Trunk Muscle Loading in Non-Sagittally Symmetric Postures as a Result of Sudden Unexpected Loading Conditions

1988 ◽  
Vol 32 (11) ◽  
pp. 665-669 ◽  
Author(s):  
Steven A. Lavender ◽  
Carolyn M. Sommerich ◽  
L.R. Sudhakar ◽  
William S. Marras
Keyword(s):  
Muscle Force ◽  
Mean Value ◽  
External Loading ◽  
Loading Conditions ◽  
Emg Signal ◽  
Sudden Loading ◽  
Four Levels ◽  
Posterior Trunk ◽  
Trunk Musculature ◽  
Warning Time

The present study investigated the effect of warning time and magnitude of an external loading on the trunk muscular response to sudden loading conditions while in a non-sagittally symmetric posture. Eleven subjects were asked to catch falling weights of three magnitudes (3, 6, and 9 kg) with four levels of warning time (0, 100, 200, and 400 ms) in an asymmetric posture. For each of the eight muscles sampled with surface electrodes the integrated electromyographic (EMG) signal was interpreted in terms of its peak value, mean value, onset rate, and lead/lag time with reference to the weight drop. Results show monotonic relations between muscle force and levels of warning time, and muscle force and levels of weight. In addition, muscular forces in the left posterior trunk musculature ranged between two and five times greater than the right posterior trunk musculature in response to sudden loading conditions. This experiment demonstrates how sudden asymmetric loading, and specifically sudden loading without adequate warning time may be involved in the development of low back pain.

scholarly journals Accident reconstructions of falls, collisions, and punches in sports

2020 ◽  
Vol 4 ◽  
pp. 205970022093695
Author(s):  
Marshall Kendall ◽  
Anna Oeur ◽  
Susan E Brien ◽  
Michael Cusimano ◽  
Shawn Marshall ◽  
...  
Keyword(s):  
Finite Element ◽  
Brain Tissue ◽  
Ice Hockey ◽  
American Football ◽  
External Loading ◽  
Loading Conditions ◽  
Head Impacts ◽  
Impact Parameters ◽  
Impact Events ◽  
Impact Mass

Objective Impacts to the head are the primary cause of concussive injuries in sport and can occur in a multitude of different environments. Each event is composed of combinations of impact characteristics (striking velocity, impact mass, and surface compliance) that present unique loading conditions on the head and brain. The purpose of this study was to compare falls, collisions, and punches from accident reconstructions of sports-related head impacts using linear, rotational accelerations and maximal principal strain of brain tissue from finite element simulation. Methods This study compared four types of head impact events through reconstruction. Seventy-two head impacts were taken from medical reports of accidental falls and game video of ice hockey, American football, and mixed-martial arts. These were reconstructed using physical impact systems to represent helmeted and unhelmeted falls, player-to-player collisions, and punches to the head. Head accelerations were collected using a Hybrid III headform and were input into a finite element brain model used to approximate strain in the cerebrum associated with the external loading conditions. Results Significant differences ( p < 0.01) were found for peak linear and rotational accelerations magnitudes (30–300 g and 3.2–7.8 krad/s2) and pulse durations between all impact event types characterized by unique impact parameters. The only exception was found where punch impacts and helmeted falls had similar rotational durations. Regression analysis demonstrated that increases to strain from unhelmeted falls were significantly influenced by both linear and rotational accelerations, meanwhile helmeted falls, punches, and collisions were influenced by rotational accelerations alone. Conclusion This report illustrates that the four distinct impact events created unique peak head kinematics and brain tissue strain values. These distinct patterns of head acceleration characteristics suggest that it is important to keep in mind that head injury can occur from a range of low to high acceleration magnitudes and that impact parameters (surface compliance, striking velocity, and impact mass) play an important role on the duration-dependent tolerance to impact loading.

Effect of Bolt Strength and Loading Conditions on a 7/8” Bolt Within an End-of-Car Arrangement

2008 ◽  
Author(s):  
Andrew D. Smyth
Keyword(s):  
Finite Element Analysis ◽  
Material Properties ◽  
External Loading ◽  
Loading Conditions ◽  
Element Analysis ◽  
Bolt Preload ◽  
Cause Of Failure ◽  
Bolt Failure ◽  
Inherent Strength ◽  
Type Of Failure

A cause of failure within end-of-car (EOC) arrangements for cushioned cars with F-shank couplers is that of the yoke bolt failing in shear. This mode of EOC failure is of particular concern due to the concealed nature of the bolt not easily allowing for early detection of the onset of failure. To this end, a finite element analysis (FEA) was performed on a 7/8” bolt and F-bracket assembly to determine the stress state developed within the bolt in an effort to understand the potential cause or causes for the bolt failure. Several parameters, including bolt strength, bolt preload (initial torque), and external loading were varied to determine their effects on bolt performance. The subsequent results indicate that both inherent strength and initial preload have a significant effect on whether a bolt can effectively withstand the various external loading conditions encountered in the field. In addition, it is also apparent that some of the simulation loading scenarios analyzed contain the potential to initiate bolt shearing during operation. From these results, some failure mechanism theories are proposed to describe the type of failure encountered by each bolt grade, either ductile or brittle depending on the inherent material properties.

scholarly journals Mechanical test suitable for detection of bug-damage wheat grains abstract

2018 ◽  
Vol 64 (No. 2) ◽  
pp. 77-84
Author(s):  
Basati Zahra ◽  
Rasekh Mansour ◽  
Abbaspour-Gilandeh Yousef
Keyword(s):  
Mechanical Properties ◽  
Mechanical Test ◽  
Compressive Loading ◽  
Mean Value ◽  
Elastic Coefficient ◽  
Wheat Grains ◽  
Significant Difference ◽  
Rupture Energy ◽  
The Mean ◽  
Four Levels

