Unitized body is the most commonly used frame in modern cars. It is a self supporting body built up as a single unit. It is built of hollow sheet steel parts onto which the other body panels such as the cross members, roof frame, side members, etc. are welded with the help of robots. It is also known as monocoque structure.
Uni-body construction was introduced to make the vehicle lighter, therefore resulting in higher mileage. It is also easier to manufacture unitized body and it provides more interior space for the passengers. It does not have any frame, instead it is made of tubular fore to make it rigid.
Unitized body is still not preferred for trucks and other heavy duty vehicles because of its less strength compared to ladder frames.
Spot welding technique is employed in welding and holding the parts together as a single unit. Multiple spot welds about 4000 to 5000 of it must be made along entire structure.
Strength and Rigidity:
The steel metal provides the strength, and the use of hollow pillars provides the torsional and bending rigidity to the structure. The rigidity should be high enough to withstand the elastic deformation.
Vibrations:
Irregular surface can cause excitation of the wheels and suspension which can transfer vibrations to the body. Apart from this, the engine and drive-train can impair the driving comfort. Varying the body wall thickness and use of cross sections can suppress the frequency of the body due to vibrations.
Integrity:
Continuous vibrations can cause stresses on body parts which can lead to cracks and welding failure. The engine support cross member is highly susceptible to such failures due to the vibration from the engine and transmission.
Collision:
In the event of an accident, huge amount of kinetic energy is transferred to the body. The body structure must be able to retain the structural integrity of the passenger cabin by preventing the kinetic energy to cause deformation to the vehicle interior. The exterior should be able to handle the deformation work.
Repair:
The body parts which deform after a accident must be easily replaceable. There must be a suitable access to the exterior body parts from the inside or outside to replace the panels, pillars,etc. and be bolted or welded. Repair work is difficult in unitized body structure.
Uni-body construction was introduced to make the vehicle lighter, therefore resulting in higher mileage. It is also easier to manufacture unitized body and it provides more interior space for the passengers. It does not have any frame, instead it is made of tubular fore to make it rigid.
Unitized body is still not preferred for trucks and other heavy duty vehicles because of its less strength compared to ladder frames.
Spot welding technique is employed in welding and holding the parts together as a single unit. Multiple spot welds about 4000 to 5000 of it must be made along entire structure.
Strength and Rigidity:
The steel metal provides the strength, and the use of hollow pillars provides the torsional and bending rigidity to the structure. The rigidity should be high enough to withstand the elastic deformation.
Vibrations:
Irregular surface can cause excitation of the wheels and suspension which can transfer vibrations to the body. Apart from this, the engine and drive-train can impair the driving comfort. Varying the body wall thickness and use of cross sections can suppress the frequency of the body due to vibrations.
Integrity:
Continuous vibrations can cause stresses on body parts which can lead to cracks and welding failure. The engine support cross member is highly susceptible to such failures due to the vibration from the engine and transmission.
Collision:
In the event of an accident, huge amount of kinetic energy is transferred to the body. The body structure must be able to retain the structural integrity of the passenger cabin by preventing the kinetic energy to cause deformation to the vehicle interior. The exterior should be able to handle the deformation work.
Repair:
The body parts which deform after a accident must be easily replaceable. There must be a suitable access to the exterior body parts from the inside or outside to replace the panels, pillars,etc. and be bolted or welded. Repair work is difficult in unitized body structure.
Great blog post..Thanks for sharing such a valuable information.
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