It is essential to meet the form, fit, and function requirements, and other design details. In a reverse engineering process, the part’s physical features are determined by measuring its geometric dimensions, and the tolerance has to be verified. Two other key elements in reverse engineering are mate- rial identification and processes verification, including material specification conformity. The material properties to be evaluated are contingent on the service environment and expected functional performance. The material properties at room temperature, high temperature, and sometimes even at cryogenic temperatures may be required. It is worth noting that the mate- rial property depends not only on its chemical composition, but also on its manufacturing process. It is critical in reverse engineering to verify the man- ufacturing process to ensure that the reinvented component will meet the functional and performance requirements of the original design.
Theoretically each individual part requires its own specific analysis or test to demonstrate its functional performance. However, this book will focus on generic comparative analysis and universal scientific methods applicable to reverse engineering. As such, part-specific tests and subjects will only be discussed in case studies. For instance, specific tests to demonstrate a reverse engineered crankshaft meeting the original design functionality will not be discussed in this book. Instead, the discussion will focus on whether the aforementioned reverse engineered crankshaft can be verified as equivalent to the OEM part by demonstrating that it has the same geometric shape, dimensions within the same tolerance, and is made of the same alloy by the same process. If additional tests are required, this book will focus on the rationales for these tests.
In light of part performance verification, communication among all stake- holders and documentation of engineering data often are among the most important factors for a successful reverse engineering project. It is advisable to keep all relevant documents and records in order, and get all stakehold- ers to buy in as early as possible. It is also highly recommended to justify any technical modifications to the part, including alterations to the design.
The following two examples of modification are usually acceptable in reverse engineering: (1) the use of a new material to substitute an obsolete material that is no longer available, and (2) using an alternate manufacturing process that is commercially available to substitute an OEM-patented process, pro- vided that they are comparable with each other, and both will produce simi- lar products.
1.3.1 accreditation
Both professional competence and data reliability are essential to reverse engineering. Engineering judgment is often called upon for the discrep- ancy between measurements due to instrumental and human inconsistency in reverse engineering practice. To ensure data reliability, all the tests and evaluations should be conducted at accredited laboratories and facilities. The following will present a brief introduction of several organizations provid- ing quality accreditation services. The Nadcap program (formerly National Aerospace and Defense Contractors Accreditation Program) is one of the most widely recognized accreditation programs in the aviation industry. The Nadcap program, as part of Performance Review Institute (PRI), was created in 1990 by the Society of Automotive Engineers (SAE). It is a global cooperative program of major companies, designed to manage a cost-effective consensus approach to engineering processes and products and provide continuous improvement within the aerospace and automotive industries. Through the PRI, Nadcap provides independent certification of engineering processes for the industry. All the following aerospace companies require their affiliates to obtain and maintain Nadcap accreditation: Boeing, Bombardier, Cessna, GEAE (short for General Electric Aircraft Engine), Hamilton Sundstrand, Honeywell, Lockheed Martin, MTU, Northrop Grumman, Pratt & Whitney, Raytheon, Rolls-Royce, Sikorsky, and Vought. It is reasonable to expect that reverse engineering a part manufactured by these OEMs should hold up to similar accreditation requirements.
The International Organization of Standardization (ISO) is another internationally recognized quality certification organization. The ISO 9001 is a series of documents that define the requirements for the Quality Management System (QMS) standard. It is intended for use in an organiza- tion that designs, develops, manufactures, installs any product, or provides any form of service. An organization must comply with these requirements to become ISO 9001 registered. Many facilities and companies are ISO 9001 registered. For instance, Wencor West, a commercial aircraft part distributor and leading PMA manufacturer, is ISO 9001 certificated. Certification to the ISO 9001 standard does not guarantee the quality of end products; rather, it certifies that consistent engineering processes are being applied.
Instead of obtaining accreditations or certifications independently from various organizations, an association can provide a universal certification service acceptable by many regulatory agencies and companies worldwide.
The International Accreditation Forum (IAF) is an association of conformity assessment accreditation bodies. It provides a single worldwide program of conformity assessment that has multilateral recognition arrangements (MLAs) between the members.
