509 results about "Magnetorheological elastomer" patented technology

In combination with a vehicle and a closure, one or more lockdown regions disposed between the closure and the vehicle body, the one or more lockdown includes a device including an active material disposed in operative communication with the closure and the vehicle body, wherein the active material includes a shape memory alloy, a magnetic shape memory material, a shape memory polymer, a magnetorheological fluid, an electroactive polymer, a magnetorheological elastomer, an electrorheological fluid, a piezoelectric material, or combinations comprising at least one of the foregoing active materials; and an activation device coupled to the active material, the activation device being operable to selectively provide an activation signal to the active material and effectuate a change in a dimension, a shape, and / or a flexural modulus property of the active material, wherein the change in the dimension, a shape, and / or flexural modulus of the active material locks down or releases the closure from the vehicle. Such active materials include shape memory alloys, magnetic shape memory alloys, electroactive polymers, shape memory polymers, magnetorheological fluids, magnetorheological elastomers, electrorheological fluids, and piezoelectric materials. Also provided herein are methods for selectively stiffening a closure hingeably attached to a vehicle body.

A tunable vibration isolation device comprising a magneto-rheological elastomer (MRE), and methods of using such a device, are provided. By manipulating a magnetic field within the MRE the device's stiffness is controlled. The vibration isolator can be constructed to provide shock absorption in one, two and three dimensions. Coupling the tunable device to a sensor feedback and a control system provides fast and accurate vibration isolation and energy dissipation for shock events in a variety of applications.

A latch for engaging and disengaging two opposing surfaces includes a pin disposed on one surface and a gate disposed on an opposite surface; an active material in operative communication with the pin or the gate, wherein the active material comprises a shape memory alloy, a shape memory polymer, a magnetorheological fluid, an electroactive polymer, a magnetorheological elastomer, an electrorheological fluid, a piezoelectric material, or combinations comprising at least one of the foregoing active materials; and an activation device in operative communication with the active material, wherein the activation device is operable to selectively apply an activation signal to the active material and effect a reversible change in a property of the active material, wherein the reversible change results in an engagement or a disengagement of the pin or the gate from the other of the pin or the gate, wherein the disengagement without the activation signal is opposed by a lifting force.

The invention relates to a magnetorheological elastomer active and passive integrated damper based on an extrusion type stress, which belongs to the structure vibration isolation and control field, wherein a magnetorheological elastomer is arranged in a magnetic conductive sleeve; the upside of the magnetorheological elastomer is connected with a joint lever; the lower part of the magnetorheological elastomer is fixedly connected with a lower positioning plate; a groove is arranged on an outer circumferential surface of the magnetic conductive sleeve positioned in a permanent magnet, embedded with a coil winding and positioned and fixed by an upper positioning plate and the lower positioning plate; the permanent magnet, the upper positioning plate, the lower positioning plate and the lower part of the joint lever are arranged in an outer magnet isolating cylinder; the upside of the outer magnet isolating cylinder is provided with an upper end closure; the upper part of the joint lever extends out from a pylome of the upper end closure and is connected with a controlled object; a pretightening spring is sleeved on the joint lever; the bottom of the outer magnet isolating cylinder is provided with a lower end closure; a sensor is fixed on the joint lever and connected with a power amplifier through a control unit module; the power amplifier is connected with the coil winding through cables. The magnetorheological elastomer active and passive integrated damper has large bearing capacity, a simple structure and can be automatically suitable for active and passive vibration control and has wide application range.

A hood lift mechanism for reversibly increasing the energy absorption capability at appropriate force levels of a vehicle hood includes a vehicle hood; an active material in operative communication with the vehicle hood, wherein the active material comprises a shape memory alloy, a ferromagnetic shape memory alloy, a shape memory polymer, a magnetorheological fluid, an electroactive polymer, a magnetorheological elastomer, an electrorheological fluid, a piezoelectric material, an ionic polymer metal composite, or combinations comprising at least one of the foregoing active materials; and an activation device in operative communication with the active material, wherein the activation device is operable to selectively apply an activation signal to the active material and effect a reversible change in a property of the active material, wherein the reversible change results in an increased clearance distance between the vehicle hood and an underlying component.

