Elastoplastic 3D Deformation and Stress Analysis of Strip Rolling

An elastoplastic method for analyzing the 3D deformation, stress and transverse distribution of tension stress during cold strip rolling is developed. The analysis is based on the elastoplastic variational principle in which a kinematically admissible velocity field is constructed with the lateral flow function as an unknown function. The stress distribution and volume strain distribution are obtained by solving the simultaneous equations formed by the longitudinal differential equation of equilibrium and constitutive equations. The lateral flow function is determined by minimizing the total energy dissipation rate. Experimental investigation was carried out on a reversible cold mill. The front tension stress distributions in cold rolled strips were measured by a multi roll segmented tension sensing shapemeter. The calculated results are in good agreement with the measured ones.

FEM analyses of stress and deformation of a flexible inner pressure bolt

The flexible inner pressure bolt is a new kind and new structural bolt (anchor rod). A number of structural improvements and performance test have been carried out. The bolt has superior compatibility to the soft crag and the large distortion tunnel with its flexibility. In order to study its stress, deformation and interaction mechanism thoroughly, a number of large distortion calcula- tions and analyses have been carried out on the bolt by FEM (finite element method), especially with the ANSYS software, based on the updated Lagrangian law. The results show that the maximum stress of the inner wall of the bolt is consistent with an elastic analytic solution. The maximum stress on the body occurs in the vicinity of the enhancement material. The link enhancement of the body seems to be quite essential. The experimental results indicate that the maximum injection pressure in the bolt is 2.5 MPa without link enhancement and 8.3 MPa with the enhancement. This link enhancement effect is highly significant. These results provide some basis for the design, application and anchoring stress analysis of the bolt.

Iterative reverse deformation optimization design of castings based on numerical simulation of solidification thermal stress

In the casting process,in order to compensate for the solidification shrinkage to obtain higher dimensional accuracy of the casting,it is often necessary to modify the original design of castings,and a suitable compensation method has a decisive impact on the dimensional accuracy of the actual casting.In this study,based on solidification simulation,a design method of reverse deformation is proposed,and two compensation methods,empirical compensation and direct reverse deformation,are implemented.The simulation results show that the empirical compensation method has problems such as difficulty in determining the parameters and satisfaction of both the overall and local accuracy at the same time;while based on the simulation results for each node of the casting,the direct reverse deformation design achieves the design with shape.In addition,the casting model can be optimized through iterative revisions,so that higher dimensional accuracy can be continuously obtained in the subsequent design process.Therefore,the direct reverse deformation design is more accurate and reasonable compared to empirical compensation method.

Numerical simulation of residual stress and deformation for submerged arc welding of Q690D high strength low alloy steel thick plate

The finite element simulation software SYSWELD is used to numerically simulate the temperature field,residual stress field,and welding deformation of Q690D thick plate multi-layer and multi-pass welding under different welding heat input and groove angles.The simulation results show that as the welding heat input increases,the peak temperature during the welding process is higher,and the residual stress increases,they are all between 330–340 MPa,and the residual stress is concentrated in the area near the weld.The hole-drilling method is used to measure the actual welding residual stress,and the measured data is in good agreement with the simulated value.The type of post-welding deformation is angular deformation,and as the welding heat input increases,the maximum deformation also increases.It shows smaller residual stress and deformation when the groove angle is 40°under the same heat input.In engineering applications,under the premise of guaranteeing welding quality,smaller heat input and 40°groove angle should be used.

Effects of Plastic Deformation and Stresses on Dilatation duringthe Martensitic Transformation in a B-bearing Steel

To provide data for improved modelling of the behaviour of steel components in a simultaneous forming and quenching process, the effects of plastic deformation and stresses on dilatation during the martensitic transformation in a B-bearing steel were investigated. It was found that plastic deformation of austenite at high temperatures enhances ferrite formation significantly, and consequently, the dilatation decreases markedly even at a cooling rate of 280'C/s. The created ferritic-martensitic microstructure possesses clearly lower hardness and strength than the martensitic structure. Elastic stresses cause the preferred orientation in martensite to be formed so that diametric dilatation can increase by nearly 200% under axial compression.

