Shock Response Spectrum Research Articles

Application of the thermal shock response spectrum (TSRS) methodology to various forms of heat sources by pulse thermography and comparison by using a rotating line scan contour search algorithm

Application of the thermal shock response spectrum (TSRS) methodology to various forms of heat sources by pulse thermography and comparison by using a rotating line scan contour search algorithm

Optimization of thermal shock response spectrum as infrared thermography post-processing methodology using Latin hypercube sampling and analytical thermal N-layer model

In this work, we continue to develop and investigate the Thermal Shock Response Spectrum (TSRS) method as an alternative data processing method for infrared thermography (IRT). We focus on improving the current TSRS algorithm and present an optimization methodology for finding the optimal thermal Q-factor and characteristic frequency pair, which is based on the widely applied random sampling method. We show the qualitative relationship between the determined optimal characteristic frequency and the corresponding maximum difference in diffusion length between reference and defective models, as calculated by selecting a specific one-dimensional thermal N-layer model The investigations were performed on an inhomogeneous plate made of carbon fiber reinforced polymer (CFRP) with artificial square defects at different depths. Furthermore, two different heat sources were used: a xenon flash lamp and a laser. These sources are not only distinct by their underlying physics but also generate inherently different pulse shapes. To quantitatively estimate the contrast between defect and non-defect areas, and to compare these results with commonly used infrared thermography (IRT) data post-processing methods such as Pulse Phase Thermography (PPT) and Thermographic Signal Reconstruction (TSR), the Tanimoto criterion (TC) and signal-to-noise ratio (SNR) were used.

Optimization of Pyroshock Test Conditions for Aerospace Components to Enhance Repeatability by Genetic Algorithms

Electronic components assembled in satellites should be able to withstand the vibration, noise, and impact loads generated by space vehicles during launch. To simulate the impact loading in a laboratory environment, a pyroshock test simulates an impact load resulting from explosions during the stage and pairing separation of launch vehicles, which imposes significant stress on the components, potentially leading to failures and damage. To ensure component reliability before the flight model (FM) stage, where components are mounted on the actual launch vehicle and sent into orbit, a pyroshock test is conducted during the qualification model (QM) stage using identical parts and specifications. This process involves measurements of the acceleration induced by pyroshock to calculate the shock response spectrum (SRS) and evaluate the components’ reliability against the required SRS to confirm their ability to endure the shock and operate normally in post-tests. The aerospace developer determines the SRS requirements based on the space launch vehicle and the installation location of the electronic components. Configuring a suitable pyroshock test to meet these requirements typically involves extensive trial and error. This study aims to minimize such trial and error by examination of SRS changes through a numerical approach by table structural vibration analysis. The structure is subjected to in-plane impacts using a steel ball via a pendulum method. Various SRS profiles are calculated by test factors such as the weight of the steel ball, the pendulum angle, and the installation position of the test specimen. Furthermore, a genetic algorithm is utilized to derive the optimal test conditions that satisfy the required SRS. An automated pyroshock test system is developed to enhance repeatability and reduce human errors.

A novel design of compact elastomer shock absorption system to protect sensitive objects from underwater shock for naval application

This research paper proposes a unique way to safeguard delicate systems on submerged platforms from the undesirable effects of underwater explosion shock loads. The underwater detonation of an explosive charge and mines produce devastating underwater shocks against underwater platforms. Shock load developed underwater has been analyzed, and a shock response spectrum (SRS) approach to compute shock peak responses has been adopted. SRS shock absorption frequency satisfies requirements for both shock absorption and delicate systems. The shock load was reduced to 2g by altering the delicate system stiffness and damping properties. The analytical model for a single DOF system was formulated, and simulation was carried out using ANSYS solver. The stiffness has been spread across various points along the length of the delicate system, allowing it to undergo translational oscillations when subjected to shock loads. This research paper presents an innovative design approach for a shock absorption system intended for underwater sensitive objects, emphasizing simplicity, distinctiveness, compactness, reliability, and electromagnetic compatibility. Experimental testing validated the shock absorption design on the prototype. Shock testing determined the absorber’s maximum displacement and sensitive object acceleration.