An active material hood impact mitigation mechanism is activated in response to a signal generated from an impact sensor or pre-impact sensor or manually. The mitigation mechanism is capable of changing either reversibly or irreversibly the stiffness, shape, location, orientation, or displacement force of the hood either globally or locally, before an impact against the hood. The active material mitigation mechanism is held in a device designed to be installed in operative communication with the hood surface. The active material is characterized by a first shape or stiffness and is operative to change to a second shape or stiffness in response to the activation signal. Such active materials include shape memory alloys, electroactive polymers, shape memory polymers, magnetic shape memory alloys, magnetorheological fluids, magnetorheological elastomers, electrorheological fluids, and piezoelectric materials.

The inventive vibration absorber comprises an execution unit, a control unit and a sensor. The execution unit consists of a magnetic inductor, a coil, a magnetic rheological elastic body, a vibration-absorbing mass block and a base. The above magnetic inductor consists of inner and outer sleeves, or a U-shaped iron-core and an armature or top and bottom plates and a column iron-core. Between inner and outer sleeves, the U-shaped iron-core and the armature or the top and bottom plates are filled the magnetic rheological elastic bodies. By regulating the voltage on the coil, the rigidity and the elasticity of the magnetic rheological elastic body are regulated to make its vibration frequency change, so as to make the vibration frequency of the vibration absorber execution unit is the same as that of the vibration-damping object.

The invention relates to a car collision cushioning device and a cushioning energy-absorbing method based on the magnetorheological technology. The cushioning device comprises a bumper, a magnetorheological buffer and a feedback circuit, wherein the magnetorheological buffer is arranged between the bumper and a frame cross member by flanges and composed of a helical spring, a field core, a piston, a piston rod, a cylinder, magnetorheological fluid, a first actuating coil, a magnetorheological elastomer and a second actuating coil, the feedback circuit is composed of a first acceleration sensor, a second acceleration sensor and a controller, in an instant of car collision, the controller judges whether the acceleration signal differential value of the acceleration sensor exceeds a preset threshold value or not, and regulates current output to the first actuating coil and the second actuating coil by self-adapting according to difference of collision speed, changes rigidity and damp of a car collision cushioning system, thereby reducing passenger injury and car damage caused by collision.

The invention relates to an engine vibration isolation device of a magneto-rheological fluid damper in extrusion mode and a magneto-rheological elastomer in shearing mode for supporting static loads. The vibration isolation device comprises two pars of a damping adjusting unit and a rigidity adjusting unit; the damping adjusting unit is connected with the rigidity adjusting unit through a rigid connecting rod; the vibration of an engine causes the connecting rod to move upwards and downwards, so that the magneto-rheological fluid in the damping adjusting unit flows in radial direction and shearing occurs to the magneto-rheological elastomer in the rigid adjusting unit; a magnetic field generated by two exciting coils can be respectively adjust damping parameters and rigidity parameters of a vibration isolator. The magneto-rheological vibration isolator can meet the independent adjustment of the damping parameters and the elastic parameters of the vibration isolator under different vibrational excitation conditions, and achieve the coupling control of the transmission of engine vibration energy, and has great realistic significance in improving the technical level and market competence of special vehicles.

The invention relates to a flexible mechanical arm vibration reduction device and method based on a magneto-rheological technology, which belongs to the technical field of flexible mechanical arm vibration control. The vibration reduction device comprises a rigid-flexible coupled mechanical arm, a magneto-rheological elastomer vibration reduction device and a feedback control loop, wherein the rigid-flexible coupled mechanical arm comprises a rigid mechanical arm, a motor mounting plate, a servo motor, a harmonic reducer, a flexible mechanical arm mounting base and a flexible mechanical arm; the magneto-rheological elastomer vibration reduction device comprises an iron core, a guide rod, a fixed seat, a magneto-rheological elastomer, a permanent magnet and an electromagnetic coil; and the feedback control loop comprises two acceleration sensors, a charge-amplifier, a data acquisition system, a PC (Personal Computer) upper computer and a programmable power supply. The PC upper computer is used for regulating the supply voltage of two ends of the electromagnetic coil through the analyzing and processing the feedback signals of the two acceleration sensors so as to change the rigidness of the magneto-rheological elastomer, thereby meeting the resonance requirement in a system. The flexible mechanical arm vibration reduction device has the characteristics of obvious vibration reduction effect and less energy consumption and is suitable for large amplitude vibration reduction.

