Cartilage Biomechanical Response Differs Under Physiological Biaxial Loads and Uniaxial Cyclic Compression

2020 ◽  
Vol 142 (5) ◽  
Author(s):  
Ali Shegaf ◽  
Andrew Speirs
Keyword(s):  
Contact Area ◽  
Biaxial Loading ◽  
Fluid Pressure ◽  
Cartilage Explants ◽  
Transverse Strain ◽  
Main Function ◽  
Surface Motion ◽  
Cyclic Compression ◽  
Static Contact ◽  
Biomechanical Response

Abstract The main function of articular cartilage is to distribute loads and provide low friction for the opposing surfaces in synovial joints. Biphasic lubrication provided by high fluid load support due to relative motion of the contact surfaces has been widely accepted as the main lubrication mode in diarthrodial joints. However, assessment of chondrocyte response to mechanical loads typically employed nonphysiological uniaxial loads with static contact area. This study aimed to introduce a more physiologically relevant loading protocol for in vitro mechanobiological testing of cartilage explants. Finite element analysis was conducted to examine the biomechanical response of cartilage to two different loading regimes, biaxial loading, that permits migrating contact area, and unconfined uniaxial cyclic compression, traditionally used in mechanobiological experiments. Results predicted in this study showed that continuous tissue rehydration provided by relative surface motion maintained constant fluid pressure and tissue strains through the simulation. On the contrary, due to rapid tissue consolidation predicted in cyclic compression simulation, fluid pressure and transverse strain were reduced by 19% and 26%, respectively. Furthermore, relative surface motion simulation resulted in depth-dependent distribution of fluid pressure and tissue strains while unconfined uniaxial cyclic compression produced nearly uniform fluid pressure through the depth but higher at the center of the sample. Based on the results obtained from this study and since sliding contact occurs in vivo, this physiological loading mode should be considered in assessing biomechanical and mechanobiological cartilage behavior.

scholarly journals Dynamic measurement of the fluid pressure in the tire contact area on wet roads

2020 ◽  
Vol 5 (1-2) ◽  
pp. 29-36
Author(s):  
J. Löwer ◽  
P. Wagner ◽  
H. J. Unrau ◽  
C. Bederna ◽  
F. Gauterin
Keyword(s):  
Contact Area ◽  
Fluid Pressure ◽  
Dynamic Measurement

scholarly journals Influence of Fluid on Seal and Assembly of Pipeline Fittings Based on the Multiscale Finite Element Model

Complexity ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-12
Author(s):  
Yangyang Yan ◽  
Yaping Fan
Keyword(s):  
Contact Area ◽  
High Stress ◽  
Fluid Pressure ◽  
Multiscale Model ◽  
Element Model ◽  
Assembly Method ◽  
Internal Fluid ◽  
Stress Zone ◽  
Multiscale Finite Element ◽  
High Stress Zone

Pipeline fittings with ferrules are applied to connect sections of hydraulic pipelines in aircraft, and their reliability and stability are essential. This paper aims at investigating the influence of internal fluid on the sealing characteristics of pipeline fittings by employing the multiscale model. Changes in the sealing characteristics induced by the fluid pressure switch are studied, and the assembly method under the internal fluid is also explored. The calculated results show that the multiscale model can accurately reflect the changes in the sealing area, and the high-pressure fluid can enhance the sealing reliability. Compared with the contact area, the fluid pressure exerts a greater influence on the change in the area of the high-stress zone. Furthermore, the unrestored sealing area enlarges with the increased maximum fluid pressure, and the change in the area of the high-stress zone is significantly larger than that in the contact area. Moreover, the optimum assembly position of ferrule decreases with the increase in fluid pressure, thus achieving the excellent sealing characteristics.

scholarly journals Elucidation of contact state on various rough surfaces via highly robust colorimetric optical interferometry

2022 ◽  
Vol 12 (1) ◽  
Author(s):  
Tatsunori Tomota ◽  
Mamoru Tohyama ◽  
Kazuyuki Yagi
Keyword(s):  
Film Thickness ◽  
Root Mean Square ◽  
Contact Area ◽  
Thickness Distribution ◽  
Optical Interferometry ◽  
Root Mean Square Roughness ◽  
Mean Square ◽  
Test Pieces ◽  
Static Contact ◽  
Nominal Contact Area

