Drop Impact Test Research Articles

自動車の側面衝突における衝撃吸収用CFRP-Steelハイブリッド材の開発(技術OS1-1 軽量化構造の強度・剛性設計,技術OS1 自動車の強度・剛性・疲労信頼性設計と評価)

In the preset study, we used the CFRP-steel hybrid members made by combining a CFRP sheet to steel as a side impact beams. For simulating the side collision, the drop impact test (at the speed of 10km/h and 20km/h) under the boundary condition of three point bending test was conducted and the PAM-CRASH Explicit Finite Element Analysis (FEA) tool was used in order to predict the impact response behavior.

Construction and evaluation of scaled korean side impact dummies

It is necessary to have a dummy that describes the anthropometry of a victim with accuracy. This study presents three scaled side impact dummies constructed for the use of MADYMO. They represent five, fifty and ninety-five percentile Korean males ranged from the age of 25 through 39. Thirty-five anthropometric data were used to scale input files required for MADYSCALE. Geometries, inertia, joints and other parameters for dummies were scaled based on the configurations of EuroSID-1. This study proposes the lateral impact response requirements for head, thorax and pelvis of Korean side impact dummies. A lateral drop impact test was conducted for the head at the height of 200 mm. Lateral pendulum impact tests were also carried out for thorax and pelvis at three specific impact velocities. All these test results were obtained from simulation based on MADYMO. All the procedures of the three tests followed the requirement of ISO/TR 9790.

A Comparison of Results on Helmet Impact Testing

Abstract Drop impact testing of head protection helmets has been based on different methods in the European Committee for Standardization (CEN) and International Organization for Standardization (ISO) standards. Since it would be desirable to unite these two into one international standard, work was initiated to find out whether the corresponding test methods could be considered equivalent and interchangeable for helmet certification.

Drop-impact simulation and experimental verification for spindle fixation of video and audio module

For the spindle fixation of video and audio module (VAM), this paper presents both the numerical drop-impact simulation via the FEA-based high performance computing technology and the experimental characterisation by physical drop-impact test in order to examine the failure mechanism of spindle fixation under the various drop-impact levels and orientations. The studies also include the determination of the g-level at which the spindle will be dislodged when the VAM drops. The effort of the drop-impact simulation is based on the finite element model, which consists of the mounting plate, spindle, motor and lightpen house in the VAM. Numerical simulation results are compared and validated against physical drop tests. Furthermore, the roadmap of robust design methodology is created and the prototype design of spindle fixation in the VAM is improved. In this way, the design experience accumulated will be very useful for the future product design in terms of guidelines. As a result, the learning cycle is reduced and more reliable products can be designed and developed.

Compressive Response of Honeycombs Under In-Plane Uniaxial Static and Dynamic Loading, Part 1: Experiments

The crushing response of polycarbonate circular cell honeycombs under in-plane uniaxial loading is studied through a combination of static and dynamic experiments. The circular cell honeycomb material has a nearly periodic microstructure. The static experiments correspond to a uniaxial loading condition under displacement control in two different principal in-plane directions. The corresponding dynamic experiments are carried out using a low-velocity impact drop test facility. Three different initial conditions (corresponding to different drop heights) are used in the dynamic tests. In the initial part of the response, the specimens deform in an almost uniform fashion. Next, a nonlinear phase characterized by progressive localization of deformation is observed. The progressive localization causes the walls of each cell to contact. The reasons for the observed orthotropic response of the honeycombs are discussed. A comparison of the collapse mechanisms between static and dynamic experiments is included. The experimental work is presented first (Part 1), followed by the simulation studies (Part 2).

Evaluation of the Head Protection Abilities of Helmets under Impact Loadings by FE Analysis.

