 1.337MPa & 0.405MPa and young modulus was found to be 36.278MPa and 17.604MPa, the elongation at break 4.744% and 2.879%, average moisture content of 4.82% to 9.59% and 3.57% to 6.62% respectively for the Unbleached and Bleached paper water hyacinth plant. For this reason, Unbleached Paper with certain different strength ranges could be considered to be applied as packaging, seedling pot, mulching or insulating material in advance application. The use of water hyacinth as biomass with the used of the roots and leaf shows a bulky structure. The study concludes that water hyacinth is a potential fiber for paper production especially in areas where it is abundant, but the tensile strength of unbleached paper is more than the bleached paper. So that the paper can be used for other purpose than writing.

Effect of neurodynamic mobilization techniques in patients with diabetic neuropathy

Purpose.Neurodynamic mobilization is a set of passive or active movements aimed at restoring the neural system’s ability to bear the normal compressive, friction, and tensile stresses encountered in daily life. This study aimed to investigate the effect of neurodynamic mobilization on sensory and motor nerve conduction studies, pain, and functional activity in patients with type 2 diabetic neuropathy (DN).Methods.A total of 42 patients were randomly assigned to the neurodynamic mobilization group (NMG) or selected therapy program group (STPG). Electrophysiological measurements for median sensory and tibial motor nerve conduction velocity, and functional activity were conducted using the Katz Index of Independence, while pain was evaluated using the visual analogue scale.Results.Improvement was noted in the post-treatment median sensory (<i>p</i> = 0.002) and tibial motor (<i>p</i> < 0.001) nerve conduction velocity, functional activity (<i>p</i> < 0.001), and pain (<i>p</i> < 0.001), and a statistically significant difference was demonstrated for the NMG, but not for the STPG.Conclusions.Neurodynamic mobilization improved the sensory and motor nerve conduction velocity, functional activity, and pain in patients with type 2 DN.

Feasibility study of using waste badminton string fibers in con-crete by morphological, microstructural and tensile characteristics

As the strings are cut off from the badminton racquet system, the whole string will be replaced with a new one and there is no other alternative. Hence those cut-off strings are considered as waste and cannot be recycled, tons of waste are retained as debris. Among many research on recycled synthetic fiber, this application of waste material is a new context in sustainable construction. Here five different samples are examined based on wide usage, recycled Waste Badminton String Fiber (WBSF) is characterized and physically examined using a Scanning Electron Microscope, Fourier Transform Infrared Spectroscopy, and X-ray diffraction to use it as a recycled synthetic fiber in various fiber reinforced concrete applications. The diameter and cross-sectional area of WBSF are studied using the Scanning Electron Microscope imaging technique and Image J application, which shows that the fiber is highly engineered with 3 layers namely elasticity outer, outer layer, and core fiber with the mean diameter and net cross-sectional area is 777.6 µm and 5,05,959 µm2 respectively. The surface roughness of fiber is analyzed using ImageJ application which varies between 16-32 nm. The fiber samples are subjected to tensile loading the average tensile stress lies between 544.34 - 639.94 MPa. From the above examinations, the accurate diameter, net cross-sectional area, and voided area of the WBSF are calculated. The structural property and polymer relationship of the fiber are investigated using the X-ray diffraction technique and Fourier transform infrared spectroscopy, this reveals that the WBSF is of polyamide 6,6 form. The superior tensile stress compared to other recycled nylon fibers. So, the use of waste badminton string fiber in concrete is a new merging idea for fiber-reinforced concrete applications like pavements, pipes, tunnel lining, and other structural elements.

Torsional and compressive properties of bolted joint under forward-reverse tightening

Obtaining the stress evolution law of bolted joint during the assembly process is of great significance for tightening process design and improving assembly performance. In this study, the bolt tightening analytical model is used to obtain the deformation coordination mechanism. Then, the evolution law of the stress during assembly process are obtained by FEA model, and the influence of different assembly parameters on the stress change is analyzed. Finally, the bolt tightening experiment is carried out, which verified the theoretical hypothesis and the FEA model. The results show that: in addition to the tensile normal stress, the thread torque also generates torsional shear stress that causes the torsional deformation of the screw during the tightening process. The torsional shear stress can be reduced by forward-reverse tightening process. Meanwhile, the utilization rate of bolted joint can be improved. This can increase the assembly design margin and improve the assembly performance.

