Lateral Bending Stiffness Research Articles

Investigation of essential parameters for the design of offshore wind turbine based on structural reliability

The probabilistic-based design method is gradually gaining attention in the wind industry because it provides more accurate modeling of uncertainty variables than that of traditional methods. Unfortunately, the numerous uncertainty variables involved in structural design are major obstacles to the successful application of this method. Therefore, this study presents a sensitivity analysis (SA) of a benchmark monopile offshore wind turbine (OWT) to screen the top-ranking variables from the viewpoint of reliability. Primarily, a comprehensive reliability SA framework of OWT is proposed, in which a novel measurement of soil uncertainties is conducted using quantitative analysis from the perspective of soil structure interaction (SSI). Subsequently, a reliability SA is conducted to explore the crucial variables influencing the structural safety from the uncertain clusters. The results indicate that Young's modulus, structural geometry, and SSI have significant effects on the structural reliability of excessive vibration failure. The hydrodynamic and aerodynamic load variables exhibit the most prominent influence on excessive deflection failure. Additionally, the SSI uncertainties exhibit a non-negligible effect in affecting the structural reliability, i.e., the lateral bending stiffness shows more sensitivity to the normal operation cases, whereas the impact of joint stiffness is more remarkable in parked scenarios.

Comparing the mechanical characteristics between leg lengthening using only an Ilizarov external fixator and leg lengthening over a nail using an external fixator manufactured in Vietnam.

The mechanical characteristics of leg lengthening over a nail (LON) using an external fixator are not well known; specifically, the number of rings and K-wires required for this method has not been determined. This study aimed to compare the mechanical characteristics of leg LON using the simplest configuration for a domestic frame and those of leg lengthening using the Ilizarov frame alone. The mechanical characteristics of cow tibial samples for lengthening over an intramedullary nail in combination with a domestic external fixator (LON samples) and for lengthening with the Ilizarov frame (Ilizarov samples) were evaluated by assessing axial compression, bending load, and torsional load. The research indices were compression stiffness, bending stiffness, torsion stiffness, yield axial load, ultimate axial load, yield bending load, and ultimate bending load. No statistically significant differences were observed in the compression stiffness, ultimate axial load, bending stiffness, and ultimate, yield bending forces between the Ilizarov samples and LON samples. The compressive stiffness, yield axial load, and ultimate axial load of the LON samples were 98 ± 1.31 N/mm, 915 ± 23.89 N, and 1032 ± 29.86 N, respectively. The anterior-posterior bending stiffness and lateral bending stiffness of the LON samples were 122.48 ± 2.92 N/mm and 116.34 ± 3.95 N/mm, respectively. The yield anterior-posterior bending and ultimate anterior-posterior bending forces of the LON samples were 616.4 ± 3.64 N and 753.2 ± 3.49 N, respectively. The yield lateral bending and ultimate lateral bending forces of the LON samples were 624.6 ± 4.04 N and 759.0 ± 3.39 N, respectively. The axial torsional stiffness of the LON samples was 1.73 ± 0.05 N m/°, which was significantly lower than that of the Ilizarov samples (2.63 ± 0.03 N m/°). No statistically significant differences were observed in the mechanical fixation characteristics of axial compression and bending between the Ilizarov samples and LON samples. However, the axial torsional stiffness of the Ilizarov samples was statistically greater than that of the LON samples. We recommend using the simplest configuration for domestic frames in combination with LON for limb lengthening. Partial weight-bearing is permitted in the distraction stage. Case-control study.

