Maximum Principle Stress Research Articles

A finite element analysis study on different angle correction designs for inclined implants in All-On-Four protocol

BackgroundThe aim of this study is to investigate, through finite element analysis (FEA), the biomechanical behavior of the built-in angle corrected dental implant versus implant with angled multiunit abutment used in All-On-Four treatment protocol.MethodsTwo (3D) finite element models of a simplified edentulous mandible were constructed with two different posterior implant designs based on the All-On-Four protocol. Four implants were placed in each model, the two anterior implants were positioned vertically at the lateral incisor/canine sites. Depending on the implant fixture design in posterior area, there are two models created; Model I; the mandible was rehabilitated with four co-axis (4 mm in diameter × 15 mm in length) implants with distally built-in angle corrected implants (24-degree angle correction) .While Model II, the mandible was rehabilitated with four conventional (4 mm in diameter × 14 mm in length) implants with a distally inclined posterior implants (25 degree) and angled multiunit abutments. CAD software (Solidworks© 2017; Dassault Systems Solidworks Corp) was used to model the desired geometry. Axial and inclined Loads were applied on the two models. A Finite element analysis study was done using an efficient software ANSYS© with specified materials. The resultant equivalent Von-Misses stresses (VMS), maximum principal stresses and deformation analysis were calculated for each part (implants and prosthetic components).ResultsWhen applying axial and non-axial forces, model II (angled multiunit model) showed higher deformation on the level of Ti mesh about 13.286 μm and higher VMS 246.68 MPa than model I (angle corrected implant). Model I exhibited higher maximum stresses 107.83 MPa than Model II 94.988 MPa but the difference was not statistically significant.ConclusionWithin the limitation of the FEA study, although angle correcting implant design is showing higher values in maximum principle stresses compared with angled multiunit abutments, model deformation and resultant VMS increased with angled multiunit abutments. The angle correcting designs at implant level have more promising results in terms of deformation and VMS distribution than angle correction at abutment level.

COMPUTATIONAL FLUID–STRUCTURE INTERACTION SIMULATION OF HEMODYNAMICS OF ARTERIOVENOUS FISTULA

The objective of this study is to show how important a compliant wall technique is in simulating non-Newtonian and pulsatile blood flows in arteriovenous fistula (AVF). The three-dimensional idealized geometry is used to investigate the local hemodynamics in the end-to-side, radio-cephalic AVF using computational fluid-stricture interaction (FSI) simulation. The third-order Yeoh law is used to model the behavior of the hyperelatic vessel walls. Hemodynamic parameters such as velocity, wall shear stress (WSS), oscillatory shear index (OSI), vorticity, and venous outflow rate are calculated. The results extracted for WSS on comparison of rigid and compliance wall, rigid wall WSS are 45–48.5% larger values than the compliance wall. The difference between compliance wall and rigid wall OSI is 11.5% and the rigid wall is a 10.86% decrease in compliance wall. The difference between the rigid wall AVF vorticity and the compliance wall vorticity is 18.34%, and the vorticity in the compliance wall is a 20.2% increase over the rigid wall. Maximum principle stress occurs at anastomosis (1335[Formula: see text]Pa) and 507[Formula: see text]Pa, 93[Formula: see text]Pa on vein and artery, respectively. Finally, we conclude that the artery bed and heel of AVF are prone areas of Intimal Hyperplasia. The structural result shows the tendency of the inflammation pattern of the vein required for AVF maturation. ANSYS is a highly effective commercial tool for modeling real-world problems and performing multi-physics numerical simulations.

The Influence of Temperature Variations on Rigid Pavement Concrete Slabs

This research aims to assess the effect of temperature gradient developed within the concrete slab of rigid pavement, and to investigate its impact when incorporated with the traffic load, and the heat transfer pattern. The rigid pavement model considers an isotropic, uniform, and linear-elastic schemes to simulate the material properties. A numerical analysis approach was employed using Abaqus software incorporated with the 3D Solid model. The traffic loads were obtained from the field surveys, while the temperature of the slabs was measured directly on the site. The dimension of the rigid panel is 2.75 m in width, 5 m long, slab thickness of 25 cm, and concrete specification of 41.33 MPa. The results showed that the temperature gradient produced a significant impact on stress development within the concrete slab of rigid pavement. It was observed that the temperature gradient during the daytime generated higher stress than at night, with a value reaching the MOR (Modulus of Rupture). The exposure of the rigid pavement to 500C tends to produce a principle slab stress of 2.395 MPa, while 1.31 MPa was developed due to the traffic load. When the two factors were combined, the concrete slab acquired a maximum principle stress of 3.322 MPa, which is close to the MOR of 83.34% fa. These results showed that the pavement is capable of withstanding stress from temperature gradient and traffic load as indicated by the ratio of less than one (1). However, this ratio is high for fatigue failure mitigation purposes, and this reduces the quality of life of the rigid pavement.

