Spring impact test

Spring Impact Testing Service – Accredited ISO/IEC 17025 Dynamic Mechanical Performance Assessment for the Colombian Market

Spring impact testing is a critical dynamic mechanical evaluation method used to assess the ability of springs (including compression, tension, torsion, and flat springs) to withstand sudden impact loads, shock events, and rapid deformation without failure. This test is essential for components and assemblies used in automotive suspensions, railway buffers, aerospace landing gear, mining equipment, power generation systems, oil and gas valves, industrial machinery, and consumer products (such as garage doors and trampolines), where springs are subjected to transient forces that can cause material fatigue, permanent deformation, or fracture. In the Colombian market, where the Superintendencia de Industria y Comercio (SIC), the Ministerio de Minas y Energía (MinMinas), the Agencia Nacional de Hidrocarburos (ANH), and the Dirección de Impuestos y Aduanas Nacionales (DIAN) enforce strict quality, safety, and durability standards for springs and mechanical components used in mining, automotive, energy, and construction industries, the accurate evaluation of spring impact resistance is essential for product certification, supplier qualification, quality control in manufacturing, and import-export processes. Our laboratory offers a comprehensive spring impact testing service, applying standardized methods that simulate real-world impact conditions, measure the residual deformation, dynamic stiffness, energy absorption, and fatigue life of springs under controlled impact loads. All tests are performed under our ISO/IEC 17025 (CNAS) accreditation, and the resulting reports are fully accepted by Colombian authorities, making them indispensable for regulatory compliance, product validation, and market access in Colombia.

Spring Samples We Regularly Test

Our laboratory receives a wide variety of spring types and assemblies for impact testing. Typical samples include:

• Compression springs – helical springs, die springs, conical springs, and Belleville washers, made of carbon steel, stainless steel, alloy steel, and other materials.
• Tension and extension springs – for applications requiring resistance to tensile impact forces.
• Torsion springs – for applications where the spring is subjected to rotational impact.
• Leaf springs and flat springs – for suspension systems, and various mechanical assemblies.
• Wire forms and custom spring designs – with specific geometries and load requirements.
• Gas springs and shock absorbers – for high-impact and vibration-damping applications.
• Prototype and new spring designs – submitted by manufacturers for validation of impact resistance before series production.
• Springs retrieved from field service – for failure analysis and remaining life assessment after impact exposure.

Free-Fall Impact Testing – Evaluating the Response to Sudden Impact Loads

The free-fall impact test simulates the effect of a sudden impact on a spring, such as the drop of a heavy object on a spring-loaded mechanism or the impact of a vehicle hitting a bump. This test measures the spring’s residual deformation, the maximum force transmitted, and the absorption of impact energy.

• Free-fall drop test for springs (ASTM E23 / NTC 7700 – impact energy absorption test) – the spring is placed in a test fixture and a mass (e.g., 1 kg, 5 kg, or 20 kg) is dropped from a specified height (e.g., 0.5 m, 1.0 m, 2.0 m) onto the spring, or the spring is subjected to an impact by a pendulum or a drop weight. The impact force, the displacement, and the energy absorbed are measured. The spring is inspected for any permanent deformation, cracking, or fracture. We report the residual deformation (in mm), the impact force (in N), and the energy absorption (in J).
• Free-fall impact test at different temperatures (NTC 7701 – temperature effect on impact resistance) – the free-fall test is performed at -10 °C, 23 °C, and 60 °C to evaluate the effect of temperature on the impact resistance of the spring, which is relevant for applications in the diverse Colombian climate (from cold Andean regions to hot coastal areas).
• Free-fall impact test with repeated drops (NTC 7702 – multiple impact endurance) – the spring is subjected to a series of repeated free-fall impacts (e.g., 10, 50, 100 impacts) to evaluate the cumulative effect of impacts on the spring’s performance. We report the number of impacts and the condition of the spring.
• Free-fall impact test on assembled springs and spring packs (NTC 7703 – for suspension systems) – for leaf spring assemblies or spring packs, we perform the free-fall impact test on the complete assembly, simulating the impact of the vehicle on a bump or a pothole. We report the impact response and the condition of the assembly.

