Using the 80/20 rule, senior engineer Paul Adams uses his own decades of experience to explore the 7 product tests (for hard goods, mainly) that have stood the test of time for him throughout his career because these few tests tend to provide the most benefits to the most importers who are checking and validating specific items in materials, components, and products, such as their hardness, durability, and chemical makeup, i.e. you’re likely to require at least some of them whenever you’re developing a product, no matter what kind of product it is.
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🎧 The 7 Key Material/Component/Product Tests YOU are most likely to Benefit from [Feat. Paul Adams]
Today’s topic: The 7 product tests most importers should consider performing and why.
We’ll explore 7 tests that should be utilized during new product development or when coming back and checking product quality after production has started.
- Tensile test
- Impact test
- Hardness test
- Flexural test (bend test)
- Chemical analysis
- Fatigue testing
- Creep test
These are NOT in order of importance. (02:56)
Why importers should have an understanding of product test machine types.
You don’t need to have an in-depth knowledge of how a machine works, but it will benefit you to know that the testing lab you’re working with has equipment that means that they’re capable of providing the product tests for your materials or products to the extent that you need in order to assure that they’re safe or of good enough quality. (16:20)
Test 1: Tensile test
The tensile test is a test that helps confirm that the material or product will be strong enough for its intended application/s by applying tension to a sample until it breaks or fractures to measure the amount of stretch it has and the force it can endure.
Products that must endure force during use are likely to require a tensile test during development.
It commonly uses a universal test machine (UTM) that clamps a sample of the material between two grips or fixtures and applies tension to it by pulling the ends apart at a controlled rate. The force applied and the amount of stretch is measured, and the test ends when the sample breaks or the machine reaches its limit.
The results provided will be the maximum force applied, the amount of stretch at maximum force, and the amount of elongation.
Most industries utilize this test for different materials – products include airplane wing spars, running sneakers, car suspension components, construction steel, medical prosthetics, and packaging. (05:44)
Test 2: Impact test.
This test helps you to understand how much force a material can withstand or how well it can withstand a shock impact, such as being dropped or if something hits it. A good example of a product where this test is relevant is bulletproof glass. If it cannot withstand the right impact, users will be at risk of death or injury. Importers with an interest in safety and durability will use this.
A Charpy Test machine includes a pendulum which swings down and impacts the test piece which is held in place. The machine measures the amount of force and the duration of the impact, and the material may or may not break or deform. From the results, engineers will gain an understanding of the material’s resistance to impact.
Any kind of product that might suffer an impact while in use will benefit from impact testing. Examples include a lawnmower which throws up a stone at high speed against its housing, vacuum cleaners, bulletproof glass for banks, stores, and vehicles, construction materials like pipes and boilers, aerospace products, and more. (17:20)
Test 3: Hardness test.
Hardness testing is one of the most widely used of all tests, and it aims to measure how resistant a product or material is to being scratched, deformed, or indented.
There are several different types of hardness tests, including Rockwell, Brinell, Vickers, and Shore. Each of the tests is a variation on applying an ‘indentor’ (diamond tip, steel ball, etc) with a determined force to the surface of the material. The machine will measure the depth or size of the indentation made which is correlated with tables to provide the calculation of how hard the material is.
During development, this test is used to provide assurances that a material is actually suitable for its intended application, and later it is used to monitor changes in the material’s microstructure over time which could lead to safety and quality problems (such as if a supplier has changed a material for some reason). It can also be used to evaluate if a product’s heat treatment is hard enough.
This is used in so many industries to assure longevity and durability, but some good examples are automotive parts like gears and ball joints, construction materials like concretes, glass, and ceramics, DIY tools such as wrenches and drill bits, medical orthopaedics such as replacement joints, etc.
The tests are regularly used to measure the hardness and consistency of different types of materials:
- Vickers – hard materials like hard steels and titanium and thin and brittle materials
- Rockwell – a wide range of harder and softer materials, including softer metals like aluminum and brass
- Brinell – especially used on castings with a rough finish as it uses larger ball indentor which is easier to measure in these cases
- Shore – better for softer materials like rubbers, elastomers, polymers (25:46)
Test 4: Flexural test (bend test).
This mechanical test will measure how stiff a material is and its flexural strength before it breaks or deforms. A flat bar or round rod-shaped sample of the material to be tested is held by the bend test machine or in a UTM (as in numerous product tests) and a load is placed on the sample at a specific point or over a specific area, with the machine measuring the amount of deflection or bending that occurs.
It allows you to understand if the material you’re using is either rigid or able to bend enough, including a safety margin, without breaking.
