Application Note | Weld Surface Inspection
Weld Surface Inspection Using a Portable 3D Profilometer
Measuring Weld Roughness, Shape, Dimensions, and Volume in the Lab or in the Field
Research & Experimental Testing
Craig Leising
Visual Design & Editorial
Andrew Shore
Introduction
It may become critical for a particular weld, typically done by visual inspection, to be investigated with an extreme level of precision. Specific areas of interest for precise analysis include surface cracks, porosity and unfilled craters, regardless of subsequent inspection procedures. Weld characteristics such as dimension/shape, volume, roughness, size etc. can all be measured for critical evaluation.
Why Use a 3D Non-Contact Profilometer for Weld Surface Inspection
Unlike other techniques such as touch probes or interferometry, the NANOVEA 3D Non-Contact Profilometer, using axial chromatism, can measure nearly any surface, sample sizes can vary widely due to open staging and there is no sample preparation needed. Nano through macro range is obtained during surface profile measurement with zero influence from sample reflectivity or absorption, has advanced ability to measure high surface angles and there is no software manipulation of results.
Easily measure any material: transparent, opaque, specular, diffusive, polished, rough etc. The 2D and 3D capabilities of the NANOVEA Portable Profilometers make them ideal instruments for full complete weld surface inspection both in the lab and in the field.
ℹ️ Learn more about non-contact profilometry lab services for weld inspection.
Measurement Objective
In this application, the NANOVEA JR25 Portable Profiler is used to measure the surface roughness, shape and volume of a weld, as well as the surrounding area. This information can provide critical information to properly investigate the quality of the weld and weld process.
NANOVEA JR25 Portable
Optical Profilometer
The Sample
Test Results
3D Profile and Weld Roughness
The image below shows the full 3D view of the weld and the surrounding area along with the surface parameters of the weld only. The 2D cross section profile is shown below.
| ISO 25178 Height Parameters (weld) | |||
|---|---|---|---|
| Sa | 2.219 | µm | Arithmetic mean height |
| Sq | 3.025 | µm | Root-mean-square height |
| Sz | 68.48 | µm | Maximum height |
| Sp | 34.17 | µm | Maximum peak height |
| Sv | 34.31 | µm | Maximum pit depth |
| Sku | 3.025 | Kurtosis | |
| Ssk | 0.1002 | Skewness | |
Table 1: ISO 25178 height parameters of the weld (values shown in Fig. 1).
Weld Dimensions, Area, and Volume
With the above 2D cross section profile removed from the 3D, dimensional information of the weld is calculated below. Surface area and volume of material are calculated for the weld only below.
| Dimension | Value |
|---|---|
| Width | 6.330 mm |
| Height | 0.7387 mm |
| Radius | 5.308 mm |
Table 2: Weld dimensions from the shape analysis (values shown in Fig. 3).
| Parameter | Hole | Peak |
|---|---|---|
| Surface | 1.01 mm² | 14.0 mm² |
| Volume | 8.799 × 10⁻⁵ mm³ | 23.27 mm³ |
| Max depth/height | 0.0276 mm | 0.6195 mm |
| Mean depth/height | 0.004024 mm | 0.2298 mm |
Table 3: Surface area, volume, and depth/height of the weld (hole and peak).
Conclusion
In this application, we have shown how the NANOVEA 3D Non-Contact Profiler can precisely characterize critical characteristics of a weld and the surrounding surface area. From the roughness, dimensions and volume, a quantitative method for quality and repeatability can be determined and or further investigated.
Sample welds, such as the example in this app note, can be easily analyzed with a standard tabletop or portable NANOVEA Profiler for in-house or field testing.
Frequently Asked Questions About Weld Surface Inspection
How can a weld be inspected quantitatively?
Instead of relying only on visual inspection, a 3D non-contact profilometer measures the weld surface and the surrounding area, giving dimensions and shape, volume, roughness and size. Areas of interest such as surface cracks, porosity and unfilled craters can then be analyzed precisely, and the results used as a quantitative measure of weld quality and repeatability.
Why use a non-contact profilometer instead of a touch probe or interferometry?
A NANOVEA 3D non-contact profilometer, using axial chromatism, can measure nearly any surface without sample preparation. It covers the nano through macro range with zero influence from sample reflectivity or absorption, measures high surface angles, and does not manipulate results in software. Transparent, opaque, specular, diffusive, polished and rough materials can all be measured.
Which weld dimensions can be measured from a 3D scan?
From a 2D cross-section extracted from the 3D scan, the shape analysis of this weld gave a width of 6.330 mm, a height of 0.7387 mm and a radius of 5.308 mm. Volume analysis of the weld alone gave a peak volume of 23.27 mm³ over a surface of 14.0 mm².
Which roughness parameters describe a weld surface?
ISO 25178 height parameters describe the areal roughness of the weld. For this weld, Sa was 2.219 µm, Sq 3.025 µm and Sz 68.48 µm (Sp 34.17 µm, Sv 34.31 µm), with a kurtosis Sku of 3.025 and a skewness Ssk of 0.1002.
Can welds be inspected in the field?
Yes. The portable NANOVEA JR25 measured this weld, and NANOVEA portable profilometers are suited to complete weld surface inspection both in the lab and in the field. Sample welds can also be analyzed on a standard tabletop NANOVEA profiler for in-house testing.
Which NANOVEA instruments are used for weld surface inspection?
This study used the NANOVEA JR25 Portable Profiler. Open staging means sample sizes can vary widely, and the same 2D and 3D measurements are available on NANOVEA's standard tabletop profilers.
