Expansion Force Research Articles

A Review on the Transport-Chemo-Mechanical Behavior in Concrete under External Sulfate Attack

Cementitious concrete structures serving in sulfate environments suffer from serious durability challenges caused by chemical sulfate attacks (CSA), which lead to the volume expansion, cracking, and spalling of concrete and the early failure of structures. CSA on concrete involves the behaviors of ion transport, chemical reactions, the crystallization of reaction products, microstructural damage to the cement matrix, and the macroscopic deterioration of concrete, namely the transport-chemo-mechanical behaviors. This paper first introduces the reaction products, such as gypsum, ettringite, brucite, and thaumasite, between sulfate and concrete under different environmental conditions and their formation mechanism. Then, aiming at the ettringite type CSA, the theories of volume increase and crystallization pressure are elaborated to explain it-induced concrete degradation. Additionally, the crystallization pressure theory is used to describe the cracking behavior in the microstructure slurry caused by the ettringite crystal filling pore. Finally, a series of transport-chemo-mechanical models for ettringite type CSA are displaced module by module. It includes the sulfate diffusion-reaction model, the free expansion of concrete, and equivalent expansive force in concrete related to the reaction behavior: the model for chemo-mechanical behavior in concrete caused by CSA. These models can be used to analyze the distribution of sulfate ions and the reaction product content, expansive stress and strain in the concrete, and the cracking and spalling degree of the concrete, which is beneficial to evaluate the durability of concrete structures serving permanently in a sulfate environment.

Biomechanical evaluation of a novel tri-blade titanium implantable vertebral augmentation device

BACKGROUND CONTEXTTitanium implantable vertebral augmentation device (TIVAD) are regarded as having potential in the treatment of vertebral compression fractures (VCFs). However, improper design in current TIVADs results in the inability to effectively restore VCF height and maintain stability. There is still an unmet clinical need for improvement. PURPOSEThe authors tested a newly developed a TIVAD (Tri-blade fixed system) that can provide enough endplate collapse support to restore the vertebral body height in a safe retraction mechanism for VCFs using minimally invasive surgery (MIS). STUDY DESIGNThe performed biomechanical tests included blade expansion force, lifetime of cement embedded and vertebral height restoration efficiency of porcine osteoporosis VCFs for its feasibility. METHODSA cylinder with 3 surface cuts that form blades that can be expanded into a conical space was designed (Tri-blade fixed system). The 3 blades can be expanded outward with angles between blades as 105°/ 105°/150° for lower left/lower right/upper arms, respectively that reach 15mm in height and 14.8 mm in width. A frame was specifically designed to measure the contact force using force sensing resistors during blade expansion. The Tri-blade fixed system was embedded into a cement block to perform fatigue testing under 2000N pressure (5*106 cycles) for understanding the device lifetime limitation. The Tri-blade system was then inserted into porcine osteoporosis VCFs to examine the vertebral height restoration efficiency. RESULTSThe average maximum contact force for the top, bottom left and right blades were 299.0N, 283.5N and 279.3N, respectively with uniformly outward expansion forces. The fatigue test found that there were no obvious cracks or damage to the cement block. The porcine osteoporosis vertebral body at the anterior, middle, and posterior heights can be restored to 21.9%, 12.6% and 6.4%, respectively. CONCLUSIONSThis study developed a novel TIVAD with conical shape that can provide a more stable structure with sufficient/uniform expansion force, passing the fatigue test with bone cement and high effective in vertebral height restoration tests for porcine osteoporosis VCFs. CLINICAL SIGNIFICANCEThe new 3D Tri-blade TIVAD may offer a new treatment option for VCFs.

