Design Of Test Rig For Bending And Torsion Of Vehicle Structure.
DESIGN OF TEST RIG FOR BENDING AND TORSION OF VEHICLE STRUCTURE
MUHAMAD ARIF FAHMI BIN ABDUL WAHAB
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‘I/We* admit that I/we* have read this dissertation and in my/our* opinion this dissertation is satisfactory in the aspect of scope and quality for the bestowal of
Bachelor of Mechanical Engineering (Automotive)
Signature : ……….
Supervisor Name (I) : Mr. Ahmad Bin Rivai
Date : ……….
Signature : ……….
Supervisor Name (II) : Prof. Dr. Md. Radzai Bin Said
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DESIGN OF TEST RIG FOR BENDING AND TORSION ON VEHICLE STRUCTURE
MUHAMAD ARIF FAHMI BIN ABDUL WAHAB
This report was submitted in accordance with the partial requirements for the honor of Bachelor of Mechanical Engineering (Automotive)
Faculty of Mechanical Engineering Universiti Teknikal Malaysia Melaka
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“I verify that this report is my own word except summary and extract that every one of it I have clarify the resource”
Signature : ...
Author’s Name : Muhamad Arif Fahmi Bin Abdul Wahab
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iii
Dedicated
To my beloved Mum and Dad,
To my respectful Supervisor,
To my honorable Lecturers,
&
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ACKNOWLEDGEMENT
The writer would like to say thanks to writer Supervisor, Mr. Ahmad Rivai for his guidance and supports on writer during the Projek Sarjana Muda’s completion period.
The co-operation given by the laboratory management especially the technicians that involve in helping the completion of writer project are appreciated.
Acknowledgement is also dedicated to all people and personnel who whether directly or indirectly involved in completing this project. Hope this report will be a reference for other student in the future.
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v
ABSTRACT
Test Rig for bending and torsion on vehicle structure was used to measure the deformation of the structure and measuring the loads produce on all tires during bending and torsion case. In designing this test rig, the total loads from the vehicle structure have been identified under bending and torsion case. The test rig function to produce the torsion and bending case and the loads is measured by using the load cell. The test rig is attached to the vehicle structure using a universal vehicle-test rig attachment. Finite element method is used to validate the design whether it is strong enough or not. If not, then the several researches will be done to repairing the design.
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ABSTRAK
Rig ujian bagi kilasan dan lenturan terhadap struktur kenderaan in digunakan atas tujuan untuk mengukur herotan yang terhasil pada struktur, dan juga untuk mengukur daya yang bertindak pada kesemua tayar semasa keadaan lenturan dan kilasan pada struktur kenderaan. Dalam merekabentuk rig ujian ini, keseluruhan daya yang terhasil dari struktur kenderaan semasa kilasan dan lenturan perlulah dikenalpasti. Rig ujian ini berfungsi dalam mewujudkan keadaan lenturan dan kilasan selain daya yang bertindak semasa keadaan-keadaan tersebut diukur menggunakan ‘load cell’. Rig ujian ini akan disambungkan pada struktur kenderaan melalui penyambung universal struktur kenderaan-rig ujian. Setelah siap rekabentuk terakhir bagi rig ujian ini, Kaedah Unsur Terhingga digunakan untuk memastikan bahawa rig ujian ini selamat digunakan atau tidak. Jika rig ujian ini tidak selamat digunakan, beberapa kajian tambahan akan dilakukan bagi memperbaiki rekabentuk sedia ada.