Effect of bone cement augmentation with different configurations of the dual locking plate for femoral allograft fixation: finite element analysis and biomechanical study

AimsImplant failure in allograft reconstruction is one of the most common problems after treating a large bone defect for a primary bone tumor. The study aimed to investigate the effect of bone cement augmentation with different configurations of dual locking plates used for femoral allograft fixation.MethodsFour finite element (FE) models of the femur with a 1-mm bone gap were developed at the midshaft with different configurations of the 10-hole fixation dual locking plate (LP) with and without intramedullary bone cement augmentation. Model 1 was the dual LP at the lateral and medial aspect of the femur. Model 2 was Model 1 with bone cement augmentation. Model 3 was the dual LP at the anterior and lateral aspect of the femur. Finally, Model 4 was Model 3 with bone cement augmentation. All models were tested for stiffness under axial compression as well as torsional, lateral–medial, and anterior–posterior bending. In addition, the FE analyses were validated using biomechanical testing on a cadaveric femur.ResultsModel 2 had the greatest axial compression stiffness, followed by Models 1, 4, and 3. Bone cement augmentation in Models 2 and 4 had 3.5% and 2.4% greater axial stiffness than the non-augmentation Models 1 and 3, respectively. In the bone cement augmentation models, Model 2 had 11.9% greater axial compression stiffness than Model 4.ConclusionThe effect of bone cement augmentation increases construct stiffness less than the effect of the dual LP configuration. A dual lateral–medial LP with bone cement augmentation provides the strongest fixation of the femur in terms of axial compression and lateral bending stiffness.

INVESTIGATING THE EFFECT OF LABORATORY-INDUCED DISC INJURIES ON THE BIOMECHANICAL BEHAVIOUR OF ISOLATED SPINAL DISC SPECIMENS SUBJECT TO CYCLIC LOADING

Injury of the intervertebral disc (IVD) can occur for many reasons including structural weakness due to disc degeneration. A common disc injury is herniation. A herniated nucleus can compress spinal nerves, causing pain, and nucleus depressurisation changes mechanical behaviour. Many studies have investigated in vitro IVD injuries including endplate fracture, incisions, and nucleotomy. There is, however, a lack of consensus on how the biomechanical behaviour of spinal motion segments is affected. The aim of this study was to induce defined changes to IVDs of spine specimens in vitro and apply 6 degree of freedom testing to evaluate the effect of these changes.Six porcine lumbar spinal motion segments were harvested from organically farmed pigs. Posterior structures were removed to produce isolated spinal disc specimens. Specimens were potted in Wood's metal, ensuring the midplane of the IVD remained horizontal. After potting, specimens were sprayed with 0.9% saline, wrapped in saline-soaked tissue and plastic wrap to prevent dehydration. A 400N axial preload was equilibrated for 30 minutes before testing. Specimens were tested intact and after a partial nucleotomy removing ~0.34g of nuclear material with a curette through an annular incision.Stiffness tests were performed using the University of Bath's custom 6-axis spine simulator with coordinate axes and displacement amplitudes. Tests comprised five cycles with data acquired at 100Hz. Stiffness matrices were evaluated from the last three motion cycles using the linear least squares method.Stiffness matrices for intact and nucleotomy tests were compared. No significant differences in shear, axial or torsional stiffnesses were noted. Nucleotomy caused significantly higher stiffness in lateral bending and flexion-extension with increased linearity and the load-displacement behaviour in these axes displayed no neutral zone (NZ).Induced changes were designed to replicate posterolaterally herniated discs. Unaffected shear, axial and torsional stiffnesses suggest the annulus is crucial in these axes. However, reduced ROM and NZ after nucleotomy suggests bending is most affected by herniation. Increased linearity and lack of defined NZ in these axes demonstrates herniation causes major changes to the viscoelastic behaviour of spine specimens in response to loading.

Mechanical evaluation of the effect of the rod to rod distance on the stiffness of uniplanar external fixator frames.

To investigate the effect of the rod-to-rod distance on the mechanical stability of single-rod and double-rod external fixator frames. Four different constructs, one single-rod and three double-rod constructs with different rod-rod distances, were subjected to the axial, bending, and torsional forces. The stiffness of different configurations was calculated. Single-rod configuration had statistically the lowest stiffness when subjected to the axial, bending, and torsional forces. Maximum stiffness against the axial and anterior-posterior bending forces was achieved when the rod-rod distance was adjusted to 50mm (halfway between the first rod and the end of the Schanz pins). There was no statistically significant difference in lateral bending stiffness among different double-rod configurations (p value: 0.435). The maximum stiffness against torsional forces was achieved when the rod-rod distance was adjusted to 100mm (the second rod at the end of the Schanz pins). Double-rod uniplanar external fixator frames are significantly stiffer than the single-rod constructs, and however, the rod-rod distance can significantly affect the construct stiffness. We found that a frame with 50mm rod-rod distance was the optimum fixator among tested configurations that allowed a balance between axial, bending, and torsional stiffness of the construct.

