Circumferential Tensile Stress Research Articles

Hole-flanging behaviour of dual-phase steel using conventional and two-stage incremental forming processes

ABSTRACT The present study aimed to analyse the hole-flanging behaviour of dual -phase steel using conventional and incremental forming processes. The sheet with different hole diameters (40, 30 and 20 mm) are prepared and tested. During conventional flanging operation, the effect of two different punch geometries (flat bottom and hemispherical) are used to study the hole-flanging ability. Whereas, in incremental forming operation, different tool paths are generated, i.e. single (90°) and two stage (45° + 90°). The results shows that the holes flanged using conventional process failed to flange the lower diameter hole which is attributed due to the higher tensile circumferential stresses acted along its circumference. Whereas, for hole flanged using incremental technique has shown similar observations except in case of two-stage strategy. The implementation two-stage strategy helps in successful formation of the flanges for lower diameter holes compared to the remaining one. Additionally, finite element simulations are performed to study various critical parameters such as strain path and thickness. The maximum value of strains and thickness reduction is found near the hole edge. The highest thinning (65%) is found in single-stage process and least (38.04%) in conventional flanging with hemispherical punch.

An adaptive extended finite element based crack propagation analysis method

In this paper, a method of crack propagation analysis based on adaptive extension finite element is proposed. This method combines adaptive mesh reconstruction technology with extended finite element method (XFEM). Firstly, the model of engineering structure is discretized with the help of mesh generation software, and the initial mesh is divided. Secondly, Construction of XFEM model, and the tip of crack strengthening function is introduced to describe the physical field properties of the crack tip. The integral equation is solved to obtain the crack tip parameters. Then, the adaptive mesh reconstruction technology is built to refine the mesh of crack tip area through the error estimation of crack tip. Finally, the SIFs at the crack tip were calculated using the interaction integral, and the path direction of crack growth was determined using the maximum circumferential tensile stress criterion. Thus, the propagation path can be well traced.

Stress evolution in enamel coating/Ni-based alloy systems during isothermal oxidation

This paper utilizes a coupled chemomechanical model that integrates chemical reactions, diffusion, and mechanical deformation to describe the high-temperature interfacial reactions and stress evolution within an enamel coating/Ni-based super-alloy system. Through finite element simulation, we conduct a comprehensive analysis of multiple reactions and processes at the interface. Experimental characterization of the concentration distribution of various elements is employed to verify the accuracy of the proposed chemomechanical model. Additionally, the simulation reveals that the interface region experiences compressive circumferential stress, which can potentially lead to interfacial failure due to buckling. On the other hand, the enamel coating undergoes tensile circumferential stress, resulting in the formation of vertical surface cracks. These findings hold practical implications for the development of advanced coatings with enhanced durability and performance. Future research can further optimize coating design and enhance the reliability of high-temperature applications based on these results.

Digital Twins to Predict Crack Propagation of Sustainable Engineering Materials under Different Loads

Computer-aided engineering (CAE) is an essential tool in a digital twin not only to verify and validate a virtual twin before it is transformed into a physical twin, but also to monitor the use of the physical twin for enhanced sustainability. This paper aims to develop a CAE model for a digital twin to predict the fatigue life of materials. Fatigue damage is represented by the size of a macro-crack that grows with a cluster of micro-cracks subjected to three different loads. The growth angle is related to the maximum circumferential tensile stress, and the growth rate is determined by the stress intensity factor (SIF) at the crack tip. The prediction model takes into consideration the main factors, including micro-cracks, crack closures, and initial configurations. Simulations are developed for the growth of macro-cracks with radially distributed micro-cracks and randomly distributed micro-cracks, and we find that (1) the macro-crack in the second case grows faster than that in the first case; (2) a pure shear load affects the macro-crack propagation more than a combined shear and tensile load or a tensional load; (3) the external stresses required to propagate are reduced when the inclination angle of the micro-crack is small and within (−25° < β < 25°); (4) micro-cracks affect the propagating path of the macro-crack and generally guide the direction of propagation. The developed model has been verified and validated experimentally for its effectiveness in predicting the fracture or fatigue damage of a structure.

