What is the meaning of torque to yield?
A torque to yield fastener (TTY) or stretch bolt is a fastener which is torqued beyond the state of elasticity and therefore undergoes plastic deformation, causing it to become permanently elongated.
Can you reuse torque to yield?
Torque-to-yield (TTY) head bolts are designed to stretch when used. Once stretched, they are not as strong as before. Consequently, they cannot provide the same amount of clamping force and may break or shear off if reused.
Are rod bolts torque to yield?
The connecting rod bolts are also TTY, but can be tightened up to three times for bearing checking. The balancer bolt is also a torque-to-yield fastener. The vertical main bolts can also be re-used, but the side bolts are often replaced because they have sealant on them. These can be re-used if sealant is re-applied.
What is the advantage of torque to yield bolts?
Torque to yield bolts have many advantages over conventional bolts. The specialised method of tightening these bolts allows them to be more efficient at clamping. Engine reliability is achieved because the assembly of the engine is far more accurate.
What happens if you over torque a torque to yield bolt?
If the bolt is over-torqued and stretched beyond its limit, this exceeds its yield strength which means it can no longer maintain the needed clamp load and must be replaced. Finally, using a breaker bar, the bolt is tightened, which moves the dial to the specified angle – hence the term torque-angle.
What happens if you over torque a torque-to-yield bolt?
How many times can you use torque-to-yield bolts?
What is a torque-to-yield bolt? It is a one-time-use fastener that is designed to stretch during the torquing process (installation). Because of this stretching, the integrity of the bolt is compromised. These bolts cannot and should not be reused due to the stress caused to the bolt during its first installation.
Why are some bolts torque to yield?
Traditional fasteners are torqued to a load that will slightly stretch the bolt but won’t over-stretch it past its yield point. Torque-to-yield (TTY) fasteners are stretched beyond the point of elongation to ensure a more consistent clamp load on the joint.
What does “torque to yield bolt” mean?
Torque-to-yield (TTY) head bolts are designed to stretch when used. Once stretched, they are not as strong as before. Consequently, they cannot provide the same amount of clamping force and may break or shear off if reused.
Why use torque to yield bolts?
Torque to Yield Bolts. With a standard bolt a technician could torque the bolt to its yield point, and it would return to its original form and length when removed. This is because of its elasticity, it is able to stretch and then return to its original form. This is not so with torque to yield bolts. There are two terms related to this phenomenon.
Can you explain torque to yield bolts?
When tightened they stretch to the point of yield. Many vehicle manufacturers use torque to yield bolts; especially on engines with aluminum heads and or in conjunction with (MLS) head
Can You reuse torque to yield bolts?
At this point the bolt has changed its form and if loosened or removed it must be replaced with a new torque to yield bolt. So you can re-use the standard head bolts, but when it comes to torque to yield bolts, if they have reached plastic deformation, they need to be replaced with new ones.