December 10 2013

1

AbstractmdashThis report analyzes the energy absorption of a

simply supported beam struck by a hammer attached to the end

of a large pendulum The acceleration of the hammer was

measured with a MEMs (Micro Electrical Mechanical system)

accelerometer and the position was measured with a Hall Effect

rotary position sensor Voltages from these devices were sent to an

OOTB DAQ device (Out of the Box Data Acquisition) The energy

is calculated using the concepts of potential energy A high speed

camera was used to capture images of the test Those images were

brought into a software program called ImageJ and analyzed

Index TermsmdashOOTB DAQ MEMS accelerometer Hall Effect

rotary position sensor ImageJ

I INTRODUCTION

HIS experiment quantifies the energy absorption of a

simply supported beam relative to its mass The goal of the

experiment was to design and manufacture a beam that would

be able to absorb at least 04 J of energy per gram of mass of

the beam The energy per mass absorbed was calculated using

the angular position of the pendulum arm mass of the

pendulum (including the hammer) and the radius to the center

of mass Angular position and the radius to the center of mass

were used to calculate the difference in height between the

initial position of the pendulum arm and its final positionmdashthe

maximum angle after swinging past vertical Then the

potential energy was found by multiplying the difference in

height by gravity and the mass of the pendulum arm and

hammer combined

II PROCEDURE

Fabrication Procedure

A Cut the balsa wood and foam to size

Cut the three-eighths inch thick balsa wood and the half-inch

thick insulation foam into three-inch by one-inch sectionsmdash

two sections of balsa wood and 5 sections of foam

B Glue the balsa wood insulation foam and aluminum

extrusion together

Adhere the two sections of balsa wood together and then

adhere the balsa wood to the aluminum extrusion using Gorilla

Glue Apply a load on top of the wood or clamp the pieces

together for best results Then adhere three sections of foam to

the front of the balsa wood and one section of foam to each end

of the aluminum extrusion on the face opposite the balsa wood

(This foam will make contact with the supports of the

pendulum) Use Loctite aerosol spray glue to adhere foam

Allow 24 hours for the glue to cure

C Adhere an eight-inch section of half-inch PVC to the

center of the aluminum extrusion

Apply Gorilla glue to the outside of an eight-inch section of

PVC that is thick enough to make contact with all inner faces

of the aluminum extrusion Allow 24 hours for the glue to cure

Test Procedure

A Create a VI

Create a VI that obtains the input voltage through channel 0

and channel 1 of the OOTB DAQ and writes the data to a

spreadsheet Channel 0 is wired to the Hall Effect rotary

position sensor and Channel 1 is wired to the MEMs

accelerometer This data will later be used to analyze the

position and acceleration of the pendulum Use an acquisition

time of ten seconds and a sample rate of 5000Hz A block

diagram of the VI is shown in the Appendix

B Part set up

Load the specimen onto the pendulum supports (The

specimen is simply supported) Lift the pendulum arm to the

release magnet Release the pendulum arm when readymdashabout

five seconds after running the VI

III RESULTS

The mass of our specimen weighed 238 grams prior to

testing The mass of the hammer was 3824 kg and this value

was measured using the mass properties feature in Solidworks

The acceleration and position of the hammer over time are

graphed in Fig 1 The range of this figure is from two to five

seconds with impact occurring between 32358 seconds and

32678 seconds TABLE I

MATERIAL DIMENSIONS

Material Dimensions [inches]

aluminum hollow extrusion 1rdquox1rdquox36rdquo

balsa wood 1rdquox38rdquox3rdquo

PVC pipe inner dia=14rdquo outer

dia=12rdquo length=6rdquo

polystyrene insulation foam 1rdquox12rdquox3rdquo

Gorilla Glue NA

Loctite medium strength spray

adhesive NA

FINAL PROJECT

Diana L Nelson (dnelsonufledu) Luis A Muniz (luismunizufledu)

