Increase In Contact Stress Research Articles

Experimental and Finite Element Investigations on the Biomechanical Consequences of Meniscectomies in the Knee Joint: A Narrative Review

Background: The knowledge of the complex biomechanical behaviour of the meniscectomised knee joints is of paramount importance in various clinical situations. A combined review of experimental and finite element analysis studies examining the consequences of meniscectomies on the biomechanics of the knee joint has not been reported in the literature. Therefore, this paper presents a combined review of experimental and finite element analysis studies on the biomechanical consequences of medial and lateral meniscectomies in the knee joint. Methods: Experimental and FEA investigations on the association between meniscectomies and the biomechanical response of the knee joint are reviewed. The effects of partial and total meniscectomies in the medial and lateral compartments are included in this paper. Results: Subtotal/total medial meniscectomies cause a significant decrease in the contact area and a substantial increase in the contact stress in comparison with that in an intact knee joint. This could give rise to severe degeneration of the cartilage surface. Partial medial meniscectomy causes a modest reduction in the contact area associated with a moderate increase in contact stress. The resection of both leaflets of the meniscus results in a substantial increase in the contact pressure and a significant reduction in contact area compared with inferior leaflet resection. Conclusion: This review recommends partial medial meniscectomy over subtotal/ total medial meniscectomy. It also suggests performing resection of the inferior leaflet rather than resection of both the leaflets. Finally, some recommendations for future work are suggested to predict the realistic biomechanical behaviour of meniscectomised knee joints.

Wheel/rail adhesion and damage under different contact conditions and application parameters of friction modifier

Friction modifier (FM) is a newly developed third medium to control the service performance of wheel/rail. The wheel/rail performance is influenced by the wheel/rail contact conditions and FM application parameters. Therefore, the effects of FM application parameter and the wheel/rail contact parameters on the adhesion and damage behaviors of wheel and rail materials should be explored. In this study, the influences of application amount of FM, the wheel/rail contact stress and the creepage on the adhesion and damage behaviors were studied using a twin-disc machine. Results indicated that the increase in contact stress would reduce the wheel/rail minimum adhesion coefficient and effective holding time of FM. The increase in the creepage would increase the adhesion coefficient and reduce the holding time. Under the wheel/rail contact stresses of 800 and 1100 MPa, the application of FM could reduce wheel/rail wear and damage. But under 1500 MPa, FM could cause serious rail surface damages. Moreover, the surface crack propagation process of rail mainly included three stages: initial stage, transition stage and rapid propagation stage. The “oil wedge effect” was the main mechanism for aggravating the surface damages of rail under 1500 MPa.

Mechanism and prediction method of fretting damage in involute spline couplings of aero-engine

Aiming at the serious fretting damage and failure of aviation involute spline couplings, this work proposes the fretting damage mechanism of involute spline couplings of aero-engine based on previous theories. The optimized Archard wear volume model and Smith-Watson-Topper critical surface method are used to establish the fretting damage prediction model of involute spline couplings of aero-engine. On this basis, the law of fretting damage is analyzed and its mechanism is verified by finite element simulation and experiment. The results show that the fretting damage failure mode of involute spline couplings of aero-engine is mainly fretting wear, fretting fatigue and fretting wear compete and influence each other. With the increase of contact stress and sliding distance, the fretting damage degree increases, but when it reaches a certain critical value, the fretting damage degree decreases. The fretting damage degree increases with the increase of angle mismatch and friction coefficient. The theory is in good agreement with the actual results, which provides a feasible way to study the fretting damage mechanism of other spline couplings.

Influence of articular step-off on contact mechanics in fractures of the posterolateral-central tibial plateau - a biomechanical study

BackgroundThe posterior quadrants of the tibial plateau are frequently involved in OTA type C tibial plateau fractures. The biomechanical influence of a residual articular step-off of the posterolateral-central (PLC) segment, which is difficult to visualize intraoperatively, remains unclear.Therefore, aim of this study was to investigate the contact area and stress of the tibial plateau in cases of different articular step-offs of the PLC segment. MethodsSeven human cadaveric knees were used to simulate articular impressions of the PLC segment with step-offs of 1 mm, 3 mm, and 5 mm. The knees were axially loaded up to 150 N during a total of 25 dynamic cycles of knee flexion up to 90°. Pressure mapping sensors were inserted into the medial and lateral joint compartments beneath the menisci to measure articular contact area and stress. ResultsBetween 60° and 90° of knee flexion, increasing PLC segment impressions of the tibial plateau led to increasing contact stress and a significantly reduced contact area. The largest decrease in the contact area was 30 %, with an articular step-off of 5 mm (0.003). An increase in contact stress, especially from a 3-mm step-off, was measured, with a doubling of the mean contact stress at 3-mm and 5-mm step-offs and 90° knee flexion (p = 0.06/0.05). ConclusionFrom a biomechanical point of view, posterior impressions of the PLC segment greater than a 1-mm step-off should be addressed as anatomically as possible, especially in active patients with the need for higher knee flexion angles.

