Hello Engineers,
Hope you enjoyed reading my posts on getting jobs and pattern of questions asked in an interview.
Hope you enjoyed reading my posts on getting jobs and pattern of questions asked in an interview.
In this post, I
will be explaining about dynamic analysis with a real life practical example
Hope you will enjoy
it☺
📌 Dynamic Analysis:
It
is mainly used to determine the response of the structure when it is subjected
to the vibration and shock loads.
For
any structure undergoing mechanical vibrations, there are two important characteristics
which determines its behavior they are:
·
Mode
shapes
·
Natural
frequencies
Mode shapes show the response pattern
of the structure in a particular frequency and they are termed as Eigen vectors.
Natural frequency is the
frequency at which the structure will resonate resulting in higher response and they are termed as Eigen
values.
Hope you remember these stuffs
are calculated with the help of matrices in numerical methods.
Modal analysis is used to
determine the above mentioned characteristics. A lot of things has to be
understood before performing modal analysis.
A lot of resources are available
to explain it but my focus here is to explain intuitively what the vibration is
!!!!
Let me explain it a more practical
example which I experienced in my life. One of my friends crashed my Apache bike 😲😲 with some crashes in Visor and made a crack in the speedometer housing. Because
of this crack the housing raised a bit upwards.
 |
Whenever I took it for a ride, the separated region will vibrate when the speed of my bike varies between 48 to 56 Km/hr. During ride, I experienced the vibration by means a sound🔊. I can hear the sound only when the speed is between that stipulated range. I cannot hear the sound once after I cross that speed range. To recheck it, I just lowered my speed below the stipulated speed and raised it again!!!
I was astonished by
seeing this phenomenon persistently during each rides and several times in a
single ride.
I do not want to go much theoretical
with vibration formula and calculations because I will be dedicating my next
blog to mathematical model of vibration.
📌 Let me explain why it has
happened?
All the components in the bike
are assembled in such a way that the system has to vibrate
as a whole when the bike exceeds a speed of around 100 km/hr. Due to the crack in the hatched region, it made the housing to vibrate when I attained the speed of around 48 km/hr.
Then another question which
raises up is why it vibrates at the particular speed alone???
Each component in bike has its
own natural frequency〰, but the natural frequency will not be the same when it
is assembled in a system and it will also vary based on how it is assembled or
constrained.
When my bike housing got cracked
it got separated from the assembly (just a minor separation of hatched region) and it was calm until
the speed of 47 km/hr (not much accurate) and started to vibrate (or we can say
resonate ♒ in a technical perspective) from 48 to 56 km/hr.
What I can conclude here
This is the beauty of
vibration!!! 👆
Stay visiting my blog for understanding
structural simulation in a more realistic way!!!!
Awesome explanation, however i can use Freq while analyzing, but how can I use Mode shape, and why we determine multiple mode shapes, when we have limited eigen vectors for a give problem equation.
ReplyDeleteHi Balaji,
DeleteThanks for your query.
I cannot understand your complete question. But I can answer a part in your query "How can I use the mode shape"
Mode shape shows you the critical location by means of a deformation contour. With this you can determine the critical location which has to be strengthened by adding ribs or you can make design changes according to your needs. In addition to it if the body is loaded with any type of forces during that particular frequency It will experience a higher amount of response corresponding to that particular mode shape. Hope I have answered by best. Regarding the rest of your question please post it a bit elaborate here.
Thanks for the detailed explanation.
ReplyDeleteGood narration , Real life example made vibration simple to understand.
ReplyDeleteThanks for your comments
DeleteHai , I have a query regarding the natural frequency of a component. What exactly happens to the natural frequency when we increase the particular mass or stiffness of the component . Theoretically I know stiffness directly and mass inversely proportional to Natural frequency.But what's the exact logic or concept behind it.
ReplyDelete