Twin Shear Stress Yield Criterion Research Articles

Punching Shear Failure Analysis of Reinforced Concrete Slabs under Close-in Explosion.

The susceptibility of reinforced concrete (RC) slabs to punching shear failure is heightened when subjected to close-in explosion loads, leading to a wider range of damage caused by the resultant leakage shock wave through the punching hole. Consequently, it is crucial to analyze the conditions for punching shear failure and the size of the punching hole in RC slabs. This study investigates the punching shear failure of RC slabs under close-in explosions through numerical simulation and theoretical analysis. Initially, a finite element model is developed to examine the distribution of the explosion load on the slab's surface. Subsequently, the critical explosion load for punching shear failure is determined using a damage criterion specific to RC slabs. Additionally, a calculation model based on the twin shear stress yield criterion is established to predict the punching hole's radius. To validate the accuracy of this method, a comparison is conducted with existing test results.

Through-wall yield ductile burst pressure of high-grade steel tube and casing with and without corroded defect

Service environment of tube and casing in deep and ultra-deep well is getting more and more complicated, and the internal pressure applied to tube and casing is higher, so that the high-grade steel tube and casing (HGTC) made of ductile material is widely used. Obviously, the calculation of ductile burst pressure for HGTC is one of the key factors in design and important to safe and efficient development of unconventional oil and gas resources. Here, based on the failure principle of through-wall yield and unified yield criterion, the unified formula of through-wall yield ductile burst pressure (TYBP) for tube and casing under practical service condition which can be used to calculate TYBP of API HGTC and non-API HGTC accurately and reasonably by using true material parameters, has been deduced in this paper with due consideration of the effect of Bauschinger effect (BE), material hardening and intermediate principal stress (IPS) on the TYBP, by which the influence rules of BE, IPS and yield criterion on TYBP of tube and casing have been investigated.（The effect of lattice effect (BE), material hardening and intermediate principal stress (IPS) on TYBP is accurately and reasonably derived from non-API HGTC by using real material parameters. The value of BE, IPS and the TYBP yield criterion of pipe and casing are studied. Eight kinds of classic through-wall yield ductile burst formulas for tube and casing made of new material have been be derived from a series of yield criterion, by which TYBP model of HGTC with and without corrosion defect has been established based on weighted twin shear stress yield criterion. The calculation results of TYBP model presented by this paper are the closest to the full-scale burst experimental data than the other burst models, which can provide an important reference for burst pressure design and estimation of HGTC in deep and ultra-deep well.

Solid expandable tubular forming behavior based on twin shear stress yield criterion: Analytical, numerical simulation and experiment

Abstract Solid Expandable Tubular (SET) technology is a recent important breakthrough in petroleum exploration and drilling. The expansion forming theory and the constitutive model of the tubular materials are the theoretical basis for the development of this technology. This work focuses on establishing analytical and finite element models on the basis of the Twin Shear Stress (TSS) yield criterion to investigate the forming behavior of solid expandable tubular. The expansion force expression of the power exponential hardening material model was derived. A constitutive model using the TSS yield criterion and related flow rules was proposed and implemented into the ABAQUS software. Further to this, variations of the expansion forces, residual stresses and plastic deformation under different expansion ratios and friction coefficients were investigated. In addition, a tubular expansion experiment was conducted to validate the analytical and finite element solutions. Results show that the expansion force expression is reliable, but there are discrepancies within a reasonable range. The finite element model is capable of predicting the expansion forces, residual stress distributions, thickness reduction and length shortening accurately. Moreover, it is found that the expansion ratio should be controlled below 35% to avoid burst and collapse of the expandable tubular in practical application. For expansion operations, suitable lubrication conditions should be determined to ensure an acceptable expansion force and maintain a certain friction coefficient.

Study on the minimum transverse impact toughness required to resist cracking of non-API high grade steel casing

Abstract In Tarim oilfield of China, the non-API high grade steel casing (HGSC) is frequently used as the intermediate and production casing in ultra-deep well with true vertical depth (TVD) more than 6000 m. So far, no internationally accepted standard has been established for non-API high grade steel casing (HGSC) presently, although some obvious shortcomings exist, such as sensitivity to crack defects and service environment, so that the fracture failure accidents of non-API HGSC happens frequently in Tarim oilfield. Here, firstly, this paper deduces the unified algorithm of burst pressure of non-API HGSC based on twin shear unified strength theory and bilinear hardening model, which takes strain-hardening, Bauschinger effect of material and effect of intermediate principal stress into consideration. Secondly, the burst pressure formula of non-API HGSC has been presented based on weighting twin shear stress yield criterion. Thirdly, the calculation method which can calculate the minimum transverse impact toughness (TITmin) required to resist cracking of non-API HGSC, has been established based on the presented burst pressure formula and API/ISO standard, and the effects of four kinds of defects, factor of effective thickness and non-destructive examination (NDE) level on the TITmin required to resist cracking of pipe body under diffenrent internal pressures have been analyzed. Finally, the full-scale ductile burst test of non-API 140 casing have been conducted, by which the accuracy and reliability of burst pressure formula and calculation method of TITmin have been validated. Research results can provide an important reference for non-API HGSC design in ultra-deep well.