T

December 10 2013

2

Fig 1 Acceleration and position graphed during the time range of impact

Fig 2 Potential energy over time during impact

Fig 2 is a graph of the potential energy versus time The

initial peak is when the hammer is suspended at maximum

height and the second peak is the final potential energy in the

hammer after impact with the specimen Fig 3 is an image of

the specimen after the impact test

Fig 3 Specimen after impact

IV DISCUSSION

The specimen needed to absorb the most amount of energy

while maintaining a light profile Insulation foam can compress

almost its initial width and has a low density compared to other

stiffer materials Using this foam at the point of impact seemed

most logical since the pressure would be the greatest at that

point Also the bending moment is created by the reaction

forces at the supports against the force of the hammer swinging

into the center of the part creating a large moment We

predicted that adhering foam to the ends of the specimen

adjacent to the supports would absorb more energy as the

entire specimen translated with the hammer for a short

distance We also predicted that the balsa wood could absorb

energy over a shorter distance than the foam because it has

greater strength than the foam but has a low density compared

to most other woods The aluminum extrusion was predicted to

absorb much of the bending moment transferring much of the

stress to the back face which should experience the greatest

tensile stress Aluminumrsquos tensile stress yield point led us to

believe that the extrusion would absorb a great amount of

energy The aluminum extrusion is also light because it is

hollow with thin walls Lastly the PVC was predicted to

support the walls of the extrusion from collapsing at the

midpoint of the specimen therefore it seemed unnecessary to

add weight by supporting the entire specimen with PVC

The specimen absorbed approximately four times the

required energy per mass By utilizing different geometries

such as the one-inch square aluminum extrusion the beam was

able to transfer much of the impact force into tensile stress on

the back face of the specimen increasing its strength Also by

adding foam at the point of impact and the two points of

contact between the pendulum supports and the specimen the

specimen absorbed much of the impact by translating in the

direction of the hammer before bending Once the specimen

began to bend the short piece of PVC inside the aluminum

extrusion added pressure on the inside of the collapsing walls

of the aluminum Since the bending occurs in the center of the

specimen the specimen did not require PVC through its entire

length

An analysis of the results is presented in the remainder of

this section Input variables and calculated variables are

defined in table II

TABLE II

DEFINITION OF VARIABLES AND THEIR UNITS

Symbol Quantity Value (if

constant) Units

V0 channel 0 voltage - V

V1 channel 1 voltage - V

V0t channel 0 tare

voltage 242 V

V1t channel 1 tare voltage

2477 V

Vθ tared channel 0

voltage - V

Va tared channel 1

voltage - V

k

calibration

constant of Hall Effect sensor

568 degV

c

calibration

constant of

accelerometer

008 V(9806 ms2)

g gravitational acceleration 9806 ms2

h height of hammera

- m

L length of

hammerb - m

U potential energy - J

mh mass of hammer 3824 kg

mpart mass of part 238 kg

a acceleration of

hammer - ms2

aWhere the height at 0deg is equal to 0 m bMeasured from axis of rotation to center of mass of hammer

The derivation of the energy absorbed by our part is shown

-100

-50

0

50

100

150

200

2 3 4 5

Acc

ele

rati

on

[m

s^2

) p

osi

tio

n (θ

)

Time (s)

acceleration

position

0

100

200

300

400

500

600

25 3 35 4 45

Po

ten

tial

En

erg

y U

[J]

Time t [s]

December 10 2013

3

in (1) through (5)

Vθ =V0- V0t (1)

(2)

( ( )) (3)

(4)

(5)

Using triangular and parallel geometry we formed an

equation for the height of the hammer (3) using (6) and (7)

below

( )

(6)

(7)

Fig 4 Diagram of the hammer and the geometry used to derive an equation for its height

The acceleration of the hammer was found by multiplying

the voltage read by the accelerometer by a calibration constant

Va =V1- Vt1 (8)

(9)

The uncertainties in the aforementioned variables were

propagated using the following equations

(

)

(

)

(10)

(

)

(

)

(11)

(

)

(

)

(12)

(

)

(

)

(13)

