Author: Bob Morrison

Introduction Ultrasonic NDT testing is an effective way to determine the integrity of a spot weld.  Below is a good description of the attenuation or decrease in signal strength that can be useful when analyzing a spot weld. Attenuation Measurements Ultrasonic wave propagation is influenced by the microstructure of the material through which it propagates. The velocity of the ultrasonic waves is influenced by the elastic moduli and the density of the material, which in turn are mainly governed by the amount of various phases present and the damage in the material. Ultrasonic attenuation, which is the sum of the absorption and the scattering, is mainly dependent upon the damping capacity and scattering from the grain boundary in the material.…

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Introduction If you are looking for a good NDT system for inspecting spot welds in the automotive industry or any other industry, there are several options available.  A good system for you to consider that is easy to use, accurate, and advanced features is SpotSight by Progenero Products. If you are curious about general information about terminology and how ultrasonic systems work, below is a good list of Q &A on Ultrasonic Testing. Ultrasonic Testing Q & A What is an ultrasonic transducer.. A transducer is any device that converts one form of energy into another. An ultrasonic transducer converts…

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Introduction An important correlation between the attenuation of an Ultrasonic A-scan reading and the strength of a spot weld can help you identify “stuck welds” or “cold welds”.  Many studies have been done over the years to better understand how Matrix Phased Array (MPA) ultrasonic NDT systems can pick up on different characteristics of a spot weld.  You want to know the diameter and thickness of a weld nugget and ultimately, it’s strength.   Many different approaches have been taken to find the best solution for you to do NDT testing of spot welds. Attenuation as a way for you to…

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Introduction There are advantages and limitations for you to consider with ultrasonic technology to do NDT (Non-Destructive Testing) of spot welds. For the most part, you can count on a well-made Ultrasonic system to be a good solution to provide accurate results for spot welds Non-Destructive Testing.  Fortunately, you don’t have to be an expert to understand the science of ultrasonic NDT systems. The transmission of ultrasonic signals through materials is just like the transmission of audible sound waves; it is straightforward and easy for you or anyone to understand.  Ultrasound is simply a high frequency sound wave and the…

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Introduction Non-Destructive Evaluation (NDE), also known as Non-Destructive Test (NDT) can provide you with 95% accuracy when compared to physical destructive testing of spot welds.  The value of using NDE is that it is much quicker, safer, and easier than destructive testing.   This requires that you have the right equipment; advanced systems make it easy for the test technician to get consistently accurate results.  There is still a need to train you operators to make sure they are aware of how the equipment works and how to identify issues that need to be resolved. The right equipment Make sure you…

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Introduction Non-Destructive Testing (NDT) systems are becoming more advanced and more accurate; however, there is still a human component that you must address to make sure you are collecting good information.  You can’t make good decisions about quality control if you don’t have confidence in the test data. Training your NDT technicians well is an essential part of a good NDT program.  Creating and implementing an effective training program for NDT technicians is crucial to good training.  Some NDT systems allow your operators to adjust settings to achieve false positive results.  Some systems require strong knowledge of the system and…

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Introduction Destructive testing of spot welds can be costly and time consuming.  Many automotive companies are adopting various forms of Non-Destructive Testing (NDT) systems.  One of the most effective that has been used in auto manufacturing for years is ultrasonic NDT.  If you have spent time creating inspection plans for an NDT system to evaluate the integrity of spot welds, you know that the process can be complex and time consuming.  It is valuable to have a tool that allows you to easily take information from a weld plan and automatically generate an inspection plan to be used on an…

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Introduction Due to an effort to reduce vehicle weights to enhance vehicle fuel efficiency, innovative high-strength steels are frequently used to both reduce the vehicle weight and to improve passenger safety.  Resistance spot welding (RSW) is the most commonly used method of joining metal sheets in car-body manufacturing because of its low cost, speed, cleanliness and ease of automation. However, the designed microstructure of steel sheets is changed during the RSW process due to the welding thermal cycle.  The microstructural evolution during RSW is highly dependent on the welding parameters.  These changes influence the mechanical strength of the steel structures. …

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Attenuation of ultrasonic signals During the resistance spot weld process, the metals rapidly melt and cool.  The resulting weld nugget has a crystalline structure that is relatively coarser than the unmelted sheet metal.  This coarse crystalline structure in the weld nugget has a much higher attenuation rate than the unmelted sheet metal.  The attenuation rate is the rate at which the ultrasound signal deteriorates due to absorption and scattering of the signals at the interface between materials or grain structures in the materials. You can see the differences in attenuation rate by looking at an A-scan.  The rate that the…

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It is important to have a way to test spot welds quickly and accurately to determine the integrity of the weld.  This is also true for the development of the inspection plan that are used to do the inspections. The Problem: There are many systems available that do NDT inspections of spot welds, but many fall short in one of these critical areas:   If a system is not quick and easy for your operators to learn and use can be costly to operate.   If a system that is not accurate, you can’t count on it for critical feedback, which…

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