Considering the fact that the presence of bug-damaged wheat in the bulk results in a decrease of the flour quality and its final product, which is bread, it is necessary to differentiate the bug-damaged wheat grains from the healthy ones. Therefore, the present study investigated the mechanical properties of bug-damaged and healthy wheat grains of the Azar cultivar. By making use of these mechanical properties, it would be possible to provide a more precise texture identification of the bug-damaged wheat grains compared to the healthy ones. In this study, the mechanical properties (rupture energy, toughness and apparent elastic coefficient) were determined under compressive loading, with four levels of loading velocity (5, 15, 25 and 35 mm.min<sup>–1</sup>) and four levels of moisture content (9, 11.5, 14 and 16.5% wet basis) in both bug-damaged and healthy wheat grains. Due to the significant difference in the mean value of apparent elastic coefficient between the bug-damaged grains (74.779 MPa) and the healthy ones (289.071 MPa), this parameter can be employed as the most appropriate factor to distinguish the bug-damaged wheat grains from the healthy ones. 

Design and Prototyping of a Shape-Changing Rigid-Body Human Foot in Gait

2018 ◽  
Author(s):  
Tanner N. Rolfe ◽  
Andrew P. Murray ◽  
David H. Myszka
Keyword(s):  
Rigid Body ◽  
Compliant Mechanisms ◽  
Shape Change ◽  
Dynamic Change ◽  
A Priori ◽  
External Loading ◽  
Loading Conditions ◽  
Kinematic Synthesis ◽  
Human Foot

Traditional ankle-foot devices such as prostheses or robotic feet seek to replicate the physiological change in shape of the foot during gait using compliant mechanisms. In comparison, rigid-body feet tend to be simplistic and largely incapable of accurately representing the geometry of the human foot. Rigidbody mechanisms offer certain advantages over compliant mechanisms which may be desirable in the design of ankle-foot devices, including the ability to withstand greater loading, the ability to achieve more drastic shape-change, and the ability to be synthesized from their kinematics, allowing for realistic functionality without a priori characterization of the external loading conditions of the foot. This work focuses on applying the methodology of shape-changing kinematic synthesis to design and prototype a multi-segment rigid-body foot device capable of matching the dynamic change in shape of the human foot in gait.

Experimental and Computational Modeling of Joint and Ligament Mechanics

2004 ◽  
Vol 20 (4) ◽  
pp. 450-474 ◽  
Author(s):  
Richard E. Debski ◽  
Shon P. Darcy ◽  
Savio L-Y. Woo
Keyword(s):  
Computational Models ◽  
Soft Tissues ◽  
Experimental Studies ◽  
Complex Loading ◽  
External Loading ◽  
Spring Model ◽  
Loading Conditions ◽  
Rehabilitation Protocols ◽  
Force Moment

Quantitative data on the mechanics of diarthrodial joints and the function of ligaments are needed to better understand injury mechanisms, improve surgical procedures, and develop improved rehabilitation protocols. Therefore, experimental and computational approaches have been developed to determine joint kinematics and the in-situ forces in ligaments and their replacement grafts using human cadaveric knee and shoulder joints. A robotic/universal force-moment sensor testing system is used in our research center for the evaluation of a wide variety of external loading conditions to study the function of ligaments and their replacements; it has the potential to reproduce in-vivo joint motions in a cadaver knee. Two types of computational models have also been developed: a rigid body spring model and a displacement controlled spring model. These computational models are designed to complement and enhance experimental studies so that more complex loading conditions can be examined and the stresses and strains in the soft tissues can be calculated. In the future, this combined approach will improve our understanding of these joints and soft tissues during in-vivo activities and serve as a tool to aid surgical planning and development of rehabilitation protocols.

Poromechanics Solutions to Plane Strain and Axisymmetric Mandel-Type Problems in Dual-Porosity and Dual-Permeability Medium

2009 ◽  
Vol 77 (1) ◽  
Author(s):  
Vinh X. Nguyen ◽  
Younane N. Abousleiman
Keyword(s):  
Plane Strain ◽  
Laboratory Testing ◽  
Time Dependent ◽  
Polar Coordinates ◽  
Dual Porosity ◽  
External Loading ◽  
Two Dimensional ◽  
Loading Conditions ◽  
Type Problem ◽  
Secondary Porosity

The two-dimensional Mandel-type problem geometry is well-known to bio-geomechanicians for testing rocks, cartilages, and bones with solutions in Cartesian coordinates for rectangular specimens or polar coordinates for cylindrical and disk samples. To date, all existing solutions are only applicable to single-porosity and single-permeability models, which could fall short when the porous material exhibits multiporosity and/or multipermeability characteristics, such as secondary porosity or fracture. This paper extends the plane strain and axisymmetric Mandel-type solutions from single-to dual-porosity and dual-permeability poromechanics. The solutions are presented in explicit analytical forms and account for arbitrary time-dependent external loading conditions, e.g., cyclic and ramping. The derived analytical solutions and results exhibit general behaviors characterized by two time scales. Stresses, pore pressures, and displacements are plotted for various time scale ratios to illustrate the interplaying effects of permeability and stiffness contrast of both porous regions, in addition to the interporosity exchange, on the overall responses of the system. Also, examples with realistic loading conditions for laboratory testing or field simulation such as cyclic and ramping are provided to demonstrate the engineering applications of the presented dual-poroelastic formulation and solutions.

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