TABLE III

UNCERTAINTIES OF CONSTANTS AND CALCULATED VALUES

Variable Uncertainty Units

V0 plusmn00011 V

V1 plusmn0001 V

V0t plusmn0008 V V1t plusmn0008 V

Vθ plusmn0008 V

Va plusmn0008 V

k plusmn07 degV

c plusmn816E-05 (ms2)V

g 02 ms2

h plusmn0098 m

L plusmn00004 m

U plusmn3679 J mh plusmn000005 kg

mpart plusmn0001 kg

a plusmn00002 ms2 Eabsorbed plusmn01546 Jg

Fig 2 is a plot of the potential energy over time The initial

potential energy was 486 J which was the energy in the

suspended hammer at 106deg The final potential energy was

8318 J and was calculated at the point where maximum height

was reached after impact Maximum height of the hammer was

reached at -38deg

The performance requirement for this project was 04 Jg

According to our calculations our specimen absorbed 169 Jg

which was 013 Jg greater than the measured value on testing

day Our propagated uncertainty for Eabsorbed was plusmn01546 Jg

so this difference falls within the measurement of uncertainty

Fig 5 Acceleration over time during impact and just after impact

Fig 5 is a graph of the acceleration of the hammer during the

time period that the specimen was being impacted Each

-100

-50

0

50

100

150

200

322 324 326 328Acc

ele

rati

on

(m

s^2

)

Time (s)

A

B C

D

E

F

G

December 10 2013

4

labeled part of the graph represents the period in time where

different materials were the primary source of deceleration To

confirm when these events occurred the images were analyzed

frame-by-frame in ImageJ Knowing that the frame rate was

0002 seconds we were able calculate how much time elapsed

while the different components went from no strain to

maximum strain

Fig 6 Top left Initial impact t=0s Top right Foam absorbs energy before specimen deflects t=0010s Middle left Wood absorbs energy specimen

begins to deflect t=0014s Middle Right Specimen deflects absorbing energy

t=0030s Bottom Left Specimen slips from supports t=0038s Bottom Right Part no longer in contact with hammer and no longer absorbing energy from

