LSPT is developing an in-service repair for fatigue and stress corrosion cracks on U. S. Navy watercraft using a portable laser peening system. Laser peening addresses the root cause of the repair problem, the stress state leading to crack growth, which is not addressed by current repair methodologies.
Existing repair methods for cracked aluminum-hulled watercraft have limitations and risks to their implementation in that they are not attempting to mitigate the tensile stress state present in the material that leads to crack formation and growth. Current repair processes are temporary because they are either inefficient or ineffective in mitigating the damage caused by fatigue cracking or stress corrosion cracking (SCC) and the related loss of water-tightness from cracks generated by these mechanisms. Crack tips, regardless of whether they are initiated by fatigue or stress corrosion cracking, are not prone to propagate when a compressive stress is applied around them.
The objective of the new contract is to develop highly portable laser peening equipment that can easily be moved around a ship, providing a method to permanently modify the stress state near a crack tip and prevent further crack growth. The project will enable efficient and effective long term onboard repairs.
Laser peening induces deep-reaching compressive residual stresses in a metallic material that reduces the realized stress state of the material under operational loading conditions, keeping the stress state below the threshold for crack growth. Laser peening alone will induce enough force to close cracks to water intrusion or clamp cracks from further growth. When combined with sealant already used in the current repair practice, such as the application of sulfide sealant, laser peening treatment will provide a long lasting water tight repair.
Recent advancements in laser peening systems allow them to rival or surpass the processing rates, cost effectiveness, and reliability of conventional surface processes such as shot peening and ultrasonic impact treatment. “This portable system would be another valuable addition to LSPT’s new line of Procudo™ laser peening systems,” said Dr. Jeff Dulaney, founder and CEO of LSP Technologies. “We anticipate that the portable laser peening system market, with the system’s ease of use and lower price point, will be significant for the company and a valuable piece of field equipment,” he added.
LSP Technologies began as a supplier of custom laser peening systems to General Electric Aviation in Cincinnati, Ohio and has recently sold Laser Bond Inspection and Procudo™ 200 laser peening systems to a large American company industry and a Chinese University. LSPT is a registered AS9100/ISO9000 provider of Laser Processing Services and Equipment.
LSPT production laser peening services customers include aerospace and power generation OEMs. “Our production laser peening business has now processed more than 47,000 gas fired turbine engines blades from aerospace and General Electric Power and Water 7F and 9F power generation engines. Our quality is outstanding and our customer care is unparalleled,” said Dr. Dulaney. “LSPT has been the leader in the laser peening industry from its inception, we have been awarded more than 50 patents on laser peening, which we include the rights to use as part of our Procudo™ laser peening system package.”
LSP Technologies invented a method to inspect bondline strength in bonded structures, called Laser Bond Inspection (LBI). The LBI inspection method, developed in association with The Boeing Company, is the only method to non-destructively evaluate the strength of adhesively bonded structures in real time. LSP Technologies delivered its first Laser Bond Inspection system to Boeing in 2012. It is on its way to becoming a mature technology for the inspection of adhesively bonded aerospace structures.
Laser Peening Technology:
Laser peening imparts deep compressive residual stresses into the surface of any metallic manufactured part or structure. It is typically applied to fatigue prone or damage susceptible areas. Its benefits are primarily achieved as a result of the deep compressive residual stress’ resistance to the initiation and growth of cracks in the material, which significantly increases fatigue life and damage tolerance. The compressive residual stresses of laser peening, or laser shock peening (as it is also known), are introduced into the material as an effect of the shockwave mechanics delivered via high energy, short pulse length laser spots onto the surface of the component. Laser peening significantly extends part service life, preventing failures from high cycle fatigue, stress corrosion cracking, foreign object damage, fretting, and erosion.
Laser Bond Inspection Technology:
Laser Bond Inspection creates a tensile stress wave in material that tests bondline interface to a determined design strength, as well as detects kissing bonds, voids and other non-conformances in the bond construction.