THE EFFECT OF PRESS MEDIA FROM CERAMIC AND METAL MATERIALS ON THE TENSILE STRENGTH OF RECYCLED POLYPROPYLENE FOR THE DEVELOPMENT OF COMPOSITE MATRIX MATERIALS

Composites generally consist of fiber (filler) and resin (matrix). Resin from recycled polypropylene (plastic) polymer was chosen because it has superior properties compared to other types. The manufacturing process with a hot air melting temperature (heat gun) of 300oC was chosen with two variations of press media, namely metal and ceramic, to compare the mechanical properties of tensile strength. Specimens were shaped according to the ASTM D638 standard. The results showed that the recycled polypropylene with ceramic press media had an average tensile stress of 15.05 MPa, which was higher than that of compressed metal media of 13.06 MPa.

Study of the Stress-Strain State of the "Bone–Fixation Plate" System in Conjunction With Cortical Tissue Mechanical Properties

Background. Bone osteosynthesis is considered one of the most efficient methods of treating fractures of long tubular bones. Deve­lopment of modern computer technology and specialized software makes it possible for a traumatologist to perform preliminary efficiency estimation of osteosynthesis using fixation plates of various designs. Results of such studies can significantly depend on calculation model parameters. In most papers related to the study of a stress-strain state of “bone–fixator” systems, bone tissue is considered as a homogeneous, isotropic, elastic medium. However, in fact it is heterogeneous and has an anisotropy of mechanical characteristics. Accordingly in a case of using a simplified isotropic model of bone tissue, when performing calculations, there is a possibility of obtaining inaccurate results. Objective. Estimation of influence of orthotropy of the bone tissue physical and mechanical properties on a stress-strain state of the “bone–fixator” system. Methods. The study is performed in the software environment based on the finite element method. Osteosynthesis of a low transverse fracture of a fibula using a smooth plate is selected as a computational case. Two computational models simplified in terms of geometry are constructed to solve the problem. These models are different only in properties of cortical bone tissue. Results. Analysis of a stress state in elements of models indicated that normal stresses reached the highest values, and tangential stresses are relatively small. In addition, the character of stress distribution turned out to be significantly inhomogeneous. However, stress state patterns are qualitatively similar for both computational models. A common feature of the maximum stresses both in the bone and in the plate turned out to be that all the maximum stresses are the result of their concentration. Conclusions. Consideration of orthotropy of elastic parameters of a bone led to significant quantitative changes in the indicators of a stress state. It is established that the minimum safety margins for both models turned out to be considered by the maximum tensile stresses acting in the vertical direction. A similar result in estimating bone strength also occurs in a case when only elastic orthotropy is considered, but the orthotropy of strength indicators is not considered. If the strength orthotropy is considered for the isotropic model of cortical bone, the pattern changes qualitatively. The normal tensile stress directed along the tangent to a circumference of bone cross-section is considered unsafe. Calculations results indicate a possibility of using an isotropic model of cortical tissue when performing comparative estimations in order to identify the most efficient, in terms of strength, fixation plate designs.

An experimental study of the transition from tensile failure to shear failure in Carrara marble and Solnhofen limestone: Does “hybrid failure” exist?