Design and Analysis of Artificial Heart Model by Using Finite Element Analysis

The human heart is a cardiac muscular organ which pumps blood through blood vessels to various tissues and organs for their function and also carries oxygen and other nutrients to tissues. The heart geometry is very complex and function of heart also plays major role in all kinds of animals for survival and carryout all kinds of functions. Investigating the biomechanical behaviour of a soft artificial heart model is a hard task as such things are very complicated in terms of both material properties and geometry. This work is focused on modelling of soft material heart model and study of static and Dynamic behaviour with easily operable, full-size. Theatrical heart model was designed using Creo Parametric 5.0 software. The developed model was further analyzed by the boundary condition such as Total Deformation, Principal stress, Maximum principle stresses and Elastic strain for five different case studies for various pressures at ventricle chamber and Expansion Chamber. The developed model can be used for further Numerical simulation and investigation of the artificial heart were implemented using Creo Parametric 5.0 and ANSYS, with different Bio-Compatible materials such as Silicon Elastomers, Teflon (PTFE), Polyethylene, Graphene, Carbon fiber. The biomechanical modelling and analysis of the soft artificial heart were implemented using the finite element modelling in ANSYS.

Design And Analysis Of Cardiac Stent

This project presents the modification and analysis of two stent designs based on an existing design. The modifications were made using SolidWorks, followed by ANSYS analysis to evaluate von Mises stress and strain, stress intensity, maximum principle stress, and total deformation. Design Expert was then utilized, employing the Response Surface Methodology (RSM) Box-Behnken method, to conclude the design.The generated ANOVA table enabled the identification of significant factors and interactions. Residual analysis was conducted to assess the model's fit and accuracy. The abstract highlights the iterative design process involving SolidWorks, ANSYS, and Design Expert, emphasizing the use of ANOVA and residual analysis to improve the stent design. The optimized stent designs exhibited improvements in stress distribution, strain, stress intensity, and deformation characteristics. This integrated approach utilizing SolidWorks, ANSYS, and Design Expert holds promise for enhancing stent performance and optimizing patient outcomes.

DESIGN AND ANALYSIS OF BIODEGRADABLE CARDIOVASCULAR STENT IN HEALTH CARE APPLICATIONS

This project presents the modification and analysis of two biodegradable stent designs based on an existing design. The modifications were made using SolidWorks, followed by ANSYS analysis to evaluate von Mises stress and strain, stress intensity, maximum principle stress, and total deformation. Design Expert was then utilized, employing the Response Surface Methodology (RSM) Box-Behnken method, to conclude the design.The generated ANOVA table enabled the identification of significant factors and interactions. Residual analysis was conducted to assess the model's fit and accuracy. The abstract highlights the iterative design process involving SolidWorks, ANSYS, and Design Expert, emphasizing the use of ANOVA and residual analysis to improve the stent design. The optimized stent designs exhibited improvements in stress distribution, strain, stress intensity, and deformation characteristics. This integrated approach utilizing SolidWorks, ANSYS, and Design Expert holds promise for enhancing stent performance and optimizing patient outcomes.

Modeling intercalation in cathode materials with phase-field methods: Assumptions and implications using the example of [formula omitted

The multiphase-field method has great potential to advance future research on battery materials. In this work, we discuss the modeling of phase-separating intercalation compounds based on the Cahn-Hilliard equation as well as a multi-phase, multi-component model operating in an Allen-Cahn framework. Modeling assumptions are introduced step-by-step to facilitate future developments and bridging the gap across scales. Dimensionality reduction reflecting the material anisotropies can be critical for combining the phase-field approach with Newman-type models. Furthermore, we discuss a nano-particle battery model starting from intercalation in a defect-free, single-crystalline platelet. The underlying modelling assumptions are reduced step-by-step, first, including in-plane diffusion as a result of crystal defects and finally accounting for a polycrystalline material section. We show how faster in-plane diffusion promotes phase separation while higher C-rates and coherency strain lead to the opposite effect. This work highlights the importance to consider pre-existing grain boundaries for nucleation at higher-order junctions, heterogeneity of the intercalation fluxes and grain-by-grain filling behaviour. Anisotropic elastic deformation leads to high stresses at the evolving phase boundaries, especially at high misorientations between neighbouring grains. The maximum principle stress is used as an estimate for degradation by fracture in polycrystals.

