package vibration testing - westpak package vibration testing ... (springs), a/a plots – design...

Download Package Vibration Testing - Westpak   PACKAGE VIBRATION TESTING ... (springs), A/A plots – Design for Vibration 3 . ... RESULTS IN “FREE VIBRATION” OF THE MASS

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  • PRODUCT & PACKAGE TESTING VIBRATION & SHOCK

    Dec 2015

    Herb Schueneman Chairman, WESTPAK, Inc.

    PRODUCT & PACKAGE VIBRATION TESTING

    Herb Schueneman Founder, Chairman

    WESTPAK, INC. March 2016

    http://www.google.com/url?sa=i&rct=j&q=&esrc=s&frm=1&source=images&cd=&cad=rja&uact=8&ved=0CAcQjRw&url=http://www.toplessrobot.com/2008/06/the_8_coolest_sesame_street_toys_ever.php&ei=fblKVcCJFdjVoATBjYGgCQ&bvm=bv.92765956,d.cGU&psig=AFQjCNHyMdrvzO1fyD4HQlK8dOqPQ-Hmfw&ust=1431046530320946http://www.google.com/url?sa=i&rct=j&q=&esrc=s&frm=1&source=images&cd=&cad=rja&uact=8&ved=0CAcQjRw&url=http://www.toplessrobot.com/2008/06/the_8_coolest_sesame_street_toys_ever.php&ei=fblKVcCJFdjVoATBjYGgCQ&bvm=bv.92765956,d.cGU&psig=AFQjCNHyMdrvzO1fyD4HQlK8dOqPQ-Hmfw&ust=1431046530320946http://www.westpak.com/?utm_source=webinar&utm_medium=slideck&utm_content=prod_pack&utm_campaign=vibration

  • Whats This All About?

    2

    Why, how, and when do we mechanically test products and package systems?

    What do we learn from this? What do we do with the information?

    http://www.westpak.com/?utm_source=webinar&utm_medium=slideck&utm_content=prod_pack&utm_campaign=vibration

  • Agenda

    Background, terminology, etc. Vibration Dynamics Spring/Mass Models; Forces vs. Free Response Types of Excitation; Sine, Random, Acoustic,

    Sources of input

    Resonance, Transmissibility, Damping, Fatigue Package Cushioning (springs), A/A plots Design for Vibration

    3

    http://www.westpak.com/?utm_source=webinar&utm_medium=slideck&utm_content=prod_pack&utm_campaign=vibration

  • Dynamics

    The study of mass that is moving in a flexible environment

    Flexibility implies springs so the study of dynamics starts with a thorough understanding of Spring/Mass Systems

    4

    http://www.westpak.com/?utm_source=webinar&utm_medium=slideck&utm_content=prod_pack&utm_campaign=vibration

  • 5

    SDOF Spring/Mass System

    MASS

    http://www.westpak.com/?utm_source=webinar&utm_medium=slideck&utm_content=prod_pack&utm_campaign=vibration

  • 6

    AN INPUT APPLIED HERE RESULTS IN FREE VIBRATION OF THE MASS

    AN INPUT APPLIED HERE RESULTS IN FORCED VIBRATION OF THE MASS

    SDOF Spring/Mass System

    MASS

    http://www.westpak.com/?utm_source=webinar&utm_medium=slideck&utm_content=prod_pack&utm_campaign=vibration

  • 7

    SDOF Spring/Mass System

    MASS

    Maximum strain energy

    Maximum velocity

    http://www.westpak.com/?utm_source=webinar&utm_medium=slideck&utm_content=prod_pack&utm_campaign=vibration

  • Spring Mode Doesnt Matter

    8

    Tension

    Compression

    http://www.westpak.com/?utm_source=webinar&utm_medium=slideck&utm_content=prod_pack&utm_campaign=vibration

  • Natural Frequency

    113.313.3

    2

    1

    M

    K

    M

    Kf

    n

    9

    K

    M

    http://www.westpak.com/?utm_source=webinar&utm_medium=slideck&utm_content=prod_pack&utm_campaign=vibration

  • Natural or Resonant Frequency

    10

    As earlier noted, excitation of the mass results in motion we call free vibration or Natural Frequency, fn.

    Excitation of the base results in forced vibration of the mass. When the forcing frequency = fn, the mass response is max and is said to be in resonance.

    http://www.westpak.com/?utm_source=webinar&utm_medium=slideck&utm_content=prod_pack&utm_campaign=vibration

  • SDOF vs. MDOF Normal products are pretty complex. A multiple degree of freedom (MDOF) model is more appropriate however much more complex and difficult to analyze.

