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Fatigue and Fracture Toughness Testing

Fatigue testing applies cyclic loading to a test specimen, to understand its performance under similar conditions when in actual use. The load application can either be a repeated application of fixed load or simulation of in-service loads. The load application may be repeated millions of times and up to several hundred times per second.

 

Many engineering metals and alloys display embrittlement at reduced (below sub-zero) temperatures. Structures fabricated from them fracture or shatter unexpectedly at low temperatures when loaded to stress levels at which performance would otherwise be satisfactory at room temperature. To avoid such incidents, selection of the right material can be done by testing them for their mechanical properties.

 

In the recent years, tremendous interest has been generated in fracture toughness testing based on linear elastic fracture mechanics. Fracture mechanics principles have been used to quantify safety factors in structural design, taking into account crack propagation and/or brittle fracture. Most structural members, components, vessels, piping, aviation, and aerospace are designed according to analysis criteria that guard against failure. CTOD testing requirement is most common in welded coupon as recommended in ONGC, EIL, DNV & API specification.

 

TCR Engineering has expanded its capabilities to include fatigue, fracture toughness, CTOD and high-temperature tensile testing with the addition of two fatigue systems with the Universal Testing Machine which has a capacity of 50 kN and 250 kN. The versatile Servo-hydraulic systems will allow the mechanical testing laboratory to perform numerous types of fatigue tests on different specimen sizes and orientations, in the temperature range from ambient to 1000° C. TCR has the capability of applying linear displacements, utilizing linear and hydraulic actuators. Comparison fatigue testing of OEM and alternate source parts can also be performed to demonstrate equivalency of fatigue life.

Fatigue, Fracture Toughness, CTOD, High Temperature Tensile Testing and High/Slow Strain Rate Testing, Mechanical Testing Lab, Aviation, Automotive, crack tip opening, mumbai, india. Fatigue, Fracture Toughness, CTOD, High Temperature Tensile Testing and High/Slow Strain Rate Testing at TCR Engineering Material Testing Laboratory, India, China and Middle East. Fatigue, Fracture Toughness, CTOD, High Temperature Tensile Testing and High/Slow Strain Rate Testing in Mumbai, India.

TECHNICAL CAPABILITIES

TCR Engineering provides a diverse range of capabilities following ASTM/BS/ISO Specifications. Both ASTM E606 (Low-cycle fatigue, strain-controlled Fatigue Testing) and ASTM E466 (Load-controlled Fatigue Testing – High or Low-cycle fatigue testing) has been widely in use at TCR Engineering. Tests are also conducted for TMT RE-BAR, COUPLERS Fatigue test (100 Cycles test & 2 million Cycles test) as per IS 16172-2014. 

Fracture Toughness Testing: Fracture toughness determines the amount of stress required to propagate an existing flaw or defect in specific materials. Since traditional methods of destructive testing cannot always predict how a material will behave during defect fracture, toughness is very important at the design stage

 

Crack-Tip Opening Displacement Testing: Crack-tip opening displacement is used as a type of fracture-toughness testing to determine if a material is appropriate for strenuous working conditions. CTOD testing is the measure of deformation, prior to failure in pre-cracked samples. This type of test is a variation of fatigue testing that has load rates more as representative of in-service conditions. TCR has capability to conduct the CTOD testing at temperature from Ambient to  -25 °C

FATIGUE TEST

  • ASTM E466: Standard Practice for Conducting Force Controlled Constant Amplitude Axial Fatigue Tests of Metallic Materials

  • ASTM E606: Standard Practice for Strain-Controlled Fatigue Testing

  • ASTM E 2714 – Standard Test Method for Creep-Fatigue Testing

  • ISO 12106: Metallic materials — Fatigue testing —Axial-strain-controlled method

  • ISO 12108-2002 (E) – Metallic materials – Fatigue testing – Fatigue crack growth Method

  • IS16172-2014 Reinforcement Couplers for Mechanical Splices of Bars in Concrete- Specification

FRACTURE TOUGHNESS TEST

  • ASTM E1290: Standard Test Method for Crack-Tip Opening Displacement (CTOD) Fracture Toughness Measurement

  • ASTM E1820: Standard Test Method for Measurement of Fracture Toughness

  • ASTM E399: Standard Test Method for Linear-Elastic Plane-Strain Fracture Toughness KIc of Metallic Materials

  • Strain Fracture Toughness (KIC) for Metallic Materials

  • ASTM E1820 Measurement of Fracture Toughness (JIC-CTOD Measurement)