Evolutionary Origins of Mammalian Axial Function Revealed through Digital Bending Experiments

The origin of mammals from non‐mammalian synapsids represents an iconic locomotor transition, often described as shift from reptile‐like sprawling limbs and extensive lateral movements of the backbone to upright limbs and sagittal backbone movements that enhance mammal specific locomotor behaviors. However, recent research in comparative anatomy has called into question the lateral‐to‐sagittal functional shift, instead suggesting that vertebral morphology in basal synapsids implies a distinct functional regime not observed in extant sprawling reptiles and represents a unique ancestral condition from which mammals evolved. To investigate this idea further, we used Autobend,a novel, experimentally validated technique for estimating vertebral osteological range of motion (oROM) from skeletons using digital modeling. We applied Autobendto seven extant mammal and reptile species and 11 exceptionally preserved non‐mammalian synapsids to estimate vertebral oROM and intervertebral joint stiffness. Results revealed a clear distinction between extant mammals and reptiles in oROM, with reptiles emphasizing lateral bending and mammals sagittal bending as expected. While most extant taxa exhibited relatively similar levels of stiffness in lateral and sagittal directions, extant lizards and salamanders displayed much more compliance in lateral bending and lower stiffness overall, in keeping with their observed axial kinematics. Conversely, most non‐mammalian synapsids displayed an intermediate condition, with stiffer intervertebral joints than extant lizards, crocodiles, and therian mammals, but similar to the pattern recovered for the modern tuatara. The mammalian condition of sagittal mobility accompanied by axial twisting in the anterior column is first observed in the crownward tritylodontid cynodont Kayentatherium. Together, these results support previous morphology‐based assertions of a distinctive ancestral vertebral function for synapsids characterized by high stiffness without the specialization for lateral bending of extant lizards or the sagittal bending and twisting observed in mammals today. This indicates a more limited role for the axial skeleton in terrestrial locomotion relative to extant groups, and a greater focus on body support than propulsion during the initial stages of synapsid evolution. This stage was followed by the evolution of mammalian‐type mobility patterns in cynodonts, and a secondary reduction in axial stiffness in certain therian clades. Given the strong association between sagittal bending and asymmetric gaits in mammals, these results provide an important first step in reconstructing the evolution of synapsid locomotor patterns.

Amplitude reduction optimization of time delay semi-active control for aircraft landing gear shimmy

Considering the time delay issue in the process of aircraft landing gear shimmy, the time delay semi-active control is used to achieve the purpose of amplitude reduction optimization. Firstly, in order to eliminate the influence of dimensionality and make the results better describe the objective universal law, after dimensionless treatment of the shimmy equations, the influence of dimensionless lateral bending damping coefficient and lateral bending stiffness coefficient of strut on the shimmy amplitude is analyzed. Then, in order to further reduce the amplitude, the time delay semi-active control term is introduced into the shimmy equations, and a mathematical method for solving the characteristic equation of the time-delay dynamic equation is proposed. Designing optimization criterion limits the amplitude of the first resonance to a small enough range. The time delay semi-active control can achieve good vibration reduction effect in the whole frequency domain and eliminate the second resonance. Finally, it is verified and compared in the frequency domain and time domain, the correctness of the calculation and the superiority of time delay semi-active control are proved.

