Torque Test: How Is the Test Conducted?
A torque test is used to identify the reaction of an object under turning and twisting conditions. Torque testing is usually applied in industries like: manufacturing, aerospace, pharmaceutical, automotive, etc. A torque tester (also called a torque analyzer) is one of the core tools for conducting torque tests.
The right torque rating ensures safety and efficiency. Before conducting a torque test, choosing the right tool and understanding the type of torque test to conduct is essential.
This article will examine a torque test and outline its importance, the tools needed, and the common applications.
A torque test is a measure of an object’s reaction to applied rotational force. Torque tests come in different forms, some mild and some excessive. These include: static, dynamic, and non-destructive torque testing.
Torque testing is important to manufacturing procedures because it evaluates the safety and efficiency of certain parts. Take the bottling industry, for example; bottle caps are torque-tested to ensure enough pressure is added to the cap to seal the container and prevent kids from opening it easily, but not so much that it damages the bottle itself. This applies to glass and polyethylene terephthalate (PET) bottles.
Similarly, torque tests help manufacturers anticipate user experience. Using the bottle example, torque testing can help determine if caps should be tighter or looser. They may be difficult to open if excessively tight, stressing the consumer or making the product unusable. The bottle may lose pressure or even allow bacterial infiltration if it is too loose.
Moreover, the torque test process helps manufacturers define parameters, adhere to quality control requirements, and measure stiffness and torsional strength. Furthermore, it is a good gauge of performance and design-parameter accuracy.
A torque test consists of three steps as discussed below:
- Movement Test: The movement check, also referred to as the first movement torque test, is done by using a torque measuring tool to test a tightened threaded fastener (nut, bolt, or screw). Mark the tightened fastener and turn the torque testing tool clockwise to start a movement check. Do this until the fastener begins to tighten further. Record the torque necessary to initiate that rotation (also called residual torque). This test is conducted to confirm that a product complies with its design and manufacturing requirements.
- Loosening Test: The loosening check, also called the breakaway test, is the opposite of the movement check. For the loosening check, the torque testing tool is applied and turned counterclockwise until the fastener loosens. Take a torque reading when the bolt or screw “breaks” and begins to move. That breaking torque is also the max torque the joint will likely experience in the counterclockwise direction. This test helps to ensure accuracy and precision. It also prevents failures.
- Markup Test: The markup test is done by marking a point on both the fastener and the surface to which it is tightened. Next, loosen and tighten the fastener to ensure it fits back to the marked points. In this test, the amount of torque required to return it to the original mark determines the torque value of the fastener.
There are several torque testing tools. These include:
- Torque tester
- Adapter and fitting
- Torque sensor
- Calibration equipment
- Test stand
- Dial torque wrench
- Load cell
- Torque screwdriver
- Torque multiplier
- Torque meter
A torque test result demonstrates what the right amount of torque should be. It will also show you whether your item’s tension or tightening rate lines up with industry standards.
Suppose a torque analyzer is applied to a ¾” galvanized and waxed bolt. Based on ASTM A325, it is acceptable if the tightening torque range is between 175–213 ft-lbs. The fastener is not too tight (or loose) and will not break or strip.
If the same bolt size has a minimum value of 28,000 N, it means the right amount of tension is applied. However, if it exceeds 34,000 N (the maximum tension), it may experience damage and must be readjusted.
Yes, Young’s modulus is used to determine the proper torque. Young’s modulus, or the modulus of elasticity, measures a material’s capacity to withstand compression or tension. It shows how materials can deform but resume their initial shape after exposure to tension.
Common applications of torque testing are:
- Mechanical lugs
- Dental implants
- Bottle caps
- Key ignition
- MSB Bussing
- Dashboard knob
Here are some important points to know about torque specifications and standards:
- Industry-governing bodies set standards for torque testing to ensure safety and efficiency. Relevant regulatory bodies include: the FDA (Food and Drug Administration), ISO (International Organization for Standardization), SAE (Society of Automotive Engineers), AIA (Aerospace Industries Association), NEC (National Electrical Code), and ASTM (American Society for Testing and Materials).
- ISO 6789-1:2017 contains numerous standards for torques. These standards include specifications for hand-torque tools, tests, etc. Hand-torque tools include: screwdrivers, wrenches, and torsion bars. During design, torque tools should undergo overloading and endurance tests.
