Drop Test Results: 24.75lb Weight at 1ft Height

In summary, the object has a maximum shear force of 130 psi when dropped from 1 foot. Brandon believes the force produced is lower than this, and is looking for help to verify his calculations.
  • #1
rampage11
6
0
im trying to calculate the drop force of falling object. we do drop test at my work and believe the figures are wrong. we drop a 24.75lb weight from different heigths to check parts . they have it now set that dropping the given weight from 1 ft only produces 24.75 ft/lb force and they add 24.75 for each foot after that. I came up with around 74.86ft/lb at 1 foot. 24.75 seems low at 1 foot. any help is appreciated. brandon
 
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  • #2
rampage11 said:
im trying to calculate the drop force of falling object. we do drop test at my work and believe the figures are wrong. we drop a 24.75lb weight from different heigths to check parts . they have it now set that dropping the given weight from 1 ft only produces 24.75 ft/lb force and they add 24.75 for each foot after that.
Are you sure it's not 24.75 ft-lbs of kinetic energy per foot drop, not force? That would make sense.
 
  • #3
the parts has to hold 130lb of sheer force
 
  • #4
The numbers in the OP don't make any seise to me. The force you apply during the impact depends very much on the deceleration of the mass, as well as the height you drop it from.

For an impact between two stiff and "hard" objects, the maximum impact force could be hundreds or thousands of times the weight of the dropped object.

Aside from that, the unit ft/lb isn't a "force" - maybe you meant ft-lbf, which is the energy of the dropped object, as Doc Al said.
 
  • #5
ft-lbf is what I meant..the part moves about 1/2 inch at impact
 
  • #6
Potential energy then is weight times height.
 
  • #7
130 psi of shear force from drop test is what our prints say
 
  • #8
It is impossible to predict the force (average or peak) during the impact without knowing what material you are dropping the weight onto. I think you said that your specimen deformed a maximum of 1/2 inch during the test? That could be useful information, if we knew the area and thickness of the specimen, and if we knew how elastic the collision is.
 
  • #10
Hey,

Since the object is having sudden impact, the impact force will be more twice the load. The general equation of the impact load is : W+[itex]\sqrt{(W^{2} + 2AWhE/L)}[/itex]

where,
W - weight of the object
A - surface area of impact
L- Length of the body perpendicular to surface of impact
h- height from which body is dropped
E- Modulus of elasticity of the object

Just put in the material and geometrical properties..
So the value comes out to be greater than twice the weight of the body. So 74.86 seems kinda ok. But I don't know the dimensions or the material dropped. So I can't tell.. If you want, just give me the details.. I'll try to work out the values :smile:
 
  • #11
ill have to remeasure it..but I believe its 4'' round stock steel..12'' long dropped from 1 ft increments..weighs 24.73lb
 
  • #12
Is the specimen being dropped onto something "rigid?" Or are you dropping something "rigid" onto the specimen? Your specimen is 4" diameter steel?
 
  • #13
rigid..dropping specimen onto a 5/8 steel rod in 1ft increments
 

1. What is a drop test and why is it performed?

A drop test is an experiment in which an object is dropped from a certain height to assess its impact resistance and durability. It is usually performed to determine the safety and reliability of a product, such as electronic devices or packaging materials.

2. What does the weight and height measurement in the drop test result signify?

In this specific drop test result, the weight of 24.75lbs and the height of 1ft represent the force and distance at which the object was dropped. These measurements are used to calculate the impact energy and determine the level of damage sustained by the object.

3. What is the significance of using a standard weight and height in a drop test?

Using a standard weight and height in a drop test ensures consistency and accuracy in the results. It allows for fair comparison between different objects and helps to establish a baseline for future tests. It also helps to replicate real-life scenarios and determine the impact resistance of a product under similar conditions.

4. How are the drop test results interpreted and analyzed?

The drop test results are interpreted by assessing the level of damage sustained by the object. This can range from no damage to complete destruction. The data is then analyzed to determine the impact energy, which is compared to the object's known impact resistance to determine its durability.

5. What factors can affect the outcome of a drop test?

The outcome of a drop test can be affected by various factors such as the shape, size, and material of the object being dropped, as well as the surface it is dropped on. Other factors include the angle and speed of impact, as well as external conditions such as temperature and humidity.

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