The influence of boundary effects on explosive damage and crack propagation in brittle materials

To investigate the influence of boundary effects on the damage and fracture characteristics of brittle materials under explosive loads, studies were conducted using explosive model experiments and simulation methods. The results indicate that the damage outcomes of single and double boundary models are significantly affected by the variation in the distance (Δl) between the explosion source and the boundary. When Δl is the same, more fragments are generated by the double boundaries. The circumferential tensile stress, produced by the superposition of incident and reflected stress waves at the boundary, is the primary cause for the continuation of crack propagation.

Simulation Study on the Influence of a Laser Power Change on the Residual Stress of a Laser-Melting RuT300 Valve Seat

In order to effectively suppress the cracking induced by the excessive residual stress of a laser-melting RuT300 valve seat, the influence of a laser power change on the residual stress was studied by constructing a finite element simulation model of a new power valve seat. The absorption rate of the laser energy on the surface of the material and the change in thermophysical parameters with temperature were taken into account in the model. The results show that the melting and phase-change-hardening areas can be obtained by the laser-melting process. With the increase in laser power, the peak temperature of the molten pool increased almost linearly. The melting zone area and the phase-change-hardening zone depth increased. When the laser power was increased from 2000 to 2600 W, the peak temperature of the laser-melting RuT300 valve seat increased from 2005.09 to 2641.93 °C, the maximum depth of the melting area increased from 0.55 to 0.86 mm, the maximum width of the melting area increased from 3.42 to 4.21 mm, and the maximum depth of the phase-change-hardening area increased from 0.55 to 0.64 mm. The circumferential residual tensile stress in the melting area was much higher than in the radial and axial directions. Along the laser scanning direction, the residual stress in the melting area increased as a whole, and the residual stress in the laser-scanning finishing area greatly increased. With the increase in laser power, the circumferential residual stress at the previous scanning moment decreased, and at the closing moment of the scan, the circumferential residual stress increased with the increase in laser power.

The investigation of shrinkage cracking of paste and mortar based on the eccentric ring test and multiphysics simulation

The eccentric ring test presents a novel approach to evaluating the occurrence of shrinkage cracking in cementitious materials. The eccentric ring test has been confirmed to induce cracks on the thin sides of the specimen. However, the underlying mechanism behind this cracking phenomenon remains inadequately explored. In this study, the eccentric ring test is used to examine cement paste with different water-cement (w/c) ratios and mortar with varying aggregate volume fractions. The examination focuses on the influence of surface sealing and immersion curing on shrinkage cracking. The integrated shrinkage model, which is applicable to both autogenous shrinkage and drying shrinkage, is introduced to simulate the shrinkage of cementitious materials. The shrinkage cracking of eccentric specimens is further investigated through a multiphysics coupling analysis that considers shrinkage, humidity field, and stress field. The simulation results show that the humidity decreases more rapidly on the thinner sides during the shrinkage of the eccentric ring. The circumferential stress in the specimen is much greater than the radial stress. Additionally, the tensile stress in the circumferential direction exceeds 4 MPa on the outer ring. As the drying time increases, the circumferential tensile stress on the thin sides of the eccentric ring develops more rapidly, resulting in cracking on the thin side. The eccentric ring test is practicable in ordinary concrete and high-strength concrete, and the simulation is of significance in examining the cracking risk of concrete pipes and some thin wall components since these components are sensitive to the shrinkage cracking.

