4.0 Theory and Equations
Tensile testing applies an axial pulling force to a standard specimen until failure occurs. The key properties derived from this test include yield strength, ultimate tensile strength (UTS), and elastic modulus (E).
Stress is defined as the load per unit area, while strain represents the elongation per unit length of the specimen.
Universal Testing Machine (UTM) Schematic
Figure: Schematic diagram of a Universal Testing Machine showing the main components including load cell, grips, specimen, extensometer, and hydraulic actuator.
Mechanics Solver (Hover to animate)
1. Stress (Engineering)
2. Strain (Engineering)
3. Young's Modulus
Material Response During Loading
Original
L₀, A₀
Elastic
Recoverable
Plastic
Permanent
Necking
Localized
Fracture
Failure
5.0 UTM Protocol
1. Measure the initial diameter (d₀) and gauge length (L₀) of the specimen.
2. Secure the specimen in the Universal Testing Machine (UTM) grips.
3. Attach the extensometer to measure elongation accurately during the test.
4. Apply the load gradually and monitor the load-extension graph in real time.
5. Observe the necking phenomenon and record the fracture load.
5.1 Safety Measures
The following safety precautions must be observed when conducting tensile testing to prevent injury and equipment damage.
1 Personal Protective Equipment (PPE)
- • Always wear safety glasses or goggles to protect eyes from flying fragments during specimen fracture.
- • Wear closed-toe shoes and avoid loose clothing that may get caught in the machine.
- • Use hearing protection if the machine generates loud noise during operation.
2 Machine Operation Safety
- • Never operate the UTM without proper training and supervision from the lab instructor.
- • Keep hands and fingers away from the grips and moving parts during testing.
- • Ensure the emergency stop button is accessible and know its location before starting.
3 Specimen Handling
- • Handle specimens carefully as metal edges may be sharp and cause cuts.
- • Ensure the specimen is properly aligned and securely gripped before applying load.
- • Stand clear of the specimen during testing as it may eject fragments upon fracture.
4 General Laboratory Safety
- • Keep the work area clean and free from obstructions.
- • Do not leave the machine unattended during operation.
- • Report any machine malfunction or unusual behavior immediately to the instructor.
- • Know the location of the first aid kit and fire extinguisher in the laboratory.
Important: Students who fail to follow safety procedures may be asked to leave the laboratory. Safety violations will be reported to the academic supervisor.
6.0 Result
Present your tensile test results in a clear and traceable format. All tables and figures must include units, labels, and proper numbering.
1. Tabulate measured specimen dimensions (d₀, L₀) and the calculated cross-sectional area (A₀).
2. Provide the raw load-extension data used to generate the stress-strain curve.
3. Convert the raw data into engineering stress-strain data and show at least one sample calculation with correct units.
4. Plot the engineering stress-strain curve and label key points including the proportional region, yield strength, UTS, necking onset, and fracture point.
5. Determine the elastic modulus (E) from the slope of the initial linear portion of the stress-strain curve.
6. Include a clear sketch or photo of the fractured specimen with the fracture appearance and necking location marked.
7.0 Discussion
Please login and complete all discussion items below. Your responses will be included in your lab report.
7.1 Interpretation of the stress-strain curve
Explain the deformation stages shown on your stress-strain curve. Describe the elastic region, yielding point, strain hardening phase, necking phenomenon, and final fracture. Relate each region to the physical changes you observed on the specimen during the test.
7.2 Yield strength determination using the 0.2% offset method
Describe the procedure you used to determine the yield strength using the 0.2% offset method. Explain how you identified the linear elastic portion, drew the offset line parallel to the elastic slope, and located the intersection point on the curve.
Step 1: Identify the linear elastic portion and determine its slope, which represents the elastic modulus E.
Step 2: From a strain offset of 0.002 (equivalent to 0.2%), draw a line parallel to the elastic slope.
Step 3: The intersection of the offset line with the stress-strain curve gives the 0.2% offset yield strength.
7.3 Comparison of strip specimen versus dog-bone specimen
Compare the stress-strain curves obtained from a strip specimen and a dog-bone specimen. Discuss the differences in curve shape, yield strength, ultimate tensile strength, elastic modulus, and ductility measures. Justify these differences based on specimen geometry and test conditions.
Consider the following aspects in your comparison:
a) Curve shape differences due to stress distribution and grip effects.
b) Variations in yield and ultimate tensile strength caused by stress concentrations.
c) Elastic modulus variations due to extensometer placement and machine compliance.
d) Ductility measures affected by gauge length definition and necking behavior.