the hammer

Fig 6 is a compilation of images taken by the high speed

camera during testing that highlight the events of impact that

are labeled in Fig 5

Section A of Fig 5 is just before impact when the hammer is

swinging downward with a constant acceleration due to

gravity Section B is during initial impact when the hammer is

being decelerated by the foam and is shown in the top right

image of Fig 6 During this time the foam on the back of the

part is also compressing against the supports The foam used

was polystyrene blue board which is easily compressible As a

result the slope in section B is constant because rather than the

foam experiencing a brittle break it is gradually compressed at

a constant rate Also the slope in section B is smaller than that

of subsequent sections due to foamrsquos low stiffness and strength

properties

There is an increase in slope at section C of Fig 5 which is

the time range that the hammer reached the wood and was

being decelerated at a high rate The middle left image of Fig

6 displays this moment in time Since wood is much stiffer

than foam it is able to slow the hammer down faster However

woodrsquos ductility is low relative to the other materials that the

specimen was composed of so the wood fractured during

impact The wood was also oriented with the grains lined up

parallel to the face of the hammer which contributed to it

failing in line with the grains Both the foam and wood

experienced shear failure which can be seen in Fig 7 Even

though the wood fractured it still remained attached to the

specimen through the duration of impact which helped in

absorbing energy

The peak of the curve is the point of maximum deceleration

During time periods D and E the aluminum bar and PVC pipe

were deforming Since the PVC pipe was inside of the

aluminum bar it was difficult to make any conclusions using

ImageJ about the PVC pipe Based on the slope of the line in

this region of Fig 5 we hypothesized that section D was where

the aluminum and PVC were initially deforming possibly prior

to reaching their respective yield points From Fig 5 one can

see that the graph levels off at section E and the rate of

deceleration of the hammer decreases because the slope

decreases We suspect that this is when the PVC was

plastically deforming

Point F of Fig 5 is the point in time when the specimen

slipped out of the supports After this event occurred the

hammer then decelerated at a constant rate until it returned to

gravitational acceleration

Fig 7 Left front impact zone in direct contact with hammer Right rear

impact zone on the side that slipped out of supports

Fig 7 contains images of the impact zones after testing As

mentioned previously the second layer of foam on top of the

aluminum experienced shear failure while remaining intact on

the specimen This allowed for the stresses to be more evenly

distributed across the aluminum Rather than having one stress

concentration at the center there were three stress

concentrations (one from hammer and two from the edges of

the wood) Consequently the aluminum deformed across a

wider area and the part was able to remain in the supports for a

longer period of time until slipping out The right image in Fig

7 is one of the ends of the beam where the foam was being

compressed between the aluminum beam and the support The

foam failed in shear as you can see from the right image in Fig

7

V CONCLUSION

The specimen absorbed approximately four times the

required energy per mass The specimen was able to bend

t=0s t=0010s

t=0014s t=0030s

t=0038s no contact

December 10 2013

5

because the walls of the aluminum extrusion collapsed and the

PVC supporting these walls also caved in The specimen could

have absorbed more energy by reinforcing the PVC with a

metal rod where the specimen was expected to bend By using

only a two inch hollow aluminum rod inside the center of the

PVC the bending area would prove much stiffer without

adding much weight Adding stiff materials for short lengths

proved stronger than weaker lighter materials throughout the

length of the specimen Anticipating the area at which the

specimen would bend and the points of concentrated force (the

impact zone and the support contacts) allowed us to strengthen

small portions of the specimen with small pieces of heavier

materials Another simple improvement is to lengthen the

specimen part so that it does not slip before absorbing all the

energy possible This would also allow more foam to be in

contact with the supports therefore absorbing more energy

initially

December 10 2013

6

APPENDIX

VI used to collect voltage readings from the MEMs accelerometer and Hall Effect rotary sensor

December 10 2013

7

REFERENCES

[1] DL Nelson ldquoLab 1B ndash Dynamic Data Acquisition Uncertainty amp

Strain Gaugesrdquo unpublished

[2] The NIST Reference on Constants Units and Uncertainty

ldquohttpphysicsnistgovcgi-bincuuValuegn|search_for=gravityrdquo [3] JK Author ldquoEML3301C ndashMechanics of Material Laboratory-Final

Projectrdquo unpublished

December 10 2013

3

in (1) through (5)

Vθ =V0- V0t (1)

(2)

( ( )) (3)

(4)

(5)

Using triangular and parallel geometry we formed an

equation for the height of the hammer (3) using (6) and (7)

below

( )

(6)

(7)

Fig 4 Diagram of the hammer and the geometry used to derive an equation for its height

The acceleration of the hammer was found by multiplying

the voltage read by the accelerometer by a calibration constant

Va =V1- Vt1 (8)

(9)

The uncertainties in the aforementioned variables were

propagated using the following equations

(

)

(

)

(10)

(

)

(

)

(11)

(

)

(

)

(12)

(

)

(

)

(13)

TABLE III

UNCERTAINTIES OF CONSTANTS AND CALCULATED VALUES

Variable Uncertainty Units

V0 plusmn00011 V

V1 plusmn0001 V

V0t plusmn0008 V V1t plusmn0008 V

Vθ plusmn0008 V

Va plusmn0008 V

k plusmn07 degV

c plusmn816E-05 (ms2)V

g 02 ms2

h plusmn0098 m

L plusmn00004 m

U plusmn3679 J mh plusmn000005 kg

mpart plusmn0001 kg

a plusmn00002 ms2 Eabsorbed plusmn01546 Jg

Fig 2 is a plot of the potential energy over time The initial

potential energy was 486 J which was the energy in the

suspended hammer at 106deg The final potential energy was

8318 J and was calculated at the point where maximum height

was reached after impact Maximum height of the hammer was

reached at -38deg

The performance requirement for this project was 04 Jg

According to our calculations our specimen absorbed 169 Jg

which was 013 Jg greater than the measured value on testing

day Our propagated uncertainty for Eabsorbed was plusmn01546 Jg

so this difference falls within the measurement of uncertainty

Fig 5 Acceleration over time during impact and just after impact

Fig 5 is a graph of the acceleration of the hammer during the

time period that the specimen was being impacted Each

-100

-50

0

50

100

150

200

322 324 326 328Acc

ele

rati

on

(m

s^2

)

Time (s)

