The assignment should produce su cient evidence for partial ful llment of the following module learning outcomes:
a. Develop a program utilizing object oriented programming
b. Apply computer based techniques engineering problems
c. Write eective formal written reports.
Additional information:
It is recommended that candidates use the LY X template as demonstrated to you in the wor kshop sessions for the nal presentation of this assignment . As per the module speci cation, this second assessment for learning activity accounts for 30% of the module.
Resources: SciLab and MAXIMA all being available on the university networks.
Special requirements: provided on a one-to-one basis for candidates requiring these in sp eci cally arranged surgeries.
Figure T1: Typical plotted test data
Background:
As candidates will be aware from their classes in mechanics, comp onents are designed in order to withstand particular design loads and/or displacements which are usually decimated by the sp eci c design co de as well as the so called ‘failure mode’ of the material . In order to compare the strengths of various materials it is necessary to carry out s ome standard form of test to establish their relative properties.
One such test is the standard tensile test in which a test sp ecimen of uniform cross-section is sub jected to a gradually increasing ten sile load until failure occurs. Measurements of the change in length of a selected gauge length of the bar are recorded throughout the loading op eration by means of extensometer. One machine which is used to carry out such experiments is the INSTRON 3367 which consists of an electromechanical load frame designed to apply a load to a test specimen via the moving cross-head. The drive system moves the cross-head up to apply a tensile load on the specimen, or down to apply a compressive load. A load transducer (load cell), mounted in series with the sp ecimen, measures the applied load. The load cell converts the load into an electrical s ignal that the control sy stem measures and displays. Strain transducers (extensometers) can also b e used on these systems to measure strain. It is usual to obtain vast amount of data from these devices which requires some degree of post-process ing. It is this post-processing that is subject of this assignment. From the data resulting from such a test machine candidates will be expected to evaluate properties such as strength, elastic modulus and stiness.
The assignment therefore has obvious links with the Engineering Analysis modules (MS1060/3) as well as Engineering Mechanics. Candidates will be expected to research information using a variety of library resources within the introductory mechanics of materials concepts and principles. The rst task of the assignment has b een designed to test the candidates computational statistical and data-analysis skills develop ed through Workshops. The final task will demonstrate document preparation (including referencing) and report writing abilities.
Task 1:
The raw force(kN) and displacement (mm) data from ve test samples of extruded p olypropylene (PE) pipe using an INSTRON 3367 will be emailed to you separately in the form of a single text (:txt) le. Note that these data are unique to you and will b e very similar to that shown in Figure T1 . Clearly justifying any assumptions when post-proces sing these data and complet e the following;
a. Identify and separate the ve individual data les within your single text le. Produce smoothed plots with error bars with 95% and 99% con dence limits and comment on the r esu lts obtained from the smo othing pro cess {10}
b. Each of the sp ecimens are 75mm diameter with a wall thickness 3mm from the smo othed data pro duce a stress-strain curve for the PE. Hence or otherwise evaluate at the 95% con dence level:
i. The ultimate tensile strength
ii. The material yield stress
iii. The elastic modulus
iv. Bulk modulus
v. Rigidity modulus
c. Describe an experimental method that could be used to simultaneously record the transverse strain and discuss how this could be employed to validate the calculations you carried out in the previous question.
21.94 24.27 26.51
23.02 24.31 22.23
26.84 24.74 23.88
24.79 22.14 24.17
18.12 24.22 24.26
24.66 24.07
25.55 25.55
24.65 24.08
23.30 23.91
23.46 26.41
Table 1: Failure loads of a sample of 25 pip es
Task 2:
The ultimate loads achieved from a sample of 25 pipes is shown in Table .
a. Using an op en-source equivalent to MATLAB (e.g. SciLab), add the ve valu es from the data sets employed in task 1 and convert all the values to stresses in MPa.
b. Produce a frequency diagram (histogram). From your diagram state the mo dal class. Hence or otherwise make an estimate of the modal yield of the pipes.
c. Produce a cumulative frequency diagram and make an estimate of the median of the data.
d. Evaluate three further measures of the central tendency of these data and comment on your results.
e. Evaluate two values of the data dispersion explaining your results clearly.
f. A Russian petroleum company requires 95 pipes made of an identical grade PE. Use a z-score or otherwise to predict the probability of a batch of pipes making the order if the minimal yield st res s should at least than 33.8MPa.
Task 3:
Write a report (1000-1200 words) entitled.Tensile testing of the polyethylene pipes for energy production.
The report should take the form of a lab oratory rep ort using, where appropriate, diagrams to describe the test performed and state the mechanical/material properties the protocol determines. Write up these nding together with the results in task 1 in an accepted scienti c manner. Ensure that at all times the rep ort is written in the third-party and the past-tense. For instance, you could consider using the LYX template which we designed in class consisting of the following sections.
Abstract: This is usually written once you have completed the rep ort. This being included as part of the pre report and be no more than a paragraph detailing: what was done?
What was the key result, and.
What was the main conclusion?
1 Introduction:
This should say a little about the use of the physics of materials and the use of any mathematical formulae. This section is usually used in order to set the scene of what the assignment is ab out. In ad dit ion, should also clearly state any assumptions evident in the work that and validate these using appropriate cit ed references.
2 Method:
Here you should include the rest of the relevant information p ertaining to the details of the tensile testing procedure as outlined in the opening paragraph of this task. Rationally, describ e the met ho ds you have employed (stating any formulae used in the completion of Task 1). Ensur ing at all times that appropriate citations are used throughout via application of a standardized referencing system.
3 Results:
Present all your tabulated and graphical results in order to answer Task 1: parts (a) to (c) and brie y comment on observation that can be inferred. Ensure that all graphs pro duced in task one are included, correctly formatted and captioned Figures so that a List of Figures and Table of Contents are generated automatically.
4 Discussion:
Include all your data comparisons for parts (d) to (f ) of Task 1 and most imp ortantly comment on each results.
5 Conclusions:
What did you and out and what did you learn?
Do you have any recommendations?
References:
Ensure that all references are cited throughout the main text and the Harvard (ISO 690a) or Vancouver system (ISO 690) is employed at all times.