The invention relates to a variable rigidity shock insulation integral intelligent support seat and belongs to the technical field of building structure shock absorption. The variable rigidity shock insulation integral intelligent support seat is characterized by comprising an upper connecting plate (1), a lower connecting plate (4), a magnetic conduction steel plate (2), a magnetorheological elastic body (3), an excitation coil (5), a magnetic conduction iron core (6), a polymer matrix composite permanent magnet material (7), a lead core (8), a conducting wire passage (9), an upper connecting screw bolt hole (10), a lower connecting screw bolt hole (11) and a driving power supply (12), wherein the a magnetorheological elastic body (3) and the magnetic conduction steel plate (2) are in a circular ring shape or a square ring shape, the excitation coil (5) and the magnetic conduction iron core (6) are arranged inside a support seat, and the polymer matrix composite permanent magnet material (7) provides a bias magnetic field for a closed magnetic circuit. The variable rigidity shock insulation integral intelligent support seat has the effects and benefits that the shock insulation and the variable rigidity are integrated, the structure is simple, the anti-interference performance is high, the two-way rigidity regulation can be realized, different horizontal rigidities can be provided for the structure according to different quake waves, and the destroy of earthquake disasters on building structures and bridge structures is effectively reduced.

The invention relates to a vibration isolator that the rigidity and damp could be controlled. The damp medium is magnetic current variable material. It is made up of inner sleeve, out sleeve, magnetic current variable elastomer, inner coil winding, out coil winding, and reluctance circle. Cavities are set in the inner sleeve and the out sleeve. The cavity in the inner sleeve has inner coil winding, and the cavity in the out sleeve has out coil winding. The inner sleeve is column shape or circularity. The magnetic current variable elastomer is circularity and is located outside the inner sleeve. The out sleeve is circularity and located outside the magnetic current variable elastomer. The magnetic current variable elastomer, the inner sleeve, and the out sleeve have the same center. And the magnetic current variable elastomer is fixed to the inner sleeve and the out sleeve. Hatches are set on the surface that the inner sleeve and the out sleeve connect to the magnetic current variable elastomer. The reluctance circles are set in the hatches. The invention is simple structure and good reliability.

The present invention relates to a variable rigidity initiative power absorber applied to vibration damping for machinery, electrical equipment and noise control. The fault that the control band width of the passive control type absorber is too narrow, the control energy needed by initiative control type absorber is excessive and the vibration absorption effect of semi- initiative control type absorber is insufficient is solved. The structure feature of the absorber is that: an execution unit includes a base frame, the top of the base frame is disposed with a pair of base seats, the base seats are disposed with annular guide rods, and the two sides of the opening of the annular guide rod are respectively connected with magnetic current variable elastic bodies, the annular guide rods are connected with movable mass blocks, power mechanisms are disposed at the lower part of the power mass blocks. The invention has good vibration absorption effect, wide oscillation damping frequency band, less consume energy, the input energy is less than the initiative control absorber, therefore, the stability is better than the initiative control absorber; the absorber is simple in structure, easy in control method, and high in system reliability.

The invention relates to a design method and a device of an anti-impact vibration isolation type magnetorheological pier bearing-damper system. According to the method, magnetorheological elastomers which are large in vertical stiffness, high in structural strength and adjustable in elasticity modulus are used as bearing bodies, and impact resistance and vibration isolation of a pier-beam structure under the action of large load are realized by adjustment of pier stiffness; a magnetorheological damper capable of providing large damping without medium settlement is used as a damping device, three-dimensional rotation capacity of the damper is improved by using a ball-and-socket joint mode at two ends thereof, and pier-beam displacement is restrained by damping adjustment for further vibration reduction and energy dissipation; magnetorheological elastomer bearings, the magnetorheological damper and a controller jointly form an anti-impact vibration-isolation pier bearing device, the controller intelligently adjusts stiffness and damping of the bearing-damper system by detecting the impact vibration of a bridge, structural strength of the pier-beam structure is improved while damping ratio thereof is increased, and when the bridge is under large-load impact vibration, impact transmission is slowed down or isolated and pier-bean displacement is restrained so as to guarantee structural safety of the bridge.

