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Bend testing for your wires and cables

What is Bend Testing and its importance?

The bend test, frequently used in the construction and electrical sector, is a simple technique designed to provide a qualitative measure of a material's ductility, which is its ability to bend without breaking or fracturing.


The bend test not only helps in identifying materials that can be safely used in applications requiring flexing and bending, but it also allows engineers to design safer, sturdier, and more durable products.



Types of Bend Testing Techniques

There are a few common methods employed in bend testing:


  • Guided bend test: A coupon is bent in half, so that its ends touch, to observe cracking or other failures on the tension surface.

  • Wrap-around bend test: A coupon is wrapped around a former of a specified diameter and observed for any visible cracking or defects.

  • Swing arm bend test: The sample is bent over a specified radius through a certain degree of motion.

Note that the tests are chosen based on the expected usage, product type, material, and industry safety standards.


Understanding Bend Radius and its Effect on Cables

Bend Radius, defined as the smallest radius to which a cable can be safely bent without damaging it, has a profound impact on the durability and lifespan of a cable.

Bend Radius (BR)

Impact on cable

​Low BR

​Increased risk of cable damage due to high stress on internal components.

High BR

Longer cable lifespan due to reduced cable stress.

By adhering to the advised bend radius, users can ameliorate mechanical and electrical performance, improving safety and reliability over time.


Factors Affecting Cable Flexibility

Certain factors influence a cable's flexibility, including:


  • Material: The nature of the material used in the cable determines its overall flexibility.

  • Diameter: Thicker cables tend to be less flexible.

  • Construction: The configuration, or design of the cable, will inevitably affect its bendability.

  • Ambient Temperature: Low temperatures can make cables more rigid, reducing flexibility.

Remember, it's essential to safeguard your cables and wires' durability through careful handling and bend testing, to ensure a longer lifespan of your products. Knowing the different ways to test your cables, the concept of bend radius, and understanding the factors that affect cable flexibility can make a world of difference.


ISO 17025 and other relevant standards for bend testing

First and foremost, let's delve into the quality standards for bend testing. Key among these is ISO 17025, a globally recognized benchmark that verifies the competency of a lab in conducting specific tests. The standard is used throughout various industries to ensure the accuracy and repeatability of testing procedures.


Compliance requirements for cables

When it comes to cables, a few standards come into play:


  • IEC 60228: This international standard specifies the requirements for the conductors in cables.

  • ASME B31.1: American standard focusing on power piping systems, including bending requirements.

  • EN 50396: European standard that outlines the test methods for cables and cords under fire conditions.

These standards are stringent, setting a high bar for the performance and safety of cables.

Below is a simple comparison table to help further understand the differences:

​Standard

Focus

Region of Applicability

IEC 60228

Conductors in cables

Global

ASME B31.1

Power Piping Systems

United States

EN 50396

Test methods for fire conditions

Europe

Bend Testing Methods

There are variations in how bend testing can be performed. Two major types are the static and dynamic bending tests. The choice of method depends on the application of the cable and the predicted strain it will endure.


Static Bend Testing

In static bend testing, strain is applied to a cable or wire at a constant rate, and deformation and physical characteristics are monitored. It provides vital data such as


  • Flexural yield strength: This is the stress at which a material yields in the flexure mode of loading.

  • Flexural modulus: It measures the stiffness of a material.

  • Stress-strain relationship: This explains the way the material responds to applied stress.

These details collected during static bend testing offer valuable insights to manufacturers and quality control professionals. By understanding how a product reacts to stresses, they can make informed decisions about durability, longevity, and application suitability.


Keep in mind that the bending standards adherence is essential, not only to meet regulatory requirements but also to ensure the quality and safety of your cables and wires. They are designed to withstand rigorous conditions and testing, ensuring that they perform well in any given application. By strictly following these standards, you are investing in quality, safety, and reliability.


Remember, only through rigorous testing, we can stand by our products and be assured that we've done our best in delivering a quality, dependable product to the market.


Dynamic Bend Testing

Dynamic Bend Testing is a critical method used to evaluate the pliability and endurance of cables and wires under repetitive flexing conditions. By consistently bending the wire back and forth at a consistent radius, it's possible to identify the limit at which the wire might fail or break. This helps in providing data that are essential for product design, improvement, and quality control.


