Friction torque is a physical manifestation of friction in an engineering system containing two parts with relative motion to each other. In accordance with the Newton law of action and reaction, two parts that are in contact and slide or rotate relative to each other experience a force of friction in the direction of relative motion.
In rotary motion, the reaction of friction between parts would create a torque that opposes the direction of motion. This oppositional torque is termed as the ‘friction torque’. The magnitude of the friction torque depends on the coefficient of the friction between the two contact surfaces and the force that causes the two surfaces to come in contact with each other.
Friction torque is a constant source of energy loss in any mechanical system. It reduces the efficiency of the system by increasing the work done in order to move the system at a certain velocity for a given distance. It also reduces the maximum power output of the system by increasing the amount of work that needs to be put in for a given power output.
It can be said that the presence of friction torque has both positive and negative aspects from an engineering point of view. From a practical engineering standpoint, it plays a significant role in the safety of a system. This is because the higher the friction torque, the more resistance the system has to motion, thus reducing the chances of it accelerating past its design specifications.
On the other hand, friction torque reduces the mechanical efficiency of the system and makes it difficult to design complex systems. The friction torque that is present in a system can’t be abolished completely, and has to be dealt with through mitigation techniques such as lubrication, wetting, material selection, and other designs.
The amount of friction torque present in a system is also highly dependent on the design and materials of the two parts in contact. If the coefficient of friction between the two surfaces is high, then the resistance to motion is significantly higher and the system will naturally generate more friction torque. This is the reason why material selection is such an important factor when designing a system to ensure that the torque and the system efficiency remain acceptable.
In order to reduce the effects of friction torque in a system or to maximize the efficiency, it is necessary to take steps to reduce the coefficient of friction. This can be done by taking appropriate steps such as lubricating and stressing the surface of the two counterfaces or by redesigning the system to reduce the coefficients. In some cases, additional devices such as flywheels, actuators, and damping systems may be added to the system in order to reduce the friction torque and improve the efficiency.
To conclude, friction torque is an important force that affects the performance of a mechanical system. The magnitude of the friction torque is highly dependent on the materials, design and conditions of the two parts in contact and is a constant source of energy loss in any system. Engineering efforts must be taken to reduce the coefficient of friction and to minimize its impacts on the system in order to maximize efficiency and minimize safety concerns.