313 Final Report1

8/8/2019 313 Final Report1

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Taking the sum of the forces in the y direction

y

z

R1 R2

L=14 in

P=14.29 lb/in

L/2 L

Shear Force

Diagram

Moment

Diagram

Figure 5: Free Body Diagram of Noseplate in Y-Z Plane with Distributed 400 lb Load

Force equations for the given free body diagram:

100

-100

(6)

(7)

(8)

(9)


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Force Analysis of Critical Components

In most situations, the hand truck is used to carry one heavy box from a delivery truck to the storage

area at Hampshire Dining Commons. In Figures 5 and 6, the loading situation is the most idealized case,

i.e. a 400 pound box situated perfectly in the middle of the noseplate. The noseplates weight is to be

neglected due to the minimal effect it will have in comparison to the weight of the box being carried.

Figure 5 is evaluating the noseplate head-on with the dimension of the front of the plate being 14inches. The distributed load is estimated to be 28.57 lb/in which is a rounded estimate of 400 lbs/ 14

inches. The reactions, R1 and R, are equivalent being found to be 200 lbs each. Using the shear force

diagram, and knowing that the area under the force diagram is equal to the maximum moment of the

moment diagram, the maximum moment is 700 lb*in for this orientation.

Figure 6 is evaluating the noseplate from the side with the dimension of the side of the plate being 10

inches. Since the dimension changed to 10 inches, the distributed load changed to 40 lbs/in or 400 lbs/

10 inches. Given the plate's symmetry, this Figure will be used for each side. Also due to the symmetry,

the reaction, R, and moment, M, will be halved when determining the values for each side. This view

used a cantilever beam approximation in order to calculate all the values because the plate is attached

to the hand truck the same way a cantilever beam is attached to the wall. The reaction was found to be

400 lbs for both (200 for each side) and the maximum moment was found to be 2,000 lb*in (1,000 lb*in

for each side).

Looking at the part, it is clear the moments in the different planes all had an impact in fracture of the

noseplate from the hand truck. As Figures 1 and 2 show, the cantilever part of the noseplate has

completely fractured while the rest of the noseplate is still somewhat connected but visibly cracked.

Given that the greatest moment of the orientations occurs in the X-Y plane as previously stated, it

makes sense that the plates connection was completely fractured this way while only partially fractured

in the Y-Z plane which had a slightly lesser moment.


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Hand Truck DesignForce Analysis Midterm Project Report

By:

Brian Goss, Anthony Carloni, Jimmy McCarthy

Force Analysis Report Prepared for:

University of Massachusetts Amherst

MIE 313 Design of Mechanical Components

Prof. Sundar Krishnamurty


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Table of Contents

Hand Truck Design ................................ ................................ ................................ ................................ ... 5

Table of Contents ................................ ................................ ................................ ................................ .... 6

Abstract ................................ ................................ ................................ ................................ ................... 8

Introduction ................................ ................................ ................................ ................................ ............ 8

Project Objectives: ................................ ................................ ................................ ............................... 8

Plan of Work: ................................ ................................ .......................... Error! Bookmark not defined.

Product Description and Operating Conditions:................................ ................................ .................... 8

Force Model ................................ ................................ ................................ ................................ .......... 11

Force Analysis of Critical Components................................ ................................ ................................ ...... 4

Case I Symmetric Loading ................................ ................................ ..... Error! Bookmark not defined.

Case II Asymmetric Loading ................................ ................................ .. Error! Bookmark not defined.

Future Work: ................................ ................................ .............................. Error! Bookmark not defined.

Conclusion: ................................ ................................ ................................ ................................ ............ 13

Appendix ................................ ................................ ................................ .... Error! Bookmark not defined.


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Abstract

A complete 3-dimensional CAD model was generated for an industrial standard hand truck dol ly. The

failed part was identified at the welded joints that attach the structural steel pipe frame to the

noseplate. A series of force analysis calculations were conducted which show free body, shear, and

bending moment diagrams at the critical elements. Two different cases were investigated in order to

present a clear understanding of the internal forces that caused failure. Along with the two cases, the

group analyzed the force model of the entire assembly in static equilibrium at the instant at which

tipping is initiated, thus subjectingt he joints to the maximum loading conditions. The minimum break

back force required to lift an estimated 400 lb load was found to be 51 lb. The first case looked at an

idealized loading condition of the hand truck, where the equivalent loading force islocated at the center

of the noseplate. The maximum shear and bending moment were calculated for both the front and side

views and was found to be 200 lb and 1000 lb*in at each of the two joints. The second case determined

the internal shear and bending forces under asymmetric loading of the noseplate. Several graphs were

generated in Microsoft Excel which show how these forces interact as the equivalent loading forces

change along the x and y axis of the noseplate.

Introduction

Project Objectives:

The objective of this project is to analyze the Von Mises stresses of the failed components of a heavy

duty hand truck in order to present a new design that seeks to prevent localized failure at the welded

joints while minimizing weight and material usage. From an engineer ing perspective, the process of re-

designing this mechanical system will involve a thorough consideration of material selection, component

geometry, and load configuration. The net cost savings of the redesign can be expected to beXX

amount over the next ___years

Product Description and Operating Conditions:

The hand truck is used to provide a mechanical advantage to its users through its double-welded

structural pipe frame, curved crossbars and 10 inch solid rubber wheels. This specif ic hand truck unit

has a height of 44 inches, an overall width of 19 inches anda frame depth of 21 inches. The

noseplate, which supports the full bulk load, is measured as 10 inches by 14 inches and can hold up to

an estimated 600 pounds, according to the manufacturer Elkay. The metal components of the

handtruck are made from 1030 structural steel that has a yield strength of 32 ksi and a ultimate tensile

stress of 62. Due to its robust wheels and ease of operation, the dolly is a simple and versatile machine

to control. It can be used outside or inside in all types of weather and temperatureconditions.

