Topic
Keyhole defect
About: Keyhole defect is a research topic. Over the lifetime, 10 publications have been published within this topic receiving 158 citations.
Papers
TL;DR: In this paper, high-speed X-ray imaging is used to probe subsurface melt pool dynamics and void-formation mechanisms inaccessible to other monitoring approaches, which directly observes the depth and dynamic behavior of the vapor depression, also known as the keyhole depression, which is formed by recoil pressure from laser driven metal vaporization.
Abstract: Laser powder bed fusion (LPBF) metal additive manufacturing provides distinct advantages for aerospace and biomedical applications. However, widespread industrial adoption is limited by a lack of confidence in part properties driven by an incomplete understanding of how unique process parameters relate to defect formation and ultimately mechanical properties. To address that gap, high‐speed X‐ray imaging is used to probe subsurface melt pool dynamics and void‐formation mechanisms inaccessible to other monitoring approaches. This technique directly observes the depth and dynamic behavior of the vapor depression, also known as the keyhole depression, which is formed by recoil pressure from laser‐driven metal vaporization. Also, vapor bubble formation and motion due to melt pool currents is observed, including instances of bubbles splitting before solidification into clusters of smaller voids while the material rapidly cools. Other phenomena include bubbles being formed from and then recaptured by the vapor depression, leaving no voids in the final part. Such events complicate attempts to identify defect formation using surface‐sensitive process‐monitoring tools. Finally, once the void defects form, they cannot be repaired by simple laser scans, without introducing new defects, thus emphasizing the importance of understanding processing parameters to develop robust defect‐mitigation strategies based on experimentally validated models.
58 citations
TL;DR: After medical treatment failure, fissurectomy with advancement flap is a valid sphincter-conserving procedure for treatment of anterior or posterior CAF, regardless of hypertonia of the internal anal spHincter.
Abstract: Lateral internal sphincterotomy is the surgical treatment of choice of chronic anal fissure after failure of conservative measures. Several randomized trials identified an overall risk of incontinence of 10 % mostly for flatus. Fissurectomy is the most commonly used procedure to preserve the integrity of the anal sphincters. However, a possible complication is keyhole defect that may lead to faecal soiling. In this study, chronic anal fissure (CAF) was treated by fissurectomy and anal advancement flap to preserve the anatomo-functional integrity of sphincters and to reduce healing time and the risk of anal stenosis. In patients with hypertonia, surgical treatment was combined with chemical sphincterotomy by injection of botulinum toxin to enhance tissue perfusion. Forty eight patients with CAF underwent fissurectomy and anal advancement flap. In 22 subjects with hypertonia of the internal anal sphincter, intrasphincter injection of 30 UI of botulinum toxin at the completion of the surgical operation was used. All patients were followed up to 24 months. Since the first defecation, the intensity and duration of pain were significantly reduced. Two patients had urinary retention, five had infections and three had partial breakdowns. No anal stenosis, keyhole deformity or necrosis flap was recorded. At the 24 months follow-up visit, anal incontinence was similar to those detected preoperatively. Only four recurrences were detected at 18 and 20 months. After medical treatment failure, fissurectomy with advancement flap is a valid sphincter-conserving procedure for treatment of anterior or posterior CAF, regardless of hypertonia of the internal anal sphincter.
32 citations
TL;DR: Although decomposition complicated the evaluation of the gunshot wound characteristics, microscopic examination confirmed large quantities of soot along the wound tract, supporting the conclusion that the range of fire was contact.
10 citations
Patent•
21 Dec 2016
TL;DR: In this article, a friction stir welding keyhole filling method is described, which is characterized by including the steps that firstly, a filling plug head is manufactured and installed; secondly, a welding machine is started, and the plug head was pressed in the position of a keyhole; in-situ stirring is conducted according to a certain parameter; and finally, a main shaft is lifted up, and filling is completed.
Abstract: The invention discloses a friction stir welding keyhole filling method. The friction stir welding keyhole filling method is characterized by including the steps that firstly, a filling plug head is manufactured and installed; secondly, a welding machine is started, and the plug head is pressed in the position of a keyhole; thirdly, in-situ stirring is conducted according to a certain parameter; and fourthly, a main shaft is lifted up, and filling is completed. According to the method, the friction stir welding keyhole is filled in an aluminum alloy in-situ stirring manner, the welding keyhole can be completely illuminated, and the mechanical performance of the filling position is not obviously reduced. Compared with an existing friction stir welding keyhole defect repair method, pump-back shafts are not needed for devices, and requirements for the devices are low; the keyhole can be completely eliminated, and no metallurgical defects are generated; and the mechanical performance of the keyhole filling part is as high as that of other positions of weld joints.
6 citations
TL;DR: A case of a gunshot skull wound "keyhole" shaped, appeared to have been made perpendicularly to the bone, and micro computed tomography analysis of the bone showed these keyhole defect features with a particular high description.
Related Topics (5)
Performance Metrics
| Year | Papers |
|---|---|
| 2019 | 2 |
| 2016 | 2 |
| 2014 | 1 |
| 2012 | 2 |
| 2000 | 1 |
| 1991 | 1 |