Metallic Failures
We investigate faults and failures across a wide range of metallic objects, to give our clients the information they need. Clients choose us for our diligence and completeness in weld failure analysis in San Diego, CA. We provide a visual and photographic inspections, chemical analysis, hardness testing, fracture examination and microstructure inspection, to help understand all of the players in an item’s failure.
In addition to our thorough approach, our capabilities also extend to a wide selection of objects and items. Some of the most common metallic fracture cases we’re called to inspect involve:
- Bikes
- Chairs
- Components
- Gears
- Structures
- Off-Road Vehicles
- Wrenches
- Crankshaft
- Socket Extension
- Cutoff Wheel
- Wrench
- Leg Prosthetic
Corrosion Failures
Exposure of unprotected metal components to the environment will cause them to corrode. The degree of corrosion depends upon the severity of the environment, as well as the metal’s inherent resistance to corrosion. A seacoast environment, with its moist, salt-laden air, is much more corrosive than the dry air in the desert. However, freshwater can also cause corrosion over time—especially when pressurized.
Fracture Investigations handles corrosion failure analysis in San Diego, CA across a wide gamut of situations, providing our clients with critical information about these damages. Some of the corrosion situations we commonly face include:
- Components
- Copper water lines
- Fencing
- Buried Pipe
- Fire Protection Sprinkler
- Sinks
- Bolts
- Propellers
- Electronic Equipment
Welding Failures
Welding failures can be catastrophic, creating the serious potential for harm. Welds are meant to be structurally supportive and when joints fail, total failure of the structure or components may not be far behind.
We examine soldering, brazing and welding failures to help clients understand the reason for joint failure and the contributing factors behind it. We’ll pinpoint issues with chemical degeneration, slag and bubble pockets, among other faults, to ensure you have a definitive understanding of your weld failure.
Expert Witness Testimony
Our licensed metallurgical and corrosion engineer, Jim Aleszka, brings 40 years of industry experience to every failure analysis job. His tenure and professionalism have been utilized as expert witness testimony in numerous court hearings at the state and federal levels. He’s Superior Court qualified and able to provide clear, concise testimony on behalf of the federal government, private industries and local attorneys.
Contact Fracture Investigations today with any questions you may have or to schedule a consultation with one of our expert professionals. We can be reached at 858-560-5530.
Metallic Failures
This category is divided into five sub-groups. Each sub-group consists of a type of failed metallic item which the company has investigated. The sub-groups are as follows:
- structures
- components
- off-road vehicles
- bicycles
- chairs
In each case, the failure investigation consists of the following tasks:
- visual examination and photography
- chemical analysis of the broken item
- hardness testing of the broken item
- chemical analysis of any corrosion products
- examination of the fracture surface to determine type and direction of crack propagation
- examination of the broken item’s microstructure for defects which may have contributed to the failure
Structures
A typical example of a structural failure is shown in the photograph. In this case, a conveyor used to construct a dam failed. The other photo shows that the failure occurred at a weld. Close examination of the weld found that the weld failure was due to lack of penetration (LOP).
Components
Crankshaft
A crankshaft from an unmanned air vehicle (UAV) fractured after approximately 100 hours of service. The investigation found that a lack of oil on one of the bearing surface created a very high temperature due to friction. The high temperature reduced the surface hardness. enabling a fatigue crack to form at the bearing/journal interface.
Socket Extension
The male end of a socket extension failed in torsion. The fracture started at the radius between the socket base and square insert. The socket had been chrome plated. Failure was due to hydrogen embrittlement which occurred during the plating operation.
Cutoff Wheel
A portion of a carbide tip on the end of a cutoff wheel broke off during use. The tip was composed of tungsten carbide particles sintered together using a cobalt binder. An insufficient amount of cobalt at the fracture origin caused the tip to break off as the blade rotated.
Wrench
A wrench failed just below the head. The wrench body was cast from aluminum. A very large porosity defect existed within the casting. During use, a crack initiated at the defect and propagated through the body.
Gear
A tooth from a reduction gear in an aircraft engine broke off. The fracture was found to originate from a large inclusion (i.e., foreign particle) within the gear tooth.