Self-Sustained Euler Buckling of an Optically Responsive Rod with Different Boundary Constraints

Self-sustained oscillations can directly absorb energy from the constant environment to maintain its periodic motion by self-regulating. As a classical mechanical instability phenomenon, the Euler compression rod can rapidly release elastic strain energy and undergo large displacement during buckling. In addition, its boundary configuration is usually easy to be modulated. In this paper, we develop a self-sustained Euler buckling system based on optically responsive liquid crystal elastomer (LCE) rod with different boundary constraints. The buckling of LCE rod results from the light-induced expansion and compressive force, and the self-buckling is maintained by the energy competition between the damping dissipation and the net work done by the effective elastic force. Based on the dynamic LCE model, the governing equations for dynamic Euler buckling of the LCE rod is formulated, and the approximate admissible trigonometric functions and Runge-Kutta method are used to solve the dynamic Euler buckling. Under different illumination parameters, there exists two motion modes of the Euler rod: the static mode and the self-buckling mode, including alternating and unilateral self-buckling modes. The triggering conditions, frequency, and amplitude of the self-sustained Euler buckling can be modulated by several system parameters and boundary constraints. Results indicate that strengthening the boundary constraint can increase the frequency and reduce the amplitude. It is anticipated that this system may open new avenues for energy harvesters, signal sensors, mechano-logistic devices, and autonomous robots.

НАПРАВЛЕНИЯ ПО УСОВЕРШЕНСТВОВАНИЮ МЕТОДА ПРЕДЕЛЬНОГО РАВНОВЕСИЯ ПРИ РАСЧЕТЕ КОМБИНИРОВАННЫХ ЖЕЛЕЗОБЕТОННЫХ ИЗГИБАЕМЫХ ПЛИТ

The purpose of the study is to adapt the method of limit equilibrium for the calculation of a reinforced, low-density concrete monolithic slab structure using prefabricated low-density concrete blocks. A numerical study was conducted based on the use of combined slab models and theories of material deformation. As a result, we obtained data on the stress-strain state of the structure and compared them using various theories and models. It has been established that calculating the combined slab structure using a method based on the finite element method (FEM) makes it possible to account for the nonlinear properties of concrete and reinforced concrete, and also affects the distribution of bending moments and expansion forces between the cross beams. Based on the limit equilibrium method, recommendations have been developed for determining the distribution of bending moments along linear plastic hinges. The practical sig-nificance of the study is to identify the features of the stress-strain state and to establish the relationship between the calculation results and experimental data.

Watching Musical Symbols Grow

The changing forms of gestures used in choral conducting (both in rehearsal and performance) exemplify processes of symbol growth that challenge interpretations of Charles S. Peirce’s later hexadic semiotic as aligning with highly deterministic, (post-)structuralist theories of semiosis. The case in point discussed, a performance of Charles Ives’s A Christmas Carol, demonstrates that the Dynamic Object represented via the conductor’s changing gestures with each new instance of practice is at every turn subject to a host of unpredictable circumstances that limit its determinative powers. This predicament continuously factors into the sign’s immediate formations (Immediate Object and Interpretant) as well as its extramusical meaning-making capabilities (the formation of Dynamic and Final Interpretants). The conducting process, from first rehearsal through concert performance, illustrates how creativity in Representamen formation is an expansive force on which every form of Symbol growth depends.

Hızlı ve Yarı Hızlı Maksiller Genişletme Etkinliğinin İskeletsel Maturasyon Aşamalarına Göre Karşılaştırılması: Retrospektif Bir Çalışma

