MEC2402 Stress Analysis Report
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Your submission for this report consists of a single .pdf file with a maximum of 10 pages inclusive of any references and appendices for which you are seeking marks, and a maximum size of 20 MB containing your own work addressing the matters identified in Question 1 and 2 below. Note that any submitted material on pages beyond number 10 will not be considered in the marking process. Your file will be named ‘Lastname_Firstname_XXXXX_R1.pdf’ where Lastname and Firstname are replaced with those specified on the UniSQ record, and XXXXX is replaced with your student number.
You must preserve relevant materials you develop and use during the process of completing this report because any student in this course may be subject to random intellectual property checks in which student(s) must discuss and demonstrate their reported work.
Question 1: Bearing stress experiment (100 marks)
This task requires an assessment of bearing and compression stresses through your own experiment designed for execution at home. The associated video clips provide an introduction to the sort of experiment that you need to design. Before commencing the design and development of your own experiment, you must read the following information thoroughly and adhere to the requirements.
Safety Risk Management
Before any physical experimentation commences, you must engage in the safety risk management process. The apparatus that you develop must not pose any significant risk of injury to yourself or others, or damage to property. Your apparatus must be developed using readily available materials and household tools that you are already familiar with. To minimise the risk of injury or property damage, the experiment must be designed to operate with relatively low loads – no more than 1 kg in mass.
The value of 1 kg is the chosen maximum limit based on potential energy considerations: if the mass is unexpectedly released from the apparatus and falls through about 1 m to the floor, it will impact with an energy ???? = ?????????, corresponding to about 9.8 Joule, since gravitational acceleration is approximately ???? =
9.8 m/s2. If such impact energy is instead absorbed by one of your toes or some other part of your body, a significant injury may be sustained.
The task of managing health and safety risks is frequently considered to be a four-step process. For example, see:
1: Identify hazards
2: Assess the risk
3: Control the risk
4: Review controls
Use of hand tools in apparatus construction
If an experimenter is required to use tools with which they are unfamiliar or the experimenter has not been adequately trained in safe work practice with the tools, then an injury may occur.
Design the apparatus in such a way that only tools with inherently low risk are needed for construction.
Scissors, staplers, tape dispensers and other standard home office tools are considered appropriate for application in apparatus construction. Tools that are not normally found in the home office should not be used in the apparatus construction unless the experimenter can demonstrate
familiarity with safe use of those tools.
You should review these controls within the context of your own experiment design as part of Task (b) to confirm compliance. If in your judgement further controls are needed, then you should implement and discuss these controls as well.
Stored elastic strain energy
If an element of the apparatus ruptures unexpectedly when loaded, energy release may generate flying objects causing damage to property
or injury to people.
Do not use brittle materials which are prone to generate isolated fragments if rupture occurs. As instructed, do not use a mass of more than 1 kg in your experiment because this amount of load will limit the quantity of stored elastic strain energy in the apparatus.
You should review these controls within the context of your own experiment design as part of Task (b) to confirm compliance. If in your judgement further controls are needed, then you should implement and discuss these
controls as well.
Stored potential energy
If the apparatus moves in an unexpected manner and the load slips, it may fall and damage property or injure people.
As instructed, do not use a mass of more than 1 kg in your experiment. This will limit the magnitude of the potential energy. You should arrange the experiment so the mass cannot fall very far, should unexpected movement occur.
You should review the design of your experiment, to further minimise the risk of the load slipping: implement and discuss these controls. This forms part of Task (b).
Overview of video clips
- loading_arrangement.mp4. You need to develop an arrangement that can apply a quantifiable compressive force to a substrate. In the example illustrated, the beam (a horizontal wooden member) supports two water bottles filled with approximately the same amount of water. In the absence of reliable scales, the force applied to the central column supporting the beam can be estimated from the total water volume. Once the total volume of water is measured, the load can be determined from the mass of water (because the density of water is known accurately) and gravitational acceleration. There will be an additional contribution to the compressive load due to the weight of the empty water bottles and other components, and this can likewise be estimated as necessary.
