Simulation of Secondary Contact to Generate Very High Accelerations

Abstract

This paper investigates the design of a typical commercially available drop system for generating very high shock and drop accelerations. Some commercially available drop towers produce accelerations greater than 5000 G by utilizing the dynamics of secondary impact, using an attachment termed a dual mass shock amplifier (DMSA). Depending on the design, some DMSAs are capable of repeatedly generating accelerations as high as 100,000 G. The results show that a finite element model (FEM) can capture the peak acceleration for the drop tower and the DMSA within 15%. In this paper, a detailed description of the test equipment and modeling techniques is provided. The effects of different design parameters, such as table mass, spring stiffness, and programmer material properties, on the drop profile, are investigated through parametric modeling. The effects of contact parameters on model accuracy are explored, including constraint enforcement algorithms, contact stiffness, and contact damping. Simple closed-form analytic models are developed, based on the basic principles of a single impact and the dynamics of secondary impact. Model predictions are compared with test results. Details of the test methodology and simulations guidelines are provided. Detailed finite element analysis (FEA) is conducted and validated against the experimental tests and compared to the simplified theoretical simulations. Benefits in exploring FEM to simulate contact between materials can be extrapolated to different architectures and materials such that with minimal experimental validation impact acceleration can be determined.

Investigation into color designs of product packaging through visual evaluations using machine learning methods

“…After calculating the gradient in the neighborhood of the extremum point according to equation ( 2), the pixel gradient is grouped and accumulated every 10°to construct a gradient histogram; finally, the histogram corresponding to the main direction of each extremum point and the histogram of the direction greater than 80% of the gradient peak value in the main direction is combined into a SIFT feature. ○ 3 The extracted SIFT features of the samples are divided into a training sample set and a test sample set, and the SVM classification function is trained and fit by the training samples. The SVM classification function is:…”

“…In the pattern of paper packages, although line modeling is very important, people usually pay attention to the color design of the pattern first. Different pattern color designs will give different imagery representations, and these imagery representations will form combinations with ceramic crafts to enhance the ornamental value [3]; therefore, it is very important to evaluate the color design for packaging of ceramic products. An accurate color design evaluation can guide the color design for packaging better.…”

A Deep Learning Approach to Recover High-g Shock Signals From the Faulty Accelerometer

“…1, the DMSA is attached to a drop shock tester to together form a high-g shock test system. Such system can generate accelerations more than 30,000 g [29]. Its working procedures are shown in Fig.…”

“…This evaluation index describes the ability of recovering maximal shock responses from the faulty signals. Considering that the peak value is a key index in board-level shock test standards [3], [28], [29], it is essential to require the proposed approach to recover the peak values from the faulty shock signals, and so that the recovered results could be used to assess the reliability of products during board-level shock tests.…”

Theoretical and experimental study of the “superelastic collision effects” used to excite high-g shock environment

“…During the striking process, the components of such systems and the systems themselves generally experience shocks equal to tens of thousands of g (1 g = 9.8 m/s2) for durations of several milliseconds. All components and the systems themselves must survive such shock loading events and be qualified for severe environments [1][2][3][4]. Therefore, it is undoubtedly essential to assess the survivability and the working performance of the components and systems by testing them in such high-g shock environments during the development and production processes.…”