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Materials & Metallurgical Testing Services

Contact DTB for simple or complex testing of materials in our A2LA accredited laboratory.

Materials Testing

The most effective method of verifying a product’s performance is via materials testing, which includes materials fatigue testing. Although analytical computational methods exist to simulate how materials react under fatigue, a materials fatigue test program is still the preferred method in understanding and therefore preventing product’s fatigue failures.

Material Fatigue

We have an extensive materials and fatigue test laboratory capable of performing coupon, component as well as fatigue testing of metals (including aerospace alloys), and product strength and performance testing of various metals, plastics, composites and paper.

DTB’s materials testing experts are available to help you build a customized mechanical fatigue test program which includes one or more of the following methods:

  • Crack Initiation
  • Crack Growth
  • Crack Fatigue (Fatigue Crack)
  • Crack Propagation
  • Crack Growth Rate (da/dN)
  • Damage Tolerance
  • Low Cycle Fatigue
  • Fatigue Fracture
  • Fatigue life prediction
  • Fatigue failure analysis
  • S-N curve

S-N curves are based on mean fatigue life with a given probability of failure and they can provide a high degree of certainty regarding cyclic performance of a product for expected fatigue loading conditions.

S-N tests focus on the nominal stress required to cause a fatigue failure in some number of cycles. This type of test results in data that is presented as a plot of stress (S) against the number of cycles (N) to failure, which is known as an S-N curve.

A log scale is normally used for N. Generating an SN curve for a material requires many fatigue test iterations performed to statistically vary the alternating stress, or stress ratio, and count the number of cycles.

Normally most DTB materials fatigue test programs have focused on situations that require more than 104 cycles (high-cycle fatigue testing) to failure where stress is low and deformation is primarily in the elastic region. However low-cycle test programs can be designed where the stress is high and deformation is primarily in the plastic deformation region.

Tailboom_PB302217Testing to Prevent Fatigue & Failure – Preventing fatigue failure is the most effective method of improving fatigue performance in designs. A DTB materials testing program will allow manufacturers to:

  • Eliminate or reduce stress risers in the part.
  • Improve manufacturing process by helping manufacturer avoid sharp surface tears resulting from punching, stamping, shearing, or surface finish processes.
  • Help prevent the development of surface discontinuities during manufacturing.
  • Eliminate or reduce tensile residual stresses caused by manufacturing.

Material fatigue is the progressive damage that occurs when a material or structure is subjected to cyclic loading. Fatigue failure is when the progressive damage caused by the cyclic loading leads to failure of the material or structure. Fatigue failures are a significant problem for the reason that they can occur due to repeated loads below the static yield strength and can result in an unexpected and catastrophic failure causing monetary loss and/or even loss of life. Many engineering designs include materials and structures that contain discontinuities or stress risers.

Most metal fatigue cracks initiate from discontinuities in highly stressed regions of the structure. The stress risers may be due the discontinuities in the material, inherent in the design, improper manufacturing technique or even improper maintenance. Our material fatigue test program and comprehensive analysis can determine the cause of the fatigue failure. Need help with materials testing? Send us your quote now, our expert team we’ll be glad to help you.

Crack Growth

The life of a fatigue crack has two parts, initiation and propagation. The most common reasons for crack growth initiation include:

  • Notches, corners, or other geometric inconsistencies that act as stress risers. These features may be inherent in the product design or mistakenly caused during manufacturing.
  • Material impurities, inclusions, or product usage causing material loss due to wear or corrosion.
  • Mechanical or thermal fatigue encountered during the products normal life cycle.

DTB_4007Material fatigue fractures have common phases, such as crack initiation, crack growth propagation (followed by) and a sudden failure. Once a crack has been initiated (crack initiation phase), repeated loadings can cause the crack to lengthen or propagate (crack growth phase). If fatigue loading is continued, crack growth will occur resulting in a final sudden fracture of the remaining cross section (overload failure). By analyzing the material fatigue fractures of several iterations of mechanical fatigue tests, a crack growth curve can be formed to assist with fatigue life predictions. The crack growth rate (da/dN) is obtained by taking the derivative of the crack length, a, versus cycles, N. A well planned and executed DTB materials test program will be able to take into account the crack growth curves, obtained from the materials fatigue testing, and establish a fatigue life prediction for the product, as well as possibly provide damage tolerances for the product. Damage tolerance is a property of a material or structure relating to its ability to sustain defects safely until repair can be made or the structure replaced. The DTB approach to damage tolerance in material testing is to account on the assumption that initial flaws exist in any structure or material and such flaws will propagate with usage. Our material test programs will locate the initial flaws, recommend the proper modification to correct the flaw, and then test again to prove that the recommendations worked.

Metallurgical Lab

DTB is a full-service metallurgical laboratory performing detailed parts inspections and comprehensive root cause failure investigations ranging from aircraft structural components to electronics packaging, test programs in corrosion-fatigue, corrosion analysis and control, wear, abrasion and erosion evaluations, coating replacement studies, weld evaluations, reverse engineering programs and the development of advanced non-destructive techniques.