Many requirements such as safety, lightness and comfort are necessary to helmets for sports and riding. Many studies regarding basic functions of helmets including safety problems were reported. In the previous studies on safety problems, however, it seems to be difficult to say that those studies were accurate reviews because a helmet model integrated with a headform model or a simplified helmet model different from a real one had been used in their simulations. In this paper, FE models were made from the real shapes of the full face type helmet of JIS C Snell and the headform of the Hybrid-III dummy model, which were used in the drop impact tests. Computer simulations for the falling impact of helmets with headform onto playing surfaces were conducted by using FE models. In simulations, the material properties of shell and liner of helmet were determined as elastic and the headform was assumed as a rigid body. As a result, the acceleration responses of headform from the simulated results were compared with those of drop impact tests to evaluate the head protection abilities of the helmet by comparing HIC values. Additionally, the parametric studies were conducted to investigate the factors that affect mainly the headform acceleration. From this study, the main physical parameters, which are important in the optimal design of helmets under impact loadings, can be decided.

Simulation of the drop impact test for moulded thermoplastic containers

An analysis is made of the drop impact test for moulded plastics containers, as a first step towards the simulation of the impact event for design and development purposes. Experimental data are analysed from instrumented base drop impact testing of water-filled blow-moulded bottles, 20 and 210 l drums. Each type of container is found to exhibit a characteristic pulse time for the internal pressure during impact. Analysis shows that the observed behaviour of the flexible container/water-filled system is normally best described in terms of solid body dynamics, rather than an approach based on water hammer concepts. A simple equivalent mass–spring model is developed which predicts the characteristic pulse time and pressure distribution on the walls of the vessel throughout the impact test. It is shown that this model should be applied when the length of the vessel does not exceed a critical length. An expression for determining this critical length is given. Loads and loading rates predicted by the mass–spring model can be used as input to a simplified FEM simulation of the drop impact test on any vessel.

Using the essential work of fracture method for studying physical aging in thin, ductile, polymeric films

AbstractWater‐filled, drop impact tests on full‐scale, blow‐molding polyester bottles showed that impact properties change significantly after 30 days of aging at 50°C. To quantify this deleterious effect of aging, we did small‐scale laboratory experiments using the essential work of fracture method (EWFM). We measured the essential work of fracture of thin specimens cut from the sides of blow‐molded bottles and aged under various conditions. Similar to the impact results, significant drops in essential work occurred after relatively short amounts of aging. Additional experiments confirmed that the decreases in essential work were due to physical aging and not to chemical degradation. A comparison of the essential work results to the full‐scale, bottle‐drop impact tests showed some inconsistencies that need to be resolved before EWFM can be recommended as a quantitative method for studying physical aging of blow‐molding polyester resins.

PEACH FIRMNESS DURING STORAGE AS AFFECTED BY TREE IRRIGATION SCHEDULES1

ABSTRACTThe effect on peach [Prunus persica (L) Batsch.] firmness during storage was investigated for the following tree irrigation schedules: no irrigation, irrigation beginning at budbreak until October, and irrigation beginning at stage III of fruit growth until October. Peaches (cv ‘Cresthaven’) from the three tree irrigation schedules were harvested at two ripeness stages and were stored at 2C, 90% RH. After 3, 6, 9, 13, and 16 days of storage, peach firmness was tested by a modified Effegi flesh probe test and drop impact test. From the flesh probe test, the bioyield force, maximum force, and elastic modulus were measured and from the drop impact test, the contact time, peak force/time‐to‐peak force, and percentage of energy absorbed were measured. None of these parameters were significantly affected by the tree irrigation schedules. Riper peaches were softer during the whole storage period. Less ripe peaches had more variation in firmness parameters during storage. The average firmness of peaches changed only slightly during the first nine days of storage, then softened quickly thereafter.

Biodynamics of steering wheel induced facial trauma

The present study was undertaken to determine the impact biomechanics of the facial skeleton secondary to steering wheel loading. Because of the particular relevance of the zygomatic bony complex in facial trauma during motor-vehicle accidents, tests were conducted by impacting the zygoma using a vertical drop impact test system. Zygoma was impacted once onto either soft or rigid wheel surfaces at velocities of up to 6.7 m/s. Peak impact forces at the cadaver zygoma were computed from the generalized force and deformation histories using matrix transformation principles. Structural abnormalities were assessed using pre- and post-test plain radiography, two-and three-dimensional computed tomography, and defleshing techniques. At impact velocities of 1.7 to 6.7 m/s, the human cadaver zygoma did not exhibit clinically significant fractures if the peak force was below 1335 N for the soft wheel interface and 1153 N for the rigid wheel interface. Consequently, to mitigate facial injuries due to unsupported rim impact, the data from the present study suggests that the peak dynamic force should be kept within these limits.

