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Massachusetts Materials Research, Inc.

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Cases


About Our Past Cases

Bearing Components

Failure Analysis

Bearing Failure
The failed components from a hydropower unit bearing were submitted to MMR in order to perform a root cause failure analysis. The bearing performed satisfactorily for an initial period of six days, then, after a brief floating period, it encountered a catastrophic failure within six hours of being placed back into service.

Chemical and metallurgical analyses of the materials and conditions of the different components showed that they met the required specifications and any material related anomalies were ruled out to be contributory to the bearing failure.

The damage pattern noted on the indicated that an external source led to the failure. The rollers were welded to the inner race/cone; minimum damage was noted on the outer race/cup; most of the cage was intact. After a detailed investigation, it was surmised that the cage and rollers were stationary due to the external obstruction. The rotating cone was spinning inside the stationary rollers generating significant friction and heat between the two components which tempered the components causing plastic deformation and eventually welding. The core experienced thermal expansion causing it to destroy the interference fit thus allowing the cone to creep up and freeze on the shaft.



Forensic Engineering

Dental Needle
In the case of a dental anesthesia needle breaking off in a patient's jaw, MMR was retained by a law firm to provide technical support in the case. Fractographic examination of the broken needle and metallurgical analysis of the of the needle microstructure concluded that the failure was the result of bending fatigue which occurred over a period of time. Upon revealing this information to the parties involved, it was disclosed that the single use needle had in fact been used for multiple anesthesia applications and the case was promptly settled.

Dental X-Rays

Hip X-Ray and Hip Implant

Hip Joint
In the case of a fractured orthopedic hip implant assembly, commonly known as a cephalomedullary nail used to repair subtrochanteric fractures, MMR was retained in order to provide non-destructive fractographic analysis and support related to the failure.

These devices are typically used in short term applications designed to facilitate healing of bone fractures, and it was suggested by the manufacturer that they do sometimes encounter failures due to higher than normal applied stresses related to non-union or poor healing. However, reportedly the patient healing in this case was considered progressing normally.

Higher magnification scanning electron microscope examination revealed that the cracks initiated on the lateral side at the inside diameter by stress corrosion cracking and propagated by fatigue under cyclic loading during normal movement of the patient.

It was determined that the SSC was facilitated by the presence of stress raisers related to processing anomalies such as mechanical deformation during machining of the hole, excessive stresses related to part design, possible metallurgical inhomogeneities present in the microstructure, and the corrosive environment typical of body fluids.



Simulated Service Testing

Research shows that a large number of service-related failures are the result of fatigue or other mechanically induced causes. And you can avoid the unexpected catastrophe of premature failure by having your products or devices tested under a variety of simulated conditions. We use standard testing equipment, such as MTS universal electro-hydraulic test machines and our own specially designed test machines.

We have a hydraulic pumping system capable of producing 90 gallons per minute at 5,000 psi, which enables dynamic testing of very large components. However, we have tested very small products, components, and devices, as well.

Testing to simulate actual service conditions should be incorporated into every design and product support program. So whether you are trying to prove the durability of a design, establish the life expectancy of a particular configuration, or recreate potential service deficiencies, MMRs Simulated Service testing department can help you to achieve your goals. Our simulated service projects have included the following:

A massive composite helicopter rotor blade was loaded to 50,000 pounds and placed under cyclic bending moments of 100,000 inch-pounds to achieve displacements of + 4 at 15 cycles per second.

A tiny surgical trocar was used to puncture the skin and abdomen wall for surgery was force tested from 0-6 pounds pressure to determine its ability to make punctures safely.

A new type of bone reamer required life testing to assure there would be no failures during surgery. We subjected reamers to multi-axial dynamic life tests in which there was a combination of controlled axial thrust, a lateral offset, and torque while running at 1200 RPM. The reamers were also subjected to controlled torsional fatigue forces of 20 inch-pounds at a specified loading rate.

A flexible natural gas supply line configuration had to be tested prior to approval by The Gas Research Institute. The test consisted of a steady axial load, 10 torsional twist, internal pressure, and a cyclic displacement of one end of the specimen at a specified rate until it survived for 1,000,000 cycles or failure by cracking, as detected by observing internal pressure drop.




Interesting & Intriguing Cases

Proof Load Testing
The Jeep® Climb was intended to simulate the Grand Cherokee driving up the side of the building to get to a Jeep Only parking space. To perform the feat, the vehicle was mounted on a carriage and pulled up the side of the building along window washing platform tracks. To fulfill a permit requirement, the expected applied stresses had to be verified. To verify that the calculated stresses were accurate, our engineers designed the fixturing and load-cell configurations necessary to perform on-site proof load testing. By using the window washing platform and working with the building engineers and film production personnel, our engineers descended the outside of the building and successfully performed hydraulic mechanical testing of the tracks on the 13th and 19th floors.
Jeep Climb Advertisement with a Model Demonstration of a Jeep Climbing the Side of a Building

Pirate Ship Discovery

Secrets of the Pirate Ship Whydah Revealed
In Cape Cod, Massachusetts, MMR helped the National Geographic Explored television series by performing nondestructive inspection of various artifacts recovered from the pirate ship Whydah. Explorer Barry Cliffords long search for the ship, which sank off the coast of Cape Cod, Mass., in 1717, ended in 1984 when the vessel was found under 5.2m (17ft) of sand.

The National Geographic Explorer program about Whydah, which included segments filmed at MMR originally premiered on Turner Broadcasting Systems. The vessel, its crew, and its cargo are also profiled in Pirates of the Whydah, an article by Donovan Webster published in the May 1999 issue of National Geographic (Vol. 195, No. 5, p. 64-77) For more information visit these websites:

 Whydah Pirate Museum  Pirates of the Whydah