Influence of Structure and Geometry on the Compressive Deformation Behavior of Macadamia Integrifolia and Bertholletia Excelsa Shells: A Validated Finite Element Simulation Study

Macadamia (Macadamia integrifolia) and Brazil nuts (Bertholletia excelsa) have an impressive mechanical resistance. To better understand the key structural features and foam‐like deformation behavior, mechanical compression tests coupled with numerical finite element simulations are performed. Models with different degrees of structural complexity highlight the effects of geometry where even small changes strongly influence the stress distribution and deformation behavior. Circumferential tensile stresses play a vital role in the failure process. Voids or vascular bundles in the shell wall redistribute stresses and bolster the overall strength of structures by preventing early crack propagation. The void arrangement has the potential to inspire the design of lightweight materials with strategically incorporated porosity, leading to improved mechanical performance. Linear elastic models, despite their oversimplification, are valuable for gaining crucial insights about the influence of geometry. The mechanical behavior is further influenced to different extents by isotropy and orthotropy. The distinctive architecture of nutshells offers valuable insights into the design of composite structures with controlled failure, capable of withstanding high compression loads combining foam‐like behavior and fibrous layers.

A gel microparticle-based self-thickening strategy for 3D printing high-modulus hydrogels skeleton cushioned with PNAGA hydrogel mimicking anisotropic mechanics of meniscus.

Developing a meniscus substitute mimicking the anisotropic mechanics (higher circumferential tensile modulus and lower compressive modulus) of native tissue remains a great challenge. In this work, based on the pendant group structure-dependent H-bonding strengthening mechanism, two kinds of amide-based H-bonding crosslinked hydrogels with distinct mechanical behaviors, that is, the flexible poly(N-acryloyl glycinamide) (PNAGA) and the ultra-stiff poly(N-acryloylsemicarbazide) (PNASC) hydrogels are employed to construct the biomimetic meniscus substitute. To this end, a gel microparticle-based self-thickening strategy is first proposed to fabricate PNASC (GMP-PNASC) high-modulus hydrogels skeleton by extrusion printing technology in mimicking the collagen fibers in native meniscus to resist the circumferential tensile stress. Then, the PNAGA hydrogel is infused into the PNASC skeleton to replicate the proteoglycan, providing a lower compressive modulus. By regulating the structural features at the interior and peripheral regions, the GMP-PNASC/PNAGA hydrogel meniscus scaffold with the higher tensile modulus (87.28±6.06MPa) and lower compressive modulus (2.11±0.28MPa) can be constructed. In vivo outcome at 12 weeks post-implantation of rabbit's medial meniscectomy model confirms the effects of GMP-PNASC/PNAGA meniscus scaffold on alleviating the wear of articular cartilage and ameliorating the development of osteoarthritis (OA).

Numerical Investigation of Longitudinal through Voids in Tunnel Secondary Lining Vaults and Steel Plate Strengthening.

This study investigates the influence of longitudinal through voids on vault lining. Firstly, a loading test was carried out on a local void model, and the CDP model was used for numerical verification. It was found that the damage to the lining caused by a longitudinal through void was primarily located at the void boundary. On the basis of these findings, an overall model of the vault's through void was established using the CDP model. The effects of the void on the circumferential stress, vertical deformation, axial force, and bending moment of the lining surface were analyzed, and the damage characteristics of the vault's through void lining were studied. The results indicated that the through void of the vault caused circumferential tensile stress on the lining surface of the void boundary, while the compressive stress of the vault increased significantly, resulting in a relatively uplifted vault. Furthermore, the axial force within the void range decreased, and the local positive bending moment at the void boundary increased significantly. The impact of the void increased gradually with the height of the void. If the height of the longitudinal through void is large, the inner surface of the lining at the void boundary will crack longitudinally, and the vault will be at risk of falling blocks or even being crushed.

