slam analysis abi
Post on 27-Oct-2014
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Slam Analysis for Closures
Presenter Abi Swaminathan
ContentIntroductionTypes of ClosuresHood Slam Analysis Hood Assembly Boundary ConditionsLoading ConditionTarget for Slam AnalysisTransient Response AnalysisAnalytical Procedure
Introduction
Doors are hanged on parts should fulfill diverse requirements over their complete life time.
The main function of hang on parts is to open and close the car.
The damage to the components of the closures induced by the slam , accumulates over the vehicle lifetime and may lead to failure.
Types of ClosuresHoodDecklidHatchbackTailgateSide doorSliding Door
Types of Closures
Hood Slam Analysis
Hood opening/closing is a necessary function in a vehicle.
But the closing often results in an impact known as hood slam.
Impact loads –special case of dynamic loads that occur when there is a sudden change in velocity.
Dynamic loads- Force generated when the vehicle is in motion
Hood Slam AnalysisThe hood slam load- Rotational velocity
applied to the hood in the open position. When the hood reaches the closed (latched)
position, Striker contacts the latching mechanism. periphery of the hood contacts seal(s) and
bumpers. Then sudden impulse results in transient
vibration of the hood sub-system.High transient stresses can result in fatigue
cracks on the hood structure or at the striker to body interface.
Hood Assembly
It includes fully trimmed closures.Body in white front structure – cut
line with SPCInner and Outer PanelsHinge assemblyDoor structural membersLatch/ StrikerAdhesive, Hem, Mastic and weldsSeal
Hood Assembly
a) hood inner b) hood outer c) main reinforcement
d) hood hinge reinforcement e) latch reinforcement
f) assembly without the outer panel.
Hood AssemblyLatch Mechanism which catches, holds, and
releases the striker in hood closing and locking systems
Found on door side in doors, decklids, and tailgates and on body side in hoods
Striker Small bar on door side of latch
mechanism which strikes the latch on closure and is then held in place until the latch is released
Found on body side in doors, decklids, and tailgates and on door side in hoods
Hood AssemblyWeather-strip seal:• Rubber seal found around doors, glass, and deck lid openings to prevent seepage of water into the vehicle interior
Hood AssemblyHood Bumper:
• This bumper is used on the radiator support and is adjustable in order to help get the correct panel alignment at the front of the hood.
• They also help reduce rattles by minimizing metal-to-metal contact.
Boundary Conditions:
The body side hinges -all six degrees of freedom.
The latch attachment - all six degrees of freedom.
Bumpers -all six degrees of freedom.
Seals -all six degrees of freedom.
Loading ConditionApply initial angular velocity to all rotating
closure parts about hinge pivot.
Angular velocity based on the hood geometry w(omega)= V / r where :w= hood rotational velocity about the hinge pin
centerlineV = the specified linear velocity (normally
specified at the tip of the front of the hood) r = the distance from the hinge pin center line
to the tip of the hood (m)
Target for Slam Analysis:
Body & Door should provide clearance for Over slam .
The product will meet customer expectations for reliable service under anticipated usage conditions for the useful life of the vehicle.
Typical Hood over travel response curve:
Initial velocity: calculated from height of fall
calculation time: approximately up to 2 ms after reversal point
Time(sec)
Dis
pla
cem
en
t (m
m)
TRANSIENT RESPONSE ANALYSIS (NASTRAN SOL. 129)
Transient response or natural response is the response of a system to a change from equilibrium.
It’s purpose is to identify areas of the hood structure subject to high stress, quantify latch, striker, bumper, and hinge loads, and calculate the structural fatigue damage due to a door impact.
Transient solution Equation Transient solution uses the following equation and
evaluates the structural response with a fixed integration time step (Δt)
[M]* {u"(t)}+ [C]* {u'(t)}+ [K]* {u(t)}= {P(t)} where [M]: Mass matrix, [C]: Damping matrix, [K]: Stiffness matrix, {u"(t)}: Acceleration matrix, {u'(t)}: Velocity matrix, {u(t)}: Displacement matrix, {P(t)}: Applied force matrix, and t: Time The damping matrix [C] =(G/ ω3)* [K] + (1/ ω4) ∑ GE*[KE]
where G: overall structural damping coefficient (PARAM, G) ω3: frequency of interest in radians per unit time (PARAM, ω3) ω4: frequency of interest in radians per unit time (PARAM, ω4), [K]: global stiffness matrix, GE: element structural damping co-efficient [KE]: element stiffness matrix.
Analytical Procedure:
Analytical Procedure:
Analytical Procedure:
Analytical Procedure:
Thank You
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