A

B C

D

E

F

G

December 10 2013

4

labeled part of the graph represents the period in time where

different materials were the primary source of deceleration To

confirm when these events occurred the images were analyzed

frame-by-frame in ImageJ Knowing that the frame rate was

0002 seconds we were able calculate how much time elapsed

while the different components went from no strain to

maximum strain

Fig 6 Top left Initial impact t=0s Top right Foam absorbs energy before specimen deflects t=0010s Middle left Wood absorbs energy specimen

begins to deflect t=0014s Middle Right Specimen deflects absorbing energy

t=0030s Bottom Left Specimen slips from supports t=0038s Bottom Right Part no longer in contact with hammer and no longer absorbing energy from

the hammer

Fig 6 is a compilation of images taken by the high speed

camera during testing that highlight the events of impact that

are labeled in Fig 5

Section A of Fig 5 is just before impact when the hammer is

swinging downward with a constant acceleration due to

gravity Section B is during initial impact when the hammer is

being decelerated by the foam and is shown in the top right

image of Fig 6 During this time the foam on the back of the

part is also compressing against the supports The foam used

was polystyrene blue board which is easily compressible As a

result the slope in section B is constant because rather than the

foam experiencing a brittle break it is gradually compressed at

a constant rate Also the slope in section B is smaller than that

of subsequent sections due to foamrsquos low stiffness and strength

properties

There is an increase in slope at section C of Fig 5 which is

the time range that the hammer reached the wood and was

being decelerated at a high rate The middle left image of Fig

6 displays this moment in time Since wood is much stiffer

than foam it is able to slow the hammer down faster However

woodrsquos ductility is low relative to the other materials that the

specimen was composed of so the wood fractured during

impact The wood was also oriented with the grains lined up

parallel to the face of the hammer which contributed to it

failing in line with the grains Both the foam and wood

experienced shear failure which can be seen in Fig 7 Even

though the wood fractured it still remained attached to the

specimen through the duration of impact which helped in

absorbing energy

The peak of the curve is the point of maximum deceleration

During time periods D and E the aluminum bar and PVC pipe

were deforming Since the PVC pipe was inside of the

aluminum bar it was difficult to make any conclusions using

ImageJ about the PVC pipe Based on the slope of the line in

this region of Fig 5 we hypothesized that section D was where

the aluminum and PVC were initially deforming possibly prior

to reaching their respective yield points From Fig 5 one can

see that the graph levels off at section E and the rate of

deceleration of the hammer decreases because the slope

decreases We suspect that this is when the PVC was

plastically deforming

Point F of Fig 5 is the point in time when the specimen

slipped out of the supports After this event occurred the

hammer then decelerated at a constant rate until it returned to

gravitational acceleration

Fig 7 Left front impact zone in direct contact with hammer Right rear

impact zone on the side that slipped out of supports

Fig 7 contains images of the impact zones after testing As

mentioned previously the second layer of foam on top of the

aluminum experienced shear failure while remaining intact on

the specimen This allowed for the stresses to be more evenly

distributed across the aluminum Rather than having one stress

concentration at the center there were three stress

concentrations (one from hammer and two from the edges of

the wood) Consequently the aluminum deformed across a

wider area and the part was able to remain in the supports for a

longer period of time until slipping out The right image in Fig

7 is one of the ends of the beam where the foam was being

compressed between the aluminum beam and the support The

foam failed in shear as you can see from the right image in Fig

7

V CONCLUSION

The specimen absorbed approximately four times the

required energy per mass The specimen was able to bend

t=0s t=0010s

t=0014s t=0030s

t=0038s no contact

December 10 2013

5

because the walls of the aluminum extrusion collapsed and the

PVC supporting these walls also caved in The specimen could

have absorbed more energy by reinforcing the PVC with a

metal rod where the specimen was expected to bend By using

only a two inch hollow aluminum rod inside the center of the

PVC the bending area would prove much stiffer without

adding much weight Adding stiff materials for short lengths

proved stronger than weaker lighter materials throughout the

length of the specimen Anticipating the area at which the

specimen would bend and the points of concentrated force (the

impact zone and the support contacts) allowed us to strengthen

small portions of the specimen with small pieces of heavier

materials Another simple improvement is to lengthen the

specimen part so that it does not slip before absorbing all the

energy possible This would also allow more foam to be in

contact with the supports therefore absorbing more energy

initially

December 10 2013

6

APPENDIX

VI used to collect voltage readings from the MEMs accelerometer and Hall Effect rotary sensor