Correlating surface structures and nanoscale friction of CVD Multi-Layered graphene

Surface structures on chemical vapor deposition (CVD) grown graphene determine its functional properties, and thus, in-depth understanding about the relationship between the structures and the properties is essential to investigate CVD graphene in a variety of scientific and engineering applications. Here, we correlate surface structures with nanoscale friction of a multi-layered graphene island. By cleaning graphene surface utilizing mechanical scratching of polymeric surface contamination, we unveiled the surface structures such as small-scale and large-scale (folded) wrinkles on graphene using atomic force microscopy (AFM) and investigated their effect on nanoscale friction. The formation of such surface structures induced twisting of the top-most graphene layer as confirmed by Raman spectroscopic analysis, and the twisted top-most graphene layer influenced the layer dependency of nanoscale friction depending on the applied normal load as revealed by friction force microscopy (FFM) measurements. No identifiable layer-dependency was observed at the low normal load due to the increased interlayer distance between the twisted top-most graphene layer and the underlying AB-stacked layers. Increasing the normal load resulted in the decrease of the interlayer distance and made the contribution of different lateral bending stiffness more dominant to nanoscale friction, resulting in the strong layer-dependency of nanoscale friction on multi-layered graphene.

Annular Defects Impair the Mechanical Stability of the Intervertebral Disc.

A biomechanical study. The purpose of this study was to investigate the effects of cruciform and square incisions of annulus fibrosus (AF) on the mechanical stability of bovine intervertebral disc (IVD) in multiple degrees of freedom. Eight bovine caudal IVD motion segments (bone-disc-bone) were obtained from the local abattoir. Cruciform and square incisions were made at the right side of the specimen's annulus using a surgical scalpel. Biomechanical testing of three-dimensional 6 degrees of freedom was then performed on the bovine caudal motion segments using the mechanical testing and simulation (MTS) machine. Force, displacement, torque and angle were recorded synchronously by the MTS system. P value <.05 was considered statistically significant. Cruciform and square incisions of the AF reduced both axial compressive and torsional stiffness of the IVD and were significantly lower than those of the intact specimens (P < .01). Left-side axial torsional stiffness of the cruciform incision was significantly higher than a square incision (P < .01). Neither incision methods impacted flexional-extensional stiffness or lateral-bending stiffness. The cruciform and square incisions of the AF obviously reduced axial compression and axial rotation, but they did not change the flexion-extension and lateral-bending stiffness of the bovine caudal IVD. This mechanical study will be meaningful for the development of new approaches to AF repair and the rehabilitation of the patients after receiving discectomy.

Effect of Rotor Geometry on Bending Stiffness Variation

Bending stiffness variation (BSV) is a common problem causing vibration in large rotating machinery. BSV describes lateral bending stiffness and its variation as a function of the rotational angle. It has been observed that BSV causes excitation exactly twice per revolution, which leads to vibration problems, especially at half critical speed. BSV is caused by rotor geometry errors if the material is assumed to be homogeneous and linearly elastic. Therefore, the study investigated BSV with harmonic roundness components, which are commonly used in industry to describe the geometry of a rotor. Hence, the results are easily applicable in the industry. The research was conducted primarily by analytical means, but also static simulations and numeric calculations were used. The results clearly showed that when the effect of single harmonic roundness components in rotor cross-sections were observed, only the second component could produce BSV. However, when component pairs were studied, they produced BSV also without the second component. If the second component was included, the profile produced BSV the most aggressively. A generated arbitrary roundness profile, including components 3–50 with random phases and amplitudes, indicated that BSV occurs always twice per revolution despite different components in the profile. The results improve the possibilities of eliminating excessive BSV in the industry, when certain components and component pairs can be avoided.

