Shear Test: Definition, Importance, and How It Works

The shear test is used to measure the shear strength of a material. Shear testing is essential in several industries because it helps to determine the strength of certain elements, items, or materials. The shear testing types are: torsion, lap, shear vane testing, etc. Shear testing works differently based on the type of test performed. However, it generally concerns applying stress to a material to cause a sliding failure along a plane parallel to the forces applied. 

This article will discuss the importance of shear testing, in addition to the equipment, advantages, disadvantages, and when to conduct shear tests.

What Is a Shear Test?

A shear test is a strength test conducted on test samples to identify their reaction to shear stress, modulus, and strain. These test samples include: metal, wood, polymer, film, plastic, ceramic, adhesive, and fasteners. Shear tests are used in rheology, quality control, material development, adhesives, and structural engineering.

What Is the Importance of the Shear Test?

The shear test is essential as it helps different industries discover how materials such as metals or plastic will react or respond to shear stress. Researchers in rheology use shear tests to identify how fluid and gel flow. These fluids include: lotions, emulsions, resins, polymer melts, slurries, and oils. They also use rheometers to identify a liquid’s properties. The results help the researchers to make sound decisions for cosmetic and pharmaceutical purposes. 

Manufacturers in several industries conduct shear tests to ensure products match industry standards regarding durability and strength. Scientists use shear testing to determine a material’s properties in material development. The results help them decide which material suits a particular purpose. Shear testing shows how well parts will glue together after adhesive use. Shear testing can help structural engineers, for example, determine the strength and safety of structures. 

Is Shear Testing the Same as Lap Shear Testing?

No, lap shear testing and shear testing are not the same. Though lap shear testing is a type of shear testing, each serves a different purpose. Shear testing determines a material’s resistance to stress or force. Lap shear testing tests the durability of an adhesive.

What Is the Shear Test Used For?

A shear test is used to discover a material’s resistance to shear stress or deformation when exposed to load or force. Shear stress occurs when two parts of a surface or two different surfaces slide past each other when force is applied. In other words, the test is used to determine the shear strength of materials.

What is the Equipment Used for Shear Testing?

The equipment used for shear testing is:

• Single/Double-Column Universal Testing Machine: A single/double-column universal testing machine tests several materials for strength. It conducts shear, hardness, tensile, and compression tests, etc. Figure 1 below shows single and double-column universal testing machines:

• Soil Shear Strength Tester: The soil shear strength tester is a hand-held device that measures soil shear strength. It provides the soil shear strength in kPa. Figure 2 below shows an example of a soil shear strength tester:

• Shear Blade: The shear blade is used to cut metal materials. Shear blades can differ in sharpness or hardness by heat treatment, material selection, and processing. Figure 3 below shows two shear blades:

• Direct/Residual Shear Data Acquisition Software: The direct/residual shear data acquisition software collects data, calculates friction angle, and saves reports during direct and residual shear testing. Figure 4 below shows an example from direct/residual shear data acquisition software:

• Tension Tester: A tension tester also tests a material’s shear strength. This tool is used in the metal wire, paper, and plastic film industries. Figure 5 shows a tension tester:

• Shear Sensor: A shear sensor measures friction and shear force in materials. Figure 6 below shows a shear sensor:

What Are the Different Types of Shear Testing?

The different types of shear testing are listed below:

1. Torsion Testing: Torsion testing helps determine how a material will react to excessive turning force. It is conducted through movement, loosening, and markup checks.
2. Cutting: The cutting shear test mainly applies to the food industry to test food texture and the force required to bite it. For this test, a researcher places a food item on a flat surface and cuts through it with a shear blade. The result helps to determine food toughness.
3. Direct: This shear test is often used in geotechnical engineering to test rock and soil strength. Researchers conduct this test by putting a rock or soil sample in a shear box and placing a weight on it. Next, the researcher applies force horizontally to begin the deformation of the samples.
4. Lap Shear Test: The lap shear test determines adhesive strength and durability. To conduct this test, a researcher applies adhesives to two flat surfaces. When the surfaces are bonded, the researcher applies a shear force to move the surfaces in opposite directions. The force applied to break the bond signifies the adhesive’s shear strength.
5. Losipescu: Losipescu shear testing is suitable for testing construction or composite materials for in-plane shear response and viability, respectively. To conduct the test, a researcher cuts a V-shaped notch into a rectangular shape and clamps it on its two sides. The researcher then tests the specimen’s shear strength by applying downward pressure to one side.

Is the Shear Test Used To Measure Shear Modulus?

Yes, the shear test is used to measure shear modulus. It does not only measure shear stress or strain. Shear modulus, also modulus of rigidity, measures a material’s ability to resist deformations from shearing or twisting. 

The shear modulus test is conducted using the static torsion and standard test. The static torsion test is performed using a torsional pendulum or a material rod. The standard test varies for different materials. ASTM A938 is used for metallic wire, while ASTM E143 is for structural materials. 

Do Shear Tests Determine Shear Stress?

Yes, shear tests determine shear stress. It is one of the material behavior shear test measures, as the test also focuses on strain and modulus. 

To learn more, see our full guide on the Shear Stress Formula.

How Does Shear Testing Work?

Shear testing works by using a shear testing tool to determine a material’s resistance to shear stress or behavior when deformed through different shear tests. The material could be polymeric, composite, metallic, or ceramic. These tests include: in-plane, punch, single, double, direct, and torsion. Shear tests help to identify a material’s ductility, toughness, yield strength, strain hardening exponent, and rigidity modulus.