Staff and Resources:

  • Experienced Metallurgists and Materials Engineers (M.S./Ph.D.)
  • Experienced Technicians (Level 2/Level 3 in various NDI techniques)
  • Resource for Failure and Engineering Investigations, R&D, and Metallurgical & Materials Testing and Analysis
  • Reference Library
  • Comprehensive Repository of Specifications
  • Fully Digital Data Capture

Facilities & Equipment:

  • Metallurgical Lab Facilities and Equipment
  • Arc Emission Spectroscopy (AES) w/Full Suite of Calibration Standards
  • Scanning Electron Microscopy/Energy Dispersive Spectroscopy (SEM/EDS)
  • Quadrupole Mass Spectroscopy/Gas Chromatography (QMS/GC)
  • Optical Metallographs (BL, PL, DF)
  • Stereomicroscopes
  • High Resolution Digital Imaging
  • Full Range of Metallographic Sample Preparation
  • Etching Hoods
  • Sectioning and Mounting
  • Low Damage Sectioning
  • Hardness (Bulk, Micro, Superficial, Scleroscopic)
  • Indexed Borescopes w/ UV
  • Magnetic Particle, Liquid Penetrant, and Eddy Current Flaw detection
  • Testing of battery performance, Grease Viscosity, Taber Abrasion and Wear
  • Accelerated Aging Ovens
  • Non-destructive Plating/Coating Thickness
  • Carbon Arc and Gold/Palladium Sputter Coating Systems

Analysis and Testing Services:

  • Magnetic Particle (MPI) per/method ASTM E 1444
  • X-Ray (Digital) (DR) per/method ASTM E 2007
  • Ultrasonic (UT) per/method AMS STD 2154
  • Fatigue Coupon Testing per/method ASTM E606, ASTM E466, ASTM E647, ASTM E1002
  • Hardness Measurements per/method ASTM E 103, ASTM E 384, ASTM D 2240, Standard Rockwell, Superficial Rockwell, Micro (Vickers, Knoop), Scleroscopic
  • Etching per/method DTB Procedure or Customer Specified
  • Microstructural Evaluation per/method (Inverted Optical Metallograph – BF/PL and SEM – SEI/BEI contrast) – ASTM E 3, ASTM E 7, ASTM E 112, ASTM E 930, ASTM E 1181, ASTM E 1382, ASTM E 1951, DTB Procedure or Customer Specified. General Microstructure, Retained Austenite, Decarburization (visual), Grain Size, Inclusions, Uniformity, Defects (voids, cracks,..), Segregation
  • Case Hardening Analysis (microhardness profile) per/method DTB Procedure or Customer Specified
  • Intergranular Attack (IGA) (chemical/visual) per/method ASTM A 262, ASTM A 763, ASTM G 28, ASTM G 110, ASTM STP 656, DTB Procedure or Customer Specified
  • Plating/Coating Composition and Thickness per/method DTB Procedure or Customer Specified
  • Bulk Composition – Quantitative (Arc Emission) per/method Machine cal with standards
  • Bulk composition – Qualitative (EDS) per/method DTB Procedure or Customer Specified
  • Viscosity Measurements per/method Internal calibration
  • Bulk composition – Qualitative per/method (EDS) – DTB Procedure or Customer Specified
  • Accelerated Aging per/method DTB Procedure
  • Macrofractography per/method Case-based
  • Liquid Penetrant (LPI) per/method ASTM E 1417
  • X-Ray (Film) per/method ASTM E 1742
  • Eddy Current (EC) per/method DTB Procedure or Customer Specified
  • Tensile Coupon Testing per/method ASTM E8, ASTM A931, ASTM D3039/D3039M
  • Metallographic Preparation per/method ASTM STP 557, ASTM STP 504, ASTM STP 839. DTB Procedure or Customer Specified
  • Temper Etch (Nital Etch) Surface Inspection per/method MIL STD 867
  • Grain Flow and Macro Characterization (Forging or Casting Quality) per/method DTB Procedure or Customer Specified
  • Decarburization (microhardness profile) per/method ASTM E 1077, ASTM F 2328, DTB Procedure or Customer Specified
  • Plating/Coating Thickness (non destructive) per/method ASTM B 244, ASTM D 7091
  • Passivation Check per/method Customer Specified
  • Bulk Composition – Semi-Quantitative (EDS) per/method DTB Procedure with standards
  • Corrosion Identification (SEM + EDS) per/method Case-based
  • Gas Analysis (GC-QMS) per/method Reference library
  • Macro-Imaging (Stereomicroscopic) per/method Case-based
  • Microfractography (SEM + EDS) per/method Case-based
  • Reports per/method Letter, Metallurgical/Materials Evaluation, Failure Analysis

Composite Materials Testing

DTB has long experience and specializes in structural analysis, simulations and testing of both metallic and composite materials. And, our comprehensive facilities and professional staff can offer fast and flexible scheduling for your composite materials testing.

More about Composite Material Testing

Composite materials testing goes hand-in-hand with tensile and fatigue testing. These tests consist of subjecting coupon samples or complete structures to test loading to establish the static strength, fatigue and damage tolerance of the parts. Aircraft, aerospace, transportation, military and consumer products may require composite materials testing. DTB provides a full range of composite material testing services including tensile and compression testing. This ranges from coupon samples to complete structures. Non-destructive inspection methods include ultrasound, x-ray and shearography. We can also provide ultrasound, x-ray, shearography inspection, strain gage installation and monitoring. Periodically during composite materials testing, parts are inspected for cracks or delamination. Impact loading, shock, or repeated cyclic exposure can separate material layers, breaking individual fibers or pulling them from the matrix. Delamination or damaged fibers degrade strength and ultimately lead to failure.