7.4 Error analysis and sources of uncertainty
Discuss the potential sources of error in your tensile test experiment. Consider measurement uncertainties, equipment limitations, specimen preparation, and human factors. How might these errors affect your calculated material properties?
8.0 Tensile Test Worksheet
Record your experimental data below. Login to save and export your worksheet.
Table 1: Dimension of the tested specimen
Material: Steel/Copper/Aluminum | Type: Rectangular/Round
| Material | Initial (unit: mm) | Final (unit: mm) | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| L0 | A0 (mm²) | d0 | b0 | h0 | Lf | Af (mm²) | df | bf | hf | |
| Steel | ||||||||||
| Copper | ||||||||||
| Aluminum | ||||||||||
| Plastic/PP | ||||||||||
d = diameter; b = width; h = height/thickness; L = length; A = area
Table 2: Observation data for the tested specimen
| No | Force (N) | Elongation (mm) | Stress (Pa) | Strain |
|---|
Table 3: Observation load for the tested specimen
| Material | Load at Elastic Limit (N) | Load at Upper Yield Point (N) | Load at Lower Yield Point (N) | Ultimate Load (N) | Breaking Load (N) |
|---|---|---|---|---|---|
| Steel | |||||
| Copper | |||||
| Aluminum | |||||
| Plastic/PP |
Table 4: Properties for the tested specimen
| Material | Proportional Limit Stress (Pa) | Nominal Fracture Stress (Pa) | Actual Fracture Stress (Pa) | % Reduction in Area | Strain | % Elongation | Ductility |
|---|---|---|---|---|---|---|---|
| Steel | |||||||
| Copper | |||||||
| Aluminum | |||||||
| Plastic/PP |
Table 5: Percentage error of the tested specimen
| Material | Properties | Modulus of Elasticity (Pa) | 0.2% Offset Yield Stress (Pa) | Yield Stress (Pa) | Ultimate Stress (Pa) |
|---|---|---|---|---|---|
| Steel | Experimental | ||||
| Reference | |||||
| % Difference | |||||
| Copper | Experimental | ||||
| Reference | |||||
| % Difference | |||||
| Aluminum | Experimental | ||||
| Reference | |||||
| % Difference | |||||
| Plastic/PP | Experimental | ||||
| Reference | |||||
| % Difference |
Note: Yield stress = Yield load / initial cross-sectional area | Ultimate stress = Ultimate load / initial cross-sectional area | Nominal fracture stress = Breaking load / initial area | Actual fracture stress = Breaking load / final area
📷 Specimen Photo Documentation
Capture photos of your specimen before and after the tensile test. These images will be included in your lab report.
1 Before Test
2 After Test (Fractured)
📝 Important Note: The generated PDF serves as supporting documentation only. Students are required to prepare a formal lab report using Microsoft Word and attach the downloaded PDF as an appendix to their submission.
Virtual Tension Lab
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Tensile Test Quiz
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Lab Assessment Matrix
| Criteria | Score 5 (Excellent) | Score 4 (Good) | Score 3 (Satisfactory) | Score 2 (Poor) | Score 1 (Very Poor) |
|---|---|---|---|---|---|
| 1. Organization and Appearance | Perfect order with intact diagrams, clean headers, typed cover, and single PDF submission. | Format is good with only 1 detail missing. Tape bound. | Rough format with multiple errors and stapled without binding. | Sloppy with damaged inserts and poor stapling. | Absent. |
| 2. Objectives | Rephrased in own words and linked to research context. | Identified with manual paraphrase. | Partial definition with manual copy. | Verbatim copy with missing content. | Absent. |
| 4. Results (x2 weight) | Accurate trends with numbered tables, walkthrough examples, and proper equation usage. | Correct trends with minor label gaps. Formulas provided. | Missing data with sloppy tables and missed units. | Bad construction with unreliable data. | Absent. |
| 5. Discussion (x2 weight) | Answers all questions with theory links and error analysis. | Misses one question with gaps in interpretation. | Incomplete logic with shallow depth. | Lack of understanding with incorrect comparison. | Absent. |
| 6. Conclusion | Summarizes data, validates objectives, and includes logical suggestions. | Missing 1 condition. | Missing 2 conditions. | Missing 3 conditions. | Absent. |
| 7. References | More than 9 sources in standard format with 30% recent. | 6-8 sources in manual format. | 3-5 sources with partial compliance. | 1-2 sources with format ignored. | None. |
Official Lab Record
Review your scores and generate a complete lab report. Your report will include game performance, quiz results, worksheet data, and discussion responses.
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Report will include:
0.00 MPa
(Game + Quiz x 10)
📝 Important: Students must refine their formal report using Microsoft Word and attach the generated PDF as supporting documentation in their final submission.