Failure of brittle rocks under axisymmetric extensional loading, when the minimum principal stress is tensile, results in the formation of one or more opening-mode cracks that are oriented normal to the extension axis. When all the principal stresses are compressive, failure occurs through the formation of numerous grain-scale tensile cracks, which coalesce into a shear-mode fault that is inclined at >20° to the maximum principal stress. There have been few attempts to study the transition between these failure modes, particularly those that incorporate microstructural analyses. A transitional mode of failure, termed “hybrid failure”, is often proposed to describe the orientation of faults between these end-member loading conditions, but this concept has traditionally been based on a parabolic, “Griffith-type” failure envelope that describes the growth of the single most critically-oriented crack. By integrating axisymmetric rock deformation experiments with microstructural analyses, it can be shown that failure under these transitional conditions involves the formation of several transgranular tensile cracks, which coalesce into a shear-mode fault that is inclined at <10° to the maximum principal stress. The stress intensity at the tip of each crack interacts with adjacent cracks to produce a stair-step geometry along the failure surface. These are what may be appropriately considered “hybrid faults”, the angle of which systematically increase as the maximum principal stress, and thus the differential stress increases. There is, however, no evidence of a distinct “hybrid failure” mode, which involves the in-plane propagation of a single crack that is subject to a combined shear stress and tensile normal stress. The results of this experimental study provide novel insights into the mechanical behaviour of carbonate rocks and into the interpretation of meso-scale natural examples of failure under mixed stress-states.

Pengaruh Suhu Pre-Heat Friction Welding Terhadap Sifat Mekanis dan Morfologi Baja AISI 201

This study aims to determine the mechanical and morphological properties of AISI 201 Steel Material. The forging pressure is 80 Psi using a rotating speed of 5600 Rpm and the preheat temperature used is 4000C, 5000C, 6000C. The method in this research is descriptive method. The test results produce an average tensile stress of 4000C preheat temperature variation of 523.1 N/mm2, 5000C preheat variation of 534.3 N/mm2, 6000C preheat variation of 566.6 N/mm2, and raw material of 696.35 N/mm2. For this reason, the largest average tensile stress in this variation of raw material is 696.35 N/mm² and from the data results obtained the average tensile strain of 4000C preheat variation is 10.83%, 5000C preheat variation is 11.05%, 6000C preheat variation is 11.73%, and raw materials 23.14%. The average bending stress of the 4000C preheat temperature variation is 21.85N/mm2, the 5000C preheat variation is 52.31 N/mm2, the 6000C preheat variation is 53.38 N/mm2, and the raw material is 117.71N/mm2. The results of the largest average tensile stress in this variation of raw material are 117.71N/mm², in the hardness test a value of 294.7 VHN is obtained and the SEM test on the specimen is the best in the HAZ area which is enlarged 5000x, 200x, and 100x, it can be seen that in the The friction welding penetration welding HAZ is completely filled with no weld defects.

Odd-viscosity-induced passivation of Moffatt vortices

Odd viscosity is associated with a number of striking physical phenomena: a disk rotating in a viscous liquid experiences a normal compressive or tensile stress depending on its sense of rotation; chiral active matter interfacial deformations level off in a manner akin to surface tension; and unstable thermocapillary films become stabilized. In this article we show that odd viscosity decreases the size and intensity of Moffatt vortices in a corner formed by a solid substrate and a free interface. The effect is present because odd viscosity creates a normal-stress-induced shear stress at the liquid–gas interface. The new shear stress is out of phase and oppositely directed with respect to the interfacial liquid velocity. It squeezes the vortices and damps their rotation. As a consequence, Moffatt vortices can now be observed with greater facility in an experiment. Odd viscosity also increases the range of corner angles over which Moffatt vortices can be observed, and, in general, it shows a tendency to moderate singular behaviour.

Evolution of Pulverized Fault Zone Rocks by Dynamic Tensile Loading During Successive Earthquakes

AbstractLarge strike‐slip faults experience numerous earthquakes during which transient tensile and compressive mean normal stress perturbations travel along opposing sides of the fault. Research exploring dynamic rock fracture through multiple earthquake cycles has focused predominantly on transient compressive loading, but little is known about off‐fault damage development due to successive tensile loading. We investigate damage accumulation by transient tensile loading over multiple earthquake cycles using a modified sample configuration for uniaxial compressive loading apparatuses consisting of a Westerly granite rock disk bonded to two lead disks. We show that fracture density increases during each successive loading cycle, and pulverized rock can be produced under tension at strain rates as low as 10−3 s−1. Therefore, pulverized rock can form at low strain rates, and its texture and extent may be controlled by the size of the coseismic tensile stress perturbation and the number of slip events on the fault.

