Influence Of Compressive Load Research Articles

Analysis of load distribution after transpedicular stabilization of burst fractures in the thoracolumbar junction

Background. In the structure of all traumatic spine injuries, the thoracolumbar junction is predominant, accounting for over 53 % of all vertebral fractures. One of the most clinically significant types of injuries in this area are burst fractures. The purpose was to study the stress-strain state of the thoracolumbar spine model with a burst fracture of the Th12 vertebra in various transpedicular fixation options under compression load. Materials and methods. The study developed and investigated a finite element model of the thoracolumbar spine with a burst fracture of the Th12 vertebra. The burst fracture was modeled by dividing the vertebral body of the Th12 into several planes, transforming it into separate fragments. The gaps between these fragments were filled with a material that simulated the interfragmentary regenerate. Variants of transpedicular stabilization using different types of screws, mono- or bicortical, and with or without cross-links, were examined. The model was analyzed under compression load. Results. The maximum level of stress among the bone structures directly involved in fixation was registered in the L2 vertebral body. It amounted to 19.9, 15.6, 19.4, and 15.1 MPa, respectively, for models with monocortical screws without cross-links, bicortical screws without cross-links, monocortical screws with cross-links, bicortical screws with cross-links. Simultaneously, the zone of screw entry into the arch of this vertebra shows values of 10.1, 15, 10.2, and 14.3 MPa for these models, respectively. Peak loads on the metal structure elements are observed on the rods, amounting to 212.5, 159.6, 203.7, 142.8 MPa, respectively, for the considered models. Conclusions. The results of the study showed that under the influence of compression load when modeling a burst fracture of the thoracolumbar junction, the use of long screws leads to a reduction in stress levels, both in the elements of the metal structure and in the bone elements of the model, while the use of cross-links has a negligible effect.

Study of the stress-strain state in models of various options for osteosynthesis of tibial bones with diaphyseal fractures in the middle third in children with osteogenesis imperfecta and incomplete growth Part 1. Compression

Background. Osteogenesis imperfecta is accompanied by multiple fractures of skeletal bones, the development of progressive deformations of the long bones of the limbs and, as a result, the inability to stand and walk. At present, the most promising means for stabilizing bone fragments are intramedullary fixators of various designs. Installation of internal fixators without the possibility of their lengthening during the skeletal growth leads to an increase in the frequency of repeated surgical interventions due to the need for their replacement. The purpose was to investigate the stress-strain state of the lower leg models under the influence of compressive load in conditions of fracture of both bones in the middle third and their osteosynthesis using intramedullary rods of various designs in children with osteogenesis imperfecta and incomplete growth. Materials and methods. A mathematical modeling of osteosynthesis of tibial bones with a fracture in the middle third in children with osteogenesis imperfecta was performed in two options: 1 — using a rod without rotational stability; 2 — a rod with rotational stability of the structure. During the research, the stress-strain state of the model was studied under the influence of vertical compressive load. Results. Under compressive loads, the use of a rod with rotational stability does not lead to any significant changes in the stress-strain state of the model compared to tibial osteosynthesis with a rotationally unstable rod. This can be explained by the fact that before resisting the loads acting along the longitudinal axis of the rods, both rods are unstable, so all loads are carried by the bone structures. This is a “fee” for the opportunity to “grow”. The presence of rotational stability of an intramedullary rod does not have a significant effect on the stress distribution in the models under compressive loading. But it should be noted that when using a rotationally stable rod, the stresses in the distal tibia are slightly reduced, and what is especially important, in the fracture zone too. Thus, a growing rod with a locked rotational movement creates more favorable conditions for the fusion of tibial fractures in the middle third, which is of great importance in the treatment of children with osteogenesis imperfecta. Conclusions. Under the influence of compressive loads, the presence of rotational stability of an intramedullary rod does not provide significant advantages from the point of view of stress distribution in the model of a tibial fracture in the middle third. However, due to the presence of a movable support at the distal end of the tibia, even with a vertical compressive load, a small torque can occur between the bone fragments, which should block the rod with a locked rotational movement. This is the cause for a decrease in the stress in the distal fragment of the tibia.