Evaluation of the mechanical shock testing standards for electric vehicle batteries

The safety of Li-ion batteries (LIB) has become an important issue with the continuously increased use of electric vehicles (EV) in the world. In a survivable vehicle crash, when the vehicle needs to maintain structural integrity, crash-induced shock may damage EV's LIB. Therefore, an evaluation of commonly used mechanical shock test standards for EV battery module and pack is performed in this study against the crash-induced shock signals collected from National Highway Traffic Safety Administration (NHTSA) New Car Assessment Program (NCAP) tests. Various shock analysis methods including signal characteristics in time domain, power spectral density (PSD) and shock response spectrum (SRS) in frequency domain, and the acceleration/velocity-change diagram are used for the evaluation. It is found that most peak accelerations of NCAP shock signals significantly exceed the peak accelerations specified in shock testing standards. Crash-induced shocks cannot be fully represented by the half-sine pulse adopted in shock testing standards. In both time and frequency domains, the existing shock testing standards generally underestimate the severities of the crash-induced shocks, and therefore, are non-conservative. It also shows that the correct selection of a filter for the processing of the original crash-induced shock signal is crucial for the specification of EV battery shock environment and shock response analyses. The results obtained in this research can support the development of more reliable shock testing standards for EV batteries.

Design and characterization of a pyroshock reduction structure based on local resonance mechanisms

In the spacecraft Pyrotechnic shock process, the explosion generated by the strong shock wave and preload force release of the vehicle structure produces a transient, high-frequency, and high-amplitude shock response, resulting in a harsh shock environment prone to failure or damage to many precision equipment or components on the spacecraft, a fatal impact on the launch mission. This paper designed a local resonance shock mitigation structure based on local resonance theory for the Pyrotechnic shock environment and optimized the parameters of the structure by the genetic algorithm. A Pyrotechnic shock simulation experimental device was built to verify the impact reduction effect of the designed shock reduction structure. This experimental device can well restore the pyrotechnic shock environment. In addition, a finite element simulation model was established, and the impact reduction effect of the protective structure was verified both numerically and experimentally. The experimental and numerical analysis results show that the impact response decays significantly in the structural band gap range with the same transfer path, and the shock response spectrum amplitude decreases 9.8 dB in the 100–10,000 Hz frequency band.

Alternative data evaluation methodology for infrared thermography analogous to the Shock Response Spectrum analysis method

We propose an alternative method for processing infrared thermography (IRT) data based on a thermal 1-layer model. The method is based on the analogy of the Shock Response Spectrum (SRS) analysis for mechanical systems (ISO 18431). A thermal Q-factor, similar to the resonance sharpness (Q-factor) of a mechanical oscillator, is introduced as a parameter for selecting a specific thermal 1-layer model. Two main aspects of this method and corresponding properties have been considered: the strictly model-based treatment of this methodology and an empirical introduction of additional bandpass filters. The method is validated with two practical examples: for a homogeneous polymer sheet with blind holes and an inhomogeneous plate made of carbon fiber reinforced polymer (CFRP) with artificial defects, the capability of defect detection is compared with established methods. The comparison of the results with the commonly used data processing methods of IRT as Pulsed Phase Thermography (PPT) and Modified Differential Absolute Contrast (MDAC) shows equivalent or sometimes improved performance.

Mechanical shock test simulation analysis of butterfly valves developed for the naval defense industry and evaluation of real test and production data

The main purpose of this study is to investigate the mechanical shock behavior and develop the shock resistance of widely preferred butterfly valves for navy defense industries by handling the real test results with computer aided design and simulation programs. The 2D and 3D drawings were realized by using solid modeling and design programs. Mechanical analyzes to determine the mechanical strength of the specimens were carried out with the finite element analysis method by using structural simulation program. Mechanical shock test simulations were carried out by with shock response spectrum analysis. Solidification, filling-time–temperature analyzes, and simulation studies of inner stresses caused by micro and macro shrinkages were performed by using the casting simulation program. Comparisons of virtual tests simulated in computer environment with real tests were done in shock test setup. Products made of bronze were preferred due to the high corrosion resistance and the desire to be a useful research article that can respond to common applications in the defense industry. Virtual shock test simulation and real shock tests were performed according to the MIL STD 810 standard. The shock test results observations showed that by revising the design with a safety factor of 18% on the specimen, it was ensured that the product could pass the mechanical shock test even at an acceleration of 4000 m/s2. Then material become safe to use. With the use of a three-way feeder in the production of the reinforced design the difference in net weight from 19% has been reduced to 12%, while the production time has been improved by 22%.