Organic-matter effects on soil strength properties

Measurements of bulk density, moisture retention, aggregate stability and shear strength were taken for sandy loam and loamy sand soils with different organic-matter contents ranging from 1.23 to 5.64%. Organic matter in soils originated from either being under grass treatment for some years or mixing two forms of peat each at 4, 11 and 17% rates to a control soil. Aggregate stability was measured by the percentage water stable aggregates (WSA) as well as individual aggregate energy (IAE) measured using single drop impact test. Organic matter from grass significantly increased percentage WSA from 2.15 to 21.62% and IAE from 4 to 33 mJ. While percentage WSA reduced significantly from 2.50 to 0.88 with increasing peat content, the IAE reduced only slightly from 3.93 to 3.45 mJ. This suggests that peat reduces the overall soil stability without affecting the strength of individual aggregates. Organic matter from both grass and peat reduced bulk density and increased moisture retention. While organic matter from grass increased soil shear strength from 19.17 to 24.44 kN m −2, that from peat reduced it from 15.47 to 11.90 kN m −2. The effects of both forms of organic matter on bulk density and moisture retention were expected to have reduced their strengths. However, since organic matter from grass improved aggregate stability, it reduced soil dispersion in water and improved shear strength, while peat only made the soil aggregates fall apart and reduced their shear strengths. The results from this study show that the influence of organic matter on soil shear strength depends on whether or not it improves soil aggregate stability.

Theoretical determination of the appropriate frequency content of strain for the optimal influence on bone adaptation

IMPACT BIOMECHANICS OF THE ZYGOMATIC COMPLEX Narayan Yoganandan, Ph.D., Frank Pintar, Ph.D., John Reinartz, M.S., Anthony Sances, Jr., Ph.D. Department of Neurosurgery, Medical College of Wisconsin, Milwaukee, WI 53226 Veterans Administration Medical Center, Milwaukee, WI 53295 and Department of Biomedical Engineering, Marquette University, Milwaukee, WI 53233 This study was undertaken to describe the impact biomechanics of the human zygomatic complex and the resulting pathologic changes to the facial skeleton. Fifteen fresh human cadavers were used. Specimens were prepared by rigidly fixing the isolated heads in a neurosurgicai halo ring. A specially designed vertical drop impact test system was used to suitably hold the specimens and dynamically load either zygoma by contacting the junction of the left lower spoke and rim of the steering wheel. The wheels were placed at 30 degrees with the horizontal. Energy absorbing (EA) and non energy absorbing (NEA) wheels were used in the study. A six-axis load cell placed under the hub of the steering wheel measured the generalized force histories. A system of lineary and rotary potentiometers placed below the impact site measured the deformations, and a triaxiai accelerometer on the skull measured the accelerations. Pre-test and post-test, x-rays, 2-D and 3-D CT’s, and defieshed skulls documented the pathology. Facial trauma was classified based on the tripianar strut classification. There was a good correlation between the 2-D and 3-D CT, and defleshed skulls. Fractures correlated well with peak transformed forces at the impact site, while a weak correlation was found with the contact areas and deformations. Further, the head injury criterion (HIC) had a weak correlation with facial fracture emphasizing that HIC is not a good predictor for facial injury. 715 THEORETICAL DETERMINATION OF THE APPROPRIATE FREQUENCY CONTENT OF STRAIN FOR THE OPTIMAL INFLUENCE ON BONE ADAPTATION Kenneth J. McLeod and Clinton T. Rubin Musculo-Skeletal Research Lab Department of Orthopaedics, SUNY at Stony Brook, NY 11754-8181 The maintenance of bone mass is known to be dependent on the dynamic mechanical environment of the bone. However, the specific parameters of the mechanical load which regulate bone remodeling remain poorly defined. in an effort to identify those components which represent osteoregulatory stimuli, we have compared the temporal characteristics of specific mechanical loading patterns to their efficacy in preventing the bone loss of disuse, or in initiating new bone formation. Fourier analysis techniques were used to obtain the induced strain spectrum arising from the loading of a bone preparation with a symmetric trapezoidal waveform. induced spectral energy was then compared to the efficacy of these same loading patterns to prevent bone loss in the isolated avian ulna model of disuse osteopenia. The best correlation between induced strain energy and efficacy is obtained within a relatively “high” frequency range (13-40 Hz). Induced energy within this range demonstrates appropriate dose dependency at both low and high strain levels, and as well, provides an indication of a source of the variability in empirical data seen at high peak strain levels. As only a small portion of the total induced energy is encompassed in the high frequency range, the analysis implies that extremely small strains at appropriately high frequencies may be sufficient to regulate the remodeling response. The apparent ability of the very small “high” frequency components of applied strain to regulate physiologic bone remodeling supports the common premise that the actual signaliing mechanism is tied to a derivative process of the strain such as electrokinetic or piezoelectric currents. COMPUTER AIDED SIMULATION OF GROWTH AND ITS APPLICATION TO BIOLOGICAL AND ENGINEERING STRUCTURES C. Mattheck, S. Burkhardt, D. Erb Kernforschungszencrum Karlsruhe, Institut fiir Materialund FestkErperforschung IV 7500 Karlsruhe, West Germany A new method of Computer Aided Shape Optimization is shown which copies the method of self-optimization of trees by growth. That means that the Finite Element structure of the mechanical structure to be optimized is allowed to swell (growth) at places of high local stresses and not to swell (or as an option even to shrink) at places of lower stresses. The method works well, as many examples (tree branch-stem joints, wound healing in trees, optimized engineering components) show. Furthermore it is shown that the design of some biological structures constitutes a mechanical optimum. The method is working well for twoas well as for threedimensional structures. It is based on a 'misuse' of the option of volumetric swelling in the FEM-code ABAQUS. The main secret is that only a thin surface layer of the FEM-structure is allowed to swell (growth) which is equivalent to the actual growth ring in trees which also alone adapts to the actual loading.