The Deformation and Stress Analysis of Na Ba Reservoir Concrete Face Rock-Fill Dam

Based on the APDL （ANSYS Parametric Design Language） and combined with the actual project related to parameters of filling material, imported Duncan-Chang constitutive model which has been widely applied in soil mass and rock-fill in the ANSYS software. With the three-dimensional nonlinear finite element analysis by the mid-point incremental method, what have been computed are the deformation and stress analysis ofNa Ba reservoir CFRD （Concrete Face Rock-fill Dam） in filling period. The calculation results provide practical reference for the dam during construction safety filling stress and deformation analysis and real-time monitoring.

Bending and stress analysis of polymeric composite plates reinforced with functionally graded graphene platelets based on sinusoidal shear-deformation plate theory

The bending and stress analysis of a functionally graded polymer composite plate reinforced with graphene platelets are studied in this paper.The governing equations are derived by using principle of virtual work for a plate which is rested on Pasternak’s foundation.Sinusoidal shear deformation theory is used to describe displacement field.Four different distribution patterns are employed in our analysis.The analytical solution is presented for a functionally graded plate to investigate the influence of important parameters.The numerical results are presented to show the deflection and stress results of the problem for four employed patterns in terms of geometric parameters such as number of layers,weight fraction and two parameters of Pasternak’s foundation.

Stress-induced deformation at A_p～M_p and thermal cycling behavior of Cu-Al-Ni single crystals

Stress induced deformation in A p～ M p and concomitant shape recovery behavior of Cu 13.4Al 4.0Ni single crystals were studied. Abnormal high stress induced deformation exists in A p～ M p under the conditions of either heating with load or cooling with load. The recovered deformation is successively composed of four parts, the recoveries from superelasticity, normal reverse transformation, thermally activated reverse transformation of partially stabilized martensite and reverse transformation of stabilized martensite by over heating. With increasing cycling number, the recovery part from normal reverse transformation decreases, while that from reverse transformation of stabilized martensite by over heating increases, which shows a typical stabilization of martensite.

Predictive analysis of stress regime and possible squeezing deformation for super-long water conveyance tunnels in Pakistan

The prediction of the stress field of deep-buried tunnels is a fundamental problem for scientists and engineers. In this study, the authors put forward a systematic solution for this problem. Databases from the World Stress Map and the Crustal Stress of China, and previous research findings can offer prediction of stress orientations in an engineering area. At the same time, the Andersonian theory can be used to analyze the possible stress orientation of a region. With limited in-situ stress measurements, the Hock-Brown Criterion can be used to estimate the strength of rock mass in an area of interest by utilizing the geotechnical investigation data, and the modified Sheorey＇s model can subsequently be employed to predict the areas＇ stress profile, without stress data, by taking the existing in-situ stress measurements as input parameters. In this paper, a case study was used to demonstrate the application of this systematic solution. The planned Kohala hydropower plant is located on the western edge of Qinghai-Tibet Plateau. Three hydro-fracturing stress measurement campaigns indicated that the stress state of the area is SH - Sh 〉 Sv or SH 〉Sv 〉 Sh. The measured orientation of Sn is NEE （N70.3°-89°E）, and the regional orientation of SH from WSM is NE, which implies that the stress orientation of shallow crust may be affected by landforms. The modified Sheorey model was utilized to predict the stress profile along the water sewage tunnel for the plant. Prediction results show that the maximum and minimum horizontal principal stres- ses of the points with the greatest burial depth were up to 56.70 and 40.14 MPa, respectively, and the stresses of areas with a burial depth of greater than 500 m were higher. Based on the predicted stress data, large deformations of the rock mass surrounding water conveyance tunnels were analyzed. Results showed that the large deformations will occur when the burial depth exceeds 300 m. When the burial depth is beyond 800 m, serious squeezing deformations will occur in the surrounding rock masses, thus requiring more attention in the design and construction. Based on the application efficiency in this case study, this prediction method proposed in this paper functions accurately.