Time-domain coupled analysis of curved floating bridge under wind and wave excitations

A floating bridge is an innovative solution for deep-water and long-distance crossing. This paper presents a curved floating bridge's dynamic behaviors under the wind, wave, and current loads. Since the present curved bridge need not have mooring lines, its deep-water application can be more straightforward than conventional straight floating bridges with mooring lines. We solve the coupled interaction among the bridge girders, pontoons, and columns in the time-domain and to consider various load combinations to evaluate each force's contribution to overall dynamic responses. Discrete pontoons are uniformly spaced, and the pontoon's hydrodynamic coefficients and excitation forces are computed in the frequency domain by using the potential-theory-based 3D diffraction/radiation program. In the successive time-domain simulation, the Cummins equation is used for solving the pontoon's dynamics, and the bridge girders and columns are modeled by the beam theory and finite element formulation. Then, all the components are fully coupled to solve the fully-coupled equation of motion. Subsequently, the wet natural frequencies for various bending modes are identified. Then, the time histories and spectra of the girder's dynamic responses are presented and systematically analyzed. The second-order difference-frequency wave force and slowly-varying wind force may significantly affect the girder's lateral responses through resonance if the bridge's lateral bending stiffness is not sufficient. On the other hand, the first-order wave-frequency forces play a crucial role in the vertical responses.

Analysis of Flexural Performance of Steel-timber Composite Cantilever Beam

Steel-timber composite member is a new kind of structural member composed of steel plates and planks which are connected by bolts. The finite element analysis results on the flexural behavior of steel-timber composite centilever beam show that the stress of steel plate exceeds the yield strength before the bearing capacity of the composite beam is lost. Under the premise of ensuring the yield of the steel plate, the increase in the thickness of plank has little effect on the in-plane bending stiffness of composite beam, and the lateral bending stiffness of the composite beam is obviously improved which means the plank can effectively restrain the lateral buckling of the core steel plate. Based on the deflection analysis of composite beams, the deflection coefficient of steel-timber composite is derived.

Optimal configuration of a dual locking plate for femoral allograft or recycled autograft bone fixation: A finite element and biomechanical analysis

BackgroundAllografts and recycled bone autograft are commonly used for biological reconstruction. The dual locking plates fixation method has been advocated for increasing allograft stability and preventing fixation failure; however, the biomechanical properties of the various configurations of dual locking plates have not been extensively studied. MethodsIn a finite element (FE) analysis, we developed 6 patterns of different dual locking plate configurations for fixation of the mid shaft of the femur. The maximum strains were recorded for each of the 6 models then axial, bending and torsion stiffness were calculated. The FE analysis was validated the results with mechanical testing (axial compression, bending, and torsional stiffness) on a cadaveric femur. FindingsThe highest axial compression (715.41 N/mm) and lateral bending (2981.24 N/mm) was found in Model 4 (with two 10-hole locking plates placed at the medial and lateral side), while the highest torsional stiffness (193.59 N·mm /mm) was found in Model 3 (with 8- and 10-hole locking plates placed at the posterior and lateral side). Excellent agreement was found between the finite element analysis and biomechanical testing (r2 = 0.98). InterpretationThe dual locking plate configuration with medial and lateral, 10-hole locking plates provided the most rigid and strongest fixation of the femur; both in terms of axial compression and lateral bending stiffness.

Restabilization of the Occipitocervical Junction After a Complete Unilateral Condylectomy: A Biomechanical Comparison of Unilateral and Bilateral Fixation Techniques.

Occipitocervical instability may result from transcondylar resection of the occipital condyle. Initially, patients may be able to maintain a neutral alignment but severe occipitoatlantal subluxation may subsequently occur, with cranial settling, spinal cord kinking, and neurological injury. To evaluate the ability of posterior fixation constructs to prevent progression to severe deformity after radical unilateral condylectomy. Eight human cadaveric specimens (Oc-C2) underwent biomechanical testing to compare stiffness under physiological loads (1.5 N m). A complete unilateral condylectomy was performed to destabilize one Oc-C1 joint, and the contralateral joint was left intact. Unilateral Oc-C1 or Oc-C2 constructs on the resected side and bilateral Oc-C1 or Oc-C2 constructs were tested. The bilateral Oc-C2 construct provided the greatest stiffness, but the difference was only statistically significant in certain planes of motion. The unilateral constructs had similar stiffness in lateral bending, but the unilateral Oc-C1 construct was less stiff in axial rotation and flexion-extension than the unilateral Oc-C2 construct. The bilateral Oc-C2 construct was stiffer than the unilateral Oc-C2 construct in axial rotation and lateral bending, but there was no difference between these constructs in flexion-extension. Patients who undergo a complete unilateral condylectomy require close surveillance for occipitocervical instability. A bilateral Oc-C2 construct provides suitable biomechanical strength, which is superior to other constructs. A unilateral construct decreases abnormal motion but lacks the stiffness of a bilateral construct. However, given that most patients undergo a partial condylectomy and only a small proportion of patients develop instability, there may be scenarios in which a unilateral construct may be appropriate, such as for temporary internal stabilization.

