MACLAMP,len,wid,thc,mlen,mwid,mthc,acl,den,ymod,sel
Bending of a double-clamped beam with a central mass under acceleration
len
length of beam in µm
wid width of beam in µm
thc thickness of beam
in µm
mlen
length of the mass in µm
mwid width of the mass in µm
mthc thickness of the mass in µm
acl acceleration as
multiples of g
an input value of 10 means 98.5m/s2
den density of the material in
kg/m3
ymod Young's modulus of the material in
GPa
sel number denoting the
selected result.
Use 1 for maximum stress, 2 for deflection and 3 for spring constant
Notes
An inertial mass suspended from two or more clamped beams is a structure often
used in MEMS accelerometers and other motion sensitive devices. A typical
structure is as shown above. When an acceleration load is applied in the
direction shown, the mass will undergo a displacement till the spring action
of the beams balance out the acceleration load.
Use this form to calculate the displacement of the mass due
to the acceleration load and the resulting stress in the beams. If there are more springs supporting the mass connected in parallel,
the effective spring constant will be the sum of spring constants of all the
beams.
The plot gives the distribution of stress on the beam
surface. It shows that the stress changes from positive maximum to negative
maximum along the length of the beam. When the mass is pushed down due to
inertia, the surface
stress near the clamped edge of the beam will be tensile and that near the mass will be
compressive.
Assumptions
-The default material is Silicon with a Young's modulus of 180GPa.
-The beam has uniform cross section.
-The weight of the beam and mass is
uniformly distributed. Deflection due to weight of the mass is negligible.
-There is no other load acting on the structure other than acceleration load
perpendicular to the mass.
-The bending of the mass is negligible.
-Damping is not
considered.
Menu Path
Mechanics > Structures > Beams > Clamped beam > Central mass >
Acceleration load