December 10 2013

7

REFERENCES

[1] DL Nelson ldquoLab 1B ndash Dynamic Data Acquisition Uncertainty amp

Strain Gaugesrdquo unpublished

[2] The NIST Reference on Constants Units and Uncertainty

ldquohttpphysicsnistgovcgi-bincuuValuegn|search_for=gravityrdquo [3] JK Author ldquoEML3301C ndashMechanics of Material Laboratory-Final

Projectrdquo unpublished

December 10 2013

4

labeled part of the graph represents the period in time where

different materials were the primary source of deceleration To

confirm when these events occurred the images were analyzed

frame-by-frame in ImageJ Knowing that the frame rate was

0002 seconds we were able calculate how much time elapsed

while the different components went from no strain to

maximum strain

Fig 6 Top left Initial impact t=0s Top right Foam absorbs energy before specimen deflects t=0010s Middle left Wood absorbs energy specimen

begins to deflect t=0014s Middle Right Specimen deflects absorbing energy

t=0030s Bottom Left Specimen slips from supports t=0038s Bottom Right Part no longer in contact with hammer and no longer absorbing energy from

the hammer

Fig 6 is a compilation of images taken by the high speed

camera during testing that highlight the events of impact that

are labeled in Fig 5

Section A of Fig 5 is just before impact when the hammer is

swinging downward with a constant acceleration due to

gravity Section B is during initial impact when the hammer is

being decelerated by the foam and is shown in the top right

image of Fig 6 During this time the foam on the back of the

part is also compressing against the supports The foam used

was polystyrene blue board which is easily compressible As a

result the slope in section B is constant because rather than the

foam experiencing a brittle break it is gradually compressed at

a constant rate Also the slope in section B is smaller than that

of subsequent sections due to foamrsquos low stiffness and strength

properties

There is an increase in slope at section C of Fig 5 which is

the time range that the hammer reached the wood and was

being decelerated at a high rate The middle left image of Fig

6 displays this moment in time Since wood is much stiffer

than foam it is able to slow the hammer down faster However

woodrsquos ductility is low relative to the other materials that the

specimen was composed of so the wood fractured during

impact The wood was also oriented with the grains lined up

parallel to the face of the hammer which contributed to it

failing in line with the grains Both the foam and wood

experienced shear failure which can be seen in Fig 7 Even

though the wood fractured it still remained attached to the

specimen through the duration of impact which helped in

absorbing energy

The peak of the curve is the point of maximum deceleration

During time periods D and E the aluminum bar and PVC pipe

were deforming Since the PVC pipe was inside of the

aluminum bar it was difficult to make any conclusions using

ImageJ about the PVC pipe Based on the slope of the line in

this region of Fig 5 we hypothesized that section D was where

the aluminum and PVC were initially deforming possibly prior

to reaching their respective yield points From Fig 5 one can

see that the graph levels off at section E and the rate of

deceleration of the hammer decreases because the slope

decreases We suspect that this is when the PVC was

plastically deforming

Point F of Fig 5 is the point in time when the specimen

slipped out of the supports After this event occurred the

hammer then decelerated at a constant rate until it returned to

gravitational acceleration

Fig 7 Left front impact zone in direct contact with hammer Right rear

impact zone on the side that slipped out of supports

Fig 7 contains images of the impact zones after testing As

mentioned previously the second layer of foam on top of the

aluminum experienced shear failure while remaining intact on

the specimen This allowed for the stresses to be more evenly

distributed across the aluminum Rather than having one stress

concentration at the center there were three stress

concentrations (one from hammer and two from the edges of

the wood) Consequently the aluminum deformed across a

