Ashmead, Michael (Cellbond Limited 5 Stukeley Business Centre Blackstone Road Huntingdon Cambs PE29 6EF, GB)
| 1. | A method for testing a vehicle component comprising the steps of: providing a support structure for supporting the vehicle component during testing, the support structure comprising a sacrificial energy absorber and having impact characteristics which mimic impact characteristics of a vehicle part for which the component is intended; mounting the vehicle component on the support structure in a manner which mimics intended spatial relationship between the vehicle part and the vehicle component; and applying an impact to the mounted vehicle component. |
| 2. | A method according to claim 1, further comprising shaping the support structure to obtain a profile which mimics that of the vehicle part. |
| 3. | A method according to claim 1 or claim 2, comprising selecting the parameters of the sacrificial energy absorber so that the support structure has impact characteristics corresponding to impact characteristics of the vehicle part. |
| 4. | A method according to any one of the preceding claims, in which the sacrificial absorber consists of a sheetlike member. |
| 5. | A method according to any one of claims 1 to 3, in which the support structure comprises a sheetlike member mounted on the sacrificial energy absorber. |
| 6. | A method according to claim 5, in which the sacrificial energy absorber is selected from the group consisting of a honeycomb structure, an eggbox type structure and a concertinalike folded structure. |
| 7. | A method according to claim 5, in which the sheet like member acts as a skin over the sacrificial energy absorber. |
| 8. | Support apparatus for supporting, during impact testing, a vehicle component which is intended to be used adjacent a known vehicle part, the support apparatus comprising a member which comprises a sacrificial energy absorber and which is configured to have impact characteristics corresponding to impact characteristics of the vehicle part. |
| 9. | Support apparatus according to claim 7, further comprising a mount for mounting the vehicle component on the support structure in a manner which mimics intended spatial relationship between the vehicle part and the vehicle component. |
| 10. | Support apparatus according to claim 8 or claim 9, in which the parameters of the sacrificial energy absorber are selected so that the support structure has impact characteristics corresponding to impact characteristics of the vehicle part. |
| 11. | Support apparatus according to any one of claims 8 to 10, in which the sacrificial energy absorber consists of a sheetlike member. |
| 12. | Support apparatus according to any one of claims 8 to 10, in which the support structure comprises a sheetlike member mounted on the sacrificial energy absorber. |
| 13. | Support apparatus according to claim 12, in which the sacrificial energy absorber is selected from the group consisting of a honeycomb structure, an eggboxtype structure and a concertinalike folded structure. |
| 14. | Support apparatus according to claim 13, in which the sheetlike member acts as a skin over the sacrificial energy absorber. |
| 15. | Support apparatus according to any one of claims 12 to 14, in which the sheetlike member has a profile corresponding to that of the vehicle part. |
| 16. | Support apparatus according to any one of claims 8 to 15, further comprising a cover for the vehicle component for spreading a localized force resulting from an impact over the vehicle component. |
For the purposes of the present invention, crash padding is defined as an energy absorbing member which is designed to permanently deform on impact so that less of the impact force generated in a vehicle accident is transmitted to the vehicle's occupants, thereby helping to avoid serious injury.
BACKGROUND ART A substantial number of impact tests are carried out on vehicles to ensure safety components perform as intended and the vehicles meet specified safety levels during collisions or other accidents. At present, large numbers of vehicles are sacrificed when checking the efficacy of the safety components. Such a process is both time consuming and expensive.
The cost of sacrificing large numbers of vehicles is addressed in U. K. application GB 2313917A1 and U. S. patents US 5,652,375 and US 5,861,544.
GB 2313917 provides a test rig for impact testing on vehicles. The test rig is re-usable and is designed to simulate a wide range of side impact crash velocity profiles and a variety of intrusion profiles. The test rig comprises an array of actuators and the extension and acceleration of each actuator is controlled, e. g. by a microprocessor, in accordance with predetermined crash and vehicle profile characteristics. The actuators may be covered by padding which is shaped to simulate the internal upholstery of a vehicle door.