AbstractIn this study, we developed and practiced colorimetric optical interferometry for the direct observation of contact states to clarify contact phenomena. We theoretically demonstrated that the effect of roughness diffuse reflection could be neglected using interferometric light intensity according to the relationship between the optical film thickness and hue. Then, we measured the static contact surfaces of spherical test pieces of different root mean square roughnesses. Results indicate that the nominal contact area is significantly larger than that obtained from the Hertzian theory of smooth contact as the surface roughness increases. The contact film thickness on the nominal contact area increases almost in proportion to the root mean square roughness. Our experiment supports the validity of the contact theory and contact simulation with very small roughnesses, which have been difficult to verify experimentally. The advantage of this measurement is that it can simultaneously capture the macroscopic contact area and microscopic film thickness distribution, which is expected to further expand the range of application.

Static Contact Characteristics Analysis of Wide Base Tire against Hot Asphalt Pavement

2014 ◽  
Vol 587-589 ◽  
pp. 1228-1232
Author(s):  
Ren Zhi Wu ◽  
Wei Du ◽  
Lin Qiang Shao ◽  
Zhi Nan Mi
Keyword(s):  
Finite Element ◽  
Stress Distribution ◽  
Contact Area ◽  
Asphalt Pavement ◽  
The Other ◽  
Inflation Pressure ◽  
Rigid Pavement ◽  
Static Contact ◽  
Characteristics Analysis ◽  
Contact Models

In order to analyze mechanism of pneumatic tire rollers compacting against hot asphalt pavement, taking the process of wide base tire of rollers compacting against hot asphalt pavement as research object, the wide base tire is loaded up with inflation pressure and axial force to study the contact characteristics. Two finite element contact models are established by ANSYS, one of which is for the contact of wide base tire against rigid pavement, and the other is for the contact of wide base tire against hot asphalt pavement. The static contact characteristics of wide base tire against hot asphalt pavement are achieved though FEA method, including whole deformation of tire, formation variation of contact patch, and stress distribution of contact area.

Characteristic Analysis of Aircraft Glyd-Ring Seal Based on Mixed Lubrication Model

2020 ◽  
Author(s):  
Wang Wei ◽  
Wenjian Xiao ◽  
Xiaoping Ouyang ◽  
Shengrong Guo ◽  
Huayong Yang
Keyword(s):  
Film Thickness ◽  
Contact Pressure ◽  
Frictional Force ◽  
Fluid Pressure ◽  
Mixed Lubrication ◽  
Fluid Film ◽  
Characteristic Analysis ◽  
Piston Seal ◽  
Static Contact ◽  
Ring Seal

Abstract Reciprocating seals are vital components in hydraulic systems. As a kind of reciprocating seal, the glyd-ring is commonly used as a piston seal. For the sealing characteristics of aircraft glyd-ring under severe working conditions, systematic research and experimental verification are not sufficient. The liquid-solid coupling model based on mixed lubrication theory is established in order to analyze the characteristics of the glyd-ring seal in the cylinder piston. The contact stress distribution on the glyd-ring under different fluid pressures or temperatures is discussed through finite element analysis. The mechanical analysis of solids and fluids are carried out separately, and the thickness of the fluid film is continuously updated until the results of the deformation analysis converged. According to the calculation results obtained by this model, three characteristics of the glyd-ring seal (static contact pressure, film thickness, friction force) are discussed. As the fluid pressure rises, the contact pressure in the sealing area increases by a rate which is greater than that of the corresponding fluid pressure, the seal length is shortened, the fluid film thickness is reduced, and the frictional force gradually increases, this force increase is proved by test data. As the temperature rises, the contact pressure in the seal area (near the O-ring) increases by a rate which is greater than that of the corresponding fluid pressure, the seal length increases, the oil film thickness decreases, and the frictional force increases significantly.

scholarly journals Evidence of a tunable biological spring: elastic energy storage in aponeuroses varies with transverse strain in vivo