Objective: This study aimed to compare the skeletal and dentoalveolar effects of the expansion force created by the semi-rapid and rapid activation protocols. Material and Methods: The study comprised 54 patients (26 female and 28 male) with transverse maxillary insufficiency. Of these patients, 22 were treated with semi-rapid maxillary expansion (SRME) and 32 with rapid maxillary expansion (RME). The SRME group consisted of 6 prepubertal, 8 pubertal, and 8 postpubertal patients, and the RME group consisted of 11 prepubertal, 11 pubertal, and 10 postpubertal patients. Treatment effects with both protocols were evaluated with 11 different measurements on posteroanterior cephalograms and plaster models taken before treatment and after a retention period of 3 months. Kruskal-Wallis analysis was used for comparisons between different maturation periods. Independent sample t-test and Mann-Whitney U test with Bonferroni correction were used for pairwise comparisons between two different activation protocols. Results: The increases in nasal and dental widths in the SRME group were found to be higher than in the RME group in the prepubertal patient group (p0.05). No statistically significant difference was found among prepubertal, pubertal, and postpubertal groups for all skeletal and dental measurements (p>0.05). Conclusion: The current study represented some evidence that the SRME activation protocol might cause less tissue resistance than the conventional RME. The efficiency of maxillary expansion therapy is similar in prepubertal, pubertal, and postpubertal patients in whom sutural resistance is resolved.

Effect of Bronchoscopic Spray Cryotherapy and Ultra-low Temperature on Physical Properties of Metallic and Silicone Airway Stents.

Bronchoscopic spray cryotherapy (SCT) is utilized in the field of interventional pulmonology for treating benign and malignant airway stenosis as a standard tool to maintain airway patency. Stent-related complications include tumor overgrowth, granulation tissue, and epithelialization. Thermal ablation can have a limited role in such scenarios due to the risk of airway fire and damage to the existing stent. SCT is a potential therapy using ultra-low temperatures that can allow stents to remain in place during treatment. However, there has been no study demonstrating the safety of SCT on the integrity and physical properties of tracheobronchial stents. We report the results of the first study demonstrating the safety of SCT utilized to treat stent-associated granulation or malignant airway disease. The aim of this study was to demonstrate the effects of SCT on the physical properties of airway stents in an ex vivo environment. Various types of airway stents were subjected to multiple intervals of SCT for up to 30 seconds, and then the cycle was repeated 3 times. After every cycle, we compressed the stents to 60% of their original size, and compression and expansion force data was collected immediately after, at 3-minute and 5-minute intervals, and compared with the baseline readings. There was no significant change in the association between diameter and compression/expansion force, including any derangement in returning to the original diameter or any physical damage to any of the stents even after 3 prolonged SCT sessions of 30 seconds. Our study provides the first evidence that the use of SCT in conjunction with existing silicone/metal stents is feasible and does not cause any physical damage to the stents or alters their ability to maintain the original diameter.

Thermo-mechanical analysis of fire effects on the structural performance of shield tunnels

Investigating fire effects is a continuing endeavour in the research and practice communities concerned with the design and safety of shield tunnels. This paper aims to provide a comprehensive model for the assessment of structural safety of a shield tunnel segmental ring exposed to fire. A thermo-mechanical model for assembled shield tunnel structure in fire is developed to provide a basis for a holistic analysis by incorporating tunnel lining segments and longitudinal joints, as well as improved predictions for the temperature, stress and deformation distributions in the tunnel structure. Validation of the numerical results against experimental data shows satisfactory agreement. Parametric studies are subsequently conducted to investigate the effects of spalling, buried depth and cooling-off phases on the fire behaviour of the shield tunnel. The results show that the damage and failure of a tunnel lining structure under high temperature are mainly due to the combined action of internal thermal expansion force and thermal stress. Spalling leads to the loss of a key “insulation” layer of a tunnel lining structure. On the other hand, the constraint of strata on the tunnel structure under high temperature not only restrains the deformation of key parts of the structure, but also helps offset the adverse effect of load on the structure through elastic resistance.

Exploring the role of the interface adhesion phenomena focusing on surface expansion distribution

This work focused on the surface expansion of the contact surface and its influence on the interface adhesion phenomena in wedge indentation of an aluminum specimen. Direct in-situ observations coupled with high-speed imaging and particle image velocimetry techniques were performed to characterize and quantify the surface expansion behavior at the contact surface. A series of experiments showed that the surface expansion distribution at the contact surface plays a pivotal role in determining the adhesion force. The quantitative relationship between the distributions of the surface expansion and adhesion force was discussed by using single-groove indenters.