US 5,652,375 proposes a reusable, accordion-like model structure designed to present the same collapse performance as a vehicle front body assembly during an impact. The structure comprises a number of support members, each having several arms which are hinged in series and with some of the arms being connected by hydraulic friction joints. Once calibrated, the model
structure is fitted with one vehicle test component (particularly single front vehicle body components) and used for impact testing. Following impact, the collapsed model structure is restored to its original configuration by hydraulic actuators.
US 5,861,544 proposes apparatus for impact testing at a sub-system level whereby full-scale testing is simulated. A sub-assembly of the vehicle, e. g. the torque box and toe-board of a vehicle shell, is mounted on a mobile unit and impacted into a rigid barrier. Analysing the results of the impact on the sub-assembly gives an indication of the crashworthiness of the vehicle in similar impact scenarios.
The applicant has recognised the need to provide an improved method and apparatus for testing safety components.
DISCLOSURE OF THE INVENTION According to a first aspect of the invention, there is provided a method for testing a vehicle component comprising the steps of: providing a support structure for supporting the vehicle component during testing, the support structure comprising a sacrificial energy absorber and having impact characteristics which mimic impact characteristics of a vehicle part for which the component is intended; mounting the vehicle component on the support structure in a manner which mimics intended spatial relationship between the vehicle part and the vehicle component; and applying an impact to the mounted vehicle
component.
The vehicle part is determined by the vehicle component, for example, if the vehicle component is to be used in car headlinings, the vehicle part may be a car roof. The sacrificial energy absorber permanently deforms on impact to absorb energy. By using a sacrificial energy absorber, the complicated accordion-like and actuator based systems of the prior art may be replaced by a simpler support structure without necessarily reducing accuracy of the testing.
The support structure may comprise a sheet-like member (e. g. of metal) forming a support surface. The sheet-like member may act as the sacrificial energy- absorber in its own right or may be mounted on or over the sacrificial energy absorber so that the combination of sheet-like member and sacrificial energy absorber provides the support structure with the desired impact characteristics. If the sheet-like member is to act as the sacrificial energy absorber, a clearance space is provided on one side of the sheet-like member to accommodate the latter during deformation. The sheet-like member may act as a skin over the sacrificial energy absorber which may comprise a cellular structure (e. g. a honeycomb) or an"egg-box"-type structure (e. g. a pressload structure as defined in WO 00/31434).
Alternatively, the sheet-like member may be self- supporting, e. g. plate-like, with the sacrificial energy absorber perhaps comprising at least one folded member
configured to collapse in a concertina-like manner under impact supplied through the support surface. Each energy absorber may be simply manufactured at low cost. The support structure may comprise more than one energy absorber.
The vehicle component may comprise crash padding, which may itself incorporate a sacrificial energy absorber e. g. a honeycomb absorber. The vehicle component may be tested in combination with another vehicle component, e. g. interior vehicle trim such as a rigid section of headlining. The vehicle component (e. g. crash padding) may be disposed between a cover (e. g. another vehicle component or part thereof) and the support structure. In this way, the cover may help to shield the vehicle component, spreading forces resulting from the impact test over an area sufficient to prevent undesirable localized deformation of the vehicle component.
The method may comprise the step of analysing the vehicle part to determine its impact characteristics. Such information may be available from previously conducted testing or may require new impact testing. By using a support structure having impact characteristics corresponding to the impact characteristics of the vehicle part and by mounting the vehicle component in the manner prescribed, the support structure simulates the effect of the vehicle part on the vehicle component during an impact.
In other words, the vehicle component and support
structure in combination respond to an impact in a similar manner to a vehicle part in combination with the vehicle component. Even though at least one component of the support structure is sacrificed in each testing, the support structure may be produced at much less cost than a vehicle, and thus the cost of performing crash testing may be greatly reduced. Also, more crash testing may be performed in a given period of time since it may be easier to set up tests with the support structure in place of the vehicle.
The support structure may have a profile which mimics that of the vehicle part. The method thus may further comprise the step of shaping the support structure to obtain the said profile.
According to a second aspect of the invention, there is provided support apparatus for supporting, during impact testing, a vehicle component which is intended to be used adjacent a known vehicle part, the support apparatus comprising a member which comprises a sacrificial energy absorber and which is configured to have impact characteristics corresponding to impact characteristics of the vehicle part.