- ASTM A325 outlines the different tension and tightening ranges required for different bolt sizes. The bolt sizes and ranges are shown in Figure 2 below:
ASTM A325 torque specifications and standards.
Image Credit: https://scfastening.com/charts-tables/torque-astm-a325/
- J1701M_202203, a paid SAE report, spells out an ideal torque-tension relationship. The report examines how torque and tension respond to: humidity, types of torque tools, friction, and surfaces. Also, the report serves as a guide for proper torque level management.
There are several ways to address torque-testing problems:
- Torque Tool Maintenance: Torque testers or other equipment must be properly used, checked, stored, and cleaned. They must also be connected to safe and reliable power sources following manufacturer instructions. Faulty or worn parts should be repaired or replaced.
- Performance Tracking: The tools’ maintenance logs, calibration, and torque test results must be monitored regularly and recorded.
- Training: Personnel who perform the torque testing should be trained to use the tools properly and interpret their test results.
Advancements in torque testing technology largely center around the sensors. They’ve trended toward miniaturization and non-contact equipment. In addition, torque sensors now form a part of smart manufacturing.
Car manufacturers have also driven torque-measuring trends toward Industry 4.0 quality control standards. They monitor and analyze real-time data and integrate torque measurements into smart manufacturing processes.
Electric vehicle manufacturers are heavy users of torque tests. The components must deliver torque to the wheels without using excessive energy. Torque transducers are positioned in the electric motor and transmission to monitor performance. The transducers generate real-time data, improving the vehicle’s performance and boosting efficiency.
The best steps to ensure accuracy in torque testing are:
- Using the right tools
- Calibrating and lubricating torque tools regularly
- Resetting a torque wrench to zero after an hour of use
- Using the right torque specifications
- Adjusting a torque wrench’s capacity by no more than 10%
Torque testing plays a significant role in quality control by ensuring products or devices meet torque requirements provided by regulatory bodies. Compliance makes them less prone to breakage, wastage, or accidents.
There are three types of torque tests: static, dynamic, and non-destructive torque tests. Their differences are discussed below:
- Static Torque Test: The static test is conducted on stationary objects or parts. It is used to confirm a part’s ability to perform under load. It is also used to check product design health.
- Dynamic Torque Test: The dynamic test is conducted by connecting a torque sensor to a rotating part. The test determines the part’s durability, efficiency, and performance.
- Non-destructive Torque Test: The non-destructive torque test applies to assembled or whole items without uncoupling their connected parts. This test is done in two ways: magnetic particle and ultrasonic torque testing.
The magnetic particle torque testing method detects changes in a surface in response to torque by measuring alterations in magnetic fields. On the other hand, the ultrasonic torque test measures applied torques with ultrasonic waves.
The IZOD test is relevant to torque testing because it can further determine a material’s resistance to breakage. It also helps engineers ascertain materials’ response to impact loading.
Yes, torque tests require certifications and compliance with regulatory standards. People who have undergone training and demonstrated adequate knowledge of torque tests can be certified as torque-testing professionals.
No, any material can be torque-tested. The industry or department conducting the torque test will determine the type of material to use.
One common target is aluminum alloys. Other regularly tested materials are ceramics, copper, steel, thermoplastic polymers, etc.
Torque testing indicates how objects react to different twisting or turning loads. On the other hand, force testing determines a material’s reaction to compression or tension at the point of failure. Both tests apply force to materials until they break.
This article presented torque tests, explained them, and discussed how they are conducted. To learn more about torque tests, contact a Xometry representative.
Xometry provides a wide range of manufacturing capabilities and other value-added services for all of your prototyping and production needs. Visit our website to learn more or to request a free, no-obligation quote.
The content appearing on this webpage is for informational purposes only. Xometry makes no representation or warranty of any kind, be it expressed or implied, as to the accuracy, completeness, or validity of the information. Any performance parameters, geometric tolerances, specific design features, quality and types of materials, or processes should not be inferred to represent what will be delivered by third-party suppliers or manufacturers through Xometry’s network. Buyers seeking quotes for parts are responsible for defining the specific requirements for those parts. Please refer to our terms and conditions for more information.