Response spectrum-based analysis of airborne radar random vibration and multi-point control improvement

During the flight of a UAV (unmanned aerial vehicle), the LiDAR device undergoes random vibrations due to the changing flight attitude and wind speed conditions of the UAV. It is important to control the frequency and amplitude of the vibrations within a reasonable range by means of a damping structure. As the vibrations caused by various factors during flight are random and non-linear, this paper innovates the analysis principle and damping control means for the random vibrations of airborne optoelectronic devices. The response spectrum analysis theory is used to establish the shock response spectrum, and an optimised and improved recursive digital filtering method is used to fit the frequencies of random vibration to the synthetic shock response. Considering the uncertainty of the vibration excitation signal, a virtual excitation method is used for the first time to simulate the random vibration to which the radar may be subjected in the air, and to simplify the calculation steps. The shock plate structure is designed using a multi-point control method to innovate a passive response to the random excitation. Finally, a modal analysis of the synthesised impact response was carried out. It is verified that the first six modal frequencies are controlled within 220 Hz, realising the frequency reduction. The amplitude of the three x, y, and z directions is controlled to within 0.5 mm, thus achieving vibration damping.

A Two-Part Analytical Solution for the Shock Response Spectrum with Coulomb Damping

A Two-Part Analytical Solution for the Shock Response Spectrum with Coulomb Damping

Shock fatigue damage failure boundary study of BGA solder joints based on shock response spectrum

Multiple shock damage failure of ball grid array (BGA) solder joints is one of the important reasons for reusable spacecraft mission failure. Shock fatigue damage failure boundary of BGA solder joints is proposed based on shock response spectrum (SRS), which can be used to assess the damage failure state. Weibull distribution is employed to characterize the shock fatigue life for a specified SRS. A Bayesian estimation method based on the Bootstrap approach is proposed to estimate Weibull distribution parameters. By using the time-domain load synthesized method based on wavelet and the experimentally validated shock fatigue life model, the shock fatigue life data of BGA solder joints corresponding to different SRS are extended. The variation patterns of the scale and shape parameters with the SRS parameters is analyzed. Then the shock fatigue damage failure boundary based on SRS is determined for a given design life and reliability. The results show that the critical SRS amplitude increase with the rise of the inflection point frequency and the low-frequency slope, respectively. The developed method is expected to provide references for the environment-adaptive design of BGA solder joints in reusable spacecraft.

Broadband shock vibration absorber based on vibro-impacts and acoustic black hole effect

A vibration absorber combining the acoustical black hole (ABH) effect with vibro-impacts is presented as a separate device that can be mounted on a primary structure for passive vibration mitigation. The vibration isolator is shown to be effective for low-frequency shock vibration attenuation. Numerical and experimental results are reported, considering a rectangular honeycomb plate as the primary structure, on which the device, consisting of a circular ABH plate with one or several impact masses, is attached. A numerical model is developed using a finite element space discretization combined with a conservative scheme in a penalty approach for the contact dynamics. The analysis shows that the device has broadband efficiency thanks to the combined effects of energy transfer due to impacts and high attenuation in mid and high-frequency range due to the ABH effect. A detailed parametric study underlines that the tuning of the linear fundamental frequency of the impact mass plays an important role. Besides, considering several impact masses is shown to improve the efficacy. An experimental setup is then used in order to demonstrate the effectiveness of the device. The results confirm the vibration mitigation trends obtained from the numerical model that could then be used as a design tool for the attenuator. Finally, an analysis based on the Shock Response Spectrum (SRS), widely used in the field of aerospace engineering, is performed, underlining the attenuator is able to reduce rapidly and efficiently the vibrations due to a mechanical shock.