The support apparatus may further comprise a mount for mounting the vehicle component on the member in a manner which mimics intended spatial relationship between the vehicle part and the vehicle component.
The sacrificial energy absorber permanently deforms on impact to absorb energy and its parameters (e. g.
dimensions, material) may be selected so that the support structure has impact characteristics corresponding to impact characteristics of the vehicle part. The support structure may comprise a sheet-like member (e. g. of metal) forming a support surface. The sheet-like member may act as the sacrificial energy-absorber in its own right or may be mounted on or over the sacrificial energy absorber so that the combination of sheet-like member and sacrificial energy absorber provides the support structure with the desired impact characteristics. If the sheet-like member is to act as the sacrificial energy absorber, a deformation space is provided to accommodate the sheet- like member during deformation. The sheet-like member may act as a skin over the sacrificial energy absorber which may comprise a cellular structure (e. g. a honeycomb) or an "egg-box"-type structure (e. g. a pressload structure as defined in WO 00/31434). Alternatively, the sheet-like member may be self-supporting, e. g. plate-like, with the sacrificial energy absorber perhaps comprising at least one folded member configured to collapse in a concertina- like manner under impact supplied through the support surface. Each energy absorber may be simply manufactured at low cost. The support structure may comprise more than one energy absorber, either of the same or different kind.
The use of a sheet-like member may be advantageous to modeling crash scenarios. Use of sheet material, especially sheet material used in the manufacture of bodywork for vehicles, e. g. metal, may enable bending
effects of bodywork to be studied.
The sheet-like member may have a profile corresponding to that of the vehicle part. The sheet-like member may be flat or curved e. g. concave or convex.
In accordance with another aspect of the present invention, there is provided a test-rig for impact testing of a predetermined vehicle component, comprising a support member for supporting the predetermined vehicle component, the support member comprising a sacrificial energy absorber having deformation characteristics mimicking those of a known vehicle part with which the vehicle component is intended to be used, whereby impact testing of the predetermined vehicle component in situ with the known vehicle part is simulated. Embodiments of the support member are as defined for the previous aspect of the present invention.
BRIEF DESCRIPTION OF THE DRAWINGS Embodiments of the invention will now be described by way of example, with reference to and as illustrated in the accompanying drawings in which: Figures la and lb are respective plan and cross- sectional view of a first embodiment of a support apparatus according to the present invention; Figure 2 is a cross-sectional view of a second embodiment of a support apparatus; Figure 3a is a perspective view of a vehicle component which may be tested by the support apparatus of Figure 2; Figure 3b is a perspective view of a cell of the
vehicle component of Figure 3a; Figure 4 is a cross-sectional view of a third embodiment of a support apparatus, and Figure 5 is a flowchart of a method according to the invention.
BEST MODES FOR CARRYING OUT THE INVENTION Figures la and 1b show a support member 10 for supporting, during impact testing, a vehicle component 16 which is intended to be used adjacent a known vehicle part. The member 10 comprises a metal sheet 28 which is secured by screws 24 to two frames 30 which rest on a platform 22, e. g. a table or the like. Each frame 30 is solid and elongate with a rectangular cross-section. The frames 30 are spaced apart whereby a spacing or cavity 32 is defined below the metal sheet 28 and hence below the vehicle component. On impact the metal sheet 28 permanently deforms into the cavity and thus acts as an energy absorber.
The parameters (e. g. dimensions, material) of the metal sheet 28 are adjusted to ensure that member 10 has impact characteristics which mimic impact characteristics of a vehicle part for which the vehicle component is intended. The dimensions (e. g. width and height) of the cavity 32 may also be adjusted to improve the impact characteristics, for example, by varying the height and/or spacing of the frames 30.
In Figures la to lb, as in all the following embodiments, the vehicle component 16 is mounted on the
member in a manner which mimics the intended spatial relationship between the component and the vehicle part.
The component may, for example, be glued in an orientation and relative position which corresponds to those it would have adjacent the vehicle part. Impacts on the vehicle component 16 are generated by an impactor having a dome- shaped head 18 which is positioned above the vehicle component 16. The impactor generates impacts in the downward direction of arrow A to simulate head-on glancing crashes.