wider area and the part was able to remain in the supports for a

longer period of time until slipping out The right image in Fig

7 is one of the ends of the beam where the foam was being

compressed between the aluminum beam and the support The

foam failed in shear as you can see from the right image in Fig

7

V CONCLUSION

The specimen absorbed approximately four times the

required energy per mass The specimen was able to bend

t=0s t=0010s

t=0014s t=0030s

t=0038s no contact

December 10 2013

5

because the walls of the aluminum extrusion collapsed and the

PVC supporting these walls also caved in The specimen could

have absorbed more energy by reinforcing the PVC with a

metal rod where the specimen was expected to bend By using

only a two inch hollow aluminum rod inside the center of the

PVC the bending area would prove much stiffer without

adding much weight Adding stiff materials for short lengths

proved stronger than weaker lighter materials throughout the

length of the specimen Anticipating the area at which the

specimen would bend and the points of concentrated force (the

impact zone and the support contacts) allowed us to strengthen

small portions of the specimen with small pieces of heavier

materials Another simple improvement is to lengthen the

specimen part so that it does not slip before absorbing all the

energy possible This would also allow more foam to be in

contact with the supports therefore absorbing more energy

initially

December 10 2013

6

APPENDIX

VI used to collect voltage readings from the MEMs accelerometer and Hall Effect rotary sensor

December 10 2013

7

REFERENCES

[1] DL Nelson ldquoLab 1B ndash Dynamic Data Acquisition Uncertainty amp

Strain Gaugesrdquo unpublished

[2] The NIST Reference on Constants Units and Uncertainty

ldquohttpphysicsnistgovcgi-bincuuValuegn|search_for=gravityrdquo [3] JK Author ldquoEML3301C ndashMechanics of Material Laboratory-Final

Projectrdquo unpublished

December 10 2013

5

because the walls of the aluminum extrusion collapsed and the

PVC supporting these walls also caved in The specimen could

have absorbed more energy by reinforcing the PVC with a

metal rod where the specimen was expected to bend By using

only a two inch hollow aluminum rod inside the center of the

PVC the bending area would prove much stiffer without

adding much weight Adding stiff materials for short lengths

proved stronger than weaker lighter materials throughout the

length of the specimen Anticipating the area at which the

specimen would bend and the points of concentrated force (the

impact zone and the support contacts) allowed us to strengthen

small portions of the specimen with small pieces of heavier

materials Another simple improvement is to lengthen the

specimen part so that it does not slip before absorbing all the

energy possible This would also allow more foam to be in

contact with the supports therefore absorbing more energy

initially

December 10 2013

6

APPENDIX

VI used to collect voltage readings from the MEMs accelerometer and Hall Effect rotary sensor

December 10 2013

7

REFERENCES

[1] DL Nelson ldquoLab 1B ndash Dynamic Data Acquisition Uncertainty amp

Strain Gaugesrdquo unpublished

[2] The NIST Reference on Constants Units and Uncertainty

ldquohttpphysicsnistgovcgi-bincuuValuegn|search_for=gravityrdquo [3] JK Author ldquoEML3301C ndashMechanics of Material Laboratory-Final

Projectrdquo unpublished

December 10 2013

6

APPENDIX

VI used to collect voltage readings from the MEMs accelerometer and Hall Effect rotary sensor

December 10 2013

7

REFERENCES

[1] DL Nelson ldquoLab 1B ndash Dynamic Data Acquisition Uncertainty amp

Strain Gaugesrdquo unpublished

[2] The NIST Reference on Constants Units and Uncertainty

ldquohttpphysicsnistgovcgi-bincuuValuegn|search_for=gravityrdquo [3] JK Author ldquoEML3301C ndashMechanics of Material Laboratory-Final

Projectrdquo unpublished

December 10 2013

7

REFERENCES

[1] DL Nelson ldquoLab 1B ndash Dynamic Data Acquisition Uncertainty amp

Strain Gaugesrdquo unpublished

[2] The NIST Reference on Constants Units and Uncertainty

ldquohttpphysicsnistgovcgi-bincuuValuegn|search_for=gravityrdquo [3] JK Author ldquoEML3301C ndashMechanics of Material Laboratory-Final

Projectrdquo unpublished