  • ASTM E647: Standard Test Method for Measurement of Fatigue Crack Growth Rates

  • BS 7448 (Part 1 to part 4) Fracture Mechanics Toughness tests. Method for Determination of KLC, Critical CTOD and Critical J Values of Welds in Metallic Materials

  • Fracture Mechanics [K1c, J1c, CTOD] Testing

  • ASTM E1290 Crack-Tip Opening Displacement (CTOD) Fracture Toughness Measurement

  • IS 16172-2014: Reinforcement Couplers for Mechanical Splices of Bars in Concrete

  • Static Tensile Test (ASTM A1034, IS 16172)

  • Cyclic Tensile Test (ASTM A1034, IS 16172)

  • Slip Test (ASTM A1034, IS 16172) High

  • Cycle Fatigue Test (ASTM A1034, IS 16172)

TCR Engineering undertakes range of testing applications based out of its dedicated Fatigue Test Laboratory  in Mumbai:

  • Fatigue Crack Propagation [da/dN vs ∆K Studies]

  • Fracture Mechanics [K1c, J1c, CTOD] Testing

  • 3 – Point Bend Testing of Materials

  • Spring Fatigue Testing

  • Room Temperature and High Temperature Tests [up to 1000 °C]

  • Tension/Compression

  • Low/High Cycle Fatigue (LCF/HCF) Testing

  • High Temperature Tensile Tests [up to 1000 °C]

  • High Strain Rate Testing [300mm/sec on 50KN and 100mm/sec on 250KN UTM]

  • Slow Strain Rate Testing [10-7 mm/sec on 100kN UTM]

Uniaxial Fatigue Test as per BS EN 14587-2

Fatigue testing of butt-welded track rail

Fatigue testing of butt-welded track rail is an important procedure used to assess the structural integrity and durability of welded rail joints commonly found in railway tracks. Butt welding is a technique used to join two rail sections end-to-end, creating a continuous track.


Fatigue testing involves subjecting the welded rail joint to repeated loading cycles that simulate the dynamic forces experienced during normal train operations. The purpose of this testing is to evaluate the performance of the welded joint under repeated stress and determine its ability to withstand the anticipated service conditions without failure or degradation over time.

UNIAXIAL FATIGUE TEST_2.png
UNIAXIAL FATIGUE TEST.png

Here are some key points regarding fatigue testing of butt-welded track rail:

1. TEST SET-UP

A representative length of welded rail joint, usually several meters long (span length 1.5 meter), is selected for testing. The rail is typically mounted on a test fixture or a specialized fatigue testing machine that applies cyclic loading (4-point bend) to the joint. The loading can be applied in the form of vertical, forces, depending on the specific requirements as per relevant national/International standards. 

2. CYCLE LOADING

The rail joint is subjected to repeated loading cycles that simulate the stress patterns encountered during train operations. The loading can vary in magnitude, frequency, and direction to simulate different operating conditions. The number of cycles applied during testing depends on the desired fatigue life assessment.

3. MONITORING & MEASUREMENTS

During the fatigue test, various parameters are monitored and measured to assess the performance of the welded joint. These may include strain, displacement, crack propagation, and other relevant factors. Advanced measurement techniques such as strain gauges or non-destructive testing methods may be employed to gather accurate data.

4. FAILURE CRITERIA

The test is typically continued until a predefined failure criterion is reached. This criterion can be defined based on the appearance of cracks, changes in strain or displacement values, or other factors indicating potential failure or significant degradation of the welded joint.

5. EVALUATION & ANALYSIS

After the test, the collected data is analysed to determine the fatigue life and performance characteristics of the welded rail joint. This analysis helps in understanding the joint's ability to withstand cyclic loading and predict its service life in real-world operating conditions.

6. STANDARDS & REGULATIONS

Fatigue testing of butt-welded track rail is often conducted in accordance with specific industry standards and regulations. These standards provide guidelines for test procedures, acceptance criteria, and performance evaluation methodologies.

By performing fatigue testing on butt welded track rail, railway authorities and manufacturers can ensure that the rail joints are robust, reliable, and capable of withstanding the anticipated stresses and strains during the operational lifespan of the railway track. This testing helps enhance safety, reduce maintenance costs, and optimize the performance of rail systems.