An active material hood impact mitigation mechanism is activated in response to a signal generated from an impact sensor or pre-impact sensor or manually. The mitigation mechanism is capable of changing either reversibly or irreversibly the stiffness, shape, location, orientation, or displacement force of the hood either globally or locally, before an impact against the hood. The active material mitigation mechanism is held in a device designed to be installed in operative communication with the hood surface. The active material is characterized by a first shape or stiffness and is operative to change to a second shape or stiffness in response to the activation signal. Such active materials include shape memory alloys, electroactive polymers, shape memory polymers, magnetic shape memory alloys, magnetorheological fluids, magnetorheological elastomers, electrorheological fluids, and piezoelectric materials.

The invention provides an adjustable-inherent-frequency composite power vibration absorber and a control method of the adjustable-inherent-frequency composite power vibration absorber. The adjustable-inherent-frequency composite power vibration absorber comprises a signal collecting unit, a control unit and an executing unit, wherein the executing unit consists of two parts including a rigidity adjustment unit and a mass adjustment unit, the rigidity adjustment unit comprises a U-shaped base frame, excitation coils and a pre-tightening screw bolt are attached to the U-shaped base frame, a vibration absorption block is positioned between two magneto-rheological elastic bodies and is fixedly arranged between two clamp plates through the pre-tightening effect of the pre-tightening screw bolt, and a liquid storage box, a liquid pump and a liquid lower cavity are connected through a hose. The adjustable-inherent-frequency composite power vibration absorber and the control method have the advantages that the design structure is simple, the vibration absorption effect is good, an effective vibration reduction frequency band is wide, the performance is stable, the control response time is short, and practical values are very high; on the basis of the existing self-adaptation type vibration absorber, the effective vibration reduction frequency band is further widened, and the problem of too short effective vibration reduction frequency band of a traditional power vibration absorber is solved; the defect that an active type power vibration absorber excessively depends on external energy is overcome.

The invention provides a magnetorheological elastomer intelligent vibration absorber used for ships, which comprises an outer shell, a magnetorheological elastomer, a magnetic coil group and an internal iron core. The outer shell, the magnetorheological elastomer, the magnetic coil group and the internal iron core are together distributed on the same concentric circle. The inner surface of the outer shell is tightly connected with the outer surface of the magnetorheological elastomer by a bond. The inner surface of the magnetorheological elastomer is stuck into a whole body with the inside iron core by the bond. The coils are divided into four groups and are respectively twisted on the internal iron core. The invention is prepared by using the characteristic that the magnetic shearing rigidity of the magnetorheological elastomer is changed with the changing of the current, and has the advantages of simple structure, good vibration absorption effect, broad applicable frequency bands(using frequency bands of several HZ to scores of HZ), strong environment adaptive capacity(resisting oil stain and dampness), good stability (the control effect is not reduced after being used for a long period), etc.

The invention discloses a preparation method and application of a PDMS (polydimethylsiloxane)-magnetic nano-particle composite optical film, and belongs to the field of optical micro electro mechanical systems and polymer optical materials. The preparation method comprises the following steps: mixing a mixture consisting of a PDMS prepolymer and a curing agent with trichloromethane and magnetic nano-particles, and performing ultrasonic oscillation to obtain a PDMS-magnetic nano-particle mixed solution; and then coating the obtained PDMS-magnetic nano-particle mixed solution to a quartz plate by adopting a spin coating technology, obtaining an anisotropic composite material coated film under the action of a strong magnetic field of 500mT, and baking to obtain the PDMS-magnetic nano-particle composite optical film. The novel polymer based nano composite film with characteristics of a magneto-rheological elastomer is relatively high in optical transparency, and the optical transmittance of the film can be adjusted by applying an external magnetic field, so that the PDMS-magnetic nano-particle composite optical film is applicable in the field of the optical micro electro mechanical systems.

The invention relates to a damping device, especially active vibration absorber and the control method. Said vibration absorber in vibration absorbing system comprises main drive part, vibration absorbing block, changeably stiffness part, magnetic insulation block and U-shaped bracket. The main drive part comprises permanent magnet and column electromagnet. The column iron core is fixed on the bottom of bracket and permanent magnet is fixed with vibration absorbing block by magnetic insulation block. The changeably stiffness part comprises U-shaped electromagnet and MR elastomer. U-shaped iron core is opened downward, of which MR elastomer are set on two inner sides respectively. Vibration absorbing block is set among two chips and the lower end of U-shaped iron core is fixed with the upper end of U-shaped bracket to form inner space where the main drive part, vibration absorbing block, MR elastomer and magnetic insulation block are accommodated. The control method is that the changeably stiffness part and main drive part are controlled respectively according to frequency, amplitude value and phase information of vibration-damping objects. The invention belongs to half-active and active combined control and is provided with low consuming and wide vibration-damping frequency so on.