Finite element analysis of the flange with different fillet radius in tubular wind tower

Today’s modern world has more demand for electricity to perform most of the activities. In this regard, wind turbines are used to convert the wind energy into electrical power, where turbines are mounted at the top of the tower called wind tower. To meet the high power generation demand, the wind energy towers will have to become taller because winds are stronger at higher altitudes. In the present, work Modal analysis of the wind tower is done using ANSYS, and Campbell diagram is plotted to check the frequency of resonance between the tower natural frequency and the natural frequency of the rotating blades. Considering the different fillet radius in the flanges, the critical conditions are simulated under the same loading condition. Finite Element Analysis (FEA) results show that by increasing the fillet radius the Equivalent stress, Maximum principle stress and, Maximum shear stress decreases. The safety of the tower is ensured through the Campbell diagram where the excitation frequency of any blade is not crossing the exciter box.

The effects of bar holder material, cantilever and vertical misfit on stresses in implant supported overdentures: Three dimensional finite element analysis

Background/Aim: The aim of this study is to examine with finite element analysis the distal bar extension, the bar substructure material type and the amount of bar substructure-abutment mismatch, and the stress caused by the implant at the surrounding bone tissue in bar-retained prostheses. Material and Methods: A bar-retained prosthesis model has been designed on three implants placed in the fully toothless lower jaw at the places of both canines and the midline. Bar holder according to distal cantilever lengths was modeled to be 0 mm, 8 mm and 14 mm. The vertical incompatibility of the bar holder substructure with the abutment was modeled to be 0 µm, 100 µm and 200 µm. A total of twenty-seven (3x3x3) different models were obtained with three different bar infrastructure materials (titanium, gold and chromium-cobalt). 150 N occlusal force was applied to the central fossa of the left 1st molar tooth with a rigid food stuff. Results: In the cortical bone, the highest maximum principle stress value (2.78 MPa) was analyzed around the anterior implant socket in the model 13 (gold, cantilever 0mm, misfit 100 µm). The highest von Mises stress value (343.43 MPa, which occurred at the selected joints in bar holders) was observed in model 27 (chrome-cobalt, cantilever 14mm, misfit 200 µm). Conclusions: When the length of the cantilever is 14 mm, it causes a significant increase in stress around the implant, especially near the cantilever. It has been observed that bar infrastructures with high elastic modulus create higher stress values.

Experimental observation and modeling of resin pocket cracking in unidirectional laminates with ply discontinuity

Experimental observations revealed that a resin pocket in a unidirectional laminate with a discontinuous ply may form several cracks prior to initiation of delamination cracks. The observed cracks typically occur within the resin pocket, rather than at the interfaces with the discontinuous ply, and are curved towards the center of the pocket. To study this unintuitive cracking behavior, a simple variational stress analysis based on the principle of minimum complementary energy is developed. It allowed to estimate the stress field in the laminate with a discontinuous ply, with or without cracks in the resin region. The observed cracking pattern is explained by assuming a higher level of residual stresses due to chemical shrinkage of the resin during curing in the confined conditions of the pocket. It is shown that the crack locations are best determined using the principle of maximum energy release rate, while the curved crack path can be governed by the distribution of the maximum principle stress. The predicted cracking sequence and the crack curvatures agree well with experimental observations.

Establishment of optimal variable elastic modulus distribution in the design of full-crown restorations by finite element analysis.

To establish optimal elastic modulus distribution throughout the entire all-ceramic crown, aiming at improvement of the mechanical properties of the restoration as well as the adhesive interface, seven 3D models of mandibular first premolars of zirconia monolithic and bilayer crowns and lithium disilicate monolithic and bilayer crowns were constructed. The elastic modulus distribution of 8-layer crown A referred to human enamel, B was calculated by a genetic algorithm (GA) to minimize the principle stresses on the crown, and C minimized the shear stresses at the cementing lines. After applying a static load of 600 N, the maximum principle stresses were calculated and analyzed by finite element analysis (FEA). Group C were found to have the lowest peak shear stress at the cementing line and moderate peak tensile stress in the crown. Introduction of the modified elastic modulus distribution from human enamel into the entire all-ceramic crown reinforces the mechanical properties of the whole restoration as well as the adhesive interface against chipping and debonding.