Figure 2 shows a support member 34 comprising a metal shell 12 forming a skin over a honeycomb energy absorber 14. The metal shell 12 is formed with flanges 26 which are screwed by screws 24 to a platform 22, e. g. a table or the like. The honeycomb energy absorber 14 rests on the platform 22. As shown in the enlarged perspective view, the honeycomb energy absorber 14 comprises a cellular structure having an array of cells 20 of hexagonal cross- section. The cellular structure may be sandwiched between skins e. g. of fibre impregnated with expanded resilient foam.
The vehicle component 16 to be impacted is crash padding for interior head impact protection. The vehicle component 16 is shown in Figures 3a and 3b and comprises an aluminium honeycomb 42 filled with low-density foam 44 and sandwiched between two fibrous clothes 46. The component may thus be of the type taught in WO 98/06553 to the present applicant. The fibrous cloth 46 is
manufactured from polyester fibres and forms a protective but non-structural layer over the honeycomb foil edges.
The foam 44 is an organic polyurethane material which does not modify the mechanical properties of the honeycomb and saturates the cloth 46 during manufacture. The energy absorption characteristic of the honeycomb structure is controlled by venting the foils through vents 50 in the cell walls.
In use, the component is positioned in a car above the C-pillar and between the headliner and roof skin.
Thus, in testing a layer of headliner material 17 shaped to match the vehicle component 16 is placed on top of the component. Furthermore, the parameters of the metal shell 12 and the parameters of the honeycomb energy absorber 14 are selected to ensure that the member 34 has impact characteristics which mimic impact characteristics of the roof skin. The metal shell 12 is formed from a lmm thick layer of aluminium and the energy absorber is made from aluminium. Each cell of the honeycomb has a diameter of 2.3cm and a wall thickness of 3/8mm. Furthermore, a layer of expanded polyester 15, e. g. Dacron (TM), is sandwiched between the metal shell 12 and a surface of the honeycomb energy absorber 14 opposed to the surface adjacent the platform 22.
When tested in a car, such crash padding gives a HIC (Human Impact Criteria) reduction of approximately 800. A similar result is obtained by using the apparatus of Figure 2.
Figure 4 shows a support member 36 which is generally similar to that of Figures la and lb. The member 36 comprises a metal plate 40 which is mounted on two arms 38 which rest on a platform 22. Each arm 28 is concertina- shaped and is formed from a metal sheet which has been folded three times to give the arm a generally W-shaped cross-section, whereby each arm 28 acts as an energy absorber. The frames 30 are spaced apart whereby a cavity 32 is defined below the metal plate 40. The metal plate 40 is thicker than the metal sheet 28 of the first embodiment.
The parameters (e. g. thickness and/or material) of the metal plate 40 and/or the parameters (e. g. sheet thickness, sheet material, spacing between and/or number of folds) of the arms 38 are adjusted to ensure that member 10 has impact characteristics which mimic impact characteristics of a vehicle part for which the vehicle component is intended.
Figure 5 shows the steps of a method embodying one aspect of to the invention. The method steps are: a) providing a support structure having a substrate for supporting a vehicle component during impact testing; b) shaping the substrate to have a desired profile; the desired profile corresponds to that of vehicle part adjacent which the vehicle component is intended to be positioned; c) determining the impact characteristics of the vehicle part;
d) providing a sacrificial energy absorber (e. g. honeycomb structure) to support the desired profile of substrate; the combined impact characteristics of the substrate and energy absorber matching that of the vehicle part. e) mounting the vehicle component on the support structure in a desired manner; the desired manner mimicking the orientation and/or an intended interrelationship between the vehicle part and the vehicle component; f) applying an impact to the vehicle part.
Steps (b) and (d) may be optional if the support structure provided at step (a) already has the desired profile. Step (c) may be completed by analysing known data or conducting additional testing. Step (d) may be optional if the substrate primarily provides the desired impact characteristics, for example, as in the embodiment of Figures la and lb.
An impact having sufficient force will deform the vehicle component and support structure in a similar way to which it would deform the vehicle component in si tu in the vehicle. The results of the impact testing may then be studied to determine the usefulness of using a particular vehicle component, e. g. a particular type of crash padding, in a particular vehicle part.