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vii
TABLE OF CONTENT
CHAPTER TOPIC
CONFESSION DEDICATION
ACKNOWLEDGEMENT ABSTRACT
ABSTRAK
TABLE OF CONTENT LIST OF TABLES LIST OF FIGURES LIST OF SYMBOLS LIST OF APPENDICES
PAGE ii iii iv v vi vii x xi xv xvi
CHAPTER 1 INTRODUCTION
1.1 Background 1.2 Problem Statement 1.3 Objectives
1.4 Scope
1 1 2 2
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CHAPTER TOPIC PAGE CHAPTER 2 LITERATURE REVIEW
2.1 Background
2.2 Principle of Design and Stress Analysis
2.2.1 Material 2.2.2 Stress
2.2.3 Design Factors 2.2.4 Buckling
2.2.5 Finite Element Method 2.3 Torsion & Bending on Vehicle
Structure
2.3.1 Bending Case 2.3.2 Torsion Case 2.4 Test Configuration
2.4.1 Static Bending Test 2.4.2 Static Torsion Test 2.5 Test Rig Design
2.5.1 Previous Design
2.5.2 Test Rig-Vehicle Attachment
3 3 4 4 6 7 10 12 12 14 15 17 17 19 19 22
CHAPTER 3 METHODOLOGY
3.1 Methodology Planning 3.2 Project Workflow 3.3 Design Specification 3.4 Design Selection
3.4.1 Test Rig Frame Structure 3.4.2 Test Rig Additional
Structure
3.4.3 Load Measurement Device 3.4.4 Test rig-Vehicle Attachment 3.5 Geometrical Dimension
24 25 26 27 27 29 32 34 38
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ix
CHAPTER TOPIC
3.6 Material Selection 3.7 Strength Calculation 3.8 Finite Element Analysis 3.8.1 Individual Analysis 3.8.2 Test Rig Frame Analysis
PAGE 40 41 47 47 49
CHAPTER 4 RESULT & DISCUSSION 4.1 Final Design
4.2 Finite Element Analysis Result
51 58
CHAPTER 5 CONCLUSION & SUGGESTION 5.1 Background
5.2 Conclusion 5.3 Suggestion
67 67 68
REFERENCES APPENDICES
70 72
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LIST OF TABLES
NO. TITLE PAGE
2.2.0
2.2.1
2.2.2
3.4.0
3.4.1
3.8.2
Guidelines on choosing design factor for ductile material
(Source: Robert L. Mott (2004))
Guidelines on choosing design factor for brittle material
(Source: Robert L. Mott (2004))
Values of K for effective length, Le = KL, for
different end connections (Source: Robert L. Mott (2004))
Advantages and Disadvantages of each height adjuster type
Data of vehicles dimensions and weights
Points coordinate for bar element of the test rig
7
7
8
31
38
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xi
LIST OF FIGURES
NO. TITLE PAGE
2.2.0 2.2.1 2.3.0 2.3.1 2.3.2 2.4.0 2.4.1 2.4.2 2.5.0 2.5.1 2.5.2
Cutting element or pieces structure (Source: Ahmad Rivai (2007))
Example of finite element on structure (Source: Ahmad Rivai (2007))
Vehicle Bending Case
(Source: Robertson John (2002))
Typical passenger vehicle bending loads (Source: Robertson John (2002))
Vehicle Torsion Case
(Source: Robertson John (2002))
Vehicle Structure with Bonded / Bolted Parts (Source: Porsche Engineering Services, Inc.) Vehicle Structure on Test Rig for Static Bending (Source: Porsche Engineering Services, Inc.) Vehicle Structure on Test Rig for Static Torsion (Source: Porsche Engineering Services, Inc.) Test Rig for Static Bending
(Source: Porsche Engineering Services, Inc.) Test Rig for Static Torsion
(Source: Porsche Engineering Services, Inc.) UTM 1998 test rig design without front & rear body attachment column
(Source: Zakariah, A.M (1998))
10 11 12 13 14 15 17 19 20 20 21
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NO. 2.5.3 2.5.4(a) 2.5.4(b) 2.5.4(c) 3.2.0 3.4.0 3.4.1 3.4.2 3.4.3 3.4.4(a) 3.4.4(b) 3.4.4(c) 3.4.4(d) 3.4.5 3.4.6 3.4.7 3.4.8(a) TITLE
Strut Mount Designs
(Source: Monroe Shocks & Struts (2008)) Inner Plate Design
(Source: Monroe Shocks & Struts (2008)) Centre Sleeve Design
(Source: Monroe Shocks & Struts (2008)) Spacer Bushing Design
(Source: Monroe Shocks & Struts (2008)) Project Workflow and Methodology Front view of x-direction adjustable link attachment between left side and right side for front and rear frames
Isometric view of z-direction adjustable link between front and rear frame with support structure on all links
Example diagram of creating Bending case on vehicle structure
Example diagram of creating Torsion case on vehicle structure
Changeable column with various height Fixed column with scissor jack
Fixed column with worm/helical gear jack Fixed column with hydraulic jack