Evaluation of Rail Overturning under the Influence of Lateral Forces by Mathematical Modeling

The article discusses the change in the rail canting of the railway track on the intermediate fastenings of the ZHBR-PSHR under the influence of the load from the rolling stock at different tightening values of the fasteners. To evaluate the change in the angle of inclination of the rail, a model of the superstructure of the railway track was developed in a finite element environment with full compliance with the geometric and physical characteristics. Based on this model, the calculation of the change in the rail canting at different degrees of screw tightening was made. Based on the results of the calculation, conclusions were drawn about the change in the rail canting and the stress-strain state of the rail sole. Changing the rail canting can lead to a change in the nature of contact in the "wheel-rail" system with a significant increase in equivalent stresses. The obtained values of the rail canting change were used to calculate the contact stresses in the rail head. As a result of the change in the rail canting, the contact patch shifted, as well as a sharp increase in the equivalent stresses by 65-67%, depending on the vertical force. An increase in contact stresses adversely affects the service life of the rail and can lead to the formation of defects, which adversely affects traffic safety.

Wear analysis and simulation of small module gear based on Archard model

With the development of micro machining technology, small module gears are widely used in the field of high precision technology. In view of the failure problems such as tooth fracture and fatigue pitting caused by dynamic wear in the process of small module gear transmission, this paper takes a micro planetary gear reducer as the research object and establishes the analysis framework of small module gear wear calculation model based on Archard wear model and Hertz contact theory. Considering the influence of installation error and position tolerance, tooth contact analysis (TCA) model of small module gear is established based on the theory of small displacement torsor (SDT) and space coordinate transformation, and the impact of these errors on the dynamic contact trajectory, contact stress, and tooth surface wear is analyzed based on the numerical simulation. The numerical simulation results show that with the increase of the installation error, the contact trajectory will deviate significantly, which will finally result in increased contact stress and wear. Moreover, with the decrease of tolerance level, the service life of the device increases under the same reliability level. The above analysis of tooth surface wear can provide references for the design and installation of a small module gear transmission.

Effect of groove textures on tribological properties of 40CrNiMoA steel under starved grease lubrication

40CrNiMoA steel is widely used in important mechanical parts under starved lubrication, such as shafts, gears and flexsplines for harmonic reducers. To improve the tribological properties of 40CrNiMoA steel and prolong the service life of the material in practical application, micro-grooves were fabricated on steel discs by laser texturing. The texture areal density is controlled by the number and width of the micro-grooves. The friction tests were carried on a ball-on-disk friction tester. The worn surfaces were observed by a scanning electron microscope and a three-dimensional microscope to discuss the friction and wear properties of textured discs under starved grease lubrication. The results show that the groove texture can effectively improve the tribological performance of the 40CrNiMoA steel. After optimizing, the tribological properties were greatly improved. The average friction coefficient reduced from 0.259 to 0.116 and wear rate was reduced by about 46 times. The contact stress of ball and textured discs was analyzed, the results shown that larger width of groove lead to higher contact stress, which may increase friction and wear. Therefore, storing lubricants and increasing contact stress should be balanced to obtain better tribological performances. In this study, the preferred range of texture areal density is 10% ∼ 22%.

Subloading-friction model with saturation of tangential contact stress

The incorporation of the saturation of the tangential contact stress with the increase of the normal contact stress is required for the analysis of the friction phenomenon of solids and structures subjected to a high normal contact stress, which cannot be described by the Coulomb friction condition, in which the tangential contact stress increases linearly with the increase of the normal contact stress. In this article, the subloading-friction model, which is capable of describing the smooth elastic—plastic transition, the static—kinetic transition, and the recovery of the static friction during the cease of sliding, is extended to describe this property. Further, some numerical examples are shown, and the validity of the present model will be verified by the simulation of the test data on the linear sliding of metals.