Influence of compressive load and heat treatment on deformation luminescence of KCl:Eu2+ single crystals exposed to X-ray

When KCl:Eu2+ single crystals were exposed to X-ray and were plastically deformed by compression at 50 µm min−1, the peak appears around 330 K on the thermoluminescence (TL) glow curve under the influence of the compressive load below 200 N. The peak is termed 330 K peak here. Its intensity becomes slightly large with the compressive load and also depends on the quenching temperature above about 473 K for the preparation of sample. Furthermore, the 330 K peak disappears on the TL glow curve by the heat treatment: annealing at 953 K for 16 h, followed by gradually cooling to room temperature within 24 h. The variations in the 330 K peak height are related to the density of dislocations in the sample. On the absorption spectrum for the crystal, the peak height at the wavelength of 560 nm decreases by the heat treatment. This result is supposed to be caused by the phenomenon that dislocation density is reduced and some colour centres on the 330 K peak etc. are removed in the annealing process of the crystal.

Discrepancy in low cycle fatigue and creep-fatigue life of 720Li alloy tested at 720 °C: Role of crystallographic texture evolution

Low cycle fatigue (LCF) and creep-fatigue (CF) interaction behavior of 720Li alloy were studied for the first time at 720 °C with different values of total strain amplitudes (Δεt/2) and hold time (HT). At Δεt/2 = 0.6%, CF life is less than LCF life. However, at Δεt/2 = 0.44, 0.48 and 0.55% CF life increased with increase in HT. Texture analysis of specimen tested at Δεt/2 = 0.44%, revealed that initial loading direction ǁ [11¯1] found to be rotated: (i) [21¯1] in LCF condition; and (ii) [11¯0] and [01¯1] in the CF condition predominantly. Notably, texture components developed in the CF specimens tested at Δεt/2 = 0.6% is quite similar to that in the LCF specimen tested at Δεt/2 = 0.44%. Development of [21¯1] texture component is due to multi planner slip (i.e. octahedral and cubic plane slip) under the influence of compressive load which is also confirmed by viscoplastic-simulation. Evolution of [21¯1] texture component leads to greater extent of inter crystalline cracks due to latent strain hardening and strain incompatibility between adjacent grains. Further, high static interfacial energy of annealing twin boundaries, confirmed through five-parameter stereological analyses, in LCF specimen tested at Δεt/2 = 0.44% and CF specimen tested at Δεt/2 = 0.6% resulted annealing twin boundary cracking. In contrast, evolution of low modulus texture components (i.e. [11¯0] & [01¯1]) has been inferred to be responsible for higher cyclic life in CF specimen tested at Δεt/2 = 0.44% and LCF specimen tested at Δεt/2 = 0.6%.

Free Vibration of Flax Braided Fabric PLA Beam under Edge Compression

ABSTRACT The present study focuses on the development of biodegradable composites to replace synthetic polymer-based composites for potential lightweight structural applications in the automobile, aeronautical, marine, and packaging industries. Initially, PLA and NFBF/PLA films are prepared by solution casting, and from these films, composite laminates are prepared by film sequencing and compression (hot-press) molding methods. First, the critical buckling load (Pcr ) of composites is analyzed, and then, the influence of compressive load on natural frequency is studied. The critical buckling load-bearing capacity of PLA is enhanced with the reinforcement of NFBF (natural fiber braided yarn fabric). The composite with three layers of NFBF registered the highest critical-buckling load (Pcr ) of 374.19 N, and this value is 172.13% high compared to the virgin PLA. Similarly, the natural frequency of the NFBF composites approaches minimum when the applied load is equal to the corresponding Pcr . However, a significant increase in the fundamental frequency is noticed when the applied load is higher than the Pcr .

О связи частот собственных колебаний и критических нагрузок при оценке жесткости несущих элементов вагонных конструкций

The regulatory and technical documentation clearly defines the requirements for assessing the bearing capacity of rolling stock units, for example, to check the design being developed for loss of stability under the influence of compressive loads. This involves performing verification by calculation methods. The article considers the possibility of determining the critical level of external overpressure on the shell of the tank cauldron on the basis of experimental data on the minimum frequency and shape of natural oscillations. In order to solve this problem, the differential equation of flat cylindrical shells is used. The equation used was proposed by Donnell and has proven itself well in calculation of cylindrical shells, in particular cauldrons of tank cars. The peculiarity of the proposed solution lies in a certain analogy of the mathematical description of the processes of loss of stability and natural oscillations. As a result of transformations of the differential equations under consideration, an expression is obtained that connects the critical level of external overpressure and the natural oscillation frequencies of the objects under consideration. Numerical values of the studied parameters are given, the reliability of which is confirmed by similarity with the data given in previously published sources. Recommendations are given on application of the proposed approach in engineering verification of carriage structure elements stability. The necessity of taking into account the forms of oscillations and loss of stability when determining the level of critical pressure by the obtained expression is shown.