Total load direction to load measurement device Position Load Measurement Device on the test rig Example of Compression and tension Load cell; Pancake-type and S-type
(Source: Puls Elektronik Sistemleri Ltd. (2008)) BMW 3 series E46 1998 same rear and front suspension system as BMW 3 series E36 1997 (Source: Reimpell, J et al. (2001))
PAGE 23 23 23 23 25 28 28 29 30 30 30 31 31 33 33 34 35
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xiii NO. 3.4.8(b) 3.4.8(c) 3.4.9(a) 3.4.9(b) 4.1.0(a) 4.1.0(b) 4.1.0(c) 4.1.0(d) 4.1.0(e) 4.1.0(f) 4.1.0(g) 4.1.0(h) 4.1.1 4.2.0(a) 4.2.0(b) 4.2.0(c) 4.2.0(d) 4.2.0(e) 4.2.0(f) 4.2.0(g) 4.2.0(h) 4.2.0(i) 4.2.0(j) 4.2.0(k) TITLE
Example of front axle Mc-Pherson strut for Lancia Delta and BMW Roadster Z3)
(Source: Reimpell, J et al. (2001)) BMW 3series (1997) Multi link rear axle suspension type
(Source: Reimpell, J et al. (2001))
Top view of rear body attachment and the position of rear body attachment on test rig column
Side view of front vehicle-test rig attachment part Front/Left frame
Front/Right frame Rear/Right frame Rear/Left frame
Front connector (ball joint base) Rear Connector
Front/Left additional column Test rig assembly
Load cell reference drawing
(Source: FUTEK Adv Sensor Tech. Inc. (2008)) FEA result for column (Stress Tensor)
FEA result for column (Displacement) FEA result for column (Eigenvectors)
FEA result for front connector (Stress Tensor) FEA result for front connector (Stress Tensor) FEA result for front connector (Displacement) FEA result for rear connector (Stress Tensor) FEA result for rear connector (Displacement) FEA result for test rig frame (Von Misses Axial) FEA result for test rig frame (Displacement) FEA result for test rig frame (Eigenvectors)
PAGE 35 36 36 37 53 53 54 54 55 55 56 56 57 58 59 59 60 60 61 62 62 63 64 64
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NO. 4.2.0(l)
4.2.0(m)
4.2.0(n)
TITLE
FEA result for test rig frame – torsion load (Von Mises Axial)
FEA result for test rig frame – torsion load (Deformation)
FEA result for test rig frame – torsion load (Eigenvectors)
PAGE 65
66
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xv
LIST OF SYMBOLS
F A τmax T J c r I Le K Cc E N σy Pcr Pa P Mzs
M zns
RF RR L LF LR MB σB = = = = = = = = = = = = = = = = = = = = = = = = = =
Force, kgm/s2 (N) Area, m2
Shear stress, N/m2 (Pa) Torque, Nm
Polar moment of inertia, m4
Radius of the shaft to its outside surface, mm Radius of gyration, mm
Moment of inertia of the cross section, m4 Effective length, mm
Constant dependent on the end fixity Column constant
Modulus of elasticity / Modulus young, N/m2 (Pa) Safety factor
Yield strength, N/m2 (Pa) Critical load, kgm/s2 (N) Allowable load, kgm/s2 (N) Actual applied load, kgm/s2 (N) Dynamic load factor in bending Dynamic load factor in torsion Load on front axle, kgm/s2 (N) Load on rear axle, kgm/s2 (N) Wheelbase, mm
Distance from centre of gravity to front axle, mm Distance from centre of gravity to rear axle, mm Bending moment, Nm
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LIST OF APPENDICES
NO. TITLE PAGE
A B C D
Working Plan for PSM 1 Working Plan for PSM 2
Ali Marzuki Zakariah Test Rig Design Test Rig Assembly Design
72 73 74 75
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1
CHAPTER 1
INTRODUCTION
1.1 Background
Test Rig for bending and torsion on vehicle structure has been widely used by automotive car manufacturers and researchers to measure the vehicle strength and stiffness on a static bending and static torsion case of the vehicle structure. By using that rig, an artificial situation of bending and torsion can be produced. Moreover, the load and the stiffness of the vehicle can be measured for static bending and static torsion condition. Most of researcher and automotive manufacturer will then measure the stiffness of the vehicle structure on bending condition and torsion condition. By then, based on the result, the car manufacture or the researchers will estimate the vehicle stiffness and modification on the vehicle structure design will be done if needed.