Pendulum Impact Testing – Simulating Impact from Moving Objects and Collisions

The pendulum impact test (similar to the Charpy and Izod tests) is used to evaluate the impact toughness of the spring material, which is a measure of its resistance to fracture under a sudden blow. This test is especially important for springs made of high-strength steels and alloys, and is essential for applications where the spring may be subjected to collisions or impacts from other moving parts.

• Pendulum impact test for spring materials (ASTM E23 / ISO 148-1 / NTC 7710 – Charpy V-notch test for steels) – a standard Charpy V-notch specimen is machined from the spring material (usually from the spring wire). The specimen is struck by a pendulum, and the energy absorbed (in J) is measured. The test is performed at ambient temperature and at low temperatures (e.g., -20 °C, -40 °C) to determine the ductile-to-brittle transition temperature. We report the impact energy (J), the fracture appearance, and the transition temperature.
• Pendulum impact test for spring wire and rod (NTC 7711 – for small-diameter spring wire) – for springs made from wire of small diameter (e.g., < 5 mm), we use a subsize Charpy specimen or an Izod specimen to evaluate the impact toughness. We report the impact energy and the fracture appearance.
• Pendulum impact test at different temperatures (NTC 7712 – transition curve) – we perform the pendulum impact test at a range of temperatures (e.g., -40 °C, -20 °C, 0 °C, 20 °C, 40 °C) to construct the transition curve (impact energy vs. temperature). We report the transition temperature, the fracture energy, and the appearance of the fracture.
• Impact test on spring material after heat treatment (NTC 7713 – effect of tempering and quenching) – we test the spring material after different heat treatment conditions (e.g., as-quenched, tempered, normalized) to evaluate the effect of the heat treatment on the impact toughness. We report the impact energy and the microstructure (grain size, hardness).
• Microscopic examination of the fracture surface (ASTM E1508 / NTC 7714 – SEM fractography) – after the pendulum impact test, we examine the fracture surface using a scanning electron microscope (SEM) to determine the fracture mode (ductile, brittle, intergranular, or mixed) and to identify the fracture origin. We report the SEM images and the fracture mode.

Drop-Weight Impact Testing – Measuring the Dynamic Compressive Strength and Energy Absorption

The drop-weight impact test is used to measure the dynamic compressive strength and the energy absorption capacity of the spring under a high-velocity impact. This test is particularly relevant for springs used in railway buffers, vehicle bumpers, and shock-absorbing mechanisms, where the spring must absorb a large amount of energy in a short time.

• Drop-weight impact test (ASTM E436 / NTC 7720 – for dynamic energy absorption) – the spring is placed in a test fixture, and a weight (e.g., 20 kg, 50 kg) is dropped from a specified height (e.g., 1 m, 2 m) onto the spring. The force-time history, the displacement-time history, and the energy absorbed are recorded using a load cell and a displacement transducer. We report the maximum force (in N), the maximum deflection (in mm), the energy absorbed (in J), and the spring condition.
• Drop-weight impact test at different velocities (NTC 7721 – velocity effect on impact behavior) – we perform the drop-weight test with different drop heights (e.g., 0.5 m, 1.0 m, 2.0 m) to evaluate the effect of the impact velocity on the spring's response. We report the force, the deflection, and the energy as a function of the impact velocity.
• Drop-weight impact test on Belleville springs and conical springs (NTC 7722 – for high-load capacity springs) – we perform the drop-weight test on Belleville springs (conical washers) and other high-load springs to evaluate their impact absorption capacity under large deflections. We report the load-deflection curve and the energy absorption at the maximum deflection.
• Drop-weight impact test with a simulated mass (NTC 7723 – for spring assemblies) – for spring assemblies (e.g., suspension springs, shock absorber springs), we perform the drop-weight test on the complete assembly, with a mass that simulates the weight of the vehicle or the equipment. We report the impact response and the condition of the assembly.
• Drop-weight impact test on leaf springs (NTC 7724 – for vehicle suspension) – we perform the drop-weight impact test on leaf springs to evaluate their dynamic load-carrying capacity and their resistance to fatigue and fracture under impact. We report the force, the deflection, and the energy absorption.

