scholarly journals Nonlinear Axial Stiffness Characteristics of Axisymmetric Bolted Joints

1990 ◽  
Vol 112 (3) ◽  
pp. 442-449 ◽  
Author(s):  
I. R. Grosse ◽  
L. D. Mitchell
Keyword(s):  
Finite Element ◽  
Linear Theory ◽  
Design Theory ◽  
Joint Stiffness ◽  
Bolted Joints ◽  
Axial Stiffness ◽  
Outer Diameter ◽  
Bolted Joint ◽  
Element Analysis ◽  
Stiffness Characteristics

A critical assessment of the current design theory for bolted joints which is based on a linear, one-dimensional stiffness analysis is presented. A detailed nonlinear finite element analysis of a bolted joint conforming to ANSI standards was performed. The finite element results revealed that the joint stiffness is highly dependent on the magnitude of the applied load. The joint stiffness changes continuously from extremely high for small applied loads to the bolt stiffness during large applied loads, contrary to the constant joint stiffness of the linear theory. The linear theory is shown to be inadequate in characterizing the joint stiffness. The significance of the results in terms of the failure of bolted joints is discussed. A number of sensitivity studies were carried out to assess the effect of various parameters on the axial joint stiffness. The results revealed that bending and rotation of the joint members, interfacial friction, and the bolt/nut threading significantly influence the axial stiffness characteristics of the bolted joint. The two-dimensional, axisymmetric finite element model includes bilinear gap elements to model the interfaces. Special orthotropic elements were used to model the bolt/nut thread interaction. A free-body-diagram approach was taken by applying loads to the outer diameter of the joint model which correspond to internal, uniformly distributed line-shear and line-moment loads in the joint. A number of convergence studies were performed to validate the solution.

EFFECTIVE DYNAMIC STIFFNESS MODEL AND ITS EFFECTS ON ROBOT SAFETY AND PERFORMANCE

2013 ◽  
Vol 37 (3) ◽  
pp. 395-403
Author(s):  
Dongjun Shin ◽  
Zhan Fan Quek
Keyword(s):  
Dynamic Stiffness ◽  
Joint Stiffness ◽  
Optimization Strategy ◽  
Design Guideline ◽  
Controller Gain ◽  
Stiffness Model ◽  
Effective Dynamic ◽  
Stiffness Characteristics ◽  
And Performance ◽  
The Impact

Due to the limited control bandwidth of pneumatic artificial muscles, joint stiffness characteristics and their effects on safety and performance of human-friendly robots should be considered in the frequency domain. This paper introduces the concept of effective dynamic stiffness and validates its model with the Stanford Safety Robot. Experimental results show that the dynamic stiffness demonstrates limited effects on the impact acceleration given the same impact velocity and controller gain, whereas it significantly affects control performance of position tracking due to pressure-induced non-linearities. A stiffness optimization strategy for safety and performance is discussed as a design guideline of human-friendly robots.

Acute exposure to foot orthoses affects joint stiffness characteristics in recreational male runners

2015 ◽  
Vol 11 (3) ◽  
pp. 183-190 ◽  
Author(s):  
P.J. Taylor ◽  
H. Vincent ◽  
S. Atkins ◽  
J. Sinclair
Keyword(s):  
Sagittal Plane ◽  
Reaction Force ◽  
Joint Stiffness ◽  
Knee Extensor ◽  
Foot Orthoses ◽  
Vertical Ground Reaction Force ◽  
Mass Model ◽  
Peak Knee ◽  
Recreational Runners ◽  
Stiffness Characteristics

Commercially available foot orthoses are advocated for the treatment of chronic running injuries, such as patellofemoral pain, yet the mechanisms behind their effects are not well understood. This study aimed to examine the limb and joint stiffness characteristics when running with and without orthotics. Twelve recreational runners ran at 4.0 m/s. Limb stiffness was obtained using a spring-mass model of running by dividing the peak vertical ground reaction force (GRF) by the amount of limb compression. Knee and ankle joint stiffness’s were calculated by dividing the peak sagittal plane joint moment by the joint angular excursion. Differences between orthotic and non-orthotic running conditions were contrasted using paired samples t-tests. The results indicate that both peak knee extensor moment (orthotic = 2.74±0.57 and no-orthotic = 3.12±0.62 Nm/kg) and knee stiffness (orthotic = 5.56±1.08 and no-orthotic = 6.47±1.40 Nm/kg rad) were significantly larger when running without orthotics. This study may give further insight into the mechanical effects of commercially available foot orthoses. The current investigation provides some evidence to suggest that orthoses may be able to improve patellofemoral pathologies in recreational runners although further investigation is required.

scholarly journals Effect Of Moxibustion On Knee Joint Stiffness Characteristics In Recreational Athletes Pre And Post Fatigue

2020 ◽  
Vol 52 (7S) ◽  
pp. 269-269
Author(s):  
Dan Wang ◽  
Peng Yuan ◽  
Yilin Xu ◽  
Yufeng Zhang ◽  
Zhiye Zhang ◽  
...  
Keyword(s):  
Knee Joint ◽  
Joint Stiffness ◽  
Recreational Athletes ◽  
Stiffness Characteristics

scholarly journals Sex Differences in Limb and Joint Stiffness in Recreational Runners

2015 ◽  
Vol 16 (3) ◽  
Author(s):  
Jonathan Sinclair ◽  
Hannah Frances Shore ◽  
Paul J. Taylor ◽  
Stephen Atkins
Keyword(s):  
Sex Differences ◽  
Joint Stiffness ◽  
Force Platform ◽  
Current Investigation ◽  
Running Injuries ◽  
Recreational Runners ◽  
Stiffness Characteristics

AbstractPurpose. Female runners are known to be at greater risk from chronic running injuries than age-matched males, although the exact mechanisms are often poorly understood. The aim of the current investigation was to determine if female recreational runners exhibit distinct limb and joint stiffness characteristics in relation to their male counterparts. Methods. Fourteen male and fourteen female runners ran over a force platform at 4.0 m · s

An Analytical Technique for Modeling Knee Joint Stiffness—Part II: Ligamentous Geometric Nonlinearities

1983 ◽  
Vol 105 (2) ◽  
pp. 145-153 ◽  
Author(s):  
M. S. Hefzy ◽  
E. S. Grood
Keyword(s):  
Knee Joint ◽  
Joint Stiffness ◽  
Geometric Nonlinearities ◽  
Analytical Technique ◽  
Human Knee ◽  
Human Knee Joint ◽  
Straight Line ◽  
Insertion Sites ◽  
Stiffness Characteristics ◽  
Anterior Cruciate

An analytical technique previously developed to evaluate the contribution of the ligaments to the nonlinear, coupled stiffness characteristics of the human knee joint [1] is extended here to include geometric nonlinearities. In [1], we assumed that the ligaments act as tensile bands running in a straight line between tibial and femoral insertion sites. Here, two forms of geometric nonlinearities are introduced and analyzed: ligaments wrapping around bone surfaces, such as occurs with the medial collateral ligament, the posterior capsule, and the anterior cruciate in hyperextension, and wrapping of ligaments around each other, such as occurs with the cruciate ligaments as the knee is flexed and internally rotated.

Influence of barefoot and shod running on limb and joint stiffness characteristics during running

2015 ◽  
Vol 7 (sup1) ◽  
pp. S79-S80
Author(s):  
Jonathan Sinclair ◽  
Stephen Atkins ◽  
Paul John Taylor
Keyword(s):  
Joint Stiffness ◽  
Stiffness Characteristics
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