The invention discloses a porous magnetorheological elastomer and a buffer device based on the same. The porous magnetorheological elastomer comprises a rubber substrate, gas somas and soft magnetic packing grains. A foaming agent is promoted to decompose and release gases under certain temperature and magnetic field actions in the crosslinking process of substrates magnetorheological elastomers by utilizing a rubber foaming technology, thus, a great number of obturated gas somas are formed in the magnetorheological elastomer; and after the solidification process of the magnetorheological elastomer is ended, the gas somas are implanted in the magnetorheological elastomer to form the porous magnetorheological elastomer. Meanwhile, the soft magnetic packing grains inside the magnetorheological elastomer are distributed in a chain-shaped structure under the action of a magnetic field so that a favorable magnetic effect is achieved. The obturated gas somas are introduced to the magnetorheological elastomer so that the rigidity and dampness changing performances of the magnetorheological elastomer under the action of the magnetic field are improved; and a compression type buffer device is designed by utilizing the porous magnetorheological elastomer so that a better buffering effect can be achieved.

A hood lift mechanism for reversibly increasing the energy absorption capability at appropriate force levels of a vehicle hood includes a vehicle hood; an active material in operative communication with the vehicle hood, wherein the active material comprises a shape memory alloy, a ferromagnetic shape memory alloy, a shape memory polymer, a magnetorheological fluid, an electroactive polymer, a magnetorheological elastomer, an electrorheological fluid, a piezoelectric material, an ionic polymer metal composite, or combinations comprising at least one of the foregoing active materials; and an activation device in operative communication with the active material, wherein the activation device is operable to selectively apply an activation signal to the active material and effect a reversible change in a property of the active material, wherein the reversible change results in an increased clearance distance between the vehicle hood and an underlying component.

A tunable vibration isolation device comprising a magneto-rheological elastomer (MRE), and methods of using such a device, are provided. By manipulating a magnetic field within the MRE the device's stiffness is controlled. The vibration isolator can be constructed to provide shock absorption in one, two and three dimensions. Coupling the tunable device to a sensor feedback and a control system provides fast and accurate vibration isolation and energy dissipation for shock events in a variety of applications.

The invention peovides a plank soft mode forming device and method based on magnetorheological elastomers, relates to a plank soft mode forming device and method, and solves the problem that the rubber performance of the conventional rubber soft mode can not be changed during forming process. The device provided by the invention is characterized in that a holding frame is arranged opposite to a die in an up and down manner, the head of a plunger piston is positioned in the inner cavity of the holding frame, the lower surface of the plunger piston is filled with a magnetorheological elastomer, and the outer sidewalls of the holding frame and the die are sleeved and mounted with coils. The method provided by the invention comprises the following steps: firstly, placing the to-be-formed plank between the lower surface of the holding frame and the die; secondly, determining the magnetic field strength B in work area according to the shape of the to-be-formed plank and the size of the elastic modulus of magnetorheological elastomer needed at each stage in forming; thirdly, connecting the coil with a direct current, enabling the magnetic field strength of the magnetorheological elastomer area to be changed by adjusting the current, and enabling the to-be-formed plank to form the needed shape under proper elasticity modulus of the magnetorheological elastomer; and fourthly, taking out the formed parts. The method provided by the invention is used for plank soft mode forming.

A hood lift mechanism for reversibly increasing the energy absorption capability at appropriate force levels of a vehicle hood includes a vehicle hood; an active material in operative communication with the vehicle hood, wherein the active material comprises a shape memory alloy, a ferromagnetic shape memory alloy, a shape memory polymer, a magnetorheological fluid, an electroactive polymer, a magnetorheological elastomer, an electrorheological fluid, a piezoelectric material, an ionic polymer metal composite, or combinations comprising at least one of the foregoing active materials; and an activation device in operative communication with the active material, wherein the activation device is operable to selectively apply an activation signal to the active material and effect a reversible change in a property of the active material, wherein the reversible change results in an increased clearance distance between the vehicle hood and an underlying component.