Numerical Simulation of the Stress Corrosion Rupture Zone for Deep Tunnels

Stress corrosion is a geological phenomenon that damages the long-term stability of underground projects. A comprehensive approach for stress corrosion prediction of underground projects combining creep experiment, particle flow code (PFC)and Finite element method (FEM) is proposed. Calibration of the numerical model was undertaken according to the data obtained from laboratory tests. Based on the numerical model, biaxial and triaxial stress corrosion compression tests were conducted to investigate the stress corrosion mechanism of Jinping marble. Through numerical tests, the stress corrosion process was visually observed. According to the development history of microcracks, the stress corrosion rupture process of surrounding rocks can be divided into 4 stages, i.e., rapid growth, slow growth, rapid growth and instant leap. The process was controlled by driving stress ratio and confining stress. On or near the tunnel wall, most stress corrosion microcracks are induced by tensile stress and the direction is parallel to the direction of the maximum principle stress. Near the yield zone of tunnel, the ratio of shear microcracks becomes larger with increasing confining stress. And the amount of microcracks is larger at the rupture stage than that on the tunnel wall, which makes the stress corrosion rupture process look like a ductile failure process. There is a linear relationship between the logarithm of stress corrosion lifetime and driving stress ratio if the confining stress keeps constant. Stress corrosion lifetime will increase when pc becomes higher or driving stress ratio becomes lower. Based on the laboratory and numerical tests, the stress corrosion rupture depth of the tunnel section was predicted using FEM, which can optimize the length of bolts.

An approximate solution to the finite deformation of an elastic rectangular plate under static and dynamic transverse loadings

In the field of structure safety, the blast resistance of glazing is increasingly important. This problem could be simplified as a finite deformation rectangular plate under dynamic loading, whose traditional solution is still insufficient in accuracy. Based on von Kármán equations, this paper aims to offer an efficient and acceptable approximate solution. Two basic assumptions are adopted: a) the strain distribution along the principle direction of the mid-plane is uniform; b) the in-plane shear stress is ignored. The membrane stresses are expressed by the deflection of the plate, and then the von Kármán equations are de-coupled.Both static and dynamic solutions of current model are verified by finite element simulations, popularly used standards and experiment data. For the simply supported plates, the deflection and stresses predicted by current model are quite accurate. For the fully clamped plates, the deflection predicted is good, but the stress given has a big error, due to the lack of high order deflection modes. Besides, in predicting stresses, the effect of higher orders of deflection modes is discussed. It is confirmed that the accuracy of current approximate solution is sufficient to determine the maximum 1st principle stress of plates, and to give an efficient failure criterion of glazing under blast loading.

Structural Optimization Design of Ship Lock Heads on Soft Soil considering Time-Varying Effects of the Structure and Foundation

Over time, the uneven settlements of the structure and foundation are prominent in constructing ship lock heads on soft soil. These deformations endanger the safety of ship lock heads during construction. This research aimed to establish the ship lock head’s structural optimization procedure on soft soil, considering the time-varying effects of the structure and foundation. By comprehensively considering the linear viscoelastic creep of concrete and the elastoplastic consolidation characteristic of soft soil, a perfect time-dependent analysis method for the lock head on soft soil was proposed. Furthermore, a hybrid particle swarm optimization, enhanced whale optimization, and differential evolution (PSO-EWOA-DE) algorithm was proposed to optimize thirty-four design variables of a lock head. With the minimal volume of the lock head as the optimization objective, the finite element model was established. In the optimization process, three types of constraints were evaluated. The result showed that the optimized design could reduce 10.45% of structure volume. Through comparing and analysing the maximum principle stresses and vertical displacements of the lock head before and after optimization, some conclusions were drawn. The optimization procedure proposed in this paper provides a new perspective for the structural optimization of hydraulic structures on soft soil.

