Oblique Impact Loading Research Articles

Numerical simulation on windowed tubes subjected to oblique impact loading and a new method for the design of obliquely loaded tubes

Tubular structures under oblique loading may collapse in axial or bending mode when the load angle is smaller or larger than certain critical value, and the bending mode has much lower energy absorption. In the present study, windowed square tubes subject to oblique impact were numerically studied, with variables being load angle, width and height of window and impact velocity. Next, a new design method was proposed which can effectively increase the tube’s critical load angle without compromising its energy absorbing capacity. The method therefore has great potential in industrial applications where large load angles are expected.

Crushing analysis and multiobjective crashworthiness optimization of tapered square tubes under oblique impact loading

In this paper, a class of axisymmetric thin-walled square (ATS) tubes with two types of geometries (straight and tapered) and two kinds of cross-sections (single-cell and multi-cell) are considered as energy absorbing components under oblique impact loading. The crash behavior of the four types of ATS tubes, namely single-cell straight (SCS), single-cell tapered (SCT), multi-cell straight (MCS) and multi-cell tapered (MCT), are first investigated by nonlinear finite element analysis through LS-DYNA. It is found that the MCT tube has the best crashworthiness performance under oblique impact regarding both specific energy absorption (SEA) and peak crushing force (PCF). Sampling designs of the MCT tube are created based on a four-level full factorial design of experiments (DoE) method. Parametric studies are performed using the DoE results to investigate the influences of the geometric parameters on the crash performance of such MCT tubes under oblique impact loading. In addition, multiobjective optimization design (MOD) of the MCT tube is performed by adopting multiobjective particle swarm optimization (MOPSO) algorithm to achieve maximum SEA capacity and minimum PCF with and without considering load angle uncertainty effect. During the MOD process, accurate surrogate models, more specifically, response surface (RS) models of SEA and PCF of the MCT tubes are established to reduce the computational cost of crash simulations by finite element method. It is found that the optimal designs of the MCT tubes are different under different load angles. It is also found that the weighting factors for different load angles are critical in the MOD of the MCT tubes with load angle uncertainty.

104 斜め衝撃荷重を受ける波付円筒の変形モード(材料力学I)

104 斜め衝撃荷重を受ける波付円筒の変形モード(材料力学I)

Dynamic energy absorption characteristics of foam-filled conical tubes under oblique impact loading

This paper treats the crush behaviour and energy absorption response of foam-filled conical tubes subjected to oblique impact loading. Dynamic computer simulation techniques validated by experimental testing are used to carry out a parametric study of such devices. The study aims at quantifying the energy absorption of empty and foam-filled conical tubes under oblique impact loading, for variations in the load angle and geometry parameters of the tube. It is evident that foam-filled conical tubes are preferable as impact energy absorbers due to their ability to withstand oblique impact loads as effectively as axial impact loads. Furthermore, it is found that the energy absorption capacity of filled tubes is better maintained compared to that of empty tubes as the load orientation increases. The primary outcome of this study is design information for the use of foam-filled conical tubes as energy absorbers where oblique impact loading is expected.

Oblique impact simulations of high strength agglomerates

Different types of particle compounds like concrete particles can be considered as a model material of high strength agglomerates. It is necessary to investigate and understand fracture behaviour of these agglomerates in order to avoid breakage during storage, handling and transportation. The aim of the research is to examine the comminution behaviour of high strength agglomerates during oblique impact loadings. A two dimensional finite element analysis has been carried out to understand stress pattern distributions before crack initiation. Then a two dimensional discrete element method has been applied to study the fragmentation behaviour of the agglomerates. Concrete particles of B35 strength category have been chosen to represent the high strength agglomerates. Analysis is done with oblique impact loadings at different velocities from 7.7 to 180 m/s. The stressing conditions comprise low flow rate transportation and handling to high speed impacts during fall down in bunker, stock piles, ship loading or stressing in crushers and mill operations. Particle size distributions and new surface generation have also been evaluated in the paper. It is shown that at higher velocities, particle size distributions are identical to each other regardless of impact angle. Increasing impact velocity does not necessarily produce more new surfaces after certain velocity limit.

854 前面および斜め衝撃荷重を受ける薄肉構造部材の動的圧潰特性(材料力学I)

854 前面および斜め衝撃荷重を受ける薄肉構造部材の動的圧潰特性(材料力学I)

Dynamic simulation and energy absorption of tapered thin-walled tubes under oblique impact loading

In real-world impact loading situations the structure could be subjected to both axial and off-axis loads. Tapered thin-walled rectangular tubes have been considered desirable impact energy absorbers due to their ability to withstand oblique impact loads as effectively as axial loads. Despite this, relatively few studies have been reported on the response of such structures under oblique loading. The aim of this paper is to compare the energy absorption response of straight and tapered thin-walled rectangular tubes under oblique impact loading, for variations in the load angle, impact velocity and tube dimensions. It is found that the mean load and energy absorption decrease significantly as the angle of applied load increases. Nevertheless, tapering a rectangular tube enhances its energy absorption capacity under oblique loading. The outcome of the study is design information for the use of straight and tapered thin-walled rectangular tubes as energy absorbers in applications where oblique impact loading is expected.

Finite element analysis of elastodynamic sliding contact problems with friction

This paper presents a general but effective finite element technique to analyze elastodynamic sliding contact problems with friction. The deformed contact area is obtained using the constraint conditions developed by a quadratic mathematic programming technique. Lagrangian multipliers are introduced to evaluate the contact pressures due to friction and determine the adhesion or release of contact surface. Based on these, the sliding process between two contact surfaces is accurately modelled. This work also provides the correction formulae for modelling the transient response of velocities and accelerations on the contact surface when the initial impact or release of the contact surface occurred. Several numerical examples are carried out to demonstrate the validity and accuracy of this work. The complete scheme of the transient sliding response of two contact components subjected to oblique impact loadings is drawn.

Static and dynamic crushing of tapered sheet metal tubes of rectangular cross-section

The use of tapered sheet metal tubes as impact energy absorbers is considered. Their behaviour is compared with tubes of uniform cross-section with regard to the stability of the gross deformation modes. Single-tapered and double-tapered tubes are considered and estimates of the variation of their mean crushing forces with reduction in length under both quasi-static and dynamic axial loading conditions are provided. The practically important question of the response of tapered tubes to oblique impact loads is also considered.