Electro-optical performance of nematic liquid crystals doped with gold nanoparticles

The effect of gold nanoparticles on the dielectric, electro-optical, and rheological properties of the ZhK-1289 liquid-crystal mixture that define the response time of liquid-crystal devices with a concentration range of 0.06–5 wt% was investigated in this study. A phase diagram of the obtained composites was formed demonstrating an increase in the clearing temperature and a broadening of the mesophase existence range in the case of doping nanoparticles. It was found that in the obtained dispersions there are structural rearrangements in the low concentration range leading to an increase in the lateral bending stiffness of the liquid-crystal matrix, a decrease in the response time and threshold voltage of the Freedericksz transition, and also an increase in the anisotropy of the dielectric permittivity and the refraction index. The improvement of the electro-optical performance of the liquid crystal can be caused by the nanoparticle adsorption of impurity ions, which reduces the field-screening effect in the liquid crystal. According to the results obtained in this study, the optimal values of the physical parameters of liquid-crystal composites doped with gold nanoparticles for their application in practice are achieved in a concentration range of 0.5–1 wt%.

The effect of vertebral body stapling on spine biomechanics and structure using a bovine model

BackgroundAdolescent idiopathic scoliosis is a common condition affecting 2.5% of the general population. Vertebral body stapling was introduced as a method of fusionless growth modulation for the correction of moderate idiopathic scoliosis (Cobb angles of 20–40°), and was claimed to be more effective than bracing and less invasive than fusion.The aim of this study was to assess the effect of vertebral body stapling on the stiffness of a thoracic motion segment unit under moment controlled load, and to assess the vertebral structural damage caused by the staples. MethodsThoracic spine motion segments from 6 to 8 week old calves (n=14) were tested in flexion/extension, lateral bending, and axial rotation. The segments were tested un-instrumented, then a left anterolateral intervertebral Shape Memory Alloy (SMA) staple was inserted and the test was repeated. Data were collected from the tenth load cycle of each sequence and stiffness was calculated. The staples were carefully removed and the segments were studied with micro-computed tomography to assess physical damage to the bony structure. Visual assessment of the vertebral bone structure on micro-CT was performed. FindingsThere was no change in motion segment stiffness in flexion/extension nor in axial rotation. There was a reduction in stiffness in lateral bending with 30% reduction bending away from the staple and 12% reduction bending towards the staple. Micro-CT showed physeal damage in all the specimens. InterpretationIntervertebral stapling using SMA staples cause a reduction in spine stiffness in lateral bending. They also cause damage to the endplate epiphyses.

The stability of long-segment and short-segment fixation for treating severe burst fractures at the thoracolumbar junction in osteoporotic bone: A finite element analysis.