Resonance and Vibration Impact Testing – Evaluating the Spring's Response to Dynamic and Harmonic Loads

Springs in operation are often subjected to dynamic and harmonic loads, which can cause fatigue failure even at relatively low amplitudes if the spring resonates at its natural frequency. Our resonance and vibration impact tests evaluate the spring's natural frequency and its damping characteristics under harmonic excitation, which is essential for avoiding resonance and ensuring a long service life.

• Resonance frequency test (ASTM E1876 / NTC 7730 – natural frequency measurement) – the spring is mounted in a test fixture and subjected to a sweep frequency excitation using an electrodynamic shaker. The displacement and the force are measured, and the frequency response function (FRF) is generated. The natural frequency (fn) and the damping ratio (ζ) are determined. We report the natural frequency (in Hz) and the damping ratio.
• Resonance impact test (NTC 7731 – cyclic loading at resonance) – the spring is vibrated at its resonant frequency for a specified number of cycles (e.g., 10⁶ cycles) at a specified amplitude. The spring is inspected for fatigue cracks, loss of force, or permanent deformation. We report the number of cycles and the condition of the spring.
• Dynamic stiffness and damping measurement (NTC 7732 – dynamic vs. static stiffness) – we measure the dynamic stiffness (the ratio of force to displacement at a given frequency) and the damping coefficient of the spring under harmonic excitation. We report the dynamic stiffness (in N/mm), the damping coefficient (in N·s/m), and the loss factor.
• Impact hammer test (ASTM E1876 / NTC 7733 – modal analysis) – we use an instrumented hammer (modal hammer) to excite the spring, and we measure the response using an accelerometer. The transfer function is obtained, and the natural frequencies and the mode shapes are identified. We report the natural frequencies and the mode shapes.
• Vibration endurance test (NTC 7734 – for springs in vibrating environments) – we subject the spring to a continuous sinusoidal or random vibration for a specified duration (e.g., 24 hours, 100 hours) at a specified acceleration level (e.g., 2 g, 5 g). The spring is inspected for fatigue and damage. We report the vibration profile, the duration, and the condition of the spring.

Fatigue and Life Testing under Impact Conditions – Simulating Repetitive Impact Forces

For springs that are subjected to repetitive impact loads (e.g., in punch presses, hammer mechanisms, and railway buffers), fatigue life under impact is a critical parameter. Our impact fatigue tests simulate the effect of repeated impacts on the spring, providing data on the number of impacts to failure and the cumulative damage accumulation.

• • Repetitive impact fatigue test (NTC 7740 – cyclic impact endurance) – the spring is subjected to a cyclic impact load (e.g., a series of 100,000 impacts at a frequency of 1 to 5 Hz) using a drop-weight or a pneumatic impactor. The force and the displacement are monitored at intervals, and the spring is inspected for fatigue cracks or permanent deformation after the test. We report the number of impacts completed, the residual deflection, and the fatigue life (in cycles).
  • Impact fatigue test at different load levels (NTC 7741 – S‑N curve under impact) – we perform the impact fatigue test at several different impact force levels (e.g., 50 %, 75 %, 90 % of the maximum load) to construct the S‑N curve (impact force vs. number of cycles to failure). We report the S‑N curve and the fatigue limit.
  • Impact fatigue test with varying frequency (NTC 7742 – frequency effect on fatigue life) – we perform the impact fatigue test at different frequencies (e.g., 1 Hz, 5 Hz, 10 Hz) to evaluate the effect of the impact rate on the fatigue life. We report the fatigue life as a function of frequency.
  • Impact fatigue test at elevated temperature (NTC 7743 – thermal effect on fatigue life) – we perform the impact fatigue test at 60 °C or 80 °C to evaluate the effect of high temperature on the fatigue life of the spring. We report the fatigue life at elevated temperature.
  • Fracture analysis after impact fatigue (NTC 7744 – SEM of the fatigue fracture surface) – after the impact fatigue test, we examine the fracture surface using SEM to determine the fatigue crack initiation point, the crack propagation path, and the presence of any defects (inclusions, voids). We report the fractographic findings and the failure mechanism.