Failure analysis of S13Cr-110 telescopic tube used in an ultra-deep gas well

The failure reason and stress corrosion cracking mechanism of S13Cr-110 telescopic tube used in an ultra-deep gas well are discussed based on physical and chemical properties, operating conditions and construction processes. The results show that: stress corrosion cracking occurred in S13Cr-110 telescopic tube during acid fracturing, the crack initiated from the bottom of the corrosion pit in the inner wall of the telescopic tube and the crack propagation mode is inter-granular cracking. The reason for cracking is that S13Cr-110, the telescopic tube material, is exposed to high-chlorine-containing acid environment for a long time in the acid fracturing process, and the corrosion inhibitor used at the temperature of ultra-deep well has poor corrosion inhibition effect, resulting in inter-granular crack originated from the bottom of the corrosion pit on the inner wall of the telescopic tube. During the subsequent acidizing operations, the telescopic tube sustained a high circumferential tensile stress, stress corrosion occurs, and the stress corrosion cracks expand rapidly. It is suggested that the S13Cr-110 pipe string used in acidic environments with high chloride concentrations should be selected with appropriate corrosion inhibitor based on well depth and formation temperature.

Research on the dynamic failure behavior of fissured tunnel subjected to combined dynamic and static loads

With the development of mining shifting to deep underground, the effect of in-situ stress on the stability of deep tunnels cannot be ignored acted upon by dynamic disturbance loads. Numerical simulations of the failure behavior of fissured tunnel model acted upon by the effect of coupled dynamic disturbance loads and in-situ stresses are conducted by using finite difference software AUTODYN. The tunnel model containing a mode I crack was made with green sandstone, a large-scale drop-hammer impact test equipment was used as dynamic disturbance loading device. The crack initiation time (CIT), crack growth rate and crack arrest time were obtained by using the crack propagation gauge (CPG). Subsequently, a series of simulations were conducted under 0.5 ∼ 3 MPa in-situ stress and dynamic loads combined conditions. The obtained results indicate that with an increasing in the level of in-situ stress in the practical tunnel, the CIT, crack propagation length, and average crack growth rate are less than that of the tunnel in the absence of in-situ stress. The dynamic circumferential tensile stress concentration at tunnel spandrel and foot increases with the level of in-situ stress. In addition, the maximum value of the dynamic initiation toughness (DIT) reaches at in-situ stress of 1.5 MPa, and then the DIT decreases with the level of in-situ stress.

Research on the propagation mechanism of hydraulic fractures in infill horizontal wells

In recent years, infill horizontal well technology has been used to develop oil and gas in the remaining oil areas of unconventional low-permeability reservoirs. However, the initial fractures in parent wells will affect the hydraulic fractures formed by fracturing infilling horizontal wells. The interaction mechanisms between initial fractures and artificial fractures in infill horizontal wells are still unclear. Combined with the boundary element method and the maximum circumferential tensile stress criterion, a numerical model of hydraulic fracturing that can simulate the evolution of fracture trajectory and stress field was established. The analytical solution of the hydraulic fracture-induced stress field was used to verify the accuracy of the model. Using this model, propagation of hydraulic fractures in infill horizontal wells under different conditions was analyzed. Simulation results show that both the fracture spacing and well spacing have a significant impact on the propagation trajectory of hydraulic fractures in infill horizontal wells. The shorter the fracture spacing and well spacing is, the stronger the inter-fracture stress interference between the initial fractures and hydraulic fractures is. Reasonable fracture spacing and well spacing can enhance the induced stress field and form a complex fracture network in the reservoir. Too small well spacing may cause artificial fractures to communicate with initial fractures, thereby reducing hydraulic fracturing efficiency and limiting the stimulation volume of the reservoir.

Simulation Analysis and Verification of Temperature and Stress of Wheel-Mounted Brake Disc of a High-Speed Train

During the braking process, a large amount of heat energy is generated at the friction surfaces between the brake disc and pads and rapidly dissipates into the disc volume. In this paper, a three-dimensional thermo-mechanical coupling model of high-speed wheel-mounted brake discs containing bolted joints and contact relationships is established. The direct coupling method is used to analyze the temperature and stress of the brake discs during an emergency braking event with an initial speed of 300 km/h. A full-scale bench test is also conducted to monitor the temperatures of the friction ring and bolted joints. The simulation result shows that the surface temperature of the friction ring reaches its peak value of 414 °C after 102 s of braking, which agrees well with the bench test result. The maximum alternating thermal stress occurs in the bolt hole where the maximum circumferential compressive stress is − 658 MPa and the maximum circumferential tensile stress is 134 MPa. During the braking process, the out-of-plane deformation of the middle part of the friction ring is larger than that of the edge, which increases the axial tensile load of the connecting bolt. This work provides support for the design of brake discs and connecting bolts.