- with_plinth.mp4. This video illustrates how the compressive load is applied through the column, via a plinth and into the substrate, which in this case is a piece of green plasticine. The plinth in this case is a small piece of wood, and this component enables the compressive load to be distributed over an area that is much larger than the cross-sectional area of the column itself. When lowering the column onto the plinth, an attempt was made to ensure that only the vertical load provided by the bottle arrangement is delivered into the plinth. The video illustrates some potential deficiencies here: the experimenter needed to provide some horizontal
support for the column because a modest pendulum motion of the bottles arose as is observable in the video. The experimenter attempted to ensure no additional vertical load was delivered into the column, but the experimenter’s fingers are in direct contact with the column throughout the experiment, so some unwanted vertical loading may have occurred.
- plinth_removal.mp4. When the plinth is removed after the experiment, only a small amount of plastic deformation of the substrate is registered. One of the objectives of this experiment is to define the maximum compressive stress (bearing stress) below which no permanent plastic deformation will be registered in your selected substate.
- without_plinth.mp4 & large_penetration.mp4. An experiment performed with no plinth demonstrates extreme plastic deformation occurs when the bearing stress exceeds the maximum bearing stress by a long margin.
The video clips illustrate one possible approach, but the apparatus illustrated has several deficiencies; you are encouraged to develop your own improved method.
- Present a photograph of the apparatus you have personally developed for this experiment, making certain that you include a photo-ID card clearly visible in the photograph. See ID photo example.jpg for illustration of requirements. Note that although this element only garners the maximum marks indicated, you need to present an adequate photo including the ID card for the remainder of Question 1 to be marked.
- Present your own safety risk management plan for the development and operation of the apparatus. You should use the table above as a guide for development of your own version. Although this element only garners the maximum marks indicated, you need to present an adequate risk management plan to receive marks for the remainder of Question 1. [10 marks]
- Describe your apparatus and its operation using a sequence of annotated photographs and/or sketches. Discuss how you quantify the force applied to the column. Make sure that you include a description of your substrate material and its arrangement. Note that you will need to have a thickness of substrate that exceeds the largest dimension of your plinth, otherwise the material supporting the substrate from below could potentially affect your results. Discuss the ways in which your apparatus is operationally superior to the device illustrated in the video clips. “Operationally superior” means it is either easier to use or provides more accurate results. [25 marks]
- Identify the maximum bearing stress that your chosen substrate material can sustain without plastic deformation. There are two different ways that this could be achieved: (1) for a given load you could test a sequence of different plinth areas, inspecting the substrate after each test to determine if any substrate deformation has occurred; or (2) for a given plinth area you could test a sequence of different loads, and as for method (1), inspect the substrate for deformation after each test. For either method (1) or (2), document your results providing photographic evidence of the deformation of the substrate in each case. Quantify and discuss the accuracy of your results. [45 marks]
- For the case of the maximum bearing stress identified in part (d), calculate the compressive stress that would have existed in the column that delivered the load into the plinth. [10 marks]
Question 2: Home water pressure pipe case study (50 marks)
- Identify the water pressure pipe that you are going to treat using a cylindrical thin-walled pressure vessel analysis within this question. This component must physically exist within your home, work, or other environment such that you are at liberty to present a photograph of it with your photo-ID presented clearly in the foreground with this component in the background. The ID photo example.jpg referred to in Question 1 illustrates the requirements here also, though obviously the hardware is different. Note that although this element only garners the maximum marks indicated, you need to present an adequate photo including the ID card to receive marks for the remainder of Question 2. [5 marks]
- Present your own solution to one of the even numbered tutorial questions that is relevant to the present case study you are performing. Explain how it is relevant. [5 marks]
- Measure the outside diameter of the pipe using Vernier callipers if available, some other physical measurement technique, or through analysis of a photograph of the pipe with an adjacent scale included. Describe your measurement method. Quantify the dimensional uncertainty with your measurement in the form of ± ???? mm, where ???? is a numerical value and justify the specified value of ????. [10 marks]
- Identify the material from which the component is made, specify its tensile strength, and the likely wall thickness of the pipe. Describe how you made these identifications and cite your sources of information as appropriate. If detailed specifications are not readily available, make some reasonable assumptions and justify these assumptions. [10 marks]
- Determine the likely maximum pressure load on the component under normal operating conditions and describe how you determined this value. Make some reasonable assumptions if needed, citing your sources of information as appropriate, and justifying assumptions as needed. [5 marks]
- Calculate the maximum direct stress within the walls of the pressure pipe according to the thin-walled pressure vessel analysis. Discuss the magnitude of this value in the context of the tensile strength of the material. [15 marks]