Research on the Shock Environment Characteristics of a Marine Diesel Engine Based on a Large Floating Shock Platform

To conduct a precise shock assessment of marine diesel engines, a 200 t floating shock platform was utilized to simulate realistic testing conditions. The testing generated the acceleration time curve and the shock response spectrum for the diesel engine. According to the applicable standards, the spectral velocity was chosen as the evaluation index, and an evaluation of the longitudinal, transverse, and vertical shock environment of the diesel engine was conducted. The shock factor interpolation method was corrected using the confidence interval based on normal distribution, and the interpolated confidence interval of the shock factor was determined. The findings reveal that shock waves were identified as the primary external force, and it was found that the influence of bubble pulsation can be disregarded when assessing a floating shock platform. This paper proposes the use of normal-distribution-based shock factor confidence intervals, which can accurately predict multidirectional shock factors and offer improved shock safety compared to the traditional method of unidirectional shock factor interpolation. The results and methods obtained in this study can provide valuable guidance and assistance for predicting the shock environment of large shipboard machinery on significant floating shock platforms.

Development of an impact based pyroshock test setup using finite element and response surface methods

In this study, a simulation and test-based procedure is created and applied to develop mechanical pyroshock test setup. In order to build an effective design, preliminary input parameters are defined with finite element simulations. The agreement between impact simulations and experimental data was achieved for resonant plate, metallic anvil plate and gun system. The obtained Shock Response Spectrum (SRS) curves are not well fitted to explicit finite element simulations for nonmetallic anvil plate materials, such as felt, which also have significant contribution to results. Therefore, further improvement is established by using test-based Response Surface Method (RSM). After validating the relationship statistically, response optimizer was used to find the best combination of design parameters to achieve target SRS curve. Finally, the prediction was checked experimentally to show the effectiveness of the developed methodology.

Data analysis of simulated fuel-loaded sea transportation tests under normal conditions of transport

In this study, to evaluate the shock and vibration load characteristics of used fuel, a sea transportation test was conducted using simulated fuel assemblies under normal transport conditions. An overall test data analysis was performed based on the measured strain and acceleration data obtained from cruise, rotation, acceleration, braking, depth of water, and rolling tests. In addition, shock response spectrum and power spectral densities were obtained for each test case. Amplification and attenuation characteristics were investigated based on the load path. The load was amplified as it passed from the overpack to the simulated used fuel-assembly. As a result of the RMS trend analysis, the fuel-loading position of the transportation package affected the measured strain in the fuel rod, and the maximum strains were obtained at the spans with large spacing. However, even these maximum strains were very small compared to the fatigue strength and the cladding yield strength. Moreover, the fuel rods located on the side exhibited a larger strain value than those at the center.

Anti-shock performance of a cockroach-inspired structure

Shock leads to negative impacts on both engineering practices and human comfort in daily life. Many species in nature possess significant shock resistance capacities. This paper introduces a cockroach-inspired structure (CIS) for effectively isolating large-amplitude shocks. The shock responses of CIS are evaluated using the Runge-Kutta method and assessed by four indices: time history response, energy conversion, shock transmissibility, and shock response spectrum. The numerical results show that the hardening effect induced by CIS leads to a leftward shift phenomenon, which can reduce transient response time and expand shock isolation area. By adjusting the geometric parameters, the damping force can be increased to improve the shock isolation performance; the stored potential energy and converted kinetic energy can be minimized, enabling the payload to quickly stabilize its position. The experimental results show that CIS achieves a significant 91.5% reduction in peak absolute acceleration. In summary, this study lays the groundwork for exploring the potential of insect-inspired structures in mitigating shocks.

On pyroshock tests for aerospace equipment qualification: A comprehensive parametric model for the simulation and the design of pyroshock test facilities