Shear strengths of joints with roughened concrete surfaces and post-installed dowel bars subjected to normal and shear stresses for seismically retrofitted structures

When reinforced concrete (RC) structures are seismically retrofitted, new members are connected via joints with roughened surfaces and post-installed dowel bars. For retrofitted RC buildings, roughened surfaces are often manufactured using vibration hammers. However, investigations on the shear strengths of the joints subjected to shear and tensile normal stresses are limited. In this study, these joints, called hybrid joints, were subjected to shear loading. The test parameters were the normal stress, dowel bar diameter dd, and roughened concrete area ratio rrc. The normal stress was set to have a compressive stress σ0 of –0.48 N/mm2 and a ratios rN of tensile stress to yield strength of 0.00, 0.33, and 0.66. In addition, dowel bars with dd = 13, 16, and 19 mm were used. The target rrc values were 0.1, 0.2, and 0.3. Bearing failure of the roughened surface was observed as a result of the test. The shear strength decreased with increasing rN and decreasing rrc. Subsequently, an expression for the shear strength of a roughened surface was proposed. In this expression, the shape of an uneven surface was regarded as a cone. To estimate the shear strengths of the hybrid joints, the shear force from the previous dowel model was added to the proposed expression. Finally, the values obtained using the calculation method were compared with the test results. It was demonstrated that the proposed expression could reasonably estimate the test results, with a correlation coefficient of 0.93. In addition, for structural designs, the proposed expression should be multiplied times 0.7 to estimate the lower limit of the test results.

Effect of the Structural Characteristics on Attachment-Detachment Mechanics of a Rigid-Flexible Coupling Adhesive Unit.

The terminal toes of adhesive animals are characterized by rigid-flexible coupling, and their structure–function relationship is an urgent problem to be solved in understanding bioinspired adhesive systems and the design of biomimetic adhesive units. In this paper, inspired by the rigid-flexible coupling adhesive system of the gecko toe, a rigid-flexible coupling adhesive unit was designed, the interface strength of the adhesives under different preloads was tested, and the model and analysis method of the compression and peeling process of the rigid-flexible coupling adhesive unit was established. Meanwhile, combined with the experimental test, the effect of the coupling mechanism of the rigid-flexible structure on the interfacial stress and the final peeling force during the compression and peeling process of the adhesive unit was studied. The research found that the length of the adhesive unit L has no apparent effect on the normal peel force of the system within a specific range, and the normal peeling force increases linearly with the increase in the compression force P; while the influence of the inclination angle θ0 of the adhesive unit and the thickness of the rigid backing layer hb on the final normal peeling force of the system presents nonlinear characteristics, when the inclination angle θ0 of the adhesive unit is 5°, and the thickness of the rigid backing layer hb is 0.2 mm or 0.3 mm, the normal peel force and the ratio of adhesion force to preload the system reaches its maximum value. Compared with the flexible adhesive unit, the compressed zone formed by the rigid-flexible coupling adhesive unit during the same compression process increased by 6.7 times, while under the same peeling force, the peel zone increased by 8 times, and the maximum normal tensile stress at the peeling end decreased by 20 times. The rigid-flexible coupling mechanics improves the uniformity of the contact stress during the compression and peeling process. The research results provide guidelines for the design of the rigid-flexible coupling adhesive unit, further providing the end effector of the bionic wall-climbing robot with a rigid-flexible coupled bionic design.

Lithological controls on fault damage zone development by coseismic tensile loading