Analysis of Initial Cracking of an Interface between a Bundled Lipped Channel–Concrete Composite Wall and an Infill Wall

The bundled lipped channel–concrete (BLC-C) composite wall structure is a new structure with several advantages such as a high bearing capacity and good seismic performance. However, interface cracks between a BLC-C composite wall and the infill wall (non-structural wall) are a severe problem and need to be urgently resolved. Interface cracks affect not only the esthetics, but also the normal use of a building. The presence of interface cracks changes the perceptions of the owners of a structure, forcing them to question its safety and even take legal action against its developer. Therefore, in this study we aimed to investigate the initial cracking of the interface between a BLC-C composite wall and an infill wall. Unidirectional horizontal loading tests were conducted on two infill wall specimens constrained by BLC-C composite walls on both sides. The finite element analysis software ANSYS was used to simulate the loading process of the tests. The test results were compared to verify the accuracy of the finite element model. A finite element analysis was conducted to determine the effect of the horizontal displacement of the specimens when the interface initially cracked under different parameters such as the widths of the BLC-C composite wall, infill wall, and opening as well as the strength grade of the bricks and maximum normal contact stress. The results showed that a decrease in the width of the BLC-C composite wall or a rise in the width of the infill wall delayed the appearance of interface cracks. A large opening also delayed the occurrence of interface cracks. An enhancement in the strength grade of the bricks led to an earlier appearance of interface cracks. Interface cracks occurred later with an increase in the maximum normal contact stress between the BLC-C composite wall and the infill wall.

Biomechanics evaluation of sacroiliac joint pain after lumbosacral fusion: A finite element analysis.

The sacroiliac joint (SIJ) constitutes the predominant pain source following lumbar or lumbosacral fusion. Although studies have investigated the biomechanical patterns of SIJ behaviors after lumbosacral fusion, the relationship between ligament strain and SIJ pain following lumbosacral fusion remains unclear. The present study developed a three-dimensional finite element model including L4, L5, sacrum, ilium, SIJ, and seven mainly ligaments. After successful validation, the model was used to investigate the biomechanics of SIJ and ligaments in simulating lumbosacral fusion process. Our results showed that small motion in a stable SIJ may significantly increases the contact pressure and stress of the SIJ, which increase the maximum contact pressure by 171%, 676%, 199%, and 203% and stress by 130%, 424%, 168%, and 241% for flexion, extension, bending, and axial rotation, respectively. An increase in contact pressure and stress in SIJ possibly causes pain at the SIJ, especially in extension and axial rotation. A comparison between the lumbosacral and intact models exhibited the maximum strain increase in the iliosacral ligament (ISL)and the ileal ligament (IL)under all loading conditions. The present study suggests that after lumbosacral fusion process, the ligament sudden increase or decrease is likely to lead sprain or strain ligament, especially ISL and IL thereby causing SIJ pain. This study may contribute to understand the relationship between SIJ ligaments and SIJ pain.

Malalignment of the total ankle replacement increases peak contact stresses on the bone-implant interface: a finite element analysis

IntroductionMalalignment of the Total Ankle Replacement (TAR) has often been postulated as the main reason for the high incidence of TAR failure. As the ankle joint has a small contact area, stresses are typically high, and malalignment may lead to non-homogeneous stress distributions, including stress peaks that may initiate failure. This study aims to elucidate the effect of TAR malalignment on the contact stresses on the bone-implant interface, thereby gaining more understanding of the potential role of malalignment in TAR failure.MethodsFinite Element (FE) models of the neutrally aligned as well as malaligned CCI (Ceramic Coated Implant) Evolution TAR implant (Van Straten Medical) were developed. The CCI components were virtually inserted in a generic three-dimensional (3D) reconstruction of the tibia and talus. The tibial and talar TAR components were placed in neutral alignment and in 5° and 10° varus, valgus, anterior and posterior malalignment. Loading conditions of the terminal stance phase of the gait cycle were applied. Peak contact pressure and shear stress at the bone-implant interface were simulated and stress distributions on the bone-implant interface were visualized.ResultsIn the neutral position, a peak contact pressure and shear stress of respectively 98.4 MPa and 31.9 MPa were found on the tibial bone-implant interface. For the talar bone-implant interface, this was respectively 68.2 MPa and 39.0 MPa. TAR malalignment increases peak contact pressure and shear stress on the bone-implant interface. The highest peak contact pressure of 177 MPa was found for the 10° valgus malaligned tibial component, and the highest shear stress of 98.5 MPa was found for the 10° posterior malaligned talar model. High contact stresses were mainly located at the edges of the bone-implant interface and the fixation pegs of the talar component.ConclusionsThe current study demonstrates that TAR malalignment leads to increased peak stresses. High peak stresses could contribute to bone damage and subsequently reduced implant fixation, micromotion, and loosening. Further research is needed to investigate the relationship between increased contact stresses at the bone-implant interface and TAR failure.