Evaluation of two CAD/CAM materials for Nayyar core and post-retained restorations: Three dimensional stress analysis

ObjectivesThe aim of this study is to assess the stress distribution of a nanoceramic resin CAD/CAM material, Lava Ultimate (LU) and a polymer-infiltrated hybrid ceramic CAD/CAM material, Vita Enamic (VE) for enamel replacement for Nayyar core (corono-radicular dowel and core) or post-retained restoration designs of a maxillary first premolar tooth with missing palatal cusp. Materials and methodsA three dimensional finite element (FE) modelof maxillary first premolar with two roots was modeled. A mesial-occlusal-distal-palatal (MODP) cavity was designed with cavity floor above cemento-enamel junction and including buccal cuspal reduction. Restoration designs consisted of Nayyar core restoration (NCR) and post-retained restoration (PRR) with a glass fiber post. Vita Enamic (VE), Lava Ultimate (LU) were used for enamel and everX Posterior was used for dentin replacement. Vertical occlusal load (100 N) was applied on a spherical solid rigid material simulating the food stuff. Von Mises (VM) and maximum principle stress values were evaluated separately for the remaining enamel, remaining dentin and restorative material in megapascal (MPa). ResultsThe analysis of both VM and maximum principle stress values revealed that the most intense stress accumulation was in the cervical region of enamel for both designs. For VM, similar stress values were observed only in dentin. Stress analysis of restorative materials showed that everX Posterior had the highest stress accumulation. ConclusionsThe comparison of the two techniques showed that PRR had better stress distribution than NCR. NCR or PRR with LU or VE exhibited similar VM stress accumulation in dentin. Maximum principle stress analyses showed that PRR with LU transmitted the least stress to enamel and dentin indicating that when LU is the material of choice, post-retained restoration would be a satisfactory design. VM stress values of enamel revealed that VE absorbed the stress in itself and transferred less stress to dentin. This could point out that for the restoration of maxillary first premolar tooth with missing palatal cusp, VE may be a suitable material for NCR and PRR restoration techniques. HighlightsWhen fiber reinforced composite is used as dentin replacement in combination with VE as enamel replacement; any technique; PRR or NCR, may be preferred in the restoration of MODP cavities of endodontically treated maxillary premolars. The clinical relevance has to be further studied in-vivo.

Geological constraints on the Western Kohat foreland basin, Khyber Pakhtunkhwa, Pakistan: Implication from 2D and 3D structural modelling

The Kohat Foreland Basin is an outcome of continental collision between Indian and Eurasian plates defining the southern edge of Himalayan Orogenic System in the north-western Pakistan. This study constrains the structural geometry and kinematics in 2-D and 3-D workflow, evaluation of the role of multiple detachments and the structural correlation between surface and sub-surface geology of the western Kohat Foreland Basin. The structural style of the western Kohat Foreland Basin evinces the thin skin deformation associated with a couple of structural detachments i.e. i) base-Eocene shale/ evaporite sequence ii) the upper interface of crystalline basement. These detachments separate the outcropping and buried stratigraphic sequence of the Kohat Foreland Basin into upper and lower structural-stratigraphic domains. The lower domain has a series of north-dipping or south-verging fold-thrust assemblages incorporating a rigid rock sequence of EoCambrian to Paleocene. The comparatively more ductile rocks of the upper domain comprising of Eocene to Pliocene are deformed into tight, overturned, doubly plunging and internally faulted anticlines intervened by broad synclines. The two domains dictate different deformational behavior and structural style, deforming in total disharmony; hence the structural geometry of shallow units does not match the sub-surface rocks. The total 37% of shortening in the sedimentary cover was revealed by structural balancing in 2-D and 3-D kinematic modelling. Stress analysis of Gurguri Fault unveiled 40% failure susceptibility and recorded positive values of effective normal stress (σn) with an orientation of maximum principle stress (σ1) as N17°.

Comparison of stress distribution on dental implant with different abutment types

Dental implants have a triumph pace of 90–98%, which in clinical terms is essentially high. Implant failure may occur at earlier or later stage. In assessment of the drawn-out accomplishment of a dental implant, the reliability and the stability of the implant–abutment play a vital role. In general, the achievement of the treatment relies upon numerous factors influencing the implant, implant–abutment and abutment–prosthesis interfaces. Early implant failure occurs due to the improper mechanical stability. This study researches the stress distribution in an implant with different implant abutments with different height and angle in different loading criteria. The abutment heights are 5.50 mm, 3.50 mm and 3.60 mm respectively. The loading conditions are applied in vertical and 30˚ angle with the value of 36 N & 100 N. Cobalt chromium alloy is used which has the superior properties like high stiffness, tightly polished, wear resistant and also it is used to avoid crevice corrosion. Computational models of abutment types with different heights were modeled using CAD software and Analyzed with FEA software for finding out the total deformation, Maximum principle stress, and Maximum shear stress. Based on the structure of a dental implant system, it gives significant performance. The minimum and maximum total deformation, Maximum principle stress, and Maximum shear stress were noted in the Type 3 under 36 N vertical condition and Type 1 under 100 N under 30˚ respectively.