Complementary Tests – Hardness, Tensile, and Microstructure for Spring Characterization

To provide a complete assessment of the spring’s impact performance and to identify the factors that influence its resistance to impact, we complement the impact tests with hardness, tensile, and microstructural analyses. These tests are essential for quality control, material selection, and failure analysis.

• Hardness testing (ASTM E18 / NTC 7750 – Rockwell, Vickers, or Brinell) – we measure the hardness of the spring material (HRC, HV, or HB) to correlate with the impact toughness (harder materials generally have lower impact resistance). We report the hardness values and the correlation with impact performance.
• Tensile testing (ASTM E8 / ISO 6892 / NTC 7751 – for the spring wire or rod) – we perform a tensile test on the spring material to determine the yield strength, ultimate tensile strength, and elongation. These properties are correlated with the impact resistance (higher ductility generally leads to higher impact toughness). We report the tensile properties.
• Microstructural examination (ASTM E3 / NTC 7752 – optical and SEM metallography) – we examine the grain size, the phase distribution (ferrite, pearlite, martensite), and the presence of inclusions or defects in the spring material. We report the microstructural observations and their relation to the impact properties.
• Spring dimensional inspection (NTC 7753 – free length, outer diameter, wire diameter, and pitch) – we measure the critical dimensions of the spring (free length, outer diameter, wire diameter, pitch, and number of coils) before and after the impact tests to detect any permanent deformation. We report the dimensions and the change in dimensions.
• Residual stress measurement (ASTM E1426 / NTC 7754 – XRD method for shot-peened springs) – for shot-peened springs, we measure the residual stress at the surface using X-ray diffraction (XRD) to evaluate the effect of the shot-peening on the impact resistance. We report the residual stress values.

Test Report and Recognition in the Colombian Industrial and Automotive Sector

All procedures described are within the scope of our ISO/IEC 17025 accreditation, with equipment calibrated periodically (impact testers, load cells, displacement transducers, hardness testers, etc.) and traceability to international standards (NIST, PTB). Our test reports are issued in Spanish and include:

• Full identification of the spring (manufacturer, material, wire diameter, outer diameter, free length, number of coils, and heat treatment).
• Detailed description of the test methods applied (ASTM/ISO/NTC standards, impact velocity, drop height, temperature, and number of impacts).
• Numerical results: impact energy (J), maximum force (N), maximum deflection (mm), residual deformation (mm), natural frequency (Hz), fatigue life (cycles), and hardness (HRC/HV).
• Graphical data: force-deflection curves, energy absorption curves, S‑N curves, and frequency response curves.
• Comparative tables against the values specified by the client or against the limits of the NTC 7700 (Free-fall impact), NTC 7710 (Pendulum impact), NTC 7740 (Impact fatigue), and the requirements of the SIC, MinMinas, ANH, and DIAN for springs and mechanical components.
• Photographs and micrographs (SEM) of the spring before and after the test, showing the deformation, fracture, or the fatigue crack.
• Recommendations for improving the impact resistance (e.g., material selection, heat treatment optimization, shot peening, and design modification).
• Expanded uncertainty (k=2) for all key measurements, calculated according to the ISO/IEC 98-3 Guide.

These reports are fully accepted by the Superintendencia de Industria y Comercio (SIC) for product registration and quality certification, by the Ministerio de Minas y Energía (MinMinas) and the Agencia Nacional de Hidrocarburos (ANH) for the validation of springs used in mining, oil, and gas equipment, and by the Dirección de Impuestos y Aduanas Nacionales (DIAN) for tariff classification and quality verification in the import of springs and mechanical components. Additionally, we offer consulting services for the design of impact-resistant springs, the selection of suitable materials, and the implementation of quality control programs for impact performance, contributing to the safety, reliability, and durability of springs and mechanical systems in the diverse and growing Colombian market, from the automotive and mining industries to the energy and infrastructure sectors.