Lab Report Format for Engineers and Engineering Students 
1. Title Page:
The title page should be specific and descriptive, but brief and clear. It should state the title, experiment number, the group members and the date submitted. The report should be addressed to the faculty member along with the course number and title.
2. Abstract or “Executive Summary”:
In one brief concise paragraph not to exceed 150 words, give the reader enough information to understand what the experiment was about, what was done, and what conclusions were drawn. It is read first and encapsulates the major portions of the report and addresses a reader who may not read the rest of the document. This is not the experimental write up from item #4, or the complete results / conclusions from items #7 and #9, but includes a summary of what was done, and what was concluded. It should contain the highlights of the major parts of the report, including the objective, results, conclusions and recommendations. It does not include details.
3. Introduction and Background Information:
The introduction is the lead into the report. It introduces the reader to the subject matter. It should state the Objectives and meaning of the work which will be contained in the report. It will likely include history of the subject, various types of units or equipment related to the subject and an overview of the theory that is applicable to the experiment. It should be written in a way to encourage the reader to continue wanting to read the remainder of the report. For many laboratory experiments, the Introduction that is provided in the handout will be a good starting point for this section.
4. Experimental Procedure:
Provide a brief explanation of how the work proceeded. Clearly note and explain
any differences that were encountered as compared to the suggested procedure outlined in
the lab handout. All photos, drawings, sketches or schematics need to be referenced
within the text, and properly labeled (described). Provide references to the laboratory
manual or to material given to the students by the professor.
5. Experimental Data:
All original measurements must be recorded no matter how trivial. The data
should be presented in an orderly manner preferably in table form with units indicted.
Before the data table is presented, an introductory paragraph must be written to inform
the reader what the table contains. This section should contain only raw information, not
results from manipulation of data. Each table must be referenced in the text and requires
a proper label with consecutive numbers as follows: Table 1. Hardness measurements
obtained from quenching.
6. Sample calculations:
Each different calculation should be presented so that the reader can understand
how the results are obtained. Statements or comments should be made during the
presentation of the calculations. The reader should be able to follow all steps. Make sure
units are included. Actual data and the resulting calculation(s) need to be included as an
example of each type of calculation performed.
7. Experimental Results:
Before presenting the results in a table or graph, a paragraph is required to inform
the reader what is to follow. All calculated quantities should be displayed clearly in an
identified Table. If graphs are used, all axes as well as data series must be properly
identified with correct units, values, and titles. Depending on the type of experiment, the
following may or may not be applicable:
Table: Repetitive and iterative calculations can be done using a spreadsheet and
displayed in tabular form. A graph may be used to help enhance a reader’s
understanding of the information.
Illustration of set up: Include a drawing of the arrangement of the equipment
and measuring devices showing the location of gages, gage markings, etc. Use
simple diagrams of essentials only.
Sketches of observations: In some experiments the results are shown by making
a sketch of what happens. Include those here.
Note: all tables, figures, and graphics in your report must be referenced in the text and
need a proper label with consecutive numbering as follows: Figure 3. Illustration of
quench tank used in the experiment.
8. Discussion of Results:
This section is devoted to your interpretation of the outcome of the experiment or
work. Comment on the graphs, results, or any other aspect of the experiment that is
pertinent to the conclusion. A set of questions is generally given to provide a starting point for the discussion. Do not confine the discussion to merely answering the questions.
Compare your results to expected behavior and explain any differences.
9. Conclusion:
State conclusions that can be justified with the data. The conclusion must be
based on experimental results and also on the entire procedure and theory of the
experiment. Report on whether the Objectives of the experiment were realized or not.
Make sure that thoughts are worded as conclusions, and not observations. Make simple
declarative statements, and do not ramble into a discussion. Conclusions should tell how
the results of this experiment can be applied to other experiments. All statements need to
refer directly to the current data. Be sure to address all questions presented in the
Laboratory Experiment write-up as well as other questions that may have been developed
during the experimental procedure in class.
10. Appendix:
Include an appendix with material (as required). Separate sections within the
appendix must be labeled as : Appendix A, Appendix B, and so forth.
Other Requirements:
 The report should be written in the Third Person – Past Tense and Passive Voice.
 All Figures and Tables need to have clear Titles and be Numbered.
 All pages are 8-1/2 x 11” white paper. The report must be typewritten and be either
single or double spaced.
 Good sentence and paragraphs composition is expected with attention to grammar,
punctuation, and spelling.