Leg Prosthetic
The aluminum support rod of a leg prosthetic fractured. The fracture was found to initiate at a forming impression which had been left in the support rod. A fatigue crack initiated at that location and propagated over time through the rod.
Off-Road Vehicles
A steel strut failed on an off-road vehicle. The fracture began at an outside edge and propagated through the strut by cyclic or fatigue loading. A stronger strut material was recommended.
Bicycles
Numerous bicycle failures have been examined, two of which are shown here. In both cases, failure occurred in or started from a weld. Typically in these instances, welding thin-walled tubing creates a defect or weakened area from which a crack can originate.
Chairs
Numerous chair failures have been examined, three of which are shown here. In the first two cases, the fracture originated at a weld. In the third case, the fracture occurred in the metallic support designed to hold the back in place. The support was cast from aluminum. No defects were noted in the casting, nor were there signs of misuse. The fracture initiated at a location where there was a reduction in thickness of the support. The thickness reduction resulted in a stress concentration from which a fatigue crack initiated and propagated.
Corrosion Failures
Exposure of unprotected metal components to the environment will cause them to corrode. The degree of corrosion depends upon the severity of the environment as well as the metal’s inherent resistance to corrosion. A seacoast environment, with its moist, salt-laden air, is much more corrosive than the dry air in the desert.
Coating systems are often used to protect metal components from the environment. Their degree of success depends upon the type of coating used and its overall thickness.
Shown below are typical examples of common corrosion failures.
Fencing
This fence is located on a western-facing hillside a few miles from the coast. As a result, it came in direct contact with the moist, salt-laden, onshore breezes. The coating system applied to the fence was not robust enough for this environment. The corroded areas were cut out and replaced. The fence was stripped of its original coating and re-coated with a much thicker coating consisting of an epoxy primer followed by a urethane topcoat.
Buried Pipe
Two examples of water main failures are shown.
The first water main developed a leak after 8 years of service. Although primed and tape-wrapped for corrosion protection, the pipe surface showed extensive pitting and corrosion damage. In contrast, the inside of the pipe was undamaged. The resistivity of the soil was measured. Based upon the readings, the soil was found to be corrosive. It was recommended that the water main be cathodically protected to prevent future failures.
The second water main was in place since the 1920s. It was bare cast iron, buried beneath the foundation of a home. When the pipe began to leak it caused the surrounding soil to settle and the foundation of the home above it to crack. In this instance, the hole in the water main started on the inside surface.
Copper Water Lines
If the soil is corrosive enough it can even attack copper water lines as these examples show. Typically, the surface of the water line at the bottom of the trench experiences the most corrosion. The difference in oxygen concentration between the soil which was dug up to create the trench and then replaced (thus high oxygen content) and the undisturbed soil at the bottom of the trench (low oxygen content) creates a corrosion cell. This cell, in addition to the soil’s general corrosiveness, causes the copper tube at the bottom of the trench to corrode.
Components
Fire Protection Sprinkler
Corrosion of a fire protection sprinkler caused it to activate inside a home while the owners were on vacation. The cause of the failure was dezincification of the brass water restraint mechanism. Dezincification is the selective leaching of zinc from a brass alloy. It typically occurs in brasses with zinc contents greater than 15%. The resulting metal is so porous and weak it can no longer withstand the applied stresses.
Sink
Pressed steel sinks are prone to corrosion. Corrosion begins in the seams of the sink between the spotwelds. As the corrosion products grow in size, they cause failure of the spotwelds due to the pressure they exert within the seam. The sink then begins to leak.
Bolt
Outdoor exposure to metal components such as bolts can cause them to severely corrode, especially near the ocean. The bolt and nut shown were left unprotected in a seacoast environment.
Propellers
Failures of brass or bronze propellers are not uncommon. Two examples are shown. In both cases, failure initiated as a result of dezincification followed by fatigue crack propagation through the propeller blade. The dark area is where the zinc leached from the brass due to dezincification. A fatigue crack then initiated in this weakened area.
Electronic Equipment
The corroded circuit board shown in the photo came from a fast food restaurant headset. It had been in service approximately 3 to 4 months. Energy dispersive x-ray analysis of the corrosion products found zinc, chloride, and phosphorus. The most like source of these elements is the flux used during soldering. Incomplete rinsing after soldering left a flux residue which corroded the tin terminals.