The majority of compressive vertebral fractures in osteoporotic bone occur at the level of the thoracolumbar junction. Immediate decompression is often required in order to reduce the extent of neurological damage. This study evaluated four fixation methods for decompression in patients with thoracolumbar burst fractures, and presented the most suitable method for osteoporotic patients. A finite element model of a T7–L5 spinal segment was created and subjected to an L1 corpectomy to simulate a serious burst fracture. Five models were tested: a) intact spine; 2) two segment fixation (TSF), 3) up-three segment fixation (UTSF), below-three segment fixation (BTSF), and four segment fixation (FSF). The ROM, stiffness and compression ratio of the fractured vertebra were recorded under various loading conditions. The results of this study showed that the ROM of the FSF model was the lowest, and the ROMs of UTSF and BTSF models were similar but still greater than the TSF model. Decreasing the BMD to simulate osteoporotic bone resulted in a ROM for the four instrumented models that was higher than the normal bone model. Of all models, the FSF model had the highest stiffness at T12-L2 in extension and lateral bending. Similarly, the compression ratio of the FSF model at L1 was also higher than the other instrumented models. In conclusion, FSF fixation is suggested for patients with osteoporotic thoracolumbar burst fractures. For patients with normal bone quality, both UTSF and BTSF fixation provide an acceptable stiffness in extension and lateral bending, as well as a favorable compression ratio at L1.

Impact of Connector Placement and Design on Bending Stiffness of Spinal Constructs

To evaluate the stability of multiple rod-connector construct designs using a mechanical 4-point bending testing frame. A mechanical study was used to evaluate the bending stiffness of 3 connectors across 12 different configurations of rod-connector-rod constructs. Stability was evaluated in flexion-extension and lateral bending. Combinations of rods having 1 of 3 diameters (4.0 mm, 5.5 mm, and 6.0 mm) connected by 1 of 3 connector types (parallel open, snap-on, and hinged) were compared. Configurations with single connectors and with double connectors with variable spacing were also compared to simulate revision surgery conditions. Constructs consisting of 4.0-mm rods connected to 4.0-mm rods were significantly less stiff as the total number of connectors used in a series exceeded 2. When single-connector configurations were compared, parallel open rod connectors demonstrated greater stiffness in flexion-extension than hinged open connectors, whereas hinged open connectors demonstrated greater stiffness in lateral bending. Using double connectors increased stiffness of 4.0- to 4.0-mm rod configurations in flexion-extension and lateral bending, 4.0- to 6.0-mm rod configurations in flexion-extension, and 5.5- to 6.0-mm rod configurations in lateral bending. Spacing the double connectors significantly improved lateral bending stiffness of 4.0- to 4.0-mm and 5.5- to 6.0-mm rod configurations. Our data indicate that the design, number, and placement of rod connectors have a significant impact on the bending stiffness of a surgical construct. Such mechanical data may influence construct design in primary and revision surgeries of the cervical spine and cervicothoracic junction.

Distal fibula oblique fracture fixation using one-third tubular plate with and without lag screw – A biomechanical study of stability

This laboratory-based study compared distal fibula simple oblique fracture fixation with one-third tubular plate with and without a single lag screw to determine which was mechanically more stable. A control group fixed with a limited contact dynamic compression plate was also tested. Biomechanical testing of 30 osteotomised saw bones under lateral bending and torsional forces was performed. There was no significant difference between the mean lateral bending and mean torsional stiffness between the fixation with tubular plate and lag screw and tubular plate alone. Limited contact dynamic compression plate conferred the best stability in lateral bending and torsion, as expected.

Effect of static axial loads on the lateral vibration attenuation of a beam with piezo-elastic supports

In this paper, vibration attenuation of a beam with circular cross-section by resonantly shunted piezo-elastic supports is experimentally investigated for varying axial tensile and compressive beam loads. The beam's first mode resonance frequency, the general electromechanical coupling coefficient and static transducer capacitance are analyzed for varying axial loads. All three parameter values are obtained from transducer impedance measurements on an experimental test setup. Varying axial beam loads manipulate the beam's lateral bending stiffness and, thus, lead to a detuning of the resonance frequencies. Furthermore, they affect the general electromechanical coupling coefficient of transducer and beam, an important modal quantity for shunt-damping, whereas the static transducer capacitance is nearly unaffected. Frequency transfer functions of the beam with one piezoe-elastic support either shunted to an RL-shunt or to an RL-shunt with negative capacitance, the RLC-shunt, are compared for varying axial loads. It is shown that the beam vibration attenuation with the RLC-shunt is less influenced by varying axial beam loads and, therefore, is more robust against detuning.