Comment [SK1]: You forgot to state your

objective of this exercise?


9/24

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10/24

In its current geometry, finite element analysis (FEA) was conducted using ANSYS workbench to identify

a single element that experiences the highest state of stress. It is reasonable to assume that this

element initiated fract ure in the material, which then propagated and ultimately caused component

failure.

A series of tests were conducted in ANSYS that altered the current geometry of the noseplate in various

configurations. Material was removed in areas where stress was negligible and reinforced in areas that

experienced critical localized stresses, such that the net material usage was always maintained at zero.

Using this methodology, different configurations could be compared in order to select the best option

for a robust design with improved performance.


11/24

Point O

Figure 3: Schematic of Upright Hand Truck Subjected to a 400 lb Distributed

Load in Static Equilibrium

From the free body diagram, the force equations are described below,

(1)

2

(3)

Force Model

Comment [SK3]: God!


12/24

The angles and were calculated experimentally and assume values 60 and 25, respectively. These

angles represent the most natural orientation when lifting heavy object with the hand truck and results

in the minimal break-back force F required to initiate tipping. At the instant the hand truck is tipped, the

normal force N of the noseplate is reduced to zero. The weight of the hand truck was measured to be

45 lb and its equivalent force is assumed to be located along the center crossbar aligned directly above

point O. Friction behind the two rubber wheels is considered to be negligible. Furthermore, geometry

symmetry requires that the reaction forces at the wheels are equal in value. In addition, it is assumed

that no translational movement occurs at the moment the hand truck is tipped backward.

The assumptions made simplify the force equation, such that there are three equation and three

unknowns. Through substitution we can simultaneous ly solve for the break-back force F, the reaction

forces R, and the leverage force P. The calculations are shown below:

Solving for P from (1) and substituted into (3),

Combined equation (5) ca n be solved for F,

Plugging this value in equation (4) gives,

Using these values in (2) gives the reaction force:

The obvious advantage here is that for a 200 lb applied load, the hand dolly only requires a 51.0 lb

break-back force in order to tip and transport the load. As the hand truck is increasingly tipped beyond

its vertical position, the bulk load is removed less and less from the welded joints on the noseplate and

is distributed throughout its steel frame, crossbars, and spines. Therefore, it is deduced that the joints

take the maximum load at the instant the hand truck is tipped backward. Because the welded joints at

the noseplate are identified as the sole failed part, further force analysis of the hand truck at various

angles is irrelevant to the redesign and will not be considered in this report.

(4)

(5)


13/24

R

M

M

R

W=200 lb

Figure 4: Model Noseplate with Equivalent Force Occurring at

End of Plate

Force Analysis of Critical Components


14/24

In most situations, the hand truck is used to carry one heavy box from a delivery truck to the storage

area at Hampshire Dining Commons. In Figures 5 and 6, the loading situation is the most idealized case,

i.e. a 400 pound box situated perfectly in the middle of the noseplate. The noseplates weight is to be

neglected due to the minimal effect it will have in comparison to the weight of the box being carried.

Figure 5 is evaluating the noseplate head-on with the dimens ion of the front of the plate being 14

inches. The distributed load is estimated to be 28.57 lb/in which is a rounded estimate of 400 lbs/ 14

inches. The reactions, R1 and R, are equivalent being found to be 200 lbs each. Using the shear force

diagram, and knowing that the area under the force diagram is equal to the maximum moment of the

moment diagram, the maximum moment is 700 lb*in for this orientation.

Figure 6 is evaluating the noseplate from the side with the dimension of the side of the plate being 10

inches. Since the dimension changed to 10 inches, the distributed load changed to 40 lbs/in or 400 lbs/

10 inches. Given the plate's symmetry, this Figure will be used for each side. Also due to the symmetry,the reaction, R, and moment, M, will be halved when determining the values for each side. This view

used a cantilever beam approximation in order to calculate all the values because the plate is attached

to the hand truck the same way a cantilever beam is attached to the wall. The reaction was found tobe

400 lbs for both (200 for each side) and the maximum moment was found to be 2,000 lb*in (1,000 lb*in

for each side).

Looking at the part, it is clear the moments in the different planes all had an impact in fracture of the

noseplate from the hand truck. As Figures 1 and 2 show, the cantilever part of the noseplate has

completely fractured while the rest of the noseplate is still somewhat connected but visibly cracked.

Given that the greatest moment of the orientations occurs in the X-Y plane as previously stated, it

makes sense that the plates connection was completely fractured this way while only partially fractured

in the Y-Z plane which had a slightly lesser moment.


15/24


M

R

L/2 L

Shear Force

Diagram

Moment

Diagram

Figure 6: Free Body Diagram of Noseplate in X-Y Plane with Distributed 400 lb Load

Force Equations for the given free body diagram:

200

-1000

y

(10)

(11)

(12)

(13)

x

L=10 in

P=200 lb


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17/24


y

z

R1 R2

L=14 in

P=14.29 lb/in

L/2 L

Shear Force

Diagram

Moment

Diagram

Figure 5: Free Body Diagram of Noseplate in Y-Z Plane with Distributed 400 lb Load

Force equations for the given free body diagram:

100

-100

(6)

(7)

(8)

(9)


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Modified nose plate with the

leaststress wasthetriangleC

followed bycircleC sD

uareC

and diamond mesh.


23/24

Shape of the hole Max Stress (Psi)

Triangle 6843

Square 9337.5

Circle 7959.8

Diamond mesh 9744.6


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Documents

313 Final Report1