Nylon fiber reinforcement for polyurethane composites

AbstractThe potential of a nylon 6 fiber was evaluated for composite applications involving rigid polyurethane systems. A study showed that the use of COMPET N, a nylon 6 based fiber surface treated to enhance wetout and adhesion, in an ISP polyurethane system results in composites with higher impact values and lower weight than those reinforced with glass fiber. A 2 percent loading of COMPET N matt increased impact values by more than 300 percent over an unreinforced control while a 3 percent loading of glass matt resulted in increases of less than 100 percent. A drop impact test showed COMPET N fabric reinforced composites to absorb twice as much energy as an unreinforced and glass reinforced composite without major damage. These advantages have also been observed in COMPET N/Glass hybrids, in which layer orientation can be used to produce composites with specific properties. Cut fiber reinforced composites were found to exhibit similar properties as fabric reinforced ones resulting in the commercialization of a canoe end cap containing cut nylon fiber. Additional property benefits such as improved impact fatigue and decreased stress cracking have also been observed in nylon 6 reinforced composites resulting in the consideration of these materials for a wide range of applications.

Charpy impact and dart drop impact

In the selection of an appropriate material which satisifes the impact strength requirement for an injection moduled product, the Charpy, Izod or dart drop test methods should be used according to the impact mode displayed by the product—that is, either snap impact on a bar or impact on a shell structure—because generally the ranking of a material determined by the Charpy test differs from that determined by the dart drop test. However, preference for the Charpy test, because of the advantage of simples evaluation work, sometimes leads to erroneous judgement of product characteristics. The breaking behaviour of various materials as determined by Charpy apparatus equipped with instrumentation was studied, and a new design of Charpy test was shown to correlate with the dart drop impact test. The procedure used was to provide a bigger notch tip radius, to break the specimen parallel to the flow direction in the injection moulding process, and to apply the energy absorbed until the beginning of fracture at the notch end.

