Course Meeting Times
Labs: 2 sessions / week, 3 hours / session
Prerequisites
Solid Mechanics, 1.050
Description
In Solid Mechanics Laboratory, 1.105, you will have the opportunity to assemble and test a variety of structural elements. You will subject them to loading, and observe and measure their behavior using both crude and relatively sophisticated instruments. Foci include:
- Testing of statements made and conclusions derived in the companion subject, 1.050;
- Study force/displacement, stiffness behavior of structural elements;
- Failure modes and mechanisms;
- Introduction to instrumentation, resolution, range, transducer response, signal conditioning;
- Coping with uncertainty; methods of data analysis;
- Experiment design; and
- Report writing.
Laboratory Conduct
Each lab session will begin with an orientation. The lab instructor will respond to questions and convey essential, tacit, knowledge regarding the smooth conduct of the experiment. The lab instructor will be available throughout the three hours to provoke your thinking in response to questions that you pose.
The laboratory exercise is not a test. It is a ‘hands-on’ experience meant to show the relevance of theoretical concepts to understanding the behavior of real hardware and instrumentation and, at the same time, reveal how non-ideal conditions and some very ‘un-theoretical’ events can obscure the theoretical behavior.
There are four test frames in the lab. You will work in groups of two or three. While you are to collaborate in setting-up and running the experiments, each of you individually will be responsible for a report of your experiences. Procedures for each experiment, other than the first, are to be read before the start of lab even though these can only sketch out what needs to be done to effect a measurement. Certain constraints are printed in bold within these descriptions. These constraints are to be strictly observed. In part this is for safety reasons, in part because we do not want to fail a test specimen or overload an instrument. If you are not sure, ask your lab instructor.
The most successful experiments in science and engineering are those in which you know what the outcome will be before you start. Indeed, you cannot design an experiment without knowing something about the range of possible deflections, a safe loading of the structure, an instruments sensitivity to some external, disturbance, and the like. So while the experiment is in progress, one of your team should do a rough data reduction and sketch out the behavior e.g., load vs. deflection, as you go along. Make the most of your time to ensure that you have ‘quality’ data by checking it with expectations. At the same time you must resist letting your expectations color or bias your readings; if your reading looks 10% low, don’t try to reduce the difference; on the other hand if it is off by a factor of 10, you had better stop everything and check your experimental setup, your theoretical deductions, or your data analysis procedures.
Report Content and Format
You will record your activities in the lab in a lab notebook. You are to use ink, make no erasures. Draw a line through that text which you find faulty or erroneous. Sketches of apparatus may be made in pencil. Make sure you record all relevant dimensions, variables, settings, (don’t neglect to record the units) and information that will enable you to write the report without coming back to the lab to check up on the value of a critical parameter.
If you use a laptop computer to record data, you must still print out pages to paste into your lab notebook. The report should include the following:
- Summary - a one page summary of purpose, method and main results;
- Introduction, including objectives;
- Experimental procedure;
- Results;
- Conclusions; and
- Appendices.
The amount of detail to include in these sections varies depending upon your audience. For our purposes, think of your audience as a fellow student who has not yet done the experiment but will do so within a few days. You can assume they are familiar with the theoretical concepts of 1.050. With respect to instrumentation, assume this student is aware of the basic principle of operation of the transducer but is not familiar with the particular application you are making. Results should not include excessive detail. Put the full data record in the appendices. Appendices are also the place for background theory, manufacturer’s specifications and the like.
Grading
This is a 6 unit subject. There are seven in-lab experiments.
- Experiment 5 - 10%;
- The remaining six experiments are 15% each; and
- There is no final exam.