Numerical research on effect of overlap ratio on thermal-stress behaviors of the high-speed laser cladding coating

High-speed laser cladding technology, a kind of surface technology to improve the wear-resistance and corrosion-resistance of mechanical parts, has the characterizations of fast scan speed, high powder utilization rate, and high cladding efficiency. However, its thermal-stress evolution process is very complex, which has a great influence on the residual stress and deformation. In the paper, the numerical models for the high-speed laser cladding coatings with overlap ratios of 10%,30%, and 50% are developed to investigate the influence rules of overlap ratio on the thermal-stress evolution, as well as the residual stresses and deformations. Results show that the heat accumulation can reheat and preheat the adjacent track coating and substrate, resulting in stress release of the previous track coating and decreased longitudinal stress peak of the next track coating. With the overlap ratio increasing, the heat accumulation and the corresponding maximum residual stress position tend to locate in the center of the cladding coating, where the coating has a high crack susceptibility. For a small overlap ratio of 10%, there are abrupt stress changes from tensile stress to compressive stress at the lap joint, due to insufficient input energy in the position. Increasing the overlap ratio can alleviate the abrupt stress change and reduce the residual deformation but increase the average residual stress and enlarge the hardening depth. This study reveals the mechanism of thermal-stress evolution, and provides a theoretical basis for improving the coating quality.

Deformation tests and failure process analysis of an anchorage structure

In order to study the failure process of an anchorage structure and the evolution law of the body＇s defor- mation field, anchor push-out tests were carried out based on digital speckle correlation methods （DSCM）. The stress distribution of the anchorage interface was investigated using the particle flow numerical simulation method. The results indicate that there are three stages in the deformation and fail- ure process of an anchorage structure： elastic bonding stage, a de-bonding stage and a failure stage. The stress distribution in the interface controls the stability of the structure. In the elastic bonding stage, the shear stress peak point of the interface is close to the loading end, and the displacement field gradually develops into a ＂V＂ shape, in the de-bonding stage, there is a shear stress plateau in the center of the anchorage section, and shear strain localization begins to form in the deformation field. In the failure stage, the bonding of the interface fails rapidly and the shear stress peak point moves to the anchorage free end. The anchorage structure moves integrally along the macro-cracl~ The de-bonding stage is a research focus in the deformation and failure process of an anchorage structure, and plays an important guiding role in roadway support design and prediction of the stability of the surrounding rock.

Stress-strain analysis of Aikou rockfill dam with asphalt-concrete core

Aikou rockfill dam with asphalt-concrete core is situated in a karst area in Chongqing City, China. In order to study the operative conditions of the rockfill dam, especially those of the asphalt-concrete core, the Duncan model is adopted to compute the stress and strain of both the rockfill dam and the asphalt-concrete core after karst grouting and other treatments. The results indicate that the complicated stress and deformation of both the dam body and the core are within reasonable ranges. It is shown that structure design and foundation treatment of the dam are feasible and can be used as a reference for other similar projects.

Nonlinearity analysis of piezoelectric micromachined ultrasonic transducers based on couple stress theory

This paper studies the static deformation behavior of a piezoelectric micromachined ultrasonic transducer （PMUT） actuated by a strong external electric field. The transducer membrane consists of a piezoelectric layer, a passive layer and two electrode layers. The nonlinearities of the piezoelectric layer caused by electrostriction under a strong electric field are analyzed. Because the thickness of the transducer membrane is on the microscale, the size dependence of the deformation behavior is evaluated using the couple stress theory. The results show that the optimal ratio of the top electrode diameter and the membrane diameter is around 0.674. It is also found that this optimal value does not depend on any other parameters if the thicknesses of the two electrodes are negligible compared with those of the piezo- electric and passive layers. In addition, the nonlinearities of the piezoelectric layer will become stronger along with the increase of the electric field, which means that softening of the membrane stiffness occurs when a strong external electric field is applied. Meanwhile, the optimal thickness ratio for the passive layer and the piezoelectric layer is not equal to 1.0 which is usually adopted by previous researchers. Because there exists size dependence of membrane deforma-tion, the optimal value of this thickness ratio needs to be greater than 1.0 on the microscale.