1. 1. Introduction

   The mechanical properties of materials are determined by performing carefully designed laboratory experiments that replicate as nearly as possible the service conditions. In real life, there are many factors involved in the nature in which loads are applied on a material. The following are some common examples of modes in which loads might be applied: tensile, compressive, and shear. These properties are important in materials selections for mechanical design. Other factors that often complicate the design process include temperature and time factors.
   The topic of this lab is confined to the tensile property of polymers. Figure 1 shows a tensile testing machine similar to the one used in this lab. This test is a destructive method, in which a specimen of a standard shape and dimensions (prepared according to ASTM D 638: standard test method for tensile properties of plastics) is subjected to an axial load. During a typical tensile experiment, a dog-bone shaped specimen is gripped at its two ends and is pulled to elongate at a determined rate to its breakpoint; a highly ductile polymer may not reach its breakpoint. The tensile tester used in this lab is manufactured by Instron (model 5569).  It has a maximum load of 2 or 50 kN and a variable pulling rate. The setup of the experiment could be changed to accommodate different types of mechanical testing, according to the ASTM standard (e.g. compression test, etc).
   For analytical purposes, a plot of stress (σ) versus strain (ε) is constructed during a tensile test experiment, which can be done automatically on the software provided by the instrument manufacturer. Stress, in the metric system, is usually measured in N/m² or Pa, such that 1 N/m² = 1 Pa. From the experiment, the value of stress is calculated by dividing the amount of force (F) applied by the machine in the axial direction by its cross-sectional area (A), which is measured prior to running the experiment. Mathematically, it is expressed in Equation 1. The strain values, which have no units, can be calculated using Equation 2, where L is the instantaneous length of the specimen and L₀ is the initial length.
   (Equation 1)
   (Equation 2)
    
   A typical stress-strain curve would look like Figure 2. The stress-strain curve shown in Figure 2 is a textbook example of a stress-strain curve. In reality, not all stress-strain curves perfectly resemble the one shown in Figure 2. This stress-strain curve is typical for ductile metallic elements. Another thing to take note is that Figure 2 shows an “engineering stress-strain” curve. When a material reaches its ultimate stress strength of the stress-strain curve, its cross-sectional area reduces dramatically, a term known as necking. When the computer software plots the stress-strain curve, it assumes that the cross sectional area stays constant throughout the experiment, even during necking, therefore causing the curve to slope down. The “true” stress-strain curve could be constructed directly by installing a “gauge,” which measures the change in the cross sectional area of the specimen throughout the experiment.
   Theoretically, even without measuring the cross-sectional area of the specimen during the tensile experiment, the “true” stress-strain curve could still be constructed by assuming that the volume of the material stays the same. Using this concept, both the true stress (σ_T) and the true strain (ε_T) could be calculated using Equations 3 and 4, respectively. The derivation of these equations is beyond the scope of this lab report. Consult any standard mechanics textbook to learn more about these equations. In these equations, L₀ refers to the initial length of the specimen, L refers to the instantaneous length and σ refers to the instantaneous stress.
   (Equation 3)
   (Equation 4)
   Figure 2 also shows that a stress-strain curve is divided into four regions: elastic, yielding, strain hardening (commonly occurs in metallic materials), and necking. The area under the curve represents the amount of energy needed to accomplish each of these “events.” The total area under the curve (up to the point of fracture) is also known as the modulus of toughness. This represents the amount of energy needed to break the sample, which could be compared to the impact energy of the sample, determined from impact tests. The area under the linear region of the curve is known as the modulus of resilience. This represents the minimum amount of energy needed to deform the sample.
   The linear region of the curve of Figure 2, which is called the elastic region (past this region, is called the plastic region), is the region where a material behaves elastically. The material will return to its original shape when a force is released while the material is in its elastic region. The slope of the curve, which can be calculated using Equation 5, is a constant and is an intrinsic property of a material known as the elastic modulus, E. In metric units, it is usually expressed in Pascals (Pa).
    