EVALUATION OF DEFORMABILITY OF MATERIAL OF PREPARATIONS IN DIRECT AND REVERSE EXTRACTION BY ROLLING STAMPING METHOD

The article presents the results of development and research of various technological schemes of the process of stamping by rolling cylindrical and conical rolls to obtain complex profile workpieces. It is shown that the achievement of significant dimensions of the various elements of the workpiece is possible by providing a directed flow of metal by changing the relative position of the roll and the workpiece. The most effective rolling operations are landing, settling, unloading, reverse and direct extrusion. The paper focuses on the analysis of operations of reverse and direct extrusion to obtain complex profile blanks with developed, including thin-walled elements. Since the technological capabilities depend on the deformability of the material, the analysis of the stress-strain state of the workpieces was performed using the method of grids, hardness measurement and microstructural analysis. The main result of the analysis was the construction of ways to deform the particles of the workpiece material in the coordinates "deformation intensity - stress index". Zones of blanks that are deformed in the conditions of "rigid" stress state are established, therefore for these zones the deformability of metals was assessed using the criteria of phenomenological theory. In addition, the assessment of deformability was also performed for areas with the maximum degree of deformation of the material. The manufacture of thin-walled elements of the workpiece, using the operation of reverse extrusion, is accompanied by the appearance of significant contact stresses. To prevent the roll from being pushed out of the workpiece and forming elements with a constant thickness, support rollers should be provided. In the case of direct extrusion, the increase in contact stresses requires the application of additional measures to increase the strength of the tool.

Patellar Tracking in Total Knee Arthroplasty-Influence on Clinical and Functional Outcome.

Anterior knee pain is a common problem after primary total knee arthroplasty (TKA). The aim of this study was to find parameters in patellar positioning which influence the clinical and functional outcome after TKA. Included were 59 patients who underwent TKA, of which three patients were treated bilaterally (n = 62 included knees). In a periodical follow-up of up to 5 years, each patient had to answer three questionnaires (HSS, WOMAC, SF-36) and underwent three radiographies of the knee (including merchant view) and a clinical examination, including Range Of Motion (ROM). All radiographs were evaluated by a single observer blinded to clinical data, who collected multiple parameters of sagittal and axial patellar alignment including newly developed methods for measuring patellar shift and tilt. Depending on the measurement results, three groups were built for each parameter and the influence on the outcome was determined. A lateral patellar tilt of more than 4° resulted in lower scores for both the HSS and WOMAC. The rarely investigated patellar facet angle showed a significantly inferior clinical and functional outcome in late follow-up of >24 months if lower than 142°, possibly due to progressive osteosclerotic changes of the patella caused by increased contact stress with corresponding patellar morphology. No significant difference was found for all other parameters. The newly developed method for measuring patellar shift has proven to be a valuable and easy instrument in the postoperative setting.

Analysis of the influence of roll size change on electromagnetic heat conversion capacity and roll profile control characteristics in the RPECT

RPECT is proposed to solve the problem of flatness control for cold-rolled strip processing. As one of the core components of this technology, the roll size is the key factor that affects the capability of the heat conversion and the roll profile control. So an electromagnetic thermal mechanical coupled axisymmetric model under the same electromagnetic rod structure and size is established to research this problem. After research, the results show that, with the roll diameter increasing, the induction heating efficiency changes a little, the average contact-stress increases, the roll crown decreases. Moreover, the control ability of roll surface cooling on roll temperature, roll crown and roll profile decreases. And the control effect on roll temperature, roll crown and roll profile weakens with the increase of roll surface cooling intensity. Therefore, when the electromagnetic rod structure is determined, the principle to be followed in the design of the roll used in the RPECT should be as follows: on the premise of meeting the strength and stiffness requirements of roll, the roller diameter should be small as much as possible.