Electrical discharge machining of polycrystalline diamond: A review

Owing to its ultra-hardness and exceptional wear resistance, polycrystalline diamond (PCD) is widely used in numerous applications such as bearing, nozzle, metal cutting, oil and gas, and hard rock mining. However, the hardness of diamond means PCD products are incredibly difficult to manufacture. Electrical discharge machining (EDM) is one of the most effective non-traditional methods used for machining PCD materials, although the unique composite structure and low electrical conductivity of PCD lead to low machining efficiency. This paper presents an overview of the methods and newly emerged state-of-the-art technologies to improve material removal rate and surface quality as well as the mechanisms behind these methods. Literature analysis shows that efficiency improvement could be achieved by increasing energy utilization and the sparking gap in EDM. The utilization of discharge energy is highly sensitive to the expansion of single discharge sparks. Further improvement in machining efficiency could be achieved by enhancing discharge expansion and explosive force through changing processing forms, dielectric, electrode shape, and power generator in the future. To provide a comprehensive insight of the machinability of PCD, EDM processes of using PCD as tool electrodes to machine other materials to improve machining performance are also discussed.

Controls of crystal shape on degassing mechanisms in crystal-rich magmas with rhyolitic groundmass melts

Understanding the mechanical effects of crystals on degassing kinetics and permeability development in silicic magmas is important for modeling eruptions and examining first order controls on eruption style. We conducted high-pressure-high-temperature isothermal decompression experiments to investigate the role of crystal shape on permeability development and pore pathway geometry. Experiments were performed on hydrous rhyolitic glass (76.3 wt.% SiO2) seeded with variable amounts of equant (aspect ratio ∼1.8 ± 0.6) corundum crystals and elongate (aspect ratio ∼10 ± 5.5) wollastonite crystals to approximate natural phenocryst and microphenocryst/microlite populations, respectively. We measured total porosity, connected pore volume and permeability directly from the experimental charges by applying Archimedes' principle to determine bulk density, helium-pycnometry to measure connected porosity, and a custom-made permeameter to measure permeability. The experimental samples developed permeability at a critical melt porosity (ϕc-melt, above which degassing is enhanced due to bubble coalescence) of ∼55 vol.% vesicles for the corundum experiments and ∼48 vol.% for the wollastonite-bearing experiments; these values are considerably lower than the ϕc-melt>63 vol.% for prior crystal-free experiments (Lindoo et al., 2016; deGraffenried et al., 2019). Critical porosity is reduced when crystals comprise at least ∼20 vol.%, regardless of shape. Connected porosity increases and average bubble size decreases with increasing abundance of elongate wollastonite crystals, explained by the onset of yield strength behavior induced by loosely touching crystal frameworks that form at decreasing crystallinities with increasing elongation of crystals comprising the network. When the population of high-aspect-ratio crystals reaches random loose packing, the resulting reduction in interstitial melt available for unimpeded bubble expansion forces the bubbles to connect at lower total vesicularity. It therefore seems likely that crystal-bearing intermediate magmas experience an abrupt increase in degassing efficiency when crystallinity attains random loose packing. In hydrous magmas, the efficiency of decompression-driven degassing and resulting formation of anisotropic groundmass crystals is controlled by magma composition and decompression rate. Enhanced gas loss in slowly ascending (and crystallizing) magma may aid the development of dense conduit plugs, thus increasing the possibility of violent Vulcanian explosions.