Ceramics, metals, composites like carbon fiber, and plastics will typically be tested in this way to measure their performance. If you consider a mountain bike with a carbon fiber frame, you can understand why this must not be allowed to bend too much under the rider. Also, construction materials, steel for bridges, QC testing to assure product consistency, prosthetic limbs, and more are typical candidates for such a test. (34:21)
Test 5: Chemical analysis.
This test checks the chemical composition of a material which is important when designing and developing products, especially metallic products. A material’s chemical composition gives it certain physical and mechanical properties, such as strength, ductility, thermal conductivity, and electrical conductivity. Therefore, you need to know for certain that the materials going into your product only have the specific composition your product needs to behave and function as specified.
A typical test machine used is the X-ray fluorescence (XRF) alloy analyzer which comes in both hand-held or bench-sized versions. Using the former, an inspector can check material samples on-site in a supplier’s factory which is really valuable for assuring quality before products are manufactured.
The machine X-rays the sample and measures the response of the beam returning to the machine which shows which elements are present in which quantities. It’s also non-destructive, fast, and safe for the user.
Inspectors also use it for fault finding when a product has failed but the reason may not be clear. They will check the chemical analysis to determine if the materials are up to specification or not because an incorrect material could be a hidden failure mode.
Aside from manufacturers checking and validating that the materials in their products reach specification, chemical analysis will also be used by metal and alloy suppliers, scrap metal recyclers and processors, scientists and researchers, government agencies and regulatory bodies (to check compliance with environmental and health regulations), and any other industry that uses alloys such as aerospace, automotive, and medical. (42:06)
Test 6: Fatigue testing.
Fatigue testing is a type of mechanical testing where a material or component will be repeatedly loaded and/or unloaded in order to evaluate its performance under cyclic stress and gain an understanding of when a product will fail or its prospective longevity including a safety margin.
A UTM can once again be used (often with a custom jig or rig to house the part or product being tested and perform the action/s) and you will enter your predicted number of cycles that the product will undergo. For example, you predict that a million cycles of hitting a key in a keypad are fair use for 10 years. So the machine actions those million cycles by applying specified stress amplitude to the keypad and recording the number of cycles until failure.
The test can be repeated at different stress amplitudes to determine the relationship between stress amplitude and the number of cycles to failure, known as the S-N curve.
The report shows you how the sample fares throughout the test and you will see early signs of failure as well as the point at which the sample does fail giving you the information you need to decide on if the material or component is adequate for the product’s required lifespan, or if you need to select something that is more durable and, therefore, make a design change.
Products where fatigue and failure are not an option, include wind turbines where a blade can’t be allowed to sheer off, blenders, vacuum cleaners’ spinning brushes, automotive and airplane parts, etc. These products must include parts that stand the test of time, therefore fatigue testing is a key tool to help provide assurances that this is the case. (49:46)
Test 7: Creep test.
The creep test is a mechanical test that measures the ductility of a material over a period of time by placing it under a constant load or stress. This can be very helpful with polymers and plastics in particular, but also metals and alloys.
If you need a product to maintain its tolerance over time because it is a key component or critical for its shape, it cannot be allowed to creep or deform. In an assembly, there may be a very slight misalignment and one component may be placing too much force on its neighboring parts over time resulting in creep which will eventually cause failure.
A UTM can be used again as in many other product tests, where a sample is held and placed under a constant load (such as pulling it apart) for a specified time. Its deformation is monitored at intervals using an extensometer or strain gages. A positive result would be that nothing occurs to the sample at any time during the test, but even if there is a fail and the sample stretches you are able to use the data to compare your sample’s results with those of similar materials or with established standards to evaluate if its creep performance is good enough.
Engine parts, drivetrains, plastic gears, construction materials that carry loads, pipelines, boilers, and more are all placed under stress during their lifetimes and so creep testing is a must to assure that they will last. (57:09)
P.S. Related content to product tests…
- What’s the real Cost of Poor Quality and Reliability? [Podcast]
- What To Do If Your Electronic Product Contains Unreliable Components?
- When and Why a Product Failure Analysis is Required [Podcast]
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- Content from Paul about selecting and testing common thermoplastics
- Checking Steel’s Properties [Video playlist including many product tests]
- Silicone Rubber Properties Testing (Tensile strength, Elongation, & Tear strength) [Video]
- How To Test Silicone Hardness? [Video]
- Plastic Testing [Video playlist including many product tests]
- How Reliability Testing Is Critical To Obtaining Great Mass-Produced Products
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- Product Reliability Testing | 7 FAQs