Nuclear

Testblocks and test specimens for NDE

Uddcomb develop and manufacture high-quality test blocks with realistic defects for NDE qualification supporting industries such as nuclear, energy, process, offshore, marine, and manufacturing.

For over 40 years, Uddcomb have delivered customized test blocks to the international market, ensuring reliable and realistic defects for NDT.

Uddcomb offer:

• Test blocks with realistic, controlled defects, tailored to customer requirements.
• Manufacturing in qualified materials, including stainless steel, nickel alloys, and high-strength steels.
• Full traceability, from material sourcing to final documentation.
• Qualification of test blocks and setups in line with industry standards.
• Technical support throughout the qualification process.

Our realistic defects representing:

• Weld solidification cracks are defects that form in the weld metal during the final stage of solidification, as the molten weld pool turns into solid metal. They typically appear along the weld centerline and are caused by factors such as poor material properties, high heat input, or improper welding parameters.

These cracks reduce the structural integrity of the weld and can lead to failure, especially in critical applications. Preventive measures include optimized welding techniques, proper material selection, and control of heat input.

• Mechanical fatigue cracks are cracks that develop in materials or welded joints due to repeated cyclic loading over time. Even when the applied loads are below the material’s ultimate strength, microscopic cracks can initiate and gradually grow with each load cycle.

These cracks often start at stress concentrations such as weld toes, sharp corners, or material defects. If undetected, they can lead to sudden and catastrophic failure. Preventing fatigue cracks involves good design, smooth transitions, proper weld profiles, and regular inspection.

• Lack of fusion is a welding defect where the weld metal fails to properly bond with the base material or with a previous weld pass. This results in weak, unbonded areas within the weld that can compromise its structural integrity.

The defect is often caused by insufficient heat input, incorrect welding technique, or poor joint preparation. Lack of fusion typically occurs at the weld root, sidewalls, or between weld passes. Preventive measures include proper joint design, optimized welding parameters, and thorough operator training.

• Geometrical defects are imperfections in the shape, size, or alignment of a weld or component that do not meet specified tolerances. These defects can affect the structural performance, fatigue resistance, and overall quality of welded structures.

Typical examples include excessive weld reinforcement, undercut, misalignment, incomplete joint penetration, and irregular weld profiles. Geometrical defects are often caused by poor joint preparation, incorrect welding technique, or inadequate control during fabrication.

• Interdendritic Stress Corrosion Cracking (IDSCC) is a form of cracking that occurs along the dendritic grain boundaries of a material exposed to a corrosive environment combined with tensile stresses. The cracks propagate between the dendrites, often following the weak, segregated areas formed during solidification.

ISCC is typically associated with materials such as stainless steels and nickel alloys, especially when exposed to aggressive environments like chlorides or high-temperature water.

The main contributing factors are a susceptible material, a corrosive environment, and the presence of tensile stresses. Preventive actions include proper material selection, stress-relief treatments, and control of the operating environment.

• Intergranular Stress Corrosion Cracking (IGSCC) is a type of cracking that occurs along the grain boundaries of a material when exposed to a specific corrosive environment combined with tensile stresses. The cracks propagate between the grains, weakening the material’s structure without significant visible surface damage initially.

IGSCC commonly affects stainless steels and nickel alloys, particularly after sensitization, where chromium depletion at grain boundaries makes the material more vulnerable to corrosion.

The key contributing factors are a susceptible microstructure, a corrosive environment (such as chlorides or high-purity water), and applied or residual stresses. Preventive measures include proper material selection, heat treatment to avoid sensitization, and controlling the operating environment.

• Primary Water Stress Corrosion Cracking (PWSCC) is a type of intergranular cracking that occurs in nickel-based alloys and stainless steels exposed to high-temperature primary water environments, typically in nuclear pressurized water reactors (PWRs). The cracking develops along grain boundaries due to the combined effect of tensile stresses, high temperatures, and the specific chemistry of primary water.

PWSCC can significantly reduce the structural integrity of critical components such as nozzles, welds, and steam generator tubes.

Key contributing factors include material susceptibility, operating temperature, water chemistry, and the presence of tensile or residual stresses. Prevention involves using resistant materials, stress-relief treatments, and strict control of water chemistry.

• Implants are artificial defects introduced into test blocks or components by embedding prefabricated flaw inserts, such as wires, discs, or small crack-like features. They are used to simulate realistic flaws for the development, qualification, and verification of non-destructive testing (NDT) methods.

Although implants provide a high degree of realism, they still represent artificial flaws and should be complemented with other defect simulations.

•  Electrical Discharge Machined (EDM) Notches. EDM notches are precisely manufactured artificial defects created using electrical discharge machining. They are used to simulate cracks or other flaw types in test blocks or components for non-destructive testing (NDT) development, qualification, and training.

EDM notches are a valuable tool for verifying inspection capability, but it is important to note that they do not fully replicate the metallurgical characteristics of real cracks.

Our test blocks are used for NDE method development, qualification, equipment verification, and personnel training — a proven solution by the use of realistic defects.