Key features of dynamic bend testing include:


  • Testing at varied bend radii

  • The ability to customize the bending speed

  • Reproducible and accurate results through automated testing


Benefits of Bend Testing

Bend Testing is an indispensable tool that enables manufacturers to certify that their products meet the required industry standards and quality parameters. Here are some key benefits of Bend Testing:


  • Reliability: Ensures the durability of the wire or cable.

  • Safety: Helps in recognizing potential failure points before the wire or cable is put into use.

  • Soundness: Validates the general structural integrity of the wire or cable.

Ensuring cable durability and reliability

In a world where we increasingly rely on advanced technologies, the durability and reliability of cables used are of high importance. Dynamic Bend Testing is instrumental in ensuring this, as it helps in determining the flexible life of a wire or cable under continuous use. This information is beneficial not only to manufacturers but also to end users who rely on these wires and cables for various applications.

Without Bend Testing

With Bend Testing

Product Life

Uncertain

Predictable and Reliable

Safety

Possible failure risks

Assured reduction in failure

Quality

Questionable

Proven and tested

Identifying potential failure points

Bend tests are comprehensive measures that allow manufacturers to identify the specific points at which a cable might fail. These failure points could originate from various factors – for instance, poor quality materials, imperfect design, or production defects. By using the Dynamic Bend Test, manufacturers can efficiently identify these points, address them, and prevent potential product breakdowns or safety hazards.


So, as we enter a new era of converging technologies, the significance of dynamic bend tests will only amplify. By ensuring that our cables and wires are reliable and durable, we create a safer and more efficient world.


Industry Applications of Bend Testing

Bend testing is not confined to a specific field but finds applications across several industries. Two of these significant sectors are the automotive and aerospace industries.


Bend Testing in the automotive industry

In the automotive world, the integrity and durability of wires and cables are paramount. These components are subjected to rigorous bending and twisting on a daily basis, whether it's associated with vehicle control systems, sensory hardware, or even entertainment systems.


Here is why bend testing is crucial in the automotive sector:


• Quality Assurance: Automotive cables and wires need to withstand heavy strain and harsh environments. Regular bend testing ensures that these components meet the industry's stringent quality standards.

• Durability & Long Life: The frequent bend testing of wires and cables helps to predict their lifespan and durability accurately.


Bend Testing in the Aerospace Industry

Just like their automotive counterparts, cables and wires in the aerospace industry also undergo thorough bend testing. The aerospace systems are subjected to extreme high-altitude conditions, which means the wires and cables used must be robust and resilient.


Here's why bend testing is significant:


• Safety Measures: Due to the criticality of aerospace operations, the consequences of a wire or cable failure could be catastrophic. Bend testing helps in detecting the weakest links beforehand.

• Reliability: Given that aerospace vehicles are more or less continuously in operation, the reliability of their components is of utmost importance.


Automotive vs Aerospace Bend Testing

Automotive

Aerospace

Nature of Environment

Extreme temperature, dust, dirt, moisture

High-altitude, low-pressure, extreme temperature

Strain on Cables

Heavy daily usage

Relative but constant pressure

Tolerance Level

Lower tolerance level

High tolerance level


Advantages of Bend Testing for Wires and Cables

Given the reliance on wires and cables across multiple industries, the importance of bend testing cannot be overstated. Here are some advantages:


• Predictability: Regular bend testing helps in predicting the lifespan of cables and wires.

• Cost-Effective: Proactively identifying faults and weaknesses can help avoid costly replacements and repairs.

• Safety Assurance: Bend testing ensures the utmost safety of the end-users by identifying potential risks early on.

• Compliance: It helps manufacturers comply with industry standards, thus preventing legal complications.

• Quality Control and Consistency: Implementing systematic bend testing protocols during production ensures that wires and cables meet consistent performance standards. This consistency is vital, especially in industries where reliability and uniformity across batches of products are essential.


In conclusion, bend testing is an indispensable process for assessing the performance, reliability, and safety of wires and cables. Its advantages extend to better predictability of product lifespan, cost-effectiveness, enhanced safety assurance, compliance with industry standards, product improvement, and consistent quality control. Manufacturers that employ bend testing as part of their quality assurance procedures can deliver higher-quality products that meet the demands of modern industries and ensure the satisfaction of their customers.


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1 Comment


Guest
Aug 28, 2023

This is a good one, thanks


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