Tensile & Shear Stress • Preload • Factor of Safety — Simulate • Explore • Practice • Quiz
Bolted joint design is a fundamental topic in mechanical engineering and machine design. Engineers use bolted connections to join structural members, flanges, brackets, and pressure vessels. Proper bolt design ensures that joints can safely carry applied loads without failure due to excessive tensile stress, shear, or fatigue. Understanding preload, stress distribution, and factor of safety is essential for reliable mechanical assemblies.
A bolted joint consists of a bolt (head, shank, and threads), nut, and the clamped parts (plates, flanges, or members). Metric bolts are classified by their nominal diameter (M6 through M24 and larger) and their property class (grade), such as 4.6, 5.8, 8.8, 10.9, and 12.9. Each grade specifies proof strength, yield strength, and ultimate tensile strength, which directly determine the bolt's load-carrying capacity.
When a bolt is tightened, it develops a preload (Fi) — a clamping force that holds the joint together even before external loads are applied. The recommended preload for reusable connections is Fi = 0.9 × At × Sp, where At is the tensile stress area and Sp is the proof strength. The tensile stress area accounts for the reduced cross-section at the thread root and is calculated as At = (π/4)(d − 0.9382p)², where d is the nominal diameter and p is the thread pitch. The tensile stress in the bolt is σ = F / At, which must remain below the proof strength with an adequate factor of safety.
In joints loaded in shear (transverse to the bolt axis), the bolt resists sliding between the plates. The shear stress is τ = F / (n × A), where n is the number of bolts and A is the bolt cross-sectional area. Bearing stress occurs where the bolt contacts the plate and is calculated as σb = F / (n × d × t), where d is the bolt diameter and t is the thinner plate thickness. For combined loading (tension plus shear), the von Mises equivalent stress must be checked against the allowable stress.
In Simulate mode, select a bolt size (M6 to M24), grade (4.6 to 12.9), number of bolts, external load, plate thicknesses, and joint type (Tension, Shear, or Combined). The canvas displays a cross-section of the bolted joint with force arrows, stress zones, and a stress distribution diagram — all updating in real time. Use presets for common joint configurations. Switch to Explore mode to study 10 concepts across Bolt Basics, Stresses, and Design with worked examples. Practice mode generates random bolt design problems, and Quiz tests your knowledge with 5 randomised questions.
This simulator is designed for mechanical engineering students, machine design trainees, manufacturing engineers, and instructors teaching bolted joint design, bolt stress analysis, and connection design. It provides visual, hands-on understanding of bolt mechanics without requiring laboratory equipment or complex software.