Durability Rig Validation Testing is often used in conjunction with Field Test Validation and Proving Ground Validation approaches. The objective of this validation approach is to compress years of field usage into a much shorter and manageable time-period so that important product design decisions can be made.
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Durability Rig Validation is by no means a cookie-cutter validation procedure as there are many variations regarding the nature of the product or its adaption to specific situations.
Upstream Design
Product design, including CAD model development and simulation, are generally handled by our customers with 6D’s role being primarily in the validation stage. However, sometimes additional data is needed to better define the loads required during the design phase.
When this is the case, there are steps that can be taken in advance of design to more clearly define the duty-cycle/loading environment in which the vehicle or structure will be operating.
Collecting the Data
Instrumenting the structures with measurement systems (such as strain gages) allows data to be collected under normal in-service operating conditions. One advantage of this is that data can be non-intrusively collected over days, weeks, or even months. This helps us to get a complete understanding of the entire duty-cycle.
Planning the Test
Properly locating strain gages is critical to collecting useful data. As part of the test planning, a Finite Element Model of the structure is used to identify areas to locate strain gages and other instrumentation. Next, loads such as inertial loads, twist loads, or any other specific loads that may relate to important operating conditions are applied to the model. While these may not be the actual loads that the structure will experience in operation, they will help indicate important “hot spots” and provide a guide as to optimum locations for locating strain gages.
Stresses should be known on all structural connections, such as bolts. Joint areas, especially those containing welds, are something to pay particular attention to in order to be sure that stresses in those areas meet welding standards. Test planning also includes defining test events. The full range of product considerations and product weights must be considered (with/without payload).
Field Loads Measurement
The next step involves measuring field loads and responses. This is sub-divided into Staged Events and Typical Operation. While staged events are important to help confirm confidence in the model, the true objective is to record actual in-service operating data.
This could include collecting data as the structure is put through its daily operations or on location at a proving-grounds. In this phase of the program, it’s important to collect as much data as possible. This generally includes various vehicle speeds, payloads, and terrains for example. Data collected here is used to support accelerated durability rig testing.
Data Processing
Numerous steps are required to process the field data so that it can be used to drive the hydraulic accelerated durability test rigs. This can be relatively straightforward or much more involved process depending on the complexity of the structure and/or the complexity of the loads.
Recorded data is compared to the structure as it was put through its duty-cycle. In addition to anticipated or structurally insignificant data, events that will have a significant bearing on the structure will likely be uncovered. The data reduction process includes compressing sometimes thousands of hours of data to filter insignificant events. This step accelerates data analysis time by a factor or 100 to 1 or greater.
Further data processing is used to create drive files to control the hydraulic actuators. This allows loads to be applied to the structure that match those in the field. The process includes correlating key responses from rig test to the same responses seen during field testing.
While this is nearly always a dynamic process, there are times when static loads are applied based on measurements, industry standards, and so on.
As rig testing is being performed, stresses and cumulative damage are evaluated. This includes inspecting the unit for failures. The objective of this validation approach is to compress years of life in the field into a much shorter and manageable time-period.
A Collaborative Approach
Like many validation approaches, Durability Rig Validation is often performed in partnership with our customers. Whether in the form of training, or to maximize budgets by leveraging customer resources, 6D often works with its customers to help support the process. 6D preforms as much of these tests as required. Our services range from complete on-site testing and analysis to provide our customers with equipment, data collection services, consulting, and so on.