Computer Integrated Product Development

School of Engineering and the Environment. Coursework Assessment Brief. Page 1 of 5

School of Engineering and the Environment

Department of Mechanical Engineering

Coursework Assessment Brief

Module Code

ME7721 Module Title

Computer Integrated Product Development Title of Assessment

Motion analysis of a typical crank- slider mechanism Summative (% of module) or Formative

Summative – this assignment is worth 35% of your module grade Typical individual student hours required to complete the assessment

35 hours, groups of up to four members are eligible Assessment set by (and contact)

Dr Xianzhi Zhang, Room RVMB121

x.zhang@kingston.ac.uk Submission deadline (date and time)

22nd May 2020, 5pm Formal feedback

20 working days after submission

All assignments must be submitted by the date and time specified above.

Students are required to submit an electronic copy of their completed assignment via the Assignments section of Canvas and follow any specific instructions. Any change to this instruction will be advised via Canvas.

In line with Faculty policy for late submission of coursework, any work submitted up to a week late will be capped at 40%. Coursework submitted after this time will receive 0%.

In case of illness or other issues affecting your studies please refer to the University Mitigating Circumstances policy. Guidance on mitigating circumstances can be found on MyKingston:

https://mykingston.kingston.ac.uk/myfaculty/sec/secstudentsupportMC/Pages/Mitigating-Circumstances.aspx

Please note that if you submit a piece of work you have judged yourself fit to undertake the assessment and cannot claim mitigating circumstances retrospectively.

Guidance on avoiding academic assessment offences such as plagiarism and collusion can be found on MyKingston

https://mykingston/myuni/academicregulations/Pages/default.aspx

Module Learning Outcomes

The following module learning outcomes and professional body learning outcomes are tested in this assessment:

(1) Generate complex 3D Solid Models including a variety of components parts and assemblies

(2) Develop a good understanding of different assembly techniques and the use of assembly geometry constrained

School of Engineering and the Environment. Coursework Assessment Brief. Page 2 of 5

(3) Understand and apply appropriate mechanism design techniques to validate product functionality. Assessment task and specific terms

The present assignment concerns the analysis of a typical crank- slider mechanism (Fig.1), which will be considered as a planar and closed kinematic chain. For the needs of the assignment, consider a 110mm long crank and a 340mm long connecting rod. Also, for the crank consider a reference angular velocity of 4rad/s and a reference angular acceleration of 15rad/s2. Also, consider that the slider is connected to the side EG of the guide frame (Figure1).

Figure 1: Schematic representation of a typical crank- slider mechanism (http://kids.britannica.com/elementary/art-7447/Slider-crank-mechanism)

The assignment comprises of four parts:

Part I: Development of a simplified 3D CAD model of the mechanism.

Part II: Motion analysis (numerical solution), using the commercial software Siemens NX, of the 3D model developed in Part I.

Part III: Derivation of the analytical equations (analytical solution) which describe the motion of the examined mechanism.

Part IV: For various cases, obtain numerical and analytical solutions, compare them and conclude with respect to the accuracy of the results.

Aims

The aims of the present assignment are:

• To become familiar with the use of industry-standard Siemens NX software as a tool for the motion analysis of mechanisms.

• To obtain fluency in validating numerical results from Siemens NX, through a comparison with results derived using analytical equations for the motion analysis of a mechanism (equations for position, velocity and acceleration).

crank

crankpin

connecting

rod

slider or sliding block

wrist pin

guide frame

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Objectives

The objectives are the following:

(a) To understand basic terms regarding the motion analysis of a mechanism.

(b) To develop and analyse a typical crank-slider mechanism using Siemens NX.

(c) To derive analytical equations describing the motion analysis of a typical crank-slider mechanism.

(d) To plot results from numerical simulation and analytical calculations and compare them.

Deliverables

The final deliverable will be a technical report adequately describing how the four parts (Part I, Part II, Part III and Part IV) have been dealt with. The layout of the report is suggested (but not limited) to be:

1. Introduction

This section includes:

(a) A brief but clear description of the crank-slider mechanism and its operation.

