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Shear Center
The point on the cross section plane for which the plane of loading must mass through to avoid twisting of the member

Principal plane
 the plane through an element at a point in a stressed body which is free of shear stress.
 HP&VP for element are principal planes

Isotropic Material
a material with the same properties in all directions throughout its volume

Octahedral stress
A stress which acts on planes which make equal angles with the principal axis. θ1=θ2=θ3

Neutral Axis
 The locus of points on a beam's cross section for which the normal stress is zero.
 *NA passes through centroid for pure bending M


any isolated part or portion of a machine or structure
 that we wish to study, may consist of
 particle, several particles, a part of a rigid body, an entire rigid body, or
 even several rigid bodies

Section modulus
 the ratio of the moment of inertia to the maximum
 distance from the centroid to the outer fiber of the cross section

Shear Strain
the change in a right angle of a stress element subject to pure shear

Elasticity
material returns to tis original shape immediately upon removal of load, property of a material that enables it to regain its original configurations after having been deformed.

Homogeneity
material has the same properties throughtout its volume

Limitations of deflection formula
 1. Bar is straight
 2. Bar is axially
 and centrally loaded
 3. Bar has uniform
 cross section
 4. No stress
 concentrations
 5. Gradually applied
 load
 6. No residual
 stresses present
 7. Hooke’s law
 applies

Mohr's circle diagram
a graphical solution to the combines stress problem

Principal stress
 a particular orientation in the stress element occurs
 in space for which all shear stress components are zero.

Normal Strain
elongation per unit length

Limitations for stress (F/A) and shear stress
 1. Bar is straight and made of homogeneous material
 2. Line of action of
 force coincides with the centroid of the cross section
 3. St. Venant’s
 principle applies
 4. No initial
 stresses in material
 5. Load is gradually
 applied, (static loading)

Center of Gravity
 the sum of the moments of the
 areas about the axis through the C.G. must equal zero

Pure bending
 when the shear force is zero and there is no net axial
 load

Limitations of stress (My/I)
 1. Beam is subjected to pure bending
 2. Material is isotropic and homogeneous
 3. Material obeys Hooke’s law
 4. Beam is initially straight with a cross section that is constant throughout the beam length
 5. Beam has an axis of symmetry in the plane of bending
 6. Cross section of beam remains plane during bending
 7. No residual stresses or stress concentration

Limitations of shear stress (VQ/It)
 1. Same as bending stress
 2. Shear stresses are uniformly distributed across the beam width
 3. Shearing stresses throughout the cross section is the same as the direction of the shear force
 4. Width of cross section where stress is being computed it small in comparison to the depth of
 the beam

True Strain
logarithmic strain, the sum of incremental elongations divided by the current gauge length at load P

Stress
a state property at a specific point within a body, a function of load, geometry, temperature, and manufacturing processing

Strength
An inherent property of a part, a property built into the part b/c of the use of a particulat material and process.

Specific modulus, specific stiffness
E/p, ratio of young;s modulus to density