Axial Compression Performance of Concrete-Filled Steel Tubular Columns with Different D/t Ratios

The impacts of three diameter/thickness (D/t) ratios (21.22, 25.46, and 31.83) and concrete strengths (40 N/mm2, 50 N/mm2, and 60 N/mm2) on the strength capabilities of concrete-filled steel tubular (CFST) columns are investigated in this study. The central composite design (CCD) of the response surface methodology (RSM) was used to design the trials in order to complete the tests in a cost-effective manner. 13 (9 distinct tests) columns were evaluated according to the CCD experimental design, and the failure mode of the specimens, load–deformation behavior, and ultimate strength capacity were investigated. Concrete strength improves, resulting in a decrease in steel tube confinement on the core. Because the steel tube longitudinal compressive stress (fsl) increases as the D/t ratio lowers, the confinement is reduced by inhibiting the circumferential tensile stress (fsc). The Reynolds stress model’s, analysis of variance (ANOVA), Pareto chart, and contour plot demonstrated that the column D/t ratio, rather than the in-filled concrete strength, has a considerable impact on the CFST column’s strength capability. The proposed design models in different international codes and literature were evaluated for their effectiveness in predicting the strength capacities of CFST columns subjected to axial compression load. Using regression analysis, a simple design model was suggested to predict the axial strength capacities of CFST short columns, taking into account material strength and column shape. In comparison to other existing and suggested design models, the proposed design model of the present study delivers a more accurate and stable forecast.

Distribution Law of Corrosion Products in a Marine Chloride Environment.

Steel corrosion is the main cause of reinforced concrete cracking. Conventionally, concrete is considered to crack when the circumferential tensile stress reaches the tensile strength of the concrete. However, few analyses have considered the fracture criteria of the internal cross-section of concrete. Based on the von Mises distribution of angle probabilities, this paper proposes a new probability distribution function for investigating the distribution law of corrosion products. The cracking process of experimental samples was numerically analyzed, and the results were consistent with those of the theoretical model. The effect of the dry–wet cycle ratio on the corrosion products was preliminarily investigated by microscopic observation of the reinforced concrete under different dry–wet cycle corrosion environments.

Formula omitted][formula omitted] morphology prediction of Zr hydride precipitates using atomistically informed Eshelby’s ellipsoidal inclusion

We energetically predicted the morphology of Zr hydride precipitates in a hexagonal close-packed (HCP) Zr matrix. Considering Zr hydride precipitates as ellipsoids, we used Eshelby’s ellipsoidal inclusions to calculate the elastic energy increment due to the presence of Zr hydride precipitates in the Zr matrix, in which the elastic anisotropy and inhomogeneity of the elastic constants between Zr and Zr hydride were considered. We compared the difference in the elastic energy increment between the ellipsoidal inclusions with different shapes: plates (mimicked by penny-shape ellipsoids), needles (mimicked by longitudinal ellipsoids) and sphere, and orientations to detect the stable structure with the minimum elastic energy increment. Eigenstrains of each Zr hydride and elastic constants of Zr hydrides and HCP Zr for Eshelby’s ellipsoidal inclusion analysis were determined using atomistic simulations based on a density functional theory calculation, achieving a parameter free abinitio morphology prediction. The morphology predictions were implemented for two cases: with and without shear components of eigenstrain (w/ and w/o shear). The 〈12̄10〉 longitudinal needle for the γ hydride (w/o shear) and plate (or disk) on the plane, which is 20° to 30° tilted about 〈12̄10〉-axis from basal plane (0001), for δ and ε hydrides (w/ shear) were successfully predicted as stable shapes and orientations of the precipitates under zero external stress conditions, qualitatively consistent with experimental observations. The external circumferential tensile stress on the basal plane reduces the elastic energy of [0001] parallel Zr hydride plates, which is also qualitatively consistent with the reoriented δ hydride precipitates observed in the experiment. On the other hand, predicted external stress for the reorientation of Zr hydride is quite high, around 10 GPa. This is inconsistent with experimental observation and further investigation is necessary. Generally, our predictions based on elasticity theory appear qualitatively consistent with experimental observations, suggesting an elastic origin of the morphology of Zr hydride precipitates in the HCP Zr matrix.