    11

    http://www.westpak.com/?utm_source=webinar&utm_medium=slideck&utm_content=prod_pack&utm_campaign=vibration

  • Spring Types

    12

    Almost all products or product/package systems can be analyzed and modeled as complex spring/mass systems. But maybe not Linear Springs..

    http://www.westpak.com/?utm_source=webinar&utm_medium=slideck&utm_content=prod_pack&utm_campaign=vibrationhttp://www.google.com/imgres?imgurl=http://gallery.burrowowl.net/index.php?q%3D/image/21749.jpg&imgrefurl=http://janjigian.blogspot.com/2012/03/goldmans-muppet-clients.html&h=250&w=374&tbnid=E0XcSCZL2Lcw8M:&docid=aSEnC4Lq0G4drM&ei=6IUcVoDwBon8jwPg_L3ICw&tbm=isch&ved=0CEMQMyhAMEA4yAFqFQoTCICEhNLLvsgCFQn-YwodYH4PuQ

  • Linear Spring

    13

    A = F X V p n D F

    k=F/D =W/k

    Spring Types

    http://www.westpak.com/?utm_source=webinar&utm_medium=slideck&utm_content=prod_pack&utm_campaign=vibration

  • Non-Linear / Hardening Spring

    14

    dd

    k

    2kd

    tan (def)

    2d SPRING FORCE =

    Spring Types

    http://www.westpak.com/?utm_source=webinar&utm_medium=slideck&utm_content=prod_pack&utm_campaign=vibration

  • Non-Linear / Softening Spring

    15

    DEFLECTION

    F

    1

    k

    SPRING FORCE =kd tanh d

    def

    Spring Types

    http://www.westpak.com/?utm_source=webinar&utm_medium=slideck&utm_content=prod_pack&utm_campaign=vibration

  • SDOF models assume linear springs Most flexibility in systems is non-linear

    However, most systems can be analyzed in a near linear portion of their deflection range so thats why we use the linear model

    16

    Spring Types

    (Printed Circuit Boards)

    http://www.westpak.com/?utm_source=webinar&utm_medium=slideck&utm_content=prod_pack&utm_campaign=vibration

  • Coupling

    M

    A B

    F1

    F2

    F 3

    17

    Coupled vs. Uncoupled Motion

    The mass is a homogenous rigid block with center of gravity (cg) at point A.

    The response of the block to F1 is pure vertical motion.

    The response of the block to F2 is pure rotational motion.

    The response of the block to F3 is pure horizontal motion.

    http://www.westpak.com/?utm_source=webinar&utm_medium=slideck&utm_content=prod_pack&utm_campaign=vibration

  • 18

    Coupled vs. Uncoupled Motion

    If (cg) is at point B, F1

    produces both vertical and rotational motion of the block. In this case, the motion is said to be coupled.

    With (cg) at point B, F3 produces uncoupled horizontal motion.

    Coupling

    M

    A B

    F1

    F2

    F 3

    http://www.westpak.com/?utm_source=webinar&utm_medium=slideck&utm_content=prod_pack&utm_campaign=vibration

  • 19

    Time for Questions !

    http://www.westpak.com/?utm_source=webinar&utm_medium=slideck&utm_content=prod_pack&utm_campaign=vibration

  • Resonance occurs when a component or system is forced at its fn.

    20

    Spring/Mass response is amplified at resonance.

    This is where damage, fatigue, etc. is most likely to happen.

    Resonance

    http://www.westpak.com/?utm_source=webinar&utm_medium=slideck&utm_content=prod_pack&utm_campaign=vibration

  • Transmissibility Plot

    21

    Ar

    Ai f

    Resonance

    http://www.westpak.com/?utm_source=webinar&utm_medium=slideck&utm_content=prod_pack&utm_campaign=vibration

  • 22

    Vibration Machine

    Example

    Types of Equipment Electrodynamic shaker Hydraulic shaker

    Single or multi-axis Acoustic (reverberant) chamber

    How the Test is Conducted

    http://www.westpak.com/?utm_source=webinar&utm_medium=slideck&utm_content=prod_pack&utm_campaign=vibration

  • Excitation can be:

    Sinusoidal Random or pseudo-random Acoustic Other

    23

    Types of Mechanical Excitation

    All Spring/Mass systems respond at their natural frequencies because they cant do anything else.

    http://www.westpak.com/?utm_source=webinar&utm_medium=slideck&utm_content=prod_pack&utm_campaign=vibration

  • Type Positive Not-So-Positive

    Sinusoidal Easy to understand Good visual feedback Grandfathered tried & true

    Gives false amplification values Over-test for fatigue potential Doesnt account for constructive and

    destructive interferences between systems

    Random Quicker Less fatigue potential Realistic Matches real life

    More complex Requires a specific controller

    Acoustic

    Usable for heavy systems Good high frequency

    Very expensive Requires large chamber & analytical

    capability

    24

    Excitation: the Good & the Bad

    http://www.westpak.com/?utm_source=webinar&utm_medium=slideck&utm_content=prod_pack&utm_campaign=vibration

  • 25

    Damping (Rc) is expressed as a ratio of observed damping to Critical Damping in a system.

    Damping

    http://www.westpak.com/?utm_source=webinar&utm_medium=slideck&utm_content=prod_pack&utm_campaign=vibration

  • Critical Damping is where the mass returns to its initial position in the minimum time without overshoot.

    26

    Damping

    http://www.westpak.com/?utm_source=webinar&utm_medium=slideck&utm_content=prod_pack&utm_campaign=vibration

  • Fatigue is the weakening of a material caused by repeatedly applied loads. It is the progressive and localized structural damage that occurs when a material is subjecte

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