VISCOELASTIC BEHAVIOR OF THE NON-HOOKE DEFORMATION BEFORE YIELDING IN UNIAXIAL DRAWING OF AMORPHOUS POLY(ETHYLENE TEREPHTHALATE)

Viscoelastic behavior of the non-Hooke deformation of amorphous PET film before yield was investigated in the temperature region 74-80.5 degreesC around the glass transition temperature. The film specimen was drawn to yield point followed by unloading to zero stress, then the residual deformation was held constant; while the subsequent evolution of the stress was recorded. An induction period was found in the course of stress evolution followed by a stress step-increase. The induction period decreases with increasing drawing temperature with an activation energy of 1.10 MJ/mol.K, which is attributed to the time needed for the relaxation of rubbery deformation through cooperative internal rotations. At temperatures lower than 74 degreesC, there is no stress increase or the induction period becomes too long to be observed. Thus the nature of anelasticity in the non-Hooke region before yielding is attributed to stress induced rubbery deformation. The experimental results are interpreted in terms of Perez' theological model of a series connected Hooks spring and a Voigt element consisting of a parallel connected elastic spring and a dashpot.

A variational differential quadrature solution to finite deformation problems of hyperelastic shell-type structures:a two-point formulation in Cartesian coordinates

A new numerical approach is presented to compute the large deformations of shell-type structures made of the Saint Venant-Kirchhoff and Neo-Hookean materials based on the seven-parameter shell theory.A work conjugate pair of the first Piola Kirchhoff stress tensor and deformation gradient tensor is considered for the stress and strain measures in the paper.Through introducing the displacement vector,the deformation gradient,and the stress tensor in the Cartesian coordinate system and by means of the chain rule for taking derivative of tensors,the difficulties in using the curvilinear coordinate system are bypassed.The variational differential quadrature(VDQ)method as a pointwise numerical method is also used to discretize the weak form of the governing equations.Being locking-free,the simple implementation,computational efficiency,and fast convergence rate are the main features of the proposed numerical approach.Some well-known benchmark problems are solved to assess the approach.The results indicate that it is capable of addressing the large deformation problems of elastic and hyperelastic shell-type structures efficiently.

Mechanical performances of shield tunnel segments under asymmetric unloading induced by pit excavation

To explore the stress and deformation responses,as well as the failure characteristics of the shield tunnel segment of Hangzhou Metro under the influences of pit excavation and other surrounding projects,a self-developed“shield tunnel segment hydraulic loading system”was used to carry out full-scale loading tests on the three-ring staggered assembled segments.The structural performances and failure process of the tunnel segment under step-by-step asymmetric unloading were studied.A safety index was proposed to describe the bearing capacity of the segment.Next,a finite element model(FEM)was established to analyze the bearing capacity of segment using the test results.Finally,the effect of reinforcement with a steel plate on the deformation and bearing capacity of the segment was analyzed.The results showed that under asymmetric unloading,the peak value and amplitude of the bending moment on the near unloading side converged with a greater value than those on the far side.The concrete internal force exhibited a directional transformation at different load stages.Cracks first appeared at the 180inner arc surface of the bottom standard block and then expanded to both sides,while the rate of crack propagation of the outer arc surface was relatively lower.The bearing capacity of the segments can be evaluated by the combination of the factors,e.g.the residual bearing capacity coefficient,moment transfer coefficient,and characterization coefficient.The segments approaching failure can facilitate the increase in the residual bearing capacity coefficient by more than 50%.This can provide guidance for the service assessment of metro tunnel operations.