Effects of Raceway Convexity on Friction Moment of Tapered Roller Bearings

The Effects of raceway convexities on friction moment of tapered roller bearings were studied in this paper. A new theoretical model of friction torque of tapered roller bearings was established considering the roughness and convexities of inner and outer ring raceways. Friction between roller and raceways were analyzed under the condition of elastohydrodynamic lubrication. Based on the theoretical model and experiments, the changes of friction torque with respected to raceway convexities of tapered roller bearings were obtained. The results show that the friction moment decreases with the increase of raceway convexities, while the increase of raceway convexity leads to the increase of contact stress. Therefore, the convexity values should be balanced between friction torque and contact stress. The convexity values should be balanced between friction torque and contact stress. The optimum values of the bearing being measured raceway convexities should be 5 ~ 6μm under the test conditions.

Effects of Increasing Contact Stress of Single Asperity on the Growth Process of ZDDP Tribofilm by Surface Roughness

Effects of Increasing Contact Stress of Single Asperity on the Growth Process of ZDDP Tribofilm by Surface Roughness

Effects of slip ratio and contact stress on rolling contact fatigue of defected rail materials

The defects on rail surface may have negative effects on the rolling contact fatigue (RCF) performance of the rail materials. This investigation researched on the RCF behaviors of the defected rail materials under various slip ratios and contact stresses. The results show that both the wear loss and the average crack length increase if the slip ratio or the contact stress increases. Moreover, the surface damage characteristics change from simple adhesion spots to significant fatigue crack grouping when slip ratio and contact stress rise. Finally, the experimental results also highlight that the slip ratio provides the deformation area for crack initiation whereas the contact stress accelerates the crack propagation by emphasizing the geometric effects.

Effects of modification on the strength–weight ratio of standard bevel gears

Because of the current rapid technological progress, in addition to achieving increased speed and momentum in machine, transmitting more power in a low-noise, lightweight, safe, and economical manner and saving material in gears is crucial. For this purpose, modified bevel gears are common. Therefore, this study investigates bevel gear profile modifications focusing on strength and raw material saving. Herein, three modification designs (Modifications I–III) were modeled using CATIA software. Finite element analysis (FEA) and experimental tests were performed to investigate the effect of the proposed modifications on the gear’s strength. Design and analysis procedures of the modifications were presented. Prototypes of the modified gear pairs were fabricated and subjected to strength and wear tests using a dynamic test device. The fatigue life of each gear pair was determined using nCode software. Modification II reduced the gear root stress by 3.98% relative to the original gear pair. Modification III resulted in 37.30% material saving, accompanied by 6.74% increase in contact stress. No fatigue damage was detected in either modification gear pair. The FEA results were compatible with the analytical, i.e., KISSsoft simulation, and experimental results; furthermore, FEA was found to be advantageous in terms of time and test costs in gear modification. Based on the obtained results for the three modifications, the Modification II gear pair is recommended for mass production.

Loading on Attune® fixed-bearing cruciate-substituting total knee implant in knee malalignment during activities of daily living: A finite element analysis

PurposeTo compare contact stresses between Attune® and PFC Sigma® total knee arthroplasty (TKA) implants in the presence of knee malalignment. MethodsMaximum contact stress after finite element analysis were compared during standing, walking, and stair climbing in 0°, 2.5° and 5°varus/valgus knee alignments. ResultsThe percentage increase in contact stress was highest during walking with PFC Sigma® in 5° varus (238.5%), standing with Attune® in 5° valgus (127.2%), and standing with Attune® in 2.5° valgus (107.8%). ConclusionThe newer Attune® design may be associated with higher maximum contact stresses and increased risk of wear and implant failure.

Laser cut seals for redox flow battery prototypes

This paper discusses redox flow batteries (RFB) prototypes on a mechanical point of view, more specific on the sealing technology and a new manufacturing technique. First part discusses the cutting methods and elastomer selection of seals for these prototype systems. The new method for elastomer manufacturing in this paper is CO2 laser cutting technology. Focus point, power intensity, feed rate and pulse frequency are parameters, which can be controlled through Human-Machine-Interface (HMI) software, but more factors influence the laser cut quality for elastomers. Elastomer seals are produced through laser engraving for a stacked RFB in future commercial use. Laser engraving is a surface modification that enhances the sealing performance by increasing contact stress over a lower contact area while increasing flexibility in design.