Spectrum of Services

At our fatigue testing division, we are equipped with a state-of-the-art Dynamic Universal Testing Machine (UTM) that offers unparalleled capabilities for conducting various fatigue tests. Our Dynamic UTM is designed to handle a wide range of testing requirements and can accommodate specimens of different sizes and strengths. Here's a detailed overview of our testing machine and the comprehensive capabilities it offers:

Dynamic UTM Specifications:

 Capacity: Our Dynamic UTM boasts impressive load capacities, allowing us to conduct fatigue testing on a diverse range of materials and components. With load capacities of 50kN, 250kN, and 1000kN, we can effectively evaluate the fatigue behaviour of various specimens.

Frequency Range: Our Dynamic UTM operates within a frequency range of 0.01Hz to 40Hz, enabling us to simulate real-world loading conditions and accurately assess the fatigue performance of materials under dynamic loading.


 

In our fatigue testing division, we specialize in a range of fatigue testing methodologies, including:

Fracture Toughness (KIC) Test

Specimen Size: We can test specimens ranging from 8mm to 75mm in thickness.
Test Method: Our testing procedures adhere to recognized industry standards such as ASTM E399, ASTM E1820, ASTM B645, BS7448 (Part 1-4), ISO12135, ISO 12737 and ISO15653, ensuring accurate and reliable results.
Test temperature range: -20°C to 1100°C

Fatigue Crack Growth Rate (FCGR) Test

Specimen Size: We can evaluate specimens with thicknesses ranging from 8mm to 75mm.
Test Method: Our testing protocols strictly follow ASTM E647, ISO 12108 guidelines, allowing us to assess the crack growth behaviour under fatigue loading accurately.
Test temperature range: -20°C to 1100°C

CTOD Test (Crack Tip Opening Displacement)

Specimen Size: We conduct CTOD tests on specimens ranging from 15mm to 100mm in thickness for bend specimens

Span Length: Our testing equipment accommodates span lengths between 55mm and 1,600mm.
Test Method: We adhere to industry standards such as ASTM E1290, ASTM E1820, BS7448 (Part 1-4), ISO12135, and ISO15653, ensuring precise CTOD measurements.
Test temperature range: -20°C to 1100°C

J-Integral (JIC) Test

Specimen Size: Our testing capabilities extend to specimens with thicknesses ranging from 8mm to 75mm for compact specimens.
Test Method: We follow standardized test methods, including ASTM E1820, ASTM B645, BS7448 (Part 1-4), ISO12135, and ISO15653, to accurately determine the J-Integral values.
Test temperature range: -20°C to 1100°C

Uni-axial Fatigue Test

Test Method: Our fatigue testing procedures align with ASTM E466, ASTM E606, and IS 5074, IS 16172 guidelines, ensuring comprehensive assessment of uni-axial fatigue behavior.
Test temperature range: ambient to 1100°C

Fatigue test of flash butt joint welding of track rail

Test Method: Our fatigue testing procedures align with BS EN 14587 (Part1 & Part2),  BS EN 13674-1, guidelines, ensuring comprehensive assessment of fatigue behaviour.

Helical Spring Test. (As per RDSO / National / International Standards)

▩ Static Load Test.
▩ Load v/s Displacement (Spring Constant/ Spring Rate)
▩ Fatigue Test

Additionally, our capabilities extend beyond traditional fatigue testing, as we offer specialized testing for Reinforcement Couplers and Grouter for Mechanical Splices of Bars in Concrete. Our testing services in this area include:

Static Tensile Test
Slip Test
Cyclic Tensile Test
Fatigue Test
Low Cycle Fatigue Test
High Cycle Fatigue Test

We can accommodate reinforced bars with nominal diameters ranging from 8mm to 40mm, adhering to relevant industry standards such as IS16172, ASTM A1034, IS16651, ISO15630, and ISO15835-2.

 

With our Dynamic UTM and comprehensive range of testing capabilities, we are well-equipped to meet your fatigue testing needs, providing accurate and reliable results for a wide range of materials.

Advantage TCR

1

Superior technology, responsive teams, unbiased reporting and exceptional performance ensure reliable and fast turnaround on all test results

2

A dedicated in-house sample machine shop ensures that all test samples are machined on site

3

Experts in the Machine shop are capable of low-stress grinding and machining sub-size specimens to very close tolerances

4

Highly qualified engineers in the machine shop are capable of undertaking custom-design fixtures, mount specimens for metallographic examinations and custom-fabricate TOFD weld blocks for NDT operators

5

Routine testing of fasteners, chain materials, weld coupons, wire rope, castings, sheet, plate, forgings and other components is done in an effective manner to provide clients an efficient and quality-driven service

6

At TCR, customers feel confident because experienced engineers and technicians not only handle routine but even the most diverse test requests with the same commitment

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