(b) A brief but clear description of two typical examples of a slider-crank mechanism (where can we find a slider-crank mechanism in the real world? Include a representative image for each example!).

2. CAD modelling

This section includes:

(a) The development of an adequately detailed 3D model of the slider-crank mechanism. Include technical drawings as an Appendix.

(b) A brief but clear description of the modelled joints: number of joints, types of joints used, parts connected per joint, degrees of freedom (constrained and unconstrained) per joint.

3. Numerical consideration (motion simulation)

This section includes:

(a) Using Siemens NX and the reference velocity and acceleration, to acquire numerical values for the position, velocity and acceleration of the crank pin (Fig1) and the wrist pin (Fig1) and for five full revolutions.

4. Analytical consideration

This section includes:

(a) The estimation of the Degrees of Freedom of the examined mechanism using Kutzbach’s equation.

(b) The derivation of the analytical equations for the position, velocity and acceleration for the examined kinematic chain through a scalar consideration.

(c) The derivation of the analytical equations for the position for the examined kinematic chain through a vector consideration.

(d) Using the reference velocity and acceleration, to acquire numerical values for the position, velocity and acceleration of the crank pin (Fig1) and the wrist pin (Fig1) and for five full revolutions.

The number of crank angles to be considered in (d) above is optional but must be justified. To get numerical values using the analytical equations, it is

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possible to select the equations from either the scalar consideration or the vector consideration and use any software, e.g. MatLab, Excel, etc.

5. Results

Based on the results from (3) and (4) above:

(a) Plot the position of the crank pin vs the crank angle. Present the analytical results as a continuous line and the results from the motion simulation with markers.

(b) Plot the velocity of the crank pin vs the crank angle. Present the analytical results as a continuous line and the results from the motion simulation with markers.

(c) Plot the acceleration of the crank pin vs the crank angle. Present the analytical results as a continuous line and the results from the motion simulation with markers.

(d) Plot the position of the wrist pin vs the crank angle. Present the analytical results as a continuous line and the results from the motion simulation with markers.

(e) Plot the velocity of the wrist pin vs the crank angle. Present the analytical results as a continuous line and the results from the motion simulation with markers.

(f) Plot the acceleration of the wrist pin vs the crank angle. Present the analytical results as a continuous line and the results from the motion simulation with markers.

(g) For a crank angle of 60deg, draw a 2D sketch of the examined mechanism, denoting the direction and the value of the velocities of all moving parts.

(h) For a crank angle of 135deg, draw a 2D sketch of the examined mechanism, denoting the direction and the value of the acceleration of all moving parts.

6. Discussion and Conclusions

Describe the outcome of the comparison between the analytical and the numerical consideration and discuss any discrepancies.

7. References

All the sources referenced in the report.

References

Uicker, J, Pennock, G, Shigley J (2003), Theory of machines and mechanisms, Oxford University Press.

Assessment Criteria

Assessment of your submission will be based on the following weighted assessment criteria as given below which relate to the specified module and PSRB learning outcomes. Assessment criteria are reproduced in Canvas in a rubric.

Specific Criteria (marking scheme) Marks available

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Introduction (crank-slider mechanism / examples)

5%

CAD modelling (3D CAD model of slider-crank mechanism / technical drawings)

15%

Numerical consideration (motion simulation) (position/velocity/acceleration with Siemens NX)

30%

Analytical consideration (Kutzbach’s equation / position, velocity and acceleration through a scalar consideration / position through a vector consideration)

20%

Results (eight plots related to position/velocity/acceleration of specific moving parts)

20%

Discussion and conclusions

10% Total = 100%

Academic skills support

For help and advice on this assessment please contact the assessment setter/s or the module leader. For advice on academic writing and referencing please contact the Faculty of Science, Engineering and Computing (SEC) Academic Success Centre (SASC). Trained staff and students will give you guidance and feedback on assessments. SASC can be contacted by email: SASC@kingston.ac.uk