During subshear earthquake rupture opposing sides of the fault experience transient impulses of tensile and compressive peak mean normal stresses exceeding the strength of the rock resulting in off-fault damage. This damage is expected to be influenced by lithology and occur preferably on the nominally tensile side of ruptures because rocks are weaker in tension than compression. Whereas the static tensile strength of many rocks is known, our capacity to relate parameters used to quantify brittle deformation in fault damage zones commonly measured in the field, including fracture density and fragment size, to earthquake rupture conditions is poor. This is due to a lack of experimental data relating tensile strength, fracture density, and fragment size to lithology under transient loading conditions. To relate brittle damage to coseismic tensile loading conditions, we use a modified sample configuration for a Split Hopkinson Pressure Bar (SHPB) designed to induce tensile rock fragmentation. Experiments cover a range of rock types including granite, diabase, welded tuff, and sandstone. All crystalline rocks fail predominantly via mode-I fracture, while sandstone fails through localized dilation bands, distributed pore space expansion, and less common mode-I fractures. Measurements of fracture density, fragment size, and porosity change are compared to tensile strength and strain rate at failure. We derive empirical relationships for (1) the transition from fracture to dilation banding as a function of initial porosity and (2) the strain rate dependence of tensile strength. These empirical relationships are used to estimate the rock strength during earthquake rupture on the side of the fault loaded under tension for comparison to predicted stress decay with distance from a fault to estimate the lithology dependent extent and nature of coseismic fault damage. Our experiments offer new insights into the lithological controls on the formation of asymmetric fault damage zones by dynamic rupture.

Revealing the influence of ultrasound/heat treatment on microstructure evolution and tensile failure behavior in 3D-printing of Inconel 718

Ultrasound is a potential method to enhance the mechanical properties during directed energy deposition (DED), however, its intrinsic strengthening mechanism has not been completely uncovered. In this study, the ultrasound-induced strengthening mechanism has been explored from perspectives of microstructure evolution (i.e., grain size and phase composition), and it has been compared with that of the heat treatment after building without ultrasound. The results indicate that the columnar grain (γ) underwent obvious transition and refinement by inducing ultrasound, along with the changes in the morphology and size of Laves phase. Yet the second phase (i.e., γ′ + γ″, Laves phase, and δ) of heat-treated samples was different than that of the samples obtained by ultrasound. Moreover, combined with grains changes and the quantitative analysis of Laves phase, the tensile properties and fracture mechanism were analyzed. The experimental results demonstrate that the tensile properties were improved by both ultrasound and heat treatment. Among them, the average ultimate tensile stress of samples treated with ultrasound increased by 10% compared to the as-built samples along the scanning direction. Consequently, the main strengthening mechanism of samples by ultrasound was found to be grain refinement, while a large number of strengthening phases (γ′ + γ″) precipitated to strengthen the matrix in heat-treated samples. Thus, clarifying strengthening mechanism is crucial for understanding the mechanical properties of as-built samples.

Research on cohesive failure behavior and parameter sensitivity of rubber – SET under cohesive zone model

Solid expandable tubular (SET) technology is widely used in oil field. The cohesive failure of rubber reduces the suspension and sealing capacity of SET. Based on cohesive failure behavior between rubber and SET and morphological characteristics of rubber after expansion experiment. The cohesive zone model was introduced to describe cohesive behavior. The coupled three-dimensional finite element model of casing - rubber - SET was established. The effects of sensitive factors such as friction factors, rubber compression, rubber length, stiffness, damage initiation strength and fracture energy on cohesive failure behavior of SET rubber were researched. The results show that (1) In order to ensure that driving force in expansion process is small and meet the requirements of suspension force and sealing pressure after expansion. The friction coefficient of casing - rubber - SET system should be about 0.15. (2) On the premise of no cohesive failure occurs, the suspension force and sealing performance of rubber can be effectively improved by increasing theoretical compression and length of rubber. The optimum theoretical compression of rubber is about 50% of rubber thickness. The length of rubber should not exceed 60 mm. (3) Reducing stiffness and increasing damage initial strength of bonding material can reduce the risk of cohesive interface failure. The normal stiffness should not be greater than 5.4 N/m3 and the tangential stiffness should not be greater than 6.3 N/m3. The normal ultimate tensile stress should not be less than 9.6 MPa and the transverse shear stress strength should not be less than 9.7 MPa. It is not significant to increase bonding property of rubber by increasing fracture energy. The research results provide theoretical guidance for the structural design and bonding process parameters of SET rubber.