Biomechanical evaluation of the pedicle screw insertion depth and role of cross-link in thoracolumbar junction fracture surgery: a finite element study under compressive loads

Introduction. The thoracolumbar junction is one of the most frequently damaged parts of the human spine when exposed to a traumatic factor. Corpectomy in combination with posterior decompression and restoration of the spinal support function is often performed using an interbody implant and posterior transpedicular stabilization to achieve adequate decompression and stabilization in severe traumatic injuries of this level. The surgery of this type is characterized by significant instability of the operated segment and determines increased requirements for the rigidity and reliability of posterior fixation. We have modeled the situation of a two-level corpectomy with subsequent replacement of bodies with a mesh implant and posterior transpedicular stabilization with 8 screws. Objective. To study the stress-strain state of the thoracolumbar spine model after resection of the Th12-L1 vertebrae with different variants of transpedicular fixation under the influence of a compressive load. Materials and methods. A mathematical finite element model of the human thoracolumbar spine has been developed, the components of which are the Th9 ‒ Th11 and L2-L5 vertebrae (vertebrae Th12-L1 are removed), as well as elements of hardware - interbody support and transpedicular system. Four variants of transpedicular fixation were modeled: using short screws and long screws passing through the cortical layer of anterior wall of vertebral body, as well as two cross links and without them. The stress-strain state of the models was studied under the influence of a vertical compressive distributed load, which was applied to the body of the Th9 vertebra and its articular surfaces. The load value was 350 N, corresponding to the weight of the upper body. Results. d It was found that transpedicular fixation of the thoracolumbar vertebrae with the use of long screws reduces the level of tension in the bone elements of the models. In the area of screw entry into the pedicle of the T10, T11, L2 and L3 vertebral arch, the load when using short screws was 3.1, 1.7, 3.9 and 12.1 MPa, respectively, when using bicortically installed screws - 2.9, 1.8, 3.8 and 10.6 MPa. The addition of two cross-links also reduces the maximum load values in critical areas of the model to a certain extent. In case of short screws combination and two cross-links, the load in these areas was 2.8, 1.7, 3.6 and 11.5 MPa, when using bicortical screws and cross-links - 2.8, 1.6, 3.3 and 9.3 MPa. The study of the stress-strain state of other parts of the model revealed a similar trend. Conclusions. The use of long screws with fixation in the cortical bone of anterior part of the vertebral bodies reduces the level of tension in the bone elements of the models. The use of cross links provides greater rigidity to the transpedicular system, that also reduces the tension in the bone tissue.

Effect of bolted shear connectors on the axial load-bending moment interaction capacity of CFT columns

In Concrete-Filled Tubular (CFT) columns under the influence of compressive loading, an omnilateral confinement pressure is exerted upon the concrete core which leads to increase in the strength, stiffness, and ductility of the column. This paper investigates the influence of bolted shear connectors on the behavior of circular and square CFT columns. Also, a comparison is made between the interactional axial load-bending moment (P–M) curves obtained from the numerical analyses and the P–M relationships put forth by different design standards. For this purpose, 18 circular and 9 square CFT columns, categorized into six groups, are subjected to eccentric compressive loading. The investigated parameters include concrete compressive strength, diameter of the steel tube, load eccentricity, and the presence of bolted shear connector. In most cases, the presence of bolted shear connectors in the column causes strength and ductility to increase, leading to an improvement in the axial load-bending moment (P–M) interaction. The employment of bolted shear connectors at 12.5 cm to 25 cm intervals results in a minimum of 5% and a maximum of 45% increase in the strength of the column.

Influence of compressive load on concrete filled steel tubular column with variable thickness

The concrete-filled tubular (CFT) structure consists of high strength, favourable ductility, fire resistance and huge energy absorption. The cost and time of construction can be reduced as there is no shuttering required for CFT columns. The confinement outcome of CFT column possesses higher stiffness as compared to hollow steel tube columns. In this article, testing is administered on twelve specimens of natural and artificial sand M25 grade CFT columns with a ratio of diameter to variable tube thickness (D/t of 27.72, 22.18 and 18.48). The twelve CFT columns have been tested under axial compression. The behaviour of CFT columns has been studied in terms of axial load-carrying capacity, deflection and buckling effects and compared the behaviour with numerical results determined using Eurocode 4 and AISC 360-10. The performance of CFT columns increased, as the thickness of tube increased with the effective confinement. The experimental and the numerical results of CFT columns have been validated by using ANSYS 14.5. The axial load-carrying capacity of an artificial sand CFT specimen has been improved significantly. Therefore, the natural sand could be replaced with artificial sand for CFT columns.