Orientation and Residual Stress Distributions in Thick Melt Spun Polystyrene and Polycarbonate Filaments

Abstract A study of orientation development and residual stresses in thick melt spun polystyrene filaments and polycarbonate filaments described. Linear relationships between spinline stress and mean birefringence under different melt spinning conditions were obtained. These results were used together with models of the dynamics of melt spinning to predict the characteristics of thick melt spun filaments. Birefringence distrbutions and residual stresses were computed. High orientations and compressive circumferential residual stresses were predicted at the larger radii and low orientation and tensile circumferential and radial residual stress in the fiber core are obtained. The distribution of birefringence across the thickness of thick melt spun filaments was measured by determining changes of retardation across a wedge. The birefringence distributions were correlated with severity of quench and model prediction. Thick melt spun fibers were peeled and found to have fibrillar cores.

Construction of three-dimensional dynamic growth TGO (thermally grown oxide) model and stress simulation of 8YSZ thermal barrier coating

A three-dimensional cylindrical numerical simulation physical and geometric model of TBCs sinusoidal surface was established based on the ultrasonic C-scan results of 8YSZ coating after thermal cycling. The stress distribution and evolution law of the TGO/BC interface and sample center and edge affected by TGO growth were simulated by the finite-element method. The results show that the stress at the TGO/BC interfaces changes from compressive stress to tensile stress with the increase of the number of thermal cycles. The center of the interface is distributed with large radial, circumferential and axial tensile stresses, while the edge of the sample is affected by thermal mismatch, which shows that shear stresses are alternately distributed in the XZ direction. The tensile stress at the center and the shear stress at the edge are the main reasons for the failure of the core and edge flakes of the thermal barrier coating. The linear elasticity, creep effect, fatigue effect and stress accumulation effect of each layer of TBCs in each thermal cycle period are fully considered by the model, which reveals the reason why the core and edges of the thermal barrier coating are most likely to form cracks.

Analysis and Control of Cracking and Wrinkling at the End of Seamless Steel Tube with Multi-Pass Large Deformation Diameter-Reducing

Axial cracking and circumferential wrinkling are found at the end of seamless steel tubes during multi-pass large deformations pushing diameter-reducing (PDR), which seriously affects product quality. However, the cracking and wrinkling mechanism of PDR has not been elucidated yet. In this paper, the Equation of circumferential residual stress at the end was deduced from the warping deformation and shear stress. It is revealed that the circumferential residual stress in the end warping area from the inner to outer surface is tensile, and the generation mechanism of circumferential wrinkling on the inner wall at the end was revealed through the deformation analysis of PDR. The geometric model of the tube with periodic alternating variation of wall thickness was established to reveal the generation and development of circumferential wrinkling. In addition, the four-pass PDR experiments and simulations were developed to reveal the influence of reducing pass and wall thickness deviation on the end warpage, unevenness and circumferential residual tensile stress. The pushing-pulling diameter-reducing (PPDR) method was proposed to control the wrinkling and cracking. The simulation and experimental results showed that the end warpage, unevenness and circumferential residual tensile stress are all greatly decreased, and the risk of axial cracking and circumferential wrinkling is eliminated.