Strength Analysis and Assessment of Ina-TEWS Wave Glider

Indonesia as a country that often experiences tsunami disasters needs to have an early warning system against tsunami disasters. This system can use various existing technologies, one of which is the tsunami buoy system. The new tsunami buoy system does not use the natural mooring system but uses the wave glider system. This paper discusses the structural strength of the surface floater of wave glider using Eva Foam and Fiberglass material for skin and Alluminium material for frame and kell. The surface floater using 16 pieces for frame and 1 piece for keel. Enviromental loads is use in this paper like hydrodynamics load and weight load. The results from this paper is material from Eva Foam has a maximum principle stress is 12693 Pa and shear stress is 6114.6 Pa. For material from Fiberglass has maximum principle stress is 11.875 Pa and shear stress is 6076.3 Pa. Safety factor (SF) from maximum principle stress and shear stress for Eva Foams is up to 6x and SF for maximum principle and shear stress for Fiberglass is up to 26x. Conclusions for this paper is the desain for surface floater of wave glider it can be operated in the sea with draugh 0.18 m.

Dynamic Response of Rigid Pavement Plate due to Localized Blast Load

In structural and transportation engineering applications, the dynamic response of orthotropic plates is an essential matter. Engineers did not consider the effects of dynamic loads such as those from machine vibrations or blast load. Dynamic analysis of rigid pavement plates due to local blast loads on concrete slabs in this research is modeled as concrete slabs with boundary condition that every edges of plates have a dowel-tie bar support and The rigid concrete pavement sitting on elastics Pasternak foundation is modeled by using the Kirchhoff theory of thin plates. Pasternak foundation have elastic vertical spring support and continuous shear layer. The main system responses that are observed are the transversal deflections at midspan and the internal stresses of the plate, particularly the maximum principle stress, minimum principle stress and maximum shear stress. Three loading phases are included in the analysis, namely: the positive phase, the negative phase, and the free vibration phase. Analyses are carried out utilizing a numeric approach termed the Modified Bolotin Method with two trancedental equation. The analysis is performed when the load is above the plate (0 ≤ t ≤ t0). Deflections resulting from various load positions on the set of slab models throughout all three phases are then compared side-by-side. Bending moment, shear forces, and stresses are calculated on all slab models with the Friedlander localized blast loading applied at midspan and the results are presented as stress contours that are then compared between each model.

Study of Wellbore Breakdown under Fluid Injection in Transversely Isotropic Poroelastic Formations

Summary Fluid injection into the formation through a completed wellbore, as an important process for the oil and gas industry, is commonly seen in well tests and hydraulic fracturing operations. The problem of wellbore breakdown during fluid injection is revisited in this work by a thorough and comprehensive consideration of some essential issues involved in this subject. First, fluid injection may not necessarily start simultaneously with the completion of wellbore drilling, as is usually assumed in the reported analytical solutions. Second, there exists a common limitation that the borehole must orient in a direction normal to the isotropic (bedding) planes in the previous analytical studies addressing the wellbore problem drilled in a transversely isotropic formation. Last, but not least, the implicit boundary condition of radial stress, which is usually ignored but essential to accurately evaluate the breakdown pressure on such fluid injection, also adds to the difficulty of solving the problem. This paper presents a novel numerical scheme enhanced by user subroutines/functions that can work with mainstream simulators to promote the in-depth study of wellbore breakdown under fluid injection with various model settings. On validation, the effects of the idle time t0 after drilling and the material anisotropy on the poromechanical responses of the wellbore are extensively studied for the most commonly encountered horizontal wells. The idle time has slight effects immediately after fluid injection starts; however, the influences become generally negligible after a short period of time of fluid injection. It is also revealed that the anisotropy in rock properties has a more significant influence on the stress responses for horizontal wells than the previously studied case of vertical wells. Another important finding is that tensile fracture may not always initiate vertically from the top/bottom of the horizontal borehole wall because the maximum tensile stress occurs elsewhere, although vertical in-situ stress is the maximum principle stress.