Mistras Group
XRF Analysis of Automotive Glass Drives Fast Inspections
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Source: Evident
Automotive glass (also known as auto glass) is a key safety feature in vehicles that protects the driver and other occupants. Auto glass is specially designed to keep you inside the vehicle during an accident, protect you from shattered glass, and shield you from flying debris.

Some types of automotive glass have extra features, such as heating, heat insulation, water-repellence, and an integrated antenna. As auto-glass production lines diversify, major auto-glass manufacturers are facing greater challenges in their glass-inspection processes.

This post explores automotive glass in depth. Learn about the unique design of auto glass, the challenges of manufacturing it, and the benefits of inspecting it using handheld X-ray fluorescence (XRF) analysis

Automotive Glass Manufacturing: How Auto Glass Is Made

Automotive glass comes in two main types: laminated safety glass and tempered safety glass. Laminated glass is used for front windshields, so it is designed to be very strong to protect the driver and occupants. Laminated glass is made by fusing two sheets of glass with a thin vinyl layer in the middle. The vinyl helps the glass stay intact even when broken, reducing the amount of glass that can shatter from the windshield during a strong impact.

Tempered glass is a heat-treated glass used for car windows and rear windshields. This glass is made by heating float glass up to a softening temperature and then rapidly cooling it. After treatment, the glass’ outer surface exerts an inward compressive stress, while the glass’ interior exerts an outward tensile stress. This means that when tempered glass is impacted, its outer surface’s compressive stress is offset immediately, providing impact resistance. While tempered glass will shatter when smashed, it breaks down into smaller, pebble-like pieces that have duller edges than ordinary glass.

Tempered Glass: Reducing the Risk of Explosions

Tempered glass must be carefully manufactured and inspected to reduce the risk of a spontaneous explosion while a vehicle is in use. The glass could explode if small amounts of impurities, such as nickel sulfide, are blended in during the production process. Impurities can enter the production process in various ways:

The glass-producing equipment contains nickel
Raw materials contain trace amounts of nickel and sulfur
Sulfur-containing fuel is used
When reaching 379 °C (714.2 °F), the nickel sulfide crystal undergoes a crystalline phase transition. At low temperatures, the nickel sulfide crystal’s volume expands by about 2% to 4%, disrupting the tempered glass’ internal stress balance and creating a potential risk of spontaneous explosion.

Integrating Extra Features into Automotive Glass

Antennas:
The antenna is printed on the inner surface of laminated glass using conductive metal paint. Then the paint and glass are integrated through sintering. The antenna is then connected to the car’s signal amplifier with wires and can receive FM/AM, TV, and GPS signals. Compared with the point antenna that used to be commonly installed in automobiles, the integrated antenna offers more stable and reliable signal reception.

Heating wires:
Auto glass can be electrically heated for defrosting and defogging, providing drivers with a clear view in cold weather.

Heat insulation
By coating its central layer with a very fine metal powder, laminated glass can absorb and reflect solar energy to achieve heat-insulation and cooling effects. This technology has been applied to many high-end car models.

The Benefits of Handheld XRF for Auto Glass Inspection
While the manufacturing of automotive glass has become more complicated with high-end car features, handheld XRF analysis can simplify the glass inspection process.

For instance, handheld XRF analyzers such as the Vanta™ series can determine the chemical composition of glass and the thickness of layers used. The Vanta analyzer can also determine the coating thickness within the 0.5–60 micron range, which is dependent on the coating composition.

This quick test enables inspectors to:

Rapidly detect nickel (Ni) content in glass. This capability helps ensure that the glass shipped from a factory does not contain nickel-sulfide impurities, mitigating the risks of the tempered glass spontaneously exploding when a vehicle is in use.
Rapidly detect thickness and uniformity of the metal coating inside laminated glass, as well as its chemical composition. This verification helps ensure that the finished product meets the design requirements.

If you’d like to learn more about XRF analysis of automotive glass and coatings, don’t hesitate to contact us for a demo.
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