The invention relates to a birotor self-powered damper based on magnetorheological elastomers. The birotor self-powered damper based on the magnetorheological elastomers comprises a power generating module, an energy module and a damping module which are integrated, the power generating module and the damping module are fixedly connected with a vehicle body, the power generating module is a birotor power generating device with a ball screw assembly as a driving part, the ball screw assembly drives dual rotors to rotate to generate power by means of up-and-down movement of the damping module when vehicle wheels meet road excitation, the electric energy is transmitted to the energy module to be stored, the energy module is provided with a battery and a controller, the battery is connected with the power generating module, the controller is connected with a vehicle control terminal, the damping module is a magnetofluid elastic device which comprises a piston and a piston rod, the piston rod is connected with the ball screw assembly, magnetofluid elastic components are arranged above and below the piston respectively, the magnetofluid elastic components are connected with the battery, and the battery is controlled by the controller to provide power for assigned magnetofluid elastic elements.

Hood lift mechanisms for reversibly increasing the energy absorption capability at appropriate force levels of a vehicle closure includes a vehicle closure; an active material in operative communication with the vehicle closure, wherein the active material comprises a shape memory alloy, a ferromagnetic shape memory alloy, a shape memory polymer, a magnetorheological fluid, an electroactive polymer, a magnetorheological elastomer, an electrorheological fluid, a piezoelectric material, an ionic polymer metal composite, or combinations comprising at least one of the foregoing active materials; and an activation device in operative communication with the active material, wherein the activation device is operable to selectively apply an activation signal to the active material and effect a reversible change in a property of the active material, wherein the reversible change results in an increased clearance distance between the vehicle closure and an underlying component.

The present invention relates to a smart golf ball comprised of one or more mantle layers juxtaposed between an inner core and outer cover, where the core, the mantle layer(s), and / or the cover are further comprised of a ferrofluid, a magnetorheological fluid, an inverse magnetorheological fluid, and / or a magnetorheological elastomer, in any of its construction. These nano-engineered materials make possible a golf ball with heretofore-unprecedented levels of adaptive play.

The invention discloses a novel intelligent shock absorber integrating multilayer magnetorheological elastomers with a magnetorheological damper. The shock absorber comprises the magnetorheological damper and a variable stiffness device comprising the multilayer annular magnetorheological elastomers and magnetorheological elastomer magnet exciting coil windings mounted between the multilayer annular magnetorheological elastomers respectively, wherein the magnetorheological damper comprises a cylinder barrel; the cylinder barrel is connected to the top end of the shock absorber through a spring; a piston plate is arranged in the cylinder barrel; a piston rod is fixedly connected to the lower side of the piston plate; the other end of the piston rod penetrates out of the cylinder barrel and is fixed at the bottom end of the shock absorber; a magnetorheological damper magnet exciting coil winding is wound on the side wall of the piston plate; the cylinder barrel is filled with a magnetorheological fluid; a damping device is connected with the variable stiffness device in parallel or in series. Due to the integration of the multilayer magnetorheological elastomers and the magnetorheological damper, the stiffness and damping change range of the shock absorber is relatively large, a relatively good shock absorption effect can be achieved, and the shock absorber is compact in structure.

In combination with a vehicle and a closure, one or more lockdown regions disposed between the closure and the vehicle body, the one or more lockdown regions comprising a device comprising an active material disposed in operative communication with the closure and the vehicle body, wherein the active material comprises a shape memory alloy, a magnetic shape memory material, a shape memory polymer, a magnetorheological fluid, an electroactive polymer, a magnetorheological elastomer, an electrorheological fluid, a piezoelectric material, or combinations comprising at least one of the foregoing active materials; and an activation device coupled to the active material, the activation device being operable to selectively provide an activation signal to the active material and effectuate a change in a dimension, a shape, and / or a flexural modulus property of the active material, wherein the change in the dimension, a shape, and / or flexural modulus of the active material locks down or releases the closure from the vehicle. Such active materials include shape memory alloys, magnetic shape memory alloys, electroactive polymers, shape memory polymers, magnetorheological fluids, magnetorheological elastomers, electrorheological fluids, and piezoelectric materials. Also disclosed herein are methods for selectively stiffening a closure hingeably attached to a vehicle body.