   (Equation 5)
   Figure 3(a) shows typical stress-strain curves of polymers. The figure shows that materials that are hard and brittle do not deform very much before breaking and have very steep elastic moduli.
   The mechanical property of polymers generally depends on their degree of crystallinity, molecular weights and glass transition temperature, T_g. Highly crystalline polymeric materials with a T_g above the room temperature are usually brittle, and vice versa. When a semi-crystalline polymer undergoes a tensile test, the amorphous chains, will become aligned. This is usually evident for transparent and translucent materials, which become opaque upon turning crystalline. Figure 3(b) shows a diagram showing the mechanical property of some common polymers.

   	Figure 3.  (a) A plot of stress-strain curves of typical polymeric materials. (b) A summary diagram of the properties of common polymers.

    

   2. Experimental Procedure

   Important!  Make sure you wear safety glasses before starting any operation. Your eyes could be hurt by a broken piece of polymer. Also wear gloves to protect against any residue on the machine and samples.
    

   2.1 Specimen Preparation

   The polymer specimens were injection-molded into dog-bone shapes. Their dimensions were determined according to the ASTM D 638 standard mentioned earlier in the introduction.
    
   (1) Measure the thickness, width and gage length of polymer samples in mm.  These dimensions should be approximately the same for each sample.
   (2) Also make note of any sample defects (e.g. impurities, air bubbles, etc.).
    
   The following samples will be tested:

   • Polypropylene (PP), polystyrene (PS), polylactic acid (biopolymer), high density polyethylene (HDPE), and Dynaflex for analysis of mechanical properties.
   • Polystyrene: to compare effects of feeding direction on mechanical properties.
   • Polypropylene: to analyze effects of strain rate on mechanical properties.

    

   2.2 Bluehill Software Setup

   1)  Turn on the tensile test machine.  The switch is located on the right side of the machine.  Also turn on the video extensometer.
   (2)  Go to the desktop and double-click on the “Bluehill” icon.
   (3) On the main page, select Test to start a new sample.  Name your test and click Browse to select the folder you would like to save it in. Click next.
   (4) Choose which method you would like to use.  Create and save a new method if needed.
   (5) Method set up: Save after any changes are made.

   • General: used for display purposes
   • Specimen: specifies sample dimensions and parameters. A dogbone sample is used for tensile testing.  Select rectangular, and specify the width, thickness and gauge length of the sample. The gauge length is the distance between the clamps before starting the test.
   • Control: describes the actual test. Select extension for mode of displacement, then specify the rate of extension.  Most use 5 mm/min or 50 min/mm, depending on if you want a slow or fast test.
   • End of Test: identifies the criteria for the end of the test. A large load drop is experienced when sample failure occurs.  For this test, when the sample load drops by a certain percentage of the peak load, the machine will stop.
   • Data: specifies if the data is acquired manually or automatically, while the strain tab recognizes whether the strain is measured from the video extensimeter or the extension.
   • Results and Graphs: select what data is shown and how it is displayed.

        