Cochlear amplification in the short-wave region by outer hair cells changing organ-of-Corti area to amplify the fluid traveling wave

Many details of the operation of the mammalian cochlea are known, but how they all work together to produce cochlear amplification is not understood. Outer-hair-cell (OHC) motility produces two kinds of amplification: non-propagating amplification (NPA) that is from local OHCs, and traveling-wave amplification (TWA) that increases basilar-membrane (BM) motion. Proposed here are a series of hypotheses that provide a new explanation, the “OoC-area-pump”, for TWA: (1) In the short-wave region OHC vibrations cause cyclic longitudinal motion of fluid in the organ of Corti (OoC) and peri‑Deiters-cell tissue, (2) the longitudinal motion changes the local OoC area, which (3) by reticular-lamina (RL) movement drives the fluid in scala media in a way that amplifies the fluid-pressure traveling wave. (4) At the NPA-TWA changeover frequency, an abrupt change in the OoC frequency-wavenumber relationship is due to positive feedback between TWA and the mode of cochlear motion that is dominant, aided by focusing of the pressure traveling wave. It is hypothesized that OoC radial expansion and radial force from the Deiters-cell phalangeal process act to advance RL and/or lateral-compartment phase. Finally, it is hypothesized that human and lab-animal frequency tuning have similar bandwidths in distance along the cochlea because their traveling-wave wavelengths are similar in the corresponding short-wave regions. Experiments are needed to test these hypotheses and to determine for TWA whether the OoC-area-pump hypothesis replaces or supplements the “OHCs-act-on-BM” hypothesis. Several tests are outlined that can be done with current methodology. A key step in the evolution of mammalian hearing was the development of the complex OoC anatomy, including Deiters cells and OoC fluid spaces that allow local wide-band NPA to produce TWA that enables small local increments of gain to accumulate in the traveling wave and sharpen tuning.

Study on Expansion Characteristics and Expansion Potential of Gypsum Rock

In this study, the relationship between four expansion indices and the expansion potential of gypsum rock was studied; on this basis, a criterion for judging expansion potential is established for gypsum rock. The results show that the free expansion rate is unsuitable for grading gypsum rocks’ expansion potential. Setting the gypsum rock in the Wuzhishan tunnel as the research subject, the ultimate expansion rate is 24.28% on the 7th day and 34.08% on the 30th day; the ultimate expansion rate on the 7th day of the indoor rock sample can be estimated by the fitting formula on the 30th day, the ultimate expansion force is 304.51 kPa, and the BET-specific surface area is 6.31 m2/g. The ultimate expansion ratio and BET-specific surface area have an excellent linear relationship with the ultimate expansion force. Setting the ultimate expansion force, ultimate expansion ratio and BET-specific surface area as the standard, the criterion for judging the expansion potential of gypsum rock is determined, which is more convenient and accurate than existing standards. The standard in this paper can predict the potential disasters that may occur in underground engineering.

Reconfigurable Shape Morphing With Origami-Inspired Pneumatic Blocks

Inflatable origami structure has immense potential in realizing fast, customizable, large-deforming, and three-dimensional shape morphing in robotics. In this letter, we developed a new modular origami block for performing reconfigurable shape transformations within fabricated hardware. Along with a paper-based block design to offer a straightforward fabrication and high power-to-mass ratio, we developed a multiblock system with foldable pneumatic passages and custom valves to manually inflate each block (13 g) by means of a single pressure input. We achieved the contraction ratio of 77% for a single block, while the response time was below 0.14 s at 100 kPa without payload. The mechanical properties were characterized to examine the stackability and reversibility as the number of blocks changed for expansion and compression forces and shape transformation. The potential benefits of our findings were demonstrated by shape morphing with individual activations of blocks using the same multiblock system. Future origami robots made of stackable pneumatic blocks may be suitable for multifunctional applications because of their reconfigurable properties.

The world is not enough: New diplomacy and dilemmas for the World Heritage Convention at 50

AbstractIn this article, we reflect on the current socio-political context of the 1972 World Heritage Convention after 50 years rather than its significant achievements and trials throughout its turbulent history. The United Nations Educational, Scientific and Cultural Organization (UNESCO) has already documented and publicized these formative episodes. Instead, we consider the World Heritage milieu today, embedded as it is within a much broader landscape of non-governmental organizations and civil society preservation initiatives than it was five decades ago. Like other United Nations agencies, UNESCO now faces challenges arising from various types of re-spatialization beyond the nation-state that further impact its effectiveness. Those challenges encompass not only the expansive force of globalization but also regionalization and localization, all of which have given rise to a new diplomacy. We discuss the proliferation of competing international agencies and individual donors, then describe the dilemmas facing World Heritage, including the rise of non-state actors and post-conflict remediation in the Middle East, the limited recognition of Indigenous Peoples and their role in decision making, and the persistent failures to remedy the inequitable position of Africa as a priority region.