Investigation on the calculation model of burst pressure for tube and casing under practical service environment

The burst strength of tube and casing is important to the storage and development of hydrogen gas and natural gas. Studies on the current classic models to calculate burst pressure of tube and casing show that they are not suitable to predict the burst pressure of tube and casing under modern manufacturing technology level due to without considering the effects of radius-thickness ratio and practical service environment (capped-end condition and capped-open conditions). Hence, for the thin-wall (20＜D/t＜40) tube and casing, based on the deformation instability and finite strain theory, this paper has established the equations to calculate burst pressure of thin-wall pipe under capped-end condition and capped-open conditions by adopting the power-law constitutive relation. For the thick-wall (5 ≤ D/t ≤ 20) tube and casing, based on the failure criterion of through-wall yield, the unified algorithms of burst pressure for thick-wall pipe under capped-end condition and capped-open condition have been derived by adopting unified strength theory. The burst pressure model which can calculate the burst pressure of thick-wall pipe under modern manufacturing technology level, has been presented combining with weighting twin shear stress yield criterion. Numerical and experimental comparisons show that the calculated results of this equation are closest to the test data, and its accuracy and reliability are obviously superior to other models, and the service environment of tube and casing has a great impact on the burst pressure.

Plastic Analysis of Metal Sheet Forming with SD Effects

Generally, many high-strength alloy materials used in aerospace, power and chemical industries have strength differential effect in tension and compression (SD effects). Usually, in mechanical calculations of sheet metal forming, Treasca yield criterion and Mises yield criterion are applied. Because the yield criterions don’t take SD effects into consideration, the calculation result may have errors for certain materials. However, generalized twin shear stress yield criterion, which takes into account the influence of the intermediate principal stress, is more suitable for most metal materials than Mohr-Coulomb strength theory. Therefore, this article has made plastic analysis on thin film stress issues of metal sheet forming with generalized twin shear stress yield criterion. We have obtained a unified plastic solution to the internal and external stretching issue of thin material with rounded holes and different tension and compression ratio. Providing a new result with wider applicability is very significant.

A new closed-form solution for circular openings modeled by the Unified Strength Theory and radius-dependent Young’s modulus

A new closed-form solution is presented for the stress and displacement distribution surrounding circular openings with finite external radii that are subject to uniform internal and external pressures under plane strain conditions. The specific solution for a deep circular tunnel in an infinite rock mass is also provided. It is assumed that the rock mass is elastic–brittle–plastic and governed by the Unified Strength Theory (UST). In the plastic zone, the radius-dependent Young’s modulus (RDM) model and a non-associated linear flow rule were adopted to establish the radial displacement solution. The new closed-form solution obtained in this paper is a series of results rather than one specific solution; hence, it is suitable for a wide range of rock masses and engineering structures. The traditional solutions, which are based on the Mohr–Coulomb failure criterion and the Generalized Twin Shear Stress yield criterion, can be categorized as special cases of this proposed solution. This new solution agrees reasonably well with the results of a borehole collapse test, a secondary development numerical simulation and an additional closed-form solution using the generalized non-linear Hoek–Brown failure criterion. Parametric studies were conducted to investigate the effects of intermediate principal stress, RDM and dilatancy on the results. It is shown herein that the effects of intermediate principal stress and dilatancy are significant; the RDM model is recommended as the optimum approach for calculating radial displacement and support pressure.

Unified solutions for stresses and displacements around circular tunnels using the Unified Strength Theory

The unified solutions are presented for stresses and displacements around a circular tunnel subjected to a hydrostatic stress field. The rock mass is assumed to be elastic-brittle-plastic and governed by the Unified Strength Theory. The displacements are obtained accounting for three different definitions for elastic strains and different Young’s modulus in the plastic zone. The unified solutions obtained in this paper are especially versatile in reflecting the intermediate principal stress effect to different extents for different materials. The conventional solutions, based on the Mohr-Coulomb failure criterion and the Generalized Twin Shear Stress yield criterion, are special cases of the present unified solutions. The new unified solutions can compare with those computed by the latest generalized Hoek-Brown failure criterion. The results obtained demonstrate the importance of the intermediate principal stress influence for the stresses and displacements analysis. The effects of different definitions for elastic strains and different Young’s modulus in the plastic zone on the displacements are significant.

Three-Dimensional Analysis of Rolling by Twin Shear Stress Yield Criterion

Abstract Using the twin shear stress yield criterion, the surface integral of the co-line vectors, and the integration depending on upper limit, Kobayashi's three-dimensional velocity field of rolling was analyzed and an analytical expression of rolling torque and single force was obtained. Through redoing the same experiment of rolling pure lead as Sims, the calculated results by the above expression were compared with those of Kobayashi and Sims formulae. The results show that the twin shear stress yield criterion is available for rolling analysis and the calculated results by the new formula are a little higher than those by Kobayashi and Sims ones if the reduction ratio is less than 30%.

Twin shear stress yield criterion

A twin shear stress yield criterion is described. This criterion was proposed by the author in 1961[1]. It assumes that yielding begins when the sum of the two larger principal shear stresses reaches a magnitude C. Thus the initial yield function is f = τ 13 + τ 12 = σ 1 − 1 2 (σ 2 + σ 3) = c [( τ 13 + τ 12) ± c][ τ 23 + τ 21) ± c][ τ 31 + τ 32) ± c] = 0.