   2.3 Instrument Setup

   (1) Make sure the proper load cell is installed, either 2 kN or 50 kN depending on the load range and sensitivity of the sample.  To switch load cells, make sure the machine is off.  Unscrew the bolts and remove using the handle.  Make sure to plug the new load cell into the port behind the machine.
   (2) Calibrate the load cell by clicking on the button in the upper right hand corner.  Make sure all loads are removed from the load cell and click calibrate.
   (3) Install the correct type of clamps for the testing.  For tensile testing, 5kN or 50kN samples can be used.  Install the clamps using the pins. Also install height brackets if needed.  Zero the load once the clamps are installed.
   (4) Press the up and down arrows on the controller until the clamps are just touching.  Press the reset gauge length button at the top of the screen to zero the position of the clamps.
   (5) Use the up and down arrows until the clamps are about 100 mm apart.  This is a typical gauge length for the dog bone samples.
   (6) Place the polymer sample between the grips of both the tensile test machine. While holding the sample vertically with one hand, use another hand to turn the handle of the top grip in the closing direction as tightly as possible.
   (The specimen should be gripped such that the two ends of the specimen are covered by the grip, approximately 3 mm away from its gage-length. It is important that the specimens are tightly gripped onto the specimen grips to prevent slipping, which will otherwise result in experimental errors. )
   (8) Make sure that the specimen is vertically aligned, if not a torsional force, rather than axial force, will result.
   (9) Turn the bottom handle in the “close” direction as tightly as possible. Visually verify that the sample is gripped symmetrically at its two ends.
   (10)Zero the extension by pushing zero extension button at the top of the screen.  Also zero the load if needed. Wait for a few seconds to let the computer return its value to zero.
    

   2.4 Tensile Test

   (1) Enter geometry of the sample before starting.
   (2) Click on the Start button.  Both the upper and bottom grips will start moving in opposite directions according to the specified pulling rate. Observe the experiment at a safe distance (about 1.5 meters away) at an angle and take note of the failure mode when the specimen fails.
   (NOTE: Be sure to wear safety glasses. Do not come close to equipment when the tensile test is running).
   (3) A plot of tensile stress (MPa) versus tensile strain (mm/mm) will be generated in real-time during the experiment.
    

   2.6 End of Test

   (1) The machine will stop automatically when the sample is broken.
   (2) Press the “Return” button on the digital controller. Both the upper and lower grips will be returned to their original positions automatically.
   (3) Turn the two handles in the open directions to remove the sample
   (4) Repeat the previous steps for any additional tests.
   (5) When finished, save your file and click Finish.  This will export your data into a PDF and individual data files.
   (6) Clean up any broken fragments from the specimens.
   (7) Turn off the machine and exit the program when finished.
    

   3. Assignments
   • Graph PP (50 mm/mm extension), PS (2 feed inputs), PLA, HDPE and Dynaflex results using raw data files. There should be two tests for each polymer, but just pick one to graph.  Construct the true stress-strain curves for each polymer (hint: use Equations (3) and (4) provided in the Introduction section).
   • Calculate Young’s Modulus for each material and testing condition and compare experimental values with literature values.
   • Discuss any differences in mechanical behavior between the polymers (use pictures!)
   • Analyze the fracture modes of each sample (ductile fracture, brittle fracture, or intermediate fracture mode).
   • Using the data for polypropylene, discuss the effects of strain rate on the mechanical behavior of the polymers.
   • Using the data for polystyrene, compare effects of feed direction on the mechanical behavior.
   • Explain any unexpected results.

Report Format

• Introduction
• Experimental
• Results
• Discussions/Conclusion

Review of Methods
Briefly comment on whether the report author has written this section to someone familiar with the field, adequately described the experiments and samples, referenced published methods with changes noted, etc. A sentence or two should suffice.
Review of Results
Review should include consideration of all items listed in the “Results” guidelines. Identify items or portions done particularly well, and others in most need of improvement. Would you have presented or highlighted data any differently?
Review of Discussion
Review should include consideration of all items listed in the “Discussion” guidelines. Identify items or portions done particularly well, and others in most need of improvement. Are there additional comparisons or discussion points that might have been made? Are there different comparisons that might have been made? Have the discussion questions been well integrated into text with logical flow?
An example of an additional comparison: “The author compared measured valued to expected influent of the Dayton Wastewater Treatment Plant. However, the report could have also compared removal percentages…”
An example of a different comparison: “The author compared the lab results to typical drinking water results, but could have used a specific town’s water quality report values.”
Overall quality
Briefly comment on characteristics of the report’s overall quality. This might include strength of conclusions (or disagreement), proper citation and referencing, formatting, grammar, and so on.