Pipeline element for upheaval buckling analysis of submarine pipelines with geometric-imperfections under high temperature high pressure

Submarine pipeline is used for transporting oil from wells to resource storage facilities. The oil inside the pipeline is heated and pressured for long-distance transportation, making the pipeline under high temperature and high pressure (HTHP). The pipeline is usually placed inside a trench where surrounding soil restraints its longitudinal expansion. The pipeline is not perfectly straight, but with geometric imperfections, so the upheaval buckling may be triggered when the accumulated compression force has reached its buckling strength. It is not easy to conduct a geometrically nonlinear analysis for the pipeline because of the nonlinear soil–pipeline interactions (SPIs). This paper proposes a new line element aiming for the geometrically nonlinear large deformation analysis of the pipeline under HTHP. The axial expansion force due to high working temperature and pressure is included in the element formulation. Furthermore, a Gauss–Legendre integral method is employed to consider continuously distributed nonlinear SPIs in both lateral and longitudinal directions. Since the pipeline might exhibit large deflections, the analysis adopts the Updated-Lagrangian approach to establish the equilibrium conditions. A Newton–Raphson procedure is developed to execute the analysis. Detailed element formulations are given. Six groups of examples are provided to examine the robustness of the numerical method.

Premolar and Molar Inclination Changes Following Micro-Implant-Assisted Maxillary Skeletal Expander (MSE): A Three-Dimensional Analysis and Visualization

Background: To assess the changes in the inclination of the premolar and molar during a maxillary expansion with a micro-implant-assisted skeletal expander (MSE). Materials and Methods: A total of 21 patients (16 females, 5 males) with a mean age of 18.6 ± 4.5 (range 11.3–26.3 years) with a transverse maxillary deficiency were included in this study. They all received an MSE appliance for the maxillary skeletal expansion. The activation protocol consisted of about 0.5 mm expansion a day until a diastema was observed and continued with about 0.25 mm a day until the desired transverse relationship between the maxilla and mandible was achieved. OnDemand3D software was used for the measurements of the inclination change in the maxillary premolars and molars, pre- and post-expansion. Graphpad was used to compare the mean change in each tooth with the zero value (no change), and the p values of these changes with every tooth were calculated. Moreover, the changes and the mean values of all the teeth on the left and right sides were calculated separately. Results: A total of sixteen measurements were conducted for each patient. The first premolars tipped palatally after the expansion, while the second premolars and molars tipped buccally. The changes were significant for the molars and the left second premolar. Conclusions: The MSE induced some changes in the tooth inclination. The first premolars moved palatally, most likely due to perioral musculature and mastication force, while the first and second molars moved buccally. The second molar buccal movement is most likely due to the craniofacial rotation caused by the MSE as they were not subject to the expansion force.

Influence of sulfate crystallization on bond-slip behavior between deformed rebar and concrete subjected to combined actions of dry-wet cycle and freeze-thaw cycle