Spacecraft and related onboard equipment are subject to strong dynamic loads during the different phases of the missions. In particular, severe high-frequency shocks - mainly caused by the activation of pyrotechnic devices (hence the name "pyroshock") - are transmitted to the entire structure and could cause mission failure and safety-critical damages. Therefore, the verification tests of the aerospace equipment are essential to prove the resistance of the instrumentation to impulsive loads. The requirements for this qualification are usually expressed in terms of Shock Response Spectrum (SRS) acceleration and different launch vehicles cause different SRS. Therefore, the laboratory tests have the objective of simulating the real shock load conditions and - at the same time - being repeatable and safe. For these reasons, the most common test facilities exploit the launch of an impacting object (e.g., hammers or bullets) on resonant plates, interposed supporting the component under test. Recently, many studies have focused attention on the development of numerical analyses to predict the shock responses of these structures, given that their calibration is currently conducted with empirical techniques and involves considerable costs and downtime. This work aims to present an effective parametric model both for the simulation of pyroshock tests and for the optimization of the design of test facilities. The novel implementation of an embedded Computer-Aided Design (CAD) modeler – integrated with a Finite Element (FE) solver – and a Genetic Algorithm (GA) optimizer makes the proposed model both accurate and flexible. Precisely its flexibility makes it possible to effortlessly and efficiently satisfy the variable SRS requirements, reducing calibration times and - consequently - entailing remarkable economic advantages. The proposed model is developed entirely in the frequency domain, making it accurate and fast in computational terms. Furthermore, a comparison between the simulated pulse and a real force profile obtained from an impact characterization is presented.

Predictive model and physical interpretation of asymmetric features in pyroshock signals

In aerospace engineering, electronic devices can be easily damaged under pyroshock environments, and therefore, shock testing is required. The shock response spectrum (SRS) is the widely adopted specification tool to compare shock severities between field pyroshocks and testing shocks. However, two shocks with almost the same SRS but different temporal features could still lead to large differences in the failure of a device. The test specification should consider temporal features of shocks in order to be more representative of the field shocks. During shock propagation, shock signal evolves from an exponentially decaying shape to an asymmetric shape with an increased initial rise stage, which is characterized by the temporal moment or asymmetric basis functions. This study explains the evolution mechanism of shock asymmetry based on elastic wave propagation theory and proposed a predictive model. The theoretical foundation for the application of signal asymmetry in pyroshock characterization, device failure analysis and SRS reconstruction is provided.

An innovative design of a compact shock isolation system to protect sensitive weapons from underwater shock & validated by shock testing for naval applications

This paper presents an innovative solution to protect the sensitive weapons stored inside strategic submerged platforms from severe shock loads (170 g) due to underwater explosions. The shock loads mainly resulted from the underwater explosion of a nuclear warhead, mines, and bomb nearby platform. The underwater shock load has been analyzed, and a shock response spectrum (SRS) method has been developed to calculate peak responses during shock. The frequency of shock isolation has been selected from SRS to meet the requirement of shock isolation and sensitive weapon. Stiffness and damping characteristics were finalized to reduce the shock load of 179 g to an acceptable limit of 5 g for a sensitive weapon. The single-degree freedom system analytical model was formulated, and the ANSYS tool was used for modeling and simulation. The stiffness has been distributed over the weapon's length at multiple locations such that the weapon will oscillate in the translational mode under shock load from the elastic model. This paper explains the novel approach and technique for the design of a simple, unique, compact, reliable, electromagnetically compatible shock isolation system for underwater sensitive weapons. A parametric study was undertaken to compute the dimensions and configuration of shock isolators. Experimental tests were performed on the prototype to validate the design of the shock isolator. The maximum displacement of the isolator and maximum force transmitted to the sensitive weapon was found by shock testing. Finally, Transient dynamic analysis was performed to evaluate the actual motion of isolators during shock.

Simulation of pyroshock environment and effect rules of shock response spectrum

AbstractThe high-frequency and high-amplitude pyroshock environment during the service of the spacecraft will cause damage to the equipment. Here, we develop a shock test device based on air cannon to simulate the above pyroshock environment. Then, a finite element model was established by explicit dynamic software ANSYS/LS-DYNA, and the simulation results were proved to be consistent with the test data. Based on the theory of Shock Response Spectrum (SRS), the effects of device parameters such as pressure, bullet material and resonant plate material on SRS were investigated via numerical simulation and shock test. This study shows that the amplitude of SRS increases with the increase of pressure in the range of 0.15–0.60 MPa, and the break frequency amplitude has a square root function relationship with the pressure. Additionally, the high-frequency amplitude of SRS was affected by the energy transfer efficiency of the bullet.