1.2 Problem Statement
In Universiti Teknikal Malaysia Melaka, the learning process for subject Vehicle Structure Analysis on Torsion and Bending has been done theoretically. It is because, currently, there is no such laboratory equipment to conduct a test for bending and torsion on vehicle structure. So, in a short term period, there is a need for student to design and develop such equipment to help faculty on providing the laboratory equipment (specifically; test rig) to support laboratory use for testing the
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bending and torsion on vehicle structure to increase the students (specifically; Automotive’s student) understanding on that matter.
1.3 Objective
This thesis is done to design and analyze a test rig for measuring torsion and bending on vehicle structure.
1.4 Scopes
- Understanding on principal of bending and torsion on vehicle structure - Study of structural design and analysis
- Design of test rig; design selection, geometrical dimension, material selection, strength calculation and solid modeling
- Strength analysis on test rig solid model using Finite Element Method - Report writing and documentation
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3
CHAPTER 2
LITERATURE REVIEW
2.1 Background
In designing the test rig for bending and torsion, it is needed to understand the related principle of design and stress analysis. Moreover, the test configuration and previous test rig design must be studied so that the suitable test rigs design, which fulfills the criteria and requirement of the test configuration, can be created.
2.2 Principle of Design and Stress Analysis
In designing the test rig, the specifications of the test rig such as functions, design requirements and evaluation criteria must be defined clearly. According Mott (2004), functions tell what the device must do, using general, non-quantitative statements that employ action phrases such as to support a load, to lift a crate, to transmit power or to hold two structural members together. Moreover he said, design requirements are detailed, usually quantitative statements of expected performance levels, environmental conditions in which the device must operate limitations on space or weight or available materials and components that may be used. Whereas, evaluation criteria are the statements of desirable qualitative characteristics of a design that assist the designer in deciding which alternative design is optimum- that is, the design that maximizes benefits while minimizing disadvantages.
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To start a design on the test rig, a lot of factors must be taken into consideration. Mott (2004) has summarized some factors to be taken into consideration, which as listed below:
- Forces exerted by the components of the machine through mounting points such as bearings, pivots, brackets, and feet of other machine elements
- Manner of support of the frame itself
- Precision of the system: allowable deflection of components - Environment in which the unit will operate
- Quantity of production and facilities available
- Availability of analytical tools such as computerized stress analysis, past- experience with similar products, and experimental stress analysis
- Relationship to other machines, walls and so on
2.2.1 Material
Selection of material has a high effect on the structure strength. The most significant factor to evaluate the material strength is by referring to the yield strength, σy and the modulus of elasticity, E of the material. Mott (2004) stated that,
yield strength can be defined as the portion of the stress-strain diagram where there is a large increase in strain with little or no increase in stress. He also stated that modulus of elasticity can be define as stress proportionality to strain when the part of the stress-strain diagram is straight. Modulus of elasticity indicates the stiffness of the material or its resistance to deformation.
2.2.2 Stress
Based on Mott (2004), there are three basic fundamental kinds of stress; tensile, compressive and shear. Tensile and compressive stress, called normal stresses, are shown acting perpendicular to opposite faces of the stress element. Tensile stresses tend to pull on the element whereas compressive stresses tend to
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5
crush it. Shear stresses are created by direct shear, vertical shear in beams or torsion. In each case, the action on an element subjected to shear is a tendency to cut the element by exerting a stress downward on one face while simultaneously exerting a stress upward on the opposite, parallel face. Stress can be defined as the internal resistance offered by a unit area of a material to an externally applied load.
σ = force/area = F/A
When a torque or twisting moment is applied to a member, it tends to deform by twisting, causing a rotation of one part of the member relative to another. Such twisting causes a shear stress in the member. For a small element of the member, the nature of the stress is the same as that experienced under direct shear stress. However, in torsional shear, the distribution of stress is not uniform across the cross section (Mott (2004)). When subjected to a torque, the outer surface of a solid round shaft experiences the greatest sharing strain and therefore the largest torsional shear stress. The value of maximum torsional shear stress is found from:
τmax = Tc/J
where; c = radius of the shaft to its outside surface J = polar moment of inertia
T = Torque
Based on Mott (2004), the behavior of members having noncircular sections when subjected to torsion is radically different from that for members having circular cross sections. However, the factors of must use in machine design are the maximum stress and the total angle of twist for such members. The formulas for these factors can be expressed in similar forms to the formulas used for members of circular section (solid and hollow round shafts).