Optimization of construction scheme and supporting technology for HJS soft rock tunnel

For a soft rock tunnel under high stress in jointed and swell soft rock （HJS）, two construction schemes pilot-tunneling enlarging excavation and step-by-step excavation were optimized using FLAC20, and the deformation effects of the two construction schemes were verified by field tests. Based on engineer- ing geological investigation and mechanical analysis of large deformations, the complex deformation mechanisms of stress expansion and structural deformation of the soft rock tunnel were confirmed, and support countermeasures from the complex deformation mechanism converted to a single type were proposed, and the support parameters were optimized by field tests. These technologies were proved by engineering practice, which produced significant technical and economic benefits.

Hot Deformation Behavior and Flow Stress Prediction of Ultra Purified 17% Cr Ferritic Stainless Steel Stabilized with Nb and Ti

The hot deformation behavior of ultra purified 17% Cr ferritic stainless steel stabilized with Nb and Ti was investigated using axisymmetric hot compression tests on a thermomechanical simulator.The deformation was carried out at the temperatures ranging from 700 to 1 100℃ and strain rates from 1to 10s-1.The microstructure was investigated using electron backscattering diffraction.The effects of temperature and strain rate on deformation behavior were represented by Zener-Hollomon parameter in an exponent type equation.The effect of strain was incorporated in the constitutive equation by establishing polynomial relationship between the material constants and strain.A sixth order polynomial was suitable to represent the effect of strain.The modified constitutive equation considering the effect of strain was developed and could predict the flow stress throughout the deformation conditions except at800℃in 1s-1 and at 700℃in 5and 10s-1.Losing the reliability of the modified constitutive equation was possibly ascribed to the increase in average Taylor factor at 800℃in 1s-1 and the increase in temperature at 700℃in 5and10s-1 during hot deformation.The optimum window for improving product quality of the ferritic stainless steels was identified as hot rolling at a low finisher entry temperature of 700℃,which can be achieved in practical production.

Study on the performance of the micropile-mechanically stabilized earth wall

The Micropile-Mechanically Stabilized Earth(MSE) wall, specially designed for mountain roads, is proposed to improve the MSE wall local stability, global stability and impact resistance of roadside barriers. Model tests and the corresponding numerical modeling were conducted to validate the serviceability of the Micropile-MSE wall and the reliability of the numerical method. Then, a parametric study of the stress and deformation of Micropile-MSE wall based on the backfill strength and interfacial friction angle between backfill and backslope is conducted to evaluate its performance.The test results indicate that the surcharge-induced horizontal earth pressure, base pressure and lateral displacement of the wall panel of Micropile-MSE wall decrease. The corresponding numerical results are nearly equal to the measured values. The basic failure mode of MSE wall in steep terrain is the sliding of backfill along the backslope, while A-frame style micropiles are capable of preventing the sliding trend.The maximum resultant displacement can be decreased by 6.25% to 46.9% based on different interfacial friction angles, and the displacement canbe reduced by 6% ~ 56.1% based on different backfill strengths. Furthermore, the reduction increases when the interfacial friction angle and internal friction angle of backfill decrease. In addition, the lateral displacement of wall panel, the deformation of backfill decrease and the tension strain of geogrid obviously, which guarantees the MSE wall functions and provides good conditions for mountain roads.

On Plane Stress State and Stress Free Deformation of Thick Plate with FGM Interface under Thermal Loading

This paper demonstrates the plane stress state and the stress free thermo-elastic deformation of FGM thick plate under thermal loading.First,the Sneddon-Lockett theorem on the plane stress state in an isotropic infinite thick plate is generalized for a case of FGM problem in which all thermo-mechanical properties are optional functions of depth co-ordinate.The proof is based on application of the Iljushin thermo-elastic potential to displacement type system of equations that reduces it to the plane stress state problem.Then an existence of the purely thermal deformation is proved in two ways:first,it is shown that the unique solution fulfils conditions of simultaneous constant temperature and linear gradation of thermal expansion coefficient,second,proof is based directly on stress type system of equations which straightforwardly reduces to compatibility equations for purely thermal deformation if only stress field is homogeneous in domain and at boundary.Finally,couple examples of application to an engineering problem are presented.