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Related Concept Videos

Screw: Problem Solving01:21

Screw: Problem Solving

In mechanical engineering, the interaction between a threaded screw shaft and a plate gear involves analyzing the resisting torque on the plate gear that can be overpowered when a specific torsional moment is applied to the shaft. To better comprehend this concept, consider a generic situation with a threaded screw shaft with a given mean radius and lead and a plate gear with a specified mean radius. The coefficient of static friction between the screw and gear is also provided.
To evaluate the...
Circular Shafts - Elastoplastic Materials01:24

Circular Shafts - Elastoplastic Materials

The study of solid circular shafts under stress shows that within the elastic limit, stress increases directly to the distance from the shaft's center. This relationship holds until the shaft reaches a critical point of stress, beyond which it begins to yield, marking the transition from elastic to plastic deformation. At this crucial juncture, the maximum torque the shaft can endure without permanent deformation is determined, signifying the limit of its elastic behavior.
As torque on the...
Residual Stresses in Circular Shafts01:10

Residual Stresses in Circular Shafts

In materials that exhibit elastic and plastic behavior, known as elastoplastic materials, residual stresses can accumulate when these materials experience plastic deformation. This deformation arises from either high levels of shearing stress or significant strains. Residual stresses are internal stresses that persist within a material after removing the external force causing deformation. This phenomenon is demonstrated when observing the behavior of a shaft under torque; notably, the shaft's...
Net Torque Calculations01:19

Net Torque Calculations

When a mechanic tries to remove a hex nut with a wrench, it is easier if the force is applied at the farthest end of the wrench handle. The lever arm is the distance from the pivot point (the hex nut in this case) to the person’s hand. If this distance is large, the torque is higher. Only the component of the force perpendicular to the lever arm contributes to the torque. Therefore, pushing the wrench perpendicular to the lever arm is more advantageous. If multiple people apply force to rotate...
Frictional Forces on Screws01:17

Frictional Forces on Screws

Screws are characterized by a helical ridge known as a thread wrapped around a cylindrical shaft. They are commonly used as fasteners to hold objects together or to transmit power and motion in machines. One type of screw that is particularly useful for transmitting power is the square-threaded screw.
A jack with a square-threaded screw is a mechanical device used to lift heavy loads by applying a force at its handle. When the force is applied, the screw turns, raising the load. The screw can...
Normal Strain under Axial Loading01:20

Normal Strain under Axial Loading

Normal strain under axial loading is an important concept in the field of mechanics of materials. Axial loading implies the application of a force along the axis of a material, like a column or bar. This force can either compress or stretch the material. In the context of axial loading, normal strain is the deformation experienced by the material in the direction of the loading force. It's calculated as the change in length divided by the original length of the material. This unitless ratio...

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Related Experiment Video

Updated: Jul 16, 2026

An Anesthesia, Surgery, and Harvest Method for the Evaluation of Transpedicular Screws Using an In Vivo Porcine Lumbar Spine Model
09:07

An Anesthesia, Surgery, and Harvest Method for the Evaluation of Transpedicular Screws Using an In Vivo Porcine Lumbar Spine Model

Published on: May 31, 2017

Effect of screw torque level on cortical bone pullout strength.

Tammy M Cleek1, Karen J Reynolds, Trevor C Hearn

  • 1School of Informatics and Engineering, Flinders University, Adelaide, SA, Australia. tammy.cleek@flinders.edu.au

Journal of Orthopaedic Trauma
|February 17, 2007
PubMed
Summary

Overtightening cortical screws past 86% of maximum torque (Tmax) in ovine tibiae significantly reduces bone holding strength. Clinical tightening levels compromise screw purchase, indicating potential damage to bone fixation.

Related Experiment Videos

Last Updated: Jul 16, 2026

An Anesthesia, Surgery, and Harvest Method for the Evaluation of Transpedicular Screws Using an In Vivo Porcine Lumbar Spine Model
09:07

An Anesthesia, Surgery, and Harvest Method for the Evaluation of Transpedicular Screws Using an In Vivo Porcine Lumbar Spine Model

Published on: May 31, 2017

Area of Science:

  • Orthopedic biomechanics
  • Surgical implant technology

Background:

  • Cortical screw fixation is crucial for fracture healing.
  • Optimizing screw tightening torque is essential for implant stability and bone integrity.

Purpose of the Study:

  • To analyze cortical screw tightening stiffness during automated insertion.
  • To evaluate the impact of three torque levels on bone holding strength via screw pullout tests.

Main Methods:

  • Ovine tibiae were used, with screws inserted at 50%, 70%, and 90% of predicted maximum torque (Tmax).
  • Screw pullout tests assessed holding strength, with force values normalized by cortical thickness.

Main Results:

  • Tightening to 86% Tmax, a clinical level, occurred post-bone yield, causing a 51% loss in stiffness.
  • Screw holding strength was highest at 70% Tmax (2707 N) and significantly lower at 90% Tmax (2344 N).

Conclusions:

  • Clinical screw tightening levels (86% Tmax) exceed bone's yield point, potentially damaging fixation.
  • High torque levels compromise screw holding strength, necessitating further research for optimal torque parameters.