The bond-slip behavior of deformed rebar with medium embedded length and surrounding concrete without stirrup under sulfate salt, dry-wet cycle and freeze–thaw cycle was investigated in this study. Physical crystallization of sulfate was produced by using a 3:1 drying/wetting time ratio in erosion specimens. Different concentrations of sodium sulfate solution (CSSS), different drying and wetting cycles (DWC), and different freeze–thaw cycles (FTC) were considered as environmental variables in central pull-out tests. The bond characteristics of post-yielding rebar and surrounding concrete under combined environmental factors were obtained. Scanning electron microscope and x-ray diffraction analysis were conducted to identify reaction products. The experimental results showed that CSSS and DWC had both beneficial and adverse effects on the bond strength.1% CSSS and 25 DWC were the turning points of increasing and decreasing of bond strength. The expansion force caused by Na2SO4 physical crystals improved the bond strength in the initial stage, but impaired it after the crack of pore wall of concrete in the later stage. After superimposed FTC, the bond strength was greatly reduced. Sulfate crystallization significantly accelerated the deterioration of bond strength under freeze–thaw cycles. The prediction models of the bond strength between deformed rebar and surrounding concrete after yielding in terms of single and multiple environmental factors had been established. The models can be used to predict the bond strength of post-yielding rebar and surrounding concrete in complex environments of sulfate, dry-wet cycle and freeze–thaw cycle.

Particle fluidization characteristics and transition in a hot gas-solid fluidized bed with liquid injection

The particle fluidization characteristics and transition in a hot gas-solid fluidized bed with liquid injection were investigated on the basis of pressure drop of fluidized bed, the side wall temperature distribution and the weight fraction of agglomerates. It was found that the particle fluidization behavior was controlled by liquid bridge force under low induction heating power, whereas both solid bridge force and liquid bridge force take control of fluidization under higher induction heating power. With increasing liquid injection flowrate, the particle fluidization behavior experienced four types, named fast defluidization, gradual defluidization, agglomerating fluidization and stable fluidization, respectively. Further the transition behaviors between different fluidization types of particles were investigated, and four fluidization regions were distinguished. A dimensionless number ζ was proposed based on the theoretical analysis of interparticle forces and bubble expansion force, thereby establishing the connection between lab-scale experiments and industrial fluidized beds, and providing guidelines for their safe operation. • The combined effect of both solid bridge force and liquid bridge force were investigated on fluidization behaviors. • Four types of particle fluidization behaviors from stable fluidization to defluidization were distinguished. • The transition boundary of different particle fluidization types was determined. • The stable operating domain of the reactor was determined. • A dimensionless number was proposed to classify particle fluidization behaviors.

Comparative study on the effect of maxillary expansion on the displacement of maxillary alveolar bone before and after alveolar bone graft: a three-dimensional finite element analysis.

This paper aimed to simulate and compare the effect of maxillary expansion on the displacement of maxillary alveolar bone before and after alveolar bone graft. On the established finite element model of the maxilla before bone grafting, ANSYS was used to simulate alveolar bone graft to form the model of maxilla after bone grafting. The same expansion force was applied to the two models, and the three-dimensional displacement of alveolar bone was observed and compared between them. Comparison of the three-dimensional displacement showed that expansion before bone grafting was significantly larger than that after bone grafting (P<0.05). For horizontal displacement, in the expansion group before bone grafting, the displacement was gradually decreased from anterior to posterior alveolar bone. In the expansion group after bone grafting, the displacement was gradually increased from anterior to posterior alveolar bone. Displacement of noncleft side alveolar bone was significantly larger than that of cleft side alveolar bone with maxillary expansion before and after alveolar bone graft (P<0.05). In terms of vertical displacement, the anteromedial alveolar bone moved downward and the posterolateral alveolar bone moved upward with maxillary expansion before and after alveolar bone graft. For sagittal displacement, the anteromedial alveolar bone moved forward and the posterolateral alveolar bone moved backward with maxillary expansion before alveolar bone graft. However, the movement trend was opposite with maxillary expansion after alveolar bone graft. The three-dimensional movement with maxillary expansion before alveolar bone graft is more obvious than that after bone grafting for patients with unilateral complete cleft lip and palate. Expander should be moved backward properly with maxillary expansion before alveolar bone graft and moved forward properly and cooperated with maxillary protraction with maxillary expansion after alveolar bone graft. Meanwhile, precaution must be taken in terms of asymmetric expansion and anterior open bite in operation.