# Mechanical Engineering Design Notes

 Design Contents

FUNDAMENTALS
Preliminary Matters
Design Methodology
..brain storming
..evaluation matrix
..QFD
Statistical Considerations
..variability in materials
..variability in dimensions
.. preferred sizes
Tolerances
Design Factor
Introduction to Failure
Failure Theories
Stress Concentration
..and notch sensitivity
..combined bending and torsion
..fatigue
..fracture mechanics
Instability - Buckling
..slender columns
..Euler formula
..effective length
..short and intermediate columns
.. theory
..deflection
..stress

MATERIALS
Range of Materials
..requirements
..performance indices
..ferrous metals
..alloy and stainless steels
..tool steels
..aluminium alloys
..titanium alloys
..magnesium alloys

MACHINE ELEMENTS
Joining
..bolts and bolted joints
..welds and welded joints

Springs
..introduction
..forces acting
..curvature effect
..equations used for design
..materials and manufacture
..effective mass
..surge
..Java spring calculation applet with plot

Transmissions
..introduction

..gears
..gear nomenclature
..gear box features
..friction belt drive
..hydraulics and pneumatics
..clutches

Mechanisms and
4 stroke ICE thermodynamics

..engine mechanism and thermodynamics - applet
..engine mechanism - slider crank - velocity, acceleration diags. and torque, hand calculations

Bearings and Lubrication
..introduction
..plain bearings
..viscous flow
..Petroff's law
..hydrodynamic bearing design

 Shear Stresses in an Array of Rivets or Bolts

The bolts or rivets are assumed to be in single shear and all must be of equal diameter. For bolts it is assumed that the full diameter is carrying the load, NOT the threaded portion. The maximum number of fasteners is 20.

Enter values in the units indicated including the first pair of 'X' and 'Y' coordinate values then click on the Calculate button. Then enter the second pair of 'X' and 'Y coordinate values and click Calculate button. Repeat until all the pairs of 'X'and 'Y' values have been entered. Clicking the Calculate button after the last pair of 'X' and 'Y' values have been entered calculates the shear stress due to the 'direct' component of the load - the 'primary' shear stress - equal on all fasteners - the maximum 'secondary' stress (due to the torsional component of the load) and the maximum shear stress after the primary and secondary components have been combined.

The layout of the fasteners is also drawn and the position of the fastener with the highest stress is shown in red. Where there is more than 1 fastener with equal highest stress, the last one entered is highlighted.

'X' and 'Y' coordinate values of the fasteners can be with respect to any convenient origin. The 'Force' is assumed to act in the negative 'Y' direction and the 'Force Offset' must be with respect to the same 'X' origin as used for the fastener coordinates.

The 'Plot size' specified should be large enough to display the array of fasteners.

Is the maximum stress acceptable?

David J Grieve, CEng, MIMechE. Updated: 29th January 2014, original: 7th July 2000