Stiffening of the nucleus pulposus upon axial loading of the intervertebral disc: An experimental in situ study.

Mechanical loading is inherently related to the function and degeneration of the intervertebral disc. We present a series of experiments aimed at measuring the effect of a loading/unloading cycle of the intervertebral disc on the mechanical properties of the nucleus pulposus. The study relies on our new minimally invasive microindenter, which allows us to quantify the storage and loss moduli of the nucleus pulposus by inserting an optomechanical probe in an intact (resected) intervertebral disk through the annulus fibrosis via a small needle. Our results indicate that, under the influence of compressive loading, the nucleus pulposus exhibits a more solid‐like behavior.

Influence of Compression Load and Counterface Roughness on Abrasive Wear Characteristic of UHMWPE

This paper studies the influence of work conditions, difference compression load and counterface roughness, on UHMWPE under abrasive wear test without lubrication according to GOST 426-77. It was found that the formation of deep and wide furrows on worn surface and abrasive intensity increased when the number of grit grade was decreased (average grit size increase). The behavior of abrasive wear can be classified as follows: the first characteristic volume loss quickly increases in the beginning of running time about 5-15 minutes, which is referred to as “run-in” wearing stage; the second characteristic volume loss regularly increases after running time about 15 minutes, which is approaching to “steady-state” wearing stage. In addition, the abrasive wear intensity increase with increasing compression load and/or decreasing number of grit grade (average grit size increase). The results of this research can be applied to abrasive applications in mechanical engineering.

Mathematical modeling of options for osteosynthesis of middle third clavicle fractures

Fore consolidation of the clavicle fragments and restoration of function in damaged extremity it is necessary to create optimum conditions including an accurate comparison of bone fragments, their reliable fixation, following the rules of asepsis, preservation of blood circulation, active management in the postoperative period. We propose to use this lock original design. Purpose: mathematical model to conduct a comparative analysis of the stress-strain state (SSS) system «collarbone – implant» fracture in the middle third of the clavicle in a different osteosynthesis holders. Methods: mathematical models clavicle fracture with the middle third. Simulated three options osteosynthesis: extramedullary plate, intramedullary nail, the original design of the machine. VAT study models performed using the finite element method. In the first stage studied VAT system «collarbone – implant» under the influence of compressive loads, the second — bending, the third — twisting. Results: It was found that the most dangerous loads are bending. Stresses in the clavicle bone in flexion, may exceed the limit of its strength and cause fractures. Extramedullary plate works well only when the bending loads acting perpendicular to its plane. But if they are parallel to the plane of the plate, the entire burden falls on the extreme screws, and critical to the strength of the bone stresses occur is around them. Intramedullary rod is equally effective when bending loads that act in both vertical and horizontal planes. However, the stresses in the bone cell models are too high. Advantage copyright apparatus is that it keeps the load bending in any direction and prevents overloading the bone.

Microstructure and Fatigue Characteristic of AM60B Magnesium Alloy

This paper summarizes and reviews the findings of our research on AM60B magnesium alloy conducted in past 8 years. It essentially covers three categories: microstructural study, environmental effect, and fatigue crack growth rate of AM60B. The experimental and numerical studies on the influence of casting defects on this particular material’s properties are reviewed in the first part. It has been shown that the non-uniform solidification of the casting results in variations of the microstructure in different layers (skin and core) of the alloy which affects the mechanical properties in those regions. Moreover, the influence of microstructure on fatigue crack initiation and propagation response of the alloy is presented. The influence of several casting defects on the failure mechanism of the material are also numerically analyzed and discussed. The influence of elevated and cold temperatures on the fatigue response of the alloy is reviewed in the second part. Our findings show that the temperature does not have a significant effect on the number of cycles to failure. However, but at some stress level, this effect cannot be dismissed. The fatigue crack growth rate (FCGR) response of the alloy at a wide range of stress ratios is also investigated in the last part. The FCGR of the alloy showed a noticeable dependency on the stress ratio. A model is proposed for estimating the FCGR of the alloy, which could provide a good prediction of alloy’s FCGR over a wide range of negative and positive stress ratios. The integrity of the new model is also compared against other models. Finally, the influence of compressive loading on fatigue life of the specimens under constant and random amplitude cyclic loading is investigated experimentally.