The American Association for Laboratory Accreditation (A2LA) is a nonprofit, nongovernmental, public service, membership society. It pro- vides laboratory accreditations based on internationally accepted criteria for competence in accordance with ISO and International Electrotechnical Commission (IEC) specifications, such as ISO/IEC 17025: General Requirements for the Competence of Testing and Calibration Laboratories. A2LA is a signatory to several bilateral and multilateral recognition agreements. These agreements facilitate the acceptance of test and calibration data between A2LA-accredited laboratories around the globe. A2LA is recognized by many federal, state, and local government agencies, companies, and associations.
Several accreditation organizations are associated with institutes rep- resenting standards and quality, for example, the Registrar Accreditation Board (RAB), which was first established in 1989. In 1991 the American National Standards Institute (ANSI) and the RAB jointly established the American National Accreditation Program (NAP) for Registrars of Quality Systems. In 1996, the ANSI-RAB NAP was formed, replacing the original joint program. On January 1, 2005, ANSI and the American Society for Quality (ASQ) established the ANSI-ASQ National Accreditation Board (ANAB), which is a member of the IAF. ANAB later expanded its confor- mity assessment services to include accreditation of testing and calibration laboratories.
1.3.2 Part Criticality
One of the driving engines propelling the advancement of modern reverse engineering is its ability to provide competitive alternatives to OEM parts.
The rigorousness of a reverse engineering project depends on the criticality of the part and cost-benefit consideration. The criticality of a part depends primarily on how it is used in the product. A fastener such as a bolt will be a less critical component if it is used to assemble a non-load-bearing bracket only for division. However, when a bolt is used with glue to hold a 2-ton con- crete ceiling in an underground tunnel, it can be a very critical component.
The fasteners are among the most popular candidates for reverse engineer- ing. It is also estimated that approximately 70% of all mechanical failures are related to fastener failures. Fortunately, most times the failures are not dev- astating, and proper corrective actions can be taken to avoid further damage.
For example, the utilization of SAE class H11 bolts in aeronautic structures was attributed to a “higher than normal” failure rate due to stress corrosion cracking. FAA Advisory Circular 20-127 discourages the use of H11 bolts in primary aeronautic structures to avoid more incidents.
The precision and tolerance required to reverse engineer a part are often determined by the criticality of the part. From operation safety point of view, the criticality of a part is determined by checking the impact of safety if the part fails. A critical aeronautic part is deemed a part that, if failed, omitted, or nonconforming, may cause significantly degraded airworthiness of the product during takeoff, flight, or landing. However, in different fields and services the definition of criticality varies significantly. When analyzing a load-bearing critical component, the critical strength varies from tension, compression, torsion to fatigue or creep when it is subject to different types of load. The service environment also plays an important role in determining the essential characteristics of the part. High-temperature properties such as creep and oxidation resistance are the determining factors for a turbine blade operating in a high-temperature gas generator. The tensile strength is critical for a static load-bearing component, and also used to determine if a turbine disk will burst out at high rotating speed. However, for a part subject to cyclic stress, such as the automobile axle, fatigue strength is more relevant than the tensile strength. The corrosion resistance becomes a key material property for a part used in the marine industry. In other words, the critical property for a critical part in reverse engineering depends on its functionality and operating condition. For a critical part, higher-dimen- sional accuracy and tighter tolerance along with higher evaluation costs are expected, and it can become prohibitively expensive for a reverse engineer- ing project.
To best meet the form, fit, and function compliance, and maximize the exchangeability, many commercial parts commonly used in industries, many of them are standardized by individual companies, government agen- cies, professional societies, or trade associations. Reverse engineering rarely applies to these standard parts because they are readily available on the shelf, and therefore lack financial sensitivity. However, a standard part set by one organization is not always a standard part according to the criteria of another organization. An FAA standard part needs to provide the public with all the relevant information of the part, while a Boeing standard part does not need to provide the public with all the relevant information of the part; as a result, a Boeing standard part is not necessarily an FAA standard part. Globalization also adds a new dimension to the business of part sup- ply. When the Boeing 727 was first introduced in 1964, all seventeen of its major components were made in the United States. By contrast, thirteen of the similar seventeen components of the Boeing 787, which had its first test flight in 2008, are made exclusively or partially overseas. Beyond standard- ization and globalization, technology advancement definitely has made it easier to reinvent the OEM part with little knowledge of original design details. More and more high-quality spare parts are manufactured through reverse engineering to substitute OEM counterparts at a competitive price.