2019 ◽  
Vol 286 (1900) ◽  
pp. 20182764 ◽  
Author(s):  
Christopher J. Arellano ◽  
Nicolai Konow ◽  
Nicholas J. Gidmark ◽  
Thomas J. Roberts
Keyword(s):  
Energy Storage ◽  
Mechanical Behaviour ◽  
Elastic Energy ◽  
Biaxial Loading ◽  
Longitudinal Direction ◽  
General Assumption ◽  
Transverse Strain ◽  
Longitudinal Stiffness

Tendinous structures are generally thought of as biological springs that operate with a fixed stiffness, yet recent observations on the mechanical behaviour of aponeuroses (broad, sheet-like tendons) have challenged this general assumption. During in situ contractions, aponeuroses undergo changes in both length and width and changes in aponeuroses width can drive changes in longitudinal stiffness. Here, we explore if changes in aponeuroses width can modulate elastic energy (EE) storage in the longitudinal direction. We tested this idea in vivo by quantifying muscle and aponeuroses mechanical behaviour in the turkey lateral gastrocnemius during landing and jumping, activities that require rapid rates of energy dissipation and generation, respectively. We discovered that when aponeurosis width increased (as opposed to decreased), apparent longitudinal stiffness was 34% higher and the capacity of aponeuroses to store EE when stretched in the longitudinal direction was 15% lower. These data reveal that biaxial loading of aponeuroses allows for variation in tendon stiffness and energy storage for different locomotor behaviours.

scholarly journals A novel compressive stress-based osteoarthritis-like chondrocyte system

2017 ◽  
Vol 242 (10) ◽  
pp. 1062-1071 ◽  
Author(s):  
In-Chi Young ◽  
Sung-Ting Chuang ◽  
Amit Gefen ◽  
Wei-Ting Kuo ◽  
Chun-Ting Yang ◽  
...  
Keyword(s):  
Gene Expression ◽  
Extracellular Matrix ◽  
Cyclic Loading ◽  
Drug Screening ◽  
Cartilage Explants ◽  
Metabolic Responses ◽  
Static Compression ◽  
Response Condition ◽  
Cyclic Compression ◽  
Ecm Degradation

Mechanical stress damage and insufficient self-repair can contribute to osteoarthritis (OA) in the affected joint. As the effects of stress on chondrocyte metabolism can regulate cartilage homeostasis, the specific stress–response condition is therefore a key to the generation of an OA disease model. We aimed to produce a specific stress- and cell-based OA model after evaluating the metabolic responses of chondrocytes in response to a series of static and cyclic compression stressors. A static load exceeding 40 psi initiated extracellular matrix (ECM) degradation through a decrease in the sulphated-glycosaminoglycan (GAG) content, upregulation of catabolic matrix metalloproteinase (MMP)-13 encoding gene expression, and downregulation of the ECM-related aggrecan and type II collagen encoding genes within 24 h. Indicators of pro-inflammatory events and oxidative stress were found to correlate with increased IL-6 expression and reactive oxygen species (ROS) production, respectively. However, chondrocytes stimulated by moderate cyclic loading (30–40 psi) exhibited increased ECM-related gene expression without significant changes in catabolic and pro-inflammatory gene expression. BMP-7 expression increased at cyclic loading levels above 30–60 psi. These results demonstrated that static compression exceeding 60 psi is sufficient to produce OA-like chondrocytes that exhibit signs of ECM degradation and inflammation. These OA-like chondrocytes could therefore be used as a novel cell-based drug screening system. Impact statement The lack of an effective treatment for osteoarthritis (OA) reflects the great need for alternative therapies and drug discovery. Disease models can be used for early-stage compound screening and disease studies. Chondrocytes are solely responsible for the maintenance of the articular cartilage extracellular matrix. Our strategy involved the generation of a cell-based model of OA, a more readily studied disease. Instead of using animal cartilage explants, we incorporated isolated porcine chondrocytes with hydrogel to form three-dimensional assemblies. We could identify the specific magnitude-dependent metabolic responses of chondrocytes by applying a series of static and cyclic compression, and therefore successfully generated a novel OA-like cell-based model for drug screening.

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