1. What is Pre Load in Bolt?

Pre Load in Bolt is the tension created in a bolt when it is tightened. It is a critical parameter in bolted joint design that ensures proper clamping force and joint integrity.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( P_i \) — Pre Load in Bolt (N)
• \( \delta_c \) — Amount of Compression of Bolted Joint (m)
• \( k \) — Combined Stiffness of Bolt (N/m)

Explanation: The preload in a bolt is calculated by multiplying the amount of compression in the bolted joint by the combined stiffness of the bolt and assembly.

3. Importance of Pre Load Calculation

Details: Accurate preload calculation is crucial for ensuring proper joint strength, preventing loosening under vibration, and maintaining seal integrity in pressurized systems.

4. Using the Calculator

Tips: Enter the amount of compression in meters and the combined stiffness in Newtons per meter. Both values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: Why is preload important in bolted joints?
A: Preload ensures that the joint remains tight under operating conditions, prevents leakage, and maintains structural integrity.

Q2: What factors affect bolt preload?
A: Factors include bolt material, thread friction, tightening torque, surface finish, and temperature variations.

Q3: How is combined stiffness calculated?
A: Combined stiffness is the reciprocal of the sum of reciprocals of individual stiffness values of bolt and connected parts.

Q4: What are typical preload values?
A: Preload typically ranges from 60-90% of the bolt's proof load, depending on application requirements and safety factors.

Q5: How to measure preload accurately?
A: Direct methods include strain gauges or ultrasonic measurement, while indirect methods include torque measurement or turn-of-nut method.