The effect of molecular weight distribution on polyethylene film properties

AbstractPolymer molecular weight heterogeneity affects the rheological properties of polymer melts such as melt viscosity, fracture and die swell. These rheological properties affect the conversion of the polymer from the bulk resin state to its final usable form. In this particular study, the effect of molecular weight distribution on polyethylene blown film characteristics was studied. The effect of the molecular weight heterogeneity on the rheological characteristics of the polymer in the molten state and its effect on the film properties is presented.The properties studied included film gloss, haze, tear resistance and film impact strength.This study shows that broadening the molecular weight distribution increases haze and reduces film gloss. Further, it was shown that a linear relationship exists between film gloss and external haze. Both values are measures of surface irregularities in the film which are affected by the drawing characteristics of the polymer.A broader molecular weight distribution results in increased impact strength as measured by the Dart Drop Impact Test. This is, it is believed, a result of the increase in long chain branching of the higher molecular weight fractions of the polymer which cause a higher degree of molecular weight entanglement at the branch sites. In contrast the tear strength is reduced as the molecular weight distribution broadens because of the low molecular weight fraction in the broad spectrum material which tend to decrease resistance to tear.

A discussion on deformation of solids by the impact of liquids, and its relation to rain damage in aircraft and missiles, to blade erosion in steam turbines, and to cavitation erosion - Practical aspects of cavitation

Damage produced by cavitation under field conditions can be a serious problem. The main causes of this damage and its characteristics are discussed briefly and possible remedial measures are examined. Accelerated laboratory tests are found to play an important part in cavitation erosion research, but interpretation of results needs care. Most past investigators have tended to treat cavitation damage and droplet erosion as unrelated phenomena and only qualitative correlations between the respective simulated tests have been possible. This paper presents an attempt to correlate quantitatively the results of three different erosion tests. A broad correlation between results of the drop impact erosion and constricted tube cavitation tests shows general agreement. A more detailed, but restricted, correlation has been obtained between results of drop impact and vibratory cavitation erosion tests. In both correlations, however, there is evidence of some discrepancies between corrodible and incorrodible materials. A number of factors which govern the rate of damage in the various laboratory tests are of interest. In particular, in the drop impact test the velocity of collision and the jet diameter are shown to have significant effects. There is a marked similarity between the behaviour of materials in this test and in fatigue tests and also evidence of a threshold velocity below which measurable damage ceases. The other laboratory tests were found to have their own particular controlling parameters, but the general phenomenon of cavitation erosion is more complex and is not discussed in detail. By conducting comparative tests under reproducible conditions it has been possible to classify a variety of new and traditional materials in order of relative erosion resistance and thus provide some guide to their selection for service. While the results add to the evidence that hardness is the major attribute controlling erosion resistance other properties such as ductility, elasticity and fatigue strength are seen to be significant.

Cu-Ag3.8%合金のPb含有による脆化

The Cu-Ag alloys containing about 4%Ag shows solid solution strengthening and age-hardening effects, and is used as a high strength and high electrical conductivity alloy. The effects of lead on the hot working properties of the Cu-3.8%Ag alloy were investigated. The experiments performed were drop hammer tests, impact tests, detections of the lead phase by means of an electron probe X-ray micro-analyser (E.P.M.A.), and observations of the alloy structure at a high temperature. Ingots 50 mm in diameter and 295 mm in height, weighing 5.1 kg, were cast from melts of the Cu-3.8%Ag alloy containing 0.005 to 0.5% lead.The results obtained were as follows: (1) By the method of drop hammer tests and impact tests, the allowable limit of the lead content in the Cu-3.8%Ag alloy was determined. The minimum lead content which caused hot embrittlement in the as-cast alloy was 0.03% and that for the solution treated alloy was 0.08%. (2) It was observed in the experiments by E.P.M.A. that when the specimen contained more than 0.035% lead, the lead phase appeared in the matrix as the secondary phase. The distribution of the lead phase in the matrix was at random both in the grains and at the boundaries. (3) The following mechanism was proposed for the embrittlement of the Cu-Ag alloy by the lead content. Below the melting temperature of the lead phase, the difference of the elastic and plastic properties between the lead phase and the matrix causes a stress concentration at the lead phase under external stress, and leads to embrittlement. At the temperatures above the melting point of the lead phase, the liquid lead “wets” the grain boundaries and decreases the binding strength of the grain boundaries, thus causing the grain boundary embrittlement in the Cu-Ag alloy.