When using the universal testing machine for a shear test, the procedures are: sample preparation, test setup, machine calibration, parameter setting, test running, data collection and analysis, and reporting. The procedures are briefly explained below:

1. The test specimen is selected based on the type of test to conduct and the standard guiding it.
2. Test setup involves placing the test specimen in the universal testing machine. The specimen is held firmly to avoid more stress or slipping.
3. The machine must be calibrated before the test. Other related instruments, like the load cell, must be checked and calibrated, too, for accurate results. 
4. The researcher sets certain parameters — loading rate, maximum rate, etc. — against which to conduct the shear test.
5. The universal testing machine applies a load to the material at the set rate until it deforms. 
6. The researcher records the applied load and deformation information. The result is analyzed by plotting a load vs. stress vs. strain graph. The graph calculates the material’s shear strength or modulus. The result is used to determine the material’s properties. 
7. Document every piece of information about the tested material. This includes: the specimen, test parameters, and results.

Shear test data obtained using the universal testing machine are: yield shear stress, shear modulus, shear stress vs. shear strain curve, and load vs. deformation data.

How To Read a Shear Test Result

Reading and interpreting shear test results involves understanding the data obtained during the test and terms like: parameters, load, shear stress, shear angle, etc.

What Is the Standard Measure for Concrete in a Shear Test?

The standard concrete measure for a shear test requires a specimen of 230 mm x 150 mm x 150 mm. An M20 concrete grade should be 2.8 MPa, while the M30 grade should be 3.5 MPa. Factors influencing concrete’s shear strength include: corrosion, stirrup size and spacing, and concrete grade. 

How Does Shear Tests Differ From Other Material Testing?

Shear tests differ from other test types like tensile and compression tests. Compression tests measure the force required to compress (or deform) a material under compression loads. Compression testing parameters include: modulus of elasticity, ultimate compressive strength, and compressive yield strength. The compression test is conducted by placing a test sample in a compression testing machine. The machine applies a constant load to the sample until it reaches a set deformation point.

On the other hand, the tensile test determines the amount of tension needed to apply to a material before it breaks. It focuses on yield strength, modulus of elasticity, and tensile strength. The shear test measures a sample's resistance to force before breaking or deforming. 

When To Do a Shear Test?

Shear testing should be conducted in various situations and applications to assess the shear strength. It can also be done when selecting a material for use. This will help to determine the material’s response to resistance to stress or strain and its suitability for use.  

How Long Does a Shear Test Take?

A shear test duration depends on the type being conducted. Direct shear testing for granular materials can take 24 hours, while clay materials can take up to three weeks. Measuring shear strength through a direct shear test can take up to four days.

What Are the Materials Used in a Shear Test?

Materials used in a shear test fall into three major categories: layered composites, adhesives, and rigid substrates. 

What Are the Advantages of the Shear Test?

Shear tests have several advantages, such as:

1. researchers can ascertain the highest load a material can bear before breaking.
2. Show whether a selected material matches regulatory standards.
3. Help to determine whether structures are safe enough to use.
4. Show the properties of materials and the purpose they suit the most.
5. Bonded surfaces are shear-tested to determine the extent to which surfaces are joined and the durability of the applied adhesive.
6. Help guarantee a material's safety for a particular use. It helps to match materials with the correct use.
7. Measure the stress level a material exceeds before failure.
8. Show how materials respond to stress. 
9. Have different types for different industries and materials.

What Are the Disadvantages of the Shear Test?

The disadvantages of shear tests are outlined below:

1. Mounting excessive shear stress on materials can cause damage. 
2. The test material must match the sizes provided in the regulatory standard. If not, there will be issues. For instance, plastics should be 2-inch-square plates with a thickness of 0.05 to 0.5 in., according to ASTM D-732.
3. Sample preparation requires strict compliance with industry standards for sample orientation, size, and shape. 
4. Shear tests have several procedural steps regardless of the type.
5. There’s no one-size-fits-all approach to shear testing. Different materials require varying tests. 
6. Failure to take safety precautions before conducting a shear test can cause issues.
7. While some shear types are affordable, some are expensive due to tooling costs and the testing time involved.

What Are the Types of Failures in Shear Tests?

The types of shear test failures are:

1. Cohesive Failure: A cohesive failure occurs if adhesives remain on a surface due to a fracture.
2. Adhesive Failure: Adhesive failure occurs when surfaces cannot bond due to dirt or surface smoothness.
3. Interfacial Failure: During shear tests, interfacial failures occur due to the presence of an element, hydrolysis, for example, at the interface.
4. Mixed Mode Failure: Mixed mode failure is caused by interlaminar tension and shear stresses resulting from remote loadings applied to composite components.
5. Ductile Failure: Ductile failure results from the plastic deformation of a material due to loading a material beyond its yield strength.
6. Brittle Failure: Brittle failure is caused by little to no plastic deformation of a material.
7. Localized Shear Failure: This failure is found in soft soil. The lack of a well-defined applied load often causes it. 

Is It Hard To Conduct a Shear Test?

No, a shear test is not hard to conduct. For example, the direct and shear vane tests are simple and cheap. 

Is the Shear Test Dangerous?

No, shear tests are not dangerous. Yet, necessary precautions must be taken when conducting them. These precautions include: maintaining a constant strain rate throughout a test, avoiding bubble formation during adhesive application to surfaces, etc.

What Is the Difference Between the Shear Test and the Tensile Test?

The shear test focuses on a material’s resistance to force. On the contrary, tensile strength measures the force needed to apply to a material to break it. Both tests determine a material’s strength and are mechanical tests. 

Summary

This article presented shear tests, explained them, and discussed their importance and how they work. To learn more about shear testing, contact a Xometry representative.

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