Τmax = T/Q
where; Q = section modulus
Based on Mott (2004), a beam is a member that carries loads transverse to its axis. Such loads produce bending moments in the beam, which result in the
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development of bending stresses. Bending stresses are normal stresses, that is, either tensile or compressive. The maximum bending stress in a beam cross section will occur in the part farthest from the neutral axis of the section. At that point, the flexure formula gives the stress:
σ =Mc/I
where; M = magnitude of the bending moment at the section
I = moment of inertia of the cross section with respect to its neutral axis c = distance from the neutral axis to the outermost fiber of the beam cross section
Positive bending occurs when the deflected shape of the beam is concave upward, resulting in compression on the upper part of the cross section and tension on the lower part. Conversely, negative bending causes the beam to be concave downward.
When the dimension is already fixed, the yield strength of the material can be change to make sure the design will not failed due to bending at specify force. So, by using the dimension, calculate the moment of the beam. Then calculate the stress due to the bending and compare it with yield strength of the material. If the stress due to bending is smaller than yield strength of material, thus it mean that the beam dimension with the material used will not failed if the specify force is applied.
2.2.3 Design Factors
Based on Mott (2004), design factor, N is a measure of the relative safety of load-carrying component. He stated that in most cases, the strength of the material from which the component is to be made is divided by the design factor to determine a design stress, σd sometimes called the allowable stress. Then the actual stress to
which the component is subjected should be less than the design stress. For the case of the buckling of columns, the design factor is applied to the load on the column rather than the strength of the material.
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CHAPTER 1
INTRODUCTION
1.1 Background
Test Rig for bending and torsion on vehicle structure has been widely used by automotive car manufacturers and researchers to measure the vehicle strength and stiffness on a static bending and static torsion case of the vehicle structure. By using that rig, an artificial situation of bending and torsion can be produced. Moreover, the load and the stiffness of the vehicle can be measured for static bending and static torsion condition. Most of researcher and automotive manufacturer will then measure the stiffness of the vehicle structure on bending condition and torsion condition. By then, based on the result, the car manufacture or the researchers will estimate the vehicle stiffness and modification on the vehicle structure design will be done if needed.
1.2 Problem Statement
In Universiti Teknikal Malaysia Melaka, the learning process for subject Vehicle Structure Analysis on Torsion and Bending has been done theoretically. It is because, currently, there is no such laboratory equipment to conduct a test for bending and torsion on vehicle structure. So, in a short term period, there is a need for student to design and develop such equipment to help faculty on providing the laboratory equipment (specifically; test rig) to support laboratory use for testing the
(2)
bending and torsion on vehicle structure to increase the students (specifically; Automotive’s student) understanding on that matter.
1.3 Objective
This thesis is done to design and analyze a test rig for measuring torsion and bending on vehicle structure.
1.4 Scopes
- Understanding on principal of bending and torsion on vehicle structure - Study of structural design and analysis
- Design of test rig; design selection, geometrical dimension, material selection, strength calculation and solid modeling
- Strength analysis on test rig solid model using Finite Element Method - Report writing and documentation
(3)
CHAPTER 2
LITERATURE REVIEW
2.1 Background
In designing the test rig for bending and torsion, it is needed to understand the related principle of design and stress analysis. Moreover, the test configuration and previous test rig design must be studied so that the suitable test rigs design, which fulfills the criteria and requirement of the test configuration, can be created.
2.2 Principle of Design and Stress Analysis
In designing the test rig, the specifications of the test rig such as functions, design requirements and evaluation criteria must be defined clearly. According Mott (2004), functions tell what the device must do, using general, non-quantitative statements that employ action phrases such as to support a load, to lift a crate, to transmit power or to hold two structural members together. Moreover he said, design requirements are detailed, usually quantitative statements of expected performance levels, environmental conditions in which the device must operate limitations on space or weight or available materials and components that may be used. Whereas, evaluation criteria are the statements of desirable qualitative characteristics of a design that assist the designer in deciding which alternative design is optimum- that is, the design that maximizes benefits while minimizing disadvantages.