Experimental study on the effect of compressive loads on uplift capacity of model piles in sand

In this study, a total of twenty one model tests were performed on single piles embedded in dense sand to investigate the influence of compressive loads on uplift capacity of piles. The tests were carried out using smooth steel pile with a 25-mm outside diameter and a 55-mm length. The piles were embedded in uniform deposit of dense sand for depth-to-diameter ratios of 10, 14 and 20. Static compressive loads of 0%, 25%, 50%, 75%, and 100% of the ultimate compressive pile capacity were applied to the model piles and the piles were subjected to pull out loads. The experimental results showed that the percentage of compressive loads is a significant parameter influencing the net uplift capacity of the pile. The net uplift capacity decreases with the increase in the percentage of compressive loads. There is almost a gradual decrease in net uplift capacity with increase in compressive loads. Maximum decrease in net uplift capacity is observed at the 100% of compressive loading.

A study on compression-induced morphological changes of nonwoven fibrous materials

Pore size is a characteristic parameter that is often defined for fibrous materials used in industrial applications. While there exist many available studies on the pore size distribution of different fibrous materials, the influence of compression load on pore size distribution has not been studied well. Studying the behavior of fibrous materials under compression is important especially because in many applications these materials are subjected to some degree of compression during use. In this work, we present a novel image-based modeling technique to study the changes in the pore size distribution of a fibrous material exposed to compressive load. This was made possible by building a miniature compression cell, and imaging the structure of a hydroentangled fabric under varying levels of compression. The 3D images obtained with Digital Volumetric Imaging were utilized to study the pore size distribution of the material and develop an empirical correlation as a function of compressive stress for these structures. This new correlation indicates that the mean pore diameter of a nonwoven material decreases exponentially with increasing the compressive stress.

Influence of compressive load on microstructure of micro-scaled DLC structures produced by FIB-CVD

Influence of compressive load on microstructure of micro-scaled diamond-like carbon (DLC) structures was investigated by high-resolution electron transmission microscopy (HRTEM) analyses. The micro-scaled structures were produced by the focused ion-beam chemical vapor deposition method. The compressive loads were applied by a dynamic ultra micro hardness tester equipped with a flat-tip diamond indenter. Microgrid images in HRTEM observation and selected area diffraction patterns were varied by the compressive loads. The variations revealed that constituent atoms arranged disorderly in DLC were clustered by compressive loads. Electron energy loss spectroscopy measurements indicated that sp3 fraction in DLC was decreased by the compressive load. Consequently, it was suggested that graphitic clusters were formed in the microstructure of DLC by the compressive loads.

459 窒化ケイ素セラミックスのき裂開閉口挙動に及ぼす圧縮負荷の影響(GS-13 き裂(4))

The effect of stress shielding near the crack tip in Silicon Nitride ceramics was investigated using the Laser speckle strain / displacement gage by which a small crack opening displacement(COD) can be measured. A special attention was put on the influence of compressive loading on the stress shielding effect. From the result of COD measurement, it was found that the COD in ceramics was strongly affected by the applied stress ratio. Especially, the compressive loading was found to play an important role on the development of the stress shielding effect.

The influence of compressive loading on growth of cartilage of the mandibular condyle in vitro

The purpose of this study was to clarify the change in mandibular condyles under compressive loading. An organ-culture system of fetal rat mandibular condyles was used, and mechanical loading was generated by compressing the gas phase within a closed chamber. After the culture period, with compressive loading, type I collagen and fibronectin were observed in the lower half of the hypertrophic chondrocyte layer in the mandibular condyles; in contrast, without compressive loading, there was no such reaction. The size of the condyle was not increased by compressive loading. These results suggest that intermittent compressive loading could induce type I collagen and fibronectin production by chondrocytes.

In vitro stability of an unconstrained total elbow prosthesis : Influence of axial loading and joint flexion angle

Total elbow arthroplasty is often used to replace elbow joints that have been severely damaged by arthritis or trauma. A great disparity of designs exists, however, in currently available elbow prostheses. This study evaluated the intrinsic stability of one popular resurfacing implant, the Capitellocondylar (Johnson and Johnson Orthopaedics, Inc., New Brunswick, NJ) total elbow. The in vitro response of this unconstrained prosthesis to valgus-varus and supination-pronation loading was investigated using a materials testing machine. The influence of compressive loading and flexion angle on the intrinsic stability of the prosthesis was studied. The Capitellocondylar prosthesis was found to have little intrinsic constraint, relying on external forces for component stabilization. Dislocations were common at 111 N of compressive loading, while larger loads progressively stabilized the prosthesis. Joint flexion angle had little influence on the intrinsic constraint of the implant except to increase varus stability at lower flexion angles. The Capitellocondylar total elbow prosthesis, as designed by F. C. Ewald, behaves as an unconstrained implant. Adequate soft tissue supports, which are properly balanced to provide controlled loading, are essential to prevent instability of this arthroplasty.