Material defects seams

No other evidence of deterioration, such as corrosion, was apparent on either surface. The cracks are probably material defects. They may be laps or seams that were present on the external surface prior to the fin-rolling operation and were exaggerated during the rolling process. 

Figure 14.6 Material defect, perhaps a lap or seam, on the external surface of a finned copper tube.

The subject of weld defects is quite extensive, and complete coverage is well beyond the scope of this chapter. Therefore, this chapter will focus on specific types of weld defects of general concern in cooling water systems. Defects of seam-welded tubes are considered under material defects in Chap. 14. 

Fig. 2 Photomicrographs of tissue induction and morphogenesis in bioptic material 90 days after implantation of naturally derived BMPs/OPs purified from bovine bone matrix in human mandibular defects, (a) Trabeculae of newly formed mineralized bone covered by continuous osteoid seams within highly vascular stroma, (b) and (c) High-power views showing...

Construction quality control and CQA consist of the physical properties of the geotextiles as they are manufactured but also the skill with which they are installed. In addition to the type of testing specified previously for MQA, this testing may include sewn seams, heat-tacked seams, and repairs of any defect that results from installation of the material. 

Another typical welding defect consists of undercuts. These are furrows displayed at the seam edges at the connection with the surface of the base metal. They reduce thickness and cause burn through. This defect is due to the excessive length of the arc. The larger the arc cone, the wider the cuts will be, and the filler metal is laid in drops and there is excessive spatter with consequent loss of filler material. 

For a composite material to prevent a defect in a pipeline from rupturing, the defect must typically plastically deform in the process of the load being transferred to the composite material. This concept may not be well understood by many users of composite repair materials for pipehne repair. Defects in brittle pipe material or brittle seam welds may only be able to tolerate a very small amount of plastic strain, which composite repairs are unable to protect against, before the defect grows and fails. 

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