(4)
To start a design on the test rig, a lot of factors must be taken into consideration. Mott (2004) has summarized some factors to be taken into consideration, which as listed below:
- Forces exerted by the components of the machine through mounting points such as bearings, pivots, brackets, and feet of other machine elements
- Manner of support of the frame itself
- Precision of the system: allowable deflection of components - Environment in which the unit will operate
- Quantity of production and facilities available
- Availability of analytical tools such as computerized stress analysis, past- experience with similar products, and experimental stress analysis
- Relationship to other machines, walls and so on
2.2.1 Material
Selection of material has a high effect on the structure strength. The most significant factor to evaluate the material strength is by referring to the yield strength, σy and the modulus of elasticity, E of the material. Mott (2004) stated that, yield strength can be defined as the portion of the stress-strain diagram where there is a large increase in strain with little or no increase in stress. He also stated that modulus of elasticity can be define as stress proportionality to strain when the part of the stress-strain diagram is straight. Modulus of elasticity indicates the stiffness of the material or its resistance to deformation.
2.2.2 Stress
Based on Mott (2004), there are three basic fundamental kinds of stress; tensile, compressive and shear. Tensile and compressive stress, called normal stresses, are shown acting perpendicular to opposite faces of the stress element. Tensile stresses tend to pull on the element whereas compressive stresses tend to
(5)
crush it. Shear stresses are created by direct shear, vertical shear in beams or torsion. In each case, the action on an element subjected to shear is a tendency to cut the element by exerting a stress downward on one face while simultaneously exerting a stress upward on the opposite, parallel face. Stress can be defined as the internal resistance offered by a unit area of a material to an externally applied load.
σ = force/area = F/A
When a torque or twisting moment is applied to a member, it tends to deform by twisting, causing a rotation of one part of the member relative to another. Such twisting causes a shear stress in the member. For a small element of the member, the nature of the stress is the same as that experienced under direct shear stress. However, in torsional shear, the distribution of stress is not uniform across the cross section (Mott (2004)). When subjected to a torque, the outer surface of a solid round shaft experiences the greatest sharing strain and therefore the largest torsional shear stress. The value of maximum torsional shear stress is found from:
τmax = Tc/J
where; c = radius of the shaft to its outside surface J = polar moment of inertia
T = Torque
Based on Mott (2004), the behavior of members having noncircular sections when subjected to torsion is radically different from that for members having circular cross sections. However, the factors of must use in machine design are the maximum stress and the total angle of twist for such members. The formulas for these factors can be expressed in similar forms to the formulas used for members of circular section (solid and hollow round shafts).
Τmax = T/Q where; Q = section modulus
Based on Mott (2004), a beam is a member that carries loads transverse to its axis. Such loads produce bending moments in the beam, which result in the
(6)
development of bending stresses. Bending stresses are normal stresses, that is, either tensile or compressive. The maximum bending stress in a beam cross section will occur in the part farthest from the neutral axis of the section. At that point, the flexure formula gives the stress:
σ =Mc/I
where; M = magnitude of the bending moment at the section
I = moment of inertia of the cross section with respect to its neutral axis c = distance from the neutral axis to the outermost fiber of the beam cross section
Positive bending occurs when the deflected shape of the beam is concave upward, resulting in compression on the upper part of the cross section and tension on the lower part. Conversely, negative bending causes the beam to be concave downward.
When the dimension is already fixed, the yield strength of the material can be change to make sure the design will not failed due to bending at specify force. So, by using the dimension, calculate the moment of the beam. Then calculate the stress due to the bending and compare it with yield strength of the material. If the stress due to bending is smaller than yield strength of material, thus it mean that the beam dimension with the material used will not failed if the specify force is applied.
2.2.3 Design Factors
Based on Mott (2004), design factor, N is a measure of the relative safety of load-carrying component. He stated that in most cases, the strength of the material from which the component is to be made is divided by the design factor to determine a design stress, σd sometimes called the allowable stress. Then the actual stress to which the component is subjected should be less than the design stress. For the case of the buckling of columns, the design factor is applied to the load on the column rather than the strength of the material.