Cracking behavior and delamination mechanism of lamellar structured TBC with localized mixed oxides

Mixed oxide (MO) with localized growth feature and high growth rate remarkably affects the lifetime of thermal barrier coatings (TBCs), which indicates that clarifying the ceramic cracking mechanism induced by MO is critical for developing new coatings with high durability. Two kinds of TBC models involving spherical and layered mixed oxides are created to explore the influence of MO growth on the local stress state and crack evolution during thermal cycle. The growth of α-Al2O3 is also included in the model. The undulating interface between ceramic coat and bond coat is approximated using a cosine curve. Dynamic ceramic cracking is realized by a surface-based cohesive interaction. The ceramic delamination by simulation agrees with the experimental observation. The effects of MO coverage ratio and growth rate on the TBC failure are also discussed. The results show that the MO growth causes the local ceramic coat to bear the normal tensile stress. The failure mode of coating is turned from α-Al2O3 thickness control to MO growth control. Once the mixed oxide appears, local ceramic cracking is easy to occur. When multiple cracks connect, ceramic delamination happens. Suppressing MO formation or decreasing MO growth can evidently improve the coating durability. These results in this work can provide important theoretical guidance for the development of anti-cracking TBCs.

Inducing Tensile Failure of Claystone Through Thermal Pressurization in a Novel Triaxial Device

Complex coupled thermo-hydromechanical (THM) loading paths are expected to occur in clay rocks which serve as host formations for geological radioactive waste repositories. Exothermic waste packages heat the rock, causing thermal strains and temperature induced pore pressure build-up. The drifts are designed in such a way as to limit these effects. One has to anticipate failure and fracturing of the material, should pore pressures exceed the tensile resistance of the rock. To characterise the behaviour of the Callovo-Oxfordian claystone (COx) under effective tension and to quantify the tensile failure criterion, a laboratory program is carried out in this work. THM loading paths which correspond to the expected in situ conditions are recreated in the laboratory. To this end, a special triaxial system was developed, which allows the independent control of radial and axial stresses, as well as of pore pressure and temperature of rock specimens. More importantly, the device allows one to maintain axial effective tension on a specimen. Saturated cylindrical claystone specimens were tested in undrained conditions under constrained lateral deformation and under nearly constant axial stress. The specimens were heated until the induced pore pressures created effective tensile stresses and ultimately fractured the material. The failure happened at average axial effective tensile stresses around 3.0 MPa. Fracturing under different lateral total stresses allows one to describe the failure with a Hoek–Brown or Fairhurst’s generalized Griffith criterion. Measured axial extension strains are analysed based on a transversely isotropic thermo-poroelastic constitutive model, which is able to satisfactorily reproduce the observed behaviour.

Analisa Pengaruh Kuat Arus Terhadap Kekuatan Tarik Dan Bending Sambungan Las Kampuh V Menggunakan Las SMAW Dengan Elektroda E6013 Pada Pengelasan Baja Karbon Rendah

Strong current in welding is something that has always been a problem in the welding process. High currents can cause penetration of the welded material, whereas low currents can cause shallow penetration. The purpose of the study was to determine the effect of current on the tensile and bending strength of V seam welded joints using SMAW welding with E6013 electrodes on low carbon steel welding. The research method used is to make a seam on a steel plate with an angle of 60 degrees and then weld it with a different current. The current used is 70, 90, 110 amperes with an electrode diameter of 2.6 mm. The samples that have been welded are then formed into tensile and bending test specimens. The results showed that the highest average tensile stress was 518.310 MPa at a welding current of 110 amperes. The highest average tensile strain is 34.00% at a welding current of 70 amperes. The highest average elastic modulus is 0.01864 GPa at a welding current of 110 amperes. For bending testing at 70 amperes, the fb1 specimen has cracks in the weld metal area with a crack length of 1.00 mm and the fb2 specimen has 0.50 mm cracks, while the 90 amperes fb1 specimen has 1.00 mm cracks, and fb2 specimens have 0.50mm crack. Current 110 amperes fb1 specimen has a crack of 4.70 mm, and fb2 specimen has a crack of 3.00 mm. From the results of the study, a good welding current for a plate with a thickness of 7.5 mm with an E6013 electrode with a diameter of 2.6 mm is at a current of 90 amperes.